JP6296471B1 - Method for producing polymerizable emulsion microemulsion and method for producing microresin emulsion - Google Patents

Abstract

[PROBLEMS] To provide a “critical point emulsification method” that utilizes the property that supercritical water dissolves oil droplets and finer and emulsifies monomers in water under milder conditions to obtain an emulsion having a uniform particle size. Establish and provide a method for producing a monomer microemulsion, and establish and provide a “critical point emulsion polymerization method” for converting the monomer critical point emulsion into resin particles. A method for producing a microemulsion of a polymerizable monomer, in which oil droplets containing one or more oil-soluble polymerizable monomers are finely emulsified in water, are oil droplet raw materials. One or more oil-soluble polymerizable monomers and water are allowed to flow into the mixer continuously or intermittently, respectively, and then the high temperature and high pressure are reduced to lower the relative dielectric constant of water to 40 or less. , Having a compatibilizing step of compatibilizing the oil-soluble polymerizable monomer and water, and then cooling to obtain an emulsion having a particle size of the polymerizable monomer of 20 nm to 400 nm by cooling. A method for producing a fine emulsion of a polymerizable monomer and a method for producing a fine resin emulsion. [Selection figure] None

Description

  The present invention relates to a method for producing a nanosized microemulsion of a polymerizable monomer (hereinafter also referred to as nanoemulsion), and emulsification of nanosized microresin particles from the nanoemulsion obtained by the production method. The present invention relates to a method for producing a fine resin emulsion (hereinafter, also referred to as nanoresin emulsion) to obtain a product. More specifically, manufacturing a nanoemulsion of a polymerizable monomer having a fine and uniform particle size that is useful as an intermediate by using a technique for bringing water into a high-temperature and high-pressure state when obtaining supercritical water The present invention relates to a method and a technique for providing a production method for obtaining a nanoresin emulsion having a uniform particle size by polymerizing a polymerizable monomer (hereinafter also referred to as a monomer) contained in the nanoemulsion. In the present invention, it is described as “a microemulsion of a polymerizable monomer (monomer)”. However, the form of finely emulsified oil droplets is not limited to oil droplets composed only of a monomer. And a non-polymerizable oil droplet component.

  As a method for obtaining an emulsion (emulsion) in which a substance insoluble in a solvent is mixed in a fine state in the solvent, mechanical stirring by a homomixer or the like is common. For example, when oil (oil) is mixed with water as a solvent, a mixture of water, an oil component, and an emulsifier is mechanically stirred to refine large oil droplets and obtain an emulsion. ing. However, in recent years, there has been a demand for an oil-in-water (O / W) emulsion in which oil droplets are dispersed in water in a finer and more uniform state. It is difficult to reduce the average particle size of these materials to nano size. In addition, when nano-sized by a mechanical emulsification method, a long process and enormous energy are required, and a method capable of industrially reducing the average particle size of the emulsion to nano-size is desired. ing.

  On the other hand, in recent years, a new technique using water characteristics has been studied for the following reasons. In the case of water, near the critical point (the critical temperature is 374 ° C. and the critical pressure is 22.1 Mpa (218 atm)), the density continuously changes greatly due to a slight pressure change. For example, the ability to “dissolve” as a solvent (solving power) correlates closely with the density of water, so even if the temperature is the same, the solvent power can be changed rapidly with only a slight change in pressure. Can do. In principle, it is possible to control various physical properties of water using only pressure and temperature as operating factors. In particular, supercritical water, which is intermediate between gas and liquid, can dissolve organic matter, so it is an industrially important organic solvent that has become a problem for its conventional use. It is also expected as a new alternative solvent. Above all, water itself is a non-toxic and inexpensive solvent that is abundant in nature, and in the future, it is expected that the direction toward environmentally conscious technologies will be further strengthened. A technique using “supercritical water” can be extremely useful. In this way, although it is a special environment of high temperature and high pressure, “supercritical water” that expresses completely different characteristics from solids, liquids, and gases while being “water” is sufficiently attractive and sustainable. It is highly expected as one of the basic technologies for realizing society.

  As a technology using “supercritical water”, for example, a method for producing an emulsion using a homogeneous solution of water and a water-insoluble substance obtained under high-temperature and high-pressure conditions near the vapor / liquid critical point of water is proposed. (Patent Document 1). This technique is an emulsification technique that does not require mechanical stirring by a general homomixer or the like, and is an unprecedented new emulsification technique that utilizes the characteristics of water under extreme conditions, and its use is expected.

Japanese Patent No. 5934455

  The present inventors have made use of the property that supercritical water disclosed in the above-mentioned technology dissolves oil droplets, and can make the monomer finer in water, and also provide a fine emulsion with uniform particle size. If it was obtained, it was recognized that it was extremely useful. As described above, if a fine and uniform emulsion having a particle diameter that cannot be obtained by a conventional mechanical emulsification method is obtained, its utilization is expected. For example, in the past, raw materials such as monomers and water were charged into a kettle, and after stirring and emulsifying for a long time, fine aqueous resin particles were produced by polymerization while stirring. If the monomer can be refined and emulsified in water with a uniform particle size, neither a kettle nor a stirrer is required, and the conventional stirring time for emulsification is basically unnecessary. In addition, if a continuous flow method enables a process of emulsifying raw materials such as monomers and a polymerization process to polymerize the resulting composite oil droplets in a series of flow operations, fine aqueous resin particles can be produced in a short time. It is thought that it becomes.

  However, what is actually considered in the above-mentioned Patent Document 1 is water and a straight-chain saturated hydrocarbon having a carbon chain length of 10 to 14 such as decane, dodecane, and tetradecane, and is relatively stable in heat resistance. This technique cannot be directly applied to a monomer which is a substance having a radical polymerizable unsaturated group. For example, in the technique of Patent Document 1, the processing temperature of saturated hydrocarbons such as water and decane is 440 ° C. where water and saturated hydrocarbons are mixed, and 445 where water, saturated hydrocarbons and surfactant are mixed. It is considered that decomposition or the like occurs in a substance such as a monomer having a very high temperature at 0 ° C. and having reactivity that is inferior in heat resistance compared to such dodecane. In other words, the above-described new emulsification technique (hereinafter also referred to as “critical point emulsification method”) has not been studied for applying to many kinds of oil-soluble organic compounds, and at least like a monomer. In order to apply to a substance that is inferior in heat resistance as compared to dodecane, there is a problem of realizing miniaturization and emulsification in water at a lower processing temperature. Furthermore, in order to enable industrial use, it is possible to maintain the characteristics of the nanoemulsion that is obtained by the critical point emulsification method and has a uniform particle size, and to be used and processed thereafter. Therefore, it is a problem to obtain a fine and uniform emulsion in a more stable state.

  Therefore, the object of the present invention is to utilize the property that supercritical water dissolves oil droplets, and finer and emulsify monomers in water under milder conditions to obtain an emulsion having a uniform particle size. It is to establish a “critical point emulsification method” that can be produced and to provide a method for producing a nanoemulsion of monomers. In addition, the object of the present invention is to establish a critical point emulsification method as described above, to realize a nanoemulsion of a monomer that is fine and has a uniform particle diameter, which has been difficult with the prior art, and further to subsequent polymerization. It is possible to provide a nanoemulsion of a monomer composed of oil droplets having a concentration that can be used in the process, thereby establishing a basic technology for producing fine water-based resin particles. A further object of the present invention is to produce a nano-emulsion of fine and uniform monomer particles obtained by the critical point emulsification method to increase industrial applicability. The object is to find a basic technique for maintaining the properties of the emulsion of fine resin particles.

  The above-described problems are achieved by the present invention described below. That is, the present invention is [1] a method for producing a microemulsion of a polymerizable monomer obtained by finely emulsifying water droplets containing one or more oil-soluble polymerizable monomers in water, The one or more oil-soluble polymerizable monomers, which are raw materials for the oil droplets, and water are allowed to flow continuously or intermittently into the mixer, and then the dielectric constant of water is increased to high temperature and pressure. The particle size of the polymerizable monomer is 20 nm to 400 nm by lowering the rate to 40 or less, and by compatibilizing the oil-soluble polymerizable monomer and water, followed by cooling. And a cooling step for obtaining an emulsion of the polymerizable monomer.

The following is mentioned as a preferable form of the manufacturing method of the nano emulsion of the polymerizable monomer of this invention.
[2] The SP value calculated from the following formula of the oil droplet raw material containing one or two or more of the polymerizable monomers alone or a mixture of two or more is 8. The manufacturing method of said [1] adjusted so that it may be 0-10.0.
δ (SP value) = (ΣEcoh / ΣV) 1/2
[3] The SP value calculated from the following formula of the oil droplet raw material containing one or more of the polymerizable monomers alone or a mixture of two or more is 8. The manufacturing method of said [1] adjusted so that it may be 5-9.5.
δ (SP value) = (ΣEcoh / ΣV) 1/2
[4] The method according to any one of [1] to [3], wherein the water is brought into a high-temperature and high-pressure state at 20 MPa or more and 200 ° C. or more in order to reduce the relative dielectric constant of the water to 40 or less.
[5] The method according to any one of [1] to [3], wherein the water is brought into a high-temperature and high-pressure state at 20 MPa or higher and 250 ° C. or higher in order to reduce the relative dielectric constant of the water to 25 or lower.
[6] In the above [1] to [5], 50% by mass or more of the one or more oil-soluble polymerizable monomers in the oil droplet raw material is a (meth) acrylic monomer. Either manufacturing method.
[7] The polymerizable monomer according to any one of [1] to [6], wherein the oil droplet raw material contains 0.1% by mass or more of a polymerizable monomer containing a hydrophilic functional group. A method for producing a microemulsion of a body. Examples of the polymerizable monomer containing a hydrophilic functional group include a carboxy group-containing polymerizable monomer such as methacrylic acid and a hydroxy group-containing polymerizable monomer.

[8] The method according to any one of [1] to [7], wherein in the cooling step for obtaining the emulsion, an emulsifier is added to suppress particle growth.

  As another embodiment, the present invention provides a method for producing an emulsion of fine resin particles, the method for producing a microemulsion of polymerizable monomers according to any one of [1] to [7]. From the resulting microemulsion of polymerizable monomer, an emulsion of fine resin particles is obtained by polymerizing the polymerizable monomer contained in the microemulsion (hereinafter referred to as “critical point emulsion polymerization method”). Also provided is a method for producing a fine resin emulsion.

  According to the present invention, there is no need for a kettle or a stirrer used in the prior art, and there is no need for a long stirring time required for the emulsification operation, and a monomer utilizing the property that supercritical water dissolves oil droplets. A method for producing a nanoemulsion of a monomer that is refined and emulsified in water is provided. In addition, according to the present invention, it is important to obtain a monomer nanoemulsion, which is an essential monomer for the nanoemulsion of the monomer of the present invention. It becomes possible to provide a nanoemulsion of monomer comprising oil droplets of a concentration that can be used in the step of establishing a selection method and then polymerizing the monomer. More specifically, according to the present invention, a monomer nanoemulsion can be rapidly obtained by treating an acrylic monomer, which is a raw material for paints and adhesives, under milder conditions. A new technology for obtaining a nanoresin emulsion is realized by polymerizing monomers in the obtained nanoemulsion. In addition, according to a preferred embodiment of the present invention, a nano-emulsion of a fine monomer having a uniform particle diameter obtained by a critical point emulsification method, and a basic technique for maintaining the properties of the polymer are provided. The

It is a schematic diagram of the apparatus for implementing the critical point emulsification method used by this invention. The particle size distribution of micro-sized particles of acrylic monomer obtained by conventional mechanical stirring and emulsification (mixer emulsification) and the particle size distribution of acrylic monomer emulsion obtained by carrying out the production method of the present invention It is a figure which shows a difference. It is a figure which shows the relationship between the processing temperature and the average particle diameter of the nano-emulsion of the 2-ethylhexyl acrylate (2EHA) monomer obtained in Example 1. It is a figure which shows the relationship between the processing temperature and the average particle diameter of the nano emulsion of the butyl acrylate (BA) monomer obtained in Example 2. It is a figure which shows the relationship between the processing temperature and the average particle diameter of the nanoemulsion of 2 types of monomers of 2EHA and BA obtained in Example 3. It is a figure which shows the relationship between the process temperature and the average particle diameter of the nanoemulsion of the 2 types monomer of cyclohexyl methacrylate (CHMA) and 2EHA obtained in Example 4. FIG. It is a figure which shows the relationship between the processing temperature and the average particle diameter of the nanoemulsion of the 2 types of monomer of CHMA and BA obtained in Example 5. FIG. It is a figure which shows the relationship between the processing temperature and the average particle diameter of the nanoemulsion of the 3 types monomer of CHMA, 2EHA, and methacrylic acid (mAAc) obtained in Example 6. It is a figure which shows the relationship between the processing temperature and the average particle diameter of the nano-emulsion of three types of monomers of BA, ethyl acrylate (EA), and styrene (ST) obtained in Example 7. It is a figure which shows collectively the SP value of each raw material monomer obtained by implementing the manufacturing method of this invention, and the relationship of the optimal processing temperature.

  Next, the present invention will be described in more detail with reference to preferred embodiments for carrying out the invention. First, a polymerizable monomer (monomer), an emulsifier, a polymerization initiator and the like that can be used in the production method of the present invention will be described. In this specification, the term “(meth) acryl” means both “acryl” and “methacryl”, and the term “(meth) acrylate” means both “acrylate” and “methacrylate”. Means. These are collectively called acrylic monomers.

  As the polymerizable monomer (monomer) used in the production method of the present invention, any monomer capable of radical polymerization may be used. (Meth) acrylic monomers and carbonyl group-containing monomers as listed below. In addition, any of aromatic vinyl monomers, nitrogen-containing polymerizable monomers, and the like can be used.

The (meth) acrylic monomers are not particularly limited, but any of those listed below can be used. Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate , Sec-butyl (meth) acrylate, t-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n -Alkyl having 1 to 18 carbon atoms such as octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylates;
Cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and pt-butylcyclohexyl (meth) acrylate;
Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2- (3-) hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and glycerol mono (meth) acrylate;
Hydroxypolyethylene oxide mono (meth) acrylate, hydroxypolypropyleneoxide mono (meth) acrylate, hydroxy (polyethyleneoxide-polypropyleneoxide) mono (meth) acrylate, hydroxy (polyethyleneoxide-propyleneoxide) mono (meth) acrylate, hydroxy (polyethyleneoxide -Polytetramethylene oxide) mono (meth) acrylate, hydroxy (polyethylene oxide-tetramethylene oxide) mono (meth) acrylate, hydroxy (polypropylene oxide-polytetramethylene oxide) mono (meth) acrylate, hydroxy (polypropylene oxide-polytetra Methylene oxide) mono (meth) acrylate, methoxypolyethylene oxide mono (meth) ) Acrylate, Lauroxy polyethylene oxide mono (meth) acrylate, stearoxy polyethylene oxide mono (meth) acrylate, allyloxy polyethylene oxide mono (meth) acrylate, nonyl phenoxy polyethylene oxide mono (meth) acrylate, nonyl phenoxy polypropylene oxide mono (meta) ) Acrylate, octoxy (polyethylene oxide-polypropylene oxide) mono (meth) acrylate, nonylphenoxy (polyethylene oxide-propylene oxide) mono (meth) acrylate and the like (meth) acrylates containing polyalkylene oxide groups;
hydroxycycloalkyl (meth) acrylates such as p-hydroxycyclohexyl (meth) acrylate;
Lactone-modified hydroxyalkyl (meth) acrylates;
Aminoalkyl (meth) acrylates such as 2-aminoethyl (meth) acrylate, 2-dimethylaminoethyl (meth) acrylate, 2-aminopropyl (meth) acrylate, 2-butylaminoethyl (meth) acrylate;
Amide group-containing (meth) acrylates such as (meth) acrylamide, N-methylolacrylamide, N-butoxymethyl (meth) acrylamide; ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, butylene glycol di (meth) Multifunctional (meth) acrylates such as acrylate, trimethylolpropane tri (meth) acrylate;
Metal-containing (meth) acrylates such as zinc di (meth) acrylate;
Silicon-containing (meth) such as γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylethyldiethoxysilane, γ- (meth) acryloxypropyltriethoxysilane Acrylates;
2- (2′-hydroxy-5 ′-(meth) acryloxyethylphenyl) -2H-benzotriazole, 1- (meth) acryloyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1 -(Meth) acryloyl-4-methoxy-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-amino-4-cyano-2,2,6,6-tetramethylpiperidine, etc. UV-resistant (meth) acrylates;
Dimethylaminoethyl (meth) acrylate methyl chloride salt, allyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylonitrile, phenyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, tetrahydrofurfuryl ( Other (meth) acrylic monomers such as (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate;
Based on aldehyde groups or keto groups such as acrolein, diacetone acrylamide, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, pivalin aldehyde, diacetone (meth) acrylate, acetonitrile acrylate, acetoacetoxyethyl (meth) acrylate A carbonyl group-containing monomer;
Aromatic vinyl monomers such as styrene (St), methylstyrene, chlorostyrene, methoxystyrene;
Conjugated diene monomers such as 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene;
Maleic anhydride, succinic anhydride, and phthalic anhydride are added to hydroxyalkyl (meth) acrylates such as (meth) acrylic acid, acrylic acid dimer, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. Carboxy group-containing polymerizable monomers such as reacted monomers;
Examples include, but are not limited to, ethylene and vinyl propionate. These can be used alone or in combination of two or more.

  As will be described later, in this specification, the monomer microemulsion obtained by the production method of the present invention has been described by taking acrylic monomers as an example, but the technology of the present invention is limited to this. is not. According to the present invention, a fine and uniform nano-emulsion of various monomers or plural kinds of monomers as mentioned above can be obtained quickly. In addition, the monomer microemulsion obtained by the production method of the present invention is only required to contain these monomers. For example, linear alkanes such as heptane, oligomers, etc. It is also possible to produce nanoemulsions composed of composite oil droplets, such as polyesters, polyethers, polycarbonates, polyolefins, urethanes, silicones, fluorine resins, etc.) dissolved in monomers. The ratio of linear alkanes and oligomers in the case of complex oil droplets is preferably less than 50% by mass, although it varies depending on the application.

Moreover, it does not specifically limit as an emulsifier (surfactant) used with the preferable form of the manufacturing method of this invention, For example, the following can be used. For example, anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, polymer emulsifiers and the like as listed below can be used.
More specifically, fatty acid salts such as sodium lauryl sulfate, higher alcohol sulfate esters, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether sulfates, polyoxyethylene polycyclic phenyl ether sulfates , Polyoxynonyl phenyl ether sulfonate, polyoxyethylene-polyoxypropylene glycol ether sulfate, anions such as so-called reactive emulsifiers having a sulfonic acid group or a sulfate ester group and a polymerizable unsaturated double bond in the molecule Surfactants;
Polyoxyethylene alkyl ether, polyoxyethylene nonylphenyl ether, sorbitan fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block copolymer, or the aforementioned skeleton and polymerizable unsaturated double bond in the molecule Nonionic surfactants such as reactive nonionic surfactants
Cationic surfactants such as alkylamine salts and quaternary ammonium salts; (modified) polyvinyl alcohol and the like. These emulsifiers may be used alone or in combination of several kinds.

  Moreover, the polymerization initiator that can be used in the method for producing a fine resin emulsion of the present invention is not particularly limited, and any conventionally known polymerization initiator can be used. For example, polymerization initiators generally used for radical polymerization as listed below can be appropriately used.

Specific examples thereof include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate;
Azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2) , 4-dimethylvaleronitrile), oil-soluble azo compounds such as 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile;
2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis {2-methyl-N- [2- ( 1-hydroxyethyl)] propionamide}, 2,2′-azobis {2-methyl-N- [2- (1-hydroxybutyl)] propionamide}, 2,2′-azobis [2- (5-methyl) -2-imidazolin-2-yl) propane] and salts thereof, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] and salts thereof, 2,2′-azobis [2- (3 , 4,5,6-tetrahydropyrimidin-2-yl) propane] and salts thereof, 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} and Its salts, 2,2'- Zobis (2-methylpropionamidine) and its salts, 2,2′-azobis (2-methylpropyneamidine) and its salts, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropion Water-soluble azo compounds such as amidine] and salts thereof;
And organic peroxides such as benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butyl peroxy-2-ethylhexanoate, and t-butyl peroxyisobutyrate.

  These polymerization initiators can be used alone or as a mixture of two or more. Further, when acceleration of the polymerization rate and low temperature polymerization at 70 ° C. or lower are desired, it is advantageous to use a reducing agent such as sodium bisulfite, ferrous sulfate, ascorbate in combination with the radical polymerization catalyst. .

  As a result of intensive studies to achieve the object of the present invention, the present inventors have utilized the characteristic that supercritical water dissolves oil droplets, which is completely different from the conventional principle of emulsification by mechanical stirring. The present inventors have found a novel emulsification method (critical point emulsification method) in which a monomer is refined and emulsified in water. In other words, in the present invention, when the supercritical water, which is in the limit state of water, is obtained, further investigation is made by using a method for bringing the water into a high temperature and high pressure state, so that the water is inherently soluble in water. First, by dissolving a monomer with poor heat resistance in water and then rapidly cooling it, the monomer is stabilized and refined and emulsified in the form of oil droplets with a uniform particle size in water, resulting in a fine nano resin. A nanoemulsion of monomers necessary to obtain an emulsion was successfully prepared.

  In the conventional emulsification method by mechanical stirring, water and oil are stirred and mixed and emulsified by mechanical stirring force, and even when sufficiently stirred for several minutes to several tens of minutes, oil droplets of about 500 nm to 5000 nm can be produced. Only. For this reason, in order to make it finer than this, it is necessary to perform mechanical stirring for a longer time. Further, even if the micronization is continued for a longer time, the particle size distribution of the fine particles becomes broad and the particles are not fine and uniform. On the other hand, according to the technique of Patent Document 1, although the use example is a linear saturated hydrocarbon having a carbon chain length of 10 to 14, by using supercritical water, It is said that fine oil droplets of about 40 nm to 500 nm can be produced from mixing to preparation of the emulsion in just 10 seconds to several tens of seconds without any mechanical stirring.

  Although water exists in the state of gas, liquid, and solid, when the temperature and pressure are increased, the boundary line between liquid and gas disappears at high temperature and high pressure (critical point) of 374 ° C. and 22 MPa. It becomes critical water. Although supercritical water is liquid, it has both gas characteristics, density is reduced, and specific induction rate is reduced. Since the relative permittivity of supercritical water decreases, a dissolving power similar to that of a solvent is generated, and supercritical water is in a state where oil is dissolved. The relative dielectric constant of water is about 79 at room temperature, and the relative dielectric constant of monomers as oil components is about 40 or less. Therefore, even when water and monomers are mixed at room temperature and normal pressure, it is uniform. It is impossible to make a phase, and the two phases are separated. On the other hand, as the temperature rises, the relative permittivity gradually decreases. For example, in a supercritical state at a temperature of 400 ° C. and a pressure of 25 MPa, the relative permittivity of water is reduced to 6 and is about the same as the oil component. Therefore, what was separated into an aqueous phase and an organic (oil) phase at room temperature and normal pressure becomes a homogeneous phase in which water and oil are compatible in the supercritical state described above. This means that compatibility with the monomers that are oil components can be improved by setting water to a high temperature and high pressure to reduce the relative dielectric constant even if it is not in a supercritical state. .

  Based on the above recognition, the present inventors diligently studied. As a result, the monomers and water were allowed to flow continuously or intermittently into the mixer, and the relative dielectric constant of water was 40 or less (for example, It was found that the monomer and water, which never became a uniform phase at room temperature and normal pressure, can be made compatible with each other. Specifically, for example, the water has a relative dielectric constant of 40 by setting water to a state of 20 MPa or higher, preferably 22 MPa or higher and 200 ° C. or higher (making water into a subcritical to supercritical state). By utilizing this fact, the present invention aims to achieve a fine emulsion in the form of oil droplets with a uniform particle size in water at a lower emulsification treatment temperature without using mechanical means. It has been found that it is possible to emulsify and emulsify.

  The present inventors use an acrylic monomer widely used in paints and adhesives as a monomer, and an apparatus for carrying out a critical point emulsification method schematically showing a schematic flow diagram in FIG. Various studies were conducted using As shown in FIG. 1, this apparatus includes a mixing section composed of an inflow path for allowing two liquids, water and monomer, to flow into each of them, a mixer in which the liquid that has flowed in, and a mixing section. Subsequently, the subcritical process part for lowering the relative dielectric constant of water to 40 or less by bringing the water into a subcritical to supercritical state by placing it at a high temperature and high pressure, and the liquid resulting from the process Is cooled to raise the relative dielectric constant of water to cause phase separation of water and the monomer to form an emulsion. This apparatus is configured so that an emulsifier liquid can be added so that the growth of particles can be suppressed by adding the emulsifier in the cooling step of obtaining an emulsion. In the above description, the subcritical process section is called for convenience, but it is a process for reducing the relative dielectric constant of water to 40 or less, and is a process for bringing water into a subcritical to supercritical state.

  By using the apparatus configured as described above, when the relative permittivity of water and the monomer introduced into each of the subcritical process parts is reduced to 40 or less, a homogeneous phase in which the monomer and water are instantaneously mixed is obtained. By forming and rapidly cooling this in the next cooling section, nanoparticles having a uniform particle diameter are rapidly formed, and a nanoemulsion of the monomer targeted by the present invention is obtained. That is, according to the apparatus having the above-described configuration, water having a specific property having a relative dielectric constant of 40 or less that appears in an extreme environment (supercritical or subcritical state) of high temperature and high pressure can be obtained. In the present invention, by using water exhibiting this unique property, it can be used industrially under milder conditions, and can be refined and emulsified in a state of uniform particle size. A method for obtaining a nanoemulsion of the monomer was investigated. In the present invention, each experiment was performed using a supercritical emulsifier “SFW-E40S” designed and manufactured by AKICO.

  When the microscopic particles of the acrylic monomer are obtained by conventional mechanical stirring emulsification (mixer emulsification), and when the acrylic monomer emulsion (oil droplets) is obtained by the critical point emulsification method of the present invention, The difference in particle size distribution is shown in FIG. Specifically, a 1: 1 mixture solution of cyclohexyl methacrylate (CHMA) and 2-ethylhexyl acrylate (2EHA) was used as the raw material monomer. The amount of emulsifier used was 25% with respect to the raw material monomer. The emulsification conditions in the above-described apparatus for carrying out the critical point emulsification method were a temperature of 350 ° C. and a pressure of 25 MPa, and the emulsification time was 5 seconds. Moreover, the emulsification conditions of the mechanical stirring emulsification which is a conventional method were 5000 rpm x 30 minutes.

  As shown in FIG. 2, in the time of about 30 minutes in the conventional method, the obtained emulsion has a broad peak at 4000 to 10000 nm and a sharp peak at 500 to 600 nm, and has a large particle size. It turned out that it becomes an emulsion of the monomer of various particle sizes containing a thing with wide particle size distribution. On the other hand, the critical point emulsification method performed in the present invention did not include any particles having a large particle size, and it was confirmed that an emulsion of a monomer having a sharp peak near 100 nm was obtained.

In the course of further study, the present inventors have obtained knowledge that the processing temperature at which a finer fine nanoemulsion can be obtained differs depending on the type of monomer or even in the same monomer. Therefore, in order to clarify this point, a test was conducted using various monomers with the above-described apparatus, and this point was examined. As a result, a monomer containing one or two or more and adjusted so that the SP value calculated from the following formula is 8.0 to 10.0, more preferably 8.5 to 9.5 is used. It was found that a finer nanoemulsion can be obtained under mild conditions at low temperatures.
δ (SP value) = (ΣEcoh / ΣV) 1/2

  Here, the SP value of the organic compound can be calculated from the molecular structure by the Fedors' estimation method. That is, it can be defined as the above formula from the total ΣEco of the cohesive energy density of each functional group of the substance and the total ΣV of the molar molecular volume. The unit of cohesive energy is often J / mol, but in this specification, cal / mol is used by dividing by a coefficient of 4.19.

  As a result, when producing nanoemulsions using the “critical point emulsification method”, the selection of monomer raw materials can be carried out by adjusting the SP value to be within the above-mentioned range, so that milder conditions at lower temperatures can be obtained. It became clear that it became possible to obtain a nanoemulsion.

  The present inventors further added a polymerization initiator to the monomer nanoemulsion obtained by the critical point emulsification method defined in the present invention, and the resin emulsion obtained by polymerization treatment is subjected to conventional mechanical stirring. It has been found that the average particle size is smaller and the particle size is uniform than the resin emulsion obtained by polymerizing the monomer emulsion obtained by the above method.

  Hereinafter, the present invention will be specifically described with reference to Examples that have led to the above conclusion. In addition, this invention is not limited to the following Example.

<Example 1: Preparation of monomer nanoemulsion>
The following liquid raw materials A to C were prepared.
Liquid A (water): Ion-exchanged water Liquid B (oil droplet raw material): 2-ethylhexyl acrylate (2EHA, SP value = 8.62)
C liquid (emulsifier): 5% diluted aqueous solution of Neugen XL-100 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyoxyalkylene branched decyl ether, HLB 14.7)

  Using the supercritical water supply apparatus “SFW-E40S” manufactured by AKICO, which can supply subcritical water to supercritical water, a test apparatus having a configuration as shown in FIG. 1 was prepared. This apparatus obtains an oil droplet raw material mixing section composed of two raw material liquid inflow passages and a mixer in which the inflowed liquid merges, and subcritical to supercritical water disposed following the mixing section. A subcritical process section for high temperature and high pressure, and a cooling section for obtaining an emulsion (oil droplets) having a nano-sized particle size by cooling the liquid discharged from the process.

  From the inflow path of the apparatus, the liquid A water and the liquid B oil droplet raw material flow in and flow into the mixer while being merged. The resulting liquid mixture of liquid A and liquid B is In the subcritical process section in the apparatus, a high temperature and high pressure is applied to lower the relative dielectric constant of water to 40 or less to dissolve the mixed monomer of the B liquid in the water of the A liquid as the solvent (specified in the present invention). Compatibility step). In the illustrated apparatus, as shown in FIG. 1, in order to suppress the growth of particles (oil droplets) formed in the cooling process, the particle size is smaller, and the emulsion is stabilized. The liquid emulsifier was added. The operating conditions of the subcritical process section of the above apparatus were a water temperature of 350 to 440 ° C. and a pressure of 25 MPa.

  The above-mentioned A liquid is allowed to flow in at a rate of 7.8 ml / min, and B liquid is 2.2 ml / min. In the subcritical process section, after a compatibilizing treatment at a water temperature of 350 to 440 ° C. and a pressure of 25 MPa, At the initial stage when oil droplets started to form, the C solution emulsifier solution was added at a rate of 10 ml / min. As a result, oil droplets having a minimum average particle diameter of 191 nm were obtained under the condition of a water temperature of 370 ° C. The particle size distribution shows a sharp normal distribution, and it was confirmed that a fine and uniform emulsion was obtained. The average particle size and particle size distribution of the obtained oil droplets were measured by a dynamic light scattering method. Measurement of the average particle diameter (diameter) by the dynamic light scattering method was performed at 25 ° C. using FPAR-1000 (trade name, manufactured by Otsuka Electronics Co., Ltd.) after the emulsion was diluted with water to an appropriate concentration. .

<Examples 2 to 7: Preparation of monomer nanoemulsion>
Examples 2 to 7 were also performed in accordance with Example 1 described above. In Examples 2 to 7, the water temperature was in the range of 300 to 440 ° C. Table 1 summarizes the types and compositions of the raw material monomers used in Examples 1 to 7 and the SP values of the raw material monomers. Table 1 collectively shows the minimum average particle size when these raw material monomers are used and the temperature at which the emulsion having this minimum average particle size was obtained.

<Particle size and treatment temperature of monomer nanoemulsion obtained in Examples 1-7>
3a to 3g, for each raw material monomer used in Examples 1 to 7 described above, a nanoemulsion comprising the treatment temperature (temperature of the compatibility step) and the respective monomers obtained at each temperature The relationship of the average particle diameter of was shown collectively. Moreover, what plotted SP value of each raw material monomer used in Examples 1-7 and the optimal process temperature in that case in FIG. 4 was shown. As a result, when using a raw material monomer adjusted to have an SP value of 8.0 to 10.0, more preferably 8.5 to 9.5, fine particles can be obtained under mild conditions at a lower temperature. It was found that a uniform nanoemulsion of monomer can be obtained.

<Examples 8 and 9: polymerization of critical point emulsion>
By the method according to Examples 1-7, the liquid nanoemulsion (emulsion) which contains two types of monomers was produced. Under the present circumstances, as said C liquid (emulsifier), Neugen TDS-80 (brand name, Dai-ichi Kogyo Seiyaku Co., Ltd. product, polyoxyethylene tridecyl ether, HLB13.3) 1% dilution aqueous solution (Example 8) or 0 A 5% diluted aqueous solution (Example 9) was used. The inflow rate of each liquid was 9.8 ml / min for liquid A, 0.2 ml / min for liquid B, 10 ml / min for liquid C, and critical point emulsification was performed at a water temperature of 350 ° C. and a pressure of 25 MPa. 250 g of the emulsion thus obtained was added as a polymerization initiator by adding 1 g of a 5% diluted aqueous solution of perbutyl H and 1 g of a 5% diluted aqueous solution of erythorbic acid, followed by polymerization at 80 ° C. for 2 hours, A resin emulsion was obtained.

  Table 2 collectively shows the average particle diameters of the nanoresin emulsions obtained by polymerization treatment obtained in Examples 8 and 9 above.

<Comparative Examples 1 and 2: Polymerization of emulsion prepared by conventional mechanical stirring>
As a comparison between Examples 8 and 9, a monomer emulsion (emulsion) prepared by conventional mechanical stirring was polymerized. In the comparative example, the monomer and the emulsifier were added to ion-exchanged water so that the monomer concentration and the emulsifier concentration were the same as in the methods of Examples 8 and 9, and the mixture was stirred with a mixer at 5000 rpm × 5 minutes. Thus, an emulsion was prepared. As a polymerization initiator, 250 g of this emulsion was added with 1 g of a 5% diluted aqueous solution of perbutyl H and 1 g of a 5% diluted aqueous solution of erythorbic acid, followed by polymerization at 80 ° C. for 2 hours. 2 resin emulsion was obtained.

  Table 3 shows the average particle diameters of the resin emulsions obtained in Comparative Examples 1 and 2 above. As a result, from the results of Examples 8 and 9 shown in Table 2 and Comparative Examples 1 and 2 shown in Table 3, a polymerization initiator was added to the nanoemulsion of the monomer obtained by the critical point emulsification method, and polymerization was performed. It was found that the average particle size of the resin emulsion obtained by treatment was smaller than that of the resin emulsion obtained by polymerizing the monomer emulsion obtained by the conventional method.

  As described above, according to the present invention, by using the monomer defined in the present invention or a composite raw material containing the monomer as the oil droplet raw material, when emulsification is performed using the critical point emulsification method, the milder It becomes possible to stably emulsify under such conditions, and a nanoemulsion composed of oil droplets containing monomers having a finer and uniform particle size distribution can be obtained without decomposing monomers having poor heat resistance. The production method of the present invention is the first case of obtaining an emulsion of acrylic monomers under mild conditions at a temperature lower than 374 ° C. which is the critical point of water. That is, in the technique of Patent Document 1 mentioned above, as described above, dodecane, which is a saturated hydrocarbon, is used as oil droplets and is treated as supercritical water at 440 ° C. or higher, and this point is completely different. .

  The ability to lower the treatment temperature in the water-monomer compatibility step is extremely important in order to obtain a nanoemulsion of monomers inferior in heat resistance, which is the object of the present invention. That is, the nano-emulsion containing oil-soluble polymerizable monomers such as acrylic monomers, which are the object of the present invention, as oil droplet components is then polymerized by a series of operations to form fine and uniform polymer particles. If the monomers are thermally decomposed in the step of obtaining the nanoemulsion, the polymer design cannot be performed. The time for the compatibilization treatment of the oil droplet raw material monomer and water, which is carried out by the production method of the present invention, is several seconds to several tens of seconds, which is an extremely short time. However, even in that case, it is expected that monomer decomposition occurs, and it is desired to obtain a nanoemulsion under mild conditions as low as possible, whereas according to the production method of the present invention, under milder conditions, A fine and uniform nanoemulsion (oil droplets) containing monomers that could not be realized by conventional manufacturing methods can be obtained and maintained in a stable state. Emulsions (oil droplets) can be easily polymerized. For this reason, if the critical point emulsification method of the present invention is used, it is expected to obtain polymer particles having a finer and more uniform particle size distribution that could not be realized by the conventional technology, and the development of the use thereof is expected. Be expected.

Claims (5)

A method for producing a microemulsion of a polymerizable monomer in which oil droplets containing one or more oil-soluble polymerizable monomers are finely emulsified in water,
The one or more oil-soluble polymerizable monomers that are the raw material of the oil droplets and water are allowed to flow into the mixer continuously or intermittently, respectively, and then a high temperature of 20 MPa or higher and 200 ° C. or higher. A high-pressure reduction of the relative dielectric constant of water to 40 or less, a compatibility step of compatibilizing the oil-soluble polymerizable monomer and water, and cooling thereafter, the polymerizable monomer particle diameter of have a cooling step to obtain an emulsion of 20Nm～400nm,
Method for producing the emulsion in the obtained cooling step, the micro emulsion of the polymerizable monomer, wherein isosamples adding an emulsifier to inhibit the growth of particles. The method for producing a microemulsion of a polymerizable monomer according to claim 1, wherein the water is brought to a high temperature and high pressure state of 20 MPa or more and 250 ° C. or more in order to lower the relative dielectric constant of water to 25 or less. The polymerizable monomer according to claim 1 or 2 , wherein 50% by mass or more of the one or more oil-soluble polymerizable monomers in the oil droplet raw material is a (meth) acrylic monomer. A method for producing a microemulsion of a body. The microemulsion of the polymerizable monomer according to any one of claims 1 to 3 , wherein the oil droplet raw material contains 0.1% by mass or more of a polymerizable monomer containing a hydrophilic functional group. Production method. A method for producing a fine resin emulsion, wherein an emulsion of fine resin particles is obtained, the polymerizable monomer obtained by the method for producing a fine emulsion of a polymerizable monomer according to any one of claims 1 to 4. A method for producing a fine resin emulsion, wherein an emulsion of fine resin particles is obtained by polymerizing a polymerizable monomer contained in the fine emulsion from a fine emulsion of a monomer.

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