Preparation method of ultralow-viscosity hydroxyethyl cellulose
By introducing cross-linking and viscosity reduction processes in the production of hydroxyethyl cellulose, and using the rational addition of hydrogen peroxide solution and cross-linking agent, the problems of easy swelling and blockage and safety risks of products are solved, and the industrial production of ultra-low viscosity HEC is achieved. And improve product performance.
Patent Information
- Application Number
- CN202411509899.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-28
- Publication Date
- 2024-12-27
AI Technical Summary
In the prior art, when producing ultra-low viscosity hydroxyethyl cellulose, the product is prone to swelling and blocking the equipment, which poses safety risks and side reactions, making it difficult to achieve industrial production, and the product transmittance decreases and the gel particles increase.
Using crosslinking process and tack reduction process, a crosslinking agent is added to the neutralized material system for crosslinking reaction, and a hydrogen peroxide solution and a crosslinking agent are added at 40-90°C for tack reduction reaction, which is detrimental, drying and Partial crosslinking is carried out simultaneously, and the dosage and addition of hydrogen peroxide solution are optimized to control viscosity and avoid side reactions.
Effectively obtain ultra-low viscosity HEC with a viscosity in the range of 5 to 400mPa.s, reducing the risk of equipment blockage, simplifying process steps, improving the light transmittance of the product and gel particle performance, and realizing industrial production.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of cellulose production, and particularly relates to a method for preparing ultra-low viscosity hydroxyethyl cellulose. Background Art
[0002] At present, hydroxyethyl cellulose (HEC) has high added value in the domestic market. Among these high added value HECs, ultra-low viscosity HEC products have great application prospects in daily chemical products. However, there are few domestic and foreign manufacturers of ultra-low viscosity HEC, which is difficult to produce and has high product prices, but has huge market prospects. Therefore, the study of ultra-low viscosity HEC has important significance and good economic value.
[0003] Due to the characteristics of the ultra-low viscosity HEC product itself, there are great difficulties in production. There are problems such as the preparation process is difficult to control and the product is easy to swell and clog pipeline equipment. Therefore, it is necessary to develop ultra-low viscosity products to expand the market.
[0004] CN102690355A discloses a liquid phase synthesis process of ultra-low viscosity hydroxyethyl cellulose, including raw material crushing, alkalization, etherification, neutralization, purification, separation, drying and crushing. The raw material is selected from cellulose powder with a degree of polymerization of 600-900 and a fineness of 0.1-0.5m. After uniformly heating during the alkalization process or during the etherification process, an oxidant is added, and the amount of the oxidant added is 0.1%-20% of the weight of the dry cellulose; the oxidant is hydrogen peroxide, hypochlorite or gas dioxide. The method replaces oxygen or air with an oxidant, and it is easier to operate by controlling the pressure in the reactor by the oxidant. The oxidant reacts and oxidizes with the material in the reactor, and its oxidation ability is stronger, and the degree of oxidation can be accurately controlled, so as to stably obtain an ultra-low viscosity hydroxyethyl cellulose liquid phase within the range of 5-300mPa.s (25°C, 5% aqueous solution, BrookfieldLVDV-I type viscometer, molar substitution MS1.4-2.4). However, in this method, due to the characteristics of the ultra-low viscosity HEC product itself, the product is very easy to absorb water, which causes the material to swell and agglomerate, blocking the etherification reactor, washing reactor, centrifuge and various discharge pipes. As a result, although the ultra-low viscosity hydroxyethyl cellulose can be prepared by reaction during the etherification process, it is actually difficult to achieve industrial production in the subsequent refining process, and there are great difficulties in production. Therefore, it is necessary to develop a production process route for ultra-low viscosity products to achieve industrial production and expand the market. At the same time, in this method, hydrogen peroxide is added during the alkalization or etherification process, and the hydrogen peroxide reacts to release oxygen. The presence of oxygen in the system will increase the safety risk of the alkalization or etherification reaction system, and the addition of hydrogen peroxide during the reaction will preferentially react with the reaction organic solvent, ethylene oxide, etc. in the reaction system to generate side reaction substances, resulting in a decrease in the light transmittance of the product, an increase in gel particles, and consumption of raw materials. Summary of the invention
[0005] In order to solve the problems of the prior art and effectively obtain ultra-low viscosity hydroxyethyl cellulose with viscosity meeting the requirements, the present invention conducts in-depth research on the viscosity reduction route and corresponding parameters of hydroxyethyl cellulose.
[0006] The present invention first provides a method for preparing ultra-low viscosity hydroxyethyl cellulose, which includes raw material crushing, alkalization, etherification, neutralization, cross-linking and viscosity reduction steps, wherein:
[0007] The cross-linking process is as follows: adding a cross-linking agent to the neutralized material system to carry out a cross-linking reaction, and after the cross-linking is completed, centrifuging and washing to obtain a wet material;
[0008] The viscosity reduction step is operated as follows: adding hydrogen peroxide solution and a crosslinking agent to the wet material, and then carrying out a viscosity reduction reaction at 40-90° C. After the viscosity reduction reaction is completed (that is, in the present invention, viscosity reduction, drying, and partial crosslinking are carried out and completed simultaneously), ultra-low viscosity hydroxyethyl cellulose is obtained; wherein the amount ratio of the hydrogen peroxide solution to the wet material is 50-300 ml: 1 kg.
[0009] Preferably, in the method for preparing the ultra-low viscosity hydroxyethyl cellulose, the viscosity reduction reaction is carried out at 50-80°C.
[0010] Preferably, in the above-mentioned method for preparing ultra-low viscosity hydroxyethyl cellulose, the dosage ratio of the hydrogen peroxide solution to the wet material is 50-300 ml: 1 kg.
[0011] Wherein, in the above-mentioned method for preparing ultra-low viscosity hydroxyethyl cellulose, the time of the viscosity reduction reaction is 20 to 60 minutes.
[0012] In the above-mentioned preparation method of ultra-low viscosity hydroxyethyl cellulose, the total amount of crosslinking agent in the crosslinking step and the viscosity reduction step is 100%, and the amount of crosslinking agent in the crosslinking step is 100% (that is, no crosslinking agent is added in the viscosity reduction step).
[0013] The inventors found in the experiment that if only one crosslinking is performed before the viscosity reduction process, hydrogen peroxide will reduce the crosslinking effect of crosslinking agents such as glyoxal, so the present invention adopts a process of first partially crosslinking and then performing viscosity reduction and simultaneous partial crosslinking. Therefore, preferably, in the above-mentioned preparation method of ultra-low viscosity hydroxyethyl cellulose, the total amount of crosslinking agent in the crosslinking process and the viscosity reduction process is 100%, the amount of crosslinking agent in the crosslinking process is 40-60%, and the amount of crosslinking agent in the viscosity reduction process is 60-40%.
[0014] Wherein, in the preparation method of the ultra-low viscosity hydroxyethyl cellulose, the pH of the neutralized material system is 5-7.
[0015] Wherein, in the above-mentioned preparation method of ultra-low viscosity hydroxyethyl cellulose, the hydrogen peroxide solution is added in a manner of soaking the wet material in the hydrogen peroxide solution.
[0016] Preferably, in the above-mentioned method for preparing ultra-low viscosity hydroxyethyl cellulose, the hydrogen peroxide solution is added by spraying the hydrogen peroxide solution on the wet material and then stirring it evenly.
[0017] In the present invention, the steps of raw material crushing, alkalization, etherification and neutralization all adopt conventional processes for producing hydroxyethyl cellulose in the art. For example, the process for producing hydroxyethyl cellulose disclosed in CN102690355A comprises the following steps:
[0018] a. Raw material crushing: Select refined cotton with a degree of polymerization of 1000-2400 as raw material, and crush the refined cotton into 0.5-0.8mm fiber powder using a cotton cellulose crusher;
[0019] b. Alkalization: add isopropanol solution into the reaction kettle and add caustic soda flakes, then add powdered cellulose into the reaction kettle, control the concentration of alkali solution at 18-25%, the concentration of isopropanol at 85-89%, evacuate, and alkalize at 4-10°C for 0.5-1.5 hours;
[0020] c. Etherification: After the alkalization is completed, a certain amount of ethylene oxide is added with nitrogen as a carrier, and the etherification is carried out at room temperature of 20-25°C for 0.5-1 hour, and then the temperature is uniformly increased (0.5-1°C per minute) to 60-70°C, and the etherification reaction is carried out at a constant temperature for 2-2.5 hours, and then the temperature is uniformly lowered (0.5-1.5°C per minute) to 30-40°C;
[0021] d. Neutralization: Add acidic substances such as hydrochloric acid, acetic acid, etc. to the material after etherification and cooling, neutralize for 20 to 30 minutes, and control the pH of the material to 5 to 7;
[0022] e. Purification: In this process, the cross-linking reaction is first performed and then washed. Aldehyde substances such as succinaldehyde or glyoxal are added to the neutralized material, and the temperature is controlled at 50-70°C and pH 5-7 to perform the cross-linking reaction for 0.5-2 hours; then, after centrifugation, it is washed with a 70-80% isopropanol aqueous solution. The centrifugation and washing process should be repeated 2-3 times;
[0023] f. After washing, separate, dry and crush to obtain hydroxyethyl cellulose.
[0024] The present invention improves the cross-linking (or purification) and viscosity reduction steps based on the existing process for producing hydroxyethyl cellulose to obtain ultra-low viscosity hydroxyethyl cellulose. Of course, in the present invention, the raw material crushing, alkalization, etherification, and neutralization steps are not limited to the above-mentioned processes, and any conventional process in the art can be applied.
[0025] In the present invention, the cross-linking agent used is an aldehyde substance conventionally used as a cross-linking agent in the art, such as succinaldehyde or glyoxal. The temperature, pH and time of the cross-linking reaction can all adopt conventional parameters of the art, and the washing centrifugation process after cross-linking is also a conventional operation in the art. For example, in the cross-linking process of the present invention, after adding all or part of the cross-linking agent, the cross-linking reaction can be carried out at 50-70°C, pH 5-7, for 0.5-2 hours, and then washed with 70-80% isopropanol aqueous solution after centrifugation, and the centrifugation and washing process are repeatedly circulated 2-3 times. The total amount of the cross-linking agent is also the conventional amount in the art. Generally, 40-60L of glyoxal or other cross-linking agents of equal amount are needed to produce 3t of hydroxyethyl cellulose finished product.
[0026] In the present invention, the hydrogen peroxide used is conventional hydrogen peroxide in the industrial field, and its concentration is usually 20-30%. When used, it is measured by the volume of the hydrogen peroxide solution.
[0027] Beneficial effects of the present invention:
[0028] The present invention optimizes the viscosity reduction route and parameters of hydroxyethyl cellulose, strictly controls the amount of viscosity reducer added, the method of adding the viscosity reducer, the timing of adding the viscosity reducer, the viscosity reduction time or time, etc., avoids more side reactions caused by adding hydrogen peroxide, and prepares 5-400mPa.s (5%) ultra-low viscosity HEC, while ensuring that other properties such as gel particles and light transmittance meet the requirements; in addition, the present invention simultaneously performs hydrogen peroxide viscosity reduction reaction, partial cross-linking reaction and drying, simplifies the process steps, and is more conducive to industrialization. DETAILED DESCRIPTION
[0029] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the scope of the examples.
[0030] Under a certain temperature condition in a reactor, cotton powder and alkali solution are subjected to an alkalization reaction to obtain alkali cellulose, and after the alkalization is completed, ethylene oxide is added to carry out an etherification reaction, and after etherification, acid is added for neutralization, and after neutralization, glyoxal is added for cross-linking, and then centrifugation and washing are performed, and the hydroxyethyl cellulose product is obtained after drying and crushing. In order to prepare ultra-low viscosity products, the present invention mainly conducts experiments on adding a viscosity reducer before washing after centrifugation and before drying after washing. In the embodiment, a hydrogen peroxide aqueous solution is used as a viscosity reducer with a concentration of 30%.
[0031] Example 1
[0032] In this example, in order to explore the viscosity reduction effect of hydrogen peroxide on hydroxyethyl cellulose and its influence on the quality of the finished product, a viscosity reduction test was first conducted on a conventional hydroxyethyl cellulose finished product using hydrogen peroxide.
[0033] In this embodiment, hydrogen peroxide was selected as the viscosity reducing agent, and the HD15000 sample (the sample of the crushed hydroxyethyl cellulose product without viscosity reducing of batch number HE2330349) was used for the test. The HD15000 sample was mixed with hydrogen peroxide, and the experimental temperatures were: room temperature, 30°C, 40°C, and 60°C, and the amount of hydrogen peroxide added (viscosity reducing agent: dry material) was 1:1, 3:5, and 5:1. The specific test conditions and test results are shown in Table 1 below.
[0034] Table 1 Hydrogen peroxide viscosity reduction test conditions and test results
[0035]
[0036] As shown in Table 1, the viscosity reduction test was carried out under the conditions of the same temperature and different hydrogen peroxide addition. Compared with the blank sample, the viscosity did not drop significantly. Therefore, under normal temperature conditions, hydrogen peroxide had no obvious effect on the viscosity reduction of the product, and the gel particles were normal and basically unchanged. However, the viscosity reduction test was carried out under the conditions of the same hydrogen peroxide addition and different temperatures. The viscosity reduction was obvious. It can be seen that with the increase of temperature, the viscosity reduction effect of hydrogen peroxide also increased, the viscosity of the product also decreased a lot, and the gel particles were normal and basically unchanged. Based on the experimental results, the viscosity reduction process was further optimized in the future.
[0037] Example 2
[0038] In this embodiment, in order to obtain the best viscosity reduction parameters, the addition amount and process route selection test of hydrogen peroxide were carried out respectively. In this embodiment, hydrogen peroxide was selected as the viscosity reducer, and the sample after etherification and neutralization (batch number of finished product without viscosity reduction H2320554) was selected for the test. The selected process scheme was: hydrogen peroxide viscosity reduction before washing and hydrogen peroxide viscosity reduction before drying after washing. Five groups of experiments were carried out under the conditions of hydrogen peroxide addition (viscosity reducer: wet material) of 50:1, 100:1, 150:1, and 200:1. The specific test process conditions and test results of the sample physical and chemical indicators are shown in Tables 2 and 3 below.
[0039] The operation of reducing viscosity with hydrogen peroxide before washing is as follows: adding glyoxal and hydrogen peroxide to the neutralized material system to reduce viscosity.
[0040] The operation of reducing viscosity with hydrogen peroxide after washing and before drying is as follows: adding 50% glyoxal to the neutralized material system, centrifuging and washing after crosslinking, adding hydrogen peroxide and remaining glyoxal to reduce viscosity.
[0041] Table 2 Experimental process conditions
[0042]
[0043]
[0044] Table 3 Physical and chemical indicators of samples
[0045]
[0046] Note: 326 (2%) is equivalent to more than 20,000 (5%).
[0047] As shown in Tables 2 and 3, the viscosity reduction effect of hydrogen peroxide before washing is not as good as the test result of adding hydrogen peroxide before drying, and the light transmittance of the product obtained by hydrogen peroxide before washing is worse, indicating that the viscosity reduction effect of adding hydrogen peroxide before drying is better, and adjusting the test process conditions can meet the product index requirements. In the viscosity reduction reaction of hydrogen peroxide added before washing, because there are more side reactions of hydrogen peroxide and solvent at the same time, the light transmittance of the product is affected, and the increase in side reactions leads to a decrease in hydrogen peroxide that has a viscosity reduction effect. The viscosity reduction effect of the product is not as good as the viscosity reduction effect before drying (after washing). Therefore, the ultra-low viscosity production process route determines the process route of viscosity reduction before drying.
[0048] Example 3
[0049] In this embodiment, the sample after etherification and neutralization (batch number of finished product without viscosity reduction H2310555, recorded as DN-2-1) was selected in the process route of viscosity reduction before drying, and two addition methods, solvent immersion and direct spraying of hydrogen peroxide, were selected. Eight groups of experiments were carried out to optimize the viscosity reduction production process, test conditions and result sample physical and chemical indicators, see Tables 4 and 5 below.
[0050] Table 4 Experimental process conditions
[0051]
[0052] Table 5 Physical and chemical indicators of samples
[0053]
[0054]
[0055] Note: 254 (2%) is equivalent to approximately 20,000 (5%).
[0056] The test results in Table 4 and Table 5 show that the viscosity of the test products can meet the project index requirements by adding hydrogen peroxide in two ways to reduce the viscosity of the product. Both hydrogen peroxide addition methods can achieve the effect of reducing viscosity, but the viscosity reduction of the spraying method is greater.
Claims
1. A method for preparing ultra-low viscosity hydroxyethyl cellulose, comprising the steps of raw material crushing, alkalization, etherification, neutralization, cross-linking and viscosity reduction, characterized in that: The cross-linking process is as follows: adding a cross-linking agent to the neutralized material system to carry out a cross-linking reaction, and after the cross-linking is completed, centrifuging and washing to obtain a wet material; The viscosity reduction step is operated as follows: adding hydrogen peroxide solution and a cross-linking agent to the wet material, and then performing a viscosity reduction reaction at 40-90° C. After the viscosity reduction reaction is completed, ultra-low viscosity hydroxyethyl cellulose is obtained; wherein the amount ratio of the hydrogen peroxide solution to the wet material is 50-300 ml: 1 kg.
2. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to claim 1, characterized in that: The viscosity reduction reaction is carried out at 50-80°C.
3. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to claim 1, characterized in that: The dosage ratio of the hydrogen peroxide solution to the wet material is 50-300 ml:1 kg.
4. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to claim 1, characterized in that: The viscosity reduction reaction time is 20 to 60 minutes.
5. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to claim 1, characterized in that: The total amount of the crosslinking agent used in the crosslinking step and the viscosity reduction step is 100%, and the amount of the crosslinking agent used in the crosslinking step is 100%.
6. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to claim 1, characterized in that: In the cross-linking process and the viscosity reduction process, the total amount of the cross-linking agent is 100%, the amount of the cross-linking agent in the cross-linking process is 40-60%, and the amount of the cross-linking agent in the viscosity reduction process is 60-40%.
7. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to claim 1, characterized in that: The pH of the neutralized material system is 5-7.
8. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to any one of claims 1 to 7, characterized in that: The hydrogen peroxide solution is added in a manner of soaking the wet material in the hydrogen peroxide solution.
9. The method for preparing ultra-low viscosity hydroxyethyl cellulose according to any one of claims 1 to 7, characterized in that: The hydrogen peroxide solution is added by spraying the hydrogen peroxide solution on the wet material and then stirring it evenly.