JPH0317820A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersion state of a magnetic coating material and to obtain a medium having excellent electromagnetic conversion characteristics and durability by using polyurethane resin for a binder of the magnetic coating film and specifying the component of the binder. 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 compd. selected from 1,4-cyclohexane dimethanol and 1,3-cyclohexane dimethanol, and at least one kind of diol expressed by formula I (wherein each R, R' has 1 - 6 carbons, R+R' has 3 - 10 carbons and at least one of R and R' is a branched alkyl group with >=3 carbons) are used as the glycol component of the resin.

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, a sulfonic acid metal base is added at a concentration of 10 to 1000 per bolamer.
A polyurethane resin having a weight/10"g has been proposed (Japanese Patent Publication No. 5B-41565), and the following general formula ((OROOCR'Co).OROOCNIIR'
A polyurethane resin represented by (NHCO) has been proposed (Japanese Patent Publication No. 6l-3 0324), or (^) adipic acid, azelaic acid, 1,l2-dodecanedioic acid, and mixtures thereof. a hydroxyl-terminated polyester which is the reaction product of a dicarboxylic acid selected from the group and 1,4-cyclohexanedimethanol and has a hydroxyl number of about 50 to 250: (B) ethylene glycol, propylene glycol, 1
．． 4 butanediol, 1.3butanediol, 1.
5 pentanediol, l 6 hexanediol, 1.4
Cyclohexane dimethanol and hydroquinone di(β
- a chain extender selected from the group consisting of (hydroxyethyl) ether;
) The hydroxyl number generated from the chain extender is approximately 1 3
0 to 300; (C) A thermoplastic polyurethane resin is proposed (specially In other words, attention has been focused on polyurethane resin as a binder for magnetic recording media, and fats such as adipic acid and sebacic acid have been used as the carbon fli component in the polyester polyol component constituting the polyurethane resin. It is possible to use an aromatic dicarboxylic acid in place of the group dicarboxylic acid, and also to use ethylene glycol, propylene glycol,
1,3-propanediol, 1,4-butanediol,
It has been proposed to use 1,5-pentanediol, 1,6-hexanediol, 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 since the solubility of such polyurethane resins decreases, magnetic The disadvantage is that the paint has poor dispersibility. [Disclosure of the Invention] The first object of the present invention is to provide a magnetic recording medium that has excellent dispersibility in magnetic paint and excellent electromagnetic 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 coated magnetic recording medium in which at least a polyurethane resin is used as a binder in a magnetic coating layer, wherein the polyester component constituting the polyurethane resin has an aromatic dicarboxylic acid component as a carboxylic acid component. The acid is selected from the group represented by the following general formula [A] and at least one selected from the group of 1,4-cyclohexanedimethanol and 1,3-cyclohexanedimethanol as a glycol component. This is accomplished by a magnetic recording medium characterized by the use of at least one type of diol. Aromatic dicarboxylic acids used in the present invention include terephthalic acid, isophthalic acid, orthophthalic acid,! , 5 naphthalic acid, other 5-sodium sulfoisophthalic acid, 5
- Aromatic dicarboxylic acids containing sulfonic acid metal salts such as potassium sulfoisophthalic acid and 2-sodium sulfoterephthalic acid. In addition, the diol represented by the general formula [A] used as one of the glycol compounds used in the present invention includes CI. CH, CHs CH3 Ct+S CII3 CL CH, CL CH3 6H Koshin CB! etc. The polyurethane resin of the present invention using the above aromatic dicarboxylic acid, 1,4-cyclohexanedimethanol, and the diol represented by the general formula [A] is synthesized as follows. i.e. closed stirrer,
In a reactor equipped with a nitrogen inlet and a two-connected reflux condenser, 1
, 1800 parts of 4-cyclohexanedimethanol and 1350 parts of terephthalic acid were added thereto, and a catalyst consisting of 1 part of tin oxalate and 4 parts of phthalimide was added thereto. Then, nitrogen blowing was started and the reaction was carried out at a reaction temperature of 230°C for 4 hours, and then at 170°C and 5mmHg.
The reaction continued for 5 hours. To a total polyol blend of 2870 parts of the polyester thus obtained and 600 parts of the above diol (1) (2,2.4-}limethyl-13-pentanediol), 3.0 parts of a phenylmercury propionate catalyst was added. part and 4.4'
2040 parts of diphenylenemethane diisocyanate was added and reacted at 120'C. The polyurethane resin thus obtained was designated as polyurethane resin A. In addition, in the same way, polyurethane resins B, C, and
D, Snake, F, G, and H were synthesized. The polyurethane resin may basically have the above-mentioned properties, but it is preferable that the ratio of carboxylic acid content to glycol content is 1:10-10:1. can be,
Also, 1,4-cyclohexanedimethanol and 1,3-
Compounds of the cyclohexanedimethanol group and the general formula [A
] is preferably 10:1 to 1:10, and the molecular weight 1Ln is preferably about 5,000 to 50,000. Further, it is preferable that the glass transition point is -20 to 80°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 resin 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. In addition to the above-mentioned binder and magnetic fine powder, the magnetic layer contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, an antirust agent,
Antifungal agents, etc. may be added as necessary. Examples of dispersants include fatty acids having 12 to 18 carbon atoms (R
ICQOH, I? , is an alkyl or alkenyl group having 11 to 17 carbon atoms), an alkali metal (Li
, Na, K, etc.) or alkaline earth metals (Mg, Ca, etc.)
, Ba), fluorine-containing compounds of the fatty acid esters mentioned above, amides of the fatty acids mentioned above, and the like are used. In addition, higher alcohols having 12 or more carbon atoms, sulfuric esters, etc. can also be used, and binders with 10 or more carbon atoms can be used.
It is added in an amount of about 0.5 to 20 parts by weight relative to 0 parts by weight. As a lubricant, the above-mentioned dispersants are also effective, but dialkylborisiloxane (alkyl group has 1 to 5 carbon atoms),
Silicone oils such as dialkoxypolysiloxanes, monoalkylmonoalkoxybolysiloxanes, phenylbolysiloxanes, fluoroalkylpolysiloxanes, conductive fine powders such as graphite, solid lubricants such as molybdenum disulfide and 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 is about 0.2 to 100 parts by weight of the binder.
It is added in an amount of 20 parts by weight. As abrasives, alumina, silicon carbide, chromium oxide (
Cries), corundum, artificial corundum, diamond, artificial diamond, emery (main precepts: corundum and magnetic iron FL), etc. are used. These abrasives have a Mohs hardness of 5 or more and an average particle size of about 0.05 to 5.
μ, particularly preferably 0.1 to 2 μ, is used, and is added in an amount of about 0.5 to 20 parts by weight based on 10 parts by weight of the binder. Antistatic agents include conductive fine powder such as carpon plack, natural surfactants such as sabonin, nonionic surfactants such as alkylene oxide, glycerin, and glycidol, higher alkyl amines, and quaternary surfactants.
cationic surfactants such as class ammonium salts, pyridine and other heterocycles, phosphoniums or sulfoniums,
Other amphoteric surfactants are used, and the above conductive fine powder is added in an amount of about 0.2 to 20 parts by weight per 100 parts by weight of the binder, and the surfactant is added in an amount of about 0.1 to 10 parts by weight. It will be done. Rust inhibitors include phosphoric acid, sulfamide, guanidine, pyridine, azol, urea, zinc chromate, calcium chromate, strontium chromate, zinc chlorhexylamine nitrite, etc. about 0.01 to 2 parts by weight per 100 parts by weight of magnetic
Used in a range of 0 parts by weight. Antifungal agents include saltylanilide, bis(tributyltin) oxide, mercuric phenyloleate, dihydroacetoic acid, etc., and the amount of antifungal agents is about 0.01 per 100 parts by weight of the binder.
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, glycol dimethyl ether, and tar types such as benzene, toluene, and xylene.
These include aromatic hydrocarbons), chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene. These magnetic fine powders, binders, dispersants, lubricants, abrasives, antistatic agents, rust preventives, antifungal agents, solvents, etc. are gamma-kneaded to form magnetic paints. For kneading and fractionating magnetic paints, for example, two-roll mills, three-roll mills, ball mills, pebble mills, sand gliders, high-speed impeller fractionators, high-speed stone mills, high-speed impact mills, kneaders, high-speed mixers, homogenizers, ultra A sonic disperser etc. is 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, reverse roll coat, transfer roll coat, gravure coat, kiss coat,
Cast coat, spin 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. Furthermore, if necessary, the surface may be smoothed or shaped into a desired shape to obtain a magnetic recording medium. [Example] The following composition was sufficiently kneaded and dispersed in a ball mill to obtain a magnetic paint. Co-r-FexOx (llc-700(Oe),
BET=38m”/g) 100 copies α-Alto3
(Average particle size 0.2μ-) 5 parts potassium sulfonate-containing vinyl chloride copolymer (MRIIO, Nippon Zeon (
Co., Ltd.) 9 parts polyurethane resin 8
6 parts carbon black (average particle size 40-μ) 0.
5 parts myristic acid 1 part stearic acid 1 part butyl stearate 1 part cyclohexanone 100 parts methyl ethyl ketone 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. I got a recording medium. In addition, a magnetic recording medium was obtained by using polyurethane resin B-H obtained in the same manner instead of polyurethane resin A. The properties of the polyurethane resin used are shown in Tables 1 and 2. Regarding the magnetic recording medium thus obtained, the electromagnetic conversion characteristics (L-SN), the Young's modulus of the magnetic coating layer, and the temperature at 40°C
The durability (number of running passes) when repeatedly driven under conditions of , humidity and 80% RH was investigated, and the results are shown in Table 3. Table 3

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 member selected from the group of 1,4-cyclohexanedimethanol and 1,3-cyclohexanedimethanol and at least one member selected from the group represented by the following general formula [A] as a glycol component. A magnetic recording medium characterized in that a diol is used. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [A] (The number of carbon atoms in R and R' is 1 to 6 each, and 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]