JPS5841564B2 - magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible magnetic recording medium in the form of a tape or sheet, in which a magnetizable layer in which fine powder magnetic particles are dispersed in a binder is laminated.

Traditionally, binders for magnetic recording media include ethyl cellulose, nitrocellulose, polyvinylidene chloride resin, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, polymethyl methacrylate resin, and vinylidene chloride-methacrylic acid. Methyl copolymers, polyurethane resins, epoxy resins, polyester resins, butadiene-acrylonitrile copolymers, etc. have been used.
At present, it cannot be said that the performance is sufficient for applications that require high performance, such as computer tapes and video tapes.

That is, the ratio B of the saturation magnetization Bm in the orientation direction of a magnetic tape using the above binder as a magnetizable material of γ-Fe203 fine particles having a known spinel structure and the residual magnetism Br.
r/Bm (squareness) is 0.5 to 0.7, porosity is 0.4
~0.5, and there has been a strong demand for an increase in the Br78m value and a decrease in the porosity.

As a method for increasing the Br78m value, it is known that when tellurium-modified ferromagnetic Cr 02 and isophthalic acid-butanediol condensed linear polyester (binder) are combined, the Br78m value becomes 0.7 to 0.9. There is (Tokuko Sho 4)
No. 7-12422, Special Publication No. 18573 (1973)).

However, in order to obtain a high-performance magnetic tape or sheet, simply increasing the Br78m value is not sufficient; at the same time, high filling properties, that is, low porosity are required.

According to the experimental results of the present inventors, usually γ-F e 20
The porosity of a magnetic tape made by combining No. 3 and ordinary linear polyester is 0.38 to 0.45, which does not satisfy the performance as a high-performance magnetic tape.

In this case, it is possible to reduce the porosity by increasing the kneading time;
As a result, the sensitivity of the magnetic tape will be reduced.

In view of these circumstances, the present inventors have developed an ordinary γF e2
Br78 while using 03 and CrOs as magnetic particles.
As a result of various research into the development of high-performance magnetic tapes with increased m value and decreased porosity, we discovered that they were obtained by copolymerizing components containing sulfonic acid metal bases into polyester resins. The Br78m value of a magnetic tape using a low molecular weight polyester resin and other thermoplastic resin and/or thermosetting resin as a binder is 0.78 to 0.9.
0, and the porosity was 0.25 to 0.38, showing very excellent performance, and the present invention was achieved.

That is, at least 0.5 mole of the dicarboxylic acid component is a dicarboxylic acid containing a sulfonic acid metal salt, and the polyester resin (I) has a reduced viscosity of less than 0.2, and other thermoplastic resins and/or Thermosetting tree JffMI[)
This is a magnetic recording medium characterized by containing finely powdered magnetic particles uniformly dispersed in a mixture with.

In the present invention, by mixing the low molecular weight polyester resin (1) with other thermoplastic resin and/or thermosetting resin (1), the magnetizable layer has a high Br78m value,
In addition to exhibiting excellent properties such as low porosity,
High performance can be achieved even when a high concentration of magnetic particles is blended.

In particular, when a low molecular compound containing a sulfonic acid metal base, such as dioctyl sulfona I-IJ umsuccinate, is mixed with the thermoplastic resin and/or thermosetting resin (If) other than the low molecular weight polyester resin (I), In comparison, in the present invention, it is possible to disperse magnetic particles at a higher concentration and more uniformly.

The carboxylic acid component of the polyester resin used in the present invention includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalic acid, p-oxybenzoic acid, p-(hydroxyethoxy)
Aromatic oxycarboxylic acids such as benzoic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid, etc. can be mentioned.

Particularly preferred are terephthalic acid, isophthalic acid, adipic acid, and sebacic acid.

Glycol components of the polyester resin used in the present invention include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-bentanediol, 1,6-hexanediol, neopentyl Glycol, diethylene glycol, cyclopylene glycol, 2,2,4-1-limethyl-1°3-bentanediol, 1,4-cyclohexane dimetatool, ethylene oxide and propylene oxide adducts of bisphenol A, hydrogenation Examples include ethylene oxide adducts and propylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Also trimethylolethane, trimethylolpropane,
Tri- and tetraols such as chrycerin and pentaerythritol may be used in combination.

The dicarboxylic acid component containing a sulfonic acid metal base that characterizes the copolymerized polyester resin used in the present invention includes 5-sodium sulfoisophthalic acid, 5-sodium sulfoisophthalic acid, and
Potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, etc. are included, and the copolymerization amount of dicarboxylic acid components containing these sulfonic acid metal bases is 0.5 mol based on the total carboxylic acid components. The amount is preferably 1.0 to 50 moles or more.

If the amount of copolymerization is less than 0.5, the performance will not be improved sufficiently.

The polyester resin used in the present invention has a reduced viscosity of less than 0.2, and when the reduced viscosity is 0.2 or more, general-purpose solvents may The solubility in this product decreases, making it unusable for practical use.

Other thermoplastic resins and/or thermosetting resins used in the present invention include vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, and acrylic esters. - Vinylidene chloride copolymer, acrylic acid ester-styrene copolymer, methacrylic acid-acrylonitrile copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, urethane resin, polyester Vinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, Polyester resins other than the polyester resin (I), chlorovinyl ether-acrylic acid ester copolymers, amino resins, phenol resins,
Examples include epoxy resin, alkynd resin, and silicone resin.

A desirable mixing ratio is 5 to 200 parts by weight of the polyester resin (I) per 100 parts by weight of the other thermoplastic resin and/or thermosetting resin (n).

The fine powder magnetic particles used in the present invention include γ
-Fe203. Co-containing r -F e2 o3. F
e3 o, .

co gold-containing Fe3O4, cobalt ferrite (CoO・
"e203)? CrO2, Co Nl p alloy,
Co-Ni-Fe alloy, Co-Ni-F e-B alloy, Fe-Ni-Zn alloy, Fe-Mn-Zn alloy, F
Known ferromagnetic fine powders such as e-CoNlp alloy and Ni-Co alloy can be used.

When the softening point of the polyester resin (I) or other thermoplastic resin and/or thermosetting resin (I) of the present invention is low, depending on the application, it may soften due to the heat between it and the tape, or the tape may There is a risk of blocking in the rolled state.

In such a case, it is desirable to mix a compound which is compatible with the resin mixture within a range that does not impair the dispersibility of the fine powder magnetic particles, and which reacts and crosslinks.

The mixing amount is generally 2 to 100 parts by weight per 100 parts by weight of the resin mixture.

As such a compound, incyanate compounds are particularly preferred.

The magnetic recording medium of the present invention may optionally contain plasticizers such as dibutyl phthalate and triphenyl phosphate, dioctylsulfonodium succinate, t-butylphenol-polyethylene ether, ethylnaphthalene-sulfonic acid sodium dilauryl succinate, and stearic acid. Lubricants and antistatic agents such as zinc, soybean oil lecithin, and silicone oil may also be added.

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

In the examples, parts simply indicate parts by weight.

Reduced viscosity ηSP/c (dl/g) is 0 for polyester resin
．． 10. ! i' was dissolved in phenol/tetrachloroethane (volume ratio 6/4) mixed solvent 257 and measured at 30°C.

The softening point was measured according to JIS K2351.

The porosity was determined using the following formula: The measured specific volume was determined by immersing the magnetizable layer in water, and the true specific volume was calculated from the specific volume of each component contained in the magnetizable layer using the following formula: Magnetization The smoothness of the layer was visually determined.

Production example of polyester resin In a reaction vessel equipped with a thermometer, a stirrer, and a partial reflux condenser, 582 parts of dimethyl terephthalate, 296 parts of dimethyl 5-sodium sulfoisophthalate, 434 parts of ethylene glycol, 728 parts of neopentyl glycol, and zinc acetate were added. Add 0.66 parts and 0.08 parts of sodium acetate to 1
Transesterification reaction was carried out at 40-220°C for 3 hours.

Next, 1212 parts of sebacic acid was added and heated at 210°C to 250°C.
After reacting at ℃ for 2 hours, the reaction yarn was heated to 201℃ for 30 minutes.
! Reduce the pressure to trLH&, further reduce the pressure to 5-20 mmHg, 2
Polycondensation reaction was carried out at 50°C for 50 minutes.

The obtained polyester resin N had a reduced viscosity of 0.182.

According to NMR analysis, etc., the composition was as follows.

Terephthalic acid 30 moles, 5-sodium sulfoisophthalic acid 10 moles, sebacic acid 60 moles, ethylene glycol 44 moles, neopentyl glycol 5
6 mole article.

Polyester resins shown in Table 1 (
B) ~(O was obtained.

Example 1 60 parts of γ-Fe203 magnetic particles, 1 part of dilauryl succinate, 1 part of silicone oil, 15 parts of methyl ethyl ketone
parts, 25 parts of toluene and 15 parts of methyl isobutyl ketone.
The mixture was mixed for 24 hours using a ball mill.

Polyester resin (A) 15 prepared separately in this mixture
25 parts of vinyl chloride-vinyl acetate resin (manufactured by Union Carbide: VAGH), 8 parts of incyanate compound (manufactured by Bayer: Desmodur L), 30 parts of tetrahydrofuran, 30 parts of toluene, 10 parts of methyl isobutyl ketone, and A solution containing 15 parts of cellulose acetate uniformly dissolved in a mixed solvent was added and mixed again using a ball mill for about 60 hours.

After filtering and defoaming the resulting mixture, it was coated onto a 2.5μ thick polyethylene terephthalate film using a doctor blade with a 30μ gap, followed by a 1.00μ thick polyethylene terephthalate film.
It was left standing in an Oersted parallel magnetic field for about 1 second.

Next, it was left in a hot air dryer at 80° C. for about 30 minutes to remove the solvent, and then left in an air constant temperature bath at 60° C. for 7 days to fully harden the magnetizable layer.

The thickness of the smooth magnetizable layer obtained was 6.3μ, and B
The r78m value was 0.81 and the porosity was 0.36.

Next, a magnetizable layer was formed on the polyethylene terephthalate film by the same method using the polyester resin shown in Table 1 in combination with other thermoplastic resin and/or thermosetting resin.

Table 2 shows the measurement results for each magnetizable layer.

Claims (1)

[Claims] 1 At least 0.5 mole of the dicarboxylic acid component is a dicarboxylic acid containing a sulfonic acid metal salt, and a polyester resin (I) with a reduced viscosity of less than 0.2 and other thermoplastic resins and/or thermoplastic resins are used. A magnetic recording medium comprising a magnetizable layer containing finely powdered magnetic particles uniformly dispersed in a mixture with a curable resin (I).