JPH0454288B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a magnetic recording medium, and an object thereof is to provide a method for manufacturing a magnetic recording medium that has good dispersibility of metal magnetic powder and excellent magnetic properties and surface smoothness of a magnetic layer. be. Magnetic recording media are usually made by applying and drying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and have excellent magnetic properties and surface smoothness. Something with excellent durability is required. Therefore, attempts have been made to improve the dispersibility of magnetic powder by treating the magnetic powder with a dispersant, etc. to improve the magnetic properties and surface smoothness, and also to improve the wear resistance. Although magnetic powders treated with alkyl titanates have been proposed, the dispersibility of magnetic powders, particularly metal magnetic powders, is still not sufficient, and improvements in magnetic properties and surface smoothness are still not fully satisfactory. The inventors conducted studies in view of the current situation, and as a result, when preparing magnetic paint, they used metal magnetic powder with a thin oxide film layer formed on the particle surface, and
When a titanium coupling agent is added as it is or dissolved in a solvent and mixed at the same time to prepare a magnetic paint, this magnetic paint is applied onto a substrate to form a magnetic layer, which improves the dispersibility of the metal magnetic powder. It was discovered that the magnetic properties and the surface smoothness of the magnetic layer were further improved, and the present invention was completed. The titanium coupling agent used in this invention has the general formula (RO) _n -Ti(-X-Y) _o or (However, R is a hydrocarbon group or -CH ₂ -C
( _C2H5 )-( _CH2 -O- _CH2 -CH= _{CH2 ) 2} , _R1 is a hydrocarbon group or _-CH2 -CO-, X is P, -O-
C.O.

[Formula] or -O-PO (OH)-O-PO, Y is a hydrocarbon group or (-O-
R ₂ ) ₂ or (-O-R ₃ ) ₂ OH and R ₂ and R ₃
is an alkyl group, m and n are 1≦m≦4, m+n
An integer of ≦6, l is an integer 2 or 4. ) is a titanium compound that acts as a bridge between organic and inorganic substances through strong chemical bonds, and when it comes into contact with metal magnetic powder that has a thin oxide film layer formed on the particle surface, it reacts strongly with the hydroxyl groups on the surface. and titanium atom and −(OR) _n or

The bond with [Formula] is broken, and the titanium atoms are firmly bonded to the surface of the magnetic powder via oxygen. Therefore, this type of titanium coupling agent is added as it is or dissolved in a solvent when preparing a magnetic paint, mixed at the same time to prepare a magnetic paint, and then this magnetic paint is applied onto a substrate to make it magnetic. When the layer is formed, the titanium coupling agent in the magnetic layer firmly adheres to the surface of the metal magnetic powder particles on which a thin oxide film layer has been formed, forming a film and sufficiently improving the dispersibility of the metal magnetic powder. , further improving the magnetic properties and surface smoothness of the magnetic layer. Specific examples of such titanium coupling agents include Prenact TTS, 9S, manufactured by Kenritzhi Petrochemical Co., Ltd., which is represented by the following structural formula.
Examples include 38S, 41B, 46B, 55, 138S, and 238S. Prenact TTS (isopropyl triisostearoyl titanate) Preneact 9S (isopropyl tridodecylbenzenesulfonyl titanate) Preneact 38S [isopropyl tris (dioctyl pyrophosphate) titanate] PreneAct 41B [Tetraisopropylbis(dioctylphosphite) titanate] (C ₈ H ₁₇ -O) ₄ --Ti[-P(-O-C ₁₃ H ₂₇ ) ₂ OH] ₂ PreneAct 46B [Tetraoctylbis(ditridecyl phosphite) titanate] Preneact 55 [tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl)]
phosphite titanate] Preneact 138S [Bis(dioctylpyrophosphate) oxyacetate titanate] Prenact 238S [Bis(dioctylpyrophosphate) ethylene titanate] In order to incorporate these titanium coupling agents into the magnetic layer, they are dissolved in a suitable solvent, and the solution obtained by this dissolution is used as a magnetic layer. This can be done by adding the titanium coupling agent when preparing the paint, or by adding the titanium coupling agent as it is to prepare the magnetic paint. If the amount used is less than 0.1% by weight of the metal magnetic powder that forms a thin oxide film layer on the surface of the particles in the magnetic layer, the desired effect will not be obtained, and if it exceeds 10% by weight, there is a risk of bleed-out. Therefore, it is preferably used in a range of 0.1 to 10% by weight, and more preferably in a range of 0.5 to 5% by weight. As the magnetic powder used in this invention, metal magnetic powder with a thin oxide film layer formed on the particle surface is preferably used. For example, Fe powder, Co powder, Fe- Ni
Any commonly used metal magnetic powder such as powder may be used. Examples of organic solvents include 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 alcohol solvents such as isopropyl alcohol. Solvents suitable for dissolving the titanium coupling agent and binder components used are particularly limited, such as acid amide solvents such as dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, and ether solvents such as tetrahydrofuran and dioxane. They can be used alone or in a mixture of two or more. Incidentally, various commonly used additives such as dispersants, lubricants, abrasives, antistatic agents, etc. may be appropriately added to the magnetic paint. Next, embodiments of the invention will be described. Example 1 1Kg of α-Fe magnetic powder and 10% of toluene at 80℃
An air blowing pipe was inserted into the bottom of the container and air was blown into the container at a flow rate of 5 per minute for 5 hours.
Generates fine air bubbles throughout the system, then
The powder was taken out and dried by heating to form a thin oxide film layer on the particle surface of the α-Fe magnetic powder. In this way, a thin oxide film layer was formed on the particle surface.
α-Fe magnetic powder that uses Fe magnetic powder to form a thin oxide film layer on the particle surface 80 parts by weight Takerak E-550 (manufactured by Takeda Pharmaceutical Co., Ltd., polyurethane elastomer) 16 〃 Coronate L (manufactured by Nippon Polyurethane Industries, Ltd., trifunctional low molecular weight isocyanate compound)
A magnetic paint was prepared by mixing and dispersing the following compositions in a ball mill for about 76 hours. This magnetic paint was applied onto a polyester film with a thickness of 11 μm to a dry thickness of about 4 μm, dried, surface treated, and then cut to a predetermined width to make a magnetic tape. Example 2 The composition of the magnetic paint in Example 1 was the same as in Example 1, except that the same amount of Prenact 9S (manufactured by Kenritzhi Petrochemical Co., Ltd., isopropyl tridodecylbenzenesulfonyl titanate) was used instead of Prenact TTS. and made magnetic tape. Example 3 The composition of the magnetic paint in Example 1 was the same as that of Example 1, except that the same amount of Prenact 138S [manufactured by Kenritzhi Petrochemical Co., Ltd., bis(dioctyl pyrophosphate) oxyacetate titanate] was used instead of Prenact TTS. A magnetic tape was made in the same manner as in 1. Comparative Example 1 Fe alloy magnetic powder 120 parts by weight Prenact TTS (manufactured by Kenritzhi Petrochemical Co., Ltd., isopropyl triisostearoyl titanate) 0.6 〃 Methyl ethyl ketone 50 〃 Toluene 50 〃 This composition was mixed for 3 hours with a high-power mixer,
Fe alloy magnetic powder was well wetted by titanium coupling agent. Next, a mixture of 18 parts by weight of acrylic double bond-introduced butyral resin (in terms of solid content), 12 parts by weight of acrylic double bond-introduced urethane elastomer (in terms of solid content), 100 methyl ethyl ketone, 100 toluene, and 3 parts lubricant (higher fatty acid) was added. After thoroughly mixing and dissolving, this was thoroughly mixed with the above-mentioned magnetic powder treated product using a high-speed mixer for 1 hour, and then further mixed using a sand grinder mill for 4 hours.
A magnetic paint was prepared by time-mixing and dispersion. This magnetic paint was applied onto a polyester film with a thickness of 11μ, and after magnetic field orientation, solvent drying, and surface smoothing treatment, an electrocurtain type radiation accelerator was used to apply the magnetic coating to an acceleration voltage of 150 KeV, electrode current of 10 mA, and total irradiation dose of 5 Mrad. The coating film was cured by irradiation with radiation in an N ₂ gas atmosphere under these conditions. After that, they were cut to a specified width to make magnetic tape. Comparative Example 2 Comparative Example 1 except that in the wet treatment of the Fe alloy magnetic powder in Comparative Example 1, the same amount of Pren Act 9S (manufactured by Kenritzhi Petrochemical Co., Ltd., isopropyl tridodecylbenzenesulfonyl titanate) was used instead of Pren Act TTS. The Fe alloy magnetic powder was wet-treated in the same manner as in Comparative Example 1, and a magnetic tape was produced in the same manner as in Comparative Example 1. Comparative Example 3 In the wet treatment of the Fe alloy magnetic powder in Comparative Example 1, the same amount of Plenact 138S [manufactured by Kenritzhi Petrochemical Co., Ltd., bis(dioctylpyrophosphate) oxyacetate titanate] was used instead of Plenact TTS. , Fe alloy magnetic powder was wet-treated in the same manner as in Comparative Example 1, and a magnetic tape was produced in the same manner as in Comparative Example 1. Comparative Example 4 In the wet treatment of the Fe alloy magnetic powder in Comparative Example 1, PreneAct 55S (manufactured by Kenritzhi Petrochemical Co., Ltd., Tetro(2,2-diallyloxymethyl-1-butyl)bis(di- The Fe alloy magnetic powder was wet-treated in the same manner as in Comparative Example 1, except that the same amount of Tridecyl) phosphite titanate was used, and a magnetic tape was produced in the same manner as in Comparative Example 1. Comparative Example 5 Example In the composition of the magnetic paint in 1, instead of the α-Fe magnetic powder with a thin oxide film layer formed on the particle surface, α-Fe without an oxide film layer on the particle surface is used.
A magnetic tape was made in the same manner as in Example 1, except that the same amount of magnetic powder was used. Comparative Example 6 In the composition of the magnetic paint in Example 2, α-Fe magnetic powder with no oxide film layer on the particle surface was replaced with α-Fe magnetic powder with a thin oxide film layer formed on the particle surface.
A magnetic tape was made in the same manner as in Example 2, except that the same amount of magnetic powder was used. Comparative Example 7 In the composition of the magnetic paint in Example 3, instead of the α-Fe magnetic powder with a thin oxide film layer formed on the particle surface, α-Fe without an oxide film layer on the particle surface was used.
A magnetic tape was made in the same manner as in Example 3, except that the same amount of magnetic powder was used. Comparative Example 8 A magnetic tape was produced in the same manner as in Example 1 except that Preact TTS was omitted from the composition of the magnetic paint in Example 1. Comparative Example 9 A magnetic tape was prepared in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 1, the same amount of tetraisopropyl titanate [Ti(OC ₃ H ₇ ) ₄ ] was used in place of Pre-Act TTS. I made it. Video SN ratio and color SN ratio were measured for the magnetic tapes obtained in each Example and each Comparative Example. The video SN ratio and color SN ratio were determined by using the obtained magnetic tape on a video deck (VT-
5000), record and playback, and measure with Shibasoku Color Video Noise Meter 925C.
The video SN ratio and color SN ratio of the magnetic tape obtained in Comparative Example 8 were assumed to be 0, and the difference therebetween was expressed. The table below shows the results.

【table】

[Table] As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1 to 3) have better video SNR and color than conventional magnetic tapes (Comparative Examples 1 to 9).
Both have a high signal-to-noise ratio, and as a result, the magnetic recording medium obtained by the present invention has particularly excellent dispersibility of metal magnetic powder, has good smoothness and gloss on the surface of the magnetic layer, and has further improved magnetic properties. I understand that.

Claims (1)

[Claims] 1. When mixing and dispersing metal magnetic powder with a thin oxide film layer formed on the particle surface together with a binder component, an organic solvent, and other necessary components, a titanium coupling agent is added as it is or dissolved in a solvent, A method for producing a magnetic recording medium, which comprises simultaneously mixing and dispersing to prepare a magnetic paint, and then coating the magnetic paint on a substrate to form a magnetic layer.