JPH0439505B2 - - Google Patents

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,
Improving the magnetic powder is important, but the binder used when applying the magnetic powder onto a support such as a tape is also an important factor. Generally, when manufacturing magnetic tapes and the like, polyurethane resins are often used as resins for surface coatings, which provide a highly flexible and tough coating. 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 dispersion ability, nitrocellulose, polyvinyl butyral,
Resins with good dispersibility such as vinyl chloride/vinyl acetate/vinyl alcohol copolymers have also been used in combination, but this has the disadvantage of poor abrasion resistance and flexibility. Various studies have been carried out with the aim of eliminating these drawbacks, such as (1) Japanese Patent Application Laid-open No. 44902/1982;
No. 51-44903, (3) No. 55-139634, (4) No. 55-
No. 139636, (5) No. 56-68925, (6) to (9) No. 56-
Magnetic recording bodies described in Nos. 101643 to 101646 are known. However, for example, in (1) and (2), a urethane-modified epoxy resin that does not contain OH groups is used.
In addition, in (3) to (9), urethane resins having OH groups are used, but these are not modified with epoxy resins, and the number of OH groups is usually 1 to 1.
The number of particles is about 5, and although the dispersibility has been improved to some extent, it is still insufficient, and it also has the disadvantage of poor hydrolysis resistance, heat resistance, etc. In addition, as a polyol component of OH group-containing polyurethane, (10) JP-A-57-60529 describes glycerin, etc.
There are methods that use hydroxy compounds with higher functionality, but in order to increase the OH group concentration and molecular weight, gelation occurs if the NCO/OH ratio approaches 1, and to avoid this, the NCO/OH ratio is When the molecular weight is lowered, the molecular weight becomes smaller, which has the disadvantage that the resulting coating film has lower strength. Furthermore, (11) JP-A-57-158022 uses a polyurethane elastomer and an epoxy resin using a specific isocyanate, but there is still room for improvement in dispersibility. An object of the present invention is to provide a magnetic paint in which the dispersibility of magnetic powder is significantly improved. Another object of the present invention is to provide a magnetic paint that has excellent hydrolysis resistance and adhesion to a base film. In the present invention, the epoxy group of a novolak-based epoxy-modified polyurethane resin is ring-opened with at least one of amines, carboxylic acids, and phenols.
OH group in the molecular chain that generated OH group
This invention relates to a magnetic coating composition whose main components are an organic solvent solution of a modified polyurethane resin containing 0.1 meq/g or more and a functional group number of 3 or more, and magnetic powder. In the present invention, the OH group is added to the molecular chain by 0.1meq/
By using an epoxy-modified polyurethane resin with a functional group count (the number of OH groups in the molecule) of 3 or more, a synergistic effect between the presence of a large number of OH groups and the presence of the bisphenol skeleton of the epoxy resin can be achieved. At the same time as improving the dispersibility of magnetic powder,
Significant improvements were achieved in hydrolysis resistance, adhesion to the base film, etc. The structure of the present invention will be described in detail below. The modified polyurethane resin having 3 or more functional groups containing OH groups in the molecular chain of the present invention is a polyol,
A urethane reaction is carried out by a known method using an isocyanate compound and a novolak-based epoxy resin,
It is then obtained by reacting with at least one of amines, carboxylic acids, and phenols. In this case it is also optional to use chain extenders. The content of OH groups in the modified polyurethane resin is preferably 0.1 meq/g or more, and the number of functional groups is 3.
Above, especially 6 or more is more preferable. 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 RUX, Vylon RV-200L), and polyester polyols. Examples include caprolactone polyol (eg, Daicel Chemical Co., Ltd., trade names Plaxel 212 and Plaxel 220). Specific examples of polyether polyols include polyoxyethylene glycol, polyoxypropylene polyol, polyoxyethylene polyoxypropylene polyol, polyoxytetramethylene polyol, and the like. In addition, other polyols include polycarbonate polyol (e.g., West Germany, Bayer AG, trade name Desmofene 2020E), polybutadiene polyol (e.g., Nippon Soda, trade name G-1000, G-
2000, G-3000, Idemitsu Petrochemical, product name Poly bd
R-45 HT), polypentadiene polyol, castor oil polyol, and the like. These polyols can be used alone or in combination of two or more. Various isocyanate compounds are exemplified, including diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), and 2,6-tolylene diisocyanate (2,6- TDI), tolylene diisocyanate (TODI), xylylene diisocyanate (XDI), naphthylene diisocyanate (NDI), isophorone diisocyanate (IPDI),
Examples include diisocyanates such as hexamethylene diisocyanate (8HDI), dicyclohexylmethane diisocyanate (HMDI), and lysine diisocyanate (LDI), and polyisocyanates such as carbodiimide-modified MDI, and these can be used alone or in combination of two or more. In the present invention, various novolac-based epoxy resins can be used as the epoxy compound,
For example, Epicote 152, 154, Sumiepoxy ELPN
-180, ESPN-180 and other phenol novolak epoxy resins, Sumiepoxy ESCN 220L,
Examples include cresol novolac epoxy resins such as EOCN-102, 103, and 104 manufactured by Nippon Kayaku Co., Ltd., such as 220F, 220HH, and ESMN-220L. In particular, epoxy resins having an epoxy group in the molecular chain represented by the following formula are preferably used. (R ¹ is hydrogen or a methyl group, n is a number of 1 or more on average, and 1<(average value of m+1)≦2) The epoxy group of the above epoxy group-modified polyurethane resin is further added to amines, carboxylic acids, etc. The ring is opened with at least one or more of phenols and phenols. Examples of amines include primary amines such as ethylamine and n-butylamine, secondary amines such as diethylamine, dipropylamine, and dibutylamine.
amines, alkanolamines such as ethanolamine, N-methylethanolamine, N-butylethanolamine, diethanolamine, and dipropanolamine, and carboxylic acids such as acetic acid, propionic acid, stearic acid, succinic acid,
Adipic acid, maleic acid, benzoic acid, phthalic acid,
Phenylacetic acid, hydroxyacetic acid (glycolic acid),
Lactic acid, 2,2-dimethylolpropionic acid, 9,
Examples include 10,12,13-tetraoxyoctadecanoic acid, acetic anhydride, succinic anhydride, maleic anhydride, and phthalic anhydride. Further, as the phenols, phenol, cresol, etc. are preferable.
These amines, carboxylic acids and phenols can be used alone or in combination. As a chain extender, for example, 2 with a molecular weight of 500 or less
~6-functional polyol and 1 with a molecular weight of 500 or less
Diamines having a primary or secondary terminal amino group are mentioned. Suitable chain extenders include (a) ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, hexanediol,
Polyols such as glycerin, trimethylolpropane, pentaerythritol, sorbitol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylylene glycol (b) hydrazine, erylenediamine, tetramethylenediamine, hexamethylenediamine, 1,
Diamines such as 4-cyclohexanediamine (c) Alkanolamines such as ethanolamine, diethanolamine, and triethanolamine (d) Hydroquinone, pyrogallol, 4,4-isopropylidene diphenol, aniline and the above polyols, diamines, Examples include polyols with a molecular weight of 500 or less obtained by adding propylene oxide and/or ethylene oxide to alkanolamines in any order. Epoxy-modified polyurethane resins are synthesized using the above-mentioned components, and in this case, the reaction is usually carried out at an NCO Index of about 0.7 to 1.2, preferably about 0.9 to 1.1. In the above-mentioned ring-opening reaction of the present invention, it is preferable to open all the epoxy groups, but it is of course possible to leave a part of the epoxy groups, and usually about 1 part of the amines and/or carboxylic acids is added to the epoxy group. It is preferable to use a double equivalent or less, preferably about 0.2 to 1 times equivalent. The reaction is usually carried out at a temperature of about 20-180°C, preferably about
It is best to do this at 100-150℃. In this case, it is possible to use known catalysts for curing epoxy resins, and tertiary amine and imidazole catalysts are particularly effective. The above ring-opened modified polyurethane resin of the present invention has a large number of OH molecules in its molecules and has extremely good dispersibility of magnetic powder. The number of OH groups is usually preferably 3 or more, generally 6 to 30, particularly preferably 10 to 20.
It is preferable to have OH groups. The magnetic coating composition of the present invention can be obtained by mixing the above-mentioned modified polyurethane resin containing a hydroxyl group, magnetic powder, and, if necessary, a polyfunctional isocyanate compound. in magnetic paint
A range of about 0.9 to 1.5 is usually appropriate for the NCO Index, but it is preferably higher when considering the active hydrogen contained in the magnetic powder and other additives. In the present invention, the modified polyurethane resin can be produced by a known method, such as a one-shot method,
It can be manufactured by a prepolymer method or the like. Urethane catalysts can also be used. The concentration of hydroxyl groups in the modified polyurethane resin of the present invention is preferably
It is 0.1meq/g or more. As the polyfunctional isocyanate compound, a polyisocyanate having two or more functional groups can be used. Preferred specific examples include the various isocyanate compounds mentioned above, and trifunctional isocyanates obtained from trimethylolpropane and TDI (trade name: Desmodyur L, manufactured by Bayer AG, West Germany; Coronate L, manufactured by Nippon Polyurethane Co., Ltd.);
Similar trifunctional isocyanates manufactured by Bayer (product names Desmodyur N-75, Desmodyur R, Desmodyur H, etc.), Hypren L-100, Sofuranate UEX-
504SS, polymethylene polyphenyl isocyanate (PAPI), polymeric polyisocyanate (PPI), 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-
Fe ₂ O ₃ , ferrite, magnetite, CrO ₂ , etc.
Examples of modified products include cobalt-doped γ-Fe ₂ O ₃ and cobalt-doped Fe ₂ O ₃ and Fe ₃
Examples include O ₄ bertolide compounds. It is also possible to use magnetic powders having various surface areas, and particularly when using ferromagnetic powders with a specific surface area of 25 m ² /g or more determined from the amount of nitrogen adsorbed by the BET method, excellent magnetic properties can be obtained.
The amount of magnetic powder blended is preferably about 50 to 2000 parts by weight per 100 parts by weight of the modified polyurethane resin. In the present invention, thermoplastic polyurethane resins, vinyl chloride resins, vinylidene chloride resins, vinyl chloride/vinyl acetate/vinyl alcohol copolymer resins (manufactured by UCC, VAGH, etc.), nitrocellulose, polyvinyl butyral may be used as long as the purpose is not impaired. Resins such as resins, polyester resins, alkyd resins, epoxy resins, and acrylonitrile-butadiene rubber can be blended. Various types of thermoplastic polyurethane resins can be used; specific examples include Paraprene 22S, 26S (manufactured by Nippon Polyurethane Co., Ltd.), Estan 5702, 5703, 5711, 5715 (manufactured by BF Gutdrich Co., Ltd.), Pandex T- 5201, 5205,
5102A (manufactured by Dainippon Ink Chemical Co., Ltd.) and the like. Furthermore, in the present invention, it is normally used as necessary. Additives such as dispersants, lubricants, abrasives, antistatic agents, etc. can be added. The magnetic paint of the present invention can be obtained by mixing the above-mentioned components by various known methods, and for example, a mixer, roll mill, ball mill, sand mill, high-speed impeller, etc. can be used. In particular, it is preferable to add the polyfunctional isocyanate compound after it has been sufficiently dispersed, since the pot life will be longer. Further, it is preferable to use an organic solvent during the production of the modified polyurethane resin of the present invention and the above-mentioned magnetic coating composition, and suitable solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; benzene, toluene,
Examples include aromatic hydrocarbons such as xylene, esters such as ethyl acetate and butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, 3-methoxybutyl acetate, ethylene glycol diacetate, dimethylformamide, and dimethylacetamide. The magnetic paint of the present invention can be applied to tapes, sheets, cards,
It is applied to various types of supports such as disks and drums. The support usually has a thickness of about 5 to 50μ,
It is preferably about 10 to 40μ, and suitable materials include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose acetate, polycarbonate, polyamide, polyimide, polyamideimide, and the like. Various methods can be used to apply the magnetic coating onto the support, such as impregnation coating, air doctor coating, air knife coating, blade coating, reverse roll coating, gravure coating, cast coating, and spray coating. After coating, the magnetic powder may be subjected to treatment to orient it if necessary, or dried if it contains a general organic solvent. The drying temperature is usually about 20 to 100°C, and the drying time is about 5 minutes or more, preferably about 5 minutes to 24 hours. After drying, it is usually preferable to cure at 50 to 140°C for about 1 minute to 2 hours. Furthermore, if necessary, a surface smoothing treatment can be performed before or after curing, or the material can be cut into a desired shape. 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 Diphenylmethane diisocyanate (MDI) 33.0 was placed in a 1 liter separable flask equipped with a thermometer, stirrer, nitrogen gas inlet tube and condenser.
g, Byron RV200L (molecular weight 2000) 88.0g, Plaxel 220 (molecular weight 2000) 88.0g, ESCN-220L
(Diol equivalent molecular weight 1300, epoxy equivalent weight 213)
18.3 g of 1,6-hexanediol, 3.2 g of cyclohexanone, and 559 g of cyclohexanone were weighed out and reacted in a dry nitrogen stream at about 80°C until no absorption at 2250 cm ^-1 based on NCO groups was detected by IR spectrum. Obtain a thick solution. Add 9.0 g of diethanolamine to this solution and heat at 140°C for 5 hours.
Allow the epoxy group to react with the NH group. The solution thus obtained had a solid content of 30%, a viscosity of 300 mpa·s (25°C), and a calculated OH group concentration of the polymer of 1.08 meq/g. 100 parts by weight of the modified polyurethane solution, 100 parts of magnetic powder and 100 parts of methyl ethyl ketone were placed in a ball mill and kneaded for 72 hours to obtain a magnetic coating composition. Pferrico 2674 (manufactured by Pfizer Magnetics) was used as the magnetic powder. Example 2 MDI 33.1g Byron RV200L 122.8g Plaxel 220 55.2g ESCN220L 14.4g Cyclohexanone 559g were reacted at 80°C for 2 hours in the same equipment as in Example 1, then 3.3g of 1,6-hexanediol was added, and the mixture was further heated at 80°C. The reaction is allowed to proceed until no absorption based on NCO groups is observed in the IR spectrum, yielding a viscous solution. Add 4.9g of hydroxyacetic acid to this solution.
Add and react at 140℃ for 14 hours. The obtained solution had a solid content of 30% and a viscosity of 350 mpa.
s (25℃), the OH group concentration of the polymer is 0.54meq/
It was hot at g. A magnetic paint was prepared in the same manner as in Example 1 except that this modified polyurethane solution was used. Example 3 MDI 32.7g Vylon RUX 104.4g (molecular weight 2000) Nitsuporan 4070 87.0g (molecular weight 2000) ESCN220L 9.1g Diethylene glycol 2.9g cyclohexanone 558g Reacted in the same manner as in Example 1 to obtain an epoxy-modified polyurethane solution, and further propionic acid 3.1 g and react at 140°C for 14 hours. The resulting solution had a solid content of 30%, a viscosity of 560 mpa·s (25°C), and an OH group concentration of 0.18 meq/g. A magnetic paint was prepared in the same manner as in Example 1 except that this modified polyurethane solution was used. Comparative Example 1 MDI 33.4g Vylon RUX 106.8g Nitsuporan 4070 89.0g ESCN220L 4.6g 1,6-hexanediol 3.8g Cyclohexanone 558g The reaction was carried out in the same manner as in Example 1 to obtain an epoxy-modified polyurethane. Furthermore, 1.6 g of propionic acid was added and reacted at 140°C for 14 hours. The resulting solution had a solid content of 30%, a viscosity of 610 mpa·s (25°C), and an OH group concentration of 0.09 meq/g. Comparative Example 2 A magnetic paint was prepared in the same manner as in Example 1, except that diethanolamine was added to the epoxy-modified polyurethane solution and no heating reaction was performed. Test Example 1 The obtained magnetic paint was applied onto a polyester film using a doctor blade, dried at room temperature for 2 hours, and then heated and dried in an oven at 100°C for 20 hours to obtain a magnetic coating film. In order to investigate the dispersibility of magnetic paint, the surface gloss of the magnetic paint film was measured using a gloss meter (manufactured by Tokyo Denshoku, TC-
108D). The better the dispersibility, the better the gloss. The results are shown in Table 1. 【table】

Claims (1)

[Scope of Claims] 1. An OH group is generated by ring-opening the epoxy group of a novolak-based epoxy-modified polyurethane resin with at least one of amines, carboxylic acids, and phenols, and 0.1 meq of OH group is generated in the molecular chain. A magnetic coating composition containing as main components an organic solvent solution of a modified polyurethane resin containing 3 or more functional groups and a magnetic powder. 2 The epoxy resin component is the formula The composition according to claim 1, which is a compound represented by the formula (R ¹ is hydrogen or a methyl group, n is a number on average of 1 or more, and 1<(average value of m+1)≦2) thing. 3. The composition according to claim 1, which contains a polyfunctional isocyanate compound.