JPH0358770B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to magnetic paints, and more particularly to a method for increasing the dispersion efficiency of magnetic paints in a pin-type mill. (Prior Art) Conventionally, magnetic paints have been dispersed by stirring a magnetic paint mixture and beads as an auxiliary medium in a disc type or pin type mill type dispersing machine. Generally, the dispersion ability of such a dispersing machine is determined by various factors such as the filling rate of the beads into the dispersing machine, bead diameter, bead specific gravity, peripheral speed of the tip of the rotating body rod, and the number of dispersion stages. . Regarding the circumferential speed of the tip of the inner rotating body rod, for the disk type mentioned above, it is 8 to 12 m/s, and for the pin type, consideration should be given to cracking of the beads due to collision between the rod and beads, abnormal wear, etc. Speeds of 4 to 7 m/s have been used. However, when trying to increase the capacity of the dispersing machine in order to obtain a good dispersion state of magnetic paint in a shorter time, generally the circumferential speed of the tip of the rotating body rod remains the same, and the diameter of the rotating body increases. Increased. Therefore, the number of revolutions of the rotating body necessarily decreases, and the frequency of intersections between the rods of the rotating body and the rods of the side walls also decreases. For this reason, the dispersion efficiency decreases to a small extent, and it takes a considerable amount of time to obtain a paint with a good dispersion state. In order to solve this problem, it was considered to increase the circumferential speed of the tip of the rotating body rod in the pin type mill or to increase the bead filling rate.
Increasing the circumferential speed of the rod tip will lead to cracking and abnormal wear of the beads, while the bead filling rate is already 70 to 70%.
Since it has reached 80%, filling the dispersion machine with more beads than this may cause a lock when starting the disperser. Therefore, the dispersion efficiency could not be easily improved. The table below lists commercially available pin type mills.

[Table] (Objective of the invention) The present invention improves dispersion efficiency in conventional pin-type mills without causing cracking or abnormal wear of beads.
The purpose is to obtain magnetic paint with good dispersion in a short time. (Summary of the Invention) According to the present invention, the rods pressed against the inner wall of the cylindrical container of a pin-type mill and the rotating body are arranged so that the frequency of intersection of the rods is determined by the circumferential speed of the tip of the rotating body rod.
The ratio between V ₁ and the circumferential speed V ₂ of the rod root, that is, the value of V ₁ /V ₂ is set separately for when it is 1.5 or more and when it is less than 1.5, and it is set within a range that does not affect bead wear and magnetic properties. Within this method, a magnetic paint with a good dispersion state can be obtained in a shorter time than before. (Description of Examples) The present invention will be described in detail below with reference to the drawings. Figure 1 shows the conventionally used pin type mill 1.
FIG. In the pin type mill 1, a cylindrical container 2 is filled with beads as an auxiliary medium for dispersion and a magnetic paint mixture as an object to be dispersed. On the other hand, a plurality of rods 5 are provided on the inner wall of the cylindrical container 3 of the mill 1 and on the outer periphery of the rotating body 4 so as to intersect with each other at equal intervals.
In order to increase the dispersion efficiency in the mill, conventional methods have been considered to increase the circumferential speed of the tip of the rotor rod or increase the bead filling rate, but these methods all cause problems such as cracking of beads and abnormal wear. In addition, there was a risk that the mill would become locked when starting up. As a result of considering a method for obtaining magnetic paint in a well-dispersed state without causing such problems, the applicant has found that the rod provided on the inner wall of the cylindrical container and the rotary rod can be We have found that the frequency of intersections can be set within a certain range. The circumferential speed of the tip of the rotating body rod is 4 m/s to 7 m/s.
In order to change the crossing frequency within the range of s, the number of rods per stage on the inner wall of the cylindrical container and the rotating body was adjusted, and the dispersion efficiency and degree of bead wear were investigated. The magnetic mixed solution shown in the composition was used under the conditions that the peripheral speed of the tip of the rotary rod was 4 to 7 m/s, the bead filling rate was 75%, and the paint flow rate was 2 to 3 m/min. Add the mixed solution to the thickness every hour.
It was coated on a 25 μm polyester film to a thickness of about 8 μm using a hand coater, the gloss was measured, and after the gloss reached 100%, the mixed solution shown in the composition was added to the mixed solution and dispersion was performed again. . After redispersion, this mixed solution was applied to a thickness of 4 μm on a 10 μm thick polyester film, the surface was smoothed, the magnetic coating was cured, and the film was cut into 8 mm wide pieces and magnetically coated. Characteristics were evaluated. In the table, Hc is coercive force (Oe-Oersted), Bm is saturation magnetic flux density (Gauss), Br is residual magnetic flux density (Gauss), and Br/Bm is squareness ratio. Composition: Fe metal magnetic powder...2500 parts by weight Acrylic modified vinyl chloride vinyl acetate resin
...313 〃 Acrylic modified polyurethane resin ...208 〃 Acrylic modified urethane oligomer resin
...104 〃 Sorbitol-based dispersant ...250 〃 Methyl ethyl ketone ...3100 〃 Methyl isobutyl ketone ...630 〃 Cyclohexanone ...1260 〃 Toluene ...210 〃 Composition cyclohexanone ...1000 parts by weight Methyl isobutyl ketone ...500 〃 Toluene ... ...200 Butyl stearate ...130 Behenic acid ...380 The results are shown in Table-1, Table-2, Fig. 3, Fig. 4, and Fig. 5. Table 1 and Figure 3 show that the peripheral speed V ₁ of the rod tip is 4, 6 (Table 1), and 7 m/s, the ratio V ₁ /V ₂ of the peripheral speed V _{2 of the rod root to the peripheral speed V 1 of} the rod is 1.59, and the rotation speed.
375 rpm, and Table 2 and Figure 4 show cases where the rod tip peripheral speed V ₁ is 4, 6 (Table 2), and 7 m/s.
The ratio of V ₁ to the peripheral speed V ₂ of the rod root is V ₁ /V ₂
1.25, and the rotation speed is 300 rpm (however, only when the crossing frequency is 6.7×10 ⁴ is 350 rpm and the circumferential speed is 7 m/s).
In the former case, the crossover frequency is 2.9×10 ⁴ to 10.0
×10 ⁴ times/min, preferably 2.9 × 10 ⁴ to 9.7 × 10 ⁴
times/min, in the latter case said crossing frequency is between 0.9×10 ⁴ and 6.5×10 ^{4 times/min, preferably between 0.9×10 4 and 6.5×10 4 times} /min.
It can be seen that when the rate is 5.5×10 ⁴ times/min, the time to achieve 100% gloss is less than 200 minutes, and bead cracking and abrasion are sufficiently suppressed. The results of FIGS. 3 and 4 and Tables 1 and 2 are summarized as shown in FIG. 5. From this, the crossing frequency range between the two solid lines in FIG. 5 is optimal. From the above, generally the circumferential speed of the tip of the rotating body rod is
V ₁ is in the range of 4 m/s to 7 m/s, and the ratio V ₁ /V ₂ of the tip circumferential speed V ₁ to the circumferential speed V ₂ of the rotor rod base is determined by the rotation body rod and the cylindrical container. The crossing frequency per minute with the rod on the inner wall is (5.9×V ₁ /V ₂ −6.5)× ¹⁰⁴ or (10.3×V ₁ /V ₂
−6.4)×10 ⁴ (however, V ₁ /V ₂ must be 1.6 or less).

【table】

【table】

[Table] Therefore, by setting the crossing frequencies of the rods 5 of the cylindrical container 3 and the rotating body 4 as described above, it is possible to obtain a magnetic paint in a good dispersed state in a shorter time than conventionally. Although the foregoing has been described based on implementation, it should be noted that many modifications may be made within the invention.

[Brief explanation of drawings]

Figure 1 is a schematic structural diagram of a pin type mill. Figure 2 is the first
A schematic plan view of the pin-type mill shown in FIG. Figure 3 shows the ratio V ₁ /
2 is a graph showing the frequency of rod crossing versus bead abrasion and the frequency of rod crossing versus residence time until reaching 100% gloss when V ₂ is 1.5 or more. Figure 4 shows the ratio
Crossing frequency of rods vs. bead wear degree and crossing frequency of said rods vs. gloss 100 when V ₁ /V ₂ is less than 1.5
It is a graph showing the residence time until reaching %.
FIG. 5 is a graph summarizing the results of FIGS. 3 and 4, Table-1, and Table-2. The names of the main parts in the figure are as follows. 1: Pin-shaped mill, 3: Cylindrical container, 4: Rotating body,
5: Rod.

Claims (1)

[Scope of Claims] 1. A cylindrical container in which a plurality of rods protruding toward the center at regular intervals on the circumference are provided in multiple stages in the axial direction on the inner wall, and the rods are rotatable concentrically within the cylindrical container. A plurality of rotary rods are provided between each of the plurality of stages of the cylindrical container, and a plurality of rotary rods protrude in the radial direction at regular intervals on the circumference from the outer wall of the outer wall. Using a dispersing machine in which the rods of the cylindrical container and the rotating body intersect with each other in the direction of the rotational axis as the body rotates, the magnetic powder is mixed with a binder resin and a solvent using beads as a dispersion medium. In the method for producing magnetic paint by mixing and dispersing, the circumferential speed of the tip of the rotating body rod is
V ₁ is in the range of 4 m/s to 7 m/s, and the ratio V ₁ /V ₂ of the tip circumferential speed V 1 to the circumferential speed V ₂ of the rotor rod base is determined by the rotation body rod and _the inside of the cylindrical container. The frequency of intersection with the wall rod per minute is (5.9×V ₁ /V ₂ −6.5)× ¹⁰⁴ or (10.3×V ₁ /V ₂
−6.4) × 10 ⁴ , thereby increasing the dispersion efficiency of the magnetic paint. 2. The method for producing a magnetic paint according to item 1 above, wherein V ₁ /V ₂ is 1.5 or less.