JPS58152065A - Magnetic paint - Google Patents

Abstract

PURPOSE:To provide a high-performance magnetic paint having excellent abrasion resistance and flexibility and useful for the coating of magnetic tape, etc., by compounding a urethane prepolymer solution having active hydrogen terminal group reactive with isocyanate group, with magnetic powder and a polyfunctional isocyanate solution. CONSTITUTION:The objective coating composition can be prepared by mixing (A) a urethane prepolymer solution derived from (i) a diisocyanate (e.g. diphenylmethane diisocyanate), (ii) a polyol having a molecular weight of 500-3,000, (iii) a chain extender having a molecular weight of <=500 e.g. aliphatic diol etc. of formulasI-V (R<1> is 2-10C alkylene; R<2> is 2-10C alkylene or cycloaliphatic group; R<3>-R<5> are phenyl, benzyl, 1-7C alkyl, or OH-containing alkyl having two OH groups in a molecule; A and B are group containing aromatic ring) , with (B) magnetic powder and (C) a polyfunctional isocyanate solution. USE:Coating of magnetic sheet, card, disk, drum, etc.

Description

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

Recently, magnetic materials for magnetic recording are required to have increasingly high performance. 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 a tape is also an important factor.

In general, polyurethane resin is often used as a surface coating resin when manufacturing magnetic tapes and the like. However, conventional polyurethane has a low ability to disperse magnetic powder, and to compensate for this, soybean lecithin is used as a dispersant.
Adverse effects such as bleeding occur during long-term use.

In order to improve such dispersibility, resins with good dispersibility such as nitrocellulose are also used in combination, but nitrocellulose/
L/Loose coating film is brittle and has the disadvantage of reducing the durability of the magnetic tape when used in combination.

An object of the present invention is to provide a magnetic paint containing a polyurethane resin as a binder, which has high abrasion resistance and flexibility.

Another object of the present invention is to provide a magnetic coating material whose binder is a polyurethane resin which has excellent dispersibility of magnetic powder.

The present inventors found that magnetic powders such as γ-Fe2O3 are generally acidic and polar, and have strong interactions, so particles tend to aggregate, making it difficult to disperse them into primary particles. If a titanium coupling agent is copolymerized in the polymer, this titanium coupling agent will strongly bond to rFe2O3 etc. through the OH group present on its surface, resulting in a transesterification reaction, resulting in an affinity between the polymer and the magnetic powder. It has been discovered that polyurethane resin can be given excellent dispersion properties in addition to its inherent wear resistance and flexibility.

That is, the present invention is a diisocyanate with a molecular weight of 500 or more.
(6) magnetic powder,
6) Pertains to a magnetic paint obtained by mixing a polyfunctional incyanate solution.

Various diisocyanates can be used in the present invention, such as Schiff-enylmethane diincyanate (MDI), ) lylene diisocyanate (T
DI), xylylene diisocyanate (XDI), naphthylene diisocyanate (isophorone diisocyanate with NDI (IPDI), hexamethylene diisocyanate (dicyclohexylmethane diincyanate (HMDI) with HDI), etc. are preferred, and MDI is particularly preferred.

As polyols having a molecular weight of 500 to 3,000, various polyester diols, polyether diols, polycarbonate diols, and others can be used. Specifically, polyethylene adipate, polybutylene adipate, poly(
neopentyl-1,6-hexamethylene) adipate,
Polycaprolactone diol, polyester diol containing terephthalic acid and aliphatic dicarboxylic acid as acid components (product names Pylon RUx and Vylon RV'-20OL, manufactured by Toyobo, Japan), polyoxyprepylene diol, polyoxytetramethylene diol, etc. can be mentioned,
Desmophene 20 is also used as a polycarbonate diol.
20E (Bayer AG, West Germany) as other diols, polybutadiene diol (trade name G-1000,
(manufactured by Nippon Soda, Japan) is an example. If the polyol molecular weight is less than 500, the polyurethane will be too hard to bend, the scratch resistance will be reduced, and the properties required for a magnetic paint will not be met. Moreover, if the molecular weight exceeds 30θO, it will be too flexible and the toughness, which is a characteristic of Frethane, will be impaired.

As chain extenders with a molecular weight of 500 or less, various diols,
Diamines, amino alcohols, etc. can be used, and preferable examples thereof include, for example, the general formula % (R' is a linear or branched alkylene group having 2 to 10 carbon atoms, and is linked to an oxygen atom). You can leave it there.

R2 is a linear or branched alkylene group or alicyclic group having 2 to 10 carbon atoms. R3゜R4 and R5 are phenyl group, benzyl group, alkyl group having 1 to 7 carbon atoms, or O
It is an alkyl group having an H group, and the molecule as a whole has two OH groups. A and B are groups having an aromatic ring. ), aliphatic diols, aliphatic diamines, tertiary amino diols, aromatic diols, aromatic diamines, etc. can be mentioned.

Preferred examples of the aliphatic diol include ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neohentyl glycol, diethylene glycol, dipropylene glycol, etc. Specific examples of the aliphatic diamine include ethylene diamine, 1.6- Specific examples of tertiary amino diols include hexamethylene diamine, inphorone diamine, etc.
Examples include methylgetanolamine, N-goutylgetanolamine, N,N-dimethyl-bis-hydroxymethylethylamine, N-phenyldiethanolamine, and N-benzylgetanolamine.

Further, as A of the above aromatic diol, for example, 0
Examples include 0.

As the titanium coupling agent, a titanium compound having at least two active hydrogens that react with incyanate groups and at least one group that is susceptible to hydrolysis is suitable. Specific examples include tetraisopropyl bis(dioctyl phosphite) titanate (trade name Prene Act 41B, manufactured by Ajinomoto Co., Japan), tetraoctyl bis(ditridecyl phosphite) titanate (trade name Prene Act 46B), and tetra(2,2-diallyl). Oxymethyl-1-butoxy)bis(ditridecyl)phosphite titanate (trade name PreneAct 55), isopropyl tri(N-ethylaminoethylamino) titanate (trade name PreneAct 43), Improvil trianthranyl titanate (trade name PreneAct 52) , Isoprobyl di(4-aminobenzoyl) isostearoyl titanate (trade name: Prene Act 37BS), 4-aminebenzenesulfonyldotecylbenzenesulfonyloxyacetate titanate (trade name: Prene Act 1 26Sλ4)
Examples include -aminobenzoyl isostearoyl ethylene titanate (product name: Prene Act 237), dianthranyl ethylene titanate (product name: Prene Act 252), and the like. When these titanium camping agents have an amino group in the molecule, ethylene oxide or propylene oxide can be added to the amino group for use. The copolymerization ratio of the titanium coupling agent is preferably such that the content as titanium atoms in the Frethane prepolymer is about 0.01 to 20 wt%, particularly about 0.05 wt%.
~lowt% is preferred.

In the present invention, the diisocyanate, polyol, chain extender, and titanium coupling agent are reacted to produce a fletane prepolymer.
The CO/active hydrogen equivalent ratio is preferably in the range of 0.7 to 1.0, the molecular weight is preferably about 30,000 or less, and the terminal group is preferably OH, NH2, NH1, or the like. A solvent is used in the prepolymerization reaction, and suitable solvents include ketones such as acetone, methyl ethyl ketone, methyl imbutyl ketone, and cyclohexanone, aromatic hydrocarbons such as benzene, toluene, and xylene, ethyl acetate, butyl acetate, etc. Examples include esters of, methyl cellosolve acetate, ethyl cellosolve acetate, dimethyl formamide, dimethyl acetamide, and the like.

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 1-Fe203, cobalt-doped bertolide compounds of F~03 and Feρ4, etc. can be mentioned. The blending amount of magnetic powder is 100w of polymer.
Preferably, it is about 50 to 100 parts by weight to t parts.

As the polyfunctional incyanate in the present invention, a polyisocyanate having two or more functional groups can be used. Preferred specific examples include various diisocyanates that can be used in the production of the Frethane prepolymer, and trifunctional incyanates obtained from trimethylolpropane and TDI (trade name: Tesmodule L1, manufactured by Bayer AG, West Germany); Examples include trifunctional isocyanate (trade name Desmodur N75), polyalkylene polyphenylinocyanate (PAPI), and polymeric polyisocyanate (PPI).

The polyfunctional incyanate is preferably used after being dissolved in a solvent, and the same solvent as used in the prepolymerization reaction can be used as the solvent.

The magnetic paint of the present invention is obtained by mixing the urethane prepolymer solution, magnetic powder, and polyfunctional isocyanate solution. The ratio of isocyanate groups to active hydrogen in the magnetic paint is preferably in the range of about 0.9 to 1.5 in terms of equivalent ratio. When considering active hydrogen contained in magnetic powder and other additives, it is preferable to increase the value even higher. Incidentally, the phretanization reaction of the present invention can also be carried out using a one-shot method.

In the present invention, the polyurethane resin is compatible with polyurethane resins such as vinyl chloride resins, vinylidene chloride resins, polyester resins, alkyd resins, epoxy resins, acrylonitrile-butadiene rubber, etc., to the extent that the purpose of the present invention is not impaired. A soluble resin can be blended. In addition, in the present invention, dispersants, lubricants,
Additives such as abrasives and antistatic agents may also be added.

As the dispersant, fatty acids having 8 to 18 carbon atoms such as caprylic acid, lafric acid, stearic acid, and linoleic acid, their alkali metal salts, alkaline earth metal salts, lecithin, and higher alcohols can be used.

As the lubricant, silicone oil, carbon black, graphite, molybdenum disulfide, fatty acid esters, etc. can be used.

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

Examples of antistatic agents include cationic surfactants such as higher amine halogenates, alkylpyridinicum halides, and quaternary ammonium salts, and anions such as higher fatty acid alkali salts, alkyl sulfates, alkyl sulfonates, and alkyl phosphates. Surfactants, nonionic surfactants such as alkylene oxide type, glycerin type, and sorbitan type, and amphoteric surfactants such as amino acids and aminosulfonic acids can be used.

The magnetic paint 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.

The magnetic paint of the present invention can be applied to supports in various forms such as tapes, sheets, cards, tapes, and drums. The support usually has a thickness of about 5 to 50μ, preferably about 10μ.
~40μ is good, and materials include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose such as cellulose acetate, etc.
W conductor, polycarbonate, polyamide, polyimide,
Polyamideimide and the like are preferably used. Various methods can be used to apply the magnetic coating onto the support, such as impregnation coating, air doctor coating, air knife coating, grade coating, reverse roll coating, gravure coating, cast coating, and spray coating. After coating, a treatment is carried out to mix in magnetic powder if necessary, and then it is dried.

The drying temperature is usually about 20 to 100°C, and the drying time is preferably about 5 minutes to 5 hours. Usually 50 after drying
It is preferable to cure at ~140°C for about 1 minute to 2 hours. Moreover, if necessary, the surface can be smoothed and cut into a desired shape.

EXAMPLES The present invention will be described in detail below with reference to Examples, Comparative Examples, and Test Examples.

Example 1 ll equipped with a thermometer, stirrer, and nitrogen gas introduction pipe! MD I, 45.1 fl (
0.18 mol), polycaprolactone diol (trade name PCP-0240, Union Carbide Company, USA)
200y (0.1 mol) and methyl ethyl ketone (ME
K) 329y was added and reacted at 80°C with stirring for 3 hours to obtain an NCO-terminated prepolymer, and further pre-act 55.11.3y (6,3X10-3 mol) and 4.4
'-Bis(hydroxyethyl)bisphenol A (trade name AE-2, molecular weight 31.6.4, Japan, Meisei Kagakusha)
25.3y (0.08 mol) and 329y of toluene are added and reacted at 75-80°C for 3 hours to obtain a fletambre polymer solution. This solution has a viscosity of 450 at 25°C.
It was a pale yellow transparent liquid with a solid content of 30% cps.

This Furetane prepolymer solution 100y, magnetic powder (r
Fe20a) 100y and Desmodur L, 8y were kneaded in a ball mill for 3 hours to obtain the magnetic paint of the present invention.

Example 2 A Fretambre polymer solution with a solid content of 30% was obtained in the same manner as in Example 1 using the following components.

MDI 45.
1y (0,18 mol) pylon RUX
2001i' (0,2 mol) MEK
298y N-methyljetanolamine 9.5y Brenact 55 10.1
y toluene 298y Next, this Frethane prepolymer solution (viscosity 520 cps/25°
A magnetic coating material of the present invention was obtained in the same manner as in Example 1 except that C (light yellow transparent liquid) was used.

Comparative Example 1 A solid content of 3 with a viscosity of 430 cps/25°C was prepared in the same manner as in Example 1 except that Pre-Act 55 was not used.
A 0% pale yellow transparent urethane prepolymer solution was obtained.

Example 1 except for using this Frethane prepolymer solution
A comparative magnetic paint was obtained in the same manner as above.

Test Example 1 Sedimentation Test The magnetic paints of Examples and Comparative Examples (solutions obtained without adding desmodules) were placed in 18m x 180m test tubes at a depth of 1Oσ and left for 24 hours.
Check the degree of O3 sedimentation. The better the dispersibility, the less likely it is to settle. The results are shown in Table 1.

Claims (1)

[Claims] (υ(a) ■ Diisocyanate ■ Polyol with a molecular weight of 500 to 3000 ■ Molecular weight 5
00 or less and a cretan prepolymer solution with an active hydrogen group terminal that can react with the incyanate group obtained from the titanium coupling agent, [F]) the magnetic powder, and (C) the polyfunctional isocyanate solution. Magnetic paint obtained by A+ CH2CR20H)2, H2N-13-NR2(
R' is a straight-chain or branched alkylene group having 2 to 10 carbon atoms, and may be linked via an oxygen atom. R
2 is a linear or branched alkylene group or alicyclic group having 2 to 10 carbon atoms. R3, R4 and R5 are a phenyl group, a benzyl group, an alkyl group having 1 to 7 carbon atoms, or an alkyl group having an OH group, and the molecule as a whole has two OH groups. A and B are groups having an aromatic ring. ) Claim 1 is an aliphatic diol, aliphatic diamine, tertiary amino diol, aromatic diol or aromatic diamine represented by
Section magnetic paint. (3) The equivalent ratio of NGO/active hydrogen of Fretan prepolymer is 0.7 to 1.0, and the molecular weight is about 30.000.
The magnetic paint according to claim 1, wherein the terminal group is OH, NR2, ]NH1, or the like. (4) The magnetic paint according to claim gg1, wherein the magnetic powder is iron-1, chromium, nickel, co-metallic acid, an alloy thereof, an oxide thereof, or a modified product thereof. (5) Approximately 50% of the magnetic powder is added to 100wt part of the polymer.
The magnetic paint according to claim 1, which is blended in an amount of 100 wt. (6) The magnetic paint according to claim 1, wherein the polyfunctional incyanate is a polyisocyanate having two or more functional groups. (7) The magnetic paint according to claim 6, wherein the polyfunctional incyanate is a trifunctional triisocyanate.