Method for reducing viscosity of high-concentration cellulose diacetate acetone slurry

Abstract

The invention discloses a method for reducing the viscosity of high-concentration cellulose diacetate acetone slurry, which can solve the filtering problem caused by overhigh viscosity of the high-concentration cellulose diacetate acetone slurry. The method for reducing the viscosity of the high-concentration cellulose diacetate acetone slurry provided by the invention comprises the following steps: dissolving cellulose diacetate by taking an acetone aqueous solution with the mass concentration of 95% as a solvent, preparing a high-concentration cellulose diacetate acetone slurry sample, and measuring the viscosity of the high-concentration cellulose diacetate acetone slurry sample; preparing acetone aqueous solutions with different mass concentrations, dissolving the cellulose diacetate, preparing a cellulose diacetate acetone slurry sample with the same mass concentration as the cellulose diacetate acetone slurry sample in the first step, and measuring the viscosity of the cellulose diacetate acetone slurry sample; and adjusting the mass concentration of the acetone aqueous solution for production, and dissolving the cellulose diacetate to obtain the cellulose diacetate acetone slurry with lower viscosity. According to the method, the viscosity of the high-concentration cellulose diacetate acetone slurry is reduced by changing the polarity of the solvent, so that the problems that the filtration pressure difference is increased, the permeation amount is reduced and the like due to overhigh viscosity of the slurry are avoided, and the aim of maintaining the production stability of acetate fiber tows can be achieved.

Description

TECHNICAL FIELD

[0001] The application relates to a method for reducing the viscosity of high-concentration cellulose diacetate acetone slurry and belongs to the field of polymer physics.

[0002] Cellulose acetate is a cellulose acetate ester formed from cellulose pulp and acetic anhydride under the catalysis of concentrated sulfuric acid. The core transformation is that the alcohol hydroxyl group (-OH) on the glucose ring in the cellulose molecular structure is replaced by the acetyl group (-COCH3) in the acetic anhydride. This chemical modification endows cellulose with excellent properties. When the degree of substitution of cellulose acetate is between 2.22 and 2.76, the product is called cellulose diacetate (abbreviated as diacetate). Diacetate can be spun into cellulose acetate tow after being dissolved. In the industrial field, cellulose acetate tow is mainly used as a filter rod material for cigarettes.

[0003] In the dry spinning process of diacetate, acetone is widely used as a medium to prepare spinning slurry. Acetone has a high solubility rate and a high solubility for diacetate. However, the viscosity of the diacetate solution is closely related to factors such as the degree of polymerization, solvent and concentration. Diacetate from different sources has significant differences in the viscosity of the acetone slurry under the same mass fraction conditions due to differences in the pulp raw materials, production process and characteristic indexes used for diacetate production. For example, the high-concentration slurry of diacetate with a high content of hemicellulose components has a viscosity significantly higher than that of low-hemicellulose-component diacetate slurry under the same conditions, and the viscosity significantly increases with a slight increase in the mass fraction of diacetate. The dramatic change in the viscosity of diacetate slurry will further affect the subsequent filtration process of the slurry, and then affect the stability of the production of cellulose acetate tow. SUMMARY

[0004] The main purpose of the application is to provide a method for reducing the viscosity of high-concentration cellulose diacetate acetone slurry in a simple operation manner without changing the concentration of the cellulose diacetate slurry when the viscosity of the slurry significantly increases due to the change of the diacetate raw material source and the change of the characteristic indexes of diacetate after the production of cellulose acetate tow, so that the viscosity of the slurry is not affected by the switching of the diacetate raw material.

[0005] TECHNICAL SCHEME 1. A method for reducing the viscosity of high-concentration cellulose diacetate acetone slurry, characterized in that the method comprises the following steps: Step 1: Dissolving cellulose diacetate in a 95% mass concentration acetone aqueous solution as a solvent to prepare a high-concentration cellulose diacetate acetone slurry sample, and measuring the viscosity of the sample; Step 2: Dissolving cellulose diacetate in different mass concentration acetone aqueous solutions to prepare cellulose diacetate acetone slurry samples with the same mass concentration as in Step 1, and measuring the viscosity of the samples; Step 3: Adjust the mass concentration of the acetone aqueous solution used in production, dissolve the cellulose diacetate, and obtain a high-concentration cellulose diacetate acetone slurry with low viscosity.

[0006] As a preferred embodiment of the present invention, the acetone aqueous solution has a mass concentration of 90-100%.

[0007] As a preferred technical solution of the present invention: the heating rate of the process of dissolving cellulose diacetate is 2~5℃ / min, the heating temperature is 25~60℃, and the stirring time is 120~480 minutes.

[0008] As a preferred technical solution of the present invention: the dissolved cellulose diacetate solution is allowed to stand for 4 hours, and then equilibrated in a water bath at 25°C for 2 to 6 hours before viscosity measurement.

[0009] Beneficial effects By employing the above technical solution, the method for reducing the viscosity of high-concentration cellulose diacetate acetone slurry of the present invention has at least the following advantages: (1) The present invention reduces the viscosity of cellulose diacetate acetone slurry by adjusting the mass concentration of acetone aqueous solution, without the need to introduce other solvents and without affecting the subsequent recovery of acetone solvent.

[0010] (2) The present invention reduces the viscosity of cellulose diacetate acetone slurry by adjusting the mass concentration of acetone aqueous solution. The viscosity of slurry can be reduced without reducing the slurry concentration, and the subsequent spinning process of cellulose acetate bundles is not affected.

[0011] (3) The present invention is simple to operate and is applicable to the preparation of cellulose diacetate acetone slurry prepared from different pulp raw materials. Detailed Implementation

[0012] The following embodiments are provided to better understand the present invention and are not intended to limit the preferred embodiments. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Where specific experimental steps or conditions are not specified in the embodiments, they should be performed according to the conventional experimental steps or conditions described in the literature in the art.

[0013] In the first step, the degree of substitution (DS) ranges from 2.22 to 2.76, and the viscosity of the cellulose acetate flakes acetone slurry at extremely low concentrations ranges from 1.56 to 1.71. This appropriate degree of substitution range ensures that the molecular chain structure of the cellulose acetate flakes in the acetone aqueous solution dissolves well without excessive dispersion, resulting in suitable molecular weight and polymerization state. Excessive or insufficient substitution will affect the solubility, which in turn affects the flowability and uniformity of the spinning solution, and subsequently the adsorption effect of the cellulose acetate tow on cigarette smoke. At extremely low concentrations, a high or low viscosity (IV) value of the cellulose acetate acetone slurry will result in either excessively high or low viscosity; excessively high viscosity will affect filtration, while excessively low viscosity will lead to poor tow quality.

[0014] The acetone-water solution in steps two and three has a mass concentration of 90-100%. For diacetate tablets, under good solubility in the acetone-water solution, the water content should be controlled below 10% (mass concentration). Excessive water content reduces solubility. The addition of water decreases the solubility of acetone in diacetate tablets, resulting in some tablets not completely dissolving, leading to the formation of colloids, suspended particles, or an uneven solution. Too low a water content (close to pure acetone) strengthens the interaction between diacetate tablet molecules, increasing the viscosity of the slurry. Regarding the dissolution process of diacetate tablets in the acetone-water solution, since both acetone and water are solvents for diacetate tablets, and both are polar solvents (water being more polar), the dissolution process is essentially a solvent diffusion process. In a good solvent, the polymer chains of the diacetate tablets expand due to solvation, and the polymer coils extend. In a poor solvent, the polymer chains of the diacetate tablets cannot expand and extend well, increasing the viscosity of the slurry. If the water content in the slurry is within a certain range, water acts as a solubilizer in the slurry system, increasing the solubility of vinegar flakes in acetone aqueous solution. If the water content exceeds a certain range, due to the strong polarity of water, the solubility of vinegar flakes in acetone aqueous solution decreases, and the viscosity of the system increases.

[0015] Example 1 This embodiment uses No. 1 diacetate tablets as an example to provide a method for reducing the viscosity of high-concentration diacetate tablets, further illustrating this solution. Specifically, it includes the following process steps: Step 1: Using a 95% acetone aqueous solution as the solvent, the heating rate of the No. 1 diacetate tablets was 3℃ / min, and the heating temperature was 60℃. The stirring time was 420 minutes to prepare a high-concentration No. 1 diacetate tablet acetone slurry sample. The dissolved high-concentration No. 1 diacetate tablet acetone slurry sample was allowed to stand for 4 hours and then equilibrated in a 25℃ water bath for 4 hours. The viscosity of the sample was measured to be 117.2 Pa·s. Step 2: Prepare acetone aqueous solutions with mass concentrations of 93%, 95%, and 98% respectively. The heating rate during the dissolution of No. 1 diacetate tablets is 3℃ / min, and the heating temperature is 60℃. The stirring time is 420 minutes. Prepare acetone slurry samples of No. 1 diacetate tablets with the same mass concentration as in Step 1. The high-concentration acetone slurry samples of the dissolved No. 1 diacetate tablets are allowed to stand for 4 hours and then equilibrated in a 25℃ water bath for 4 hours. The viscosity measurements are 103.4 Pa·s, 117.2 Pa·s, and 99.5 Pa·s, respectively. Step 3: Adjust the mass concentration of the acetone aqueous solution used in production to 98%, the heating rate during the dissolution of No. 1 diacetate tablets is 3℃ / min, the heating temperature is 60℃, the stirring time is 420 minutes, the dissolved high-concentration No. 1 diacetate tablet acetone slurry sample is allowed to stand for 4 hours, and then equilibrated in a 25℃ water bath for 4 hours to obtain a lower viscosity No. 1 diacetate tablet acetone slurry with a viscosity of 94.8 Pa·s.

[0016] Example 2 This embodiment uses No. 2 diacetate tablets as an example to provide a method for reducing the viscosity of high-concentration diacetate tablets, further illustrating this solution. Specifically, it includes the following process steps: Step 1: Using a 95% acetone aqueous solution as the solvent, dissolve No. 2 diacetate tablets at a heating rate of 5℃ / min and a heating temperature of 40℃; stir for 300 minutes to prepare a high-concentration No. 2 diacetate tablet acetone slurry sample. The dissolved high-concentration No. 2 diacetate tablet acetone slurry sample was allowed to stand for 4 hours and then equilibrated in a 25℃ water bath for 6 hours. Its viscosity was measured to be 90.3 Pa·s. Step 2: Prepare acetone aqueous solutions with mass concentrations of 93%, 95%, and 98% respectively. During the dissolution of No. 2 diacetate tablets, the heating rate is 5℃ / min, and the heating temperature is 40℃. The stirring time is 300 minutes. Prepare acetone slurry samples of No. 2 diacetate tablets with the same mass concentration as in Step 1. The high-concentration acetone slurry samples of the dissolved No. 2 diacetate tablets are allowed to stand for 4 hours and then equilibrated in a 25℃ water bath for 6 hours. The viscosity measurements are 130.0 Pa·s, 90.3 Pa·s, and 135.6 Pa·s, respectively. Step 3: Adjust the mass concentration of the acetone aqueous solution used in production to 95%, the heating rate during the dissolution of No. 2 diacetate tablets is 5℃ / min, the heating temperature is 40℃, the stirring time is 300 minutes, the dissolved high-concentration No. 2 diacetate tablet acetone slurry sample is allowed to stand for 4 hours, and then equilibrated in a 25℃ water bath for 6 hours to obtain a lower viscosity No. 2 diacetate tablet acetone slurry with a viscosity of 90.3 Pa·s.

[0017] Example 3 This embodiment uses No. 3 diacetate tablets as an example to provide a method for reducing the viscosity of high-concentration diacetate tablets, further illustrating this solution. Specifically, it includes the following process steps: Step 1: Using a 95% acetone aqueous solution as the solvent, the heating rate of the No. 3 diacetate tablets was 2℃ / min, and the heating temperature was 25℃. The stirring time was 120 minutes to prepare a high-concentration No. 3 diacetate tablet acetone slurry sample. The dissolved high-concentration No. 3 diacetate tablet acetone slurry sample was allowed to stand for 4 hours and then equilibrated in a 25℃ water bath for 3 hours. The viscosity of the sample was measured to be 77.3 Pa·s. Step 2: Prepare acetone aqueous solutions with mass concentrations of 93%, 95%, and 98% respectively. During the dissolution of No. 3 diacetate tablets, the heating rate is 2℃ / min, and the heating temperature is 25℃. The stirring time is 120 minutes. Prepare acetone slurry samples of No. 3 diacetate tablets with the same mass concentration as in Step 1. The high-concentration acetone slurry samples of the dissolved No. 3 diacetate tablets are allowed to stand for 4 hours and then equilibrated in a water bath at 25℃ for 3 hours. The viscosity measurements are 51.4 Pa·s, 77.3 Pa·s, and 53.9 Pa·s, respectively. Step 3: Adjust the mass concentration of the acetone aqueous solution used in production to 93%, the heating rate during the dissolution of No. 3 diacetate tablets is 2℃ / min, the heating temperature is 25℃, the stirring time is 120 minutes, the dissolved high-concentration No. 3 diacetate tablet acetone slurry sample is allowed to stand for 4 hours, and then equilibrated in a 25℃ water bath for 3 hours to obtain a lower viscosity No. 3 diacetate tablet acetone slurry with a viscosity of 51.4 Pa·s.

Claims

1. A method for reducing the viscosity of high-concentration cellulose diacetate acetone slurry, characterized in that, Includes the following steps: Step 1: Using a 95% acetone aqueous solution as a solvent, dissolve cellulose diacetate to prepare a high-concentration cellulose diacetate acetone slurry sample, and measure its viscosity. Step 2: Prepare acetone aqueous solutions of different mass concentrations, dissolve cellulose diacetate, prepare cellulose diacetate acetone slurry samples with the same mass concentration as in Step 1, and measure their viscosity. Step 3: Adjust the mass concentration of the acetone aqueous solution used in production, dissolve the cellulose diacetate, and obtain a cellulose diacetate acetone slurry with low viscosity.

2. The method for reducing the viscosity of cellulose diacetate acetone slurry according to claim 1, characterized in that: The degree of substitution of cellulose diacetate is between 2.20 and 2.79, and the viscosity (IV) value of cellulose diacetate acetone slurry at very low concentrations is between 1.56 and 1.

71.

3. The method for reducing the viscosity of cellulose diacetate acetone slurry according to claim 1, characterized in that: The acetone aqueous solution used in steps two and three has a mass concentration of 90-100%.

4. The method for reducing the viscosity of cellulose diacetate acetone slurry according to claim 1, characterized in that: The heating rate for dissolving cellulose diacetate is 2-5°C / minute, and the heating temperature is 25-60°C; the stirring time is 120-480 minutes.

5. The method for reducing the viscosity of cellulose diacetate acetone slurry according to claim 1, characterized in that: The dissolved cellulose diacetate solution was allowed to stand for 4 hours, and then equilibrated in a water bath at 25°C for 2-6 hours before its viscosity was measured.