Preparation method and application of trihydroxyalkyl cellulose ether for sustained-release coating material

Abstract

The invention relates to the technical field of polymer materials, and in particular to a preparation method and application of trihydroxyalkyl cellulose ether for sustained-release coating materials. Alkali metal catalyst, purified water, polyol and cellulose are put into a high-pressure reactor, the temperature is increased and vacuum is drawn, methyl chloride and propylene oxide are first introduced for etherification reaction for a certain period of time, potassium hydroxide is added after the temperature is reduced, ethyl chloride is introduced after vacuum is drawn and the temperature is increased to complete the etherification reaction, and the trihydroxyalkyl cellulose ether is obtained through washing, drying and pulverization synthesis. The prepared trihydroxyalkyl cellulose ether has hydrophilic and hydrophobic characteristics to different degrees, is applied to the formula of film coating premix, and the prepared coating film has excellent properties such as slow release, high salt resistance and high release stability.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a preparation method and application of trihydroxyalkyl cellulose ether for sustained-release coating materials. Background Art

[0002] Film coating technology is one of the commonly used technologies for the preparation of sustained-release preparations. It controls the diffusion rate of drugs in gastrointestinal fluid by coating a layer of film on the surface of preparations such as tablets, granules, pellets and even drug powders, thereby regulating the release rate of drugs in preparations, maintaining a constant drug concentration in the blood, reducing the frequency of medication, reducing drug side effects, and improving the taste of drugs. These advantages have made film coating technology widely used and recognized in the field of pharmaceutical preparations.

[0003] The key to this technology is to select suitable coating materials to achieve the expected sustained-release effect. In pharmaceutical film-coated drugs, commonly used sustained-release coating materials include acrylic resins and hydroxypropyl methylcellulose ethers. Among them, hydroxypropyl methylcellulose ether is widely used due to its good film-forming properties and excellent biocompatibility.

[0004] However, conventional hydroxypropyl methylcellulose ether is a water-soluble polymer compound. The coating film prepared with it as the main raw material has weak hydrophobicity, making it difficult to reduce the speed at which drugs enter the human body core. Moreover, in the high ionic strength environment of gastrointestinal fluid, the drug coating film cannot effectively dissolve and release the active ingredients to achieve the effect of delaying the release of the drug, and the sustained-release rate has poor repetitive stability. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a preparation method and application of trihydroxyalkyl cellulose ether for sustained-release coating materials, which improves the sustained-release effect, high ionic strength resistance and high release repetitive stability of the sustained-release coating materials.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing trihydroxyalkyl cellulose ether for sustained-release coating material comprises the following steps:

[0008] S1. Place an alkali metal catalyst, purified water and polyol into a high-pressure reactor, start stirring, and lower the temperature in the reactor to below 30°C through a chilled water coil;

[0009] S2. Add cellulose pulp, stir and mix for 30-50min, control the temperature in the kettle below 20°C, evacuate to -0.09-0Mpa, pressurize with nitrogen to 0.05-0.07MPa, and repeat the replacement 6-8 times;

[0010] S3. Methyl chloride and propylene oxide were added to the reactor, heated while stirring, and the temperature was controlled at 60-90 ° C. The etherification reaction was carried out for 3-6h, and the reaction pressure was controlled to be 2.5-3.2MPa. After the reaction timer was completed, vacuum degassing was performed for 1-2h;

[0011] S4. After degassing, cool to 50 ° C, add alkali metal catalyst, seal the reactor, stir for 30-50 min, evacuate to -0.09-0 MPa, pressurize with nitrogen to 0.05-0.07 MPa, and repeat replacement 6-8 times;

[0012] S5. Ethyl chloride was added to the reactor, and the temperature was raised while stirring, and the temperature was controlled at 100-130 ° C. The etherification reaction was carried out for 4-8 hours, and the reaction pressure was controlled to be 2.5-3.5Mpa. After the reaction timer was completed, the vacuum degassing was carried out for 1-2 hours to obtain a special cellulose ether slurry;

[0013] S6. Add hydrochloric acid solution to the special cellulose ether slurry, neutralize and stir for 1-2 hours, and then heat to 85-95°C to remove unreacted monomers;

[0014] S7. Add 90-100°C water for extraction and washing once; centrifuge the water mixture obtained after the first washing, and bake the filter cake obtained by centrifugation at 85-95°C for 10-20h; wash the baked material twice with 90-100°C water, and adjust the pH of the reaction solution to neutral, centrifuge the secondary neutralized and washed material, send it to a dryer for drying, crushing, sieving, and packaging to obtain a trihydroxyalkyl cellulose ether product for sustained-release coating material.

[0015] Preferably, the mass proportion of the raw materials, in parts by mass, is 20-37 parts of alkali metal catalyst, 10-20 parts of purified water, 2-10 parts of polyol, 15-25 parts of cellulose pulp, 25-35 parts of methyl chloride, 5-15 parts of propylene oxide, and 2-10 parts of ethyl chloride; more preferably, 31 parts of alkali metal catalyst, 15 parts of purified water, 6 parts of polyol, 20 parts of cellulose pulp, 30 parts of methyl chloride, 10 parts of propylene oxide, and 6 parts of ethyl chloride.

[0016] Preferably, the alkali metal catalyst is a mixture of one or more of sodium hydroxide, potassium hydroxide and barium hydroxide.

[0017] Preferably, the polyol is a mixture of one or more of propylene glycol, glycerol, diethylene glycol, triethylene glycol, ethylene glycol and pentaerythritol.

[0018] Preferably, the cellulose pulp is a mixture of one or more of wood pulp, cotton pulp and sisal pulp.

[0019] Preferably, the trihydroxyalkyl cellulose ether product used as the sustained-release coating material has a methoxy content of 27-32%, a hydroxypropoxy content of 7-12%, an ethoxy content of 2-5%, and a 2% aqueous solution viscosity of 4-6 mPa.s.

[0020] The present invention also provides an application of trihydroxyalkyl cellulose ether for sustained-release coating material, which adopts the following technical scheme:

[0021] The invention discloses an application of trihydroxyalkyl cellulose ether for sustained-release coating material, and the application of the trihydroxyalkyl cellulose ether for sustained-release coating material in a coating film; the raw materials of the coating film material include component A and component B; the raw materials of component A include 5-7 parts of trihydroxyalkyl cellulose ether for sustained-release coating material, 0.2-0.6 parts of glyceride, 0.1-0.2 parts of Tween, and 0.03-0.07 parts of silicone oil in parts by mass; the raw materials of component B include purified water.

[0022] Preferably, the mass ratio of component A to component B is 1:8-10.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention uses polyols and cellulose as composite main raw materials, and adopts a highly catalytic alkali metal catalyst to promote the staged polymerization reaction to generate a trihydroxyalkyl cellulose ether for coating film sustained-release function with a methoxy content of 27-32%, a hydroxypropoxy content of 7-12%, an ethoxy content of 2-5%, and a 2% aqueous solution viscosity of 4-6 mPa.s. The polyol is miscible with water, has excellent hydrophilicity and high ionic strength mutual solubility stability, and becomes the main initiator to bring high ionic strength water solubility and high water solubility to the cellulose ether.

[0025] 2. The present invention adopts etherifying agent ethyl chloride for high temperature end-capping, and ethoxy groups evenly enter the interior of the molecular chain segments, giving cellulose ether excellent hydrophobicity, forming a water-impermeable barrier, slowing down the speed of drug dissolution from the core, thereby achieving a sustained release effect of the drug.

[0026] 3. The present invention adopts segmented catalysis to synthesize cellulose ether in one step, the reaction substitution is more uniform, the molecular weight concentration is high, and the quality stability between batches of cellulose ether is effectively improved, bringing excellent high release stability. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the embodiments. The feasibility of the present method is further described below through specific implementation examples, but it does not mean that the present invention is limited to these examples.

[0028] Embodiment 1:

[0029] In this embodiment, the alkali metal catalyst used is sodium hydroxide; the polyol used is propylene glycol; the cellulose pulp used is wood pulp, and the specific process for preparing trihydroxyalkyl cellulose ether for sustained-release coating material is as follows:

[0030] S1. 20kg of alkali metal catalyst, 10kg of purified water and 2kg of polyol were put into the autoclave, stirring was started, and the temperature in the autoclave was lowered to below 30°C by the chilled water coil;

[0031] S2. Add 15kg of cellulose pulp, stir and mix for 30min, control the temperature in the kettle below 20°C, evacuate to 0Mpa, pressurize with nitrogen to 0.07MPa, and repeat the replacement 6 times;

[0032] S3. Add 25kg of methyl chloride and 5kg of propylene oxide into the reactor, heat with stirring, control the temperature at 60 ° C, etherification reaction for 3h, control the reaction pressure to 2.5MPa, after the reaction timer, vacuum degassing 1h;

[0033] S4. After degassing, cool to 50 ° C, add 5 kg of alkali metal catalyst, seal the reactor, stir for 30 min, evacuate to 0 MPa, pressurize with nitrogen to 0.07 MPa, and repeat the replacement 6 times;

[0034] S5. Add 2kg of ethyl chloride to the reactor, heat it while stirring, control the temperature at 100 ° C, etherification reaction for 4h, control the reaction pressure to 2.5Mpa, after the reaction timer is over, vacuum degassing for 1h to obtain a special cellulose ether slurry;

[0035] S6. Add 0.5 kg of 35% hydrochloric acid solution to the special cellulose ether slurry, neutralize and stir for 1 hour, and then heat to 85 ° C to remove unreacted monomers;

[0036] S7. Add 90°C water for extraction and washing once; centrifuge the water mixture obtained after the first washing, and bake the filter cake obtained by centrifugation at 85°C for 10 hours; wash the baked material with 90°C water for a second time, and adjust the pH of the reaction solution to neutral, centrifuge the secondary neutralized and washed material, send it to a dryer for drying, crush, sieve, and package to obtain a trihydroxyalkyl cellulose ether product for sustained-release coating material.

[0037] Embodiment 2:

[0038] In this embodiment, the alkali metal catalyst used is sodium hydroxide; the polyol used is propylene glycol; the cellulose pulp used is wood pulp; the specific process for preparing trihydroxyalkyl cellulose ether for sustained-release coating material is:

[0039] S1. 25kg of alkali metal catalyst, 15kg of purified water and 6kg of polyol were put into the autoclave, stirring was started, and the temperature in the autoclave was lowered to below 30°C by the chilled water coil;

[0040] S2. Add 20kg cellulose pulp, stir and mix for 30min, control the temperature in the kettle below 20°C, evacuate to -0.04Mpa, pressurize with nitrogen to 0.06MPa, and repeat the replacement 7 times;

[0041] S3. Add 30kg methyl chloride and 10kg propylene oxide into the reactor, heat with stirring, control the temperature at 75 ° C, etherification reaction 4.5h, control the reaction pressure to 2.9MPa, after the reaction timer, vacuum degassing 1.5h;

[0042] S4. After degassing, cool to 50 ° C, add 6 kg of alkali metal catalyst, seal the reactor, stir for 40 min, evacuate to -0.04 MPa, pressurize with nitrogen to 0.06 MPa, and repeat the replacement 7 times;

[0043] S5. 6 kg of ethyl chloride was added to the reactor, heated while stirring, and the temperature was controlled at 115 ° C. The etherification reaction was carried out for 6 hours, and the reaction pressure was controlled to be 2.9 MPa. After the reaction timer was completed, the vacuum was degassed for 1.5 hours to obtain a special cellulose ether slurry;

[0044] S6. Add 1 kg of 35% hydrochloric acid solution to the special cellulose ether slurry, neutralize and stir for 1.5 hours, and then heat to 90°C to remove unreacted monomers;

[0045] S7. Add 95°C water for extraction and washing once; centrifuge the water mixture obtained after the first washing, and bake the filter cake obtained by centrifugation at 90°C for 15 hours; wash the baked material with 95°C water for a second time, and adjust the pH of the reaction solution to neutral, centrifuge the secondary neutralized and washed material, send it to a dryer for drying, crush, sieve, and package to obtain a trihydroxyalkyl cellulose ether product for sustained-release coating material.

[0046] Embodiment 3:

[0047] In this embodiment, the alkali metal catalyst used is sodium hydroxide; the polyol used is propylene glycol; the cellulose pulp used is wood pulp; the specific process for preparing trihydroxyalkyl cellulose ether for sustained-release coating material is:

[0048] S1. 30kg of alkali metal catalyst, 20kg of purified water and 10kg of polyol were put into the autoclave, stirring was started, and the temperature in the autoclave was lowered to below 30°C by the chilled water coil;

[0049] S2. Add 25kg cellulose pulp, stir and mix for 50min, control the temperature in the kettle below 20°C, evacuate to -0.09Mpa, pressurize with nitrogen to 0.05MPa, and repeat the replacement 8 times;

[0050] S3. Add 35kg methyl chloride and 15kg propylene oxide into the reactor, heat with stirring, control the temperature at 90 ° C, etherification reaction 6h, control the reaction pressure to 3.2MPa, after the reaction timer, vacuum degassing 2h;

[0051] S4. After degassing, cool to 50 ° C, add 7 kg of alkali metal catalyst, seal the reactor, stir for 50 min, evacuate to -0.09 MPa, pressurize with nitrogen to 0.05 MPa, and repeat the replacement 8 times;

[0052] S5. 10 kg of ethyl chloride was added to the reactor, heated while stirring, and the temperature was controlled at 130 ° C. The etherification reaction was carried out for 8 hours, and the reaction pressure was controlled to be 3.5 MPa. After the reaction timer was completed, the vacuum was degassed for 2 hours to obtain a special cellulose ether slurry;

[0053] S6. Add 1.5 kg of 35% hydrochloric acid solution to the special cellulose ether slurry, neutralize and stir for 2 hours, and then heat to 95 ° C to remove unreacted monomers;

[0054] S7. Add 100°C water for extraction and washing once; centrifuge the water mixture obtained after the first washing, and bake the filter cake obtained by centrifugation at 95°C for 20 hours; wash the baked material twice with 100°C water, and adjust the pH of the reaction solution to neutral, centrifuge the secondary neutralized and washed material, send it to a dryer for drying, crushing, sieving, and packaging to obtain a trihydroxyalkyl cellulose ether product for sustained-release coating material.

[0055] Embodiment 4:

[0056] The difference between this embodiment and embodiment 1 is that the alkali metal catalyst used is potassium hydroxide and barium hydroxide in a mass ratio of 1:1, and the rest is the same as embodiment 1.

[0057] Embodiment 5:

[0058] The difference between this embodiment and embodiment 1 is that the polyol used is pentaerythritol, and the rest is the same as embodiment 1.

[0059] Embodiment 6:

[0060] The difference between this embodiment and embodiment 1 is that the polyol used is a mixture of propylene glycol and diethylene glycol, and the mass ratio of the two is 1:1. The rest is the same as embodiment 1.

[0061] Embodiment 7:

[0062] The difference between this embodiment and embodiment 1 is that the polyol used is a mixture of triethylene glycol and ethylene glycol, and the mass ratio of the two is 1:1. The rest is the same as embodiment 1.

[0063] Embodiment 8:

[0064] The difference between this embodiment and embodiment 1 is that the cellulose pulp used is sisal, and the rest is the same as embodiment 1.

[0065] Embodiment 9:

[0066] The difference between this embodiment and embodiment 1 is that the cellulose pulp used is a mixture of cotton pulp and sisal pulp, and the mass ratio of the two is 1:1. The rest is the same as embodiment 1.

[0067] Comparative Example 1:

[0068] The difference between Comparative Example 1 and Example 1 is that no ethyl chloride is added to carry out the reaction in Comparative Example 1, and the specific reaction steps are as follows:

[0069] S1. 20kg of alkali metal catalyst, 10kg of purified water and 2kg of polyol were put into the autoclave, stirring was started, and the temperature in the autoclave was lowered to below 30°C by the chilled water coil;

[0070] S2. Add 15kg of cellulose pulp, stir and mix for 30min, control the temperature in the kettle below 20°C, evacuate to 0Mpa, pressurize with nitrogen to 0.07MPa, and repeat the replacement 6 times;

[0071] S3. Add 25kg of methyl chloride and 5kg of propylene oxide into the reactor, heat with stirring, control the temperature at 60 ° C, etherification reaction for 3h, control the reaction pressure to 2.5MPa, after the reaction timer, vacuum degassing 1h;

[0072] S4. Add 0.5 kg of 35% hydrochloric acid solution to the special cellulose ether slurry, neutralize and stir for 1 hour, and then heat to 85 ° C to remove unreacted monomers;

[0073] S5. Add 90°C water for extraction and washing once; centrifuge the water mixture obtained after the first washing, and bake the filter cake obtained by centrifugation at 85°C for 10 hours; wash the baked material with 90°C water for a second time, and adjust the pH of the reaction solution to neutral, centrifuge the secondary neutralized and washed material, send it to a dryer for drying, crush, sieve, and package to obtain a trihydroxyalkyl cellulose ether product for sustained-release coating material.

[0074] Comparative Example 2:

[0075] The difference between Comparative Example 2 and Example 1 is that no alkali metal catalyst is added before adding ethyl chloride for reaction. The specific reaction steps are as follows:

[0076] S1. 20kg of alkali metal catalyst, 10kg of purified water and 2kg of polyol were put into the autoclave, stirring was started, and the temperature in the autoclave was lowered to below 30°C by the chilled water coil;

[0077] S2. Add 15kg of cellulose pulp, stir and mix for 30min, control the temperature in the kettle below 20°C, evacuate to 0Mpa, pressurize with nitrogen to 0.07MPa, and repeat the replacement 6 times;

[0078] S3. Add 25kg of methyl chloride and 5kg of propylene oxide into the reactor, heat with stirring, control the temperature at 60 ° C, etherification reaction for 3h, control the reaction pressure to 2.5MPa, after the reaction timer, vacuum degassing 1h;

[0079] S4. Add 2kg of ethyl chloride to the reactor, heat it while stirring, control the temperature at 100 ° C, etherification reaction for 4h, control the reaction pressure to 2.5Mpa, after the reaction timer is over, vacuum degassing for 1h to obtain a special cellulose ether slurry;

[0080] S5. Add 0.5 kg of 35% hydrochloric acid solution to the special cellulose ether slurry, neutralize and stir for 1 hour, and then heat to 85 ° C to remove unreacted monomers;

[0081] S6. Add 90°C water for extraction and washing once; centrifuge the water mixture obtained after the first washing, and bake the filter cake obtained by centrifugation at 85°C for 10 hours; wash the baked material with 90°C water for a second time, and adjust the pH of the reaction solution to neutral, centrifuge the secondary neutralized and washed material, send it into a dryer for drying, crushing, sieving, and packaging to obtain a trihydroxyalkyl cellulose ether product for sustained-release coating material.

[0082] Application Example 1:

[0083] The sustained-release coating material prepared in Example 1 is used in a coating film with trihydroxyalkyl cellulose ether. The coating film material includes component A and component B. The preparation method is as follows:

[0084] Weigh 5 kg of trihydroxyalkyl cellulose ether for sustained-release coating material prepared in Example 1, 0.2 kg of glyceride, 0.1 kg of Tween, and 0.03 kg of silicone oil, and mix them evenly to obtain component A; the component B is purified water; 1 kg of component A and 9 kg of component B are mixed, and the coating film material is obtained after mixing evenly.

[0085] Application Example 2:

[0086] The sustained-release coating material prepared in Example 1 is used for coating film with trihydroxyalkyl cellulose ether. The coating film material includes component A and component B. The preparation method is as follows:

[0087] Weigh 5 kg of trihydroxyalkyl cellulose ether for sustained-release coating material prepared in Example 1, 0.2 kg of glyceride, 0.1 kg of Tween, and 0.03 kg of silicone oil, and mix them evenly to obtain component A; the component B is purified water; 1 kg of component A and 8 kg of component B are mixed, and the coating film material is obtained after mixing evenly.

[0088] Application Example 3:

[0089] The sustained-release coating material prepared in Example 1 is used to prepare a coating film with trihydroxyalkyl cellulose ether; the coating film material includes component A and component B, and the preparation method is as follows:

[0090] Weigh 5 kg of trihydroxyalkyl cellulose ether for sustained-release coating material prepared in Example 1, 0.2 kg of glyceride, 0.1 kg of Tween, and 0.03 kg of silicone oil, and mix them evenly to obtain component A; the component B is purified water; 1 kg of component A and 10 kg of component B are mixed, and the coating film material is obtained after mixing evenly.

[0091] Application Example 4-11:

[0092] The difference between Application Examples 4-11 and Application Example 1 is that the trihydroxyalkyl cellulose ether used as the sustained-release coating material in Application Examples 4-11 is from Examples 2-9, respectively.

[0093] Comparative application example 1-2:

[0094] The difference between Comparative Application Examples 1-2 and Application Example 1 is that the trihydroxyalkyl cellulose ether used as the sustained-release coating material in Comparative Application Examples 1-2 comes from Comparative Examples 1-2, respectively.

[0095] Performance testing

[0096] 1. The contents of methoxy, hydroxypropoxy and ethoxy in trihydroxyalkyl cellulose ether for sustained-release coating materials obtained in Examples 1-9 and Comparative Examples 1-2 were detected by gas chromatography, and the sustained-release coating materials obtained in Examples 1-9 and Comparative Examples 1-2 were formulated into 2% aqueous solutions with trihydroxyalkyl cellulose ether by mass, and the viscosity was measured at 25°C ± 0.2°C using a NDJ-79 rotary viscometer. The results are shown in Table 1.

[0097] Table 1: Content of methoxy, hydroxypropoxy and ethoxy in cellulose ether and viscosity of 2% aqueous solution

[0098]

[0099] It can be seen from the test results in Table 1 that the trihydroxyalkyl cellulose ether for a sustained-release coating material provided in the present application has a methoxy content of 27-32%, a hydroxypropoxy content of 7-12%, an ethoxy content of 2-5%, and a 2% aqueous solution viscosity of no more than 15 mPa.s.

[0100] The coating film materials obtained in Application Examples 1-11 and Comparative Application Examples 1-2 were sprayed on the surface of acetaminophen tablets using a closed coating pan to form a stable and uniform tablet film. The dissolution and disintegration effects of the coated tablets in a high ionic strength buffer solution (citric acid solution with a pH of 5.5) were tested. The results are shown in Table 2.

[0101] Table 2: Effect of coating on tablet dissolution and disintegration

[0102]

[0103] It can be seen from the test results in Table 2 that the trihydroxyalkyl cellulose ether used in the sustained-release coating material prepared by the present invention can significantly improve the sustained-release ability of the coating film, resistance to high ionic strength disintegration and dissolution stability, and prepare a coating material with slow release function, high salt resistance and high release stability.

[0104] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for preparing trihydroxyalkyl cellulose ether for sustained-release coating material, characterized in that: The following steps are involved: S1. Put the alkali metal catalyst, purified water and polyol into the autoclave, start stirring, and lower the temperature in the autoclave to below 30°C through the chilled water coil; S2. Add cellulose pulp, stir and mix for 30-50min, control the temperature in the kettle below 20°C, evacuate to -0.09-0MPa, pressurize with nitrogen to 0.05-0.07MPa, and repeat the replacement 6-8 times; S3. Methyl chloride and propylene oxide were added to the autoclave, heated while stirring, and the temperature was controlled at 60-90 ° C. The etherification reaction was carried out for 3-6h, and the reaction pressure was controlled to be 2.5-3.2MPa. After the reaction timer was completed, the vacuum was degassed for 1-2h; S4. After degassing, cool to 50°C, add alkali metal catalyst, seal the autoclave, stir for 30-50min, evacuate to -0.09-0MPa, pressurize with nitrogen to 0.05-0.07MPa, and repeat replacement 6-8 times; S5. Ethyl chloride was added to the autoclave, and the temperature was raised while stirring, and the temperature was controlled at 100-130 ° C. The etherification reaction was carried out for 4-8 hours, and the reaction pressure was controlled to be 2.5-3.5 MPa. After the reaction timer was completed, the vacuum was degassed for 1-2 hours to obtain a special cellulose ether slurry; S6. Add hydrochloric acid solution to the special cellulose ether slurry, neutralize and stir for 1-2 hours, and then heat to 85-95°C to remove unreacted monomers; S7. Add 90-100°C water for extraction and washing once; centrifuge the water mixture obtained after the first washing, and bake the filter cake obtained by centrifugation at 85-95°C for 10-20h; wash the baked material twice with 90-100°C water, and adjust the pH of the reaction solution to neutral, centrifuge the secondary neutralized and washed material, send it into a dryer for drying, crush, sieve and package, and obtain a trihydroxyalkyl cellulose ether product for sustained-release coating material; wherein the alkali metal catalyst is 20-37 parts, the purified water is 10-20 parts, the polyol is 2-10 parts, the cellulose pulp is 15-25 parts, the methyl chloride is 25-35 parts, the propylene oxide is 5-15 parts, and the ethyl chloride is 2-10 parts, all by mass.

2. The method for preparing a trihydroxyalkyl cellulose ether for a sustained-release coating material according to claim 1, characterized in that: The alkali metal catalyst is a mixture of one or more of sodium hydroxide, potassium hydroxide and barium hydroxide.

3. The method for preparing a trihydroxyalkyl cellulose ether for a sustained-release coating material according to claim 1, characterized in that: The polyol is a mixture of one or more of propylene glycol, glycerol, diethylene glycol, triethylene glycol, ethylene glycol and pentaerythritol.

4. The method for preparing a trihydroxyalkyl cellulose ether for a sustained-release coating material according to claim 1, characterized in that: The cellulose pulp is a mixture of one or more of wood pulp, cotton pulp and sisal pulp.

5. The method for preparing a trihydroxyalkyl cellulose ether for a sustained-release coating material according to claim 1, characterized in that: The trihydroxyalkyl cellulose ether product used as the sustained-release coating material has a methoxy content of 27-32%, a hydroxypropoxy content of 7-12%, an ethoxy content of 2-5%, and a 2% aqueous solution viscosity of 4-6 mPa.s.

6. Use of trihydroxyalkyl cellulose ether for sustained-release coating material prepared by the method according to any one of claims 1 to 5, characterized in that: The trihydroxyalkyl cellulose ether for sustained-release coating material is used in a coating film; the raw materials of the coating film material include component A and component B; the raw materials of component A include 5-7 parts of trihydroxyalkyl cellulose ether for sustained-release coating material, 0.2-0.6 parts of glyceride, 0.1-0.2 parts of Tween, and 0.03-0.07 parts of silicone oil in parts by mass; the raw materials of component B include purified water.

7. The use of trihydroxyalkyl cellulose ether for sustained-release coating material according to claim 6, characterized in that: The mass ratio of component A to component B is 1:8-10.

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