JPS63133316A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder, surface characteristic of a magnetic coated film and electromagnetic conversion characteristic by using a binder consisting of a specific vinyl chloride copolymer, rubber binder and polyisocyanate. CONSTITUTION:The magnetic layer is formed on a magnetic recording medium by using the binder consisting of the vinyl chloride copolymer consisting of vinyl chloride, vinyl alcohol and amine-modified vinyl compd., the rubber binder and the polyisocyanate. The component ratios at this time are 80-20wt% vinyl chloride copolymer and 20-80wt% rubber binder and the polyisocyanate is mixed therewith at 5-30% per the resin component of the binder. As a result, the dispersibility of the magnetic powder and the surface characteristic of the magnetic coated film and electromagnetic conversion characteristic are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media used as magnetic tapes and floppy disks. It relates to magnetic recording media.

BACKGROUND OF THE INVENTION Generally, coated magnetic recording media are made by coating a magnetic paint mainly consisting of magnetic powder, binder resin, and solvent onto a support such as a polyester film. The properties of the magnetic coating film formed on the support are not only related to physical properties such as running properties, but also to magnetic properties and electromagnetic conversion properties, and these are largely influenced by the binder resin and various additives. be controlled. Various binder resins have thus far been proposed, and one of them is a vinyl chloride-vinyl acetate-vinyl alcohol copolymer that has been widely used. The characteristics of this copolymer are that it is relatively inexpensive, easily soluble in solvents, has good compatibility with other resins, and has a high affinity with magnetic powder due to the hydroxyl group in its molecules. , which has advantages such as improved dispersibility, resulting in excellent magnetic properties and electromagnetic conversion properties. However, in recent years, with the improvement in the performance of magnetic recording devices, magnetic recording media have been required to have even higher recording densities and There is a need for high reproduction output in short wavelength recording. In response to this,
The magnetic powder used is becoming more finely divided, and it is becoming increasingly difficult to obtain satisfactory characteristics using only the above-mentioned resins.

In order to solve the above problems, there is a method of introducing various hydrophilic groups into the molecular structure of the binder resin to increase the affinity with the magnetic powder and improve the dispersibility of the magnetic powder. When a vinyl chloride-vinyl acetate-vinyl alcohol copolymer is used as the binder resin, the hydrophilic group introduced into the molecular structure thereof is a carboxyl group (Japanese Patent Application Laid-open No. 1983-1999, etc.).

Problems to be Solved by the Invention However, as magnetic powder has become finer in the past, there has been a need to provide a magnetic recording medium with better dispersibility of magnetic powder, better surface properties of magnetic coating, and electromagnetic conversion characteristics. There was a problem in that a binder resin that could be used was not available.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention comprises a vinyl chloride copolymer consisting of vinyl chloride, vinyl alcohol, and a hyamine-modified vinyl compound, a rubber binder, and a polyisocyanate. Magnetic powder is dispersed in a binder consisting of , which is coated on a support.

The present inventors have improved the dispersibility of the magnetic powder and the surface properties of the magnetic coating by using a vinyl chloride copolymer containing vinyl chloride, vinyl alcohol, and an amine-modified vinyl compound as essential components as the binder resin. By adding a rubber binder and polyincyanate to this vinyl chloride copolymer, the running properties, abrasion resistance, etc. of the magnetic coating film are improved. It has also been found that improvements in the physical properties of

In the present invention, the vinyl chloride copolymer, which is used as one of the binder resin components and has vinyl chloride, vinyl alcohol, and a hyamine-modified vinyl compound as essential components, has a hydrophilic group called an amino group in its molecular structure. This increases the affinity with magnetic powder. As a result, the dispersibility of the magnetic powder is improved, and good magnetic properties and electromagnetic conversion properties can be obtained. This vinyl chloride copolymer is particularly suitable for vinyl chloride 60 to 95% by weight, vinyl alcohol 2%
-18% by weight, 0.05-5% by weight of an amine-modified vinyl compound, and some amount of other vinyl compounds as required, and preferably has an average degree of polymerization of 200-SOO.

If the amount of vinyl chloride is too small, the physical strength will decrease, and if it is too large, the solubility in a solvent will decrease, which is disadvantageous in use. Furthermore, if the amount of vinyl alcohol is too small, the dispersibility of the magnetic powder will decrease, and the compatibility with the rubber binder used in combination will decrease. On the other hand, if it is too large, physical strength and thermal stability will decrease. If the amount of the amine-modified vinyl compound is too small, the dispersibility of the magnetic powder will decrease and the surface properties of the magnetic coating will decrease.

On the other hand, if the amount is too high, the dispersibility and surface properties will decrease, and the solubility in solvents will also decrease, making it impossible to use it as a binder resin.

If the average degree of polymerization of a copolymer composed of such unit components is too low, the magnetic coating film will become brittle and its physical strength will decrease, and the durability of the magnetic coating film will also decrease. On the other hand, if the average degree of polymerization is too high, the viscosity of the paint at a given concentration will increase, resulting in significantly poor workability and difficulty in handling.
It is desirable that the average degree of polymerization is in the range of 200 to 800.

This copolymer can be produced using general suspension polymerization method, emulsion polymerization method,
It is produced by solution polymerization method, bulk polymerization method, etc., but in order to introduce vinyl alcohol, lower fatty acid vinyl such as vinyl acetate or vinyl propionate is copolymerized, and the resulting copolymer is hydroxylated in an appropriate solvent. Alkali such as potassium, sodium hydroxide, sodium alcolade, or hydrochloric acid.

This is carried out by saponification using an acid such as sulfuric acid as a catalyst and purification by a conventional method. Vinyl acetate, vinyl propionate, etc. may be present in small amounts as unsaponified moieties, or vinyl versatate, alkyl esters of acrylic acid or methacrylic acid, esters of maleic acid or itaconic acid, vinylidene chloride, Some amount of various vinyl ethers may be copolymerized.

Since the amount of vinyl alcohol introduced is within the above-mentioned range of 2 to 15% by weight, the copolymerization amount of lower fatty acid vinyl and the rate of saponification (molti) must be adjusted so as to maintain this range.

On the other hand, the amine-modified vinyl compound can be introduced simultaneously with the saponification reaction. That is, vinyl alcohol is introduced by adding various amine compounds described later to the saponification reaction system and heating and stirring at 10 to 80°C for a certain period of time until the desired degree of saponification is obtained, and at the same time, the chlorine atoms of vinyl chloride and An amine is introduced into the side chain by reaction with an amine compound. In this amine modification, the usage of the amine compound is that the amine modified vinyl compound in the copolymer is 0.
．． It is necessary to set the amount within the range of 0.05 to 5% by weight.

The amine compounds used include primary, secondary or tertiary amines such as aliphatic amines, cycloaliphatic amines, aromatic amines, and specifically ethylamine, propylamine, butylamine, cyclohexyl amine,
Ethanolamine, naphthylamine, aniline, 0-toluidine, diethylamine, dioctylamine, diisobutylamine, jetanolamine, N-methylaniline, trimethylamine, triethylamine.

Triisobutylamine 2-tridecylamine, N-methyldiphenylamine, hexamethylenetetramine, triethanolamine, tributylamine.

Examples include pyridine, α-picoline, β-picoline, γ-picoline, 2,4-lutidine, quinoline, and morpholine.

The ratio of the binder resin components used in the present invention is 80 to 20% by weight of the vinyl chloride copolymer and 20 to 80% by weight of the rubber binder, and the polyisocyanate is 80 to 20% by weight based on the total binder resin component. The content is preferably 5 to 30% by weight. If the ratio of the vinyl chloride copolymer is too low or the ratio of the rubber binder is too high, the dispersibility of the magnetic powder will decrease and the surface properties of the magnetic coating will decrease. On the other hand, if the ratio of the vinyl chloride copolymer is too high or the ratio of the rubber binder is too low, the physical strength of the magnetic coating will decrease. Also, if the amount of polyisocyanate is too small, the physical strength of the magnetic coating will be insufficient, and if it is too large, unreacted polyisocyanate will float to the surface of the magnetic coating, causing calender adhesion.
This causes problems such as reduced running performance.

The rubber binder used in the present invention is a polyurethane resin, a polyester resin, or a combination of both. As these polyurethane resins or polyester resins, known ones that have been conventionally used as binder resins for magnetic recording media can be used.

Examples of the polyisocyanate used in the present invention include bifunctional isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, and trifunctional isocyanates such as trimethylolpropane tolylene diisocyanate. Any polyisocyanate that can be used as a curing agent can be used.

The magnetic powder used in the present invention includes γ-Fe2
0. , Fe, 04 and these adsorbed or doped with cobalt ions, oxide-based magnetic powders such as Cry, furthermore, Fe, Go, Ni, or metal-based magnetic powders containing these as components, and other conventional magnetic powders. More well-known ones can be mentioned. The mixing ratio of magnetic powder and binder resin is 10 to 4 parts by weight of binder resin per 100 parts by weight of magnetic powder.
Good results are obtained when the amount is 0 parts by weight.

Incidentally, when preparing magnetic paint by uniformly dispersing magnetic powder and binder resin, abrasives, antistatic agents, dispersants, and lubricants have been conventionally used.

Adding plasticizers, etc., as well as methyl ethyl ketone, methyl imbutyl ketone, and nclohexanone.

The use of various organic solvents such as toluene is the same as in the past, and there are no special restrictions on these points.Supports include synthetic resins such as polyester, polyimide, and polyvinyl chloride, other non-magnetic metals, Conventionally known materials such as ceramics can be used. Conventionally known methods are still used for the manufacturing process of magnetic recording media.

Example The present invention will be further explained below with reference to Examples and Comparative Examples.

Example 1 A magnetic paint was prepared by first dispersing the following composition in a ball mill and then in a sand mill.

Vinyl chloride-based copolymer containing vinyl chloride, vinyl alcohol, and an amine-modified vinyl compound as essential components (hereinafter abbreviated as vinyl chloride-based coelectrolyte 1) 10 parts by weight Polyurethane resin 10 parts by weight C〇-Adhesive 1- Fe? 05 (BJCτ specific surface area 36rr?/'
l) 100 parts by weight Alumina 3 parts by weight Carbon black 5 parts by weight n-butyl stearate 1 part by weight Stearic acid 1 part by weight Polyisocyanate (trimethylolpropane tolylene diisocyanate) 5 parts by weight Methyl ethyl ketone 160 parts by weight Toluene 100 parts by weight Cyclohexanone 50 The composition of vinyl chloride copolymer 1 in parts by weight is shown in Table 1.

The magnetic paint prepared with the above composition was coated on a polyethylene terephthalate film with a thickness of 14 μm to a final film thickness of 6 μm.
After passing through the steps of drying, surface smoothing, and curing, the magnetic tape was cut to a width of about 12.65 cm (A inches).

Example 2 In Example 1, magnetic powder ico deposition 1-Fe2O.

(BET specific surface area: 46rr+1/g) and made into a paint, and a magnetic tape was produced in the same manner as in Example 1.

Example 3 A magnetic tape was produced in the same manner as in Example 1, except that the metal magnetic powder (BICT specific surface area: 50 rn'/f) containing the magnetic powder 1Fai as the main component was used to make a paint.

Comparative Example 1 In Example 1, vinyl chloride copolymer 1 was changed to vinyl chloride-vinyl acetate-vinyl alcohol copolymer (hereinafter abbreviated as vinyl chloride copolymer 2. The composition is shown in Table 1). This was made into a paint, and a magnetic tape was prepared in the same manner as in Example 1.

Comparative Example 2 In Example 2, a magnetic tape was produced in the same manner as in Example 1 except that vinyl chloride copolymer 1 was changed to total vinyl chloride copolymer 2 to form a paint.

Comparative Example 3 In Example 3, vinyl chloride copolymer 1 was changed to vinyl chloride copolymer 2 to form a paint, and a magnetic tape was obtained in the same manner as in Example 1.

Table 2 shows the measurement results of magnetic properties such as saturation magnetization and surface gloss of the magnetic tapes of Examples and Comparative Examples created as described above, and the measurement results of electromagnetic conversion characteristics (S/N) and durability. are shown in Table 3. However, in Table 2, the magnetic properties are the values measured using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.), and the surface glossiness is the value measured using a crossmeter (Nihon Shinshoku Kogyo Co., Ltd.). This is a value comparing the previous 60° reflectance with that of a standard glass plate. Also, in Table 3,
The S/N was measured using a noise meter (manufactured by Shibaku) and '/TR (
NY-s2oo)i manufactured by Matsushita Electric Industrial Co., Ltd. was used, and the difference from Comparative Example 1 was determined. Furthermore, the results are obtained when 100 bus running tests were carried out using durable running UVTR (NY-8200 manufactured by Matsushita Electric Industrial Co., Ltd.) f, and the number of N was 10.

As shown above, the magnetic recording medium using the binder resin of the present invention has improved surface properties and magnetic properties (particularly squareness ratio) of the magnetic coating film, and as a result, electromagnetic conversion properties such as S/N are also improved. be done. On the other hand, deterioration in durability, which tends to occur when a hydrophilic group is introduced into the binder resin, is not observed in the present invention.

Effects of the Invention As described above, according to the present invention, a vinyl chloride copolymer consisting of vinyl chloride, vinyl alcohol, and an amine-modified vinyl compound, a rubber binder, and a polyincyanate are used as a binder resin for a coated magnetic recording medium. By using this, it is possible to obtain a magnetic recording medium with improved dispersibility of magnetic powder, surface properties of magnetic coating film, and electromagnetic conversion characteristics.

Claims (4)

[Claims] (1) Magnetic powder dispersed in a binder consisting of a vinyl chloride copolymer consisting of vinyl chloride, vinyl alcohol, and an amine-modified vinyl compound, a rubber binder, and a polyisocyanate is coated on a support. Features of magnetic recording media. (2) Vinyl chloride copolymer is vinyl chloride 60-95
% by weight, vinyl alcohol 2-16% by weight, amine-modified vinyl compound 0.05-5% by weight, average degree of polymerization 2
The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a number of 00 to 800. (3) The magnetic recording medium according to claim 1 or 2, wherein the rubber binder is a polyurethane resin, a polyester resin, or a combination thereof. (4) The ratio of the binder resin components is 80 to 20% by weight of the vinyl chloride copolymer, 20 to 80% by weight of the rubber binder, and 5 to 30% by weight of the polyisocyanate based on the total binder resin content. The magnetic recording medium according to any one of claims 1 to 3, which is % by weight.