JPS61151276A - Magnetic coating - Google Patents

Abstract

PURPOSE:To improve dispersibility of a magnetic powder in a magnetic coating and surface appearance of the coating film, by incorporating a partially oxidized nitrocellulose and particular polyisocyanate simultaneously as a binder in the magnetic coating. CONSTITUTION:A partially oxidized nitrocellulose with a carboxyl group content of at least 2mmol/100g of nitrocellulose and 1,8-diisocyanato-4-isocyanatometh yloctane (hereinafter referred to as triisocyanate) are used simultaneously as a binder in a magnetic coating consisting mainly of a magnetic powder and a binder. The triisocyanate is a trifunctional polyisocyanate of the formula. Said partially oxidized nitrocellulose is prepd. by oxidation of common nitrocellu lose with an oxidant (e.g., nitrogen oxides, chlorates). Said triisocyanate is used in an amt. of about 0.1-1.0 isocyanate equivalent based on 1 equivalent total of the active hydrogen equivalent of the partially oxidized nitrocellulose and that of other resins used simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic coating material for providing magnetic recording media such as video tapes, audio tapes, magnetic disks, magnetic cards, and the like.

[Conventional technology and its problems]

A magnetic recording medium is obtained by coating a magnetic paint made of magnetic powder, a binder, an organic solvent, and other components onto a support such as a polyester film, and then drying the coating.

Recently, in order to obtain magnetic recording media with higher performance, efforts have been made to make magnetic powder particles finer and to have higher magnetic force.

However, such magnetic powder has poor fractional properties, resulting in a disadvantage that the surface properties of coating films made using it are reduced. For this reason, there is an increasing demand for improved dispersibility in magnetic paints.

Conventionally, in order to improve the dispersibility of magnetic powder, dispersants such as oleic acid and lecithin were cooled in magnetic paints, and resins such as nitrocellulose, vinyl chloride, and hinyl acetate copolymers and polyisocyanates were added. Compounds (for example, Desmodur L, a trifunctional adduct consisting of tolylene diisocyanate and trimethylolpropane, manufactured by Bayer)
Toga is manufactured by Nippon Polyurethane Industries Co., Ltd. Product name: Coronate L
etc.) have been used in combination. However, a coating material with sufficient magnetic powder dispersibility has not yet been obtained.

[Means for solving problems]

Partially oxidized nitrocellulose with cardixyl group is
It has excellent dispersion performance for magnetic powder and is already used in magnetic paints. (Japanese Unexamined Patent Publication No. 58-34872). The present inventors have discovered that when a specific polyisocyanate is added to this partially oxidized nitrocellulose, a magnetic coating material with improved dispersibility and a coating film with excellent surface properties can be obtained, leading to the present invention.

That is, the present invention provides a magnetic paint mainly composed of magnetic powder and a binder, in which the binder has a carboxyl group content of 2.
mmoB/Nitrocellulose 10 (a magnetic paint containing one or more partially oxidized nitrocellulose and 1,8-diisocyanate-4-isocyanate methyloctane (hereinafter referred to as triisocyanate)).

The triisocyanate used in the present invention is a new trifunctional polyisocyanate having the structure shown below.

0ON-OHz-CH2-OHM -0H-OHr-O
Hr-OH20H2-NOOOH2-Ne.

It is not clear why the combination of this compound and partially oxidized nitrocellulose provides higher dispersibility than before, but it is probably because it has a lower viscosity and better compatibility than conventional polyisocyanates.

The carboxyl group content of the partially oxidized nitrocellulose used in the present invention is 2 mmol/1 nitrocellulose
001 or more, and if it is less than this, it is difficult to improve the dispersibility.

Here, the carboxyl group content is measured as follows. Approximately 1.5 fff of partially oxidized nitrocellulose
Weigh and add 0, IN HC to a 100WLl Erlenmeyer flask.
Add about 50 mJ of λ water bath solution, shake well, and leave to stand for about 2 hours. Next, the contents are filtered, the partially oxidized nitrocellulose is thoroughly washed with deionized water, and the main washing is stopped to confirm that the washing liquid is completely neutral. Put this in a beaker with a small amount of water, weigh the sample and water, and then
11I! Add to a beaker, shake well and leave overnight.

20 d of supernatant liquid is taken from this beaker and titrated with a 0.01 N NaOH aqueous solution using phenolphthalein as an indicator. A blank test is performed using 20 wt1 of a 9.05M calcium acetate aqueous solution, and the carboxyl group content is calculated using the following formula.

This partially oxidized nitrocellulose is produced by oxidizing ordinary nitrocellulose with oxidizing agents such as nitrogen oxides, hypochlorous acids, chlorous acids, chloric acids, perchloric acids, permanganic acids, dichromic acids, and hydrogen peroxide. It can be obtained by Alternatively, it can be obtained by oxidizing cellulose raw materials such as linters and pulps in advance with the oxidizing agent described above, and then converting them into nitric acid esters with nitric acid or a sulfur-nitric acid mixed acid.

In the present invention, it is also possible to use the following resins as a binder. Such resins include vinyl chloride-vinyl acetate copolymers, vinylidene chloride copolymers, acrylic ester copolymers, polyamide resins, polyester resins, polyurethane resins, polyvinyl butyral resins, nitrile rubber, epoxy resins,
Examples include phenoxy resins, urea resins, melamine resins, and cellulose enzymes.

In the magnetic paint of the present invention, the partially oxidized nitrocellulose is used in an amount of 5 to 80 parts by weight, preferably 10 to 60 parts by weight, based on 100 parts by weight of the total binder.

In addition, triisocyanate has an isocyanate equivalent of 0 per equivalent of the active hydrogen equivalent of partially oxidized nitrocellulose and the active hydrogen equivalent of other resins used together.
．． 1 to 1.0 equivalents, preferably 0.3 to 0.8 equivalents are used.

The magnetic powder used in the present invention includes γF''
iron oxide such as to@m Fem04, iron oxide containing conozult doped with or coated with conozult, chromium dioxide, or Fe e Fa-Co,
Examples include ferromagnetic metal powders such as Fe-Oo-N I.

These magnetic powders are used in an amount of 10 parts by weight per 100 parts by weight of the total binder.
0 to 1500 parts by weight, preferably 150 to 1000 parts by weight are used.

The magnetic paint of the present invention may also contain a dispersant, a lubricant, an abrasive, an antistatic agent, and the like, if necessary.

As dispersants, fatty acids having 12 to 18 carbon atoms such as capric acid, lauric acid, myristic acid, stearic acid, oleic acid, and linoleic acid, alkali metal salts or alkaline earth metal salts of these fatty acids, lecithin, etc. are used. can.

In addition, these dispersants are used in an amount of 1 to 100 parts by weight of the binder.
It is preferable to add 20 parts by weight. As a lubricant,
Solid lubricants such as molybdenum disulfide and tungsten disulfide,
and various silicone oils, fluorocarbons, fatty acid esters, etc. can be used, but the amount of binder added is 1
It is preferably controlled to 0.1 to 20 parts by weight relative to 0.00 parts by weight. dl, fused alumina, as abrasive
Examples include materials with relatively high hardness such as silicon carbide, chromium oxide, and control, and the average particle size of these materials is preferably 2 μm or less.

Antistatic agents include carbon black, natural surfactants such as saponin, alkylene oxy-P type, glycerin type nonionic surfactants, higher alkylamines, quaternary ammonium salts, pyridine and other complex salts, etc. Cationic surfactants, anionic surfactants with acidic groups such as carboxylic groups, sulfonic groups, phosphoric acid groups, sulfuric ester groups, phosphoric ester groups, amino acids, aminosulfonic acids, sulfuric esters or phosphoric esters of amino alcohols Amphoteric surfactants such as can be used alone or in combination. These surfactants are used as antistatic agents, but may also be used for the purpose of improving dispersibility and lubricity depending on the case.

The magnetic paint of the present invention is produced by mixing the above-mentioned binder, magnetic powder, and optionally used dispersant, lubricant, abrasive, antistatic agent, etc. with an organic solvent, and then using a dispersion machine such as a sol mill, sand mill, or attritor. It can be obtained by sufficiently cross-talking and dispersing using . Examples of organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, amyl acetate,
Examples include esters such as ethyl cellosolve acetate and butyl cellosolzoacetate, ethers such as dioxane and tetrahydrofuran, aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic hydrocarbons such as hexane and heptane.

Although these organic solvents may be used alone, they are usually used in combination. The amount used is 100 to 2000 parts by weight per 100 parts by weight of the binder.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples. In the following examples, all "parts" refer to one scenic town.

Example 1 A magnetic paint having the following composition was produced.

Co coated type r Fe2O3 100 parts Lecithin 2 parts Alumina 2 parts Carzen black 3 parts, r<butyl rumitate
1 part methyl ethyl ketone
60 parts toluene
90 parts cyclohexanone 60 parts The above composition was placed in a sol mill, mixed and dispersed for 48 hours, and then 1.8 parts of triisocyanate (approximately 0.6 isocyanate equivalents based on the total hydrogen equivalent) was added.
A magnetic paint was prepared by dispersing for 0 minutes.

This magnetic paint was applied onto a 15μ thick polyester film.
It was applied to a dry film thickness of 5 μm and dried to obtain a magnetic tape.

The surface gloss of the obtained magnetic tape was measured.

The results are shown in Table-1. Please note that the measurement was performed using a variable angle gloss meter (
[manufactured by Suga Test Instruments] was used to measure the 600-60' f1 surface gloss, and the results are shown as values when a standard blackboard is set to 91.5.

Example 2 Instead of partially oxidized nitrocellulose in Example 1,
Viscosity type 2%, calzexyl group amount 8 mmoj! /Nitrocellulose 10 (1 (manufactured by Mukasei Kogyo Co., Ltd.)) was coated on a polystyrene film and dried to obtain a magnetic tape.

The surface gloss of the obtained magnetic tape was measured in the same manner as in Example 1. The results are shown in Table-1.

Example 3 In place of the partially oxidized nitrocellulose in Example 1, a partially oxidized nitrocellulose of viscosity type; 8L, calxyl group weight 15 mmoA/nitrocellulose 10 (manufactured by Mukasei Kogyo Co., Ltd.) was used. A magnetic coating material was prepared in exactly the same manner as in Example 1, and in the same manner as in Example 1, it was coated on a polyester film and dried to obtain a magnetic tape.

The surface gloss of the obtained magnetic tape was measured in the same manner as in Example 1. The results are shown in Table-1.

Comparative Example 1 Same as Example 1 except that 4 parts of Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.) (approximately 0.6 incyanate equivalent to the total hydrogen equivalent) was used in place of the triisocyanate in Example 1. A magnetic paint was prepared, and in the same manner as in Example 1, this was applied onto a polystyrene film and dried to obtain a magnetic tape.

The surface gloss of the obtained magnetic tape was measured in the same manner as in Example 1. The results are shown in Table-1.

Comparative Example 2' A magnetic coating material was prepared in the same manner as in Example 2, except that Coronet L4 was used in place of the triisocyanate in Example 2, and it was coated on a polystyrene film and dried in the same manner as in Example 2. and obtained a magnetic tape.

The surface gloss of the obtained magnetic tape was measured in the same manner as in Example 1. The results are shown in Table-1.

Comparative Example 3 A magnetic paint was prepared in the same manner as in Example 3, except that Coronate ~ L4 part was used in place of the triisocyanate in Example 3, and it was applied and dried on a polystyrene film in the same manner as in Example 3. A magnetic tape was obtained.

The surface gloss of the obtained magnetic tape was measured in the same manner as in Example 1. The results are shown in Table-1.

Reference Example 1 Same as Example 1, except that ordinary nitrocellulose, H3A calxyl group weight 0.2 mmol/nitrocellulose 100f (manufactured by Mukasei Kogyo Co., Ltd.) was used in place of the partially oxidized nitrocellulose in Example 1. A magnetic paint was prepared in exactly the same manner as in Example 1, and was applied onto a polystyrene film and dried to obtain a magnetic tape.

The surface gloss of the obtained magnetic tape was the same as in Example 1. It was measured as follows. The results are shown in Table-1.

Reference Example 2 In Example 2, instead of the partially oxidized nitrocellulose, ordinary nitrocellulose was used, and AlH3 parts% cardexyl group amount: 0.5 mmol, /nitrocellulose 10
A magnetic paint was prepared in exactly the same manner as in Example 2, except that 1 (manufactured by Mukasei Kogyo Co., Ltd.) was used, and in the same manner as in Example 2, it was applied onto a polystyrene film and dried to obtain a magnetic tape. Ta.

The surface gloss of the obtained magnetic tape was measured in the same manner as in Example 1. The results are shown in Table-1.

Reference Example 3 In Example 3, in place of the partially oxidized nitrocellulose, normal nitrocellulose was used, and 5L-1°carxyl group i; 1. OmmoA/Nitrocellulose 10
Example 3 except that (1 (manufactured by Mukasei Kogyo Co., Ltd.) was used)
A magnetic paint was prepared in exactly the same manner as in Example 3, and it was applied onto a polystyrene film and dried to obtain a magnetic tape.

The surface gloss of the obtained magnetic tape was measured in the same manner as in Example 1. The results are shown in Table-1.

Table 1 [Effects of the invention] The magnetic paint containing partially oxidized nitrocellulose and triisocyanate of the present invention has a surface gloss that is easily removed (dispersibility of magnetic powder) compared to the conventional magnetic paint using Coronate L. magnetic tape can be given.

Watch applicant Asahi Kasei Kogyo Co., Ltd. Procedural amendment (voluntary) January 3, 1985 Manabu Shiga, Commissioner of the Patent Office 1, Indication of the case 1988 Patent application No. ρ2/n e 2, Name of the invention Magnetic paint 3. Relationship with the case of the person making the amendment Patent applicant 1-2-6-4 Dojimahama, Kita-ku, Osaka-shi, Osaka Prefecture Subject of the amendment As per the attached sheet Contents of the amendment (1) Line 3 of page 2 of the specification Correct "The fractional property is poor" to "The dispersibility is poor."

(2) On page 2, lines 9-10, "vinyl chloride, vinyl acetate copolymers, etc." is corrected to "vinyl chloride-vinyl acetate copolymers, etc."

(3) On page 3, line 7, "magnetic powder and binder" is corrected to "magnetic powder and binder".

(4) "Ion conversion" on page 4, line 13 is corrected to "ion exchange."

(5) On page 7, line 5, "capric acid" is corrected to "capric acid."

(6) On page 11, line 12, [on polystyrene film] is corrected to [on polyester film].

(7) On page 12, lines 11-12, "on polystyrene film" is corrected to "on polyester film."

(8) On page 12, line 20, "on polystyrene film" is corrected to "on polyester film."

(9) On page 13, lines 8 and 18, "on polystyrene film" is corrected to "on polyester film."

(10) "On polystyrene film" in lines 8 and 18 of page 14 is corrected to "on polyester film."

that's all

Claims (1)

[Claims] In a magnetic paint mainly composed of magnetic powder and a binder, the binder comprises partially oxidized nitrocellulose having a carboxyl group content of 2 mmol/100 g or more of nitrocellulose and 1,8-diisocyanate-4-isocyanate methyloctane. A magnetic paint characterized by containing