Starch sulfonate and preparation method thereof

Abstract

The present invention relates to a starch sulfonate and a preparation method thereof, the starch sulfonate contains a structure represented by a formula I, n is a natural number of 75-3000, at least two of S1, S2 and S3 are substituent groups-(CH2) X-SO3M, the balance is H, x is an integer of 3-5, and M is Na < + > or K < + >. The preparation method comprises the step of etherifying alkalized starch through a sultone etherifying agent. A high-substitution-degree product can be obtained through a one-pot method and can be used as an efficient surface active auxiliary agent. The product has excellent water solubility, anion characteristic and biocompatibility, and can be applied to water treatment, medicine carriers, water-based additives and food industry.

Description

Technical Field

[0001] The present invention relates to a starch derivative, in particular to a sulfonic acid group-modified starch and a preparation method thereof. Background Art

[0002] Sulfonic acid-based modified starch is formed by grafting sulfonic acid groups onto the glucose units of natural starch (such as corn starch and cassava starch). There are currently three main types of modified starch: the first is sulfonated grafted starch, which is achieved by free radical grafting copolymerization to introduce a synthetic polymer containing sulfonic acid groups (such as olefin sulfonic acid monomers) into the starch molecular chain. An example is the graft copolymer of starch and 2-acrylamido-2-methylpropanesulfonic acid (AMPS); the second is starch sulfonate, which is achieved by directly introducing sulfonic acid groups (-SO3H) onto the starch hydroxyl groups through an esterification reaction to form a sulfonate bond (CO-SO3). A typical example is dextrin sulfonate prepared with sodium bisulfite or chlorosulfonic acid as a sulfonating agent; the third is starch ether with sulfonic acid groups, which is achieved by an etherification reaction to generate a stable ether bond (COC). The sulfonic acid groups are connected with alkyl chains (such as hydroxypropyl sulfonic acid groups). A typical example is 2-hydroxy-3-sulfonic acid propyl starch ether.

[0003] The introduction of sulfonic acid groups imparts numerous properties to starch: 1) Strong hydrophilicity and dispersibility: The high polarity of sulfonic acid groups makes them readily soluble in water and effectively adsorbs on the surfaces of solid particles, preventing aggregation. 2) Anionicity: They carry a negative charge in solution, dispersing colloids and microparticles through electrostatic repulsion. 3) Retarding effect: They delay crystallization during cement hydration, improving later-stage strength. Due to these properties, sulfonated starch is used as a cement water reducer, drilling fluid treatment agent, and green scale inhibitor. It can also be used as a thickener or emulsifier in the food and pharmaceutical industries.

[0004] There are relatively few types of sulfonated starch available, and the range of options is limited. There is a demand in this field for sulfonic acid-modified starch with a new structure in order to seek a more efficient water treatment agent. Summary of the Invention

[0005] The purpose of the present invention is to provide a new modified starch based on sulfonic acid groups to make up for the deficiency of the narrow selection range of modified starch in the prior art.

[0006] The starch sulfonate according to the present invention has a structural unit shown in formula I,

[0007]

[0008] Wherein, n is a natural number from 75 to 3000, wherein at least two of S1, S2 and S3 are substituents -(CH2) X -SO3M, the rest are H, x is an integer from 3 to 5, M is Na + or K+ .

[0009] In a typical implementation, n is a natural number between 75 and 300.

[0010] The second aspect of the present invention provides a method for preparing the starch sulfonate, comprising the following steps:

[0011] 1) alkalizing starch with alkali;

[0012] 2) Using sultone as an etherifying agent to carry out etherification reaction with starch.

[0013] In a preferred embodiment, the sultone is 1,3-propane sultone, 4-butane sultone

[0014] The alkali is at least one of: lactone, 1-propenyl-1,3-propane sultone, 1-methyl-1,3-propane sultone, 1,1-dimethyl-1,3-propane sultone, 1-ethyl-1,3-propane sultone, 1,2-dimethyl-1,3-propane sultone, 1,3-dimethyl-1,3-propane sultone, 1-methyl-2-ethyl-1,3-propane sultone, 1,3-propane sultone, 1-methyl-1,4-butane sultone, 1-methyl-1,4-butane sultone, 1-propenyl-1,4-butane sultone and 1,5-pentane sultone. The alkali is sodium hydride, potassium hydride, sodium hydroxide or potassium hydroxide.

[0015] The product of the invention has a high degree of hydroxyl substitution and good surface activity, and can be used as a cement water reducer, scale inhibitor, food and medicine additive, etc. DETAILED DESCRIPTION

[0016] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter of the present invention belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal manner unless otherwise explicitly defined herein.

[0017] According to the present invention, the modified starch has the structure of formula I.

[0018]

[0019] Among them, at least two of S1, S2 and S3 are substituents -(CH2) X -SO3M, the rest are H. Wherein, x is an integer from 3 to 5, M is Na + or K + .

[0020] According to the starch sulfonate of the present invention, different values ​​of x can be selected as needed to adjust the hydrophilicity of the target product. Another advantage of the present invention is that the introduction of sulfonic acid groups in the form of sulfonates allows the modified starch to consume a certain amount of acidic substances, reducing its degradation rate under natural conditions.

[0021] In a typical embodiment, S1, S2 and S3 are all -(CH2) X In the present invention, the higher the degree of substitution, the higher the water-based adjustment effect of the modified starch. Under the condition of the same efficacy, the dosage can be significantly reduced.

[0022] The starch used in the present invention can be cereal starch and tuber starch. Cereal starch includes but is not limited to corn starch, wheat starch, rice starch, sorghum starch, etc. Tuber starch includes potato starch, sweet potato starch (sweet potato starch, sweet potato starch), cassava starch, yam starch, etc. Legume starch can be used in the present invention, such as mung bean starch, pea starch, broad bean starch, cowpea starch, small black kidney bean starch and lentil starch.

[0023] In the present invention, the above-mentioned starch raw material can be used as a sulfonation raw material to obtain starch sulfonate with a degree of polymerization of 300-6000. In another embodiment, the starch can be partially degraded as needed to obtain starch sulfonate with a predetermined degree of polymerization, such as starch sulfonate with a degree of polymerization in the range of 75-300. The degree of polymerization can be reduced by acid hydrolysis or enzymatic hydrolysis.

[0024] In the acid hydrolysis method, an acid (such as hydrochloric acid or sulfuric acid) is used under heating to hydrolyze the α-1,4 and α-1,6 glycosidic bonds of starch, reducing the degree of polymerization. To do this, the starch is first dispersed in water to form a 5%-10% starch suspension. Dilute hydrochloric acid or sulfuric acid is added to adjust the pH to 1.5-3.0. The suspension is then stirred at 50-60°C for 1-4 hours. The longer the reaction time, the lower the degree of polymerization. The reaction is terminated by neutralization with NaOH to a pH of 6-7. Finally, the starch is centrifuged or filtered, washed, and dried. Acid-hydrolyzed starch with a selected degree of polymerization can also be purchased commercially.

[0025] In the enzymatic hydrolysis method, amylase (such as α-amylase, β-amylase) is used to selectively cut glycosidic bonds to produce oligosaccharides or malt. The specific method is to first gelatinize the starch and heat the starch suspension to 70-90°C to gelatinize it; add amylase and react for the required time at the selected temperature and pH value. For α-amylase, react at 70-90°C and pH 6-7 for 30-60 minutes; for β-amylase, react at 50-60°C and pH 4-5 for 1-2 hours. Finally, boil for 5 minutes to inactivate the enzyme. The desired degree of polymerization is selected by controlling the enzyme dosage (usually 0.1%-1% of starch mass) and reaction time. Enzymatic starch with a selected degree of polymerization can also be purchased commercially.

[0026] In the present invention, sultone is used as an etherifying agent and an etherification reaction is carried out in an alkaline environment. This reaction can achieve multiple substitutions of glucose units in starch. This reaction is applicable to the introduction of propylsulfonic acid groups (x is 3), butylsulfonic acid groups (x is 4) and even pentylsulfonic acid groups (x is 5) on the glucose unit. These sultones can also carry C1-C3 hydrocarbon substituents. Typical examples include 1-propenyl-1,3-propane sultone, 1-methyl-1,3-propane sultone, 1,1-dimethyl-1,3-propane sultone, 1-ethyl-1,3-propane sultone, 1,2-dimethyl-1,3-propane sultone, 1,3-dimethyl-1,3-propane sultone, 1-methyl-2-ethyl-1,3-propane sultone, 1-methyl-1,4-butane sultone, 1-methyl-1,4-butane sultone and 1-propenyl-1,4-butane sultone.

[0027] Alkyl sultones with smaller or higher x values ​​are not preferred in the present invention because three-membered or four-membered ring lactones are unstable, and seven-membered or higher carbon number ring lactones are difficult to prepare in high yield. In a preferred embodiment of the present invention, the etherifying agents are 1,3-propane sultone and 1,4-butane sultone. Taking 1,4-propane sultone as an example, its reaction formula is:

[0028]

[0029] This reaction formula shows an etherification reaction with a substitution number of 3. The input ratio of the etherifying agent can be adjusted as needed to obtain a reaction product with a substitution number of 2.

[0030] In the present invention, the method for determining the amount of sultone based on the degree of substitution is based on the molar ratio of anhydroglucose to sultone. Anhydroglucose is a building block of starch. Sultone is added at a ratio of 2 to the equivalent of anhydroglucose to produce a modified starch with a degree of substitution of 2. Sultone is added at a ratio of 3 to the equivalent of anhydroglucose to produce a modified starch with a degree of substitution of 3. Further excess above this ratio is not recommended.

[0031] To prepare the starch sulfonate according to the present invention, the starch is first alkalized. An alkalizing agent acts on the hydroxyl groups (-OH) on the glucose units, converting them into the corresponding salt intermediates, which then undergo a nucleophilic reaction with the sultone. The amount of alkali used is 2 or 3 times the equivalent of the dehydrated glucose, depending on the degree of substitution of the target product. Powdered alkali is suspended in a solvent and then thoroughly stirred with the starch. Alkalizing agents that can be used in the present invention include sodium hydride, potassium hydride, sodium hydroxide, or potassium hydroxide, with sodium hydride and potassium hydride being preferred.

[0032] In one embodiment, sodium hydroxide is used as the alkalizing agent. The alkali is prepared into an aqueous solution with a mass concentration of 15-60%, preferably 20-40%, and then added to the starch and stirred evenly. A concentration that is too low will introduce too much water into the starch, reducing the reaction rate of the subsequent etherification reaction. A concentration that is too high will not allow the starch to be fully moistened. The amount of water should ideally be sufficient to fully moisten the starch. After adding the alkali and stirring evenly, the mixture is allowed to stand for 24-48 hours, kneading it several times in a kneader during this time to fully alkalize the starch.

[0033] In one embodiment, sodium hydride is used as the alkalizing agent, and the powdered alkali is suspended in an organic solvent, and then fully stirred with starch and allowed to stand for 2-8 hours to promote a full reaction, during which the mixture can be kneaded multiple times.

[0034] Next, the alkalized starch is subjected to an etherification reaction. Sultone is added to the starch in solution. The amount of solvent used is sufficient to maintain the reaction mixture in a slurry or paste state for smooth stirring. Polar aprotic solvents are preferably used, with typical examples including N,N-dimethylformamide, acetonitrile, tetrahydrofuran, N-methylpyrrolidone, N-ethylpyrrolidone, and dioxane. The etherification reaction temperature can be controlled between 40°C and 120°C, preferably between 60°C and 100°C, and is generally not higher than the boiling point of the solvent. At this temperature, the etherification reaction time is 1 to 10 hours, preferably 4 to 10 hours.

[0035] Example 1, Preparation of Trisubstituted Sodium Starch Sulfonate

[0036]

[0037] Take 178g of acid-hydrolyzed corn starch (DP between 100-300), add 240g of 50% sodium hydroxide solution to the starch, stir evenly, and let it sit at room temperature for 48 hours, kneading it every two to three hours. After the alkalization is complete, spread the starch and dry it in a vacuum drying oven at 60°C for 1 hour to remove some of the introduced water.

[0038] Add 150ml of N,N-dimethylformamide to the starch and stir manually until the mixture becomes a slurry. Transfer the mixture to a three-necked flask equipped with a thermometer, stirrer, and condenser. Slowly add 366g of 1,3-propane sultone at room temperature. Rinse the remaining sultone in the container with 30ml of DMF and transfer it to the three-necked flask. Stir at room temperature for 1 hour, then slowly raise the temperature to 80°C and react at this temperature for 7 hours, while maintaining stirring.

[0039] The reacted material was transferred out, the solvent was separated by filtration, and the filter cake was washed 3-5 times with 300 ml of acetone to remove free sultone and other impurities, and then the filter cake was washed with an appropriate amount of water to remove free alkalizing agent, and finally dried under reduced pressure at 60°C to obtain the product.

[0040] Take 1g of sample, mix it with sufficient 20% copper sulfate solution, stir it thoroughly, filter it, wash it, combine the washing liquid and the filtrate, and titrate the remaining copper ions in the filtrate with EDTA standard solution. The degree of substitution is estimated to be 2.32 based on the consumption.

[0041] Example 2

[0042] The operation of Example 1 was repeated, except that the material was not dried after the alkalization. The degree of substitution of the obtained product was 1.61, which was significantly lower than that of Example 1.

[0043] Example 3, Preparation of Trisubstituted Starch Sulfonate

[0044]

[0045] Take 178g of acid-hydrolyzed corn starch (DP between 100-300), add a suspension made from 72g of sodium hydride and 200ml of DMF to the starch, stir thoroughly to mix, and let it stand at room temperature for 4 hours, kneading it every hour during this period. This operation is carried out in an airtight environment.

[0046] Add 100ml of N,N-dimethylformamide to the starch and stir manually until the mixture becomes a paste or slurry. Transfer the mixture to a three-necked flask equipped with a thermometer, stirrer, and condenser. Slowly add 366g of 1,3-propane sultone at room temperature. Rinse any remaining sultone in the container with 30ml of DMF and transfer it to the three-necked flask. Stir at room temperature for 1 hour, then slowly raise the temperature to 80°C and react at this temperature for 7 hours, maintaining stirring.

[0047] The reacted material was transferred out, the solvent was separated by filtration, and the filter cake was washed 4-5 times with 150 ml of acetone to remove free sultone and other impurities, and then the filter cake was washed with an appropriate amount of water to remove free alkalizing agent, and finally dried under reduced pressure at 60°C to obtain the product.

[0048] Take 1g of sample, mix it with sufficient 20% copper sulfate solution, stir it thoroughly, filter it, wash it, combine the washing liquid and the filtrate, and titrate the remaining copper ions in the filtrate with EDTA standard solution. The degree of substitution is estimated to be 2.72 based on the consumption.

[0049] Example 4, Preparation of Disubstituted Sodium Starch Sulfonate

[0050] Take 178g of acid-hydrolyzed corn starch (DP between 100-300), add 200g of 40% sodium hydroxide solution to the starch, stir evenly, and let it sit at room temperature for 48 hours, kneading it every two to three hours. After the alkalization is complete, spread the starch and dry it in a vacuum oven at 60°C for 1 hour.

[0051] Add 100ml of N,N-dimethylformamide to the starch and stir manually until the mixture becomes a slurry. Transfer the mixture to a three-necked flask equipped with a thermometer, stirrer, and condenser. Slowly add 244g of 1,3-propane sultone at room temperature. Rinse any remaining sultone in the container with 30ml of DMF and transfer it to the three-necked flask. Stir at room temperature for 1 hour, then slowly raise the temperature to 80°C and react at this temperature for 10 hours, maintaining stirring.

[0052] The reacted material was transferred out, the solvent was separated by filtration, and the filter cake was washed 3-5 times with 250 ml of acetone to remove free sultone and other impurities, and then the filter cake was washed with an appropriate amount of water to remove free alkalizing agent, and finally dried under reduced pressure at 60°C to obtain the product.

[0053] Take 1g of sample, mix it with sufficient 20% copper sulfate solution, stir it thoroughly, filter it, wash it, combine the washing liquid and the filtrate, and titrate the remaining copper ions in the filtrate with EDTA standard solution. The degree of substitution is estimated to be 1.28 based on the consumption.

[0054] Example 5, Preparation of Disubstituted Sodium Starch Sulfonate

[0055] Take 178g of acid-hydrolyzed corn starch (DP between 100-300), add a suspension made from 48g of sodium hydride and 200ml of DMF to the starch, stir evenly, and let it sit at room temperature for 4 hours, kneading it every hour. This operation should be carried out in an airtight environment. After alkalization, spread the starch and dry it in a vacuum drying oven at 60°C for 1 hour.

[0056] Add 100ml of N,N-dimethylformamide to the starch and stir manually until the mixture becomes a slurry. Transfer the mixture to a three-necked flask equipped with a thermometer, stirrer, and condenser. Slowly add 244g of 1,3-propane sultone at room temperature. Rinse any remaining sultone in the container with 30ml of DMF and transfer it to the flask. Stir at room temperature for 1 hour, then slowly raise the temperature to 80°C and react at this temperature for 7 hours, maintaining stirring.

[0057] The reacted material was transferred out, the solvent was separated by filtration, and the filter cake was washed 3-5 times with 150 ml of acetone to remove free sultone and other impurities, and then the filter cake was washed with an appropriate amount of water to remove free alkalizing agent, and finally dried under reduced pressure at 60°C to obtain the product.

[0058] Take 1g of sample, mix it with sufficient 20% copper sulfate solution, stir thoroughly, filter, wash, combine the washing liquid and the filtrate, and titrate the remaining copper ions in the filtrate with EDTA standard solution. Based on the consumption, the degree of substitution is estimated to be 1.88.

[0059] Using 2-hydroxy-3-sulfonic acid propyl starch ether (monosubstituted) as a reference, the water-reducing properties of the products of Examples 1 and 2 as cement water-reducing agents were tested. The cement used was Aotaili brand (produced by Aotaili Building Materials Technology Co., Ltd.). A cement slurry was prepared by mixing 300g of cement, 87g of water, and the selected amount of the test product. The slurry was poured into a truncated cone mold (36mm upper diameter, 60mm lower diameter, 60mm height). The mold was lifted and the maximum diameter of the cement slurry flowing freely on the glass was measured. Table 1 shows the results for 3g (1%) and 1.5g (0.5%) of the test product.

[0060] Table 1 Cement paste fluidity

[0061]

[0062] As can be seen from Table 1, at an addition level of 1%, the products of Examples 1 and 2 and the control all exhibit excellent surfactant effects. At an addition level of 0.5%, the performance of the products of the present invention remains excellent, while the control does not perform well. There is no significant difference in performance between the example products at addition levels of 0.5% and 1.0%, indicating that a dosage exceeding 0.5% is unnecessary. Table 1 also shows that a dosage of 0.3% of the example products can meet most industrial needs.

[0063] The above embodiments are not exhaustive of specific implementation methods, and there may be other embodiments. The purpose of the above embodiments is to illustrate the present invention, and the scope of protection of this application is not limited thereto. Therefore, any equivalent changes made based on the structure, shape, and principle of this application should be included in the scope of protection of this application.

Claims

1. A starch sulfonate having a structural unit shown in formula I, in, n is a natural number from 75 to 3000, wherein at least two of S1, S2 and S3 are substituents -(CH2) X -SO3M, the rest are H, x is an integer from 3 to 5, M is Na + or K + .

2. The starch sulfonate according to claim 1, wherein n is a natural number between 75 and 300.

3. The method for preparing starch sulfonate according to claim 1 or 2, comprising the steps of: 1) alkalizing starch with alkali; 2) Using sultone as an etherifying agent to carry out etherification reaction with starch.

4. The preparation method according to claim 3, wherein The sultone is at least one of 1,3-propane sultone, 4-butane sultone, 1-propenyl-1,3-propane sultone, 1-methyl-1,3-propane sultone, 1,1-dimethyl-1,3-propane sultone, 1-ethyl-1,3-propane sultone, 1,2-dimethyl-1,3-propane sultone, 1,3-dimethyl-1,3-propane sultone, 1-methyl-2-ethyl-1,3-propane sultone, 1,3-propane sultone, 1-methyl-1,4-butane sultone, 1-methyl-1,4-butane sultone, 1-propenyl-1,4-butane sultone and 1,5-pentane sultone.

5. The preparation method according to claim 3, wherein The base is sodium hydride, potassium hydride, sodium hydroxide or potassium hydroxide.

6. The preparation method according to claim 3, wherein The solvent used in step 2) is selected from the group consisting of N,N-dimethylformamide, acetonitrile, tetrahydrofuran, N-methylpyrrolidone, N-ethylpyrrolidone and dioxane; among which dimethylformamide and N-ethylpyrrolidone are preferred.

7. The preparation method according to claim 5, wherein The base is sodium hydride or potassium hydride. In the alkalization step, the base is suspended in the solvent, then mixed with starch and left for 4 to 12 hours; and then mixed with a required amount of sultone.

8. The preparation method according to claim 5, wherein The alkali is sodium hydroxide or potassium hydroxide, and the alkali is introduced in the form of a 20-40% aqueous solution. After the alkali is added and stirred evenly, the mixture is left to stand for 24 to 48 hours, during which time it is kneaded several times.

9. The preparation method according to claim 8, wherein After alkalization, the material is vacuum dried to remove some moisture.

10. The preparation method according to claim 3, wherein The etherification reaction temperature is 40° C. to 120° C., more preferably 60° C. to 100° C.; the etherification reaction time is 4 to 10 hours.

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