High-stability salt-free imidazoline as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of imidazoline surfactant preparation, and discloses high-stability salt-free imidazoline as well as a preparation method and application thereof. The preparation method comprises the following steps: adding molten fatty acid and hydroxyethyl ethylenediamine into a loop reactor, and reacting in nitrogen to obtain an imidazoline intermediate; carrying out hydrolysis reaction on the imidazoline intermediate and water to obtain a hydrolysis product; and carrying out quaternization reaction on the hydrolysate, a basic catalyst and an acrylic acid compound to obtain a quaternization reaction product, adding alkali liquor into the quaternization reaction product, and reacting to obtain the salt-free imidazoline. According to the preparation method disclosed by the invention, the materials realize self-circulation reaction in the loop reactor, and compared with a traditional kettle type stirring process, the mass transfer and heat transfer efficiency is greatly enhanced, the reaction time is short, and the energy consumption is low; the by-product water is cyclically removed in the loop reactor by adopting a nitrogen system, vacuum control dehydration is not needed, the raw material loss is reduced, and the process operation is relatively simple.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of imidazoline surfactants, and particularly to a highly stable salt-free imidazoline and its preparation method and application. Background Art

[0002] Salt-free imidazoline is often used as a detergent, metal corrosion inhibitor and rust remover, etc. due to its high surface activity, low irritation and excellent biodegradability, and is widely used in acidic, neutral and alkaline environments. For example, imidazoline corrosion inhibitors have obvious effects on delaying metal corrosion. It has strong adsorption and can form a persistent protective film on the metal surface. It belongs to a metal corrosion inhibitor with a long action time and high efficiency, which can effectively reduce the speed of metal corrosion and thus reduce oxidation loss.

[0003] At present, the quaternization reagents used in the production process of traditional amphoteric imidazoline surfactants are mainly chloroacetic acid or sodium chloroacetate, and the products usually contain 6-10% of by-product sodium chloride. When applied to personal care products, it will cause certain irritation to the human body; when formulating, too high sodium chloride content may change the micelle aggregation form of the surfactant, resulting in solution turbidity; and its application in the fields of high-end personal care and precision instrument cleaning is also greatly restricted. The amphoteric imidazoline synthesis process usually includes two parts: the preparation of imidazoline intermediate and the quaternization reaction. At present, there are mainly two methods for synthesizing imidazoline intermediate from fatty acid and polyamine as raw materials: the solvent method and the vacuum method. The solvent method and the vacuum method are prone to loss of low-boiling polyamine raw materials when the vacuum degree is high or the reaction temperature is high during the synthesis process. Such processes have problems such as complex operation steps, low atom utilization rate, deep product color and environmental pollution. Therefore, developing salt-free amphoteric imidazoline products can well solve these problems.

[0004] In this regard, Patent CN114380710A uses fatty acid and polyamine as raw materials, and obtains imidazoline intermediate through vacuum dehydration reaction, and then synthesizes salt-free imidazoline through ring-opening and quaternization reaction with acrylic acid or acrylate, where the molar ratio of fatty acid to polyamine is 1:1.1-2. Under vacuum conditions, to ensure a high conversion rate of fatty acid, the feeding ratio of polyamine will increase accordingly, increasing the reaction cost and bringing environmental problems of wastewater treatment; the residue of polyamine in the product will also affect the product quality and application stability.

[0005] In addition, currently commercially available salt-free imidazolines usually have problems such as poor product stability, easy precipitation, and poor water solubility after long-term storage. This may be due to the complexity of the synthesis reaction of imidazoline intermediates, resulting in the generation of by-products such as polyamides and amide esters, which is not conducive to the subsequent quaternization reaction; incomplete reaction in the quaternization stage will also cause too high a residual amount of imidazoline intermediates with poor water solubility. In Patent CN101215808A, diethylenetriamine is mixed with stearic acid in a dropwise manner and dehydrated to synthesize bis-alkylamide imidazoline, where the molar ratio of stearic acid to diethylenetriamine is 3-4:1. The excessive amount of stearic acid added makes it easy to generate insoluble tri-alkylamide by-products in the reaction system, and the excess stearic acid will also remain in the product, which will have an adverse effect on the product stability and affect the product quality. Patent CN102850275A discloses a preparation method of a water-soluble salt-free imidazoline product. This method uses naphthenic acid and organic polyamine as raw materials, generates imidazoline intermediates through dehydration condensation reaction, and then conducts quaternization reaction with acrylic acid under the action of an acid-binding agent such as triethylamine or pyridine to synthesize the target product. However, since naphthenic acid is derived from crude oil and inevitably contains impurities such as benzene and sulfides, the product is toxic to the human body to a certain extent, restricting its application in the fields of daily chemicals, etc.; and a large amount of acid-binding agent needs to be added during the reaction process, which not only increases the production cost, but also the residual amount of the excessive acid-binding agent will reduce the product purity and affect the product quality.

[0006] Therefore, it is of great significance to study and obtain a high-stability salt-free imidazoline with high conversion rate, simple preparation process, and environmental friendliness, as well as its preparation method and application. Summary of the Invention

[0007] In view of this, the present invention provides a high-stability salt-free imidazoline, its preparation method and application, aiming to solve the problems of low reaction conversion rate, complex steps, high energy consumption, relatively high toxicity of the finished product, and poor stability existing in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a preparation method of a high-stability salt-free imidazoline, comprising the following steps:

[0010] 1) Adding molten fatty acid and hydroxyethyl ethylenediamine to a loop reactor, reacting in nitrogen to obtain an imidazoline intermediate;

[0011] 2) Conducting a hydrolysis reaction on the imidazoline intermediate and water to obtain a hydrolysis product;

[0012] 3) Conducting a quaternization reaction on the hydrolysis product, a basic catalyst, and an acrylic acid compound to obtain a quaternization reaction product, and reacting after adding an alkali solution to the quaternization reaction product to obtain a salt-free imidazoline.

[0013] Preferably, in the step 1), the structural formula of the molten fatty acid is as follows:

[0014] Among them, R is C n H 2n+1 , and n is 7, 9, 11, 13, 15 or 17.

[0015] Preferably, in the step 1), the molar ratio of the molten fatty acid to hydroxyethyl ethylenediamine is 1:1 to 1.05.

[0016] Preferably, in the step 1), the pressure of nitrogen in the loop reactor is 0.01 to 1 MPa;

[0017] The temperature of the reaction is 150 to 230 °C, and the reaction time is 4 to 6 h.

[0018] Preferably, in the step 2), the molar ratio of the imidazoline intermediate to water is 1:1.1 to 3;

[0019] The temperature of the hydrolysis reaction is 50 to 80 °C, and the hydrolysis reaction time is 1 to 2 h.

[0020] Preferably, in the step 3), the basic catalyst includes an organic base compound or an organic quaternary ammonium base surfactant, and the acrylic acid compound includes acrylic acid, butyl acrylate or ethyl acrylate;

[0021] The organic base compound includes triethylamine, triethanolamine, methyldiethanolamine, dimethylethanolamine, dimethylformamide, diethylformamide or pyridine;

[0022] The structural formula of the organic quaternary ammonium base surfactant is as follows:

[0023] Among them, R1 is an alkyl group of C1 to C2 or a straight-chain alkyl group of C8 to C 18 , and R2 is a straight-chain alkyl group of C8 to C 18 .

[0024] Preferably, the mass ratio of the sum of the masses of the molten fatty acid and hydroxyethyl ethylenediamine to the mass of the basic catalyst is 100:0.1 to 0.5;

[0025] The molar ratio of the imidazoline intermediate to the acrylic acid compound is 1:1 to 1.5;

[0026] The temperature of the quaternization reaction is 50 to 80 °C, and the quaternization reaction time is 2 to 4 h.

[0027] Preferably, in the step 3), the lye is an aqueous sodium hydroxide solution with a concentration of 25-35 wt%, and the addition amount of the lye is such that the pH value of the solution after the reaction is 9-10;

[0028] The reaction temperature is 50-80 °C, and the reaction time is 1-3 h.

[0029] The present invention also provides a highly stable salt-free imidazoline prepared by the preparation method of a highly stable salt-free imidazoline.

[0030] The present invention also provides the application of the highly stable salt-free imidazoline in surfactants.

[0031] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention does not use the traditional vacuum method and does not require a water-carrying agent. In the preparation method, the materials are self-circulated and reacted in a loop reactor, which greatly enhances the mass transfer and heat transfer efficiency compared with the traditional kettle stirring process. The reaction time is short, the energy consumption is low, the atomic utilization rate is high, and the conversion rate is good; the nitrogen system is used in the loop reactor to circulate and remove the by-product water, and vacuum control for dehydration is not required, reducing raw material loss, and the process operation is relatively simple; and the relatively closed reaction system can isolate the external air, the product has clear color, high quality and almost no inorganic salts, and the production process is simple and safe, providing a good production process for large-scale production.

[0033] In the present invention, the conversion rates of fatty acids and organic amines are high, and there is no need to distill amines after the reaction, which greatly reduces the amount of organic amines used, reduces raw material residues, and reduces environmental pollution; in the quaternization stage, the use of a basic catalyst can promote the reaction of the imidazoline intermediate to be basically complete, reduce the residue of the intermediate in the final product, and the raw material utilization rate of the product is high, and the quality and application performance are stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0035] Figure 1 It is a schematic diagram of the loop reaction system described in the present invention;

[0036] Figure 2 It is the detection result of the room temperature stability of the salt-free imidazoline obtained in Example 1 and the salt-free amphoteric imidazoline described in Comparative Example 1. Among them, (1) is the salt-free imidazoline obtained in Example 1, and (2) is the salt-free amphoteric imidazoline described in Comparative Example 1;

[0037] Figure 3 It is the water solubility test result on the 7th day of the salt-free imidazoline obtained in Example 1 and the salt-free amphoteric imidazoline described in Comparative Example 1. Among them, (1) is the salt-free imidazoline obtained in Example 1, and (2) is the salt-free amphoteric imidazoline described in Comparative Example 1. Detailed implementation manners

[0038] The present invention provides a preparation method of a highly stable salt-free imidazoline, which comprises the following steps:

[0039] 1) Adding molten fatty acid and hydroxyethyl ethylenediamine into a loop reactor, and reacting in nitrogen to obtain an imidazoline intermediate;

[0040] 2) Carrying out a hydrolysis reaction on the imidazoline intermediate and water to obtain a hydrolysis product;

[0041] 3) Carrying out a quaternization reaction on the hydrolysis product, a basic catalyst and an acrylic compound to obtain a quaternization reaction product, and reacting after adding an alkali solution to the quaternization reaction product to obtain a salt-free imidazoline.

[0042] In the present invention, the preparation method is carried out in a loop reaction system, and the loop reaction system comprises a loop reactor, an external circulation heat exchange device, a separation tower, a cooling water storage tank and a storage tank; the bottom of the loop reactor is connected to the bottom of the external circulation heat exchange device, and the top of the external circulation heat exchange device is connected to the top of the loop reactor; the inlet at the bottom of the separation tower is connected to the upper outlet of the loop reactor, the outlet at the bottom of the separation tower is connected to the storage tank, and the top outlet of the separator is connected to the cooling water storage tank through a condenser; the top outlet of the cooling water storage tank is connected to the top of the loop reactor for introducing water into the loop reactor; the external circulation heat exchange device comprises a circulation pump and an external circulation heat exchanger.

[0043] The side surface of the loop reactor is provided with a feed port, the top is connected to the external circulation heat exchanger through a Venturi nozzle, and the bottom is connected to the inlet end of the loop circulation pump; the outlet end of the circulation pump is connected to the bottom of the external circulation heat exchanger; the top of the loop reactor is provided with an air hole for introducing nitrogen; the side surface of the loop reactor is provided with a first through hole and a second through hole near the top of the loop reactor, the first through hole is connected to the inlet at the bottom of the separation tower for introducing part of the hydroxyethyl ethylenediamine and by-product water in the reaction process into the separation tower, and the second through hole is connected to the outlet at the bottom of the separation tower for returning the hydroxyethyl ethylenediamine condensed by the separation tower into the loop reactor.

[0044] The side of the external circulation heat exchanger is provided with a first through hole and a second through hole; the first through hole is opened on the side surface near the top of the external circulation heat exchanger for inputting hot oil into the external circulation heat exchanger; the second through hole is opened on the side surface near the bottom of the external circulation heat exchanger for discharging hot oil.

[0045] The side of the separation tower is provided with a first through-hole and a second through-hole; the first through-hole is opened on the side surface near the top of the separation tower for inputting hot oil into the separation tower; the second through-hole is opened on the side surface near the bottom of the separation tower for discharging hot oil; an outlet is provided at the top of the separation tower for introducing nitrogen gas with by-product water into the condenser.

[0046] The preparation method of the present invention is to mix molten fatty acid and hydroxyethyl ethylenediamine to obtain a mixed material, place the mixed material in a loop reactor, displace nitrogen in the loop reaction system, and maintain the nitrogen pressure in the system at 0.01 - 1.0 MPa. Start the loop circulation pump, heat the mixed material through an external circulation heat exchanger, and then spray the mixed material into the loop reactor by a Venturi nozzle to make the mixed material circulate and undergo dehydration condensation to generate an imidazoline intermediate; during the reaction, part of the hydroxyethyl ethylenediamine and the generated by-product water are carried into the separation tower by nitrogen from the upper part of the loop reactor. The temperature at the top of the separation tower is controlled at 60 - 100 °C, so that the hydroxyethyl ethylenediamine is condensed and refluxed into the loop reactor, and the by-product water flows into the condenser from the top of the separation tower. The outlet temperature of the condenser is lower than 30 °C, so that the by-product water is condensed into the water storage tank, and the remaining nitrogen is drawn into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation.

[0047] Subsequently, cool down the imidazoline intermediate in the loop reactor and reduce the loop reaction system to normal pressure. Add an appropriate amount of water to the loop reactor and carry out the hydrolysis reaction described in step 2) to obtain a hydrolysis product.

[0048] Add an acrylic compound and a basic catalyst to the loop reactor to carry out a quaternization reaction with the hydrolysis product, and then add an alkali solution for acid-base neutralization to obtain salt-free imidazoline.

[0049] In the present invention, the temperature at the top of the separation tower is preferably 65 - 95 °C, more preferably 70 - 90 °C, and even more preferably 75 - 80 °C; the outlet temperature of the condenser is preferably ≤29 °C, more preferably ≤28 °C, and even more preferably ≤27 °C.

[0050] In the present invention, the Venturi nozzle can convert the mixed material from a liquid continuous phase to a gas continuous phase, and the mixed material is atomized into micron-sized small droplets, which greatly increases the reaction area.

[0051] In the present invention, the external circulation heat exchange device enhances the heat transfer efficiency of the reaction system. Compared with the traditional kettle stirring device, the mass transfer and heat transfer efficiency of the external circulation heat exchange device applied in the present invention is significantly enhanced, and it can shorten the reaction time, save energy and protect the environment.

[0052] In the loop reaction system of the present invention, compared with the vacuum method and the solvent method, the loop reaction system is relatively closed, can achieve zero emissions to the environment, and effectively reduces the usage amount and external dissipation of hydroxyethyl ethylenediamine.

[0053] In the present invention, in the step 1), the structural formula of the molten fatty acid is as follows:

[0054] Among them, R is C n H 2n+1 , and n is preferably 7, 9, 11, 13, 15 or 17.

[0055] In the present invention, in the step 1), the molar ratio of the molten fatty acid to hydroxyethyl ethylenediamine is preferably 1:1 to 1.05, further preferably 1:1.01 to 1.04, and more preferably 1:1.02 to 1.03.

[0056] In the present invention, in the step 1), the pressure of nitrogen in the loop reactor is preferably 0.01 to 1 MPa, further preferably 0.1 to 0.9 MPa, and more preferably 0.2 to 0.5 MPa;

[0057] The temperature of the reaction is preferably 150 to 230 °C, further preferably 160 to 220 °C, and more preferably 170 to 210 °C. The reaction time is preferably 4 to 6 h, further preferably 4.5 to 5.5 h, and more preferably 5 h.

[0058] In the present invention, the reaction equation of the reaction in the step 1) is as shown in Formula I:

[0059]

[0060] In the present invention, in the step 2), the molar ratio of the imidazoline intermediate to water is preferably 1:1.1 to 3, further preferably 1:1.5 to 2.8, and more preferably 1:2 to 2.5;

[0061] The temperature of the hydrolysis reaction is preferably 50 to 80 °C, further preferably 55 to 75 °C, and more preferably 60 to 70 °C. The hydrolysis reaction time is preferably 1 to 2 h, and further preferably 1.5 h.

[0062] In the present invention, the reaction equation of the reaction in the step 2) is as shown in Formula II:

[0063]

[0064] In the present invention, in the step 3), the basic catalyst includes an organic base compound or an organic quaternary ammonium base surfactant, and the acrylic acid compound preferably includes acrylic acid, butyl acrylate or ethyl acrylate;

[0065] The organic base compound preferably includes triethylamine, triethanolamine, methyldiethanolamine, dimethylethanolamine, dimethylformamide, diethylformamide or pyridine;

[0066] The structural formula of the organic quaternary ammonium base surfactant is as follows:

[0067] Among them, R1 is preferably an alkyl group with 1 to 2 carbon atoms or a straight-chain alkyl group with 8 to C 18 and R2 is preferably a straight-chain alkyl group with 8 to C 18 straight-chain alkyl group;

[0068] In the present invention, the preparation method of the organic quaternary ammonium base surfactant refers to Patent CN104313634A.

[0069] In the present invention, the mass ratio of the sum of the mass of the molten fatty acid and hydroxyethyl ethylenediamine to the mass of the basic catalyst is preferably 100:0.1 to 0.5, more preferably 100:0.2 to 0.4, and even more preferably 100:0.3;

[0070] The molar ratio of the imidazoline intermediate to the acrylic acid compound is preferably 1:1 to 1.5, more preferably 1:1.1 to 1.4, and even more preferably 1:1.2 to 1.3;

[0071] The temperature of the quaternization reaction is preferably 50 to 80 °C, more preferably 55 to 75 °C, and even more preferably 60 to 70 °C. The time of the quaternization reaction is preferably 2 to 4 h, more preferably 2.5 to 3.5 h, and even more preferably 3 h.

[0072] In the present invention, the reaction equations of the reaction in step 3) are shown in Formulas III and IV:

[0073]

[0074] In the present invention, in step 3), the alkali solution is preferably an aqueous sodium hydroxide solution. The concentration of the aqueous sodium hydroxide solution is preferably 25 to 35 wt%, more preferably 28 to 34 wt%, and even more preferably 30 to 32 wt%. The addition amount of the alkali solution is such that the pH value of the solution after the reaction is preferably 9 to 10, more preferably 9.2 to 9.8, and even more preferably 9.5 to 9.7;

[0075] The purpose of adding the alkali solution is to adjust the pH value;

[0076] The reaction temperature is preferably 50 to 80 °C, more preferably 55 to 75 °C, and even more preferably 60 to 70 °C. The reaction time is preferably 1 to 3 h, more preferably 1.5 to 2.5 h, and even more preferably 2 h.

[0077] In the present invention, in the step 3), the temperature of the quaternization reaction is preferably the same as the temperature of the reaction.

[0078] The present invention also provides a highly stable salt-free imidazoline prepared by the preparation method of highly stable salt-free imidazoline.

[0079] The present invention also provides the application of highly stable salt-free imidazoline in surfactants.

[0080] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0081] Example 1

[0082] 192.32 kg of molten lauric acid was mixed with 100 kg of hydroxyethyl ethylenediamine to obtain a mixed material. The mixed material was placed in a loop reactor, the system was purged with nitrogen, and the nitrogen pressure of the system was maintained at 0.01 MPa. The loop circulation pump was started, and the mixed material was heated through an external circulation heat exchanger. Then, it was sprayed into the loop reactor by a Venturi nozzle to make the mixed material circulate. When the material temperature rose to 160 °C, timing started. It was heated from 160 °C to 220 °C at a heating rate of 10 °C / min, and the reaction time from 160 °C to 220 °C was 6 h. During the reaction, due to the high temperature, part of the hydroxyethyl ethylenediamine and the generated by-product water were carried from the upper part of the loop reactor into the separation tower by nitrogen. The temperature at the top of the separation tower was 60 °C. The hydroxyethyl ethylenediamine was condensed and refluxed from the bottom of the separation tower back into the loop reactor for continuous reaction. The by-product water was carried into the condenser (the outlet temperature was 30 °C) by nitrogen at the top of the separation tower and condensed, and then entered the water storage tank. The remaining nitrogen was drawn into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 252.1 kg of imidazoline intermediate was obtained. The acid value was measured to be 0.9589 mgKOH / g, and the conversion rate of lauric acid was 99.57%.

[0083] Subsequently, the imidazoline intermediate in the loop reactor was cooled to 60 °C, and the loop reaction system was reduced to atmospheric pressure. 18 kg of water was added to the loop reactor, and hydrolysis reaction was carried out at 60 °C for 1 h to obtain a hydrolysis product.

[0084] 103.47 kg of ethyl acrylate and 0.8 kg of triethylamine were added to the loop reactor, and quaternization reaction was carried out with the hydrolysis product at 60 °C for 2 h. Finally, an aqueous sodium hydroxide solution with a concentration of 30 wt% was added to make the pH value of the reaction system 9.5, and reaction was carried out at 60 °C for 2 h to obtain a light yellow salt-free imidazoline.

[0085] Example 2

[0086] 200.3 kg of molten lauric acid was mixed with 109 kg of hydroxyethyl ethylenediamine to obtain a mixed material. The mixed material was placed in a loop reactor, and the system was purged with nitrogen, and the nitrogen pressure of the system was maintained at 0.05 MPa. The loop circulation pump was started, and the mixed material was heated by an external circulation heat exchanger. Then, it was sprayed into the loop reactor through a Venturi nozzle to make the mixed material circulate. When the material temperature rose to 160 °C, timing started. It was heated from 160 °C to 220 °C at a heating rate of 10 °C / min, and the reaction time from 160 °C to 220 °C was 6 h. During the reaction, the high temperature caused part of the hydroxyethyl ethylenediamine and the generated by-product water to be carried into the separation tower through nitrogen from the upper part of the loop reactor. The temperature at the top of the separation tower was 75 °C. The hydroxyethyl ethylenediamine was condensed and refluxed from the bottom of the separation tower to the loop reactor for continuous reaction. The by-product water was carried into the condenser (the outlet temperature was 27 °C) through nitrogen from the top of the separation tower and condensed, and then entered the water storage tank. The remaining nitrogen was sucked into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 290.26 kg of imidazoline intermediate was obtained. The acid value was measured to be 0.1271 mg KOH / g, and the conversion rate of lauric acid was 99.94%.

[0087] Subsequently, the imidazoline intermediate in the loop reactor was cooled to 60 °C, and the loop reaction system was reduced to atmospheric pressure. 38.99 kg of water was added to the loop reactor, and hydrolysis reaction was carried out at 60 °C for 2 h to obtain a hydrolysis product.

[0088] 129.97 kg of ethyl acrylate and 0.7 kg of methyldiethanolamine were added to the loop reactor, and quaternization reaction was carried out with the hydrolysis product at 60 °C for 2 h. Finally, an aqueous sodium hydroxide solution with a concentration of 30 wt% was added to make the pH value of the reaction system 10, and the reaction was carried out at 60 °C for 1 h to obtain light yellow salt-free imidazoline.

[0089] Example 3

[0090] Mix 200.3 kg of molten lauric acid with 109 kg of hydroxyethyl ethylenediamine to obtain a mixed material. Place the mixed material in a loop reactor, displace the system with nitrogen, and maintain the nitrogen pressure in the system at 0.1 MPa. Start the loop circulation pump and heat the mixed material through an external circulation heat exchanger. Then, spray it into the loop reactor through a Venturi nozzle to make the mixed material circulate. Start timing when the material temperature rises to 160 °C, and raise the temperature from 160 °C to 210 °C at a heating rate of 10 °C / min. The reaction time from 160 °C to 210 °C is 5 h. During the reaction, the high temperature causes some hydroxyethyl ethylenediamine and the generated by-product water to be carried into the separation tower from the upper part of the loop reactor by nitrogen. The temperature at the top of the separation tower is 90 °C. The hydroxyethyl ethylenediamine is condensed and refluxed from the bottom of the separation tower to the loop reactor for continuous reaction. The by-product water is carried into the condenser (outlet temperature is 30 °C) by nitrogen at the top of the separation tower and condensed, then enters the water storage tank. The remaining nitrogen is sucked into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 240.6 kg of imidazoline intermediate is obtained. The acid value is measured to be 0.9589 mgKOH / g, and the conversion rate of lauric acid is 99.57%.

[0091] Subsequently, cool the imidazoline intermediate in the loop reactor to 50 °C, and reduce the loop reaction system to atmospheric pressure. Add 32.32 kg of water to the loop reactor and carry out a hydrolysis reaction at 50 °C for 2 h to obtain a hydrolysis product.

[0092] Add 116.71 kg of ethyl acrylate and 1.5 kg of triethanolamine to the loop reactor and carry out a quaternization reaction with the hydrolysis product at 50 °C for 2 h. Finally, add an aqueous sodium hydroxide solution with a concentration of 30 wt% to make the pH value of the reaction system 9, and react at 60 °C for 2 h to obtain a light yellow salt-free imidazoline.

[0093] Example 4

[0094] 200.3 kg of molten lauric acid was mixed with 105 kg of hydroxyethyl ethylenediamine to obtain a mixed material. The mixed material was placed in a loop reactor, and the system was purged with nitrogen and maintained at a nitrogen pressure of 0.01 MPa. The loop circulation pump was started, and the mixed material was heated through an external circulation heat exchanger. Then, it was sprayed into the loop reactor by a Venturi nozzle to make the mixed material circulate. When the material temperature rose to 160 °C, timing started. It was heated from 160 °C to 220 °C at a heating rate of 10 °C / min, and the reaction time from 160 °C to 220 °C was 6 h. During the reaction, the high temperature caused part of the hydroxyethyl ethylenediamine and the generated by-product water to be carried into the separation tower through nitrogen from the upper part of the loop reactor. The temperature at the top of the separation tower was 60 °C. The hydroxyethyl ethylenediamine was condensed and refluxed from the bottom of the separation tower to the loop reactor for continuous reaction. The by-product water was carried into the condenser (outlet temperature 30 °C) through nitrogen at the top of the separation tower and condensed, and then entered the water storage tank. The remaining nitrogen was drawn into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 253 kg of imidazoline intermediate was obtained. The acid value was measured to be 0.1311 mg KOH / g, and the conversion rate of lauric acid was 99.95%.

[0095] Subsequently, the imidazoline intermediate in the loop reactor was cooled to 65 °C, and the loop reaction system was reduced to atmospheric pressure. 50.98 kg of water was added to the loop reactor, and hydrolysis reaction was carried out at 65 °C for 2 h to obtain a hydrolysis product.

[0096] 65.7 kg of ethyl acrylate and 0.6 kg of pyridine were added to the loop reactor, and quaternization reaction was carried out with the hydrolysis product at 65 °C for 1.5 h. Finally, an aqueous sodium hydroxide solution with a concentration of 30 wt% was added to make the pH value of the reaction system 10, and reaction was carried out at 65 °C for 1 h to obtain a light yellow salt-free imidazoline.

[0097] Example 5

[0098] 120 kg of molten capric acid was mixed with 75 kg of hydroxyethyl ethylenediamine to obtain a mixed material. The mixed material was placed in a loop reactor, and the system was purged with nitrogen and maintained at a nitrogen pressure of 0.2 MPa. The loop circulation pump was started, and the mixed material was heated through an external circulation heat exchanger. Then, it was sprayed into the loop reactor by a Venturi nozzle to make the mixed material circulate. Timing started when the material temperature rose to 160 °C. It was heated from 160 °C to 220 °C at a heating rate of 15 °C / min, and the reaction time from 160 °C to 220 °C was 4 h. During the reaction, the high temperature caused part of the hydroxyethyl ethylenediamine and the generated by-product water to be carried into the separation tower through nitrogen from the upper part of the loop reactor. The temperature at the top of the separation tower was 90 °C. The hydroxyethyl ethylenediamine was condensed and refluxed from the bottom of the separation tower to the loop reactor for continuous reaction. The by-product water was carried into the condenser (outlet temperature 28 °C) through nitrogen at the top of the separation tower and condensed, then entered the water storage tank. The remaining nitrogen was drawn into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 172.84 kg of imidazoline intermediate was obtained. The acid value was measured to be 0.1326 mg KOH / g, and the conversion rate of capric acid was 99.94%.

[0099] Subsequently, the imidazoline intermediate in the loop reactor was cooled to 80 °C, and the loop reaction system was reduced to atmospheric pressure. 12.96 kg of water was added to the loop reactor, and hydrolysis reaction was carried out at 80 °C for 1 h to obtain a hydrolysis product.

[0100] 54.3 kg of ethyl acrylate and 0.7 kg of triethylamine were added to the loop reactor and subjected to a quaternization reaction with the hydrolysis product at 60 °C for 3 h. Finally, an aqueous sodium hydroxide solution with a concentration of 30 wt% was added to make the pH value of the reaction system 10, and the reaction was carried out at 60 °C for 3 h to obtain a light yellow salt-free imidazoline.

[0101] Example 6

[0102] Mix 139.49 kg of molten myristic acid with 65 kg of hydroxyethyl ethylenediamine to obtain a mixed material. Place the mixed material in a loop reactor, displace the system with nitrogen, and maintain the nitrogen pressure in the system at 0.02 MPa. Start the loop circulation pump and heat the mixed material through an external circulation heat exchanger. Then, spray it into the loop reactor through a Venturi nozzle to make the mixed material circulate. Start timing when the material temperature rises to 160 °C, and raise the temperature from 160 °C to 210 °C at a heating rate of 10 °C / min. The reaction time from 160 °C to 210 °C is 5 h. During the reaction, the high temperature causes part of the hydroxyethyl ethylenediamine and the generated by-product water to be carried into the separation tower through nitrogen from the upper part of the loop reactor. The temperature at the top of the separation tower is 70 °C. The hydroxyethyl ethylenediamine is condensed and refluxed from the bottom of the separation tower to the loop reactor for continuous reaction. The by-product water is carried into the condenser (outlet temperature is 29 °C) through nitrogen from the top of the separation tower and condensed, and then enters the water storage tank. The remaining nitrogen is drawn into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 183.06 kg of imidazoline intermediate is obtained, the acid value is measured to be 0.01 mg KOH / g, and the conversion rate of myristic acid is 99.99%.

[0103] Subsequently, cool the imidazoline intermediate in the loop reactor to 80 °C, and reduce the loop reaction system to atmospheric pressure. Add 22.26 kg of water to the loop reactor and carry out a hydrolysis reaction at 80 °C for 2 h to obtain a hydrolysis product.

[0104] Add 80.4 kg of ethyl acrylate and 0.9 kg of dimethyl monoethanolamine to the loop reactor, carry out a quaternization reaction with the hydrolysis product at 80 °C for 3 h, and finally add an aqueous sodium hydroxide solution with a concentration of 30 wt% to make the pH value of the reaction system 10, and react at 80 °C for 2 h to obtain a light yellow salt-free imidazoline.

[0105] Example 7

[0106] 192.32 kg of molten lauric acid was mixed with 105 kg of hydroxyethyl ethylenediamine to obtain a mixed material. The mixed material was placed in a loop reactor, and the system was purged with nitrogen, and the nitrogen pressure of the system was maintained at 0.3 MPa. The loop circulation pump was started, and the mixed material was heated through an external circulation heat exchanger. Then, it was sprayed into the loop reactor by a Venturi nozzle to make the mixed material circulate. When the material temperature rose to 160 °C, timing started. It was heated from 160 °C to 210 °C at a heating rate of 10 °C / min, and the reaction time from 160 °C to 210 °C was 5 h. During the reaction, the high temperature caused part of the hydroxyethyl ethylenediamine and the generated by-product water to be carried into the separation tower by nitrogen from the upper part of the loop reactor. The temperature at the top of the separation tower was 100 °C. The hydroxyethyl ethylenediamine was condensed and refluxed from the bottom of the separation tower to the loop reactor for continuous reaction. The by-product water was carried into the condenser (the outlet temperature was 30 °C) by nitrogen from the top of the separation tower and condensed, and then entered the water storage tank. The remaining nitrogen was drawn into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 239.78 kg of imidazoline intermediate was obtained. The acid value was measured to be 0.9665 mg KOH / g, and the conversion rate of lauric acid was 99.48%.

[0107] Subsequently, the imidazoline intermediate in the loop reactor was cooled to 70 °C, and the loop reaction system was reduced to atmospheric pressure. 48.31 kg of water was added to the loop reactor, and hydrolysis reaction was carried out at 70 °C for 1 h to obtain a hydrolysis product.

[0108] 116.31 kg of ethyl acrylate and 1.5 kg of diethylformamide were added to the loop reactor, and quaternization reaction was carried out with the hydrolysis product at 70 °C for 2 h. Finally, an aqueous sodium hydroxide solution with a concentration of 30 wt% was added to make the pH value of the reaction system 9.5, and reaction was carried out at 70 °C for 2 h to obtain light yellow salt-free imidazoline.

[0109] Example 8

[0110] 120 kg of molten capric acid was mixed with 73.5 kg of hydroxyethyl ethylenediamine to obtain a mixed material. The mixed material was placed in a loop reactor, the system was purged with nitrogen, and the nitrogen pressure of the system was maintained at 0.5 MPa. The loop circulation pump was started, and the mixed material was heated through an external circulation heat exchanger. Then, it was sprayed into the loop reactor by a Venturi nozzle to make the mixed material circulate. When the material temperature rose to 160 °C, timing started. It was heated from 160 °C to 210 °C at a heating rate of 10 °C / min, and the reaction time from 160 °C to 210 °C was 5 h. During the reaction, high temperature caused some hydroxyethyl ethylenediamine and the generated by-product water to be carried into the separation tower through nitrogen from the upper part of the loop reactor. The temperature at the top of the separation tower was 100 °C. Hydroxyethyl ethylenediamine was condensed and refluxed from the bottom of the separation tower to the loop reactor for continuous reaction. The by-product water was carried into the condenser (outlet temperature was 29 °C) through nitrogen from the top of the separation tower and condensed, and then entered the water storage tank. The remaining nitrogen was drawn into the loop reactor by the Venturi nozzle to achieve continuous gas circuit circulation. After the reaction, 162.04 kg of imidazoline intermediate was obtained. The acid value was measured to be 0.1327 mg KOH / g, and the conversion rate of capric acid was 99.96%.

[0111] Subsequently, the imidazoline intermediate in the loop reactor was cooled to 60 °C, and the loop reaction system was reduced to atmospheric pressure. 36.46 kg of water was added to the loop reactor, and hydrolysis reaction was carried out at 60 °C for 1 h to obtain a hydrolysis product.

[0112] 43.07 kg of ethyl acrylate and 0.4 kg of triethylamine were added to the loop reactor, and quaternization reaction was carried out with the hydrolysis product at 60 °C for 2 h. Finally, an aqueous sodium hydroxide solution with a concentration of 30 wt% was added to make the pH value of the reaction system 9, and reaction was carried out at 60 °C for 2 h to obtain light yellow salt-free imidazoline.

[0113] Comparative Example 1

[0114] Salt-free amphoteric imidazoline was purchased from Qinhuangdao Yuexiang Technology Co., Ltd.

[0115] The salt-free imidazolines obtained in Examples 1 to 8 were respectively subjected to the following performance tests:

[0116] Stability test:

[0117] The salt-free imidazolines obtained in Example 1 and Example 4 and the salt-free amphoteric imidazoline described in Comparative Example 1 were subjected to the following stability test, and the test results are shown in Table 1 and Figure 2 as shown.

[0118] (1) Low-temperature stability: The sample was frozen in a refrigerator at 4 °C for 3 months, then taken out and restored to 25 °C, and the change in the sample state was observed; if there was no stratification, no suspended matter, and the transparent liquid was not turbid, the low-temperature stability of the sample was good.

[0119] (2) Ambient temperature stability: Place the sample in an incubator at 37 °C for 3 months and observe the change in the state of the sample; if there is no change in the appearance of the sample, no precipitation, and no suspended matter, the sample has good ambient temperature stability.

[0120] Table 1 Stability test results of the salt-free imidazoline obtained in Example 1 and Example 4 and the salt-free amphoteric imidazoline described in Comparative Example 1

[0121]

[0122] As can be seen from Table 1, after being placed at low temperature and ambient temperature for 3 months, both Example 1 and Example 4 are light yellow transparent liquids, having good low-temperature stability and ambient temperature stability. However, in Comparative Example 1, there are more suspended insoluble substances at low temperature, and the solution is turbid and there are also many suspended substances under ambient temperature conditions. It can be seen that the salt-free imidazoline obtained in the present invention has obvious advantages in terms of low-temperature and ambient temperature stability.

[0123] Water solubility test:

[0124] Perform the following water solubility test on the salt-free imidazoline obtained in Example 1 and Example 4 and the salt-free amphoteric imidazoline described in Comparative Example 1. The test results are shown in Table 2 and Figure 3 as follows.

[0125] Under ambient temperature conditions, dissolve 1 g of the sample in 100 g of deionized water and mix well. Observe the change in the appearance of the solution on the 1st, 3rd, and 7th days; if there is no change in the appearance of the solution, no precipitation, and no suspension, the sample has good water solubility.

[0126] Table 2 Water solubility test results of the salt-free imidazoline obtained in Example 1 and Example 4 and the salt-free amphoteric imidazoline described in Comparative Example 1

[0127]

[0128] As can be seen from Table 2, the salt-free imidazoline obtained in Example 1 and Example 4 is still a colorless transparent liquid on the 7th day, indicating that the product has good water solubility; the salt-free amphoteric imidazoline described in Comparative Example 1 is in a state of emitting blue light on the 3rd day and presents a milky white turbid liquid on the 7th day, with poor water solubility. It can be seen that the salt-free imidazoline obtained in the present invention shows excellent performance in terms of water solubility compared with the commercially available salt-free amphoteric imidazoline, ensuring the stability of the product in terms of application performance.

[0129] Corrosion inhibition test:

[0130] Perform the following metal corrosion inhibition performance test on the salt-free imidazoline obtained in Example 1 and Example 4 and the salt-free amphoteric imidazoline described in Comparative Example 1. The test results are shown in Table 3.

[0131] Use the static weight loss method to test the corrosion inhibition performance of the sample:

[0132] The carbon steel used is of type Q235A, with a specification of 50 mm × 25 mm × 2 mm (surface area of 28 cm 2 ), and the chemical composition is as follows: C 0.14 - 0.22 wt%, Mn 0.30 - 0.65 wt%, P ≤ 0.045 wt%, Si ≤ 0.03 wt%, and the balance is Fe.

[0133] Treatment method: Take 10 carbon steel specimens. Grind the carbon steel specimens with metallographic sandpapers of different specifications, wash them with deionized water and ethanol respectively, dry them and weigh them. Then immerse the carbon steel specimens into the salt - free imidazoline solution of Example 1 with a concentration of 20 mg / L, the salt - free imidazoline solution of Example 4 with a concentration of 20 mg / L, the salt - free amphoteric imidazoline solution of Comparative Example 1 with a concentration of 20 mg / L, the salt - free imidazoline solution of Example 1 with a concentration of 40 mg / L, the salt - free imidazoline solution of Example 4 with a concentration of 40 mg / L, the salt - free amphoteric imidazoline solution of Comparative Example 1 with a concentration of 40 mg / L, the salt - free imidazoline solution of Example 1 with a concentration of 80 mg / L, the salt - free imidazoline solution of Example 4 with a concentration of 80 mg / L, the salt - free amphoteric imidazoline solution of Comparative Example 1 with a concentration of 80 mg / L, and a single solvent. The solvents of the above imidazoline solutions and the single solvent are all 4 wt% hydrochloric acid. After standing for 4 h, take them out, wash them with deionized water and ethanol, and then dry and weigh them.

[0134] The calculation formula of the corrosion rate ν is shown in Formula I, and the calculation formula of the corrosion inhibition rate η is shown in Formula II.

[0135]

[0136] In Formula I and Formula II:

[0137] Δm is the mass difference of the carbon steel specimen before and after the corrosion inhibition test, g;

[0138] A is the surface area of the carbon steel specimen, m 2 ;

[0139] T is the test time, h;

[0140] ν0 is the corrosion rate of the carbon steel specimen when immersed in the solvent, g·(m 2 ·h) -1 ;

[0141] ν is the corrosion rate of the carbon steel specimen when immersed in the imidazoline solution, g·(m 2 ·h) -1 .

[0142] Table 3 Corrosion inhibition test results of the salt - free imidazolines obtained from Example 1 and Example 4 and the salt - free amphoteric imidazoline of Comparative Example 1

[0143]

[0144] As can be seen from Table 3, the corrosion inhibition performance of Comparative Example 1 is the worst; the metal corrosion inhibition of Example 1 and Example 4 is basically the same, and even the corrosion inhibition efficiency at a concentration of 20 mg / L is higher than 98.5%, showing excellent corrosion inhibition performance. Thus, it can be seen that the raw materials of the present invention react relatively completely, with less residue of imidazoline intermediate and by-products, ensuring the product stability and good water solubility, and endowing the product with better metal corrosion inhibition performance. This makes the salt-free imidazoline obtained by the present invention also have good market application value in the fields of daily chemical washing and industrial cleaning, etc.

[0145] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a highly stable salt-free imidazoline, characterized in that, It includes the following steps: 1) Add molten fatty acid and hydroxyethyl ethylenediamine into a loop reactor, and react in nitrogen to obtain an imidazoline intermediate; 2) Carry out a hydrolysis reaction on the imidazoline intermediate and water to obtain a hydrolysis product; 3) Carry out a quaternization reaction on the hydrolysis product, an alkaline catalyst and an acrylic compound to obtain a quaternization reaction product, and react after adding an alkali solution to the quaternization reaction product to obtain a salt-free imidazoline.

2. The preparation method of a highly stable salt-free imidazoline according to claim 1, characterized in that, In the step 1), the structural formula of the molten fatty acid is as follows: Among them, R is C n H 2n+1 , and n is 7, 9, 11, 13, 15 or 17.

3. The preparation method of a highly stable salt-free imidazoline according to claim 1, characterized in that, In the step 1), the molar ratio of the molten fatty acid to hydroxyethyl ethylenediamine is 1:1 to 1.

05.

4. The preparation method of a highly stable salt-free imidazoline according to claim 2 or 3, characterized in that, In the step 1), the pressure of nitrogen in the loop reactor is 0.01 to 1 MPa; The temperature of the reaction is 150 to 230 °C, and the reaction time is 4 to 6 h.

5. The preparation method of a highly stable salt-free imidazoline according to claim 1, characterized in that, In the step 2), the molar ratio of the imidazoline intermediate to water is 1:1.1 to 3; The temperature of the hydrolysis reaction is 50 to 80 °C, and the hydrolysis reaction time is 1 to 2 h.

6. The preparation method of a highly stable salt-free imidazoline according to claim 5, characterized in that, In the step 3), the alkaline catalyst includes an organic base compound or an organic quaternary ammonium base surfactant, and the acrylic compound includes acrylic acid, butyl acrylate or ethyl acrylate; The organic base compound includes triethylamine, triethanolamine, methyldiethanolamine, dimethylethanolamine, dimethylformamide, diethylformamide or pyridine; The structural formula of the organic quaternary ammonium base surfactant is as follows: Among them, R1 is an alkyl group with 1 to 2 carbon atoms or a straight-chain alkyl group with 8 to C 18 and R2 is a straight-chain alkyl group with 8 to C 18 carbon atoms.

7. The preparation method of a highly stable salt-free imidazoline according to claim 5 or 6, characterized in that, The mass ratio of the sum of the mass of the molten fatty acid and hydroxyethyl ethylenediamine to the mass of the alkaline catalyst is 100:0.1 to 0.5; The molar ratio of the imidazoline intermediate to the acrylic compound is 1:1 to 1.5; The temperature of the quaternization reaction is 50 to 80 °C, and the quaternization reaction time is 2 to 4 h.

8. The preparation method of a highly stable salt-free imidazoline according to claim 7, characterized in that, In the step 3), the alkali solution is an aqueous sodium hydroxide solution, the concentration of the aqueous sodium hydroxide solution is 25 to 35 wt%, and the addition amount of the alkali solution is such that the pH value of the solution after the reaction is 9 to 10; The temperature of the reaction is 50 to 80 °C, and the reaction time is 1 to 3 h.

9. The highly stable salt-free imidazoline prepared by the preparation method of the highly stable salt-free imidazoline according to any one of claims 1 to 8.

10. The application of the highly stable salt-free imidazoline according to claim 9 in a surfactant.

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