JPS6226629A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium which has a low coefft. of friction in a wide temp. and humidity range, considerably decreases the change thereof and excels in wear resistance, durability and surface smoothness by combining an ester compd. as a specific lubricating agent with a specific polyurethane resin. CONSTITUTION:This magnetic recording medium is constituted by coating and forming the magnetic layer contg. the polyurethane resin having the metallic salt group of a sulfonic acid at 10-1,000equiv./10<6>g per polymer, satd. or unsatd. fatty acid of 10-18c, 1 or >=2 kinds of ester compds. of butyl cellulose and pulverous ferromagnetic material particles on a nonmagnetic substrate. An increase of Br/Bm value is not expected and at the same time, the high packability of the magnetic particles is not obtainable when the metallic salt group of the sulfonic acid is below 10equiv./10<6>g. The solvent solubility of the polyurethane resin is defective when the content thereof exceeds 1,000equiv./10<6>g.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention has a coating film (magnetic layer) with excellent surface smoothness, and a particularly low coefficient of friction over a wide range of temperature and humidity, with very little change in the coefficient of friction. The present invention also relates to a magnetic recording medium with excellent wear resistance and durability.

(Prior art) Conventionally, in order to improve the abrasion resistance and durability of magnetic recording media, a combination of a thermosetting binder and various lubricants has been used to strengthen the coating film and make the surface slippery. Many have been proposed.

For example, it is known to use polyurethane resins, epoxy resins, polyester resins, nitrocellulose, vinyl chloride-vinyl acetate copolymers, and the like as binders, and to bind these with polyfunctional incyanate compounds and the like. On the other hand, m Ifl.

Fixed d? such as graphite or molybdenum disulfide as a lubricant to reduce the coefficient of friction of the surface? 1. Liquid lubricants such as 1 lubricant, silicone fluorine, higher fatty acids and their ester compounds are mixed in the coating process.
It has been proposed to disperse it or, if necessary, to add it externally by impregnation, spraying, coating, etc. after forming the magnetic layer.

(Problems to be Solved by the Invention) However, in the above-mentioned prior art, the magnetic layer surface is smooth and has wear resistance over a wide temperature range, which is the objective of the present invention. f (It is difficult to obtain a magnetic recording medium that has sufficient durability. For example, if polyurethane resin or polyester resin is used as a binder, it is difficult to disperse magnetic powder such as ferromagnetic fine particles. Therefore, a dispersant such as a surfactant is required.Furthermore, when nitrocellulose or vinyl chloride-vinyl acetate copolymer is used as a binder, a plasticizer is required because the coating film lacks flexibility.

When surfactants and plasticizers are added, the adhesive force between the magnetic layer (coating film) and the non-magnetic base material decreases, and if the tape or disk is run or rotated for a long time, the coating film may separate. A problem arises. Even when lubricant is added,
Similar to surfactants and plasticizers, the adhesion between the magnetic layer and the non-magnetic base material decreases due to compatibility with the binder.In addition, plumping at high temperatures can cause not only a decrease in durability but also damage to the head. This will cause staining etc.

(An unsuccessful means to solve the problem) ``To solve the problem of interlocking,'' Ganto Motoyama had previously developed a binder that had excellent dispersibility of magnetic powder and good adhesion to non-magnetic substrates. Invented and already applied for
0450), in order to obtain a magnetic recording medium which has a low coefficient of friction over a wide temperature and humidity range, which is the object of the present invention, and has extremely little change in the coefficient of friction, and which has excellent wear resistance, durability, and surface smoothness. As a result of further study and intensive research, the inventors of the present invention were able to obtain a magnetic recording medium that satisfactorily meets the above purpose.

That is, the present invention comprises a polyurethane resin having 10 to 1000 equivalents/106 g of sulfo/acid metal base per polymer, one or more ester compounds of a saturated or unsaturated fatty acid having 10 to 18 carbon atoms, and butylcellulose. This is a magnetic recording medium characterized in that a magnetic layer formed by cooperating with fine ferromagnetic particles is coated and formed on a non-magnetic base layer.

The polyurethane resin used in the present invention contains 10 to 1000 equivalents of sulfo/acid metal base per polymer.
It is sufficient if it contains g. If the amount of sulfonic acid metal base per polymer is less than 10 equivalents/10''g, not only is it not possible to increase the Ilr/I1m value, but at the same time it is not possible to obtain high packing properties of the magnetic particles. If the amount of acid metal base exceeds 1 t/10@g per 1000, the polyurethane resin will have poor solvent solubility and will be impractical.

The polyurethane resin of the present invention is obtained by the reaction of a polyhydroxy compound and a polyincyanate,
Part or all of the polyhydroxy compound contains a sulfo/acid metal base.

As the polyhydroxy compound having a sulfonate metal base, a polyester polyol having a sulfonate metal base is particularly desirable. The polyester polyol containing a sulfonic acid metal base is composed of a carboxylic acid component that does not have a sulfonic acid metal base, a glycol component, and a dicarboxylic acid component that has a sulfonic acid metal base.

Examples of the carboxylic acid component not having a sulfonic acid metal base include terephthalic acid, inphthalic acid, orthophthalic acid
, aromatic dicarboxylic acids such as 1,5-naphthalic acid, P-
Aromatic oxycarbo/acids such as oxybenzoic acid, P-(hydroxyethoxy)benzoic acid, succinic acid, adipic acid, azelaic acid, Sepacif wt%, resinous dicarboxylic acids such as dodecanedicarboxylic acid, trimellitic acid, trimesic acid, pyro Examples include tri- and tetracarboxylic acids such as mellitic acid.

Glycol components include ethylene glycol, propylene glycol, 1.3-propanediol, 1.4-butanediol, 1.5-bentanediol, 1.6-hexanediol, neopentyl glycol, diethylene glycol, diethylene glycol, 2,2. 4-) trimethyl-1,3-bentanediol, 1,4-cyclohexane dimetatool, ethylene oxide and propylene oxide adducts of bisphenol A, ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A, polyethylene glycol, Examples include polypropylene glycol and polytetramethidi/glycol. Further, tri- and tetraols such as trimethylol ethyl alcohol, trimethylol propane, glyceryl pentaerythritol, etc. may be used in combination.

Examples of dicarboxylic acid components containing sulfo/acid metal bases include 5-sodium sulfoiphthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, and 2-potassium sulfoterephthalic acid. The copolymerization amount of the dicarboxylic acid component containing these sulfonic acid gold (salt) 1ξ is 0.5 mol% or more, preferably 1 to 50 mol%, based on the total carboxylic acid component.

There may be one or more types of polyhydroxy compounds having the sulfonic acid metal salt W.

It may also be used in combination with polyhydroxy compounds without sulfo/acid metal bases, such as ordinary polyester polyols, polyether polyols, acrylic polyols, Himashiura derivatives, tall oil derivatives, and their Sendai hydroxyl group compounds.

The polyinsyanates used in the polyurethane resin of the present invention include 2.4-) lylene diisocyanate, 2.
16-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m
-buenile/diisocyanate, hexamethylene diisocyanate, 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'-1 incyanate-diphenylneedle,
1.5-naphthalene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate,
1.3-diisocyanate methylcyclohexane 7%1.
4-Diincyanate methylcyclohexane, 4,'
4'-Diincyanate dicyclohexane, 4.4'
-Diisocyanates include dicyclohexylmethane, inholonodiincyanate, etc., but if necessary,
2.4.4′-triisocyanate-diphenyl,
Small amounts of benzene triisocyanate and the like can also be used.

A polyurethane resin can be obtained by reacting a polyhydroxy compound and a polyisocyanate in a solvent or in the absence of a solvent by a known method, but the desirable blending ratio is NCO group of polyincyanate/0.5 of 011 group of polyhydroxy compound. ~2/1. It is desirable that the polyurethane resin obtained has a molecular weight of aooo to 100,000.

The magnetic powder (ferromagnetic fine particles) used in the present invention includes γ-Fe having a spinel structure; ,Cry,
, =+Balto ferrite (Coo, Fe2O,) Examples include cobalt-adsorbed iron oxide, ferromagnetic Fe--Co--Ni alloy, and hexagonal ferrite. When the softening point of the polyurethane resin of the present invention is low, depending on the application, there is a risk that the resin may soften due to the heat generated between it and the head, or that it may block when it is wrapped in tape. In such a case, within the range that does not impair the dispersibility of the magnetic powder,
It is desirable to add a resin that is compatible with the polyurethane resin of the present invention and/or to mix a compound that reacts with the polyurethane resin to form a chemical compound. Examples of the compound include epoxy resins, incyanate compounds, melamine resins, urea resins, etc. Among these, incyanate compounds are particularly preferred.

If necessary, fine particles of carbon may be added to the magnetic recording medium of the present invention to improve conductivity, and fine particles of non-magnetic metal oxide or the like can be added as an anti-wear agent.

The lubricant used in the present invention is an ester compound of a saturated or unsaturated fatty acid having a carbon number of 0 to 18 and butyl cellosolve. Examples include butyl cellosolve stearate, butyl seron rubuorate, butyl cellosolve isosubuarate, and among these, butyl cellosolve palmitate and butyl cellosolve stearate are particularly preferred.

These lubricants may be used alone or in a mixture of two or more, and the amount of the lubricant is determined based on the above-mentioned 1 teriurethane resin in order to sufficiently reduce the coefficient of friction and prevent head contamination due to pluming. The amount of fn is suitably 1 to 20% by weight, and more preferably 3 to 15% by weight. The reason why this lubricant exhibits particularly excellent effects when combined with the sulfonic acid group-containing polyurethane resin of the present invention is unknown, but the two have appropriate interaction and compatibility. Therefore, it is difficult to bloom even at high temperatures, and the oil film is strongly bonded to the coating surface, forming a tough oil film.
Furthermore, it is considered that it does not have a negative effect on the contact with the non-magnetic base material. Therefore, it is thought that the coefficient of friction of the coating film is lowered and changes in it are also reduced from low temperatures to high temperatures, from low humidity to high 1υ degrees. The J1 magnetic base material used in the present invention is made of polymers such as polyester (particularly polyester mainly composed of polyethylene terephthalate), polyphenylene sulfite, or these polymers are supplemented with fibrous or powdery reinforcing materials or fillings. It is appropriately selected from tapes, films, and sheets made of materials containing additives.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the Examples in any way.

(Example) Examples 1 to 5, Comparative Examples 1 to 6 [Manufacture of polyester polyol] Temperature 31, stirrer and partial reflux condenser
582 parts of dimedyltere 7 tallate, 5-
Sodium dimethyl sulfoisophthalate 296 parts, ethylene glycol 434 parts, neopentyl glycol 72 parts
8 parts of zinc acetate, 0.66 parts of zinc acetate, and 0.08 parts of sodium acetate were added, and transesterification reaction was carried out at 140 to 220°C for 3 hours. Next, add 1212 parts of sebacic acid and add 210 to 25 parts of sebacic acid.
2i at 0℃! After reacting for 7 hours, the pressure of the reaction system was reduced to 20 mm and 11 g over 30 minutes, and the reaction system was further heated for 5 to 20 minutes. .

A polycondensation reaction was carried out at 250° C. for 50 minutes. The obtained polyester polyol (a) has ysp/c=
0.182, and had a hydroxyl number of 38. NMR
From analysis, etc., its composition was as follows. Terephthalic acid 30 mol%, 5-sodium sulfoisophthalic acid 10
mol%, sebacic acid 60 mol%, ethylene glycol 4
4 mol%, neopentyl glycol 56 mol%. Polynispolyol (b) was obtained in the same manner. ysp/c=
0.302, with a hydroxyl value of 22, N
According to MR analysis, its composition was as follows. Terephthalic acid 30 mol%, isophthalic v 20 mol%, adipic acid 50 mol%, ethylene glycol 65 mol%, 1.5-
Bentanediol 35 mol%.

[Production of polyurethane resin]

7 parts 1 1280 parts of toluene and 78 parts of methyl isobutyl ketone were added to a reaction vessel equipped with a meter, a stirrer, and a reflux condenser.
Add 50 parts of polyester polyol part, 71 parts of diphenylmethane diacyane), and 1.2 parts of dibutyltin silaurylate, and heat at 70 to 90°C.
Allowed time to react. The sulfonic acid metal base of the obtained polyurethane resin (I) was 378 equivalents/10''g, and the molecular weight was 18 o.o.O. By the same method, 10 parts of polyester polyol (4) was added. A polyurethane resin (II) was obtained using 990 parts of the polyester polyol (b).

The sulfonic acid metal base of the obtained polyurethane resin (II) was aO equivalent/106 g, and the molecular weight was 30,000.
Met.

[Manufacture of magnetic recording media]

After mixing and dispersing in a water mill for 60 hours, add Coronate (an adduct of tolylene diincyanate to trimethylolpropane manufactured by Nippon Polyurethane Co., Ltd.) aG part and lubricant W part (FA listed in Table 1) and stir. Mix in a downward direction. Each adjusted magnetic paint was passed through the mouth, degassed, applied onto a 75μ thick polyethylene terephthalate film using a doctor blade with a 25μ gap, and left in a hot air dryer at approximately 80°C to remove the solvent. After removing the
Perform the same glue and drying process on the back side of Baidu at 60℃ and 65% R1.
The magnetic layer was sufficiently cured by being left in a constant temperature bath. The thickness of the resulting coating film was about 25μ. Thereafter, a disk was punched out to a size of 3.4 inches in diameter. Table 1 shows the composition of the components used in the magnetic layer and the performance of the disk, along with comparative examples.

Below margin In addition, the measurement method of each other performance is described below.

-Surface roughness: Measured using "Surfcom" manufactured by Tokyo Seimitsu ■.

Dynamic friction coefficient: The friction force was detected and measured using a strain gauge when the disk was rotated at 300 r, p, m and contacted with a head load of 20 g.

・Compressive elastic modulus: 10 to 5 cm diameter sample area using TM^
The instantaneous recovery rate was measured after applying a load up to 50 g at a rate of g/win.

(Effects of the invention) From the results in Table 1, only when the specific polyurethane resin of the present invention is selected and combined with a specific ester compound as a lubricant, the coefficient of friction is small even in a wide general humidity range.
It can be seen that a magnetic recording medium that exhibits less change and is more durable can be obtained.

Patent Applicant Toyobo Co., Ltd. Procedural Amendment 11 JJ 8, 1985 1 Indication of the Case 1985 Patent Application No. 166214 2 Name of the invention Magnetic recording medium a Person making the amendment Relationship to the case Patent Applicant Osaka City Kita No. 2-2-8 Dojimahama, Ward, October 9, 1985 (Delivery date: October 29, 1985) & Column a for detailed explanation of the invention in the specification subject to amendment 5I11'? Replace Table 1 on page 16 of J with Attached Table 1.

7. List of attached documents

Claims (1)

[Claims] A polyurethane resin having 10 to 1000 equivalents/10^6g of sulfonic acid metal base per polymer, and a carbon number of 10
A magnetic layer containing one or more ester compounds of ~18 saturated or unsaturated fatty acids and butyl cellosolve and ferromagnetic fine particles is coated and formed on a non-magnetic base material. magnetic recording medium.