JP2867399B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium such as a magnetic tape and a magnetic disk. More specifically, the present invention relates to a magnetic recording medium using a polyesteramide resin having excellent properties as a binder component of a magnetic layer provided on a nonmagnetic support.

(Prior Art) A magnetic tape which is a general-purpose magnetic recording medium has a major axis of 1 μm.
Add the following needle-shaped magnetic particles to appropriate additives (dispersant, lubricant,
A magnetic paint is prepared by dispersing it in a binder solution together with an antistatic agent, etc., and then applied to a polyethylene terephthalate film.

The properties required for the binder of the magnetic recording medium include the dispersibility, filling property, orientation, magnetic layer durability, abrasion resistance, heat resistance, smoothness, adhesiveness with the non-magnetic support, etc. of the magnetic particles. And binders play 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 resin, polyester resin, acrylonitrile / butadiene. Copolymers, nitrocellulose, cellulose acetate butyrate, epoxy resins, acrylic resins and the like are used.

(Problems to be Solved by the Invention) Among these resins, polyurethane resins are excellent in properties such as toughness and abrasion resistance as compared with other resins due to intermolecular hydrogen bonding by urethane bonds, but are always satisfactory. Not something.

Further, the conventional adipate-type or caprolactone-type polyurethane resin alone is inferior in properties such as blocking resistance, heat resistance and running stability. For this reason, a mixed system of a polyurethane resin and nitrocellulose or a vinyl chloride / vinyl acetate copolymer is particularly used. However, characteristics such as durability, abrasion resistance, and running stability are still insufficient in fields requiring high performance such as video tapes, tapes for electronic computers, floppy disks, and the like.

In particular, the recent high quality of magnetic tapes is remarkable, and the fineness of the magnetic powder and the smoothness of the magnetic coating film are progressing, and accordingly, the binder resin is required to have higher dispersibility and higher durability. Have been. Further, metal magnetic powder and barium ferrite magnetic powder have become popular due to the increase in recording density, and a binder resin having higher performance is strongly demanded.

Conventionally, as a method of improving the dispersibility of magnetic particles, for example, Japanese Patent Publication No. 57-3134, Japanese Patent Publication No. 58-41564, a polyester resin containing a sulfonic acid metal base in the resin as shown in JP-A-58-41564 and the like, Alternatively, it is described that a polyurethane resin is used as a binder resin.
Indeed, with respect to hitherto universally used is BET30m ² / g or less of Fe ₂ is a magnetic particle has _{O 3, Co-Fe 2 O} 3 or the like magnetic particles, such polyester resin, or polyurethane resin Shows excellent dispersibility, but finer BET40m ² /
g or more of Fe ₂ O ₃ , Co-Fe ₂ O ₃ or metal, barium
Higher dispersibility is required for magnetic particles for high recording density magnetic recording materials such as ferrite.

Further, as described above, the smoothing of the magnetic recording material has progressed, and the magnetic recording material is required to have higher running durability. In order to meet the demands of the market, the present invention has been studied to maintain the dispersibility of polyurethane resin and to improve abrasion resistance and durability.However, it is difficult to achieve both durability performance and magnetic properties. The response has been required.

As a method of improving the durability performance, means such as increasing the urethane group concentration in order to increase the hydrogen bond concentration, or imparting a branched structure to increase the crosslink density have been proposed and studied. Although the durability performance tends to be improved, there is a problem that the glossiness on the light surface of the coating film or the squareness ratio, which is a major measure of dispersibility, is lowered particularly in the case of metal magnetic powder.

(Means for Solving the Problems) The present inventors have conducted intensive studies on magnetic particles for high recording density magnetic recording materials, particularly metal magnetic powder, in order to obtain a resin having excellent dispersibility and running durability. The present inventors have found a binder resin having excellent surface gloss and squareness ratio, and excellent durability.

That is, the present invention relates to a magnetic recording medium in which a magnetic coating material containing a ferromagnetic powder in a binder is applied on a non-magnetic support, wherein a metal sulfonate group is used as a component of the binder in an amount of 4 to 400 equivalents per polymer. / 10 ⁶ g, a number average molecular weight of the amide bond containing ⁶ polymer per 1,250～3,000 eq / 10 g 8,000 to
A magnetic recording medium comprising 60,000 polyesteramide resins.

The polyesteramide resin of the present invention can be obtained by a known production method.

That is, (1) at least one kind of aromatic dicarboxylic acid, alicyclic dicarboxylic acid or aliphatic dicarboxylic acid, and (2) at least one kind of aromatic diamine, alicyclic diamine, aliphatic diamine, aminocarboxylic acid or lactam. , (3) an alkylene oxide adduct of an aliphatic glycol, alicyclic glycol or aromatic diol having a molecular weight of 400 or less by a known method.

The polyesteramide resin of the present invention is characterized in that the resin contains 4 to 400 equivalents / 10 ⁶ g of a metal sulfonic acid base. It is preferable to use a dicarboxylic acid containing an aromatic metal salt of a sulfonic acid.

Compounds containing a sulfonate group among the dicarboxylic acid components include 5-sodium sulfoisophthalic acid,
-Lithium sulfoisophthalic acid, 2-sodium sulfoisophthalic acid, 2-lithium sulfoisophthalic acid, 2-
And potassium sulfoterephthalic acid. On the other hand, dicarboxylic acids containing no sulfonic acid metal base include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid (anhydride), 2,6-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid; 4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, succinic acid, apicinic acid, azelaic acid, sebacic acid, aliphatic dicarboxylic acids such as dodecandioic acid, and the like. . In addition, hydroxycarboxylic acids such as p- (hydroxyethoxy) benzoic acid and the like, and lactones such as caprolactone and valerolactone can also be used as long as the properties are not impaired. The content of the dicarboxylic acid containing a sulfonic acid metal base in all dicarboxylic acid components in the polyesteramide resin is 0.5 to 8 mol%, preferably 2 to 5 mol%.

Examples of the amino compound used in the production of the polyesteramide resin of the present invention include ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, 2,2,4-trimethyl-1,6-hexamethylenediamine, neopentylenediamine and the like. Aromatic diamines such as aliphatic diamines, piperazine, 1,4-diaminopiperazine, 1,3-bis (aminomethyl) cyclohexane, dicyclohexylmethanediamine and isophoronediamine, and aromatics such as diphenylmethanediamine, phenylenediamine and tolylenediamine Aromatic diamines Also, aromatic ring-containing aliphatic diamines such as xylylenediamine can be used.

Also, amino acids such as 11-aminoundecanoic acid and 12-aminodotecanic acid, or lactams such as caprolatatam can be used.

Ethylene glycol, propylene glycol, 1,3-propanediol as the glycol having a molecular weight of 400 or less used in the production of the polyesteramide resin of the present invention,
1,4-butanediol, 1,5-pentanediol, 1,6-
Aliphatic glycols such as hexanediol, neopentyl glycol, 3-methylpentanediol, and 1,9-nonanediol; alicyclic glycols such as 1,4-cyclohexanedimethanol; ethylene oxide adducts of bisphenol A; ethylene of hydroquinone Alkylene oxide adducts of aromatic diols such as oxide adducts can be mentioned.

In the production of the polyesteramide resin of the present invention, a dicarboxylic acid component, an amino compound, and a glycol component are simultaneously charged into a reaction vessel, and after a dehydration reaction, a method of polymerizing under reduced pressure, or a method in which a dicarboxylic acid and an amino compound are first reacted, and After obtaining a carboxyl group-terminated polyamide oligomer, adding a glycol component, esterifying and then performing a polycondensation reaction, or conversely, adding an amino compound to a carboxyl group-terminated polyester oligomer and performing a polycondensation reaction, or There is a method of performing a polycondensation reaction after obtaining a carboxyl group-terminated polyester oligomer and an amino group-terminated polyamide oligomer in advance, and the method can be appropriately selected.

The polyesteramide resin of the present invention has 1,250 to 3,000 equivalents of amide bond in the molecule / 10 ⁶ g, preferably 600 to 2,000.
It is characterized by containing, but if the amide bond is less than 1,250, friction and wear will be poor, if it exceeds 3,000, on the other hand, the solubility in solvents will be poor, and the stability of the magnetic paint will be extremely poor .

The polyesteramide resin of the present invention has a number average molecular weight of 8,000
0 to 60,000 desirably 15,000 to 50,000, but if the number average molecular weight is less than 8,000, excellent abrasion resistance and durability cannot be obtained.Conversely, if it exceeds 60,000, the solution viscosity when dissolved in an organic solvent will increase. It becomes too high and the paint stability deteriorates, making it difficult to implement industrially.

In the present invention, in addition to the polyesteramide resin used in the present invention, for the purpose of adjusting flexibility, improving cold resistance, improving heat resistance, etc., another resin is added, and / or a polyesteramide resin is added. It is desirable to mix compounds that react and crosslink. Other resins include vinyl chloride resin, polyester resin, cellulose resin, epoxy resin, phenoxy resin, polyvinyl butyral, acrylonitrile-butadiene copolymer, and polyurethane resin.

On the other hand, compounds that crosslink with the polyesteramide resin include polyisocyanate compounds, epoxy resins, melamine resins, urea resins and the like, and 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 γ-fe ₂ O ₃ , crystals of γ-Fe ₂ O ₃ and Fe ₃ O ₄ ,
O ₂ , γ-Fe ₂ O ₃ or Fe ₃ O ₄ coated with cobalt, metal,
Examples include barium ferrite and ferromagnetic alloy powders such as Fe-Co and Fe-Co-Ni.

In the magnetic recording medium of the present invention, if necessary, a plasticizer such as dibutyl phthalate and triphenyl phosphate, dioctyl sulfo sodium succinate, t-butyl phenol / polyethylene ether, ethyl naphthalene /
Lubricants such as sodium sulfonate, dilauryl succinate, zinc stearate, soybean oil lecithin and silicone oil and various antistatic agents can also be added.

(Operation) The polyesteramide resin of the present invention is characterized by containing an appropriate amount of a metal sulfonate group and an amide group in the resin, and has excellent dispersibility in magnetic particles. A magnetic recording medium having a high ratio can be obtained.

Further, the magnetic recording medium using the polyesteramide resin of the present invention has excellent durability, and in the conventional technology, there is a problem that the gloss and the squareness ratio of the coating film decrease with the improvement of the durability. However, the polyesteramide resin of the present invention has made it possible to achieve both magnetic properties and durability.

(Examples) Hereinafter, the present invention will be specifically illustrated by examples.

 In the examples, “parts” means “parts by weight”.

 In the examples, each measurement item was based on the following method.

Magnetic layer gloss: Surface gloss was measured with a gloss meter. The higher the gloss, the better the dispersibility of the magnetic particles.

Wear state after 100 times of running: The wear state after 100 times of running with a Sony 8 mm video deck EV-A300 was visually observed.

○: Slight damage to the magnetic layer △: Slight damage to the magnetic layer ×: Slight damage to the magnetic layer Still characteristics: The time until the recording disappears in the steel state on the VCR was measured. .

(Ambient temperature 20 ° C., Humidity 50% RH) Preparation Examples A and B of Amide Group-Containing Compounds 71.9 parts of sebacic acid, 28.1 parts of 2,2 ′, 4-trimethylhexamethylenediamine, 50% aqueous solution of hypophosphorous acid 0.4 And 75 parts of water were placed in a reaction vessel and purged with nitrogen, and then reacted under pressure at a temperature of 200 ° C. for 1.5 hours. The temperature was raised to 240 ° C while further distilling off water, and the reaction was continued for 2 hours. When both ends of the reaction were reacted with sebacic acid / 2,2 ', 4-trimethylhexamethylenediamine at a ratio of 1/2 mol, carboxyl groups were formed. Was obtained. The acid value of this is
The amide bond concentration was 3800 equivalents / 10 ⁶ g and the amide bond concentration was 3800 equivalents / 10 ⁶ g.

Similarly, an amide group-containing compound B obtained by reacting 1,6-hexamethylenediamine with sebacic acid at a molar ratio of 1: 2
I got This had an acid value of 4,100 equivalents / 10 ⁶ g and an amide bond concentration of 4,100 equivalents / 10 ⁶ g.

Product C of Amide Group-Containing Compound A solution of 204 parts of isophthaloyl chloride and 150 parts of N-methylpyrrolidone while stirring and cooling a solution consisting of ethyl 4-aminobenzoate, 160 parts of pyridine and 200 parts of N-methylpyrrolidone. Was added dropwise over 30 minutes. Drip end part 6
After the temperature was raised to 0 ° C and reacted for 1 hour, it was poured into 3,000 parts of water.
Precipitated and filtered. After washing with water ethanol, recrystallization was performed with methyl ethyl ketone / acetone = 3/1.

The obtained amide group-containing compound C was the following compound by elemental analysis and NMR, and the amide bond concentration was 4,460 equivalents / 10 ⁶ g. Met.

Synthesis Examples 1 to 7 of Polyesteramide In a 2 flask equipped with a thermometer, a cooling tube and a stirrer, 116 parts of dimethyl terephthalate, 109 parts of dimethyl isophthalate,
11.8 parts of dimethyl 5-sodium sulfoisophthalate,
149 parts of ethylene glycol, neopentyl glycol 166
And 0.07 part of tetrabutyl titanate, and a transesterification reaction was carried out at 160 to 220 ° C. for 6 hours. After the atmosphere in the system was replaced with nitrogen, 421 parts of the amide group-containing compound 1 shown in Table 1 were added, and 2
The esterification reaction was performed at 00 to 220 ° C. for 3 hours. Next, the pressure inside the system was gradually reduced, and the excess glycol component was distilled off. After 30 minutes, the pressure was adjusted to 5 mmHg at 250 ° C. And even 0.2-0.5mm
A polycondensation reaction was carried out at 250 ° C. for 80 minutes at Hg to obtain a polyesteramide resin 1.

The obtained resin was analyzed by high performance liquid chromatography to have a number average molecular weight of 23,000 in terms of standard polystyrene. From elemental analysis, the sulfonic acid metal base was 54 equivalents / 10 ⁶ g. The same amount of the amide group of the amide group-containing dibasic acid used as the starting material was detected in the polyesteramide by infrared absorption spectrum and NMR. The resin composition was as described in Table 1.

Similarly, using the raw materials described in Table 1, the polyester amide 2 was subjected to a transesterification reaction / polycondensation reaction.
7 was obtained. Table 1 shows the composition and characteristics of the obtained resin.

In Table 1, the solubility was evaluated as good when the solid content concentration was 10% and methyl ethyl ketone / toluene / cyclohexanone could be uniformly dissolved in 1/1/1.

Comparative Synthesis Examples 1 to 6 of Polyesteramide Polyesteramide was obtained in the same manner as in Synthesis Example 1 of polyesteramide except that dimethyl 5-sodium sulfoisophthalate was not contained as an acid component. According to the same analysis as in Synthesis Example 1, the polyesteramide obtained in Comparative Synthesis Example 1 did not contain a metal sulfonic acid salt, had an amide bond concentration of 2,200 equivalents / 10 ⁶ g, a number average molecular weight of 25,000, and had good solubility. there were.

Polyester amides having the compositions shown in Table 2 were obtained in the same manner as in Synthesis Example 1 or 3.

The polyesteramide obtained in Comparative Synthesis Example 2 had poor solubility.

The polyesteramide obtained in Comparative Synthesis Example 3 had an amide bond concentration of 87 equivalents / 10 ⁶ g.

In Comparative Synthesis Examples 4 and 5, the sulfonic acid metal salt concentrations were
3,450 equivalents / 10 ⁶ g.

 In Comparative Synthesis Example 6, the number average molecular weight was 6,500.

Example 1 A composition having the following composition ratio was placed in a ball mill and dispersed for 48 hours. Then, 4 parts of coronate EH (trimer of hexamethylene diisocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added as a curing agent, and further 1 hour. The mixture was mixed to obtain a magnetic paint. This was applied and dried on a 12 μm-thick polyethylene terephthalate film while applying a magnetic field of 4,000 gauss so that the thickness after drying would be 4 μm. After leaving it at 50 ° C. for 2 days, it was slit into 8 mm width to obtain a magnetic tape.

100 parts of a solution of the polyesteramide obtained in Synthesis Example 1 (solvent cyclohexanone / methyl ethyl ketone / toluene =
1/1/1, solid content concentration 30%) Needle-shaped metal magnetic substance (BET 50m ² / g) 120 parts Stearic acid 1 part Butyl stearate 0.5 part Alumina (average particle size 0.5 μm) 5 parts Toluene 150 parts Methyl ethyl ketone 100 Table 3 shows the properties of the obtained magnetic tape.

Examples 2 to 10 Magnetic tapes were obtained in the same manner as in Example 1 except that the resins listed in Table 3 were used as binder resins. Table 3 shows the properties of the obtained magnetic tape.

Comparative Examples 1 to 9 Using the polyesteramide resin, adipate-type polyurethane resin and vinyl chloride / vinyl acetate copolymer obtained in Comparative Synthesis Examples 1 to 6 in the proportions shown in Table 3, magnetic properties were obtained in the same manner as in Example 1. I got the tape. Table 4 shows the properties of the obtained magnetic tape.

In Comparative Examples 2 and 6, the polyesteramide resin used was dissolved at 80 ° C. at a solids concentration of 8.6% and a weight ratio of cyclohexanone / toluene / methylethylketone = 7.3 / 54.2 / 38.5. The resulting solution was cloudy. Using this solution, the magnetic paint was allowed to act in the same manner as in Example 1 except that toluene and methyl ethyl ketone were not added. The magnetic paint was non-uniform due to the deposition of the resin component.

(Effects of the Invention) As a binder component, a magnetic recording medium using an appropriate amount of a metal sulfonic acid salt and a polyesteramide resin containing an amide group according to the present invention is fine magnetic particles of BET-40 m ² / g or more, or It has excellent dispersibility of magnetic particles such as metal magnetic powder and barium-ferrite, and has high gloss and squareness characteristics of a magnetic coating film, and shows excellent durability.

In the prior art, there was a problem that the gloss and the squareness ratio of the coating film were reduced with the improvement of the durability. However, the magnetic recording medium of the present invention enabled both high magnetic properties and high durability. It is.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C09D 5 / 23,177 / 12 G11B 5/702

Claims (1)

(57) [Claims] A magnetic recording medium in which a magnetic paint containing a ferromagnetic powder in a binder is coated on a non-magnetic support.
As a component of the binder, 4-400 a metal sulfonate polymer per equivalent / 10 ⁶ g, a number average molecular weight of the amide bond containing 1,250～3,000 eq / 10 ⁶ g polymer per 8,000
A magnetic recording medium comprising 60,000 polyesteramide resins.