JP3097781B2 - Processing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a magnetic recording medium in which a magnetic layer, a non-magnetic layer and / or a back layer are easily separated from a non-magnetic support.

[0002]

2. Description of the Related Art In recent years, demands for tape-shaped magnetic recording media having a magnetic recording layer (hereinafter referred to as a magnetic layer) for audio, video, and computer use, and disk-shaped magnetic recording media such as floppy disks have been increasing. It is increasing significantly for both general and commercial use. With the increase in demand for such magnetic recording media, the amount of defective products, waste products, and used waste products produced when manufacturing magnetic recording media has been increasing. This type of magnetic recording medium generally has a magnetic layer in which ferromagnetic powder is dispersed in a binder on a non-magnetic support such as polyester.

[0003] As described above, the amount of defective products, waste products, and used waste products produced during the production of magnetic recording media is also increasing. Conventionally, incineration is mainly used as a disposal method. Although it is a part, a method is used in which the waste or defective product is rubbed and used as a string or the like. However, the magnetic layer was peeled off from the film base of this waste or defective product, and the base was separated.
In addition to collecting and reusing the magnetic layer, it has been studied to use the peeled magnetic layer as a pigment such as iron oxide by removing the binder by baking or the like.

For example, it has been proposed to apply a mechanical or physical force to a magnetic recording medium to peel off a magnetic layer. JP 5
Japanese Patent Application Laid-Open No. 7-20319 discloses a method in which a layer of a magnetic material adhered to a magnetic tape is strained, and then the magnetic material is removed by a physical force. Methods for producing tapes have been proposed. Japanese Patent Application Laid-Open No. 58-118212 proposes a magnetic tape processing apparatus for reusing a magnetic tape by locally heating and stretching, and peeling off an adhered substance such as magnetic powder on the tape at the time of stretching. I have. Similarly, JP-A-61-2795
No. 14 proposes a magnetic tape processing method in which magnetic powder is peeled off by tensioning the magnetic tape. However, the binders conventionally used for magnetic tapes have a large bonding force with the base, making it difficult to easily peel off the magnetic layer, and because an effective separation method after peeling cannot be found, the above-described method is used. As expected, there was no choice but to use a treatment method such as incineration.

However, the non-magnetic support of most magnetic recording media uses a polyethylene terephthalate (PET) film, which is not a preferable method because incineration generates high heat and requires an incinerator. If the tape is to be melt-molded at a high temperature, there is a magnetic layer, so that PET is decomposed and a material that can be used for another purpose cannot be obtained. In addition, burial in the ground was considered as another treatment, but such a method is becoming unacceptable from the viewpoint of global environmental protection in the future. Therefore, it was necessary to separate the PET and the magnetic layer for processing the unnecessary tape.

As a method for recovering a base film, Japanese Patent Laid-Open Publication No. 59-52433 discloses a method for recovering a raw material in which a magnetic tape is cut, dipped in an alkali, swollen, separated by high-speed stirring, washed with water, dried and magnetically separated. JP-A-59-91
No. 028 has been proposed. In the treatment of magnetic tape waste, a method of heating, stirring, incinerating and solidifying the waste, and further pulverizing the same is disclosed in Japanese Patent Application Laid-Open No. Sho 63/1988.
No. 194905.

As described above, various efforts have been made to recover the base film from the commercially available magnetic tape. However, the conventional magnetic tape only has a strong adhesion between the non-magnetic support and the magnetic layer. Since the material of the undercoat layer is constituted for the purpose, it was not possible to actually peel off without using an extremely strong alkaline aqueous solution or using a special organic solvent. When such a strong alkaline aqueous solution is used, the base film itself is hydrolyzed, and the quality is not sufficient for reuse. The mechanism of this peeling is strong in hydrolysis for the magnetic layer, and the magnetic layer itself rarely dissolves because a binder cured with polyisocyanate is used,
The aqueous alkaline solution enters through the gaps in the magnetic layer, hydrolyzes the polymer such as polyester of the undercoat layer usually made of polyester or the like, and peeling starts. At the same time, the polyester base (PET) itself starts to hydrolyze and peeling starts. As described above, in the conventional alkali treatment, the peeling proceeds by hydrolysis rather than dissolution, so that the peeling is slow, and the quality of the recovered polyester base film is deteriorated by the hydrolysis.

Accordingly, the present inventors have conducted intensive studies on a method for recovering these non-magnetic supports without using such an aqueous alkaline solution. As a result, an organic solvent that dissolves or swells the undercoat material and a dispersion using a dispersion medium are obtained. The present inventors have found that by combining the magnetic recording media, commercially available magnetic recording media such as audio, video, and floppy disks can be peeled and collected extremely easily.

[0009]

That is, an object of the present invention is to provide a method of processing a magnetic recording medium which is suitable for environmental protection. Secondly, the object of the present invention is to easily form a magnetic layer, a non-magnetic layer and / or a back layer and a non-magnetic support using a magnetic recording medium using a material which is easily dissolved or swelled in a commercially available organic solvent. It is an object of the present invention to provide a method for treating a magnetic recording medium to be peeled, separated and collected.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to cut into a predetermined size having at least an undercoat layer between a nonmagnetic support and a magnetic layer, a nonmagnetic layer and / or a back layer. The non-magnetic support and the magnetic layer, the non-magnetic layer and / or the non-magnetic support are dispersed by dispersing the magnetic recording medium using a dispersing medium and an organic solvent that dissolves or swells the material constituting the undercoat layer
Alternatively, it can be achieved by a method for processing a magnetic recording medium, which is characterized in that the back layer is peeled off.

That is, the present invention merely cuts a commercially available magnetic recording medium and melts or expands the undercoat material provided between the magnetic layer and / or the back layer and the nonmagnetic support.
Select a Jun easy organic solvent, an undercoat material to swell, and the dispersion with a specific force or dispersion medium in this state, by applying a force, very easily the magnetic layer, nonmagnetic layer and / or In this method, the back layer is peeled off, and the nonmagnetic support is recovered. No attempt has ever been made to use a dispersing method that uses a dispersing medium that is usually used in the production of magnetic paint in this manner in combination with the processing of cut pieces of magnetic recording media such as magnetic tapes and floppy disks that have already been completed. That is.

The reason that the excellent effect of being easily peeled off by such a simple method of the present invention is obtained is that by using an organic solvent which easily dissolves or swells the undercoat material, swelling of the undercoat layer, This is probably because partial dissolution occurs, and a strong twisting or rubbing force is applied to the dispersing medium to rapidly promote peeling.

The processing method of the present invention comprises a step of cutting, peeling and separating a magnetic recording medium. As a cutting method, any ordinary cutter can be used, and for example, a rotary cutter, a slit cutter, a guillotine cutter, a shredder, or the like can be used. The size is not particularly limited, as long as it can enter a dispersing apparatus using a dispersion medium and can be appropriately dispersed. Normal length is 0.5cm ~
It is about 5cm in size. For example, when a 1/2 inch wide tape is used, if the length of the tape is as large as 10 cm, the tape may be wound around a core rod of a dispersing machine, cut into pieces, or broken and attached to form a medium. No force is applied and peeling becomes difficult.

The organic solvent used is not particularly limited as long as it dissolves or swells the material constituting the undercoat layer of a commercially available magnetic recording medium. For example, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone, diethyl ketone, methyl propyl ketone, ethyl butyl ketone, holon, isophorone, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol acetate mono Ester system such as ethyl ether, ether system such as ethyl-ether, glycol dimethyl ether, glycol monoethyl ether, dioxane and tetrahydrofuran, aromatic hydrocarbon system such as benzene and xylene, methylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin And chlorinated hydrocarbons such as dichlorobenzene can be selected and used. In the present invention, it is preferable to use an organic solvent from the viewpoint of ease of post-treatment and recovery, and in particular, the above-mentioned ketone-based organic solvent is preferable from the viewpoint of easily dissolving or swelling the undercoat layer. Particularly, MEK and cyclohexanone are preferable. The organic solvent does not need to be one kind, and two or more kinds of organic solvents may be used in combination, but preferably, a ketone-based organic solvent is used in an amount of 40% by weight or more.
The point of the present invention is to use an organic solvent for dissolving and swelling the undercoat layer, and to perform a release treatment by dispersion using a dispersion medium. Materials that promote peeling, such as organic amines and DMF, may be used together.

The following are examples of the distributed media. For example, glass beads, zirconia balls ,
These are dispersion media such as steel balls, which may be used alone or in combination. The particle size of the dispersion medium may be large or small depending on the dispersion device.
Practically preferred are those having a particle size of about 0.7 to 2 mm. Medium with large particle size is partially applied,
Non-uniform, but strong. On the other hand, a medium having a small particle diameter exerts a weak force but a uniform force. Therefore, the particle size of the medium can be arbitrarily determined according to the magnetic recording medium to be peeled, in consideration of the required force and the degree of uniformity. It is preferable that the used amount of the dispersion medium is an upper limit that can be used according to the size of the apparatus. If the used amount of the dispersion medium is large, the number of collisions between the pieces and the dispersion medium increases, and the separation medium is more easily peeled off. On the other hand, if the amount is too large, the dispersion medium may jump out of the lid. Therefore, the usage amount of the dispersion medium can be arbitrarily selected according to the size of the dispersion apparatus.

Examples of the dispersing machine used for the dispersion of the present invention include a sand mill of a circulation type, a vertical type, a horizontal type, a continuous type, a batch type and the like.
Roll mills, ball mills, attritors and the like can be used. For example, when a 1 / 4G machine is used, the larger the number of disks, the more the portion with a high shearing rate can be formed. However, this is a matter of efficiency. If the rotation speed is constant, the maximum value of the shear force is determined. The holes formed in the disc are preferably at least larger than the particle size of the dispersion medium. This is due to the convenience of supplying the dispersing media through this hole in the device. The higher the number of rotations of the disk, the better the efficiency, but if the number of rotations is too high, there is a possibility that the dispersed medium may fly out and noise may be generated.

Although the dispersion time depends on the peeling speed, there is no problem if the dispersion time is long, so it may be longer. Depending on the sample of the magnetic tape, if the dispersion is performed for about 2 hours, the peeling is sufficiently completed in many cases. The evaluation of whether the peeling was completed is based on whether the ratio of the black portion / transparent portion of the sample is 5% or less. When this ratio is about 5%, although black portions can be seen in appearance, the peeling has progressed, and they are merely adhered and can be peeled off by a process such as washing with water. The temperature in the dispersion treatment is preferably higher from the viewpoint of peeling efficiency. Although there may not be heated by the dispersing apparatus, the apparatus of the type capable of heating is lower than the boiling point of the organic solvent as the organic solvent does not evaporate,
Nonmagnetic support used also is preferably a temperature below its Tg in order not to deform the PET case Unaryo of PET. If it is about 60 ° C. to 80 ° C., no problem occurs.

As the magnetic recording medium of the present invention, commercially available audio tapes, video tapes, floppy disks and the like can be applied. For example, an undercoat layer is provided on a non-magnetic support such as a video tape such as VHS or β, an audio tape, or a floppy disk, and a single magnetic layer is provided thereon. An undercoat layer is provided, and a lower magnetic layer and an upper magnetic layer are provided thereon, and a multilayer type. An undercoat layer is provided on a nonmagnetic support, and a lower nonmagnetic layer and an upper magnetic layer are provided thereon. And a magnetic recording medium having an undercoat layer, such as a magnetic recording medium in which an undercoat layer is provided on a nonmagnetic support and a back layer is provided thereon. The magnetic recording medium used in the present invention has a basic structure comprising a non-magnetic support, an undercoat layer provided thereon, a magnetic layer, a non-magnetic layer and / or a back layer. Further, in the present invention, the magnetic layer may be a medium in which ferromagnetic powder is dispersed in a binder or a medium of a ferromagnetic metal thin film formed by oblique evaporation.

As the non-magnetic support used in the present invention, various materials such as synthetic resin film, paper, and metal such as aluminum can be used. Of these, polyethylene terephthalate (P
Various synthetic resin films such as ET), polyethylene naphthalate (PEN), polypropylene, polycarbonate, polyamide, polyaromatic amide (aramid), polyimide, and polyamide imide are preferable. Particularly preferred are polyethylene terephthalate, polyethylene naphthalate, polyamide, polyaromatic amide (aramid), polyimide, polyamide imide and the like. Nonmagnetic plastic supports are generally 2.5 to 1
One having a thickness of 00 μm, preferably 3 to 80 μm is used.

In the case of a magnetic recording medium coated with ferromagnetic powder, the composition of the ferromagnetic powder used (iron oxide, cobalt-containing iron oxide, iron-based alloy, barium ferrite, etc.)
There are no particular restrictions on the size or surface treatment. The shape of the ferromagnetic powder is not particularly limited, but is usually acicular, granular,
Dice-shaped, rice-grained and plate-shaped ones are used.
For example, JP-A-58-119609 (US44)
55345), JP-A-60-171631, JP-A-61-8726 (US Pat. No. 4,690,863), JP-A-61-16024, and JP-A-61-158023.
JP, JP-A-63-78334, JP-A-63-78334
No. 103423, JP-A-1-187903,
JP-A-1-189025 and the like can be mentioned.

The binder for forming the magnetic layer used in the present invention can be selected from ordinary binders. Examples of the binder include a vinyl chloride copolymer, a vinyl chloride-vinyl acetate copolymer, a copolymer of vinyl chloride and vinyl acetate with vinyl alcohol, maleic acid and / or acrylic acid,
Vinyl chloride / vinylidene chloride copolymer, vinyl chloride / acrylonitrile copolymer, ethylene / vinyl acetate copolymer, cellulose derivatives such as nitrocellulose resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin, Polyurethane resin, polycarbonate polyurethane resin and the like can be mentioned. In order to further enhance dispersibility and durability, the binder molecules listed above include -COOM, -SO3M,-
PO3 M2, -OSO3 M, -OPO3 M2 (where M
Represents H, an alkali metal salt, or an ammonium salt), wherein at least one kind of polar group or epoxy group is introduced. When there are a plurality of M in one group, they may be different from each other. The content of the polar group is preferably 10 @ -6 to 10 @ -4 equivalent per gram of the polymer. The above-listed polymer binders are used alone or in combination of several kinds,
It is often cured by adding a known isocyanate-based crosslinking agent.

The undercoat layer of the present invention is also applied to a binder which uses an acrylic ester-based oligomer and a monomer as a binder and is cured by irradiation with radiation. The content of all binders in the magnetic layer of the magnetic recording medium of the present invention,
Usually, it is 10 to 60 parts by weight, preferably 20 to 40 parts by weight, per 100 parts by weight of the ferromagnetic powder. Examples of the binder include JP-A-59-8127, JP-A-61-8127.
JP-A-123017, JP-A-62-23329, JP-A-62-146432, JP-A-1-20
No. 5721, JP-A-1-205724, JP-A-3-44819, and JP-B-3-18247.

The magnetic layer of the magnetic recording medium of the present invention preferably further contains inorganic particles having a Mohs hardness of 5 or more. The inorganic particles used are not particularly limited as long as the Mohs hardness is 5 or more. Examples of inorganic particles having a Mohs hardness of 5 or more include Al ₂ O ₃ (Mohs hardness of 9), TiO ₂ (5), TiO (6.5), SiO ₂ (7), and SnO.
₂ (6.5), Cr ₂ O ₃ (9) and α-Fe ₂ O
₃ (5.5), and these can be used alone or as a mixture. For example, JP
-6439, JP-A-62-134827 (US Pat. No. 4,761,243), JP-A-1-106332, JP-A-1-140421, JP-A-1-205
726, Japanese Patent Application Laid-Open No. 1-222019 and the like.

Particularly preferred are inorganic particles having a Mohs hardness of 8 or more. When inorganic particles having a Mohs hardness lower than 5 are used, the inorganic particles easily fall off the magnetic layer,
Also, since the head has almost no polishing action, head clogging is likely to occur, and running durability is poor.

The content of the inorganic particles is usually in the range of 0.1 to 20 parts by weight, preferably in the range of 1 to 10 parts by weight, per 100 parts by weight of the ferromagnetic powder. In addition to the above-mentioned inorganic particles, the magnetic layer may be made of carbon black (in particular, having an average particle size of 10 to 300 nm (nanometer;
10 ^-9 m)).
For example, JP-A-59-75431, JP-A-59-75431
172123, JP-A-1-243227,
JP-A-3-8113 and the like can be mentioned.

Next, an example of a method for manufacturing the magnetic recording medium of the present invention will be described. First, an undercoat layer is applied on a nonmagnetic plastic support. The polymer of the primer is a suitable solvent such as cyclohexanone, MEK, acetone, MIBK,
It is dissolved in butyl acetate and applied. An ordinary method can be used for the application method. As a general method of applying the undercoat layer, a rod coater (normal, reverse), a wire bar coater (normal, reverse), a blade coater, a curtain coater, an extrusion coater, a gravure coater, a kiss roll coater, and the like can be applied. Particularly preferred are a load coater (reverse rotation) and an extrusion coater. Examples of the polymer used in the undercoat layer include polyester (for example, JP-A-59-19230), and a copolymer comprising a diolefin-based monomer and a vinyl monomer (for example, JP-A-58-1).
25231) can be used.

Next, the ferromagnetic powder, the binder, and, if necessary, other fillers and additives are kneaded with a solvent to prepare a magnetic coating material. As a solvent used in kneading, a solvent usually used for adjusting a magnetic paint can be used. The method of kneading is not particularly limited, and the order of addition of each component can be appropriately set. That is, after preliminarily kneading the binder, solvent and ferromagnetic powder,
In some cases, a method of adding a hardener solution or a method of finally adding a lubricant in a solution state may be adopted. When preparing the magnetic paint, known additives such as a dispersant, an antistatic agent and a lubricant can be used together.

Examples of the dispersant include fatty acids having 12 to 22 carbon atoms, salts or ester compounds thereof, compounds in which part or all of the hydrogen atoms of the compounds are substituted with fluorine atoms, amides of the above fatty acids, and fatty acids. Aliphatic amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl borate esters,
Known dispersants such as sarcosinates, alkyl ether esters, trialkyl polyolefins, oxyquaternary ammonium salts and lecithin can be mentioned. When a dispersant is used, it is usually used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the ferromagnetic powder used.

Examples of the antistatic agent include conductive fine powders such as carbon black and carbon black graft polymer; natural surfactants such as saponin; higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles. Cationic surfactants such as salts of compounds, phosphoniums or sulfoniums; carboxylic acids, phosphoric acids,
Anionic surfactants containing an acidic group such as a sulfate group or a phosphate group; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphate esters of amino alcohol; When the above conductive fine powder is used as an antistatic agent, for example, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the ferromagnetic powder, and the same applies when a surfactant is used. It is used in the range of 0.12 to 10 parts by weight.

The additives such as the above-mentioned dispersants, antistatic agents, lubricants and the like are not strictly described as having only the above-mentioned effects and effects. It can also act as a lubricant or antistatic. Therefore, it goes without saying that the effects of the compounds and the like exemplified by the above classification are not limited to those described in the above classification, and when a substance having a plurality of effects is used, the amount of addition is It is preferable to determine in consideration of the following.

The magnetic paint thus prepared is applied on the undercoat layer provided on the above-mentioned nonmagnetic plastic support. The thickness of the magnetic layer thus formed is generally 0.5 μm to 10 μm. Further, the magnetic recording medium of the present invention may be of a multilayer type having a plurality of magnetic layers. For example, JP-A-57-143732, JP-A-61-214223, and JP-A-2-11.
0823, JP-A-2-158913, JP-A-2-254627, and the like. A backcoat layer may be provided on the nonmagnetic plastic support on the side opposite to the magnetic layer side. In this case, it is preferable to provide the undercoat layer of the present invention between the nonmagnetic plastic support and the back coat layer. The thickness of the back coat layer is 0.1 to 2 microns, preferably 0.3 to 1 micron.

A known backcoat layer can be used. For example, JP-A-60-5417 and JP-A-60-60
JP-B-38725, JP-A-60-229227, JP-A-61-273722, JP-B-2-62
No. 894, JP-B-3-12370, and the details of the method of dispersing the ferromagnetic powder and the binder and the method of applying the ferromagnetic powder to a non-magnetic plastic support are described in JP-A-54-46011.
JP-A-5-21805, JP-A-57-21805
No. 130234 (US Pat. No. 4,414,270);
JP-A-7-150130 (US Pat. No. 4,496,626), JP-A-58-200423, JP-A-60-38725.
No. 4,582,775, JP-A-60-7602
No. 3, JP-A-62-60748, JP-A-62-60748
JP-A-214524, JP-A-62-298927, and JP-A-2-17971.

When the magnetic recording medium is used in the form of a tape, the magnetic layer coated on the non-magnetic plastic support is usually treated to orient the ferromagnetic powder in the magnetic layer, ie,
After performing the magnetic field orientation treatment, it is dried. On the other hand, in the case of a disk-shaped medium, in order to remove anisotropy of magnetic properties,
Non-orientation treatment by a magnetic field is performed. Thereafter, if necessary, a surface smoothing treatment is performed.

[0034]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” indicates “parts by weight”.

Upper magnetic coating material Co-γ-iron oxide 1000 parts Coarse particle carbon 20 parts Maleic acid group-containing vinyl chloride vinyl acetate copolymer 100 parts Carboxyl group-containing polyurethane 200 parts Butyl stearate 20 parts Butyl acetate 1600 parts Methyl ethyl ketone 500 parts Stearic acid 10 parts Polyisocyanate 100 parts Among the above compositions, compositions other than stearic acid and polyisocyanate were dispersed for 3 hours using a sand grinder. Thereafter, stearic acid and polyisocyanate were added and dispersed for 15 minutes, and filtered using a filter having an average pore diameter of 1 μm to obtain an upper layer magnetic coating material. Lower magnetic coating material Co-γ-iron oxide 1000 parts Coarse particle carbon 20 parts Maleic acid group-containing vinyl chloride vinyl acetate copolymer 100 parts Carboxyl group-containing polyurethane 100 parts Butyl stearate 10 parts Butyl acetate 1500 parts Methyl ethyl ketone 500 parts Stearic acid 10 Part polyisocyanate 200 parts Of the above composition, a composition other than stearic acid and polyisocyanate was dispersed for 3 hours using a sand grinder. Thereafter, stearic acid and polyisocyanate were added, dispersed for 15 minutes, and filtered using a filter having an average pore diameter of 7 μm to obtain a lower magnetic coating material. Magnetic coating for upper layer and lower layer
The polyester was coated on a support which had been coated and dried in advance so that the dry film had a thickness of 0.8 μm and 4 μm, and dried. Thereafter, a super calender treatment was performed to smooth the magnetic layer. This was slit to obtain a 1/2 inch wide consumer videotape.

Example of peeling treatment Treatment 1 The magnetic tape provided with an undercoat layer (hereinafter referred to as "manufactured product") and the high-grade type VHS video tape manufactured by Fuji Photo Film (hereinafter referred to as "commercial product") manufactured in the above manner were halved.
The sample was cut to a size of inch × 2.5 cm with a rotary cutter, and 5 g of a sample was collected to prepare a sample. The adhesion of the undercoat layer was 70 to 80 g in each case. Put the above sample into Igarashi 1 / 4G machine (model number 1 / 4G / 6H / 13g),
Dispersed under the following conditions. Dispersion conditions Glass beads: 600 g2. 2. Glass bead particle size: 1.5φmm 3. Number and shape of discs: A SUS rod is equipped with four discs at predetermined intervals, and the discs are 70 mm in diameter and four holes of 13 mm in diameter are symmetrically formed on the periphery. Rotation speed: 2000 rpm 5. Dispersion time: 3 hours Solvent: cyclohexanone Temperature: 20 to 30 ° C. Next, a dispersion in a 1 / 4G machine was taken out on a wire mesh, and first, glass beads, a PET base, and a cyclohexanone solvent containing a magnetic layer were separated. Then, the glass beads on the wire mesh and P
Put the ET base in a stainless steel vat and dry
C. and dried for 2 hours. After drying, the PET base was sucked with an inhaler covered with gauze from above the glass beads and the PET base. This means that the specific gravity of the glass beads is 2.75.
And the PET-based specific gravity is 1.4, and this is a separation method utilizing this difference in specific gravity. When the PET was collected on the gauze, the inhaler was stopped and the PET base on the gauze was collected.
Each of the obtained PET bases was sample No. 1-1
(Processed product), No. 1-2 (processed commercial product).

Treatment 2 Sample N was treated in the same manner as in Treatment 1 except that a mixed organic solvent of methyl ethyl ketone / toluene = 1/1 was used instead of cyclohexanone as the organic solvent in Treatment 1.
o. 2-1 (processed product), No. 2-2 (a commercially available product) was obtained.

Treatment 3 In treatment 1, glass beads 600 were used as dispersion media.
g instead of steel beads 1700g, bead size 1
Except that a φmm one was used, the processing was performed in the same manner as in Processing 1 and the sample No. No. 3-1 (processed product) 3-2 (commercially available processed product) was obtained.

Treatment 4 In treatment 1, a 1 / 4G machine and a disperser were used instead of the dispersion conditions, and the mixture was stirred under the following conditions. Stirring conditions 1. 1. Stirrer: Use of 3.5 cm diameter disperser 2. Number of revolutions: 800 rpm Stirring time: 30 minutes 4. Stripping solution: 0.1 g of NaOH dissolved in 400 g of ethylene glycol Then, the stirred material in the disper was taken out on a wire mesh and separated. Subsequently, the obtained separated product was subjected to cyclohexanone 500
In g, the mixture was stirred using a disper. The stirring conditions were the same as those described above, with the same stirrer, rotation speed, and stirring time. The PET base was separated from the obtained agitated product with a wire mesh, further washed with cyclohexanone, taken out, and dried with a hair dryer for about several minutes. Sample No. 4-
No. 1 (processed product) 4-2 (commercially processed product)
I got

Treatment 5 Sample No. 3 was prepared in the same manner as in Treatment 4 except that a tape (with an adhesion of 0 to 10 g) having no undercoat layer was used in the production example of the magnetic tape. 5 was obtained.

Treatment 6 In treatment 4, the stripping solution (0.1 g of NaOH was added to 400
g of ethylene glycol) instead of cyclohexanone and methyl ethyl ketone (MEK).
6, except that 500 g of a solvent having a mixing ratio of 6 was used. No. 6-1 (processed product of manufactured product), 6-2 (commercially available processed product) was obtained.

Treatment 7 In the production example of the magnetic tape, a tape without an undercoat layer (adhesion strength: 0 to 10 g) was used, and in treatment 4, a release solution (0.1 g of NaOH dissolved in 400 g of ethylene glycol) ) Was replaced with sample No. 4 except that 500 g of a solvent having a mixing ratio of 4/6 of cyclohexanone and methyl ethyl ketone (MEK) was used. 7 was obtained.

Treatment 8 In treatment 1, the same treatment as in treatment 1 was carried out except that the solvent used in the dispersion conditions was toluene instead of cyclohexanone. No. 8-1 (processed product) 8-
2 (commercially available product) was obtained. Using the respective PET-based samples, the following measurement of adhesion strength and evaluation of the degree of peeling were performed.

Evaluation method (1) Adhesion strength A tape slit to a width of 1/2 inch was attached to an adhesive tape, and the peel strength when pulled in a direction of 180 ° was measured. The measurement temperature and humidity conditions are 23 ° C. and 65% RH.

(2) Degree of Peeling The PET base samples obtained in the above treatments 1 to 8 were all arranged on white paper, and visually judged by the following five evaluations. Evaluation point 5 is an example, and evaluation points 1 to 4
Has a practical problem and is a comparative example. Evaluation point Sample condition 1 The ratio of black part / transparent part of sample is 95% or more 2 The ratio of black part / transparent part of sample is 65% or more and 95% or less 3 The ratio of black part / transparent part of sample is 35% or more and 65% or less 4 The ratio of the black portion / transparent portion of the sample is 5% or more and 35% or less 5 The ratio of the black portion / transparent portion of the sample is 5% or less

The results obtained by the above method are shown below. Sample No. Release liquid Disperser Dispersion media Adhesion strength Degree of peeling 1-1 * Cyclohexanone 1 / 4G machine Glass beads 70-80 g 5 1-2 * {}} @ 5 2-1 * MEK / toluene = {@} 5 1/1 2 -2 * 〃 〃 〃 〃 5 3-1 * Cyclohexanone 〃 Still beads 〃 53-3 * 〃 〃 〃 ５ 54-1 0.1 g NaOH / disper-〃2 Ethylene glycol 4-2 〃 〃-〃 25 〃 〃-0 to 10 g 4 6-1 Cyclohexane / 〃-70 to 80 g 1 MEK = 4/6 6-2 〃 〃-１ 17 〃 〃-0 to 10 g 48-1 Toluene 1 / 4G machine Glass beads 70 8080 g 3 8-2 〃 〃 〃 ＊ 3 * Experiment treated by the method of the present invention

As is clear from the above results, the processing No. treated using the method of the present invention. All of the samples Nos. 1 to 3 exhibited an extremely good degree of peeling despite high adhesion strength between the magnetic layer and the support. Treatment No. having no undercoat layer
5 and No. Sample No. 7 was easily peeled off due to low adhesion strength, but the stripping degree was still not at a practical level at a peeling degree of 4 with 0.1 g NaOH / ethylene glycol. Naturally, the adhesion strength is not at a practical level. Japanese Patent Publication No. 60-23134
400 g of 0.1% NaOH as disclosed in
In the case of the treatment 4 which was carried out in a solution of ethylene glycol dissolved in ethylene glycol, the peeling degree 2 was not at a practical level. Simply stirring with a disper using a mixed solvent of cyclohexanone / MEK = 4/6 was extremely difficult to peel at a peeling degree of 1. Toluene, in which the material of the undercoat layer is difficult to dissolve even when using a 1 / 4G machine using a dispersing medium, has a peeling degree of about 3 and is insufficient.

[0048]

According to the present invention, a magnetic recording medium having a lower coating layer, to dissolve or swell the material constituting the subbing layer
The magnetic layer and the non-magnetic layer can be extremely easily processed by a wet dispersion process using an organic solvent and a dispersion medium.
The non-magnetic plastic support can be recovered by peeling off the back layer.

Claims (3)

(57) [Claims] A non-magnetic support, a magnetic layer , a non-magnetic layer and / or
Alternatively, a magnetic recording medium cut into a predetermined size having at least an undercoat layer provided between the back layer and the back layer is dispersed using an organic solvent and a dispersion medium that dissolve or swell the material constituting the undercoat layer. Separating the non-magnetic support and the magnetic layer, the non-magnetic layer and / or the back layer from the non-magnetic support. 2. The organic solvent is one organic solvent having a ketone group in the molecule or at least 40% by weight of the organic solvent.
2. The method for processing a magnetic recording medium according to claim 1, wherein the mixed solvent comprises the above. 3. The method according to claim 1, wherein the dispersion medium is at least one kind of dispersion medium selected from glass beads, zirconia balls , and steel balls.