JP3385437B2 - Halogen-free magnetic coating composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic coating composition for a magnetic recording medium such as a magnetic tape.

[0002]

2. Description of the Related Art Magnetic recording media such as audio recording, video recording, magnetic recording tape for computers, cards and disks are usually combined with a ferromagnetic powder on a non-magnetic support such as a polyester film. It is manufactured by applying a magnetic coating material comprising an agent, an organic solvent and, if necessary, other additives, orienting the magnetic powder, and then drying and curing. High sensitivity, high recording density and high S / N required for magnetic recording media
In order to obtain excellent performances such as ratio and high reliability, magnetic paint has excellent properties such as dispersibility of ferromagnetic powder in resin, smoothness of coating film, adhesion to support, and mechanical strength. Must be

Binders in magnetic paints used for magnetic recording media which have been generally used conventionally are, for example, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, polyols. Polyurethane resins, bisphenol A-type phenoxy resins and isocyanates, which have been produced by the reaction of polyisocyanate with polyisocyanate, have been widely used. In recent years, particularly in magnetic recording media for VTRs (video tape recorders) and the like, it has become possible to make the magnetic powder finer and to have a higher magnetic force, thereby increasing the packing density of the magnetic powder in the magnetic layer. By doing so, a method of obtaining a high reproduction output has been adopted. As a result, due to the increase in the specific surface area of the magnetic powder and the increase in the cohesive force due to the high magnetization, the dispersibility of the magnetic powder and the surface smoothness of the coating film cannot be obtained with the binder of the magnetic paint that has been conventionally used. . Also,
Since the vinyl chloride copolymer contains halogen, it has a problem of environmental pollution at the time of disposal.

[0004]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a halogen-free magnetic coating material containing a phosphorus-containing phenoxy resin having a phosphorus content of 0.01% by weight or more as an essential component. It is a composition. That is, the present invention improves the dispersibility of magnetic powder and the surface smoothness of a magnetic layer in a magnetic recording medium such as a magnetic tape by including a phosphorus compound-containing phenoxy resin as a binder component in the magnetic recording layer. Durability of the obtained magnetic recording medium,
It is intended to improve the magnetic characteristics and the like.

The phenoxy resin used in the present invention is produced from, for example, bisphenols and epihalohydrin, or phenols epoxy resin and bisphenol.
It is produced by an addition polymerization reaction from silanes. Bisphenols used as raw materials for phenoxy resin are typically 2,2 bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, bis (4
-Hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfide, 3,4,5,6-dibenzo-
1,2-oxaphosphane-2-oxide hydroquinone and the like can be mentioned. Bisphenol epoxy resin,
It can be obtained from the above-mentioned bisphenols and epihalohydrin by a known method. The phenoxy resin of the present invention can be easily produced by a known method by adjusting the reaction mole ratio of the above-mentioned bisphenols and the epoxy resin thereof, or epihalohydrin. Alternatively, a copolymerized phenoxy resin can be similarly obtained by combining the above-mentioned bisphenols.

In the present invention, when a phosphorus compound is introduced into the above-mentioned phenoxy resin, it exhibits high affinity with magnetic powder,
The effect that the dispersibility with the magnetic powder is even more effective can be achieved. As a method for introducing a phosphorus compound in a phenoxy resin, one introduced by copolymerizing a phosphorus compound in a main chain, in particular 3, 4,5,6-dibenzo-1,2-oxa phosphane 2- Oxide hydroquinone is mentioned. One is to introduce the epoxy group of the terminal residue by reacting a phosphorus compound, typically 3, there is 4,5,6-dibenzo-1,2-oxa phosphane-2-oxide, and the like. Of course, addition of the above phosphorus compound and triphosphoric acid ester other than the above can also be used. It is effective that the phosphorus compound is introduced in an amount of 0.01 to 1 part by weight as phosphorus in the total amount of resin.

The magnetic coating composition according to the present invention comprises the above phosphorus-containing phenoxy resin, another binder resin, a curing agent, and
The magnetic powder, other additives (for example, antistatic agent, lubricant, abrasive, etc.), organic solvent, and other components are added as necessary. Then, this magnetic coating composition is applied onto a non-magnetic support to form a magnetic layer. Therefore,
As one example of the magnetic layer, a magnetic coating prepared by dissolving a ferromagnetic powder in the phosphorus-containing phenoxy resin of the present invention and an isocyanate as a curing agent in an organic solvent is applied to the surface of a non-magnetic support of a polyester film. Orient, dry, and cure to form.

The components of the magnetic coating composition will be described below. The phosphorus-containing phenoxy resin, which is the main part of the present invention, increases the polarity by introducing a phosphorus compound into the molecule, improves the affinity with the magnetic powder, and increases the crosslink density by the curing reaction with the isocyanate to improve the durability. A coating film having properties can be formed. In addition, since it has a hydroxyl group on the inner chain of the molecule, it has adhesiveness with the non-magnetic support layer, and it has the function of providing dispersibility of magnetic powder, and eventually electromagnetic exchange characteristics and surface smoothness of the coating film. is there. The phosphorus-containing phenoxy resin can be used in combination with other binder resin (for example, polyurethane resin) in that it functions as a binder.

As the curing agent component, an isocyanate capable of reacting with the hydroxyl group of the side chain of the phosphorus-containing phenoxy resin can be used. In order to accelerate the curing by this isocyanate,
It is also possible to use an organotin-based or amine-based catalyst. The polyurethane resin used in combination can be synthesized by the reaction of polyol and polyisocyanate. Examples of usable polyols include organic dibasic acids such as phthalic acid, adipic acid, dimerized linoleic acid, and maleic acid, and ethylene glycol, propylene glycol, butylene glycol.
Or glycols such as diethylene glycol, trimethylolpropane, hexatriol, glycerin, hexatriol, trimethylolmethane, polyalcohols such as petaerythritol, or glycols thereof. And polyester polyol synthesized by reaction with any two or more polyols selected from polyhydric alcohols; or s-caprolactam, α
Lactone polyester polyols synthesized from caprolactams such as -1-caprolactam; polyester polyols synthesized from ethylene oxide, propylene oxide and the like.

These polyols are reacted with an isocyanate compound such as tolylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, metaxylylene diisocyanate, and the like. Thus, urethanized polyester polyurethane and polyether polyurethane are synthesized. Further, it may be in the form of a urethane resin containing a free isocyanate group and / or a hydroxyl group, or a urethane prepolymer, or may not have these reactive terminal groups. Polyurethane, urethane prepolymer and urethane elastomer are produced by a known method. Among these, those containing free isocyanate also act as a curing agent for the phosphorus-containing phenoxy resin.

The ferromagnetic powder used in the magnetic layer includes ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder,
Examples include hexagonal barium ferrite fine particles, iron nitride, and metal powder. Further, a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive, etc. may be added to the magnetic layer as other additives.

These constituent materials are prepared by dissolving them in an organic solvent. Typically, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc., methyl acetate, ethyl acetate, glycol monoethyl ether acetate, etc. Ester, glycol dimethyl ether, ethers such as dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, aliphatic hydrocarbons such as hexane and heptane, chlorinated hydrocarbons and mixed solvents thereof Can be mentioned. The magnetic coating material composed of the above constituents contains 5 parts by weight of magnetic powder and 5 parts by weight of the binder resin component
It is used in the range of 400 parts by weight, preferably 10 to 200 parts by weight.

As a method of applying the magnetic coating material of the present invention to a support, a general coating method of coating material can be used. The coated magnetic layer is excellent in dispersibility with the magnetic powder using the magnetic coating material of the present invention by subjecting the magnetic layer in the layer to a treatment for aligning the magnetic powder if necessary, and then drying and curing the formed magnetic layer. A magnetic recording medium having excellent surface smoothness and durability can be obtained.

[0014]

The phosphorus-containing phenoxy resin, which is the binder in the magnetic coating composition of the present invention, contains a hydroxyl group, a phosphorus compound, etc. as polar groups in the molecule, so that the affinity for magnetic powder is greatly improved. Then, the atomized magnetic powder is well dispersed. Further, since it is also excellent in compatibility with other binder components and curing agent components, the strength, surface smoothness and durability of the coating film after curing and crosslinking can be obtained. Further, since the phenoxy resin does not contain halogen, there is no problem of dehalogenation at the time of use and environmental pollution due to halogen at the time of disposal.

[0015]

EXAMPLES The present invention will be specifically described below with reference to examples.

[0016]

Synthesis Example 1 Epoxy equivalent 186.5 g / eq. Bisphenol A
Type epoxy resin YD-128 (manufactured by Tohto Kasei) 251.8
Part and bisphenol A (abbreviated as BPA below) 144.8
Part is dissolved in 200 parts of cyclohexanone (hereinafter abbreviated as anone), and the temperature is raised with stirring in a nitrogen atmosphere. After adding 0.1 part of trimethylammonium chloride as a catalyst and reacting at 160 ° C. for 5 hours, phosphorus-containing 14.
3.4 parts of 3% 3,4,5,6-dibenzo-1,2-oxaphosphane-2-oxide was added, and the mixture was further stirred for 4 hours. Then, 200 parts of toluene and 200 parts of methyl ethyl ketone were added. The phosphorus content of the obtained phenoxy resin was 0.13%.

Synthesis Example 2 YD-128, 251.7 parts and BPA, 142.3 parts,
Phosphorus content of 9.5% 3,4,5,6-dibenzo-1,2
6 parts of -oxaphosphan-2-oxide hydroquinone and 200 parts of anone were charged, 0.1 part of catalyst trimethylammonium chloride was added, and after reacting at 160 ° C for 5 hours, toluene and MEK were each diluted with 200 parts. The phosphorus content of the obtained phenoxy resin was 0.14% . Each binder by the upper Symbol Synthesis Example - comparing magnetic coating using the resin examples (* I and * II) will be described with.

The coating compositions of Examples and Comparative Examples were prepared as the respective compositions shown below. Magnetic powder (Co-γ-Fe ₂ O ₃ ) 80 parts Synthetic resin (resin of the synthesis example and comparative example) 10 parts Polyurethane 10 parts Cyclohexanone 25 parts Toluene 50 parts Methyl ethyl ketone 75 parts Each of the above compositions is paint conditioner The mixture was thoroughly mixed and dispersed for 4 hours, and uniformly mixed to prepare magnetic paints. This magnetic paint was applied to one side of a polyethylene terephthalate film so that the dry coating film would be 5 μm.
The sample thus obtained was dried at 60 ° C. for 24 hours, and the gloss of the coating film was measured. The higher the gloss, the better the dispersibility. The results obtained are listed in Table 1. In addition,
The indications in Table 1 are as follows. * I is a commercially available BPA type phenoxy resin (YP
-50 Toto Kasei Co., Ltd.) * II is a commercially available vinyl chloride vinyl acetate resin (manufactured by VAGH UCC). ○ mark is compatible, X mark is not compatible.

[0020]

[Table 1]

[0021]

As described above, in the present invention, by incorporating a phosphorus compound in a phenoxy resin composed of bisphenols and epihalohydrin or diglycidyl ether as a magnetic paint, the dispersibility of magnetic powder is improved,
As a result, it is possible to obtain a magnetic recording medium having excellent characteristics such as high sensitivity, high recording density, high durability, and high reliability.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-229740 (JP, A) JP-A-61-922 (JP, A) JP-A-5-140483 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C09D 1/00-10/00 C09D 101/00-201/10 G11B 5/62-5/82 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A coating type magnetic coating material having a phosphorus content of 0.01% by weight or more, which is 3,4,5,6-dibenzo-.
1,2-oxaphosphane-2-oxide hydroquino
A halogen-free magnetic coating composition, characterized by containing a phosphorus-containing phenoxy resin containing nitrogen as an essential component. 2. A coating type magnetic coating material having a phosphorus content of 0.01% by weight or more, which is 3,4,5,6-dibenzo-.
A halogen-free magnetic coating composition comprising a phosphorus-containing phenoxy resin containing 1,2-oxaphosphan-2-oxide as an essential component. A halogen-free magnetic coating composition comprising a phosphorus-containing phenoxy resin having a phosphorus content of 0.01% by weight or more as an essential component in a coating type magnetic coating.