CN104830297A - Preparation method of W/O/W type multiple emulsion delaying chromium sol cross-linking system - Google Patents

Abstract

The present invention relates to a preparation method of a W/O/W multiple emulsion delayed chromium sol crosslinking system. The preparation method of this W/O/W multiple emulsion delayed chromium sol crosslinking system: (A) adding Stir the emulsifier Span-80 and residual oil evenly, and use it as the oil phase; (B) prepare a cross-linking agent with a mass fraction of 8%~10% based on CrCl ₃ , weigh CrCl ₃ ?6H ₂ O, CH ₃ COONa?3H ₂ O and dissolved, in which n(Cr ³⁺ ):n(Ac ^- )=1:3 in the obtained solution, and then made into a solution with a volume fraction of 2% as the internal water phase for use; (C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, and emulsify to form colostrum; (D) make polyacrylamide into a 2000ppm aqueous solution, in which the emulsifier mSpan-80:mTween-80= 7:3, Span-80 and Tween-80 are 1.0%~2.0% of the mass of the aqueous solution; (E) Mix and emulsify colostrum and polyacrylamide solution at a volume ratio of 1~7:1~3; (F) The pH of the prepared emulsion was adjusted to 7-10. The invention can delay the crosslinking time, and the freezing time can reach 480h.

Description

Preparation method of W/O/W type multiple emulsion delayed chromium sol crosslinking system

technical field

The invention relates to a preparation method of multiple emulsions, in particular to a preparation method of a W/O/W type multiple emulsion delayed chromium sol crosslinking system.

Background technique

Multiple emulsions were discovered by Seifritz in 1925. He described in the article "Stadies in emulsions (Ⅲ): Double reversal of oil emulsions occasioned by the same electrolyte" that the oil droplets of O/W emulsions contain water droplets, and noticed that The water droplets of the W/O emulsion also contain fine oil droplets. But it was not until 1965 that people began to purposefully prepare and study multiple emulsions. Multiple emulsion is a composite system shared by O/W type and W/O type emulsion. The emulsion formed by the suspension and dispersion of oil droplets containing water droplets in the water phase is called W/O/W type emulsion, and its external phase is water. The internal phase is oil droplets, but the oil droplets contain dispersed water droplets. This multiple emulsion is called water-in-oil-in-water type, which is a three-phase system. Structurally, multiple emulsions have a unique "two-membrane three-phase" multi-compartment structure. It is this special structure that can dissolve some substances with different properties in different phases to play the role of isolation, protection, and controlled release.

Due to the good slow-release and dispersion performance of multiple emulsions, Hou Jirui proposed in 1996 the idea of W/O/W multiple emulsions with cross-linking agents as internal phase components to delay cross-linking and profile control in deep reservoirs, and to prepare stable multiple emulsions. latex, and carried out experimental research on delayed crosslinking. This method gets rid of the conventional idea of relying on multi-component coordination to achieve delayed cross-linking, and overcomes the limitations of cross-linking agent adsorption in the near-wellbore zone and adverse effects of temperature on delayed reaction in traditional deep reservoir profile control methods. In addition, the W/O/W structure can protect the cross-linking agent from being adsorbed by the formation near the wellbore, overcome the adverse effect of temperature on delaying the cross-linking reaction, and thus realize deep profile control of water injection wells. In 2009, Zhao Juan et al. prepared a W/O/W multiple emulsion cross-linking agent with the cross-linking agent Cr(Ac) ₃ as the internal aqueous phase. The cross-linking agent wrapped in the multiple structure needs to pass through two interfaces to be released. out, the release rate is slow, and the purpose of delaying cross-linking can be achieved. Studies have shown that under the same conditions, the freezing time of the system added with multiple emulsion cross-linking agents is significantly longer than that of traditional Cr(Ac) ₃ cross-linking agents. The multiple emulsion system is conducive to entering deep formations and realizing deep profile control.

The key to the application of multiple emulsions in oil reservoirs is to have good thermal stability. High temperature and the interaction between emulsifier molecules with different properties are important factors leading to the decrease of the stability of multiple emulsions. At present, the research on the stability of multiple emulsions has little consideration of temperature, mostly at room temperature, and mostly focuses on the macroscopic stability investigation, lacking the understanding of the mechanism of stability. However, the stability of common multiple emulsions is limited, so maintaining the stability of multiple emulsions is the key to preparation. The mechanism of the instability of multiple emulsions is very complex, and although it is important in practical applications, there is not yet a complete theory to explain this problem.

Florence and Whitehill analyzed the instability mechanism of multiple emulsions, and proposed several possible ways for multiple emulsions to decompose: multiple droplets can coalesce with other simple oil droplets or multiple droplets; Discharged or more than one internal aqueous phase droplet is expelled at once; internal aqueous phase droplets may be expelled all at once, but this is rare; internal aqueous phase droplets may coalesce before being expelled; or The water phase gradually passes through the oil film by diffusion, causing the inner water phase droplets to shrink and disappear. Matsumoto believes that of all these pathways, reservoir fracture is very important. Because in the W/O/W multiple emulsion, each dispersed droplet contains one or more inner water phase droplets, and these water droplets are separated from the outer water phase by the oil layer. If the oil layer breaks, the inner water phase disappears immediately and mixes with the outer water phase, which is very similar to the bursting of soap bubbles suspended in the air. Therefore, the persistence of the oil layer can be used to measure the stability of W/O/W multiple emulsions.

Contents of the invention

The purpose of the present invention is to provide the preparation method of W/O/W type multiple emulsion delayed chromium sol crosslinking system, the preparation method of this W/O/W type multiple emulsion delayed chromium sol crosslinking system is used to solve the problems in the prior art The freezing time of multiple emulsion cross-linking agents is still short.

The technical scheme adopted by the present invention to solve its technical problems is: the preparation method of this W/O/W type multiple emulsion delayed chromium sol crosslinking system:

(A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 1.5%~2.8% of the total mass of the oil phase. The amount of oil added is 5%~8% of the total mass of the oil phase;

(B) Prepare a cross-linking agent with a mass fraction of 8%~10% based on CrCl ₃ , accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, and add distilled water to fully dissolve them in a small beaker , where n(Cr ³⁺ ):n(Ac ^- )=1:3 in the obtained solution, then add the obtained solution into a 100mL volumetric flask, constant volume, fully shake, and the aging time is more than 3d, the crosslinking agent chromium sol mother liquor is Dark green or slightly purple transparent liquid, prepared as a solution with a volume fraction of 2% as the inner aqueous phase;

(C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify with FA25 high-shear dispersing emulsifier at a speed of 10000r/min for 2~5min to form colostrum, and detect the emulsion by dilution method type;

(D) Make polyacrylamide into a 2000ppm aqueous solution, in which the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.0% of the mass of the aqueous solution~ 2.0%;

(E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a volume ratio of 1~7:1~3, the emulsification speed is 4000r/min, and the emulsification time is 2~5min. After the double emulsion is formed, the emulsion is detected by the dilution method type;

(F) Adjust the pH of the prepared emulsion to 7-10.

The pH value of the emulsion prepared in step (F) in the above scheme is adjusted to 8, and the emulsion is most stable at pH=8.

Further, the preparation method of this W/O/W type multiple emulsion delayed chromium sol crosslinking system in the above scheme:

(A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 2.8% of the total mass of the oil phase, and the residual oil The amount is 5% of the total mass of the oil phase;

(B) Prepare a cross-linking agent with a mass fraction of 8% based on CrCl ₃ , accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, and add distilled water to fully dissolve them in a small beaker. In the solution, n(Cr ³⁺ ):n(Ac ^- )=1:3, then add the obtained solution into a 100mL volumetric flask, constant volume, fully shake, aging time more than 3d, the cross-linking agent chromium sol mother liquor is dark green or Slight purple transparent liquid, made into a solution with a volume fraction of 2% as the inner water phase for later use;

(C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify with FA25 high-shear dispersing emulsifier at a speed of 10,000r/min for 150s to form colostrum, and use the dilution method to detect the type of emulsion;

(D) Make polyacrylamide into a 2000ppm aqueous solution, wherein the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.5% of the aqueous solution mass;

(E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a ratio of 7:3 by volume, the emulsification speed is 3000r/min, and the emulsification time is 180s. After the double emulsion is formed, the type of the emulsion is detected by the dilution method;

(F) Adjust the pH value of the prepared emulsion to 8, and the emulsion is most stable at pH=8.

The present invention has the following beneficial effects:

1. The W/O/W multiple emulsion delayed chromium sol system prepared by the present invention is a single-liquid method profile control agent, which has a long delayed crosslinking time. The prepared W/O/W multiple emulsion delayed chromium sol system is injected into the formation. The multiple emulsions rely on flow and collision to generate shear force to demulsify. The crosslinking agent in the internal phase meets the polyacrylamide in the external phase to form a frozen phase. After the gel is formed, the viscosity increases greatly, and the fluidity is lost, so that the flow profile is improved, thereby enhancing the recovery factor.

2. Under the condition of low pH value, there are a large number of hydrogen ions in the solution, and the hydrogen ions are strongly adsorbed on the carboxylate, the electrical repulsion between the polymer group and the molecular chain is greatly reduced, the polymer molecules curl up, and the solution viscosity Very low, it is difficult to form a gel. The increase of pH is conducive to the formation of gel and the increase of stability, which may be due to the following two reasons. First, when Cr(Ac) ₃ is cross-linked with the polymer, it must first be hydrolyzed into chromium (Ⅲ) hexahydrate, and then the chromium (Ⅲ) hexahydrate will be polymerized with the hydroxyl group of the polymer to form a colloid. Alkaline conditions are beneficial to the hydrolysis of Cr ³⁺ crosslinking agent and the formation of colloids. Second, alkaline conditions are favorable for the hydrolysis of HPAM, increasing the charged groups in the molecule. On the one hand, the increase of the charged group makes the molecular chain extend, and the cross-linking reaction is easy to carry out. On the other hand, the cross-linking point may also increase, so that the strength of the colloid formed increases. Through experiments, the optimum pH for this system is 8.0.

3. In 1996, Hou Jirui and others prepared a multiple emulsion type profile control agent. In the HT-II automatic mixer, the aqueous solution of sodium dichromate was dispersed into kerosene with the help of an oil-soluble emulsifier, and then the water-soluble emulsifier was used to disperse the The oil external phase dispersion system is dispersed into polyacrylamide and sodium sulfite aqueous solution to obtain W/O/W multiple emulsions. In this experiment, oxidation-reduction reaction was used to achieve the purpose of gelling. The formed multiple emulsion is a single-liquid method profile control agent, in which the oxidizing agent Na ₂ Cr ₂ O ₇ and the reducing agent Na ₂ SO ₃ are covered by kerosene phase and two-layer The interfacial film is isolated, no reaction occurs, only multiple emulsions are completely broken, and the two water phases accumulate to form a single water phase containing Na ₂ Cr ₂ O ₇ , Na ₂ SO ₃ and HPAM, that is, the profile control agent solution phase, Na ₂ Cr ₂ O ₇ and Na ₂ SO ₃ can undergo oxidation-reduction reaction to generate Cr ³⁺ , and Cr ³⁺ can cross-link HPAM macromolecules to form gel. This is more demulsification process than general solution type profile control agent, so that multiple emulsion type profile control agent has the characteristic of delaying crosslinking.

The multiple emulsion type profile control agent prepared in the present invention uses chromium trichloride to prepare chromium sol as a crosslinking agent, while Hou Jirui and others use trivalent chromium ions generated by redox reactions between sodium dichromate and sodium sulfite Used as a cross-linking agent. All chromium compounds are toxic, of which hexavalent chromium is the most toxic. Hexavalent chromium is extremely toxic by inhalation, and skin contact may cause sensitivity; it is more likely to cause hereditary gene defects, may cause cancer if inhaled, and has persistent hazards to the environment. These are properties of hexavalent chromium, which are not toxic to chromium metal, trivalent or tetravalent chromium. Trivalent chromium is less harmful than hexavalent chromium, and it belongs to the environmental protection series in the current product application.

The multi-emulsion profile control agent prepared by the invention is more environmentally friendly, and the Cr ³⁺ in the chromium sol is derived from the Cr ³⁺ coordination chelate, which avoids the harm of Cr ⁶⁺ to oilfield applications. In a chromium acetate solution with a mass ratio of sodium acetate to chromium trichloride of 3:1, a pH value of 4, and a fully aged chromium acetate solution, the dominant particle is a chromium ring containing 6 acetate groups and a central oxygen like trimer, as shown in Figure 1. When the pH value of the solution increases, the hydroxide replaces the bridging acetate group of the cyclic chromium trimer, forming an acetate group with a bidentate structure; when the second hydroxide replaces the bridging acetate group After grouping, the ring-shaped chromium acetate trimer junction as shown in Figure 1 is transformed into a linear chromium trimer structure as shown in Figure 2.

The particle distribution in the chromium acetate solution is also related to the aging time of the solution. When sodium acetate is mixed with chromium trichloride, in the crosslinking agent system, firstly, the monomeric Cr ³⁺ coordinates with the monoconical acetate group; then It is the formation of particles with a bidentate structure at a slower rate; after 20 minutes, a ring-shaped trimer structure begins to form, and as the aging time of the cross-linking agent goes on, there are more and more ring-shaped trimers in the system, 3d Afterwards, the system is basically stable. At this time, the dominant particle in the system is the ring-shaped chromium acetate trimer.

Freezing time is an important index to evaluate the performance of multiple emulsion type profile control agent. Move the newly prepared quantitative multiple emulsion into a stoppered measuring cylinder, keep it at a constant temperature of 45°C, take it out regularly for measurement, and take the time when the liquid level does not move when the measuring cylinder is tilted at 30°C is the freezing time. The freezing time of the multiple emulsion profile control agent prepared by Hou Jirui is 400 hours, and the freezing time of the W/O/W type multiple emulsion delayed chromium sol crosslinking system prepared according to the first process step of the method of the present invention can reach 480 hours.

In 2009, Zhao Juan and others prepared a W/O/W multiple emulsion cross-linking agent, using diesel oil as the oil phase, Cr(Ac) ₃ cross-linking agent as the internal water phase, T20 as the oil-in-water emulsifier, and T161 as the water-in-oil emulsifier Made under the condition of emulsifier, the active ingredient Cr(Ac) ₃ is wrapped in multiple structures, and the effective ingredient is released by the shear and temperature of the formation pore throat to achieve demulsification, so as to achieve the effect of delaying crosslinking. In addition, due to long-term water injection flushing, the surface near the wellbore is hydrophilic, and the W/O/W structure can protect the cross-linking agent from being adsorbed by the formation near the wellbore.

Only the cross-linking agent was prepared in this experiment, and the multi-emulsion cross-linking agent should be slowly added to the prepared polyacrylamide solution under the condition of stirring, and it can be used after stirring evenly. In this experiment, different mass fractions of HPAM solutions were prepared from Shengtuo sewage, and multiple emulsion cross-linking agents with the same effective Cr(Ac) ₃ content and uncoated Cr(Ac) ₃ cross-linking agents were added respectively. The freezing time was used to study the delayed crosslinking performance, and the results are shown in Table 1. As can be seen from Table 1, under the same effective content, the freezing time of the system added with multiple emulsion cross-linking agent is significantly longer than that _of the system with uncoated Cr(Ac) The compound has the effect of delaying cross-linking, which is conducive to entering deep formations and realizing deep profile control.

Table 1 Effect of multiple emulsion cross-linking agent on delayed cross-linking of polymers

The present invention conducts research on delayed crosslinking performance by investigating the freezing time and jelly strength of the W/O/W type multiple emulsion delayed chromium sol crosslinking system. (1) Freezing time: transfer the newly prepared quantitative W/O/W multiple emulsion delayed chromium sol crosslinking system into a stoppered measuring cylinder, keep a constant temperature of 45°C, take it out regularly for observation, and measure the liquid level when the measuring cylinder is tilted at an angle of 30 degrees The time of immobility is the freezing time. (2) Jelly strength: The viscosity of the jelly measured with a Brookfield viscometer at 45°C is used as the measure of the jelly strength. The results are shown in Table 2. As can be seen from Table 2, the freezing time of the W/O/W type multiple emulsion delayed chromium sol cross-linking system prepared by the present invention can reach 480h, and the freezing time of the multiple emulsion cross-linking agent prepared in this experiment is far less than the present invention. Invented multiple emulsion type profile control agent.

Table 2-1 W/O/W multiple emulsion delayed chromium sol crosslinking system.

time/h 0 24 48 72 96 120 144 168 192 216 240 Frozen Phenomenon Tilt Tilt Tilt Tilt Tilt Tilt Tilt Tilt Tilt Tilt Tilt Tilt Viscosity/mPa s 112 168 296 878.5 2587 4297 5871 8222 10257 13078 15582

Table 2-2 W/O/W multiple emulsion delayed chromium sol crosslinking system.

time/h 264 288 312 336 360 384 408 432 456 480 Freezing Phenomenon Tilt Tilt tilt tilt tilt tilt tilt tilt tilted not tilted Viscosity/mPa s 19507 21542 23106 23893 25303 26550 27491 27808 28278 28354

Description of drawings

Fig. 1 is the structural diagram of the cyclic chromium acetate trimer;

Figure 2 is a structural diagram of a linear chromium acetate trimer.

Detailed ways

The present invention is described further below:

Example 1

(A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 2.8% of the total mass of the oil phase, and the residual oil The amount is 5% of the total mass of the oil phase;

(B) Prepare a cross-linking agent with a mass fraction of 8% (calculated as CrCl ₃ ), accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, and add distilled water to fully dissolve them in a small beaker. In the obtained solution, n(Cr ³⁺ ):n(Ac ⁻ )=1:3, then add the obtained solution into a 100mL volumetric flask, dilute to volume, and shake fully. After the aging time is more than 3 days, the cross-linking agent chromium sol mother solution is dark green or slightly purple transparent liquid. A solution with a volume fraction of 2% was prepared as the inner aqueous phase for later use.

(C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify for 150 s with a FA25 high-shear dispersing emulsifier at a speed of 10,000 r/min to form colostrum, and detect the type of emulsion by dilution method.

(D) Make polyacrylamide into a 2000ppm aqueous solution, wherein the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.5% of the aqueous solution mass;

(E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a volume ratio of 1:1, the emulsification speed is 4000r/min, and the emulsification time is 150s. The emulsification speed cannot exceed 5000r/min, because the structure of polyacrylamide will be destroyed when the emulsification speed exceeds 5000r/min. After the formation of double emulsion, the type of emulsion was detected by dilution method.

(F) Adjust the pH value of the prepared emulsion to 8, and the emulsion is most stable at pH=8.

Take the W/O/W type multiple emulsion delayed chromium sol crosslinking system prepared according to the method of Example 1 in a stoppered measuring cylinder, place it in a constant temperature box at 45°C for 20 days, and read the values of the free water layer and oil layer. Volume sum, the stability of the emulsion is measured by the percentage of the total volume of the emulsion after deducting the volume of the free water layer and the oil layer and the total volume. The test results show that the stability of the W/O/W multiple emulsion delayed chromium sol crosslinking system is 92% after 20 days.

Take the W/O/W type multiple emulsion delayed chromium sol crosslinking system prepared according to the method of Example 1 in a stoppered measuring cylinder, place it in a constant temperature chamber at 45°C, take it out for measurement at regular intervals, and measure it when the measuring cylinder is tilted at 30°C. The time when the surface does not move is the freezing time, and the viscosity of the system when freezing is measured with a Brookfield viscometer. The test result shows that the freezing time of the system is 408h, and the viscosity of the system is 22994mPa·s at this time.

Example 2

(A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 2.8% of the total mass of the oil phase, and the residual oil The amount is 5% of the total mass of the oil phase;

(B) Prepare a cross-linking agent with a mass fraction of 8% (calculated as CrCl ₃ ), accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, and add distilled water to fully dissolve them in a small beaker. In the obtained solution, n(Cr ³⁺ ):n(Ac ⁻ )=1:3, then add the obtained solution into a 100mL volumetric flask, dilute to volume, and shake fully. After the aging time is more than 3 days, the cross-linking agent chromium sol mother solution is dark green or slightly purple transparent liquid. A solution with a volume fraction of 2% was prepared as the inner aqueous phase for later use.

(C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify for 150 s with a FA25 high-shear dispersing emulsifier at a speed of 10,000 r/min to form colostrum, and detect the type of emulsion by dilution method.

(D) Make polyacrylamide into a 2000ppm aqueous solution, wherein the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.5% of the aqueous solution mass;

(E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a volume ratio of 3:2, the emulsification speed is 5000r/min, and the emulsification time is 120s. The emulsification speed cannot exceed 5000r/min, because the structure of polyacrylamide will be destroyed when the emulsification speed exceeds 5000r/min. After the formation of double emulsion, the type of emulsion was detected by dilution method.

(F) Adjust the pH value of the prepared emulsion to 8, and the emulsion is most stable at pH=8.

Take the W/O/W type multiple emulsion delayed chromium sol crosslinking system prepared according to the method of Example 2 in a stoppered measuring cylinder, place it in a constant temperature box at 45°C for 20 days, and read the values of the free water layer and oil layer. Volume sum, the stability of the emulsion is measured by the percentage of the total volume of the emulsion after deducting the volume of the free water layer and the oil layer and the total volume. The test results show that the stability of the W/O/W multiple emulsion delayed chromium sol crosslinking system is 90% after 20 days.

Take the W/O/W type multiple emulsion delayed chromium sol cross-linking system prepared according to the method of Example 2 in a stoppered measuring cylinder, place it in a constant temperature chamber at 45°C, take it out for measurement at regular intervals, and measure it when the measuring cylinder is tilted at 30°C. The time when the surface does not move is the freezing time, and the viscosity of the system when freezing is measured with a Brookfield viscometer. The test result shows that the freezing time of the system is 408h, and the viscosity of the system is 24395mPa·s at this time.

Example 3

(A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 2.8% of the total mass of the oil phase, and the residual oil The amount is 5% of the total mass of the oil phase;

(B) Prepare a cross-linking agent with a mass fraction of 8% based on CrCl3, accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, add distilled water to a small beaker and fully dissolve, and the resulting solution In n(Cr ³⁺ ):n(Ac ^- )=1:3, then add the obtained solution into a 100mL volumetric flask, constant volume, fully shake, aging time more than 3d, the cross-linking agent chromium sol mother liquor is dark green or slightly Purple transparent liquid, made into a solution with a volume fraction of 2% as the inner water phase for later use;

(C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify with FA25 high-shear dispersing emulsifier at a speed of 10,000r/min for 150s to form colostrum, and use the dilution method to detect the type of emulsion;

(D) Make polyacrylamide into a 2000ppm aqueous solution, wherein the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.5% of the aqueous solution mass;

(E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a ratio of 7:3 by volume, the emulsification speed is 3000r/min, and the emulsification time is 180s. After the double emulsion is formed, the type of the emulsion is detected by the dilution method;

(F) Adjust the pH value of the prepared emulsion to 8, and the emulsion is most stable at pH=8.

Take the W/O/W type multiple emulsion delayed chromium sol crosslinking system prepared according to the method of Example 3 in a stoppered measuring cylinder, place it in a constant temperature box at 45°C for 20 days, and read the values of the free water layer and oil layer. Volume sum, the stability of the emulsion is measured by the percentage of the total volume of the emulsion after deducting the volume of the free water layer and the oil layer and the total volume. The test results show that the stability of the W/O/W multiple emulsion delayed chromium sol crosslinking system is 98% after 20 days.

Take the W/O/W type multiple emulsion delayed chromium sol crosslinking system prepared according to the method of Example 3 in a stoppered measuring cylinder, place it in a constant temperature chamber at 45°C, take it out regularly for measurement, and measure it when the measuring cylinder is inclined at 30°C. The time when the surface does not move is the freezing time, and the viscosity of the system when freezing is measured with a Brookfield viscometer. The test result shows that the freezing time of the system is 480h, and the viscosity of the system is 25994mPa·s at this time.

Example 4

(A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 2.8% of the total mass of the oil phase, and the residual oil The amount is 5% of the total mass of the oil phase;

(B) Prepare a cross-linking agent with a mass fraction of 8% (calculated as CrCl ₃ ), accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, and add distilled water to fully dissolve them in a small beaker. In the obtained solution, n(Cr ³⁺ ):n(Ac ⁻ )=1:3, then add the obtained solution into a 100mL volumetric flask, dilute to volume, and shake fully. After the aging time is more than 3 days, the cross-linking agent chromium sol mother solution is dark green or slightly purple transparent liquid. A solution with a volume fraction of 2% was prepared as the inner aqueous phase for later use.

(C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify with FA25 high-shear dispersing emulsifier at a speed of 10,000r/min for 150s to form colostrum, and use the dilution method to detect the type of emulsion .

(D) Make polyacrylamide into a 2000ppm aqueous solution, wherein the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.5% of the aqueous solution mass;

(E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a volume ratio of 7:3, the emulsification speed is 4000r/min, and the emulsification time is 180s. The emulsification speed cannot exceed 5000r/min, because the structure of polyacrylamide will be destroyed when the emulsification speed exceeds 5000r/min. After the formation of double emulsion, the type of emulsion was detected by dilution method.

(F) Adjust the pH value of the prepared emulsion to 8, and the emulsion is most stable at pH=8.

Take the W/O/W type multiple emulsion delayed chromium sol crosslinking system prepared according to the method of Example 4 in a stoppered measuring cylinder, place it in a constant temperature box at 45°C for 20 days, and read the values of the free water layer and oil layer. Volume sum, the stability of the emulsion is measured by the percentage of the total volume of the emulsion after deducting the volume of the free water layer and the oil layer and the total volume. The test results show that the stability of the W/O/W multiple emulsion delayed chromium sol crosslinking system is 99% after 20 days.

Take the W/O/W type multiple emulsion delayed chromium sol cross-linking system prepared according to the method of Example 4 in a stoppered measuring cylinder, place it in a 45°C thermostat to keep the temperature constant, take it out regularly for measurement, and use the graduated cylinder to incline at 30°C. The time when the surface does not move is the freezing time, and the viscosity of the system when freezing is measured with a Brookfield viscometer. The test result shows that the freezing time of the system is 480h, and the viscosity of the system is 28354mPa·s at this time.

According to Matsumoto's research, the rupture of oil layer is very important in the way of multiple emulsion decomposition. Because in the W/O/W multiple emulsion, each dispersed droplet contains one or more inner water phase droplets, and these water droplets are separated from the outer water phase by the oil layer. If the oil layer breaks, the inner water phase disappears immediately and mixes with the outer water phase. This situation is very similar to the bursting of soap bubbles suspended in air. Therefore, the persistence of the oil layer can be used to measure the stability of W/O/W multiple emulsions. Therefore, the present invention first determines the formula of the W/O emulsion.

There are many factors that affect the stability of W/O emulsion. After preliminary exploration in this experiment, the formulation of the emulsion was determined first, and the emulsifier dosage, oil-water ratio, emulsification time, and residual oil content were selected as the main factors. Four levels were taken, according to L16( 45) Design an orthogonal test, and the evaluation criterion of each test result is the stability of the emulsion, that is, the percentage. The test results are shown in Table 3.

Table 3 Orthogonal test results and analysis

Orthogonal test results show that the factors affecting W/O emulsion are B>A>C>D; the visual analysis of the results shows that the best combination is A4B4C4D1, that is, the emulsifier content is 2.8%, the oil-water ratio is 30:70, and the emulsification time is 150s , The residual oil content is 5%. Using the above test conditions to do a verification test, the stability evaluation of the result is 92.5%, which is higher than the 16 test results in the orthogonal table, so the A4B4C4D1 combination should be selected.

Claims (3)

1. A preparation method of a W/O/W type multiple emulsion delaying chromium sol crosslinking system, characterized in that: the preparation method of this W/O/W type multiple emulsion delaying chromium sol crosslinking system: (A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 1.5%~2.8% of the total mass of the oil phase. The amount of oil added is 5%~8% of the total mass of the oil phase; (B) Prepare a cross-linking agent with a mass fraction of 8%~10% based on CrCl ₃ , accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, and add distilled water to fully dissolve them in a small beaker , where n(Cr ³⁺ ):n(Ac ^- )=1:3 in the obtained solution, then add the obtained solution into a 100mL volumetric flask, constant volume, fully shake, and the aging time is more than 3d, the crosslinking agent chromium sol mother liquor is Dark green or slightly purple transparent liquid, prepared as a solution with a volume fraction of 2% as the inner aqueous phase; (C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify with FA25 high-shear dispersing emulsifier at a speed of 10000r/min for 2~5min to form colostrum, and detect the emulsion by dilution method type; (D) Make polyacrylamide into a 2000ppm aqueous solution, in which the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.0% of the mass of the aqueous solution~ 2.0%; (E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a volume ratio of 1~7:1~3, the emulsification speed is 4000r/min, and the emulsification time is 2~5min. After the double emulsion is formed, the emulsion is detected by the dilution method type; (F) Adjust the pH of the prepared emulsion to 7-10. 2. The preparation method of the W/O/W multiple emulsion delayed chromium sol crosslinking system according to claim 1, characterized in that: the pH value of the emulsion prepared in the step (F) is adjusted to 8. 3. The preparation method of the W/O/W type multiple emulsion delayed chromium sol crosslinking system according to claim 1, characterized in that: the preparation method of this W/O/W type multiple emulsion delayed chromium sol crosslinking system : (A) Add emulsifier Span-80 and residual oil to a certain amount of diesel oil, stir evenly, and use it as the oil phase. The amount of emulsifier Span-80 added is 2.8% of the total mass of the oil phase, and the residual oil The amount is 5% of the total mass of the oil phase; (B) Prepare a cross-linking agent with a mass fraction of 8% based on CrCl ₃ , accurately weigh CrCl ₃ 6H ₂ O and CH ₃ COONa 3H ₂ O with an analytical balance, and add distilled water to fully dissolve them in a small beaker. In the solution, n(Cr ³⁺ ):n(Ac ^- )=1:3, then add the obtained solution into a 100mL volumetric flask, constant volume, fully shake, aging time more than 3d, the cross-linking agent chromium sol mother liquor is dark green or Slight purple transparent liquid, made into a solution with a volume fraction of 2% as the inner water phase for later use; (C) Mix the prepared oil phase and water phase at a volume ratio of 3:7, emulsify with FA25 high-shear dispersing emulsifier at a speed of 10,000r/min for 150s to form colostrum, and use the dilution method to detect the type of emulsion; (D) Make polyacrylamide into a 2000ppm aqueous solution, wherein the emulsifier mSpan-80:mTween-80=7:3 in the aqueous solution, the sum of the contents of Span-80 and Tween-80 is 1.5% of the aqueous solution mass; (E) Mix and emulsify the prepared colostrum and polyacrylamide solution at a ratio of 7:3 by volume, the emulsification speed is 3000r/min, and the emulsification time is 180s. After the double emulsion is formed, the type of the emulsion is detected by the dilution method; (F) Adjust the pH value of the prepared emulsion to 8, and the emulsion is most stable at pH=8.