JPH0317818A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersion state and rigidity of a magnetic coating film and to obtain a medium having excellent durability by using polyurethane resin for a binder of the magnetic coating film, specifying the component of the binder and treating the magnetic powder with Al and Si. CONSTITUTION:Polyurethane resin is used for the binder of the magnetic coating material, and as for carboxylic acid in the ester component which constitutes the polyurethane resin, aromatic dicarboxylic acid is used. Also, at least one kind of diol expressed by formula I (wherein each R, R' has 3-10 carbons and at least one of R and R' is a branched alkyl group with >=3 carbons) is used as the glycol component of the resin. The magnetic powder is priorly treated with Al and Si and then used for the magnetic coating layer. The aromatic carboxylic acid in the polyurethane resin is terephthalic acid, isophthalic acid, etc.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to magnetic recording media.

[Background of the invention]

Conventionally, ethylcellulose, nitrocellulose, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, polymethyl methacrylate, and vinylidene chloride-methyl methacrylate copolymer have been used as binders for magnetic recording media. , polyurethane resins, epoxy resins, polyester resins, etc. have been used, but these types of binders are no longer satisfactory. As a binder to replace such a resin, for example, the following general formula ( (OROOCR'Co).OROOClIHR'
A polyurethane resin represented by NHCO) has been proposed (Japanese Patent Publication No. 6130324), or [A
] a reaction product of a dicarboxylic acid selected from the group consisting of adipic acid, azelaic acid, 1,12-dodecanedioic acid and mixtures thereof and 1,4-cyclohexanedimethanol, having a hydroxyl number of about 50 to 250. Hydroxy-terminated polyester: (B) Ethylene glycol, propylene glycol, 1
, 4-butanediol, 1,3-butanediol, 1.5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and hydroquinone di(β-hydroxyethyl) ether. : Here, the hydroxyl value produced from the polyester [A] and the chain extender (B) is about 130 to 300.
; (C) A thermoplastic polyurethane resin has been proposed which is a reaction mixture of an aliphatic or aromatic diisocyanate in an amount approximately equal to the total molar amount of the above (^) polyester and (B) a chain extender (JP-A-57 -30718 Publication). That is, we focused on polyurethane resin as a binder for magnetic recording media, and used aromatic dicarboxylic acids instead of aliphatic dicarboxylic acids such as adipic acid and sebacic acid as the carboxylic acid component in the polyester polyol component that makes up this polyurethane resin. It is also possible to use ethylene glycol, propylene glycol, 1,
3-brobanediol, l,4-7'tanediol, l
, 5-pentanediol, 1,6-hexanediol,
It has been proposed to use neopentyl glycol and 1,4-cyclohexanedimethanol. In other words, it has been proposed to use aromatic dicarboxylic acids and 1,4-cyclohexanedimethanol to increase the rigidity of polyurethane resins, but such polyurethane resins have poor solubility and are difficult to use in magnetic paints. It has the disadvantage of poor dispersibility. [Disclosure of the Invention] The first object of the present invention is to provide a magnetic paint with excellent dispersibility! The objective is to provide a magnetic recording medium with excellent magnetic conversion characteristics. A second object of the present invention is to provide a magnetic recording medium in which the magnetic coating film has high rigidity and excellent durability.

The object of the present invention is to provide a coating-type magnetic recording medium in which at least a polyurethane resin is used as a binder in a magnetic coating layer, wherein an aromatic acid component is used as a carboxylic acid component in a polyester component that binds the polyurethane resin. Dicarboxylic acid and glycol component have the following general formula [
This is achieved by a magnetic recording medium characterized in that at least one diol selected from the group represented by A] is used, and the magnetic powder in the magnetic coating layer is treated with AI or Si. It will be done. Examples include aromatic dicarboxylic acids containing a sulfonic acid metal base such as sulfonic acid and 2-sodium sulfoterephthalic acid. Further, the diol represented by the general formula [A] used as the glycol fraction used in the present invention includes terephthalic acid, isophthalic acid, orthophthalic acid, 1. 5 naphthalic acid,
Others 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalate CI. CH3 CI+. CH. CH. CH. C11, CI! CH. CH. cut CH. Examples include Cll, DiN3CHff, etc. Then, aromatic dicarboxylic acids such as those mentioned above and the general formula [A
] The polyurethane resin of the present invention using the diol represented by is synthesized as follows. That is, 679 parts of dimethyl terephthalate, 434 parts of ethylene glycol, and diol (+) (2,2.4-trimethyl-1) of the general formula [A] were placed in a reaction vessel equipped with a thermometer, a stirrer, and a partial reflux condenser. .3 pentanediol), 0.66 part of zinc acetate, and 0.08 part of sodium acetate were added, and the transesterification reaction was carried out at 150 to 2 lO゛C for 3 hours, and then 1212 parts of sebacic acid
After adding 1 part and reacting at 210 to 250 °C for 2 hours,
The pressure of the reaction system was reduced to 20 s Hg over 40 minutes, and the condensation reaction was further carried out at 240°C for 60 min at 5 to 20 s Hg. The polyester polyol thus obtained (
1) has a hydroxyl value of 40, and from NMR analysis etc., its & - Trimethyl-1,3-pentanediol was 56 mol%. Then, in a reaction vessel equipped with a concentration meter, a stirrer, and a reflux type condenser, 200 parts of toluene and methyl ethyl ketone were added.
Part o, 1000 parts of the above polyester polyol (1), 70 parts of diphenylmethane diisocyanate, one sip of dibutyltin dilaure. 2 parts were added and reacted at 70 to 90'C for 10 hours to obtain polyurethane resin A. Also, similar to this. and polyurethane resins B and C, which will be described later.
, D, E and F, G were synthesized. In addition, as a polyurethane resin, basically, it is acceptable as long as it has the above-mentioned components, but if the ratio of carboxylic acid content and glycol component is 1.
Preferably, the ratio is 10-10 to 1, and the molecule i1Mn is preferably about 5,000 to 50,000. In addition, the glass transition point is -20 to 8
Preferably it is 0°C. Also, although this polyurethane resin is used as a binder for the magnetic coating layer, it is also possible to use other binder resins together with the polyurethane resin, and in such cases, the other resin may be 50% or less. It is preferable that there be. The amount of binder citrus in the magnetic layer of the magnetic recording medium according to the present invention is about 30 parts by weight per 100 parts by weight of magnetic powder.
~5 parts by weight, preferably about 25-10 parts by weight. Here, as the magnetic powder, ferromagnetic iron oxide (Cr, Mn,
Co, Ni, Cu, Zn, etc. may be added), ferromagnetic chromium dioxide (Na, K,
Metals such as Ti, V, Mn, Fe, Go, Ni,
ferromagnetic alloy powder, etc. can be used as appropriate, but it is necessary that such ferromagnetic powder has been treated with AI or Si. It is. In addition, as a method for treating ferromagnetic rice with AI or Si, for example, oxide magnetic powder is dispersed in an aqueous solution of an aluminum salt, and an alkali hydroxide aqueous solution is poured into this dispersion, so that the surface of the oxide magnetic powder is After adhering aluminum hydroxide to the powder, it was washed with water and filtered, and the thus obtained aluminum element-containing oxidized powder was mixed with a water-soluble silicon compound,
For example, by dispersing water glass in an aqueous solution and adding acid to make it weakly acidic, Sin. There is a method of attaching the magnetic oxide to the surface, washing it with water, filtering it, and drying it.
The degree of treatment with AI and Si is 0.1 = 0.7 wL% of Si, preferably about 0.2 to 0.65-1%, with respect to 100 parts by weight of ferromagnetic powder; ．．
oi~0.2ht%, preferably about 0.03~0.15
It is wt%.

In addition to the above-mentioned binder and AI-Si treated magnetic fine rice powder, the magnetic layer may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive agent, an anti-mold agent, etc. as necessary. May be added. Examples of dispersants include fatty acids having 12 to 18 carbon atoms (R
ICOOH, Rl is an alkyl or alkenyl group having 11 to 17 carbon atoms), an alkali metal of the above fatty acid (Li,
(Na, K, etc.) or alkaline earth metals (Mg, Ca,
Metal soaps consisting of Ba), fluorine-containing compounds of the above-mentioned fatty acid esters, amides of the above-mentioned fatty acids, etc. are used. In addition, higher alcohols with carbon numbers of 12 or more, sulfuric esters, etc. can also be used, and binders with
It is added in an amount of about 0.5 to 20 parts by weight.

As a lubricant, the above-mentioned dispersants are also effective, but dialkylborisiloxane (alkyl group has 1 to 5 carbon atoms),
Silicone oil such as dialkoxybolysiloxane, monoalkylmonoalkoxybolysiloxane, phenylbolysiloxane, fluoroalkylpolysiloxane, conductive fine powder such as graphite, solid lubricant such as molybdenum disulfide, tungsten disulfide, polyethylene, polypropylene , polyethylene-vinyl chloride copolymer, plastic fine powder such as polytetrafluoroethylene, carbon number 12 or more
20 monobasic fatty acids and monohydric alcohols having 3 to 12 carbon atoms, fatty acid esters, fluorocarbons, etc. can be used, and the amount of about 0.2 to 100 parts by weight of the binder can be used.
It is added in an amount of 20 parts by weight.

As abrasives, alumina, silicon carbide, chromium oxide (
Cry(h), corundum, artificial corundum, diamond, artificial diamond, emery (main components: corundum and magnetic iron), etc. are used. These abrasives have a Mohs hardness of 5 or more, an average particle size of about 0.05 to 5μ,
Particularly preferably, it is 0.1 to 2 μm, and is added in an amount of about 0.5 to 20 parts by weight per 100 parts by weight of the binder. Antistatic agents include conductive fine powder such as carbon plaque, natural surfactants such as sabonin, nonionic surfactants such as alkylene oxide, glycerin, and glycidol, higher alkylamines, and quaternary ammonium salts. , pyridine and other heterocycles, cationic surfactants such as phosphonium or sulfonium, and other amphoteric surfactants, and the above conductive fine powder is used in an amount of about 0.2 to 20 parts by weight per 100 parts by weight of the binder. The surfactant is added in an amount ranging from about 0.1 to 10 parts by weight. Rust inhibitors include phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, zinc chlorhexylamine nitrite, and other volatile rust inhibitors (amine, amide, or imide inorganic acid salts or organic acid salts),
Approximately 0.0% per 100 parts by weight of magnetic powder. It is used in a range of 20 parts by weight. Antifungal agents include salutylanilide, bis(tributyltin) oxide, mercuric phenyloleate, dihydroacetoic acid, etc., and the amount of these agents is about 0.0% per 100 parts by weight of the binder. Ol
It is used in the range of ~5 parts by weight. Organic solvents used in magnetic paints include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone;
Ester types such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol acetate monoethyl ether; glycol ether types such as ester and glycol dimethyl ether; and tar types such as benzene, toluene, and xylene.
These include aromatic hydrocarbons), methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorohenzene, and other chlorinated hydrocarbons. These magnetic powders, binders, dispersants, lubricants, abrasives, antistatic agents, rust preventives, antifungal agents, solvents, etc. are then kneaded to form a magnetic paint. For kneading and fractionating magnetic paints, for example, two-roll mills, three-roll mills, ball mills, pebble mills, sand gliders, high-speed inveler fractionators, high-speed stone mills, high-speed impact mills, kneaders,
High-speed mixers, homogenizers, ultrasonic dispersers, etc. are used. The method of applying magnetic paint onto a non-magnetic support is as follows:
Air doctor coat, blade coat, air knife coat, squeeze coat, rehearsing roll coat, transfer roll coat, gravure coat, kiss coat,
Cast coat, Subin coat, etc. can be used. Then, the magnetic layer coated on the support by the method described above is subjected to a treatment to orient the magnetic powder, if necessary, and then dried. Further, if necessary, the surface may be smoothed or shaped into a desired shape to obtain a magnetic recording body.

[Example] The following composition was thoroughly kneaded and dispersed in a ball mill to obtain a magnetic paint.

Precepts for magnetic paint> ^1 -Si-treated ferromagnetic powder 100
Part α-Aj! z(h (average particle size 0.2 ttm)
5 parts vinyl chloride-vinyl acetate-vinyl alcohol copolymer (VAGH, manufactured by Union Carbide) 8
Part polyurethane Citrus A 7 parts Carbon black (average particle size 40 microns) 1 part myristic acid 1 part stearic acid 1 part butyl stearate 1 part cyclohexanone
100 parts Methylene ethyl ketone 7 100 parts Toluene
100 parts of the thus obtained magnetic paint was adjusted by adding 5 parts of Coronate L (polyisocyanate manufactured by Nippon Polyurethane Industries ■), coated on a given non-magnetic support to a given thickness, and then dried to make it magnetic. Obtained a recording medium.

Moreover, instead of the above polyurethane resin A, polyurethane resins B, C, D, E and F obtained in the same manner were used.
, G was used to obtain a magnetic recording medium. In addition, the characteristics of the polyurethane resin and magnetic powder used are listed below! , shown in Tables 2 and 3. We investigated the durability (number of running passes) when running the vehicle, and the results are shown in Table 4. Table 4

Claims (1)

[Scope of Claims] A coated magnetic recording medium in which at least a polyurethane resin is used as a binder in a magnetic coating layer, wherein an aromatic dicarboxylic acid is used as a carboxylic acid component in a polyester component constituting the polyurethane resin. , and at least one diol selected from the group represented by the following general formula [A] is used as the glycol component, and further, the magnetic powder in the magnetic coating layer is treated with Al or Si. A magnetic recording medium characterized by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [A] [The number of carbon atoms in R and R' is 1 to 6 each, the number of carbon atoms in R + R' is 3 to 10, and at least one of R and R' has a carbon number Alkyl group having 3 or more branches]