JPH01251416A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the thermal decomposition resistance of the title medium by using specific polyurethane as the essential component of a binder. CONSTITUTION:A magnetic coated film mainly consisting of magnetic powder and the binder is provided on the title medium and the polyurethane contg. 5-50% polyhydric alcohol expressed by the formula is used for the binder. In the formula, R1, R2 denote H, alkyl, etc. This polyurethane is obtd. by condensing the polyol (e.g.: polycarbonate polyol) contg. the polyhydric alcohol expressed by the formula (e.g.: bisphenol A) with polyisocyanate, chain extender, etc. The binder is preferably incorporated therein with >=1 kinds among vinyl chloride copolymer, polyvinyl butyral and nitrocellulose.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media, and more particularly to improvements in binders thereof.

[Conventional technology]

In recent years, with the rapid development of information technology, magnetic recording media, such as magnetic disks and magnetic tapes, have come to be required to have higher performance even under a wide range of usage environments. For example, in floppy disks, it is desired to improve not only electromagnetic conversion characteristics but also physical properties, particularly reliability and durability. In order to obtain a magnetic recording medium with such excellent physical properties, from the viewpoint of the binder system, it is necessary to increase the elongation at break, the elastic modulus, the strength at break, and the heat resistance.

Polyurethane resin has traditionally been widely used as a binder that satisfies the above physical properties, but while this polyurethane resin has the advantages of high elongation at break and good wear resistance, it has low elastic modulus and strength at break. It has the disadvantage of being small. For this reason, magnetic recording media using polyurethane resin have reliability problems such as stick-slip phenomenon in tapes and adhesive phenomenon in disks, so the elastic modulus and breaking strength of the binder are increased. In order to improve the dispersibility of the magnetic powder while imparting lubricity, it is common to use a polyurethane resin together with a relatively hard cellulose resin or vinyl chloride resin.

However, although stick-slip and adhesion phenomena are improved with the above-mentioned binder systems, both cellulose resins and vinyl chloride resins have higher thermal decomposition properties than polyurethane resins, so The durability of the medium was not satisfactory because the binder deteriorated during heat curing or when used for a long time in a high temperature environment.

[Problem that the invention seeks to solve]

This invention improves the f resistance of the binder system that the above conventional products had.
It is an object of the present invention to provide a magnetic recording medium that solves the drawback of poor i-characteristics and has durability under a wide range of usage environments.

[Means to solve the problem]

The present inventors have conducted intensive studies to obtain a binder system that has good thermal decomposition resistance and is poor in elongation at break, elastic modulus, and strength at break. 21 in the skeleton of polyurethane resin! i) It is sufficient to use a polyurethane resin that has the following structure introduced.Furthermore, when this polyurethane resin is used, the heat decomposition resistance of the binder system can be maintained well even when used in combination with vinyl chloride resin, cellulose resin, etc. They discovered what they could do and came up with the present invention.

A polyurethane resin having such a structure is basically obtained by condensation using a polyol, a polyisocyanate, and, if necessary, a chain extender by a conventional method. The polyol used here is the polyol Yoshii L@, which was synthesized according to the purpose.

or I (Rr, R2:H, alkyl group or aryl group, R3
A polycarbonate polyol obtained by condensing a polyhydric alcohol represented by the structural formula of , R4ney CnH2n-1n is an integer) with phosgene, chloroformic acid ester, dialkyl carbonate or diallyl carbonate, and these polycarbonate polyols and organic dibasic acids. polycarbonate polyester polyol obtained by condensation of polyether polyol obtained by adding alkylene oxide to a polyhydric alcohol having the above structure,
Examples include a polyester polyol obtained by dehydration condensation from an organic dibasic acid and a polyhydric alcohol having the above structure, or a polymerized lactone glycol ester polyol of a lactone and a polyhydric alcohol having the above structure. In addition, during the synthesis of this polyol, polyhydric alcohols that do not have the above structure, such as 116-hexanediol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, 1,5-bentanediol, etc. Aliphatic alconope HOQ←'(=CHz)8H
Conventionally known aromatic alcohols such as 1HO(CHg)n1W(CH2)n20H can also be used in combination.

Organic dibasic acids used in polyol synthesis include:
Known acids such as succinic acid, adipic acid, phthalic acid, and maleic anhydride can be used, and lactones such as -
Any known compound such as caprolactone or valerolactone can be used.

Examples of polyisocyanates used in urethanizing these polyols include hexamethylene diisocyanate, lysine diisocyanate, inphorone diisocyanate, xylylene diisocyanate, cyclohexane diisocyanate, toluidine diisocyanate, 2.4
-tolylene diisocyanate), 2.6-tolylene diisocyanate, 4.4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, and 1.5-naphthylene diisocyanate. Further, as the chain extender, conventionally known ones such as the polyhydric alcohol, aliphatic polyamine, aromatic polyamine, alicyclic polyamine, etc. can be used.

The polyurethane resin obtained by the reaction of the above polyol, polyisocyanate, and chain extender has an average molecular weight of 2.
0.000~200. One that is OOO and contains R2 is preferable.

Molecule ff120,000 or less, content of the above structure is 5%
In the following cases, the effects of the present invention cannot be obtained, and on the other hand, the molecular structure is 200. If the content of the above-mentioned structure exceeds OO0 or exceeds 50%, the solubility of the resin decreases, the viscosity of the paint becomes too high, and workability becomes poor.

In addition to the polyurethane resin, conventionally known thermoplastic resins, thermosetting W resins, and radiation-curing resins may be used in combination with the binder of the present invention. Among these, from the viewpoint of dispersibility of the magnetic powder, it is preferable to use one or more resins selected from vinyl chloride resins, polyvinyl butyral resins, and cellulose resins. Examples of the vinyl chloride resin include copolymers containing vinyl chloride and vinyl acetate. Namely, there are vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinyl acetate-vinyl alcohol-maleic anhydride copolymers, and the like.

Commercially available products include VAGH, VYHH%, manufactured by UCC, Ku A, manufactured by Sekisui Kagakuso Kagaku, S-LEC 01, manufactured by Denki Kagaku, and Tenkahinil 1000 G.

As polyvinyl butyral resin, manufactured by Tanesui Kagaku Co., Ltd., B
LS, BMS, etc. can be used.

As the cellulose-based fat, cellulose ether, cellulose inorganic acid ester, cellulose 9-organic acid ester, etc. can be used. Among these IjAm base resins, nitrocellulose is preferred. This commercially available product includes Asahi Kasei Co., Ltd.
Seltsuba BTHI, BTH1/2, Nitrocellulose 5
Examples include L-1, manufactured by Daicel Corporation, and nitrocellulose R8I/2.

The blending ratio of polyurethane resin/(one or more resins selected from vinyl chloride resin, polyvinyl butyral resin, and cellulose resin) in the binder of the present invention is l
It is preferable to have a power ratio of 1 t and a vA range of 10 to 50,150 IO. This is because if the ratio of polyurethane resin is less than 50%, the heat decomposition resistance of the binder system will deteriorate.

A low molecular weight polyisocyanate compound may also be added to the binder as a curing agent.

Examples of the low molecular weight incyanate compound include Coronate L, Coronate HL manufactured by Nippon Polyurethane Co., Ltd., Takenate 300S1 Kukeo, and -to 500 manufactured by Takeda Pharmaceutical Company Limited.
, Bayer AG, Desmodur N, etc.

The magnetic powder used in the present invention includes r-Fe203
, Fe3O4, CO containing 1 Fe2O3, CO containing F
Acicular iron oxide powder such as e3O4, barium ferrite,
Any of those conventionally known as recording elements for magnetic recording media can be used, such as hexagonal ferrite powder such as strontium ferrite, and metal magnetic powders such as Fe, Co, Ni, and alloys thereof.

As the non-magnetic support, various synthetic resin materials can be used, such as polyesters such as polyethylene terephthalate and polyethylene-2-6-naphthalate, cellulose acetates such as cellulose triacetate and cellulose diacetate, and polyimide. , polyamide, etc.

Furthermore, the solvent used when making magnetic paint is
Toluene, xylene, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, acetone, tetrahydrofuran, dioxane, methylene chloride, etc. can be used alone or in combination of 24 or more.

The magnetic layer provided on the non-magnetic support may be formed according to a conventional method, that is, a magnetic paint containing magnetic powder and a binder may be prepared, and this may be applied onto the support and dried. Various conventionally used additives such as dispersants, lubricants, abrasives, and antistatic agents may be appropriately blended into the above-mentioned magnetic paint.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Synthesis of polyurethane resin 1> 200 parts of bisphenol A, 1.6 parts of bovine sandiol
0 parts', 257 parts of diphenyl carbonate, and 0.003 parts of trimethylene (triphenylphosphonium) bis-tetraphenylborate at 180-230°C, pressure 100
The reaction was carried out for 4 hours under the conditions of layer Hg, and then the pressure was lowered to 20 mHg, and the reaction was carried out at 230°C for 10 hours, after which the phenol was sufficiently distilled off to obtain a polycarbonate polyol. Next, 100 parts of this polycarbonate polyol, 6 parts of 1.6 hexanediol, 4 parts of bisphenol, 50 parts of MDI, and 0.01 part of dibutyltin dilaurate were reacted in 700% THF to obtain a polycarbonate polyol polyurethane sphere resin. The molecular weight of the obtained resin was 28,000.

Synthesis of polyurethane resin 2> Bisphenol A 200 parts, 1.6 hexanediol 1
After reacting 0 parts of diphenyl carbonate, 257 parts of diphenyl carbonate, and 0.003 parts of trimethylene (triphenylphosphonium) bis-tetraphenylborate at 150 to 220°C for 12 hours, the phenol was removed at 150°C under a pressure of 20 μHg. A polycarbonate polyol was obtained. To 100 parts of this polyol, add 200 parts of adipic acid to 200 to 200 parts of adipic acid.
The reaction was carried out at 220°C to obtain polycarbonate polyester polyol. 100 parts of the obtained polycarbonate polyester polyol were reacted with 6 parts of 1.6 hexanediol, 4 parts of bisphenol A, 50 parts of Ml) I, and 0.01 part of dibutyltin dilount in THF at 70°C to form a polycarbonate polyester polyurethane. Resin was obtained. The molecular weight of the obtained polyurethane resin was 45.
．． It was 000.

Synthesis of polyurethane resin 3> [4(hydroxyethoxy)phenol]propane 20
To 100 parts of polyester polyol obtained by reacting 0 parts of isophthalic acid and 290 parts of isophthalic acid at 210°C, 6 parts of 1.6 hexanediol, 4 parts of neopentyl glycol, MD
70 parts of I and 001 parts of diptyltin dilaurate
A polyester polyurethane resin was obtained by reacting in THF at .degree. The molecular weight of the obtained polyurethane was 43,00
It was 0.

Synthesis of polyurethane resin 4> Polyether polyol 509 obtained by addition reaction of bisphenol A and propylene oxide and polycarbonate polyol 50fflH used in synthesis 1
This, 6 parts of 1,6-hexanediol, 4 parts of neopentyl glycol, 50 parts of MD I, and 0.01 part of dibutyltin dilaurate were reacted in THF at 70°C to obtain polyether polyurethane W fat. The molecular weight of the obtained polyurethane resin was 30,000.

Example 1゜Co-containing 7''-Fe203 100g Polyurethane resin obtained in Synthesis Example 1 3°C Lecithin 5n Alumina
101I carbon black
1011 (Pulcan XC72 manufactured by Cabot) Oleyl oleate 1211TH
F/cyclohexanone/toluene 392 u (1/
1/1) After grinding the above composition in a sand grinder mill for 4 hours, 8 parts of an incyanate compound (Coronate, manufactured by Nippon Polyurethane Co., Ltd.) was added, and the mixture was subjected to redistribution M treatment to prepare a magnetic paint. This magnetic paint was coated on both sides of a polyethylene terephthalate film with a thickness of 75 parts to a thickness of 1.0 μm after drying.
A magnetic layer was formed by applying one coat and drying. After calendering, the material was punched out into a disk shape with a diameter of 5 inches to produce a magnetic disk.

Example 2゜The polyurethane resin of Synthesis Example 2 was used instead of the resin of Synthesis Example 1 as the polyurethane resin of Example 1.
A magnetic disk was produced in the same manner as in Example 1.

Example 3゜The polyurethane resin of Synthesis Example 3 was used instead of the resin of Synthesis Example 1 as the polyurethane resin of Example 1.
A magnetic disk was produced in the same manner as in Example 1.

Example 4゜The polyurethane resin of Synthesis Example 4 was used instead of the resin of Synthesis Example 1 as the polyurethane resin of Example 1.
A magnetic disk was produced in the same manner as in Example 1.

Example 5 In Example 1, Synthesis Example 1 was used as the polyurethane resin.
A magnetic disk was produced in the same manner as in Example 1, except that 31 parts of the resin in Synthesis Example 1 was replaced with 25 parts of the resin in Synthesis Example 1, and 6 parts of polyester polyurethane m resin manufactured by Nippon Polyurethane Co., Ltd.

Example 6゜Co containing r Fe2O3 100 parts chloride vinyl acetate vinyl alcohol copolymer 8I/synthesis example 1
Polyurethane jlBBH23# alumina obtained from
71/Carbon black 10/L oleyl oleate
12//THF/cyclohexanone/
Toluene 385 u (1/1/1) After dispersing the above composition in a sand grinder mill for 4 hours, 8 parts of incyanate compound (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added and redispersed to form a magnetic paint. Obtained. After that, a magnetic disk was produced in the same manner as in Example 1.

Example 7 A magnetic disk was produced in the same manner as in Example 6, except that the same amount of polyvinyl butyral was used in place of the vinyl chloride, vinegar, and vinyl alcohol copolymer.

Example 8 A magnetic disk was produced in the same manner as in Example 6, except that the same amount of nitrocellulose was used in place of the vinyl chloride, vinegar, and vinyl alcohol copolymer.

Example 9゜Example 6 except that 8 parts of chloride-vinyl-acetate-vinyl alcohol copolymer in the magnetic paint of Example 6 was replaced with 6 parts of chloride-vinyl-acetate-vinyl alcohol copolymer and 2 parts of nitrocellulose.
A magnetic disk was produced in the same manner as above.

Implementation eAJI O.

8 parts of the chloride-vinyl-acetate-vinyl alcohol copolymer in the magnetic paint of Example 6 was replaced with 4 parts of the polyurethane resin of Synthesis Example 1.
A magnetic disk was produced in the same manner as in Example 6 except that 3 parts were changed to 27 parts.

Comparative Example 1゜Co-containing r-Fe203 100 parts Nitrocellulose 20I/Polyurethane resin (manufactured by Nippon Polyurethane 1171, polyester polyurethane) Alumina 7〃Carbon black l Q a Oleyl onoate 12I/THF/Cyclohexanone/Toluene 38511 (1/l /1) After dispersing the above composition in a sand grinder mill for 4 hours, an incyanate compound (manufactured by Nippon Polyurethane Co., Ltd.,
Coronet) L)6f5 was added and redispersed to prepare a magnetic paint. After that, a magnetic disk was produced in the same manner as in Example 1.

Comparative Example 2 A magnetic disk was produced in the same manner as in Comparative Example 1, except that chloride, vinegar, and vinyl alcohol copolymer was used in place of the nitrocellulose in the magnetic paint of Comparative Example 1.

Comparative Example 3 A magnetic disk was produced in the same manner as in Comparative Example 1, except that polyvinyl butyral was used in place of nitrocellulose in the magnetic paint of Comparative Example 1.

Comparative Example 4 A magnetic disk was produced in the same manner as in Example 1, except that a polyester polyurethane resin manufactured by Nippon Polyurethane Co., Ltd. was used in place of the polyurethane resin of Synthesis Example 1 in the magnetic paint of Example 1.

and the starting torque of the magnetic disk obtained in the examples and comparative examples,
The dynamic friction coefficient, durability at 5°C, durability at 60°C, and S/N ratio were measured. The results obtained are shown in Table 1.

〔Effect of the invention〕

As is clear from the above explanation, when I R2 tan resin is used as the main component in the binder system of the magnetic recording medium, the polyurethane resin has poor thermal decomposition resistance.
Compared to conventional products, it has better high-temperature durability, and its starting torque, coefficient of dynamic friction, and S/N ratio are the same or better than conventional products.

Applicant: Hitachi Maxell, Ltd. Representative Atsushi Nagai

Claims (2)

[Claims] (1) In a magnetic recording medium in which a magnetic coating film consisting mainly of magnetic powder and a binder is provided on a non-magnetic support, the binder contains a polyurethane resin having 5 to 50% of the following structure as the main component: A magnetic recording medium characterized by containing. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R_1, R_2: H, alkyl group or aryl group) (2) As a binder, in addition to the polyurethane resin,
The magnetic material according to claim 1, wherein the magnet contains one or more resins selected from vinyl chloride resin, polyvinyl butyral resin, and cellulose resin in an amount equal to or less than the polyurethane resin. recoding media.