JPH0153574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a stable oil-in-water emulsion of fine particles, and more particularly, the present invention relates to a method for producing a stable oil-in-water emulsion of fine particles, and more particularly, the emulsion particles are extremely uniform in size and fine;
The present invention also relates to a method for producing an oil-in-water emulsion with good viscosity stability over time.

Conventionally, the method for producing this type of oil-in-water emulsion involves dispersing and emulsifying an oil phase at a temperature above the transition temperature into an aqueous phase at a temperature above the transition temperature of the oil phase using a homogenizer or the like under high shear force, and then slowly cooling the resultant mixture. This method was common. In some cases, contrary to the above method, a phase inversion emulsification method is used in which an oil phase with a temperature higher than the transition temperature is dispersed and emulsified with a high shear force, and then slowly cooled. Ta.

However, in these methods, the fine particles of the oil phase are usually kept at a high temperature of 60°C or higher, which is higher than the transition temperature of the oil phase, for a long time, so some of the emulsified particles cause a coalescence phenomenon to obtain uniform particles. Moreover, there is a time delay in mass transfer between the dispersoid and the continuous phase, and it takes several days to several months to reach an equilibrium system, resulting in poor viscosity stability over time. It was hot.

Furthermore, the method for producing the emulsion described above involves heating the aqueous phase, which makes up the majority of the composition, at high temperatures and cooling, which requires a long period of time, so it cannot be said to be an efficient method in terms of process.

Therefore, various processes have been proposed to solve these problems. For example, special public relations
In the method described in Publication No. 29213, as a first step, a hydrophilic nonionic surfactant is added to a water-soluble solvent, and then an oil phase is added thereto to prepare an oil-in-water-soluble solvent emulsion. As a second step, water is added to the emulsion. However, this method is limited to emulsions based only on hydrophilic nonionic surfactants, so its range of applications is narrow, and since emulsification is carried out at a high temperature above the transition temperature of the oil phase, a cooling operation is required after dispersion and emulsification. However, it cannot be said to be an efficient emulsion manufacturing method in terms of process.

The purpose of the present invention is to provide a method for producing a highly stable oil-in-water emulsion with uniform fine particles that solves these problems. An oil-in-aqueous solvent emulsion is prepared by dispersing the oil phase at a temperature higher than the transition temperature in the oil with a shear force of 5 m/sec or higher, and in the second step, the oil phase is heated to a temperature lower than the transition temperature of the oil phase and close to room temperature. It is characterized in that emulsification and cooling are performed simultaneously by adding and dispersing the emulsion to the retained aqueous phase.

According to the method of the present invention, since the oil phase is first dispersed in a water-soluble solvent having a lower surface tension than water, it is possible to obtain emulsified particles that are more uniform and finer than usual. Since the oil-in-neutral solvent emulsion is dispersed in an aqueous phase that is kept at a low temperature close to room temperature, the fine particles of the oil phase are not kept at a high temperature above the transition temperature of the oil phase for a long time, and as a result, the combination of emulsified particles is prevented. It is possible to easily obtain an oil-in-water emulsion in which no phenomenon occurs, the emulsion particles are extremely uniform and fine in size, and the viscosity is stable over time.

In particular, when a cationic surfactant and a higher alcohol are included as oil phase components as in the present invention,
Since a portion of these cationic surfactants and higher alcohols aggregate to form a liquid crystal structure, contrary to the present invention, they are mixed in an oil-in-aqueous solvent emulsion maintained at a temperature higher than the transition temperature of the oil phase. When water at a temperature lower than the transition temperature of the oil phase and close to room temperature is added, the water is rapidly incorporated into the liquid crystal structure described above, causing gelling and thickening, and at the same time, the dispersed particles aggregate and form lumps. However, in the present invention, an oil-in-water emulsion is added to the continuous phase of water, so there is no rapid thickening and the oil particles are uniformly dispersed without agglomeration. It turns out.

Here, the transition temperature of the oil phase containing the above-mentioned cationic surfactant and higher alcohol is the transition temperature of a normal single oil phase (actually, it is often a mixture of oil phase components with different alkyl chain lengths). temperature, that is, the temperature at which the oil phase undergoes a phase change between a solid phase and a liquid phase, and this phase transition temperature has different values depending on the mixing ratio of the cationic surfactant and the higher alcohol. show.

The method of the present invention will be explained in more detail below.

In the present invention, as a first step, an oil phase having a temperature higher than the transition temperature of the oil phase is added to a water soluble solvent having a temperature higher than the transition temperature of the oil phase to prepare an oil-in-water emulsion. The following can be mentioned. In other words, lower monohydric alcohols such as methanol, ethanol, propanol, isopropanol, and benzyl alcohol, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, 2,3-butylene glycol, heptanediol, propylene glycol, 1,3-butylene glycol, and Lower polyhydric alcohols such as propylene glycol, ketones such as acetone, acetonyl acetone, diacetone alcohol, aldehydes such as formaldehyde, ethylene oxide, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl Ethers such as ether, ethylene glycol monobutyl ether, dimethylene glycol monoethyl ether, monopropylene glycol methyl ether, acetic acid ethylene glycol monomethyl ether, monoethanolamine, diethanolamine, triethanolamine, ethylene diamine, propylene diamine, ethylamine, pyridine, etc. Amines, formic acid, acetic acid, butyric acid,
These include lower fatty acids such as lactic acid.

On the other hand, examples of the composition of the oil phase include those shown below. That is, cationic surfactants, higher alcohols, emulsifiers, oily components, water, etc. Specifically, cationic surfactants such as stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, distearyldimethylammonium chloride, cetyl alcohol, Higher alcohols such as stearyl alcohol, cetostearyl alcohol, behenyl alcohol, polyoxyethylene stearyl ether, polyoxyethylene sorbitate tetraoleate, monopyroglutamic acid, polyoxyethylene glyceryl monoisostearate, polyoxyethylene, glyceryl triisostearate, Emulsifiers such as propylene glycol monostearate, sorbitan monostearate, diglycerin monostearate, sorbitan sesquiolate, silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, liquid paraffin, squalane, etc. These include oily components of hydrocarbons.

Here, one of the important conditions of the present invention is that when the oil phase is added to a water-soluble solvent, the shear force during dispersion is 5 m/sec or more. 5m/
If it is more than sec, it is the limit of the current machine ability.
It can be of any size up to 20m/sec.
Note that if the speed is less than 5 m/sec, poor dispersion occurs and uniform fine particles cannot be obtained.

Next, in the second step, the oil-in-water emulsion obtained in the first step is added to the aqueous phase, which is maintained at a temperature lower than the transition temperature of the oil phase and close to room temperature, and the emulsion is An oil-in-water emulsion is formed while simultaneously cooling the oil phase particles. Here, the aqueous phase is composed of the following composition. That is, they include water, organic salts, inorganic salts, fragrances, pigments, and the like, and to these, a low-temperature stabilizer, a nonionic surfactant, etc. can be added within a range that does not impair the effects of the present invention.

Therefore, as mentioned above, maintaining the temperature of the aqueous phase at a temperature lower than the transition temperature of the oil phase and close to room temperature when adding an oil-in-water emulsion is important in preventing the formation of fine particles in the oil phase. It is extremely effective in accelerating cooling and preventing it from being left in a high temperature state for a long time, and in obtaining an oil-in-water emulsion with fine and uniform emulsified particles and good stability over time in viscosity. That is, if the temperature of the aqueous phase is higher than the transition temperature of the oil phase, part of the emulsification after dispersion will coalesce, making it impossible to obtain uniform particles, and it will take time for mass transfer between the dispersoids and the continuous phase. A lag occurs, and it takes a long time to reach an equilibrium system, and the stability of the viscosity over time also deteriorates. Furthermore, a cooling step is required in terms of process.
It should be noted that if the temperature of the oil-in-aqueous solvent emulsion is lower than the transition temperature of the oil phase, it is of course difficult to add the emulsion, resulting in poor dispersion.

The shearing force applied when adding the above-mentioned oil-in-aqueous solvent emulsion has already finely dispersed the oil phase particles in the first step, and since the continuous phase is a water-soluble solvent, the emulsion is added to the aqueous phase. If it does, it will be easily dispersed and therefore strong shearing forces are not required.

Next, the effects of the present invention will be specifically explained with reference to Examples.

Example 1 Solvent emulsification tank (1st stage) Tank volume: 2.5 Stirring blade: Homo mixer Blade tip circumferential speed 5 m/sec (shear force) Main emulsification tank (2nd stage) Tank volume: 25 Stirring blade: Homo mixer Blade tip Peripheral speed: 5 m/sec (shear force) First, as a first step, a water-soluble solvent, glycerin (5%) at 65°C, is placed in the solvent emulsification tank, and stearyltrimethylammonium chloride (1.0%), Cetostearyl alcohol (3.5
%), diglycerin monostearate (0.6%),
An oil phase with a transition temperature of 60°C containing sorbitan sesquiolate (0.4%) and liquid paraffin (0.3%) was heated to 65°C.
The mixture is heated to and gradually supplied, and at the same time as the supply, a dispersion treatment using a stirring blade is performed for 10 minutes to emulsify the mixture, thereby preparing an oil-in-aqueous solvent emulsion at 65°C.

Next, in the second step, an aqueous phase at 30°C containing a nonionic surfactant, polyoxyethylene noriphenyl ether (0.3%), a fragrance (0.5%), and a trace amount of pigment, was placed in the main emulsification tank. The 65°C oil-in-aqueous solvent emulsion obtained in the first step above was gradually fed into this aqueous phase, and at the same time as it was fed, a dispersion treatment using a stirring blade was performed for 20 minutes to emulsify it. Thus, 20 oil-in-water emulsions were obtained at 35°C. It was confirmed that the particle size of the emulsion at that time was extremely fine and uniform as shown in Figure 1a. The viscosity of the emulsion at that time was 1600 cp, which was extremely stable, and the viscosity one year later was 1640 cp, which was almost the same as the viscosity immediately after production.

Comparative Example 1A With the same composition as Example 1, glycerin, which is a water-soluble solvent, was added in advance to the 30°C water phase of Example 1, and the same 65°C oil phase as in Example 1 was gradually supplied to this water phase. , was supplied and emulsified by performing a dispersion treatment using a stirring blade for 20 minutes, thereby obtaining an emulsion of 20 at 35°C. The particle size of the emulsion at that time was confirmed to be non-uniform, with a large average particle size and a wide viscosity distribution, as shown in Figure 1b. Also, the viscosity of the emulsion immediately after production was 1200 cp,
After one year, the viscosity was 3200 cp, showing severe thickening.
The viscosity stability was extremely unstable.

Comparative Example 1B A 30°C aqueous phase was gradually added over 20 minutes to an oil-in-aqueous solvent emulsion at 65°C prepared in the same manner as in Example 1 while performing a dispersion treatment using a stirring blade. , yielded 20 emulsions. The relationship between the addition time and the viscosity of the emulsion at this time is shown in FIG.

As can be seen from this figure, the viscosity rapidly increased with the addition of the aqueous phase, resulting in gelation, and at the same time, the dispersed particles agglomerated to form lumps (0.5 to 2 mm).

This phenomenon occurs because when a cationic surfactant and a higher alcohol are included as oil phase components, a portion of these cationic surfactants and higher alcohols form an aggregate and take on a liquid crystal structure. This is caused by the rapid incorporation of the added aqueous phase into the structure.

In contrast, in the case of the present invention, there was no rapid thickening and the oil particles were uniformly dispersed without agglomeration (average particle size: 0.55μ).

Example 2 Solvent emulsification tank (1st stage) Tank volume: 2.5 Stirring blade: Jet agitator Blade tip circumferential speed 10 m/sec (shear force) Main emulsification tank (2nd stage) Tank volume: 25 Stirring blade: Jet agitator Blade tip circumferential speed 10 m/sec (shear force) First, add 70 m/sec (shear force), a water-soluble solvent, to the solvent emulsification tank
Accommodate propylene glycol (8.0%) at °C.
This includes distearyldimethylammonium chloride (1.5%), stearyl alcohol (3.2%), polyoxyethylene hydrogenated castor oil triisostearate (0.1%), and polyoxyethylene alkyl phenyl ether phosphate (0.5%). Temperature 61℃
The oil phase is heated to 70°C and gradually supplied, and at the same time the oil phase is fed, a dispersion treatment using a stirring blade is performed for 20 minutes to emulsify it, and as a first step, an oil-in-aqueous solvent emulsion at 70°C is prepared. .

Next, the main emulsification tank contains polyoxyethylene nonyl phenyl ether (0.2%), a nonionic surfactant, fragrance (0.5%), and minute pigments.
Contain an aqueous phase at 27°C, and gradually feed the 70°C oil-in-aqueous solvent emulsion obtained in the first step above into this aqueous phase, and at the same time perform a dispersion treatment using a stirring blade for 30 minutes. emulsify it by
This gave 20 emulsions at 35°C.
It was confirmed that the particle size of the emulsion at that time was extremely fine and uniform as shown in Figure 2a. Also, the viscosity of the emulsion at that time is
1200cp, this viscosity is extremely stable,
The viscosity after one year is almost the same as the viscosity immediately after production.
It was 1200 cp.

Comparative Example 2 With the same composition as Example 2, propylene glycol, which is a water-soluble solvent, was added in advance to the 27°C aqueous phase of Example 2, and this aqueous phase was heated to 70°C, the same as Example 2.
The oil phase was gradually supplied and emulsified by performing a dispersion treatment using a stirring blade for 30 minutes while supplying the oil phase, thereby obtaining an emulsion of 20 at 35°C. The particle size of the emulsion at that time is b in Figure 2.
As shown in , it was confirmed that the average particle size was large and the particle size was non-uniform with a wide viscosity distribution.
Further, the viscosity of the emulsion immediately after production was 1400 cp, but after one year, the viscosity was 2500 cp, which showed a severe increase in viscosity and the viscosity stability was extremely unstable.

Comparative Example 3 Same composition as Example 1, except that the shear force (blade tip peripheral speed) was 3 m/sec.
An oil-in-water emulsion was obtained under the same conditions.

When the dispersion state of this oil-in-water emulsion was examined, it was found that the particles were partially agglomerated to a size of about 0.5 to 1.0 mm. This is thought to be due to poor dispersion of the water-soluble oil-in-solvent emulsion into the aqueous phase due to the weak shearing force. Also,
Immediately after the emulsion was produced, the viscosity was 1300 cp, but one year later, the viscosity had increased to 2400 cp.
It was unstable.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams showing the particle size distribution of emulsions obtained by the method of the present invention, respectively, and Figure 3 shows the case where an oil-in-water emulsion is added to the aqueous phase and the oil-in-aqueous solvent emulsion. FIG. 2 is a characteristic diagram showing the relationship between addition time and viscosity when an aqueous phase is added to a mold emulsion.

Claims (1)

[Claims] 1. In the production of an oil-in-water emulsion of an oil phase containing a cationic surfactant and a higher alcohol,
In the first step, the oil phase having a temperature higher than the transition temperature of the oil phase is dispersed in a water soluble solvent having a temperature higher than the transition temperature of the oil phase with a shear force of 5 to 20 m/sec or more to prepare an oil-in-water emulsion. A stable oil-in-water emulsion characterized by simultaneously performing emulsification and cooling by adding and dispersing the emulsion to an aqueous phase maintained at a temperature lower than the transition temperature of the oil phase and close to room temperature. manufacturing method.