JPS5951569B2 - Method for producing resin-coated fine particles - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for modifying the surface of fine particles.

More specifically, in order to produce resin-coated fine particles with improved required properties such as dispersibility in other media, dispersion stability, abrasion resistance, and electrical properties, resin is coated on the surface of the substrate fine particles. The present invention relates to a method for producing resin-coated fine particles characterized by carrying out a polymerization reaction of monomers. Fine particles are often used in the form of being mixed and dispersed or suspended in other media, for example, as pigments in paints, printing inks, resin molding, and the like.

Therefore, fine particles are required to have dispersibility when mixed into a medium, dispersion stability in the mixed state, and abrasion resistance, and depending on the use, electrical properties are also required. Therefore, various methods have been used to modify fine particles, especially their interfacial properties. For example, methods of imparting lipophilicity to inorganic fine particles to improve their miscibility with organic binders have been used. Examples include a method of adsorbing metal soap or other surfactants, and a method of dispersing it in a solution of an organic polymer substance.

However, the coated fine particles obtained by these methods have low adsorption layer strength, and the adsorption layer falls off from the surface of the fine particles during kneading to produce a resin compound, resulting in a decrease in performance. Also γ-Fe.

O. , Fe. O. , modified γ-Fe. O. (γ-Fe.O
. A magnetic material based on, for example, Co-doped γ
-Fe2O3, γ-Fe2O3-Fe3o4, etc.)
Magnetic substances such as these are used, for example, in the manufacture of magnetic paints and other magnetic products, but when coating such magnetic substances, it is required that the magnetic properties of the interfacial properties described above do not deteriorate significantly. be done. The present inventors have completed the present invention as a result of various studies on a method for producing coated fine particles that can satisfy the various properties required of coated fine particles.

The resin-coated fine particles produced by the method of the present invention have excellent miscibility with organic binders, and even when they are kneaded, they have a strong adhesive force that prevents the coating from falling off during the kneading operation.

For example, a magnetic substance is the material to be coated (substrate fine particles)
In this case, the magnetic properties do not deteriorate significantly. A feature of the present invention is that the surface of the fine particles to be resin-coated is activated in advance to impart polymerization initiation activation ability to the surface, and the surface imparted with polymerization initiation activation ability is used to coat acrylonitrile. , vinyl acetate, vinylidene chloride, and other monomers.

Surface activation is carried out in a reducing atmosphere, usually in a hydrogen stream at 50 to 450°C, preferably 150 to 350°C.
The heating time is 0.5 to 10 hours, preferably 1 to 3 hours.

The hydrogen flow rate is 0.1 to 81/min, preferably 0.5 to 41/min, per 100 g of particles. The coating on the fine particles allows polymerization of the monomer to occur on the surface of the individual particles in an atmosphere containing the gas phase monomer, preferably in an inert atmosphere.

Coatings on fine particles with activated surfaces are
The monomer is entrained in a preheated monomer bath (varies depending on the boiling point of the monomer, but usually about 40 to 80°C is preferable) through an inert gas such as nitrogen or argon, and the monomer is deposited on the activated surface of the fine particles. This is achieved by introducing In this case, it is preferable to carry out the reaction under the following conditions, taking into consideration the heat generated by the polymerization reaction, the degree of polymerization, etc.
The reaction temperature is room temperature to 100°C, preferably 40 to 80°C.
It is ℃.

The monomer supply amount is 0.1 per 100g of substrate fine particles.
-50 g/hour, preferably 2-20 g/hour. Inert gas flow rate is 10cc per 100g of substrate fine particles
/min to 41/min, preferably 50 cc/min to 11/min. The monomer supply amount is adjusted by the monomer preheating temperature and the inert gas flow rate. For example, in Example 1, the monomer preheating temperature is 50°C and the inert gas amount is 100cc/
min, and the monomer feed rate was on average 6.5 g/h. The raw material monomers used in the present invention include monomers that can be polymerized or copolymerized, such as vinyl acetate, vinyl chloride,
Examples include acrylic esters, methacrylic esters, acrylonitrile, vinylidene chloride, etc., and one or a combination of two or more selected from acrylonitrile, vinyl acetate, and vinylidene chloride is particularly preferred.

The particle size of the raw material fine particles is approximately 0.01 to 5 microns in the case of lumps or spheres, 0.1 to 5 microns in the average distance between the apexes in the case of cubic objects, and 0.1 to 5 microns in the case of acicular objects. It is preferable that the average major axis length is in the range of 0.1 to 5 microns, and α-F particles falling within these particle size ranges
eOOWα-Fe.

O,, Fuera Ito, Fe. O,, transformed Fe, O,, γ
-Fe. O. , metamorphosed γ-Fe. Fine particles of O, Fe and Fe alloys are used. The amount of coating according to the method of the present invention is 2 to 40 g per 100 g of substrate fine particles,
In particular, it is preferably 7 to 25 g. If the amount is less than 2 g, the coating effect will not be significant, and if it is more than 40 g, the properties of the particles themselves, such as magnetic properties, may deteriorate significantly.

The present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto, and various modifications can be made within the spirit of the present invention.

Example 1 Fe with an average major axis length of 0.5 microns.

O. Powder (coercive force 4250e, saturation magnetic flux density 85.0e
100 g of 2 m/g) was charged into a tube with a length of 2 m and a diameter of 20 cm, the temperature was raised to 300 °C in a nitrogen atmosphere, and at this temperature the nitrogen atmosphere was switched to a hydrogen flow (21/min) and kept for 1 hour. After that, the temperature was changed to nitrogen again and the temperature was cooled to 80°C. While keeping the powder at this temperature, nitrogen was bubbled into the acrylonitrile that had been preheated to 50°C (100 to 2
50 cc/min), thereby removing nitrogen entrained with acrylonitrile from the Fe. O, led to powder. After carrying out this operation for 20 hours, it was cooled to room temperature in a nitrogen atmosphere to obtain a stable coated Fe that did not generate heat when taken out. O. 115g
Obtained. The coercive force of this coated Fe3O4 is 4330e
The saturation magnetic flux density was 74.2 emu/g, and the specific resistance was 1.3×10 12 Ω-Cm. Furthermore, the substrate Fe3O
The specific resistance of No. 4 was 1.5×10 6 Ω-Cm. Example 2 A coated Fe powder obtained in the same manner as in Example 1 using Fe powder having an average major axis length of 0.2 microns had a specific resistance of 8.8 x 10<11 >Ω-Cm.

The specific resistance of the raw material Fe powder was 5.6×10 5 Ω-Cm. Comparative Example 1 Same Fe3O4 as used in Example 1
10 kg of PVC compound (4) H manufactured by Zeon Co., Ltd.
10 kg of B2OOOO x 10) were kneaded in a pen shell mixer for 2 hours, and the specific resistance of the kneaded product was measured and found to be 2.4 x 10 7 Ω-Cm.

Therefore, it can be seen that the coating of the coated particles of Example 1 has sufficient strength to withstand kneading.

Comparative Example 2 It was found that when the monomer was not blown in in Example 2, the product ignited when taken out and was completely oxidized to α-Fe2O3.

Claims (1)

[Claims] 1. When producing resin-coated fine particles, substrate fine particles are activated in a reducing atmosphere to impart polymerization initiation activation ability to their surfaces, and then a monomer is blown into the fine particles for polymerization. A method for producing resin-coated fine particles, characterized in that a polymerization reaction is carried out on a surface having initiation activation ability. 2 Fine particles are α-FeOOH, α-Fe_2O_3,
Ferrite, Fe_3O_4, modified Fe_3O_4, γ
-Fe_2O_3, modified γ-Fe_2O_3Fe, and Fe alloy. 3. If the fine particles are agglomerated or spherical, their average diameter, if they are cubic, their average vertex distance, and if they are acicular, their average major axis length is in the range of 0.01 to 5 microns. A method according to claim 1. 4. The method according to claim 1, wherein the monomer is one or more selected from vinyl acetate, vinyl chloride, acrylic esters, methacrylic esters, acrylonitrile, and vinylidene chloride.