JPH04182931A - Production of magnetic recording medium and kneading device - Google Patents

Abstract

PURPOSE:To allow a stable operation with good feed so as to avoid exerting overload on a driving rotor while assisting shearing with sufficient kneading by executing continuous kneading under the respective specific conditions of the total length of total kneading paddles and the length of a screw or paddle which makes backward feed operation. CONSTITUTION:The lengths of the respective transporting screws 4, 10 and the lengths of the kneading paddles 13, 14 (the lengths along the central axis of a kneading machine or a revolving shaft 12) are respectively designated as l1, l2 and l3 and n1, n2 and l1+l2+l3+n1+n2=100. The total length n1+n2=N of the lengths n1 and n2 of the respective kneading paddles 13 and 14 and the length R of the transporting screw 10a to make the backward feed operation are expressed by equation I. The kneading is executed continuously under the conditions. The stable operation is possible with the good feed in a manner as to avoid the exertion of the overload to the driving motor while the kneading is assisted with the sufficient shearing.

Description

Detailed Description of the Invention B. Field of Industrial Application: Prior Art Magnetic recording media usually contain magnetic powder, antistatic agent, abrasive, binder resin, etc. on a support such as a polyester film. Manufactured by applying magnetic paint and drying it.

When manufacturing this magnetic recording medium, magnetic powder is dispersed in a solvent solution of binder resin using a dispersing machine such as a ball mill or a sand grinder in order to quickly finish the magnetic paint into a paint with good dispersibility. Previously, a series of steps have been known in which magnetic powder and a small amount of binder resin solution are kneaded using a powerful kneader such as a kneader.

In addition, regarding the manufacturing equipment that performs cross-dispersion when preparing magnetic paint and its operating conditions, there is a method of operating a kneading machine under a specific shear stress (the kneading machine uses a kneader) or a method of operating a dispersing machine under specific conditions. Techniques for increasing dispersibility and RF specific output are known.

Regarding the above-mentioned kneading method, please refer to JP-A Nos. 46-3030, 48-1.0450, 49-14537, 53-9102, 53-76012, and 55-25.
It is described in No. 406 and No. 57-141026.

With the recent improvement in the recording density of magnetic recording media, magnetic powders with smaller particle sizes and larger specific surface areas are used. However, dispersion of particles becomes extremely difficult as the particle size becomes smaller.

In order to solve this problem, it is known to knead magnetic powder and a binder in a highly concentrated state using a continuous twin-screw kneader while applying high shear force. As a conventional technique for manufacturing a magnetic recording medium using a continuous twin-screw kneader, there is
-41274, 64-79274, 64-79
No. 275, JP-A-2-107674, etc.

However, in reality, the shearing force applied to the kneaded material is limited compared to the continuous twin-screw kneading described above.

Therefore, depending on external factors (intermixing conditions), sufficient shearing force may not be applied to the kneaded material, resulting in insufficient dispersion.

C1. Purpose of the Invention The purpose of the present invention is to provide a method and apparatus for reliably applying a high shearing force to obtain a highly dispersed magnetic coating material in continuous kneading such as a twin-screw kneading machine. be.

29 Structure of the Invention That is, the present invention provides that when a magnetic paint is prepared through a step of supplying a powder raw material and a liquid raw material to a continuous kneading machine and performing kneading, all of the parts of the continuous kneading machine are When the total length of the conveying screw and all the kneading paddles (the length in the direction along the central axis of the continuous kneading machine is equal to or less than 2) is 100, the total length of all the kneading paddles N, the reverse feed The present invention relates to a method for producing a magnetic recording medium, in which kneading is performed continuously under conditions in which the length R of a moving screw or paddle is 30≦N≦80 and 0≦R≦15.

Further, in the present invention, in order to continuously knead powder raw materials and liquid raw materials, a conveying screw and a kneading paddle are arranged, and the total length of all conveying screws and all kneading paddles (the total length of this kneading device) When the length in the direction along the central axis is 100, the total length N of all kneading paddles and the length R of the screw or paddle that moves in reverse are 30≦N≦80, respectively. The present invention also provides a continuous kneading device in which 0≦R≦15.

E, Example The present invention will be explained in detail below.

1 to 5 show the apparatus used to carry out the method according to this embodiment.

First, regarding Figures 1 to 4, we will explain the continuous twin-screw kneader used in this example (KEXN manufactured by Kurimoto Iron Works Co., Ltd.).
30) will be explained.

In this continuous twin-screw kneading machine 1, powder 3 such as magnetic powder charged from a powder inlet 2 is transferred to a screw-type conveying means 4.
The mixture is sent to the kneading section 5, where it is fully kneaded under the action of shearing force with the binder solution 7 simultaneously supplied from the liquid inlet 6, and further together with the binder solution or organic solvent 9 from the liquid inlet 8. It is sent to a kneading and diluting section 11 by a screw-type conveying means 10. Here, if there are several types of powder to be introduced, they are mixed uniformly using a mixer such as a ■-type cone mixer or a W-type cone mixer, and then the powder is mixed uniformly using a powder metering device (screw feeder, rotary feeder, vibrating feeder, belt feeder, etc.). feeders, etc.) in a fixed amount. As shown in FIG. 2, two parallel rotating shafts 12A,
For the 12th, the above 1 sending means 4.1o is 4A and 4B
, 10A and 10B, respectively, and
In particular, in the kneading section 5 and the kneading/diluting section 11, sufficient shearing force is applied to the material to be kneaded by the paddles 13A, which are rotatable in the same direction, and the kneading members 13, 14, which are a combination of the 13th, 14A, and 14th. It is configured. As shown in FIG. 4, a pair of paddles 13A and 13B (or 14A and 14) are provided at different angles from each other, and the tip of one paddle always rotates so as to rub the other paddle. The shear forces mentioned above are generated. Regarding the arrangement of the paddles, as shown in Fig. 3, the angles of the front and rear paddles are shifted by 30 to 90 degrees in the axial direction of a common rotation axis, and the angle between the left and right paddles is always 90 degrees. The degree phase can be shifted. In addition, various other arrangements of the paddles are possible. Further, the kneading section 5 (or the kneading and diluting section 11 in some cases) is made up of a combination of a plurality of unit barrels 15, and the outer wall of each barrel is
It has a double structure with a cold and hot water channel 19 between an inner wall 17 and an outer wall 18 for passing cold and hot water 16. 2 in the diagram
0 is a cold and hot water inlet, and 21 is a cold and hot water outlet, which are provided in each barrel 15, but the cold and hot water channels 19 are blocked between each barrel by a partition wall (not shown).

In addition, the kneaded product 24 obtained with the above-mentioned continuous twin-screw kneader 1
As shown in FIG. 5, the solution is introduced into a dilution/dispersion machine 25 equipped with stirring blades 30, and diluted by the addition of an organic solvent 26.

After that, the diluted dispersion liquid 27 is passed through a dispersion machine 2 equipped with a stirring plate 31.
8, where it is subjected to dispersion treatment, and if necessary, a curing agent,
A lubricant, an organic solvent, etc. are added to the magnetic paint 29, which is sent to a coating section (not shown). Devices used for dilution and dispersion include daysilver, flow jet mixer, line flow, and the like. As the above-mentioned dispersing machine 28, a ball mill, a sand mill, etc. can be used. When using a sand mill, glass, alumina, zirconia, etc. can be used as a dispersion medium, and zirconia is preferable from the viewpoint of improving dispersibility. After the disperser 28, it is preferable to guide the material through a filter to the application means. The subsequent steps (coating, orientation, drying, calendering) are carried out in the usual manner, so their explanation will be omitted. Examples of coating means include a gravure roll coater, a reverse roll coater, and an extrusion coater.

The continuous twin-screw kneader 1 constructed as described above is constructed and operated as follows based on the present invention.

That is, the kneading machine 1 is provided with a conveying screw 4 on the inlet side, a conveying screw 10 between the kneading section 5 and the kneading dilution section 11, and a conveying screw 34 on the exit side. As for the conveying screw 10, the part 10a of the screw immediately after the kneading section 5 makes a backward feeding movement, and the other screw part 10b makes a feeding movement in the forward direction. Configure it as follows. Further, the kneading paddle of the kneading section 5 has three types of blocks 13a+, 1113a-113 from the upstream side to the downstream side.
a3, block 13a.

is the paddle in FIG. 3(A), block 13a2 is the paddle in FIG. 3(B), and block 13a3 is the third block 1.
Block 1 is divided into 4a+, 14az, and 14a3.
4a is the paddle in FIG. 3(B), block 14a2 is the paddle in FIG. 3(C), and block 14a3 is the paddle in FIG. 3(D).
) consists of a paddle. Here, in Figure 3,
Paddle (A) has a large feeding force, paddle (B) has a smaller feeding force than (A), paddle (C) has good feeding force and kneading force, and paddle (D) has a good kneading force. The combination of these (A) to (D) produces the desired feeding and kneading movements. Generally, e is selected so that the angle between the paddles gradually increases from the upstream side to the downstream side (the above combination is an example).
The combination is arbitrary. In the above, the reason why the paddle shown in FIG. 3(A) is used in the kneading section 5 is to generate sufficient feeding force, and the paddle shown in FIG.
) is not used in order to avoid insufficient shearing force (kneading force).

In the above, according to the invention, each conveying screw 4.
Lengths of 10 and 34 and lengths of kneading paddles 13 and 14 (lengths along the central axis or rotating shaft 12 of the kneader: the same hereinafter)
2 respectively. ．． 2. as well as! .

and n + , n z , ff, +1. -me3+
When n, +nz = 100, each kneading paddle 13
and the length n of 14, and the total length n of n2, +n2=N,
It has been found that it is extremely important to continuously cross-wire under the following conditions: 30≦N≦80 and 0≦R≦15, regarding the length R of the conveying screw foa that moves in reverse. That is, the total length N of the kneading valve I
If it is less than 30, the kneading will be insufficient, and if it exceeds 80, the kneading will be sufficient, but the paddle drive motor will be overloaded and the process will become unstable. Due to the length R of the reverse conveyance screw 10a, shearing is insufficient, and if it exceeds 15, the return force is too large and the load on the drive motor becomes excessive due to the large pressing force. In addition, N and R are further N
=35-70, R=O-12 is preferable, N=40-6
0 and R=0 to 8 are more preferable.

In this way, only by specifying N and R within the range disclosed in the present invention, it is possible to sufficiently knead and promote shearing, while also ensuring stable operation with good feed and no overload on the drive motor. It becomes.

Further, since the reverse feeding screw 10a is located immediately after the kneading section 5, kneading can be performed while returning the material to the kneading section, and therefore sufficient shearing can be performed. Such a screw 10a applies pressure in the opposite direction to the kneaded material, resulting in a pressurized state. Also, this is the kneading paddle 1
Since it is located immediately after 3a3, the pressurized kneaded material is kneaded, and a high shearing force is applied. Furthermore, the position where the screw 10a is provided is such that the solid content of the kneaded material is 70% by weight or more (70 parts by weight or more based on 100 parts of the kneaded material) (or more preferably 90% by weight). It is recommended that the position be as follows. At such a position, the kneaded material becomes relatively hard, and when kneaded under pressure as described above, when diluted and dispersed with a sand mill, etc., a highly dispersed magnetic paint is obtained. The magnetic recording medium obtained by this method exhibits excellent magnetic properties and electromagnetic conversion properties.

In the above method, the magnetic powder to be added is, for example, 7-Fe,03, Co-containing 7-FezO,, Co
Adhering T FezO3, Fe3O4, Co-containing Fe,,
There are oxide magnetic powders such as 04, Co-coated Fe, 04, Cry, etc. Further, metal magnetic powder may also be used, or may be used in combination with oxide magnetic powder. Usable metal magnetic powders include Fe, Ni, Co, and Fe-Al! , system, F
e-Affi-Ni system, Fe-Al-Co system, Fe-A
/! -Zn series, Fe-Al-Ca series, Fe-Ni-Co
system, Fe-Mn-Zn system, Fe-Ni system, Fe-N1-
Al2 series, Fe-Ni-Zn series, Fe-Co-Ni-C
r system, Fe-Co-N1-P system, Co-Ni system, Fe,
Examples include ferromagnetic powders such as metal magnetic powders containing Ni, Co, etc. as main components. Among them, Fe-based metal magnetic powders containing 80 atm% or more of Fe have excellent electrical properties, and are particularly suitable for Fe-Al, Fe-Al2-Ni, Fe-
Af-Zn, Fe-Af-Co, Fe-Ni, Fe-N
i-Al and Fe-Ni-Zn based metal magnetic powders are preferred. As additives for these metal magnetic materials, Si
, Cu, Zn, Aj! , P, Mn, Cr, or a compound thereof. Hexagonal ferrite such as barium ferrite and iron nitride are also used.

Examples of the binder (binder resin) include urethane resin, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer. Polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, various synthetic rubbers, phenol resins, epoxy resins, urea resins, melamine resins, phenoxy resins, silicone resins, acrylic reactive resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/high Examples include mixtures of molecular weight diols/isocyanates and mixtures thereof.

At least one endogenous component of the above-mentioned resin includes SOxM,
Hydrophilic polar group (negative functional group) represented by C00M, PO(OM')z (where M and M' are hydrogen, alkali metals such as lithium, potassium, and sodium, or substituted or unsubstituted hydrocarbon residues) It is preferable to use a resin containing . The metal of the salts, such as sulfonic acids, carboxylic acids or phosphoric acids, is an alkali metal (especially sodium, potassium, lithium). The amount of the modified group (polar group) introduced is 0.0
It is preferably 1 to 1.0+u+o i,/g, more preferably 0.1 to 0.5a+a+o j2
/g range. The above polar group introduction amount is 1.0+am
If ol/g is exceeded, intermolecular or intramolecular aggregation tends to occur, which not only adversely affects dispersibility but also causes selectivity to the solvent, which may make it impossible to use ordinary general-purpose solvents. The above polar group introduction amount is 0.0
If it is less than 1 mmol/g, a sufficient effect in dispersing the ferromagnetic powder will not be recognized.

In particular, it is preferable to use at least a urethane resin, and it is also preferable to use a vinyl chloride copolymer, an epoxy resin (especially a phenoxy resin), a polyester resin, or a nitrocellulose resin (hereinafter referred to as other resins). good.

In this case, the blending ratio of the urethane resin and the other resin is 90 to 10 parts by weight, more preferably 80 to 10 parts by weight.
Preferably, the amount is 20 parts by weight. If the above-mentioned blending ratio exceeds 90 parts by weight, the coating film becomes too brittle and the durability of the coating film is significantly deteriorated, and the adhesion to the support also deteriorates. Moreover, if the above-mentioned blending ratio is less than 10 parts by weight, the magnetic powder tends to fall off.

Furthermore, in the present invention, durability can be improved by further adding a polyisocyanate curing agent to the magnetic paint containing the binder resin.

In addition to the above-mentioned magnetic powder and binder resin, various additives may be added at any step, and fatty acids and/or fatty acid esters such as myristic acid and butyl stearate may be added as three lubricants. As a result, while demonstrating the respective features of both, it offsets the defects that occur when used alone, improves the lubrication effect, and improves the durability of still images.
Running stability, S/N ratio, etc. can be improved. In addition to fatty acids and fatty acid esters, other lubricants (for example, silicone oil, carboxylic acid modification, ester modification, etc.) may be added. Furthermore, in addition to the above-mentioned lubricants, known abrasives (for example, alumina), antistatic agents (for example, carbon black), etc. may also be added.

When each of the above-mentioned additive substances is added at the time of mixed dilution or dilution, it is preferable to use substances dispersed in a separate process.

Usable solvents include ketones (e.g. methyl ethyl ketone), ethers (e.g. diethyl ether),
Examples include esters (for example, ethyl acetate), aromatic solvents (for example, toluene), and these can be used alone or in combination.

Next, the method and apparatus according to the present embodiment will be explained in more detail using a specific example. In addition, in the following, "parts" indicate parts by weight.

The above powder composition is mixed in a powder mixer, and a constant feeder is used to mix the powder in a two-shaft continuous kneading mixer (EX
(manufactured by Kurimoto Iron Works) as shown in Figure 1 (3).

The above binder solution was supplied to a two-screw continuous kneading mixer as 7 in FIG. 1 at the same time as the powder.

The above binder solution was supplied as 9 in FIG. 1 to a twin-screw continuous kneading mixer during kneading and dilution. The paddle pattern of the kneader used is shown in Table 1 below.

The following raw materials were added to the above-mentioned kneaded and diluted solution, diluted to an appropriate viscosity, and then dispersed using a daysilver, sand mill, etc.

Methyl ethyl ketone toluene
5.0 parts by weight of a polyisocyanate compound was added to an appropriate amount of the above magnetic paint, and the mixture was coated, oriented, and dried on a polyethylene terephthalate base.
It was cut into widths and made into magnetic tape.

Actual 1, Part 1, E-J, 6-1.8.9-, -, -1 Precept Example-1 C-a-y-FeOx x = 1.378ET
= 30m2/g, compression degree changed to -30, Example-1
A corresponding magnetic tape was obtained in the same manner except that 5 parts of carbon black was used, and the paddle pattern was changed as shown in Table 1 below.

This ""1-1.2.3.4, x of Cor-F e Ox in Example-1 = 1.3
78ET = 30a+2/g, compression degree -30, change to 5 parts carbon black, paddle pattern as shown in Table 1 below.
A corresponding magnetic tape was obtained in the following manner.

Disaster Ensho 1 In Example-1, a reverse paddle (
A magnetic tape was obtained in the same manner by placing a kneading paddle (which moves in the opposite direction) in the same position. The paddle patterns used are shown in Table 2 below.

x of 06-7-FeOx in Example-11 = 1.37, B
A corresponding magnetic tape was obtained in the same manner except that ET = 3On+2/g, compression degree = 30, and 5 parts of the carbon blank of Example = 11 was used, and the paddle pattern was changed as shown in Table 2 below. .

-, 8, 9, 1 x = 1.37, B of C6-T-FeOX of Example-11
ET=30+”/g, degree of compression=30, carbon bray:
A corresponding magnetic tape was obtained by changing the number of z-rips to 5 parts and changing the paddle pattern as shown in Table 2 below.

Table 1 In the table, "actual" indicates an example and "ratio" indicates a comparative example, and the total was 100.

Table 2 The following measurements were performed on each sample or tape obtained above, and the results are shown in Table 3 below.

<Torque current value> If the current value consumed when driving the paddle drive motor of the KEXN-30 extruder manufactured by Kurimoto Iron Works Co., Ltd. is the same as the no-load state (dry operation), then the no-load current value + 1 to 2 A. And underwater, it was bigger than that.

<Glossiness after dispersion> Collect the paint downstream of the sand mill outlet, apply it on the hearth, dry it, then measure the glossiness of the coated layer surface at an angle of incidence of 60° perpendicular to the coating direction. Displayed based on the standard plate.

<Bm> A known measuring device (V manufactured by Toei Kogyo Co., Ltd.)
Measured with SM-II [).

<RF Output> The output during playback using a 100% white signal was compared with the tape of Example 19 as a reference.

From this result, by carrying out crosstalk under the conditions disclosed in the present invention, sufficient and uniform kneading and dilution can be performed, and the electromagnetic conversion characteristics of the medium can be greatly improved.

The embodiments described above can be modified in various ways based on the technical idea of the present invention.

For example, the above-mentioned continuous twin-screw kneader is
The kneader described in No. 1274 (no kneading/dilution section) may be used, or a single-screw kneader may be used.

A continuous twin-screw kneader may be followed by a dilution kneader. The configuration of the continuous twin-screw kneader may be varied in various ways; for example, the shape and arrangement of the paddles are not limited to those described above.

Effects of the Invention As described above, in the present invention, the total length N of all the kneading paddles and the length R of the reverse feed screw or paddle are set to N=30 with respect to the total length of all the conveying screws and the kneading paddles 100. ~8
0. Since R=0 to 15, it is possible to sufficiently knead and promote shearing, while also ensuring good feeding and stable operation without overloading the drive motor.

[Brief explanation of drawings]

The drawings illustrate the present invention; Fig. 1 is a schematic cross-sectional view of a continuous twin-screw kneader used for manufacturing magnetic recording media, and Fig. 2 is a schematic cross-sectional view of the same kneader. Figures 3 (A), (B), (C), and (D) are front views of various kneading paddles, Figure 4 is a cross-sectional perspective view of a portion of the kneading machine, and Figure 5 is the magnetic paint. 1 is a schematic flow diagram showing the main steps for the preparation of In addition, in the symbols shown in the drawings, 1...... Continuous twin-screw kneader -der) 2.
......Powder inlet 3...Powder 4.10.34...Screw type conveyance means 5... Kneading section 6.8 Inlet a Binder solution 9 Binder solution or organic solvent 10a
・・・・・・Screw 11 that moves in reverse.
......Kneading and diluting section 12.12A, 12B...Rotating shaft 13.
13A, 13th, 14.14A, 14B...
...Kneading paddle 13a+, 13az, 13az, 14a+, 14az, 14a3, ......Kneading paddle block 15...
... Barrel 24 ... Kneaded material 25 ... Dilution and dispersion machine 28 ... Dispersion machine. Agent Patent Attorney Hiroshi Osaka 3 (A) ('B) 30° Koto (Komo LN! Sai U Mi Pad) 45
°5 strain; Kei 8 miz Toyuo L7j pa self-send force tree 2) 6♂ 1 bowl p≦i machine desk paddle 9♂5°
1 gotu included, and the two Shiba Senzoku met in a white manner) (Onwar Nakashaku)

Claims (1)

[Claims] 1. When preparing a magnetic paint through a step of supplying powder raw materials and liquid raw materials to a continuous kneading machine and kneading them, all conveyance screws and all kneading paddles of the continuous kneading machine are used. (The length in the direction along the central axis of the continuous kneading machine:
same as below. ) is 100, and the total length N of all kneading paddles and the length R of the screw or paddle that moves in reverse are 30≦N≦80 and 0≦R≦15, respectively. A method for manufacturing a magnetic recording medium that involves kneading. 2. To continuously knead powder raw materials and liquid raw materials,
When a conveying screw and a kneading paddle are arranged, and the total length of all conveying screws and all kneading paddles (the length in the direction along the central axis of this kneading device: the same applies hereinafter) is 100, the total kneading A continuous kneading device in which the total length N of the paddles and the length R of the screw or paddle that moves in reverse are 30≦N≦80 and 0≦R≦15, respectively.