JPH02209972A - Magnetic coating compound and magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic coating compound providing a magnetic recording medium having excellent magnetic characteristics, electromagnetic conversion characteristics and durability, comprising a vinyl chloride copolymer using a specific hydroxyl group-containing monomer as a binder component. CONSTITUTION:The aimed coating compound which comprises a vinyl chloride copolymer containing hydroxyl group and carboxyl group or a strong acid group having carboxyl sulfur or phosphoric acid, wherein a monomer to supply the hydroxyl group is a monoallyl ether of polyhydroxy compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic coating material using a vinyl chloride resin as a binder for magnetic powder, and a magnetic recording medium using the same.

(Prior Art) Generally, magnetic recording media such as magnetic tapes and floppy disks are produced by coating a polymer film or sheet with a magnetic paint in which ferromagnetic powder is dispersed in an organic solvent using an organic polymer as a binder. Manufactured by.

The organic polymer in this magnetic paint is usually a combination of a relatively hard resin such as PVC, polyvinyl butyral, nitrocellulose, or acetylcellulose, and a soft material such as polyester, polyurethane, or acrylonitrile-butadiene copolymer. In addition, polyisocyanate compounds are often used as thermosetting components to improve the durability of paint films. It is required not only to have appropriate compatibility with molecules and reactivity with polyisocyanates, but also to be compatible with magnetic particles and to disperse them uniformly into the paint.

In recent years, with the increase in the recording density of magnetic recording media and the demand for improved S/N ratio, magnetic particles have become finer and have higher coercive force. In order to form a magnetic layer with a high degree of filling and to achieve the above-mentioned improvement in performance as a medium, the dispersion performance of the binder is a decisively important factor.

Until now, it has been customary to use a low molecular weight surfactant as a dispersant to improve the dispersion of magnetic particles.
There is a natural limit to the amount of dispersant used in terms of durability of the magnetic recording medium, head contamination, etc. Furthermore, from the perspective of improving the reliability of the magnetic recording medium, the binder itself must have a high degree of It is required to have dispersion ability. On the other hand, in order to improve the durability and reliability of the media, it is commonly used, especially in recording magnetic tapes, to crosslink the magnetic layer by incorporating a curable compound, typically a polyisocyanate compound, into the paint. Therefore, it is required to have appropriate reactivity with polyisocyanate as a binder.

In this case, if the reactivity is too good, the pot life of the paint will be short and uneconomical, and if the reactivity is too slow, the expected improvements in durability and runnability will not be seen.

The present inventor conducted an investigation on improving binders for PvC to meet the demands for higher performance of magnetic recording media.
An evaluation of the known PvC binders revealed that the dispersion performance of magnetic particles of vinyl chloride-vinyl alcohol-vinyl acetate copolymer improves as the ratio of vinyl alcohol increases, but the degree of dispersion is low; In addition, as the amount of vinyl alcohol increases, the pot life becomes shorter, the moisture resistance of the coating film decreases, and the rate of thermal decomposition increases. On the other hand, vinyl chloride-maleic acid-vinyl acetate copolymer strongly adsorbs to magnetic particles and exhibits excellent dispersion ability, but the paint tends to thicken and gel, and reactions with polyisocyanate tend to occur locally. be.

In an attempt to solve the problems of these typical PVC binders, a vinyl chloride-vinyl alcohol-vinyl acetate-maleic acid copolymer has been proposed;
Although it has the reactivity of vinyl chloride-vinyl alcohol-vinyl acetate copolymer and the good dispersibility of vinyl chloride-maleic acid-vinyl acetate copolymer, its level is insufficient. Further, this copolymer is usually obtained by saponifying a vinyl chloride-maleic acid-vinyl acetate copolymer, but the polymer deteriorates during saponification and thus has poor chemical thermal stability.

As another attempt, a method using vinyl chloride-hydroxyethyl acrylate-acrylic acid copolymer has been proposed, but in order to satisfy the solubility in the solvent, a relatively large amount of hydroxyethyl acrylic 1 note is used. , the pot life becomes short when a polyisocyanate compound is added. On the other hand, if the amount of copolymerized hydroxyethyl acrylate is reduced to a level where the pot life is appropriate, the solubility in the solvent decreases, and the solution tends to gel and thicken.

[Problem to be solved by the invention]

These conventional pvcO containing alcoholic hydroxyl groups
As a result of intensive studies on how to solve the problem, the present inventors have shown that by using a specific vinyl chloride copolymer, excellent dispersibility and stability of dispersion over time can be achieved even with extremely small amounts of hydroxyl group content. Furthermore, this resin can be used as a binder and polyisocyanate as a curing agent, and a paint with magnetic particles dispersed can be made into polyester. It was confirmed that the magnetic recording medium obtained by coating the film has excellent magnetic properties, electromagnetic conversion properties, and durability.

That is, in the present invention, by using monoallyl ether of a polyhydroxy compound as a monomer that provides a hydroxyl group, sufficient reactivity can be achieved with a smaller amount of hydroxyl group than with other monomers that provide a hydroxyl group. In addition, the magnetic paint using the resin of the present invention as a binder can exhibit good dispersion stability, and the paint can be used to improve chemical and thermal stability. It was discovered that the resulting magnetic recording medium has a coating film with good surface smoothness and durability, as well as excellent running properties, magnetic properties, and electromagnetic conversion properties, leading to the completion of the present invention.

[Means to solve the problem]

That is, the first aspect of the present invention is that at least one component of the binder of the magnetic powder is a copolymer of vinyl chloride containing a hydroxyl group and a carboxylic acid group or a strong acid group containing sulfur or phosphorus, and a monomer supplying the hydroxyl group. The second invention relates to a magnetic paint characterized in that the body is a monoallyl ether of a polyhydroxy compound, and the second invention relates to a magnetic paint in which at least one component of the binder of the magnetic powder is a strong acid containing a hydroxyl group and a carboxylic acid group, or sulfur or phosphorus. The present invention relates to a magnetic recording medium characterized in that a magnetic paint is used, which is a copolymer of vinyl chloride containing hydroxyl groups, and the monomer supplying the hydroxyl groups is a resin of monoallyl ether of a polyhydroxy compound.

The amount of monotriether used in these polyhydroxy compounds is such that the hydroxyl group in the copolymer is O,OS ~ 3.0% by weight.
It is preferably used in an amount of 0.1 to 2.0% by weight. If it is less than 0.05% by weight, the crosslinking effect with the polyisocyanate will not be exhibited, and if it exceeds 3.0% by weight, the pot life will be too short.

Examples of monoallyl ethers of polyhydroxy compounds that provide hydroxyl groups in the copolymer according to the present invention include allyl-
2-hydroxyethyl ether, allyl-2-hydroxypropyl ether, allyl-3-hydroxypropyl ether, allyl-2-hydroxybutyl ether, allyl-3-hydroxybutyl ether, allyl-4-hydroxybutyl ether, allyl-6-hydroxyethyl ether Alkylene glycol monoallyl ethers such as diethylene glycol monoallyl ether,
Polyoxyalkylene glycol monoallyl ethers such as dipropylene glycol monoallyl ether, glycerin monoallyl ether, allyl-2-chloro-3
-Halogen-substituted (poly)alkylene glycols such as hydroxypropyl ether, allyl-2-hydroxy-3=chloropropyl ether, monoallyl ethers of hydroxy-substituted products, and monoallyls of polyhydric phenols such as eugenol and isoeugenol. In addition to the ethers of allyl alcohol and polyhydroxy compounds listed above, which include ethers and their halogen-substituted products, thioethers using allyl thiol instead of allyl alcohol are also monomers that provide hydroxyl groups according to the present invention. Examples include allyl-2-
Examples include hydroxyethyl thioether and allyl-2-hydroxypropyl thioether.

A carboxylic acid group-containing monomer is used as a method for imparting a carboxylic acid group to the copolymer according to the present invention.

Examples of carboxylic acid group-containing monomers include unsaturated mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and crotonic acid, and monoalkyl esters of unsaturated dicarboxylic acids such as maleic acid and itaconic acid. etc. can be used. This monomer is preferably used in a range where the carboxylic acid group in the copolymer is 0.3 to 5.0% by weight; if it is less than this, the dispersibility of the magnetic powder will be poor; If the amount is higher, the paint tends to gel and thicken.

Further, the equivalent ratio of hydroxyl group to carboxylic acid group is 0.1 to 3.
0, preferably 0.2 to 2.0; if this ratio exceeds 3.0, the dispersibility of the magnetic powder will decrease significantly, and if it is less than 0.1, the monomerization of the polyhydroxy compound will decrease. There is no effect of adding allyl ether.

Monomers for introducing strong acid groups containing sulfur or phosphorus into the polymer according to the present invention include strong acids containing sulfur or phosphorus, such as sulfonic acid, sulfuric acid, phosphoric acid, and phosphonic acid, and alkali metal salts thereof, or Examples include radically polymerizable monomers having ammonium salts. Among the strong acids,
Sulfonic acids and their salts are readily available (and there are many types, such as vinyl sulfonic acid, methylvinyl sulfonic acid, (meth)allylsulfonic acid, styrene sulfonic acid,
Examples include acids such as ethyl meth)acrylate-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid, and their alkali metal salts and ammonium salts. Examples of monomers containing sulfuric acid and its salts include acids such as (meth)acrylic M-2-ethyl sulfate and 3-allyloxy-2-hydroxypropane sulfate, and their alkali metal salts or ammonium salts.

Examples of monomers containing phosphoric acid salts include propyl (meth)acrylate-3-chloro-2-phosphate, ethyl (meth)acrylate-2-phosphate, and 3-allyloxy-
Examples of monomers in which acids such as 2-hydroxypropane phosphoric acid and their alkali metal salts or ammonium salts have phosphonic acid salts include vinylphosphonic acid, acrylamide methanephosphonic acid, and ethyl 2-phosphonate.
Examples include acids such as (meth)acrylate and 3-allyloxy-2-hydroxypropanephosphonic acid, and their alkali metal salts or ammonium salts.

The content of strong acid groups containing sulfur or phosphorus in the copolymer is determined by burning the resin using an oxygen combustion flask method and measuring the amount of sulfur or phosphorus in the resin as sulfuric acid or phosphoric acid.
O4- or po-- is used in an amount of 0.1 to 4.0% by weight, preferably 0.3 to 2.0% by weight. If it is less than 0.1% by weight, the dispersibility of the magnetic powder will be insufficient, and if it exceeds 4.0% by weight, the hydrophilicity of the strong acid group will become strong, which will not only result in insufficient solubility in solvents, but also cause the coating film to deteriorate. Moisture resistance decreases, and furthermore, magnetic powder agglomerates, resulting in poor dispersibility.

Moreover, it is also possible to use other copolymerizable monomers in combination, if necessary. Examples of other comonomers include carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; methyl vinyl ether, isobutyl vinyl ether,
Vinyl ethers such as cetyl vinyl ether; vinylidenes such as vinylidene chloride and vinylidene fluoride; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; unsaturated carboxylic acid anhydrides such as maleic anhydride; diethyl maleate , unsaturated carboxylic acid alkyl esters such as dibutyl maleate, diethyl itaconate, methyl (meth)acrylate, and ethyl (meth)acrylate; olefins such as ethylene and propylene; unsaturated nitriles such as (meth)acrylonitrile; styrene,
Examples include aromatic vinyls such as α-methylstyrene and p-methylstyrene; epoxy-containing carmers such as allyl glycidyl ether, glycidyl methacrylate, and vinyl cyclohexene monoxide.

These comonomers adjust the compatibility and softening point of the copolymer and other resin when they are mixed together. Used to improve the solubility of copolymers.

In particular, when copolymerizing an epoxy-containing monomer with a hydroxyl-containing monomer and vinyl chloride, sulfur or phosphorus may be added to the epoxy group site in an aqueous or non-aqueous system during the copolymerization reaction, or before or after the reaction. It is also possible to adopt a method of adding an alkali metal salt or ammonium salt of a strong acid. Examples of alkali metal salts or ammonium salts of strong acids containing sulfur or phosphorus in that case include potassium sulfite, sodium thiosulfate, ammonium hydrogen sulfate, disodium hydrogen phosphate, ammonium hydrogen phosphite, potassium sulfanilate, Examples include potassium sulfate and sodium superphosphate. The method of adding a strong acid salt containing sulfur or phosphorus in the copolymerization of this epoxy group-containing monomer and vinyl chloride is disclosed in Japanese Patent Application Laid-Open No. 60-238306.
, JP-A-60-238371 and JP-A-61-5336
7 is described in more detail.

The degree of polymerization of the copolymer is 200 to 900, preferably 250
~500. If it is less than 200, the abrasion resistance of the magnetic layer will be insufficient, and if it exceeds 900, the viscosity of the paint will be high and the dispersion of magnetic particles will tend to be insufficient.

The resin for magnetic coatings according to the present invention can be produced by any known polymerization method.From the viewpoint of solubility of a single polymer, the resin can be produced by solution polymerization or by using a lower alcohol such as methanol or ethanol alone as a polymerization medium, or a lower alcohol such as methanol or ethanol. Preferably, they are prepared by a suspension polymerization method using a combination of 1 and 2 and deionized water, and emulsion polymerization is advantageous when water-soluble salts with strongly acidic radicals containing sulfur or phosphorus are used in the reaction.

Examples of polymerization initiators used in the production of resins include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, and 3.5.5-trimeprhexa. Examples include organic peroxides such as noyl peroxide, ab compounds such as α,α′ azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and the like. Suspending agents include, for example, polyvinyl alcohol, partially saponified polyvinyl acetate, cellulose derivatives such as methylcellulose, polyvinylpyrrolidone, maleic anhydride-vinyl acetate copolymer, synthetic polymeric substances such as polyacrylamide, and starch. Examples include anionic emulsifiers such as natural high acid sodium chloride such as gelatin, and nonionic emulsifiers such as polyoxyethylene alkyl ether and polyoxyethylene sorbitan fatty acid partial ester. Further, molecular IT regulators such as trichlorethylene and thioglycol can also be used if necessary. The above-described polymerization initiator, vinyl chloride and other monomers, suspending agents, emulsifiers, molecular weight regulators, etc. may be added to the polymerization system all at once at the start of polymerization, or they may be added in portions during polymerization. 0 polymerization is usually 35~
It is carried out under stirring at a temperature of 80°C.

The vinyl chloride copolymer obtained in this way is generally used as a vinyl chloride resin binder for magnetic paints, and is generally used in an arbitrary solvent solution together with a polyurethane resin, a curing agent typified by polyisocyanate, and magnetic powder. It is prepared and ready for use.

Typical examples of polyurethane resins include those obtained by reacting polyester polyols or polyether polyols with isocyanates.
Particularly preferred are those in which hydroxyl groups remain. In addition, vinyl chloride-vinyl acetate copolymer resin, cellulose resin, phenoxy resin, epoxy resin, butyral resin,
It is also possible to use common resin binders for magnetic coatings, such as acrylic resins and acrylonitrile-butadiene rubber, as long as the object of the present invention is achieved.

In addition, as magnetic powder, r-Fe40x+ Pe30
*,C.

In addition to powders of iron oxides such as γ-PezO,, Co-containing Fe-04, and Cry powders, Fe powders, Fe-Co
Metallic magnetic powders such as powders are also used. .

In the resin according to the present invention, as a hydroxyl group-containing component,
By replacing the saponified hydroxyl group in the vinyl acetate portion with the above-mentioned hydroxyl group, the reactivity with isocyanate can be greatly improved, thereby making it possible to significantly reduce the number of hydroxyl groups required for the reaction. The reason for this is not clear, but the hydroxyl groups that participate in the reaction are separated from the main chain of the copolymer, increasing the degree of freedom.
This is probably due to the uniform distribution of hydroxyl groups.

The mechanism of the dramatic improvement in magnetic powder dispersibility is thought to be due to the fact that reactivity is achieved with a smaller amount of hydroxyl groups, which reduces the interaction between carboxyl groups and hydroxyl groups, resulting in stable dispersion of the magnetic paint. The high properties are also thought to be due to the low interaction with fatty acids commonly used as lubricants.

The present invention will be specifically explained below using examples. Note that parts and percentages on each side are based on weight.

Example 1 100 parts of inyl chloride, 3 parts of glycerin monoallyl ether
180 parts of acetone, and 2 parts of benzoyl peroxide were charged into an autoclave, and after degassing, polymerization was started at a temperature of 50°C. Immediately after, 3 parts of maleic anhydride, 10 parts of vinylidene chloride, and 40 parts of methanol were thoroughly mixed in advance. After continuously injecting the material into the autoclave, the reaction pressure is 1 k.
g/cd, unreacted vinyl chloride is collected,
Resin A was obtained by adding 250 parts of water and heating to 70°C to separate the solvent and copolymer, followed by drying. The suitability of this resin for use in magnetic recording media was evaluated by the test method (1) for evaluation of resin properties described below.

Example 2 100 parts of vinyl chloride, 8 parts of vinyl acetate, 5 parts of allyl-2-hydroxyethyl ether, 3 parts of itaconic acid, 120 parts of methanol, 120 parts of deionized water, 0.6 parts of methyl cellulose, 0.2 parts of sodium lauryl sulfate. 1.2 parts of lauroyl peroxide were placed in an autoclave and heated to 60°C after degassing.
Polymerization was started, and when the weight reached 3 kg/-, unreacted vinyl chloride was collected, and the copolymer was collected by dehydration, washed with cold water, and dried to obtain resin B. This resin was evaluated for resin properties (evaluated by 11 test methods).

Example 3 Resin C was obtained in the same manner as in Example 2 except that allyl-2-hydroxy-3-chloropropyl ether was used instead of allyl-2-hydroxyethyl ether.

This resin was evaluated by the test method of evaluation of resin properties (1).

Example 4 60 parts of vinyl chloride, 5 parts of allyl-2-hydroxypropyl ether, 2 parts of monomethyl maleate, 8 parts of vinyl acetate
1 part, deionized water 150 parts, azobisisobutyronitrile 1 part, polyoxyethylene stearyl ether 1 part, and methyl cellulose 0.1 part were charged into an autoclave, and after degassing, polymerization was started at 60°C, and vinyl chloride 4
0 part was continuously injected into an autoclave from 3 hours after the start of polymerization to 7 hours, and when the pressure of the autoclave reached 3 kg/cd, unreacted vinyl chloride was recovered, and after dehydration, deionized water was added. The resin was washed with water and dried to obtain a resin. This resin was evaluated by the test method of evaluation of resin properties (1).

Example 5? Resin E was obtained in the same manner as in Example 5, except that allyl-6-hydroxyethyl ether was used instead of 1J-2-hydroxypropyl ether. This resin was evaluated by the test method of evaluation of resin properties (1).

Comparative Example 1 Resin F was obtained in the same manner as in Example 1 except that 2-hydroxyethyl methacrylate was used instead of glycerin monoallyl ether. This resin was evaluated by the test method of evaluation of resin properties (1).

Comparative Example 2 100 parts of vinyl chloride, 10 parts of isobutyl vinyl ether, 180 parts of acetone, and 2 parts of benzoyl peroxide were charged into an autoclave, and after degassing, polymerization was started at 55°C. Immediately after that, 4.5 parts of acrylic acid, 1 part of water, 5 parts, methanol 44
A mixture of 5 parts of 2-hydroxyethyl methacrylate and 5 parts of 2-hydroxyethyl methacrylate
Continuously inject a mixture of 1 part and 45 parts of methanol from separate injection ports until the pressure of the autoclave reaches 2.0 kg/-, and when the pressure reaches 1.0 kg/-, Collect unreacted vinyl chloride and add 25 ml of deionized water.
After adding 0 parts and heating, the solvent and copolymer were separated and dried to obtain Resin G. This resin was evaluated by the test method of resin characteristics (1).

Comparative Example 3 Example 4 except that hydroxypropyl methacrylate was used instead of allyl-2-hydroxypropyl ether
Resin H was obtained in the same manner as above.

This resin was evaluated by the test method of resin characteristics (1).

Comparative Example 4 Resin I was obtained in the same manner as Comparative Example 2, except that 2-hydroxyethyl methacrylate was used as 20 parts and that isobutyl vinyl ether was not used. This resin was evaluated by the test method of resin properties [1].

Comparative Examples 5 to 7 50 parts of vinyl chloride, 20 parts of vinyl acetate, 180 parts of acetone
1 part and 2 parts of benzoyl peroxide into an autoclave.
After degassing, polymerization was started at 55° C., and 50 parts of vinyl chloride was injected into the autoclave in 5 parts each time the pressure of the autoclave decreased by 0.5 kg/d. On the other hand, immediately after the start of polymerization, 5 parts of maleic anhydride and 45 parts of methanol were continuously injected into the autoclave until the pressure of the autoclave was 1.
kg/-, unreacted vinyl chloride was collected.Next, the reaction solution was added to a mixture of 1000 parts of methanol and 6 parts of 65% nitric acid, and the mixture was stirred and heated at 70°C for 12 hours. An additional 1000 parts of deionized water was added to separate and recover the copolymer from the medium.

Thereafter, 500 parts of acetone and the copolymer were stirred and mixed at 60° C., then 1000 parts of methanol was added, the copolymer was separated and recovered, and further washed with water and dried to obtain Resin J. This resin was evaluated by the test method of evaluation of resin properties (1).

The compositions of these copolymers are shown in Table 1 along with commercially available vinyl chloride-vinyl acetate-maleic acid terpolymer (K) and vinyl chloride-vinyl acetate-vinyl alcohol (L). The percentage of carboxy groups in the copolymer was determined by titration, and the percentage of hydroxyl groups in the copolymer was determined by infrared absorption analysis.

(Evaluation of resin properties (1)) Next, the samples obtained in Examples 1 to 5 and Comparative Examples 1 to 7 were evaluated as magnetic paints and magnetic recording media by the following method. The results are shown in Table 1.

■) Add 100 parts of pot-life vinyl chloride copolymer to 2 parts of methyl ethyl ketone.
00 parts of vinyl chloride copolymer, 100 parts of methyl isobutyl ketone, and 100 parts of toluene with stirring at 65°C for 1 hour.
20 parts per part was added and stored at 23°C, and the pot life was defined as the number of days until the solution stopped flowing even when the container was turned upside down.

2) A sheet obtained by casting the solution used in the reactivity pot life test on a glass plate is treated at 60° C. for 24 hours. After accurately weighing 0.5 g of this sheet and mixing it with 50 g of tetrahydrofuran for 24 hours, insoluble matter is filtered and washed, dried, and accurately weighed.

Gel fraction = weight of undissolved content / weight of sample (%) 3) The solution used for the thermal stability pot life test was cast onto a glass plate kept horizontal with a spirit level, and a 0.2 mm thick sample was cast. This sheet is heated in an oil bath at 80° C. according to JIS-6723, and the time until the Congo red paper changes color is measured.

4) 400 parts of glossy cobalt-coated magnetic iron oxide powder (specific surface area: 30 m
/g), 50 parts of vinyl chloride copolymer, 40 parts of polyurethane resin (hydroxyl group content 0.3%, 1.4-butanediol adipate-MDI system molecular weight 70.000), 500 parts methyl ethyl ketone, 300 parts methyl isobutyl ketone, After dispersing a mixture consisting of 300 parts of toluene, 2 parts of carbon blank, 4 parts of alumina, 2 parts of myristic acid, and 1 part of butyl stearate under high-speed shearing for 90 minutes, 15 parts of polyisocyanate (Coronate L manufactured by Nippon Polyurethane Industries, Ltd.) was added. In addition, the mixture was further dispersed for 15 minutes to obtain a magnetic paint.

The obtained magnetic paint was applied to a polyester film with a film thickness of 5
It was coated to a thickness of μm, subjected to magnetic field orientation treatment, and then dried.

The reflectance of the magnetic coating film at a reflection angle of 60 parts was measured using a glossmeter.

5) Dispersion stability After allowing the paint used to evaluate glossiness to stand for 1 hour, it was applied onto a polyester film to a film thickness of 5 μm.
After being subjected to magnetic field orientation treatment, it was dried, and the reflectance of the magnetic coating film at a 60 parts reflection angle was measured using a gloss meter.

6) Squareness ratio (fir/am) The magnetic coating used for gloss evaluation was 12.5 n+ x
It was cut into 50 mm pieces and measured using a magnetic property measuring machine.

7) The magnetic coating used for durability and gloss evaluation was smoothed with a calendar roll and then heat-treated at 65°C for 65 hours, and then brought into contact with a rotating drum covered with abrasive paper under a load of 100 g. It was rotated at 150 rpm, and the extent to which the magnetic paint adhered to the abrasive paper was visually observed and measured in three stages A, B, and C.

A: No stain, B: Slight stain, C: Much stain Example 6 117 parts of methanol and 0.6 parts of methylcellulose were added to the polymerization vessel.
1 part, 0.2 part of polyoxyethylene sorbitan fatty acid partial ester was charged, the can was sealed, and after degassing under reduced pressure, 1 part of vinyl chloride was charged.
00 parts of vinyl acetate, 10 parts of vinyl acetate, and 6 parts of allyl-2-hydroxypropyl ether were charged and stirred at 50°C. Then 3,5,5-trimethylhexanoyl peroxide 0.
At the same time, 8 parts of methanol was added to start polymerization.
After 10 hours of 0 reaction, 3 parts of 2-acrylamido-2-methylpropanesulfonic acid dissolved in 0 parts was continuously charged at a constant rate so that the entire amount was consumed in 8 hours, and the pressure in the polymerization vessel was 2 kg/c+J. At the point when
I got it. The suitability of this resin for use in magnetic recording media was evaluated by the test method (2) for evaluation of resin properties described below.

Example 7 Resin (0) was obtained in the same manner as in Example 6 except that ethyl methacrylate-2-phosphate was used instead of 2-acrylamido-2-methylpropanesulfonic acid. This resin was evaluated by the test method of evaluation of resin properties (2).

Example 8 Resin CP) was obtained in the same manner as in Example 6, except that sodium styrene sulfonate was used instead of 2-acrylamido-2-methylpropanesulfonic acid. This resin was evaluated by the test method of evaluation of resin properties (2).

Example 9 Resin (Q) was obtained in the same manner as in Example except that eugenol was used instead of allyl-2-hydroxyethyl ether. This resin was evaluated by the test method of evaluation of resin properties (2).

Example 10 Acetone at 180°C, 70 parts of deionized water, 2 parts of lauroyl peroxide, 6 parts of allyl-2-hydroxy-3-chloropropyl ether, and 10 parts of 3-allyloxy-2-hydroxypropane ammonium sulfate were placed in a polymerization vessel. After adding 10 parts of isobutyl vinyl ether and degassing, 100 parts of vinyl ether was added.
The polymerization pressure was 3 kg/- when the temperature was raised to 55℃.
When the temperature reached 1, unreacted vinyl chloride was recovered under reduced pressure, the reaction solution was mixed with 1000 parts of deionized water, and the resin was separated and dried to obtain resin (R).

Example 11 A polymerization vessel was charged with 150 parts of deionized water, 1 part of sodium lauryl sulfate, and 1 part of potassium persulfate, and after degassing, 60 parts of vinyl chloride, 3 parts of vinyl acetate, 3 parts of isobutyl vinyl ether, and allyl-2- 6 parts of hydroxypropyl ether was charged and the temperature was raised to 60°C to start polymerization. After the start of polymerization, a mixture of 2 parts of sodium styrene sulfonate and 50 parts of water was continuously injected over 10 hours, while 40 parts of Vinyl chloride was divided into four parts and reacted for 10 hours, and unreacted vinyl chloride was collected to obtain a polymerization solution. 100 parts of this polymerization solution was mixed with 5 parts of methyl ethyl ketone, frozen and thawed, and the polymer was collected, washed and dried to obtain a resin (S). This resin was evaluated by the test method of resin property evaluation method (2).

Comparative Example 8 Without using allyl-2-hydroxypropyl ether, 2
Resin (T) was obtained in the same manner as in Example 6, except that 8 parts of -hydroxypropyl methacrylate and 3 parts of 2-acrylamido-2-methylpropanesulfonic acid were charged during the reaction. This resin was evaluated by the test method of resin property evaluation method (2).

Comparative Example 9 Resin (U) was obtained in the same manner as Comparative Example 8 except that propyl methacrylate was used instead of 2-hydroxypropyl methacrylate. This resin was evaluated by the test method of resin property evaluation method (2).

Comparative Example 10 Resin (
V) was obtained. This resin was evaluated by the test method of resin property evaluation method (2).

Comparative Example 11 100 parts of commercially available vinyl chloride-vinyl acetate-vinyl alcohol copolymer (Mi composition: 91% by weight of vinyl chloride, 3% by weight of vinyl acetate, 6% by weight of vinyl alcohol), 10 parts of sodium 2-chloroethylsulfonate and 500 parts of dimethylformamide were stirred and mixed at 20° C., 5 parts of pyridine was added dropwise little by little into this mixed solution, and stirring was continued for 3 hours. The resulting reaction solution was mixed with 5000 parts of deionized water to recover the resin, dissolved in tetrahydrofuran, reprecipitated with methanol, dried, and the resin (
W> was obtained. This resin was evaluated by the test method of resin property evaluation method (2).

Comparative Examples 12 to 14 180 parts of acetone, 2 parts of benzoyl peroxide, and 25 parts of vinyl acetate were charged into a polymerization vessel, and after degassing, 50 parts of vinyl chloride was charged and polymerization was started at 55°C, followed by 3 parts of sodium styrene sulfonate. A mixture of 50 parts of vinyl chloride and 17 parts of deionized water was continuously injected at a constant rate for 8 hours, while 50 parts of vinyl chloride was charged in 4 parts and reacted for 10 hours, after which unreacted vinyl chloride was recovered. A polymerization solution was obtained. To this polymerization solution, 300 parts of methanol and 6 parts of 65% nitric acid were added.
After heating and stirring at 0°C for 12 hours, 1000 parts of deionized water was added to separate the resin. Furthermore, acetone 400
1 part and 5 parts of propion oxide were added thereto, mixed at 60° C. for 2 hours, mixed with 1000 parts of methanol, and dried to obtain resin (X). This resin was evaluated by the test method of resin property evaluation method (2).

The properties of these resins are as follows: commercially available vinyl chloride-vinyl acetate-
It is shown in Table 2 together with the maleic acid terpolymer (Y) and the vinyl chloride-vinyl acetate-vinyl alcohol terpolymer (Z). The amount of hydroxyl groups in the resin was determined by infrared absorption analysis, the amount of vinyl chloride was determined by quantifying chlorine by combustion, and the amount of strong acid groups was determined by a combination of elemental analysis and infrared absorption analysis.

(Evaluation of resin properties (2)) Next, the resins obtained in Examples 6 to 11 and Comparative Examples 8 to 14 were evaluated as magnetic paints and magnetic recording media. The results are shown in Table 2. The evaluation method was as follows.

1) 100 parts of soluble vinyl chloride copolymer, 20 parts of methyl ethyl ketone
Prepare a solution consisting of 0 parts of toluene and 200 parts of toluene, and visually check the degree of transparency of this solution.

Judgment was made in three stages: B and C.

A: Transparent, B: Few insolubles, C: Many insolubles 2) 1.0 g of heat-stable vinyl chloride copolymer was placed in a 15 cc test tube, and the opening was covered with absorbent cotton with Congo red test paper in between. The container was sealed with a stopper and placed in an oil bath at 150° C., and the time until Congo red test paper changed color due to the generated hydrochloric acid was measured.

3) 400 parts of dispersion-stable metal iron magnetic powder, 100 parts of vinyl chloride copolymer,
A mixture consisting of 300 parts of methyl ethyl ketone, 300 parts of methyl isobutyl ketone, and 300 parts of toluene was subjected to high-speed shear dispersion for 90 minutes. This dispersed paint was collected in a sample bottle and stored in a constant temperature bath at 25° C., and the state of gel formation was observed. The generation of gel was determined by taking out a portion of the dispersed paint onto a glass plate, diluting it with about 5 times the amount of methyl ethyl ketone, mixing with a glass rod, and visually observing. They are shown as A, B, and C in descending order of gel formation.

4) 400 parts of shiny metallic iron magnetic powder, 70 parts of vinyl chloride copolymer, 30 parts of polyurethane resin (Nipporan 2304 manufactured by Nippon Polyurethane Industry Co., Ltd.), 300 parts of methyl ethyl ketone, 300 parts of methyl isobutyl ketone, 300 parts of toluene, higher fatty acid 90 parts of a mixture of 4 parts and 2 parts of silicone oil.
After high-speed shear dispersion for a minute, 15 parts of polyisocyanate (Coronate, manufactured by Nippon Polyurethane Industries) and 100 parts of cyclohexanone were added, and the mixture was further dispersed for 90 minutes to obtain a magnetic paint. The obtained magnetic paint was applied onto a polyester film to a film thickness of 5 μm, subjected to magnetic field orientation treatment, and then dried. The reflectance of the magnetic coating film at a reflection angle of 60 parts was measured using a glossy needle.

5) Squareness ratio (Br/Bad) The magnetic coating used for gloss evaluation was 12.5 fl x 50
It was cut out into a dragon shape and measured using a magnetic property measuring machine.

6) The magnetic coating used for durability and gloss evaluation was smoothed with a calendar roll, then heat treated at 6.5°C for 65 hours, and then brought into contact with a rotating drum covered with abrasive paper under a load of 100g. The paper was rotated at 150 rpm, and the degree of adhesion of the magnetic paint to the abrasive paper was visually observed and evaluated in four grades: A, B, C, and D.

A: No stain, B: Slight stain, C: Slight stain, D: Lots of stain 7) The force generated between the paint film and the rotating drum was measured at 65°C and relative humidity using the same method as in running performance and durability evaluation. Measured using a U gauge in an 80% atmosphere, A is ranked in descending order of running resistance.

Judgment was made in three stages: B and C.

A: Low, B: Medium, C: High

Claims (1)

[Claims] 1. At least one component of the binder of the magnetic powder is a vinyl chloride copolymer containing a hydroxyl group and a carboxylic acid group or a strong acid group containing sulfur or phosphorus, and the monomer supplying the hydroxyl group is A magnetic paint characterized by being a monoallyl ether of a polyhydroxy compound. 2. At least one component of the binder of the magnetic powder is a copolymer of vinyl chloride containing a hydroxyl group and a carboxylic acid group or a strong acid group containing sulfur or phosphorus, and the monomer that supplies the hydroxyl group is a monoallyl of a polyhydroxy compound. A magnetic recording medium characterized by using a magnetic paint made of ether resin.