JPH09204640A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the deterioration in the characteristics and adhesiveness of a magnetic recording medium which is caused by partial crystallization and improve the blocking strength of the magnetic recording medium by a method wherein polyurethane resin is used as binder. SOLUTION: Magnetic particles are dispersed in binder which is applied to a nonmagnetic supporter. Polyurethane resin which is composed of long chain polyole whose fusion heat is not less than 150kJ/mol and organic diisocyanate or polyurethane resin which is composed of long chain polyole whose fusion heat is not less than 150kJ/mol, chain extendion agent and organic diisocyanate is used as the binder. Further, polyurethane resin which is composed of long chain polyole whose fusion heat is not less than 150kJ/mol and organic diisocyanate or is composed of long chain polyole whose fusion heat is not less than 150kJ/mol, chain extendion agent and organic diisocyanate and whose glass transition temperature is not higher than 25 deg.C may be used as the binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium in which a magnetic recording layer having magnetic particles dispersed in a binder is formed on a non-magnetic support. More specifically, it relates to a magnetic recording medium which has improved mechanical properties and blocking resistance of a magnetic coating film and is excellent in durability and productivity.

[0002]

2. Description of the Related Art Binders of coating type magnetic recording media (specifically, audio tapes, video tapes, floppy disks, computer data tapes, etc.) have been used as binders for resins such as polyurethane resin, vinyl chloride resin and nitrocellulose. Are used alone or in combination. Vinyl chloride resin and nitrocellulose are generally used for maintaining the rigidity of the magnetic tape, and polyurethane resin is generally used for flexibility, toughness, abrasion resistance, adhesiveness and the like.
However, since the polyurethane resin is flexible, it has a drawback in that the resin softens due to sliding friction during running after being formed into a tape, a slight vibration is generated due to deformation, so-called “squeaking” occurs, and blocking occurs. Further, there is a manufacturing problem that blocking also occurs during winding during the manufacturing process. On the other hand, a method of increasing the glass transition point (Tg) of the polyurethane resin to harden the resin is adopted, but an imbalance in physical properties such as deterioration of flexibility and adhesiveness occurs, or Regarding blocking, it is necessary to raise Tg to a level close to that of vinyl chloride resin, and none of them has achieved a sufficient result.

[0003]

In view of the above circumstances, the inventors of the present invention have made extensive studies on the constituent components of the polyurethane resin, and as a result, have completed the present invention.

[0004]

That is, the present invention provides a magnetic recording medium formed by dispersing magnetic particles in a binder and coating the magnetic particles on a non-magnetic support.
A long-chain polyol and an organic diisocyanate having a heat of fusion of 150 kJ / mol or more, or a heat of fusion of 150 kJ / m
A magnetic recording medium is characterized by using a polyurethane resin composed of a long-chain polyol having a molar ratio of ol or more, a chain extender and an organic diisocyanate. Furthermore, in a magnetic recording medium formed by dispersing magnetic particles in a binder and coating it on a non-magnetic support, the binder has a long-chain polyol having a heat of fusion of 150 kJ / mol or more and an organic diisocyanate, or a heat of fusion. Is 150 kJ / mol
A magnetic recording medium characterized by using a polyurethane resin having a glass transition point of 25 ° C. or lower, which comprises the above long-chain polyol, a chain extender and an organic diisocyanate.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The components constituting the polyurethane resin of the present invention will be described below. Examples of the long-chain polyol used in the present invention include polyester-based, polylactone-based, polycarbonate-based, polyether-based polyols and copolyols thereof. Further, these long-chain polyols may be used alone or in combination. These long chain polyols are obtained by a known method, and the molecular weight is preferably 300 to 10,000. The heat of fusion of these polyols is required to be 150 kJ / mol or more.

Generally, the majority of the constituent components of the polyurethane resin are polyols, and the properties of the polyol are strongly reflected in the polyurethane. If the heat of fusion of the polyol is 150 KJ / mol or less, the crystallinity of the polyol will be lost after the urethanization reaction, and the physical properties will change significantly around Tg as an amorphous solid. When the heat of fusion of the polyol is 150 KJ / mol or more, the crystallinity derived from the polyol is exhibited even after the urethanization reaction, so that the physical properties can be maintained by the partial crystallization, the tackiness can be reduced, and the blocking resistance can be improved. In addition, in the heat of fusion measurement of polyurethane resin,
Only broad and unclear peaks are obtained due to the nature and structure of the polymer, and it is difficult to quantify the melting behavior due to a clear polyol.

Examples of the polyester polyol which can be used in the present invention include known succinic acid, adipic acid, sebacic acid, azelaic acid, terephthalic acid, isophthalic acid, orthophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, Hexahydroorthophthalic acid, naphthalenedicarboxylic acid or its acid ester, dicarboxylic acid / acid ester such as acid anhydride, acid anhydride and ethylene glycol, 1,3-propylene glycol,
1,2-propylene glycol, 1,3-butanediol, 1,4-
Butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, 1, 4-cyclohexanedimethanol, or ethoxide or propylene oxide adduct of bisphenol A, glycol such as adduct of propyroxide, hexamethylenediamine, xylenediamine, isophoronediamine, diamine or aminoalcohol such as monoethanolamine, or a mixture thereof. Examples thereof include polyester polyols, polyesteramide polyols obtained by the dehydration condensation reaction, and lactone polyester polyols obtained by ring-opening polymerization of cyclic ester (lactone) monomers such as epsilon-caprolactone.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and the like obtained by ring-opening polymerization of ethylene oxide, propylene oxide and tetrahydrofuran, and copolyether.

Polycarbonate polyols are generally obtained by dealcoholation reaction of polyhydric alcohols with diethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and the like. Examples of the polyhydric alcohols are ethylene glycol and 1,3-propylene glycol. 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol , 1,8-octanediol, 1,9-nonanediol, diethylene glycol, 1,
Polycarbonate polyols such as 4-cyclohexanedimethanol, which are used alone or in combination of two or more thereof, are used.

The chain extender used in the present invention is generally a substance having a molecular weight of 300 or less and containing two or more active hydrogens, and known alcohols, amines, amino alcohols and the like are used. For example, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 3-methyl-
1,5-pentanediol, neopentyl glycol, 1,8
-Octanediol, 1,9-nonanediol, trimethylolpropane, glycerin, diethylene glycol, 1,
4-cyclohexanedimethanol, glycol such as ethylenoxide of bisphenol A or propyleneoxide adduct, hexamethylenediamine, xylenediamine, isophoronediamine, diamine or aminoalcohol such as monoethanolamine, and the like. Water and urea can also be used as chain extenders. The above compounds can be used alone or as a mixture.

Examples of the polyisocyanate used in the present invention include aromatic polyisocyanates such as:
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, 4,4'-
Difermethane diisocyanate, 2,4'-difermethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4 '
-Diisocyanate, 2,2'-diphenylpropane-
4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4 '
-Diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, etc. Examples of the diisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, 3-
Methyl-1,5-pentane diisocyanate, lysine diisocyanate, etc., as alicyclic diisocyanate, for example, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate,
Hydrogenated diphenylmethane diisocyanate, tetramethyl xylene diisocyanate and the like, and examples of modified products thereof include dimer, trimer, prepolymer modified product, carbodiimide modified product and urea modified product of the above polyisocyanate. .

In producing the polyurethane resin used in the present invention, when the polyurethane resin is linear, the NCO / OH molar ratio of polyol and diisocyanate is 0.6.
/1-1.15/1 is preferable, and when the polyurethane resin has a branch, it is necessary to avoid gelation. Further, an ordinary polyisocyanate curing agent can be added to the magnetic recording medium using the same, if necessary. Examples of the polyisocyanate curing agent include a compound having three or more isocyanate groups in one molecule, which is a reaction product of diisocyanate and a low molecular weight triol, and a diisocyanate trimer. Examples thereof include Coronate L, Coronate HL, Coronate 2030, and Millionate MR manufactured by Nippon Polyurethane Industry.

The polyurethane resin of the present invention may contain a hydrophilic polar group (SO ₃ M, COOM, tertiary amine, quaternary ammonium salt, -P = O (OM) ₂ ) or the like. The concentration of these polar groups is 0.00 per polymer.
The range of 1 to 1.0 mmol / g is desirable.

Further, as a catalyst, triethylamine,
Tertiary amines such as triethylenediamine, potassium acetate,
Metal salts such as zinc stearate, dibutyltin laurate,
Examples thereof include organic metal compounds such as dibutyltin oxide. By incorporating a stabilizer such as substituted benzotriazoles against ultraviolet rays as a stabilizer and a stabilizer against thermal oxidation such as a phenol derivative, various performances of the polyurethane resin can be significantly stabilized.

The glass transition point of the polyurethane resin obtained from the above composition must be 25 ° C. or lower.
If the glass transition point is 25 ° C. or higher, the resin becomes hard and brittle, and the adhesiveness of the magnetic recording medium to the substrate and the flexibility of the magnetic recording medium are deteriorated, and peeling and powder falling easily occur, which is not preferable. .

Further, in producing this polyurethane resin, a conventionally known method can be adopted, and toluene, xylene, benzene, dioxane, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone,
Solution reaction method of reacting with ethyl acetate, butyl acetate, etc. alone or in a mixed solvent system, or after thoroughly mixing the reactants in the absence of solvent, heat the reaction mixture by placing it on a flat plate or a flat surface and then heating. Usual production methods such as a pulverization method and a method of injecting the reaction mixture into an extruder can be used.

The magnetic powder used in the present invention is γ-
Fe ₂ O ₃ , Co-γ-Fe ₂ O ₃ , Co-FO.Fe
Iron oxide magnetic powder such as ₂ O ₃ , CrO ₂ , hexagonal barium ferrite fine particles, and Fe, Ni, Co: Fe—N
Fe such as i-Co alloy and Fe-Mn-Zn alloy, Ni,
Various ferromagnetic powders such as metal magnetic powders containing Co as a main component can be mentioned.

In the magnetic recording medium of the present invention, if necessary,
Carbon fine particles as an antistatic agent, nonpolar metal oxide fine particles as an abrasive, higher fatty acids, fatty acid esters, liquid paraffin, siloxanes and fluorocarbons as lubricants for reducing the friction coefficient, and lecithin as a dispersant. Etc. can be added.

Examples of the material for the non-magnetic substrate used in the present invention include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyimides, polyamide imides, polyphenylene sulfides, and the like.
Depending on the application, it is used in the form of tape, film or sheet.

In the binder component used in the present invention, if necessary, a thermoplastic polyurethane resin, vinyl chloride-, which is usually used as a binder component of a magnetic recording medium, is used.
Dispersion of magnetic powder by using vinyl acetate copolymer, fibrin resin, polyvinyl butyral resin, thermoplastic polyester resin, vinyl chloride-vinyl propionate copolymer, epoxy resin, phenoxy resin, etc. together. And the smoothness of the magnetic layer surface.

[0021]

EFFECT OF THE INVENTION By using the polyurethane resin of the present invention, the crystallinity derived from the polyol is developed, so that the physical properties of the magnetic recording medium are maintained by the partial crystallization and the tackiness is lowered.
Further, the blocking resistance can be improved. Further, the polyurethane resin of the present invention can be applied as an adhesive for film lamination, an ink binder, a surface treatment agent for plastics, other adhesives, and a coating agent.

[0022]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples. In addition, "parts" and "%" in the synthesis examples, examples and comparative examples represent "parts by weight" and "% by weight" unless otherwise specified.

Synthesis Example of Polyol A In a reactor equipped with a stirrer, a thermometer and a partial reflux type cooling tube, 703 parts of adipic acid (100 mol% of acid component),
471 parts of 1,4-butanediol (glycol component 10
0 mol%) and 0.01 part of tetrabutyl titanate were charged, and a polycondensation reaction was performed at 140 to 220 ° C. The number average molecular weight of the polyol A thus obtained is 2
The heat of fusion was 400 kJ / mol.
These are shown in Table 1.

Synthesis Example of Polyols B to N A polyol was obtained by selecting an acid component and a glycol component in a reactor equipped with a stirrer, a thermometer and a partial reflux type cooling tube. The formulations, number average molecular weights, and heats of fusion of these polyols are summarized in Tables 1-2. The amounts of the raw materials used in the table are 100 mol% of the total acid component and 1 mol of the total alcohol component in the acid / alcohol polyester polyol system.
The amount of the other polyols was shown to be 100 mol% and the total amount of the other raw materials used was 100 mol%.

[0025]

[Table 1]

[0026]

[Table 2]

Polyurethane Resin Synthesis Example 1 271.7 parts of Polyol A shown in Table 1 and methyl ethyl ketone 3 were placed in a reactor equipped with a stirrer, a thermometer and a cooling tube.
After charging 00 parts and dissolving and mixing at 50 ° C., 0.06 part of dioctyltin dilaurate as a urethanization catalyst was added, and then 28.3 parts of 4,4′-diphenylmethane diisocyanate was added and reacted at 75 ° C. . As the reaction progresses, the viscosity increases, so when appropriate, dilute with methyl ethyl ketone and toluene, and confirm that the peak of the isocyanate group disappeared in the infrared spectrum,
A homogeneous, transparent solution containing a hydroxy-terminated resin was obtained. The polyurethane resin solution thus obtained has a solid content of 3
It was 0%, and the number average molecular weight in terms of polystyrene by GPC measurement was about 100,000. Let the obtained polyurethane be PU-1. These are summarized in Table 3.

Polyurethane Resin Synthesis Examples 2 to 19 A polyol, a chain extender, and an isocyanate were selected in a reactor equipped with a stirrer, a thermometer, and a cooling tube to obtain a polyurethane resin solution in the same manner as in Polyurethane Resin Synthesis Example 1. It was
These are summarized in Tables 3-5.

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

Abbreviations in Tables 3 to 5 are as follows. EG: Ethylene glycol IPDA: Isophorone diamine MDI: 4,4'-diphenylmethane diisocyanate TDI: Tolylene diisocyanate My: Yield point modulus M100: Elongation 100% modulus TB: Breaking strength EB: Breaking elongation Tg: Glass transition point E'25 ℃: Young's modulus at 25 ℃

My, M100 and TB are JIS K
It was measured according to 6301. In addition, Tg and E ′ are measuring devices = Reovibron DDV-II, heating rate: 2 ° C.
/ min, E = peak when measured at frequency = 35Hz
Was defined as Tg. The heat of fusion of the polyol is DSC-200 manufactured by Seiko Denshi KK and the rate of temperature rise is 5 ° C.
/ Min, temperature range = −100 to 150 ° C.

Example 1 Using the polyurethane resin PU-1 thus obtained, the ratio was adjusted according to the following composition, and dispersed by a sand grind mill (manufactured by Igarashi Kikai) for 10 hours to prepare a paint. Then, it is coated on a base film of polyethylene terephthalate having a thickness of 15 μm so as to have a dry film thickness of 3 μm.
It was dried at 0 ° C for 3 minutes and further cured at 60 ° C for 24 hours to form a coating film. The magnetic surface of the obtained coating film was measured with a gloss meter (manufactured by Suga Test Instruments Co., Ltd.) at an incident angle of 45 degrees and a reflection angle of 45.
When the reflectance in degrees was measured, the glossiness was 90%.

[Compound] Metal magnetic powder (BET number 56 m ² / g) 100 parts Polyurethane resin (solid content) 20 parts Methyl ethyl ketone 105 parts Toluene 105 parts Cyclohexanone 70 parts

Further, the polyethylene terephthalate film was overlaid on this coating film, and a pressure of 5 kg / cm ² was applied thereto, and the film was allowed to stand at 60 ° C. for 1 week and at 25 ° C. for 24 hours to check the blocking resistance. In addition, the squareness ratio was measured after the blocking property was evaluated. Table 6 shows the results.

Examples 2 to 13 and Comparative Examples 1 to 6 Instead of the polyurethane resin solution used in Example 1, the polyurethane resin solutions shown in Tables 3 to 5 were used and evaluated in the same manner as in Example 1. did. Table 6 shows the results.

[0038]

[Table 6]

[Evaluation Method of Blocking Resistance] The peeling property of the polyethylene terephthalate film laminated on the magnetic coating film was evaluated by measuring the sample width of 10 mm according to JIS K6301. However, the pulling speed is 300 mm
/ Min. The peeling strength and peeling strength from the magnetic coating film at this time are represented by the following symbols. ⊚: The film is easily and completely peeled off from the coating film, and there is no blocking. Peel strength: 0 g / 10 mm. ◯: The film is completely peeled off and there is almost no blocking. Peel strength: <30/10 mm Δ: The film is hard to peel off from the coating film. Blocking Peel strength:> 30/10 mm ×; The film completely adheres to the coating film and does not peel off at all, and the material is destroyed. [Electromagnetic conversion characteristics measurement method] The squareness ratio was measured using a total VSM-3KA type (manufactured by Toei Industry Co., Ltd.). The comparative example could not be measured due to material destruction or blocking.

Claims (2)

[Claims] 1. A magnetic recording medium formed by dispersing magnetic particles in a binder and coating the magnetic particles on a non-magnetic support, wherein the binder has a heat of fusion of 150 kJ / mol.
A magnetic recording medium comprising a polyurethane resin comprising the above long-chain polyol and an organic diisocyanate, or the long-chain polyol having a heat of fusion of 150 kJ / mol or more, a chain extender and an organic diisocyanate. 2. A magnetic recording medium formed by dispersing magnetic particles in a binder and coating the magnetic particles on a non-magnetic support, wherein the binder has a heat of fusion of 150 kJ / mol.
A long-chain polyol and an organic diisocyanate as described above, or a long-chain polyol having a heat of fusion of 150 kJ / mol or more, a chain extender and an organic diisocyanate, and a polyurethane resin having a glass transition point of 25 ° C. or less are used. Magnetic recording medium.