JP2861386B2 - Magnetic recording material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording material, and more particularly, to a magnetic recording material that has good dispersibility of magnetic powder in a magnetic layer, and has excellent surface properties and magnetic properties.

2. Description of the Related Art Magnetic recording materials such as magnetic disks and magnetic tapes are generally kneaded with a magnetic powder such as ferrite together with an organic binder and a solvent to prepare a magnetic paint, which is applied to a sheet or film-like resin. It is manufactured by At this time, the dispersibility of the magnetic powder in the organic binder has a significant effect on the magnetic properties and abrasion resistance of the magnetic recording material.However, since the magnetic powder is an inorganic substance having a large surface energy, it cannot be used with a resin having a small surface energy. It is poorly familiar and has very poor dispersibility as it is.

As a method for solving such a problem, a surface treatment for making the surface of the magnetic powder hydrophobic may be mentioned. The surface treatment is usually performed using a higher fatty acid, a silane coupling agent, a titanium coupling agent, or the like. However, in the case of higher fatty acids, there is no direct reaction with a functional group oriented on the surface of the inorganic substance to form a covalent bond. Moreover, surface water is usually present on the surface of the inorganic material, and since the H2O layer is oriented on the surface with the H2O layer interposed therebetween, it can be said that it is very easy to remove. In the case of a conventional coupling agent, it is generally said that a covalent bond is formed with a functional group on the surface of an inorganic substance. When a surface-treated filler is filled in a resin, a silane-based resin improves the strength and a titanium-based resin improves the processing characteristics. As an example of the surface treatment of the magnetic powder, treatment with a titanium-based coupling agent is often performed as shown in JP-A-60-229306, and it is shown that this is actually effective.

However, as is generally the case with composite materials, the better the dispersibility of the magnetic powder, the better the magnetic properties and the like.
From these points, a more excellent surface treatment technology is required.

Problems to be Solved by the Present Invention That is, the problem to be solved by the present invention is to develop a magnetic powder having a very excellent dispersibility in a binder, and further develop a magnetic recording material having excellent magnetic properties and surface properties. It is to develop.

Means for Solving the Problems In order to solve the above problems, the present inventors have found that a magnetic powder treated with a surface modifier comprising a mixture of a titanium oligomer and a higher organic acid ester has a very excellent dispersion in an organic binder. The present invention has been found, and the present invention has been completed. That is, the present invention relates to 1 part by weight of a titanium oligomer and 0.5 to 5 organic acid esters.
Magnetic powder surface-treated with 0.01 to 10% by weight of a surface modifier prepared by mixing 0 parts by weight, an organic binder of 15 to 60% by weight based on the magnetic powder, and a solvent of 1 to 5 times by weight based on the organic binder A magnetic recording material obtained by applying a magnetic coating composition comprising a resin to a resin.

It is.

 Hereinafter, the present invention will be described in more detail.

The titanium oligomer in the present invention is not basically limited as long as it has a transesterification catalytic activity. For example, JP-A-1-
Titanium acylate polymer found in 203470 can be mentioned, but it may have no hydrophobic group,
Also, there may be no hydrolyzable group such as an alkoxy group. Further, those having a sulfonic acid residue or a phosphoric ester residue in the side chain may be used. Examples of such a titanium oligomer include the following.

Such as linear type, Ladder type Etc. in the cyclic form or in the molecular structure And the like.

(However, X represents OH or / and an alkoxy group or / and an acylate group or / and a sulfonic acid residue or / and a phosphate ester residue or / and a pyrophosphate ester residue.) Further, the organic acid in the present invention. The ester preferably has an organic acid residue having hydrophobicity, and more preferably has an alcohol residue having a low molecular weight. Examples of the organic acid residue of such an organic acid ester include, in the case of a fatty acid residue, isostearic acid, stearic acid, palmitic acid, myristic acid, lauric acid, decanoic acid, octanoic acid, oleic acid, linoleic acid, and the like. Of these, isostearic acid is preferred from the viewpoint of imparting hydrophobicity. Also in the case of sulfonic acid, phosphoric acid, and pyrophosphate residues, those having an alkyl group having the same carbon number as in the case of fatty acid residues are preferable. Examples of the alcohol residue of the organic acid ester include isopropyl, propyl, ethyl, methyl, butyl, isobutyl, t-butyl and the like. Among them, isopropyl is preferred from the viewpoint of easy hydrolysis and volatility after hydrolysis. Is preferred.

The method for preparing the surface modifier is not particularly limited, but is a method in which an alkoxytitanium such as TPT is reacted with water or acetic acid to prepare an oligomer, and an organic acid ester is mixed with the oligomer 0.5 to 50 times by weight. There is a method of preparing a mixture of an ester and a titanium oligomer by reacting an alkoxytitanium with a higher organic acid as shown in 02-18463.
If the amount of the ester is large, the catalytic rate of the oligomer is reduced, and if the amount of the ester is small, the oligomer is not sufficiently imparted with hydrophobicity.

Although the magnetic powder in the present invention is not particularly limited, α-Fe2O
3, surface treatment with γ-Fe2O3 and its Co, SrO.F
e2O3, BaO ・ Fe2O3, CoO ・ Fe2O3, MnO ・ Fe2O3, CuO ・ Fe2
O3, MgOFe2O3, ZnOFe2O3, and some of their Fe atoms
Substituted with Ti, Co, Zn, V, Nb, etc., Fe metal powder,
And treated products thereof with Ti, Ni, Si, Co, Al and the like. The shape is not limited.

The surface modification method of the magnetic powder is 0.1 to 10 with respect to the filler.
%, Preferably 0.5 to 5% by weight, of a dry method in which a surface modifier is directly added and uniformly dispersed with a Henschel mixer or the like, or a wet method in which a solvent is removed after infiltrating a filler into a solution. At most, no effect is obtained at most. Further, as in the case of a general coating material, the magnetic powder, the organic binder and the solvent may be added at the time of kneading without any problem.

The organic binder filling the magnetic powder in the present invention is also extremely
It is not limited as long as the SP value is not large or small, but polyester, polyurethane, polyvinyl chloride, and its copolymer with vinyl acetate or vinylidene chloride, polyacrylonitrile and its vinylidene chloride copolymer, nitrile rubber, alkyd resin, polyamide , Polyvinyl acetate,
Examples thereof include polyvinyl butyral, a cellulose resin, and an epoxy resin. These binders are 2
It is perfectly acceptable to mix more than one seed.

Examples of the resin serving as a support on which the magnetic paint is applied include film-shaped molded products such as polyethylene terephthalate, polycarbonate, polypropylene, polyvinyl chloride, and cellulose triacetate.

The amount of the organic binder to be added is 15 to 60% by weight based on the magnetic powder. If the amount is less than this, the adhesive strength of the coating film is reduced.

The solvent in the present invention is preferably a solvent capable of dissolving an organic binder and having a boiling point of 50 to 150 ° C. If it is lower than that, it will be dried before magnetic field orientation, and if it is higher than that, it will be difficult to dry.

The effects of the present invention are exhibited by the following mechanism. When the titanium oligomer has a hydrophobic group, these titanium compounds bind to the inorganic surface and make the surface hydrophobic as conventionally known. For this, a covalent bond, a hydrogen bond or the like works. On the other hand, when the titanium oligomer cannot completely cover the surface by this mechanism, or when the titanium oligomer does not have a hydrophobic group, the following action mechanism operates. In many cases, surface water is adsorbed on a hydrophilic inorganic surface by hydrogen bonding. For silica gel, the outermost layer of adsorbed water that can be removed by heating to
It is said that there is bound water that is removed by heating at ° C. When a surface treatment is performed with a higher fatty acid or the like, the surface water is oriented on the surface with the surface water interposed therebetween, so that the surface water is easily separated from the surface. On the other hand, the surface modifier used in the present invention has an action of chemically removing this surface water. That is,
In the presence of a titanium oligomer having transesterification catalytic ability,
Organic acid esters are hydrolyzed to organic acids and alcohols by surface water. By this reaction, undesired surface water is removed during the surface treatment, and the generated organic acid is oriented directly or closer to the place where the surface water was adsorbed, that is, the inorganic surface. Considering the strength of surface water adsorption, the adsorption of this organic acid to the surface is quite strong.

Since the mechanism is considered as described above, any filler that has a functional group capable of hydrogen bonding with an organic acid on the surface and has surface water may be used as the filler. In addition, it was confirmed that the ester alone or the titanium oligomer having no hydrophobic group in the molecule alone did not have a surface modifying effect, and that the effect was exhibited when both were used in combination. In addition, this mechanism requires that the organic acid ester be hydrolyzed by surface water. However, when a titanium compound having many hydrolyzable groups, for example, tetraisopropyl titanate (TPT) is used, the ester is hydrolyzed. This is not effective because TPT consumes surface water before. In this regard, highly condensed titanium oligomers are preferred. In addition, it is considered that the above reaction proceeds when the generated volatile alcohol goes out of the system and the equilibrium of the esterification reaction shifts.

As described above, in the magnetic recording material containing the titanium oligomer and the organic acid ester, the dispersibility of the magnetic powder in the organic binder is remarkably improved as a result that the energy of the surface of the magnetic powder is reduced and the compatibility with the resin is improved. Is done.

Next, the contents of the present invention will be described in detail with reference to examples.
In addition, comparison was made with untreated and titanium oligomers represented by JP-A-61-118438. It should be noted that the following examples do not limit the scope of the present invention, but rather exemplify the properties of the present invention more clearly.

Example 1 10.2 g (170 mmol, 3.2 eq) of acetic acid was gradually added dropwise to 15 g (52.8 mmol) of tetraisopropyl titanate at room temperature with stirring, and the mixture was heated and stirred and reacted at reflux temperature for 2.5 hours. During this time, the clear reaction solution gradually became cloudy. Next, by-produced isopropyl alcohol, isopropyl acetate, and unreacted acetic acid were distilled off under reduced pressure, and the remaining acetic acid was azeotropically distilled with toluene to obtain a white powder. Melting point is over 200 ° C, but it is soluble in chloroform. A solution of 1 part by weight of this titanium polymer and 9 parts by weight of isopropyl isostearate in 490 parts by weight of chloroform was prepared to obtain a surface modifier solution. 100 parts by weight of this surface modifier solution (2 parts by weight of the surface modifier) was treated with Co-treated γ-Fe2O3 (diameter
(0.03 μm, 0.35 μm length) was added to 100 parts by weight, stirred for 10 minutes, and then chloroform was distilled off at 60 ° C. This processed powder
20 parts by weight of vinyl chloride-vinyl acetate copolymer (manufactured by Union Carbide), 20 parts by weight of polyurethane resin (manufactured by Nippon Polyurethane Industry Co., Ltd.), 80 parts by weight of cyclohexanone, and 80 parts by weight of methyl ethyl ketone are added to 100 parts by weight. After kneading for 48 hours in a ball mill, Coronate L
Add 15 parts by weight (manufactured by Nippon Polyurethane Industry Co., Ltd.)
The mixture was mixed to obtain a magnetic paint. This was applied to a polyethylene terephthalate film (thickness: 12 μm), dried by magnetic orientation, dried to form a 7 μm coating film, and calendered. The squareness ratio, residual magnetic flux density, and wear resistance of this magnetic tape were examined. The abrasion resistance was evaluated visually by rubbing 5000 times with a Taber abrasion tester (Table 1).

Example 2 At room temperature with stirring, 10 g (35.2 mmol) of tetraisopropyl titanate was stirred at room temperature with 32 g of isostearic acid (112.7 mmol,
3.2eq) is gradually added dropwise and then heated and stirred at reflux temperature.
The reaction was performed for 2.5 hours. Next, the by-produced isopropyl alcohol was distilled off under reduced pressure to obtain a brown liquid. Dissolve 10 parts by weight of this surface modifier in 490 parts by weight of chloroform,
This was a surface modifier solution. Except that this surface modifier solution was used in place of the surface modifier solution prepared in Example 1, the squareness ratio, residual magnetic flux density, and abrasion resistance of the magnetic tape were exactly the same as in Example 1. (Table 1).

Example 3 10 g of isopropyl titanate having an average degree of condensation of 10 (4.16 mmo
l) to 1.3 g of isostearic acid (4.58 mmol, 1.1e
q) was slowly added dropwise. Then, the mixture was stirred at 40 ° C. and reacted for 2 hours while removing by-produced isopropyl alcohol under reduced pressure to obtain a light brown liquid. This titanium oligomer 1
A solution of 490 parts by weight of chloroform and 9 parts by weight of isopropyl isostearate was prepared as a surface modifier solution. Except that this surface modifier was used in place of the surface modifier solution obtained in Example 1, the squareness ratio, residual magnetic flux density, and abrasion resistance of the magnetic tape were examined in the same manner as in Example 1. (Table 1).

Example 4 10 g of isopropyl titanate having an average degree of condensation of 10 (4.16 mmo
1), 17.8 g of isostearic acid (62.7 mmol, 15.1 g)
eq) was slowly added dropwise. Then, while stirring at 40 ° C, 4.5
After reacting for an hour, isopropyl alcohol by-produced was removed under reduced pressure to obtain a light brown liquid. A solution of 5 parts by weight of this titanium oligomer and 5 parts by weight of isopropyl isostearate in 490 parts by weight of hexane was prepared. Except for using this surface modifier instead of the surface modifier solution obtained in Example 1, the squareness ratio, residual magnetic flux density, and wear resistance of the magnetic tape were examined in the same manner as in Example 1 ( Table 1).

Comparative Example 1 The squareness ratio, residual magnetic flux density, and abrasion resistance of the magnetic tape were observed in exactly the same manner as in Example 1, except that untreated magnetic powder was used instead of the treated powder (Table 1).

Comparative Example 2 10 g of isopropyl titanate having an average degree of condensation of 10 (4.16 mmo
1), 17.8 g of isostearic acid (62.7 mmol, 15.1 g)
eq) was slowly added dropwise. Then, while stirring at 40 ° C, 4.5
After reacting for an hour, isopropyl alcohol by-produced was removed under reduced pressure to obtain a light brown liquid. This surface modifier
A 10 parts by weight solution of 490 parts by weight of chloroform was prepared. Except that this surface modifier solution was used instead of the surface modifier solution prepared in Example 1, the squareness ratio, residual magnetic flux density, and abrasion resistance of the magnetic tape were exactly the same as in Example 1. (Table 1).

Comparative Example 3 A titanium oligomer solution prepared by dissolving 10 parts by weight of the titanium oligomer obtained in Example 1 in 490 parts by weight of chloroform was used in place of the surface modifier solution obtained in Example 1. In exactly the same manner as in Example 1, the squareness ratio, residual magnetic flux density, and wear resistance of the magnetic tape were observed (Table 1).

Comparative Example 4 Exactly the same as Example 1 except that an ester solution prepared by dissolving 10 parts by weight of isopropyl isostearate in 490 parts by weight of chloroform was used instead of the surface modifier solution obtained in Example 1. Then, the squareness ratio, residual magnetic flux density, and wear resistance of the magnetic tape were observed (Table 1).

Effect of the Invention As described above, in the magnetic recording material containing the titanium oligomer and the organic acid ester, the magnetic powder was well dispersed in the organic binder, and exhibited excellent magnetic properties and surface properties.

Claims (1)

(57) [Claims] 1. A magnetic powder which is surface-treated with 0.01 to 10% by weight of a surface modifier comprising 1 part by weight of a titanium oligomer and 0.5 to 50 parts by weight of an organic acid ester, and 15 to 60% by weight based on the magnetic powder. 1 to 5 for organic binder and organic binder
A magnetic recording material obtained by applying a magnetic paint containing a solvent in a weight double amount to a resin.