JPS6240616A - Binder for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a binder for magnetic recording media and a magnetic recording medium, and more specifically to a magnetic recording medium having excellent magnetic powder dispersibility and wear resistance. The present invention relates to a binder for use with a magnetic recording medium and a magnetic recording medium using the binder.

[Conventional technology]

Various technologies have been developed for magnetic materials for magnetic recording, but in recent years there has been an increasing demand for high-performance materials, and in particular, materials with excellent electrical properties are in high demand. requested. For this purpose, in addition to the conventional Co-coated FezO3, magnetic powders such as metal powders with a large surface area per unit weight are attracting attention and are being considered as ferromagnetic materials suitable for high-density magnetic recording. .

Furthermore, the binder used when coating these magnetic powders on a non-magnetic support to form a film is also an important factor that influences the performance of the magnetic recording medium. If the dispersibility of magnetic powder in the binder is poor, it often impairs various performances, including electrical properties, such as generating noise and reducing output. In particular, ferromagnetic powder with a large specific surface area may suffer from agglomeration of particles. It is easy to be affected by negative effects, and the degree of influence is also large.

Regarding this point, the surface of magnetic powder is modified (surface treatment).
There is a movement to improve the dispersibility of magnetic powder by introducing polar groups into the binder itself, and a movement to improve the dispersibility of magnetic powder. The present invention belongs to the latter category.

[Problem that the invention seeks to solve]

Conventionally, vinyl chloride/vinyl acetate copolymers, polyurethane, nitrocellulose, and the like have been used as binders for magnetic paints. However, these resins have problems such as unsatisfactory heat resistance and abrasion resistance, and increased costs due to complicated manufacturing processes such as solvent recovery. In order to solve these problems, a method has been proposed in which an unsaturated resin having an ethylenic double bond in its molecule is used and cured by radiation such as an electron beam. Furthermore, JP-A-57-
No. 92421, JP-A-59-77624, JP-A-59
-198528 has a sulfonic acid group, a carboxyl group,
A radiation-curable magnetic paint has been proposed that has excellent dispersibility of magnetic powder containing a compound having a polar group such as a hydroxyl group and an acrylic double bond. Although these materials have improved dispersibility of magnetic powder, they have the disadvantage of slightly poor wear resistance.

[Means for solving problems]

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on magnetic paints that have excellent dispersibility of magnetic powder and excellent wear resistance. Unsaturated phosphate ester resin, which is made by reacting a compound with a phosphoric acid group with a chemical or poxy resin, has excellent dispersibility of magnetic powder, and it is also possible to create a coating film from a magnetic paint containing this unsaturated phosphate ester resin. It was discovered that radiation-cured products have excellent wear resistance, leading to the present invention.

That is, the present invention provides a binder for magnetic recording media comprising a novel unsaturated phosphate ester resin obtained by reacting a compound having both an ethylenic double bond and a phosphoric acid group in one molecule and an epoxy resin. It is also 1
Magnetism made by dispersing ferromagnetic fine powder in a binder for magnetic recording media made of a new unsaturated phosphate ester resin obtained by reacting a compound with both an ethylenic double bond and a phosphoric acid group in its molecule and an epoxy resin. A magnetic recording medium is provided in which a layer is provided on a non-magnetic support.

As a preferred embodiment of the present invention, the above-mentioned 1
A compound having both an ethylenic double bond and a phosphoric acid group in the molecule has the following general formula (R is hydrogen or methyl group, R2 is C00Y, 0COY
, OY, Y, C0NHY, C0(OC82C
H2)ll, C0(OCII2CH2)l11--0
-Ph- (Y is 0H1OR, a straight chain, cyclic, branched, aliphatic, having 1 to 30 carbon atoms, which may be substituted with halogen,
Alicyclic, aromatic hydrocarbon residue, where R is a hydrocarbon residue having 1 to 8 carbon atoms, m % n is a number of I to 5), R3 is hydrogen or a linear or cyclic residue having 1 to 3 carbon atoms. , a branched aliphatic, alicyclic, or aromatic hydrocarbon residue].

Examples of compounds having an ethylenic double bond and a phosphoric acid group in one molecule used in the present invention include vinylphosphonic acid,
vinyl phosphate, or the general formula (R1 is hydrogen or methyl group, R2 is C00Y, 0CO
Y, OYY, C0NIIY, Co(OCII□
Hz), 1, C0(OC82CH2), --O-P
h-(Y is 011.OR, a linear, cyclic, branched aliphatic group having 1 to 30 carbon atoms that may be substituted with halogen,
alicyclic, aromatic hydrocarbon residue, where R is a hydrocarbon residue having 1 to 8 carbon atoms, m% n is a number of 1 to 5), R3 is hydrogen or a linear or cyclic residue having 1 to 30 carbon atoms. , branched aliphatic, alicyclic, and aromatic hydrocarbon residues]. Specific examples of the compound represented by the above general formula include 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxyethyl acid phosphate, 1-chloromethyl-2-methacryloyloxyethyl acid phosphate, 1 -Methyl-2-methacryloyloxyethyl acid phosphate, alkyl-2-hydroxy-3-methacryloyloxybrobyl acid phosphate, sesqui(2-methacryloyloxyethyl) acid phosphate, di(2-methacryloyloxyethyl) acid phosphate, (royloxyethyl) acid phosphate and the like. Of course, it is not limited to these, and those represented by the general formula (1) are preferably used.

The epoxy resin used in the present invention is preferably a compound having two or more epoxy groups in one molecule, and specific examples include bisphenol-type epoxy resin, novolak-type epoxy resin, cresol-type epoxy resin, and halogenated bisphenol-type epoxy resin. Examples include resins, aliphatic epoxy resins, spiroacecooled epoxy resins, and urethanized epoxy resins. The epoxy resin is not limited to those mentioned above, and any compound having an epoxy group may be used. Furthermore, a compound having one epoxy group in one molecule can also be used as long as the physical properties of the phosphoric acid ester resin used in the present invention are not deteriorated. The molecular weight of the epoxy resin that can be used in the present invention is preferably in the range of 340 to 10,000, and particularly preferably in the range of 340 to 4.00.

The unsaturated phosphate ester resin of the present invention is produced, for example, according to the following reaction.

■ CH2CI Cl1z OR' OCHzCHC1
to h0' to 07 0HO■ 0H,0H (R" represents the central skeleton of the epoxy resin) In the above formula, an example was shown in which the molar ratio of the hydroxyl group to the epoxy group in the acidic phosphoric ester was 2. There are no limitations, and the desired product can be obtained as long as the amount of the compound having both an ethylenic double bond and a phosphoric acid group in one molecule is 1 mol or more per 1 mol of the epoxy resin.

The above method for producing the unsaturated phosphoric acid ester resin used in the present invention is an exothermic reaction accompanied by ring-opening addition of epoxy groups, and as the reaction progresses, the molecular weight increases and the viscosity increases. do. Therefore, by using a suitable solvent, the unsaturated phosphate ester resin of the present invention can be preferably produced. The solvent that can be used at this time is not particularly limited as long as it is non-reactive. Preferably, ketone type, ester type, ether type, etc. can be used. After completion of the reaction, the used solvent may be removed by topping, or depending on the use case, it may be used as is without any problem. In addition, 2.4.6-
Tertiary amines such as tris(dimethylaminomethyl)phenol, ring-opening catalysts such as triphenylphosphine, trialkylphosphine, etc. may also be used. Although the reaction temperature for the above reaction is not particularly limited, it is desirable to carry out the reaction below the boiling point of the solvent used. Further, if the temperature is too high, side reactions such as dehydration reactions occur, which is not preferable. Usually 10-15
It is desirable to conduct the heating at 0°C, preferably at about 20 to 120''C.

The binder for a magnetic recording medium of the present invention can be obtained as described above, but the magnetic recording medium of the present invention can be obtained by providing a magnetic layer in which ferromagnetic fine powder is dispersed in the above-mentioned binder on a non-magnetic support. Manufactured. In this case, the blending ratio of the binder and the ferromagnetic fine powder is 10 to 100 parts by weight of the binder to 100 parts by weight of the ferromagnetic fine powder, taking into consideration the mechanical strength, abrasion resistance, and magnetic density of the magnetic layer. The range is preferably 15 to 60 parts by weight, particularly preferably 15 to 60 parts by weight.

Various types of ferromagnetic fine powder can be used in the present invention, such as iron, chromium, nickel, cobalt, alloys thereof, oxides thereof, or modified products thereof. can be mentioned.

Specific examples of oxides include r-Fe, O, ferrite, magnetite, Cry, etc., and examples of modified compounds include γ-FezO+ compounds doped with cobalt. Furthermore, surface-treated magnetic powders of these types are also effective.

When manufacturing the magnetic recording medium of the present invention, reactive oligomers such as epoxy acrylate, polyester acrylate, urethane acrylate, etc. can be added within a range that does not impair the purpose. Furthermore, an ethylenically unsaturated compound can be used if necessary. Typical examples thereof include styrene, α-methylstyrene, (meth)acrylic acid, (meth)acrylic acid ester, polyol poly(meth)acrylate, divinylbenzene, and triallylisocyanurate.

In addition to the above-mentioned magnetic powder, binder, and monomer, the magnetic paint contains suitable additives such as antistatic agents, lubricants,
It is desirable to add abrasives, dispersants, etc.

As the antistatic agent, conductive fine powder such as carbon black, graphite, carbon black graft polymer, etc. is used. When these antistatic agents are added, the amount thereof is 10 parts or less, preferably 3 to 10 parts, per 100 parts of magnetic powder.

As a lubricant, silicone oil, Goo 77ite,
Molybdenum disulfide, basic fatty acids from CI□ to CI6 and 0
A fatty acid ester consisting of m alcohols of 3 to C1□ is used. The amount is 10 parts per 100 parts of magnetic powder.
parts, preferably 3 to 10 parts.

As the dispersant, fatty acids having 12 to 18 carbon atoms such as capric acid, caprylic acid, and lauric acid, and metal soaps made of alkali metals or alkaline earth metals of the fatty acids are used. It is preferable to add 2 to 5 parts of these dispersants to 100 parts of magnetic powder.

Further, an abrasive is added as necessary, but the amount thereof is an appropriate amount.

〔Example〕

The present invention will be specifically explained below with reference to Production Examples, Comparative Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Production Examples and Examples.

[Production example of unsaturated phosphate ester resin] Production example 1 In a 11-separable flask equipped with a stirrer and a cooler, 206 g of mono(2-methacryloyloxyethyl) acid phosphate (acid value 431 mg KO) 1/g) and 93 g of methyl ethyl ketone were added. , 0.52 g of polymerization inhibitor methylhydroquinone was charged. To this, a solution of 312 g of bisphenol A type epoxy resin (epoxy equivalent: 188 g/eq) dissolved in 134 g of methyl ethyl ketone was added to the solution at a temperature of 50°C.
It was dripped so that it was kept at a constant temperature. After the dropwise addition is complete, the reaction is completed by keeping at the same temperature for 1 hour, and the unsaturated phosphate ester resin (
Solid content: 69.5%) was obtained.・Production Example 2 Sesqui(2-methacryloyloxyethyl) acid phosphate (acid value 269 mg) was used instead of mono(2-methacryloyloxyethyl) acid phosphate in Production Example 1.
Unsaturated phosphate ester resin B (solid content 69.4%) was prepared in the same manner as in Example 1 except that 200 g of OH/g) was used.
I got it.

Production Example 3 Using the same reaction apparatus as Production Example 1, sesqui(2-methacryloyloxyethyl) acid phosphate) 313
g, 141 g of methyl ethyl ketone, and 0.52 g of methyl hydroquinone. To this, 240 g of novolac type epoxy resin (1180 g/eq per epoxy) and methyl ethyl ketone were added dropwise so that the liquid temperature was maintained at 50°C. Thereafter, in the same manner as in Example 1, unsaturated phosphate ester resin C (solid content 69.6%) was obtained.

Comparative Production Example 1 Example-5 of JP-A No. 57-92421: The following was synthesized by phosphorylating bisphenol A type epoxy acrylate, dissolved in methyl ethyl ketone, and resin D (solid content 69.5%) was synthesized. I got it.

0 P (OH)2 CHzCIICHz-00CCH-CHz Comparative production example 2 Bisphenol^ type topyl ester (Dow Chem
Delakane 411-45 (manufactured by Manufacturer) was dissolved in methyl ethyl ketone to obtain resin E (solid content: 69.5%).

[Example of manufacturing surface-treated magnetic powder]

Production Example 4 A 500ml separable flask with a cooler, Co-coated T-FezOxC long axis diameter 0.35um, axial ratio 1/10
) 150g.

300g of toluene, an organic silane compound (C113
0) 3 g of zsiczlToOcIlz-CO-Cll□, and sesquidodecylpolyoxyethylene (9 mole addition) phosph x
) and stirred at 75°C to 85°C for 2 hours. The magnetic material was then washed with excess toluene and heated at 60° under reduced pressure.
C. and toluene was removed to obtain surface-treated magnetic powder.

Production Example 5 Instead of the organic silane compound of Production Example 4, an organic titanium compound (CH.)zcHOTi (OCzHaNH
5 g of CJJH2)3, and 3 g of sesquinonylphenyl polyoxyethylene (10 mol addition) phosphate in place of sesquidodecyl polyoxyethylene phosphate.
A surface-treated magnetic powder was obtained in the same manner as in Production Example 4 except that the powder was used.

[Evaluation of magnetic powder dispersibility]

Examples 1 to 5 and Comparative Examples 1 to 3 Dispersibility was obtained using the unsaturated resins A-E produced in Production Examples 1 to 3 and Comparative Production Examples 1 to 2, and the magnetic powder or untreated powder of Production Examples 4 to 5. was evaluated.

To unsaturated resin ~ E (solid powder 69.5%) 72 parts magnetic powder
100 parts methyl ethyl ketone 331 parts cyclohexanone
139 parts After kneading the above mixture in a sand mill for 4 hours, the obtained magnetic coating material was applied onto a polyethylene terephthalate base film with a thickness of 75 μm,
The surface reflectance of the coating film was measured and the results are shown in Table 1.

[Durability evaluation of magnetic disks]

Examples 1 to 5 and Comparative Examples 1 to 3 Magnetic disks were manufactured using the unsaturated resins A-E and magnetic powder manufactured in Manufacturing Examples 1 to 3 and Comparative Manufacturing Examples 1 to 2, and their durability was evaluated.

Unsaturated resin A-E (solid content 69.5%) 43 parts Acrylic modified polyurethane resin 20 parts (Mitsubishi Yuka Fine Atl-1100) Magnetic powder
100 parts carbon black
3 parts Lubricant 2 parts Methyl ethyl ketone 230 parts Cyclohexane 100 parts The above mixture was kneaded in a sand mill for 4 hours to obtain a magnetic paint. The obtained magnetic paint was applied onto a polyethylene terephthalate base film with a thickness of 75 μm using an applicator so that the thickness after drying would be 2 μm. After drying, it was subjected to mirror processing by calendering, and then applied at an accelerating voltage of 200 kV.
, electron beam irradiation was performed at an irradiation dose of 5 Mrad.

Thereafter, the film was attached to a predetermined magnetic disk drive, and the durability was evaluated by measuring the time until the playback output decreased to 50%. The results are shown in Table 1.

Table 1 (Incidence angle of 60°/Acceptance angle of 60°) is constant [Effect of the invention] By using the unsaturated phosphate ester resin of the present invention as a binder for magnetic recording media, the dispersibility of magnetic powder is improved. As a result, as specifically shown in the examples, it has become possible to manufacture a magnetic recording medium with excellent wear resistance and high output.

Claims (1)

[Claims] 1. Binder 2 for magnetic recording media comprising a novel unsaturated phosphate ester resin obtained by reacting a compound having both an ethylenic double bond and a phosphoric acid group in one molecule and an epoxy resin. , a compound that has both an ethylenic double bond and a phosphoric acid group in one molecule has the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [R_1 is hydrogen or methyl group, R_2 is COOY, OC
OY, OY, Y, CONHY, CO(OCH_2CH_
2)_n, CO(OCH_2CH_2)_m--O-P
h-(Y is a linear, cyclic, branched, aliphatic, alicyclic, or aromatic hydrocarbon residue having 1 to 30 carbon atoms that may be substituted with OH, OR, or halogen; however, R is a carbon number 1 to 8 hydrocarbon residues, n and m are numbers of 1 to 5), R_3 is hydrogen or a linear, cyclic, branched, aliphatic, alicyclic group having 1 to 30 carbon atoms,
Aromatic hydrocarbon residue] Binder 3 for magnetic recording media according to claim 1, which is a compound having a structure represented by: A magnetic layer in which fine ferromagnetic powder is dispersed in a binder for magnetic recording media made of a new unsaturated phosphate ester resin obtained by reacting a compound having both a group and an epoxy resin is provided on a non-magnetic support. Magnetic Recording Media 4 A compound that has both an ethylenic double bond and a phosphoric acid group in one molecule has the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [R_1 is hydrogen or methyl group, R_2 is COOY, OC
OY, OY, Y, CONHY, CO(OCH_2CH_
2)_n, CO(OCH_2CH_2)_m--O-P
h-(Y is a linear, cyclic, branched, aliphatic, alicyclic, or aromatic hydrocarbon residue having 1 to 30 carbon atoms that may be substituted with OH, OR, or halogen; however, R is a carbon number 1 to 8 hydrocarbon residues, n and m are numbers of 1 to 5), R_3 is hydrogen or a linear, cyclic, branched, aliphatic, alicyclic group having 1 to 30 carbon atoms,
Aromatic hydrocarbon residue] The magnetic recording medium according to claim 3, wherein the magnetic recording medium is a compound having a structure represented by: