KR950015137B1 - Method for reclaiming magnetic material from magnetic record materila - Google Patents

Abstract

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Description

[Name of invention]

Method for recovering magnetic powder from magnetic recording material

Detailed description of the invention

[Background of invention]

The present invention relates to a method for recovering high purity magnetic powder from a magnetic recording material such as magnetic tape or magnetic disk.

For example, the coated magnetic tape consists of a base layer and a magnetic layer formed by uniformly applying a magnetic coating prepared by mixing together magnetic powder, a binder and an organic solvent and drying them.

Films of polyester, polypropylene or polycarbonite may be used as the base film.

The magnetic powder may be composed of metal powders such as Fe and Fe-Co-Ni, or metal oxides such as γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O _3, or CrO ₂ . Typically, the binder may consist of polyvinyl chloride, polyvinyl acetate, vinylchloride-vinylacetate homopolymer, polyurethane resin, polyester resin, epoxy resin or nitro cellulose.

Binders are broadly classified into thermoplastic and thermoset forms. In the field of magnetic tape, thermosetting binders are generally selected in view of strength and durability. Such thermosetting binders hardly dissolve due to the three-dimensional structure.

The method for recovering the base film and the magnetic powder from the magnetic tape coated with the defective material necessarily produced at the manufacturing stage has been studied. Examples of the method include a method having a treatment with an alkaline aqueous solution or an alcohol solution (Japanese Patent Laid-Open Nos. 66985/1979, 70404/1978 and 112979/1978), and a treatment with alkaline glycol (British patent 1134967). Method comprising, a method of treating with alkaline glycol and a method of treating with a liquid halogenated hydrocarbon (Japanese Patent Laid-Open Publication No. 94381/1978), and a method of treating with alkaline glycol and ketones, esters and other groups (Japanese Patent Publication 23134/1985), and a method comprising a method of treating with an organic solvent having at least one group selected.

However, these methods aim primarily at recovering the base film. As described above, the magnetic powder particles separated from the base film are bonded to each other by the remaining binder, which is almost insoluble in the solvent, so that even when the recovered magnetic powder is mixed with a clean binder in an organic solvent, a uniform dispersion is obtained. It cannot be formed.

When the method for simultaneously recovering the base film and the magnetic powder is actually carried out, the steps such as cutting, splitting and mixing the magnetic tape are unavoidable. Thus, even though most of the base film is recovered, a portion of the base film is necessarily incorporated in the magnetic layer in the form of cracks or powder.

The use of such magnetic powder as a raw material for magnetic tape only provides a magnetic tape of no value at all.

For example, it is possible to peel magnetic powder from the base film using specific gravity or magnetic properties. However, from the point of view of production and cost, it will be difficult to completely separate them from each other on an industrial scale.

Therefore, the use of the magnetic powder recovered by the above-described method is limited to the field that provides only a small added usefulness such as the field of toys and magnetic rubber. The cost of the magnetic powder used in the magnetic tape is much higher than that of the base film. Therefore, reuse of the magnetic powder recovered as a raw material for magnetic tape is very important from the viewpoint of resource protection and reuse.

In order to realize reuse of the recovered magnetic powder as described above, the amount of binder remaining in the recovered magnetic powder should be minimized so that the magnetic powder can be well dispersed in the magnetic layer.

Accordingly, it is an object of the present invention to recover a magnetic powder without impairing its properties during the actual removal of the binder so that the recovered magnetic powder can be used on the magnetic tape where the dispersion state of the magnetic powder is of the greatest importance.

In particular, according to a first aspect of the present invention, there is provided a method for recovering magnetic powder from a coated magnetic recording material, which method provides a method for recovering a binder contained in the magnetic recording material at a temperature ranging from the normal temperature of the solution to the boiling point Treating in a solution consisting of an organic solvent, water and an alkali that can partially dissolve or swell.

According to a second aspect of the invention, there is provided a method for recovering magnetic powder from a magnetic recording material in a coated form, which method is carried out in a magnetic recording material at a temperature in a range from the ordinary temperature of the solution to the boiling point. And treating at least once in a solution consisting of an organic solvent, an alcohol, and an alkali that can partially dissolve or swell the contained binder.

According to a third aspect of the present invention, there is provided a method for recovering magnetic powder from a magnetic recording material in a coated form, which method provides a method for recovering a binder contained in a magnetic recording material at a temperature ranging from room temperature to a boiling point of a solution. At least once in a solution consisting of an organic solvent, an alcohol, water and an alkali that can be partially dissolved or swollen. Water may be added before or during the treatment.

After treatment in accordance with the second or third feature as described above, it may be treated at least once in an aqueous solution of 0.5 (W / V)% of alkali at temperatures ranging from room temperature to boiling point to provide better results.

Any organic solvent may be used in the present invention so long as it can satisfy the following two requirements:

(1) Partially dissolve or bulge the binder.

(2) The reaction rate should be slow even if it does not react with the alkali or reacts under its use conditions so as not to deactivate the alkali.

Organic solvents that meet the above requirements include, for example, ketones such as acetone, methyl ethyl ketone or cyclohexanone; Esters such as ethyl acetate; Halogenated hydrocarbons such as chloroform; Or sulfur compounds such as dimethyl sulfoxide. Mixed solvents that partially contain solvents that do not meet the above requirements can be used as long as the mixed solvent can satisfy the requirements as a whole.

As such alkalis, general alkalis such as caustic soda and caustic potassium can be used.

Any alcohol can be used as long as it has a dissolution capacity with respect to the required amount of alkali and can be dissolved in the aforementioned organic solvents and water. Such alcohols can be, for example, methanol, ethanol, or isopropyl alcohol. Low cost alcohols are preferred.

Adding water initially is convenient considering the fact that complete separation of water is undesirable from an economic point of view when it is necessary to recover solvents and the like from the solution used in the treatment. The best effect can be obtained when water is added during the treatment.

Alkali may be added in such an amount that the solution exhibits strong alkalinity even after completion of the reaction. If the amount of alkali is too small, the reaction rate will be slow. In extreme cases, the alkali disappears during the process and no further decomposition reactions occur. Although the suitable alkali amount varies depending on the amount of binder and the base film incorporated in the magnetic layer, the alkali amount is always 5 to 20 (W / W)% of the amount of the magnetic layer.

The required amount of alcohol or water is such that the required amount of decomposed binder, base film and alkali can be dissolved there. If the amount of alcohol or water is too large, the ratio of the organic solvent is too low, which lowers the effect of the present invention obtained by the use of an organic solvent. Therefore, the ratio of alcohol or water in the solution is preferably 5 to 40 (V / V)%.

The higher the treatment temperature, the faster the reaction. Long term low temperature treatment will be satisfactory when high temperature cannot be applied due to other factors. Although it is possible to process to a temperature above the boiling point under pressure, the temperature is generally in the range of normal temperature to boiling point of the solution.

As for the water-soluble alkaline solution which can be used in the present invention, caustic soda, potassium hydroxide and the like are suitable as described above. Concentrations of 0.5 (W / V)% or more will be satisfactory. The treatment temperature is in the range of room temperature to boiling point of the aqueous alkaline solution. The higher the treatment temperature, the faster the reaction. Long term low temperature treatment will be satisfactory when high temperatures cannot be applied due to other factors.

Treatment with a solution of organic solvent-alcohol or water-alkaline (step I) is carried out at least once and can be repeated twice or more. The treatment (step II) with an aqueous alkaline solution can be carried out at least once after the treatment step I described above. The processing sequence can be, for example, step I-step II, step I-step I-step II, or step I-step II-step I-step II.

In the present invention, not only the binder which binds the magnetic powders with each other but also the base film is decomposed to give a substance that can be dissolved in water or an organic solvent. Therefore, the magnetic powder can be recovered in high purity. Therefore, the object of the present invention is fundamentally different from the conventional method in this respect.

In particular, when the base film and the magnetic powder are recovered, the base film and the magnetic layer are peeled off from each other in a pretreatment step by a known method to recover the base film. Thereafter, the binder which bonds the magnetic powders with each other and the base film partially incorporated in the magnetic layer are decomposed and dissolved in the post-treatment step by the method of the present invention to remove them.

Therefore, the magnetic powder is recovered in high purity.

[Detailed Description of Suitable Embodiments]

Pretreatment :

Co-containing γ-Fe ₂ O ₃ type video tape was physically peeled into the base film and the magnetic layer.

The resulting magnetic layer (hereinafter referred to as the "skinned magnetic layer") contained 22 to 24 (W / W)% of the binder and base film (hereinafter collectively referred to as "impurity"). It was black and contained magnetic powder completely bonded to each other.

Example 1

100 g of peeled magnetic layer was mixed at the boiling point for 3 hours in a solution consisting of 1000 ml of methyl ethyl ketone, 100 ml of water, and 10 g of caustic soda, and then filtered.

Thereafter, the same treatment was repeated, followed by filtration, washing with water and drying.

The impurity content in the recovered magnetic powder was 1.3 (W / W)% and the recovered magnetic powder was estimated to have a reddish color.

[Example 2 and Example 1 to be compared]

10 g of the peeled magnetic layer obtained in the above-mentioned pretreatment step were prepared using 100 ml of (A) dimethyl sulfoxide (Example 2), (B) methyl ethyl ketone (Example 2), (C) acetone (Example 2) or (D). In a solution consisting of methanol (Comparative Example 1) and 10 ml of 10 (W / V)% caustic soda-methanol solution, the mixture was stirred at 55 ° C. for 5 hours, followed by filtration, washing with water and drying.

-Fe₂O₃의 원색에 가까운 불그스레한 색을 나타내었고, (라)의 경우에는 거무스레한 색을 나타내었다. 이것은 (가) 내지 (다)의 경우 결합제에 의해 서로 결합된 자기분말의 비율의 상당한 감소에 의한 것으로 귀착된다.The content of impurities in the recovered magnetic powder is 2.2 (W / W)% for (A), 1.8 (W / W)% for (B), 1.8 (W / W)% for (C) and ) Was 3.9 (W / W)%. The recovered magnetic powder is Co-containing in the case of (A) to (C).

A reddish color close to the primary color of -Fe ₂ O ₃ was shown, and in the case of (D), a darkish color was shown. This results in a significant reduction in the proportion of magnetic powders bound to each other by the binder in cases (a) to (c).

Example 3

The 100 g peeled magnetic layer was mixed at its boiling point for 3 hours in a solution consisting of 1000 ml methyl ethyl ketone, 100 ml methanol and 10 g caustic soda, and then filtered. Thereafter, the same treatment was repeated, followed by filtration, washing with water and drying.

The content of impurities in the recovered magnetic powder was 1.2 (W / W)% and the recovered magnetic powder had a reddish color.

Example 4

The 100 g peeled magnetic layer was mixed at 55 ° C. for 5 hours in a solution consisting of 1000 ml of methyl ethyl ketone, 300 ml of methanol and 10 g of caustic soda, followed by filtration, washing and drying.

The content of impurities in the recovered magnetic powder was 2.2 (W / W)% and the recovered magnetic powder had a reddish color.

Example 5

The 100 g peeled magnetic layer was mixed at its boiling point for 3 hours in a solution consisting of 600 ml of methyl ethyl ketone, 90 ml of methanol, and 9 g of plastic soda, followed by filtration, washing and drying.

The content of impurities in the recovered magnetic powder was 1.9 (W / W)% and the glass value was 59.

Glossiness evaluates the dispersibility of magnetic powder. The recovered magnetic powder was used in the production of the video tape and applied to the base film and mixed with the binder and the organic solvent. As a result, the gloss of the surface of the film was measured with a gloss meter. The values obtained were multiplied by 100 divided by the surface gloss for magnetic powders not used to obtain gloss values as in the following equation:

Example 6

The magnetic powder obtained in Example 5 was mixed at 90 ° C. for 3 hours in an aqueous solution of 12 (W / V)% caustic soda (600 ml), followed by filtration, washing with water and drying.

The content of impurities in the recovered magnetic powder was 1.7 (W / W)% and its gloss value was 78.

Example 7

The treatment was carried out according to the procedure of Example 5 using a solution consisting of 600 mL methyl ethyl ketone, 90 mL methanol, 60 mL water and 9 g caustic soda.

The content of impurities in the recovered magnetic powder was 1.6 (W / W)% and its gloss value was 72.

Example 8

The magnetic powder obtained in Example 7 was further stirred at 90 ° C. for 3 hours in an aqueous 12 (W / V)% caustic soda solution (600 ml), followed by filtration, washing with water and drying.

The content of impurities in the recovered magnetic powder was 1.3 (W / W)% and its gloss value was 87.

Example 9

100 g of peeled magnetic powder was mixed at 90 ° C. for 1 hour in the same solution as used in Example 5, followed by the addition of 60 ml of water. Thereafter, the mixture was stirred again at 90 ° C. for 2 hours, followed by filtration, washing with water and drying.

The content of impurities in the recovered magnetic powder was 1.2 (W / W)% and its gloss value was 81.

Example 10

The magnetic powder obtained in Example 9 was further stirred at 90 ° C. for 3 hours in an aqueous 12 (W / V)% caustic soda solution (600 ml), followed by filtration, washing with water and drying.

The content of impurities in the recovered magnetic powder was 0.9 (W / W)% and its gloss value was 94.

Example 11

100 g of the peeled magnetic layer was mixed at its boiling point for 2.5 hours in the solutions (a), (b), (c) or (d) described below, followed by filtration and washing:

(A) 600 ml of methyl ethyl ketone, 50 ml of methanol, 30 ml of water and 9 g of caustic soda;

(B) 600 ml of methyl ethyl ketone, 90 ml of methanol, 60 ml of water and 9 g of caustic soda;

(C) 600 ml of methyl ethyl ketone, 120 ml of methanol, 120 ml of water and 9 g of caustic soda;

(D) 600 ml of methyl ethyl ketone, 160 ml of methanol, 160 ml of water and 9 g of caustic.

The resulting material was then further stirred at 80 ° C. for 2.5 hours in 12 (W / V)% caustic soda solution (600 mL), followed by filtration, washing with water and drying.

The gloss value of the recovered magnetic powder was 86 for (A), 88 for (B), 82 for (C), and 75 for (D).

Example 12

The 100 g peeled magnetic layer was mixed at its boiling point for 2 hours in a solution consisting of 600 ml methyl ethyl ketone, 90 ml methanol, 60 ml water and 9 g caustic soda, followed by filtration. Thereafter, the filtered material was further mixed at its boiling point for 1 hour in a solution having the above composite, followed by filtration and washing to recover the magnetic powder (a).

10 g of magnetic powder (a) was stirred at 90 ° C. for 2 hours in 60 ml of solution (b), (c), (d) or (e) described below, followed by filtration, washing and drying. All.

(Herbs

(C) 4% caustic soda solution

(D) 12% caustic soda solution

(E) 24% caustic soda solution

The gloss value of the recovered magnetic powder was 89 for (a) and (b), 96 for (c), 94 for (d) and 91 for (e).

Example 13

The 100 g peeled magnetic layer was mixed at its boiling point for 2 hours in a solution consisting of 600 ml methyl ethyl ketone, 90 ml methanol, 60 ml water and 9 g caustic soda, followed by filtration. Thereafter, the filtered material was further mixed in a solution having the above composite, followed by filtration and washing with water.

In addition, the resulting material was mixed at 90 ° C. for 6 hours in an aqueous 1% caustic soda solution (450 mL), followed by filtration. At that time, the filtered material was mixed at 90 ° C. for 2 hours in an aqueous 1% caustic soda solution (450 mL), followed by filtration, washing with water and drying.

The gloss value of the recovered magnetic powder was 95.

Example 14

The 6 kg peeled magnetic layer was mixed at its boiling point for 2 hours in a solution consisting of 36 L methyl ethyl ketone, 5.4 L methanol, 3.6 L water and 540 g caustic soda, followed by filtration. Thereafter, the same treatment was repeated, followed by removal of the superatant, addition of 30 liters of water, filtration and washing with water.

Furthermore, the resulting material was mixed at 90 ° C. for 6 hours in a solution consisting of 36 liters of water and 1440 g of caustic soda followed by filtration, washing and drying.

The content of impurities in the recovered magnetic powder was 0.8 (W / W)% and its gloss value was 98. Video tapes actually produced using the recovered magnetic powder have been found to have practically the same characteristics as those using pure magnetic powder.

[Comparative Example 2]

100 g of video tape was mixed at 90 ° C. for 1 hour in 6 (W / V)% caustic soda solution (5 L), followed by filtration and washing with water, thereby peeling off the magnetic layer and base film. All.

The recovered base film was transparent while the recovered magnetic powder had 6.6 (W / W)% impurities and showed a dark color.

Its gloss value was 30 or less.

[Comparative Example 3]

100 g of the peeled magnetic layer were mixed at 90 ° C. for 12 hours (a) for 5 hours, (b) 10 hours or (c) 20 hours in a 12 (W / V)% aqueous solution of caustic soda, followed by filtration, 9 Water washing and drying at 80 ° C. were performed to reduce the pH below.

The recovered magnetic powder had 4.7 (W / W) impurity for (A), 4.1 (W / W)% impurity for (B) and 3.9 (W / W)% impurity for (C). , A dark red color.

The gloss value of each magnetic powder was 30 or less.

With respect to the recovered magnetic powder for (C), the same treatment was repeated, and as a result, no change in color or impurities occurred.

[Comparative Example 4]

In Comparative Example 3, the recovered 10 g of magnetic powder of (C) was recovered at 80 ° C. (or below 80 ° C.) for 30 minutes in 1000 ml of (a) dimethyl formamide, (b) ethanol or (c) acetone. At the boiling point), followed by filtration. Thereafter, the same treatment was repeated, followed by drying.

The recovered magnetic powder contains 3.1 (W / V)% impurities in (a), 3.5 (W / V)% impurities in (b) and 3.3 (W / V)% impurities in (c). It had a reddish color. The gloss value of each magnetic powder was 30 or less.

Recovery of magnetic powder from bad magnetic tape has been described so far. Of course, recovery of the magnetic powder from the waste cleaning solution generated in the production of the washed magnetic coating or the magnetic tape can also be made by the process as described above.

As described above, according to the method for recovering the magnetic powder from the magnetic recording material according to the present invention, the binder partially dissolved or swollen by the organic solvent is decomposed and dissolved by alkali to be soluble in water or an organic solvent. . Thus, the fragments and binder of the base film contained in the magnetic layer peeled from the base film by one of several methods can be almost completely removed. Therefore, high purity magnetic powder can be easily recovered in a high amount. Therefore, the dispersibility of the recovered magnetic powder is remarkably improved, and as a result, the recovered magnetic powder can be reused as a material for producing magnetic tape.

The addition of water during the treatment can increase the purity of the magnetic powder. In addition, the use of a water-soluble alkaline solution in subsequent processing steps can greatly increase the purity of the magnetic powder, so that the performance of the magnetic tape using the recovered magnetic powder is comparable to the use of a magnetic powder that has never been used.

Claims (13)

A method for recovering magnetic powder from a magnetic recording material in a coated form, comprising: an organic solvent capable of partially dissolving or swelling a binder contained in the magnetic recording material in a temperature range from a normal temperature of a solution to a boiling point, A process for recovering magnetic powder from a magnetic recording material comprising the step of treating in a solution consisting of water and alkali. The method of claim 1 wherein the solution consists of a solvent and a solute, wherein the solvent consists of 60 to 95 (V / V)% of organic solvent and 40 to 5 (V / V)% of water, and the solute is magnetic A method for recovering magnetic powder from a magnetic recording material, characterized in that an alkali of 5 to 20 (W / W)% of the layer amount. A method for recovering magnetic powder from a magnetic recording material in a coated form, the organic solvent capable of partially dissolving or swelling the binder contained in the magnetic recording material in a temperature range from the normal temperature of the solution to the boiling point. 18. A method for recovering magnetic powder from a magnetic recording material, characterized by treating at least once in a solution consisting of a solvent, an alcohol and an alkali. The organic solvent of claim 3, wherein the solution consists of a solvent and a solute, wherein the solvent is 60 to 95 (V / V)% of an organic solvent that can partially dissolve or swell the binder contained in the magnetic recording material. And 40 to 5 (V / V)% of alcohol, wherein the solute is 5 to 20 (W / W)% of the amount of the magnetic layer of the magnetic recording material. A method for recovering magnetic powder from a coated magnetic recording material, comprising: an organic solvent alcohol capable of partially dissolving or swelling a binder contained in the magnetic recording material in a temperature range from room temperature to a boiling point of a solution And treating at least once in a solution consisting of alkali and at least once in an aqueous alkali solution of 0.5 (W / V)% or more in a temperature range from room temperature to boiling point of the aqueous alkali solution. A method for recovering magnetic powder from a magnetic recording material. A method for recovering magnetic powder from a coated magnetic recording material, the method comprising: a solution in a solution consisting of an organic solvent, alcohol, water, and alkali capable of partially dissolving or swelling the binder contained in the magnetic recording material. And recovering the magnetic powder from the magnetic recording material at least once in a temperature range from room temperature to boiling point. 7. The solution of claim 6, wherein the solution consists of a solvent and a solute, wherein the solvent consists of 60 to 95 (V / V)% of an organic solvent and 40 to 5 (V / V)% of alcohol and water, and the solute is A method for recovering magnetic powder from a magnetic recording material, characterized in that an alkali of 5 to 20 (W / W)% of the amount of magnetic layers. A method for recovering a magnetic powder from a magnetic recording material in a coated form, the method comprising: dissolving or swelling a binder contained in the magnetic powder material in a solution consisting of an organic solvent, an alcohol and an alkali. 17. A method for recovering magnetic powder from a magnetic recording material, comprising treating at least once in a temperature range from room temperature to boiling point and adding water during processing. The solution of claim 8, wherein the solution consists of a solvent and a solute, wherein the solvent consists of 60 to 95 (V / V)% of organic solvent, 40 to 5 (V / V)% of alcohol and water, and the solute Is an alkali of 5 to 20 (W / W)% of the amount of the magnetic layer, wherein the magnetic powder is recovered from the magnetic recording material. A method for recovering magnetic powder from a magnetic recording material in a coated form, the method comprising: a solution in a solution consisting of an organic solvent, alcohol, water, and alkali capable of partially decomposing or swelling the binder contained in the magnetic recording material. Treating at least once in a temperature range from room temperature to boiling point, and additionally treating at least once in a temperature range from room temperature to boiling point of the aqueous alkali solution in 0.5 (W / V)% or more of aqueous alkali solution. And recovering the magnetic powder from the magnetic recording material. The solution of claim 10, wherein the solution consists of a solvent and a solute, wherein the solvent consists of 60 to 95 (V / V)% of an organic solvent and 40 to 5 (V / V)% of alcohol and water, Is 5 to 20 (W / W)% of the alkyl layer in the magnetic layer amount. A method for recovering magnetic powder from a magnetic recording material in a coated form, the method comprising the steps of: dissolving or swelling the binder contained in the magnetic recording material in a solution consisting of an organic solvent, alcohol, water, and alkali. Treating at least once in a temperature range from room temperature to a boiling point of the solution and adding water during the treatment, and at least in a temperature range from room temperature to boiling point of the aqueous alkali solution in 0.5 (W / V)% or more of aqueous alkali solution. And once again treating the magnetic powder from the magnetic recording material. 13. The solution of claim 12, wherein the solution consists of a solvent and a solute, wherein the solvent consists of 60 to 95 (V / V)% organic solvent and 40 to 5 (V / V)% alcohol and water, Is an alkali of 5 to 20 (W / W) of the amount of magnetic layer, the method for recovering the magnetic powder from the magnetic recording material.