JPS60119631A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance dispersibility of a magnetic powder by successively coating the surface of the magnetic powder with polyisocyanate and aliphatic amine. CONSTITUTION:A magnetic recording medium is prepared by feeding a kneader with 100pts.wt. Co-deposited alpha-Fe2O3, stirring it in reduced pressure, spraying 3pts.wt. of ethyl acetate soln. of toluene diisocyanate on the surface of said Fe2O3 with a spray gun, further continuing stirring and kneading, again spraying 5pts.wt. of ethyl acetate soln. of stearylamine likewise, stirring and kneading at 50 deg.C, after that, washing the obtained powder, coating the dried surface with toluene diisocyanate and stearylamine in succession, dispersing a liquid prescribed compsn. contg. 100pts.wt. of the obtained. Co-coated alpha-Fe2O3 (1) thus covered, etc. in a ball mill, coating a polyester film with said liquid with a blade in a dried thickness of 3mum blade, and drying to form a magnetic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a magnetic recording medium used as a magnetic tape, magnetic flexible disk, or the like.

PRIOR TECHNOLOGY A general magnetic recording medium consists mainly of magnetic powder such as iron oxide or chromic acid and a binder consisting of various thermoplastic resins, thermosetting resins, or reactive resins on a non-magnetic support such as a plastic film. It is equipped with a magnetic layer. In order to obtain good external magnetic properties in such a magnetic recording medium, it is necessary to use as fine a magnetic powder as possible and to uniformly disperse it in the magnetic layer. For this reason, in the past, surfactants such as lecithin, higher fatty acids, phosphoric esters, higher alcohols, and diamine salts were added to the magnetic layer as dispersants for the magnetic powder, or in order to improve the dispersibility of the magnetic powder itself,
Magnetic powders coated with silane-based, titanium-based, aluminum-based camping agents, etc. have been used. However, conventional dispersants or dispersion coatings are insufficiently effective, and have the disadvantage that the finer the magnetic powder becomes, the lower the dispersibility becomes.

Object The object of the present invention is to provide a magnetic recording medium in which fine magnetic powder is uniformly dispersed in a binder, and therefore has excellent magnetic properties.

Structure The magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a resin binder is provided on a non-magnetic support, and the magnetic powder is sequentially coated with polyisocyanate and aliphatic amine. It is characterized by this.

It is believed that the dispersion effect of the dispersant or dispersion coating agent on the magnetic powder depends on the bonding force between these materials. However, in conventional magnetic recording media, this bonding force is based on the adsorption force between the materials and is therefore relatively weak. On the other hand, since the magnetic recording medium of the present invention utilizes the reactivity between materials,
This binding force is strong, and therefore the dispersion effect is also large. That is, in the case of the present invention, a polyisocyanate that is reactive with the magnetic powder itself is used as a base, and the surface of the magnetic powder is coated with a uniform and strong bond due to its reactivity, and then an aliphatic powder that is reactive with the polyisocyanate is coated on top of that. This is a turtle coated with Anne as a dispersion coating agent, which is also uniformly and strongly bonded due to its reactivity.

To make the coated magnetic powder used in the present invention, generally first,
While stirring the magnetic powder in a kneader under reduced pressure, the polyisocyanate solution is added dropwise into the powder, sprayed, etc. to cause the addition reaction, and the reaction is completed and at the same time drying is carried out at room temperature. Or, if necessary, after stirring and kneading at a temperature of about 50 to 90 °C for a sufficient time (about 15 minutes or more), add a solution of aliphatic amine to the mixture in the same manner as described above to cause the reaction to complete. In order to carry out drying and drying at the same time, stirring and mixing may be continued for a sufficient period of time (about 30 minutes or more) at a temperature of about 50 to 90°C.

Next, since excess or unreacted polyisocyanate and/or aliphatic amine may be attached to the surface of the coated magnetic powder thus obtained, in order to remove this, the coated magnetic powder is coated with polyisocyanate and aliphatic amine. Wash and purify with a solvent for group amines. The concentrations of each solution of polyisocyanate and aliphatic amine are preferably as low as 1 weight percent or less in order to carry out a uniform reaction. Also, the amount of polyisocyanate and aliphatic amine used is 1-10% of the magnetic powder.
If each component is less than 1%, it is difficult to obtain the desired effect, and if it is more than 10%, it becomes excessive as a reaction component and becomes uneconomical. - Polyisocyanates used as primers include diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate,
Bifunctional incyanates such as dicyclohexylmethane diisocyanate and isophorne diisocyanate, trifunctional isocyanates such as triphenylmethane triisocyanate, and polyisocyanate adducts made from these, blocked isocyanates, and polymerized preisocyanates (commercially available products include Nippon Polyurethane). Coronet)
L, ptlHL; Desmodur L manufactured by Noninil; and Azizolene LD-213 manufactured by DuPont. ) can be exemplified. Aliphatic amines as dispersants include dodecylamine, tridecylamine, natodecylamine, pentadecylamine, cetylamine, heptadecylamine,
Primary amines such as oftadecylamine and nonadecylamine; Secondary amines such as dioctylamine, dinonylamine, dibutylamine, didodecylamine, didodecylamine, ditetradecylamin, dioctadecylamin, dioctadecylamine; ethylenediamine , trimethylene diamine, tetramethylene diamine, pentamethylene diane, hexamethylene diane, 1,7-diaminohebutane, and 1.8-cya-2-octane. Also, as magnetic powder coated with the above materials.

r-Ft40B, Fe104, Oo-containing Fe2
0B, Oo deposited r-Pe*Oa *Oo-containing Fe1
A ferromagnetic alloy composed of at least two types such as O, Oo, Fa, and N1 can be used. As a solvent, ethyl acetate, xylene, methyl ethyl ketone, toluene, dimethylformado, dihydrofene, etc. are used alone or in combination for both polyisocyanates and aliphatic amines.

As the binder used in the magnetic layer, common thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used. Examples of thermoplastic resins include vinyl chloride resin,
Vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer,
Acrylic acid ester acrylonitrile copolymer, acrylic acid ester disdene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer polymer,
Urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, poly1 amide resin, polyvinyl butyral, cellulose derivative, styrene citadiene copolymer,
Polyester resins, amine resins, various synthetic rubber-based thermoplastic resins (polycitadiene, polychloroprene, polyisoprene, styrene-citadiene copolymers, etc.), and mixtures thereof are used. Emulsions of these are also used.

Examples of thermosetting resins or reactive resins include phenol-formalin-2 rank resin, phenol-formalin-resol ml phenol-furfural resin, xylene-formaldehyde resin, urea resin, melamine resin, dry oil-modified alkyd resin, and phenol resin. Modified alkyd resins, maleic acid resins modified alkyd resins, unsaturated polyester resins, epoxy resins and curing agents (boria resins, acid anhydrides, boria resins, etc.), terminal incyanate polyester moisture-curing resins, terminal incyanate resins These include polyether moisture-curable resins, polyisocyanate prepolymers, resins containing polyisocyanate prepolymers and active hydrogen, and mixtures thereof. Emulsions of these are also used.

These binders may be used alone or in combination;
Other additives may be added. The amount of binder in each magnetic layer is in the range of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the coated magnetic powder.

In addition to the binder and coated magnetic powder, additives such as a lubricant, abrasive, and antistatic agent may be added to each magnetic layer.

Antistatic agents include car 2 cylinder blank, graphite,
Conductive fine powder such as carbon black graft polymer; Natural surfactant such as saponin; Nonionic surfactant such as alkylene oxide type, glycerin type, glycidol type; Higher alkylaquines, quaternary ammonium salts, pyridine Cationic surfactants such as other heterocycles, phosphoniums or sulfoniums; calzenic acid,
Anionic surfactants containing sulfonic acid, phosphoric acid, sulfuric acid ester groups, and acidic groups in the phosphoric ester ring; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric or phosphoric esters of amino alcohols are used.

As lubricants, conductive fine powders such as carbon blank, graphite, carbon black graft polymers; inorganic fine powders such as molybdenum disulfide and tungsten disulfide; polyethylene, polypropylene, ethylene vinyl chloride copolymer, polytetrafluorocarbon Ethylene corner plastic fine powder; a-olefin polymer; unsaturated aliphatic hydrocarbon that is liquid at room temperature (a compound in which an n-olefin double bond is bonded to the terminal carbon, carbon number 20): carbon number 12-2
A list of fatty acid esters consisting of 0 monobasic fatty acids and monohydric alcohols having 3 to 12 carbon atoms can be used.

Commonly used abrasive materials include fused alumina,
Silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. are used.

These abrasives have a Mohs hardness of 5 or more and an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm.

Examples of the non-magnetic support used in the present invention include polyesters containing polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate, paper, synthetic paper, aluminum-based films, and composites thereof. is used.

To make the magnetic recording medium of the present invention, coated magnetic powder, a binder, and various additives if necessary are dissolved or dispersed in a suitable solvent, and the resulting magnetic coating is coated on a non-magnetic support and dried. If necessary, perform heat treatment to harden the coating film to a thickness of 1
, a magnetic layer having a thickness of approximately 0 to 5.0 μm may be formed.

Note that acetone, methyl ethyl ketone, cyclohexanone, xylene, hexane, heptane, etc. are used as the solvent.

Effect When the surface of the magnetic powder is sequentially coated with polyisocyanate and aliphatic amine as described above, the reactivity of these materials causes them to bond strongly and uniformly to the magnetic powder.
The dispersibility of the magnetic powder in the binder is significantly improved, and thus a magnetic recording medium with excellent magnetic properties can be obtained.

Examples of the present invention are shown below. All parts are parts by weight.

Example 1 100 parts of 0 parts coated r-Fe20g (coercive force Hc=640 engineering, Ted, particle size 0.3μ) were placed in a kneader, and while stirring under reduced pressure, the r-Fe1O1
Spray 3 parts of a 1% ethyl acetate solution of toluene diisocyanate (2) onto the surface of the surface of the mixture with a spray gun, stir and knead for about 15 minutes, and then add 5 parts of a 1% ethyl acetate solution of stearylamine in the same manner. After spraying and stirring and kneading at 50°C for about 30 minutes, the resulting powder was washed with ethyl acetate, dried, and the surface was sequentially coated with toluene diisocyanate and stearylamine.
Ol (1) was obtained. Next, the coating Oo coating r −F1
! 110B (11,100 parts Urethane resin (0A-310 manufactured by Morton Chemical Co.) 255 parts Dimethylformamide 1150 parts Methyl ethyl ketone 150 parts A solution of the following formulation was dispersed in a 2-liter 2-liter tube for 30 hours, and then dispersed into a 75-μ thick I-lyester film. A magnetic recording medium was prepared by applying a blade coat onto the film to a dry thickness of 3 μm and drying to form a magnetic layer.

Example 2 The same method as in Example 1 except that a 1% ethyl acetate solution of distearyldiamine (DUOMBEIN-T manufactured by Ion Akzo) was used instead of a 1% ethyl acetate solution of stearylamine during the production of coated magnetic powder. O whose surface was sequentially coated with toluene diisocyanate and distearyl diamine
o Deposited y-Fe20B (2) was obtained.

Thereafter, a magnetic recording medium was produced in the same manner as in Example 1 using this coating r-FetOl(2).

Example 3 The surface of the coated magnetic powder was coated with toluene diisocyanate and tolystylamine in the same manner as in Example 1, except that a 1% solution of myristylamine in ethyl acetate was used instead of the IIs ethyl acetate solution of stearylamine. oDeposition r-Pe10g (3) was obtained.

A magnetic recording medium was then produced in the same manner as in Example 1 using this coating r-Fe,01 (3).

Comparative Example 1 A magnetic recording medium was prepared in the same manner as in Example 1 except that 100 parts of untreated Oo-coated r-Fe2O3 and 3 parts of lecithin were used as a dispersant instead of 100 parts of coated Oo-coated r-Fe20 g (1) It was created.

Comparative Example 2 Coating Oo coating r-FeHO@ (1) Instead of 100 parts, 100 parts of untreated Oo coating-Fe101 and a phosphate ester surfactant (GAF manufactured by Toho Chemical Co., Ltd.) were used as a dispersant.
AOR) ii-610) A magnetic recording medium was prepared in the same manner as in Example 1 except that three copies were used.

Next, the magnetic properties and dispersibility of the magnetic powder of the above magnetic recording medium were investigated, and the results shown in the table below were obtained.

It is expressed as 'II B'/Bm (Br: residual magnetic flux density, Bm: saturation magnetic flux density), and a large value indicates good root dispersibility.

From this table, it can be seen that when the surface of the magnetic powder is coated with polyisocyanate and higher aliphatic amine as in the present invention, a magnetic recording medium with good dispersion of the magnetic powder and excellent magnetic properties can be obtained.

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a resin binder is provided on a non-magnetic support, characterized in that the magnetic powder is sequentially coated with /IJ isocyanate and aliphatic 72 magnetic recording media.