JPH08249651A - Magnetic recording medium and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention provides a magnetic recording medium composed of a biodegradable base material and a magnetic recording layer, even if it is landfilled without being incinerated after use or scattered in a natural environment. An object of the present invention is to provide a magnetic recording medium having a decomposability as a whole including the magnetic recording layer, which spontaneously decomposes and disappears even if it is left after being discarded, and a manufacturing method thereof. [Structure] A magnetic recording layer obtained by melting a mixture of a biodegradable plastic which is decomposed by microorganisms and a magnetic material is laminated on at least one surface of a biodegradable plastic substrate which is decomposed by microorganisms by coextrusion molding. A magnetic recording medium and a method for manufacturing the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used for, for example, a magnetic ticket, a magnetic commuter pass, a magnetic coupon ticket, a prepaid card, an admission ticket, a membership card, and the like, and particularly when these are placed in a natural environment. However, the present invention relates to a magnetic recording medium and a method for manufacturing the same, in which almost all of them are decomposed.

[0002]

2. Description of the Related Art Conventionally, as a recording medium for information and the like, it has been used in many fields such as a membership card, a prepaid card, a commuter pass and a pass ticket.
Plastic, polyethylene terephthalate (PET)
A magnetic recording layer is provided by directly coating a magnetic paint on a substrate such as paper or paper, or by transferring a magnetic transfer foil.

In this case, not only a magnetic coat but also a magnetic transfer foil is used in which a polymer resin is dissolved in a general-purpose solvent as a binder, and a water-dispersible emulsion may be used in some cases. is there. Further, these magnetic recording layers are required to have physical and chemical properties such as durability, abrasion resistance, heat resistance, and chemical resistance, and therefore, a polymer resin forming the layer often contains a crosslinking agent. May be used.

At the time of discarding such a plastic product or a product using a part of plastic after use, it is currently incinerated or disposed of as a waste by landfill or the like. However, wastes containing plastics have a high incineration temperature during incineration, resulting in durability problems of incinerators, pollution problems such as incineration gas, or landfills, or by any chance in the natural environment as garbage. When scattered, it remains as it is, and remains semi-permanently as garbage, which poses a problem of affecting the natural environment. Furthermore, for a special purpose such as a magnetic recording layer, since a crosslinking agent is added to the binder, it is visibly apparent that it remains as it is.

Therefore, in order to eliminate environmental problems caused by plastics to the natural environment, in recent years, for example, JP-A-57-
150393, JP-A-59-220192, JP-A-51-93001, and JP-A-63-26.
No. 0912 Publication, a plastic that can be decomposed under natural environment such as light or underground has been developed, and it has come to be used especially for disposable products, and is now partly commercialized. .

In the case of processing these decomposable plastics mentioned above, the injection molding method and the melt extrusion molding method after melting are the most suitable processing methods, but since they are hardly soluble in general-purpose solvents, magnetic recording is possible. It did not become a magnetic paint as a binder that constitutes the layer.

[0007]

That is, in an information recording medium represented by a conventional magnetic card or the like, a base material,
Since the magnetic recording layer contains a non-degradable plastic,
There was a problem with disposal.

The present invention has been made in view of the above problems. The problem is that a magnetic recording medium comprising a biodegradable substrate and a magnetic recording layer is not incinerated after use. Even if it is landfilled in or scattered in the natural environment, the entire medium including the magnetic recording layer has degradability,
It is an object of the present invention to provide a magnetic recording medium that can be naturally decomposed even if it is left after being discarded to improve the disposal property, and a manufacturing method thereof.

[0009]

In order to achieve the above object, the magnetic recording medium of the present invention comprises a mixture of a biodegradable plastic and a magnetic substance on at least one surface of a degradable substrate. It is characterized in that a magnetic recording layer is formed.

The degradable base material is made of a biodegradable plastic which is decomposed by microorganisms.

Further, in the method for producing a magnetic recording medium, a mixture of a biodegradable plastic which is decomposed by microorganisms and a magnetic material is melted on at least one surface of a biodegradable plastic substrate which is decomposed by microorganisms. Magnetic recording layer,
It is characterized in that they are laminated by coextrusion molding.

The term "biodegradable" as used herein means that a polymer is decomposed into an oligomer, a monomer, or a substance having a lower molecular weight by the action of an enzyme produced by a microorganism existing in the environment such as mold, bacteria and yeast. Finally, it is preferable that it is finally decomposed into water, carbon dioxide gas, methane and the like. The present invention will be described in detail below.

Examples of biodegradable plastics used in the present invention include microorganism-produced polyesters such as 3-hydroxybutyric acid / 3-hydroxyvaleric acid copolymer (hereinafter referred to as P (3HB-3HV)) and poly. Aliphatic polyesters such as caprolactone, polyglycolides such as polylactic acid, polyvinyl alcohol / starch composites and the like can be used, and a mixture or laminate of these biodegradable plastics may be used.

Furthermore, various additives and non-degradable substances such as polymers may be added to these biodegradable plastics in an amount of 50% or less by weight. However, if 50% or more of a non-degradable substance is added, the biodegradability is remarkably reduced, and processing problems occur, which is not preferable.

As described above, the printing / processing on the magnetic recording medium in which all the medium is made of biodegradable plastic is performed by the conventional paper,
The same method as in the case of plastics, that is, the offset printing method, the screen printing method, the gravure printing method, etc., can be used to print characters or patterns and then form a card using a punching machine.

[0016]

In the magnetic recording medium of the present invention, since the magnetic recording medium generally used in the past is non-decomposable, the shape of the magnetic recording medium is almost permanently retained unless it is incinerated. By using biodegradable plastics as a binder for the magnetic recording layer, the entire magnetic recording medium has biodegradability and decomposes and disappears in landfills and in the natural environment.

[0017]

Embodiments will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of the magnetic recording medium of the present invention. As shown in the figure, the magnetic recording medium (1
0) has a constitution in which a degradable magnetic recording layer (13) is laminated on one surface of a degradable substrate (12).

As the base material (12), a biodegradable plastic that is decomposed by microorganisms is used. For example, 3-hydroxybutyric acid-3-hydroxyvaleric acid copolymer (P (3HB-3HV)) Polyesters produced by microorganisms such as polycaprolactone (PCL), aliphatic polyesters such as polycaprolactone (PCL), polyglycolide such as polylactic acid, polyvinyl alcohol / starch complex, and the like can be used. It may be a laminated body.

On the other hand, for the magnetic recording layer (13), a biodegradable plastic which is decomposed by microorganisms can be used as a binder. This binder may be the same as the biodegradable plastic used in the base material (12), for example, 3-hydroxybutyric acid / 3-hydroxyvaleric acid copolymer (P (3HB-3HV), etc.). Microbial polyester, aliphatic polyester such as polycaprolactone (PCL), polyglycolide such as polylactic acid, polyvinyl alcohol / starch complex, etc. Magnetic powder, additives, etc. are dispersed in these binders to make a masterbatch. .

Further, the magnetic property used for the magnetic recording layer (13).
As the powder, for example, γ-Fe₂O ₃, Fe₃O₂, F
e₃O_Four, Co-doped Fe₂O₃, Co deposited Fe
₂O₃, CrO₂Of any one of the needle crystal structure
It is an acidic iron oxide that has, necessary coercive force, average particle size,
Axial ratio (long / short / single axis) and specific surface area can be selected and used.
Just do it. Silicone oil may also be present in other magnetic paints.
Antistatic agents such as graphite and graphite can be used
It

As shown in FIG. 5, the lamination in the method for producing the magnetic recording medium (10) of the present invention is carried out by magnetic recording using a base material (12) made of biodegradable plastic and a mixture of biodegradable plastic and magnetic material. The layer is melted and coextrusion is performed. Thereby, stable workability and thickness can be controlled. In the co-extrusion molding, the biodegradable base material layer (12) and the biodegradable magnetic recording layer (13) are magnetically aligned while being extrusion-molded in an overlapping state, and then sent out in a long shape. It is superposed on the peeling release paper (16), formed into a predetermined thickness by the rollers (33, 34), and taken up by the take-up roller (36). The magnetic recording medium (10) shown in FIG. 1 is obtained by peeling off the release paper (16) from the medium after the coextrusion molding.

Specific examples will be described below.

<Example 1> As shown in FIG.
As 2), P (3HB-3HV) (Biopol, hydroxyvaleric acid content 5%, made by Zeneca), thickness 188μ
A biodegradable magnetic recording layer (13) having the composition shown below and having a thickness of 15 μm was formed on the release paper (16) by a coextrusion molding method at 15 μm. "Composition" and acid iron oxide _{Co-γFe 2 O 3 (CTX} -970, Toda Kogyo Ltd. Co.): 100 parts · P (3HB-3HV) (Biopol, hydroxyvaleric acid content of 5%, manufactured by Zeneca) : 80 parts-Carbon black (# 40, manufactured by Mitsubishi Kasei Co., Ltd.): 3 parts A mixture having the above composition was melted at 200 ° C and then mixed to form a masterbatch.

When the magnetic recording medium (10) was buried in a field soil and the decomposition state was observed regularly, the magnetic recording layer (13) was almost completely decomposed after one month and the shape was maintained. However, only the base material (12) remained, and after 6 months, the shape was not retained, and the base material (12) remained in only about half. .

<Example 2> As shown in FIG.
As 2), P (3HB-3HV) (Biopol, hydroxyvaleric acid content 5%, manufactured by Zeneca) is set to 188 μm, and a biodegradable magnetic recording layer (13a) having the following composition is set to 15 μm. The medium was formed on the release paper (16) by the coextrusion molding method. "Composition" and acid iron oxide _{Co-γFe 2 O 3 (CTX} -970, Toda Kogyo Ltd. Co.): 100 parts chemically synthesized polyester (Bionolle, Showa Kobunshi, Ltd. Co.): 80 parts Talc: 10 parts-Carbon rack (# 40, manufactured by Mitsubishi Kasei Co., Ltd.): 3 parts A mixture having the above composition was melted at 200 ° C and then mixed to prepare a master patch.

When the magnetic recording medium (10) was buried in field soil and the decomposed state was observed periodically, the magnetic recording layer (13a) was almost completely decomposed after one month and the shape was maintained. However, only the base material (12) remained, and after 6 months, the shape was not retained, and the base material (12) remained in only about half.

<Comparative Example 1> As shown in FIG.
As 2), P (3HB-3HV) (Biopol, hydroxyvaleric acid content 5%, made by Zeneca), thickness 188μ
m, and urethane magnetic ink (MAG3000
A, made by Dainichiseika Co., Ltd., with wire bar coater about 1
Coated to 2 μm and dried to form a magnetic recording layer (23),
A magnetic recording medium (20) was obtained.

When the magnetic recording medium (20) was buried in field soil and the decomposed state was observed regularly, after 6 months, the base material on the surface where the magnetic recording layer (23) was not laminated was The shape is not retained and only about half remains, and the surface on which the magnetic recording layer (23) is laminated has the magnetic recording layer (23) completely remaining and is slightly left on the surface. Reproduction of mildew was observed.

Comparative Example 2 As shown in FIG. 4, the base material (2
2) Milky-white PET (Lumirror, which has a thickness of 188 μm)
A magnetic recording layer (13) having the same composition as in Example 1 was formed on Toray Co., Ltd. by a melt extrusion method to give a thickness of 15 μm.
To obtain a magnetic recording medium (30).

When the magnetic recording medium (30) was buried in field soil and the decomposition state was observed regularly, the degradable magnetic recording layer (13) was almost completely decomposed in one month. However, the base material (22) was in a state of no change, and it was the same after 6 months, and only PET of the base material remained.

When the magnetic recording media obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were encoded by a commercially available reader / writer (R / W), recording could be performed without any problem.

As described above, in the magnetic recording medium (20) of Comparative Example 1, the base material (12) itself has decomposability, but the magnetic recording layer (23) has the decomposability of the magnetic recording medium. Hinders and reduces the rate of decomposition. Further, in the magnetic recording medium (30) of Comparative Example 2, although the magnetic recording layer (13) itself has decomposability, the base material (22) hinders the decomposability of the magnetic recording medium and the shape remains. .

On the other hand, in the magnetic recording media (10) of Examples 1 and 2, not only the base material (12) but also the magnetic recording layer (13) had decomposability, so that it was extremely excellent. It can be said that the magnetic recording medium has decomposability. Therefore, it is possible to perform magnetic recording with a security function as a recording medium, and at the same time, it is assumed that the entire recording medium including the magnetic recording layer has biodegradability. This makes it possible to eliminate the above-mentioned effects on the natural environment.

[0035]

According to the magnetic recording medium of the present invention having the above-mentioned constitution, a biodegradable magnetic recording layer is coextruded and laminated on at least one surface of a biodegradable substrate, Magnetic recording is possible as a recording medium, and it can be used for prepaid cards, commuter passes, etc., and at the same time, the entire medium, including the magnetic recording layer, is degradable, so that even if it is used up and left for disposal, it will naturally disappear. It is possible to provide a magnetic recording medium that can be disassembled to improve the discardability.

The biodegradable plastic used in the magnetic recording medium of the present invention is inferior in physical properties and workability to various plastics which have been conventionally used.
It is also possible to combine multiple biodegradable plastics and to mix additives and non-degradable plastics to the extent that biodegradability is not deteriorated. It is possible to obtain a magnetic recording medium having

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an embodiment of a magnetic recording medium of the present invention.

FIG. 2 is an explanatory view in cross section showing another embodiment of the magnetic recording medium of the present invention.

FIG. 3 is an explanatory view in cross section showing another laminated structure of the magnetic recording medium according to the present invention.

FIG. 4 is an explanatory view in cross section showing another laminated structure of the magnetic recording medium according to the present invention.

FIG. 5 is an explanatory view showing lamination of a base material and a magnetic recording layer of the magnetic recording medium of the present invention by a coextrusion molding method.

[Explanation of symbols]

 10, 20, 30 ... Magnetic recording medium 12, 22 ... Base material 13, 13a, 23 ... Magnetic recording layer 16 ... Release paper 33, 34 ... Roller 36 ... Winding up

Claims (3)

[Claims] 1. A magnetic recording medium comprising a degradable base material and a magnetic recording layer made of a mixture of a binder made of biodegradable plastic and a magnetic material, which is laminated on at least one surface of the base material. 2. The magnetic recording medium according to claim 1, wherein the degradable substrate is made of biodegradable plastic. 3. A magnetic recording layer obtained by melting a mixture of a biodegradable plastic which is decomposed by microorganisms and a magnetic material is coextruded on at least one surface of a biodegradable plastic substrate which is decomposed by microorganisms. A method of manufacturing a magnetic recording medium, comprising: