Modified hydroxypropyl methyl cellulose as well as preparation method and application thereof

Abstract

The invention provides modified hydroxypropyl methyl cellulose as well as a preparation method and application thereof, and belongs to the technical field of pharmaceutic adjuvants. Straw is subjected to alkali pretreatment and acid liquor purification and then added into alkali liquor to prepare alkali cellulose, then chloromethane and epoxypropane are added, heating etherification reaction is carried out to prepare hydroxypropyl methyl cellulose, after modification is carried out through a silane coupling agent KH560, the hydroxypropyl methyl cellulose and carboxymethyl chitosan are subjected to stirring reaction, collagen and EDC are added, stirring reaction and drying are carried out, and the modified hydroxypropyl methyl cellulose is prepared. The modified hydroxypropyl methyl cellulose prepared by the invention has better mechanical property, barrier property, degradability, low allergy, biocompatibility and proper drug dissolution rate, is excellent in chemical stability and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of pharmaceutical excipients, and in particular to modified hydroxypropyl methylcellulose and a preparation method and application thereof. Background Art

[0002] Hydroxypropyl methylcellulose (HPMC) (its structural formula is shown in Formula I) is one of the most popular pharmaceutical excipients at home and abroad. Due to its different relative molecular weight and viscosity, it has the characteristics and uses of emulsification, bonding, thickening, viscosity enhancement, suspension, gelation and film formation, and is widely used in pharmaceutical technology. At present, the industrial production of hydroxypropyl methylcellulose (HPMC) is basically to obtain purified cellulose from cotton wool or wood pulp, and react with sodium hydroxide solution to obtain swollen alkali cellulose, which is more chemically active than untreated cellulose. Alkali cellulose is treated with methyl chloride and propylene oxide to obtain methyl hydroxypropyl ether of cellulose, and the resulting fibrous product is purified.

[0003]

[0005] With the increasing depletion of oil resources, the development of new fine chemical products using cellulose as raw materials will be one of the important topics in the field of chemical engineering research in the 21st century. Cellulose can be modified to obtain more new materials with excellent properties, which are widely used in various fields such as medicine, clothing, daily chemicals, adsorbents, etc. As a large agricultural country, my country produces nearly 700 million tons of crop straw annually, and 70% of it is burned and not fully utilized, while the content of cellulose in straw is as high as 40%-50%. Therefore, it is of great significance to replace cotton pulp or paper pulp with straw to produce hydroxypropyl methylcellulose. Summary of the invention

[0006] The purpose of the present invention is to provide a modified hydroxypropyl methylcellulose and a preparation method and application thereof, which has good mechanical strength and barrier properties to oxygen, water, carbon dioxide molecules, etc., and at the same time, has good degradability, low allergy, biocompatibility and suitable drug solubility, and good chemical stability. Since it does not contain aldehyde groups, it is not easy to be oxidized, and the addition of some auxiliary materials, such as preservatives, colorants, sunscreens, etc., affects the cross-linking of the material, so it has broad application prospects.

[0007] The technical solution of the present invention is achieved in this way:

[0008] The invention provides a method for preparing modified hydroxypropyl methylcellulose. The method comprises the following steps: pre-treating straw with alkali, purifying the straw with acid solution, adding the straw into alkali solution to obtain alkali cellulose, then adding methyl chloride and propylene oxide, heating and performing etherification reaction to obtain hydroxypropyl methylcellulose, modifying the straw with a silane coupling agent KH560, stirring and reacting the straw with carboxymethyl chitosan, adding collagen and EDC, stirring and reacting the straw, and drying the straw to obtain the modified hydroxypropyl methylcellulose.

[0009] As a further improvement of the present invention, the following steps are included:

[0010] S1. Wash the straw, dry it, crush it, add it to an alkali mixture for pretreatment, filter it, wash it, and dry it to obtain pretreated straw powder;

[0011] S2. The pretreated straw powder is added to an acid solution, heated to reflux for extraction, filtered, washed, and dried to obtain straw cellulose;

[0012] S3. Adding straw cellulose to an alkali solution, heating and stirring the reaction, filtering, washing, and drying to obtain alkali cellulose;

[0013] S4. The alkali cellulose is added to an organic solvent, methyl chloride and propylene oxide are added, heated for etherification reaction, filtered, washed, and dried to obtain hydroxypropyl methylcellulose;

[0014] S5. The hydroxypropyl methylcellulose was added to methanol, stirred and dispersed uniformly, a silane coupling agent KH560 was added, the reaction was heated and stirred, filtered, washed, and dried to obtain silane-modified hydroxypropyl methylcellulose;

[0015] S6. Add carboxymethyl chitosan into water, add silane-modified hydroxypropyl methylcellulose, stir to react, add collagen and EDC, stir to react, and dry to obtain modified hydroxypropyl methylcellulose.

[0016] As a further improvement of the present invention, the straw in step S1 is selected from at least one of wheat straw, corn straw, rice straw, and sorghum straw, the alkaline mixture is an aqueous solution containing 10-15wt% NaOH, 3-5wt% urea, and 2-3wt% thiourea, and the pretreatment temperature is 40-50°C and the time is 1-3h.

[0017] As a further improvement of the present invention, the solid-liquid ratio of the pretreated straw powder and the acid solution in step S2 is 1:10-15 g / mL, the heating reflux extraction time is 2-3 h, and the acid solution is a 1-3 mol / L nitric acid solution.

[0018] As a further improvement of the present invention, the alkali solution in step S3 is an aqueous solution containing 7-10wt% NaOH, 10-20wt% isopropanol and 7-12wt% ethanol, and the temperature of the heating and stirring reaction is 55-65°C and the time is 1-2h.

[0019] As a further improvement of the present invention, the mass ratio of alkali cellulose, methyl chloride and propylene oxide in step S4 is 10:14-17:2-3, the temperature of the heating etherification reaction is 60-70°C, the time is 1-3h, and the organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 4-6:3.

[0020] As a further improvement of the present invention, in step S5, the mass ratio of hydroxypropyl methylcellulose to silane coupling agent KH560 is 10:2-3, the temperature of the heating and stirring reaction is 40-50° C., and the time is 2-4 hours.

[0021] As a further improvement of the present invention, the mass ratio of carboxymethyl chitosan, silane-modified hydroxypropyl methylcellulose, collagen and EDC in step S6 is 12-15:18-20:7-10:0.5-1.

[0022] The present invention further protects modified hydroxypropyl methylcellulose obtained by the above-mentioned preparation method.

[0023] The present invention further protects an application of the modified hydroxypropyl methylcellulose in preparing capsule shell materials, coating materials and skeleton materials.

[0024] The present invention has the following beneficial effects:

[0025] The natural macromolecular substances in straw are cellulose, hemicellulose and lignin. These three components are interlocked in straw to form the cell wall of plants, and the highest content is cellulose. Straw is not only a natural raw material that is safe and friendly to the environment, but also has the excellent properties of being cheap, easy to obtain, and resistant to mildew and antibacterial, and is widely used as the raw material of synthetic materials. The industrial synthesis process of hydroxypropyl methylcellulose is basically to obtain etherified cotton pulp or paper pulp after hydrolysis, which is equivalent to direct one-step synthesis, but the later processing process is more complicated. The present invention adopts straw as raw material, and etherifies and synthesizes after purifying cellulose by pretreatment, which is equivalent to two-step synthesis. Subsequent treatment is simple and easy to operate, and the preparation method is simple, and the process conditions are mild, and the yield is high, and the cost is relatively low. It is easy to realize industrial production, and the obtained hydroxypropyl methylcellulose has good emulsification, dispersion, thickening, bonding, water retention and glue retention performance, and is soluble in water and most of the polar solvents. Its aqueous solution has high transparency, excellent stability, and has the advantages of low allergy and chemical stability. However, directly using hydroxypropyl methylcellulose as capsule shell material, coating material, skeleton material, etc. also has some disadvantages, such as poor mechanical strength, high cost, and poor oxygen barrier properties, which leads to degradation of some oxygen-sensitive drugs during storage.

[0026] The invention prepares hydroxypropyl methylcellulose obtained from straw by modifying it with a silane coupling agent KH560, so that the surface of the hydroxypropyl methylcellulose has epoxy groups, and the hydroxypropyl methylcellulose is mixed with carboxymethyl chitosan, and the amino groups on the carboxymethyl chitosan can react with the silane-modified hydroxypropyl methylcellulose, thereby achieving coupling, forming a preliminarily cross-linked composite, and improving the mechanical properties and barrier properties of the hydroxypropyl methylcellulose. Subsequently, collagen is added, and under the action of EDC, the carboxyl groups in the collagen molecules are activated, so that the carboxyl groups can react with their own amino groups and the amino groups in the preliminarily cross-linked composite, and the cross-linking is further strengthened, so that the prepared modified hydroxypropyl methylcellulose further improves the mechanical strength and the barrier properties to oxygen, water, carbon dioxide molecules and the like, and at the same time, has good degradability, low allergy, biocompatibility and suitable drug solubility, and has good chemical stability. Since the hydroxypropyl methylcellulose does not contain an aldehyde group, it is not easy to be oxidized, and the addition of some auxiliary materials, such as preservatives, colorants, sunscreens and the like, affects the cross-linking of the material, and thus has broad application prospects. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0028] EDC, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, is commercially available.

[0029] Collagen, content>99%, was purchased from Hebei Runying Biotechnology Co., Ltd.

[0030] Carboxymethyl chitosan, water-soluble, content>99%, carboxylation degree>80%, purchased from Jinan Xinzhiyuan Biotechnology Co., Ltd.

[0031] Example 1

[0032] This embodiment provides a method for preparing modified hydroxypropyl methylcellulose, comprising the following steps:

[0033] S1. Wash 2 g corn stalks, dry them, crush them, add them to 100 mL of alkali mixture, heat them to 40 ° C for 1 h, filter, wash them, and dry them to obtain pretreated stalk powder;

[0034] The alkaline mixture is an aqueous solution containing 10wt% NaOH, 3wt% urea, and 2wt% thiourea;

[0035] S2. Add 2 g of pretreated straw powder to 20 mL of 1 mol / L nitric acid solution, heat and reflux for 2 h, filter, wash, and dry to obtain straw cellulose;

[0036] S3. Add 1 g of straw cellulose to 100 mL of alkali solution, heat to 55°C, stir and react for 1 h, filter, wash, and dry to obtain alkali cellulose;

[0037] The alkali solution is an aqueous solution containing 7wt% NaOH, 10wt% isopropanol and 7wt% ethanol;

[0038] S4. Add 10 g of alkali cellulose to 200 mL of an organic solvent, add 14 g of methyl chloride and 2 g of propylene oxide, heat to 60 ° C, etherify for 1 h, filter, wash, and dry to obtain hydroxypropyl methylcellulose;

[0039] The organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 4:3.

[0040] S5. 10 g of hydroxypropyl methylcellulose was added to 200 mL of methanol, and the mixture was stirred and dispersed at 500 r / min for 10 min. 2 g of silane coupling agent KH560 was added, and the mixture was heated to 40° C., stirred and reacted for 2 h, filtered, washed, and dried to obtain silane-modified hydroxypropyl methylcellulose.

[0041] S6. Add 12 g of carboxymethyl chitosan to 1 L of water, add 18 g of silane-modified hydroxypropyl methylcellulose, stir and react at 40° C. for 1 h, add 7 g of collagen and 0.5 g of EDC, stir and react at room temperature for 2 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0042] Example 2

[0043] This embodiment provides a method for preparing modified hydroxypropyl methylcellulose, comprising the following steps:

[0044] S1. Wash 2 g of wheat straw, dry it, crush it, add it to 100 mL of alkali mixture, heat it to 50 ° C for 3 h, filter it, wash it, and dry it to obtain pretreated straw powder;

[0045] The alkaline mixture is an aqueous solution containing 15wt% NaOH, 5wt% urea, and 3wt% thiourea;

[0046] S2. 2 g of pretreated straw powder was added to 30 mL of 3 mol / L nitric acid solution, heated under reflux for extraction for 3 h, filtered, washed, and dried to obtain straw cellulose;

[0047] S3. Add 1 g of straw cellulose to 100 mL of alkali solution, heat to 65°C, stir and react for 2 h, filter, wash, and dry to obtain alkali cellulose;

[0048] The alkali solution is an aqueous solution containing 10wt% NaOH, 20wt% isopropanol and 12wt% ethanol;

[0049] S4. Add 10 g of alkali cellulose to 200 mL of an organic solvent, add 17 g of methyl chloride and 3 g of propylene oxide, heat to 70 ° C, etherify for 3 h, filter, wash, and dry to obtain hydroxypropyl methylcellulose;

[0050] The organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 6:3.

[0051] S5. 10 g of hydroxypropyl methylcellulose was added to 200 mL of methanol, stirred and dispersed at 500 r / min for 10 min, 3 g of silane coupling agent KH560 was added, heated to 50° C., stirred and reacted for 4 h, filtered, washed, and dried to obtain silane-modified hydroxypropyl methylcellulose;

[0052] S6. Add 15 g of carboxymethyl chitosan to 1 L of water, add 20 g of silane-modified hydroxypropyl methylcellulose, stir and react at 40° C. for 2 h, add 10 g of collagen and 1 g of EDC, stir and react at room temperature for 3 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0053] Example 3

[0054] This embodiment provides a method for preparing modified hydroxypropyl methylcellulose, comprising the following steps:

[0055] S1. Wash 2 g of wheat straw, dry it, crush it, add it to 100 mL of alkali mixture, heat it to 45 ° C for 2 h, filter it, wash it, and dry it to obtain pretreated straw powder;

[0056] The alkaline mixture is an aqueous solution containing 12wt% NaOH, 4wt% urea, and 2.5wt% thiourea;

[0057] S2. 2 g of pretreated straw powder was added to 25 mL of 2 mol / L nitric acid solution, heated under reflux for extraction for 2.5 h, filtered, washed, and dried to obtain straw cellulose;

[0058] S3. Add 1 g of straw cellulose to 100 mL of alkali solution, heat to 60°C, stir and react for 1.5 h, filter, wash, and dry to obtain alkali cellulose;

[0059] The alkali solution is an aqueous solution containing 8wt% NaOH, 15wt% isopropanol and 10wt% ethanol;

[0060] S4. 10 g of alkali cellulose was added to 200 mL of organic solvent, 15.5 g of methyl chloride and 2.5 g of propylene oxide were added, heated to 65 ° C, etherified for 2 h, filtered, washed, and dried to obtain hydroxypropyl methylcellulose;

[0061] The organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 5:3.

[0062] S5. Add 10g of hydroxypropyl methylcellulose to 200mL of methanol, stir and disperse at 500r / min for 10min, add 2.5g of silane coupling agent KH560, heat to 45°C, stir and react for 3h, filter, wash, and dry to obtain silane-modified hydroxypropyl methylcellulose

[0063] S6. Add 13 g of carboxymethyl chitosan to 1 L of water, add 19 g of silane-modified hydroxypropyl methylcellulose, stir and react at 40° C. for 1.5 h, add 8 g of collagen and 0.7 g of EDC, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0064] Comparative Example 1

[0065] Compared with Example 3, the difference is that step S1 is not performed.

[0066] The details are as follows:

[0067] S1. 2 g of wheat straw was dried, crushed, added to 25 mL of 2 mol / L nitric acid solution, heated under reflux for extraction for 2.5 h, filtered, washed, and dried to obtain straw cellulose;

[0068] S3. Add 1 g of straw cellulose to 100 mL of alkali solution, heat to 60°C, stir and react for 1.5 h, filter, wash, and dry to obtain alkali cellulose;

[0069] The alkali solution is an aqueous solution containing 8wt% NaOH, 15wt% isopropanol and 10wt% ethanol;

[0070] S4. 10 g of alkali cellulose was added to 200 mL of organic solvent, 15.5 g of methyl chloride and 2.5 g of propylene oxide were added, heated to 65 ° C, etherified for 2 h, filtered, washed, and dried to obtain hydroxypropyl methylcellulose;

[0071] The organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 5:3.

[0072] S5. Add 10g of hydroxypropyl methylcellulose to 200mL of methanol, stir and disperse at 500r / min for 10min, add 2.5g of silane coupling agent KH560, heat to 45°C, stir and react for 3h, filter, wash, and dry to obtain silane-modified hydroxypropyl methylcellulose

[0073] S6. Add 13 g of carboxymethyl chitosan to 1 L of water, add 19 g of silane-modified hydroxypropyl methylcellulose, stir and react at 40° C. for 1.5 h, add 8 g of collagen and 0.7 g of EDC, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0074] Comparative Example 2

[0075] Compared with Example 3, the difference is that step S2 is not performed.

[0076] The details are as follows:

[0077] S1. Wash 2 g of wheat straw, dry it, crush it, add it to 100 mL of alkali mixture, heat it to 45 ° C for 2 h, filter it, wash it, and dry it to obtain pretreated straw powder;

[0078] The alkaline mixture is an aqueous solution containing 12wt% NaOH, 4wt% urea, and 2.5wt% thiourea;

[0079] S2. Add 1 g of pretreated straw powder to 100 mL of alkali solution, heat to 60 ° C, stir and react for 1.5 h, filter, wash, and dry to obtain alkali cellulose;

[0080] The alkali solution is an aqueous solution containing 8wt% NaOH, 15wt% isopropanol and 10wt% ethanol;

[0081] S3. 10 g of alkali cellulose was added to 200 mL of an organic solvent, 15.5 g of methyl chloride and 2.5 g of propylene oxide were added, heated to 65 ° C, etherified for 2 h, filtered, washed, and dried to obtain hydroxypropyl methylcellulose;

[0082] The organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 5:3.

[0083] S4. Add 10g of hydroxypropyl methylcellulose to 200mL of methanol, stir and disperse at 500r / min for 10min, add 2.5g of silane coupling agent KH560, heat to 45°C, stir and react for 3h, filter, wash, and dry to obtain silane-modified hydroxypropyl methylcellulose

[0084] S5. Add 13 g of carboxymethyl chitosan to 1 L of water, add 19 g of silane-modified hydroxypropyl methylcellulose, stir and react at 40° C. for 1.5 h, add 8 g of collagen and 0.7 g of EDC, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0085] Comparative Example 3

[0086] Compared with Embodiment 3, the difference is that step S5 is not performed.

[0087] The details are as follows:

[0088] S1. Wash 2 g of wheat straw, dry it, crush it, add it to 100 mL of alkali mixture, heat it to 45 ° C for 2 h, filter it, wash it, and dry it to obtain pretreated straw powder;

[0089] The alkaline mixture is an aqueous solution containing 12wt% NaOH, 4wt% urea, and 2.5wt% thiourea;

[0090] S2. 2 g of pretreated straw powder was added to 25 mL of 2 mol / L nitric acid solution, heated under reflux for extraction for 2.5 h, filtered, washed, and dried to obtain straw cellulose;

[0091] S3. Add 1 g of straw cellulose to 100 mL of alkali solution, heat to 60°C, stir and react for 1.5 h, filter, wash, and dry to obtain alkali cellulose;

[0092] The alkali solution is an aqueous solution containing 8wt% NaOH, 15wt% isopropanol and 10wt% ethanol;

[0093] S4. 10 g of alkali cellulose was added to 200 mL of organic solvent, 15.5 g of methyl chloride and 2.5 g of propylene oxide were added, heated to 65 ° C, etherified for 2 h, filtered, washed, and dried to obtain hydroxypropyl methylcellulose;

[0094] The organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 5:3.

[0095] S5. Add 13 g of carboxymethyl chitosan to 1 L of water, add 19 g of hydroxypropyl methylcellulose, stir and react at 40° C. for 1.5 h, add 8 g of collagen and 0.7 g of EDC, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0096] Comparative Example 4

[0097] The difference compared with Example 3 is that collagen is not added in step S6.

[0098] The details are as follows:

[0099] S6. Add 13 g of carboxymethyl chitosan to 1 L of water, add 19 g of silane-modified hydroxypropyl methylcellulose, stir and react at 40° C. for 1.5 h, add 0.7 g of EDC, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0100] Comparative Example 5

[0101] Compared with Example 3, the difference is that EDC is not added in step S6.

[0102] The details are as follows:

[0103] S6. Add 13 g of carboxymethyl chitosan to 1 L of water, add 19 g of silane-modified hydroxypropyl methylcellulose, stir and react at 40° C. for 1.5 h, add 8 g of collagen, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0104] Comparative Example 6

[0105] Compared with Example 3, the difference is that no silane-modified hydroxypropyl methylcellulose is added in step S6.

[0106] The details are as follows:

[0107] S6. Add 32 g of carboxymethyl chitosan to 1 L of water, add 8 g of collagen and 0.7 g of EDC, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0108] Comparative Example 7

[0109] Compared with Example 3, the difference is that carboxymethyl chitosan is not added in step S6.

[0110] The details are as follows:

[0111] S6. Add 32 g of silane-modified hydroxypropyl methylcellulose to 1 L of water, add 8 g of collagen and 0.7 g of EDC, stir and react at room temperature for 2.5 h, and dry to obtain modified hydroxypropyl methylcellulose.

[0112] Test Example 1

[0113] The modified hydroxypropyl methylcellulose prepared in Examples 1-3 and Comparative Examples 1-7 was dissolved in water, heated to a viscosity of 200±10 mPa·s, defoamed, and evenly spread in a plastic culture dish by casting, dried, and cut into a rectangular film of 15 mm×30 mm and a thickness of 0.08-0.10 mm. According to the national standard GB / T1040.1-2018, an electronic universal tensile testing machine was used to measure the elongation at break and tensile strength of the film, the initial clamping distance was set to 40 mm, and the tensile speed was set to 10 mm / s. The results are shown in Table 1.

[0114] Table 1

[0115]

[0116]

[0117] It can be seen from the above table that the films prepared from the modified hydroxypropyl methylcellulose prepared in Examples 1-3 of the present invention have good mechanical properties.

[0118] The oxygen permeability and water permeability of the membrane prepared above were tested, and the results are shown in Table 2.

[0119] Table 2

[0120] Group <![CDATA[Oxygen permeability (cc / m 2 ·d)]]> <![CDATA[Water permeability (g / m 2 ·d)]]> Example 1 0.14 0.85 Example 2 0.12 0.83 Example 3 0.11 0.82 Comparative Example 1 0.33 1.17 Comparative Example 2 0.29 1.10 Comparative Example 3 0.45 1.46 Comparative Example 4 0.57 1.62 Comparative Example 5 0.38 1.24 Comparative Example 6 0.95 2.25 Comparative Example 7 0.82 1.89

[0121] It can be seen from the above table that the films prepared from the modified hydroxypropyl methylcellulose prepared in Examples 1-3 of the present invention have good oxygen and water barrier properties.

[0122] The membrane prepared above was dried, weighed as m0, placed in an aqueous solution, and the degradation test was carried out in an air bath shaker at a temperature of 37°C and a shaking speed of 100 rpm. Samples were taken out at regular intervals, freeze-dried, and weighed as m1. New degradation solution was then replaced. When (m0-m1 / m0) was greater than 0.99, it was considered to be completely degraded. The complete degradation time was recorded. The results are shown in Table 3.

[0123] Table 3

[0124] Group Degradation time (h) Example 1 35 Example 2 32 Example 3 30 Comparative Example 1 40 Comparative Example 2 45 Comparative Example 3 37 Comparative Example 4 42 Comparative Example 5 38 Comparative Example 6 36 Comparative Example 7 47

[0125] It can be seen from the above table that the films prepared from the modified hydroxypropyl methylcellulose prepared in Examples 1-3 of the present invention have good degradability.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing modified hydroxypropyl methylcellulose, characterized in that: The straw is pretreated with alkali, purified with acid, and then added into alkali solution to obtain alkali cellulose. Then, methyl chloride and propylene oxide are added, and heated for etherification reaction to obtain hydroxypropyl methylcellulose. After being modified with silane coupling agent KH560, the cellulose is stirred and reacted with carboxymethyl chitosan. Then, collagen and EDC are added, stirred and reacted, and dried to obtain modified hydroxypropyl methylcellulose.

2. The preparation method according to claim 1, characterized in that: The following steps are involved: S1. Wash the straw, dry it, crush it, add it to an alkali mixture for pretreatment, filter it, wash it, and dry it to obtain pretreated straw powder; S2. The pretreated straw powder is added to an acid solution, heated to reflux for extraction, filtered, washed, and dried to obtain straw cellulose; S3. Adding straw cellulose to an alkali solution, heating and stirring the reaction, filtering, washing, and drying to obtain alkali cellulose; S4. The alkali cellulose is added to an organic solvent, methyl chloride and propylene oxide are added, heated for etherification reaction, filtered, washed, and dried to obtain hydroxypropyl methylcellulose; S5. The hydroxypropyl methylcellulose was added to methanol, stirred and dispersed uniformly, a silane coupling agent KH560 was added, the reaction was heated and stirred, filtered, washed, and dried to obtain silane-modified hydroxypropyl methylcellulose; S6. Add carboxymethyl chitosan into water, add silane-modified hydroxypropyl methylcellulose, stir to react, add collagen and EDC, stir to react, and dry to obtain modified hydroxypropyl methylcellulose.

3. The preparation method according to claim 2, characterized in that: In step S1, the straw is selected from at least one of wheat straw, corn straw, rice straw and sorghum straw, the alkaline mixture is an aqueous solution containing 10-15wt% NaOH, 3-5wt% urea and 2-3wt% thiourea, the pretreatment temperature is 40-50°C and the time is 1-3h.

4. The preparation method according to claim 2, characterized in that: In step S2, the solid-liquid ratio of the pretreated straw powder and the acid solution is 1:10-15 g / mL, the heating reflux extraction time is 2-3 hours, and the acid solution is a 1-3 mol / L nitric acid solution.

5. The preparation method according to claim 2, characterized in that: The alkali solution in step S3 is an aqueous solution containing 7-10wt% NaOH, 10-20wt% isopropanol and 7-12wt% ethanol, and the temperature of the heating and stirring reaction is 55-65°C and the time is 1-2h.

6. The preparation method according to claim 2, characterized in that: In step S4, the mass ratio of alkali cellulose, methyl chloride and propylene oxide is 10:14-17:2-3, the temperature of the heating etherification reaction is 60-70°C, the time is 1-3h, and the organic solvent is a mixed solvent of toluene and isopropanol in a volume ratio of 4-6:

3.

7. The preparation method according to claim 2, characterized in that: In step S5, the mass ratio of hydroxypropyl methylcellulose to silane coupling agent KH560 is 10:2-3, the temperature of the heating and stirring reaction is 40-50° C., and the time is 2-4 hours.

8. The preparation method according to claim 2, characterized in that: The mass ratio of carboxymethyl chitosan, silane-modified hydroxypropyl methylcellulose, collagen and EDC in step S6 is 12-15:18-20:7-10:0.5-1.

9. A modified hydroxypropyl methylcellulose obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the modified hydroxypropyl methylcellulose as claimed in claim 9 in the preparation of capsule shell materials, coating materials and skeleton materials.

Images