CN108503855A - A kind of Pickering emulsion emulsifiers agent and its preparation method and application - Google Patents

Abstract

The invention provides an emulsifier for a Pickering emulsion, the inner core is PVP-DADMAN graft-modified nano-gold particles, and the inner core is embedded in PEOS; the mass ratio of the nano-gold, PVP-DADMAN and PEOS is 4:1 :2-2:3:10; the average diameter of the emulsifier is 35-75nm; the shape is an irregular polygon. The above-mentioned emulsifier for Pickering emulsion can be applied to papermaking, especially for preparing liquid paraffin emulsion for papermaking. The emulsifier of the present invention can obtain a stable Pickering paraffin emulsion, which can effectively reduce the coalescence between paraffin oil droplets, greatly improve the stability of the emulsion, and the emulsion is stable for several months without precipitation of the water phase and the oil phase, and does not need to add any surface active agent and other modifiers, the steps are simple and easy to operate.

Description

A kind of Pickering emulsion emulsifier and its preparation method and application

technical field

The invention belongs to the field of nanomaterial preparation and application, in particular to an emulsifier capable of forming Pickering emulsion and its application in liquid paraffin emulsion.

Background technique

Emulsion is a dispersion system formed by dispersing one liquid in another immiscible liquid. It is mostly formed by mixing water-insoluble oil phase and water phase. It is used in papermaking, food, cosmetics, medicine and other industries. widely. Emulsion is a thermodynamically unstable system. In order to maintain the relative stability of the emulsion (kinetic stability), an emulsifier or stabilizer must be added during the emulsion preparation process. Traditional emulsifiers or stabilizers are mostly surfactants and surface-active polymers, which maintain the stability of the emulsion by reducing the interfacial tension between the oil-water two-phase liquid, providing a stable interfacial film and increasing the viscosity of the continuous phase . In recent years, solid particles have received more and more attention because they can avoid the adverse effects of surfactants on the environment, stabilize high-concentration dispersed phase emulsions, and the emulsions are less affected by changes in pH, salt concentration, temperature and oil phase composition. s concern. For example, in the papermaking industry, the water-insoluble papermaking sizing agent needs to be emulsified into an oil-in-water emulsion to be compatible with the papermaking system using water as the medium, and the purpose of papermaking sizing is to improve the water resistance of paper, and the presence of surfactants In addition to causing adverse effects on the environment, it generally reduces the water resistance of the paper, and the use of solid particles to stabilize the sizing agent emulsion can avoid these adverse effects of surfactants.

Pickering emulsion is also called solid (particle) stable emulsion. It is a kind of emulsion that can be emulsified and stable only with solid particles without adding traditional polymer organic surfactants. The solid particles adsorbed at the oil-water interface have extremely high The adsorption energy E makes it difficult for solid particles to detach from the oil-water interface. It can be considered that this method of emulsifying and stabilizing the emulsion by solid particles is irreversible, and the Pickering emulsion has very strong stability. At present, this emulsification technology and research are being used. Widely used in various industries and fields. Pickering emulsion can reduce the complexity of the emulsification process by avoiding the use of polymer organic emulsifiers, improve the stability of the emulsion and reduce the environmental pollution caused by emulsifiers. It is a new type of emulsion with great potential application value. The emulsifier of Pickering emulsion is mainly amphiphilic (lipophilic and hydrophilic) solid particles (organic and inorganic), and a small amount of surfactant is a stable system. US Patent No. 5,962,555 discloses a method for emulsifying Pickering emulsions using a mixture of ionene polymer and polyethyleneimine, wherein the ionene polymer can not only improve the sizing efficiency but also have a bactericidal effect. Although these inventions have avoided the inconvenience brought by surfactant pretreatment, however, in order to obtain a stable Pickering emulsion, it is still necessary to add about 2% of surfactant. U.S. Patent No. 6,284,099 discloses a method for preparing ASA Pickering emulsion by emulsifying anionic particle retention aids for papermaking such as bentonite, colloidal silicon dioxide, organic particles and a small amount of surfactant and chelating agent. Combining two into one simplifies the operation and reduces the amount of surfactant. However, the adverse effects brought by the surfactant cannot be completely avoided, and the added amount of the microparticle component is too large, the concentration of the prepared ASA emulsion is very low, which is not conducive to the storage of the emulsion, and the product hydrolysis is also serious.

Contents of the invention

Aiming at the problems that current Pickering emulsions still need surfactants in the preparation process and the concentration of the prepared emulsions is low, the invention provides a Pickering emulsion emulsifier with good lipophilicity, a contact angle of 90°, and no need to add surfactants A high concentration of Pickering can be formed with only a single agent, and the stability time is long.

Another object of the present invention is to provide a kind of liquid paraffin emulsion containing above-mentioned emulsifier and its preparation method.

In order to achieve the above object, the present invention adopts the following technical solutions.

An emulsifier for Pickering emulsions, the core is PVP-DADMAN (poly(diallyldimethyl-ammonium nitrate) vinylpyrrolidone) grafted modified gold nanoparticles, and the core is embedded in PEOS (polyethoxylated Siloxane); the mass ratio of the nano-gold, PVP-DADMAN and PEOS is 4:1:2-2:3:10; the average diameter of the emulsifier is 35-75nm; the shape is irregular polygon.

A kind of preparation method of above-mentioned emulsifying agent, comprises the following steps:

(1) Dissolve HAuCl ₄ (tetrachloroauric acid) and PVP-DADMAN (poly(diallyldimethyl-ammonium nitrate) vinylpyrrolidone) in water and boil, then add reducing agent, and stir the reaction in the dark, After centrifugation, the supernatant was vacuum-dried to obtain modified gold nanoparticles;

(2) Dissolve PEOS (polyethoxysiloxane) in an organic solvent as the oil phase; dissolve the modified nano-gold prepared in step (1) in water, add a protective agent, adjust the pH to be acidic, and use it as the water phase Phase; the water phase and the oil phase are ultrasonically stirred at room temperature, and after standing still, an oil-in-water Pickering emulsion is obtained, washed and concentrated by centrifugation, and dried at room temperature to obtain an emulsifier of the Pickering emulsion.

The weight average molecular weight M _w of the PVP-DADMAN is 55-68 kg/mol, more preferably 60 kg/mol.

The mass ratio of HAuCl ₄ and PVP-DADMAN is 60:1-20:1, preferably 35:1. The concentration of the HAuCl ₄ is preferably 1×10 ^-2 -1×10 ^-4 M, more preferably 3×10 ^-3 M; the concentration of the PVP-DADMAN is preferably 1×10 ^-7 -1×10 ^{- 5} M, more preferably 6×10 ^-6 M.

The reducing agent is selected from ascorbic acid or thiourea; preferably ascorbic acid.

The mass ratio of the HAuCl ₄ to the reducing agent is 3:1-1:5, preferably 1:2.

In the step (1), the boiling time is 1 hour; the reduction reaction temperature is 98° C., and the reaction time is 1 hour; the centrifugation speed is 5000-20000 rpm, and the centrifugation time is 5-30 minutes.

The shape of the modified nano-gold particles is nearly hexagonal; the average particle diameter is 30-45nm.

The PEOS has a weight average molecular weight M _w of 1-3 kg/mol, more preferably 1.3 kg/mol.

In step (2), the organic solvent is selected from toluene, xylene or ethylbenzene; preferably toluene. Further, the mass ratio of PEOS to toluene is 1:2-1:8; more preferably 1:5.

In step (2), the mass percent concentration of the modified nano-gold solution is 0.1%-2%.

The mass ratio of PEOS to modified gold nanoparticles is 1:2-5:1, preferably 2:1.

The protecting agent is water-soluble alcohol; preferably C1-C4 alcohol; more preferably n-butanol. The mass ratio of the modified nano-gold to the protective agent is 5-2:1.

The volume ratio of the oil phase to the water phase is 1:5-1:1, preferably 1:3.

The pH is 1-4; preferably 2. The acid for adjusting the pH may be an inorganic acid or an organic acid; preferably selected from hydrochloric acid or citric acid.

In step (2), the standing time is 3-5 days.

An application of an emulsifier for the aforementioned Pickering emulsion in papermaking.

A liquid paraffin emulsion prepared using the above emulsifier.

A kind of preparation method of above-mentioned liquid paraffin emulsion, comprises the following steps:

The above emulsifier is dispersed in water as the water phase; the liquid paraffin is mixed with the water phase under ultrasonic vibration stirring to obtain the liquid paraffin emulsion. The liquid paraffin is C ₁₆ -C ₂₀ normal alkanes.

The mass ratio of the emulsifier to water is 1:8-1:15; more preferably 1:10. The mass ratio of the liquid paraffin to the water phase is 1:8-3:1; more preferably 1:1.

In the above method, mixing the liquid paraffin with the water phase can be adding the water phase to the liquid paraffin, or adding the liquid paraffin to the water phase; preferably adding the water phase to the liquid paraffin.

In the present invention, through the reduction reaction of PVP-DADMAN and _HAuCl4 , the long skeleton of diallyldimethyl-ammonium nitrate is grafted on the surface of nano-gold, and the nano-gold is modified to improve its lipophilicity; then coated with PEOS Modified nano-gold to further improve its lipophilic performance, and finally obtain an emulsifier for Pickering emulsion with higher lipophilicity. By adjusting the pH value, the charge repulsion of the emulsifier is reduced to form dense and stable emulsifier particles, and the emulsifier is obtained after drying.

The present invention has the following advantages:

The size of the gold nanoparticles in the present invention directly determines the coverage density and stability of the surface particles of the emulsifier micelle; when the pH value is lower than 4, the charge repulsion between the emulsifiers is the lowest, which is most conducive to the formation of compactness and stability higher surface structure. The invention obtains the emulsifier of the Pickering emulsion emulsifier with good density and high stability through the screening of the particle size of the nano-gold and the control of the pH.

The present invention can effectively improve the lipophilicity of gold nanoparticles through the long skeleton of diallyldimethyl-ammonium nitrate in PVP-DADMAN; the Pickering emulsion obtained by the prepared emulsifier has a three-phase contact angle close to 90°, zeta The potential is about 0, which is a very ideal emulsifier for plasma Pickering emulsion; through the emulsification of this emulsifier, a stable Pickering paraffin emulsion can be obtained, which can effectively reduce the coalescence between paraffin oil droplets, greatly improve the stability of the emulsion, and the emulsion stability number There is no precipitation of water phase and oil phase, and there is no need to add any surfactants and other modifiers. The steps are simple and easy to operate.

Description of drawings

Fig. 1 is the structural representation of emulsifier;

Fig. 2 is the transmission electron microscope picture of nano-gold particle micelle in embodiment 1;

Fig. 3 is the transmission electron microscope picture of emulsifying agent in embodiment 1;

FIG. 4 is a microscopic picture of the liquid paraffin Pickering emulsion prepared in Example 1.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the present invention is not limited by the following embodiments.

Example 1

Emulsifiers for Pickering emulsions were prepared using the following steps:

(1) Dissolve 60 parts by weight of HAuCl ₄ and 1 part by weight of PVP-DADMAN with a _Mw of 55 kg/mol in water to obtain a HAuCl ₄ solution with a concentration of 1×10 ^-2 M and a solution with a concentration of 1×10 ^{- 7} M solution of PVP-DADMAN, mixed and boiled for 1 hour, then added 20 parts by weight of ascorbic acid, stirred and reacted in the dark at 98°C for 1 hour, centrifuged at 5000rpm for 5 minutes to obtain the supernatant, the TEM picture of the supernatant is shown in Figure 2 shown; the supernatant was vacuum-dried to obtain modified gold nanoparticles, with an average particle size of 45nm.

(2) Dissolve 1 part by weight of PEOS with a _Mw of 1 kg/mol in 2 parts by weight of toluene as the oil phase; dissolve 2 parts by weight of the modified nano-gold prepared in step (1) in water to prepare A solution with a mass percent concentration of 0.1%; add 0.4 parts by weight of n-butanol, drop dilute hydrochloric acid to adjust the pH to 1, and use it as the water phase; add the water phase to the oil phase, and the volume ratio of the oil phase to the water phase is 1 : 5 at room temperature ultrasonic stirring, after standing for 3 days to obtain the oil-in-water Pickering emulsion, cleaning and centrifugal concentration, precipitation, drying at room temperature to obtain the emulsifier of the Pickering emulsion.

The particle size of the obtained emulsifier is 35nm, the Zeta potential is 0±0.8mV, and the three-phase contact angle with water and liquid paraffin is 90±3°

Preparation of liquid paraffin emulsion: disperse 1 part of emulsifier particles prepared above into 8 parts of deionized water, add 1 part of liquid paraffin under ultrasonic stirring, and stir and mix in an ultrasonic bath for 15 minutes to obtain an oil-in-water liquid paraffin emulsion. The picture under the microscope is shown in Figure 3; the average particle size of the suspended particles in the emulsion is 43±0.5 μm, and no water phase or oil phase precipitates out after standing for 30 days.

Example 2

(1) Dissolve 35 parts by weight of HAuCl ₄ and 1 part by weight of PVP-DADMAN with a _Mw of 60 kg/mol in water to obtain a HAuCl ₄ solution with a concentration of 3×10 ^-3 M and a solution with a concentration of 6×10 ^{- 6} M solution of PVP-DADMAN, mixed and boiled for 1 hour, then added 70 parts by weight of thiourea, stirred and reacted in the dark at 98°C for 1 hour, centrifuged at 10,000 rpm for 15 minutes to obtain the supernatant, the TEM picture of the supernatant is shown in Figure 2 Shown; The supernatant was vacuum-dried to obtain modified gold nanoparticles, with an average particle size of 43nm.

(2) 1 part by weight of PEOS with a _Mw of 1.3 kg/mol is dissolved in 5 parts by weight of xylene as the oil phase; 2.5 parts by weight of the modified nano-gold prepared in step (1) is dissolved in water, Make the solution that mass percentage concentration is 1%; Add the propanol of 1 weight part, drop dilute hydrochloric acid and adjust pH to 2, as water phase; Add water phase in the oil phase, the volume ratio of oil phase and water phase is 1:3, ultrasonic stirring at room temperature, standing for 4 days to obtain oil-in-water Pickering emulsion, washing and centrifugal concentration, precipitation, room temperature drying to obtain the emulsifier of Pickering emulsion.

The zeta potential of the obtained emulsifier is 0±1mV, and the three-phase contact angle with water and liquid paraffin is 90±4°.

Preparation of liquid paraffin emulsion: disperse 1 part of microcapsule particles prepared above into 10 parts of deionized water, add 10 parts of liquid paraffin under ultrasonic stirring, and stir and mix in an ultrasonic bath for 15 minutes to obtain an oil-in-water type liquid paraffin emulsion, emulsion The average particle size of suspended particles in the medium is 39±2 μm, and no water phase or oil phase precipitates out after 60 days of storage.

Example 3

(1) Dissolve 20 parts by weight of HAuCl ₄ and 1 part by weight of PVP-DADMAN with a _Mw of 68 kg/mol in water to obtain a HAuCl ₄ solution with a concentration of 1×10 ^-4 M and a solution with a concentration of 1×10 ^{- 5} M solution of PVP-DADMAN, mixed and boiled for 1 hour, then added 100 parts by weight of ascorbic acid, stirred and reacted for 1 hour at 98°C in the dark, centrifuged at 20,000 rpm for 30 minutes to obtain a supernatant, the TEM picture of the supernatant is shown in Figure 2 shown; the supernatant was vacuum-dried to obtain modified gold nanoparticles, with an average particle size of 40nm.

(2) 1 weight part of PEOS with _Mw of 3kg/mol is dissolved in 8 weight parts of ethylbenzene as the oil phase; 0.2 weight part of the modified nano-gold prepared in step (1) is dissolved in water to prepare A solution with a mass percent concentration of 0.1% is added; 0.1 parts by weight of ethanol is added, and a citric acid aqueous solution is added dropwise to adjust the pH to 4 as the water phase; the water phase is added to the oil phase, and the volume ratio of the oil phase to the water phase is 1 : 1, ultrasonically stirred at room temperature, left to stand for 5 days to obtain the oil-in-water Pickering emulsion, cleaned and centrifugally concentrated, precipitated, dried at room temperature to obtain the emulsifier of the Pickering emulsion. The zeta potential of the obtained emulsifier is 0±0.5mV, and the three-phase contact angle with water and liquid paraffin is 90±8°.

Preparation of liquid paraffin emulsion: disperse 1 part of microcapsule emulsifier particles prepared above into 15 parts of deionized water, add 45 parts of liquid paraffin under ultrasonic stirring, and stir and mix in an ultrasonic bath for 15 minutes to obtain an oil-in-water liquid paraffin emulsion , the average particle size of suspended particles in the emulsion is 67±5 μm, and no water phase or oil phase precipitates out after standing for 90 days.

Claims (12)

1. an emulsifier of Pickering emulsion, it is characterized in that, inner core is the nano-gold particle of PVP-DADMAN graft modification, and inner core is embedded in PEOS; The mass ratio of described nano-gold, PVP-DADMAN and PEOS is 4 :1:2-2:3:10; the average diameter of the emulsifier is 35-75nm; the shape is irregular polygon. 2. a preparation method of emulsifying agent as claimed in claim 1, is characterized in that, comprises the following steps: (1) Dissolve HAuCl ₄ and PVP-DADMAN in water and boil, then add reducing agent, avoid light and stir for reaction, centrifuge and vacuum-dry the supernatant to obtain modified gold nanoparticles; (2) Dissolve PEOS in an organic solvent as an oil phase; dissolve the modified gold nanoparticles prepared in step (1) in water, add a protective agent, adjust the pH to be acidic, and use it as a water phase; mix the water phase and the oil phase in Ultrasonic stirring at room temperature, standing still to obtain oil-in-water Pickering emulsion, washing and centrifugal concentration, drying at room temperature to obtain the emulsifier of Pickering emulsion. 3. The preparation method according to claim 2, characterized in that, the weight average molecular weight _Mw of the PVP-DADMAN is 55-68kg/mol; the concentration of the PVP-DADMAN is 1× ^10-7-1 × 10 ^-5 M; the concentration of HAuCl ₄ is 1×10 ^-2 -1×10 ^-4 M; the mass ratio of HAuCl ₄ and PVP-DADMAN is 60:1-20:1. 4. preparation method according to claim 2 is characterized in that, described reducing agent is selected from ascorbic acid or thiourea; The mass ratio of described _HAuCl4 and reducing agent is 3:1-1:5. 5. The preparation method according to claim 2, characterized in that, the PEOS has a weight-average molecular weight _Mw of 1-3kg/mol; the organic solvent is selected from toluene, xylene or ethylbenzene; preferably toluene; Preferably, the mass ratio of PEOS and toluene is 1:2-1:8; the mass ratio of PEOS and modified nano-gold is 1:2-5:1; the mass percent concentration of the modified nano-gold solution 0.1%-2%. 6. preparation method according to claim 2, is characterized in that, described protective agent is water-soluble alcohol; Be preferably the alcohol of C1-C4; More preferably n-butanol; Described modified nano-gold and protective agent The mass ratio is 5-2:1; the volume ratio of the oil phase and the water phase is 1:5-1:1. 7. The preparation method according to claim 2, characterized in that, the pH is 1-4; the acid for adjusting the pH may be an inorganic acid or an organic acid; preferably selected from hydrochloric acid or citric acid. 8. The preparation method according to claim 2, characterized in that, in the step (1), the boiling time is 1 h; the temperature of the reduction reaction is 98°C, and the reaction time is 1 h; the centrifugal speed is 5000-20000 rpm, and the The time is 5-30 minutes; in step (2), the standing time is 3-5 days. 9. The use of an emulsifier for the aforementioned Pickering emulsion in papermaking. 10. A liquid paraffin emulsion that adopts the emulsifying agent as claimed in claim 1 to prepare. 11. a preparation method of liquid paraffin emulsion as claimed in claim 10, is characterized in that, comprises the following steps: emulsifying agent is dispersed in water, as water phase; Liquid paraffin is mixed with water phase under ultrasonic vibration stirring, obtains Liquid paraffin emulsion; the liquid paraffin is C ₁₆ -C ₂₀ normal alkanes. 12. The preparation method according to claim 11, characterized in that, the mass ratio of the emulsifier to water is 1:8-1:15; the mass ratio of the liquid paraffin to the water phase is 1:8-3 :1.