JPS6017337B2 - Method for producing resin-coated inorganic 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 inorganic fine particles with improved required properties such as dispersibility in other media, dispersion stability, abrasion resistance, and electrical properties, the surface of the inorganic fine particles as a substrate is The present invention relates to a method for producing resin-coated inorganic fine particles, which comprises carrying out a polymerization reaction of a resin monomer as described above. Fine particles are often used as pigments in coatings, printing inks, resin molding, etc., in the form of being mixed and dispersed or suspended in other media. Therefore, fine particles are required to have dispersibility at the stage of mixing into a medium, dispersion stability in the mixed state, wear 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, by imparting lipophilicity to inorganic fine particles and improving their miscibility with organic binders. Examples of methods for improving this 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, coated fine particles obtained by these methods have low strength adsorption layers, and during drilling for resin compound production, the adsorption layer falls off from the surface of the fine particles, resulting in a decrease in performance. Again-Fe203,
Fe303, modified y-Fe203 (magnetic material based on y-Fe203, such as Co-doped y-Fe
Magnetic substances such as 203, y-Fe203-Fe304, etc.) are used, for example, in the production of magnetic paints and other magnetic products, but when coating such magnetic substances, in addition to the interfacial properties mentioned above, It is required that the magnetic properties do not deteriorate over time.

The present inventors have completed the present invention as a result of various studies on methods for producing coated fine particles that can satisfy the various properties required of the coated fine particles described above.

The resin-coated fine particles produced by the method of the present invention have excellent miscibility with organic binders and have strong adhesion that prevents the coating from falling off during the bran mixing operation even when mixed.

For example, a magnetic substance is a coating material (substrate fine particles)
Even if it is, the magnetic properties will not deteriorate significantly. The resin-coated fine particles produced by the method of the present invention can be used not only by being mixed with a liquid medium, but also in air or other gaseous phases (for example, as a carrier for electrophotography). The feature of the present invention is that a resin coating or coating can be applied to the surface of each fine particle by directly polymerizing monomers such as acrylonitrile, vinyl chloride, pinylidene chloride, etc. in the presence of substrate fine particles. The specific method is as follows.

That is, a polymerization initiator is attached to substrate fine particles in advance, and then the fine particles are placed in a solvent containing a monomer (for example, while the fine particles are added to the solvent), and a polymerization reaction is carried out on the surface of each fine particle. This forms a resin coating. As a method for attaching the polymerization initiator to the substrate fine particles, a preferred method is to dissolve the polymerization initiator in advance in a solvent, add the substrate particles to this solution, and then remove the solvent by evaporation. As the polymerization initiator used in the present invention, YamaBN (2,2'-azobisisobutyrilonitrile)
, LP0 (lauroyl peroxide), BP0 (penzoyl peroxide), KPS (potassium persulfate)-Na2S03, and the like.

The amount of polymerization initiator added is generally 0 to the raw material monomer.
．． Adjust to 1 to 1 skin t%, preferably 0.5 to fine t%. If the amount of the polymerization initiator added is less than 0.1 wt%, the polymerization reaction rate is too slow to be practical, and if it is more than 1 t%, the reaction will proceed rapidly and the heat generated during the reaction will be large and difficult to control. Sometimes. Although the solvent for the polymerization reaction is not particularly limited, it is preferable to use a solvent that dissolves the monomers used but does not dissolve or hardly dissolves the resulting polymer.

For example, ethyl alcohol, ethyl acetate, methyl ethyl ketone, benzene, toluene, monochlorobenzene, dichlorobenzene and the like are preferred. These solvents can be appropriately selected depending on, for example, the monomers used and the reaction conditions, but in the Examples described below, good results were obtained with toluene and monochlorobenzene. The raw material monomer is selected depending on the application of the coated fine particles.
Polymerizable or copolymerizable monomers such as vinyl acetate, vinyl chloride, acrylic esters, methacrylic esters, acrylonitrile, vinylidene chloride, and the like can be used.

A combination of two or more of these monomers may be used.
As raw material fine particles, for example, Q-Fe00 days, Q-F
e203, ferrite, Fe304, transformed Fe304,
y-Fe203, transformed y-Fe203, Fe, Fe alloy, and other inorganic fine particles are used. Since the material of the fine particles is determined by their intended use, it goes without saying that the method of the present invention can be applied to fine particles other than those specifically mentioned above. Regarding the particle size of the raw material fine particles, in the case of lumps or spheres, the average diameter is about 0.
In the case of a cubic object, the average vertex distance is preferably in the range of about 0.01 to 5 microns, and in the case of a needle-shaped object, the average long length is in the range of about 0.01 to 5 microns.

However, there is no intention to preclude the use of particles having particle sizes outside these ranges. The appropriate amount range of the resin coated on the fine particles by the method of the present invention should be stabilized depending on the specific use of the resin-coated fine particles.

For example, in the case of iron oxide or iron particles as shown in the examples, 10
2 to 40 g of resin per particle of female r, especially 7 to 2
It is preferable that the particle size is less than 23, the effect of the coating will not be significant, and if it is more than 40, the properties of the particles themselves, such as magnetic properties, may be excessively reduced. EXAMPLES Hereinafter, the present invention will be further explained with reference to Examples and Comparative Examples, but the present invention is not limited by these Examples.

Example 1 Fe304 powder with an average major axis length of 0.3 microns (coercive force 44
e, saturation magnetic flux density 84. Add 10k9 of 10k9 μg/g), stir lightly, and evaporate to dryness with an evaporator to obtain A.
IBN initiator was deposited on the surface of Fe304.

Next, monochlorobenzene 40k9 containing 3k9 acrylonitrile mo/mer was heated to 70qo, and the initiator-attached Fe304 was added little by little to the Fe304.
Polymerization was started as soon as the monomer solution entered, and the addition was completed in 2 hours, and after heating for another 2 hours,
Cooled and separated into furnaces. After furnace separation, the cake was dried at 8000 for 30 hours to obtain 12k9 coated Fe304. This coated Fe304 had a coercive force of 4470e and a saturation magnetic flux density of 70.2 mu/g. (Note that no polymerized product or unreacted acrylonitrile monomer was detected in the furnace solution). 10k9 of the obtained dried material was converted into PCV resin compound (manufactured by Nippon Zeon Co., Ltd.: HB2000 x 10)
It was put into a Henschel mixer with 10k9 and kneaded for 2 hours.

The specific resistance of the raw material Fe304 and the slag product was measured, and the resistivities were 1.5×1 and 40 mm, respectively.
(This specific resistance value was measured in order to show that the resin coating was not substantially removed from the particles by comparison with Comparative Example 1, which will be described later). Example: Two mountains of BN are in love
Add 10k9 of cubic Fe304 powder (coercive force 8XX, saturation magnetic flux density 85.$mu/g) with an average distance of 0.5 microns to the dissolved acetone 12k9, stir, and then evaporate and dry with an evaporator to form MBN. The initiator was deposited on the 4 surfaces of Fe.

Next, 25k9 of monochlorobenzene containing 1.2k9 of acrylonitrile was heated to 70°C and treated in the same manner as in Example 1. mu/g) was obtained. 10k of this dried material
9 was made of 10k9 PVC compound (similar to Example 1).
(same as in Example 1). The specific resistance value of the thickened product was 7.8 x 1 and 40 mm, and that of the raw material Fe304 was 2.4 x 1 mm. Comparative Example 1 10k9 of Fe304 used in Example 1 and 10k9 of PVC compound (same as Example 1) were kneaded for 2 hours in a Henschel mixer, and the specific resistance value was measured.
A value of 1070 one skin was obtained.

A comparison of the resistivity values of Examples 1 to 2 and Comparative Example 1 shows that the coated Fe203 coatings obtained in Examples 1 and 2 have sufficient strength to prevent them from breaking or falling off during kneading.

Example 3 Fe powder with an average major axis length of 0.3 microns (coercive force 117 ratio, saturation magnetic flux density 15 μ/g, specific resistance 5.6×1
In the same manner as in Example 1, 10 pieces of LPO initiator were attached to the (P-Q-arc).

Next, 85 wt% pinylidene chloride and 15 wt% vinyl acetate.
40 kg of toluene containing 3k9 of a mixture of was heated to 6,000 ℃, and the initiator-attached Fe powder was added little by little to this, aged for 3 hours after addition, separated in an oven, and dried. This coated powder had a coercive force of 125 e, a saturation magnetic flux density of 12 mu/g, and a resistivity of 4.5×1 and 30 mu/g. Comparative Example 2 Same raw material Fe powder 10k9 as Example 3
was mixed with PVC compound (same as Example 1) 10k9 in a Henschel mixer.

The specific resistance of this falcon paste was 4.4 x 1 pi.
Example 4 y-Fe203 with an average major axis length of 0.5 microns (coercive force 4
2" Oh, saturation magnetic flux density 74. Positive mu/g, specific resistance 4.
A coated dry product of 12.4 [9] was obtained by treating 4 x 1 pi○ 1 仇) in the same manner as in Example 1.

The coercive force of this dried material is 4340e, and the saturation magnetic flux density is 60
．． 7 emu/g, and the specific resistance was 9.0×1 and 40. Example 5 10k9 of Q-Fe2Q with an average diameter of 1.2 microns was treated in the same manner as in Example 1 to obtain a coated dry product of 12.1
I got k9.

The specific resistance of this dry product was 5.2×1 and 40×1. Comparative Example 3 Dissolve 0.3k9 of sodium oleate in 100ml of water, add 10k9 of the same Fe304 used in Example 1, adsorb the oleic acid ion to Fe304, filter it in an oven, and dry it. I got about 10k9.

This 10k9 product was mixed into a PVC compound (Example 1
) 10k9 and strained for 2 hours in a Henschel mixer. The specific resistance of this deer paste product was 3.2×1070. Comparative Example 4 YamaBNIOgy and acrylonitrile monomer 3k9
40 kg of monochlorobenzene containing Fe304 powder (AIBN
(without predeposition) was added in small portions over 2 hours.

After the addition was completed, the mixture was further aged for 2 hours, then cooled and separated from the furnace. 12. Dry the obtained cake at 80 qo for 30 hours.
2k9 coated Fe304 was obtained. The coercive force of this dry coated Fe304 is 44 e, and the saturation magnetic flux density is 6.
9. It was step mu/gy. This dry product was kneaded with a PVC compound as described in Example 1.

The specific resistance of the thickened product was 2.3 x 1 pi.
As shown in Comparative Example 1 above, the resistivity of the product obtained by mixing the raw material itself with PVC compound is 2.4 × 1070 arc, and the resistivity of the product obtained by mixing the coated particles of Example 1 with PVC compound is 2.4 × 1070 arc. Since the specific resistance is 4.2 x 1 and 40 - skin, in this comparative example 4, although almost the same amount of resin as in Example 1 is generated around the Fe304 particles, P
It can be seen that the VC compound contributes little to the increase in the resistivity of the falsified product, ie to the formation of a strong continuous coating on the particle surface. This means that when the monomer is mixed with the polymerization initiator and polymerized without adhering the polymerization initiator to the surface of the substrate particle in advance as in Comparative Example 4, the resin coating on the surface of the substrate particle is incomplete. This shows that the substrate particles are easily removed by physical force and the surface of the substrate particles is exposed.

Brief Explanation of Drawings Figure 1 is an electron micrograph (magnification x 10,000) of Fe304 powder used as a raw material in Example 1.

Figure 2 is an electron micrograph of the acrylonitrile resin-coated Fe304 powder obtained in Example 1 (magnification xlo,
000). The Fe304 powder in Figure 1 is Fe203
Because it was obtained by partial reduction of , there are voids formed by oxygen elimination and the surface is rough. In contrast, the individual particles of the resin-coated powder shown in FIG. 2 have no voids and appear smooth because of the resin attached to the surface. Further, agglomeration of particles is not recognized. Thus, the monomer selectively polymerizes on the surface of each individual particle to which the polymerization initiator has been applied, forming a continuous coat tightly adhered to the surface;
It is believed that this causes an increase in the specific resistance value.
Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. When producing resin-coated inorganic fine particles, a polymerization initiator is attached to the surface of the inorganic fine particles as a substrate, and then a polymerization reaction of the monomer is carried out on the surface of the fine particles in a solvent containing the monomer. A method for producing resin-coated inorganic fine particles, the method comprising: 2 Inorganic fine particles are α-FeOOH, α-Fe_2O
_3, ferrite, Fe_3O_4, transformed Fe_3O_
4, γ-Fe_2O_3 transformation γ-Fe_2O_3,Fe
The method according to claim 1, wherein the fine particles are selected from: and Fe alloys. 3 If the inorganic fine particles are agglomerated or spherical, their average diameter, if cubic, their average distance from the apex, and if they are acicular, their average major axis length is in the range of 0.01 to 5 microns. A method as claimed in 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. 5. The method according to claim 1, wherein the solvent is one or more selected from ester alcohol, ethyl acetate, methyl ethyl ketone, benzene, toluene, monochlorobenzene, and dichlorobenzene.