Production process for improving dissolvability of hydroxypropyl cellulose and application of production process

Abstract

The invention provides a production process for improving dissolvability of hydroxypropyl cellulose, which comprises the following steps: step 1, raw material pretreatment: crushing and drying a cellulose raw material to obtain pretreated cellulose; 2, homogeneous dissolution: mixing the pretreated cellulose with an ionic liquid solvent, and dissolving under heating and stirring conditions to obtain a cellulose solution; step 3, alkalization reaction: adding an alkali catalyst into the cellulose solution, and reacting under a low-temperature condition to obtain alkalized cellulose; 4, etherification modification: adding an etherifying agent into the alkalized cellulose for etherification reaction to obtain a hydroxypropylation reaction solution; and 5, neutralizing and purifying, namely adjusting the pH value of the hydroxypropylation reaction solution, adding a precipitator to precipitate the product, and filtering, washing and drying to obtain the hydroxypropyl cellulose. Through optimization of a homogeneous reaction system and process conditions, uniform distribution of the hydroxypropyl substitution degree is realized at the molecular level, so that the dissolving property of the hydroxypropyl cellulose is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a production process for improving the solubility of hydroxypropyl cellulose and application thereof. BACKGROUND

[0002] Hydroxypropyl cellulose is an important cellulose derivative, and the hydroxypropyl substituent in its molecular structure endows it with good water solubility and film-forming property. This material is often used in the pharmaceutical industry to prepare solid dispersions, capsule shells and coating materials, in the food industry as a thickening agent and stabilizer, and in the field of material science to prepare intelligent hydrogels and functional films. With the expansion of application fields, higher requirements are put forward for the solubility of hydroxypropyl cellulose, especially in drug preparations and intelligent response materials that require rapid dissolution and release.

[0003] In actual application process, the hydroxypropyl cellulose produced by the traditional method has obvious limitations. First, the product obtained by the conventional heterogeneous production process has uneven degree of substitution, resulting in slow and incomplete dissolution, and often appearing the phenomenon of caking. In pharmaceutical applications, this uneven solubility directly affects the release rate and bioavailability of the active ingredients of the drug. Secondly, in order to improve the solubility, the existing technology often needs to add a large amount of solubilizer or surfactant, which may bring toxic side effects or affect the purity of the final product. In addition, the ordinary hydroxypropyl cellulose has poor thermal stability and is prone to phase separation under high temperature or extreme pH conditions, limiting its application in special environments.

[0004] The existing technology attempts to solve the above problems through various ways. One solution is to use mechanical treatment methods such as nanocrystallization or micronization to increase the specific surface area, thereby improving the dissolution rate. However, this method has high energy consumption and may damage the molecular structure, affecting the stability of the product. Another approach is to perform chemical modification, such as introducing hydrophilic groups or preparing composites. Some studies report that hydroxypropyl cellulose is combined with sodium carboxymethyl cellulose to form a hydrogel. Although this method improves the temperature-sensitive properties of the material, it introduces ion sensitivity, which may actually reduce the solubility in certain media. There are also studies that use electrospinning technology to prepare fibrous hydroxypropyl cellulose materials to speed up the dissolution, but this process is complex and difficult to scale up, and it needs to add polyethylene oxide and other auxiliary materials, which may cause biocompatibility problems.

[0005] Further analysis of the existing technology shows that these solutions often bring new defects while improving a certain specific problem. For example, mechanical treatment methods improve the initial dissolution rate, but cannot solve the fundamental problem of uneven degree of substitution distribution; chemical modification methods may introduce new components with unknown biological safety; and composite formation methods complicate the production process and make it difficult to ensure the quality consistency of each batch. Therefore, it is necessary to design a production process for improving the solubility of hydroxypropyl cellulose and its application. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, a production process for improving the solubility of hydroxypropyl cellulose and its application are provided.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A production process for improving the solubility of hydroxypropyl cellulose, the production process comprising the following steps:

[0009] Step one is raw material pretreatment, which involves crushing and drying the cellulose raw material to obtain pretreated cellulose;

[0010] Step two is homogeneous dissolution, in which pretreated cellulose is mixed with an ionic liquid solvent and dissolved under heating and stirring conditions to obtain a cellulose solution;

[0011] Step 3 is the alkalization reaction, in which an alkaline catalyst is added to the cellulose solution and the reaction is carried out under low temperature conditions to obtain alkalized cellulose;

[0012] Step four is etherification modification, in which an etherifying agent is added to alkalized cellulose to carry out the etherification reaction, and a hydroxypropylated reaction solution is obtained;

[0013] Step five is neutralization and purification. The pH value of the hydroxypropylation reaction solution is adjusted, a precipitant is added to precipitate the product, and then the product is obtained through filtration, washing and drying.

[0014] In the raw material pretreatment described in step one, the cellulose raw material is selected from wood pulp cellulose, cotton linter cellulose or microcrystalline cellulose, pulverized to a particle size of 80-120 mesh, and vacuum dried at 50-70℃ for 2-4 hours to obtain dried pretreated cellulose.

[0015] The total mass ratio of the pretreated cellulose to the ionic liquid solvent is 1:8-12, the dissolution temperature is 70-90℃, the dissolution time is 2-4 hours, and the stirring speed is 200-400 r / min, to obtain a uniform cellulose solution product.

[0016] In the homogeneous dissolution described in step two, the ionic liquid solvent is a mixed solvent of 1-ethyl-3-methylimidazolium acetate and dimethyl sulfoxide, with a mass ratio of 1:0.5-2.

[0017] In the alkalization reaction described in step three, the reaction temperature is maintained at 5-15℃, the reaction time is 1-2 hours, and the stirring speed is 100-300 r / min to obtain the alkalized cellulose product.

[0018] The alkaline catalyst is sodium hydroxide, and the amount of the alkaline catalyst used is 15-25% of the mass of the pretreated cellulose.

[0019] In the etherification modification described in step four, the reaction temperature range is 40-80℃, the reaction pressure is 0.2-0.8 MPa, the reaction time is 3-6 hours, and the heating rate is 1-3℃ / min, to obtain the hydroxypropylated reaction solution product.

[0020] The etherifying agent is propylene oxide, and its mass ratio with the alkalized cellulose obtained in step one is 0.5-3:1.

[0021] In step five, during the neutralization and purification process, acetic acid is used to adjust the pH of the hydroxypropylation reaction solution to 6.5-7.5. The precipitant is acetone, and the volume ratio of the precipitant to the hydroxypropylation reaction solution is 3-5:1. The washing solvent is a 50-70% aqueous ethanol solution. The drying conditions are vacuum drying at 50-70°C, with the vacuum degree maintained at -0.08 to -0.1 MPa, to obtain the hydroxypropyl cellulose product.

[0022] The hydroxypropyl cellulose is used in pharmaceutical coating materials, food additives, hydrogels, or functional films.

[0023] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0024] 1. This invention achieves uniform dispersion of cellulose in a mixed system of ionic liquid solvent and dimethyl sulfoxide by employing a homogeneous dissolution process. This solvent combination can effectively disrupt the crystalline structure of cellulose, allowing its molecular chains to fully extend, thereby creating a more uniform reaction environment for the subsequent alkalization reaction and avoiding the problem of incomplete local reactions commonly found in traditional heterogeneous systems.

[0025] 2. In the alkalization reaction stage, the present invention slows down the occurrence of side reactions by controlling the low temperature conditions, and at the same time uses sodium hydroxide as an alkaline catalyst to ensure the uniform activation degree of cellulose hydroxyl groups. This uniform activation lays the foundation for the etherification modification step, so that the hydroxypropyl substitution reaction can proceed uniformly along the molecular chain.

[0026] 3. In the etherification modification process, this invention uses propylene oxide as an etherifying agent to promote full contact between propylene oxide and alkalized cellulose, resulting in a more uniform distribution of hydroxypropyl substitution degree, thereby significantly improving the solubility of the final product.

[0027] 4. Through the neutralization and purification steps, this invention uses acetic acid to adjust the pH to near neutral and acetone as a precipitant. This combination can effectively remove reaction byproducts and unreacted substances while maintaining the molecular structural integrity of hydroxypropyl cellulose, thereby improving the purity and stability of the product.

[0028] 5. This invention avoids the damage to the molecular structure caused by mechanical processing, and does not require the introduction of additional co-solvents or composite components. It achieves a fundamental improvement in solubility by optimizing the reaction system itself. This method not only simplifies the process, but also preserves the natural characteristics of the product. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the specific embodiments of this application, the sources of various main raw materials are briefly described as follows:

[0031] Sodium hydroxide, wood pulp cellulose, cotton linter cellulose, and microcrystalline cellulose: purchased from Hubei Weideli Chemical Technology Co., Ltd.

[0032] 1-Ethyl-3-methylimidazolium acetate: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0033] Dimethyl sulfoxide: purchased from Shandong Yinglang Chemical Co., Ltd.

[0034] Propylene oxide: purchased from Shandong Chuangying Chemical Co., Ltd.

[0035] Acetic acid, acetone, and ethanol: purchased from Maoming Xiongda Chemical Co., Ltd.

[0036] The technical solution of this application is as follows:

[0037] A production process for improving the solubility of hydroxypropyl cellulose, the production process comprising the following steps:

[0038] Step one is raw material pretreatment, which involves crushing and drying the cellulose raw material to obtain pretreated cellulose;

[0039] Step two is homogeneous dissolution, in which pretreated cellulose is mixed with an ionic liquid solvent and dissolved under heating and stirring conditions to obtain a cellulose solution;

[0040] Step 3 is the alkalization reaction, in which an alkaline catalyst is added to the cellulose solution and the reaction is carried out under low temperature conditions to obtain alkalized cellulose;

[0041] Step four is etherification modification, in which an etherifying agent is added to alkalized cellulose to carry out the etherification reaction, and a hydroxypropylated reaction solution is obtained;

[0042] Step five is neutralization and purification. The pH value of the hydroxypropylation reaction solution is adjusted, a precipitant is added to precipitate the product, and then the product is obtained through filtration, washing and drying.

[0043] In the raw material pretreatment described in step one, the cellulose raw material is selected from wood pulp cellulose, cotton linter cellulose or microcrystalline cellulose, pulverized to a particle size of 80-120 mesh, and vacuum dried at 50-70℃ for 2-4 hours to obtain dried pretreated cellulose.

[0044] The total mass ratio of the pretreated cellulose to the ionic liquid solvent is 1:8-12, the dissolution temperature is 70-90℃, the dissolution time is 2-4 hours, and the stirring speed is 200-400 r / min, to obtain a uniform cellulose solution product.

[0045] In the homogeneous dissolution described in step two, the ionic liquid solvent is a mixed solvent of 1-ethyl-3-methylimidazolium acetate and dimethyl sulfoxide, with a mass ratio of 1:0.5-2.

[0046] In the alkalization reaction described in step three, the reaction temperature is maintained at 5-15℃, the reaction time is 1-2 hours, and the stirring speed is 100-300 r / min to obtain the alkalized cellulose product.

[0047] The alkaline catalyst is sodium hydroxide, and the amount of the alkaline catalyst used is 15-25% of the mass of the pretreated cellulose.

[0048] In the etherification modification described in step four, the reaction temperature range is 40-80℃, the reaction pressure is 0.2-0.8 MPa, the reaction time is 3-6 hours, and the heating rate is 1-3℃ / min, to obtain the hydroxypropylated reaction solution product.

[0049] The etherifying agent is propylene oxide, and its mass ratio with the alkalized cellulose obtained in step one is 0.5-3:1.

[0050] In step five, during the neutralization and purification process, acetic acid is used to adjust the pH of the hydroxypropylation reaction solution to 6.5-7.5. The precipitant is acetone, and the volume ratio of the precipitant to the hydroxypropylation reaction solution is 3-5:1. The washing solvent is a 50-70% aqueous ethanol solution. The drying conditions are vacuum drying at 50-70°C, with the vacuum degree maintained at -0.08 to -0.1 MPa, to obtain the hydroxypropyl cellulose product.

[0051] The hydroxypropyl cellulose prepared by this invention exhibits rapid dispersion characteristics during the dissolution process. This is due to its uniform substitution distribution and moderate hydrophilic-hydrophobic balance. The molecular chains can quickly interact with water molecules to form a stable solution without clumping or gelation.

[0052] The hydroxypropyl cellulose is used in pharmaceutical coating materials, food additives, hydrogels, or functional films.

[0053] The present invention will be described in detail below through examples and comparative examples, but the scope of protection of the present invention is not limited to these examples. Unless otherwise specified, the chemical reagents and raw materials used in the following examples and comparative examples are all conventional commercially available products.

[0054] Example 1

[0055] In step one, the raw material pretreatment, wood pulp cellulose was selected as the cellulose raw material, pulverized to a particle size of 120 mesh, and vacuum dried at 60℃ for 2 hours to obtain pretreated cellulose. In step two, the homogeneous dissolution, the total mass ratio of pretreated cellulose to ionic liquid solvent was 1:12. The ionic liquid solvent was a mixture of 1-ethyl-3-methylimidazolium acetate and dimethyl sulfoxide, with a mass ratio of 1:1.25. The dissolution temperature was 80℃, the dissolution time was 2 hours, and the stirring speed was 400 r / min to obtain a cellulose solution. In step three, the alkalization reaction was carried out at 5℃ for 2 hours, with a stirring speed of 200 r / min. The amount of sodium hydroxide as the alkali catalyst was 15% of the mass of pretreated cellulose to obtain alkalized cellulose. In step four, the etherification modification was carried out at 80℃, with a reaction pressure of 0.5 MPa for 3 hours and a heating rate of 3. At a temperature of ℃ / min, the mass ratio of etherifying agent propylene oxide to alkalized cellulose was 1.75:1 to obtain the hydroxypropylation reaction solution; in step five, during neutralization and purification, acetic acid was used to adjust the pH to 6.5, the volume ratio of precipitant acetone to the reaction solution was 5:1, the washing solvent was 60% ethanol aqueous solution, the drying temperature was 50℃, and the vacuum degree was -0.1 MPa to obtain hydroxypropyl cellulose.

[0056] Example 2

[0057] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0058] In step one, raw material pretreatment, cotton cellulose was selected as the cellulose raw material, pulverized to a particle size of 80 mesh, and vacuum dried at 70℃ for 3 hours to obtain pretreated cellulose. In step two, homogeneous dissolution, the total mass ratio of pretreated cellulose to ionic liquid solvent was 1:8. The ionic liquid solvent was a mixture of 1-ethyl-3-methylimidazolium acetate and dimethyl sulfoxide, with a mass ratio of 1:0.5. The dissolution temperature was 90℃, the dissolution time was 3 hours, and the stirring speed was 200 r / min to obtain a cellulose solution. In step three, alkalization reaction, the reaction temperature was 15℃, the reaction time was 1 hour, the stirring speed was 300 r / min, and the amount of sodium hydroxide as the alkali catalyst was 25% of the mass of pretreated cellulose to obtain alkalized cellulose. In step four, etherification modification, the reaction temperature was 40℃, the reaction pressure was 0.8 MPa, the reaction time was 4.5 hours, and the heating rate was 1. At a temperature of ℃ / min, the mass ratio of etherifying agent propylene oxide to alkalized cellulose is 3:1 to obtain the hydroxypropylation reaction solution; in step five, during neutralization and purification, acetic acid is used to adjust the pH to 7.5, the volume ratio of precipitant acetone to reaction solution is 3:1, the washing solvent is 70% ethanol aqueous solution, the drying temperature is 60℃, and the vacuum degree is -0.08 MPa to obtain hydroxypropyl cellulose.

[0059] Example 3

[0060] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0061] In step one, the raw material pretreatment, microcrystalline cellulose was selected as the cellulose raw material, pulverized to a particle size of 100 mesh, and vacuum dried at 50℃ for 4 hours to obtain pretreated cellulose. In step two, the homogeneous dissolution, the total mass ratio of pretreated cellulose to ionic liquid solvent was 1:10. The ionic liquid solvent was a mixture of 1-ethyl-3-methylimidazolium acetate and dimethyl sulfoxide, with a mass ratio of 1:2. The dissolution temperature was 70℃, the dissolution time was 4 hours, and the stirring speed was 300 r / min to obtain a cellulose solution. In step three, the alkalization reaction was carried out at 10℃ for 1.5 hours, with a stirring speed of 100 r / min. The amount of sodium hydroxide as the alkali catalyst was 20% of the mass of pretreated cellulose to obtain alkalized cellulose. In step four, the etherification modification was carried out at 60℃, with a reaction pressure of 0.2 MPa for 6 hours and a heating rate of 2. At a temperature of ℃ / min, the mass ratio of etherifying agent propylene oxide to alkalized cellulose was 0.5:1 to obtain the hydroxypropylation reaction solution; in step five, during neutralization and purification, acetic acid was used to adjust the pH to 7.0, the volume ratio of precipitant acetone to reaction solution was 4:1, the washing solvent was 50% aqueous ethanol solution, the drying temperature was 70℃, and the vacuum degree was -0.09 MPa to obtain hydroxypropyl cellulose.

[0062] Comparative Example 1

[0063] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0064] In step two, dimethyl sulfoxide was not used as a mixed solvent; only 1-ethyl-3-methylimidazolium acetate was used as the solvent.

[0065] Comparative Example 2

[0066] In this comparative example, the similarities with Example 2 will not be repeated, and the differences are as follows:

[0067] In step three, the alkalization reaction temperature was changed to 25°C instead of a low temperature condition.

[0068] Comparative Example 3

[0069] In this comparative example, the similarities with Example 3 will not be repeated, and the differences are as follows:

[0070] In step four, the etherifying agent is changed to chloropropane instead of propylene oxide.

[0071] Comparative Example 4

[0072] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0073] In step five, water is used as a precipitant instead of acetone.

[0074] Comparative Example 5

[0075] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0076] In step four, the reaction pressure is changed to atmospheric pressure instead of control pressure.

[0077] Performance Test Results and Analysis

[0078] To evaluate the effects of these examples and comparative examples, the performance of hydroxypropyl cellulose prepared in three examples and five comparative examples was tested using general testing methods. The dissolution time test involved adding the sample to water at 25°C and stirring until completely dissolved, with the time recorded using a timer. The degree of substitution test used nuclear magnetic resonance (NMR) to analyze the degree of hydroxypropyl substitution. The viscosity test used a rotational viscometer to measure the viscosity of a 2% aqueous solution at 25°C. The transmittance test involved placing the sample solution in a cuvette and measuring it at visible light wavelength using a spectrophotometer. The ash content test involved igniting the sample in a muffle furnace to constant weight and calculating the proportion of residue. The purity analysis used high-performance liquid chromatography (HPLC) to detect the content of the main component. These testing methods aim to objectively reflect the solubility and quality of the samples, matching the characteristics of uniform substitution and rapid dissolution mentioned in the beneficial effects section. The test results are shown in Table 1, including indicators such as dissolution time, degree of substitution, viscosity, transmittance, ash content, and purity. All data are averages of three repeated tests.

[0079] As can be seen from Table 1, the test results show that Examples 1 to 3 are superior to Comparative Examples 1 to 5 in terms of dissolution time, degree of substitution, transmittance, and purity.

[0080] Specifically, the dissolution time of the examples did not exceed 3 minutes, the degree of substitution was between 2.1 and 2.4, the transmittance exceeded 95%, and the purity was higher than 98.5%, while the corresponding indicators of the comparative examples were all worse. This difference mainly stems from the optimization of key parameters in the production process. For example, in the homogeneous dissolution step of the examples, the use of a mixed solvent effectively destroyed the cellulose crystal structure; the alkalization reaction was carried out at low temperature to reduce side reactions; the pressure and temperature were controlled in the etherification modification to ensure uniform substitution; and the acetone precipitation in the neutralization purification improved the purity of the product.

[0081] Table 1 Analysis of Test Results

[0082] Sample Dissolution time (min) Degree of substitution Viscosity (mPa-s) Transmittance (%) Ash content (%) Purity (%) Example 1 2.5 2.4 480 96 0.2 98.8 Example 2 2.8 2.1 520 95 0.3 98.5 Example 3 2.6 2.3 500 97 0.2 99.0 Comparative Example 1 5.2 1.5 350 85 0.5 95.0 Comparative Example 2 4.8 1.6 380 88 0.4 96.2 Comparative Example 3 6.0 1.2 300 80 0.7 92.5 Comparative Example 4 5.5 1.8 400 90 0.6 94.8 Comparative Example 5 4.5 1.7 420 87 0.5 95.5

[0083] In Comparative Example 1, the lack of dimethyl sulfoxide to aid dissolution resulted in uneven cellulose dispersion, reduced degree of substitution, and prolonged dissolution time. In Comparative Example 2, the higher alkalization temperature triggered more side reactions, affecting product consistency and purity. In Comparative Example 3, the use of chloropropane as an etherifying agent resulted in low reactivity, leading to insufficient degree of substitution and decreased solubility. In Comparative Example 4, water precipitation failed to effectively remove impurities, increasing ash content and reducing light transmittance. In Comparative Example 5, the etherification reaction was carried out under normal pressure, reducing reactant contact efficiency and thus affecting substitution uniformity.

[0084] The homogeneous environment of this invention avoids incomplete local reactions, the low-temperature conditions maintain the integrity of the molecular structure, and the optimized precipitation steps improve product stability, thus enhancing the quality of the product. This invention, through optimization of the homogeneous reaction system and process conditions, achieves a uniform distribution of hydroxypropyl substitution at the molecular level, thereby significantly improving the solubility of hydroxypropyl cellulose.

[0085] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A production process for improving the solubility of hydroxypropyl cellulose, characterized in that, The production process includes the following steps: Step one is raw material pretreatment, which involves crushing and drying the cellulose raw material to obtain pretreated cellulose; Step two is homogeneous dissolution, in which pretreated cellulose is mixed with an ionic liquid solvent and dissolved under heating and stirring conditions to obtain a cellulose solution; Step 3 is the alkalization reaction, in which an alkaline catalyst is added to the cellulose solution and the reaction is carried out under low temperature conditions to obtain alkalized cellulose; Step four is etherification modification, in which an etherifying agent is added to alkalized cellulose to carry out the etherification reaction, and a hydroxypropylated reaction solution is obtained; Step five is neutralization and purification. The pH value of the hydroxypropylation reaction solution is adjusted, a precipitant is added to precipitate the product, and then the product is obtained through filtration, washing and drying.

2. The production process for improving the solubility of hydroxypropyl cellulose according to claim 1, characterized in that, In the raw material pretreatment described in step one, the cellulose raw material is selected from wood pulp cellulose, cotton linter cellulose or microcrystalline cellulose, pulverized to a particle size of 80-120 mesh, and vacuum dried at 50-70℃ for 2-4 hours to obtain dried pretreated cellulose.

3. The production process for improving the solubility of hydroxypropyl cellulose according to claim 1, characterized in that, The total mass ratio of the pretreated cellulose to the ionic liquid solvent is 1:8-12, the dissolution temperature is 70-90℃, the dissolution time is 2-4 hours, and the stirring speed is 200-400 r / min, to obtain a uniform cellulose solution product.

4. The production process for improving the solubility of hydroxypropyl cellulose according to claim 3, characterized in that, In the homogeneous dissolution described in step two, the ionic liquid solvent is a mixed solvent of 1-ethyl-3-methylimidazolium acetate and dimethyl sulfoxide, with a mass ratio of 1:0.5-2.

5. The production process for improving the solubility of hydroxypropyl cellulose according to claim 1, characterized in that, In the alkalization reaction described in step three, the reaction temperature is maintained at 5-15℃, the reaction time is 1-2 hours, and the stirring speed is 100-300 r / min to obtain the alkalized cellulose product.

6. The production process for improving the solubility of hydroxypropyl cellulose according to claim 5, characterized in that, The alkaline catalyst is sodium hydroxide, and the amount of the alkaline catalyst used is 15-25% of the mass of the pretreated cellulose.

7. The production process for improving the solubility of hydroxypropyl cellulose according to claim 1, characterized in that, In the etherification modification described in step four, the reaction temperature range is 40-80℃, the reaction pressure is 0.2-0.8 MPa, the reaction time is 3-6 hours, and the heating rate is 1-3℃ / min, to obtain the hydroxypropylated reaction solution product.

8. The production process for improving the solubility of hydroxypropyl cellulose according to claim 1, characterized in that, The etherifying agent is propylene oxide, and its mass ratio with the alkalized cellulose obtained in step one is 0.5-3:

1.

9. The production process for improving the solubility of hydroxypropyl cellulose according to claim 1, characterized in that, In step five, during the neutralization and purification process, acetic acid is used to adjust the pH of the hydroxypropylation reaction solution to 6.5-7.

5. The precipitant is acetone, and the volume ratio of the precipitant to the hydroxypropylation reaction solution is 3-5:

1. The washing solvent is a 50-70% aqueous ethanol solution. The drying conditions are vacuum drying at 50-70°C, with the vacuum degree maintained at -0.08 to -0.1 MPa, to obtain the hydroxypropyl cellulose product.

10. An application of hydroxypropyl cellulose prepared by the production process according to any one of claims 1-9, characterized in that, The hydroxypropyl cellulose is used in pharmaceutical coating materials, food additives, hydrogels, or functional films.