Preparation method of high-stability cross-linked hydroxypropyl starch ether

Abstract

The application provides a preparation method of high-stability cross-linked hydroxypropyl starch ether and relates to the technical field of starch ether processing. First, starch raw materials are configured into starch milk by adding water, and part of an alkalizing agent is added and stirred to activate; then, the temperature is increased to a first temperature, the remaining alkalizing agent is added, and stirring is performed until mixing is uniform; an etherifying agent is added, the temperature is increased to a second temperature, and one-stage etherification is performed until the hydroxypropyl substitution degree DS of the starch reaches 0.10; then, a cross-linking agent is added, and two-stage etherification is performed at the second temperature; finally, post-treatment is performed on the etherification product, and the cross-linked hydroxypropyl starch ether is obtained. The cross-linked hydroxypropyl starch ether produced by the method overcomes the problems of local gelatinization and by-product residue of the current cross-linked hydroxypropyl starch ether, realizes the industrialized production of high-stability, food-grade and safe hydroxypropyl cross-linked starch ether, and makes the product better meet the market demand.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of starch ether processing, and particularly relates to a preparation method of high-stability cross-linked hydroxypropyl starch ether. BACKGROUND

[0002] Hydroxypropyl starch ether (HPSE) is a modified starch prepared by etherification reaction of starch and propylene oxide under alkaline conditions. The hydroxypropyl groups (-O-CH2-CHOHCH3) in the molecular structure of the product replace the hydroxyl groups on the starch glucose units, endowing the product with certain thickening stability, low-temperature stability, transparency, solubility, acid and alkali resistance. However, the hydroxypropyl starch ether is difficult to meet the requirements when subjected to complex processing and use environment, and the stability and functionality are still insufficient when facing the production requirements of some high-end products, and therefore it is urgent to improve the comprehensive performance of the starch ether.

[0003] Cross-linking in the production process of hydroxypropyl starch ether can endow the starch with more excellent comprehensive performance on the basis of hydroxypropyl etherification modification, and can meet the stability and functionality thereof under harsh conditions. The cross-linked hydroxypropyl starch ether combines the advantages of the two modification methods, endows the product with the stability and tolerance required under harsh conditions such as high temperature, high shear, acidic / alkaline environment and repeated freezing and thawing, and makes it become an ideal choice in the fields such as food industry (especially products requiring high-temperature treatment, mechanical processing or frozen storage), pharmaceutical industry (sustained-release carrier), papermaking industry (wet-end additive) and other fields with extremely high stability requirements.

[0004] At present, the production methods of cross-linked hydroxypropyl starch ether on the market mostly use glyoxal as a cross-linking agent, a large amount of glyoxal is added, and a solvent method is adopted to react with starch at high temperature to prepare cross-linked hydroxypropyl starch ether. For example, patent CN113444185A discloses that the raw material ratio is: 10 parts of potato starch, 2-5 parts of propylene oxide, 50-200 parts of ethanol, and 0.2-1 part of glyoxal. After adding the potato starch, pre-alkalization is first carried out at a temperature of 70 DEG C, then the low-temperature alkalization is carried out for a period of time, the propylene oxide and the glyoxal are synchronously added, the etherification reaction is carried out by increasing the temperature to 70-80 DEG C, and finally the finished product is prepared by neutralization and washing. In this preparation method, the reaction temperature is >70 DEG C, which is easy to cause starch gelatinization, leading to molecular degradation, the 95 DEG C viscosity retention rate is <70%, and the stability is poor; the glyoxal as a cross-linking agent is hydrolyzed to generate formaldehyde residues under alkaline conditions, which cannot be completely removed by washing; the ethanol amount is 5-20 times the mass of the starch, and the recovery cost is high.

[0005] The academic journal literature [1] Zhang Jiayan, Liang Shuying, Xiong Jianwen, et al. Response surface optimization of microwave method for preparation of cross-linked potato starch process [J]. China food additives, 2016 (10): 7. DOI: 10.3969 / j.issn.1006-2513.2016.10.014. It is mentioned that sodium hexametaphosphate is used as crosslinking agent, and the production process is: sodium hexametaphosphate mass fraction 0.6%, starch milk mass fraction 24%, pH 10, temperature 44℃, sedimentation 4.86mL. But the production by microwave method will cause surface layer gelatinization due to local overheating of microwave, which is difficult to form industrial production; the addition amount of sodium hexametaphosphate 0.6% leads to combined phosphorus residue >500 ppm (EU food additive limit ≤50 ppm) which cannot be used for infant food; the phosphate ester bond is easy to hydrolyze in acidic conditions, the viscosity loss is serious, the stability is poor, and it cannot meet the needs of acidic food and high temperature industry, so the application range is greatly limited.

[0006] Therefore, there is currently a lack of a preparation method of high-stability cross-linked hydroxypropyl starch ether. SUMMARY

[0007] The purpose of the present application is to overcome the deficiencies of the prior art, provide a preparation method of high-stability cross-linked hydroxypropyl starch ether, overcome the problems of local gelatinization and by-product residue of the current cross-linked hydroxypropyl starch ether, realize the industrialized production of high-stability, food-grade safe hydroxypropyl cross-linked starch ether, and make the product better meet the market demand.

[0008] To achieve the above purpose, the technical solution adopted by the present application is as follows:

[0009] A preparation method of high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0010] S1, alkalization: the starch raw material is configured into starch milk by adding water, and part of the alkalizing agent is added and stirred to activate; then the temperature is raised to the first temperature, the remaining alkalizing agent is added, and stirred evenly;

[0011] S2, etherification: add etherifying agent, raise the temperature to the second temperature for one-stage etherification, and then add crosslinking agent after the hydroxypropyl substitution degree DS of the starch reaches 0.10, and carry out two-stage etherification at the second temperature;

[0012] S3, post-treatment: the etherification product is post-treated, and the high-stability cross-linked hydroxypropyl starch ether is obtained.

[0013] Further, in step S1, the starch raw material is selected from any one or more of corn starch, cassava starch, and potato starch, and is preferably potato starch; the mass ratio of the starch raw material to water is 100: (120-180).

[0014] Further, in step S1, the alkalizing agent is an aqueous solution of an alkali metal hydroxide, the mass concentration of the alkalizing agent is 20-40%, the alkali metal hydroxide is selected from potassium hydroxide, sodium hydroxide or a mixture of the two, the mass ratio of the two in the mixture of potassium hydroxide and sodium hydroxide is preferably 3:2, and the mass ratio of the alkali metal oxide to the starch is (2.2-3):100, based on the weight of the alkali metal oxide.

[0015] Further, in step S1, the part of the alkalizing agent is 50-60% of the total amount of the alkalizing agent.

[0016] Further, in step S1, the stirring activation time is 25-35 min.

[0017] Further, in step S1, the first temperature is 40-45℃.

[0018] The present application first uses an appropriate amount of alkalizing agent to alkalize the starch to form a moderate swelling layer, then adds the remaining alkalizing agent and an etherifying agent for heating etherification, at this time the etherification and alkalization are carried out simultaneously, which can activate the hydroxyl groups in the deep layer of the starch raw material, avoid the formation of a gelatinization layer caused by the local pH being too high in the first alkalization, and thus help to improve the product quality; it can also reduce the process switching time, shorten the production cycle, and avoid the influence of multiple heating and cooling on the product stability.

[0019] Further, in step S2, the etherifying agent is selected from any one or more of chloroacetic acid, chloromethane, chloroethane, propylene glycol ether, propylene oxide and ethylene oxide, and is preferably propylene oxide; the mass ratio of the etherifying agent to the starch raw material is (28-35):100.

[0020] Further, in step S2, the second temperature is 50-55℃.

[0021] Further, in step S2, the crosslinking agent is selected from any one or more of phosphorus oxychloride, epichlorohydrin and borax, and is preferably epichlorohydrin; the weight ratio of the crosslinking agent to the starch raw material is (0.05-0.15):100.

[0022] The present application finds that when the crosslinking agent is added after the first etherification reaction to a hydroxypropyl substitution degree DS of 0.10 of the starch, the swelling degree of the starch particles is in the range of 35-40% observed by a microscope at this time, and the addition of the crosslinking agent can ensure that the molecular chains are fully stretched, the crosslinking reaction is carried out simultaneously in the second etherification process, the crosslinking efficiency is effectively improved, and thus a more dense, more uniform or more stable network structure is established between the molecular chains, which can significantly improve the acid and alkali resistance and thermal stability of the starch ether.

[0023] Further, in step S2, the second etherification time is 7-9 h.

[0024] Further, the post-treatment comprises: lowering the etherification product to room temperature, adding acid to adjust the pH to neutral, and then washing, drying, and crushing to obtain the cross-linked hydroxypropyl starch ether.

[0025] Optionally, in the post-treatment process, the acid is dilute hydrochloric acid or dilute sulfuric acid, and the washing is performed using anhydrous ethanol.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The cross-linked hydroxypropyl starch ether preparation method provided by the present application has high utilization rate of alkalization agent and etherification agent, is highly efficient, has low cost, and improves production stability; the cross-linking temperature is low, the amount of cross-linking agent added is small, the cross-linking efficiency is high, and the additive residue is low; the obtained cross-linked starch ether can maintain high viscosity, is not easy to over-paste or degrade, has excellent acid resistance, is more stable in acidic food or environment, and is not easy to become thin; and also has good shear resistance, and has very small viscosity loss under the action of pumping, stirring, homogenization, and the like. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the infrared spectrum of the cross-linked hydroxypropyl starch ether in Example 2 of the present application. DETAILED DESCRIPTION

[0029] The following non-limiting examples can enable those of ordinary skill in the art to more fully understand the present application, but do not limit the present application in any way. The following content is only an exemplary description of the scope of the present application, and those skilled in the art can make various changes and modifications to the application disclosed herein, and such changes and modifications should also belong to the scope of the present application.

[0030] The present application will be further described below in the form of specific examples. The various chemical reagents used in the examples of the present application are obtained through conventional commercial channels unless otherwise specified.

[0031] Example 1

[0032] A preparation method of a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0033] S1, alkalization: 100 parts of potato starch are mixed with 120 parts of deionized water to prepare a starch milk, then 5.5 parts of KOH solution (20% by mass fraction) is added, and stirring is activated for 25 min; then the temperature is raised to 40℃, 5.5 parts of KOH solution (20% by mass fraction) is added, and stirring is performed to mix uniformly;

[0034] S2, etherification: 28 parts of chloroacetic acid is added, the temperature is raised to 50℃, and the reaction is kept at 50℃ until the degree of hydroxypropyl substitution of the starch reaches 0.10; then 0.05 parts of phosphorus oxychloride is added, and the reaction is continued at 50℃ for 7h;

[0035] S3, post-processing: the etherification product is cooled to room temperature, and the pH is adjusted to neutral by adding dilute hydrochloric acid, then washed with anhydrous ethanol, dried, crushed, and obtained.

[0036] Example 2

[0037] A method for preparing a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0038] S1, alkalization: 100 parts of corn starch is mixed with 150 parts of deionized water to prepare a starch slurry, then 4 parts of KOH solution (mass fraction 40%) is added, and stirred for 30 min; then heated to 45°C, 3 parts of KOH solution (mass fraction 40%) is added, and stirred evenly;

[0039] S2, etherification: 28 parts of propylene oxide is added, and heated to 55°C for constant temperature reaction until the hydroxypropyl substitution degree of the starch reaches 0.10; then 0.1 parts of epichlorohydrin is added, and continue to react at 55°C for 7h;

[0040] S3, post-processing: the etherification product is cooled to room temperature, and the pH is adjusted to neutral by adding dilute hydrochloric acid, then washed with anhydrous ethanol, dried, crushed, and obtained.

[0041] The cross-linked hydroxypropyl starch ether prepared in this example is pressed into a tablet with KBr, and tested on a Nicolet Nexus460 infrared spectrometer. The measured infrared spectrum is shown in Figure 1 It can be seen that the stretching vibration absorption peak of -OH is near 3415cm -1 , the characteristic peak of -CH3 is near 1378cm -1 , 1262cm -1 , 1150cm -1 , the stretching vibration peak of ether bond is near, and the vibration peak of epoxy group is near 920cm -1 , indicating that the cross-linked hydroxypropyl starch is successfully prepared.

[0042] Example 3

[0043] A method for preparing a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0044] S1, alkalization: 100 parts of corn starch is mixed with 150 parts of deionized water to prepare a starch slurry, then 4 parts of KOH solution (mass fraction 40%) is added, and stirred for 30 min; then heated to 45°C, 3 parts of KOH solution (mass fraction 40%) is added, and stirred evenly;

[0045] S2, etherification: 28 parts of propylene oxide is added, and heated to 55°C for constant temperature reaction until the hydroxypropyl substitution degree of the starch reaches 0.10; then 0.1 parts of epichlorohydrin is added, and continue to react at 55°C for 7h;

[0046] S3, post-processing: the etherification product is cooled to room temperature, and the pH is adjusted to neutral by adding dilute hydrochloric acid, then washed with anhydrous ethanol, dried, crushed, and obtained.

[0047] Example 4

[0048] A method for preparing a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0049] S1, alkalization: 100 parts of corn starch is mixed with 180 parts of deionized water to prepare a starch slurry, then 6 parts of KOH solution (mass fraction 30%) is added, and stirred for 35 min; then heated to 45℃, 4 parts of NaOH solution (mass fraction 30%) is added, and stirred evenly;

[0050] S2, etherification: 35 parts of propylene oxide is added, and heated to 55℃ for constant temperature reaction until the degree of hydroxypropyl substitution of the starch reaches 0.10; then 0.15 parts of epichlorohydrin is added, and continue to react at 55℃ for 7h;

[0051] S3, post-processing: the etherification product is cooled to room temperature, and the pH is adjusted to neutral by adding dilute hydrochloric acid, then washed with anhydrous ethanol, dried, crushed, and obtained.

[0052] Comparative Example 1

[0053] A method for preparing a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0054] S1, alkalization: 100 parts of corn starch is mixed with 150 parts of deionized water to prepare a starch slurry, then 4 parts of KOH solution (mass fraction 40%) is added, and stirred for 30 min; then heated to 45℃, 3 parts of KOH solution (mass fraction 40%) is added, and stirred evenly;

[0055] S2, etherification: 28 parts of propylene oxide and 0.1 parts of epichlorohydrin are added, and heated to 55℃ for constant temperature reaction for 7h;

[0056] S3, post-processing: the etherification product is cooled to room temperature, and the pH is adjusted to neutral by adding dilute hydrochloric acid, then washed with anhydrous ethanol, dried, crushed, and obtained.

[0057] Comparative Example 2

[0058] A method for preparing a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0059] S1, alkalization: 100 parts of corn starch was mixed with 150 parts of deionized water to prepare starch milk, then 4 parts of KOH solution (mass fraction 40%) and 0.1 parts of epichlorohydrin were added, and stirring activation was carried out for 30 min; then the temperature was raised to 45℃, 3 parts of KOH solution (mass fraction 40%) was added, and stirring was carried out until uniform;

[0060] S2, etherification: 28 parts of propylene oxide was added, and the temperature was raised to 55℃ and reacted for 7h;

[0061] S3, post-treatment: the etherification product was cooled to room temperature, the pH was adjusted to neutral with dilute hydrochloric acid, then washed with anhydrous ethanol, dried, and crushed to obtain the product.

[0062] Comparative example 3

[0063] A method for preparing a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0064] S1, alkalization: 100 parts of corn starch was mixed with 150 parts of deionized water to prepare starch milk, then 4 parts of KOH solution (mass fraction 40%) and 0.1 parts of epichlorohydrin were added, and stirring activation was carried out for 30 min; then the temperature was raised to 45℃, 3 parts of KOH solution (mass fraction 40%) was added, and stirring was carried out until uniform;

[0065] S2, etherification: 28 parts of propylene oxide was added, and the temperature was raised to 55℃ and reacted for 7h;

[0066] Then 0.1 parts of epichlorohydrin was added, and the constant temperature reaction was continued for 2 hours to complete the cross-linking reaction;

[0067] S3, post-treatment: the etherification product was cooled to room temperature, the pH was adjusted to neutral with dilute hydrochloric acid, then washed with anhydrous ethanol, dried, and crushed to obtain the product.

[0068] Comparative example 4

[0069] A method for preparing a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0070] S1, alkalization: 100 parts of corn starch was mixed with 150 parts of deionized water to prepare starch milk, then 4 parts of KOH solution (mass fraction 40%) and 0.1 parts of epichlorohydrin were added, and stirring activation was carried out for 30 min; then the temperature was raised to 45℃, 3 parts of KOH solution (mass fraction 40%) was added, and stirring was carried out until uniform;

[0071] S2, etherification: 28 parts of propylene oxide was added, and the temperature was raised to 55℃ and reacted for 7h;

[0072] S3, post-treatment: the etherification product was cooled to room temperature, the pH was adjusted to neutral with dilute hydrochloric acid, then washed with anhydrous ethanol, dried, and crushed to obtain the product.

[0073] Comparative Example 5

[0074] A preparation method of a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0075] S1, alkalization: 100 parts of corn starch is mixed with 150 parts of deionized water to prepare a starch milk, then 4 parts of KOH solution (mass fraction 40%) is added, and stirring is activated for 30 min; then the temperature is raised to 45℃, 3 parts of KOH solution (mass fraction 40%) is added, and stirring is mixed uniformly;

[0076] S2, etherification: 28 parts of propylene oxide is added, the temperature is raised to 52℃, and the reaction is kept constant until the degree of substitution of hydroxypropyl of the starch reaches 0.15; then 0.1 parts of epichlorohydrin is added, and the reaction is continued at 55℃ for 7h;

[0077] S3, post-treatment: the etherification product is reduced to room temperature, the pH is adjusted to neutral with dilute hydrochloric acid, then washed with anhydrous ethanol, dried, and crushed to obtain.

[0078] Comparative Example 6

[0079] A preparation method of a high-stability cross-linked hydroxypropyl starch ether, comprising the following steps:

[0080] S1, alkalization: 100 parts of corn starch is mixed with 150 parts of deionized water to prepare a starch milk, then 4 parts of KOH solution (mass fraction 40%) is added, and stirring is activated for 30 min; then the temperature is raised to 45℃, 3 parts of KOH solution (mass fraction 40%) is added, and stirring is mixed uniformly;

[0081] S2, etherification: 28 parts of propylene oxide is added, the temperature is raised to 52℃, and the reaction is kept constant until the degree of substitution of hydroxypropyl of the starch reaches 0.15; then 0.1 parts of epichlorohydrin is added, and the reaction is continued at 55℃ for 7h;

[0082] S3, post-treatment: the etherification product is reduced to room temperature, the pH is adjusted to neutral with dilute hydrochloric acid, then washed with anhydrous ethanol, dried, and crushed to obtain.

[0083] Experimental Example

[0084] The cross-linked hydroxypropyl starch ethers obtained in the above examples and comparative examples, and three commercial products (A, B, and C) are used as samples to perform the following tests:

[0085] (1) Cross-linking degree: Cross-linked starch is insoluble in water, but can absorb solvent and swell in water to form a gel. The higher the cross-linking degree, the tighter the three-dimensional network structure, the less water absorbed, and the smaller the swelling degree or swelling volume. Therefore, the cross-linking degree of the product can be indirectly represented and compared by measuring the swelling degree (SC) or the swelling volume (SV). In this experiment, the cross-linking degree of cross-linked starch was evaluated by measuring the swelling degree SC after water absorption and swelling. Specifically, 5.00 g of each sample was placed in a 105°C oven and dried to constant weight, and then accurately weighed m1. Then the dried sample was respectively placed in 250 mL of deionized water, and was allowed to stand at 25°C for 24 h to ensure that the swelling equilibrium was reached. The excess water was drained until no more water was dripping, and then the mass m2 was immediately weighed. Then the swelling degree SC was calculated according to the formula

[0086] (2) 95°C viscosity retention rate: The sample was added with water to prepare a starch milk, and the Brabender viscometer was used to test the viscosity of the starch milk at room temperature and at 95°C, respectively, and the viscosities were recorded as viscosity I and viscosity II, respectively. The viscosity retention rate was calculated using the ratio of viscosity I to viscosity II.

[0087] (3) Freeze-thaw water separation rate (-18°C / 5 times): 6.00 g of sample was accurately weighed and added with water to prepare a 6% starch milk, which was placed in a 90°C water bath and stirred for 30 min to obtain a uniform transparent starch paste. The starch paste was poured into two weighed 50 mL centrifuge tubes (W0) while hot, and after cooling to room temperature, it was placed in a 4°C refrigerator for cold storage and aging for 24 h to form a starch gel. After taking out, it was weighed again (W1), and the total mass of each sample was accurately recorded;

[0088] Freeze-thaw cycle: The centrifuge tubes were placed in a -18°C low-temperature refrigerator for 18 h, then taken out and thawed in a 25°C constant temperature water bath for 6 h to complete one freeze-thaw cycle. The process was repeated for a total of 5 cycles, and then the sample was placed in a high-speed centrifuge at a speed of 4000 r / min for 30 min. The supernatant was poured out and the residual water in the tube was absorbed with water-absorbing paper.

[0089] Weighing calculation: The total weight of the centrifuge tube and the remaining gel (W2) was weighed. The freeze-thaw water separation rate was calculated according to the following formula: freeze-thaw water separation rate (%) = [(W1-W2) / (W1-W0)]x100%.

[0090] (4) Acid resistance (pH 4.0 viscosity loss): The sample was added with water to prepare a neutral starch milk and a pH=4.0 starch milk, respectively, and the Brabender viscometer was used to test the viscosity, which was recorded as viscosity I and viscosity II, respectively. The viscosity loss was calculated using the formula (viscosity I-viscosity II) / viscosity I.

[0091] ​(5) Chloropropanol residue: tested according to GB / T 5009.191-2016;

[0092] (6) Formaldehyde residue: tested according to GB / T 31604.48-2016;

[0093] (7) Phosphorus residue: tested according to GB / T 5009.268-2016;

[0094] (8) Ash content: tested according to GB / T 5009.4-2016.

[0095] The test results are shown in Tables 1 and 2.

[0096] Table 1. Properties of cross-linked hydroxypropyl starch ether

[0097]

[0098] Table 2. Characteristics of cross-linked hydroxypropyl starch ether

[0099]

[0100] As shown in the table, compared with commercially available products A, B and C hydroxypropyl cross-linked starch ethers, the cross-linked degree of the cross-linked hydroxypropyl starch ether obtained by the method of the present application is significantly improved, and the heat resistance, acid resistance and freeze-thaw stability are also significantly improved, and the ash content is reduced. In addition, the product obtained by the method of the present application has a trace amount of chloropropanol residue of ≤0.12 ppm (reaching the EU limit value) after washing with 70% ethanol, while the phosphorus residue of product A exceeds the limit value by 10 times (EU limit value 50 ppm), the formaldehyde residue (5.8 ppm) of product B produced by using glyoxal as a cross-linking agent is a carcinogenic risk, and the chloropropanol residue of product C is high. Therefore, the cross-linked hydroxypropyl starch ether produced by the method provided by the present application has the advantages of high cross-linking degree, high viscosity retention rate, good freeze-thaw stability, low chloropropanol residue and low ash content, and can meet the industry demand; overcomes the industry pain points of partial gelatinization and by-product residue, realizes the industrialized production of high-stability, food-grade safe hydroxypropyl cross-linked starch ether, and expands the product use range.

[0101] The above description of the embodiments is to facilitate the understanding and use of the invention by those of ordinary skill in the art. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the present application is not limited to the above embodiments, and those skilled in the art can make improvements and modifications to the present application without departing from the scope of the present application.

Claims

1. A process for the preparation of a highly stable cross-linked hydroxypropyl starch ether, characterized in that, The method comprises the following steps: S1, alkalization: starch raw material is configured into starch milk by adding water, and part of the alkalizing agent is stirred to activate; then the temperature is raised to 40-45 DEG C, the remaining alkalizing agent is added, and stirred to mix evenly; S2, etherification: adding etherifying agent, raising the temperature to 50-55 DEG C to carry out the first stage of etherification, and then adding crosslinking agent to carry out the second stage of etherification at the second temperature, the time of the second stage of etherification being 7-9 h; S3, post-treatment: the etherification product is post-treated, and the crosslinked hydroxypropyl starch ether is obtained. In step S1, the alkalizing agent is an aqueous solution of alkali metal hydroxide, the mass concentration of the alkalizing agent is 20-40%, and the mass ratio of alkali metal oxide to starch is (2.2-3):100, based on the weight of alkali metal oxide. In step S1, the part of the alkalizing agent is 50-60% of the total amount of the alkalizing agent. In step S2, the etherifying agent is selected from any one or more of chloroacetic acid, chloromethane, chloroethane, propylene oxide and ethylene oxide, and the mass ratio of the etherifying agent to the starch raw material is (28-35):

100. In step S2, the crosslinking agent is selected from any one or more of phosphorus oxychloride, epichlorohydrin and borax, and the weight ratio of the crosslinking agent to the starch raw material is (0.05-0.15):

100.

2. The production method according to claim 1, characterized by, The starch raw material is selected from any one or more of corn starch, cassava starch and potato starch.

3. The production method according to claim 1, characterized by, The post-treatment comprises: The etherification product is cooled to room temperature, the pH is adjusted to neutral by adding acid, and then the product is washed, dried, and crushed to obtain the crosslinked hydroxypropyl starch ether.

Images