JPS629521A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of the magnetic powder of ultrafine particles in a magnetic coated film by incorporating a copolymer consisting of respectively prescribed weight % of vinyl chloride, vinyl ester of carboxylic acid, hydroxyalkyl acrylate and phosphate and the magnetic powder into said film. CONSTITUTION:The content of the vinyl chloride is adequately 50-90wt% of the total component. The viscosity of the magnetic paint obtd. by mixing the same with the magnetic powder increases and a large amt. of a solvent is required to maintain the adequate viscosity in the stage of coating when the content exceeds 90wt%. The strength of the coated film deteriorates when the content is below 50wt%. The adequate content of the vinyl ester of carboxylic acid is 0.1-40wt% of the content of the copolymer and the dispersibility deteriorates when the content exceeds 40wt%. The adequate content of the hydroxyalkyl acrylate is 0.1-30wt% of the content of the copolymer and the solubility with solvents deteriorates when the content exceeds 30wt%. The adequate content of the copolymerizable vinyl-contg. phosphate is 0.1-10wt% of the content of the copolymer and the solubility with solvents deteriorates when the content exceeds 10wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic cards.

[Conventional technology]

Generally, a magnetic recording medium is one in which a magnetic coating film is formed by fixing magnetic powder with a binder on a non-magnetic support such as polyester, and magnetic tapes, magnetic cards, etc. are known.

And magnetic recording media in general, especially audio tape,
In order to obtain excellent electromagnetic conversion characteristics, t-deo tape requires uniform dispersibility of the magnetic powder in the magnetic coating film and high surface smoothness of the magnetic coating film, and in order to satisfy these requirements, various types of Binders have been proposed.

Among them, dilychloride/vinegar a! is commonly used. It is known that Nyl-based copolymers have good dispersibility of magnetic powder and provide excellent electromagnetic properties, but this copolymer also has excellent adhesion to the base film and wear resistance of the magnetic coating. In order to improve properties and durability, im-based binder,
In particular, polyurethane is often used together.

However, polyurethane generally has poor dispersibility of magnetic powder, so the blending ratio with the vinyl chloride/vinyl acetate copolymer is determined by sacrificing some of its various properties, or by using other blending agents. These problems have been solved by improving the balance of properties and by making five different complex formulations.

Furthermore, BF, a magnetic powder that aims to improve the performance of recent magnetic tapes! For ultrafine particles of 7507112/17 or more, conventional binders lack the dispersibility of the mother powder, and it has become extremely difficult to obtain a magnetic coating film sufficient for practical use.

Also, JP-A-56-77950, JP-A-57-1
As shown in Japanese Patent Publication No. 35437, vinyl chloride/hydroxyl group-containing -nyl monomer system copolymers have been proposed, and in addition to these, there are also
Application to a magnetic recording medium using ultrafine resin magnetic powder as shown in Publication No. 2-24558 is also considered,
In either case, the dispersibility of the ultrafine magnetic powder is not sufficient.

[Problem that the invention seeks to solve]

Dispersibility of ultrafine magnetic powder in magnetic coatings.

[Means for solving problems]

The present invention includes 50 to 90% by weight of vinyl chloride, 0.1 to 4011% of vinyl carboxylate, 0.1 to 50111:td of hydroxyargyl acrylate, and 0.1% of vinyl group-containing phosphoric acid ester copolymerizable with these. This is a magnetic recording medium containing a copolymer consisting of ~10% by weight of each unit and magnetic powder.

The copolymer used in the present invention is a resin or resin solution obtained by copolymerizing each monomer so that the proportion of each unit is as follows.The weight proportion of each component unit is as follows. It is as follows.

The appropriate amount of vinyl chloride is 50 to 90% by weight of the total components; if it exceeds 90% by weight, the magnetic paint obtained by mixing with the magnetic powder will have a high viscosity, so a large amount must be used to maintain the appropriate viscosity during application. of solvent, and less than 50% by weight requires 3% of solvent.
! ! The strength of the membrane decreases.

Examples of carboxylic acid vinyl esters include diyl acetate, ♂yl furoate, and t-nyl stearate. Among these, W=l acetate is preferable, and the content in the copolymer is 0. 1 to 40% by weight is preferred, and 2 to 20% by weight is particularly preferred.

If it exceeds 40% by weight, dispersibility will decrease.

Examples of hydroxyargyl acrylate include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-1-methylethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, and 2-hydroxy-1-methylethyl methacrylate. etc. The appropriate content in the copolymer is 0.1 to 50% by weight, and if it exceeds 60% by weight, the solubility in solvents will decrease.

As the copolymerizable vinyl group-containing phosphate ester, 2
-Ashitsu V phosphooxyethyl acrylate, 6-chloro-2-Ashitsu W phosphooxypropyl acrylate,
2-acid phosphooxyprotacrylate, 2-
Acid F phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate, 2-acid phosphooxypropyl methacrylate,
2-diphenylphosphooxyethyl acrylate, 2-
Examples include dibutylphosphooxyethyl acrylate, 2-cyphenylphosphooxyethyl methacrylate, and 2-dibutylphosphooxyethyl methacrylate. The appropriate content in the copolymer is 0.1 to 10% by weight, and if it exceeds 10% by weight, the solubility in solvents will decrease.

Next, a general method for producing the copolymer used in the present invention will be explained.

Polymerization can be carried out by a commonly used solution polymerization method.

That is, a suitable polymerization solvent and a predetermined amount of vinyl chloride, vinyl carboxylate ester, hydroxyargyl acrylate, and copolymerizable vinyl group-containing phosphate ester may be charged, a polymerization initiator may be added, and the mixture may be heated. Here, the vinyl group-containing phosphoric acid ester that can be copolymerized with hydroxyargyl acrylate can be added all at once at the initial stage of polymerization, or added in portions as the polymerization progresses. In order to obtain the desired copolymer powder, it is better to add it in portions.Next, from the copolymer solution obtained in this way, remove the solvent by a conventional method to obtain the desired copolymer powder, or It can also be used in solution form depending on the solvent composition.

The method for producing the magnetic recording medium of the present invention is based on 100 parts by weight of the above copolymer, 200 to 600 parts by weight of magnetic powder, preferably 500 to 500 parts by weight, and 600 to 1,200 parts by weight of organic solvent, preferably 800 to 1,000 parts by weight. 5 to 50 parts by weight, preferably 10 to 60 parts by weight of the thermosetting resin.

Furthermore, other thermoplastic resins, dispersants, lubricants, antistatic agents, abrasives, etc. can be added as necessary.

Other thermoplastic resins include vinyl chloride copolymers such as vinyl chloride/vinyl acetate copolymers, vinyl chloride/acrylonitrile copolymers, ♂yl chloride/C-nylidene chloride copolymers, and vinylidene chloride/acrylonitrile copolymers. Copolymers, vinylidene chloride copolymers such as vinylidene chloride/methacrylic acid ester copolymers, cellulose derivatives such as nitrocellulose and cellulose acetate, thermoplastic urethane elastomers 1. Butadiene/acrylonitrile copolymer, polyester resin, styrene/butadiene copolymer, amino resin, saturated polyester resin, thermoplastic acrylic ester resin, thermoplastic methacrylic ester resin, synthetic thermoplastic resin etc. and mixtures thereof are used.

As thermosetting resins, polyisocyanates such as aromatic polyisocyanates and aliphatic polyisocyanates, or urethane prepolymers are mainly used, and in addition, phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, and acrylic resins are used. Reactive resins, epoxy polyamide resins, nitrocellulose melamine resins and mixtures thereof are used, among which urethane resins, epoxy resins and phenolic resins are suitable.

Further, as the magnetic powder used in the present invention, for example, γ-
ye2o3 powder, lFe3O4 powder, 1-Tt containing co
e 203 powder, co containing 18. In addition to O, powder, etc.
θ powder, c.

A wide variety of known 21 boron powders such as metal powders are included, from general products to ultrafine particles of BIT 3 Q m2 / 9 or more.

Dispersants include capric acid, lafric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolic acid, carboxylic acids having 11 to 170 carbon atoms, or -1, Ma, K, Mg,
Oh, ! 35L salt, lecithin, alcohols having 12 or more carbon atoms, sulfuric esters of alcohols having 12 or more carbon atoms, etc. are used.

As a lubricant, silicone oil, graphite, molybdenum disulfide, tungsten disulfide, carbon number 12-16
Fatty acid esters of higher fatty acids and monohydric alcohols having 3 to 12 carbon atoms are used.

Antistatic agents include natural surfactants such as saponin, nophonic surfactants (alkylene oxide r-based, glycerin-based, glycidol-based), cationic surfactants (phosphonium-based, sulfonium-based), and anionic surfactants. Surfactants (carboxylic acid type, sulfonic acid type, phosphoric acid type,
(sulfuric acid ester type, phosphoric acid ester type), amphoteric surfactants (amino acids or aminosulfonic acids or amino alcohols and sulfuric acid or phosphoric acid ester), etc. are used.

As the abrasive, fused alumina, silicon carbide, chromium oxide, corundum, etc. are used.

〔Example〕

The present invention will be explained in more detail by giving Examples and Comparative Examples below.

Example 1 In a stainless steel autoclave with an internal volume of 5 mm, vinyl chloride 162011 vinyl acetate 250 g, 2-hydroxyethyl methacrylate)15. F2-acid phosphooxyethyl methacrylate) 10,9 acetone 1450# As a polymerization initiator, 9 g of benzoyl peroxide was charged and polymerization was initiated at 45°C. After that, for every 15 degrees of polymerization, 15 Jil of 2-hydroxyethyl methacrylate, 109 Jil of 2-acid phosphooxyethyl methacrylate, 25 I of acetone
A solution consisting of i was added five times, and the polymerization was stopped by cooling at a polymerization rate of 90%.

Using the obtained copolymer, a magnetic coating material was prepared according to the magnetic coating test method and magnetic coating evaluation method described below, and a magnetic coating film was also produced.

Example 2 In a stainless steel autoclave with an internal volume of 51, vinyl chloride 1000.9. , 610 g of vinyl acetate, 45 g of 2-hydroxyethyl acrylate, 20 g of 2-hydroxyethyl acrylate, 12 g of methyl ethyl ketone
809, benzoyl peroxide 20Ii was charged as a polymerization initiator, and polymerization was started at 45°C. After that, the polymerization rate was 151
2-hydroxyethyl methacrylate 45.9,2 for every j
- Ashitsu r phosphooxyethyl acrylate 2011,
A solution consisting of methyl ethyl chloride 1'6511 was added five times and the polymerization was stopped by cooling at a polymerization rate of 90%.

A magnetic coating film was prepared using this copolymer.

Example 3 A chlorinated hydrogen copolymer was obtained in the same manner as in Example 1, except that the type of monomer and the charging ratio were changed.

A magnetic coating film was prepared using these copolymers.

Comparative Example 1 Denkabinylsha 10 was used instead of the copolymer resin according to the present invention.
00 GKT (Denki Kagaku Kogyo Co., Ltd.) Vinyl chloride/hinyl acetate/male alcohol = 9115/6 (weight ratio)
] was used to prepare a magnetic coating film.

Comparative Example 2 Contents fi5J stainless steel autoclave with El chloride 1480! i, vinyl acetate 240,9,2-hydroxyethyl methacrylate) 55,9. Acetone 1600L
Add benzoyl peroxide 211 as a polymerization initiator, and
Polymerization was started at 5°C. After that, 2-e for every 15% of polymerization rate
Add 45 g of droxyethyl methacrylate 5 times,
The polymerization was stopped by cooling at a polymerization rate of 90%.

A magnetic coating film was prepared using this copolymerized valley body.

Comparative Example 3 In the same manner as in Example 3, an r=nyl chloride copolymer was obtained by changing the type of monomer and the charging ratio.

A magnetic coating film was prepared using these copolymers.

Test method for making magnetic paint A magnetic paint was prepared using the resin obtained in the example or the resin of the comparative example with the following formulation.

♂Nyl chloride copolymer resin 15 parts by weight Polyurethane resin 5 parts by weight Magnetic powder (containing co-Fe203,
80 parts by weight BIIfT 40 parts 2/I) Carbon black 4 parts by weight Methyl ethyl ketone 60 parts by weight cyclohexanone 60 parts by weight Toluene
60 parts by weight lecithin
2 parts by weight Coronet) L (Nippon Poly
4 Parts by weight Urethane Kogyo Co., Ltd. JRl (Product name) Method for evaluating magnetic coatings The magnetic properties obtained in the previous section were diagonally coated onto a 10μ thick polyester film using a doctor spray F so that the thickness of the magnetic layer was 10A. The coated layer was applied, and while the coated layer was still wet, magnetic field orientation was performed using an electromagnet of 2000 Gauss, and the coated layer was placed in a hot air dryer at 100° C. for 1 minute to dry. After that, the magnetic coating film was
It was pressed at 0° C. for 50 seconds at 2 kll/cs” to give it smoothness, and the following performance test was conducted.

(1) Glossiness The reflectance at a reflection angle of 60° was measured using a gloss meter.

This value represents the dispersibility of the magnetic powder in the magnetic coating film, and it is determined that the larger the value, the better the dispersibility.

(2) Residual magnetic flux density (Br) and maximum magnetic flux density (B, ) when measured in an external magnetic field of 2 kOe using a rectangular ratio vibration sample demagnetometer [RIKEN DENSHI Co., Ltd. BHV-55 type] The ratio of

This value also represents the dispersibility of the magnetic powder in the magnetic coating film, and it is determined that the larger the value, the better the dispersibility.

〔Effect of the invention〕

The magnetic recording medium of the present invention has great practical value because the ultrafine magnetic powder in the magnetic layer has excellent dispersibility.

Patent applicant Denki Kagaku Kogyo Co., Ltd. Procedural amendment dated August 6, 1985 Michibe Uga, Commissioner of the Patent Office 1, Indication of case 1985 Patent Application No. 148405 2, Title of invention Magnetic recording medium 6, Relationship with the case of the person making the amendment Patent applicant address 1-4-1 Yurakucho, Chiyoda-ku, Tokyo Column 5 of the detailed description of the invention in the specification, content of amendment 1) “Saturated polyester” on page 7, line 16 Correct "resin" to "saturated polyester resin".

2) On page 9, line 8, correct it to "Nohon Jt-r nonion."

3) "In the autoclave" on page 10, line 3, r1620gJ on line 4, r15 on line 5. ! After i'J and r1450.9J on the 7th line, "," is fully added.

Manual continuation supplementary book January 17, 1986

Claims (1)

[Claims] 50 to 90% by weight of vinyl chloride, 0.1 to 40% by weight of vinyl carboxylate, 0.1 to 50% by weight of hydroxyalkyl acrylate, and 0.1 to 10% by weight of vinyl group-containing phosphoric acid ester copolymerizable with these. A magnetic recording medium containing a copolymer consisting of each unit and magnetic powder.