JPS61158024A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a glossy magnetic recording tape hardly causing sick slip friction and having high wear resistance even during use for a long period or under severe conditions by using polyester polyurethane as a binder. CONSTITUTION:Polyester polyurethane used as a binder is polyurethane consisting of polyol and polysocyanate or further contg. a chain extender. The polyol is polyester polyol having >=300mol.wt. obtd. by polymerizing lactone having a 4- or 7-membered ring with an initiator having hydroxyl, amino or carboxyl groups at terminals and three or more functional groups.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention consists of a non-magnetic support provided with a magnetic layer pasting magnetic powder dispersed in a binder, and the magnetic layer contains a special polyurethane as a binder. It is related to recording media.

With the rapid development of magnetic recording materials, high demands have been placed on the performance of magnetic tapes in the fields of video magnetic tape, computer magnetic tape, and audio magnetic tape.

Generally, in video magnetic tapes and computer magnetic tapes which have a high relative speed, a particularly wear-resistant binder is used to bind magnetic powder onto a non-magnetic support. For example, a polyester-based polyurethane resin made by reacting polyester (trade name Desukamihen 2200, manufactured by Bayer) with polyisocyanate is generally used because of its abrasion resistance. However, since the aforementioned polyester type polyurethane does not have slipperiness, the frictional force increases while the tape is running, and the tape sticks to the drum, resulting in six-slip phenomenon. Therefore, attempts have been made to blend lubricating agents such as polyvinyl chloride and nitrified cotton into polyester-type polyurethane.

By adding polyvinyl chloride or nitrified cotton to the above-mentioned non-polyester type polyurethane, the surface smoothness can be improved during short-term use.
Deterioration easily occurs due to light and heat. Furthermore, the use of a mixture of vinyl chloride and nitrified cotton tends to accelerate deterioration rather than the use of urethane alone. For this reason, surface properties are improved with an increase in polyvinyl chloride and nitrified cotton, which did not cause problems during long-term use or under harsh conditions such as in automobiles, but if too much is used, the coating film becomes brittle. There were drawbacks such as poor adhesion to non-magnetic supports, difficulty in surface finishing, and a low content of polyurethane weakened adhesion and increased the coefficient of friction.

The inventors of the present invention have repeatedly conducted various studies to overcome the drawbacks of conventional binders, and have found that by using polyester polyurethane as a binder, a magnetic recording tape with good abrasion resistance can be obtained. Based on these findings, we have arrived at the present invention.

That is, the present invention provides a magnetic recording medium comprising a magnetic powder coated on a non-magnetic support together with a binder, in which the binder comprises a lactone having 4 to 7 ring members with a hydroxyl group, an amino group, or an epoxy group at the end. One or more of the carbonate polyesters to be polyvarnished are synthesized using a polyester polyol with a molecular weight of 500 or more obtained by polymerization using an initiator having a trifunctional or higher functional group. This magnetic recording medium is characterized in that it is used in combination with polyurethane.

To explain the present invention in more detail, the polyester polyurethane used as a binder in the present invention is a polyurethane composed of a polyol, a polyisocyanate, and, if necessary, a chain extender. Polyol is a molecular weight product obtained by polymerizing lactones with 4 to 7 ring members using an initiator that has a hydroxyl group, an amino group, or a carboxylic acid group at the end and has a trifunctional or higher functional group. 300 or more polyester polyol.

The lactones having 4 to 7 ring members used in the present invention include lactones having 4 to 7 ring members with or without one or more methyl groups as a substituent, such as β-propiolactone, pivalolactone, δ- Valerolactone, ε-
Examples include caprolactone, methyl-ε-caprolactone, dimethyl-ε-caprolactone, and trimethyl-ε-caprolactone.

Examples of the initiator include trifunctional or higher functional polyhydric alcohols such as trimethylolpropane and pentaerythritol. Furthermore, polyhydric aminos such as 1,2,5-benzenetriamino, polycarboxylic acids such as trimellitic acid and pyromellitic acid, or polyhydric alcohols such as polyoxyalkylated derivatives of trimethylolpropane. For the purposes of the present invention, polyester polyols such as polyhydric alcohols and polyoxyalkylated derivatives of polyvalent aminos, such as polyoxyalkylated derivatives of polyhydric aminos and 22,000 and a hydroxyl value of about 5 to 300. Such polyester polyols are preferably used alone, but other polyester polyols, polyether polyols, or polyesters known for polyurethane production may also be used. - Can also be used in combination with polyether polyol 0 When used in combination, the amount of other polyols is desirably less than about 1 part by weight per 100 parts by weight of the polyester polyol; if this range is exceeded, the desired effect cannot be obtained. I can't do it.

The polyisocyanate to be reacted with the specific polyester polyol as mentioned above is tolylene diisocyanate (T
Dr), 4.4'-diphenylmethane diinocyanate (MDI), xylene diisocyanate (XDI), 1
, 5-naphthylene diisocyanate (NDI), hexamethylene diisocyanate (E (D■), water-added TDr
, water-added MDI, inphorone diinocyanate (IPD)
I), lysine isocyanate) (LDI), inpropylidene bis(4-cyclohexyl isocyanate) (IP
CI) and other known polyisocyanates can be used. From the viewpoint of light resistance of the resulting polyurethane, it is preferable to use aliphatic or alicyclic polyisocyanates, and from the viewpoint of cost and physical properties, it is preferable to use water-added M.
DI, IPDI, etc. are particularly suitable.

When producing polyurethane from polyester polyol and polyisocyanate as described above, appropriate amounts of chain extenders known in the prior art such as polyhydric alcohols, aliphatic polyamino, alicyclic polyamino, aromatic polyamino, etc. as described above are used. It is preferable.

In the present invention, the above-mentioned polycarbonate polyester polyurethane alone can be used as the main component of the binder, but thermoplastic resins that are compatible with it, such as polyvinyl butyral resin, vinylidene chloride resin, nitrified cotton, vinyl chloride-vinyl acetate, etc. One type or a combination of two or more types selected from copolymers (product name: VACH Union Carbide Co., Ltd.) and epoxy resins are used.

When blending nitrified cotton or the like with the polycarbonate polyester polyurethane, 0 to 100% by weight of the nitrified cotton or the like is blended with respect to 100% by weight of the polycarbonate polyester polyurethane.

The magnetic powder to be dispersed in the binder of the present invention is r-
Fe202. Fe3O4, CrO2, Cor
Metal oxide powder such as Fe2O3, pure Fe, Fe
-Co-based alloy.

A metal powder such as a Fe-Co-Ni alloy is used.

The ratio of magnetic powder to binder is generally 1 to 10 parts by weight of magnetic powder, particularly 4 to 6 parts by weight, and 1 part type.

Further, examples of the nonmagnetic support used in the present invention include spherical polyester, particularly polyethylene terephthalate film.

The magnetic recording medium according to the present invention is manufactured by a known method.

A dispersion liquid, for example, a magnetic powder, a binder, a dispersant, and a solvent are respectively blended in a pot ball mill or a stirred mill, and the produced magnetic powder dispersion liquid is filtered, and this dispersion liquid is coated with a non-magnetic powder using a conventional coating device. This is done by coating on a support. Usually, the magnetic molecules are aligned before the liquid film forming agent is dried on the support. Even if it is not used, the coefficient of friction is extremely small (0), so no weeping phenomenon occurs.

Furthermore, since it has extremely good wear resistance, it exhibits stable performance in terms of durability, runnability, and electromagnetic conversion characteristics.

Next, the present invention will be specifically explained with reference to Examples.Example 1 164 parts of sorbitol was taken as an initiator, 2700 parts of ε-caprolactone was added thereto, and 2.8 parts of diphenyltin dilaurate were further added. The reaction was carried out at 200° C. for 10 hours, and unreacted substances were distilled off under reduced pressure for another hour to obtain a polycaprolactone polyester polyol with a molecular weight of about 3,200 and an oxidation value of 0.5.

1015 parts of this polyol, 53 parts of water-added MDI, 345 parts of dimethylformamide and 2 parts of methyl ethyl ketone.
Polyester polyurethane A was obtained by reacting 30 parts at about 80 to 120°C for 8 hours.

Co-containing - Fe203 100 parts by weight Antistatic agent (carbon black) 2 Methyl ethyl ketone 67/y Doluol
67〃Cyclohexanone
67〃The above composition was kneaded in a ball mill for 45 hours, and 2.6 parts by weight of a reactant of trimethylolpropane and water-added MDI was added and mixed for 3 hours.The resulting mixed mixture was passed through a filter and mixed with a reverse roll coater. It is coated onto a polyethylene terephthalate film having a thickness of 16μ so that the thickness after drying becomes thicker. followed by 40
The product was aged for 748 hours at 748°C, and the surface was finished using a calendar roll, and the tape was cut into 12.65-inch pieces to obtain a video tape. The physical properties of the binder of the tape obtained are shown in Table 1.
The properties of the magnetic coating were as shown in Table 2, and the physical properties of the magnetic coating were as shown in Table 3.

Comparative Example I Co-containing-F e203 100
Part by weight Polyester type polyurethane resin 85〃 (Product name: Rezamin ME12 Dainichiseika Industries product) Lecithin
2 “Carbon Black
2 〃Methyl ethyl ketone
67 Dollar All 6
7 Cyclohexane 67 A video tape was obtained using the same composition as in Example 1. The physical properties of the binder of the obtained tape were as shown in Tables 1 and 2, and the physical properties of the magnetic coating were as shown in Table 3. Comparative Example 2 Co-containing - Fe203 100 parts by weight Polyester type Polyurethane resin (35%) 85
(Product name: Rezamin ME12 Dainichiseika Kagaku Kogyo product) Silicone oil 3 〃 (Product name: KF
96 Shin-Etsu Shin-Etsu Silico Fluorine Product Chin
2 Carbon black
2 〃Methyl ethyl ketone 67〃
Dorol 67 Cyclohexane 67 A video tape was obtained using the same composition as in Example 1. The physical properties of the binder of the obtained tape are as shown in Tables 1 and 2, and the physical properties of the magnetic coating are as shown in Table 3. is a test piece (thickness 0.04~0.
05aq, width 15 shoulders, length 60 ram).
02 left for 400 hours with gear open at 120℃
Table Hot water resistance physical properties of binder *Hot water resistance physical properties are measured by leaving it in an atmosphere with a temperature of 70°C and a humidity of 95% for two weeks0 Table 3 Physical properties of magnetic coating *Abrasion resistance is measured at a tape speed of 240 inches/see 4
The surface condition was repeatedly run 00 times and the degree of damage was observed using a microscope, and the following evaluation was made: Q 〇 - Almost no damage △ - Slightly damaged × - Significantly damaged

Claims (3)

[Claims] (1) In a magnetic recording medium formed by coating magnetic powder together with a binder on a non-magnetic support, lactones having 4 to 7 ring members are terminated with a hydroxyl group, an amino group, or a carboxyl group, and are trifunctional. Molecular weight 3 obtained by polymerization using an initiator having the above functional group.
A magnetic recording medium characterized in that a polyester polyurethane is synthesized from a polyester polyol of 0.00 or more and is used as the binder. (2) The magnetic recording medium according to claim 1, in which a thermoplastic resin compatible with polyester polyurethane is used in combination as a binder. (3) The magnetic recording medium according to claim 1, wherein the thermoplastic resin compatible with the polyester polyurethane is nitrified cotton, vinyl chloride-vinyl acetate copolymer, or epoxy resin.