CN108503855B - A kind of Pickering emulsion emulsifier and preparation method and application thereof - Google Patents

Abstract

The invention provides an emulsifier for 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 emulsifier of the above Pickering emulsion can be used in papermaking, especially for preparing liquid paraffin emulsion for papermaking. The emulsifier of the present invention can obtain a stable Pickering paraffin wax emulsion, can effectively reduce the coalescence between paraffin oil droplets, greatly improve the stability of the emulsion, the emulsion is stable for several months without the precipitation of the water phase and the oil phase, and does not need to add any surface activity agent and other modifiers, the steps are simple and easy to operate.

Description

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

technical field

The invention belongs to the field of nanomaterial preparation and application, and particularly relates 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 a liquid in another immiscible liquid. It is mostly formed by mixing a water-insoluble oil phase with a 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 (dynamic stability) of the emulsion, an emulsifier or stabilizer must be added during the preparation of the emulsion. 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 the papermaking sizing is to improve the water resistance of the paper, and the presence of surfactants In addition to causing adverse effects on the environment, which generally reduce the water resistance of the paper, the use of solid particles to stabilize the sizing emulsion avoids these adverse effects of surfactants.

Pickering emulsion, also known as solid (particle) stabilized emulsion, is a kind of emulsion that can be emulsified and stabilized only with solid particles without adding traditional macromolecular organic surfactants. The solid particles adsorbed at the oil-water interface have extremely high The adsorption energy E makes it difficult for the solid particles to separate from the oil-water interface. It can be considered that this method of emulsification and stabilization of the emulsion by solid particles is irreversible, and Pickering emulsion has very strong stability. At present, this emulsification technology and research have been Widely used in various industries and fields. Pickering emulsion can reduce the complexity of the emulsification process, improve the stability of the emulsion and reduce the environmental pollution caused by the emulsifier because it avoids the use of polymer organic emulsifiers. It is a new type of emulsion with great potential application value. The emulsifier of Pickering emulsion is mainly based on solid particles (organic and inorganic) with amphiphilic (lipophilic and hydrophilic), supplemented by a small amount of surfactant. US Pat. No. 5,962,555 discloses a method for emulsifying Pickering emulsion by 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 avoid the inconvenience brought by the surfactant pretreatment, however, in order to obtain a stable Pickering emulsion, it is still necessary to add about 2% of the surfactant. US Patent US6284099 discloses a method for preparing ASA Pickering emulsion by emulsification of papermaking anionic particulate retention aids such as bentonite, colloidal silica, organic particulates and a small amount of surfactant and chelating agent. The particulate retention aid and sizing agent can be emulsified Combined into one, it simplifies the operation and reduces the amount of surfactant. However, the adverse effects of surfactants cannot be completely avoided, and if the amount of particulate components added 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 hydrolysis of the product is also serious.

SUMMARY OF THE INVENTION

In view of the problems that the current Pickering emulsion still needs surfactant in the preparation process; the concentration of the prepared emulsion is low, the present invention provides a Pickering emulsion emulsifier, which has good lipophilicity, a contact angle of 90°, and does not need to add surface activity The agent can form a high concentration of Pickering, and the stability time is long.

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

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

An emulsifier for Pickering emulsions, the core is PVP-DADMAN (poly(diallyldimethyl-ammonium nitrate) vinylpyrrolidone) graft-modified gold nanoparticles, and the core is embedded in PEOS (polyethoxyl) 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 an irregular polygon.

A preparation method of the above-mentioned emulsifier, comprising the following steps:

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

(2) Dissolve PEOS (polyethoxysiloxane) 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 as water The aqueous phase and the oil phase were ultrasonically stirred at room temperature, and after standing, an oil-in-water Pickering emulsion was obtained, washed, centrifuged and concentrated, 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 the 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 1h; the temperature of the reduction reaction is 98°C, and the reaction time is 1h; the centrifugation speed is 5000-20000rpm, and the centrifugation time is 5-30min.

The shape of the modified gold nanoparticles is nearly hexagonal; the average particle size is 30-45nm.

The weight average molecular weight M _w of the PEOS is 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 percentage concentration of the modified nano-gold solution is 0.1%-2%.

The mass ratio of the PEOS to the modified nano-gold 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 and the water phase is 1:5-1:1, preferably 1:3.

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

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

Application of an emulsifier of the above Pickering emulsion in papermaking.

A liquid paraffin emulsion prepared by adopting the above-mentioned emulsifier.

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

Disperse the above-mentioned emulsifier in water as the water phase; mix the liquid paraffin with the water phase under ultrasonic vibration stirring to obtain a liquid paraffin emulsion. The liquid paraffin is C ₁₆ -C ₂₀ n-paraffin.

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 by 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, the long skeleton of diallyldimethyl-ammonium nitrate is grafted on the surface of nano-gold by reducing reaction between PVP-DADMAN and HAuCl ₄ , and the nano-gold is modified to improve its lipophilicity; then it is coated by PEOS Modified nano-gold to further improve its lipophilic performance, and finally obtain the emulsifier of 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 covering compactness and stability of the surface particles of the emulsifier colloid; 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 an emulsifier of Pickering emulsion emulsifier with good density and high stability through the screening of nano-gold particle size and the control of pH.

The invention can effectively improve the lipophilicity of gold nanoparticles through the diallyldimethyl-ammonium nitrate long skeleton in PVP-DADMAN; the Pickering emulsion obtained by the prepared emulsifier has a three-phase contact angle close to 90°, and the zeta The potential is about 0, which is a very ideal plasma Pickering emulsion emulsifier; a stable Pickering paraffin wax emulsion is obtained by emulsification with this emulsifier, which can effectively reduce the coalescence between paraffin oil droplets and greatly improve the emulsion stability. There is no precipitation of water phase and oil phase, and there is no need to add any surfactants and other modifiers, and 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 emulsifier in embodiment 1;

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

Detailed ways

The present invention will be further described below with reference to the embodiments and the 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 M _w of 55 kg/mol in water respectively to obtain a solution of HAuCl ₄ with a concentration of 1 × 10 ^-2 M and a concentration of 1 × 10 ^{- 7} M PVP-DADMAN solution, mixed and boiled for 1 h, then added 20 parts by weight of ascorbic acid, stirred at 98°C in the dark for 1 h, and centrifuged at 5000 rpm for 5 min to obtain the supernatant. The TEM image of the supernatant is shown in Figure 2. The supernatant was vacuum-dried to obtain modified gold nanoparticles with an average particle size of 45 nm.

(2) Dissolving 1 part by weight of PEOS with _Mw of 1kg/mol in 2 parts by weight of toluene as an oil phase; dissolving 2 parts by weight of the modified nano-gold prepared in step (1) in water to make A solution with a mass percentage concentration of 0.1%; adding 0.4 parts by weight of n-butanol, adding dilute hydrochloric acid dropwise to adjust the pH to 1, as the water phase; adding the water phase to the oil phase, and the volume ratio of the oil phase and the water phase is 1 : 5, ultrasonic stirring at room temperature, standing for 3 days to obtain oil-in-water Pickering emulsion, washing and centrifugal concentration, precipitation, drying at room temperature to obtain the emulsifier of 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 the 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 is precipitated 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 M _w of 60 kg/mol in water respectively to obtain a solution of HAuCl ₄ with a concentration of 3 × 10 ^-3 M and a concentration of 6 × 10 ^{- 6} M PVP-DADMAN solution, mixed and boiled for 1 h, then added 70 parts by weight of thiourea, stirred at 98°C for 1 h in the dark, and centrifuged at 10,000 rpm for 15 min to obtain the supernatant. The TEM image of the supernatant is shown in Figure 2. As shown; the supernatant was vacuum-dried to obtain modified gold nanoparticles with an average particle size of 43 nm.

(2) Dissolving 1 weight part of PEOS with _Mw of 1.3kg/mol in 5 weight parts of xylene as an oil phase; dissolving 2.5 weight parts of the modified nano-gold prepared in step (1) in water, Making mass percent concentration is 1% solution; Add the propanol of 1 weight part, drip dilute hydrochloric acid and adjust pH to 2, as water phase; Water phase is added in oil phase, the volume ratio of oil phase and water phase is 1:3, ultrasonically stirred at room temperature, left standing for 4 days to obtain an oil-in-water Pickering emulsion, washed and centrifuged to concentrate, precipitated and dried at room temperature to obtain an 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 the 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 liquid paraffin emulsion. The average particle size of the suspended particles was 39±2 μm, and no water phase or oil phase was precipitated after being placed for 60 days.

Example 3

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

(2) 1 part by weight of PEOS with _Mw of 3kg/mol was dissolved in 8 parts by weight of ethylbenzene as an oil phase; 0.2 part by weight of the modified nano-gold prepared in step (1) was dissolved in water to prepare A solution with a mass percentage concentration of 0.1% was added; 0.1 weight part of ethanol was added, and an aqueous citric acid solution was added dropwise to adjust the pH to 4, as the water phase; the water phase was added to the oil phase, and the volume ratio of the oil phase and the water phase was 1 : 1, ultrasonically stirred at room temperature, and after standing for 5 days, oil-in-water Pickering emulsion was obtained, washed and centrifuged to concentrate, precipitated, and dried at room temperature to obtain the emulsifier of 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 ultrasonic bath for 15 minutes to obtain oil-in-water liquid paraffin emulsion , the average particle size of the suspended particles in the emulsion is 67±5 μm, and no water phase or oil phase is precipitated after standing for 90 days.

Claims (12)

1. an emulsifying agent of Pickering emulsion, 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 an irregular polygon. 2. a preparation method of emulsifier as claimed in claim 1, is characterized in that, comprises the following steps: (1) Dissolving HAuCl ₄ and PVP-DADMAN in water and boiling, then adding a reducing agent, stirring the reaction in the dark, centrifuging the supernatant and drying the supernatant in vacuum to obtain modified gold nanoparticles; (2) Dissolving PEOS in an organic solvent as an oil phase; dissolving the modified gold nanoparticles prepared in step (1) in water, adding a protective agent, adjusting the pH to be acidic, and using it as a water phase; dissolving the water phase and the oil phase in the water phase; Ultrasonic stirring at room temperature, standing to obtain oil-in-water Pickering emulsion, washing, centrifugal concentration, drying at room temperature to obtain an emulsifier of Pickering emulsion. 3. preparation method according to claim 2 is characterized in that, the weight-average molecular weight _Mw of described PVP-DADMAN is 55-68kg/mol; The concentration of described PVP- ^DADMAN is 1×10-7-1× 10 ^-5 M; the concentration of the HAuCl ₄ is 1×10 ^-2 -1×10 ^-4 M; the mass ratio of the 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 HAuCl and reducing agent is ₃ :1-1:5. 5. preparation method according to claim 2 is characterized in that, the weight-average molecular weight M of described _PEOS is 1-3kg/mol; Described organic solvent is selected from toluene, xylene or ethylbenzene; Described PEOS and The mass ratio of the modified nano-gold is 1:2-5:1; the mass percentage concentration of the modified nano-gold solution is 0.1%-2%. 6. preparation method according to claim 2, is characterized in that, described protective agent is water-soluble alcohol; The mass ratio of described modified nano-gold and protective agent is 5-2:1; Described oil phase and water The volume ratio of the phases is 1:5-1:1. 7 . The preparation method according to claim 2 , wherein the pH is 1-4; the acid for adjusting pH is an inorganic acid or an organic acid. 8 . 8 . The preparation method according to claim 2 , wherein, 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 centrifugal The time is 5-30min; in step (2), the standing time is 3-5 days. 9. the application of the emulsifier of a Pickering emulsion as claimed in claim 1 in papermaking. 10. A liquid paraffin emulsion prepared by using the emulsifier as claimed in claim 1. 11. a preparation method of liquid paraffin emulsion as claimed in claim 10, is characterized in that, comprises the following steps: emulsifier is dispersed in water, as water phase; Under ultrasonic vibration stirring, liquid paraffin is mixed with water phase, obtains Liquid paraffin emulsion; the liquid paraffin is C ₁₆ -C ₂₀ n-alkane. 12. preparation method according to claim 11 is characterized in that, the mass ratio of described emulsifier and water is 1:8-1:15; The mass ratio of described liquid paraffin and water phase is 1:8-3 :1.

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