Inverse emulsion stabilizer as well as preparation method and application thereof

Abstract

The invention relates to a stabilizer, in particular to an inverse emulsion stabilizer as well as a preparation method and application thereof. The preparation method of the inverse emulsion stabilizer comprises the following steps: adding acetic acid into a water-in-oil emulsion consisting of medium chain triglyceride, zein, Ca-EDTA (Ethylene Diamine Tetraacetic Acid) and an alginate aqueous solution for cross-linking, and freeze-drying after cross-linking to obtain the inverse emulsion stabilizer. The use amount of the prepared inverse emulsion stabilizer is small, and the stability of the W / O emulsion can be greatly improved.

Description

Technical Field

[0001] This invention relates to a stabilizer, and more specifically, to a reverse emulsion stabilizer, its preparation method, and its application. Background Technology

[0002] Reverse emulsions can be simply categorized as water-in-oil (W / O) emulsions, a type of emulsion in which an aqueous phase is dispersed within a continuous, nonpolar oil phase using surfactants. Compared to oil-in-water (O / W) emulsions, water-in-oil (W / O) emulsions are more prone to instability due to their higher interfacial tension, especially W / O emulsions with high water content.

[0003] Emulsifiers are substances that enable the formation of stable emulsions from mixtures of two or more immiscible components. Their working principle is that during emulsification, the dispersed phase is dispersed in the continuous phase in the form of microdroplets (micrometer-scale). The emulsifier reduces the interfacial tension of the components in the mixture and forms a relatively robust film on the surface of the microdroplets, or an electric double layer on the surface of the microdroplets due to the charge donated by the emulsifier, preventing the microdroplets from agglomerating and maintaining a homogeneous emulsion. Based on their HLB value, emulsifiers can be classified into lipophilic and hydrophilic emulsifiers. Currently, W / O emulsions typically use oil-soluble emulsifiers (lipophilic emulsifiers) for stabilization.

[0004] Existing oil-soluble emulsifiers, when used to stabilize W / O emulsions, suffer from poor stability (difficulty in achieving long-term, high-temperature stability). Therefore, W / O emulsions are typically stabilized using large amounts of oil-soluble emulsifiers. Furthermore, the temperature sensitivity of oil-soluble emulsifiers and their high adsorption to reservoir rocks limit their use as a fluid for improving oil recovery. Moreover, some oil-soluble emulsifiers also pose pollution problems. Although some environmentally friendly emulsifiers, such as modified cellulose and modified starch, have been developed for stabilizing W / O emulsions, their application is not yet widespread due to the complexity of modification techniques and insufficient stabilization capabilities. Summary of the Invention

[0005] Addressing the current technical challenge of conventional W / O emulsion emulsifiers failing to achieve stable W / O emulsions over extended periods and at higher temperatures, this invention addresses this issue by reacting an alginate solution with Ca in the oil phase. 2+ An inverse emulsion stabilizer was prepared by ionic crosslinking. This invention provides an inverse emulsion stabilizer that requires a small amount of material and can significantly improve the stability of W / O emulsions.

[0006] One of the objectives of this invention is to provide a reverse emulsion stabilizer.

[0007] The second objective of this invention is to provide a method for preparing a reverse emulsion stabilizer.

[0008] A third objective of this invention is to provide an application of a reverse emulsion stabilizer.

[0009] One of the objectives of the invention is to obtain the reverse emulsion stabilizer by adding acetic acid to a water-in-oil emulsion composed of medium-chain triglycerides, zein, disodium calcium EDTA, and an aqueous solution of alginate, stirring, and freeze-drying; wherein the water-in-oil emulsion has a suspension of medium-chain triglycerides and zein as the oil phase and an aqueous solution of disodium calcium EDTA and the aqueous solution of alginate as the aqueous phase.

[0010] The alginate is sodium alginate. The aqueous solution of the alginate is preferably a deionized aqueous solution of the alginate. The medium-chain triglyceride used can be any existing medium-chain triglyceride; the zein used can be any existing zein; both can be obtained commercially.

[0011] This invention increases H by using acetic acid + The concentration of Ca 2+ Ions are released and cross-link with alginate chains, leading to internal cross-linking within the droplets. H+ in acetic acid... + When ions encounter calcium complexes, they react with the carboxylic acid ions of EDTA, releasing free Ca2+. 2+ Ions. Then, free Ca... 2+ Ions crosslink with alginate chains, leading to alginate and Ca 2+ Ions undergo in-situ gelation, forming a uniform gel network.

[0012] Specifically, when acetic acid encounters a water-in-oil (W / O) emulsion, its solubility in the oil phase is limited because it cannot form molecular bonds with nonpolar medium-chain triglycerides. Therefore, acetic acid tends to separate from the oil phase and migrate to the W / O interface, where it can diffuse into the aqueous phase. Hydrogen ions in acetic acid encounter Ca-EDTA in the aqueous phase and react with its carboxylic acid ions, releasing free Ca2+. 2+ Free Ca 2+ Crosslinking with alginate in the aqueous phase allows alginate to interact with Ca. 2+ In-situ gelation occurs, forming calcium alginate gel. Simultaneously, hydrogen ions from acetic acid react with Ca... 2+ Competition and interaction with alginate lead to the formation of alginate gel. Under suitable acid concentrations, the hydrogen ions of acetic acid react with Ca... 2+ After the competition, Ca 2+ The complete release of the gel results in a more uniform structure.

[0013] Zeatin is rich in hydrophobic amino acids, insoluble in neutral and acidic aqueous solutions, and has an average particle size of approximately 50–200 nm. In the oil phase, zeatin can coat the surface of alginate / alginate gel. At the W / O interface, zeatin particles are tightly stacked to form a dense layer, constructing a zeatin-coated gel network structure. This gel network is the crude inverse emulsion stabilizer. Freeze-drying this gel network yields a solid inverse emulsion stabilizer.

[0014] Ca-EDTA has the advantage of high solubility in water, therefore it can be well mixed with alginate aqueous solutions. By completely dissolving Ca-EDTA in the alginate aqueous solution, a uniform distribution of Ca-EDTA is achieved, thus realizing the desired Ca... 2+ Uniform cross-linking within alginate droplets yields a homogeneous gel network. After freeze-drying, this homogeneous gel network effectively emulsifies and stabilizes inverse emulsions when used as a stabilizer.

[0015] When medium-chain triglycerides are chosen as the oil phase solvent, the addition of acetic acid does not emulsify the aqueous solution of acetic acid, nor does it reduce the emulsifying effect on the Ca-EDTA and alginate aqueous solutions.

[0016] The reverse emulsion stabilizer provided by this invention is a microgel. When used in polymer emulsions, its gel network swells upon contact with water, and at the same time, it can disperse the aqueous phase in the gel network, restricting the flow of the aqueous phase (water locking). The zein on its surface can prevent polymer aggregation, hardening, and coagulation. The polymer forms a diffusion system between the gel networks, which is conducive to the release of the polymer, thereby improving the stability of the polymer emulsion.

[0017] The reverse emulsion stabilizer provided by this invention is a stabilizer that can be used to emulsify and stabilize reverse emulsions; for example, it can be used as a stabilizer for nonionic water-in-oil emulsion polyacrylamide. In use, the reverse emulsion stabilizer does not require water dispersion. Reverse emulsions emulsified and stabilized using the reverse emulsion stabilizer provided by this invention do not separate into layers and retain a certain viscosity within 180 days at 20–45°C.

[0018] The method for preparing the reverse emulsion stabilizer described in the second objective of the invention includes the following steps:

[0019] (1) Disodium calcium ethylenediaminetetraacetate and an aqueous alginate solution were mixed under stirring to obtain an aqueous phase;

[0020] (2) Medium-chain triglycerides and zein were mixed under stirring conditions to obtain the oil phase;

[0021] (3) The aqueous phase and the oil phase are mixed and emulsified to obtain a water-in-oil emulsion;

[0022] (4) Add the acetic acid to the water-in-oil emulsion and stir to carry out the crosslinking reaction;

[0023] (5) After the cross-linking reaction, freeze-dry to obtain the reverse emulsion stabilizer.

[0024] In step (1) of the above preparation method:

[0025] The concentration of the alginate aqueous solution is 1-5 wt%, preferably 2-3 wt%.

[0026] The amount of calcium disodium ethylenediaminetetraacetate (Ca-EDTA) used relative to the alginate aqueous solution is 0.1-2 mol / L, preferably 0.3-0.5 mol / L.

[0027] In step (2) of the above preparation method:

[0028] The mass ratio of zein to medium-chain triglycerides is 1:1-2, preferably 1:1-1.5.

[0029] In step (3) of the above preparation method:

[0030] The mass ratio of the oil phase to the water phase is 40-50:1, preferably 45-50:1.

[0031] Emulsification is performed using a homogenizer with a rotation speed of 4000-6000 rpm, preferably 4500-6000 rpm.

[0032] In step (4) of the above preparation method:

[0033] The volume fraction of acetic acid relative to the water-in-oil emulsion is 0.5-2%, preferably 1-2%.

[0034] Crosslinking is carried out under stirring conditions: the stirring speed is 300-500 rpm, preferably 300-450 rpm; the stirring time is 8-10 min, preferably 10 min.

[0035] The step of "adding the acetic acid to the water-in-oil emulsion" allows for precise control of the crosslinking process. When acetic acid is added to the water-in-oil emulsion, the amount of acetic acid relative to the emulsion is relatively small. A small amount of acetic acid reacts with Ca-EDTA, causing Ca... 2+ Ions are slowly released and crosslinked with alginate chains, resulting in uniform crosslinking inside the droplet to overcome the clumping problem encountered during external gelation.

[0036] The preparation method of the water-soluble reverse emulsion stabilizer specifically includes the following steps:

[0037] (1) Dissolve sodium alginate in deionized water to prepare a 1-5% (w / w), preferably 2-3% (w / w) sodium alginate aqueous solution;

[0038] (2) Weigh Ca-EDTA; the amount of Ca-EDTA relative to the sodium alginate aqueous solution is 0.1-0.5 mol / L, preferably 0.2-0.5 mol / L, more preferably 0.3-0.5 mol / L;

[0039] (3) Ca-EDTA and sodium alginate aqueous solution are mixed using a magnetic stirrer to obtain an aqueous phase; the rotation speed of the magnetic stirrer is 300-450 r / min, preferably 350-450 r / min;

[0040] (4) Mix zein with medium-chain triglycerides to obtain an oil phase. The mass ratio of zein to medium-chain triglycerides is 1:1-2, preferably 1:1-1.5.

[0041] (5) The aqueous phase and the oil phase are mixed and emulsified using a high-speed homogenizer to prepare a water-in-oil emulsion; the mass ratio of the oil phase to the aqueous phase is 40-50:1, preferably 45-50:1; the rotation speed (emulsification speed) of the high-speed homogenizer is 4000-6000 rpm, preferably 4500-6000 rpm.

[0042] (6) After the emulsification process is completed, acetic acid is added to the water-in-oil emulsion prepared in step (5) and stirred; the amount of acetic acid relative to the water-in-oil emulsion is 0.5-2% (v / v), preferably 1-2% (v / v); the stirring speed is 300-500 rpm, preferably 300-450 rpm; the stirring time is used as the crosslinking time, and the crosslinking time is 8-10 min, preferably 10 min;

[0043] (7) After cross-linking is completed, freeze-drying is performed to obtain the reverse emulsion stabilizer.

[0044] The application of the reverse emulsion stabilizer described in the third objective of the invention refers to its use as a stabilizer for water-in-oil emulsions; for example, as a stabilizer for nonionic water-in-oil emulsion polyacrylamide. The reverse emulsion stabilizer requires a small amount and can significantly improve the stability of W / O emulsions.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] The reverse emulsion stabilizer prepared by this invention can prevent polymer particles from agglomerating and causing emulsion instability.

[0047] The reverse emulsion stabilizer prepared in this invention significantly improves the stability of reverse emulsions by inhibiting the aggregation of dispersed droplets through steric hindrance or electrostatic repulsion. Reverse emulsions emulsified and stabilized using the stabilizer prepared in this invention do not separate into layers and retain a certain viscosity within 180 days at 20–45°C, making them more suitable for improving oil recovery and thus increasing production capacity.

[0048] The reverse emulsion stabilizer prepared by this invention also has the characteristics of being biodegradable, biocompatible, non-toxic, relatively low cost, and thermally stable. Detailed Implementation

[0049] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0050] The raw materials used in the following embodiments and performance tests are all commercially available products, and their manufacturers are shown in Table 1.

[0051] Table 1

[0052]

[0053] Example 1

[0054] Using a magnetic stirrer at 400 rpm, Ca-EDTA and a 2% sodium alginate aqueous solution were mixed at a ratio of 0.5 mol:1 L to obtain the aqueous phase. Using a high-speed homogenizer at 5000 rpm, medium-chain triglycerides and zein were mixed at a mass ratio of 1:1.2 to obtain the oil phase. The oil phase was then mixed and emulsified with the aqueous phase at a mass ratio of 50:1 to obtain a water-in-oil emulsion. Acetic acid (2% by volume relative to the water-in-oil emulsion) was added to the water-in-oil emulsion, and the mixture was magnetically stirred at 400 rpm for 10 min to complete crosslinking. After crosslinking, the mixture was freeze-dried to obtain #1 reverse emulsion stabilizer.

[0055] Example 2

[0056] Using a magnetic stirrer at 450 rpm, Ca-EDTA and a 2.5% sodium alginate aqueous solution were mixed at a ratio of 0.3 mol:1 L to obtain the aqueous phase. Using a high-speed homogenizer at 4500 rpm, medium-chain triglycerides and zein were mixed at a mass ratio of 1:1.1 to obtain the oil phase. The oil phase was then mixed and emulsified with the aqueous phase at a mass ratio of 45:1 to obtain a water-in-oil emulsion. Acetic acid (1% by volume relative to the water-in-oil emulsion) was added to the water-in-oil emulsion, and the mixture was magnetically stirred at 450 rpm for 8 min to complete crosslinking. After crosslinking, the mixture was freeze-dried to obtain the No. 2 reverse emulsion stabilizer.

[0057] Example 3

[0058] Using a magnetic stirrer at 350 rpm, Ca-EDTA and a 3% sodium alginate aqueous solution were mixed at a ratio of 0.45 mol: 1 L to obtain the aqueous phase. Using a high-speed homogenizer at 4800 rpm, medium-chain triglycerides and zein were mixed at a mass ratio of 1:1.3 to obtain the oil phase. The oil phase was then mixed and emulsified with the aqueous phase at a mass ratio of 48:1 to obtain a water-in-oil emulsion. Acetic acid (1.5% by volume relative to the water-in-oil emulsion) was added to the water-in-oil emulsion, and the mixture was magnetically stirred at 350 rpm for 9 min to complete crosslinking. After crosslinking, the mixture was freeze-dried to obtain the No. 3 reverse emulsion stabilizer.

[0059] Example 4

[0060] Using a magnetic stirrer at 400 rpm, Ca-EDTA and a 2% sodium alginate aqueous solution were mixed at a ratio of 0.2 mol:1 L to obtain the aqueous phase. Using a high-speed homogenizer at 6000 rpm, medium-chain triglycerides and zein were mixed at a mass ratio of 1:1.4 to obtain the oil phase. The oil phase was then mixed and emulsified with the aqueous phase at a mass ratio of 50:1 to obtain a water-in-oil emulsion. Acetic acid (2% by volume relative to the water-in-oil emulsion) was added to the water-in-oil emulsion, and the mixture was magnetically stirred at 300 rpm for 8 min to complete crosslinking. After crosslinking, the mixture was freeze-dried to obtain the No. 4 reverse emulsion stabilizer.

[0061] Example 5

[0062] Using a magnetic stirrer at 380 rpm, Ca-EDTA and a 2.7% sodium alginate aqueous solution were mixed at a ratio of 0.3 mol:1 L to obtain the aqueous phase. Using a high-speed homogenizer at 6000 rpm, medium-chain triglycerides and zein were mixed at a mass ratio of 1:1.5 to obtain the oil phase. The oil phase was then mixed and emulsified with the aqueous phase at a mass ratio of 49:1 to obtain a water-in-oil emulsion. Acetic acid (2% by volume relative to the water-in-oil emulsion) was added to the water-in-oil emulsion, and the mixture was magnetically stirred at 450 rpm for 10 min to complete crosslinking. After crosslinking, the mixture was freeze-dried to obtain #5 reverse emulsion stabilizer.

[0063] Comparative Example 1

[0064] XJ-169IT produced by Chongqing Baohua Chemical Additives Factory was used as an emulsion stabilizer.

[0065] Comparative Example 2

[0066] AEROSOL A103, a strong supplier of Zhenlishi, was used as the emulsion stabilizer.

[0067] Comparative Example 3

[0068] CO-436 produced by Haian Petrochemical Plant in Jiangsu Province was used as an emulsion stabilizer.

[0069] Comparative Example 4

[0070] Polyglycerol ricinoleate (PGPR) produced by Shandong Binzhou Jinsheng New Material Technology Co., Ltd. was used as an emulsion stabilizer.

[0071] Comparative Example 5

[0072] OP-40, produced by Haian Petrochemical Plant in Jiangsu Province, was used as the emulsion stabilizer.

[0073] Performance testing

[0074] Take 0.5g of the reverse emulsion stabilizer prepared in Examples 1-5 (which does not need to be dispersed with deionized water when used) and add it to 100g of reverse emulsion. Stir magnetically for 5 minutes to fully dissolve the stabilizer and use it as the sample to be tested.

[0075] Take 5g of each of the comparative examples 1-5 and add them to 100g of reverse emulsion. Stir magnetically for 5 minutes until fully dissolved to obtain the test samples.

[0076] Take 50 mL of reverse emulsion and the sample to be tested into test tubes respectively, and conduct static stability observation test (observe the emulsion separation time) and viscosity test at room temperature (25℃).

[0077] Take 50 mL of reverse emulsion and the test sample into test tubes respectively, and conduct thermal stability observation tests in an oven at 45℃ (observe the emulsion separation time).

[0078] The DV-Ⅱ rotational viscometer was used to test the viscosity of the reverse emulsion and the sample to be tested. The test conditions were: rotor No. 62, rotation speed of 6 r / min, and shear time of 5 min.

[0079] The test results are shown in Table 2.

[0080] Table 2

[0081]

[0082] In Table 2, a "-" indicates that no stabilizer was added.

[0083] Table 2 shows that the reverse emulsion used in the performance test, without the addition of stabilizers, had an emulsion separation time of 35 days, a viscosity of 724.8, and a thermal stability of 0 days at 45℃.

[0084] During performance testing, the amount of emulsion stabilizer added relative to the reverse emulsion in Comparative Examples 1-5 was 5 wt%; the amount of reverse emulsion stabilizer added relative to the reverse emulsion in Examples 1-5 was 0.5 wt%. Compared with the emulsion stabilizer in Comparative Examples 1-5, the amount of reverse emulsion stabilizer used in Examples 1-5 was reduced by 90%.

[0085] Table 2 shows that the reverse emulsions stabilized with the emulsion stabilizers of Comparative Examples 1-5 had a viscosity of 730-987 cP·s, exhibited stratification at 36-69 days, and had a thermal stability of 0 days at 45°C. The reverse emulsions stabilized with the emulsion stabilizers of Examples 1-5 had a viscosity of 1505-1665 cP·s, exhibited stratification at 185-199 days, and had a thermal stability of 3-6 days at 45°C. Compared with the emulsion stabilizers used in the comparative examples, the reverse emulsions stabilized with the emulsion stabilizers of the examples showed significantly increased viscosity, significantly improved static stability (longer time to stratification), and significantly improved thermal stability.

[0086] Therefore, the reverse emulsion stabilizer prepared in this invention can give reverse emulsions good stability and thermal stability. The emulsion does not separate within 180 days and does not separate within 3 days at 45°C, and it can also increase the viscosity of the emulsion system. This reverse emulsion stabilizer achieves dual stabilization of the reverse emulsion through its interaction with the oil phase network structure in the reverse emulsion. The formulated reverse emulsion is suitable for improving oil recovery.

Claims

1. A reverse emulsion stabilizer, characterized in that, The reverse emulsion stabilizer is prepared by adding acetic acid to a water-in-oil emulsion composed of medium-chain triglycerides, zein, disodium calcium EDTA, and an aqueous solution of alginate, stirring, and then freeze-drying. The water-in-oil emulsion comprises a suspension of medium-chain triglycerides and zein as the oil phase, and an aqueous solution of disodium calcium ethylenediaminetetraacetate and alginate as the aqueous phase.

2. The reverse emulsion stabilizer as described in claim 1, characterized in that, The alginate is sodium alginate.

3. A method for preparing the reverse emulsion stabilizer as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Disodium calcium ethylenediaminetetraacetate and an aqueous alginate solution were mixed under stirring to obtain an aqueous phase; (2) Medium-chain triglycerides and zein were mixed under stirring conditions to obtain an oil phase; (3) The aqueous phase and the oil phase are mixed and emulsified to obtain a water-in-oil emulsion; (4) Add the acetic acid to the water-in-oil emulsion and stir to carry out the crosslinking reaction; (5) After the crosslinking reaction is completed, the reverse emulsion stabilizer is obtained by freeze drying.

4. The preparation method according to claim 3, characterized in that, In step (1), The concentration of the alginate aqueous solution is 1-5 wt%; or / and, The amount of calcium disodium ethylenediaminetetraacetate relative to the aqueous alginate solution is 0.1-2 mol / L.

5. The preparation method according to claim 4, characterized in that, In step (1), The concentration of the alginate aqueous solution is 2-3 wt%; or / and, The amount of calcium disodium ethylenediaminetetraacetate relative to the aqueous alginate solution is 0.3-0.5 mol / L.

6. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of the zein to the medium-chain triglyceride is 1:1-2.

7. The preparation method according to claim 6, characterized in that, In step (2), the mass ratio of the zein to the medium-chain triglyceride is 1:1-1.

5.

8. The preparation method according to claim 3, characterized in that, In step (3), the mass ratio of the oil phase to the water phase is 40-50:

1.

9. The preparation method according to claim 8, characterized in that, In step (3), the mass ratio of the oil phase to the water phase is 45-50:

1.

10. The preparation method according to claim 3, characterized in that, In step (4), The acetic acid has a volume fraction of 0.5-2% relative to the water-in-oil emulsion; or / and, The stirring speed is 300-500 rpm, and the stirring time is 8-10 minutes.

11. The preparation method according to claim 10, characterized in that, In step (4), The acetic acid has a volume fraction of 1-2% relative to the water-in-oil emulsion; or / and, The stirring speed is 300-450 rpm.

12. The use of the reverse emulsion stabilizer as described in claim 1 or 2 as a stabilizer for water-in-oil emulsions.

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