JPS61177628A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the filling degree and dispersibility of magnetic powder and to obtain the title magnetic recording medium having excellent durability, etc. by forming a magnetic layer obtained by dispersing ferromagnetic powder in a binder contg. a polyester resin having an imide group in the molecule or a polyurethane resin on a nonmagnetic carrier. CONSTITUTION:A polyester resin having an imide in the molecule is obtained, for example, by the condensation of a diol component shown by the formula with an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, etc., or a polyurethane resin is obtained by the reaction of the diol component with a polyisocyanate. The polyester resin or the polyurethane resin is dissolved in an org. solvent as a binder, and ferromagnetic powder is dispersed in the soln. to obtain a paint. The paint is coated on a carrier of a polyester film, etc. while impressing a magnetic field, and dried. Then the magnetic powder is oriented to form a magnetic layer. Consequently, the filling degree and the uniform dispersibility of the magnetic powder are improved, and a tough magnetic recording medium having excellent traveling stability, abrasion resistance and durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks. More specifically, the present invention relates to a magnetic recording medium using a polyester resin or polyurethane resin having excellent properties as a magnetic r-binder component provided on a nonmagnetic support.

(Prior art) Magnetic tape, which is a general-purpose magnetic recording medium, is made by dispersing acicular magnetic particles with a long axis of 1 μm or less in a binder solution together with appropriate additives (dispersants, lubricants, antistatic agents, etc.). This is used to create a magnetic paint, which is then applied to polyethylene terephthalate film.

The properties required of binders for magnetic recording media include dispersibility, filling properties, and orientation of magnetic particles, durability, abrasion resistance, heat resistance, smoothness, and adhesion to nonmagnetic supports of the magnetic layer. The binder plays a very important role. Conventionally used binders include vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinylidene chloride copolymer,
Polyurethane resins, polyester resins, acrylonitrile-butadiene copolymers, nitrocellulose, cellulose acetate-butyrate, epoxy resins, acrylic resins, etc. are used.

Among these resins, polyurethane resin is stronger and stronger than other resins due to intermolecular hydrogen bonding caused by urethane bonds.
Although properties such as abrasion resistance are excellent, conventional noadipate type or cabrolactone type polyurethane resins alone have poor properties such as blocking resistance, heat resistance, and running stability. For this reason, mixed systems of polyurethane resin and nitrocellulose or vinyl chloride/vinyl acetate copolymers are particularly used.
It is still insufficient in fields that require high performance, such as computer tapes and floppy disks.

In addition, polyester resin has excellent adhesion to polyethylene terephthalate film, which is a general-purpose non-magnetic support.
Although it has good heat resistance, it has poor properties such as durability and abrasion resistance.

(Problem to be solved by the invention) Increasing recording density in magnetic recording media! Smoothness of the surface of the magnetic layer is required in order to improve the /(Schiff carry noise) ratio. The better the smoothness, the better the durability, abrasion resistance,
Although characteristics such as running stability are further superimposed, conventional magnetic recording media have the problem that these characteristics are still insufficient.

(Means for Solving the Problems) In order to achieve the objective of the present invention, which is to provide a magnetic recording medium with excellent durability, durability, and running stability, as a result of intensive studies on polyester resins and polyurethane resins, We have discovered that this can be achieved by introducing imide groups into polyester resins and polyurethane resins.

That is, the present invention provides a magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, and a polyester resin having an imide group in the molecule and/or A magnetic recording medium characterized by containing a polyurethane resin.

In the present invention, the imide group is the following general formula) or (B)
What is desirable is something that will be hailed as such.

IJ Q In the production of the polyester resin used in the present invention, the dicarboxylic acid component and diol component used contain an imide group as an essential component, and these are, for example, those expressed by the following general formula. .

(In the formula, u, l R2+ R3+ R5+ R6+
R7+ R8' Hydrocarbon group having an ester bond-forming functional group R4: divalent hydrocarbon group) Imide group-containing dicarboxylic acids or imide group-containing diols are combined with acid anhydrides such as trimellitic anhydride and pyromellitic anhydride. It is obtained by the reaction of aminocarboxylic acids, aminoalcohols, and diamine compounds containing primary amino groups, such as aminobenzoic acid, phenylenediamine, monoethanolamine, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl ether. Further, a diol containing a diimide group can be obtained by esterifying an imide group-containing dicarboxylic acid with a glycol.

Other carboxylic acid components of the polyester resin include terephthalic acid, inphthalic acid, orthophthalic acid, 1.5-
Aromatic dicarboxylic acids such as naphthalic acid, aromatic oxycarboxylic acids such as p-oxybenzoic acid and p-(hydroxyethoxy)benzoic acid, conolic acid, adipic acid, azelaic acid, sepacic acid, dodecanedicarboxylic acid, etc. Examples include aliphatic dicarboxylic acids.

In addition, the glycol components of the polyester resin include ethylene glycol, globylene glycol, 1,3-propanediol, 1,4-butanediol, 1, s-
Hentanediol, 1,6-hexanediol, neohentyl glycol, diethylene glycol, dipropylene glycol, 2,2.4-17methyl-1,3-bentanediol, cyclohexane dimetatool, ethylene oxide adduct of bisphenol A and propylene oxide adducts, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A,
polyethylene glycol, polypropylene glycol,
Examples include polytetramethylene glycol.

Raw materials other than the above include Fi5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, sodium sulfoterephthalic acid, 2-sodium sulfo-1,4-
Examples include ester group-forming sulfonic acid metal salt-containing compounds such as butanediol and 3-sodium sulfo-1,2-butanediol, and phosphorus-containing compounds represented by the following general formulas ['D and [Il].

(In the formula, R1 is a monovalent ester-forming functional group.

R2 and RS are the same or different groups, and are selected from the group consisting of a monovalent hydrocarbon group having 1 to 10 carbon atoms/% rogen atom and a monovalent ester-forming functional group.

A represents a divalent or trivalent organic residue. Also, nl is 1
or 2, n2+''s each represents an integer of θ to 4.) (In the formula, R4 is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may contain an ester-forming functional group, or Ml.

R6 is a divalent or trivalent hydrocarbon group having 1 to 6 carbon atoms. R2 has 1 carbon atom, which may include a hydrogen atom or a hydroxyl group
~12 hydrocarbon groups or Ml r M+ is an alkali metal atom. m represents an integer of 0 or 1; / represents an integer of 1t or 2; ) Sulfonic acid metal base-containing compound, general formula CI), (n)
When a phosphorus-containing compound represented by is used as at least one component of the raw material, it is effective in greatly improving the drawback of low dispersibility of inorganic pigments and fillers found in conventional polyester resins. When used as a binder for a magnetic layer in a type magnetic recording medium, the dispersibility of the magnetic particles is improved, and the properties caused by the dispersibility of the magnetic particles, such as the electromagnetic conversion properties of the magnetic recording medium, are greatly improved.

The polyurethane resin used in the present invention is obtained by the reaction of a diol component and an organic diisocyanate, and contains an imide group in the molecule. Examples of methods for introducing imide groups include a method using an imide group-containing polyester diol among the aforementioned polyester resins as a component of the raw material, or a method using another imide group-containing diol.

Other imide group-containing diols include general formulas (1) and (2).
1, (4), (5), R, l R2+ R5+
R5+ R6+ R7+ Those containing a hydroxyl group in R1 are preferred.

The polyurethane resin used in the present invention may be prepared using raw material components that do not contain imide groups. For example, long-chain diol components include polyester diols, polyether diols, polycarbonate diols, etc., and chain extenders include glycols, amino alcohols, diamines, water, etc.

Examples of the organic diisocyanate used in the production of the polyurethane resin used in the present invention include 2.4-tolylene diisocyanate, 2.6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate,
Hexamethylenecy! Cyanate, 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'-cyinocyanate diphenyl ether, 1,5-naphthalene diisocyanate, p-
xylylene diisocyanate, m-xylylene diisocyanate), 1,3-diisocyanate methylcyclohexane/, 1,4-diisocyanate methyl cyclohexane, 4,4'-diisocyanate cyclohexane, 4, l
-Diisocyanate cyclohexylmethane, inphorone diincyanate, etc.

The content of imide groups in the polyester resin or polyurethane resin used in the present invention is preferably in the range of 0.05 to 5%, based on the nitrogen content of imide groups in the resin. If the amount is less than 0.05%, the effect of containing an imide group may not be seen.

In the magnetic recording medium of the present invention, in addition to the polyester resin or polyurethane resin used in the present invention, one other resin may be added for the purpose of adjusting flexibility, improving cold resistance, heat resistance, etc. It is desirable to mix a compound that crosslinks by reacting with the polyurethane resin. Other resins include vinyl chloride resin, polyester resin, cellulose resin, epoxy resin, phenoxy resin,
Examples include polyvinyl butyral, acrylonitrile-butadiene copolymer, and the like.

On the other hand, compounds that crosslink with polyurethane resins include polyisocyanate compounds, epoxy resins, melamine resins, urea resins, etc. Among these, polyisocyanate compounds are particularly desirable.

The ferromagnetic particles used in the magnetic layer of the magnetic recording medium of the present invention include r''203+ r-Fe205 and Fe3.
O4 crystal, CrO2, cobalt-doped γ-F'
e203 or uF8s04, barium ferrite and F
Examples include ferromagnetic alloy powders such as e-co and Pe-C1o-Ni.

The magnetic recording medium of the present invention may optionally contain plasticizers such as dibutyl phthalate and triphenyl phosphate, dioctyl sulfonodium succinate, t-7' tylphenol polyethylene ether, ethelnaphthalene, etc.
Lubricants such as sodium sulfonate, dilauryl succinate, zinc stearate, soybean oil lecithin, silicone oil and moderate amounts of antistatic agents may also be added.

(Function) The polyester resin or polyurethane resin used in the present invention contains imide groups with rigid molecular chains, and has better lubricity and toughness than conventional polyester resins and polyurethane resins. It's improving. By using a polyester resin or a polyurethane resin having such characteristics as a binder for the magnetic layer of a magnetic recording medium, the magnetic recording medium of the present invention has excellent durability and
It is considered to have excellent wear resistance and running stability.

(Example) Hereinafter, the present invention will be specifically explained using examples.

In the examples, parts simply indicate parts by weight.

Each measurement item follows the method below.

Running stability: We ran a magnetic tape over a video deck and observed unevenness during running.

0: Stable running.

Δ: Slightly uneven running.

×: Uneven running and squeaks.

Still characteristics: Time for a still image to disappear. The longer this time, the better the durability and secondary wear resistance.

Synthesis Examples 1 to 3 of Polyester Resin 291 parts of dimethyl terephthalate, 272 parts of dimethyl isophthalate, 29.6 parts of dimethyl 5-sodium sulfoisophthalate, 372 parts of ethylene glycol, 416 parts of neopentyl glycol, imide groups listed in Table 1 1088 parts of the dicarboxylic acid containing and 0.5 part of tetrabutoxytitanium were placed in a 51 autoclave and heated to 200~
At 230°C for 4 hours, reduce the pressure to an esthetician, then at 250°C, 101
Excess glycol is distilled out with 11 HP, and finally 260
The polycondensation reaction was carried out at 0.1 to 0.3 °C for 90 minutes to obtain a yellowish brown polyester resin with a reduced viscosity of 0.58.

The composition of the resin is shown to be 1iK by analysis such as 111MR. Similarly, using the raw materials listed in Table 11,
Thus, an imide group-containing polyester resin was obtained.

The composition is shown in Table 1.

Table 1 Polyester resin In the table, the abbreviations indicate the following.

ηsp/c: Phenol/tetrachloroethane=-(
Reduced viscosity measured at 30°C with a concentration of 0.1/25 CO (weight ratio) Synthesis examples 1 to 6 of polyurethane resins with a mole of hydroxycarboxylic acid relative to the key dicarboxylic acid component Thermometer, stirrer, reflux type After thoroughly drying the imide group-containing diol ■ listed in Table 2 in a reaction vessel equipped with a cooling tube, 231 parts of cyclohexanone and 2 parts of toluene were charged.
After adding 31 parts and 82 parts of 4.4'-diphenylmethane diincyanate and raising the temperature to 80°C, 0.08 part of diptyltin dilaurate was added as a reaction catalyst, and the mixture was reacted for 2 hours. Next, 100 parts of polybutylene adipate having a molecular weight of 12,000 was added, and 1 hour later, 15 parts of neopentyl glycol was further added, followed by a reaction at 80 to 90°C for 10 hours.

After the reaction was completed, the mixture was diluted with 231 parts of methyl ethyl ketone to obtain a brown polyurethane resin solution with a solid content of 30 parts.

The solution viscosity is 85 boids (25°C), and the molecule i of the polyurethane resin is determined by gel permeation chromatography.
It was 25,000 in terms of polystyrene.

Similarly, an imide group-containing polyurethane resin was obtained using the raw materials listed in Table 2. The imide group-containing diol (2) used in polyurethane resin synthesis example 6 was obtained by deglycolizing the imide group-containing diol (2) at 250° C. and 0.5111 HP for 60 minutes.

Table 2 Polyurethane resin In the table, the abbreviations indicate the following.

NPG: Neopentyl glycol TlpN: Ester of neopentyl glycol and hydroxypivalic acid MDX: 4.4'-diphenylmethane diisocyanate IPD: Inphorone diisocyanate TD: 2.4
-) Lylene diisocyanate PBjl Polybutylene adipate PTMG: Polytetramethylene glycol @
[Phase] [Stock] ◎ O■
: Polyester diol=98.5/1.5 775/25 molar ratio) Example 1 Polyester resin listed in Table 1 (Synthesis Example 1) Lamethyl ethyl ketone/toluene/cyclohexane (=1/1
/1 weight ratio) to a solid concentration of 30%, and using the obtained solution, put a composition with the following blending ratio in a ball mill and disperse for 48 hours. Polyurethane Kogyo (trade name)) was added as a curing agent in an amount of 5 parts, and the mixture was kneaded for an additional hour to obtain a magnetic paint. This was applied onto a 12 μm thick polyethylene terephthalate film while applying a magnetic field of 2.000 Gauss so that the thickness after one drying would be 5 μm. After being left at 50° C. for 2 days, it was slit into h inch width to obtain a magnetic tape.

Polyester resin solution (solid content 30%) 100 parts Cobalt coated 1-Fe2O3 120 parts Olive oil 1 part Methyl ethyl ketone 50 parts Toluene
100 copies Examples 2 to 7, Comparative Examples 1 to 5 Magnetic recording media of Examples 2 to 7 were obtained in the same manner as in Example 1 using the resins listed in Table 3.

In addition, the magnetic recording media of Comparative Examples 1 to 5 were prepared in the same manner as in Example 1 using polyester resins 4 and 5 that do not contain imide groups, adipate type polyurethane resin, nitrified cotton, and a vinyl chloride/vinyl acetate copolymer. I'm good at Table 3 shows the properties of the obtained magnetic tape.

Adipate type polyurethane resin Nippate type polyurethane resin 2 Nippon Polyurethane Co., Ltd. Niboran-230 Nitrified cotton: Daicel Co. PVC/acetate resin: Ty, C, C Co. [VA()H,
J Example 8 A solution of the polyurethane resin listed in Table 2 obtained in Synthesis Example 1 (
Bath agent dichlorohexanone/toluene/methyl ethyl)
A magnetic tape was obtained in the same manner as in Example 1 using a weight ratio of /-/1/1 and a solid content concentration of 30 parts.

Examples 9 to 15, Comparative Examples 6 to 12 Magnetic tapes were obtained in the same manner as in Example 8 using the imide group-containing polyurethane resins listed in Table 4. Table 4 shows the properties of the magnetic tape obtained.

Further, magnetic tapes of Comparative Examples 6 to 12 were obtained in the same manner as in Example 8 using a polyurethane resin containing no imide group. The properties are shown in Table 14.

(Effects of the Invention) Polyester resins or polyurethane resins containing imide groups in their molecules have increased toughness and better lubricity than those that do not contain imide groups. The magnetic recording medium of the present invention using these resins as a binder for the magnetic layer has excellent running stability, abrasion resistance, and durability, as is clear from the examples.

Claims (1)

[Claims] A magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, which contains a polyester resin and/or polyurethane resin having imide groups in the molecule as a component of the binder. A magnetic recording medium characterized by: