A super low viscosity ethyl cellulose and its preparation method and application

Abstract

The application discloses a kind of extra-low viscosity ethyl cellulose and its preparation method and application, belong to the technical field of ethyl cellulose preparation. The preparation method comprises: after mixing ethyl cellulose crude product and pure water, pH regulator is added, then at least one of washing aid, viscosity reducer, stabilizer and penetrant is added, and then it is cooked and washed, then dehydrated, continue to cook and wash 3~4 times, then dehydrate and dry, to obtain extra-low viscosity ethyl cellulose;Among them, pH regulator is added in the first 2 times of cooking and washing, washing aid is added in the first 2 times of cooking and washing, viscosity reducer is added in the second 4 times of cooking and washing, stabilizer is added in the second 4 times of cooking and washing, and penetrant is added in the first 3 times of cooking and washing. The multi-stage deep viscosity reduction process adopted in the present application does not produce caking during production process, and can produce low color, high purity, high storage stability, and low dynamic viscosity of 3~4.5 mPaS of extra-low viscosity ethyl cellulose product.

Description

Technical Field

[0001] This invention belongs to the field of ethyl cellulose preparation technology, specifically relating to an ultra-low viscosity ethyl cellulose, its preparation method, and its application. Background Technology

[0002] Energy issues are increasingly becoming a bottleneck restricting international economic development, prompting more and more countries to implement "solar energy initiatives," develop photovoltaic resources, and vigorously develop photovoltaic cells. Against this backdrop, electronic pastes, as raw materials for photovoltaic cell production, have also experienced rapid development. Using ultra-low viscosity ethyl cellulose as a thickener imparts characteristics such as lower grid resistance, better leveling properties, high solids content, and ease of sintering to electronic pastes, enabling the fabrication of finer grid lines and their application in high-end photovoltaic cell manufacturing.

[0003] The preparation of ultra-low viscosity ethyl cellulose involves a polymer degradation reaction to reduce the molecular weight of crude ethyl cellulose (containing a large amount of alkali, salt, and other impurities) to a certain level, resulting in a low-viscosity product. This process is also known as viscosity reduction. The traditional refining process for ultra-low viscosity ethyl cellulose involves adding a sufficient amount of viscosity reducer in a single step. However, this process introduces several problems: firstly, the single addition of a high concentration of viscosity reducer leads to the formation of low-molecular-weight products on the product surface. At high temperatures, the product's low surface modulus causes it to clump together, increasing the difficulty of viscosity reduction and potentially leading to uneven viscosity reduction. Secondly, achieving the desired viscosity reduction effect often requires a long reaction time, which can cause the product to yellow and turn acidic due to excessive oxidation, and problems arise during storage. Furthermore, the traditional process suffers from significant ineffective decomposition of the viscosity reducer, resulting in low viscosity reduction efficiency and making it difficult to obtain ultra-low viscosity products with a dynamic viscosity below 4.5 mPa·s. Therefore, addressing the technical challenges of product clumping and achieving ultra-low viscosity in existing ethyl cellulose production processes is of great significance. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide an ultra-low viscosity ethyl cellulose, its preparation method and application, so as to solve the technical problems of easy product agglomeration and difficulty in achieving ultra-low viscosity in the existing ethyl cellulose production process.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing ultra-low viscosity ethyl cellulose is provided, comprising the following steps: Crude ethyl cellulose is mixed with pure water, and a pH adjuster is added. Then, at least one of a washing aid, a viscosity reducer, a stabilizer, and a penetrant is added, followed by boiling and washing. The mixture is then dehydrated and boiled and washed 3-4 times, and then dehydrated and dried to obtain ultra-low viscosity ethyl cellulose. The pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant are added during the first and second boiling and washing processes, respectively.

[0006] The beneficial effects of this invention are as follows: This invention systematically solves the technical bottlenecks of easy product agglomeration and difficulty in achieving ultra-low viscosity products with a dynamic viscosity of less than 4.5 mPaS in traditional processes by using multi-level deep viscosity reduction and the staged synergistic effect of multiple additives.

[0007] To address the clumping problem, the main causes are residual solvent in crude ethyl cellulose and the formation of low-molecular-weight products on the product surface due to a single high-concentration addition of viscosity reducers. At high temperatures, the product adheres and clumps due to its low surface modulus. Therefore, this invention employs multiple additions of viscosity reducers, resulting in a gentler viscosity reduction process. Simultaneously, the addition of a penetrant in the first to third additions enhances the wetting and penetration of the washing solution into the particles, ensuring sufficient penetration of the viscosity reducer and preventing excessive viscosity reduction on the particle surface, which would otherwise lead to the formation of low-molecular-weight products.

[0008] The difficulty in achieving ultra-low viscosity stems from insufficient penetration of viscosity reducers within the product, resulting in incomplete viscosity reduction and low efficiency. By employing multi-stage viscosity reduction processes and the synergistic effect of various additives, not only can viscosity reduction efficiency be improved, but the completeness of viscosity reduction can also be enhanced, thereby obtaining ethyl cellulose products with even lower viscosity.

[0009] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, the mass ratio of crude ethyl cellulose to pure water is 1:4 to 11; preferably, the mass ratio of crude ethyl cellulose to pure water is 1:5 to 10; more preferably, the mass ratio of crude ethyl cellulose to pure water is 1:8 to 9.

[0010] Furthermore, the pH adjuster is at least one of hydrochloric acid, nitric acid, and acetic acid.

[0011] Furthermore, a pH adjuster is added to make the pH of the washing environment 5-10.

[0012] Furthermore, the mass ratio of crude ethyl cellulose to pH adjuster is 10:1 to 5; preferably, the mass ratio of crude ethyl cellulose to pH adjuster is 10:1 to 4; even more preferably, the mass ratio of crude ethyl cellulose to pH adjuster is 10:1 to 3; and most preferably, the mass ratio of crude ethyl cellulose to pH adjuster is 10:1 to 2.

[0013] Furthermore, the detergent additive is oxalic acid.

[0014] Furthermore, the mass ratio of crude ethyl cellulose to oxalic acid is 1000:1 to 10, preferably 1000:2 to 9, even more preferably 1000:3 to 9, and most preferably 1000:4 to 7.

[0015] Furthermore, the viscosity reducer is at least one of sodium hypochlorite, hydrogen peroxide, and chlorine dioxide.

[0016] Furthermore, the mass ratio of crude ethyl cellulose to viscosity reducer is 10:1 to 8, preferably 10:2 to 7, even more preferably 10:3 to 6, and most preferably 10:4 to 6.

[0017] Furthermore, the stabilizer is at least one of sodium bicarbonate, sodium silicate, and EDTA.

[0018] Furthermore, the mass ratio of crude ethyl cellulose to stabilizer is 100:1 to 10, preferably 100:2 to 8, even more preferably 100:3 to 7, and most preferably 100:4 to 6.

[0019] Furthermore, the penetrant is at least one of EL-90, JFC-M, AEP-98, and OEP-70.

[0020] Furthermore, the mass ratio of crude ethyl cellulose to penetrant is 100:5~0.1, preferably 100:4~0.5, even more preferably 100:2~1, and most preferably 100:1.8~1.2.

[0021] The pH adjuster, detergent aid, viscosity reducer, stabilizer and penetrant mentioned above are sometimes added only in one boiling and washing process, and sometimes added in multiple boiling and washing processes. However, the total amount added is added according to the above mass ratio with crude ethyl cellulose. When adding multiple times, the total amount is divided into multiple additions. There are no special requirements for the amount added each time. That is, whether it is added multiple times or added once, the total amount remains unchanged.

[0022] Furthermore, the boiling and washing temperature is 80~120℃ each time, and the boiling and washing time is 0.5~3h each time.

[0023] Applications of ultra-low viscosity ethyl cellulose prepared by the above method in the preparation of thickeners or electronic pastes.

[0024] The present invention has the following beneficial effects: (1) Compared with traditional processes, the multi-stage deep viscosity reduction process of the present invention does not produce agglomeration during production, and can produce ultra-low viscosity ethyl cellulose products with low color, high purity, high storage stability and dynamic viscosity as low as 3~4.5 mPaS.

[0025] (2) By implementing multi-stage viscosity reduction, the viscosity reducer concentration is lower and the viscosity reduction process is more gentle. At the same time, it also gives the viscosity reducer enough time to fully penetrate into the ethyl cellulose. This not only avoids excessive viscosity reduction and excessive oxidation on the product surface, reduces clumping and yellowing of the product, inhibits the generation of acidic and other off-odor substances, but also improves the uniformity of the viscosity reduction reaction.

[0026] (3) The detergent additives added in this invention also have reducing properties and can complex with heavy metal ions such as iron and nickel. This not only prevents the metal ions from oxidizing ethyl cellulose and reducing the yellowing of the product, but also inhibits the decomposition of the viscosity reducer catalyzed by metal ions, thus improving the viscosity reduction efficiency and helping to reduce viscosity deeply.

[0027] (4) The stabilizer added in this invention can provide a stable pH environment for the viscosity reducer reaction, which can reduce the ineffective decomposition of the viscosity reducer in sync with the detergent additive, and can also make the viscosity reducer continuously and uniformly release active free radicals, improve the viscosity reduction efficiency and obtain a product with lower viscosity.

[0028] (5) The multi-stage viscosity reduction process of the present invention is coordinated with multi-stage washing. Through the efficient coupling of the two, metal ions, excess viscosity reducers and other by-products can be removed from ethyl cellulose products in a timely manner, which improves product purity, reduces the residue of metal ions and viscosity reducers in the product, avoids viscosity reduction of the product during storage, and improves the storage stability of the product.

[0029] (6) The addition of the penetrant of the present invention can not only reduce the surface tension of the washing liquid, promote the penetration of each component into the interior of ethyl cellulose, and accelerate the diffusion of by-products such as sodium chloride, ethanol, ether and residual solvent toluene inside ethyl cellulose outward, but also enhance the stabilizing effect on the viscosity reducer. It has a synergistic effect with the detergent and stabilizer, and together improves the viscosity reduction efficiency. Detailed Implementation

[0030] The examples given below are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, conditions in the examples are performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0031] Example 1: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10 each time. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 1. After each washing, the product was centrifuged to remove water before proceeding to the next washing process.

[0032] Table 1. Multi-stage washing and viscosity reduction process parameters

[0033] No clumping occurred during the boiling and washing process according to Table 1. The resulting product underwent colorimetry testing: ethyl cellulose was dissolved in 95% ethanol to achieve a 5% mass concentration. Colorimetry was measured using a CS-700 colorimeter, with liquid platinum-cobalt colorimetry as the reference standard. The platinum-cobalt standard colorimetric method is a colorimetric method for determining the color of liquids. It uses a standard color series prepared with potassium chloroplatinate and cobalt chloride as a reference, and determines the colorimetric value by comparing it with the sample color. The tested product had a colorimetry of 102 and a dynamic viscosity of 3.2 mPaS (test conditions: solvent was a 4:1 mass ratio of toluene and ethanol, polymer mass concentration was 5%, and the capillary viscometer was used at 25±0.1℃). The product contained 25 ppm of residual iron ions, 92 ppm of residual oxides, 0.05% of residual toluene, and 0.15% of residual diethyl ether.

[0034] Example 2: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:8 each time. The product underwent 5 washes. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 2. After each wash, the product was centrifuged to remove water before entering the next washing process.

[0035] Table 2 Multi-stage washing viscosity reduction process parameters

[0036] No clumping occurred during the boiling and washing process according to the process in Table 2. The tested product had a color of 76, a dynamic viscosity of 3.0 mPaS, a residual iron ion content of 12 ppm, a residual oxide content of 56 ppm, a residual toluene content of 0.03%, and a residual ether content of 0.05%.

[0037] Comparative Example 1: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 3. After washing, the product was centrifuged and dehydrated, and then dried to obtain the final product.

[0038] Table 3 Multi-stage washing viscosity reduction process parameters

[0039] During the washing process according to the process in Table 3, it was found that about 13% of the material by mass had agglomeration. The product obtained by testing had a color of 112, a dynamic viscosity of 4.9 mPaS, a residual iron ion content of 56 ppm, a residual oxide content of 203 ppm, a residual toluene content of 0.08%, and a residual ether content of 0.45%.

[0040] Comparative Example 2: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 4. After washing, the product was centrifuged and dehydrated, and then dried to obtain the final product.

[0041] Table 4 Multi-stage washing viscosity reduction process parameters

[0042] No clumping occurred during the boiling and washing process according to Table 4. The tested product had a color of 129, a dynamic viscosity of 5.7 mPaS, a residual iron ion content of 108 ppm, a residual oxide content of 123 ppm, a residual toluene content of 0.06%, and a residual ether content of 0.27%.

[0043] Comparative Example 3: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 5. After washing, the product was centrifuged and dehydrated, and then dried to obtain the final product.

[0044] Table 5 Multi-stage washing viscosity reduction process parameters

[0045] During the washing process according to the process in Table 5, it was found that about 3% of the material by mass had agglomeration. The product obtained by testing had a color of 109, a dynamic viscosity of 4.7 mPaS, a residual iron ion content of 67 ppm, a residual oxide content of 154 ppm, a residual toluene content of 0.056%, and a residual ether content of 0.3%.

[0046] Comparative Example 4: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 6. After washing, the product was centrifuged and dehydrated, and then dried to obtain the final product.

[0047] Table 6 Multi-stage washing viscosity reduction process parameters

[0048] During the washing process according to the process in Table 6, it was found that about 4% of the material by mass had agglomeration. The product obtained by testing had a color of 111, a dynamic viscosity of 4.9 mPaS, a residual iron ion content of 89 ppm, a residual oxide content of 178 ppm, a residual toluene content of 0.063%, and a residual ether content of 0.24%.

[0049] Comparative Example 5: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 7. After washing, the product was centrifuged and dehydrated, and then dried to obtain the final product.

[0050] Table 7 Multi-stage washing viscosity reduction process parameters

[0051] During the washing process according to the process in Table 7, it was found that about 9% of the material by mass had agglomeration. The product obtained by testing had a color of 135, a dynamic viscosity of 6.4 mPaS, a residual iron ion content of 102 ppm, a residual oxide content of 213 ppm, a residual toluene content of 0.063%, and a residual ether content of 0.32%.

[0052] Comparative Example 6: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 8. After washing, the product was centrifuged and dehydrated, and then dried to obtain the final product.

[0053] Table 8 Multi-stage washing and viscosity reduction process parameters

[0054] No clumping was observed during the boiling and washing process according to Table 8. The tested product had a color of 104, a dynamic viscosity of 3.6 mPaS, a residual iron ion content of 30 ppm, a residual oxide content of 118 ppm, a residual toluene content of 0.09%, and a residual ether content of 0.5%.

[0055] Comparative Example 7: A method for preparing ultra-low viscosity ethyl cellulose includes the following steps: 1000 kg of crude ethyl cellulose was added to pure water for washing, with a fixed mass ratio of crude ethyl cellulose to pure water of 1:10. The product underwent four washings. The amounts of pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant added, as well as the process parameters such as pH, temperature, and time for washing, are shown in Table 9. After washing, the product was centrifuged and dehydrated, and then dried to obtain the final product.

[0056] Table 9 Multi-stage washing viscosity reduction process parameters

[0057] During the washing process according to the process in Table 9, it was found that about 19% of the material by mass had agglomeration. The product obtained by testing had a color of 186, a dynamic viscosity of 6.7 mPaS, a residual iron ion content of 187 ppm, a residual oxide content of 367 ppm, a residual toluene content of 0.1%, and a residual ether content of 0.45%.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing ultra-low viscosity ethyl cellulose, characterized in that, Includes the following steps: Crude ethyl cellulose is mixed with pure water, and a pH adjuster is added. Then, at least one of a washing aid, a viscosity reducer, a stabilizer, and a penetrant is added, followed by boiling and washing. The mixture is then dehydrated and boiled and washed 3-4 times, and then dehydrated and dried to obtain ultra-low viscosity ethyl cellulose. The pH adjuster, washing aid, viscosity reducer, stabilizer, and penetrant are added during the first and second boiling and washing processes, respectively.

2. The method for preparing ultra-low viscosity ethyl cellulose according to claim 1, characterized in that, The mass ratio of crude ethyl cellulose to pure water is 1:4~11.

3. The method for preparing ultra-low viscosity ethyl cellulose according to claim 1, characterized in that, The pH adjuster is at least one of hydrochloric acid, nitric acid, and acetic acid; the mass ratio of crude ethyl cellulose to pH adjuster is 10:1~5.

4. The method for preparing ultra-low viscosity ethyl cellulose according to claim 1, characterized in that, The detergent additive is oxalic acid; the mass ratio of crude ethyl cellulose to oxalic acid is 1000:1~10.

5. The method for preparing ultra-low viscosity ethyl cellulose according to claim 1, characterized in that, The viscosity reducer is at least one of sodium hypochlorite, hydrogen peroxide, and chlorine dioxide; the mass ratio of crude ethyl cellulose to the viscosity reducer is 10:1~8.

6. The method for preparing ultra-low viscosity ethyl cellulose according to claim 1, characterized in that, The stabilizer is at least one of sodium bicarbonate, sodium silicate and EDTA; the mass ratio of crude ethyl cellulose to stabilizer is 100:1~10.

7. The method for preparing ultra-low viscosity ethyl cellulose according to claim 1, characterized in that, The penetrant is at least one of EL-90, JFC-M, AEP-98 and OEP-70; the mass ratio of crude ethyl cellulose to penetrant is 100:5~0.

1.

8. The method for preparing ultra-low viscosity ethyl cellulose according to claim 1, characterized in that, Each boiling and washing session should be at a temperature of 80~120℃ and last for 0.5~3 hours.

9. Extra-low viscosity ethyl cellulose prepared by the preparation method according to any one of claims 1 to 8.

10. The use of the ultra-low viscosity ethyl cellulose according to claim 9 in the preparation of thickeners or electronic pastes.

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