JPH0578607A - Production of coating - Google Patents

Abstract

PURPOSE:To provide a method for efficiently producing a coating containing a pigment dispersed therein in a good state. CONSTITUTION:A pigment (e.g. magnetic powder such as gamma-Fe2O3),a binder component (e.g. vinyl chloride-vinyl acetate copolymer), an organic solvent (e.g. cyclohexanone) and other required components are mixed with each other. The mixture is fed into the mixing tank of a preliminary dispersing machine comprising a rotating column-like rotor and a cylindrical stationary stator surrounding the rotor, a gap being formed therebetween, subjected to a preliminary dispersion treatment, fed into a medium-dispersing type dispersing machine preliminarily received a dispersing medium which is repeatedly moved and corrided each other, and subsequently subjected to a final dispersion treatment to obtain the objective coating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a paint, and more particularly to a method for efficiently producing a paint in which a pigment is well dispersed.

[0002]

2. Description of the Related Art Generally, a paint is prepared by mixing a pigment, a binder component, an organic solvent and other necessary components directly in a suitable order in a disperser such as a ball mill or the like, or by mixing or dispersing them in a tank. After blending, pre-mixing is performed in advance with a stirrer such as a high-speed disperser, and further, liquid is fed to a disperser such as a sand mill at an arbitrary speed by a liquid feed pump or the like to mix and disperse.

[0003]

However, in these conventional methods, when a high hardness pigment or a fine particle pigment such as carbon black is dispersed, undispersed lumpy pigment may remain or the desired dispersion may occur. However, the manufacturing efficiency is extremely poor because it takes a lot of time to finish the dispersion to a desired degree.

[0004]

The present invention has been made as a result of extensive studies to solve the above problems.
After the pigment was mixed with the binder component, the organic solvent and other necessary ingredients, the mixture was formed with a gap between the rotating cylindrical rotor and the surrounding stationary cylindrical stator. The pigment is dispersed sufficiently well by sending it into the mixing tank of the pre-disperser for pre-dispersion, and then by sending it to a disperser in which a dispersion medium that moves and repeatedly collides with each other is pre-stored and finish-dispersed. At the same time, a paint in which the pigment is well dispersed can be efficiently produced.

According to the present invention, a mixture of a pigment, a binder component, an organic solvent and other necessary components is mixed before finishing dispersion in a media medium type disperser such as a sand mill containing a dispersion medium. , Because it is fed into a mixing tank of a predispersing machine formed with a gap between a rotating cylindrical rotor and a cylindrical stationary stator that surrounds it, and shear energy is applied to preliminarily disperse it. The aggregate of pigment particles is crushed by this preliminary dispersion. Therefore, the finish dispersion in the media medium type disperser containing the dispersion medium is performed without a coarse aggregate of pigment particles, and the time required to reach the desired dispersity in the finish dispersion step is shortened. At the same time, the degree of dispersion is sufficiently improved,
A paint in which a pigment is well dispersed is efficiently produced.

In particular, magnetic fine particles such as a magnetic paint produced when forming a magnetic recording medium, as well as fine-particle ferromagnetic powders, powders such as α-Al ₂ O ₃ and Cr ₂ O _{3 having} high hardness, and general It is ideal for dispersing paints containing carbon black, which is extremely fine and difficult to disperse, and is effective in improving productivity, improving the surface smoothness of the magnetic layer, and reducing dropout. is there.

In the present invention, the pre-dispersion carried out before the finish dispersion is carried out in a mixing tank formed by a gap between a rotating cylindrical rotor and a cylindrical stationary stator surrounding the rotor. A mixture in which a pigment, a binder component, an organic solvent and other necessary components are mixed is fed, and the stirring is carried out by forcibly stirring by a high speed rotation of a rotating cylindrical rotor. Therefore, a shearing action acts on the gap between the rotating cylindrical rotor and the cylindrical stationary stator that surrounds it,
This shearing energy breaks up the aggregates of pigment particles.

However, after this preliminary dispersion, when the final dispersion is carried out with a media medium type disperser containing a dispersion medium, the dispersion is carried out in a state without coarse aggregates of pigment particles, so that the dispersion is carried out quickly and satisfactorily. Dispersed pigments, even if it is difficult to disperse fine magnetic powder or high hardness α-Al
_Even with powders of ₂ O ₃ , Cr ₂ O _3, etc., and even carbon black, primary particles are well dispersed.

The mixing tank formed by the gap between the rotating cylindrical rotor and the cylindrical stationary stator surrounding the rotating rotor is a cylindrical rotor forming the inner wall of the mixing tank. By rotating the rotor at high speed, a strong shearing action is applied to disintegrate the aggregates of pigment particles, so that sufficient shearing energy can be obtained in the gap between the rotor and the stator forming this mixing tank. It is preferably within 1 mm so that if the gap is wider than this, sufficient shearing action cannot be applied to the mixture in the mixing tank, and the aggregate of pigment particles cannot be sufficiently crushed.

Further, in order to apply a stronger shearing action to the mixture sent into the mixing tank, the pyramid or the tip of the pyramid is cut off on the outer peripheral surface of the rotor and the inner peripheral surface of the stator, respectively. It is preferable to provide a large number of protrusions having such a shape.Furthermore, these protrusions are formed by the pyramidal slopes of the rotor-side and stator-side protrusions, the tip of the rotor-side protrusion, and the inside of the stator. Circumferential surface, tip of stator side protrusion
It is preferable that the outer peripheral surfaces of the tabs face each other.

Further, such a rotating cylindrical rod
The rotating speed of the rotor for mixing and dispersing the mixture in the mixing tank formed with the gap between the rotor and the cylindrical stationary stator surrounding the rotor is 20 to 30 in terms of peripheral speed.
It is preferable to carry out in the range of m / sec. If the rotation speed is too slow, the mixture cannot be mixed and dispersed well, and if it is too fast, an extremely large amount of heat is generated when the mixture is forcibly stirred in the mixing tank.
May adversely affect paint.

After such preliminary dispersion, further finish dispersion is carried out by a media medium type disperser such as a sand mill or a ball mill in which a dispersion medium is stored in advance. In this final dispersion, coarse pigment particles are used. Since it is dispersed without agglomerates, quick and good dispersion is achieved,
Even if the pigment is a fine magnetic powder that is difficult to disperse, a powder of high hardness α-Al ₂ O ₃ , Cr ₂ O ₃ or the like, or even carbon black, the primary particles are well dispersed.

When finishing and dispersing with such a media medium type disperser, the dispersion medium to be contained in advance has a particle diameter of 0.5 to 2.0 so that the pigment in the paint can be mixed and dispersed sufficiently uniformly. It is preferable to use the one having a particle size of 0.1 mm, and if the particle size is too large, the impact force increases, but the dispersion becomes coarse and cannot be sufficiently finely dispersed, and if it is too small, after mixing and dispersing,
It may interfere with the separation of the paint and the dispersion medium. Further, the use ratio of the dispersion medium to the paint is preferably within the range of 80 to 150% by volume, and if it is too small, the number of shearing of the dispersion medium is reduced and the dispersibility is deteriorated. And the dispersion medium is extremely worn. As such a dispersion medium, any of various materials conventionally used such as glass, ceramics and steel is preferably used.

As described above, preliminary dispersion is performed in a mixing tank formed with a gap between a rotating cylindrical rotor and a cylindrical stationary stator surrounding the rotor, and further, a sand mill and a ball mill. When finish dispersion is performed with a media medium type disperser such as, a pigment in which the pigment is sufficiently well dispersed is efficiently produced, and when the magnetic coating used for producing a magnetic recording medium is produced by this method, A strong shearing action is applied by the gap between the rotating cylindrical rotor and the cylindrical stationary stator that surrounds it, and the pigment particle agglomerates are crushed well, and further finish dispersion is performed. In particular, fine magnetic powder and carbon black having poor dispersibility are also well dispersed to prepare a magnetic coating having good dispersibility. The magnetic coating is applied onto a substrate and dried to form a magnetic layer. Form When a magnetic recording medium having excellent electromagnetic conversion characteristics can be obtained more.

Here, as the magnetic powder used in the production of the magnetic paint, for example, γ-Fe ₂ O ₃ powder, F
e ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, Co-containing Fe ₃ O ₄ powder, Fe powder, Co powder, Fe-Ni
Various conventionally known magnetic powders such as metal powders such as powders are widely used.

As the binder component, vinyl chloride-
Vinyl acetate-based copolymers, fibrin-based resins, butyral-based resins, polyurethane-based resins, polyester-based resins, epoxy-based resins, polyether-based resins, isocyanate compounds, etc. Any binder resin that is present is used.

As the organic solvent, ketone solvents such as cyclohexanone, methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as benzene, toluene and xylene, and dimethyl sulfoxide. Solvents suitable for dissolving the binder resin to be used, such as sulfoxide-based solvents such as, ether solvents such as tetrahydrofuran and dioxane, are used alone or in combination of two or more without particular limitation. ..

[0018]

EXAMPLES Next, examples of the present invention will be described. Example 1 Co-γ-Fe ₂ O ₃ (specific surface area 30 m ² / g) 100.0 parts by weight α-Al ₂ O ₃ (average particle size 0.4 μm) 8.0 〃 carbon black (average particle size 25 mμm) 2.5 〃 stearin Zinc acid salt 0.5 〃 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 61.5 〃 (20 wt% cyclohexanone / toluene solution) Cyclohexanone / toluene = 1/1 mixed solvent 151.2 〃 This composition in a tank in an appropriate order Add and mix,
Stirring was performed with a high speed disperser.

Then, this mixture was subjected to a peripheral speed of 22.5 m / sec.
The gap between the rotating rotor and the stationary stator is about 5
It was fed into the mixing tank of a 00 μm preliminary disperser (160 protrusions / m ² , protrusion height 8 mm), and the residence time was 1
Mix and disperse for 0 seconds. After that, the mixture was further sent to a sand mill and mixed and dispersed for a retention time of 45 minutes.

Next, a polyurethane resin (20% by weight cyclohexanone / toluene 34.1 parts by weight solution) myristic acid 1.5 〃 n-butyl stearate 1.2 〃 Coronet L (manufactured by Nippon Polyurethane Industry Co .; (75% by weight ethyl acetate solution of isocyanate amount of isocyanate compound) A mixed solvent of cyclohexanone / toluene = 1/1 mixed solvent 33.2 was added in an appropriate order and mixed and dispersed for 1 hour to produce a magnetic paint.

Then, the obtained magnetic paint is nominally 0.3 μm.
After passing through the filter of No. 1 above, it was applied on a polyester film having a nominal thickness of 14 μm, calendered, and cut into ½ inch width to prepare a video tape.

Example 2 A magnetic paint was produced in the same manner as in Example 1 except that the mixing and dispersion in the sand mill was changed from 45 minutes as the residence time to 30 minutes as the residence time. -Created a page.

Example 3 In the composition of Example 1, which was stirred by a high speed disperser in a tank, the amount of cyclohexanone / toluene mixed solvent in the composition was appropriately reduced in advance, and the mixture was kneaded by a kneader to form a paste. After that, a reduced amount of cyclohexanone / toluene mixed solvent was added to prepare a mixed solution, which was transferred to a tank and stirred with a high speed disperser to prepare a magnetic coating material in the same manner as in Example 1 to prepare a video tape.

Example 4 A magnetic paint was produced in the same manner as in Example 3 except that the mixing and dispersing in the sand mill was changed from 45 minutes as the residence time to 30 minutes as the residence time. -Created a page.

Comparative Example 1 A magnetic coating material was prepared in the same manner as in Example 1 except that the mixing and dispersing in the mixing tank formed with the gap between the rotating rotor and the stationary stator was omitted. Was manufactured to prepare a video tape.

Comparative Example 2 A magnetic coating material was prepared in the same manner as in Example 3 except that the mixing and dispersing in the mixing tank formed with the gap between the rotating rotor and the stationary stator was omitted. Was manufactured to prepare a video tape.

The surface roughness, RF output and dropout of the magnetic layer were measured for the video tapes produced in each of the examples and comparative examples. The surface roughness of the magnetic layer was measured using a stylus type surface roughness meter, and indicated by the center line average roughness (Ra). As the RF output, an RF signal was recorded with a standard recording current, and the reproduction output was shown as a relative value with respect to the reference tape. Furthermore, the dropout is 50% at standard recording current.
It records and reproduces gray signals, and uses the NCSC method for 5 μsec.
It was measured with a dropout counter under the condition of -18 dB. Table 1 below shows the results.

[0028]

[0029]

As is apparent from Table 1 above, the video tapes obtained in the present invention (Examples 1 to 4) are all compared with the conventional video tapes (Comparative Examples 1 and 2). Even when the surface roughness was smooth, the RF output was high, the dropout was small, and the dispersion treatment speed in the sand mill was high in Examples 2 and 4, good results were obtained. It can be seen that the paint obtained by the method has good dispersibility of the pigment and is effective for improving the productivity of the paint.

Claims (6)

[Claims] 1. A pigment is mixed with a binder component, an organic solvent and other necessary ingredients, and the mixture is then rotated into a cylindrical rotor and a cylindrical stationary stator surrounding the rotor. It is characterized in that it is fed into a mixing tank of a pre-disperser formed with a gap to carry out pre-dispersion, and then a dispersion medium that moves and repeatedly collides with each other is sent to a pre-stored disperser for finish dispersion. Paint manufacturing method 2. An outer peripheral surface of a rotor for performing preliminary dispersion and an inner peripheral surface of a stator are provided with projections opposed to each other, and are formed with a gap between the outer peripheral surface of the rotor and the inner peripheral surface of the stator. The method for producing a paint according to claim 1, wherein the paint is pre-dispersed in a mixed tank. 3. The protrusions provided on the outer peripheral surface of the rotor and the inner peripheral surface of the stator so as to face each other have a pyramid shape or a shape in which the tip of the pyramid is cut off, and the rotor side and the stator are formed. Side projections are formed with a gap in which the pyramidal slopes of the two side projections, the tip of the rotor side projection and the inner peripheral surface of the stator, and the tip of the stator side projection and the outer peripheral surface of the rotor face each other. The method for producing a paint according to claim 2, wherein the dispersion is pre-dispersed in a mixing tank. 4. The method for producing a coating composition according to claim 1, wherein the dispersing machine in which the dispersing medium is contained in advance is a media medium type dispersing machine. 5. The method for producing a paint according to claim 4, wherein the media medium type disperser is a sand mill. 6. The method for producing a paint according to claim 1, wherein a magnetic powder is used as a pigment to produce a magnetic paint.