JPS639296B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium such as a magnetic tape having a magnetic layer containing magnetic powder. Conventionally, vinyl chloride-based binders such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl propionate copolymer, and vinyl chloride-vinyl acetate-vinyl alcohol copolymer have been used as binders for magnetic recording media. Especially PVC
Vinyl acetate-vinyl alcohol copolymer is particularly widely used because the OH of vinyl alcohol contributes to the dispersion of magnetic powder, and the active hydrogen of OH reacts with isocyanate compounds to form a crosslinked structure in the coating film. ing. The present invention is directed to the use of vinyl alcohol in the copolymer.
In order to improve the dispersibility of OH groups, −SO ₃ M, −
COOM, −OSO ₃ M or

By introducing a hydrophilic group containing [formula], this improves the dispersibility of magnetic powder, improves magnetic properties and electromagnetic conversion properties (frequency properties, S/N, C/N), and improves magnetic properties. Because the powder is strongly bonded to the binder and the hydrophilic group, there is less detachment of the magnetic powder, which reduces level fluctuations and
The durability of the media due to powder fallout such as power attenuation, clotting, etc. is significantly improved. That is, the binder used in the present invention is represented by the following general formula. [However, R is -CH ₃ or -CH ₂ CH ₃ ; X is -
SO ₃ M, −COOM, −OSO ₃ M or

[Formula] (M is H, Li, Na or K, M' is H, Li, Na, K or an alkyl group CnH _2o+1 ,
n is preferably 23 or less), i=
200-800, j=0-200, l=1-200, k+l≦
It is 200. ] In this binder, in order to obtain the above-mentioned excellent effects, the vinyl chloride component contributes to the strength of the medium, and for this reason, i should be set at i=200 to 800. i
If it is less than 200, the strength will be too low, and if it exceeds 800, the solubility in solvents will be poor. The vinyl acetate component is necessary to increase the solubility of the vinyl chloride component and improve its flexibility, but it is not necessary, but
When exceeds 200, the strength decreases, so j=
It needs to be between 0 and 200. Furthermore, the vinyl alcohol component contributes to the dispersibility of magnetic powder due to its hydrophilicity, but in order to further improve this dispersibility, it is extremely important to replace at least a portion of OH with X as described above. be. As this amount of substitution, l=
1 to 200, k+l≦200. When l is 0, there is no effect, and when it exceeds 200, the moisture resistance deteriorates.On the other hand, even when k exceeds 200, the effect of improving dispersibility is not as good as that of conventional techniques, and the moisture resistance deteriorates. In addition, the equivalent weight (molecular weight) per functional group X is
It is desirable to set it at 200,000 to 50,000. If the equivalent weight is less than 200, the hydrophilicity becomes too strong, causing problems in terms of compatibility with other binders to be mixed and moisture resistance, and if it exceeds 50,000, the effect becomes insufficient. Note that as other binders, conventionally known polyurethane resins, AB resins, polyester resins, etc. that impart flexibility may be used. Examples of starting materials for the binder in the present invention include vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinyl propionate-vinyl alcohol, and vinyl chloride-vinyl acetate-vinyl propionate-vinyl alcohol copolymers. It will be done. in this case,
The proportion of vinyl alcohol is 0.5% to 20% by weight
It is preferable that the degree of As a synthesis method, vinyl alcohol OH and ClCH ₂ CH ₂ OSO ₃ M,
_{ClCH2CH2SO3M , ClCH2COOM ,}

[Formula] etc. are reacted with a dehydrochloric agent such as amines such as pyridine, picoline, and triethylamine, and epoxy compounds such as ethylene oxide and propylene oxide in the presence of a solvent such as dimethylformamide and dimethyl sulfoxide, and the following reaction is performed. generate a chemical compound. Although some byproducts are produced in these reactions, they can also be synthesized by the following method. That is,
HOCH ₂ CH ₂ OSO ₃ M, HOCH ₂ CH ₂ SO ₃ M,
HOCH ₂ COOM,

[Formula] and a difunctional isocyanate compound (for example, 4,4'-
Diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate) are reacted in equimolar amounts to obtain a reaction product resulting from the reaction between one isocyanate group of the diisocyanate and OH in the above molecule. Next, by reacting the OH of the copolymer with the remaining -NCO groups, a binder usable in the present invention can be obtained. The reaction formula is as follows. In these reactions, R is a diisocyanate compound as exemplified above. In the present invention, magnetic powders that can be used in the magnetic layer include mixed crystals of γ-Fe ₂ O ₃ , γ-Fe ₂ O ₃ and Fe ₃ O ₄ ;
γ-Fe ₂ O ₃ or Fe ₃ O ₄ doped with cobalt,
CrO ₂ , barium ferrite, other ferromagnetic alloy powders (e.g. Fe-Co, Co-Ni, Fe-Co-Ni, Fe
-Co-B, Fe-Co-Cr-B, Mn-Bi, Mn-
Al, Fe-Co-V), iron nitride, etc. The magnetic layer also contains aluminum oxide, chromium oxide,
It is also possible to add silicon oxide as a reinforcing agent, squalane as a lubricant, carbon black as an antistatic agent, and lecithin as a dispersant. In addition, the constituent materials of the magnetic layer are dissolved in an organic solvent to prepare a magnetic paint, and this is applied onto the base.The solvent for the magnetic paint is ketones (e.g., acetone, methyl erketone, methyl isobutyl ketone, cyclohexanone), Alcohols (e.g. methanol, ethanol, propanol, butanol), esters (e.g. methyl acetate,
ethyl acetate, butyl acetate, ethyl lactate, glycol acetate, monoethyl ether), glycol ethers (e.g. ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, dioxane, aromatic hydrocarbons (e.g. benzene, toluene, xylene),
aliphatic hydrocarbons (e.g. hexane, heptane),
Examples include nitropropane. The base on which this magnetic paint is applied is non-magnetic and can be made of polyester (e.g. polyethylene terephthalate), polyolefin (e.g. polypropylene), cellulose derivatives (e.g. cellulose triacetate, cellulose diacetate), polycarbonate, polyvinyl chloride, polyimide, polyamide, polyester. It may be made of hydrazides, metals (eg aluminum, copper), paper, etc. Examples of the present invention will be described below. Example 1 The following compound A was synthesized using the above reaction formula-(1). Next, a prototype tape was made with the following composition. γ-Fe ₂ O ₃ 100 parts Compound A 17.5 parts Polyurethane (Nippon Polymer Co., Ltd. 2304) 7.5 parts Dimethyl silicone 1 part Methyl ethyl ketone 100 parts Methyl isobutyl ketone 50 parts Toluene 50 parts The above composition was mixed in a ball mill for 48 hours, and 3μ
After filtering, it is coated on a 12μ thick polyester film to a thickness of 6μ.
Surface treated with super calendering, then 3.81
Cut into mm width. Example 2 The following compound B was synthesized using the above reaction formula-(3). Next, a magnetic paint was prepared with the composition shown below, and a tape was prototyped using this. γ-Fe ₂ O ₃ 100 parts Compound B 10 parts Nitrocellulose 5 parts Polyurethane (Nippon Polymer Co., Ltd. 2304) 10 parts Dimethyl silicone 1 part Methyl ethyl ketone 100 parts Methyl isobutyl ketone 50 parts Toluene 50 parts The above composition was mixed in a ball mill for 48 hours. and 3μ
After filtering with a filter, add 5 ml of Desmodyur L.
After stirring, it was coated on a 12μ thick polyester film to a thickness of 6μ. Thereafter, the surface was treated with a super calendar and cut into 3.81 mm width. Example 3 The following composition C was synthesized using the above reaction formula-(2). Next, compound C was substituted for compound A in Example 1.
A tape was prototyped using the process of Example 1. Example 4 The following compound D was synthesized according to the above reaction formula-(4). Next, compound D was substituted for compound A in Example 1.
A tape was prototyped using the composition of Example 1. Comparative Example 1 A tape was prototyped using the composition and process of Example 1, using the following Compound E in place of Compound A of Example 1. The experimental data obtained for the tapes of each of the above examples are shown in the table below, and it can be seen that this example has good characteristics in all respects.

[Table] * Powder falls off after running in the cassette.
The current state was expressed using a point deduction method (=5 points=0 points).

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer containing a compound represented by the following general formula and magnetic powder. [However, R is -CH ₃ or -CH ₂ CH ₃ ; X is -
SO ₃ M, -COOM, -OSO ₃ M or [Formula] (M is H, Li, Na or K, M' is H, Li, Na, K or an alkyl group C _o H _2o+1 )
a hydrophilic group containing i=200-800, j=0-200,
l=1-200, k+l≦200. ]