A preparation method of lithium carboxymethyl cellulose

Abstract

The present invention relates to the technical field of chemical modification of natural polymer materials, and in particular to a method for preparing lithium carboxymethyl cellulose. The present invention uses lithium diisopropylamide and butyl lithium as auxiliary reagents to activate and alkalize cellulose, and then performs an etherification reaction to finally obtain lithium carboxymethyl cellulose, thereby overcoming the defects of insufficient contact between LiOH and cellulose and low alkalization degree during the alkalization process, greatly improving the utilization rate of the etherifying agent, reducing side reactions, thereby greatly improving the purity of the finished product of lithium carboxymethyl cellulose on the basis of reducing production costs, so that the lithium carboxymethyl cellulose prepared by the present invention not only has good solubility, but also has high viscosity.

Description

Technical Field

[0001] The invention relates to the technical field of chemical modification of natural polymer materials, and in particular to a method for preparing lithium carboxymethyl cellulose. Background Art

[0002] As a new type of auxiliary material for the negative electrode binder of lithium batteries, carboxymethyl cellulose lithium plays two main roles. First, as a binder, it tightly bonds the negative electrode active materials such as graphite and silicon carbon of the negative electrode to the collector to maintain the stability of the battery during the charge and discharge process; second, as an auxiliary lithium supplement material, it provides a lithium ion reservoir, which can improve the charge and discharge specific capacity and rate performance of lithium batteries. Therefore, carboxymethyl cellulose lithium actually plays a role in improving the performance of lithium-ion batteries, and its application in the field of lithium-ion batteries is becoming more and more common.

[0003] At present, the most commonly used preparation method of lithium carboxymethyl cellulose is a two-step method, which adopts the traditional preparation process of sodium carboxymethyl cellulose to prepare lithium carboxymethyl cellulose, that is, cellulose powder is used as raw material, first alkalized, then etherified to obtain sodium carboxymethyl cellulose, and then sodium carboxymethyl cellulose is used as raw material, acidified and lithified to obtain lithium carboxymethyl cellulose. However, the preparation of lithium carboxymethyl cellulose using the traditional sodium carboxymethyl cellulose preparation process still has the following defects: the alkalinity and solubility of LiOH are much smaller than those of NaOH, so that in the alkalization process, the contact between cellulose and alkali solution is not uniform enough, the degree of alkalization is not high, the lithiation efficiency is poor, and a high-purity product cannot be obtained; too much free alkali, excessive acidification and alkalization are easy to destroy the molecular chain, resulting in low utilization of the etherifying agent, increased by-products, low purity of the finished product, and ultimately high production costs and a large drop in product viscosity.

[0004] Therefore, it is an urgent problem to seek an alkalizing agent and provide a new preparation process using the alkalizing agent to solve the defects in the prior art. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing lithium carboxymethyl cellulose. The present invention uses lithium diisopropylamide and butyl lithium as an auxiliary reagent to activate and alkalize cellulose, and then performs an etherification reaction to finally obtain lithium carboxymethyl cellulose, thereby overcoming the defects of insufficient contact between LiOH and cellulose and low alkalization degree during the alkalization process, and greatly improving the utilization rate of the etherifying agent and reducing side reactions, thereby improving the purity of the finished product of lithium carboxymethyl cellulose, so that the lithium carboxymethyl cellulose prepared by the present invention not only has good solubility, but also has high viscosity; the present invention has a simple production process, a short reaction cycle, low raw material consumption, and can achieve continuous and large-scale production of lithium carboxymethyl cellulose on the basis of ensuring the performance of lithium carboxymethyl cellulose, thereby greatly reducing production costs.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing lithium carboxymethyl cellulose comprises the following steps:

[0008] S1. Alkalization: 20-30 parts by mass of lithium diisopropylamide, 5-10 parts of butyl lithium, 200-250 parts of cellulose, 80-100 parts of isopropanol, 20-40 parts of tetrahydrofuran were put into a reaction vessel, mixed thoroughly and then alkalized under a protective atmosphere;

[0009] S2. Etherification: 10-30 parts of an etherifying agent were added to the reactor by mass, and the etherification reaction was carried out by gradient heating after thorough mixing;

[0010] S3 lithiation: 5-10 parts of lithium diisopropylamide and 1-5 parts of butyl lithium were added to the reactor by mass, and the mixture was thoroughly mixed and then subjected to lithiation reaction to obtain a crude product of lithium carboxymethyl cellulose;

[0011] S4. Purification: The crude lithium carboxymethyl cellulose obtained in step S4 is neutralized, washed, dried, and crushed to obtain the lithium carboxymethyl cellulose.

[0012] Preferably, the protective atmosphere is selected from nitrogen and argon.

[0013] Preferably, in step S1, the reaction time of the alkalization reaction is 1-2h and the reaction temperature ranges from 5-20°C.

[0014] Preferably, in step S2, the etherifying agent is an isopropanol solution of chloroacetic acid with a mass concentration of 60-70%.

[0015] Preferably, the etherification reaction comprises the following steps:

[0016] S11. First temperature etherification: the reactor was heated to 20-30 ° C, etherification 1-1.5h;

[0017] S12. Second temperature etherification: the reactor was heated to 30-40 ° C, etherification 0.5-1h;

[0018] S13. Etherification at the third temperature: raise the temperature of the reactor to 40-50°C and etherify for 0.25-0.5h.

[0019] Preferably, in step S3, the time of the lithiation reaction is 10-50 min; and the temperature range of the lithiation reaction is 0-30°C.

[0020] Preferably, before performing step S4, the crude lithium carboxymethyl cellulose may be treated by repeating steps S2 and S3 to increase the degree of substitution of the crude lithium carboxymethyl cellulose.

[0021] Preferably, in step S4, the neutralizing agent is glacial acetic acid; 80wt% or more ethanol is used for washing; the mixture is dried in an oven at 80-100°C for 1-2h; and the particle size of the crushed lithium carboxymethyl cellulose is ≥200 mesh.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention uses lithium diisopropylamide and butyl lithium as auxiliary reagents to activate and alkalize cellulose, and then performs etherification reaction to finally obtain lithium carboxymethyl cellulose, thereby overcoming the defects of insufficient contact between LiOH and cellulose and low alkalization degree during the alkalization process, greatly improving the utilization rate of the etherifying agent, reducing side reactions, thereby improving the purity of the finished product of lithium carboxymethyl cellulose, so that the lithium carboxymethyl cellulose prepared by the present invention has not only good solubility but also high viscosity.

[0024] 2. The present invention has a simple production process, a short reaction cycle, low raw material consumption, and can realize continuous and large-scale production of lithium carboxymethyl cellulose while ensuring the performance of lithium carboxymethyl cellulose, thereby greatly reducing production costs.

[0025] 3. The present invention successfully avoids the defects of the existing two-step method that sodium carboxymethyl cellulose needs to be synthesized first and then acidified and alkalized at high temperature, which leads to further damage to the molecular chain. Generally, the viscosity of the lithium carboxymethyl cellulose product obtained by the two-step method in the prior art is at least 20% lower than the viscosity of the sodium carboxymethyl cellulose of the raw material, and even reaches 60%. The viscosity reduction of the product is relatively large. The present invention better solves the problem of further reduction in product viscosity and maintains the high viscosity characteristic of lithium carboxymethyl cellulose. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of the preparation of lithium carboxymethyl cellulose according to the present invention;

[0027] Figure 2 This is the infrared spectra of the cellulose and the prepared lithium carboxymethyl cellulose in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1-2 , the present invention provides a technical solution:

[0030] Example 1

[0031] A preparation method of lithium carboxymethyl cellulose:

[0032] S1. Alkalization: 20 g of lithium diisopropylamide, 5 g of butyl lithium, 200 g of cellulose, 80 g of isopropanol, and 20 g of tetrahydrofuran were added to a reaction vessel, mixed thoroughly, and then subjected to an alkalization reaction under a nitrogen atmosphere at a temperature of 10° C. for 1 h;

[0033] S2. Etherification: 10 ml of a 60% chloroacetic acid isopropanol solution was added to the reactor, and the etherification reaction was carried out in a gradient heating manner after thorough mixing;

[0034] S3. Lithiation: 5 g of lithium diisopropylamide and 1 g of butyl lithium were added to the reaction vessel, mixed thoroughly, and then subjected to lithiation reaction at 10 ° C for 30 min to obtain crude lithium carboxymethyl cellulose;

[0035] S4. Purification: The crude lithium carboxymethyl cellulose obtained in step S4 is neutralized with acetic acid to neutrality, washed three times with 85wt% isopropanol, dried in an oven at 100°C for 1h, and then the sample is crushed to a particle size of more than 200 mesh to obtain the lithium carboxymethyl cellulose.

[0036] In the above preparation process, in step S2, the etherification reaction is carried out by the following steps:

[0037] S11. First temperature etherification: the reactor was heated to 20°C and etherified for 1h;

[0038] S12. Second heating etherification: The reactor was heated to 30°C and etherified for 0.5h;

[0039] S13. Third temperature-raising etherification: raise the temperature of the reactor to 40° C. and etherify for 0.25 h.

[0040] Example 2

[0041] A preparation method of lithium carboxymethyl cellulose:

[0042] S1. Alkalization: 30 g of lithium diisopropylamide, 10 g of butyl lithium, 250 g of cellulose, 100 g of isopropanol, and 40 g of tetrahydrofuran were added to a reaction vessel, mixed thoroughly, and then subjected to an alkalization reaction under a nitrogen atmosphere at a temperature of 20° C. for 2 h;

[0043] S2. Etherification: 30 ml of a 70% chloroacetic acid isopropanol solution was added to the reactor, and the etherification reaction was carried out in a gradient heating manner after thorough mixing;

[0044] S3. Lithiation: 10 g of lithium diisopropylamide and 5 g of butyl lithium were added to the reaction vessel, mixed thoroughly, and then subjected to lithiation reaction at 10 ° C for 30 min to obtain crude lithium carboxymethyl cellulose;

[0045] S4. Purification: The crude lithium carboxymethyl cellulose obtained in step S4 is neutralized with acetic acid to neutrality, washed three times with 85wt% isopropanol, dried in an oven at 100°C for 1h, and then the sample is crushed to a particle size of more than 200 mesh to obtain the lithium carboxymethyl cellulose.

[0046] In the above preparation process, in step S2, the etherification reaction is carried out by the following steps:

[0047] S11. First temperature etherification: The reactor was heated to 30 ° C and etherified for 1.5 h;

[0048] S12. Second heating etherification: The reactor was heated to 40°C and etherified for 0.5h;

[0049] S13. Third temperature-raising etherification: raise the temperature of the reactor to 50° C. and etherify for 0.25 h.

[0050] Example 3

[0051] A preparation method of lithium carboxymethyl cellulose:

[0052] S1. Alkalization: 25 g of lithium diisopropylamide, 7 g of butyl lithium, 225 g of cellulose, 90 g of isopropanol and 30 g of tetrahydrofuran were added to a reaction vessel, mixed thoroughly and then subjected to alkalinization reaction under nitrogen atmosphere at a temperature of 15 ° C for 1.5 h;

[0053] S2. Etherification: 20 ml of a 65% chloroacetic acid isopropanol solution was added to the reactor, and the etherification reaction was carried out in a gradient heating manner after thorough mixing;

[0054] S3. Lithiation: 8 g of lithium diisopropylamide and 3 g of butyl lithium were added to the reaction vessel, mixed thoroughly, and then subjected to lithiation reaction at 20 ° C for 40 min to obtain crude lithium carboxymethyl cellulose;

[0055] S4. Purification: The crude lithium carboxymethyl cellulose obtained in step S4 is neutralized with acetic acid to neutrality, washed three times with 85wt% isopropanol, dried in an oven at 100°C for 1h, and then the sample is crushed to a particle size of more than 200 mesh to obtain the lithium carboxymethyl cellulose.

[0056] In the above preparation process, in step S2, the etherification reaction is carried out by the following steps:

[0057] S11. First temperature etherification: the reactor was heated to 30°C and etherified for 1h;

[0058] S12. Second heating etherification: The reactor was heated to 40°C and etherified for 0.5h;

[0059] S13. Third temperature-raising etherification: raise the temperature of the reactor to 50° C. and etherify for 0.25 h.

[0060] Example 4: Example 4 is different from Example 1 in that, in Example 4, before performing step S4, steps S2 and S3 are repeated once in sequence to reprocess the obtained crude lithium carboxymethyl cellulose, and the remaining steps are exactly the same in Example 4 and Example 1.

[0061] Comparative Example

[0062] Comparative Example 1: Comparative Example 1 is different from Example 1 in that step S2 originally existing in Example 1 is omitted in Comparative Example 1, thereby canceling the etherification reaction by gradient heating. In step S2 of Comparative Example 1, the reactor is directly heated to 40°C and etherified for 1.75h. The remaining steps are exactly the same in Comparative Example 1 and Example 1.

[0063] Comparative Example 2: Comparative Example 2 is different from Example 1 in that steps S1 and S3 originally existing in Example 1 are omitted in Comparative Example 2, and lithium diisopropylamide and butyl lithium are replaced with lithium hydroxide of equal mass in steps S1 and S4 of Comparative Example 2. The remaining steps are exactly the same in Comparative Example 2 and Example 1.

[0064] Performance Testing:

[0065] Figure 2 The infrared spectra of the cellulose and the prepared lithium carboxymethyl cellulose in Example 1 are shown in the figure. -1The absorption peak at 2922 cm -1 The absorption peak at 1602cm -1 、1424cm -1 The absorption peaks at 1050cm-1 correspond to the asymmetric and symmetric stretching vibration absorption peaks of the carbonyl group. -1 The absorption peak at 723 cm corresponds to the CO stretching vibration absorption peak in the cellulose molecule. -1 The absorption peak at corresponds to the characteristic absorption peak of carboxymethyl cellulose salt. This shows that the H in some hydroxyl groups OH in cellulose is replaced by -CH2COOLi.

[0066] The physical and chemical properties of the lithium carboxymethyl cellulose prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and the results were as follows:

[0067]

[0068] As can be seen from the above content, the viscosity and transmittance of the lithium carboxymethyl cellulose prepared in Examples 1-3 of the present invention are significantly higher than those in Comparative Examples 1-2, which strongly proves that the present invention uses lithium diisopropylamide and butyl lithium as an auxiliary reagent to activate and alkalize cellulose, and then performs an etherification reaction. The final obtained lithium carboxymethyl cellulose overcomes the defects of insufficient contact between LiOH and cellulose and low alkalization degree during the alkalization process, and greatly improves the utilization rate of the etherifying agent and reduces side reactions, thereby improving the purity of the finished product of lithium carboxymethyl cellulose, so that the lithium carboxymethyl cellulose prepared by the present invention not only has good solubility, but also has a higher viscosity.

[0069] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing lithium carboxymethyl cellulose, characterized in that: The following steps are involved: S1. Alkalization: 20-30 parts by mass of lithium diisopropylamide, 5-10 parts of butyl lithium, 200-250 parts of cellulose, 80-100 parts of isopropanol, 20-40 parts of tetrahydrofuran were put into a reaction vessel, mixed thoroughly and then alkalized under a protective atmosphere; S2. Etherification: 10-30 parts of an etherifying agent were added to the reactor by mass, and the etherification reaction was carried out by gradient heating after thorough mixing; S3 lithiation: 5-10 parts of lithium diisopropylamide and 1-5 parts of butyl lithium were added to the reactor by mass, and the mixture was thoroughly mixed and then subjected to lithiation reaction to obtain a crude product of lithium carboxymethyl cellulose; S4 purification: the crude lithium carboxymethyl cellulose obtained in step S3 is neutralized, washed, dried, and pulverized to obtain the lithium carboxymethyl cellulose; The etherification reaction comprises the following steps: S11. First temperature etherification: the reactor was heated to 20-30 ° C, etherification 1-1.5h; S12. Second temperature etherification: the reactor was heated to 30-40 ° C, etherification 0.5-1h; S13. Etherification at the third temperature: raise the temperature of the reactor to 40-50°C and etherify for 0.25-0.5h.

2. The method for preparing lithium carboxymethyl cellulose according to claim 1, characterized in that: The protective atmosphere is selected from nitrogen and argon.

3. The method for preparing lithium carboxymethyl cellulose according to claim 1, characterized in that: In step S1, the reaction time of the alkalization reaction is 1-2h and the reaction temperature ranges from 5-20°C.

4. The method for preparing lithium carboxymethyl cellulose according to claim 1, characterized in that: In step S2, the etherifying agent is an isopropanol solution of chloroacetic acid with a mass concentration of 60-70%.

5. The method for preparing lithium carboxymethyl cellulose according to claim 1, characterized in that: In step S3, the time of the lithiation reaction is 10-50 minutes; the temperature range of the lithiation reaction is 0-30°C.

6. The method for preparing lithium carboxymethyl cellulose according to claim 1, characterized in that: Before performing step S4, the crude lithium carboxymethyl cellulose is treated by repeating steps S2 and S3 to increase the degree of substitution of the crude lithium carboxymethyl cellulose.

7. The method for preparing lithium carboxymethyl cellulose according to claim 1, characterized in that: In step S4, the neutralizing agent is glacial acetic acid; 80wt% or more ethanol is used for washing; in an oven, Dry at 80-100°C for 1-2h; the particle size of the crushed lithium carboxymethyl cellulose is ≥200 mesh.

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