JP2658599B2 - Magnetic paint and magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape having a magnetic layer containing magnetic powder provided on a non-magnetic substrate.

[0002]

2. Description of the Related Art In recent years, higher recording densities of magnetic recording media have been demanded. For example, even in a magnetic tape, the surface area of a magnetic recording medium has a high saturation magnetic flux density Bm and a high squareness ratio Rs (residual magnetic flux density Br / saturated magnetic flux density Bm). A material having a small roughness and excellent flexibility and abrasion resistance is required. The demand for high S / N ratio, specific surface area using a fine magnetic powder 30m ² / g~70m ² / g, in order to firmly bond by uniformly dispersing this excellent binder It is required to have both dispersing performance and strong bonding force. However, conventionally, as the binder, polyester resin, cellulose resin,
Polyurethane resin, phenolic resin, epoxy resin, polyamide resin, vinyl chloride, vinylidene chloride, vinyl acetate, (meth) acrylic acid ester, (meth) acrylamide, acrylonitrile, butadiene, styrene, vinyl ester, etc. Are used together with a low-molecular-weight surfactant called a dispersant, a fatty acid, and the like, but none of them could obtain sufficient characteristics in both the dispersibility of the magnetic powder and the abrasion resistance of the magnetic layer. Also, in order to improve the dispersibility of the magnetic powder,
Treatment of magnetic powder with an aminosilane compound or
-205929), vinyl chloride which has been widely used.
Applying a binder obtained by modifying a vinyl alcohol-vinyl acetate terpolymer with an aminosilane compound (JP-B-1)
However, it has not been possible to obtain a magnetic paint having good coatability by dispersing the fine magnetic powder as described above. On the other hand, in order to increase the strength of the magnetic layer and obtain a medium having good durability, it is necessary to sufficiently disperse the magnetic powder to obtain a magnetic layer having high filling properties, while increasing the strength of the binder. In order to increase the strength of the binder, it is effective to increase the molecular weight of the binder. However, if the molecular weight is increased, the viscosity of the coating material in which the magnetic powder is dispersed increases, and the dispersibility decreases. As the magnetic powder becomes finer, the viscosity of the paint increases more easily.Therefore, a method for improving the strength without increasing the molecular weight is required.One of the methods is to broaden the crosslinking of the binder with a polyisocyanate compound. It's being used. Then, in order to enable crosslinking by the polyisocyanate compound, a group having an active hydrogen represented by a hydroxyl group capable of reacting with an isocyanate group has been introduced into a binder. However, when a large amount of hydroxyl groups is introduced into the binder, the magnetic paint containing a lubricant such as a fatty acid or an ester thereof decreases the dispersion stability of the magnetic powder and stabilizes a magnetic recording medium having good characteristics. And cannot be manufactured. On the other hand, if the amount of the hydroxyl group is small, the crosslinking is insufficient, and the purpose of improving the strength cannot be achieved.In addition, the isocyanate group of the isocyanate compound is excessive with respect to the hydroxyl group of the binder, and the excess isocyanate compound has a water content in the air. , Resulting in brittleness of the magnetic layer.

[0003]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies on the above-mentioned conventional problems with respect to the demand for higher recording density and higher durability of a magnetic recording medium, and as a result, have found that a specific resin and a specific resin have been identified. By using a silane compound as a binder for magnetic powder, a low-viscosity magnetic paint in which fine magnetic powder is stably dispersed can be obtained, and this paint is applied on a non-magnetic substrate. The present invention has been completed by confirming that the obtained magnetic recording medium can stably exhibit excellent magnetic properties, durability and running properties under a wide range of environmental conditions.

[0004]

According to the first aspect of the present invention, the magnetic powder is mixed and dispersed with a polymer containing an epoxy group as a binder of the magnetic powder, and then the silane compound containing an amino group or a thiol group is mixed. A magnetic paint characterized by being added is provided.

According to the second aspect of the present invention, a magnetic layer obtained by mixing and dispersing a magnetic powder with a polymer containing an epoxy group as a binder for the magnetic powder and then adding a silane compound containing an amino group or a thiol group. The magnetic recording medium characterized by having the following.

According to the third aspect of the present invention, the polymer containing an epoxy group in the second aspect of the invention is a vinyl chloride resin, a polyurethane resin, a polyester resin, a butadiene polymer or a vinyl epoxy polymer. A recording medium is provided.

Further, according to the fourth invention, the polymer containing an epoxy group in the second invention is COOM, SO ₃ M,
_{SO 4 M, PO (OM)} 2, PO 4 M 3 or

Embedded image (M is an alkali metal or ammonium; R ₁ , R ₂ , R
₃ represents a hydrocarbon, and X represents an anion group).

In the present invention, in the silane compound, an amino group or a thiol group reacts with an epoxy group in a binder polymer to bond thereto, while a silanol portion reacts with the surface of the magnetic powder to form a strong bond between the magnetic powder and the binder. It forms a natural bond, or is hydrolyzed and polymerized by moisture in the atmosphere or the magnetic layer to form a siloxane bond, increasing the strength of the binder and reducing the frictional resistance of the magnetic layer to improve running properties. I think that the. On the other hand, although the silane compound having a siloxane moiety does not react with water or magnetic powder, it is considered that the same effect can be obtained because it is bonded to the binder via the epoxy group.

Examples of the polymer having an epoxy group used in the present invention include an epoxy group-containing vinyl chloride resin, an epoxy group-containing polyurethane resin, an epoxy group-containing polyester resin, and a vinyl epoxy polymer.
Further, an acrylonitrile-butadiene copolymer, a styrene-butadiene copolymer, or a butadiene-based polymer such as polybutadiene containing an epoxy group may be used.

The vinyl chloride resin having an epoxy group used in the present invention includes (1) vinyl chloride, a radical polymerizable monomer having an epoxy group copolymerizable with vinyl chloride and, if necessary, a monomer thereof. Polymerizing a monomer copolymerizable with a polymer in the presence of a radical generator, or (2)
A method in which a partially dehydrochlorinated resin is epoxidized with an epoxidizing agent such as percarboxylic acid by heating polyvinyl chloride or a copolymer resin containing vinyl chloride as a main component, or by contact with a dehydrochlorinating agent. Can be
The chlorinated polyvinyl chloride resin having an epoxy group can be obtained by the method (2) using a chlorinated polyvinyl chloride resin or a chlorinated polyvinyl chloride copolymer resin as a starting material.

Examples of the radically polymerizable monomer having an epoxy group used in the production of a vinyl chloride resin having an epoxy group include glycidyl ethers of unsaturated alcohols such as allyl glycidyl ether and methallyl glycidyl ether. Glycidyl acrylate, glycidyl methacrylate, glycidyl-p-vinylbenzoate,
Glycidyl esters of unsaturated acids such as methyl glycidyl itaconate, glycidyl ethyl malate, glycidyl vinyl sulfonate, glycidyl (meth) allyl sulfonate, butadiene monooxide, vinyl cyclohexene monooxide, 2-methyl-5,6-epoxyhexene Epoxide olefins.

Examples of monomers having an epoxy group and optionally used monomers other than vinyl chloride include vinyl carboxylate esters such as vinyl acetate and vinyl propionate: methyl vinyl ether, isobutyl vinyl ether, and the like. Vinyl ethers such as cetyl vinyl ether: vinylidene chloride, vinylidene fluoride and the like: diethyl maleate, butyl benzyl maleate, di-2-hydroxyethyl maleate, dimethyl itaconate, methyl (meth) acrylate, (meth) acrylic Ethyl acid, lauryl (meth) acrylate, (meth)
Unsaturated carboxylic acid esters such as 2-hydroxypropyl acrylate: olefins such as ethylene and propylene: unsaturated nitriles such as (meth) acrylonitrile:
Examples thereof include aromatic vinyls such as styrene, α-methylstyrene, and p-methylstyrene. These monomers are used not only for improving the solubility of the resin while adjusting the compatibility and softening point of the resin of the present invention and other resins when they are mixed, but also for the properties and coating properties of the coating film. It is appropriately selected according to the necessity such as improvement of the process.

As the epoxy group-containing polyurethane resin, those having a molecular weight of 1,000 to 200,000 are used. If the molecular weight is less than 1,000, the durability of the coating film is insufficient, and if it exceeds 200,000, the viscosity of the coating becomes too high, which causes practical problems. The epoxy group-containing polyurethane resin is an epoxy resin having two or more functional epoxy groups per molecule, for example, an aromatic epoxy resin such as bisphenol A type, halogenated bisphenol type, resorcinol type, bisphenol F type, aliphatic, An alicyclic epoxy resin is reacted with a dibasic acid such as adipic acid, phthalic acid, dimerized linoleic acid, or maleic acid to synthesize a terminal hydroxyl group type polyester resin, which is reacted with a polyfunctional polyisocyanate Can be synthesized. Alternatively, an epoxidizing agent such as a percarboxylic acid is allowed to act on a polyurethane resin synthesized from an unsaturated polyester resin obtained by the reaction of an unsaturated fatty acid such as maleic acid, fumaric acid, and itaconic acid with a polyhydric alcohol. Can also be synthesized. Furthermore, it can also be synthesized by reacting an epoxy group-containing polyester resin described below as a raw material with a diisocyanate.

As the epoxy group-containing polyester resin, those having a molecular weight of 1,000 to 200,000 are used. If the molecular weight is less than 1,000, the durability of the coating film is insufficient, and if it exceeds 200,000, the viscosity of the coating becomes too high, which causes practical problems. Epoxy group-containing polyester resins include unsaturated dibasic acids such as maleic acid, fumaric acid and itaconic acid or saturated dibasic acids such as phthalic acid, adipic acid and terephthalic acid, and 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,10
-It is obtained by epoxidizing an unsaturated polyester resin obtained by heat condensation with a polyol such as decanediol or a butadiene oligomer having hydroxyl groups at both ends with an epoxidizing agent such as percarboxylic acid. Instead of the unsaturated polyester, a modified unsaturated polyester resin obtained by melt-mixing this with a polycarbonate resin or a saturated polyester resin in the presence of a catalyst and subjecting to a transesterification reaction may be used as a starting material. .

The epoxy group-containing acrylonitrile-butadiene copolymer resin generally has an acrylonitrile content of 12 to 50% by weight and a molecular weight of 5,000 to 5,000.
500,000 ones are used. When the content of acrylonitrile is less than 12% by weight, compatibility with other binders such as polyvinyl chloride and nitrocellulose generally used for magnetic recording media is poor, and when it is more than 50% by weight, the solvent solubility is reduced, The dispersibility of the magnetic powder is greatly reduced. If the molecular weight is less than 5,000, the durability of the coating film is low, and if it is more than 500,000, the viscosity of the coating is too high to be practical. Acrylonitrile containing epoxy group
Butadiene copolymer resin is obtained by copolymerizing radical copolymerizable monomer containing epoxy group with acrylonitrile and butadiene in the presence of radical generator together with other monomers that can be copolymerized if necessary. While
It can also be obtained by partially epoxidizing a double bond in the acrylonitrile-butadiene copolymer resin using an epoxidizing agent such as percarboxylic acid.

The vinyl epoxy polymer is a polymer of at least one vinyl monomer having an epoxy group or a copolymer of the vinyl monomer with at least one copolymerizable monomer. Examples of these monomers having an epoxy group and copolymerizable monomers are listed as examples of radically polymerizable monomers having an epoxy group used in the production of epoxy group-containing vinyl chloride resins. Things are available.

Examples of these include methyl methacrylate-glycidyl methacrylate copolymer resin, methyl methacrylate-acrylic acid-glycidyl methacrylate copolymer resin, styrene-glycidyl methacrylate copolymer resin, and the like.

The epoxy group concentration in the epoxy group-containing resin used in the present invention is in the range of 0.1 to 30% by weight. If the amount is less than 0.1% by weight, the reaction with the silane compound used in the present invention becomes insufficient, and a durable medium cannot be obtained.

The epoxy group-containing resin according to the present invention contains COOM, SO ₃ M, SO ₄ M, PO (O) in the epoxy group-containing resin for the purpose of improving the dispersibility of the magnetic powder.
M) ₂ , PO ₄ M ₃ ,

Embedded image (However, M represents a hydrogen atom or an alkali metal or ammonium, and R ₁ , R ₂ , and R ₃ represent an alkyl group, an allyl group,
An organic residue such as an alkenyl group or an alkoxyl group is represented by X
Is preferably an anion group). Further, a group having active hydrogen such as a hydroxyl group may be contained. It is preferable that the amount of these functional groups is 1 × 10 ⁻⁶ to 1 × 10 ⁻² equivalent per 1 g of the resin.

The silane compound containing an amino group or a thiol group used in the present invention includes N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane,
-(2-aminoethyl) -3-aminopropyltrimethoxysilane, p- [N- (2-aminoethyl)] aminomethylphenethyltrimethoxysilane, 1- (3-aminopropyl) -1,1,3, 3,3-pentamethyldisiloxane, 3-aminopropyltriethoxysilane, 3-aminopropyltris (trimethylsiloxy) silane, 3
-[N-allyl-N- (2-aminoethyl)] aminopropyltrimethoxysilane, N- [3- (trimethoxysilyl) propyl] diethylenetriamine, N- [3-
(Trimethoxysilyl) propyl] triethylenetetramine, 3-trimethoxysilylpropyl-m-phenylenediamine, 1,3-vir (3-aminopropyl) -1,
1,3,3-tetramethyldisiloxane, α, ω-bis (3-aminopropyl) polydimethylsiloxane, N,
N-bis [(methyldimethoxysilyl) propyl] amine, N, N-bis [3- (methyldimethoxysilyl) propyl] ethylenediamine, N, N-bis [3- (trimethoxysilyl) propyl] amine, N, N -Bis [3- (trimethoxysilyl) propyl] ethylenediamine, hexamethyldisilazane, α, ω-bis (3-mercaptopropyl) polydimethylsiloxane, 1,3-bis (3-
(Mercaptopropyl) -1,1,3,3-tetramethyldisiloxane, 1,3-bis (mercaptomethyl) -1,
1,3,3-tetramethyldisiloxane, α, ω-bis (mercaptomethyl) polydimethylsiloxane, 3-mercaptopropyltris (trimethylsiloxy) silane, 3-mercaptopropyltrimethoxysilane, 1-
(3-mercaptopropyl) -1,1,3,3,3-pentamethyldisiloxane, 1-mercaptomethyl-1,1,
Examples thereof include 3,3,3-pentamethyldisiloxane. These silane compounds are used in the range of 0.5 to 10 parts by weight per 100 parts by weight of the magnetic powder.

In the magnetic recording medium of the present invention, in addition to the above-mentioned polymer containing an epoxy group and a silane compound containing an amino group or a thiol group, a binder generally known as a binder can be used in combination. Examples of these include polyurethane resins, vinyl chloride resins, polyester resins, acrylonitrile-butadiene copolymers, (meth) acrylate acrylonitrile copolymers, (meth) acrylate vinylidene chloride copolymers, ) Acrylate styrene copolymer, nylon-silicone resin, nitrocellulose-polyamide resin, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, styrene butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate) Rate, cellulose acetate propionate, cellulose diacetate, cellulose triacetate,
Nitrocellulose), chlorovinyl ether acrylate copolymers, thermoplastic resins such as various synthetic rubbers, phenolic resins, phenoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, nitrocellulose melamine A thermosetting resin such as a resin may be used. Further, a polyisocyanate compound usually used as a curing agent can also be used as a binder component, and examples thereof include tolylene diisocyanate-trimethylolpropane adduct, hexamethylene diisocyanate-trimethylolpropane adduct, and tolylene diisocyanate 3 Resin having a urethane bond formed by the reaction of diisocyanate and polyol, in addition to an isomer, a trimer of hexamethylene diisocyanate, a magnetically cured polyurethane, a terminal isocyanate urethane prepolymer, and the like. It has the above isocyanate group and has a number average molecular weight of 2.0
Not less than 00 and not more than 10,000 and a molecular weight of 1,000
Examples thereof include polyurethane resins in which 0 or less components are less than 20%. The ratio of these co-usable resins to the total amount of the binder component should not exceed 50%.

Further, these binders may have other functional groups known per se, and among these functional groups, particularly, -SO ₄ M, -SO ₃ M, -SO ₂ M, -CO
OM, -NH ₂ , -N ⁺ R ₃ , -OH, a phosphate group, at least one functional group selected from the group consisting of a phosphate group (where M represents a hydrogen atom or an alkali metal atom, R represents an organic residue such as an alkyl group, an allyl group, an alkenyl group or an alkoxyl group). The amount of these functional groups is 1 × 1 / g of resin.
It is preferably contained in an amount of 0 ^-6 to 1 × 10 ^-2 equivalent.

The content of the total binder in the magnetic layer of the magnetic recording medium of the present invention is 10 to 10 parts by weight of the ferromagnetic powder.
100 parts by weight, preferably 15 to 40 parts by weight. The magnetic recording medium of the present invention is mixed with a solvent mainly composed of ketones together with the binder and known materials such as a magnetic powder, a lubricant, an abrasive, an antistatic agent and, if necessary, a dispersant, and then subjecting the mixture to a dispersion treatment. To obtain a magnetic paint, which is applied on a non-magnetic film represented by a polyester film,
After performing the orientation treatment and the surface forming treatment, the magnetic recording medium of the present invention is obtained through a heat treatment for cross-linking and a surface polishing depending on the application, and cutting and incorporating.

The stage at which the silane compound used in the present invention is added in the mixing and dispersing step is an important point in relation to the characteristics of the coating machine. That is, in order to obtain a coating material having a small yield value, increase the coating efficiency, and ensure the smoothness of the coated surface, it is necessary to put it into a so-called let-down process in the latter half of mixing.

[0025] When turned in the previous step to medium stage of mixing and dispersing, but becomes small paint values of Casson equation K _1, difficult to obtain a magnetic layer of a smooth surface yield value not decrease, the effect of the present invention can be obtained Absent. When a polyisocyanate compound is also used as a binder, simultaneous addition of the polyisocyanate compound with the silane compound should be avoided. Further, when producing the medium of the present invention, prior to crosslinking, the magnetic layer is lubricated with water, and the relative humidity of the heat treatment atmosphere is reduced to 50%.
% Or more, and when performed under humidified conditions, durability,
It is effective for stabilization of running performance.

The ferromagnetic powder used in the present invention is particularly preferably a fine powder, such as γ-Fe ₂ O ₃ , Fe ₃ O ₄ , γ-Fe.
Ferromagnetic iron oxide powder such as FeO _x (1.33 <x <1.5), Co-doped ferromagnetic iron oxide powder, ferromagnetic chromium dioxide powder, ferromagnetic metal powder, barium ferrite, Fe ₅
Iron carbide powders such as C _2, and the like iron nitride powder.

[0027] The ferromagnetic metal powder is a ferromagnetic metal powder containing iron, cobalt or nickel.
The metal content in the ferromagnetic metal fine powder is 75% by weight or more,
At least 80% by weight of the metal component is at least one type of ferromagnetic metal or alloy (eg, Al, Fe, Co, Ni,
Fe-Co, Fe-Ni, Co-Ni, Co-Ni-F
e) and other components (eg, Al, Si, S, Sc, Ti, V, Cr, M) within a range of 20% by weight or less of the metal content.
n, Cu, Zn, Y, Mo, Rh, Pd, Ag, Sn,
Sb, Te, Ba, Ta, W, Re, Au, Hg, P
b, Bi, La, Ce, Pr, Nd, B, P).

The methods for producing these ferromagnetic powders are already known, and the ferromagnetic powder used in the present invention can also be produced according to these known methods.

The shape of the ferromagnetic powder is not particularly limited, but usually, needle-like, granular, dice-like, rice-granular, plate-like, and the like can be used.

Examples of the lubricant which can be used in the present invention include:
Fatty acids having 8 to 18 carbon atoms, higher alcohols, amides, fatty acid esters and the like can be used. For example, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid , Linolenic acid, stearolic acid, stearyl alcohol, palmityl alcohol, lauryl amide, dimethyl stearyl amide, butyl lauryl amide, butyl stearate, octyl stearate, sorbitan oleate and the like. In addition, silicon oil, fluorinated oils such as polyperfluoroalkylene oxide and perfluoroalkane, paraffin wax, polyethylene oxide and the like can also be used. Further, solid lubricants such as carbon black, graphite, molybdenum disulfide, and tungsten disulfide can be used. These lubricants are used in a range of 1 part by weight to 6 parts by weight based on 100 parts by weight of the magnetic powder.

As abrasives, TiO ₂ , TiO,
ZnO, CaO, SnO ₂ , SiO ₂ , α-Fe ₂ O ₃ , C
r ₂ O ₃ , α-Al ₂ O ₃ , ZnS, MoS ₂ , BaSO ₄ ,
Examples include CaSO ₄ , MgCO ₃ , BN, and SiC. These inorganic fillers may be used alone or in combination of two or more.

Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymer; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin and glycidol; Cationic surfactants such as alkylamines, quaternary ammonium salts, salts of pyridine and other heterocyclic compounds, phosphonium or sulfonium; carboxylic acid, sulfonic acid, phosphoric acid, sulfate group, phosphate group, etc. Anionic surfactants containing an acidic group; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphoric acid esters of amino alcohols.

A dispersant can be used in the magnetic recording medium of the present invention, if necessary. Examples of the dispersant that can be used in the present invention include fatty acids having 10 to 22 carbon atoms (eg, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid) Acid, stearic acid), a metal soap comprising the above fatty acid and an alkali metal (eg, lithium, sodium, potassium) or an alkaline earth metal (eg, magnesium, calcium, barium), an ester of the above fatty acid and its compound Compounds in which part or all of hydrogen has been substituted with fluorine atoms, amides of the above fatty acids, fatty acid amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphates,
Known dispersants such as alkylborates, sarcosinates, alkyletheresters, trialkylpolyolefinoxyquaternary ammonium salts and lecithin can be mentioned.

[0034]

The present invention will be described more specifically with reference to the following examples.

The epoxy-containing polymer Synthesis Example 1 Allyl glycidyl ether, by emulsion polymerization of vinyl chloride and 2-hydroxypropyl methacrylate by potassium persulfate, an epoxy group of 3.5 wt%, - SO ₄ is 0.
A vinyl chloride copolymer resin (a) having 7% by weight, 0.7% by weight of hydroxyl groups, 84% by weight of vinyl chloride and an average degree of polymerization of 300 was obtained.

Synthesis Example 2 of Epoxy Group-Containing Polymer A bisphenol A type epoxy resin having an epoxy equivalent of 182 to 194 and a molecular weight of 355 was synthesized, and 4,4′-
Diphenylmethane diisocyanate was added and heated, and the following compounds were further added and mixed to obtain an epoxy group-containing polyurethane resin (b) having a molecular weight of about 17,000 and an epoxy group amount of 10% by weight.

[0037]

Embedded image

Using these samples, magnetic paints and magnetic tapes were prepared and evaluated by the following methods.

The results are shown in Table 1.

Example 1 400 parts by weight of cobalt-coated magnetic iron oxide powder (specific surface area: 3
2 m ² / g), resin (a) 50 parts by weight, methyl ethyl ketone 49 parts by weight, toluene 49 parts by weight, cyclohexanone 32 parts by weight, carbon black 3 parts by weight, alumina 4
After a high-speed shearing dispersion of a mixture consisting of 1 part by weight of myristic acid, 0.5 part by weight of butyl stearate and 90 parts by weight, 30 parts by weight of the resin (b) and 3 parts of methyl ethyl ketone
0 parts by weight, 30 parts by weight of toluene, 20 cyclohexanone
Parts by weight and dispersed for 30 minutes. Further, a total of 50 parts by weight of the above mixed solvent and 15 parts by weight of γ-aminopropyltriethoxysilane (TSL-83 manufactured by Toshiba Silicone Co., Ltd.)
After adding 31), the mixture was further dispersed for 10 minutes to obtain a magnetic paint. The obtained magnetic paint was applied on a polyester film so as to have a coating thickness of 5 μm, subjected to a magnetic field orientation treatment, and dried. The gloss of the magnetic coating film was measured with a gloss meter (Murakami Color Research Laboratory MD-3).

Next, the magnetic coating film used for the evaluation of the gloss was cut into a size of 6 mm × 6 mm, and a magnetic property measuring machine (Toei Kogyo Co., Ltd.)
The magnetic characteristics were measured using VSM-7P (trade name, manufactured by Co., Ltd.).

Further, the magnetic coating film used for the gloss evaluation was smoothed with a calender roll and then subjected to 60 ° C. and a relative humidity of 6 ° C.
After heat treatment at 0% for 25 hours, 40 ° C. and 50% relative humidity
%, A load of 100 g was applied thereto, and a rotating drum having abrasive paper attached thereto was brought into contact therewith, and rotated at 150 rpm for 10 minutes.
The durability was determined in four stages of B and C.

A: No stain B: Slight stain C: Stain

The running performance was measured by a U gauge in the atmosphere of 65 ° C. and a relative humidity of 80% using a U gauge in the same manner as in the evaluation of durability. Was determined in three stages.

A: low, B: medium, C: high

Example 2 α, ω instead of γ-aminopropyltriethoxysilane
A coating film was obtained and evaluated in the same manner as in Example 1, except that -bis (3-aminopropyl) polydimethylsiloxane (TSL-9386 manufactured by Toshiba Silicone Co., Ltd.) was used.

Example 3 Instead of γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane (Toshiba Silicone
Example 1 except that TSL-8380 manufactured by Co., Ltd. was used.
A coating film was obtained in the same manner as described above and used for evaluation.

Example 4 Polybutylene adipate was used in place of resin (b),
Using a 4′-diphenylmethane diisocyanate, an epoxy group-free polyurethane resin having a hydroxyl group concentration of 0.2% by weight and comprising 1,4-butanediol and trimethylolpropane, TSL-8331 is added to 10 parts by weight, and TSL-8331 is added to After the addition, tolylene diisocyanate-trimethylolpropane adduct (manufactured by Nippon Polyurethane Co., Ltd.)

A coating film was obtained and evaluated in the same manner as in Example 1 except that 10 parts by weight of Coronate L) was added and mixing was performed for 5 minutes.

Comparative Example 1 A coating film was obtained and evaluated in the same manner as in Example 1, except that polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was used instead of γ-aminopropyltriethoxysilane. Was served.

Comparative Example 2 A vinyl chloride-vinyl alcohol-vinyl acetate copolymer modified with γ-aminopropyltriethoxysilane was used in place of resin (a), and coronate L was used in place of γ-aminopropyltriethoxysilane. Example 4 except used
A coating film was obtained and operated for evaluation in the same manner as described above. Aminosilane modification of a vinyl chloride-vinyl alcohol-vinyl acetate copolymer is described in JP-B 1-44926, Example 2.
And the composition of the resulting modified product was as follows.

Vinyl chloride unit 88 Vinyl alcohol unit 7.6 Vinyl acetate unit 2.3 Aminosilane modified unit 1.4 Average polymerization degree 330

Comparative Example 3 15 parts by weight of γ-aminopropyltriethoxysilane was used in place of 50 parts by weight of resin (a), and VAGH (UC) was used in place of 15 parts by weight of γ-aminopropyltriethoxysilane.
Except for using 50 parts by weight of a vinyl chloride-vinyl alcohol-vinyl acetate copolymer (manufactured by Company C), a coating film was obtained in the same manner as in Example 1 and used for evaluation.

As can be seen from Table 1, according to the present invention, the magnetic powder is well dispersed, and a coating film having good filling properties can be obtained.
The medium of the present invention obtained by subjecting this to calendering, cross-linking, cutting, and incorporation shows good durability and running properties.

[0055]

[Table 1]

Comparative Example 4 Prior to high-speed shear dispersion, γ-aminopropyltriethoxysilane was premixed with magnetic iron oxide, methyl ethyl ketone, toluene, and cyclohexanone myristic acid alone for 4 hours, and then the remaining components were added. A magnetic paint was obtained in the same manner as in Example 1 (of course, γ-aminopropyltriethoxysilane was not added at the time of letdown), its viscosity characteristics were measured, and a coating film was obtained in the same manner as in Example 1. The membrane was subjected to a solvent extraction test. As shown in Table 2 in comparison with Example 1, the coating material of the present invention has a small yield value and a small amount of solvent extracted from the coating film.

[0057]

1) Measured with a rotor # 4 using a BL type rotational viscometer. When the viscosity at 6 rotations is V ' ₆ cps and the viscosity at 12 rotations is V' ₁₂ cps, a numerical value obtained by the following equation.

(Equation 1)

2) The coating film having a weight of Wg was immersed in 100 g of tetrahydrofuran, treated 24 hours later with an ultrasonic dispersing machine for 1 hour, then ultracentrifuged, and the supernatant was collected to obtain a solid content concentration (t) % By weight) measured by the evaporation method, and the value obtained by the following equation.

(Equation 2)

[0060]

As described above, according to the present invention, a low-viscosity coating material in which fine magnetic powder is stably dispersed is obtained, and the magnetic recording medium obtained by using the coating material has a surface smoothness and durability of a coating film. And good running properties and magnetic properties.

Claims (4)

(57) [Claims] 1. A magnetic paint comprising a magnetic powder mixed and dispersed with a polymer containing an epoxy group, which is a binder of the magnetic powder, and then adding a silane compound containing an amino group or a thiol group. 2. A magnetic layer obtained by mixing and dispersing magnetic powder with a polymer containing an epoxy group as a binder for the magnetic powder, and then adding a silane compound containing an amino group or a thiol group. Magnetic recording medium. 3. The magnetic recording medium according to claim 2, wherein the polymer containing an epoxy group is a vinyl chloride resin, a polyurethane resin, a polyester resin, a butadiene polymer or a vinyl epoxy polymer. 4. The polymer containing an epoxy group is COOM, SO
₃ M, SO ₄ M, PO (OM) ₂ , PO ₄ M ₃ or (M is an alkali metal or ammonium; R ₁ , R ₂ , R
_3. The magnetic recording medium according to claim 2, wherein _{3 further} comprises a hydrocarbon and X represents an anion group.