JPH06101111B2 - Magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium having excellent magnetic properties and mechanical properties.

(Prior Art) A general-purpose magnetic tape is prepared by dispersing needle-shaped magnetic particles having a major axis of 1 μm or less in a binder solution together with an appropriate additive (dispersant, lubricant, antistatic agent, etc.) to prepare a magnetic paint. Is applied to a polyethylene terephthalate film.

A magnetic recording medium is required to have a high density of magnetic recording and a high reproduction output. For that purpose, it is necessary to highly pack and orient the magnetic particles having a high coercive force. In order to achieve high packing and high orientation, magnetic particles must be dispersed up to primary particles. The dispersion of magnetic particles is greatly influenced by the binder,
Even if a disperser having high dispersion efficiency is used, the magnetic particles are not dispersed in the coating material if the dispersibility of the binder is low. Also, magnetic particles with high coercive force have been developed, but as the coercive force increases, the magnetic particles become difficult to disperse.

Conventionally, as binders for magnetic paints, vinyl chloride / vinyl acetate copolymers, vinyl chloride / vinyl acetate / vinyl alcohol copolymers, vinyl chloride / vinylidene chloride copolymers, thermoplastic polyurethane resins, thermosetting polyurethane resins, Polyester resin, acrylonitrile-butadiene copolymer, nitrocellulose, cellulose acetate butyrate, epoxy resin, acrylic resin, etc. are used.

It is known to use a surfactant as a dispersant for the purpose of improving magnetic properties, but there are drawbacks such as deterioration of physical properties and deterioration with time due to the presence of a low molecular weight surfactant in the magnetic coating film. is there.

The magnetic tape must have not only excellent magnetic properties, but also excellent mechanical properties such as abrasion resistance, running property, flexibility, and adhesion to a support. Magnetic tapes using polyester resins and polyurethane resins as binders are available in Japanese Patent Publications Sho 44-17947, Sho 44-18222, Sho 45-24900, Sho 44-23500, Sho 45-24902, Sho 49-48126,
Japanese Patent Publication 48-31611, Japanese Patent Publication 48-31610, Japanese Patent Publication 42-1543
2, as disclosed in Japanese Examined Patent Publication No. 51-6522, it has excellent mechanical properties and is useful as a magnetic tape binder.

(Problems to be Solved by the Invention) The fact that the dispersibility of magnetic particles is dramatically improved by introducing a metal salt of sulfonic acid into a polyester resin or a polyurethane resin is disclosed in JP-B-57-3134 and JP-B-58-41565. The effect of the metal salt of sulfonic acid is disclosed in Japanese Patent Publication No.
Due to its hydrophilicity, a metal salt of a phosphorus compound such as phosphinic acid and phosphonic acid can be expected to have the same effect, and also a radiation curable resin can be expected to have the same effect. However, metal salts of phosphorus compounds such as phosphinic acid and phosphonic acid may cause deactivation of the catalyst during the production of polyester resin, polyurethane resin, etc., reduce the physical properties of the polymer obtained by the formation of ether bonds, or reduce the polarity. Since they are different, they do not react uniformly and are separated. Even in polyurethane resins and the like, metal salts of phosphorus compounds such as phosphinic acid and phosphonic acid are highly inorganic, so it is impossible to introduce this hydrophilic group into the resin by reaction in a general-purpose solvent or in the absence of solvent. It was

(Means for Solving the Problems) In view of the above circumstances, the inventors of the present invention have made the coating film magnetic while maintaining the mechanical properties of the polyester resin, polyurethane resin, epoxy resin, acrylic resin and the like. As a result of extensive studies aimed at improving the dispersibility of particles, stable production of a polyurethane resin or the like can be achieved by using a phosphorus compound having the characteristics, and the desired dispersibility of magnetic particles can be significantly improved. I found that

That is, the present invention relates to a magnetic recording medium in which a non-magnetic support is coated with a magnetic material in which a ferromagnetic powder is dispersed in a binder, and the following formula (I) or (I
A magnetic recording medium comprising a phosphorus-containing polyurethane resin having a molecular weight of 6,000 to 50,000, which is obtained by reacting at least one of the phosphorus compounds represented by I).

(In the formulas (I) and (II), X and Y are ester-forming functional groups, R ₁ and R ₂ are lower alkylene groups having 1 to 6 carbon atoms, and m, n, o and p are 0 to 10 Any value can be taken, provided that o = 0 and p = 0 in formula (II),
X = OH and Y = OH. M represents an alkali metal atom, a hydrogen atom, or a lower alkyl group having 1 to 6 carbon atoms. ) The polyurethane resin of the present invention is a polyurethane having a molecular weight of 6,000 to 50,000 obtained by reacting a polyester diol (A) having a molecular weight of 500 to 20,000, a chain extender (B) having a molecular weight of less than 500 and a polyisocyanate (C). It is a resin.

In the present invention, the phosphorus compound is preferably copolymerized in polyester diol which is a raw material of the polyurethane resin.

Polyester diol (A) used in the present invention
Examples of carboxylic acid components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid, and aromatic oxycarboxylic acids such as p-oxybenzoic acid and p- (hydroxyethoxy) benzoic acid. , Succinic acid, adipic acid, azelaic acid, sebacic acid, aliphatic dicarboxylic acids such as dodecanedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, tetrahydrophthalic acid,
Unsaturated aliphatic and alicyclic dicarboxylic acids such as hexahydrophthalic acid, and tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid and pyromellitic acid can be mentioned.

Further, as the glycol component of the polyester diol (A), ethylene glycol, propylene glycol, 1,
3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol , 1,4-cyclohexanedimethanol, ethylene oxide adduct and propylene oxide adduct of bisphenol A, ethylene oxide and propylene oxide adduct of hydrogenated bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. . Further, tri- and tetraols such as trimethylolethane, trimethylolpropane, glycerin and pentaerythritol may be used in combination.

Examples of the polyester diol include lactone polyester diols obtained by ring-opening polymerization of other lactones such as ε-caprolactone.

Examples of the phosphorus compound represented by the formula (I) used in the present invention are as follows.

Examples of the phosphorus compound represented by the formula (II) used in the present invention are as follows.

The chain extender (B) having a molecular weight of less than 500 used in the present invention has the effect of adjusting the concentration of the urethane group or urea group in the resin and imparting the toughness peculiar to the polyurethane resin. Erylene glycol, 1,3-propylene glycol, 1,4-tetramethylene glycol, 1,6-hexanediol, cyclohexanedimethanol, xylylene glycol, diethylene glycol,
Triethylene glycol, linear glycol such as ethylene oxide adduct of bisphenol A, propylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2,2,4-trimethyl-1,3 −
Examples include branched glycols such as pentanediol and propylene oxide adducts of bisphenol A, amino alcohols such as monoethanolamine and N-methylethanolamine, diamines such as ethylenediamine, hexamethylenediamine, isophoronediamine, piperazine, and water.

As chain extenders other than the above, trifunctional components such as trimethylolpropane, diethanolamine, triethanolamine, and glycerin are used in a range that does not impair the performance, and 5 equivalent% of the total of the polyester diol (A) and the chain extender (B). May be used below.

If the molecular weight of the chain extender exceeds 500, the toughness peculiar to the polyurethane resin decreases, which is not preferable.

Examples of the polyisocyanate (C) used in the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenyl methane diisocyanate, m-phenylene diisocyanate and hexamethylene diisocyanate. , Tetramethylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 2,4-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-
Biphenylene diisocyanate, 4,4'-diphenylene diisocyanate, 4,4'-diisocyanate-diphenyl ether, 1,5'-naphthalene diisocyanate,
p-xylylene diisocyanate, m-xylylene diisocyanate, 1,3-diisocyanate methylcyclohexane, 1,4-diisocyanate methylcyclohexane, 4,4′-diisocyanate dicyclohexane, 4,4 ′
Diisocyanate compounds such as diisocyanate cyclohexylmethane and isophorone diisocyanate, or triisocyanate compounds such as trimer of 2,4-tolylene diisocyanate and trimer of hexamethylene diisocyanate in an amount of 7 mol% or less of all isocyanate groups. .

The polyaddition reaction of the polyurethane resin used in the present invention is a one-shot method in which all components are reacted at the same time, first, a long-chain diol is reacted under the condition of excess isocyanate, and the resulting isocyanate group-terminated prepolymer is treated with a chain extender.
There is a prepolymer method for further polymerizing. The thermoplastic polyurethane resin used in the present invention can be manufactured by either the one shot method or the prepolymer method.
Examples of the reaction method include a method in which the raw materials are melted and a method in which they are dissolved in a solution.

As a reaction catalyst, stannous octylate, dibutyltin dilaurate, triethylamine and the like may be used.

The molecular weight of the polyurethane resin is in the range of 6,000 to 50,000. If the molecular weight is less than 6,000, the mechanical strength of the polyurethane resin will decrease, and if it exceeds 50,000, the solution viscosity will be too high and handling will be difficult.

The phosphorus compounds represented by the above general formulas (I) and (II) are appropriately used so that the resin contains 200 ppm to 50,000 ppm as atoms. If the phosphorus compound is smaller than the above range, the dispersibility in the magnetic particles is low. On the other hand, if it exceeds the above range, the hygroscopicity is increased, the physical properties are deteriorated, the adhesion to the non-magnetic support is deteriorated, and the practicality is reduced.

In the present invention, in addition to the resin obtained by reacting the phosphorus compounds represented by the general formulas (I) and (II), the flexibility of the magnetic tape is adjusted, the heat resistance and cold resistance are improved, the wear resistance is improved, and the like. For this purpose, it is desirable to add another compatible resin or to mix a compound which reacts with the resin of the present invention to crosslink.

Examples of the resin compatible with the resin of the present invention include vinyl chloride resin, polyester resin, cellulose resin, acrylic resin, epoxy resin, phenoxy resin, polyvinyl butyral, acrylonitrile-butadiene copolymer and the like. On the other hand, examples of the compound that crosslinks with the thermoplastic polyurethane resin include a polyisocyanate compound, an epoxy resin, a melamine resin, a urea resin and the like, and among these, the polyisocyanate compound is particularly desirable.

The ferromagnetic particles used in the present invention include γ-Fe ₂ O
₃ , γ-Fe ₂ O ₃ and Fe ₃ O ₄ mixed crystal, CrO ₂ , cobalt ferrite, cobalt adsorbed iron oxide, barium ferrite, Fe-C
Examples thereof include ferromagnetic alloy powders such as o and Fe-Co-Ni.

The magnetic recording medium of the present invention may optionally contain a plasticizer such as dibutyl phthalate, triphenyl phosphate, dioctyl sulfo sodium succinate, t-butyl phenol-polyethylene ether, ethylnaphthalene-sodium sulfonate, dilauryl succinate. Lubricating oils such as zinc stearate, soybean oil lecithin, and silicone oil, and various antistatic agents can also be added.

A magnetic material in which ferromagnetic powder is dispersed in a binder generally uses a solvent, and the solvent includes acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, alcohols such as methanol, methyl acetate, acetic acid. Esters such as ethyl, butyl acetate, ethyl butyrate, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, glycol ethers such as dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, and aliphatic carbonization such as hexane and heptane. Hydrogen or a mixture thereof can be used.

In the magnetic recording medium of the present invention, the above magnetic material is coated on a non-magnetic support. As the material of the non-magnetic support that can be used,
Examples thereof include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, polycarbonate, polyvinyl chloride, polyimide, metals such as aluminum and copper, and paper.

A magnetic material is coated on a non-magnetic support according to a conventional method and dried, and the coating film is calendered if necessary and then heat treated. It is also possible to carry out calendering after the heat treatment.

(Function) In the present invention, by using a resin obtained by reacting a specific phosphorus compound as at least one component of the binder, the resulting coating film retains the mechanical properties of the polyurethane resin, and the dispersibility of magnetic particles is improved. It is possible to improve the properties, the properties due to the dispersibility, for example, the filling property of the magnetic particles, the orientation, the smoothness of the magnetic layer are excellent, and the powder is less likely to fall and the durability is good.

Methylene chain or alkylene oxide bond in phosphorus compound,
By having a cycloalkylene oxide bond or an arylene oxide bond, the dispersibility of magnetic particles is particularly excellent.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples. In the examples, "parts" means "parts by weight".

Production Example of Raw Polyester Thermometer, 485 parts of dimethyl terephthalate, 485 parts of dimethyl isophthalate in an autoclave equipped with a stirrer,
409 parts of ethylene glycol, 458 neopentyl glycol
Part and tetrabutoxytitanate 0.68 parts, 15
Transesterification was carried out by heating at 0 to 230 ° C. for 120 minutes, then 23.6 parts of the phosphorus compound (F) was charged, and the reaction was further conducted at 220 to 230 ° C. for 1 hour. Next, the reaction system is heated to 250 ° C. in 30 minutes, the system pressure is gradually reduced to 45 mm after 10 mmHg,
The reaction was continued for another 60 minutes under these conditions. The raw material polyester A thus obtained had a molecular weight of 2000 and a phosphorus content of 3300 ppm. Raw material polyesters B to G obtained by the same manufacturing method are shown in Table 1.

The resin composition was analyzed by NMR. No increase in viscosity was observed during the polymerization of the raw material polyester F in Table 1. Further, the raw material polyester E was completely separated from the resin by agglomeration of the sodium salt of the phosphorus compound into particles. The constituent units of the raw material polyesters E and F represent the molar ratio of the acid component and the glycol component when the raw material was charged.

In Table 1, the phosphorus compound (K) means one represented by the following formula.

Synthesis Example of Polyurethane Resin In a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 147 parts of toluene, 147 parts of methyl ethyl ketone, 100 parts of the polyester diol A, and 5 parts of neopentyl glycol.
Parts and p-toluenesulfonic acid as an anti-gelling agent.
After 01 parts were charged and dissolved, 21 parts of 4,4'-diphenylmethane diisocyanate and 0.05 parts of dibutyltin dilaurate were charged and reacted at 70 to 80 ° C for 10 hours.

The obtained polyurethane resin solution had a solid content concentration of 30%, a solution viscosity of 50 poise (25 ° C.), and a polyurethane resin (A-1) having a molecular weight of 21,000. The polyurethane resins (BD) and (G) obtained by the same production method are shown in Table 2.

Example 1. A composition having the following blending ratio was placed in a hole mill and dispersed for 48 hours, and then an isocyanate compound, Coronate 2030
5 parts (manufactured by Nippon Polyurethane Industry Co., Ltd.) was added as a curing agent and further mixed for 1 hour to obtain a magnetic paint. This thickness
It was applied onto a 12 μm polyethylene terephthalate film while applying a magnetic field of 2,000 glass so that the thickness after drying was 5 μm. After standing at 50 ° C. for 2 days, it was slit to a 1/2 inch width to obtain a magnetic tape.

Polyurethane resin A solution 100 parts (solid content 30%, MEK / toluene = 1/1 solution) Cobalt-deposited γ-Fe ₂ O ₃ 120 parts Olive oil 1 part Cyclohexanone 50 parts Toluene 100 parts MEK 50 parts Table 3 shows each physical property.

As is clear from Table 3, the magnetic recording media using polyurethane resins A and B are excellent in Br / Bm, adhesion, smoothness and solvent resistance.

(Effect of the Invention) Conventionally, it was difficult to introduce a metal base of a phosphorus compound such as phosphinic acid and phosphonic acid into a resin, but not only can these hydrophilic groups be easily introduced, It is effective for the dispersibility of magnetic powder and does not impair the properties of the base resin forming the basic skeleton.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support coated with a magnetic material in which a ferromagnetic powder is dispersed in a binder.
A molecular weight of 6, which is obtained by reacting at least one phosphorus compound represented by the following formula (I) or (II) as a component in the binder:
A magnetic recording medium comprising 000 to 50,000 phosphorus-containing polyurethane resin. (In the formulas (I) and (II), X and Y are ester-forming functional groups, R ₁ and R ₂ are lower alkylene groups having 1 to 6 carbon atoms, and m, n, o and p are 0 to 10). Any value can be taken, provided that in the formula (II), when o = 0 and p = 0, X = OH and Y = OH, M is an alkali metal atom, a hydrogen atom or a carbon number of 1 to 6 The lower alkyl group of is shown.)