Preparation method of temperature-resistant and salt-resistant high-substituted hydroxyethyl methyl cellulose ether

Abstract

The invention belongs to the technical field of preparation of cellulose ether, and particularly relates to a preparation method of temperature-resistant and salt-resistant high-substituted hydroxyethyl methyl cellulose ether, which comprises the following steps: S1, contacting at least one cellulose material with at least one alkalization reagent to form an alkalized cellulose material; s2, contacting the alkalized cellulose material obtained in the step S1 with chloromethane and ethylene oxide, and carrying out a reaction to obtain an initial reaction material; s3, enabling the primary reaction material in the step S2 to be in contact with ethylene oxide and lewis acid, and continuously reacting to obtain a final reaction material; and S4, carrying out reduced pressure distillation to remove the lewis acid in the final reaction material, and filtering and washing the product to obtain the HEMC gel material. According to the preparation method disclosed by the invention, firstly, the high substitution degree of the HEMC is realized through step-by-step etherification and catalytic ring opening, so that the temperature resistance and salt resistance of the HEMC are enhanced.

Description

Technical Field

[0001] This invention belongs to the field of cellulose ether preparation technology, and particularly relates to a method for preparing a high-substituted hydroxyethyl methyl cellulose ether that is heat- and salt-resistant. Background Technology

[0002] Cellulose ethers are cellulose derivatives formed by the partial or complete etherification of the hydroxyl groups of cellulose. Due to their excellent properties and physiological safety, they are widely used in pharmaceuticals, food, cosmetics, building materials and other fields, such as thickeners, adhesives, binders and dispersants, water-retaining agents, protective colloids, stabilizers, suspending agents, emulsifiers and film-forming agents.

[0003] Cellulose ethers have been produced by well-known conventional methods, which involve subjecting a cellulose starting material, such as cellulose pulp, to two process operations (steps or stages): (1) alkalization and (2) etherification. For example, CN113710708A discloses a method for producing crosslinked cellulose ethers, comprising the steps of: (1) alkalizing the cellulose material; and (2) contacting the alkalized cellulose material with an etherifying agent to form a cellulose ether, wherein the etherifying agent is selected from the group consisting of ethylene oxide, propylene oxide, butane oxide, chloromethane, chloroethane, and mixtures thereof. After the production of the cellulose ether, it may undergo further process steps such as washing the cellulose ether; drying the cellulose ether; and grinding the cellulose ether into granular form.

[0004] However, hydroxyethyl methyl cellulose ether produced by this conventional method exhibits a significant decrease in viscosity when applied in high-temperature and high-salt environments, making it unsuitable for use in such environments. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a highly substituted hydroxyethyl methyl cellulose ether that is resistant to high temperature and salt. By optimizing the preparation method, the obtained hydroxyethyl methyl cellulose ether has better high temperature and salt resistance properties and can be used in high temperature and high salt environments.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether includes the following steps: S1. To contact at least one cellulose material with at least one alkalizing agent to form an alkalized cellulose material; S2. The alkalized cellulose material from step (S1) is brought into contact with chloromethane and ethylene oxide and reacted to obtain the initial reaction material; S3. Contact the initial reaction material from step (S2) with ethylene oxide and Lewis acid, and continue the reaction to obtain the final reaction material; S4. Remove Lewis acids from the final reaction material by vacuum distillation, and filter and wash the product to obtain HEMC gel.

[0007] Preferably, the above preparation method further includes the following steps: S5. Mix glyoxal with trehalose solution and spray it onto the surface of hydroxyethyl methyl cellulose ether gel to obtain surface-treated hydroxyethyl methyl cellulose ether; S6. The surface-treated hydroxyethyl methyl cellulose ether is subjected to cold air drying and granulation to obtain the hydroxyethyl methyl cellulose ether product.

[0008] Preferably, the molar ratio of chloromethane to ethylene oxide is 1:1 to 3. Preferably, based on the molar amount of hydroxyethoxy in step S2, the amount of ethylene oxide added in step S3 is 1 to 3 mol equivalents.

[0009] Preferably, the Lewis acid is SnCl4.

[0010] Preferably, in step S3, the amount of SnCl4 added is 5 mol%, relative to the molar amount of ethylene oxide.

[0011] Preferably, the reaction temperature in step S2 is 60~80℃ and the reaction time is 3~4h.

[0012] Preferably, in step S3, the reaction temperature is 50~60℃ and the reaction time is 1~2h.

[0013] Preferably, in step S5, the concentration of the trehalose solution is 20-30 wt%, and the mass ratio of glyoxal to trehalose solution is 3:1-5.

[0014] Preferably, in step S5, the mixture of glyoxal and trehalose solution is sprayed onto the surface of the HEMC gel at a rate of 45-55 mL / min.

[0015] Preferably, the spraying ratio of the mixture of glyoxal and trehalose solution to the mass ratio of HEMC gel material is 1:3 to 6.

[0016] Preferably, in step S6, the drying temperature is controlled at 70~80℃.

[0017] In another aspect, the present invention provides a high-temperature resistant hydroxyethyl methyl cellulose ether, which is prepared by the above method.

[0018] By implementing the above technical solution, compared with the prior art, the present invention has the following beneficial effects: This invention first achieves a high degree of substitution in HEMC through stepwise etherification and catalytic ring-opening, thereby enhancing the dual properties of HEMC in terms of temperature and salt resistance.

[0019] Furthermore, during the surface treatment with glyoxal, a trehalose solution was added simultaneously. Trehalose synergistically treats the HEMC surface with glyoxal. Under suitable temperature and pressure conditions, the dialdehyde groups of glyoxal achieve synergistic cross-linking of the three components, resulting in a dense cross-linked network, which further improves the temperature and salt resistance, as well as the moisture retention properties of HEMC.

[0020] Furthermore, a low-temperature drying process is used for granulation to ensure the stability of the grafted chain and the content of the wetting agent. Attached Figure Description

[0021] Figure 1 The graph shows the viscosity and temperature sensitivity data of hydroxyethyl methyl cellulose ether obtained in each embodiment and comparative example; Figure 2 The graph shows the salt tolerance data of hydroxyethyl methyl cellulose ether at different salt concentrations obtained in each embodiment and comparative example. Detailed Implementation

[0022] The present invention will be further described in detail below through specific embodiments.

[0023] It should be noted that the following embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0024] Example 1 This embodiment provides a method for preparing a high-temperature resistant hydroxyethyl methyl cellulose ether, as follows: Cellulose material (cotton wadding), isopropanol as a reaction solvent, and an aqueous solution of sodium hydroxide with a concentration of 50 wt% as an alkalizing agent are mixed and stirred at room temperature for 60 minutes to obtain alkalized cellulose.

[0025] After washing and drying, alkalized cellulose was added to a reactor containing anhydrous DMSO at a solid-liquid ratio of 1:50 (g / mL). Then, chloromethane and ethylene oxide were added sequentially in a molar ratio of 1:2. The reactor was heated to 65°C, and the reaction time was set to 3 hours. After the reaction was complete, 1 mol equivalent of ethylene oxide was added, followed by the slow addition of 5 mol% SnCl4. The reaction temperature was set to 50°C, and the reaction time was set to 1.5 hours. After the reaction was complete, SnCl4 was removed by vacuum distillation, and the reaction product was filtered and washed to obtain the chain-extended HEMC gel.

[0026] Glyoxal was mixed with 20 wt.% trehalose solution at a mass ratio of 3:2 and sprayed onto the surface of HEMC gel at a rate of 50 mL / min. The spray volume to HEMC gel mass ratio was 1:4, achieving synergistic crosslinking of the wetting agent, glyoxal, and HEMC. Finally, the surface-treated HEMC was subjected to cold air drying and granulation (the low-temperature cold air drying system could maintain the outlet temperature at 70–80 °C) to obtain a highly substituted HEMC synthesized in a step-by-step process with high temperature and salt resistance.

[0027] The final product was characterized by 2wt.% solution viscosity test, temperature-sensitive viscosity test, salt-resistant viscosity test, dyne value, and surface group content detection.

[0028] Example 2 This embodiment provides a method for preparing a high-temperature resistant hydroxyethyl methyl cellulose ether, as follows: The alkalized cellulose from Example 1 was added to a reactor containing anhydrous DMSO at a solid-liquid ratio of 1:50 (g / mL). Then, chloromethane and ethylene oxide were added sequentially in a molar ratio of 1:2. The reactor was heated to 80°C, and the reaction time was set to 3 hours. After the reaction was complete, 1 mol equivalent of ethylene oxide was added, followed by the slow addition of 5 mol% Lewis acid catalyst SnCl4. The reaction temperature was set to 56°C, and the reaction time was set to 1 hour. After the reaction was complete, SnCl4 was removed by vacuum distillation, and the reaction product was filtered and washed to obtain the chain-extended HEMC gel.

[0029] Glyoxal was mixed with 20 wt.% trehalose solution at a mass ratio of 3:2 and sprayed onto the surface of HEMC gel at a rate of 50 mL / min. The spray volume to HEMC gel mass ratio was 1:3, achieving synergistic crosslinking of the wetting agent, glyoxal, and HEMC. Finally, the surface-treated HEMC was subjected to cold air drying and granulation (the low-temperature cold air drying system could maintain the outlet temperature at 70–80 °C), yielding a novel, highly substituted daily chemical-grade HEMC synthesized in a one-step process with high temperature resistance and moisture retention properties.

[0030] The final product was characterized by 2wt.% solution viscosity test, temperature-sensitive viscosity test, salt-resistant viscosity test, dyne value, and surface group content detection.

[0031] Example 3 This embodiment provides a method for preparing a high-temperature resistant hydroxyethyl methyl cellulose ether, as follows: The alkalized cellulose from Example 1 was added to a reactor containing anhydrous DMSO at a solid-liquid ratio of 1:50 (g / mL). Then, chloromethane and ethylene oxide were added sequentially in a molar ratio of 1:2. The reactor was heated to 65°C, and the reaction time was set to 3 hours. After the reaction was complete, 1 mol equivalent of ethylene oxide was added, followed by the slow addition of 5 mol% SnCl4. The reaction temperature was set to 50°C, and the reaction time was set to 1.5 hours. After the reaction was complete, SnCl4 was removed by vacuum distillation, and the reaction product was filtered and washed to obtain the chain-extended HEMC gel.

[0032] Glyoxal was sprayed onto the surface of the HEMC gel at a rate of 50 mL / min. Finally, the surface-treated HEMC was subjected to cold air drying and granulation treatment (the low-temperature cold air drying system can maintain the outlet temperature at 70-80℃) to obtain a novel high-substituted daily chemical grade HEMC with high temperature resistance and moisturizing properties synthesized in a step-by-step process.

[0033] The final product was characterized by 2wt.% solution viscosity test, temperature-sensitive viscosity test, salt-resistant viscosity test, dyne value, and surface group content detection.

[0034] Comparative Example 1 This comparative example provides a method for preparing hydroxyethyl methylcellulose ether, as follows: 1 kg of cellulose material (cotton wool), 1 kg of dimethyl ether as a reaction solvent, and 1.25 kg of a 50 wt% sodium hydroxide aqueous solution as an alkalizing agent were stirred at 80 rpm for 60 minutes at room temperature to obtain alkalized cellulose.

[0035] Alkalized cellulose was added to a reactor containing anhydrous DMSO at a solid-liquid ratio of 1:50 (g / mL). Then, chloromethane and ethylene oxide were added sequentially in a molar ratio of 1:2. The reactor was heated to 65°C, and the reaction time was set to 3 hours. Alternatively, the reaction time could be set to 1.5 hours. After the reaction, SnCl4 was removed by vacuum distillation, and the reaction product was filtered and washed to obtain the chain-extended HEMC gel.

[0036] Glyoxal was mixed with 20 wt.% trehalose solution at a mass ratio of 3:2 and sprayed onto the surface of HEMC gel at a rate of 50 mL / min to achieve synergistic crosslinking of the wetting agent, glyoxal, and HEMC. Finally, the surface-treated HEMC was subjected to cold air drying and granulation (the low-temperature cold air drying system maintained the outlet temperature at 70–80 °C) to obtain a novel, highly substituted daily chemical-grade HEMC synthesized in a one-step process, exhibiting high temperature resistance and moisture retention properties.

[0037] The final product was characterized by 2wt.% solution viscosity test, temperature-sensitive viscosity test, salt-resistant viscosity test, dyne value, and surface group content detection.

[0038] Comparative Example 2 This comparative example provides a method for preparing hydroxyethyl methylcellulose ether, as follows: 1 kg of cellulose material (cotton wool), 1 kg of dimethyl ether as a reaction solvent, and 1.25 kg of a 50 wt% sodium hydroxide aqueous solution as an alkalizing agent were stirred at 80 rpm for 60 minutes at room temperature to obtain alkalized cellulose.

[0039] Alkalized cellulose was added to a reactor containing anhydrous DMSO at a solid-liquid ratio of 1:50 (g / mL). Then, chloromethane and ethylene oxide were added sequentially in a molar ratio of 1:2. The reactor was heated to 65°C, and the reaction time was set to 3 hours. After the reaction was complete, 1 mol equivalent of ethylene oxide was added, and the reaction temperature was set to 50°C. The reaction time was set to 1.5 hours. After the reaction was complete, SnCl4 was removed by vacuum distillation, and the reaction product was filtered and washed to obtain the chain-extended HEMC gel.

[0040] Glyoxal was mixed with 20 wt.% trehalose solution at a mass ratio of 3:2 and sprayed onto the surface of HEMC gel at a rate of 50 mL / min to achieve synergistic crosslinking of the wetting agent, glyoxal, and HEMC. Finally, the surface-treated HEMC was subjected to cold air drying and granulation (the low-temperature cold air drying system maintained the outlet temperature at 70–80 °C) to obtain a novel, highly substituted daily chemical-grade HEMC synthesized in a one-step process, exhibiting high temperature resistance and moisture retention properties.

[0041] The final product was characterized by 2wt.% solution viscosity test, temperature-sensitive viscosity test, salt-resistant viscosity test, dyne value, and surface group content detection.

[0042] Test results: Table 1. Viscosity and Temperature Sensitivity Data of Hydroxyethyl Methylcellulose Ether The viscosity of the test solution in the table is 2 wt.%, the unit of viscosity test is cP, the viscosity test rotor is #7, and the viscosity test speed is 20 r.

[0043] Table 2. Viscosity and Salt Tolerance Data of Hydroxyethyl Cellulose Ether The concentration of the test solution in the table is 1 wt.%, the salt solution used is NaCl solution, the test temperature is 20℃, the viscosity test rotor is #5, the viscosity test speed is 20 r, and the viscosity test unit is cP.

[0044] Table 3. Hydroxyethyl methylcellulose ether dyne value data table For the dyne value test, a hydroxyethyl methyl cellulose ether solution was coated onto a glass slide, dried to form a film, and then subjected to a dyne pen scratch test.

[0045] Table 4. Data on the content of surface groups of hydroxyethyl methyl cellulose ether

Claims

1. A method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether, characterized in that, Includes the following steps: S1. To contact at least one cellulose material with at least one alkalizing agent to form an alkalized cellulose material; S2. The alkalized cellulose material from step (S1) is brought into contact with chloromethane and ethylene oxide and reacted to obtain the initial reaction material; S3. Contact the initial reaction material from step (S2) with ethylene oxide and Lewis acid, and continue the reaction to obtain the final reaction material; S4. Remove Lewis acids from the final reaction material by vacuum distillation, and filter and wash the product to obtain HEMC gel.

2. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, It also includes the following steps: S5. Mix glyoxal with trehalose solution and spray it onto the surface of hydroxyethyl methyl cellulose ether gel to obtain surface-treated hydroxyethyl methyl cellulose ether; S6. The surface-treated hydroxyethyl methyl cellulose ether is subjected to cold air drying and granulation to obtain the hydroxyethyl methyl cellulose ether product.

3. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, The molar ratio of chloromethane to ethylene oxide is 1:1 to 3.

4. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, In step S3, the amount of ethylene oxide added is 1-3 mol equivalent.

5. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, The Lewis acid is SnCl4.

6. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, In step S3, the amount of SnCl4 added is 5 mol%, relative to the molar amount of ethylene oxide.

7. The method for preparing a temperature- and salt-resistant hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, The reaction temperature in step S2 is 60~80℃, and the reaction time is 3~4h.

8. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, In step S3, the reaction temperature is 50~60℃ and the reaction time is 1~2h.

9. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, In step S5, the concentration of the trehalose solution is 20-30 wt%, and the mass ratio of glyoxal to trehalose solution is 3:1-5.

10. The method for preparing a temperature- and salt-resistant highly substituted hydroxyethyl methyl cellulose ether according to claim 1, characterized in that, In step S6, the drying temperature is controlled at 70~80℃.

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