A hydrophobically modified starch ether, its preparation method and application

Abstract

This invention discloses a hydrophobically modified starch ether, its preparation method, and its application. The preparation method of the hydrophobically modified starch ether of this invention includes the following steps: 1) Wetting starch with distilled water, adding dimethyl sulfoxide while stirring, and simultaneously adding alkali solution, then heating at 90℃~100℃ to gelatinize the starch to obtain a starch paste; 2) Adjusting the starch paste to the reaction temperature, adding C12-C14 alkyl glycidyl ether dropwise, maintaining the temperature and stirring to carry out the reaction, adding alkali solution multiple times during the reaction, neutralizing the alkali with acid after the reaction is completed, adding ethanol dropwise to precipitate the starch paste, and then washing, drying, pulverizing, and sieving to obtain the hydrophobically modified starch ether. This invention introduces long-chain hydrophobic groups into hydrophilic starch through ether bonds, obtaining a hydrophobically modified starch ether with high chemical stability, which has broad application prospects in the field of daily chemical products.

Description

Technical Field

[0001] This invention relates to the field of modified starch technology, specifically to a hydrophobic modified starch ether, its preparation method, and its application. Technical Background

[0002] Starch is the most important energy storage substance in green plants in nature. It is widely found in plant seeds, roots and tubers. Some starch can also be found in pollen, fruits and green leaves. As a natural biological macromolecule, it has a wide range of sources and excellent biodegradability.

[0003] Etherified starch is a starch derivative obtained by linking the hydroxyl groups on the anhydrous glucose units of starch to substituents via ether bonds (St-OR). Common products include carboxymethyl starch ether, hydroxyalkyl (hydroxyethyl, hydroxypropyl) starch ether, and cationic starch ether. Carboxymethyl starch ether, due to the introduction of carboxyl groups, enhances the cation exchange capacity of starch, making it suitable for adsorbing heavy metals from wastewater. Carboxymethyl starch also possesses good viscosity stability and is commonly used as a food thickener. Hydroxyethyl and hydroxypropyl starch, by replacing the hydroxyl groups in starch, inhibit the formation of hydrogen bonds within the starch, reducing its retrogradation properties and enhancing viscosity stability. As food additives, they can improve the refrigeration and freeze-thaw stability of food. In the paper industry, they are used for surface sizing and coating, resulting in paper with good gloss, softness, and low drying shrinkage, giving it good printability and writeability. Due to the similarity between amylopectin and human glycogen, hydroxyethyl starch has low rejection by the human body, allowing it to be used in the preparation of human blood plasma substitutes. Etherified starch possesses many excellent properties, and due to the chemical stability of the ether bond, starch ethers are more stable to hydrolysis in alkaline environments than starch esters, thus having a wider range of applications.

[0004] Hydrophobically modified starch is a type of starch derivative with hydrophobic alkane chains as substituents. Currently, the hydrophobic starch prepared by etherification reaction commonly has substituent chain lengths of 2 to 4 carbon atoms, such as hydroxyethyl starch ether, hydroxypropyl starch ether, and hydroxybutyl starch ether. However, there is less research on substituents with higher chain lengths, such as hydrophobic starch ethers with 12 or more carbon atoms, and the reaction results are generally unsatisfactory. They often need to be carried out under high temperature and high pressure conditions, and the reaction time is relatively long.

[0005] In studies on the modification of starch using epoxy etherifying agents with carbon chain lengths of less than four, Jung-Ah Han et al. dissolved NaCl or Na2SO4 in water and added starch, stirred evenly, adjusted the pH to 10.7-11.7, added propylene oxide, sealed and heated to 44-54℃, reacted for 24 h to obtain hydroxypropyl starch, with the highest reaction efficiency of 64.66% (Carbohydrate Polymers, 2006, 64(2):158-162); Gu Benzhi et al. first mixed starch with alkaline solution, heated to 75℃ for gelatinization, added butyl glycidyl ether, and continued to react at 75℃ for 5 h to prepare 2-hydroxy-3-butoxy starch ether, with the highest reaction efficiency of 69.57% (Carbohydrate Polymers, 2012, 87(2):1404-1409); Derong Lin et al. dispersed starch in a 20% sodium sulfate solution, adjusted the pH to 10.50, and then added propylene oxide. The reaction was assisted by microwave with a certain power to obtain hydroxypropyl starch, with the highest reaction efficiency being 86.02% (International Journal of Biological Macromolecules, 2019, 125: 290-299).

[0006] In studies on starch modification using long-chain hydrophobic epoxy etherifying agents, water-oil separation occurs in aqueous reaction systems, with the etherifying agent existing in the form of small droplets. In addition, the long alkane chains at the microscopic level bring greater steric hindrance, which severely limits the reaction between the etherifying agent and the starch hydroxyl groups. Therefore, many studies have adopted strategies such as high temperature and high pressure or long-term stirring reaction to ensure the modification effect. Funke et al. first added an alkaline solution to starch slurry and stirred to obtain starch gel, then added epoxides (C6, C12, C16, C18) and heated to 140°C to react and obtain long-chain hydroxyalkyl starch ethers. The reaction efficiency decreased with increasing chain length (C6, 60-80%; C12, 20-50%; C16, 10%; C18, 7%-15%) (Starch-Starke, 2001, 53(11): 547-554). Gillet et al. used a similar process to Funke to obtain hydroxydodecyl starch ethers with a reaction efficiency of 37% (Industrial & Engineering Chemistry Research, 2019, 58(7): 2437-2444). Bien used a one-pot method to mix starch, sodium sulfate solution, sodium hydroxide solution, and 1,2-epoxide dodecane evenly and heated to 140°C to react and obtain hydroxydodecyl starch ethers with a reaction efficiency of 60% (Starch-Starke, 2001, 53(11): 547-554). 2001, 53(11):555-559); Wesslén first stirred and mixed NaH with DMSO under N2 atmosphere, then added it to the DMSO solution of starch, added dodecyl oxide and reacted at room temperature for 286 h to obtain hydroxydodecyl starch ether, with a reaction efficiency of 86.67% (Carbohydrate Polymers, 2002, 47(4):303-311.). Patent CN202111589062 describes a method for hydrophobic modification of sodium carboxymethyl starch using C8-C10 alkyl glycidyl ether under tertiary amine catalysis in a water-ethanol system, with a reaction efficiency of up to about 30%.

[0007] C12-C14 alkyl glycidyl ether (CAS: 68609-97-2) is a common epoxy diluent with wide industrial applications. Using it as an epoxy etherifying agent to hydrophobically modify starch can attach long-chain hydrophobic groups to starch and avoid the problem of generating toxic waste when using halogenated etherifying agents. It is expected to have better hydrophobic properties than hydroxyethyl and hydroxypropyl starch ethers at the same degree of substitution. Moreover, the process of this invention can significantly improve the reaction efficiency of starch modification using long-chain epoxy etherifying agents without the need for harsh conditions of high temperature and high pressure, with a maximum of 98.50%. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a hydrophobically modified starch ether with high reaction efficiency and high raw material utilization, as well as its preparation method and application.

[0009] The technical solution adopted in this invention is:

[0010] A method for preparing a hydrophobically modified starch ether includes the following steps:

[0011] 1) Moisten the starch with distilled water, add dimethyl sulfoxide while stirring, and add alkaline solution dropwise. Then heat at 90℃~100℃ to gelatinize the starch to obtain starch paste.

[0012] 2) Adjust the starch paste to the reaction temperature, add C12-C14 alkyl glycidyl ether dropwise, keep warm and stir to carry out the reaction, add alkali solution in several batches during the reaction, neutralize the alkali with acid after the reaction is completed, add ethanol dropwise to precipitate the starch paste, and then wash, dry, crush and sieve to obtain hydrophobic modified starch ether.

[0013] Preferably, a method for preparing a hydrophobically modified starch ether includes the following steps:

[0014] 1) First, wet the starch with distilled water, then add dimethyl sulfoxide (DMSO) while stirring, and slowly add 1 / 3 of the total amount of alkali solution to obtain an alkali-containing starch dispersion. Then heat to 95°C to completely gelatinize the starch.

[0015] 2) Adjust the starch paste to the reaction temperature, add a fixed amount of C12-C14 alkyl glycidyl ether, keep warm and stir to carry out the reaction. Add the remaining 2 / 3 of the alkali solution in two batches during the reaction. After the reaction is completed, neutralize the remaining alkali in the system with acetic acid solution, add ethanol dropwise to precipitate the starch paste, and then wash, dry, crush and sieve to obtain hydrophobic modified starch ether.

[0016] Preferably, a method for preparing a hydrophobically modified starch ether includes the following steps:

[0017] 1) First, wet the starch with distilled water, then add dimethyl sulfoxide (DMSO) while stirring, and slowly add 1 / 3 of the total amount of alkali solution to obtain an alkali-containing starch dispersion. Then heat to 95°C to completely gelatinize the starch.

[0018] 2) Adjust the starch paste temperature to the reaction temperature, and slowly add a portion of C12-C14 alkyl glycidyl ether to initiate the reaction. Then, add the remaining alkali solution and C12-C14 alkyl glycidyl ether at 6h and 12h respectively, and continue the reaction at this temperature for 12h. After the reaction is complete, neutralize the excess alkali with acetic acid solution, and then slowly add the starch paste dropwise to at least three times its volume of anhydrous ethanol for precipitation. Subsequently, wash with 50% ethanol, 75% ethanol, and anhydrous ethanol, dry, pulverize, and sieve to obtain hydrophobically modified starch.

[0019] Preferably, the starch in step 1) is one of the plant starches extracted from corn, wheat, cassava, rice, potato and sweet potato.

[0020] Preferably, in the starch paste of step 1), the mass ratio of DMSO to water is 2:1 to 9:1.

[0021] Preferably, in the starch paste of step 1), the mass of starch is 5% to 10% of the total mass of dimethyl sulfoxide, water and starch;

[0022] Preferably, the heating and gelatinization time in step 1) is 0.5h to 1h.

[0023] Preferably, the alkali in steps 1) and 2) is sodium hydroxide; the total amount of alkali added is in a mass ratio of 1:2 to 1:10 with respect to starch.

[0024] More preferably, the amount of alkali added in step 1) is 25%-40% of the total amount of alkali added in steps 1) and 2).

[0025] Preferably, the mass concentration of the alkaline solution in steps 1) and 2) is 10%-20%;

[0026] Preferably, the mass ratio of the C12-C14 alkyl glycidyl ether added in step 2) to the starch is 1:2 to 1:10.

[0027] Preferably, the C12-C14 alkyl glycidyl ether in step 2) is added in multiple batches by dripping.

[0028] Preferably, the reaction temperature in step 2) is 60℃~100℃, and the reaction time is 12h~60h.

[0029] Preferably, the acid in step 2) is an acetic acid solution.

[0030] Preferably, the washing in step 2) is performed 2-3 times by stirring and centrifugation with 50%, 75% and anhydrous ethanol solutions.

[0031] Preferably, the drying temperature in step 2) is 50°C.

[0032] Preferably, the sieving in step 2) is sieve 100 mesh.

[0033] A hydrophobically modified starch ether is prepared by the above-described preparation method.

[0034] The above-mentioned hydrophobically modified ethers are used in the preparation of personal care products.

[0035] The principle of this invention:

[0036] Starch is dissolved by heating with DMSO, which disrupts its crystalline structure and exposes a large number of hydroxyl groups. Then, concentrated sodium hydroxide solution is added to promote the breakdown of hydrogen bonds and simultaneously alkalize the hydroxyl groups on the starch into oxonions. These oxonions act as nucleophiles, attacking the unstable epoxy groups on C12-C14 alkyl glycidyl ethers, causing a specific nucleophilic substitution reaction that generates starch ether. The specific reaction formula is as follows:

[0037]

[0038] Compared with other preparation techniques for etherified starch, the advantages of this invention are:

[0039] (1) In this invention, an alkane chain with more than 12 carbons is attached to the hydrophilic starch molecule through an etherification reaction. Due to the high chemical stability of the ether bond, a hydrophobic starch with excellent hydrophobic properties and wide applicability is obtained.

[0040] (2) The DMSO of the present invention is a strong polar organic solvent that can dissolve starch and also has a certain solubility for hydrophobic etherifying agents. A certain mass fraction of DMSO aqueous solution can not only make the reaction proceed in a homogeneous form, but also limit the hydrolysis side reaction of epoxy groups in alkaline water environment, and promote the main reaction in the modification.

[0041] (3) The preparation process of this invention is simple and the raw material utilization rate is high. The reaction efficiency can reach up to 98.49% at 80℃, which overcomes the high energy consumption and high waste problems caused by the traditional wet process of hydrophobic etherified starch using high temperature and high pressure strategy to promote etherification. Attached Figure Description

[0042] Figure 1 The original starch and the hydrophobic starch ether prepared in Example 5 1 H-NMR spectrum (left) and structural formula of hydrophobic starch ether (right).

[0043] Figure 2 FTIR images of native starch and the hydrophobic starch ether prepared in Example 5. Detailed Implementation

[0044] The present invention will be further explained and described below with reference to specific embodiments.

[0045] Example 1:

[0046] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0047] (1) Dissolve 0.57g sodium hydroxide in 4.19g distilled water to prepare an alkaline solution, and then wet and disperse 5.81g of ordinary corn starch with 5g distilled water. Slowly pour 90g DMSO into the starch slurry while stirring, and slowly add 1.59g alkaline solution dropwise. Then heat at 95℃ for 0.5h to gelatinize and obtain starch paste.

[0048] (2) Weigh 1.74 g of alkyl (C12) glycidyl ether, adjust the starch paste temperature to 90 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.59 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0049] Example 2:

[0050] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0051] (1) Dissolve 0.91g of sodium hydroxide in 4.19g of distilled water to prepare an alkaline solution, and then wet and disperse 5.81g of ordinary corn starch with 5g of distilled water. Slowly pour 90g of DMSO into the starch slurry while stirring, and slowly add 1.70g of alkaline solution dropwise. Then heat at 95℃ for 0.5h to gelatinize and obtain starch paste.

[0052] (2) Weigh 1.74 g of alkyl (C12) glycidyl ether, adjust the starch paste temperature to 80 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.70 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0053] Example 3:

[0054] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0055] (1) Prepare an alkaline solution by dissolving 0.74g of sodium hydroxide in 4.19g of distilled water, and then wet and disperse 5.81g of ordinary corn starch with 15g of distilled water. Slowly pour 80g of DMSO into the starch slurry while stirring, and slowly add 1.64g of alkaline solution dropwise. Then heat at 95℃ for 0.5h to gelatinize and obtain starch paste.

[0056] (2) Weigh 1.74 g of alkyl (C12) glycidyl ether, adjust the starch paste temperature to 90 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.64 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0057] Example 4:

[0058] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0059] (1) Dissolve 0.91g of sodium hydroxide in 4.19g of distilled water to prepare an alkaline solution, and then wet and disperse 5.81g of ordinary corn starch with 15g of distilled water. Slowly pour 80g of DMSO into the starch slurry while stirring, and slowly add 1.70g of alkaline solution dropwise. Then heat at 95℃ for 0.5h to gelatinize and obtain starch paste.

[0060] (2) Weigh 1.74 g of alkyl (C14) glycidyl ether, adjust the starch paste temperature to 70 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.70 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0061] Example 5:

[0062] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0063] (1) Dissolve 0.74g of sodium hydroxide in 4.19g of distilled water to prepare an alkaline solution, and then wet and disperse 5.81g of ordinary corn starch with 25g of distilled water. Slowly pour 70g of DMSO into the starch slurry while stirring, and slowly add 1.64g of alkaline solution dropwise. Then heat at 95℃ for 0.5h to gelatinize and obtain starch paste.

[0064] (2) Weigh 1.74 g of alkyl (C12) glycidyl ether, adjust the starch paste temperature to 80 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.64 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0065] Comparative Example 1:

[0066] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0067] (1) Dissolve 0.74g of sodium hydroxide in 4.19g of distilled water to prepare an alkaline solution, and then wet and disperse 5.81g of ordinary corn starch with 25g of distilled water. Slowly pour 70g of DMSO into the starch slurry while stirring, and slowly add 1.64g of alkaline solution dropwise. Then heat at 95℃ for 0.5h to gelatinize and obtain starch paste.

[0068] (2) Weigh 1.74 g of alkyl (C12) glycidyl ether, adjust the starch paste temperature to 50 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.64 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0069] Comparative Example 2:

[0070] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0071] (1) Prepare an alkaline solution by dissolving 0.57g sodium hydroxide in 4.19g distilled water, and then wet and disperse 5.81g of ordinary corn starch with 35g distilled water. Slowly pour 60g DMSO into the starch slurry while stirring, and slowly add 1.59g alkaline solution dropwise. Then heat at 95℃ for 0.5h to gelatinize and obtain starch paste.

[0072] (2) Weigh 1.74 g of alkyl (C12) glycidyl ether, adjust the starch paste temperature to 70 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.59 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0073] Comparative Example 3:

[0074] A hydrophobically modified starch ether, the preparation method of which includes the following steps:

[0075] (1) Dissolve 0.74g sodium hydroxide in 4.19g distilled water to prepare an alkaline solution. Then disperse 5.81g of ordinary corn starch in 95g distilled water to form a starch slurry. While stirring, slowly add 1.64g of alkaline solution. Then heat at 95℃ for 0.5h to gelatinize and obtain an alkaline starch paste.

[0076] (2) Weigh 1.74 g of alkyl (C14) glycidyl ether, adjust the starch paste temperature to 80 °C, and slowly add 0.58 g of alkyl glycidyl ether to start the reaction. Then, add 1.64 g of alkali solution and 0.58 g of alkyl glycidyl ether again at 6 h and 12 h respectively, and keep warm for 12 h to continue the reaction. After the reaction is completed, neutralize with acetic acid, and then slowly add the starch paste to 350 mL of anhydrous ethanol for precipitation. Then wash with 50%, 75% and anhydrous ethanol respectively, dry, pulverize and sieve to obtain hydrophobic modified starch.

[0077] Performance testing:

[0078] The hydrophobically modified starch ethers of each embodiment and comparative example were subjected to performance tests, and the test methods were as follows:

[0079] Molar substitution degree: The starch sample was dissolved in 90% (m / m) DMSO by heating, and the starch precipitate was recovered in ethanol. After washing, drying and pulverizing, a defatted sample was obtained. 4 mg of the defatted sample was dissolved in 550 μL of d6-DMSO by heating in a glass test tube. After cooling, 20 μL of d-TFA was added, mixed well, and the entire liquid was transferred to an NMR tube for 600 MHz analysis. 1 H-NMR. Integral calculation 1 The peak areas at σ = 0.85 ppm, 5.11 ppm, and 4.75 ppm in the H-NMR spectrum are used to calculate the molar substitution degree (MS) using formula (1-1):

[0080]

[0081] The reaction efficiency RE is calculated according to formula (1-2):

[0082]

[0083] Contact angle: Starch was pressed into discs using a powder tablet press. The contact angle of 85% (m / m) glycerol aqueous solution on the disc surface was measured using a Biolin Theta Flex contact angle meter. Each sample was measured three times and the average value was taken.

[0084] The test results are shown in the table below:

[0085] Table 1 Performance test results of hydrophobic modified starch ether

[0086]

[0087] As shown in Table 1, compared with native starch (NMS), the molar substitution degree of the hydrophobic starch ethers prepared in Examples 1 to 5 ranged from 0.1448 to 0.1970. Among them, Example 5 had the highest reaction efficiency of 98.49%. After modification, the contact angle of the sample increased from 32.90° to about 102.61°, showing good hydrophobic properties.

[0088] Comparing Example 5 with Comparative Example 1, it is evident that lowering the reaction temperature in Comparative Example 1 significantly reduced the reaction efficiency, with a molar substitution degree of only 0.0481. Comparing Example 5 with Comparative Examples 2, 1, 2, and 3, it is clear that the water content, alkali content, and reaction temperature of the reaction system need to be controlled within certain ranges to achieve high reaction efficiency. Comparative Example 3, with similar preparation parameters to Example 5, differed most notably in the absence of DMSO, resulting in a significant decrease in reaction efficiency. The reason for the decrease in reaction efficiency mentioned above is that long-chain epoxy etherifying agents require more energy to reach and overcome the activation energy barrier due to greater steric hindrance. Therefore, a decrease in reaction temperature leads to a decrease in the efficiency of the main reaction. However, excessively high temperatures can exacerbate the hydrolysis side reaction of epoxy groups, which can also decrease the efficiency of the main reaction. The water content of the reaction system, i.e., the final DMSO concentration, affects the solubility of alkyl glycidyl ethers by controlling the polarity of the solution. When the water content of the system increases, the solution polarity becomes stronger, causing the alkyl glycidyl ethers to separate into two phases and disperse in the reaction system as small droplets. The probability of contact with starch hydroxyl groups is small, resulting in a decrease in reaction efficiency. However, water also participates in the etherification reaction to some extent. Therefore, too low a water content will also lead to a decrease in reaction efficiency. Maintaining a certain water content is necessary to achieve a high reaction efficiency.

[0089] The theoretical structure of the hydrophobically modified starch ether prepared in Example 5 of this invention and 1 H-NMR spectrum as shown Figure 1 As shown in the figure, compared to native starch, the hydrophobically modified starch ether exhibits characteristic peaks of long-chain alkyl groups, specifically a terminal methyl peak of a long-chain alkane structure at 0.85 ppm (H-21), accompanied by a methylene characteristic peak at 1.22 ppm (H-(11-20)). Integrating the peak areas of the corresponding terminal methyl and methylene characteristic peaks, the ratio of terminal methyl (-CH3) to methylene (-CH2-) is found to be 1:10.79, consistent with a long-chain structure of 12 carbons. In conclusion, the 1H NMR results confirm that the product conforms to this theoretical structure.

[0090] The FTIR spectrum of the hydrophobically modified starch ether prepared in Example 5 of this invention is as follows: Figure 2As shown in the figure, the infrared spectra of native starch and hydrophobically modified starch ether show changes at three main positions: 1. Compared to native starch, the hydroxyl stretching vibration peak at wavenumber 3270 shifts to the left, indicating that the hydrogen bond interactions within the starch are weakened after modification. 2. The CH bond stretching vibration peak at wavenumber 2930 changes significantly, indicating the successful introduction of long-chain alkyl groups. 3. The peak at wavenumber 1022 is significantly enhanced. In the infrared spectrum, the peak intensity ratio of 1047 / 1022 at wavenumbers 1047 and 1022 reflects the short-range order of starch. In this experiment, the hydrophobically modified starch ether underwent gelatinization and ethanol precipitation, which disrupted the structure of native starch particles and reduced short-range order; therefore, the change in peak intensity at this position is as expected.

[0091] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing hydrophobically modified starch ether, characterized in that, Includes the following steps: 1) Wet the starch with distilled water, add dimethyl sulfoxide while stirring, and simultaneously add alkali solution dropwise. Then heat at 90°C to 100°C to gelatinize the starch to obtain a starch paste; the mass ratio of dimethyl sulfoxide to water is 2:1 to 9:1; the mass of starch is 5% to 10% of the total mass of dimethyl sulfoxide, water, and starch. 2) Adjust the starch paste to the reaction temperature, add C12-C14 alkyl glycidyl ether dropwise, keep warm and stir to carry out the reaction, add alkali solution in several batches during the reaction, neutralize the alkali with acid after the reaction is completed, add ethanol dropwise to precipitate the starch paste, and then wash, dry, crush and sieve to obtain hydrophobic modified starch ether; the reaction temperature is 60°C ~ 100°C; the total amount of alkali added to the mass ratio of starch is 1:2 ~ 1:

10.

2. The method for preparing hydrophobically modified starch ether according to claim 1, characterized in that: In step 1), the heating and gelatinization time in the starch paste is 0.5 h to 1 h.

3. The method for preparing hydrophobically modified starch ether according to claim 1, characterized in that: The base mentioned in steps 1) and 2) is sodium hydroxide.

4. The method for preparing hydrophobically modified starch ether according to claim 1, characterized in that: Step 2) The mass ratio of the C12-C14 alkyl glycidyl ether added to the starch is 1:2 to 1:

10.

5. The method for preparing hydrophobically modified starch ether according to claim 1, characterized in that: Step 2) The C12-C14 alkyl glycidyl ether is added in multiple batches.

6. The method for preparing hydrophobically modified starch ether according to claim 1, characterized in that: Step 2) The reaction time is 12 h ~ 60 h.

7. The method for preparing hydrophobically modified starch ether according to claim 1, characterized in that: Step 2) The acid is an acetic acid solution.

8. The application of the hydrophobically modified starch ether prepared by any one of claims 1-7 in the preparation of personal care products.

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