Betaine surfactant as well as preparation method and application thereof

Abstract

The invention provides a betaine surfactant as well as a preparation method and application thereof, and belongs to the technical field of surfactants. The invention designs a novel betaine surfactant with a structure as shown in a formula I. The surfactant has a unique chemical structure, so that the stability of an emulsion can be remarkably enhanced in an emulsion polymerization process, including long-term storage, mechanical stirring and under the conditions of different temperatures and pH values. The demulsification and flocculation risks of the emulsion can be effectively reduced, and the emulsion system is ensured to be uniform and stable. Meanwhile, the surfactant can more efficiently emulsify polymerized monomers, improve the conversion rate and polymerization reaction rate of the monomers, and optimize the particle size distribution of polymerized products. Therefore, sustainable development and high performance of the emulsion polymerization process are realized. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of surfactants, and in particular relates to a betaine surfactant and a preparation method and application thereof. Background Art

[0002] Fluorosurfactants are special surfactants that contain fluorinated carbon chains as nonpolar groups in their molecular structure. Compared with ordinary surfactants, fluorinated surfactants have attracted increasing attention due to their unique properties, such as thermal and chemical stability, high surface activity, high surface capacity, and low critical micelle concentration (CMC). Among them, perfluoroalkyl and polyfluoroalkyl surfactants, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) chemicals, have been widely used in fluoropolymer production, chip manufacturing, fire extinguishers, coatings and other fields. Compared with hydrocarbon surfactants, perfluoroalkyl and polyfluoroalkyl surfactants have superior interfacial properties and chemical inertness and have been proven to be the most suitable surfactants for the synthesis of fluoropolymer emulsions. However, they pose risks to the environment due to their potential bioaccumulation in wildlife, long-distance migration, and biomagnification in the food web. In particular, long carbon-fluorinated chains (≥7) are extremely difficult to degrade under enzymatic or metabolic decomposition. For these reasons, since perfluorooctane sulfonyl fluoride / sulfonic acid / sulfonate and related derivatives (collectively referred to as PFOS) were listed as persistent organic pollutants (POPs) in the Stockholm Convention on Persistent Organic Pollutants, the production and application of PFOS have been regulated and restricted by the international community.

[0003] In recent years, several fluorocarbon surfactants have been developed as substitutes for perfluorooctane sulfonic acid (PFOS). The main idea is to shorten the perfluorocarbon chain or replace the perfluoroalkyl with a fluorinated polyether segment. However, the disadvantage is that simply reducing the number of carbon fluorine atoms will reduce the hydrophobic segment of the surfactant, resulting in weak performance durability. Due to its structural characteristics, in the emulsion polymerization process of the final product, the performance provided by the short-chain fluorosurfactant, such as the reduction of surface tension, is not durable enough and has poor stability, resulting in the poor ability of the short-chain fluorosurfactant to stabilize the emulsion. In the emulsion polymerization process, it cannot well prevent the aggregation of emulsion particles, which easily causes the emulsion system to lose stability and demulsification. At the same time, short-chain fluorosurfactants also have the disadvantages of being difficult to degrade, bioaccumulative, toxic, high preparation cost and excessive foam stability. For example, CN104861091A and CN105924375A both disclose a short-chain fluorinated surfactant. Although this alternative short-chain fluorinated surfactant has lower bioaccumulation than perfluoroalkyl chains of 8 or more carbon atoms, it is still a highly fluorinated compound and still has a certain bioaccumulation, which does not meet the requirements of green chemistry for the development of fluoropolymers.

[0004] In summary, the surfactants used in the emulsion polymerization of fluorinated polymers in the prior art still have many defects, such as poor emulsification effect, poor stability, poor environmental friendliness, and limited improvement in the performance of fluorinated polymer products. Summary of the invention

[0005] In view of the defects of the prior art, the object of the present invention is to provide a betaine surfactant and a preparation method and use thereof.

[0006] The present invention provides a betaine surfactant, the structure of which is shown in Formula I:

[0007]

[0008] Wherein, n1 is selected from 1, 2, 3, 4, 5, 6;

[0009] n2 is selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12;

[0010] R1 and R2 are each independently selected from C 1～3 alkyl.

[0011] Furthermore, the betaine surfactant is one of the following structures:

[0012] The present invention also provides a method for preparing the above-mentioned betaine surfactant, the method comprising the following steps:

[0013]

[0014] (1) reacting with a sulfonating agent to prepare an intermediate product;

[0015] (2) The intermediate product and Reaction to obtain betaine surfactant;

[0016] Among them, n1 and n2 are as described above.

[0017] Furthermore, in step (1), the sulfonating agent is sodium bisulfite or sodium sulfite; The molar ratio of the sulfonating agent is 1:0.5-5, and the reaction conditions are: reacting at 60-95°C for 6-15 hours;

[0018] In step (2), the reaction is carried out under the action of a base, which is an inorganic base; the intermediate product and The molar ratio is 1.2 to 2:1; the solvent of the reaction is an organic solvent; and the reaction conditions are: reacting at 40 to 100° C. for 5 to 20 hours.

[0019] Further, in step (1), the The molar ratio of the sulfonating agent to the sulfonating agent is 1:0.8-1.5, and the reaction conditions are: reacting at 85°C for 10-12 hours;

[0020] In step (2), a base is added to adjust the pH to 7-9; the base is sodium hydroxide or potassium hydroxide; the intermediate product and The molar ratio is 1.5-1.8:1; the solvent of the reaction is selected from one or a mixture of two or more of methanol, ethanol, isopropanol, dichloromethane and toluene; the reaction conditions are: reacting at 60-80°C for 8-18 hours.

[0021] The present invention also provides use of the betaine surfactant in preparing an emulsifier.

[0022] Furthermore, the emulsifier is an emulsifier for preparing fluorine-containing polymers.

[0023] The present invention also provides a fluorine-containing polymer, which is a product prepared by taking the above-mentioned betaine surfactant, initiator, fluorine-containing monomer and water as raw materials.

[0024] Furthermore, the mass ratio of the betaine surfactant, the initiator, the fluorine-containing monomer and water is 0.1-1:0.01-0.1:10-60:100.

[0025] Further, the initiator is ammonium persulfate or potassium persulfate;

[0026] The fluorine-containing monomer is one or a mixture of two or more of hexafluorobutyl methacrylate, hexafluorobutyl acrylate, tridecafluorooctyl acrylate, 2-(perfluorooctyl)ethyl methacrylate or 2,2,2-trifluoroethyl acrylate.

[0027] The present invention also provides a method for preparing the above-mentioned fluorine-containing polymer, the method comprising the following steps:

[0028] (i) reacting water, part of the initiator and the betaine surfactant to obtain a mixed solution;

[0029] (ii) adding the fluorine-containing monomer and the remaining initiator to the mixed solution for reaction, adjusting the pH to 5-9, condensing and separating the fluorine-containing polymer in the reaction emulsion, washing with water, and drying to obtain a solid fluorine-containing polymer.

[0030] Furthermore, the mass ratio of the initiator in step (i) to the initiator in step (ii) is 1 to 2:1.

[0031] Further, in step (i), the reaction conditions are: stirring at a speed of 100 rpm to 2500 rpm;

[0032] In step (ii), the reaction conditions are: first, the fluorine-containing monomer and the remaining initiator are added to the mixed solution at a rate of 5 to 25 min / 100 ml at 30 to 50° C., and then reacted at 60 to 110° C. for 3 to 8 hours.

[0033] Further, in step (i), the reaction conditions are: stirring at a speed of 300 rpm to 2200 rpm;

[0034] In step (ii), the reaction conditions are: first, the fluorine-containing monomer and the remaining initiator are added to the mixed solution at a rate of 5 to 25 min / 100 ml at 35 to 40° C., and then reacted at 70 to 80° C. for 3 to 5 hours.

[0035] Furthermore, in step (ii), the acid-base regulator for adjusting the pH is aqueous ammonia, sodium bicarbonate or acetic acid.

[0036] The present invention designs a novel betaine surfactant, the unique chemical structure of which enables the stability of the emulsion to be significantly enhanced during the emulsion polymerization process, including under long-term storage, mechanical stirring, and different temperature and pH conditions, the risk of emulsion demulsification and flocculation can be effectively reduced, and the emulsion system can be ensured to be uniform and stable. At the same time, the surfactant can more efficiently emulsify the polymerization monomer, improve the conversion rate of the monomer and the polymerization reaction rate, and optimize the particle size distribution of the polymerization product. Thus, the sustainable development and high performance of the emulsion polymerization process are achieved.

[0037] The present invention has achieved the following beneficial effects:

[0038] (1) The novel betaine surfactant prepared by the present invention can more effectively reduce the interfacial tension between the fluorinated monomer and the aqueous phase, making the monomer more evenly dispersed in the aqueous phase, thereby reducing the agglomeration phenomenon caused by excessively high local concentration of the monomer during the polymerization process;

[0039] (2) The novel betaine surfactant prepared by the present invention has better electrostatic stability and steric hindrance effect in the emulsion system, which can effectively prevent the mutual collision and aggregation of emulsion particles, thereby improving the stability of the emulsion;

[0040] (3) The novel betaine surfactant prepared by the present invention has good biodegradability. In the natural environment, microorganisms can decompose betaine and reduce its accumulation in the environment;

[0041] (4) The novel betaine surfactant prepared by the present invention can effectively control the particle size and distribution of the emulsion, making the size of the emulsion particles more uniform and the particle size smaller.

[0042] Obviously, according to the above contents of the present invention, in accordance with common technical knowledge and customary means in the art, without departing from the above basic technical ideas of the present invention, other various forms of modification, replacement or change may be made.

[0043] The above contents of the present invention are further described in detail below through specific implementation methods in the form of examples. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples. All technologies realized based on the above contents of the present invention belong to the scope of the present invention. DETAILED DESCRIPTION

[0044] The raw materials and equipment used in the present invention are all known products, which are obtained by purchasing commercially available products.

[0045] The "room temperature" referred to in the present invention is 25±5°C.

[0046] The present invention prepares the novel betaine surfactant according to the following synthetic route:

[0047]

[0048] Example 1. Preparation of betaine surfactant 1

[0049]

[0050] Step (1): First, sodium bisulfite (NaHSO3) (64.51 g) and epichlorohydrin (49.95 g) were added to a reaction kettle equipped with a stirring device, a thermometer and a condenser, and the reaction was stirred at 85°C and 1900 rpm for 10 hours to generate an intermediate product (yield: 89%. Properties: white solid).

[0051] Step (2): Then, slowly drop NaOH solution into the reaction system to adjust the pH of the reaction system to 8.0, and simultaneously add N,N-dimethylethylamine (23.6 g), raise the temperature to 60° C. under the condition of ethanol as solvent, and stir the reaction at a speed of 2500 rpm for 10 hours. After the reaction is completed, the product is post-treated, and the solvent is removed by vacuum distillation. The obtained white solid is dissolved in methanol, filtered, and the solvent in the filtrate is removed by vacuum distillation. Then the obtained solid product is dissolved in water, filtered to remove solid impurities, and a white solid is obtained after the solvent is evaporated, that is, a high-purity novel betaine surfactant 1 (yield: 91%; purity: ≥95%. Properties: white solid).

[0052] Example 2, Preparation of Betaine Surfactant 2

[0053]

[0054] Step (1): First, sodium bisulfite (NaHSO3) (54.08 g) and epichlorohydrin (52.80 g) were added to a reaction kettle equipped with a stirring device, a thermometer and a condenser, and the reaction was stirred at 85°C and 2300 rpm for 12 hours to generate an intermediate product (yield: 83%. Properties: white solid).

[0055] Step (2): Then, slowly drop NaOH solution into the reaction system to adjust the pH of the reaction system to 7.5, and simultaneously add triethylamine (29.6 g), raise the temperature to 70° C. under the condition of ethanol as solvent, and stir the reaction at a speed of 1900 rpm for 12 hours. After the reaction is completed, the product is post-treated, and the solvent is removed by vacuum distillation. The obtained white solid is dissolved in methanol, filtered, and the solvent in the filtrate is removed by vacuum distillation. Then the obtained solid product is dissolved in water, filtered to remove solid impurities, and the solvent is evaporated to obtain a white solid, that is, a high-purity novel betaine surfactant 2 (yield: 90%; purity: ≥95%. Properties: white solid).

[0056] Example 3. Preparation of betaine surfactant 3

[0057]

[0058] Step (1): First, add NaHSO3 (64.51 g) and epichlorohydrin (49.95 g) into a reaction kettle equipped with a stirring device, a thermometer and a condenser, and react at 85°C and 1700 rpm for 10 hours to generate an intermediate product (yield: 89%. Properties: white solid).

[0059] Step (2): Then, slowly drop KOH solution into the reaction system, adjust the pH of the reaction system to 8.3, and add N,N-dimethylbutylamine (30.1 g) at the same time. Heat to 80°C with isopropanol as solvent, and stir at 1200 rpm for 14 hours. After the reaction is completed, the product is post-treated, and the solvent is removed by vacuum distillation. The obtained white solid is dissolved in methanol, filtered, and the solvent in the filtrate is removed by vacuum distillation. Then the obtained solid product is dissolved in water, filtered to remove solid impurities, and the solvent is evaporated to obtain a white solid, that is, a high-purity new betaine surfactant 3 (yield: 95%; purity: ≥95%. Properties: white solid).

[0060] Example 4. Preparation of fluorinated polymer 1

[0061] 20g of deionized water was added to the polymerization reactor, and the stirring device (1800rpm) was turned on. Then, ammonium persulfate (0.02g) and the new betaine surfactant 1 (0.1g) were added to the aqueous solution in sequence. After stirring evenly, the temperature was raised to 35°C. Then, 50ml of a mixed solution of hexafluorobutyl acrylate and tridecafluorooctyl acrylate (7:3) was uniformly added to the reactor using a constant pressure dropping funnel within 8min, and ammonium persulfate (0.01g) was added at the same time. Under nitrogen protection, the reaction was carried out at 80°C for 3.5 hours. The obtained emulsion had a concentration of 34.6wt% and an emulsion particle size of 95nm. There was no obvious coagulant in the emulsion. After the reaction was completed, the pH of the emulsion was controlled to 7.5 with sodium bicarbonate, and the fluorinated polymer in the reaction emulsion was condensed and separated, washed with water three times, and dried in a vacuum oven for 24h to obtain a solid fluorinated polymer 1 (yield: 97%).

[0062] Example 5. Preparation of Fluoropolymer 2

[0063] 20g of deionized water was added to the polymerization reactor, and the stirring device (1500rpm) was turned on. Then, ammonium persulfate (0.02g) and the new betaine surfactant 3 (0.15g) were added to the aqueous solution in sequence. After stirring evenly, the temperature was raised to 40°C. Then, 50ml of a mixed solution of 2-(perfluorooctyl)ethyl methacrylate and 13-fluorooctyl acrylate (7:3) was uniformly added to the reactor using a constant pressure dropping funnel within 8min. At the same time, ammonium persulfate (0.02g) was added. Under nitrogen protection, the reaction was carried out at 70°C for 4.8 hours to obtain an emulsion with a concentration of 32.6wt% and an emulsion particle size of 234nm. There were obvious coagulation products (7.4g) in the emulsion. After the reaction was completed, the pH of the emulsion was controlled to 7.8 with sodium bicarbonate. The fluorinated polymer in the reaction emulsion was condensed and separated, washed with water three times, and dried in a vacuum oven for 24h to obtain a solid fluorinated polymer 2 (yield: 87%).

[0064] The following is a control sample preparation.

[0065] Comparative Example 1: Preparation of Fluoropolymer 3

[0066] 20g of deionized water was added to the polymerization reactor, and the stirring device was turned on (1800rpm). Then potassium persulfate (0.02g) and traditional betaine surfactant 1 (N-dodecyl-N,N-dimethyl-N-carboxymethyl betaine (0.15g)) were added to the aqueous solution in sequence, and after stirring evenly, the temperature was raised to 40°C. Then, 50ml of a mixed solution of hexafluorobutyl acrylate and tridecafluorooctyl acrylate (7:3) was uniformly added to the reactor using a constant pressure dropping funnel within 8min, and potassium persulfate (0.02g) was added at the same time. Under nitrogen protection, the reaction was carried out at 70°C for 8 hours to obtain an emulsion with a concentration of 42.6wt%, an emulsion particle size of 540nm, and obvious coagulants (15.6g) in the emulsion. After the reaction, the pH of the emulsion was controlled to 7.6 with sodium bicarbonate, and the fluorine-containing polymer in the reaction emulsion was condensed and separated, washed with water three times, and dried in a vacuum oven for 24 hours to obtain a solid fluorine-containing polymer 3 (yield: 71%).

[0067] Comparative Example 2: Preparation of Fluoropolymer 4

[0068] 20g of deionized water was added to the polymerization reactor, and the stirring device (1600rpm) was turned on. Then potassium persulfate (0.02g) and traditional betaine surfactant 2 (dodecyl hydroxypropyl sulfobetaine (0.15g)) were added to the aqueous solution in sequence. After stirring evenly, the temperature was raised to 45°C. Then, 50ml of a mixed solution of hexafluorobutyl acrylate and tridecafluorooctyl acrylate (7:3) was uniformly added to the reactor using a constant pressure dropping funnel within 8min, and potassium persulfate (0.02g) was added at the same time. Under nitrogen protection, the reaction was carried out at 75°C for 6 hours to obtain an emulsion with a concentration of 30.5wt% and an emulsion particle size of 145nm. There was a small amount of coagulant (6.6g) in the emulsion. After the reaction was completed, the pH of the emulsion was controlled to 7.8 with sodium carbonate, and the fluorinated polymer in the reaction emulsion was condensed and separated, washed with water three times, and dried in a vacuum oven for 24h to obtain a solid fluorinated polymer 4 (yield: 85%).

[0069] The beneficial effects of the present invention are demonstrated by experimental examples below.

[0070] Experimental Example 1: Testing the Stability of Surfactants on Fluorinated Emulsions

[0071] 1. Experimental methods

[0072] (1) Using a centrifugal stability test, the reaction emulsions in Example 4 and Comparative Examples 1 and 2 (emulsion systems before pH adjustment with sodium carbonate) were respectively placed in centrifuge tubes and centrifuged at 3000 rpm for 5 minutes to observe the emulsion phenomenon;

[0073] (2) Static stability test: The reaction emulsions in Example 4 and Comparative Examples 1 and 2 (emulsion systems before pH adjustment with sodium carbonate) were respectively taken and left to stand at room temperature for 15 days, and their appearance changes were regularly observed.

[0074] 2. Experimental results

[0075] The results are shown in Table 1.

[0076] Table 1. Test results of surfactant stability in fluorinated emulsions

[0077]

[0078] Comparing Example 4 with Control Examples 1 and 2, the novel betaine surfactant prepared by the present invention shows significant advantages in fluorine-containing emulsion polymerization compared with the traditional betaine surfactant. Among them, the novel betaine surfactant 1 has the best effect. In terms of polymerization reaction stability, the reaction system under the action of the traditional betaine surfactant is prone to coagulants, while the novel betaine surfactant can effectively maintain the stability of the emulsion polymerization process, reduce the occurrence of coagulation, and make the polymerization reaction more stable and continuous. At the same time, the novel betaine surfactant helps to form polymer particles with smaller and more uniform particle size, thereby performing better in terms of physical properties and other aspects.

[0079] In summary, the present invention provides a betaine surfactant and a preparation method and use thereof. The present invention designs a new type of betaine surfactant, the unique chemical structure of which enables it to significantly enhance the stability of the emulsion during the emulsion polymerization process, including under long-term storage, mechanical stirring, and different temperature and pH conditions, it can effectively reduce the risk of emulsion demulsification and flocculation, and ensure that the emulsion system is uniform and stable. At the same time, the surfactant can more efficiently emulsify the polymerization monomers, improve the conversion rate of the monomers and the polymerization reaction rate, and optimize the particle size distribution of the polymerization product. Thereby achieving sustainable development and high performance of the emulsion polymerization process.

Claims

1. A betaine surfactant, characterized in that The structure of the betaine surfactant is shown in Formula I: Wherein, n1 is selected from 1, 2, 3, 4, 5, 6; n2 is selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12; R1 and R2 are each independently selected from C 1～3 alkyl.

2. The betaine surfactant according to claim 1, characterized in that The betaine surfactant is one of the following structures:

3. A method for preparing the betaine surfactant according to claim 1 or 2, characterized in that: The method comprises the following steps: (1) reacting with a sulfonating agent to prepare an intermediate product; (2) The intermediate product and Reaction to obtain betaine surfactant; Among them, n1 and n2 are as described in claim 1.

4. The method according to claim 3, characterized in that In step (1), the sulfonating agent is sodium bisulfite or sodium sulfite; The molar ratio of the sulfonating agent to the sulfonating agent is 1:0.5-5, and the reaction conditions are: reacting at 60-95°C for 6-15 hours; In step (2), the reaction is carried out under the action of a base, which is an inorganic base; the intermediate product and The molar ratio is 1.2 to 2:1; the solvent of the reaction is an organic solvent; and the reaction conditions are: reacting at 40 to 100° C. for 5 to 20 hours.

5. The method according to claim 3, characterized in that: In step (1), the The molar ratio of the sulfonating agent to the sulfonating agent is 1:0.8-1.5, and the reaction conditions are: reacting at 85°C for 10-12 hours; In step (2), a base is added to adjust the pH to 7-9; the base is sodium hydroxide or potassium hydroxide; the intermediate product and The molar ratio is 1.5-1.8:1; the solvent of the reaction is selected from one or a mixture of two or more of methanol, ethanol, isopropanol, dichloromethane and toluene; the reaction conditions are: reacting at 60-80°C for 8-18 hours.

6. Use of the betaine surfactant according to claim 1 or 2 in the preparation of an emulsifier.

7. A fluorine-containing polymer, characterized in that The invention is a product prepared by taking the betaine surfactant as claimed in claim 1 or 2, an initiator, a fluorine-containing monomer and water as raw materials.

8. The fluorine-containing polymer according to claim 7, characterized in that The mass ratio of the betaine surfactant, the initiator, the fluorine-containing monomer and water is 0.1-1:0.01-0.1:10-60:

100.

9. A method for preparing the fluorine-containing polymer according to claim 7 or 8, characterized in that: The method comprises the following steps: (i) reacting water, part of the initiator and the betaine surfactant to obtain a mixed solution; (ii) adding the fluorine-containing monomer and the remaining initiator to the mixed solution for reaction, adjusting the pH to 5-9, condensing and separating the fluorine-containing polymer in the reaction emulsion, washing with water, and drying to obtain a solid fluorine-containing polymer.

10. The method according to claim 9, characterized in that In step (i), the reaction conditions are: stirring at a speed of 100 rpm to 2500 rpm; In step (ii), the reaction conditions are: first, the fluorine-containing monomer and the remaining initiator are added to the mixed solution at a rate of 5 to 25 min / 100 ml at 30 to 50° C., and then reacted at 60 to 110° C. for 3 to 8 hours.

Images