JPS59174660A - Magnetic coating - Google Patents

Abstract

PURPOSE:To obtain titled coating for magnetic tape, with high flexibility and wear resistance, by incorporating magnetic powder in a carboxyl group-contg. polyurethane plus a hydroxyl group-contg. polyurethane prepared by the reaction of epoxy compound. CONSTITUTION:The objective coating can be obtained by incorporating (A) 100pts.wt. of (i) a carboxyl group-cong. polyurethane prepared by the reaction between a polyol, isocyanate, and dihydroxycarboxylic acid having two hydroxyl groups and carboxyl group plus (ii) a hydroxyl group-contg. polyurethane (with a hydroxyl group concentration >=0.1meq./g) prepared by the reaction of an epoxy compound with (B) 2,000pts.wt. of a magnetic powder and, if required (C) a polyfunctional isocyanate. USE:Coating for sheets, cards, discs, drums, 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, when manufacturing magnetic tapes and the like, polyurethane resins are often used as surface coating resins, which provide a highly flexible and tough coating film. 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,
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) JP-A-51-44902 and (2) JP-A-51-51.
No. 1'-44903, (3) No. 55-139634,
(4) No. 55-139636, (5) No. 5'6-68
No. 925, (6)-(9) 56-101643~]
Magnetic recording bodies described in No. 016i and the like are known.

However, for example, in (1) and (2), a urethane-modified epoxy resin containing no OH group is used, and (3) to (9)
), urethane resins with OH groups are used, but these are not modified with epoxy resins, and the number of OH groups is usually about 1 to 5, making it difficult to improve dispersibility. Although this has been achieved to some extent, it is still insufficient, and it also has drawbacks such as poor hydrolysis resistance and heat resistance.

Also, as OH group-containing polyurethane, 0Q JP-A-57-6
No. 0529 uses a trifunctional or higher functional hydroxy compound such as glycerin, but if the NC010H ratio approaches 1 in order to increase the OH group concentration and molecular weight using the above method, V conversion will occur; NC to avoid
When the 010H ratio is lowered, the molecular weight becomes smaller,
The resulting coating film has the disadvantage of low strength.

An object of the present invention is to provide a magnetic coating material 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 OH groups.

The present invention relates to (a) a polyurethane having a carboxyl group obtained by reacting a polyol, an isocyanate compound, and two hydroxyl groups with a dihydroxycarboxylic acid having a carboxyl group, and (b) a hydroxyl group-containing polyurethane obtained by reacting an epoxy compound ( 5) and a magnetic paint containing magnetic powder (c).

In the present invention, using dihydroxycarboxylic acid, NC010
) Since the urethanization reaction is carried out at a ratio of approximately 1, a high molecular weight polyurethane having carboxyl groups can be obtained, and then an epoxy compound is reacted to generate OH groups, resulting in a high molecular weight and OH group. A polyurethane with a high group content 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 (a) 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 RUX, Vylon R, V-20OL), Specific examples of polyether polyols include polycaprolactone polyols (eg, Daicel Chemical Co., Ltd., trade names Plaxel 212, Plaxel 220), and polyoxyethylene glycol, polyoxypropylene polyol, polyoxytetramethylene polyol, and the like.

Other polyols include polycarbonate polyols (e.g., West Germany, Bayer AG, trade name: Desmofene 2020E), polybutadiene polyols (e.g., Nippon Soda, trade names: G-, 1000, G-2000, G).
-3000, Idemitsu Petrochemical, trade name PolybdR-4
5HT), polypentadiene polyol, castor oil polyol, etc., and one type or two or more types can be used.

The isocyanate compound used in the present invention may be any polyisocyanate known in polyurethane chemistry, for example hexamethylene diisocyanate (1-), DI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate. (HMDI), 2,4-tolylene diisocyanate (2,4-TDI), 2, G-tolylene diisocyanate (2, (3-TDI), 4.4'
-Diphenylmethane diisocyanate (MDI), carposiimide-modified MDI, polymethylene polyphenyl polyisocyanate (PAPI), orthotoluidine diisocyanate (']''0DI), naphthylene diisocyanate (NDI), xylylene diisocyanate (MD)
I), lysine diisocyanate (L D I ), etc., and one type or two or more of them can be used.

fd as the dihydroxycarboxylic acid of the present invention Example 2
, 2-dimethylolpropionic acid (DMPA), tartaric acid, dioxyadipic acid, furionic acid, etc. can be used.

As a chain extender, for example, a molecular weight of 500 or less, 02 to G
Functional polyol and primary or secondary having a molecular weight of 500 or less
Examples include diamines having a terminal amino group of 100%. Suitable chain extenders include, for example, (a) ethylene glycol, diethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,4-butanediol, 2,3-butanediol, 1,3-propylene glycol, 1 , 6-hexanediol, glycerin,
Trimethylolpropane, pentaerythritol, sorbitol, 1,4-cyclohexanediol, 1,4-
Polyols (L
+) Diamines such as hydrazine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, I,4-cyclohexanediamine (C) Alkanolamines such as ethanolamine, jetanolamine, and 1′iethanolamine (d) Hydroquinone, Pyrogallol, 4,4'-isopropylidenediphenol, aniline and the above polyols, diamines, alkanolamines with propylene oxide and/or
Alternatively, polyols having a molecular weight of 500 or less obtained by adding ethylene oxide in any order may be mentioned.

The polyurethane (a) of the present invention is synthesized using the above-mentioned components, and the NCOIndex is usually about 09~]
2, preferably in the range of about 095-11.

The manufacturing method may be any known method, such as a one-shot method or a prepolymer method. Urethane catalysts can also be used.

In the present invention, a hydroxyl group-containing polyurethane (4) produced by reacting the above polyurethane (2) and the epoxy compound (1) to generate OH groups is used.

As the epoxy compound (b), each 'Kin' can be used, for example, epoxy compounds such as ethylene oxide, propylene oxide, epichlorohydrin, etc.
O such as glycidol, glycerin diglycidyl ether, etc.
H group-containing epoxy compound, Epicote 828.834.
1001.1002.1003.1004.1007.
Examples include epoxy resins such as 1009 (manufactured by Shell Chemical Co., Ltd.).

In the above reaction of the present invention, all of the carboxyl groups may be reacted, or of course some carboxyl groups may remain. Usually, the equivalent ratio of epoxy groups to carboxyl groups is about 0.05 to 1.0. It is preferable to use the epoxy compound within a certain range, and if there is an excess of the epoxy compound, it can be removed by reducing pressure or the like. On the other hand, when carpoxyl groups remain, neutralization with a base improves the dispersibility of the magnetic powder.

The reaction between a carboxyl group and an epoxy compound is usually about G O
-180°C1, preferably at about 80-150'C; it is also possible to use known catalysts.

The hydroxyl group-containing polyurethane of the present invention obtained as above (
5) OH group concentration per 1f of polyurethane, Q, Im
Eq or more is preferable.

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 203, ferrite, magnetite, CrO2, etc., and examples of modified products include cobalt-doped 1-Fe2O3, cobalt-doped belts of Fe 203 and Fe 304. Examples include ride compounds and the like. The blending amount of the magnetic powder is preferably about 50 to 2000 parts per 100 parts of the polymer.

As the polyfunctional isocyanate compound used if necessary in the present invention, a polyisocyanate having two or more functional groups can be used. As a preferable specific example,
Various isocyanate compounds, trimethylolpropane, and TDI that can be used to produce the polyurethane (a).
trifunctional isocyanate (trade name: Desmodur L, West Germany, Bayer: Coronate L, Nippon Polyurethane Co., Ltd.), a trifunctional isocyanate obtained from Bayer (trade name: Desmodur N75, Coronate R1, same H)
etc.), polymeric polyisocyanate (PPI), and the like.

The magnetic paint of the present invention can be obtained by mixing the hydroxyl group-containing polyurethane (a), magnetic powder, and, if necessary, a polyfunctional isocyanate compound. N C in magnetic paint
A range of about 09 to 15 is usually appropriate for the OIndex, but it is preferable to set it higher when taking active hydrogen contained in the magnetic powder and other additives into consideration.

In the present invention, vinyl chloride resins, vinylidene chloride resins, vinyl chloride/vinyl acetate copolymer resins, vinyl chloride/vinyl alcohol copolymer resins (manufactured by UCC,
V A GH etc.), nitrocellulose, polyvinyl butyral resin, polyvinyl acecool resin, polyester resin, alkyd resin, epoxy resin, acrylonitrile-butadiene rubber, and other resins can be blended. Further, in the present invention, additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent may be added as necessary.

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. In particular, it is preferable to add a polyfunctional isocyanate compound to a well-dispersed solution to extend the pot life. Further, it is preferable to use a solvent during the production of the polyurethane (a) of the present invention, the reaction with the epoxy compound (b), and the production of the above-mentioned magnetic paint. Suitable solvents include acetone, methyl ethyl ketone, methyl Ketones such as isobutyl ketone and cyclohexanone, aromatic hydrocarbons such as henzhen, toluene and xylene, esters such as ethyl acetate and butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, 3-methoxybutyl acetate, ethylene glycol diacetate , dimethylformamide.

Dimethylacetamide, tetrahydrofuran and the like can be mentioned.

The magnetic paint of the present invention can be applied to supports in various forms such as tapes, sheets, cards, disks, and drums. The support usually has a thickness of about 2 to 50μ, preferably about 4 to 2
It is preferably about 0 μm, 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 1-. Can be used as fred coat, reverse roll coat, gravure coat, cast coat, or spray coat. After coating and performing treatment to orient the magnetic powder if necessary, it is dried.

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 can be cut into a desired shape usually at 50 to 140°C.

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 In a 1e separable flask equipped with a thermometer, stirrer, nitrogen inlet tube and reflux condenser, Byron UX (molecular weight 200o) 242y, MDI 60.6f and cyclohexanone 1301 were weighed and placed in a stream of dry nitrogen. at 80°
React at C for 1 hour. Next is DMPA, 16.2! Add P and 348 g of cyclohexanone and react at 80 to 90°C for 3 hours to obtain a solid content of 40% and a viscosity of 9800 Cp.
'3 (25°C) to obtain a solution of polyurethane (a) with a molecular weight of 29,000.

Next, 9.0y of glycidol and 142% of cyclohexanone were added to this solution (a) and reacted at 120-130°C for 8 hours to obtain a solid content of 40% and a viscosity of 8700 cps (2
5°C), molecular weight 24000, OH group concentration 0.74 m
eq/f (7) Obtain a solution (AI) of polyurethane (g).

75 parts of polyurethane solution (A1), 100 parts of cobalt-modified r-ferrite, 40 parts of cyclohexanone and 110 parts of methyl ethyl ketone were placed in a ball mill.
After kneading for 0 hours, 75 parts of Coronate L was added and kneaded for an additional 2 hours to obtain the magnetic paint of the present invention.

Example 2 Glycidol 3 in polyurethane solution M (a) of Example I
02, cyclohexanone 172 and triethylamine 8
．． 2ii' was added and reacted at 120-130°C for 8 hours, solid content 40%-1-viscosity 9100 cps (25
°C), molecule (K, 28000, OH group concentration 0.12
A solution (A2) of polyurethane <A) with mcq/y is obtained.

Hereinafter, using this polyurethane solution (A2), Example I
A magnetic coating material of the present invention was obtained in the same manner as described above.

Example 3 Polycaprolactone diol (molecular weight 550) 1717
, TD I-100 (1o8!il) and cyclohexanone 1209 were heated at 75-85 °C for 1 hour, then DMPA4], 5f and cyclohexanone 3617 were added and heated at 80-90 °C for 3 hours. A solution of polyurethane having carboxyl groups is obtained by reaction.

Next, glycidol 231 and cyclohexanone 357 were added to this solution and reacted for 8 hours at 120-130"C, solid content 40%, viscosity 7'900 cps (25 °C).
Molecular weight: 28000.0 Group concentration: 1,81+neq/'
A solution (A3) of polyurethane (5) is obtained.

Hereinafter, using this polyurethane solution (83), Example 1
- A magnetic paint of the present invention was obtained in the form of a front gate.

Comparative Example I A magnetic paint was obtained in the same manner as in Example 1 except that the polyurethane (a) of Example 1 was used instead of the polyurethane solution (A1).

Comparative Example 2 In place of the polyurethane solution (AI), 9.9% of glycidol was added to the polyurethane (a) of Example 1. A magnetic coating material was obtained in the same manner as in Example 1 except that a 40% cyclohexanone solution obtained only by adding Of and cyclohexanone 14f without reacting was used.

Comparative example 3 Bayon RUX (27Or), MDI (40,6F),
DMPA (3,3r) and cyclohexanone (136f
and 34'4f) to obtain a solution of polyurethane (a) in the same manner as in Example 1.

Next, add epichlorohydrin (2,3S') to this solution (a).
) and cyclohexanone (32) and similarly obtain a solution of polyurethane (A) having a solid content of 40%, a viscosity of 9200 cps (25°C), a molecular weight of 29000, and an OH group concentration of 0.08'me q/l.

Using this solution, a magnetic paint with a low OH group concentration was obtained in the same manner as in Example 1.

Comparative Example 4 SU-450 (a polyol manufactured by Mitsui Nisso Tsurethane Co., Ltd. with an OH value of 450) 2469 was dissolved in cyclohexanone 4802, then MDI (73,81F) was added and heated at 80°C.
After reacting for 3 hours, the solid content was 40% and the viscosity was 230CpS.
(25°C), molecular weight 3400, OH group concentration 4.3 m
A low molecular weight polyurethane solution of eq/7 was obtained.

Using this solution, a magnetic coating material was obtained in the same manner as in Example 1 except that a magnetic coating material was obtained.

Test Example 1 The magnetic coatings obtained in Examples and Comparative Examples were applied onto a polyester film using a doctor blade, and dried to obtain a coating film with a thickness of 6 μm. The gloss of the obtained coating film was measured using a gloss meter 5-60 manufactured by Toyo Seiki Co., Ltd., and the results are shown in Table 1.

Test Example 2 Coronate LIO parts were added to 100 parts of each of the polyurethane solutions of Examples 1 and 3 and Comparative Examples 1 and 4, mixed well, and cast on a polyester film to form a film with a thickness of 0.2 mm. After volatilizing the solvent, the film was cured at 80° C. for 24 hours, and the resulting film was subjected to a taper abrasion test. The test conditions were: wear wheel C8-17, load 100 (1, rotation speed aooorpm).
, the temperature is 20°C. Table 1 shows the wear amount of each film.

Chapter 1 Table (that's all)

Claims (3)

[Claims] (1) (a) A polyurethane having a carboxyl group obtained by reacting a polyol, an isocyanate compound, and two hydroxyl groups with a dihydroxycarboxylic acid having a carboxyl group, and (b) a hydroxyl group-containing polyurethane obtained by reacting an epoxy compound ( 5) and a magnetic paint containing magnetic powder (c). (2) The magnetic paint according to claim 1, further comprising a polyfunctional isocyanate-1 compound. (3) The hydroxyl group concentration of the hydroxyl group-containing polyurethane (5) is 0
．． The magnetic paint according to claim 1, which has a magnetic flux of 1 m eq /liter or more.