JPH0317819A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersion state end rigidity of a magnetic coating film and to obtain a medium having excellent electromagnetic conversion characteristics 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, aliphatic 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. The magnetic powder is treated with Al and Si.

Description

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

[Background of the Invention] Conventionally, ethyl cellulose, nitrocellulose, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, polymethyl methacrylate, and vinylidene chloride-methacrylate have been used as binders for magnetic recording media. Although methyl acrylate copolymers, polyurethane resins, epoxy resins, and polyester resins have been used, these types of binders are no longer satisfactory. As a binder to replace such resin, [A
] is the 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, and has a hydroxyl number of about 50 to 250. Roux-terminated polyester: (B) Ethylene glycol, propylene glycol, 1
．． Chain extenders selected from the group consisting of 4-butanediol, 1.3-butanediol, 1.5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and hydroquinone di(β-hydroxyethyl) ether. ;Here, the above [A] polyester and (B) Ream 1
The hydroxyl value generated from the ￥ extension agent is approximately 130-30
0; (C) A thermoplastic polyurethane resin which is a reaction product of an aliphatic or aromatic diisocyanate in an amount approximately equal to the total molar amount of the polyester [A] and the chain extender (B) has been proposed (JP-A-57 -30718 Publication). That is, focusing on polyurethane resin as a binder for magnetic recording media, the glycol component in the polyester polyol component that makes up this polyurethane resin is 1.4
- by using cyclohexanedimethanol,
This is an attempt to increase the rigidity of polyurethane resin,
Such polyurethane resins have drawbacks such as poor solubility and poor dispersibility of magnetic powder.

[Disclosure of the Invention] A first object of the present invention is to provide a magnetic recording medium that has excellent dispersibility in a 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 carboxylic acid fraction in the polyester component constituting the polyurethane resin is aliphatic. dicarboxylic acid, and as a glycol component], at least one selected from the group of 4-cyclohexanedimethanol and 1,3-cyclohexanedimethanol, and from the group represented by the following general formula [A] This is accomplished by a magnetic recording medium characterized in that at least one selected diol is used, and the magnetic powder in the magnetic coating is treated with Al or Si. CH, HO-CH-C -CH-0}1 [A]
I1'C}l. RCH. CL Typical aliphatic dicarboxylic acids used in the present invention include adivic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, etc., but are not limited to these. Further, the diol (chain extender) represented by the general formula [A] used as one of the glycol components used in the present invention includes CI1. Clli Cl+! I CI'l1 CI. Shil'lkoL■ko1;I+, Shin3 CL C11, CHs CHs CH2 CH. Examples include shiH3 and shi+11. The polyurethane resin of the present invention using the above aliphatic dicarboxylic acid, 1,4-cyclohexanedimethanol, and the diol represented by the general formula [A] is synthesized as follows. That is, 1.
1,800 parts of 4-cyclohexanedimethanol, 818 parts of Adipine M, and 451 parts of azelaic acid are added, and a catalyst consisting of 1 part of tin oxalate and 4 parts of phthalide is added thereto. Then, blowing nitrogen was started, and the reaction was carried out at a reaction temperature of 230°C for 4 hours, and then continued at 170°C and 5 mJg for 5 hours. To 2870 parts of the polyester thus obtained, the above diol (1) (2
．． 2,4-trimethyl-1,3-pentanediol)6
3.0 parts of phenylmercury propionate catalyst and 2040 parts of 4,4' diphenylenemethane diisocyanate were added to a total polyol formulation containing 0.00 parts of polyol and heated at 120°C.
I reacted with The polyurethane resin thus obtained was designated as polyurethane resin A.

In addition, in the same manner as above, polyurethane resins B and C, which will be described later, are
, D was synthesized. Basically, the polyurethane resin may be one having the above-mentioned properties, but it is preferable that the ratio of carbon NI content to glycol content is 1:10 to 10:1, Further, it is preferable that the ratio of the compound of the group of 1,4-cyclohexanedimethanol and 1,3-cyclohexanedimethanol to the compound represented by the general formula [A] is 1:1 to 1:10. and the molecular lMn is preferably about 5,000 to 50,000. Also, the glass transition point is -30~80°C
It is preferable that 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 to 5 parts by weight, preferably about 25 to IO parts by weight, based on the magnetic $5) l00 parts by weight. It will be done. Here, ferromagnetic iron oxide (C', Mn
, Co, Ni, Cu, Zn, etc.), ferromagnetic chromium dioxide (Na, K,
Metals such as Ti, VMn, Fe, Co, and Ni, semiconductors such as p, sb, and The magnetic powder must be treated with Al and Si. In addition, as a method for treating ferromagnetic powder with SL, for example, oxide magnetic powder is dispersed in an aqueous solution of aluminum salt, and this dispersion is added with alkaline hydroxide water N? After injecting a and adhering aluminum hydroxide to the surface of the oxide magnetic powder,
After washing with water and filtration, the aluminum element-containing oxide magnetic powder thus obtained is dispersed in an aqueous solution containing a water-soluble silicon compound, such as water glass, and acid is added to make it weakly acidic, thereby producing Sing. After attaching the oxide magnetic substance to the surface, there is a method of washing with water, filtering, and drying.
, the degree of treatment with Si is 0.1-0.7 wt%, preferably about 0.2 wt% Si based on 100 parts by weight of ferromagnetic powder.
~0.65w (%, and AI is 0.01~0.2
wt%, preferably about 0.03 to 0.15 wL%. In addition to the above-mentioned binder and AI-Si treated magnetic fine powder, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive, and a fungicide are added to the magnetic layer as necessary. You can. Examples of dispersants include fatty acids having 12 to 18 carbon atoms (R
ICOOH, R, is an alkyl or alkenyl group having 1 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 in the fatty acid esters mentioned above, adoyl acids of the fatty acids mentioned above, etc. are used. In addition, higher alcohols with a carbon number of 12 or more, sulfuric esters, etc. can also be used, and the binder 100
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 dialkyl polysiloxane (alkyl group has 1 to 5 carbon atoms),
Silicone oils such as dialkoxypolysiloxanes, monoalkylmonoalkoxybolysiloxanes, phenylbolysiloxanes, and fluoroalkylpolysiloxanes, conductive fine powders such as graphite, solid lubricants such as molybdenum disulfide and tungsten disulfide, polyethylene, and polypropylene. , polyethylene-vinyl chloride copolymer, plastic fine powder such as polytetrafluoroethylene, carbon number 12 ~
Fatty acid esters consisting of 20 monobasic fatty acids and monohydric alcohols having 3 to 12 carbon atoms, fluorocarbons, etc. can be used, and 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 (
Crabs), corundum, artificial corundum, diamond, artificial diamond, emery (main ingredients: corundum and magnetic iron K), 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 black, natural surfactants such as sabonin, nonionic surfactants such as alkylene oxide, glycerin, and glycidol, higher alkylamines, quaternary ammonium salts, and pyridine. Other heterocycles, cationic surfactants such as phosphonium or sulfonium, and other amphoteric surfactants are used, and the above conductive fine powder is used in an amount of about 0.2 to 20 parts by weight based on 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, sulfur trichloride, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, zinc chlorhexyl nitrite, and other volatile rust inhibitors (amine, amide or Imide (Ia-free or organic acid salts) is used in an amount of about 0.01 to 20 parts by weight per 100 parts by weight of magnetic powder. 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 a range of 5 parts by weight.

Examples of solvents used in magnetic paints include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid glycol monoethyl ether, ethers, and glycols. These include glycol ethers such as dimethyl ether, tars (aromatic hydrocarbons) such as benzene, toluene, and xylene, and chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorohenzene. ．． These magnetic fine powders, a binder, a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive agent, an antifungal agent, a solvent, etc. are then kneaded to form a magnetic paint. For kneading and dispersing magnetic paint, for example, two-roll mills, three-roll mills, pole mills, bevel mills, sand gliders, high-speed impeller separators, 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, 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. <Composition of magnetic paint> ^1 -Si-treated ferromagnetic powder 100
Part α-^1zo3 (average particle size 0.2μm) 5
1 part vinyl chloride-vinyl acetate-vinyl alcohol copolymer (VAGH, manufactured by Union Carbide) 8 parts polyurethane resin A 7 parts carbon black (average particle size 40 mμ) 1 part myristic acid 1 part stearic acid 1 part butyl Stearate 1 part cyclohexanone
100 parts methyl ethyl ketone
100 parts toluene
Coronate L (polyisocyanate manufactured by Nippon Polyurethane Industries ■) was added to 100 parts of the magnetic paint thus obtained.
A magnetic recording medium was obtained by adding 5 parts of the solution and coating it to a predetermined thickness on a predetermined non-magnetic support, followed by drying. In addition, magnetic recording media were obtained using polyurethane resins B, C, and D, which were obtained in the same manner, in place of the polyurethane resin A described above. The properties of the polyurethane resin and magnetic powder used are shown in Tables 1 and 2. Table 2 Regarding the magnetic recording medium thus obtained, electromagnetic conversion characteristics (L-SN), Young's modulus of the magnetic coating layer, and 40° C1
The durability (number of bus trips) was investigated when the vehicle was repeatedly driven under conditions of 80% RH and humidity, and the results are shown in Table 3. As can be seen, the magnetic recording medium according to the present invention is
It has excellent electromagnetic conversion characteristics because the magnetic powder in the magnetic paint has excellent dispersibility, and the magnetic coating film has high rigidity and excellent durability.

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 aliphatic 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. In addition, the magnetic powder in the magnetic coating film contains Al diol.
, a magnetic recording medium characterized in that it is treated with Si. ▲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]