JPS59139135A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an electromagnetic conversion characteristic by incorporating the magnetic powder coated thereon with the resultant product of reaction of a specific compd. having an isocyanate group and a compd. selected from the specific compd. group having a functional group that can react with the isocyanate group in a titled medium. CONSTITUTION:An isocyanate group is exemplified by the resultant product of reaction, as shown by the chemical formula, of 1mol trimethylolpropane and 3mol toluene diisocyanate. Aliphat. alcohol of 6-22 carbon atom is exemplified by stearyl alcohol, oleyl alcohol, etc., aliphat. carboxylic acid of 6-22 carbon atom by stearic acid, palmitic acid, etc., hydroxy fatty acid, etc. of 6-22 carbon atom by 12-hydroxystearic acid, 12-magnesium hydroxystearate, etc., fatty acid partial ester of polyhydric alcohol by pentaerythritol tripalmitate, sorbitan trioleate, etc., and aliphat. amine of 4-22 carbon atom by the amine compd. expressed by the general formula, respectively.

Description

[Detailed description of the invention] The present invention relates to improved magnetic recording media.

More specifically, the present invention relates to a magnetic recording medium with excellent magnetic properties and durability, which is manufactured using a magnetic paint that improves the dispersibility of magnetic powder and the adhesion between the magnetic powder and a binder.

Magnetic powder in magnetic recording media such as magnetic tapes and magnetic disks is required to have a high degree of dispersibility.

Magnetic recording media are generally produced by kneading magnetic powder, binder, various additives, and solvents, then applying a magnetic paint evenly onto a plastic film or sheet substrate, drying it, and then applying a magnetic layer. Although it is formed by mirror finishing, it is not possible to create a uniform and smooth magnetic layer with a high packing density unless the magnetic powder in the magnetic paint is sufficiently dispersed and peptized to remove aggregated particles.

The non-uniformity of the magnetic layer due to the agglomerated particles of magnetic powder does not have a serious negative effect on the electromagnetic conversion characteristics and magnetic properties of the magnetic tape.

In other words, it causes a decrease in output, an increase in noise, dropouts, etc.

Also, if the adhesive force between the magnetic powder and the binder is weak,
When a magnetic recording medium and a recording head or a reproducing head slide, magnetic powder from the magnetic coating layer is likely to cause powder drop (so-called powder falling), and the coating surface becomes rough, causing damage to the magnetic recording medium. In reality, the durability of conventional magnetic recording media is insufficient for practical use.

Therefore, the dispersibility of the magnetic powder in the magnetic paint and the adhesion with the binder are very important in improving the performance of the magnetic recording medium.

Improvements in the dispersibility of magnetic powder have been studied from various viewpoints, and it has been proposed to improve the dispersibility by adding a suitable surfactant to the magnetic paint formulation. Examples of such surfactants include those using alkylimidacillin compounds (% opening 54-52504), and those using alkyl polyoxyethylene phosphates neutralized with alkyl amines (Japanese Patent Laid-Open No. 1983-78810). , those using long-chain alkyl phosphate esters (JP-A-54-14750)
7. As disclosed in Japanese Patent Application No. 55-49629, amines and their derivatives, phosphoric acid esters, polyoxyethylene phosphoric esters, etc. are often used. In addition, a proposal has been made that dispersibility can be improved by surface-treating magnetic powder and then turning it into a paint.
49769), which treats metal powder with a titanium coupling agent to measure dispersion stability and at the same time prevent the deterioration of the magnetic coating film over time (% opening 56-88471). Furthermore, as a method for improving the durability of the magnetic coating film by improving the adhesion between the magnetic powder and the binder, a method using a silane coupling agent having a functional group reactive with the binder (Japanese Patent Laid-Open No. 54-7510 ), those imitated by the reaction products of amino 7-antional silane coupling agents, incyanate compounds, and epoxy compounds (% opening 5
6-145555), a method in which magnetic powder is treated with a titanium coupling agent having a double bond in the binder and an unsaturated bond capable of radical polymerization (JP-A-56-111129).
) There is a method in which a compound having at least four radiation-sensitive acrylic double bonds in one molecule is used as a binder (JP-A-57-40744). in this way,
Although much research has been carried out on improving the dispersibility of magnetic powder in magnetic coatings and the durability of magnetic coatings, no satisfactory improvement has yet been achieved.

In view of the above-mentioned problems of magnetic recording media, the present inventors conducted extensive research to obtain a magnetic recording medium with excellent dispersibility of magnetic powder and durability of the coating layer, and as a result, the present inventors discovered a specific A magnetic recording medium containing a magnetic powder compounded by a reaction product of a compound and one or more compounds selected from a specific group of compounds having a functional group capable of reacting with an incyanato group. They discovered that the magnetic powder has good dispersibility and the coating layer has excellent durability, and completed the present invention.

That is, the present invention provides the following (Il and (III) polyisocyanate compounds having a molecular weight of 100 to 100° having two or more isocyanate groups in one molecule, (■) hydrated in one molecule) Degradable alkoxysilane group and 1
having a molecular weight of 14 or more incyanato groups
One or more isocyanate compounds selected from the group consisting of 0 to 1500 isocyanate compounds, and the following
II aliphatic alcohol having 6 to 22 carbon atoms, (R'l
Aliphatic carboxylic acid having 6 to 22 carbon atoms, ffl Hydroxy fatty acid having 6 to 22 carbon atoms or its salt or ester thereof, (Ml Fatty acid partial ester of polyhydric alcohol, 6
- ■ To provide a magnetic recording medium characterized by containing magnetic powder coated with a reaction product with one or more compounds selected from the group consisting of aliphatic amines having 4 to 22 carbon atoms. It is something.

Examples of the incyanate compounds belonging to the group consisting of (11 and (III) according to the present invention include toluene diincyanate, methylene bisphenylene diisocyanate,
Hexamethylene diisocyanate, reaction product with 5 moles of trimethylol propafumol toluene diisocyanate, 0ON-(0H2)6-NHOONH(0H2
), 81 (OOH,), 0ON-■-0H2-■-
NI(00-8-(OH2),-81(OCH,),,
etc. can be mentioned.

Examples of the monohydric alcohol according to the present invention include aliphatic alcohols having 6 to 22 carbon atoms, stearyl alcohol, oleyl alcohol, and dodecyl alcohol.

Examples of the aliphatic carboxylic acids having 6 to 22 carbon atoms according to the present invention include fatty acids such as stearic acid and valmitic acid.

Examples of the human autooxyfatty acid having 6 to 22 carbon atoms, a salt thereof, or an ester thereof according to the present invention include 12-hydroxystearin [, magnesium 12-hydroxystearate, butyl 12-hydroxystearate, and the like.

Examples of the fatty acid partial ester of polyhydric alcohol according to the present invention include pentaerythritol tripalmitate, sorbitan trioleate, glycerin dilaurate, and the like.

The aliphatic amino acid having 4 to 22 carbon atoms (R1R'
, 'f represents an alkyl group),
Secondary amine or tertiary amine, further alkyl diamine,
Amine compounds such as alkyl triadenene can be mentioned.

The magnetic powder according to the present invention is fine needle-shaped γ-F.
θ20. , Fθ, 0%s 0r02, and also CO deposited r-Fe20. ．． 00 dope y-F
e20. y-1'θ203, which has undergone processing such as
Examples include iron metal powder. Among these, iron metal powder has particularly poor chemical stability, so small amounts of nickel, cobalt, titanium, silicon, aluminum, etc. in the form of metal atoms, salts, and oxides are added or surface treated to improve this. However, these can also be used. In order to stabilize the iron metal powder, a thin oxide film may be formed on the surface in a weakly oxidizing atmosphere, and metal powder treated in this way can also be used.

The size of these magnetic powders is from 1μ to 0.15μ on the long axis.
It is preferable that the minor axis is 0.15μ to 0.015μ.

If the long axis becomes larger than 1 μm, dispersion becomes easier, but recording of short wavelengths becomes disadvantageous and noise increases, which is not preferable. When the long axis is smaller than 0.15μ, even the magnetic recording medium of the present invention cannot be said to have sufficient dispersibility.
9- Difficult.

In the present invention, a method for obtaining a magnetic powder coated with a reaction product of the isocyanate compounds of (1) and (I[) above and a compound selected from the compound group of (II[J-Ceramics) is particularly provided. For example, the method shown below is exemplified without limitation.

b) Magnetic powder (1) is first heat-treated with incyanato compound (11) in an inert organic solvent, and then the above (I)
A method of heat-treating one or more compounds (ill) selected from the compound group of (b).

(1), (11) and (1+) in an inert organic solvent
A method in which +1 is mixed all at once and heat treated.

)9 First, in an inert organic solvent, the above (11) and (Ill
) is reacted, and then (1) is added and heat treated.

The magnetic recording medium of the present invention can be obtained by adding a binder and a solvent to the magnetic powder treated by the above processing method to form a paint, and applying it to a polyester film, etc. This will be explained in Examples together with the powder processing method.

10- The amount of the isocyanate compound (1) and (II) used in the present invention is about 0.05 to 3% by weight, preferably 0.2 to 1.5% by weight, based on the magnetic powder. It is. In addition, the amount of the compound selected from the group of compounds (II) to (4) above should be such that, from a stoichiometric perspective, they do not remain as unreacted substances, and in the above-mentioned nopolyisocyanate compound. The amount is preferably such that at least one incyanato group remains. It goes without saying that it is preferable to set reaction conditions such as reaction temperature and reaction time so that the reaction rate is the highest.

Examples of inert solvents that can be used in the treatment of magnetic powder include methyl ethyl ketone, methyl imbutyl ketone, diethyl ketone, cyclohexanone, benzene, xylene, and toluene.

The binder used when turning the treated powder into a paint is a resin binder that is soluble in organic solvents, and is used to fix the above magnetic powder onto the substrate and the magnetic powder together with the necessary strength to form a magnetic layer. It is sufficient that it fulfills its role in as small a quantity as possible, and even those that are concerned about deteriorating the dispersibility of magnetic powder in conventional paints can be used in normal paint-forming methods. Examples of these resin binders include polyurethane,
Polyester, Bo1Jtl, vinyl, vinyl chloride vinyl acetate copolymer, polyacrylonitrile, nitrile rubber,
Epoxy resins, alkyd resins, polyamides, polyacrylic esters, polymethacrylic esters, polyvinyl acetate, polyvinyl butyral, vinylidene chloride, vinylidene chloride copolymers, nitrified cotton, ethyl cellulose, etc. may be used alone. However, two or more types are usually used in combination. Further, in order to adjust the hardness of the resin, a plasticizer or a hardening agent may be added. Furthermore, the amount of binder blended is generally 15 to 60 parts by weight per 100 parts by weight of magnetic powder. Even if the binder has the highest binding strength, if it is less than 15 parts by weight, the strength of the magnetic coating will be weak and the adhesive force between the substrate and the magnetic coating will be insufficient.

If the amount exceeds 60 parts by weight, the concentration of magnetic powder in the magnetic coating film will decrease, which is disadvantageous as the reproduction output will decrease, and the properties of the coating film may also deteriorate. It is desirable to have a melting power for the binder and a boiling point between 50C and 150C. If the boiling point is too low, the magnetic powder will dry after application before being oriented in the magnetic field, making it impossible to carry out any treatment. The binder is selected from the above viewpoints depending on the type of binder, but it goes without saying that it should be selected in consideration of toxicity and environmental issues.

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

Example 1 4 tube flask with cooling tube, long sleeve diameter 0.35μm.

■Deposition r-Fe20.150 with axial ratio 1/10? , methyl ethyl ketone 5001. 1.5 f of methylene bisphenylene diisocyanate was stirred at 9.90C for 1 hour, and then the magnetic powder was washed with a large amount of methyl ethyl ketone. Then the magnetic powder 120v1 methyl ethyl ketone 300? and stearyl alcohol 1.42 in 4 Turow flasks KJ&? The mixture was stirred at 80 to 90C for 1 hour to obtain treated magnetic powder. The treated magnetic powder was then washed with a large amount of methyl ethyl ketone. A 1=1 (weight ratio) mixture of the treated magnetic powder and a vinyl chloride-vinyl acetate copolymer (VAGH manufactured by Union Carbide Co., USA) and a polyurethane resin (Nilaboran 2504 manufactured by Nippon Polyurethane Industries, Ltd.) as a binder was used. A mixture of 255% by weight based on the magnetic powder and 1:1 (weight ratio) of methyl ethyl ketone and cyclohexanone as a solvent 13
A magnetic paint was obtained by mixing 0f and kneading in a ball mill for 24 hours.

Further, this magnetic paint was applied onto a polyester film using a 60 μm applicator, subjected to magnetic field orientation, dried with hot air, and then calendered to smooth the coating film to obtain a magnetic recording medium 14-. . Next, the magnetic recording medium was measured for its squareness ratio, which is a measure of evaluating the dispersibility of magnetic powder, and its wear loss, which is a measure of evaluating the durability of the magnetic recording medium.

The results are shown in Table-1. Measurement of wear loss was performed using a width of 5 t.
m, length 50an magnetic recording medium with emery paper OC~
This was done by rubbing for 50 minutes under a constant load of 1000.

Example 2 Substitute b for stearyl alcohol used in Example 1 J)
A treated magnetic powder, a magnetic paint, and a magnetic recording medium were obtained in the same manner as in Example 1, except that 1.6 t of K, 12-hydroxystearic acid was used. The squareness ratio and abrasion loss of the magnetic recording medium were measured in accordance with Example 1. The results are shown in Table 1.

Example 5 In place of stearyl alcohol used in Example 1, 12
A treated magnetic powder, a magnetic coating material, and a magnetic recording medium were obtained in the same manner as in Example 1 except that magnesium -hydroxystearate 52 was used. For the magnetic recording medium,
The squareness ratio and abrasion loss were measured according to Example 1.

The results are shown in Table-1.

Example 4 A treated magnetic powder, a magnetic paint, and a magnetic recording medium were obtained in the same manner as in Example 1, except that pentaerythritol tripalmitate 4F was used in place of the stearyl alcohol used in Example 1. Ta. The squareness ratio and abrasion loss of the magnetic recording medium were measured in accordance with Example 1. The results are shown in Table-1. Example 5 Methylene bisphenylene diane used in Example 1 A treated magnetic powder, a magnetic paint, and a magnetic recording medium were obtained in the same manner as in Example 1. The squareness ratio and abrasion loss of the magnetic recording medium were measured according to Example 1. The results are shown in Table-1.

Example 6 A treated magnetic powder, a magnetic paint, and a magnetic recording medium were obtained in the same manner as in Example 5, except that 1.41% of palmitic acid was used in place of the dodecylamine used in Example 5. The squareness ratio and abrasion loss of the magnetic recording medium were measured according to Example 1. The results are shown in Table-1.

Example 7 A treated magnetic powder, a magnetic paint, and a magnetic recording medium were obtained in the same manner as in Example 5, except that 5 g of sorbitan trioleate was used in place of the dodecylamine used in Example 5. The squareness ratio and abrasion loss of the magnetic recording medium were measured according to Example 1. The results are shown in Table-1.

Example 8 Methylene bisphenylene diisocyanate used in Example 1 1°5? Kawashi Torirangein Cyanur) (
80% by weight of 2,4-) lylene diisocyanate and 2,6
1. A treated magnetic powder, a magnetic paint, and a magnetic recording medium were obtained in the same manner as in Example 1, except that Of was used. The squareness ratio and abrasion loss of the magnetic recording medium were measured according to Example 1. The results are shown in Table 1. Example 9 (OH, O) used in Example 5, 810H20H20H
A treated magnetic powder, a magnetic paint, and a magnetic recording medium were obtained in the same manner as in Example 5 except that 2f of 2NHOONH was used. The squareness ratio and abrasion loss of the magnetic recording medium were measured according to Example 1. The results are shown in Table 1.

Comparative Example 1 Magnetic powder was prepared by simply adding 4.5 f of soybean oil lecithin as a dispersant to the Co-coated Fe 12.150 f with a major axis diameter of 0.55 μm and a uniaxial ratio of 1/10 used in Example 1. A magnetic paint and a magnetic recording medium were obtained in the same manner as described in Example 1 below without surface treatment. The squareness ratio and abrasion loss of the magnetic recording medium were measured according to Example 1.

The results are shown in Table-1.

, Comparative Example 2 A magnetic coating material and a magnetic recording medium were obtained in the same manner as in Comparative Example 1, except that octylphos(7A) 4.5 F was used in place of the soybean oil lecithin used in Comparative Example 1. The squareness ratio and abrasion loss of the magnetic recording medium were measured according to Example 1. The results are shown in Table 1.

As is clear from Table 1, the magnetic recording medium of the present invention is excellent in both the dispersibility of magnetic powder and the abrasion resistance of the coating layer.

Applicant's agent Kaoru Furuya Procedural amendment (spontaneous) 1. Indication of the case Japanese Patent Application No. 12274/1982 2. Name of the invention Magnetic recording medium 3. Person making the amendment Relationship to the case Patent applicant (091) Kao Soap Co., Ltd. 4, Agent 1-3 Nihonbashi Yokoyama-cho, Chuo-ku, Tokyo Nakai Building Column 8 of the detailed description of the invention in the specification, contents of the amendment Magnetic powder substituted with the above types, Go, Fa-Co, Fe-
Procedural amendment to insert "ultrafine powder of metal or alloy such as Ni" (voluntary) October 31, 1988 1. Indication of the case Patent Application No. 12274/1982 2. Name of the invention Magnetic recording medium 3. Person making the amendment Relationship to the case Patent applicant (091) Kao Soap Co., Ltd. 4, Detailed explanation of the invention column 6 in the agent's specification, Contents of amendment (1) Lines 3 to 4 of page 6 of the specification "excellent""It has excellent electromagnetic conversion characteristics," revised (1) same page 15, 7.
- Insert a new line after ``I went.'' on line 8 and insert the following: ``Also, in order to examine the electromagnetic conversion characteristics, the magnetic recording medium was cut into a width of 6.25 i + m and cut into a commercially available open reel. The reproduction output of the magnetic recording medium prepared in Comparative Example 1 (described later) was expressed as a relative value, with the reproduction output of the magnetic recording medium prepared in Comparative Example 1 (described later) being 0. (1) Page 15, line 15, page 16, line 3, line 11, 20
Insert "and reproduction output" next to "Wear loss" on page 17, line 7, line 14, page 18, line 4, line 13, page 19, line 2, line 9. 2- (1) Table on page 19- Correct 1 as below:
Table 1 3- Procedural Neho (spontaneous) April 20, 1981 Patent Application No. 12274/1982 2, Name of the invention Magnetic recording medium 3, Person making the amendment Relationship to the case Patent applicant (091 ) Kao Soap Co., Ltd. 4, Agent Nakai Building 6, 1-3 Nihonbashi Yokoyama-cho, Chuo-ku, Tokyo, Contents of the amendment (1) Page 20 of the specification, line 3 after "I understand.", and the following statement on a new line: Insert 4 not 0 (50□-4, l' and 1... oath.

[Example 10 Methyl ethyl keto 7 was added to a 4 tube flask equipped with a cooling tube.
300g 2g of the isocyanate compound used in Example 5,
Take 1 g of dodecylamine and stir at 90°C for 1 hour.
Next, the Co-coated r-Fe20. used in Example 1. 15
0 g was added, and the mixture was further stirred at 90'C for 1 hour to obtain treated magnetic powder. The treated magnetic powder was then washed with a large amount of toluene. The treated magnetic powder was mixed with a vinyl chloride-vinyl acetate copolymer (VAGH manufactured by Union Carbide, USA) and a polyurethane resin (Nysten 5) as a binder.
033) and 50% by weight of the magnetic powder, and carbon blank (Lion Akzo's Ketjen Black E) as an antistatic agent was added at 0.4% by weight based on the magnetic powder.
0.2% by weight of alumina with an average particle size of 0.7μ as an abrasive based on the magnetic powder, 0.7% by weight of butyl stearate as a lubricant based on the magnetic powder, and methyl ethyl ketone/cyclohexanone as a solvent. /toluene (1:1:1 (weight/IT ratio)) was mixed with 400% by weight of the magnetic powder, kneaded in a ball mill for 72 hours, and then a hardening agent (Coronate from Nippon Polyurethane Industries) was added to the magnetic powder. A magnetic paint was obtained by adding 8% by weight to the mixture and stirring until the system became uniform.

Further, the magnetic paint was applied onto a polyester film using a 30 μm applicator, dried with hot air without magnetic field orientation, and then calendered to smooth the coating and punched out into a disk shape to obtain a magnetic recording medium.

Glossiness, residual magnetic flux density (Br),
Durability (output drop after 10 million passes/track) and PR-out were measured. The results are shown in Table-2. However, the measurement conditions for PR-out are as follows.

Relative velocity; 4. Om/sec Recording frequency B4MHz Recording head; Sendust playback head; Ferrite Comparative Example 3 GAFAC IE6 was used as a dispersant without surface treatment of the Co-coated Fe 203 powder used in Example 1.
10 (polyoxyethylene-added alkylaryl sesquiphosphate) was added in an amount of 3% by weight to the magnetic powder, a magnetic paint and a magnetic recording medium were prepared by the method of Example 10, and the four items shown in Example 10 were measured. I did it. The results are shown in Table-2.

Table 2 * FR-out is O for the magnetic recording medium of Comparative Example 3.

Example 11 500 g of toluene, 0.8 g of the isocyanate compound used in Example 10, and 1.2 g of dodecylamine were placed in a 4-tube flask equipped with a condenser and stirred at 90° C. for 1 hour.

Next, ultrafine-grained Fe-Go alloy (average particle size 2
50 people, Ilc: 15000es σs: 1
50 g of 50 emu) was added thereto, and the mixture was further stirred at 90° C. for 1 hour to obtain treated magnetic powder. The treated magnetic powder was then washed with a large amount of toluene.

Hereinafter, a magnetic paint and a magnetic recording medium were obtained according to the procedure of Example 10. The four measurements shown in Example 10 were performed on the magnetic recording medium. The results are shown in Table-3.

Comparative Example 4 The ultrafine Fe-Co alloy used in Example 11 was subjected to no surface treatment, the dispersant used in Comparative Example 3 was added in an amount of 3% by weight to the magnetic powder, and the method of Example 10 was followed. A magnetic paint and a magnetic recording medium were prepared, and the four items shown in Example 10 were measured. The results are shown in Table-3.

Table-3

Claims (1)

[Scope of Claims] The following (I) and (I[) (1) A polyisocyanate compound having a molecular weight of 100 to 1000 and having two or more isocyanate groups in one molecule, (■) One molecule Hydrolyzable alkoxysilane group and 1
having a molecular weight of 14 or more isocyanate groups
Nli or two or more isocyanate compounds selected from the group consisting of 0 to 1500 isocyanate compounds, and the following o(n+lt (■)l (v), (vl and ■(
[111 Aliphatic alcohol having 6 to 22 carbon atoms, (R'l
A group consisting of aliphatic carboxylic acids having 6 to 22 carbon atoms, ffl hydroxy fatty acids or salts thereof or esters thereof having 6 to 22 carbon atoms, 100) fatty acid partial esters of polyhydric alcohols, and aliphatic amines having 4 to 22 carbon atoms. A magnetic recording medium comprising magnetic powder coated with a reaction product with one or more carefully selected compounds.