Preparation method of high-viscosity cationic starch

Abstract

The invention discloses a preparation method of high-viscosity cationic starch, which belongs to the technical field of modified starch, and comprises the following steps: crosslinking epichlorohydrin, ball-milling and cationizing; the epoxy chloropropane crosslinking comprises the following steps: mixing starch, calcium hydroxide and deionized water, stirring at 40-50 DEG C, adding sodium stearoyl lactylate, stirring at 50-55 DEG C, naturally cooling to room temperature, adding sodium chloride and epoxy chloropropane, stirring, dropwise adding a potassium hydroxide aqueous solution, stirring, adjusting the pH value to 6, filtering, taking filter residues, washing and drying to obtain crosslinked starch; in the step of ball milling, calcium hydroxide, sucrose fatty acid ester SE-11 and deionized water are mixed and then subjected to ball milling, and a ball-milled material is obtained; the prepared high-viscosity cationic starch is high in paste liquid viscosity and cationic substitution degree, good in paste liquid viscosity stability, uniform in substitution degree and paste liquid viscosity, high in reaction efficiency in cationization and low in alkali consumption.

Description

Technical Field

[0001] This invention relates to the field of modified starch technology, and more specifically to a method for preparing high-viscosity cationic starch. Background Technology

[0002] Starch is a natural high-molecular-weight carbohydrate composed of a single type of sugar unit. Its basic building block is α-D-glucose, which forms starch molecules after glucose loses water and is linked by glycosidic bonds. Starch generally exists in the form of granules with a diameter of 1-10 μm or larger, and these starch granules are mainly deposited in the seeds, tubers, and roots of plants. Starch is not a homogeneous substance, but is composed of two very different polymers—amylose and amylopectin. Amylose is a linear polymer with a molecular weight of hundreds of thousands to millions, and its glucose residues are linked by α-D-(1→4) glycosidic bonds; amylopectin is a branched polymer with a molecular weight of millions, and most of its glucose residues are linked by α-D-(1→4) glycosidic bonds, while 2-4% of the glucose residues are linked by α-D-(1→6) glycosidic bonds.

[0003] Natural starch is a water-soluble polymer. Although it possesses certain adhesive and film-forming properties and is used industrially, these properties are quite limited, especially in meeting the requirements of modern new technologies, processes, and equipment. To improve starch performance, the most common method is to modify natural starch to create starch derivatives. For example, oxidizing natural starch yields oxidized starch with good adhesive properties, which is used in adhesive preparation; grafting cationic groups onto natural starch produces cationic starch with strong adsorption capacity for negatively charged substances, which is used in the preparation of paper strengthening agents, retention aids, and filter aids; and grafting hydrophobic groups onto natural starch produces hydrophobic starch, which is used in the preparation of biodegradable plastics. Starch derivatives are now widely used in various industries.

[0004] Cationic starch is prepared by reacting starch with cationizing reagents containing amino, imino, ammonium or phosphine under alkaline conditions. The commonly used cationizing reagents are 3-chloro-2-hydroxypropyltrimethylammonium chloride and 2,3-epoxypropyltrimethylammonium chloride. In an alkaline medium, 3-chloro-2-hydroxypropyltrimethylammonium chloride can lose one molecule of hydrogen chloride to convert it into 2,3-epoxypropyltrimethylammonium chloride. Regarding cationizing agents, as mentioned in the article "Preparation and Application Research of Highly Substituted Cationic Starch" by Ben Zhi, Dalian University of Technology, December 2000, 3-chloro-2-hydroxypropyltrimethylammonium chloride was frequently used in the past. However, recent research reports have primarily used 2,3-epoxypropyltrimethylammonium chloride. The reason for this shift is likely that using 3-chloro-2-hydroxypropyltrimethylammonium chloride requires converting it to 2,3-epoxypropyltrimethylammonium chloride during the reaction, necessitating at least one mole of base. This inevitably results in a large amount of salts in the reaction product, requiring substantial amounts of solvent to remove these impurities, increasing costs and causing environmental pollution. Furthermore, the reaction efficiency of 3-chloro-2-hydroxypropyltrimethylammonium chloride is lower. Therefore, 2,3-epoxypropyltrimethylammonium chloride is now the most commonly used cationizing agent.

[0005] Regarding the preparation methods of cationic starch, as described in "Research on the Preparation and Application of High-Substitution Cationic Starch" by Ben Zhi, Dalian University of Technology, December 2000, the commonly used methods are the organic solvent method, the aqueous solvent method, and the dry method. The organic solvent method and the aqueous solvent method have the advantages of mild reaction conditions, simple production equipment, and high reaction conversion rate. However, they also have the following drawbacks: First, the cationizing reagent used must be purified; otherwise, residual epichlorohydrin and byproducts will affect the quality of the cationic starch. Second, chemical reagents, such as catalysts and anti-gelling agents, must be added during preparation. Third, the post-processing is complex, requiring a large amount of water for washing and drying. The dry method involves spraying a mixture of cationizing reagent and alkali onto dry starch and stirring at 60-80℃ to obtain cationic starch. Compared with the organic solvent method and the aqueous solvent method, the dry method has the following advantages: First, the cationizing reagent used does not need to be purified; second, no chemical reagents need to be added during preparation; third, the post-processing is simple, and there are basically no waste problems. Furthermore, the dry process has the advantages of mild reaction conditions and high conversion rate. Therefore, in the preparation of cationic starch, especially in the preparation of highly substituted cationic starch, the dry process is currently the most widely used preparation method.

[0006] Regarding the technical specifications of cationic starch, as described in "Preparation and Application Research of High-Substitution Cationic Starch" by Ben Zhi, Dalian University of Technology, December 2000, the most important technical indicators are the degree of substitution and the viscosity of the paste. Among these, the paste viscosity is an easily measurable indicator that reflects the performance characteristics of cationic starch. The paste viscosity not only reflects the degree of substitution of cationic starch but also the degree of degradation and cross-linking of starch during the preparation reaction. Under certain conditions, the paste viscosity and the degree of substitution have a good correlation; an increase in the degree of substitution leads to a rapid increase in paste viscosity. This is due to the enhanced interaction between quaternary ammonium cations and starch hydroxyl groups in the paste. When the temperature and moisture content of the paste are constant, a higher paste viscosity indicates a higher degree of substitution and molecular weight of cationic starch, and a greater degree of cross-linking.

[0007] Furthermore, as Zhu Weiqun et al. stated in their study on the synthesis and paste viscosity of cationic starch (Shandong Chemical Industry, February 1998), there is a certain correlation between the degree of substitution and the viscosity of the paste. The degree of substitution can be inferred by conveniently testing the paste viscosity. Moreover, the paste viscosity test can be completed within half an hour, while the degree of substitution test takes longer. Therefore, the paste viscosity test can serve as a simple method for controlling the industrial production of cationic starch. Thus, high-viscosity cationic starch possesses characteristics of high degree of substitution, high molecular weight, and high degree of cross-linking. Currently, the demand for high-viscosity cationic starch is increasing, especially when it is used as a fixing agent, retention aid, flocculant, dehydrating agent, dispersant, and natural gum compound. In these applications, cationic starch with high degree of substitution and high molecular weight is required, i.e., high-viscosity cationic starch is needed.

[0008] Furthermore, as mentioned in Quan Yi et al.'s "Synthesis and Functional Properties of Crosslinked Cationic Corn Starch," *Journal of Jiangsu Petroleum and Chemical Engineering*, December 1996, cationic starch is widely used as a wet-end additive in the papermaking industry to increase paper strength and improve particle retention. It is also a good filler. However, the viscosity of cationic starch varies greatly between 50-95℃, affecting the stability of its paste viscosity. Crosslinking increases both the paste viscosity and its stability. Further, Chinese patent CN102382197B discloses a method for preparing high-viscosity cationic starch. By organically combining etherification, crosslinking, and acidification—three modification methods—the process design is scientifically sound, attaching multiple chemical bonds to the starch molecule structure, resulting in high starch paste viscosity and high acid and alkali resistance. This indicates that appropriate crosslinking during the preparation of high-viscosity cationic starch can improve the stability of the paste viscosity.

[0009] However, when combining etherification and crosslinking methods to prepare high-viscosity cationic starch via a dry process, the following problems arise: First, as mentioned in Quan Yi et al.'s "Synthesis and Functional Properties of Crosslinked Cationic Corn Starch," *Journal of Jiangsu Petroleum and Chemical Engineering*, December 1996, there are two methods for preparing crosslinked cationic corn starch: cationization followed by crosslinking and crosslinking followed by cationization. In the cationization followed by crosslinking method, the viscosity of the prepared crosslinked cationic corn starch is greatly affected by the crosslinking agent. However, in the crosslinking followed by cationization method, since there are still a large number of hydroxyl groups available for cationization after crosslinking, the crosslinking has little effect on the cationization reaction rate. Therefore, the commonly used method for preparing crosslinked cationic corn starch is crosslinking followed by cationization. However, as described in "Preparation and Application Research of Highly Substituted Cationic Starch" by Ben Zhi, Dalian University of Technology, December 2000, when using the cross-linking followed by etherification method, it is difficult to expand or relax the cross-linked starch granules. If the expansion or relaxation of the starch granules is insufficient, it is not conducive to the penetration of the cationizing agent into the starch granules. Therefore, more alkali catalyst is required. However, as described in "Performance Study of Highly Substituted Cationic Starch" by Zhang Peng, Shandong University, May 2010, as the amount of alkali increases, the cationization reaction efficiency and the degree of substitution increase proportionally. But when the amount of alkali exceeds a certain level, it will cause the hydrolysis reaction of epoxy groups and quaternary ammonium groups in the cationizing agent, and at the same time accelerate the decomposition of the formed cationic starch, which will reduce the reaction efficiency. Furthermore, it will lead to a decrease in the reaction efficiency in cationization and a decrease in the viscosity of the prepared high-viscosity cationic starch paste.

[0010] Secondly, as mentioned in Qi Xiaoyan et al.'s "Research on the Preparation of Cationic Starch by Novel Dry Process" (Chinese Journal of Cereals and Oils, February 2012), although the dry process has advantages such as low water consumption, high yield, and no pollution, the reaction reagents are difficult to penetrate into the starch granules, resulting in uneven substitution degree of the prepared cationic starch. Furthermore, this leads to uneven substitution degree and paste viscosity of the prepared high-viscosity cationic starch.

[0011] To address the aforementioned issues, commonly used methods include, for example, Feng Bo's study on the preparation of cross-linked cationic cassava starch and its effect on Cr in wastewater. 6+Adsorption studies. Science, Technology and Engineering. March 2014 and, as mentioned in Luo Wenzheng et al. Application of microwave technology in the dry-process production of high-viscosity, high-substitution-degree cationic starch. China High-tech Enterprises. December 2016, the reaction between cross-linked starch and cationizing agents is promoted by ultrasound or microwave to reduce the amount of alkali used and promote the penetration of cationizing agents into the starch granules. However, as mentioned in Zhang Hui. Study on the relationship between preparation method and physicochemical properties and substituent group distribution of cationic starch. Shandong Agricultural University. May 2016, cationic starch prepared by different processes... The degree of unevenness in the distribution of substituent groups is: ultrasonic wet process > microwave dry process > dry process. The reason may be that the dry process destroys part of the starch crystalline region, so the substituents can enter the molecular chain of the crystalline region. However, the ultrasonic wet process and microwave dry process destroy the crystalline region less, so most of the substituents are distributed in the non-crystalline region, resulting in a concentrated distribution of substituents. The high degree of unevenness can lead to the degradation of amylopectin during the preparation. In addition, ultrasound and microwaves themselves can also cause the degradation of amylopectin. Furthermore, the degradation of amylopectin will lead to a decrease in the viscosity of the prepared high-viscosity cationic starch paste. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention provides a method for preparing high-viscosity cationic starch. The high-viscosity cationic starch prepared has high paste viscosity and cationic substitution degree, good paste viscosity stability, uniform substitution degree and paste viscosity, high reaction efficiency in cationization, and low alkali consumption.

[0013] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing high-viscosity cationic starch comprises the following steps: epichlorohydrin crosslinking, ball milling, and cationization; The epichlorohydrin crosslinking process involves mixing starch, calcium hydroxide, and deionized water, stirring at 40-50°C for 1-1.5 hours at a stirring speed of 100-300 rpm, adding sodium stearoyl lactylate, stirring at 50-55°C for 2-3 hours, allowing it to cool naturally to room temperature, adding sodium chloride and epichlorohydrin, stirring for 0.5-1 hours, adding potassium hydroxide aqueous solution dropwise, continuing to stir for 18-20 hours after the addition is complete, adjusting the pH to 6, filtering, taking the filter residue, washing the filter residue 2-3 times with deionized water, and drying to obtain crosslinked starch. In the epichlorohydrin crosslinking process, the starch is one of corn starch, cassava starch, wheat starch, and potato starch. The mass concentration of the potassium hydroxide aqueous solution is 80%. The mass ratio of oven-dried starch, calcium hydroxide, deionized water, sodium stearoyl lactylate, sodium chloride, epichlorohydrin, and potassium hydroxide aqueous solution in starch is 100:0.45-0.5:150-160:0.6-0.7:2.8-3:0.4-0.5:11-12. The potassium hydroxide aqueous solution is added dropwise over a period of 10-15 minutes. Use glacial acetic acid to adjust the pH to 6. The ball milling process involves mixing calcium hydroxide, sucrose fatty acid ester SE-11, and deionized water, followed by ball milling to obtain the ball milling material. In the ball milling process, the mass ratio of calcium hydroxide, sucrose fatty acid ester SE-11, and deionized water is 0.45-0.5:0.5-0.6:9-10. In ball milling, agate grinding balls with a diameter of 6mm are used, the ball milling speed is 400-450rpm, the ball-to-material ratio is 3-4:1, and the ball milling time is 10-15min; The cationization process involves mixing ball milled material and cross-linked starch, stirring at 60-65°C for 10-15 minutes at a stirring speed of 200-300 rpm, adding a mixture of 2,3-epoxypropyltrimethylammonium chloride, potassium hydroxide, and deionized water, and continuing stirring for 3.5-4 hours. The mixture is then removed, the pH is adjusted to 6.5-7, dried, and repeatedly washed with an ethanol-water solution and filtered until the filtrate is free of chloride ions. After drying, high-viscosity cationic starch is obtained. The mass ratio of the oven-dried starch in the starch used in the epichlorohydrin crosslinking, the calcium hydroxide used in the ball milling, and the 2,3-epoxypropyltrimethylammonium chloride, potassium hydroxide, and deionized water in the mixture used in the cationization is 100:0.45-0.5:54-56:28-30:52-55. During the cationization process, a 1 mol / L hydrochloric acid aqueous solution is used to adjust the pH value to 6.5-7. During drying, dry until the moisture content is 12-14%; The volume concentration of the ethanol aqueous solution is 80%.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) As mentioned by Xiao Luting et al., Effect of Ca(OH)2 on the gel properties of rice starch. Food and Fermentation Industries, August 2022, Ca 2+At low concentrations, it can promote the dissolution of amylose and enhance the mechanical strength of swollen starch granules through "cross-linking" with amylose molecules via van der Waals forces; as described by Gong Benqian et al., "The Influence of Emulsifiers on the Retrogradation Characteristics of Glutinous Wheat Starch," China Food Additives, April 2012, amylose and emulsifiers can form complexes, and different emulsifiers can be compounded. This invention first utilizes the effect of calcium ions to promote the dissolution of amylose, then adds the emulsifier sodium stearoyl lactylate, which can fix the amylose by complexing with it, and then uses epichlorohydrin for cross-linking to achieve uniform cross-linking between starches. As described by Tang Peipei et al., "The Effect of Calcium Hydroxide on Gelatinization of Corn Flour," *Food Science and Technology*, September 2016, at higher pH levels, calcium hydroxide can interact with starch and promote starch swelling. The emulsifier sucrose fatty acid ester SE-11 can bind to calcium hydroxide, improving its fluidity, and can also be combined with the emulsifier sodium stearoyl lactylate to further complex with amylose, promoting starch structure relaxation. Furthermore, this facilitates the penetration of cationizing agents into the starch granules, shortens cationization time, reduces alkali usage, and improves the uniformity of the cationization reaction. (2) The preparation method of the present invention uses less alkali; the 2% paste of high viscosity cationic starch obtained has a viscosity of 19100-21500 mPa•s, a nitrogen content of 3.012-3.124%, a degree of substitution of 0.506-0.535, a reaction efficiency of 87.63-90.93%, a paste viscosity thermal stability of 96.6-97.5%, and good uniformity of paste viscosity and nitrogen content. Detailed Implementation

[0015] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0016] The corn starch used in Examples 1-3 and Comparative Examples 1-3 was from the same production batch, and the moisture content of the corn starch was 12% and the nitrogen content was 0.05%.

[0017] Example 1 A method for preparing high-viscosity cationic starch specifically includes the following steps: Step 1: Epichlorohydrin crosslinking 113.6g of corn starch (including 100g of oven-dried corn starch), 0.45g of calcium hydroxide, and 150g of deionized water were added to a three-necked flask. The temperature in the three-necked flask was controlled at 40℃, and the stirring speed was controlled at 100rpm. The mixture was stirred for 1 hour. Then, 0.6g of sodium stearoyl lactylate was added to the three-necked flask, and the temperature in the three-necked flask was controlled at 50℃. The mixture was stirred for 2 hours. The temperature in the three-necked flask was allowed to cool naturally to room temperature. 2.8g of sodium chloride and 0.4g of epichlorohydrin were added to the three-necked flask, and the mixture was stirred for 0.5 hours. 11g of 80% potassium hydroxide aqueous solution was added dropwise to the three-necked flask, and the addition time was controlled at 10min. After the addition was completed, the mixture was stirred for 18 hours. Glacial acetic acid was added to the three-necked flask to adjust the pH value to 6. The mixture was filtered, and the filter residue was washed twice with deionized water and dried to obtain cross-linked starch. Step 2: Ball milling Add 0.45g calcium hydroxide, 0.5g sucrose fatty acid ester SE-11, and 9g deionized water to a ball mill. Use agate grinding balls with a diameter of 6mm. Control the ball mill speed to 400rpm, the ball-to-material ratio to 3:1, and ball mill for 10min to obtain the ball milling material. Step 3: Cationicization Add all the ball milling material obtained in step 2 and all the cross-linked starch obtained in step 1 to a mixer. Control the temperature in the mixer to 60℃ and the stirring speed to 200 rpm. Stir for 10 min. Then add a mixture of 54 g of 2,3-epoxypropyltrimethylammonium chloride, 28 g of potassium hydroxide and 52 g of deionized water to the mixer. Continue stirring for 3.5 h. Remove the mixture and add 1 mol / L hydrochloric acid aqueous solution to adjust the pH value to 6.5. Dry the mixture until the moisture content is 12%. Then wash and filter the mixture repeatedly with 80% ethanol aqueous solution until the filtrate is free of chloride ions. Dry the mixture to obtain high-viscosity cationic starch.

[0018] Example 2 A method for preparing high-viscosity cationic starch specifically includes the following steps: Step 1: Epichlorohydrin crosslinking 113.6g of corn starch (including 100g of oven-dried corn starch), 0.47g of calcium hydroxide, and 155g of deionized water were added to a three-necked flask. The temperature in the three-necked flask was controlled at 45℃, and the stirring speed was controlled at 200rpm. The mixture was stirred for 1.5h. Then, 0.65g of sodium stearoyl lactylate was added to the three-necked flask. The temperature in the three-necked flask was controlled at 52℃, and the mixture was stirred for 2.5h. The temperature in the three-necked flask was allowed to cool naturally to room temperature. 2.9g of sodium chloride and 0.5g of epichlorohydrin were added to the three-necked flask, and the mixture was stirred for 1h. 11.5g of 80% potassium hydroxide aqueous solution was added dropwise to the three-necked flask. The dropwise addition time was controlled at 12min. After the dropwise addition was completed, the mixture was stirred for 19h. Glacial acetic acid was added to the three-necked flask to adjust the pH value to 6. The mixture was filtered, and the filter residue was washed three times with deionized water and dried to obtain cross-linked starch. Step 2: Ball milling Add 0.47g calcium hydroxide, 0.55g sucrose fatty acid ester SE-11, and 9.5g deionized water to a ball mill. Use agate grinding balls with a diameter of 6mm. Control the ball mill speed to 450rpm, control the ball-to-material ratio to 4:1, and ball mill for 12min to obtain the ball milling material. Step 3: Cationicization Add all the ball milling material obtained in step 2 and all the cross-linked starch obtained in step 1 to a mixer. Control the temperature in the mixer to 62℃ and the stirring speed to 250 rpm. Stir for 12 min. Then add a mixture of 55 g of 2,3-epoxypropyltrimethylammonium chloride, 29 g of potassium hydroxide and 54 g of deionized water to the mixer. Continue stirring for 4 h. Remove the mixture and add a 1 mol / L hydrochloric acid aqueous solution to adjust the pH to 6.5. Dry the mixture until the moisture content is 12%. Then wash and filter the mixture repeatedly with an 80% ethanol aqueous solution until the filtrate is free of chloride ions. Dry the mixture to obtain high-viscosity cationic starch.

[0019] Example 3 A method for preparing high-viscosity cationic starch specifically includes the following steps: Step 1: Epichlorohydrin crosslinking 113.6g of corn starch (including 100g of oven-dried corn starch), 0.5g of calcium hydroxide, and 160g of deionized water were added to a three-necked flask. The temperature in the three-necked flask was controlled at 50℃, and the stirring speed was controlled at 300rpm. The mixture was stirred for 1.5h. Then, 0.7g of sodium stearoyl lactylate was added to the three-necked flask. The temperature in the three-necked flask was controlled at 55℃, and the mixture was stirred for 3h. The temperature in the three-necked flask was allowed to cool naturally to room temperature. 3g of sodium chloride and 0.5g of epichlorohydrin were added to the three-necked flask, and the mixture was stirred for 1h. 12g of 80% potassium hydroxide aqueous solution was added dropwise to the three-necked flask, and the addition time was controlled at 15min. After the addition was completed, the mixture was stirred for 20h. Glacial acetic acid was added to the three-necked flask to adjust the pH value to 6. The mixture was filtered, and the filter residue was washed three times with deionized water and dried to obtain cross-linked starch. Step 2: Ball milling Add 0.5g calcium hydroxide, 0.6g sucrose fatty acid ester SE-11, and 10g deionized water to a ball mill. Use agate grinding balls with a diameter of 6mm. Control the ball mill speed to 450rpm, the ball-to-material ratio to 4:1, and ball mill for 15min to obtain the ball milling material. Step 3: Cationicization Add all the ball milling material obtained in step 2 and all the cross-linked starch obtained in step 1 to a mixer. Control the temperature in the mixer to 65℃ and the stirring speed to 300 rpm. Stir for 15 min. Then add a mixture of 56 g of 2,3-epoxypropyltrimethylammonium chloride, 30 g of potassium hydroxide and 55 g of deionized water to the mixer. Continue stirring for 4 h. Remove the mixture and add a 1 mol / L hydrochloric acid aqueous solution to adjust the pH to 7. Dry the mixture until the moisture content is 14%. Then wash and filter the mixture repeatedly with an 80% ethanol aqueous solution until the filtrate is free of chloride ions. Dry the mixture to obtain high-viscosity cationic starch.

[0020] Comparative Example 1 The preparation method of high-viscosity cationic starch is basically the same as in Example 2, except that: in step 1: epichlorohydrin crosslinking, the use of calcium hydroxide is omitted. Specifically, step 1: epichlorohydrin crosslinking is changed to: 113.6g of corn starch (including 100g of oven-dried corn starch) and 155g of deionized water were added to a three-necked flask. The temperature in the three-necked flask was controlled at 45℃, and the stirring speed was controlled at 200rpm for 1.5h. Then, 0.65g of sodium stearoyl lactylate was added to the three-necked flask, and the temperature in the three-necked flask was controlled at 52℃ for 2.5h. The temperature in the three-necked flask was allowed to cool naturally to room temperature. 2.9g of sodium chloride and 0.5g of epichlorohydrin were added to the three-necked flask, and the mixture was stirred for 1h. 11.5g of 80% potassium hydroxide aqueous solution was added dropwise to the three-necked flask, and the addition time was controlled at 12min. After the addition was completed, the mixture was stirred for 19h. Glacial acetic acid was added to the three-necked flask to adjust the pH value to 6. The mixture was filtered, and the filter residue was washed three times with deionized water and dried to obtain cross-linked starch.

[0021] Comparative Example 2 The preparation method of high-viscosity cationic starch is basically the same as in Example 2, except that: in step 1: epichlorohydrin crosslinking, the use of sodium stearoyl lactylate is omitted. Specifically, step 1: epichlorohydrin crosslinking is changed to: 113.6g of corn starch (including 100g of oven-dried corn starch), 0.47g of calcium hydroxide, and 155g of deionized water were added to a three-necked flask. The temperature in the three-necked flask was controlled at 45℃, and the stirring speed was controlled at 200rpm. The mixture was stirred for 1.5h. The temperature in the three-necked flask was allowed to cool naturally to room temperature. 2.9g of sodium chloride and 0.5g of epichlorohydrin were added to the three-necked flask, and the mixture was stirred for 1h. 11.5g of 80% potassium hydroxide aqueous solution was added dropwise to the three-necked flask, and the addition time was controlled at 12min. After the addition was completed, the mixture was stirred for 19h. Glacial acetic acid was added to the three-necked flask to adjust the pH value to 6. The mixture was filtered, and the filter residue was washed three times with deionized water and dried to obtain cross-linked starch.

[0022] Comparative Example 3 The preparation method of high-viscosity cationic starch is basically the same as in Example 2, except that: Step 2: The use of sucrose fatty acid ester SE-11 is omitted in the ball milling. Specifically, Step 2: Ball milling is changed to: Add 0.47g of calcium hydroxide and 9.5g of deionized water to a ball mill. Use agate grinding balls with a diameter of 6mm. Control the ball mill speed to 450rpm and the ball-to-material ratio to 4:1. Grind for 12 minutes to obtain the ball milling material.

[0023] Test Example 1 The viscosity and nitrogen content of the high-viscosity cationic starch pastes prepared in Examples 1-3 and Comparative Examples 1-3 were tested. Then, the degree of substitution (DS) and reaction efficiency (RE%) were calculated according to the calculation method published by Ben Zhi in "Preparation and Application Research of High-Degree-of-Substitution Cationic Starch" (Dalian University of Technology, December 2000). When calculating the molar weight of starch in the reaction efficiency, the weight of the starch used was the weight of the oven-dried corn starch, i.e., 100g.

[0024] When testing the viscosity of the high-viscosity cationic starch paste, 2g of cationic starch was dissolved in 98g of water and left for 24 hours. The viscosity of the paste was then tested at 25℃ using a rotational viscometer. The rotor used in the test was a No. 4 rotor with a rotation speed of 12rpm. The Kjeldahl method was used to determine the nitrogen content of high-viscosity cationic starch.

[0025] The results for paste viscosity, nitrogen content, and reaction efficiency are as follows (for both paste viscosity and nitrogen content, 10 samples were taken and the average value was used; the average nitrogen content was used to calculate the degree of substitution):

[0026] Furthermore, after testing the viscosity of the paste, the paste was transferred to a constant temperature water bath. The stirring speed in the water bath was controlled at 20 rpm, and the temperature was raised to 50°C and held for 1 hour. The viscosity of the paste was then tested, and the test was repeated every 2 hours for a total of 5 times (i.e., tests were conducted at 50°C for 1 hour, 3 hours, 5 hours, 7 hours, and 9 hours). The viscosity stability of the paste was then calculated using the following formula: Paste viscosity stability = [1 - (maximum paste viscosity in 5 tests - minimum paste viscosity in 5 tests) / paste viscosity after holding at 50℃ for 1 hour] × 100%; The calculation results are as follows:

[0027] Furthermore, to verify the degree of substitution and the uniformity of the paste viscosity of the prepared high-viscosity cationic starch, the differences between the maximum and minimum paste viscosity and the differences between the maximum and minimum nitrogen content were calculated in 10 sampling tests when testing the paste viscosity and nitrogen content. The calculation results are as follows:

[0028] The results of this test show that, compared with Comparative Examples 1-3, the high-viscosity cationic starch prepared in Examples 1-3 has the advantages of high paste viscosity, high degree of substitution and reaction efficiency, good thermal stability of paste viscosity, and good uniformity of paste viscosity and nitrogen content.

[0029] Test Example 2 To verify the effect of alkali dosage, the amount of potassium hydroxide used in step 3 (cationization) of Examples 1-3 and Comparative Examples 1-3 was multiplied by 1.2, and then the nitrogen content of the prepared high-viscosity cationic starch was tested. For each test, 10 samples were taken, and the average value was calculated. The results are as follows:

[0030] The results of this test show that after increasing the amount of alkali used in cationization, the average nitrogen content of the high-viscosity cationic starch prepared in Examples 1-3 fluctuated less, indicating that the starch had achieved sufficient expansion when the amount of alkali used in the preparation methods of Examples 1-3 was low. However, in the preparation methods of Comparative Examples 1-3, the starch could not achieve sufficient expansion when the amount of alkali used was low, which further affected the nitrogen content of the high-viscosity cationic starch prepared.

Claims

1. A process for the preparation of a high viscosity cationic starch, characterized in that, It is composed of the following steps: epichlorohydrin crosslinking, ball milling, cationization; The epichlorohydrin crosslinking, after mixing the starch, calcium hydroxide, deionized water, stirring at 40-50℃, adding sodium stearoyl lactylate, stirring at 50-55℃, naturally cooling to room temperature, adding sodium chloride, epichlorohydrin, stirring, adding potassium hydroxide aqueous solution dropwise, stirring, adjusting the pH value to 6, filtering, taking the filter residue, washing, drying, to obtain crosslinked starch; The ball milling, after mixing the calcium hydroxide, sucrose fatty acid ester SE-11, deionized water, ball milling, to obtain the ball milling material; The cationization, after mixing the ball milling material and crosslinked starch, stirring at 60-65℃, adding the mixed solution composed of 2,3-epoxypropyl trimethylammonium chloride, potassium hydroxide, deionized water, stirring, taking out, adjusting the pH value to 6.5-7, drying, repeating washing with ethanol aqueous solution, filtering to the filtrate containing no chloride ion, drying, to obtain high-viscosity cationic starch.

2. The process for the preparation of high viscosity cationic starch according to claim 1, characterized in that, In the epichlorohydrin crosslinking, the starch is one of corn starch, cassava starch, wheat starch, potato starch; The mass concentration of the potassium hydroxide aqueous solution is 80%.

3. The process for the preparation of high viscosity cationic starch according to claim 1, characterized in that, In the epichlorohydrin crosslinking, the mass ratio of the absolute dry starch in the starch, calcium hydroxide, deionized water, sodium stearoyl lactylate, sodium chloride, epichlorohydrin, potassium hydroxide aqueous solution is 100:0.45-0.5:150-160:0.6-0.7:2.8-3:0.4-0.5:11-12.

4. The process for the preparation of high viscosity cationic starch according to claim 1, characterized in that, In the epichlorohydrin crosslinking, the dropwise adding time of the potassium hydroxide aqueous solution is 10-15min; When adjusting the pH value to 6, use glacial acetic acid to adjust.

5. The process for the preparation of high viscosity cationic starch according to claim 1, characterized in that, In the ball milling, the mass ratio of calcium hydroxide, sucrose fatty acid ester SE-11, deionized water is 0.45-0.5:0.5-0.6:9-10.

6. The process for the preparation of high viscosity cationic starch according to claim 1, characterized in that, In the ball milling, the grinding ball uses agate grinding ball with a diameter of 6mm, the ball milling speed is 400-450rpm, the ball-to-material ratio is 3-4:1, and the ball milling time is 10-15min.

7. The process for the preparation of high viscosity cationic starch according to claim 1, characterized in that, In the epichlorohydrin crosslinking, the mass ratio of the absolute dry starch in the starch used, the calcium hydroxide used in the ball milling, 2,3-epoxypropyl trimethylammonium chloride, potassium hydroxide, deionized water in the mixed solution used in the cationization is 100:0.45-0.5:54-56:28-30:52-55.

8. The process for the preparation of high viscosity cationic starch according to claim 1, characterized in that, In the cationization, when adjusting the pH value to 6.5-7, use 1mol / L hydrochloric acid aqueous solution to adjust; When drying, dry to a moisture content of 12-14%; The volume concentration of the ethanol aqueous solution is 80%.

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