A cationic etherifying agent modified starch composition and its preparation method

Abstract

This invention discloses a cationic etherifying agent modified starch composition and its preparation method, belonging to the field of papermaking. It includes mixing carboxylated carbon nanotubes and a cationic starch solution, freeze-drying at -70 to -100°C for 4 to 8 hours to form a freeze-dried sample, thereby forming a porous aerogel structure with initially stable channels; immersing a beaker in ethanol / FeCl3 (0.8wt%) at -20°C for 48 to 72 hours to thaw it and promote Fe... 3+ The modified starch composition is obtained by coordinating and crosslinking with carboxylated carbon nanotubes in a porous aerogel structure, followed by gelatinization of the crosslinked solution at a specific temperature. The modified starch composition of this invention significantly improves the rheological and adhesive properties of starch compositions, meeting the requirements for papermaking and is suitable for use as a component in papermaking.

Description

Technical Field

[0001] This invention relates to the field of papermaking, and more specifically to a cationic etherifying agent modified starch composition and its preparation method. Background Technology

[0002] Starch, a natural high-molecular-weight carbohydrate, is widely found in plant seeds, tubers, and fruits. It possesses advantages such as being renewable, non-toxic, and biodegradable, leading to its extensive industrial applications. However, the structural and performance defects of natural starch limit its application range. Cationic starch, an important derivative of starch, offers advantages over natural starch, including better flowability, higher viscosity stability, stronger penetration, and better binding force, making it widely used in the papermaking industry.

[0003] Traditional methods for preparing cationic starch mainly include wet and dry processes. Wet processes consume large amounts of water, cause severe environmental pollution, and involve long processes, high drying energy consumption, and high production costs. Dry processes suffer from uneven mixing of starch and chemical reagents and poor product solubility, limiting their application. Cationic starch prepared using existing technologies does not meet the physical properties, such as rheological and adhesive properties, required for papermaking and is therefore unsuitable for use as a wet-end additive in papermaking.

[0004] To improve the rheological and adhesive properties of starch and meet the requirements for papermaking, several invention patents have been developed. For example, patent CN104119455A discloses a cationic modified starch and its preparation method. The method involves preparing a starch slurry, adding a mixed solution of at least one sodium hydroxide and sodium carbonate with a cationic etherifying agent to the starch slurry, mixing and stirring to obtain a first mixed solution, then adding a silane coupling agent and mixing and stirring to obtain a second mixed solution. The mixture is reacted at a certain temperature for a period of time, and the pH of the second mixed solution after the reaction is completed is adjusted to neutral or acidic and diluted to a certain concentration. Borax is then added and stirred to obtain a fourth mixed solution. The mixture is then heated and gelatinized under stirring conditions for a period of time, and diluted to a certain concentration to obtain the cationic modified starch. However, this patent still has the problem of further optimizing the addition ratio of the composite modifier and the silane coupling agent to obtain better adhesive properties. Patent CN117166285A discloses a paper product, cationic starch, and a method for preparing the same. The method includes: preparing a solution by taking a certain amount of native starch, a cationic etherifying agent, and an alkaline catalyst; heating the solution to a preset temperature and allowing it to stand for a preset time to react; and extruding and curing the reacted solution using a screw extruder. A crosslinking agent and a plasticizer are added during the extrusion and curing process. However, this patent still requires further research and optimization of the parameters of the dry process. Summary of the Invention

[0005] 1. The problem to be solved

[0006] To address the problem that the rheological and adhesive properties of cationic starch prepared in the prior art do not meet the requirements for papermaking, this invention provides a cationic etherifying agent modified starch composition and its preparation method.

[0007] 2. Technical Solution

[0008] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a cationic etherifying agent modified starch composition according to the present invention includes the following steps:

[0010] (1) Mix starch with water to prepare starch slurry;

[0011] (2) Adjust the pH of the starch slurry to alkaline;

[0012] (3) Add swelling inhibitor to the pH-adjusted slurry and stir evenly, wherein the amount of swelling inhibitor added is 5-10 wt% of the dry weight of starch;

[0013] (4) Mix the alkaline material and the cationic etherifying agent in water to form a mixed solution, then add the mixed solution to the starch slurry and stir evenly. React at 60-80°C for 12-24 hours to obtain the first mixed solution; wherein the amount of alkaline material is 2-10 wt% of the dry weight of starch, and the amount of cationic etherifying agent is 5-10 wt% of the dry weight of starch;

[0014] (5) Add carboxylated carbon nanotubes to the first mixed solution and stir until homogeneous to obtain a second mixed solution; wherein the amount of carboxylated carbon nanotubes is 10-30 wt% of the dry weight of starch;

[0015] (6) Pour the second mixed solution into a beaker and freeze-dry it at -70~-100°C for 4~8 hours to form a freeze-dried sample, so that it forms a porous aerogel structure with preliminary stable channels;

[0016] In the above steps, carboxylated carbon nanotubes initially crosslink with cationic starch molecular chains through their surface carboxyl groups to form a network structure. A specific freeze-drying process then forms a porous aerogel structure with channels formed between the crosslinked chains. This facilitates the subsequent introduction of Fe... 3+ This laid the spatial foundation for the further formation of a stable coordination structure.

[0017] (7) Immerse the beaker in ethanol / FeCl3 (0.8wt%) at -20°C for 48~72 hours to thaw it and promote Fe 3+ Coordinated crosslinking with carboxylated carbon nanotubes in porous aerogel structures;

[0018] (8) The solution in step (7) is kept warm and gelatinized to obtain a modified starch composition.

[0019] Furthermore, the starch and water are mixed in a mass ratio of 1:(3~8) to form a starch slurry.

[0020] Furthermore, the starch is selected from any one of tapioca starch, corn starch, potato starch, or wheat starch.

[0021] Furthermore, in step (2), the pH of the starch slurry is adjusted to 8-12 using sodium hydroxide solution.

[0022] Furthermore, the swelling inhibitor includes sodium chloride or sodium sulfate.

[0023] Further, in step (4), the alkaline material includes any one of sodium hydroxide, potassium hydroxide or sodium carbonate; the cationic etherifying agent includes 3-chloro-2-hydroxypropyltrimethylammonium chloride or 4-chloro-2-butenyltrimethylammonium chloride.

[0024] Further, in step (5), after adding carboxylated carbon nanotubes, the mixture is stirred at a speed of 3000~10000 rpm for 0.5~6 hours to obtain a second mixed solution.

[0025] Furthermore, the carboxylated carbon nanotubes are obtained by oxidizing carbon nanotubes using a strong acid oxidation method.

[0026] Further, in step (8), the modified starch composition is obtained by gelatinizing at 90-100°C for 20-40 minutes.

[0027] The present invention also provides a cationic etherifying agent modified starch composition, which is prepared by any one of the preparation methods described above.

[0028] 3. Beneficial effects

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) A cationic etherifying agent modified starch composition and its preparation method of the present invention, by adding carboxylated carbon nanotubes and performing freeze drying, thawing and cross-linking processes, the starch forms a stable cross-linked porous structure with channels. Moreover, when it is not cured, the coordinating ion iron ion can coordinate with the carboxyl group and flow in the channel. After curing, the carboxylated carbon nanotubes, cationic starch molecular chains and iron ions can form a stable complex network structure, thereby significantly improving the rheological properties and adhesive properties of the starch composition, meeting the index requirements of papermaking, and suitable for use as a component in papermaking.

[0031] (2) It avoids the disadvantages of traditional wet preparation of cationic starch, such as large water consumption, serious environmental pollution, long process flow, high drying energy consumption and high production cost.

[0032] (3) It overcomes the problems of uneven mixing of starch and chemical reagents and poor product solubility in the dry preparation of cationic starch, and expands the application range of starch. Detailed Implementation

[0033] The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and does not limit the description of the features and characteristics of the invention, in order to suggest the best mode for carrying out the invention and to enable those skilled in the art to practice the invention. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of research and development and significance of the technology, and is not intended to limit the invention or the scope of application of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0035] In the series of embodiments of this application, the synthesis method of carboxylated carbon nanotubes uniformly adopts a strong acid oxidation method to oxidize carbon nanotubes. The diameter of the carbon nanotubes is 1~20nm and the length is 5~100μm, as detailed below:

[0036] 1) Add carbon nanotubes to a mixture of concentrated sulfuric acid and concentrated nitric acid. The volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:3. The ratio of carbon nanotubes to the mixed acid is 1.5g of carbon nanotubes to 100mL of mixed acid.

[0037] 2) Perform ultrasonic treatment at 50℃ for 6 hours to allow the carbon nanotubes to fully react with the mixed acid.

[0038] 3) After the reaction is complete, dilute the reaction solution with 6 times the amount of water, and then separate the solid and liquid by centrifugation at 3000 rpm for 10 min.

[0039] 4) Finally, wash the separated solid product with water until neutral, and then dry it in an 80℃ oven for 12 hours to obtain carboxylated carbon nanotubes.

[0040] It should be noted that carboxylated carbon nanotubes are a technologically mature material in the prior art. The embodiments of this application only provide a method for synthesizing carboxylated carbon nanotubes that is suitable for cross-linking complexes composed of starch and iron ions in this application, and have no unique limiting effect.

[0041] The present invention will be further described below with reference to specific embodiments. Example 1

[0042] This embodiment provides a cationic etherifying agent modified starch composition and its preparation method, including the following steps:

[0043] Step 1: Mix starch and water to prepare a starch slurry. Specifically, mix starch and water at a mass ratio of 1:4 to form a starch slurry. Tapioca starch is used as the starch.

[0044] Step 2: Adjust the pH of the starch slurry to alkaline. Specifically, adjust the pH of the starch slurry to 8.5 using sodium hydroxide solution;

[0045] Step 3: Add a swelling inhibitor to the pH-adjusted slurry and stir until homogeneous. Specifically, add sodium sulfate as a swelling inhibitor at a rate of 7 wt% of the dry weight of the starch, and stir until homogeneous.

[0046] Step 4: Mix sodium hydroxide with a cationic etherifying agent to form a mixed solution. Specifically, mix sodium hydroxide with 3-chloro-2-hydroxypropyltrimethylammonium chloride, wherein the amount of sodium hydroxide used is 3 wt% of the oven-dry weight of starch, and the amount of cationic etherifying agent used is 7 wt% of the oven-dry weight of starch.

[0047] Step 5: Add the mixed solution to the starch slurry, stir evenly, and react at 60°C for 12 hours to obtain the first mixed solution;

[0048] Step 6: Add carboxylated carbon nanotubes to the first mixed solution, disperse them in deionized water at 10,000 rpm for 1 hour, and stir until homogeneous to obtain the second mixed solution. Specifically, the amount of carboxylated carbon nanotubes added is 20 wt% of the oven-dry weight of the starch;

[0049] Step 7: Pour the second mixed solution into a beaker and freeze-dry it at -80°C for 5 hours to form a freeze-dried sample, which forms a porous aerogel structure with preliminary stable channels;

[0050] Step 8: Immerse the beaker in -20°C ethanol / FeCl3 (0.8wt%) for 72 hours to thaw it and promote Fe... 3+ Coordinated crosslinking with carboxylated carbon nanotubes in porous aerogel structures;

[0051] Step 9: Gelatinize the solution from Step 8 at 95°C for 25 minutes to obtain the modified starch composition.

[0052] In this process, carboxylated carbon nanotubes and cationic starch molecular chains crosslink to form a channel structure. Iron ions can coordinate with the carboxyl groups in the channel structure to form a stable complex structure, resulting in a denser network structure after the starch composition is mixed and cured with other papermaking components, increasing its cohesive strength after curing. Furthermore, the branches of this channel structure are permeated with carboxyl groups. Before curing, iron ions can coordinate with the carboxyl groups of the carboxylated carbon nanotubes and flow within the channels to alter the conformation of the polymer chains and intermolecular forces. This makes it easier to spread or coat (before curing) while maintaining adhesive strength (after curing). This comprehensively improves the rheological and adhesive properties of the modified starch composition solution, meeting the requirements for papermaking and making it suitable for use as a component in papermaking.

[0053] To verify the performance of the modified starch composition in Example 1, a pulp with a mass concentration of 4.0% (NBKP:LBKP:BCTMP = 20:70:10; where LBKP is short fiber, NBKP is long fiber, and BCTMP is bleached chemimechanical groundwood pulp), diluted with water, and mixed evenly to obtain a pulp with a mass percentage concentration of 0.3%. While stirring, filler (18% solid content) at 20% of the dry weight of the pulp, 1% of the cationic modified starch prepared in Example 1 (concentration 1%), 250 ppm of RA (0.2% solid content, cationic polyacrylamide aqueous solution), and silica stock solution (1% solid content, anionic silica aqueous solution, diluted 100 times) were added sequentially. After mixing evenly, the mixture was formed into sheets to prepare base paper of 30-200 g / m². 2 .

[0054] The paper products prepared by applying the cationic modified starch obtained in Example 1 to papermaking pulp are recorded in Table 1:

[0055] Table 1. Performance comparison of paper products prepared according to different implementation methods

[0056] Implementation Cohesion (kg*cm) Tensile index (N*m / g) <![CDATA[Bursting strength index (kPa*m 2 / g)]]> Example 1 1.87 59.5 3.36 Example 2 1.91 60.3 3.58 Example 3 1.82 58.3 3.22 Comparative Example 1 1.21 42.4 2.55 Comparative Example 2 1.32 44.5 2.60 Example 2

[0057] This embodiment provides a cationic etherifying agent modified starch composition and its preparation method. The steps and process principle of the preparation method are similar to those of Example 1, but the specific materials and proportions differ, as follows:

[0058] Step 1: Mix starch and water at a mass ratio of 1:5 to form a starch slurry. Corn starch is used as the starch.

[0059] Step 2: Adjust the pH of the starch slurry to 9.0 using sodium hydroxide solution;

[0060] Step 3: Add sodium chloride as a swelling inhibitor, the amount added is 8 wt% of the dry weight of starch, and stir well;

[0061] Step 4: Mix sodium carbonate with 4-chloro-2-butenyltrimethylammonium chloride to form a mixed solution, wherein the amount of sodium carbonate used is 4 wt% of the dry weight of starch, and the amount of cationic etherifying agent used is 6 wt% of the dry weight of starch.

[0062] Step 5: Add the mixed solution to the starch slurry, stir evenly, and react at 65°C for 11 hours to obtain the first mixed solution;

[0063] Step 6: Add carboxylated carbon nanotubes to the first mixed solution, disperse them in deionized water at 8000 rpm for 80 minutes, and stir until homogeneous to obtain the second mixed solution. The amount of carboxylated carbon nanotubes used is 25 wt% of the dry weight of starch.

[0064] Step 7: Pour the second mixed solution into a beaker and freeze-dry it at -80°C for 5 hours to form a freeze-dried sample, thereby forming a stable cross-linked porous structure with channels.

[0065] Step 8: Immerse the beaker in ethanol / FeCl3 (0.8wt%) at -20°C for 72 hours to allow it to thaw and crosslink.

[0066] Step 9: Gelatinize the solution from Step 8 at 98°C for 30 minutes to obtain the modified starch composition.

[0067] To verify the performance of the modified starch composition in Example 2, a pulp with a mass concentration of 4.0% (NBKP:LBKP:BCTMP = 20:70:10; where LBKP is short fiber, NBKP is long fiber, and BCTMP is bleached chemimechanical groundwood pulp), diluted with water, and mixed evenly to obtain a pulp with a mass percentage concentration of 0.3%. While stirring, filler (18% solid content) at 20% relative to the oven-dry weight of the pulp, 1% of the cationic modified starch prepared in Example 2 (concentration 1%), 250 ppm of RA (0.2% solid content, cationic polyacrylamide aqueous solution), and silica stock solution (1% solid content, anionic silica aqueous solution, diluted 100 times) were added sequentially. After mixing evenly, the mixture was formed into sheets to prepare base paper of 30-200 g / m². 2 .

[0068] The paper products prepared by applying the cationic modified starch obtained in Example 2 to paper pulp are recorded in Table 1. Example 3

[0069] This embodiment provides a cationic etherifying agent modified starch composition and its preparation method. The steps and process principles of the preparation method are basically the same as those in Example 1. The same parts are omitted here. The main difference is that the amount of carboxylated carbon nanotubes used is 12 wt% of the dry weight of starch.

[0070] To verify the performance of the modified starch composition in Example 3, a pulp with a mass concentration of 4.0% (NBKP:LBKP:BCTMP = 20:70:10; where LBKP is short fiber, NBKP is long fiber, and BCTMP is bleached chemimechanical groundwood pulp), diluted with water, and mixed evenly to obtain a pulp with a mass percentage concentration of 0.3%. While stirring, filler (18% solid content) at 20% relative to the oven-dry weight of the pulp, 1% of the cationic modified starch prepared in Example 3 (concentration 1%), 250 ppm of RA (0.2% solid content, cationic polyacrylamide aqueous solution), and silica stock solution (1% solid content, anionic silica aqueous solution, diluted 100 times) were added sequentially. After mixing evenly, the mixture was formed into sheets to prepare base paper of 30-200 g / m². 2 .

[0071] The paper products prepared by applying the cationic modified starch obtained in Example 3 to paper pulp are recorded in Table 1.

[0072] Comparative Example 1

[0073] This comparative example provides a conventional cationic etherifying agent modified starch composition and its preparation method. The main difference between this example and Example 1 is that the carboxylated carbon nanotubes and subsequent freeze-drying and iron ion immersion processes are not included. Specifically, the following steps are included:

[0074] Step 1: Mix starch and water to prepare a starch slurry. Specifically, mix starch and water at a mass ratio of 1:4 to form a starch slurry. Tapioca starch is used as the starch.

[0075] Step 2: Adjust the pH of the starch slurry to alkaline. Specifically, adjust the pH of the starch slurry to 8.5 using sodium hydroxide solution;

[0076] Step 3: Add a swelling inhibitor to the pH-adjusted slurry and stir until homogeneous. Specifically, add sodium sulfate as a swelling inhibitor at a rate of 7 wt% of the dry weight of the starch, and stir until homogeneous.

[0077] Step 4: Mix sodium hydroxide with a cationic etherifying agent to form a mixed solution. Specifically, mix sodium hydroxide with 3-chloro-2-hydroxypropyltrimethylammonium chloride, wherein the amount of sodium hydroxide used is 3 wt% of the oven-dry weight of starch, and the amount of cationic etherifying agent used is 7 wt% of the oven-dry weight of starch.

[0078] Step 5: Add the mixed solution to the starch slurry, stir evenly, and react at 60°C for 12 hours to obtain the first mixed solution;

[0079] Step 6: Gelatinize the first mixed solution from Step 5 at 95°C for 25 minutes to obtain the modified starch composition.

[0080] The starch composition prepared according to this embodiment was subjected to relevant performance tests, and the test results are shown in Table 1.

[0081] Comparative Example 2

[0082] This comparative example provides a cationic etherified starch composition and its preparation method. The main difference between this example and Example 1 is that the starch composition is prepared by directly mixing carboxylated carbon nanotubes and ethanol / FeCl3 (0.8 wt%) with cationic starch. Specifically, the method includes the following steps:

[0083] Step 1: Mix starch and water to prepare a starch slurry. Specifically, mix starch and water at a mass ratio of 1:4 to form a starch slurry. Tapioca starch is used as the starch.

[0084] Step 2: Adjust the pH of the starch slurry to alkaline. Specifically, adjust the pH of the starch slurry to 8.5 using sodium hydroxide solution;

[0085] Step 3: Add a swelling inhibitor to the pH-adjusted slurry and stir until homogeneous. Specifically, add sodium sulfate as a swelling inhibitor at a rate of 7 wt% of the dry weight of the starch, and stir until homogeneous.

[0086] Step 4: Mix sodium hydroxide with a cationic etherifying agent to form a mixed solution. Specifically, mix sodium hydroxide with 3-chloro-2-hydroxypropyltrimethylammonium chloride, wherein the amount of sodium hydroxide used is 3 wt% of the oven-dry weight of starch, and the amount of cationic etherifying agent used is 7 wt% of the oven-dry weight of starch.

[0087] Step 5: Add the mixed solution to the starch slurry, stir evenly, and react at 60°C for 12 hours to obtain the first mixed solution;

[0088] Step 6: Add carboxylated carbon nanotubes and 0.8 wt% FeCl3 ethanol solution to the first mixed solution, disperse them in deionized water at 10,000 rpm for 1 hour, and stir until homogeneous to obtain the second mixed solution; specifically, the amount of carboxylated carbon nanotubes added is 20 wt% of the dry weight of starch, and the amount of ferric chloride added is 5 wt% of the dry weight of carboxylated carbon nanotubes.

[0089] Step 7: Gelatinize the second mixed solution from Step 6 at 95°C for 25 minutes to obtain the modified starch composition.

[0090] The starch composition prepared according to this embodiment was subjected to relevant performance tests, and the test results are shown in Table 1.

[0091] By comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that the modified starch composition prepared in this application can effectively improve the cohesive and adhesive properties of paper products, and can also improve the rheological properties of the starch composition to facilitate spreading and use, thereby meeting the index requirements of papermaking and being suitable for use as a component in papermaking. Comparative Example 1, which did not use the carboxylated carbon nanotubes and subsequent freeze-drying and iron ion impregnation processes of this application, produced conventional paper products with performance far lower than that of this application. In Comparative Example 2, although carboxylated carbon nanotubes and ferric chloride were also used in the preparation with starch, its paper performance was also far lower than that of this application. This shows that without the unique preparation process of this application, this mechanical addition method is difficult to form the multi-channel coordination network structure of this application, resulting in difficulty in improving the adhesive properties of the modified starch composition.

[0092] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or the scope of application of the present application.

[0093] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

[0094] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail. When flow rate, power, refractive index, time, or other values ​​or parameters are expressed as ranges, preferred ranges, or a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, the range 1-50 should be understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values ​​between the integers mentioned above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider "nested subranges" extending from any endpoint of the range. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30 and 1-40 in one direction, or 50-40, 50-30, 50-20 and 50-10 in another direction.

Claims

1. A method for preparing a starch composition modified with a cationic etherifying agent, characterized in that, Includes the following steps: (1) Mix starch with water to prepare starch slurry; (2) Adjust the pH of the starch slurry to alkaline; (3) Add swelling inhibitor to the pH-adjusted slurry and stir evenly, wherein the amount of swelling inhibitor added is 5-10 wt% of the dry weight of starch; (4) Mix the alkaline material and the cationic etherifying agent in water to form a mixed solution, then add the mixed solution to the starch slurry and stir evenly. React at 60-80°C for 12-24 hours to obtain the first mixed solution; wherein the amount of alkaline material is 2-10 wt% of the dry weight of starch, and the amount of cationic etherifying agent is 5-10 wt% of the dry weight of starch; (5) Add carboxylated carbon nanotubes to the first mixed solution and stir until homogeneous to obtain a second mixed solution; wherein the amount of carboxylated carbon nanotubes used is 10-30 wt% of the dry weight of starch; the carboxylated carbon nanotubes are obtained by oxidizing carbon nanotubes using a strong acid oxidation method, and the preparation method of the carboxylated carbon nanotubes includes: 1) Add carbon nanotubes to a mixture of concentrated sulfuric acid and concentrated nitric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:3, and the ratio of carbon nanotubes to the mixed acid is 1.5g of carbon nanotubes to 100mL of mixed acid; 2) Perform ultrasonic treatment at 50℃ for 6 hours to allow the carbon nanotubes to fully react with the mixed acid; 3) After the reaction is complete, dilute the reaction solution with 6 times the amount of water, and then separate the solid and liquid by centrifugation at 3000 rpm for 10 min; 4) Finally, wash the separated solid product with water until neutral, and then dry it in an 80℃ oven for 12 hours to obtain carboxylated carbon nanotubes. (6) Pour the second mixed solution into a beaker and freeze-dry it at -70~-100°C for 4~8 hours to form a freeze-dried sample, so that it forms a porous aerogel structure with preliminary stable channels; (7) Immerse the beaker in a 0.8wt% FeCl3 ethanol solution at -20°C for 48-72 hours to thaw it and promote Fe 3+ Coordinated crosslinking with carboxylated carbon nanotubes in porous aerogel structures; (8) The solution in step (7) is kept warm and gelatinized to obtain a modified starch composition.

2. The method for preparing a cationic etherifying agent modified starch composition according to claim 1, characterized in that, The starch and water are mixed in a mass ratio of 1:(3~8) to form a starch slurry.

3. The method for preparing a cationic etherifying agent modified starch composition according to claim 1, characterized in that, The starch is selected from any one of cassava starch, corn starch, potato starch, or wheat starch.

4. The method for preparing a cationic etherifying agent modified starch composition according to claim 1, characterized in that, In step (2), the pH of the starch slurry is adjusted to 8-12 using sodium hydroxide solution.

5. The method for preparing a cationic etherifying agent modified starch composition according to claim 1, characterized in that, The swelling inhibitor includes sodium chloride or sodium sulfate.

6. The method for preparing a cationic etherifying agent modified starch composition according to claim 1, characterized in that, In step (4), the alkaline material includes any one of sodium hydroxide, potassium hydroxide or sodium carbonate; the cationic etherifying agent includes 3-chloro-2-hydroxypropyltrimethylammonium chloride or 4-chloro-2-butenyltrimethylammonium chloride.

7. The method for preparing a cationic etherifying agent modified starch composition according to claim 1, characterized in that, In step (5), after adding carboxylated carbon nanotubes, the mixture is stirred at a speed of 3000~10000 rpm for 0.5~6 hours to obtain a second mixed solution.

8. The method for preparing a cationic etherifying agent modified starch composition according to claim 1, characterized in that, In step (8), most modified starch compositions are obtained by gelatinizing at 90-100°C for 20-40 minutes.

9. A starch composition modified with a cationic etherifying agent, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.