JPS6279241A - Method of recovering magnetic powder from magnetic recording material - Google Patents

Abstract

PURPOSE:To decompose a base film of a binder and to recover only magnetic powder in high purity, by treating coated type magnetic tape with a mixed solution of an organic solvent and an alkali aqueous solution, etc. CONSTITUTION:Waste magnetic tape is treated with a solution consisting of an organic solvent to partially dissolve or swell a binder in a coated type magnetic recording material and a solution of an alkali in water or an alcohol at normal temperature - the boiling point of the solution. The mixed solution consists of 60-95(V/V)% organic solvent and 40-5(V/V)% solution of an alkali in water or an alcohol. Acetone, chloroform, etc., are used as the organic solvent, caustic soda or caustic potash as the alkali and methanol, etc., as the alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for recovering magnetic powder from magnetic recording materials such as magnetic tapes and magnetic disks.

[Prior Art] For example, a coated magnetic tape consists of a base film and a magnetic layer on which a magnetic coating material containing magnetic powder, a binder, an organic solvent, etc. is uniformly applied and dried.

As the base film, films of polyester, polypropylene, polycarbonate, etc. are used.

On the other hand, the magnetic powder is γ-Fe203, Co-containing γFe2O
3. Metal oxide powder such as CrO2 or Fe, Fe-C
There are metal powders such as o-Ni, and binders generally include vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymer, polyurethane resin, polyester resin, Epoquin resin, and nitrified cotton.

Binders are broadly classified into thermoplastic and thermosetting binders, but thermosetting binders are often included in magnetic tapes for their strength and durability. hardly soluble in

Methods for recovering base film and magnetic powder from coated waste magnetic tape that is inevitably generated during the manufacturing process have been studied for a long time, and for example, a method of treating it with an alkaline aqueous solution or an alkaline alcohol solution is a method that has been studied for a long time. (Unexamined Japanese Patent Publication No. 54
-66985, 53-70404, 53-1i
2979), a method of treatment with alkaline glycol (
British Patent No. 1134967), a method of treating with both alkaline glycol and liquid halogenated hydrocarbon (Japanese Patent Application Laid-open No. 53-94381), treatment with alkaline glycol process and ketones,
A method in which both steps are treated with an organic solvent having at least one of ester and ether groups (Japanese Patent Publication No. 1983)
-23134) etc.

[Problems to be Solved by the Invention] However, these methods are mainly aimed at recovering the base film, and since the magnetic powder separated from the base film is bound by a residual binder, organic solvents cannot be used for the reasons mentioned above. Even if it is kneaded with a new binder inside, it is impossible to achieve a uniform/well-dispersed state at the bottom of the side.

In addition, when actually carrying out the method of recovering the base film and magnetic powder at the same time, cutting and crushing the magnetic tape 1. Stirring and other steps are essential, and even if most of the base film is recovered, some of the base film becomes fragments or powder and mixes into the magnetic layer.

If such magnetic powder were to be used as a raw material for magnetic tape, the resulting magnetic tape would be completely worthless.

Therefore, it is conceivable to separate the magnetic powder and base film using specific gravity or magnetism, but it is presumed that it is quite impossible to completely separate the magnetic powder from an industrial point of view considering yield, cost, etc. .

Therefore, the magnetic powder recovered by the method described above can be used for toys,
It is limited to applications with low added value such as rubber magnets.

In terms of price, the magnetic powder used in magnetic tape is considerably more expensive than the base film.

Making it possible to reuse the recovered magnetic powder as a raw material for magnetic tape is of great value from the standpoint of resource conservation and effective use.

[Means for Solving the Problems] For this purpose, it is necessary to reduce the residual binder ffi in the recovered magnetic powder as much as possible and to improve the dispersion state of the magnetic powder in the magnetic layer.

In the present invention, the binder is virtually completely removed without impairing the properties of the magnetic powder, and the magnetic powder is recovered as magnetic powder that can be used in magnetic tapes, where the dispersibility of magnetic powder is of paramount importance. That is.

That is, the present invention provides a coating method in which the binder in the magnetic recording material is treated in a solution consisting of an organic solvent and an alkaline water or alcohol solution that partially dissolves or swells the binder in the magnetic recording material at a temperature ranging from room temperature to the boiling point of the solution. The invention relates to a method for recovering magnetic powder from magnetic recording materials.

The organic solvent used in the present invention is: (1) Partially dissolving or swelling the binder.

■ It does not react with alkali to inactivate it under the conditions in which it is used, or its reaction rate is slow.

Anything is fine as long as it satisfies the following two conditions:
Specifically, Ia yellow gold compounds such as acetone, methyl ethyl ketone, and cyclohexanone, esters such as ethyl acetate, halogenated hydrocarbons such as chloroform, and dimethyl sulfoxide meet this condition. . Even if a part of the solvent does not meet these conditions, it can be used as a mixed solvent as long as it satisfies the above conditions.

As the alkali, common alkalis such as caustic soda and caustic potash can be used.

The alcohol only needs to have enough solubility to dissolve the necessary amount of alkali, and inexpensive ones such as methanol, ethanol, and isopropyl alcohol are preferable.

Looking at the ω relationship, it is sufficient to add alkali to the extent that the solution remains strongly alkaline even after the reaction is complete; if there is too little, the reaction rate will slow down, and in extreme cases, the alkali will disappear midway through, causing the decomposition reaction to proceed further. It stops progressing. The appropriate amount varies depending on the binder in the magnetic layer and the amount of the base film mixed, but in general, it is 5 to 20 (W/W)% of the magnetic layer.
It is.

Alcohol or water can dissolve the necessary alkali.
However, for industrial use, it is necessary to recover the solution after α-processing by evaporation, etc., and the recovered solution is a mixed solution of organic solvent and water or alcohol (the two must be completely separated). Although it is possible to do so, it is not desirable from an economic standpoint). Therefore, it is convenient to dissolve the alkali in this recovery solution, but if the amount of alcohol or water is low, it is better to dissolve the alkali in the recovered solution. ? [is extremely difficult. Furthermore, if the amount is too large, the proportion of the organic solvent will become too low, and the effect of the present invention of using an organic solvent will be lost. Therefore, the proportion of alcohol or water in the solution is between 5 and 5.
40 (V/V)% is preferred.

The reaction is faster at a higher treatment temperature, but if it is not possible to raise the temperature to a higher temperature due to other constraints, the treatment time may be increased at a lower temperature.

51 at a temperature above the boiling point under pressure! Although it is possible to do so immediately, it is generally preferred to use a temperature in the range from room temperature to the boiling point of the solution.

[Function] In the present invention, not only the binder that binds the magnetic powder but also the base film is decomposed and converted into something soluble in water or an organic solvent, making it possible to recover only the magnetic powder with high purity. . In this respect, it is fundamentally different from conventional methods.

More specifically, when recovering both the base film and the magnetic powder, the base film and magnetic layer are separated in the pre-process by a known method and the base film is recovered first, and then the post-process is also carried out using the method according to the present invention. By decomposing and dissolving the binder binding the magnetic powder and the base film partially mixed in, it is possible to recover only the magnetic powder with high purity.

[Example] Pre-treatment step A CO-containing Fe203 type videotape was physically separated into a base film and a magnetic layer.

The obtained magnetic layer (hereinafter abbreviated as peelable layer) was 23 to 24
It contains (W/W)% binder and base film (hereinafter referred to as impurities), is black in color, and is in a state in which the magnetic powder is completely bound.

Example 1 and Comparative Example 1 In a solution of 100 rf of ■ dimethyl sulfoxide, ■ methyl ethyl ketone, ■ acetone (the above examples), ■ methanol (comparative example), 101 of a 10 (W/V)% caustic soda methanol solution was added. 1 in the above pretreatment step of 10 g
The peeled layer was stirred at 55°C for 5 hours,
Filtration, washing with water, and drying were performed.

The impurities are ■2.2 (W/W)%, ■1.8 (W/W)
)%, ■1. a(W/W)%, ■3.9(S/W)%, and the color of the magnetic powder was blackish in ■, but reddish in ■ to ■, which is the original CO content. The color was close to that of Fe203. This is presumed to be because the binding of the magnetic powder by the binder was considerably reduced.

Example 2 Peel off! lla 111000 to methyl ethyl ketone 1
000xf, methanol 100if, caustic soda 10(
The mixture was stirred in a solution of J at boiling point for 3 hours, filtered, and the same treatment was repeated again, followed by filtering, washing with water, and drying.

Impurities were 1.2 (W/W)%, and the color was reddish.

Example 3 The same procedure as in Example 2 was carried out except that water was used instead of methanol.

Impurities were 1.3 (W/W)%, and the color was reddish.

Example 4 The exfoliated MIfi sioog was treated with methyl ethyl ketone 10
00if, methanol 30hyf, caustic soda 10(l
After stirring in the solution at 55° C. for 5 hours, the mixture was filtered, washed with water, and dried.

Impurities were 2.2 (W/W)%, and the color was reddish.

Comparative Example 2 Videotape 1001j was stirred in a 6 (W/V)% caustic soda aqueous solution 51 at 90° C. for 1 hour, and then separated into a magnetic layer and a base film by filtration and washing with water.

A colorless and transparent base film was obtained, but the impurities in the magnetic layer were 6.6 (W/W)% and were blackish.

Comparative Example 3 The peelable magnetic layer 100 (l) was stirred at 90° C. for 5 hours, 10 hours, and 20 hours in a 12 (t4/V)% caustic soda aqueous solution of 1000xf, and then adjusted to pH 9 or less by filtering and washing with water. Dry at °C.

The impurities are ■4.7 (W/W)%, ■4.1 (W/W)%
)%, ■3.9 (W/W)%, the magnetic powder was blackish.

Although the process (2) was repeated once more, there was no change in impurities or color.

Comparative Example 4 Comparative Example 3-10g of the magnetic powder of ■ was heated at 80°C in 10011i of ■ dimethylformamide, ■ ethanol, and ■ acetone.
(Those with a low boiling point were stirred for 30 minutes beyond that boiling point.) After filtration, the same process was repeated once and then dried.

The impurities are ■3.1 (W/W)%, ■3.5 (W/W)%
)%, ■3.3 (W/W)%, the magnetic powder was blackish.

Although recovery from waste magnetic tape has been described above, it goes without saying that the same method can be used to recover magnetic powder from waste magnetic paint or cleaning fluid generated during the magnetic tape manufacturing process.

[Effect of the invention]

Claims (1)

[Claims] 1) Treatment in a solution consisting of an organic solvent and an alkaline water or alcohol solution that partially dissolves or swells the binder in the coated magnetic recording material at a temperature between room temperature and the boiling point of the solution. A method for recovering magnetic powder from a magnetic recording material, characterized by: 2) 60 to 95 (V/V)% of an organic solvent that partially dissolves or swells the binder in the coating type magnetic recording material;
Alkaline water or alcohol solution is 40-5 (V/V)
% of magnetic powder from a magnetic recording material according to claim 1).