Self-thickening system of glutamic acid-based surfactants and its preparation method

Abstract

This invention provides a self-thickening system of glutamic acid-based surfactants and its preparation method. By mass fraction, the system comprises 2-15% glutamic acid-based surfactant, 2-15% cocamidopropylamine oxide, 1-5% pH adjuster, and the balance being water. The preparation method involves mixing the glutamic acid-based surfactant, cocamidopropylamine oxide, and water, mechanically stirring, and adjusting the pH of the mixture to acidic. This results in an increase in the viscosity of the system, yielding a self-thickening system. This thickening system exhibits excellent thickening effects and has significant application potential in the detergent field.

Description

Technical Field

[0001] This invention relates to the field of detergents, and more specifically, to a self-thickening system of glutamic acid-type surfactants and its preparation method. Background Technology

[0002] Traditional detergents often contain thickeners to give them a certain viscosity for easier use. Common thickeners are mainly polymers or high molecular weight substances, which can cause some deposition after use, leading to stickiness and a strong residue. Self-thickening systems can solve this problem. Self-thickening systems form worm-like micelles through the self-assembly behavior of surfactants, increasing the system viscosity. When diluted with water or oils are added, the self-thickening system is disrupted, the viscosity drops rapidly, and the residue is minimal.

[0003] Currently, commonly used amino-type surfactants include sodium cocoyl glutamate, disodium cocoyl glutamate, sodium cocoyl aminopropionate, sodium lauroyl sarcosinate, and sodium cocoyl sarcosinate; some published patents mention self-thickening systems, details of which are as follows:

[0004] Patent document CN104095764B discloses a self-thickening system of cocamidopropyl betaine and sodium lauroyl sarcosinate, which can achieve good thickening effect in the pH range of 4.9-5.5; patent document CN104095771B discloses a self-thickening system of cocamidopropyl betaine and sodium lauroyl sarcosinate, which can achieve good thickening effect in the pH range of 4.0-5.6; patent document CN108567583B discloses a self-thickening system of sodium lauroyl sarcosinate, compound surfactant, and alkyl glycoside, which can achieve good thickening effect; and patent document CN104800091B discloses a self-thickening system of lauroyl glutamic acid / cocoyl glutamic acid and triethanolamine, which can achieve good synergistic effect.

[0005] In summary, research on self-thickening systems has mainly focused on sodium lauroyl sarcosinate and sodium cocoyl sarcosinate systems, while there is a lack of relevant research on sodium cocoyl glutamate and / or disodium cocoyl glutamate systems. Moreover, project engineers in the industry generally agree that sodium cocoyl glutamate and / or disodium cocoyl glutamate are a class of amino acid-based surfactants that are relatively difficult to thicken.

[0006] Therefore, how to develop a glutamic acid-based surfactant self-thickening system is the problem that this invention aims to solve. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a self-thickening system of glutamic acid-type surfactants and its preparation method.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] The first aspect of the present invention provides a self-thickening system of a glutamic acid type surfactant, comprising, by mass fraction, 2-15% glutamic acid type surfactant, 2-15% cocamidopropylamine oxide, 1-5% pH adjuster, and the balance being water.

[0010] The glutamate-type surfactants in this invention include disodium cocoyl glutamate and / or sodium cocoyl glutamate. Since sodium cocoyl glutamate and disodium cocoyl glutamate are prepared using the same process, the only difference lies in the degree of final alkali neutralization. Manufacturers label products with a high degree of neutralization as disodium cocoyl glutamate, while those with a low degree of neutralization label products as a mixture of disodium cocoyl glutamate and sodium cocoyl glutamate. Therefore, both sodium cocoyl glutamate and disodium cocoyl glutamate are within the scope of this invention.

[0011] Preferably, the pH adjuster includes citric acid.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned self-thickening system of glutamic acid-type surfactants:

[0013] (1) Dissolve glutamic acid type surfactant and cocamidopropylamine oxide in water, mix them in proportion, and stir to obtain a surfactant system;

[0014] (2) Dissolve the pH adjuster in water and then slowly add it to the surfactant system in step (1) to adjust the pH to acidic, thus obtaining the self-thickening system of glutamic acid type surfactant.

[0015] Preferably, in step (1), the mass ratio of glutamic acid surfactant to cocamidopropylamine oxide is (1-1.6):1.

[0016] Preferably, in step (1), the stirring is mechanical stirring.

[0017] Preferably, the mechanical stirring speed is 50-300 rpm.

[0018] Preferably, in step (2), the mass ratio of pH adjuster to water is 1:(4-10).

[0019] Preferably, the acidity in step (2) refers to the pH of the aqueous solution after the self-thickening system is diluted 10 times to be 5.5-6.5.

[0020] A third aspect of the present invention provides the application of the above-described self-thickening system in detergent products.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention successfully achieves self-thickening of glutamic acid-type surfactants in the pH range of 5.5-6.5, and there are currently no related literature reports.

[0023] 2. The present invention has a good thickening effect, with the self-thickening system reaching a maximum viscosity of 51050 mPa.s, which far exceeds the conventional viscosity of shampoo (5000 mPa.s);

[0024] 3. This invention features a simple process that aligns with the principles of green, environmentally friendly, and low-carbon development. In aqueous solutions of surfactants, surfactant molecules can form various micelle structures through self-assembly. When the concentration approaches the critical micelle concentration (CMC), spherical micelles appear; as the surfactant concentration increases, rod-shaped micelles gradually emerge, and further aggregation and entanglement of these rod-shaped micelles significantly increase the solution viscosity; when the surfactant concentration reaches a certain level, layered micelles are formed, at which point the solution viscosity is extremely high, almost non-flowing. The micelle state formed by surfactants in solution can be described by the critical packing parameter C. p Prediction, expression C p =V / L c A c Where V represents the volume of the hydrophobic chain tail, and L c A represents the maximum extension length of the hydrophobic chain. c This represents the cross-sectional area of ​​the head base on the interface. C p C changes due to the influence of self-assembly conditions. p When ≤1 / 3, spherical micelles are generally formed; when 1 / 3 < C p When <1 / 2, rod-shaped micelles are formed; when 1 / 2 ≤ C p When the concentration is ≤1, lamellar micelles are formed; therefore, it can be seen that within a certain range, the surfactant C... p The larger the head group, the easier it is to form rod-shaped and lamellar micelles, and the higher the viscosity of the solution system. Amino acid surfactants, due to their larger head groups (A... c A larger value leads to its C p Smaller sizes are difficult to thicken. Glutamic acid-based surfactants and cocamidopropylamine oxide rapidly self-assemble into rod-shaped micelles under acidic conditions and cross-link to form a larger network structure, causing the viscosity of the system to rise rapidly, comparable to the thickening effect of polymers. Detailed Implementation

[0025] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0026] Experimental instruments

[0027] Equipment models: Digital display rotational viscometer (model: JNDJ-5S); Digital display stirrer (model: KW 20D5025); Constant temperature water bath (model: HWS-24).

[0028] Experimental materials

[0029] Reagent source: ACS22S P0 (Guangzhou Baifurun Chemical Co., Ltd., batch number: 362022022204; active ingredient is glutamic acid type surfactant, disodium cocoyl glutamate mass fraction 20%, sodium cocoyl glutamate mass fraction 5%, water mass fraction 75%); FS CAO-30 (Sichuan Huayu Fine Chemical Co., Ltd., batch number: 20230817-551; active ingredient is cocamidopropylamine oxide, cocamidopropylamine oxide mass fraction 30%, water mass fraction 70%); citric acid (Weifang Yingxuan Industrial Co., Ltd., 3AX2105209; all ingredients are labeled as 100% citric acid).

[0030] Table 1. Formulations and viscosity measurement results for Examples 1-18

[0031]

[0032]

[0033] In Table 1, the total mass is the sum of the masses of glutamic acid surfactant, cocamidopropylamine oxide, citric acid, and water, controlled at 100g; pH (10%) is the pH of the aqueous solution after the self-thickening system is diluted 10 times; and viscosity is the test viscosity of the self-thickening system.

[0034] Examples 1-6

[0035] Weigh 8.25g of glutamic acid surfactant, 8.25g of cocamidopropylamine oxide and an appropriate amount of water and add them to a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until uniform. Then, add an appropriate amount of citric acid according to the formula in Table 1, dissolve it in an appropriate amount of water and add it to the beaker in three batches. Stir for 20min until uniform to obtain a self-thickening system. Measure the viscosity and pH value of the system.

[0036] Example 7

[0037] Weigh 8.25g of glutamic acid surfactant, 7.20g of cocamidopropylamine oxide, and an appropriate amount of water into a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then, dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20min until homogeneous to obtain a self-thickening system with a viscosity of 6450mPa.s. Then, take a small amount of sample and prepare a 10% aqueous solution, and the pH is measured to be 5.92.

[0038] Example 8

[0039] Weigh 8.25g of glutamic acid surfactant, 9.00g of cocamidopropylamine oxide, and an appropriate amount of water into a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then, dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20min until homogeneous to obtain a self-thickening system with a viscosity of 18650mPa·s. Then, take a small amount of sample and prepare a 10% aqueous solution, and determine the pH to be 6.06.

[0040] Example 9

[0041] Weigh 4.125g of glutamic acid surfactant, 4.125g of cocamidopropylamine oxide, and an appropriate amount of water into a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then, dissolve 1.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20min until homogeneous to obtain a self-thickening system with a viscosity of 6650mPa.s. Then, take a small amount of sample and prepare a 10% aqueous solution, and the pH is measured to be 6.03.

[0042] Examples 10-15

[0043] Weigh 10.00g of glutamic acid surfactant, 6.30g of cocamidopropylamine oxide and an appropriate amount of water and add them to a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until uniform. Then, dissolve an appropriate amount of citric acid in an appropriate amount of water according to the formula in Table 1 and add it to the beaker in three batches. Stir for 20min until uniform to obtain a self-thickening system. Measure the viscosity and pH value of the system.

[0044] Example 16

[0045] Weigh 10.00g of glutamic acid surfactant, 8.00g of cocamidopropylamine oxide, and an appropriate amount of water into a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then, dissolve 2.50g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20min until homogeneous to obtain a self-thickening system with a viscosity of 17600mPa.s. Subsequently, take a small amount of sample and prepare a 10% aqueous solution, and the pH is measured to be 5.81.

[0046] Example 17

[0047] Weigh 10.00g of glutamic acid surfactant, 5.00g of cocamidopropylamine oxide, and an appropriate amount of water into a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then, dissolve 2.50g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20min until homogeneous to obtain a self-thickening system with a viscosity of 13500mPa.s. Then, take a small amount of sample and prepare a 10% aqueous solution, and determine the pH to be 5.70.

[0048] Example 18

[0049] Weigh 5.00 g of glutamic acid surfactant, 3.15 g of cocamidopropylamine oxide, and an appropriate amount of water into a 150 mL beaker. Turn on the mechanical stirrer and stir at 200 rpm for 10 min until homogeneous. Then, dissolve 1.25 g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20 min until homogeneous to obtain a self-thickening system with a viscosity of 5640 mPa·s. Then, take a small amount of sample and prepare a 10% aqueous solution, and the pH is measured to be 5.87.

[0050] Comparative Example 1

[0051] Weigh 8.25g of glutamic acid surfactant and add an appropriate amount of water to a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches. Stir for 20min until homogeneous. The viscosity of the system is 75mPa.s. Then take a small amount of sample and prepare a 10% aqueous solution. The pH is measured to be 6.08.

[0052] Compared to Example 3, the amounts of glutamic acid surfactant and citric acid added to the system were the same; the difference was that cocamidopropylamine oxide was not added, but the viscosities of the two were significantly different. This indicates that the addition of cocamidopropylamine oxide can significantly increase the viscosity of the system.

[0053] Comparative Example 2

[0054] Weigh 8.25g of cocamidopropylamine oxide and add an appropriate amount of water to a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches. Stir for 20min until homogeneous. The viscosity of the system is 56mPa.s. Then take a small amount of sample and prepare a 10% aqueous solution. The pH is measured to be 3.97.

[0055] Compared to Example 3, the amounts of cocamidopropylamine oxide and citric acid added to the system were the same; the difference was that no glutamic acid-based surfactant was added, but the viscosity of the two was significantly different. This indicates that cocamidopropylamine oxide and glutamic acid-based surfactant have a synergistic effect, which can significantly increase the viscosity of the system.

[0056] Comparative Example 3

[0057] Weigh 16.50g of glutamic acid surfactant and add an appropriate amount of water to a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches. Stir for 20min until homogeneous. The viscosity of the system is 82mPa.s. Then take a small amount of sample and prepare a 10% aqueous solution. The pH is measured to be 6.42.

[0058] Compared with Example 3, the total amount of glutamic acid surfactant and cocamidopropylamine oxide was 16.50g, and the amount of citric acid added was also the same, but the viscosity of the system was still low. This shows that even if the content of glutamic acid surfactant is increased, the viscosity of the system cannot be significantly increased. Therefore, it can be considered that cocamidopropylamine oxide and glutamic acid surfactant have a synergistic effect and can significantly increase the viscosity of the system.

[0059] Comparative Example 4

[0060] Weigh 16.50g of cocamidopropylamine oxide and add an appropriate amount of water to a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then, dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches. Stir for 20min until homogeneous. The viscosity of the system is 63mPa.s. Then, take a small amount of sample and prepare a 10% aqueous solution. The pH value is 4.67.

[0061] Compared with Example 3, the total amount of glutamic acid surfactant and cocamidopropylamine oxide was 16.50g, and the amount of citric acid added was also the same, but the viscosity of the system was still low. This shows that even if the content of cocamidopropylamine oxide is increased, the viscosity of the system cannot be significantly increased. Therefore, it can be considered that cocamidopropylamine oxide and glutamic acid surfactant have a synergistic effect and can significantly increase the viscosity of the system.

[0062] Comparative Example 5

[0063] Weigh 8.25g of glutamic acid surfactant, 8.25g of cocamidopropyl betaine, and an appropriate amount of water into a 150mL beaker. Turn on the mechanical stirrer and stir at 200rpm for 10min until homogeneous. Then, dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20min until homogeneous. The viscosity of the system is 63mPa.s. Then, take a small amount of sample and prepare a 10% aqueous solution. The pH value is 5.72.

[0064] Compared to Example 3, cocamidopropylamine oxide was replaced with commercially available cocamidopropyl betaine. The results showed that the viscosity was very low and there was no self-thickening phenomenon. This proves that cocamidopropylamine oxide and glutamic acid-type surfactants have a synergistic effect and can significantly increase the viscosity of the system.

[0065] Comparative Example 6

[0066] Weigh 8.25g of glutamic acid-type surfactant, 8.25g of sodium lauroamphoacetate, and an appropriate amount of water into a 150mL beaker. Start mechanical stirring at 200rpm for 10min until homogeneous. Then, dissolve 2.00g of citric acid in an appropriate amount of water and add it to the beaker in three batches, stirring for 20min until homogeneous. The system viscosity is 75mPa·s. A small sample is then taken and prepared as a 10% aqueous solution, with a pH of 6.15. Compared to Example 3, cocamidopropylamine oxide was replaced with commercially available sodium lauroamphoacetate. The results showed a very low viscosity and no self-thickening phenomenon. This demonstrates that cocamidopropylamine oxide and glutamic acid-type surfactant have a synergistic effect, significantly increasing the viscosity of the system.

[0067] As can be seen from Examples 1-18, when glutamic acid-type surfactants and cocamidopropylamine oxide are prepared in the mass fraction range of (4.125%-10.00%) and (3.15%-9.00%), at pH 5.62-6.07, the viscosity of the self-thickening system exceeds the conventional viscosity of shampoo (5000 mPa.s).

[0068] According to Examples 1-6, when glutamic acid-type surfactant and cocamidopropylamine oxide are prepared in a mass ratio of 1:1, the viscosity of the self-thickening system can reach 51050 mPa·s at pH 5.82-6.07.

[0069] According to Examples 10-15, when glutamic acid-type surfactants and cocamidopropylamine oxide are prepared in a mass ratio of 1.6:1, the viscosity of the self-thickening system can reach 26450 mPa·s at pH 5.62-5.83.

[0070] Because glutamic acid-type surfactant molecules have amphiphilic properties, and cocamidopropylamine oxide is cationic under acidic conditions, under appropriate ratios and pH synergistic effects, glutamic acid-type surfactants and cocamidopropylamine oxide rapidly self-assemble into worm-like micelles under acidic conditions, cross-linking to form a large network structure. The viscosity of the self-thickening system reaches a maximum of 51050 mPa·s, far exceeding the conventional viscosity of shampoo (5000 mPa·s).

[0071] In summary, this invention successfully achieves self-thickening of glutamic acid-based surfactants, a process not previously reported in the market. This invention offers excellent thickening effects, and its process is simple, requiring only simple mixing to achieve self-thickening of the system.

[0072] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A self-thickening system of a glutamic acid-based surfactant, characterized in that, By mass fraction, it includes 2-15% glutamic acid-type surfactant, 2-15% cocamidopropylamine oxide, 1-5% pH adjuster, and the balance is water; Glutamic acid-type surfactants are disodium cocoyl glutamate and sodium cocoyl glutamate; The pH of the aqueous solution of the self-thickening system after being diluted 10 times is 5.5-6.

5.

2. The self-thickening system of glutamic acid-type surfactant according to claim 1, characterized in that, pH adjusters include citric acid.

3. A method for preparing the self-thickening system of the glutamic acid-type surfactant according to claim 1, characterized in that, Includes the following steps: (1) Dissolve glutamic acid type surfactant and cocamidopropylamine oxide in water, mix them in proportion, and stir to obtain a surfactant system; (2) Prepare an aqueous solution of pH adjuster and then slowly add it to the surfactant system in step (1) to obtain a self-thickening system of glutamic acid surfactant and adjust the pH to acidic.

4. The method according to claim 3, characterized in that, In step (1), the mass ratio of glutamic acid surfactant to cocamidopropylamine oxide is (1-1.6):

1.

5. The method according to claim 3, characterized in that, In step (1), the stirring is mechanical stirring.

6. The method according to claim 5, characterized in that, The mechanical stirring speed is 50-300 rpm.

7. The method according to claim 3, characterized in that, In step (2), when preparing the pH adjuster aqueous solution, the mass ratio of pH adjuster to water is 1:(4-10).

8. According to the method of claim 3, the acidity in step (2) refers to the pH of the aqueous solution after the self-thickening system is diluted 10 times to be 5.5-6.

5.

9. The application of the self-thickening system according to claim 1 in a detergent product.

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