JPS58155703A - Preparation of magnetic recording substance - Google Patents

Abstract

PURPOSE:To improve the dispersibility of a magnetic recording substance by such an arrangement wherein ferromagnetic fine powders are treated by a silane coupling agent containing amino groups or epoxy groups and then further treated by a specific organic oligomer which reacts with reactive residues and after that it is coated together with an organic binder on a substrate. CONSTITUTION:Ferromagnetic fine powders are primary treated by such a method that they are poured into a solution of silane coupling agent containing amino groups or epoxy groups, mixed by stirring, water is removed by filtering, dried and then pulverized again. Next, the primary treated substance is secondary treated by such a method that said primary treated substance is caused to suspend in a solution of methyl isobutyl ketone (MIBK) in a flask equipped with a cooling reflux tube, and an organic oligomer is added and heated while being stirred, and after the mixture is cooled off, MIBK is filtered. Said organic oligomer is to be selected from groups composed of a copolymer of which molecular weight is 500-8,000 of olefine of which number of carbon is 4-30 and maleic anhydride or its hydrolytic substance and maleic polybutadiene of which molecular weight is 500-8,000. The dispersibility of the magnetic recording substance can be improved by coating the substance thus treated together with organic binder on a substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing a one-shot recorder. More specifically, in the production of magnetic recording media such as magnetic recording and reproducing magnetic tapes and a-air disks, the dispersibility of gIi magnetic fine powder is improved to make it easier to turn magnetic paints into paints, and coating properties are improved.
The present invention relates to a method for manufacturing a magnetic recording medium with improved workability and improved magnetic properties.

A high degree of dispersion is required for the magnetic powder in an all-at-once recording medium such as a magnetic tape or an a-air disk. The magnetic film that serves as a recording medium is formed by uniformly coating a magnetic paint onto a plastic film or sheet substrate, drying it, and then giving the magnetic layer a mirror finish. - Unless the am particles are removed, a uniform and smooth a layer cannot be formed. Non-uniformity in the magnetic layer due to agglomerated particles of magnetic powder such as grains has a serious adverse effect on the electromagnetic conversion characteristics and XA1 characteristics of the magnetic tape.

In other words, it causes a decrease in output, an increase in noise, dropouts, etc. In addition, if the magnetic powder in the paint is poorly dispersed, the physical properties of the paint film will be poor, and the durability will be poor.Furthermore, the orientation of the magnetic powder, which is required for audio tapes and VTR tapes, will be insufficient and the magnetic properties will be poor. becomes.

As described above, dispersion of magnetic powder in magnetic paint is very important for improving the performance of magnetic recording media. Therefore, the improvement of the dispersibility of magnetic powder has been studied from various viewpoints, and it has been proposed to improve the dispersibility by adding an appropriate surfactant to the magnetic paint formulation. Examples of such surfactants include those using alkylimidacillin compounds (% opening 54-!52iS04) and those using alkyl polyoxyethylene phosphates neutralized with alkyladenone (4I Kaisho 5!). $-78810).

Uses amines and their I conductors, phosphoric esters, polyoxyethylene phosphoric esters, etc., such as those using long-chain alkyl phosphoric esters (411 1975-147507.41 Application No. 5 N-4961). I often do this. There is a proposal that dispersibility can be improved by surface-treating the a-type powder and then turning it into a paint.
4508, 54-49769), treatment of metal powder with a titanium coupling agent to improve dispersion stability and prevent the deterioration of magnetic coatings over time (JP-A-56-88471), rich functional groups reactive with binders. (49 Kaisho 54-7iS10), coating with a reaction product of an aminofunctional silane coupling agent, an isocyanate compound, and an epoxy compound (% opening 56-145555) and so on.

Many methods have been proposed for selecting and using binders that are advantageous in improving the dispersibility of magnetic powder.
As a step, knead only the inder, which is advantageous for dispersion, or add an appropriate surfactant to it, and then add a binder, which is disadvantageous to dispersion but has excellent properties as a magnetic coating, and knead for a short time. A method for producing a paint with good dispersibility has also been proposed.In many cases, the binders that are considered to be advantageous for dispersing magnetic powder are nitrified cotton and vinyl chloride-vinyl acetate copolymer.

Polyvinyl butyral, polyvinyl formal, etc., and binders that are considered disadvantageous for dispersion are polyurethane resin and phenol resin.

It is an epoxy resin. However, even with the binders mentioned here that are advantageous for dispersion, the dispersibility of magnetic powder is not necessarily satisfactory. It must have excellent properties, and cannot be selected based solely on the quality of dispersibility.

Although much research has been carried out on improving the dispersibility of magnetic paints, KFi has not yet reached the stage of satisfactory improvement. and crosstalk time.

There is a need to improve the storage stability of paints, 1111 properties, coating film properties, etc. by improving the order of addition of paint constituents, etc. On the other hand, magnetic recording media such as magnetic tapes and magnetic disks The magnetic powder used for high-density recording.

In order to reduce noise and improve acoustic properties in the high frequency range, it has become necessary to use particles with smaller particle sizes and larger coercive force. iron oxide.

It is necessary to use metal powders with a size of 0.3μ or smaller, but as the particle size of magnetic powders decreases, the surface area increases, so Dispersion of particles becomes difficult. Also,
Magnetic powder is more difficult to disperse than ordinary powder due to interparticle interaction (attractive force) due to magnetic moment. Since the dispersibility of the magnetic powder is insufficient, selecting only the currently developed binder that is advantageous for dispersion at the expense of the physical properties of the magnetic coating film will have a terrible effect on the durability of tapes, etc., and is therefore impractical.

In addition, the dispersion ability of surfactants, which have been proposed to improve the dispersibility of magnetic paints, is excellent when dissolved in an organic solvent and mixed with magnetic powder. If a paint system is created by adding a binder such as a polyurethane resin to the dispersion system, which is essential for improving the coating properties, the dispersibility deteriorates and agglomeration occurs. The dispersibility of dispersed magnetic powder is more or less affected by the presence of a binder in the solvent. When polyurethane resin and vinyl chloride vinyl acetate copolymer resin, which are essential binders for the necessary physical properties of magnetic coatings such as flexibility and abrasion resistance, coexist, 11 has exceptional dispersibility ( Deterioration 0 This is because the surfactant is adsorbed to the surface of the magnetic powder, lowering the interfacial energy at the magnetic powder-solvent interface and stabilizing the dispersion, but when a binder coexists, the interfacial energy increases again and the dispersibility deteriorates. It is conceivable that either the deterioration or the aggregation effect caused by K, such as interparticle crosslinking of the binder, occurs at tt where the interfacial energy is low.

The inventors investigated the amount of surfactant adsorbed to the magnetic powder surface in the coexistence of a binder in order to understand one factor behind the agglomeration effect of the binder. Surprisingly, it has been found that certain surfactant-binder combinations that significantly reduce the amount of adsorption can be reduced to zero. Based on this fact, the present inventors have conducted extensive research into the structure of the surface coating layer necessary for the best dispersion of ferromagnetic powder particles in the paint system without being desorbed from the magnetic powder surface in the presence of any binder. As a result, the present invention has been completed.

That is, in the present invention, a ferromagnetic fine powder is treated with a silane coupling agent, then treated with an organic oligomer compound having a molecular weight of 500 to 8,000 that can react with the reactive residue of the silane coupling agent, and then applied to a substrate together with an organic binder. The present invention provides a method for manufacturing a magnetic recording medium, characterized in that the magnetic recording medium is coated on top of the magnetic recording medium.

Examples of the silane coupling agent used in the present invention include H2N02H4NEC, H681[)OH,
), .

Silane coupling agent containing amino groups.

5) Epoxy group-containing silane coupling agents such as 5 can be mentioned.

The treatment of these silane coupling agents on the surface of the ferromagnetic powder can be carried out by dissolving the silane coupling agent in water or an organic solvent, adding the ferromagnetic powder, stirring and mixing, separating the P, and heating and drying. Another treatment method is to directly spray coat the ferromagnetic powder with a silane coupling agent solution in a fluidized bed apparatus or a powder stirrer such as a Henschel mixer, and then heat and dry it. As a result, the alkoxy group of the silane coupling agent is hydrolyzed on the surface of the ferromagnetic fine powder, and the silane coupling agent is fixed.

The amount of the silane coupling agent used is 0.1 to 10, preferably 0.2 to 2, in weight ratio to the ferromagnetic powder.

The ferromagnetic powder treated with Kamiayu's method is then treated with an organic oligomeric compound that reacts with the reactive residues of the silane coupling agent.

These organic oligomer compounds have a functional group that reacts with a reactive residue of a silane coupling agent, such as a 72 group or an epoxy group, and have a molecular weight of 500 to 800.
0, preferably in the range of 1000 to 5000. When the molecular weight is less than 500, the dispersing effect is insufficient, and when it exceeds 8,000, the dispersing effect is also reduced.

Such organic oligomer compounds include leg prime numbers of 4 to
! Examples include copolymers of 50° olefin and maleic anhydride or hydrolysates thereof, maleated olefins such as maleated liquid polybutadiene, maleated boiled oil, and the like.

Among them, a copolymer of olefin having a leg prime number of 4 to 50 and maleic anhydride or a hydrolyzate thereof.

Maleated polyolefins are preferred. here.

Olefins include linear and branched aliphatic olefins, olefins with aromatic rings such as styrene,
Includes any cycloaliphatic olefins such as cyclohexene.

The amount of these oligomers that react with the reactive silane coupling agent residues on the surface of the ferromagnetic powder should ideally be such that the amount of oligomers that have a molar equivalent amount of reactive groups as the silane coupling agent residues is used. However, in reality, stoichiometric reactions do not necessarily occur, so it is necessary to use more than the theoretical amount. Generally 1 to 20% by weight based on powder
, preferably from 2 to 10 wt.

For the reaction between these oligomers and reactive silane coupling agent residues, ferromagnetic fine powder containing the silane coupling agent in an organic solvent is generally used. After making the mixture cloudy, a predetermined amount of reactive oligomer is added, and if necessary, a catalyst is added and heated to cause a reaction. At the end of the reaction, excess solvent is removed with P, and the surface treatment is completed by drying or drying.

The ferromagnetic fine powder that has been surface-treated in this way is well compatible with solvents when it is made into a paint, and has an adsorption layer with an optimal thickness for dispersion stabilization, which greatly improves the dispersion stability of magnetic* materials. It is easy to fabricate, the ferromagnetic particles are easily oriented by magnetic field orientation, and the magnetic film has high uniformity, so the electromagnetic properties of this magnetically inert material are excellent.

The magnetic powder used in the present invention is needle-shaped fine &r-Fθ
Metal oxides such as O2.

2 5' 5 41 t i co broken rle20. ．． Co-doped r-IF
r-νe20J subjected to heat processing such as e, O,
Examples include iron metal powder. Among these, iron metal powder F'i is particularly susceptible to chemical stability, so to improve this, the surface is treated by adding small amounts of nickel, cobalt, titanium, silicon, aluminum, etc. in the form of metal atoms, salts, and oxides. However, these can also be used.

In order to stabilize iron metal powder, a thin oxide film may be formed on the surface in a weakly oxidizing atmosphere, and metal powder treated in this way can also be used.

The size of these magnetic powders is from 1μ to 0.15μ on the long axis.
The short axis is from 0.15μ to 0. (US μ is also preferable. If the long axis is larger than 1 μ, dispersion becomes easier, but recording of short wavelengths becomes disadvantageous and noise increases, so it is not preferable. If the long axis becomes smaller than 0.15 μ, it is not preferable.) It is difficult to achieve strong dispersion in the magnetic recording material of the present invention.

The organic binder used in this development is a resin binder that is soluble in the organic layer agent, and is used in as small a quantity as possible in order to fix the above-mentioned magnetic powder onto the substrate and the magnetic powder together with the necessary strength to form a magnetic layer. It would be good if you could always play that role,
Even materials that are concerned about deteriorating the dispersibility of magnetic powder in conventional paints can be used in normal paint-forming methods. Examples of these resin binders include polyurethane, polyester, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, polyacrylonitrile dinitrile rubber, epoxy resin, and alkyd resin.

Polyamide, polyacrylic ester, polymethacrylic ester, polyvinyl acetate, polyvinyl butyral,
Vinylidene chloride, vinylidene chloride copolymer, nitrified cotton, ethyl cellulose, etc. may be used alone, but two or more types are usually used as a mixture. Additionally, plasticizers and hardeners can be added to increase the hardness of the resin.

In the present invention, the blending amount of the binder is 15 to 60 parts by weight per 100 parts by weight of the magnetic powder. Even if the binder has the highest binding strength, if it is less than 15 parts by weight, the *1 of the magnetic coating will be weak and the adhesion between the t9 substrate and the magnetic coating will be insufficient. If the amount is more than 60 parts by weight, the magnetic powder IIkf in the magnetic coating film becomes small, which is disadvantageous because the reproduction rate decreases. However, the properties of the coating film may deteriorate.

The solvent used in the present invention preferably has a dissolving power for the binder used and a boiling point between 50°C and 150°C. If the boiling point is too low, the magnetic powder will dry before being oriented in the magnetic field after application, making this treatment impossible.0 Binder species IIIK are selected from the above viewpoints, but toxicity and environmental issues must be taken into account. It goes without saying that you should choose accordingly.

By using the production method of the present invention, it is possible to significantly improve the dispersibility in the production of magnetic paint, and it is possible to create a magnetic recording medium that is excellent in coatability and processability, and has excellent electromagnetic properties.

The present invention will be described in detail below with reference to Examples, but the present invention is not limited thereto.

Example-1 Long axis average particle diameter 0. Spn+, r-Fe2 with axial ratio 1/10
0゜20 parts by weight of N-/-(annnoethyl)-r-i
Nogrobil trimethoxysilane (Toshi Silicone 8H6
020) The mixture was added to 100 parts by weight of a 0.2 ml aqueous solution and stirred and mixed for 50 minutes using a lab mixer.

After water was removed from each house, the mixture was dried at 120°C for 2 hours and then crushed to perform the primary treatment. 0 A flask equipped with a cooling reflux tube was treated with a silane coupling agent. 1. r-Fe, 0. 20 f was suspended in methyl isobutyl ketone (K1100f from M), and 2 f of various reactive oligomers shown in Table 1 were added and heated for 1 to S hours with stirring to perform a secondary treatment. After cooling, MIBK was separated from F and After removing the sample, the r-Fe20 obtained by surface treatment was added to 50 parts by weight (in terms of dry matter) of vinyl chloride vinyl acetate resin (TTM material) without drying.
VAGH manufactured by Union Carbide) 5 parts by weight.

Methyl ethyl ketone (MIiC)! After kneading 1 part by weight of i and 1 part by weight of cyclohexanone s in a ball for 20 hours, 2.5 parts by weight of polyurethane resin (Nistan 5702 manufactured by Gutdrich), 0.2 parts by weight of leveling agent (Kao soap, homogenol L-100), hardening agent. (Sumitomo Bayern, Dismodule N-75) 0.75 parts by weight was added and mixed for another 4 hours to prepare a magnetic paint. These paints were dried on a polyester film until the thickness of the magnetic paint film was 3 cm. After coating and magnetic field orientation, it was dried with hot air. This magnetic coating film was calendered and smoothed to obtain a magnetic recording body. The coating film properties and magnetic properties were evaluated. The results are shown in Table-1.

The comparative product “Untreated rFe20.
fi7(1'-8H-6020 111 r Fe!
Os J performs only silane coupling agent treatment,
A magnetic recording medium was manufactured without treatment with a reactive oligomer [7]. In addition, "lecithin addition" is untreated r
-Fe20. When making a paint using the magnetic powder, three weight bags of soybean oil lecithin was added to the magnetic powder [7] to produce a magnetic recording medium. Further, the molecular weight of the reactive oligomer was determined by the usual vapor pressure drop method.

As is clear from Table 1, it can be seen that the magnetic recording material obtained by the method of the present invention exhibits excellent characteristics.

Example-2 Instead of 〇H-4020 used in Example-1, r-
Silane coupling agent treatment was carried out in exactly the same manner except that glycidoxypropyltrimethoxysilane (Toshi Silicon 8H-6040) was used.

r-Fe20. thus obtained. Example-1 for
After being treated with various reactive oligomers by the method described in Section 9, magnetic inorganic bodies were prepared by the same method and the coating film characteristics and aeration characteristics were evaluated.The results are shown in fi-2. As is clear from this, it can be seen that the magnetic sickle body of the present invention has excellent characteristics.

Example 5 In place of the 9r-F 2o5 used in Example 1, CO-coated ryθ with a major axis average particle diameter of 0.55μ and an axial ratio of 1A was used.
20. using the silane coupling agent 8H-60
20 in place of r-a-noprobyltriethoxysilane (
Example-1 except that Shin-Etsu Kagaku handmade KB1903) is used.
Silane coupling agent treatment was performed using the method described in .

The CO-coated r-Fe20. The samples were treated with various reactive oligomers according to the method described in Example 1, and then magnetic plates were produced using the same method, and the coating film properties and magnetic properties were evaluated.

The results are shown in Table-5. As is clear from this, it can be seen that the magnetic sickle body of the present invention has excellent characteristics.

Procedural amendment (spontaneous) October 25, 1980 Commissioner of the Patent Office Kazuo Chikusugi Aya 1 Indication of the case Patent Application No. 57-37144 2 Name of the invention Method for manufacturing magnetic recording bodies 5 Related: Patent Applicant +0911 Kao Soap Co., Ltd. 4 Agent Nakai Building, 1-5 Nihonbashi Yokoyama-cho, Chuo-ku, Tokyo This is a detailed description of the claims and invention of the specification. '' has been corrected as follows: ``In other words, the present invention provides ferromagnetic fine powder with one or two selected from amino group-containing or epoxy group-containing silane coupling agents.
After treatment with one or more organic oligomers selected from the group consisting of (1) and (IO), which can react with the reactive residue of the silane coupling agent, The present invention provides a method for producing a magnetic recording material, which is characterized in that it is coated on a substrate together with an organic binder.

(I) A copolymer of an olefin having 4 to 50 carbon atoms and T-leic anhydride with a molecular weight of 500 to 8,000, or a hydrolyzate thereof (II) A molecular weight of SOD to 8,000! Reinated polybutadiene (1) Insert "contains an amino group or epoxy group" next to "Used" on page 9, line 2. Insert "one or more selected from the group consisting of" (1) Page 10, line 10-i, line 11F9 "Includes any of these organic oligomers." amended as follows [These organic oligomer compounds have a molecular weight of 500 to 8
If the molecular weight is less than 500, the dispersion effect will be insufficient, and if it exceeds 8000, the dispersion effect will also be reduced.

(9) The preferred molecular weight is 1,000 to 5,000.

The olefins having 4 to 50 carbon atoms according to the present invention include linear and branched aliphatic olefins.

It includes both olefins with aromatic rings such as styrene and alicyclic olefins such as cyclohexene. 2. Scope of Claims (Voluntary) (Showa 58-sho February 911 #+t, ii Director-General Name Material Husband 1, Table of 1R1, 1<Kuchigan No. 57-37164 2 Name of the invention Method for manufacturing magnetic recording material 3 Relationship with the namesake making the 11 Patent applicant (091) Hana] Mi Soap Co., Ltd. 3 Nakai Building Specification Detailed Description of the Invention Column 6 Sleeve 11. Contents (1) Next to “Metal Powder” on page 12, line 16 of the specification [,
Magnetic powder substituted with platelet-like barium ferrite and its seeds or 2-inserted 1-, Co.

Ultrafine powder of metals or alloys such as Fe-Go, Fe-Ni etc.

Claims (1)

[Claims] 1. Treating ferromagnetic fine powder with a silane coupling agent,
411. A method for producing a recording medium at once, which comprises treating with an organic oligomer compound having a molecular weight of 500 to 8,000 capable of reacting with the reactive residue of the silane coupling agent, and then applying KIk onto a substrate together with an organic binder. 2. The method for producing a one-shot recording medium according to claim 1, wherein the silane/coupling agent is an adeno group-containing silane coupling agent. 5. The method for producing a magnetic recording medium according to claim 1, wherein the silane coupling agent is an epoxy group-containing silane coupling agent. 4. The one-shot recording medium according to claim 1, 2 or S, wherein the organic oligomer compound is a copolymer of an olefin having 4 to SO carbon atoms and maleic anhydride or a hydrolyzed product thereof. Manufacturing method. 5. The method for producing a one-shot recording medium according to claim 1, 2, or 5, wherein the organic oligomer compound is maleated polybutadiene.