JPH03281669A - Manufacture of magnetic coating material - Google Patents

Abstract

PURPOSE:To realize the constant feeding of a ferromagnetic powder into a kneader to thereby facilitate the preparation of a magnetic coating material which gives a magnetic recording medium of high quality by feeding a ferromagnetic powder into a grinder to grind the agglomerate in the powder and then into a kneader to knead with a binder resin and a solvent. CONSTITUTION:A magnetic coating material is prepared by a process comprising the first step of grinding the agglomerate in a ferromagnetic powder in a grinder and then feeding the ferromagnetic powder into a kneader and the second step of kneading the ferromagnetic powder with a binder resin and a solvent in the kneader. It is desirable that the ground ferromagnetic powder is fed into the kneader by using a device for constantly feeding the powder and that the relation between the accuracy R1 of the rate of flow from the grinder and the accuracy R2 of the flow rate through the device for constantly feeding the powder satisfies the equation: 0.05<=R2/R1<=1.0 (wherein the accuracy of flow rate is shown by the magnitude of variation in flow rate from a preset flow rate value).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing magnetic paint, and more specifically,
The present invention relates to a method for producing magnetic paint that allows ferromagnetic powder to be uniformly supplied to a paddle 1 and machine.

[Prior Art and Problems to be Solved by the Invention] A coated magnetic recording medium has a structure in which a single or multiple magnetic layers are laminated on a non-magnetic support, and the magnetic layer is strong in a binder resin. It is made by dispersing magnetic powder.

Therefore, forming the magnetic layer requires a step of mixing ferromagnetic powder with binder resin, solvent, etc. in a kneader.

Conventionally, when feeding ferromagnetic powder to a kneading machine, the ferromagnetic powder was first fed to a hopper of a powder quantitative feeder, and then fed from the feeder to the kneading machine.

However, in the past, ferromagnetic powder tends to form agglomerates in the hopper, which makes it difficult to feed ferromagnetic powder into a kneading machine in a fixed amount, even though it is a quantitative feeder.

Particularly when feeding a large amount of ferromagnetic powder at once, the ferromagnetic powder may form a bridge (bridge) at the exit of the hopper, and in addition to the above problem, even discharge from the hopper may not be smooth. Ta.

This phenomenon occurs especially in magnetite-type ferromagnetic powders with strong cohesive force (Fe"/Fe3" = 13 to 45%).
If it cannot be supplied quantitatively to the kneading machine, it will have an adverse effect on the quality of the magnetic recording medium (electromagnetic conversion characteristics, etc.), so a solution to this problem has been desired.

The present invention meets these demands.

That is, an object of the present invention is to provide a method for producing a magnetic coating material that can quantitatively supply ferromagnetic powder to a kneader.

[Means for Solving the Problems] The present invention for achieving the above objects includes a first step of pulverizing aggregates in ferromagnetic powder using a pulverizer and supplying the ferromagnetic powder to a kneader; This method of producing a magnetic paint is characterized by comprising a second step of kneading ferromagnetic powder together with a binder resin and a solvent in the kneader.

The present invention will be explained in detail below.

1. Grinding of aggregates in ferromagnetic powder (first step) - What is important in the present invention is 1. Before feeding the ferromagnetic powder to the kneader, the aggregates in the ferromagnetic powder must first be pulverized. It is.

Note that pulverization as used in the present invention means substantially separating the aggregate into particles.

The pulverization of the ferromagnetic powder in the present invention may be carried out before the ferromagnetic powder is supplied to the kneader, or may be carried out while the ferromagnetic powder is supplied to the kneader.

In any case, the following favorable conditions exist for this pulverization.

That is, the degree of compaction C (C
chemical engineering -Jan
18.1965 pages 163 to 168) is usually in the range of 10 to 40, preferably 15 to 25, and the degree of aggregation T is usually in the range of 0 to 55, preferably 0.
Grind the agglomerates in the ferromagnetic powder to a range of ~30.

<Compression degree C> C=]00 (P-A)/P where P: density (g/c 3) A: apparent density (g/c 3) degree of agglomeration T> See the table below. Select a sieve, apply vibration, and sieve 2 g of sample.

(Sieve opening) T = a + b + ri [%] Compression degree C] If it is less than 0, the powder may have extremely high jetting property or the powder may contain large lumps.
Moreover, if it exceeds 40, it is not preferable because it may cause clogging in the hopper or deteriorate the flow stability.

Furthermore, if the degree of agglomeration T exceeds 55, the number of irregular particles will increase, making it impossible to stably supply the powder, which is not preferable.

The crusher used in the present invention may be any type as long as it can effectively separate the aggregates of ferromagnetic powder into individual particles, and specifically, for example, a screw feeder, screw conveyor, Nauta mixer, etc. , crushers, etc. can be mentioned.

Furthermore, the degree of pulverization by the pulverizer is preferably one that passes through 14 to 24 meshes in terms of the number of meshes.

The ferromagnetic powder thus crushed is usually fed using a screw feeder, table feeder, rotary feeder,
The powder is supplied to the hopper of a powder quantitative feeder selected from a vibrating feeder, a belt feeder, etc., and from the same feeder to the hopper of a kneading machine.

Here, a preferable condition also exists between the flow rate accuracy R1 from the crusher and the flow rate accuracy R2 of the powder metering machine when supplying the crushed ferromagnetic powder to the powder metering machine (however, Flow rate accuracy is indicated by the amount of variation in flow rate relative to the set flow rate.)

That is, it is preferable that the flow rate accuracy R3 and the flow rate accuracy R2 satisfy the following formula.

0.05≦R2/R+≦1.0 Preferably 0.5≦Rt/Rh≦1.0 where R
If the l/R ratio is less than 0.05, the value of R+ will become too large and the hopper of the powder metering machine may become clogged with powder or become insufficient, and R+ may become too large.
/Ra exceeds 1.0, the flow rate of the feeder directly feeding the kneader will vary, and a stable paint may not be obtained.

Preparation of a magnetic paint (second step) - The pulverized ferromagnetic powder is sufficiently kneaded with a binder resin, a solvent, etc. using a kneader, thereby preparing a magnetic paint.

Examples of this kneading machine include a twin-screw continuous mixer (for example, NEX extruder, S-type KRC kneader, T-type KRC kneader, KRC-E-kneader, etc. manufactured by Awamoto Tekkosho Co., Ltd.), pressurized Kneader, two roll mill, Miki roll mill, ball mill, pebble mill, sight grinder, Sq
egvari attritor, high speed impeller disperser, high speed stone mill, high speed impact mill, disper kneader
1 High-speed mixer, homogenizer, ultrasonic disperser, etc.

According to the present invention, there are almost no aggregates in the ferromagnetic powder due to the pulverization process, and the ferromagnetic powder after the pulverization process hardly re-agglomerates, so that the ferromagnetic powder is quantitatively added to the kneader. Moreover, it can be supplied smoothly.

Therefore, the magnetic paint obtained from the above-mentioned kneading machine has a desired composition, and by coating and drying this magnetic paint on a non-supporting material, a high-quality magnetic recording medium with stable quality can be manufactured. It comes.

Next, the raw materials necessary to obtain the magnetic recording medium, ie, the ferromagnetic powder, binder resin solvent, etc., and the manufacturing method will be explained in more detail.

1 ferromagnetic powder 1 Examples of the ferromagnetic powder used in the present invention include C.

Contained y - Fe2O, powder, CO-containing Fe: +04 powder, Co-containing Fed, (4/3 < x < 3/2
) powder, or Fe- mixed metal powder, Fe-Ni metal powder, Fe-AIL-Ni metal powder, Fe-AM-
P metal powder, Fe-Ni-3i-An metal powder, Fe
-Ni-3i-^l-Mn metal powder, Ni-Co metal powder, Fe-In-Zn metal powder, Fe-Ni-Zn metal powder, Fe-Co-Ni-Cr metal powder, Fe-C
o-N1-P metal powder, Co-Ni metal powder and Co
-Fine ferromagnetic metal powder such as P metal powder, etc. can be mentioned.

These ferromagnetic powders can be used alone or in combination of two or more.

Among these, one particularly preferred for the purpose of the present invention is Co-containing iron oxide;

Among the contained iron oxides, a Co-containing iron oxide that satisfies the ratio of Fe2° to Fe34 (magnetite l-ratio) or the following formula % is preferable.

When the Fe24/Fe16 magnetite ratio is less than 13%, the output of the 4 ferromagnetic powder is insufficient, causing performance deterioration, and the surface resistivity increases, which increases static electricity, attracts dust, and increases Dlo.

Furthermore, if the FeRI/F,3N'' ratio exceeds 45%, the thermal stability of the magnetic properties deteriorates, and the electromagnetic conversion properties tend to deteriorate over time, which is not preferable.

The ferromagnetic powder has large saturation magnetization and coercive force Hc, and is excellent in high-density recording.

In addition, the ferromagnetic powder used in the present invention has a BET value of usually 25 m"/g or more, preferably 40 to 80 m"7g.
and particularly preferably 40 to fi1m'/g.

For example, if a ferromagnetic powder with a large surface area (BET value of 40 m"/g or more) is used, high-density recording is possible and the S/N is
It is possible to easily realize a magnetic recording medium with excellent ratios, etc.

The shape of the ferromagnetic powder is not particularly limited as long as it is fine, and for example, any shape such as an acicular trispherical shape or an ellipsoidal shape can be used.

Binder Resin As the binder resin contained in the magnetic layer, it is preferable to use a resin modified by introducing a functional group, particularly a modified vinyl chloride resin, a modified polyurethane resin, or a modified polyester resin.

Examples of the functional group include -3o3M, O8O□M
, -COOM and OM' / (The folding formula φM is a hydrogen atom or an alkali metal such as lithium or sodium, Ml and M2 are each a hydrogen atom, lithium, potassium, sodium, or an alkyl group, and Ml and M2 may be the same or different.) is preferred.

When the modified resin contains such a functional group, the compatibility between the modified resin and the ferromagnetic powder is improved, and the dispersibility of the ferromagnetic powder is further improved, and its aggregation is also prevented. The stability of the coating liquid is further improved, the frequency characteristics from high to low frequencies are improved in a well-balanced manner, and the durability of the magnetic recording medium is improved in addition to the electromagnetic conversion characteristics.

The modified resins can be used alone or in combination of two or more.

The modified resin is a vinyl chloride shelf, a polyurethane resin or a polyester resin, and a compound having a negative functional group and chlorine in the molecule, such as ell -CH, CH, S.
O3M, C Lee CLCH20SOJC1-C1l
, COO1lI, ov'C1-CH2-P
=00M2 (However, M, M', M2 have the same meanings as above.) It can be produced by condensing with a compound such as 00M2 (M, M', M2 have the same meanings as above) by a desalting butyrolysis reaction.

Note that thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, or mixtures thereof, which are conventionally known in the field of magnetic recording media, can be used.
Alternatively, these may be used in combination with the modified resin.

Examples of the thermoplastic resin include vinyl chloride-vinylacetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, and acrylic ester-vinylidene chloride copolymer. Polymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-phtadiene copolymer, polyamide superplastic, polyvinyl phthyral,
Cellulose derivative (cellulose acetate phthylate)
, cellulose tiacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.)
, styrene phtadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, and synthetic rubber-based thermoplastic resin.

These may be used alone or in combination.

Examples of the thermosetting resin or reactive resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reactive resin, high molecular weight polyester resin, and isocyanate prepolymer. mixtures of methacrylate copolymers and shiisocyanate brevolimers, urea-formaldehyde adhesives, and polyamine resins.

These may be used alone, or 24! The above may be used in combination.

Examples of the electron beam irradiation curable resin include unsaturated prepolymers such as maleic anhydride type, urethane acrylic type, epoxy acrylic type, polyester acrylic type, polyether acrylic type, polyurethane acrylic type, polyamide acrylic type; ether acrylic type; , urethane acrylic type, epoxy acrylic type, phosphoric acid ester acrylic type, asol type, and hydrocarbon type.

These may be used alone or in combination of 211 or more.

The blending amount of the binder resin in the magnetic layer is usually 1 to 200 parts by weight per 100 parts by weight of the ferromagnetic powder.
Preferably it is 1 to 50 parts by weight.

If the amount of binder resin blended is too high, the amount of ferromagnetic powder blended will be reduced, which may reduce the recording density of the magnetic recording medium, and if the blended amount is too small, the strength of the magnetic layer will be reduced. However, the running durability of the magnetic recording medium may be reduced.

Note that an aromatic or aliphatic polyisocyanate may be used as a curing agent in combination with the binder resin.

Examples of aromatic polyisocyanates include tolylene diisocyanate (TDI) and adducts of this with active hydrogen compounds, and have average molecular weights of 100 to 1,0.
A value in the range of 00 is preferable.

Examples of aliphatic polyisocyanates include hexamethylene diisocyanate (HMDI) and adducts of this with active hydrogen compounds, and have an average molecular weight of 10.
Those in the range of 0 to 3,000 are preferred, and non-alicyclic polyinsyanates and adducts of these with active hydrogen compounds are more preferred.

The amount of the aromatic or aliphatic polyisocyanate added is usually 1/20 to 1/20 by weight relative to the binder resin.
7/10. Preferably it is 1/10 to 1/2.

Other Components - In the magnetic recording medium, various additive components such as a lubricant, nonmagnetic abrasive particles, conductive powder, and surfactant can be contained in the magnetic layer as necessary.

Examples of the lubricant include silicone oil, graphite, molybdenum disulfide, and
About 0 monobasic fatty acids (for example.

Examples include fatty acid esters consisting of stearic acid) and a monohydric alcohol having about 3 to 26 carbon atoms.

Examples of the non-magnetic abrasive particles include alumina [
[alpha]-Al 203 (corundum), etc.], artificial corundum, fused alumina, silicon carbide, chromium oxide, tire cent, artificial diamond, garnet, emery (main components: corundum and magnetite). The content of the abrasive particles is preferably 20 parts by weight or less based on the 5 ferromagnetic powder, and the average particle size is 0.5B.
m or less, preferably 0.4 μm or less.

Incidentally, if the above-mentioned lubricant and non-magnetic abrasive particles are contained in the magnetic layer, the contact characteristics with the head (sliding performance, wear resistance, etc.) can be significantly improved.

Examples of the conductive powder include carbon black, graphite, silver powder, and nickel powder, and examples of the surfactant include natural, nonionic, anionic, and
Examples include cationic and amphoteric surfactants.

Appropriate inclusion of these conductive powders and surfactants, especially in the outermost magnetic layer, can effectively lower the surface electrical resistance, thereby reducing noise generation due to electrical charge discharge and dropouts due to dust adhesion. It is possible to prevent the occurrence.

- Magnetic support - Materials for forming the non-magnetic support include, for example, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, and cellulose derivatives such as cellulose triacetate and cellulose diacetate. ,polyamide,
Plastics such as polycarbonate, Cu, 1.2
Examples include metals such as n, glass, boron nitride, Si carbide, and ceramics.

The form of the non-magnetic support is not particularly limited, and main forms include tape, film, sheet, cart, disk, and drum.

There are no particular restrictions on the thickness of the non-magnetic support, but for example, in the case of a film or sheet, it is usually 3 to 100 μm,
The thickness is preferably 5 to 50 μm, approximately 30 μm to 10 mm in the case of a disk or card shape, and appropriately selected depending on the recorder etc. in the case of a drum shape.

Note that this nonmagnetic support may have a single layer structure or a multilayer structure.

Further, this non-magnetic support may be subjected to surface treatment such as corona discharge treatment.

1. Manufacture of magnetic recording media ~ As described above, a magnetic paint is prepared by cross-dispersing ferromagnetic powder in a binder resin, a solvent, etc. using the method of the present invention, and then this magnetic paint is applied to the surface of a non-magnetic support. .

Examples of the above solvent include acetone, methyl ethyl ketone (IIEK), methyl isobutyl ketone (MARK
), ketones such as cyclohexanone; alcohols such as methanol, ethanol, and propatool; esters such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol monoacetate:
Ethers such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; Aromatic hydrocarbons such as benzene, toluene, and xylene; methylene chlorite, ethylene chloride, carbon tetrachloride chloroform, ethylene chlorohydrin, dichlorobenzene, etc. halogenated hydrocarbons and the like can be used.

When preparing a magnetic paint, the ferromagnetic powder and other magnetic layer forming components are charged into a kneader simultaneously or individually.

For example, adding the ferromagnetic powder to a solution containing a dispersant,
After kneading for a predetermined time, the remaining components are added and kneading is continued to form a magnetic paint.

The coating method is preferably a wet-on-wet method or a wet-on-dry method, with the former being particularly preferred.

Compared to other coating methods, the wet-on-wet method can coat multiple layers at the same time, reducing coating time, and can be coated in almost the same process as a single layer. In addition, it has advantages over the wet-on-try method, such as better adhesion between the upper and lower layers.

Application methods for magnetic paint include, for example, extreme resin method, clavia coating method, knife coach ink method, wire bar coating method, doctor plate coating method, reverse roll coating method, dip coating method, air knife coating method, and calendar coach method. Examples include the ink method, the squeeze coating method, the kiss coach ink method, and the fantine coating method.

After a magnetic paint is applied to the surface of a non-magnetic support, the undried paint film is generally subjected to a magnetic field orientation treatment, and then a surface smoothing treatment is performed using a supercalendar roll or the like to achieve the desired shape. A magnetic recording medium can be obtained by cutting into shapes.

The thickness of the magnetic layer is not particularly limited in the present invention, and is usually 4 gm or less, preferably 3 μm or less.

[Example] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that in the following, "parts" indicate "parts by weight."

(Example 1) Raw material A Co-γFeO++ powder 100 parts (, Hc700, BET value 35, x = 1.46, F
e"/Fe"=10%) 100 parts α to 8, IO3......5 parts Carbon black...1 part Grind the above raw material A A mixed powder is prepared by supplying the mixed powder to a powder quantitative feeder A (screw feeder, manufactured by Maencinia Song Co., Ltd., with a flow rate accuracy of 10%, a Nauta mixer with a discharge function, manufactured by Hosokawa Micron Co., Ltd.). The accuracy is listed in Table 1) and feed it to a two-shaft continuous mixer (KEX extruder, manufactured by Kurimoto Iron Works Co., Ltd.). 8 parts of powder (manufactured by Zeon Co., Ltd.) was supplied using a powder metering supply 41B (flow rate accuracy 1%, screw feeder: manufactured by Kumaencinia Link Co., Ltd.) different from the above.

Raw material B Polyurethane resin with functional groups...7 parts (LIR8
700: Manufactured by Toyobo Co., Ltd.) Cyclohexanone...... Appropriate amount Methyl ethyl ketone...... Appropriate amount Toluene...
・・・・・・・・・A moderate amount again. The raw material B was supplied to the twin-screw continuous mixer.

In this way, each raw material was sufficiently kneaded in the two-wheel continuous mixer.

Raw IC Stearic acid・・・・・・・・・・・・o, 5 parts Myristic acid・・・・・・・・・ 0.5 parts Butyl stearate・・・・・・・・・], 0 parts cyclohexanone
......Appropriate amount of methyl ethyl ketone...
...Appropriate amount of toluene...Appropriate amount Next, take out the liquid mixed substance from the above twin-screw continuous mixer, add the above raw NC to this liquid mixed substance, and mix thoroughly. The mixture was mixed to obtain a magnetic paint with an appropriate viscosity.

Next, a polyisocyanate compound (AD
-30: manufactured by Mitsubishi Kasei Corporation) 5.0 parts, a magnetic paint was applied onto a polyethylene terephthalate film by an extrusion method, and subjected to a magnetic field orientation treatment.
After drying, a magnetic layer with a thickness of 3.0 μm was formed on the polyethylene terephthalate film.

Next, the polyethylene terephthalate film on which the magnetic layer was formed was slit into 1/2 inch diameter to obtain a magnetic tape.

The results of measuring the electromagnetic conversion characteristics of this magnetic tape are shown in Table 1, as well as the flow rate accuracy of the powder quantitative feeder A, the degree of clogging of the hopper, and the glossiness of the ferromagnetic powder after pulverization.

(Example 2) A magnetic tape was manufactured in the same manner as in Example 1, except that a screw feeder (flow rate accuracy of 5%) was used instead of the crusher of Example 1.

The measurement results of physical properties are shown in Table 1.

(Example 3) CO-γ-Fcd instead of the ferromagnetic powder of Example 1.

(X = 1.37, Fe''/Fc'' = 35%) A magnetic tape was manufactured in the same manner as in Example 1 except that powder was used.

The measurement results of physical properties are shown in Table 1.

(Comparative Example 1) A magnetic tape was manufactured in the same manner as in Example 1 except that the use of the crusher in Example 1 was omitted.

The measurement results of physical properties are shown in Table 1.

(Comparative Example 2) A magnetic tape was produced in the same manner as in Example 1, except that the use of the twin-screw continuous mixer in Example 1 was omitted and each raw material was kneaded using a stirrer.

The measurement results of physical properties are shown in Table 1.

No. 1 table *2 Comparison with standard tape (Comparative Example 2) [Effect of the invention]

Claims (1)

[Scope of Claims] (1) A first step of pulverizing the aggregates in the ferromagnetic powder using a pulverizer and supplying the ferromagnetic powder to a kneader; A method for producing a magnetic paint, the method comprising: a second step of kneading the magnetic paint. (2) The method for producing a magnetic paint according to claim 1, wherein the ferromagnetic powder is supplied to the kneader using a powder metering machine. (3) The method for manufacturing a magnetic paint according to claim 2, wherein the flow rate accuracy R_1 from the crusher and the flow rate accuracy R_2 of the powder metering machine satisfy the following formula. 0.05≦R_2/R_1≦1.0 (However, flow rate accuracy is indicated by the amount of variation in flow rate with respect to the set flow rate.) (4) The ferromagnetic powder is Co-containing iron oxide, and this iron oxide contains 4. The method for producing a magnetic paint according to claim 1, wherein the ratio of Fe^2^+ and Fe^3^+ (magnetite ratio) satisfies the following formula. 13%≦Fe^2^+/Fe^3^+≦45%