JPS6015473A - Magnetic paint - Google Patents

Abstract

PURPOSE:To provide a magnetic paint in which dispersibility of magnetic powder is improved and which has improved resistance to hydrolysis and heat and improved compatibility with other resins and gives a film having improved hardness, containing a specified polyurethane contg. carboxyl groups and a magnetic powder. CONSTITUTION:A magnetic paint contains a polyurethane (A) contg. carboxyl groups, obtd. by reacting a polyol, as ioscyanate compd. and a dihydroxycarboxylic acid, and a magnetic powder (B). Examples of the polyols are polyester polyols and polyether polyols. Examples of the isocyanate compds. are hexamethylene diisocyanate and polymethylene-polyphenyl polyisocyanate. Examples of the dihydroxycarboxylic acids re 2,2-dimethylolpropionic and tartaric acid.

Description

[Detailed description of the invention] The present invention relates to magnetic paint.

Recently, there has been a demand for magnetic particles with increasingly higher performance for magnetic recording. For this purpose, it is important to improve the magnetic powder, but the binder used when applying the magnetic powder onto a support such as tape is also an important factor1. During manufacturing, polyurethane resins are often used as surface coating resins because they are highly flexible and can form strong coatings. However, conventional polyurethane has a low ability to disperse magnetic powder, and to compensate for this, soybean lecithin or the like is used as a dispersant, but adverse effects such as bleeding occur during long-term use. To improve such dispersibility, nitrocellulose, polyvinyl butyral,
PVC/1! Il: Although resins with good dispersibility such as vinyl/vinyl alcohol copolymers have been used, they have the disadvantage of poor abrasion resistance and flexibility.

An object of the present invention is to provide a magnetic coating 1 in which the dispersibility of magnetic powder is significantly improved.

Another object of the present invention is to provide a magnetic coating material that has excellent hydrolysis resistance, heat resistance, film hardness, compatibility with other resins, etc.

A further object of the present invention is to provide a magnetic paint having a high molecular weight and a high content of carboxyl groups.

The present invention relates to a magnetic paint containing a polyurethane (5) having a carboxyl group obtained by reacting a polyol, an incyanate compound, and a dihydroxycarboxylic acid having two hydroxyl groups and a carboxyl group, and a magnetic powder (13).

In the present invention, using dihydroxycarboxylic acid, NC010
Since the urethanization reaction is carried out when the f-I ratio is close to 1, a high molecular weight polyurethane having carboxyl groups can be obtained. As a result, in the present invention, not only excellent dispersibility of the magnetic powder was improved, but also significant improvements were achieved in hydrolysis resistance, heat resistance, film hardness, compatibility with other resins, etc.

The structure of the present invention will be described in detail below.

The carboxyl group-containing polyurethane (5) of the present invention can be obtained by reacting a polyol, an isocyanate compound, and two OH groups with a carboxyl group-containing dihydroxycarboxylic acid, using a chain extender if necessary. You can also do that.

In the present invention, various polyester polyols, polyether polyols, and other polyols can be used as the polyol. Specific examples of polyester polyols include adipate polyols such as polyethylene adipate polyol, polybutylene adipate polyol, and polyethylene propylene adipate polyol, terephthalic acid polyols (e.g., Toyobo Co., Ltd., trade names Vylon ILUX, Vylon V-20OL), and polyester polyols. Specific examples of polyether polyols include caprolactone polyol (eg, Daicel Chemical, trade names Plaxel 212, Plaxel 220), and polyoxyethylene glycol, polyoxypropylene polyol, polyoxytetramethylene polyol, and the like.

In addition, other polyols include polycarbonate polyol (e.g., Bayer AG, West Germany, trade name Tesmofuen 2020E), polybutadiene polyol (e.g., Nippon Soda, trade name G-1000, G-2000, G-30).
00, Idemitsu Petrochemical, trade name Polybd-451-
IT), polypentadiene polyol, castor oil polyol, etc., and one or more types can be used. .

The isocyanate compound used in the present invention may be any polyisocyanate known in polyurethane chemistry, such as hexamethylene diisocyanate (HJ) I), isophorone diisocyanate (I
PDI), 4,4-dicyclohexylmethane diisocyanate (HMDI), 2.4-1-lylene diisocyanate (24-TD I ), λ6-lylene diisocyanate (2,6-TD I ), 4.4'- Diphenylmethane diisocyanate (M DI), carposiimide modified M DI, polymethylene polyphenyl polyisocyanate (PA PI), orthotoluidine diisocyanate (TOI) I), naphthylene diisocyanate (NDI), xylylene diisocyanate (
XDI), lysine diisocyanate (LDI), etc., and one type or two or more types can be used.

Examples of dihydroxycarboxylic acids of the present invention include 42-
Dimethylolpropionic acid (DMPA), tartaric acid, dioxyadipic acid, furionic acid, etc. can be used.

Examples of chain extenders include 2- to G-functional polyols with a molecular weight of 500 or less and diamines having a primary or secondary terminal amino group with a molecular weight of 500 or less. Suitable chain extenders include, for example, (a) ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, hexanediol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, ■, 4-cyclohexanediol, 1, Polyols such as 4-cyclohexane dimetatool and xylylene glycol (1)) Diamines such as hydrazine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, and 1.4-cyclohexanediamine (C) Ethanolamine, jetanolamine , alkanolamines such as triethanolamine (d) hydroquinone, pyrogallol, 4,4-isopropylidenediphenol, aniline, and the polyols and diamines listed in 2.
Examples include polyols having a molecular weight of 500 or less obtained by adding propylene oxide and/or ethylene oxide to alkanolamines in any order.

The polyurethane (a) of the present invention is synthesized using the above components, and the N COIndex is usually about 09 to 1.
．． 2, preferably in the range of about 0.95 to 11. The manufacturing method may be any known method, such as a one-shot method or a prepolymer method.

Carboxyl group-containing polyurethane (5) of the present invention obtained as above, in which a urethanization catalyst can also be used
The carboxyl group concentration in polyurethane 12 is Q,
Q5meq or more is preferred. - The carboxyl group may be in the form of various salts thereof such as alkali metal salts and ammonium salts.

Various types of magnetic powder can be used in the present invention, including iron, chromium, nickel, cobalt, alloys thereof, oxides thereof, and modified products thereof. Specific examples of oxides include γ-Fe2O3, ferrite, magnetite, CrO2, etc., and examples of modified products include cobalt-doped γ-Fe2O3, cobalt-doped F'e20B and Fe3O4 bertolide compounds, etc. can be mentioned. The blending amount of magnetic powder is polymer 1
Preferably, 00ω is approximately 50 to 20,000 Jt parts.

As the polyfunctional isocyanate compound used if necessary in the present invention, a polyisocyanate having two or more functional groups can be used.4, Preferred specific examples include the polyisocyanate compound used in the production of the polyurethane (5) described in +iiJ, !
) and trifunctional isocyanate obtained from I.limethylolpropane and TDI (product name Desmodur L1 West Germany, Bayer AG; Coronate L1 Nippon Polyurethane Co., Ltd.), trifunctional isocyanate (trade name) obtained from Bayer AG (trade name: Product name: Desmodur N75, same (■, same 1-1, etc.), polymeric polyisocyanate (P) The magnetic paint of the present invention is a mixture of carboxyl group-containing polyurethane (5), magnetic powder, and optionally a polyfunctional isocyanate compound. It can be obtained by

N COIndex in magnetic paint is usually about 09~
A range of 1.5 is appropriate, but it is preferable to increase it even higher when considering active hydrogen contained in magnetic powder and other additives.

In the present invention, vinyl chloride resins, vinylidene chloride resins, vinyl chloride/vinyl acetate copolymer resins, vinyl chloride/vinyl acetate/vinyl alcohol copolymer resins (manufactured by UCC,
VAG I-1, etc.), nitrocellulose, polyvinyl butyral resin, polyvinyl acecool resin, polyester resin, alkyd resin, epoxy resin, acrylonitrile-butadiene rubber, and other resins can be blended. In the present invention, dispersants, lubricants,
Additives such as abrasives and antistatic agents may also be added.

The magnetic coating material of the present invention can be produced by mixing the above-mentioned components by various methods. For example, it is preferable to use a mixer, roll mill, ball mill, sand mill, high-speed impeller, etc. In particular, it is preferable to add the polyfunctional isocyanate compound after thorough dispersion, as this will extend the pot life. In the production of the polyurethane (2) of the present invention and in the production of the above-mentioned magnetic paint, it is particularly preferable to use a solvent, and suitable solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Ketones such as benzene, toluene, xylene, etc., esters such as ethyl acetate, butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate,
Examples include 3-methoxybutyl acetate, ethylene glycol diacetate, dimethylpolamide, dimethylacetamide, and tetrahydrofuran.

The magnetic coating material of the present invention can be applied to supports in various forms such as tapes, sheets, cards, disks, drums, etc. according to known methods.

EXAMPLES The present invention will be described in detail below with reference to Examples, Comparative Examples, and Test Examples. Note that parts and % simply indicate parts by weight and % by weight.

Example 1 Byron I (, U X
(Molecular weight 2000) 500f, MDI 125ii' and cyclohexanone 1987 were weighed and reacted at 80°C for 2 hours in a stream of dry nitrogen. Next, DMPA33.5
Add ii' and cyclohexanone 7907 and heat to 80°C.
After reacting for 5 hours, the solid content was 40% and the viscosity was 580 cps.
(25°C), number average molecular weight I G 000, C0O
A solution of polyurethane (A) having an I-I group concentration of 0.38 meq/7 polymers is poured into I4I.

75 parts of polyurethane solution (5), 100 parts of modified γ-ferrite from 1 for edges, 40 parts of cyclohexanone and 85 parts of methyl ethyl ketone were placed in a ball mill and kneaded for 20 hours, followed by 75 parts of Desmodur L. In addition, the mixture was kneaded for an additional 2 hours to obtain the magnetic coating material of the present invention.

Example 2 DMP A of Example 1 33.5 f! D instead of
M1) A1687 and diethylene glycol 13
Similarly, using 2y, the solid content was 40% and the viscosity was 25°.
C) 550 cpS, number average molecular weight 15 (300, C0
A solution of polyurethane (5) with 0I-1 group concentration of 0.19 meq/f polymer was obtained.

Thereafter, a magnetic coating material of the present invention was obtained in the same manner as in Example 1 using this polyurethane solution.

・Example 3 Instead of MPA33.5f in Example 1, D M i'
Similarly, using A67y and diethylene glycol 2122, solid content 40%, viscosity (25°C) 010C
pS, l;! 1. A polyurethane solution of a polymer having an average molecular weight of 16,800 and a C00H group concentration of 0.08 mcq/f was obtained.

Thereafter, a magnetic coating material of the present invention was obtained in the same manner as in Example 1 using this polyurethane solution.

Comparative Example 1 DMP, A34 instead of DMPA33.5y in Example 1
1 and diethylene glycol 2391, solid content 40%, viscosity (25°C) 030 cps,
Number average molecular weight] (3700, C00I-I M&Q degree 0, 04 meq/f Polyurethane soluble itl
I got it. Hereinafter, a magnetic coating material was obtained in the same manner as in Example 1 using this polyurethane solution.

Comparative Example 2 In the same manner as in Example I, using 265 g of diethylene glycol instead of 33.5 y of DMP A, solid content 40%, viscosity (25°C) 590 cps, number average molecular weight 1 (iloo, C0OH A polyurethane solution with a base concentration of 0 was obtained.

Step 1': Using this polyurethane solution, apply magnetic paint in the same manner as in Example 1.

Test example ■ The magnetic # and Nil obtained in the old paper and comparative example were applied to polyester film soil using a doctor blade and dried to obtain a coating film with a thickness of 6μ. The degree of hardness was measured using a gloss meter 5-ao manufactured by Toyo Seiki Co., Ltd., and the results are shown in Table 1.

Table 1 (hereinafter “2”) Patent applicant: Toyo Rubber Industries, Ltd. Agent: Patent attorney Iwao Yamamura

Claims (3)

[Claims] (1) A magnetic paint containing a polyurethane (A) having a carboxyl group obtained by reacting a polyol, an isocyanate compound, two hydroxyl groups, and a dihydroxycarboxylic acid having a carboxyl group, and a magnetic powder (I3). (2) The magnetic paint according to claim 1, further comprising a polyfunctional isocyanate compound. (3) The magnetic paint according to claim 1, wherein the carboxyl group-containing polyurethane (g) has a carboxyl group concentration of 0.05 meq/f or more.