An imidazoline-type amphoteric surfactant and its preparation method

Abstract

This invention relates to an imidazoline-type amphoteric surfactant and its preparation method, belonging to the field of surfactant technology. The preparation method of the imidazoline-type amphoteric surfactant of this invention includes the following steps: S1, weighing fatty acids or fatty acid esters, adding hydroxyethyl ethylenediamine, mixing evenly, and reacting under vacuum to obtain an imidazoline ring intermediate; S2, weighing water, catalyst, and alkaline compound, mixing evenly to obtain a mixed solution, adding the imidazoline ring intermediate obtained in step S1 to perform a hydrolysis reaction to obtain a hydrolysate; S3, weighing a quaternizing reagent and the hydrolysate obtained in step S2, mixing evenly, adding an alkaline solution to perform a quaternization reaction to obtain the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant obtained by the preparation method of this invention has good stability, production efficiency, and yield, and can remain turbid even after long-term storage at low temperatures.

Description

Technical Field

[0001] This invention belongs to the field of surfactant technology, specifically relating to an imidazoline-type amphoteric surfactant and its preparation method. Background Technology

[0002] Imidazolyl-type amphoteric surfactants are excellent amphoteric surfactants, meaning they have both positively and negatively charged groups. Under alkaline conditions, they exhibit the properties of anionic surfactants, while under acidic conditions, they exhibit the properties of cationic surfactants. They have the following characteristics: (1) Imidazolyl-type amphoteric surfactants have good compatibility with various surfactants and are well-matched with soap bases; (2) They have low irritation and are very gentle on the skin and eyes. When matched with cationic surfactants, they can significantly reduce irritation; (3) They have excellent foaming power, producing rich, delicate foam with a good skin feel, and can significantly improve the foam fineness of the formula management system; (4) They have high tolerance to hard water and can be compounded with anionic surfactants, thereby reducing the irritation of anionic surfactants to the eyes. They also have excellent foam-increasing and foam-stabilizing properties.

[0003] Imidazolino-type amphoteric surfactants are gentle surfactants that can reduce the irritation of other surfactants. They have good water hardness resistance and compatibility with other surfactants, and are less irritating to human eyes and skin, making them widely used in low-irritant baby care products.

[0004] The imidazoline-type amphoteric surfactants produced by existing processes are very prone to turbidity when stored at low temperatures (5°C). Turbidity will appear in as little as 7 days and at most a month, a problem that has remained unresolved in the industry. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an imidazoline amphoteric surfactant with high production efficiency and yield, good stability, and the ability to remain turbid even after long-term storage at low temperatures.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing an amphoteric surfactant, comprising the following steps:

[0008] S1. Weigh out fatty acids or fatty acid esters, add hydroxyethyl ethylenediamine, mix well, and react under vacuum to obtain an imidazoline ring intermediate.

[0009] S2. Weigh water, catalyst and alkaline compound, mix them evenly to obtain a mixed solution, add the imidazoline ring intermediate product mentioned in step S1 to carry out a hydrolysis reaction to obtain the hydrolysis product.

[0010] S3. Weigh the quaternization reagent and the hydrolysis product described in step S2, mix them evenly, add alkaline solution to carry out the quaternization reaction, adjust the pH value to 8.5-9.5, and obtain the imidazoline amphoteric surfactant.

[0011] In step S2, the catalyst is triethanolamine or diethanolamine.

[0012] The inventors of this invention have discovered that adding the catalyst in the specific ratio described in this invention during the hydrolysis reaction of the imidazoline ring intermediate can promote the preparation of an imidazoline amphoteric surfactant that does not become turbid at low temperature (5°C) and after long-term storage.

[0013] Furthermore, through extensive comparative studies of catalysts, the inventors of this invention discovered that the specific catalyst described in this invention facilitates hydrolysis in a specific direction, thereby improving production efficiency and yield. In contrast, other types of catalysts result in two hydrolysis pathways, leading to decreased product stability and causing turbidity in the product at low temperatures.

[0014] In a preferred embodiment of the preparation method of the present invention, the fatty acid is at least one of lauric acid, myristic acid, palmitic acid, stearic acid, and coconut oil acid, and the fatty acid ester is at least one of laurate, myristic acid, palmitic acid, stearate, and coconut oil ester.

[0015] In a preferred embodiment of the preparation method described in this invention, the alkaline compound is at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0016] In a preferred embodiment of the preparation method of the present invention, the reaction steps in step S1 are as follows: weigh fatty acids or fatty acid esters, add hydroxyethyl ethylenediamine, mix evenly, introduce nitrogen gas, heat to 120°C, turn on the vacuum, set the vacuum degree to -0.05 to -0.09 MPa, raise the temperature to 170 to 210°C, react under vacuum for 2 to 6 hours, increase the negative pressure to ≤ -0.1 MPa, distill the unreacted hydroxyethyl ethylenediamine at a temperature of 190 to 220°C, cool, and obtain the imidazoline ring intermediate product.

[0017] The inventors of this invention have discovered that using the above-mentioned vacuum level will not produce diamide.

[0018] In a preferred embodiment of the preparation method of the present invention, in step S2, the mass ratio of the catalyst to the imidazoline ring intermediate is 0.005 to 0.2.

[0019] The inventors of this invention have discovered that when the mass ratio of the catalyst to the imidazoline ring intermediate is within the above-mentioned range, and when the catalyst is compounded with an alkaline compound and water, the hydrolysis reaction of the imidazoline ring intermediate can be better promoted, causing the hydrolysis reaction to proceed in a single direction. The hydrolysis product obtained is relatively simple, thus enabling the imidazoline amphoteric surfactant to remain stable at low temperatures and during long-term storage without turbidity.

[0020] In a preferred embodiment of the preparation method of the present invention, in step S2, the mass ratio of the catalyst to the imidazoline ring intermediate is 0.01 to 0.1.

[0021] The inventors of this invention conducted extensive experimental research on the dosage of the catalyst and discovered that when the mass ratio of the catalyst to the imidazoline ring intermediate is 0.01–0.1, the stability of the imidazoline amphoteric surfactant can be further improved, preventing precipitation even after storage at low temperatures for 6 months. It also promotes the hydrolysis reaction, reducing the temperature and time required for the reaction and resulting in a higher yield. However, when a larger amount of catalyst is used, the excessively high triethanolamine content in the product leads to a decrease in the active ingredient content, resulting in reduced product stability.

[0022] In a preferred embodiment of the preparation method described in this invention, in step S2, the OH groups in the mixed solution... - The concentration is 0.1–3 mol / L.

[0023] The inventors of this invention have discovered that the OH in the mixed solution of this invention... - When the concentration of OH is within the above range, and a specific catalyst is added to the mixed solution, the hydrolysis reaction of the imidazoline ring intermediate can be promoted, so that the prepared imidazoline amphoteric surfactant will not show turbidity at low temperature and during long-term storage, and has a high yield. When the OH content in the mixed solution is within the above range, the hydrolysis reaction of the imidazoline ring intermediate can be promoted, so that the prepared imidazoline amphoteric surfactant will not show turbidity at low temperature and during long-term storage, and will have a high yield. - At low concentrations, the hydrolysis rate of the imidazoline ring intermediate decreases significantly, leading to reduced production efficiency. Furthermore, the inability of the hydrolysis reaction to proceed in a single direction causes turbidity in the prepared imidazoline amphoteric surfactant when stored at low temperatures. When the OH- concentration in the mixed solution is low... - When the concentration is high, the hydrolysis reaction rate is faster, which causes the prepared imidazoline amphoteric surfactant to become turbid when stored at low temperature.

[0024] In a preferred embodiment of the preparation method described in this invention, in step S2, the OH groups in the mixed solution... - The concentration is 0.5–2 mol / L.

[0025] The inventors of this invention have discovered that the OH in the mixed solution of this invention... - When the concentration is within the above range, and it works synergistically with a specific catalyst in the mixed solution, it can better promote the hydrolysis reaction of the imidazoline ring intermediate and improve production efficiency. This not only ensures that the prepared imidazoline amphoteric surfactant will not become turbid at low temperatures and during long-term storage, but also results in a higher yield of the product.

[0026] In a preferred embodiment of the preparation method of the present invention, in step S2, the hydrolysis reaction temperature is 30-55°C and the hydrolysis reaction time is 0.3-2h.

[0027] The inventors of this invention have discovered that, within the aforementioned temperature and time range, the hydrolysis reaction of the imidazoline ring intermediate described in this invention not only better promotes the hydrolysis reaction in a single direction, ensuring that the prepared imidazoline amphoteric surfactant does not become turbid at low temperatures and exhibits good stability, but also improves the production efficiency of the hydrolysis reaction. Conversely, when the hydrolysis reaction time is too short or the temperature is too low, incomplete hydrolysis or a slow reaction rate can prevent the hydrolysis products from proceeding in a single direction, resulting in turbidity of the prepared imidazoline amphoteric surfactant at low temperatures. Furthermore, a longer hydrolysis reaction time leads to reduced production efficiency and wasted manpower. Higher hydrolysis temperatures can cause explosive boiling of the liquid, reducing production safety and decreasing product stability.

[0028] In a preferred embodiment of the preparation method of the present invention, in step S2, the temperature of the hydrolysis reaction is 30-45°C and the time of the hydrolysis reaction is 0.5-1h.

[0029] The inventors of this invention have discovered that, within the aforementioned temperature and time range, the hydrolysis reaction of the imidazoline ring intermediate described in this invention, by adding a specific catalyst, not only ensures that the prepared imidazoline amphoteric surfactant does not become turbid during long-term storage at low temperatures, but also promotes the hydrolysis reaction, reduces the temperature and time of the hydrolysis reaction, and achieves a high yield.

[0030] Secondly, the present invention also provides an imidazoline amphoteric surfactant obtained by the above-described method for preparing an imidazoline amphoteric surfactant.

[0031] The imidazoline-type amphoteric surfactant obtained by the preparation method described in this invention can remain stable at low temperatures and during long-term storage without becoming turbid, thus solving a problem that has been difficult to solve in the industry.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) By adding the catalyst of the specific ratio described in this invention during the hydrolysis reaction of the imidazoline ring intermediate, the present invention can promote the preparation of imidazoline amphoteric surfactants after hydrolysis and quaternization reactions, and the resulting surfactants will not show turbidity at low temperature (5°C) and during long-term storage.

[0034] (2) The catalyst of the present invention is combined with water and an alkaline compound to obtain a mixed solution, while controlling the OH content of the mixed solution. - The concentration of [specific concentration] can better promote the hydrolysis reaction of the imidazoline ring intermediate, allowing the hydrolysis reaction to proceed in a single direction, resulting in a more singular product. This enables the imidazoline amphoteric surfactant to avoid turbidity at low temperatures and during long-term storage, solving a problem that has been unresolved in the industry. It also promotes the hydrolysis reaction, reducing the temperature and time required, resulting in higher production efficiency and product yield. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the methods or operations used in the embodiments are conventional methods or operations in the art.

[0036] Example 1

[0037] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0038] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment includes the following steps:

[0039] S1. Weigh 200g of lauric acid, add 135g of hydroxyethyl ethylenediamine, mix well, place in a three-necked flask equipped with a stirring distillation device, introduce nitrogen gas, heat to 120℃, turn on the vacuum and set the vacuum degree to -0.07MPa, slowly increase the temperature, react at 200℃ under vacuum for 2h, set the vacuum degree to -0.1MPa, distill off the unreacted hydroxyethyl ethylenediamine to dryness, cool, and obtain the imidazoline ring intermediate product;

[0040] S2. Weigh 5.6g of sodium hydroxide and 3g of triethanolamine as catalysts, add 250g of water, mix well to obtain a mixed solution; add 268g of imidazoline ring intermediate to carry out hydrolysis reaction at a temperature of 40℃ for 1h to obtain hydrolysis product.

[0041] S3. Weigh 122.8g of chloroacetic acid and 100g of 32% sodium hydroxide solution, add the intermediate product from step S2, mix well, heat to 80℃, slowly add 192g of 32% sodium hydroxide solution to carry out quaternization reaction for 2 hours, add 15g of 32% sodium hydroxide solution to adjust the pH to 12, heat to 100℃, and continue the reaction for 3 hours; cool down, add citric acid to adjust the pH of the solution to 9.0, and obtain the imidazoline amphoteric surfactant.

[0042] In the mixed solution of this embodiment, OH - The concentration was 0.56 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.0112.

[0043] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 98.1%.

[0044] Example 2

[0045] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0046] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that, in step S2, the amount of sodium hydroxide added is 10g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0047] In the mixed solution of this embodiment, OH - The concentration was 1 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.0112.

[0048] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 94.8%.

[0049] Example 3

[0050] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0051] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that, in step S2, the amount of sodium hydroxide added is 20g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0052] In the mixed solution of this embodiment, OH - The concentration was 2 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.0112.

[0053] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 94.3%.

[0054] Example 4

[0055] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0056] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that, in step S2, the amount of sodium hydroxide added is 30g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0057] In the mixed solution of this embodiment, OH - The concentration was 3 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.0112.

[0058] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 93.7%.

[0059] Example 5

[0060] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0061] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that, in step S2, the amount of sodium hydroxide added is 1g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0062] In the mixed solution of this embodiment, OH - The concentration was 0.1 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.0112.

[0063] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 93.4%.

[0064] Example 6

[0065] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0066] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that: in step S2, the amount of triethanolamine added is 2.68 g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0067] In the mixed solution of this embodiment, OH - The concentration was 0.56 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.01.

[0068] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 97.7%.

[0069] Example 7

[0070] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0071] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that: in step S2, the amount of triethanolamine added is 26.8 g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0072] In the mixed solution of this embodiment, OH - The concentration was 0.56 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.1.

[0073] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 98.2%.

[0074] Example 8

[0075] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0076] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that: in step S2, the amount of triethanolamine added is 1.34 g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0077] In the mixed solution of this embodiment, OH - The concentration was 0.56 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.005.

[0078] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 96.3%.

[0079] Example 9

[0080] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0081] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that: in step S2, the amount of triethanolamine added is 53.6 g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0082] In the mixed solution of this embodiment, OH - The concentration was 0.56 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.2.

[0083] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 98.5%.

[0084] Example 10

[0085] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0086] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that the hydrolysis reaction time in step S2 is 0.5 h. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0087] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 98.2%.

[0088] Example 11

[0089] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0090] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that the hydrolysis reaction time in step S2 is 2 hours. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0091] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 96.3%.

[0092] Example 12

[0093] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0094] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that the hydrolysis reaction temperature in step S2 is 30°C. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0095] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 97.1%.

[0096] Example 13

[0097] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0098] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that the hydrolysis reaction temperature in step S2 is 45°C. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0099] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 98.0%.

[0100] Example 14

[0101] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium lauroyl amphoteric acetate.

[0102] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that the hydrolysis reaction temperature in step S2 is 55°C. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0103] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 95.5%.

[0104] Example 15

[0105] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium myristoyl amphoteric acetate.

[0106] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that, in step S1, lauric acid is completely replaced with myristic acid in equal amounts. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0107] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 97.7%.

[0108] Example 16

[0109] This invention provides an embodiment of the imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this embodiment is sodium palmitoyl amphoteric acetate.

[0110] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that, in step S1, lauric acid is completely replaced with palmitate in equal amounts. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0111] The yield of the imidazoline-type amphoteric surfactant described in this embodiment is 97.5%.

[0112] Comparative Example 1

[0113] This invention provides a comparative example of an imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this comparative example is sodium lauroyl amphoteric acetate.

[0114] The only difference between the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example and Example 1 is that, in step S2, the amount of sodium hydroxide added is 0.5 g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example are the same as in Example 1.

[0115] In this comparative mixed solution, OH - The concentration was 0.05 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.0112.

[0116] The yield of the imidazoline amphoteric surfactant described in this comparative example was 79.6%.

[0117] Comparative Example 2

[0118] This invention provides a comparative example of an imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this comparative example is sodium lauroyl amphoteric acetate.

[0119] The preparation method of the imidazoline-type amphoteric surfactant described in this comparative example differs from that in Example 1 only in that, in step S2, the amount of sodium hydroxide added is 35g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example are the same as in Example 1.

[0120] In the mixed solution of this embodiment, OH - The concentration was 3.5 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.0112.

[0121] The yield of the imidazoline-type amphoteric surfactant described in this comparative example was 83.7%.

[0122] Comparative Example 3

[0123] This invention provides a comparative example of an imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this comparative example is sodium lauroyl amphoteric acetate.

[0124] The only difference between the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example and Example 1 is that in step S2, the amount of triethanolamine added is 0.536 g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example are the same as in Example 1.

[0125] In this comparative mixed solution, OH - The concentration was 0.56 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.002.

[0126] The yield of the imidazoline-type amphoteric surfactant described in this comparative example was 80.2%.

[0127] Comparative Example 4

[0128] This invention provides a comparative example of an imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this comparative example is sodium lauroyl amphoteric acetate.

[0129] The preparation method of the imidazoline-type amphoteric surfactant described in this comparative example differs from that in Example 1 only in that: in step S2, the amount of triethanolamine added is 67g. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example are the same as in Example 1.

[0130] In this comparative mixed solution, OH - The concentration was 0.56 mol / L, and the mass ratio of the catalyst to the imidazoline ring intermediate was 0.25.

[0131] The yield of the imidazoline amphoteric surfactant described in this comparative example was 98.3%. Although the yield was very high, the large amount of catalyst used resulted in a decrease in the percentage of active ingredient in the product.

[0132] Comparative Example 5

[0133] This invention provides a comparative example of an imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this comparative example is sodium lauroyl amphoteric acetate.

[0134] The preparation method of the imidazoline-type amphoteric surfactant described in this comparative example differs from that in Example 1 only in that the hydrolysis reaction time in step S2 is 15 min. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example are the same as in Example 1.

[0135] The yield of the imidazoline amphoteric surfactant described in this comparative example was 76.5%.

[0136] Comparative Example 6

[0137] This invention provides a comparative example of an imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this comparative example is sodium lauroyl amphoteric acetate.

[0138] The preparation method of the imidazoline-type amphoteric surfactant described in this comparative example differs from that in Example 1 only in that the hydrolysis reaction temperature in step S2 is 25°C. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this comparative example are the same as in Example 1.

[0139] The yield of the imidazoline-type amphoteric surfactant described in this comparative example was 81.6%.

[0140] Comparative Example 7

[0141] This invention provides a comparative example of an imidazoline-type amphoteric surfactant. The imidazoline-type amphoteric surfactant in this comparative example is sodium lauroyl amphoteric acetate.

[0142] The preparation method of the imidazoline-type amphoteric surfactant described in this embodiment differs from that in Example 1 only in that the hydrolysis reaction temperature in step S2 is 70°C. All other steps in the preparation method of the imidazoline-type amphoteric surfactant described in this embodiment are the same as in Example 1.

[0143] The yield of the imidazoline amphoteric surfactant described in this comparative example was 79.4%.

[0144] Example of effect

[0145] To verify the performance of the imidazoline amphoteric surfactant of the present invention, the imidazoline amphoteric surfactants of Examples 1-15 and Comparative Examples 1-7 of the present invention were stored at 5°C for 0 days, 7 days, 15 days, 30 days and 6 months respectively, and the presence of turbidity was observed.

[0146] The test results are shown in Table 1 below.

[0147] Table 1. Summary of Stability Tests for Examples and Comparative Examples

[0148]

[0149]

[0150] As can be seen from Table 1, using the preparation method described in this invention, none of the imidazoline amphoteric surfactants in Examples 1 to 16 showed precipitation after being stored at 5°C for 15 days. Furthermore, the imidazoline amphoteric surfactant in Example 1 did not produce any white precipitate after being stored at 5°C for 6 months, and it also showed high yield and the best performance.

[0151] Comparing Example 1 with Comparative Examples 1-2 and 5-7, it can be seen that the OH in the mixed solution... - The concentration of the surfactant, as well as the temperature and time of hydrolysis, not only affect the rate of hydrolysis and lead to a decrease in yield, but also reduce the stability of imidazoline amphoteric surfactants. A small amount of precipitation appears after 7 days of storage at low temperature, and a large amount of precipitation appears after 15 days of storage.

[0152] Comparing Example 1 with Comparative Examples 3-4, it can be seen that the addition of a large amount of catalyst leads to a decrease in the percentage content of the active ingredient in the product, and causes waste and increased costs; while the addition of a small amount of catalyst leads to a decrease in yield, and the stability of imidazoline amphoteric surfactants at low temperatures is also greatly reduced.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an imidazoline-type amphoteric surfactant, characterized in that, Includes the following steps: S1. Weigh out fatty acids or fatty acid esters, add hydroxyethyl ethylenediamine, mix well, purge with nitrogen, heat to 120°C, turn on the vacuum, set the vacuum degree to -0.05 to -0.09 MPa, raise the temperature to 170 to 210°C, react under vacuum for 2 to 6 hours, increase the negative pressure to ≤ -0.1 MPa, distill off the unreacted hydroxyethyl ethylenediamine at 190 to 220°C, cool, and obtain the imidazoline ring intermediate product; S2. Weigh water, catalyst and alkaline compound, mix them evenly to obtain a mixed solution, add the imidazoline ring intermediate product mentioned in step S1 to carry out a hydrolysis reaction to obtain the hydrolysis product. S3. Weigh the quaternization reagent and the hydrolysis product from step S2, mix them evenly, add alkaline solution to carry out the quaternization reaction, adjust the pH value to 8.5-9.5, and obtain the imidazoline amphoteric surfactant; in step S2, the catalyst is triethanolamine or diethanolamine; In step S2, the mass ratio of the catalyst to the imidazoline ring intermediate is 0.005–0.2, and the OH content of the mixed solution is... - The concentration of the substance is 0.1–3 mol / L, the temperature of the hydrolysis reaction is 30–55℃, and the time of the hydrolysis reaction is 0.3–2 h.

2. The preparation method according to claim 1, characterized in that, The fatty acid is at least one of lauric acid, myristic acid, palmitic acid, stearic acid, and coconut oil acid, and the fatty acid ester is at least one of laurate, myristic acid, palmitic acid, stearate, and coconut oil ester.

3. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of the catalyst to the imidazoline ring intermediate is 0.01 to 0.

1.

4. The preparation method according to claim 1, characterized in that, In step S2, the OH- in the mixed solution - The concentration is 0.5–2 mol / L.

5. The preparation method according to claim 1, characterized in that, In step S2, the hydrolysis reaction temperature is 30–45°C, and the hydrolysis reaction time is 0.5–1 h.

6. An imidazoline amphoteric surfactant obtained by the preparation method of the imidazoline amphoteric surfactant according to any one of claims 1 to 5.

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