JP2849146B2 - Plate-shaped polymer fine particles and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to plate-like polymer fine particles and a method for producing the same, and more particularly, to cosmetics, paints, base materials for ion-exchange resins, fillers for chromatography, and the like. The present invention relates to uniform plate-like polymer fine particles that can be used and a method for producing the same.

[Conventional technology]

As a method for producing plate-shaped polymer fine particles, there is a method of mechanically pulverizing and flattening a polymer film and a spherical polymer powder. For example, a method in which a polymer film is formed and then cooled and pulverized under liquid nitrogen (JP-A-57-78466)
JP-A-62-164731 discloses a method of flattening a spherical polymer powder by mixing and stirring in a solvent inert to the polymer in the presence of (glass) beads. In addition to these methods, there is also a method of solidifying fine droplets of a polymer solution on a flat plate (JP-A-63-117040).

[Problems to be solved by the invention]

The conventional production methods as described above have problems that plate-like polymer particles cannot be uniformly and reliably obtained, the operation is complicated and difficult, and the selection range of polymer species is narrow. Furthermore, it was not easy to obtain finer plate-like polymer particles (having an average thickness of 1 μm or less) by the conventional production method.

Therefore, an object of the present invention is to provide uniform plate-like polymer fine particles and a method for producing the same, that is, a simple and easy operation, and moreover, to obtain uniform and reliable plate-like polymer fine particles. By selecting the conditions, the thickness and size (long piece) of the plate-like polymer fine particles can be easily controlled, and the finer plate-like polymer fine particles (for example, the average thickness of about 0.1 μm is about 10 times the thickness of the long piece) can be obtained. It is easy to manufacture, and furthermore, it is possible to form into a plate even a cross-linked polymer that is stable against heat and solvents, and to produce plate-shaped polymer fine particles with a very wide choice of polymer types. Is to provide a law.

[Means for solving the problem]

The object of the present invention is to provide plate-like polymer fine particles of the following (1), and to provide the following method (2).
The present invention has been attained by providing a method for producing plate-like polymer fine particles.

(1) After cooling the fine particle polymer dispersion below the freezing temperature of the dispersion medium and then raising the temperature to below the glass transition temperature of the polymer, the average thickness is 0.01 to 100 μm, and the long piece is 10 times the thickness. The above-mentioned plate-like polymer fine particles.

(2) After cooling the fine particle polymer dispersion having an average particle size of 500 nm or less to a temperature lower than the freezing temperature of the dispersion medium, the temperature is raised to a temperature lower than the glass transition temperature of the polymer, and the average thickness is 0.01 to 10
A method for producing plate-shaped polymer fine particles, comprising obtaining plate-shaped polymer fine particles having a length of 0 μm and a long piece having a thickness of 10 times or more.

Hereinafter, the plate-shaped polymer fine particles of the present invention will be described in detail based on the production method of the present invention.

The type of the polymer used as a raw material in the present invention is not particularly limited, and a general-purpose polymer,
For example, styrene-based, acrylic acid-based, methacrylic acid-based and copolymers thereof, and those crosslinked with divinylbenzene can be used, and a fine particle polymer dispersion can be easily formed by a generally known emulsion polymerization method. Those obtained are preferred.

As the polymer, a fine particle polymer having an average particle diameter of 500 nm or less, preferably 30 to 250 nm is used. When a polymer having an average particle diameter of more than 500 nm is used, fusion between the fine particles is weak, and plate-like molding becomes difficult.

The particle size of the polymer can be measured by a submicron particle analyzer (submicron particle analyzer COULTER N4, manufactured by Coulter Electronic Company).

Further, as the dispersion medium of the polymer dispersion, any one can be used as long as it can be dispersed without dissolving the polymer, for example, water and a solvent compatible with water are used, and For convenience, water, lower alcohols and mixtures thereof are preferred.

It is preferable to add a dispersant to the dispersion medium. As such a dispersant, a water-soluble polymer, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a ionic surfactant and a mixture thereof are used. In particular, an anionic surfactant and a cationic surfactant are preferred.

Therefore, in order to carry out the method for producing plate-shaped polymer fine particles of the present invention, first, a dispersion liquid in which the fine particle polymer is dispersed in the dispersion medium is cooled to a temperature lower than the freezing temperature of the dispersion medium to freeze the dispersion medium. Let it.

At this time, by appropriately changing the manufacturing conditions at the time of freezing, namely, the cooling freezing temperature, the fine particle polymer concentration of the polymer dispersion, the particle size of the fine particle polymer, the type of the dispersant, the shape of the freezing container, etc. The size and thickness of the polymer fine particles can be easily controlled.

For example, by rapidly cooling the polymer dispersion, finer plate-shaped polymer fine particles can be obtained. That is,
By selecting conditions such as lowering the cooling / freezing temperature or setting the shape of the freezing container so as to increase the contact area between the polymer dispersion and the cooling medium, finer plate-like polymer fine particles can be obtained.

Also, by reducing the polymer concentration of the polymer dispersion, finer plate-shaped polymer fine particles can be obtained.

The conditions for the freezing are not limited as long as the polymer dispersion is completely frozen.
It is preferable to hold for 15 minutes or more.

In addition, the preparation of the polymer dispersion may be performed, for example, by mixing and stirring the fine particle polymer, the dispersion medium and the dispersant, and using a polymer that can easily obtain a fine particle polymer dispersion by an emulsion polymerization method. Is
The emulsion polymerization solution obtained by emulsion polymerization can be used as it is as a polymer dispersion.

The polymer concentration of the polymer dispersion varies depending on the type of the polymer and the size and thickness of the target plate-like polymer fine particles, but is usually preferably 1 to 20% by weight.

Next, the polymer dispersion frozen as described above is heated to a temperature lower than the glass transition temperature of the polymer, preferably about 5 ° C. lower than the glass transition temperature, and is thawed. Examples of the method of raising the temperature include a method in which a frozen polymer dispersion is dissolved in room temperature or heated water and further heated as necessary, a method in which the dispersion is freeze-dried and heated, and a method in which the dispersion is left at room temperature. And a method of heating the dispersion liquid gradually, such as a method of leaving the frozen polymer dispersion liquid at room temperature.

If the temperature exceeds the glass transition temperature when the temperature is raised, the polymer surface has viscoelasticity, and the shape is not maintained due to fusion between the polymers. Therefore, the polymer used as a raw material has a glass transition temperature of preferably room temperature or higher, more preferably 50 ° C. or higher, and especially those having a glass transition temperature of 50 to 90 ° C. in consideration of the temperature raising conditions during production. preferable.

Thus, the plate-like polymer fine particles of the present invention are formed.

The formed plate-like polymer fine particles can be isolated from the dispersion medium by a known method such as a suction filtration method and a centrifugal separation method.

The plate-like polymer fine particles of the present invention obtained in this way have an average thickness of 0.01 to 100 μm, and the long pieces have a thickness of 10 times or more, and have a uniform fine plate-like shape. Useful for coloring and the like.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 1000 m equipped with a nitrogen gas inlet tube, a reflux condenser, a thermometer and a stirrer (a stirrer is a half-moon type having a string length of 6 cm).
400 ml of a 3% aqueous solution of sodium dodecyl sulfate was added to a 5-neck separable flask, and 1.0 g of ammonium persulfate, a polymerization initiator, was added to the flask. While keeping the mixture at 100 rpm, 100 g of styrene monomer was added dropwise over 1 hour. Then, polymerization is performed for 3 hours, and then the temperature in the system is reduced.
When the temperature was raised to 75 ° C., stirring was stopped, and the mixture was aged for about 1 hour, the residual monomer odor almost disappeared. Then, the mixture was gradually cooled to room temperature to obtain a polystyrene emulsion (particle size: 72.3 nm).
Then, 5 ml of this 20% polystyrene emulsion was added
The samples were placed in cm sample bottles and refrigerated in liquid nitrogen for 15 minutes. This was left to melt at room temperature. As a result, plate-like polystyrene having an average thickness of 5 μm and a long piece about 10 times the thickness was obtained.

Example 2 The 20% polystyrene emulsion obtained in Example 1 was diluted to 5% and frozen and melted in the same manner as in Example 1. As a result, the average thickness was 1 μm,
A double-fold plate-like polystyrene was obtained.

Example 3 1000 m equipped with a nitrogen gas inlet tube, a reflux condenser, a thermometer and a stirrer (the stirrer is a half-moon type having a string length of 6 cm).
400 ml of a 3% aqueous solution of lauryltrimethylammonium chloride was added to a 5-neck separable flask, and 0.7 g of 2,2 azobis (2-amidinopropane) dihydrochloride as a polymerization initiator was added thereto. 100 g of a 1: 1 mixture of ethyl methacrylate and n-butyl methacrylate was added dropwise over 1 hour while blowing the gas and keeping the oil bath at 65 ° C. and stirring at 100 rpm. Then, the polymerization was carried out for 3 hours, and then the temperature in the system was raised to 75 ° C., stirring was stopped, and the mixture was aged for about 1 hour. Then, the mixture was gradually cooled to room temperature, and a polyethyl methacrylate / n-butyl copolymer emulsion (having a particle size of 80.8 n
m). Next, the 20% polyethyl methacrylate /
5 ml of the n-butyl copolymer emulsion was placed in a sample bottle having a diameter of 2 cm, and cooled and frozen in liquid nitrogen for 15 minutes. Then, it was left to melt at room temperature, immersed in an aqueous solution at 50 ° C., and heat-treated and sintered for 1 hour (the mechanical strength of the platy polymer increased). Then it is filtered to obtain an average thickness of 3
A plate-shaped polyethyl methacrylate / n-butyl copolymer having a length of about 30 μm and a length of about 30 times the thickness was obtained as a powder.

Example 4 20% polyethyl methacrylate / n- obtained in Example 3
5 ml of a butyl copolymer emulsion (having a particle size of 80.8 nm) was placed in a sample bottle having a diameter of 2 cm, and cooled, frozen and thawed at -23 ° C. As a result, a plate-like poly (ethyl methacrylate / n-butyl) copolymer having an average thickness of 20 μm and a long piece about 15 times the thickness was obtained.

Example 5 20% polyethyl methacrylate / n- obtained in Example 3
5 ml of a butyl copolymer emulsion (having a particle size of 80.8 nm) was placed in a sample bottle having a diameter of 4 cm, cooled in liquid nitrogen for 15 minutes, frozen and thawed. As a result, the average thickness was 2 μm,
Plate-shaped poly (ethyl methacrylate) whose long piece is about 30 times the thickness
/ n-butyl copolymer was obtained.

Example 6 1000 m provided with a nitrogen gas inlet tube, a reflux condenser, a thermometer and a stirring device (the stirring piece is a half-moon type having a string length of 6 cm).
400 ml of a 4% aqueous solution of sodium dodecyl sulfate was added to a 5-neck separable flask, and 1.5 g of potassium persulfate as a polymerization initiator was added thereto. The nitrogen bath was blown into the system at 65 ° C. while blowing nitrogen gas into the system. , And 100 g of styrene monomer was added dropwise over 1 hour while stirring at 300 rpm.
Then, polymerization was performed for 3 hours, and then the temperature in the system was increased to 75 ° C.
When the temperature was raised to a low level and the stirring was stopped, the mixture was aged for about 1 hour. Then, the mixture was gradually cooled to room temperature to obtain a polystyrene emulsion (particle size: 29.0 nm). Then, 5 ml of this 20% polystyrene emulsion was placed in a sample bottle having a diameter of 2 cm, and cooled and frozen in liquid nitrogen for 15 minutes. This was left to melt at room temperature. As a result, plate-like polystyrene having an average thickness of 0.5 μm and a long piece of about 50 times the thickness was obtained.

〔The invention's effect〕

The plate-like polymer fine particles of the present invention have an average thickness of 0.01 to 10
Since it has a thickness of 0 μm and a length of 10 or more times the thickness, and has a fine plate shape and a uniform shape, it can be used as a cosmetic, a paint, a base material of an ion exchange resin, a filler for chromatography, and the like.

In addition, the method for producing the plate-like polymer fine particles of the present invention is simple and easy to operate, and can uniformly and reliably obtain the plate-like polymer fine particles of the present invention. Thickness and size (long piece)
Can be easily controlled and finer (for example, an average thickness of about 0.
It is also possible to easily produce plate-like polymer fine particles (1 μm, the length of which is about 10 times the thickness), and it is also possible to mold cross-linked polymers that are stable against heat and solvents on the plate. Further, there is an effect that the selection range of the polymer type is very wide.

Claims (2)

(57) [Claims] An average thickness of a fine particle polymer dispersion obtained by cooling the dispersion to a temperature lower than the glass transition temperature of the polymer after cooling the dispersion to a temperature lower than the freezing temperature of the dispersion medium.
Plate-shaped polymer fine particles whose long pieces are 10 times or more the thickness. 2. A fine particle polymer dispersion having an average particle size of 500 nm or less is cooled to a temperature lower than the freezing temperature of the dispersion medium, and then heated to a temperature lower than the glass transition temperature of the polymer.
A method for producing plate-like polymer fine particles, wherein plate-like polymer fine particles having a length of 100 μm or more and a long piece having a thickness of 10 times or more are obtained.