JPS61126182A - Magnetic coating - Google Patents

Abstract

PURPOSE:To provide a magnetic coating exhibiting excellent dispersion of magnetic powder, prepared by blending a polymer which contains a residue of tetrahydrofurfuryl ester of an ethylenically unsatd. aliphatic carboxilic acid, a solvent for the polymer and magnetic powder. CONSTITUTION:A polymer which contains 5-95wt% at least one residue to tetrahydrofurfuryl ester of an ethylenically unsatd. aliphateic carboxylic acid in the molecule, magnetic powder and a solvent for the polymer are blended together. For improved wear resistance, a polyurethane resin may be added to the resulting magnetic coating. Even when the residue is introduced in less than 5%, the coating shows good dipersion of magnetic poder, but dispersibility is markedly lowered by combined use of polyurethane resin. When the residue content exceeds 95%, the strength of the polymer is greatly reduced and the coating loss its practical effect, although it shows good dispersion of magnetic powder.

Description

[Detailed description of the invention] Benefits of the soil The present invention relates to a magnetic coating material with excellent dispersibility of magnetic powder.

2. Description of the Related Art Generally, as a type of magnetic recording medium, a magnetic layer is formed by applying a magnetic paint containing magnetic powder, a binder component, a solvent, various additives, etc. onto a substrate such as a polyester film, and drying the coating. However, its performance (especially electromagnetic conversion characteristics) largely depends on the state of dispersion of the magnetic powder in the magnetic layer.

Therefore, in order to obtain a high-performance magnetic recording medium by applying a magnetic paint, it is necessary to select a binder component that has excellent dispersibility of magnetic powder.

Conventionally, nitrocellulose and vinyl chloride-vinyl acetate copolymers have been widely used as binder components with excellent dispersibility, but these are not always satisfactory. In particular, a polyurethane resin is often used in combination for the purpose of improving abrasion resistance, but in this case, dispersibility decreases.

Although it is conceivable to use a large amount of a generally known surfactant in order to improve dispersibility, such substances generally have a small molecular weight, and the molecular weight of such substances is about several hundred at most.

Such low-molecular-weight materials cause oozing, so-called bleed, over time after the magnetic layer is formed, lowering electromagnetic conversion characteristics and worsening runnability.

Problems to be Solved by Application B The present invention provides a paint with excellent dispersibility in order to solve these problems.

That is, by using a polymer containing 5 to 95% by weight of at least one type of ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester residue in the molecule as a binder component, the dispersibility of the magnetic powder is greatly improved. It was discovered that

Moreover, this high fractional property was maintained even when polyurethane resin was used in combination for the purpose of improving wear resistance.

SUMMARY OF THE INVENTION The present invention provides a polymer containing 5 to 95% by weight of at least one ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester residue in the molecule.

The present invention relates to a magnetic paint comprising a magnetic powder and a solvent for the polymer. The present invention also relates to a magnetic paint containing a polyurethane resin in addition to the above components.

Next, the present invention will be explained in more detail. When the amount of ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester residue introduced into the polymer is lower than 5% by weight, the magnetic powder alone has excellent dispersibility, but when used in combination with polyurethane resin, the same There is a significant decrease in dispersibility. If it exceeds 95% by weight, the strength of the polymer will drop significantly, and although the dispersibility of the magnetic powder is excellent, it will lack practical effects.

From the above viewpoint, the amount introduced is 5 to 95% by weight, preferably,
It becomes 15 to 80% by weight.

The polymer used in the present invention is usually produced by copolymerization of ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester and other copolymerizable monomers, but ethylenically unsaturated aliphatic carboxylic acid or its acid anhydride It is also possible to produce it by copolymerizing and other copolymerizable monomers and then esterifying the resultant mixture with tetrahydrofurfuryl alcohol.

Ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester is tetrahydrofurfuryl acrylate,
Tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl crotonate.

Tetrahydrofurfuryl incrotonate; includes mono- or di-tetrahydrofurfuryl esters obtained by the esterification reaction of maleic acid, maleic anhydride, fumaric acid, itaconic acid, etc. and tetrahydrofurfuryl alcohol.

Other copolymerizable monomers can generally be used as long as they have ethylenically unsaturated bonds, but in particular, cyano groups,
Particularly preferred are ethylenic monomers having a carboxyl group, a phosphono group, a sulfo group, an amino group, a hydroxyl group, or a grindyl group. Copolymerizable monomers having any of the above specific functional groups include acrylonitrile, acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, citraconic acid, β-
Methacryloxyacyphdophthalate, β-methacryloxyethyl ambutohexahydrophthalate.

Methacryloquine ethyl phosphate, 2-acrylamido-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, etc. includes.

In addition, those that do not have the above-mentioned specific functional group can also be used,
Esters of acrylic acid or methacrylic acid (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, 2-ethylhexyl, n-octyl,
lauryl, stearyl, 2-butoxyethyl, cyclohexyl, benzyl esters, etc.), styrene and its derivatives (e.g. α-, O-, m- or p-methylstyrene).

pt-butylstyrene), vinyltoluene, etc.

Commonly used polymerization initiators can be used, such as ketone peroxides (eg, methyl ethyl ketone peroxide).

methyl isobutyl ketone peroxide, cyclohexanone peroxide, etc.).

Diacyl peroxides (eg, acetyl peroxide, benzoyl peroxide, etc.).

Hydroperoxides (eg, t-butyl hydroperoxide, etc.).

Examples include dialkyl peroxides, alkyl peresters, percarbonates, and azobisisobutyronitrile.

The reaction solvent may be any inert solvent, but if the reaction solution is used as a product as it is, toluene, xylene,
Methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate.

It is preferable to use butyl acetate, tetrahydrofuran, or the like.

The polymerization reaction can be carried out by blending ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester and another copolymerizable monomer such that the amount of the former is 5 to 95%, and then carrying out solution polymerization.

The polymerization temperature varies depending on the reaction solvent and polymerization initiator used, but is preferably in the range of 50 to 150°C. Polymerization time is usually 7
Requires ~48 hours.

The total monomer concentration in the solution during polymerization is 10 to 70
The weight percent is preferably 20 to 60 weight percent.

The amount of polymerization initiator used is 0.05 to I based on all monomers.
A weight percent range is preferred.

The polymer obtained by the above polymerization reaction preferably has a number average molecular weight of 5.000 or more.

If the number average molecular weight is less than 5.000, the polymer alone has poor film-forming properties, and film-forming properties can be improved by using a curing agent such as polyepoxynde or polyisocyanate, but the drawback is that a large amount of curing agent must be used. will occur.

When the number average molecular weight is 5.000 or more, good film forming properties are exhibited whether used alone or in combination on the curing side.

A method for producing a magnetic paint using the polymer obtained by the above method as a binder component is outlined below.

Solvents used for coating are not particularly limited, but include methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene,
Cyclohexanone, ethyl acetate.

Butyl acetate, tetrahydrofuran and the like are preferred.

In carrying out the present invention, any magnetic powder conventionally used in magnetic paints can be used, such as T-iron oxide powder, cobalt-coated T-iron oxide powder, iron powder, iron-cobalt alloy. Examples include powder.

The polymer containing 5 to 95% by weight of at least one ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester residue in the molecule used as the binder component of the present invention is usually used as a solid content in the magnetic powder. 10-50
% by weight is added.

In the present invention, a polyurethane resin can be blended for the purpose of improving wear resistance. As polyurethane resins, all those conventionally used in magnetic paints can be used;
Basic acids or lactones such as caprolactone, ■ diols such as 2-ethyl-1,3-hexanediol, L,4-butanediol, trimethylbentanediol, and ■
Hexamethylene diisonanate, lysine diiso/anate, methylene bis-4-phenyl diisonanate,
A polyurethane resin comprising a diunisocyanate such as dibutyl fumarate diisonanate or toluene diisonanate, having hydroxyl groups at both ends, and having a molecular weight of 10,000 to 100,000 is preferably used.

A specific example of such polyurethane resin is Unistan 57025703.5711.571 manufactured by BF Gutdrich.
5. Nipporan 2301.2302 manufactured by Nippon Polyurethane
．． Examples include 2304.

The appropriate amount of polyurethane resin to be used is 20 to 150% by weight of the solid content based on the polymer used as the binder component.

Further, in the present invention, a curing agent can be used as necessary. As a curing agent, a low molecular weight polyisocyanate having isocyanate groups at both ends and branches in the main chain,
For example, Coronate, Coronate HL manufactured by Nippon Polyurethane, Takena) D-1 (12, manufactured by Takeda Pharmaceutical Co., Ltd.), etc. are used.

The isocyanate group of these curing agents reacts with the binder component and the hydroxyl group in the polyurethane resin to form a crosslinking bond.
Improves the strength of the paint film. The appropriate amount of the curing agent used is 5 to 50% by weight as a solid content based on the total of the polymer and polyurethane resin used as the binder component.

Further, other binder components such as nitrocellulose, vinyl chloride/vinyl acetate copolymer 1 dispersant, and other additives may be added to the system as long as they do not impair the effects of the present invention.

There are many methods for producing magnetic paint using the above raw materials, one example of which is the following method. That is, the entire amount of the magnetic powder to be used and the entire amount of the binder component, which is an essential component of the present invention, are mixed while adding a solvent to form a suitable clay, and then dispersed using a dispersing machine. When a polyurethane resin is used, a polyurethane resin solution previously dissolved in a solvent is added to the dispersion and the dispersion is performed again.

If necessary, a curing agent can be added to this dispersion to obtain a magnetic paint.

The magnetic paint obtained by the above method includes magnetic powder,
Binder component, polyurethane resin, li! ! It is appropriate that the solid content of the curing agent and various additives be 30 to 75% by weight, and the remaining volatile components, mainly the solvent, be 70 to 25% by weight.

Examples, test examples, and reference examples of the present invention are shown below. In addition, in Examples etc., "parts" means parts by weight.

Example 1 l-1) Production of resin liquid 600 parts of methyl isobutyl ketone was charged into a reactor equipped with a thermometer, an i-stirrer, and a reflux type condenser, and the temperature was raised to 80°C.

To this, 200 parts of methyl methacrylate.

A mixture of 190 parts of tetrahydrofurfuryl methacrylate, 10R of dimethylaminoethyl methacrylate and 2R of azobisisobutyronitrile was added dropwise over 3 hours,
Aging was performed for 10 hours to obtain a resin solution with a solid content of 40%.

1-2) i! Preparation of i-type paint 100 parts of magnetic iron oxide (X-600R; manufactured by Titan Kogyo),
1-1) 75 parts of the resin liquid, 75 parts of methyl ethyl ketone and 75 parts of cyclohexanone were placed in a ball mill and heated for 24 hours.
A magnetic paint was obtained by time cross-dispersion.

Example 2 2-1) Production of resin liquid Instead of each component of Example 1-■), cyclohexanone (
Solvent) 600 parts, acrylonitrile 100 L tetrahydrofurfuryl methacrylate)! , 01. A resin solution having a solid content of 40% was prepared in the same manner as in Example 1-1) except that 180 parts of butyl methacrylate, 20 parts of methacrylic acid and 2 parts of azobisisobutyronitrile were used.

2-2) Preparation of magnetic paint A magnetic paint was obtained in the same manner as in Example 1-2), except that the resin liquid in Example 2-1) was used in place of the resin liquid in Example 1-1. .

Example 3 100 parts of magnetic iron oxide (X-60OR), Example 1-1)
37.5 parts of the resin solution, 64 parts of methyl ethyl ketone, and 64 parts of cyclohexanone were placed in a ball mill and cross-dispersed for 24 hours. A polyurethane resin liquid (25% methyl ethyl ketone solution of Niskun 5703 manufactured by Gutdrich Co., Ltd.) 605B was added to the obtained dispersion and mixed uniformly to obtain a magnetic paint.

Example 4 The magnetic paint was treated in the same manner as in Example 3, except that the resin liquid of Example 2-1) was used in place of the resin liquid of Example 1-1).

Comparative Example 1 ■-1) Production of resin liquid In place of each component in Example 1-1), cyclohexanone 6
A resin solution with a solid content of 40% was obtained in the same manner as in Example 1-1) except that 00 parts of acrylonitrile, 100 L of acrylonitrile, 280 parts of butyl methacrylate, 201 parts of methacrylic acid, and 2 parts of azobisisobutyronitrile were used.

1-2) Preparation of magnetic paint A magnetic paint was obtained in the same manner as in Example 1-1) except that the resin liquid in 1-1) above was used instead of the resin liquid in Example 1-1).

Comparative Example 2 2-1) 'Production of resin liquid Vinyl chloride/vinyl acetate copolymer resin (Union Carbide Co., Ltd. III VAf:, H) was dissolved in methyl ethyl ketone to obtain a resin solution with a solid content of 25%.

2-2) Example 1-2 was prepared using 100 parts of magnetic iron oxide (X-60OR), 1 part of resin solution 12 (1 part of 2-■) above, 53 parts of methyl ethyl ketone and 53 parts of cyclohexanone. ) to obtain a magnetic paint.

Comparative Example 3 3-1) Production of resin liquid A methyl ethyl ketone solution of nitrocellulose (manufactured by Daicel, FM-200) (solid content 25%) was used.

3-2 Preparation of Magnetic Paint Comparative Example A magnetic paint was treated in the same manner as in Comparative Example 2-2) except that the resin liquid in 3-1) above was used instead of the resin liquid in Comparative Example 2-1).

Comparative Example 4 4-1) Production of resin liquid Polyvinyl butyral resin (Made by Block Chemical Co., Ltd., S-LEC B
LS) was dissolved in methyl ethyl ketone to obtain a resin liquid with a solid content of 25%.

4-2) Preparation of magnetic paint A magnetic paint was obtained in the same manner as in Comparative Examples 2-2), except that the resin liquid of 4-1) above was used instead of the resin liquid of Comparative Example 2-1).

Comparative Example 5 A magnetic paint was obtained in the same manner as in Example 3, except that the resin liquid of Comparative Example 1-1) was used instead of the resin liquid of Example 1-1).

Comparative Example 6 Magnetic iron oxide (X-60OR) 100 parts, Comparative Example 2-1
), 53 parts of methyl ethyl ketone, and 53 parts of cyclohexanone were used to treat the magnetic paint in the same manner as in Example 3.

Comparative Example 7 A magnetic paint was obtained in the same manner as in Comparative Example 6 except that the resin liquid of Comparative Example 3-1) was used instead of the resin liquid of Comparative Example 2-1).

Comparative Example 8 A magnetic paint was obtained in the same manner as in Comparative Example 6 except that the resin liquid of Comparative Example 4-1) was used instead of the resin liquid of Comparative Example 2-1).

Test Example 1 Compatibility Test Example 1-1), 2-1), Comparative Example 1-1), 2-
The compatibility of the polymers 1), 3-1), and 4-1) with the polyurethane resin was tested by the following method. That is, polyurethane resins (B, F, Nistan 5703 manufactured by Gutdrich Co., Ltd.) were dissolved in methyl ethyl ketone to prepare a resin liquid with a solid content of 25%.This resin liquid and Example 1-1
), 2-1), Comparative Example 1-1), 2-1),
3-11° and resin liquid of 4-1), respectively, with solid content ratio l:
Mix with l, transfer to a test tube, cover with aluminum foil and 72
The appearance was observed after leaving it for a while. When combining resins with poor compatibility, it is observed that the liquid separates into two phases, but in Comparative Example 1
-1) and 4-1), separation was observed.

Test Example 2 Dispersibility Evaluation Each of the magnetic paints of Examples 1 to 4 and Comparative Examples 1 to 8 was coated on polyethylene terephthalate with a dry film thickness of 20μ,
After drying, the 60° specular reflection gloss of the coating film was measured using a digital automatic colorimeter (Model: 3CH-2D-GV3) manufactured by Toyo Rika Kogyo ■. The results are shown in Table 1.

Chapter 1 Table Note: The higher the gloss (%), the better the dispersibility.

From Table 1, it is clear that the magnetic paint according to the present invention has excellent dispersibility of magnetic powder and maintains sufficiently excellent dispersibility even when polyurethane resin is mixed therein.

Effects of the Invention The magnetic paint of the present invention has excellent dispersibility of magnetic powder. In particular, it has excellent dispersibility even when mixed with polyurethane resin to improve the abrasion resistance of the coating film.

Claims (2)

[Claims] (1) At least one ethylenically unsaturated aliphatic carboxylic acid tetrahydrofurfuryl ester residue in the molecule.
A magnetic paint comprising a polymer containing ~95% by weight, a magnetic powder, and a solvent for the polymer. (2) The magnetic paint according to claim 1, further containing a polyurethane resin.