JP3519418B2 - Sintered fine particles of uniform particle size and method for producing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fired fine particles having a uniform particle size distribution and a monodispersed particle size distribution, and a method for producing the same. 2. Description of the Related Art
Fired fine particles are excellent in abrasion resistance, heat resistance, lubricity, and conductivity, so fired fine particles are used as they are or mixed with resin, etc., in the fields of automobile parts, electric parts, industrial machinery, office equipment, etc. , Lubricants, pigments, conductors, etc. In addition, natural graphite,
Natural products such as coal, coke and various pitches, or synthetic products such as acrylonitrile resin and phenol / formaldehyde resin are used. However, when a natural product is used as a raw material of the fired fine particles, since the shape is a block or a lump, pulverization is required before or after firing. Since the fired fine particles obtained by this pulverization process have a sharp fracture surface, they are not suitable for use as a lubricant. In addition, when the fired fine particles are mixed with a resin, the dispersibility and fluidity of the resin are impaired. On the other hand, when a synthetic material is used as a raw material of the fired fine particles, spherical fine particles are obtained by preparing polymer fine particles and firing the fine particles without the need for pulverization as in the case of the natural products. However, when the fired fine particles are used as a lubricant or conductive particles, the performance is improved as the particle diameter of the fired fine particles is more uniform. However, it is difficult to control the standard deviation of the particle diameter of the polymer fine particles, which are the raw materials of the fired fine particles, to 20% or less of the average particle diameter by the ordinary synthesis method. At present, no fine particles have been obtained. Means for Solving the Problems In view of such circumstances, the present inventors have made intensive studies and as a result, it has been found that fired fine particles having a uniform particle diameter are extremely suitably used for lubricants, conductive fine particles and the like. They have found that they can do this and have completed the present invention. That is,
The present invention provides an organic polymer fine particle synthesized using a seed polymerization method, which is fired in a non-oxidizing atmosphere , and has an average particle diameter of 2%.
~ 30μm, standard deviation of particle size distribution is 20 of its average particle size
There is provided a method for producing% or less is uniformly particles径焼formed microparticles. A method for obtaining fired fine particles having a uniform particle size according to the present invention.
Has a particle size of
Use standard deviation of 20% or less of the average particle size
This is a method of firing such polymer fine particles. As a method for obtaining polymer fine particles having a standard deviation of the particle diameter of not more than 20% of the average particle diameter used in the present invention, there is a seed polymerization method. With seed polymerization method,
In general, a method in which a vinyl monomer is absorbed into monodisperse seed particles such as a styrene polymer and polymerization is performed to uniformly increase the particle size. A two-stage swelling seed polymerization method typified by Japanese Patent Publication No. 57-24369 is an improved polymerization method of the seed polymerization. In this method, a hydrophobic organic compound called a swelling aid is previously absorbed on the seed particles,
After increasing the swelling ability of the seed particles, the seed particles are swollen with a vinyl monomer to carry out polymerization. On the other hand, the present inventors have disclosed a diffusion-promoted seed polymerization method typified by JP-A-1-81810 as a seed polymerization method. This method utilizes the fact that a specific nonionic organic compound is added to an oil-soluble ethylenically unsaturated monomer, and the microemulsion liquid finely dispersed in water is rapidly absorbed by the seed polymer particles at room temperature. Then, compared with the conventional seed polymerization, the vinyl monomer is absorbed into the seed particles in a shorter time. Polymer fine particles synthesized using any of these seed polymerization methods can be used as a base for fired fine particles having a target particle diameter of monodispersed, but a simple operation efficiently, in a short time, and a wide range of monomer compositions It is particularly preferable to use a diffusion-promoted seed polymerization method that can obtain polymer fine particles having a uniform particle size. [0007] In the present invention, the oil-soluble ethylenically unsaturated monomer used in the seed Polymerization, such as styrene, p- methyl styrene, p- chlorostyrene, p- chloromethylstyrene, styrene sulfonic acid, p- styrene monomers such as t-butoxystyrene, α-methyl-pt-amyloxystyrene, pt-amyloxystyrene; ethyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, dimethylaminoethyl acrylate, Acrylic ester monomers such as diethylaminoethyl acrylate; methacrylate monomers such as methyl methacrylate, ethyl methacrylate, lauryl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; acrylic acid, methacrylic acid Carboxylic acid-based monomers such as maleic acid and maleic acid; polyethylene glycol mono (meth) acrylate; alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; vinyl ester-based monomers such as vinyl acetate and vinyl butyrate; N-methylacrylamide; N-alkyl-substituted (meth) acrylamides such as acrylamide, N-methylmethacrylamide, N-ethylmethacrylamide; acrylonitrile;
Examples thereof include nitrile monomers such as methacrylonitrile. These monomers can be used alone or as a mixture of two or more kinds. However, when the particles are deformed due to softening or melting during firing, it is necessary to crosslink with a polyfunctional monomer. Examples of polyfunctional monomers include divinylbenzene, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate,
Examples include trimethylolpropane triacrylate, 1,4-divinyloxybutane, divinyl sulfone, diallylamine, and the like. These polyfunctional monomers can be used alone or in combination of two or more. Although any combination of the monomer and the polyfunctional monomer may be used, it is preferable to crosslink a styrene monomer or a nitrile monomer with an aromatic polyfunctional monomer from the viewpoint of carbon yield. [0008] As the oil-soluble polymerization initiator used in the present invention, generally used oil-soluble polymerization initiators can be used. Specifically, peroxide initiators such as benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide and orthomethoxybenzoyl peroxide; 2,2′-azobisisobutyronitrile, 2,2′-azobis And azo initiators such as (2,4-dimethylvaleronitrile). These are usually 0.1 to 10 parts by weight per 100 parts by weight of the monomer,
Preferably, 0.5 to 5 parts by weight is used. The average particle diameter of the polymer fine particles according to the present invention can be arbitrarily designed according to the use of the fired fine particles when the seed polymerization method is used. In the seed polymerization method, the standard deviation of the particle size distribution can be set to 20% or less of the average particle size. However, when ordinary suspension polymerization is used, the standard deviation of the particle size distribution is set to 20% of the average particle size. % Is difficult. In the present invention, the method of firing the polymer fine particles is not particularly limited, and for example, nitrogen, helium, argon,
300 ~ 20 under non-oxidizing atmosphere such as hydrogen or carbon monoxide
What is necessary is just to raise the temperature to a temperature at which the required properties are obtained at about 00 ° C. When some of the fine particles are fused during firing, the fusion of the particles may be released by an air jet or the like. The average particle diameter of the fired fine particles having a uniform particle diameter of the present invention is 2 to 30 μm. The particle diameter distribution of the fired fine particles having a uniform particle diameter of the present invention is such that the standard deviation is 20% of the average particle diameter.
Or less (that is, the coefficient of variation is 20% or less). For example, in the case of using fired fine particles as a lubricant, if the variation coefficient of the particle size distribution exceeds 20%, the amount of fired fine particles effectively used as a lubricant decreases, which is not preferable. . Also, when used as conductive particles for anisotropic conductive film, if the variation coefficient of the particle size distribution exceeds 20%, the distance between connectable electrodes increases,
Further, connection reliability is undesirably reduced. Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. The parts in the examples are on a weight basis. Reference Example (Production example of seed polymer) 7.2 parts of polyvinylpyrrolidone (molecular weight: 40,000), 2 parts of aerosol OT (anionic surfactant manufactured by Wako Pure Chemical Industries, Ltd.), 0.5 part of azoisobutyronitrile The ethanol
70 ° C under a nitrogen stream while stirring the solution dissolved in 340 parts
Then, 50 parts of styrene were added, and the mixture was kept at the same temperature for 24 hours to obtain polymer fine particles. The average particle diameter of the fine particles was 1.83 μm, and the ratio of the standard deviation of the particle diameter distribution to the average particle diameter (hereinafter, abbreviated as a coefficient of variation) was 2.5%. Example 1 To 2.0 parts of the polymer fine particles obtained in Reference Example, 300 parts of ion-exchanged water and 0.8 part of sodium lauryl sulfate were added and uniformly dispersed. 50 parts of acrylonitrile and divinylbenzene (purity
A mixture of 100 parts of a monomer mixture consisting of 50 parts of 55%) and 80 parts of ethanol and 1 part of benzoyl peroxide was mixed with 700 parts of ion-exchanged water and 2 parts of sodium lauryl sulfate. Sonicated. The obtained emulsion is mixed with 4
The mixture was divided, a part thereof was added to the dispersion liquid of the seed polymer particles, and the mixture was stirred at 30 ° C. for 1 hour, so that the monomer was completely absorbed by the seed polymer. This operation was repeated to completely absorb all the monomers into the seed polymer, and then added polyvinyl alcohol (GH-17; saponification degree: 86.5 to 89 mol%,
200 parts of a 3% aqueous solution of Nippon Synthetic Chemical Industry Co., Ltd.) was added, and polymerization was carried out at 80 ° C. for 12 hours under a nitrogen stream while stirring. The obtained polymer particles having a uniform particle size were washed with ion-exchanged water and a solvent, then isolated and dried. 94% yield. The average particle size of the particles was 7.8 μm, and the coefficient of variation was 3.0%. A 100 mmφ alumina sintering tube containing 50 g of the uniform polymer fine particles obtained by the above method was placed in a heating furnace, and nitrogen gas was introduced therein at a flow rate of 100 ml / min. Up to 3 hours, then 1000 ℃
At the set temperature for 2 hours. After cooling the obtained fired fine particles to room temperature, the fused particles were released from aggregation by an air jet. The average particle size of these particles is 6.5 μm,
The coefficient of variation was 8%. Examples 2 to 4 Using the various monomer compositions shown in Table 1, diffusion-promoted seed polymerization was carried out in the same manner as in Example 1 to obtain polymer fine particles having a uniform particle size. These polymer particles having a uniform particle diameter were fired in the same manner as in Example 1. The results are shown in Table 1. The standard deviation of the particle size distribution was within 20% of the average particle size, and the monodispersity of the particle size distribution was good. Comparative Example 1 A 3% aqueous solution of polyvinyl alcohol (GH-17, manufactured by Nippon Synthetic Chemical Industry Co., Ltd .; saponification degree: 86.5 to 89 mol%) 800
In parts, 50 parts of acrylonitrile, 50 parts of divinylbenzene,
A mixture of 2.0 parts of benzoyl peroxide is added and finely dispersed,
The polymerization was carried out at 80 ° C. for 15 hours under a nitrogen stream while stirring. The obtained fine particles were washed with ion-exchanged water and a solvent, subjected to a classification operation, and further isolated and dried. The yield of the obtained polymer particles having a uniform particle size is 62%, the average particle size is 20 μm, and the variation coefficient is 15%.
%Met. This was fired at 800 ° C. in the same manner as in Example 1. The average particle size of the obtained fired fine particles was 17 μm, and the coefficient of variation was 15%. Comparative Example 2 A 3% aqueous solution of polyvinyl alcohol (GH-17, manufactured by Nippon Synthetic Chemical Industry Co., Ltd .; saponification degree: 86.5 to 89 mol%) 800
In parts, 50 parts of acrylonitrile, 50 parts of divinylbenzene,
A mixture of 2.0 parts of benzoyl peroxide is added and finely dispersed,
The polymerization was carried out at 80 ° C. for 15 hours under a nitrogen stream while stirring. The obtained fine particles were washed with ion-exchanged water and a solvent, and then isolated and dried. The yield of the obtained polymer particles of uniform particle size is 80%,
The average particle size was 20 μm and the coefficient of variation was 40%. This was fired at 800 ° C. in the same manner as in Example 1. The average particle size of the obtained fired fine particles was 17 μm, and the coefficient of variation was 60%. Comparative Example 3 A 3% aqueous solution of polyvinyl alcohol (GH-17, manufactured by Nippon Synthetic Chemical Industry Co., Ltd .; saponification degree: 86.5 to 89 mol%) 800
A mixed solution of 50 parts of styrene, 50 parts of divinylbenzene, and 2.0 parts of benzoyl peroxide was added to the mixture, finely dispersed, and polymerized at 80 ° C. for 15 hours under a nitrogen stream while stirring. The obtained fine particles were washed with ion-exchanged water and a solvent, and then isolated and dried.
The yield of the obtained polymer particles having a uniform particle size was 85%, the average particle size was 18 μm, and the coefficient of variation was 45%. This was fired at 1000 ° C. in the same manner as in Example 1. The average particle size of the obtained fired fine particles was 15.5 μm, and the coefficient of variation was 62%. Table 1 summarizes the results of Examples 1 to 4 and Comparative Examples 1 to 3 . [Table 1] As is clear from the above examples, it has been found that according to the present invention, fired fine particles having excellent monodispersity in particle size distribution can be easily and efficiently produced. Therefore, the fired fine particles having a uniform particle diameter of the present invention are suitably used in lubricants, pigments, conductive particles for anisotropic conductive films, and the like.

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Claims (1)

(57) [Claim 1] A model containing an oil-soluble ethylenically unsaturated monomer.
Organic polymer particles synthesized by a seed polymerization method using a nomer component are fired in a non-oxidizing atmosphere. The average particle size is 2 to 30 μm, and the standard deviation of the particle size distribution is 20% or less of the average particle size. A method for producing fired fine particles having a uniform particle diameter.