JPH064786B2 - Magnetic coating composition - Google Patents

Description

The present invention relates to a magnetic coating composition, and more particularly to a radiation curable magnetic coating composition capable of forming a magnetic recording medium having high durability.

Conventionally, various thermoplastic resins or thermosetting resins have been used as binders for magnetic recording media such as audio tapes, video tapes, and magnetic disks.
No satisfactory magnetic properties, surface smoothness and wear resistance have been obtained. Further, there is a method of adding a crosslinkable binder by a chemical reaction, such as an isocyanate compound or an epoxy compound, to the thermoplastic resin.

However, when a crosslinkable binder is used, the storage stability of the resin solution in which the magnetic material is dispersed is poor. That is, there is a disadvantage that the pot life is short and the uniformity of the magnetic coating liquid physical properties, and thus the homogeneity of the magnetic tape cannot be maintained, and a heat treatment step is required for curing the coating film after coating and drying. However, it has a drawback that it takes a long time to commercialize it.

Furthermore, recently, a radiation-curable magnetic coating composition comprising a combination of a compound having a polymerizable unsaturated group in the molecule and a thermoplastic resin has been proposed (for example, JP-A-58-1).
(See Japanese Patent No. 00227). The magnetic paint has improved magnetic properties and durability and does not have the above-mentioned drawbacks, but there is a problem in that the dispersibility in dispersing the magnetic pigment is not satisfactory and the surface smoothness is poor. Improvement is desired.

Therefore, the present inventors have conducted extensive studies to improve the dispersibility of the above magnetic pigment, and found that the dispersibility is greatly improved by treating the magnetic pigment with a metal coordination compound of aluminum. The present invention has been completed.

Thus, according to the present invention, (a) urethane acrylic oligomers, oligoester acrylic orgomers, butadiene oligomers, epoxy acrylic oligomers, spirane ring-containing acrylic oligomers, ether acrylic oligomers and acrylic polyvalent esters are selected. At least one compound having a radiation-polymerizable unsaturated bond in the molecule having a molecular weight of 100 to 20,000, (b) a vinyl chloride copolymer resin, a cellulose resin, a polyvinyl butyral resin , At least one organic resin selected from polyester resins, polyurethane resins and epoxy resins, and (c) selected from lower alkanolamines, acetoacetic acid esters, diketone alcohols, diketones, glycols and oxycarboxylic acids. Radiation-curable magnetic coating composition characterized by containing a magnetic pigment which has been surface treated with a metal coordination compound of the chelated aluminum-based in one chelating agent is provided even without.

The compound (a) having a radiation-polymerizable unsaturated bond in the molecule used in the present invention (hereinafter, simply referred to as an unsaturated compound (a)) has a molecular weight of 100 to 20,000, and it is known in the art, for example Urethane acrylic oligomers, oligoester acrylic oligomers, butadiene oligomers described in JP-A-58-100227.
Examples thereof include an epoxy acrylic oligomer, a spirane ring-containing acrylic oligomer, an ether acrylic oligomer, and an acrylic polyvalent ester.

The urethane acryl-based oligomer has a molecular weight of 500 to 20,000, preferably 2, with a urethane bond in the main chain of the molecule and an acrylic double bond at both ends of the molecule.
It is a compound that is liquid at room temperature of 000 or less and is generally synthesized by subjecting polyurethane polyol to an esterification reaction with an acrylic unsaturated acid such as acrylic acid or methacrylic acid.

The oligoester acrylic-based oligomer is a compound which has an ester bond in the main chain of the molecule and an acrylic double bond at the end of the molecule and has a molecular weight of usually 500 to 20,000, preferably 2,000 or less and which is liquid at room temperature. Generally, polyester polyol is synthesized by esterifying acrylic unsaturated acid such as acrylic acid or methacrylic acid. Specific examples of commercially available products include, for example, Aronix products manufactured by Toagosei Co., Ltd., which are synthesized from phthalic acid-based polyester polyols.

The butadiene-based oligomer usually has a molecular weight of 500 to 2
It is a compound that is liquid at room temperature of 10,000 or less, preferably 4,000 or less, and is attached to both ends of the molecule by esterifying an acrylic unsaturated acid such as acrylic acid or methacrylic acid with a butadiene oligomer having a terminal hydroxyl group. It includes those having an acrylic double bond and ordinary butadiene oligomers having no such acrylic double bond.

The epoxy acrylic-based oligomer has a molecular weight of usually 500 to 20,0 which is obtained by reacting an acrylic unsaturated acid such as acrylic acid or methacrylic acid with a low molecular weight epoxy resin.
00, preferably 2,000 or less, and a liquid compound at room temperature, and the epoxy resin includes various types such as novolac type (intramolecular epoxy group) and bisphenol type (terminal epoxy group).

The spirane ring-containing acrylic oligomer is a compound which has a spirane ring in the molecule and has an acrylic double bond at both ends of the molecule and which has a molecular weight of usually 500 to 20,000, preferably 2,000 or less and which is liquid at room temperature. Yes, commercially available products include Spyrac T-500 and T- manufactured by Showa High Polymer Co., Ltd.
510X-7N, T-502X-4, U-3000, U
3150, U-3151, E-4000, etc.

The ether acryl-based oligomer generally has a molecular weight of usually 500 to 20,0, which is synthesized by esterifying an etherified oligomer of bisphenol A with an acrylic unsaturated acid such as acrylic acid or methacrylic acid.
00 is preferably a compound which is liquid at room temperature of 2,000 or less. Specific examples of commercial products of such oligomers include:
NK ester A-BPP-2, N manufactured by Shin Nakamura Chemical Co., Ltd.
K ester A-BPE-4, NK ester BPE-4, etc. are mentioned.

The acrylic polyhydric ester has a molecular weight of 100 or more, preferably 200 to 1,000, which is liquid at room temperature and is obtained by subjecting a polyhydric alcohol and an acrylic unsaturated acid such as acrylic acid or methacrylic acid to an esterification reaction. Is a compound,
The polyhydric alcohol broadly includes polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polybutylene glycol, and triols such as trimethylolpropane.

Specific examples of commercial products of the above-mentioned acrylic polyvalent ester include NK ester manufactured by Shin-Nakamura Chemical Co., Ltd.

The organic resin (b) used in the present invention is at least one selected from vinyl chloride copolymer resin, cellulose resin, polyvinyl butyral resin, polyester resin, polyurethane resin and epoxy resin, and these resins are cured films. It has a function of imparting flexibility to, and a function of enhancing dispersibility of the magnetic powder with good affinity with the magnetic powder.

The vinyl chloride-based copolymer resin includes vinyl chloride-vinyl acetate-based copolymer resin, vinyl chloride-vinyl propionate-based copolymer resin, and the like.

A typical cellulosic resin is nitrocellulose. The average degree of polymerization of nitrocellulose is 30 to 5
00, and a nitrogen content of about 10 to 14% by weight is preferable.

Polyvinyl butyral resin is polyvinyl alcohol 5-5.
Those having an average degree of polymerization of about 200 to 1,000 and having a hydroxyl group content of 17% by weight can be used.

Polyester resin usually has a molecular weight of 2,000 to 3
Approximately 10,000, preferably used, and examples of commercially available products include pylon manufactured by Toyobo Co., Ltd.

The polyurethane resin is a high molecular weight urethane resin having no free isocyanate group, and specific examples thereof include:
For example, Nippon Polyurethane Industry Co., Ltd. Nippon Polan # 23
01, Crisbon 720 manufactured by Dainippon Ink and Chemicals, Inc.
9, Pandex T-5250, TMV-2 and the like.

As the epoxy resin, a relatively high molecular weight thermoplastic resin having a molecular weight of usually about 300 to 5,000 is used, and specific examples thereof include Epicron manufactured by Dainippon Ink and Chemicals, Inc.

Acrylic acid or the like may be added to the organic resin (b) to be unsaturated.

In the present invention, the unsaturated compound as a binder component
The ratio of the component (a) and the organic resin (b) used is 5-9
5% by weight, preferably 10-80% by weight, the latter 5
˜95 wt%, preferably 90 to 20 wt%.

The magnetic pigment (c) used in the present invention is obtained by surface-treating a magnetic pigment with an aluminum-based metal coordination compound described below (hereinafter, also simply referred to as “metal coordination compound”). .

The aluminum-based metal coordination compound is known per se and can be obtained by treating an organoaluminum compound with a chelating agent. As the organoaluminum compound, especially the following formula (I) In the formula, at least one of R ₁ , R ₂ and R ₃ is C ₁ to
C ₁₃ alkoxy group (eg methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, isoamyloxy, n-hexyloxy, n-heptyloxy, n - octyl oxy) or C ₃ -C ₁₀
Alkoxyalkoxy groups (eg, methoxymethoxy, methoxyethoxy, ethoxybutoxy, butoxybenthoxy groups, etc.) and the rest are C _{1 to} C ₆ alkyl groups (eg, methyl, ethyl, n-propyl, isopropyl,
n-butyl, isobutyl, sec-butyl, tert-butyl, amyl groups, etc.) and aryl groups (especially phenyl and toluyl groups) are preferable, and specifically, for example, aluminum isopropylate , Aluminum sec-butyrate, aluminum tert-butyrate, and the like.

Examples of the chelating agent that can be reacted with the organoaluminum compound include lower alkanolamines (eg, triethanolamine, diethanolamine, dimethylaminoethanol, etc.), acetoacetic acid esters (eg, methyl acetoacetate, ethyl acetoacetate, etc.) , Diketone alcohol (eg diacetone alcohol, etc.),
Examples thereof include diketones (eg: acetylacetone etc.), glycols (eg: ethylene glycol, octylene glycol etc.), oxycarboxylic acids (eg: lactic acid, tartaric acid etc.), among which acetoacetic acid esters are preferred.

Then, as the metal coordination compound advantageously used in the present invention, specifically, for example, methyl acetoacetate aluminum diisopropylate, ethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate), etc. may be mentioned. You can Examples of commercially available products include AL-M manufactured by Ajinomoto Co., Inc.
Is mentioned.

Examples of the magnetic pigment applied to the present invention include γ-F
e ₂ O ₃ powder, Fe ₃ O ₄ , γ-Fe ₂ O ₃ and Fe ₃ O ₄
Magnetic powder in the intermediate oxidation state with, Co-containing iron oxide magnetic powder, Cr
In addition to metal oxide magnetic powder such as O ₂ powder, Fe, Co, N
Various conventionally known magnetic pigments such as i or metal magnetic powders such as these alloys can be used.

As a method of surface-treating the magnetic pigment with a metal coordination compound, the metal coordination compound is dissolved in a suitable solvent such as butanol, hexane, cyclohexane, toluene, methyl ethyl ketone, ethyl acetate, etc., and the magnetic pigment is added to this solution. It may be immersed and sufficiently stirred. In this case, the solution concentration of the metal coordination compound is generally in the range of 0.5 to 50% by weight, preferably 1 to 30% by weight. The amount of the metal coordination compound used is usually 0.1 to 20% by weight, preferably 1 to 10% by weight, more preferably 1 to 10% by weight based on the magnetic pigment.
It is 5% by weight. 0.1% by weight of metal coordination compound
If it is less, the desired effect cannot be obtained, while on the other hand, 20% by weight
If it exceeds the range, there is a drawback that bleeding occurs in the coating film.

As a method of surface-treating the magnetic pigment with a metal coordination compound, a method of adding a solution of the metal coordination compound to the coating composition and thoroughly stirring it may be performed in addition to the method described above.

When the magnetic pigment is surface-treated with a metal coordination compound, the metal coordination compound strongly reacts with a functional group existing on the surface of the pigment particle, for example, a hydroxyl group to firmly adhere to the surface of the magnetic pigment particle,
A film is formed to remarkably improve the dispersibility of the magnetic pigment. Further, since the metal coordination compound has an action of lowering the viscosity of the magnetic paint, the filling property of the magnetic pigment can be improved, that is, the pigment volume concentration can be increased. As a result, the magnetic characteristics and surface smoothness of the magnetic recording medium obtained using the present coating composition are further improved.

The magnetic coating composition of the present invention is prepared by mixing and dispersing the components (a), (b) and (c) described above using an organic solvent by a conventionally known method. As the organic solvent, a methyl isobutyl ketone, a ketone solvent such as cyclohexanone, an ester solvent such as ethyl acetate and butyl acetate, an aromatic solvent such as toluene and xylene, an alcohol solvent such as methanol, ethanol and isopropanol, tetrahydrofuran , A solvent having an ether bond such as dioxane, and an organic solvent such as dimethylformamide vinylpyrrolidone.

The amount of magnetic pigment used is magnetic pigment / binder = 500-
It is in the range of 250/100 (weight ratio), preferably magnetic pigment / binder = 400 to 300/100.

The radiation used for crosslinking and curing the radiation-curable magnetic coating composition according to the present invention is an electron beam using an electron beam accelerator as a radiation source, an r-ray using Co-60 as a radiation source, and an x-ray generator as a radiation source. X-rays and UV rays are used.

In particular, as the irradiation source, electron beam irradiation is suitable from the viewpoints of controlling absorbed dose and not requiring an initiator for blocking ionizing radiation.

The absorbed dose is 0.5 to 20 megarads, preferably 2 to
It is 10 megarads. If it is less than 0.5 Mrad, the curing reaction is insufficient and strength cannot be obtained, and if it is more than 20 megarads, the energy efficiency used for curing is lowered and the irradiated body is heated to deform the plastic support, which is not preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples.
In addition, "part" shows a "weight part."

Example 1 Ethyl acetoacetate aluminum diisopropylate represented by the following formula (trade name AL-M manufactured by Ajinomoto Co., Inc.) was dissolved in toluene to give a 2 wt% solution.

Then, 80 parts of Co-containing γ-Fe ₂ O ₃ powder was immersed in the above solution, sufficiently stirred for 15 minutes for surface treatment, and dried. The obtained Fe ₂ O ₃ powder has a weight of 8
It was 2 parts, and 2 parts of the metal coordination compound was attached.
82 parts of this treated Fe ₂ O ₃ powder, VAGH (UC.
C. 10 parts by vinyl chloride vinyl chloride copolymer resin, Aronix M
A magnetic coating material was prepared by thoroughly mixing and dispersing 10 parts of -6100 (oligoester acrylic oligomer manufactured by Toagosei Co., Ltd.), 80 parts of toluene and 80 parts of methyl ethyl ketone in a ball mill. This paint was applied on a polyester film having a thickness of 15 μm to a dry film thickness of 5 μm, and then 90
Preheating was carried out for 1 minute at .degree. C., and then the solvent was irradiated with an electron beam at an irradiation dose of 5 Mrad, followed by curing calendering and cutting into a predetermined width to prepare a magnetic tape.

Example 2 Nitrocellulose R was used instead of VAGH used in Example 1.
A magnetic tape was produced in the same manner as in Example 1 except that 10 parts of S1 / 4 (a fiber-based resin manufactured by Daicel) was used.

Example 3 Unidic V46 instead of Aronix M-6100
A magnetic tape was produced in the same manner as in Example 1 except that 10 parts of 01 (urethane acrylic oligomer manufactured by Dainippon Ink and Chemicals, Inc.) was used.

Example 4 Lipoxy SP-15 instead of Aronix M-6100
A magnetic tape was produced in the same manner as in Example 1 except that 10 parts of 09 (Epoxy acrylic oligomer manufactured by Showa High Polymer Co., Ltd.) was used.

Example 5 Instead of Aronix M-6100, U-3000 (spiran ring-containing acrylic oligomer manufactured by Showa High Polymer Co., Ltd.) 1
A magnetic tape was prepared in the same manner as in Example 1 except that 0 part was used.

Example 6 A magnetic tape was prepared in the same manner as in Example 1 except that 80 parts of Cr ₂ O ₂ powder was used instead of the Co-containing iron oxide magnetic powder.

Comparative Example 1 A magnetic material was prepared in the same manner as in Example 1 except that 80 parts of Co-containing γ-Fe ₂ O ₃ was used untreated and 10 parts of Byron-300 (a polyester resin manufactured by Toyobo Co., Ltd.) was used instead of VAGH. I made a tape.

Comparative Example 2 A magnetic tape was prepared in the same manner as in Comparative Example 1 except that 80 parts of metal magnetic powder was used untreated and 10 parts of Aronic M-8030 (oligoester acrylate oligomer described above) was used instead of VAGH. Created.

The surface smoothness (visual) gloss value (60 ° reflectance) of powder drop was determined for each magnetic tape of the above-mentioned Examples and Comparative Examples.

Claims (1)

[Claims] 1. At least one selected from (a) urethane acrylic oligomers, oligoester acrylic oligomers, butadiene oligomers, epoxy acrylic oligomers, spirane ring-containing acrylic oligomers, ether acrylic oligomers and acrylic polyvalent esters. A compound of a molecular weight of 100 to 20,
Compound having a radiation-polymerizable unsaturated bond in the molecule of (000), (b) at least one selected from vinyl chloride copolymer resin, cellulose resin, polyvinyl butyral resin, polyester resin, polyurethane resin and epoxy resin
Type organic resin and (c) an aluminum-based metal chelated with at least one chelating agent selected from lower alkanolamines, acetoacetic acid esters, diketone alcohols, diketones, glycols and oxycarboxylic acids A radiation-curable magnetic coating composition comprising a magnetic pigment surface-treated with a coordination compound.