JPH02192013A - Binder and magnetic recording material - Google Patents

Abstract

PURPOSE:To improve dispersibility and paint stability by incorporating an active hydrogen-contg. compd. having a nitro group as a functional group into a binder. CONSTITUTION:The active hydrogen compd. of the binder for magnetic recording materials consisting of the active hydrogen compd. and a polyurethane resin consisting of org. polyisocyanate contains the active hydrogen-contg. compd. having the nitro group as the functional group in a part thereof. The dispersibility to magnetic powder and the stability of the paint viscosity are improved in this way and the need for using a dispersant which exerts adverse influence on the durability of the magnetic paint is eliminated. The deterioration in the properties of the magnetic coated film is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to binders and magnetic recording materials.

[Prior Art] Conventionally, as binders for magnetic recording materials, polyurethane resins obtained by reacting organic polyisocyanates with polyol components consisting of high molecular weight polyols and low molecular weight polyols including trifunctional or higher functional low molecular weight polyols have been known. (Japanese Unexamined Patent Publication No. 57-60531).

[Problem to be solved by the invention] However, conventional binders have almost no dispersion function for magnetic materials, and the dispersion function is left to the dispersant. There are problems such as adversely affecting the durability of the magnetic material and deteriorating the physical properties of the magnetic coating.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of intensive studies on binders for magnetic recording materials and magnetic recording materials that have excellent dispersibility and coating stability.

That is, the present invention provides a binder for magnetic recording materials comprising a polyurethane resin (C) made from an active hydrogen compound (A) and an organic polyisocyanate (B), in which (A) has a nitro group as a functional group as a part thereof. A binder for magnetic recording materials, characterized in that it is a compound containing an active hydrogen-containing compound ¥R (A3). ; (A) has an equivalent weight of 20
The binder according to claim 1, comprising a high molecular weight polyol (A1) of 0 to 2000 and a low molecular weight polyol (A2); (A) is selected from the group consisting of the following (a), (b), and (C): Active hydrogen-containing compound with a functional group￥Ij(
A4) The binder according to claim 1 or 2, containing (a) -COOL /p (b) -5C1aXt7p (C) -PO(OX+ 7p, where p is 1 or 2); (A) is a compound having a fluorine group and an active hydrogen-containing group in the molecule (A5
) The binder according to any one of claims 1 to 3, comprising: ; and a magnetic recording material comprising a binder according to any one of claims 1 to 4 and a magnetic material.

The active hydrogen-containing compound having a nitro group in the present invention (
A3) is the general formula % formula % (1) [wherein, X is OH, NHR, NH2 or sH; Z is an organic group; m is 1 or more, preferably 1 or 2; n is 1 or more, preferably 1 or 2].

Specifically, HOCH2NO2 HOCH2CH2NO2 HOCH(NO2)2 (HOCH2)2C(CH3)NO2 (HOCH2CH2)2NCH2CH2NO2(HOC
H2CH20CO)2caHJO2H2NCH2NO2 and derivatives thereof (polyether polyols, polyester polyols, polyurethane prepolymers, etc. derived from these compounds, such as reactants with propylene oxide, reactants with caprolactone, reactants with polyisocyanate, etc.). It will be done.

Among these, preferred are 2-methyl-2-nitro-1,3-propanediol, nitrophthalic acid glycol diester and bishydroxyethylaminonitroethane.

Examples of the polymer polyol (A1) having an equivalent weight of 200 to 2000 in the present invention include the following.

Examples of polyether diols include low-molecular diols [ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4- or 1,3-butanediol, neopentyl glycol, 1
, 6-hexanediol, 1,8-octamethylenediol, 1,10-decanediol, alkyl dialkanolamine; low molecular diols having a cyclic group [e.g. glycols such as cyclohexanediol, cyclohexane dimetatool, and No. 45-1474: Bis(hydroxymethyl)cyclohexane, m-
and p-xylylene glycol, bis(hydroxyethylbenzene, 1,4-bis(2-hydroxyethoxy)benzene, 4゜4-bis(2-hydroxyethoxy)
-diphenylpropane (ethylene oxide addition 'a) of bisphenol A, etc.], and mixtures of two or more of these], alkylene oxides (alkylene oxides having 2 to 4 carbon atoms: ethylene oxide, propylene oxide,
(1,2-12,3-11,3-butylene oxide, etc.) adducts, and those obtained by ring-opening polymerization or ring-opening copolymerization (block and/or random) of alkylene oxides, cyclic ethers (tetrahydrofuran, etc.) , such as polyethylene glycol, polypropylene glycol, polyethylene-polypropylene (block and/or
or random) glycol, polytetramethylene ether glycol, polytetramethylene-ethylene (block and/or random) glycol, polytetramethylene-propylene (block and/or random) glycol, polyhexamethylene ether glycol, polyoctamethylene ether Glycols and mixtures of two or more thereof are included.

Examples of polyester diols include condensed polyester diols obtained by reacting the low-molecular-weight shearols and/or polyether diols with a molecular weight of 1000 or less with dicarboxylic acids, and polylactone diols obtained by ring-opening polymerization of lactones. . Molecule Ji1
000 or less, the polyether diols mentioned above, such as polyethylene glycol, polytetramethylene ether glycol, polypropylene glycol, triethylene glycol;
Examples include mixtures of more than one species. Dicarboxylic acids include aliphatic dicarboxylic acids (succinic acid, adipic acid, sebacic acid, glutaric acid, azelaic acid, maleic acid, fumaric acid, etc.), aromatic dicarboxylic acids (terephthalic acid, isophthalic acid, etc.), and these two. Examples include mixtures of more than one species, and the lactone includes ε-caprolactone.

Polyester diols can be prepared by conventional methods, such as adding low-molecular diols and/or polyether diols with a molecular weight of 1000 or less to dicarboxylic acids or their ester-forming derivatives [e.g., anhydrides (martoleic anhydride, phthalic anhydride, etc.), lower esters ( dimethyl terephthalate, etc.), halides, etc.], or their anhydrides and alkylene oxides (e.g., ethylene oxide and/or propylene oxide), or initiators (low molecular diols and/or polyesters with a molecular weight of 10oO or less). It can be produced by adding lactone to (ether diol, polyester diol).

Specific examples of these polyester diols include polyethylene phthalate, polybutylene phthalate, polyhexamethylene phthalate, polyneopentyl phthalate, polyethylene adipate, polybutylene adipate,
Polyhexamethylene adipate, polyneopentyl adipate, polyethylene propylene adipate, polyethylene butylene adipate, polybutylene hexamethylene adipate, polydiethylene adipate, poly(polytetramethylene ether) adipate, polyethylene azelate, polyethylene sebacate, polybutylene Examples include azelate, polybutylene sebacate, polycaprolactone diol, and mixtures of two or more thereof.

Examples of polycarbonate diols include compounds obtained by reacting low-molecular diols and carbonates. Examples of low molecular diols include aliphatic diols having 4 to 17 carbon atoms (e.g. 1,4-butanediol, 1,5-bentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-hebutanediol, 1,8-octanediol, 2-ethyl-1,6-hexanediol, 2,2.4-trimethyl-1,6hexanediol, 1,10-decanediol, hydrogenated silylyl glycol, hydrogenated dioleyl glycol ), cycloaliphatic diols (e.g. 1,3-cyclohexanediol, 1,4-dimethylolcyclohexane, 1,4-cyclohexanediol, 1,3-dimethylolcyclohexane, 1,4
-endomethylene-2-hydroxy-5-hydroxymethylcyclohexane) and polyoxyalkylene glycol. The diol used is
It may be a single diol or a mixture of diols depending on the properties desired for the final product. Examples of carbonates include ethylene carbonate, trimethyl carbonate, tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,
Examples include 3-butylene carbonate and 1,2-ethylene carbonate.

Polycarbonate diol can be prepared by a conventional method, for example, by combining diol and carbonate in a molar ratio of 10:1 to 1:10,
The reaction is preferably from 3:1 to 1:3, in the presence or absence of a transesterification catalyst, at a temperature of 100-300°C and a pressure of 0.1-301-SO0, during which a low-boiling diol is added. It can be produced by removing it by distillation.

Additionally, polymer polyols, polybutadiene polyols, and the like can also be used.

Among these, aromatic dicarboxylic acid-based polyester diols, adipic acid-based polyester diols, polycaprolactone diols and polycarbonate diols are preferred.

The equivalent weight of the polymer polyol (A+) is usually 200 to 20
00, preferably 250-1500. When it is less than 200, the resulting urethane resin becomes a brittle resin with poor film-forming properties, and is not sufficient as a binder for magnetic recording materials. On the other hand, if the equivalent weight exceeds 2000, the dispersibility of the magnetic powder decreases, film strength becomes insufficient, and abrasion resistance, scratch resistance, and hydrolysis resistance decrease.

As the low molecular polyol (A2) in the present invention, (
Low molecular weight diols and glycerin, trimethylolpropane, trimethylolethane, hexanetriol, pentaerythritol, diglycerin, explained in A1)
α-methyl glucoxide, sorbitol, xylit,
3 to mannitol, glucose, fructose, sucrose, etc.
Examples include octahydric alcohols.

Among these, preferred are alkylene glycols having 2 to 10 carbon atoms and trimethylolpropane.

In the present invention, (a) -COOXs /D, (b)
-S03X+ 7p, (C)-PO(Ox1/p)2,
An active hydrogen-containing compound (A
By using 4) in combination, the dispersibility can be further improved. This compound has the general formula % formula % (2) [wherein X'' is OH, NHR, NH2 or SH; 2'
is an organic group; Y'haC00Xt7p, 5O3Xt/p, and haPO(
Ox1/p)2; X is H1 metal, NH, I or an amine cation; m is preferably 1 or 2; n is 1 or more; p is 1 or 2].

(A4) is specifically C00Xs. Active hydrogen compound # (as aυ, HOCH2COOXt7p HOCH(COOXI7p)2 (HOChCH2)2NcH2c1hcOOXt 7p
and derivatives thereof (polyether polyols, polyester polyols, polyurethane prepolymers, etc. derived from these compounds, for example, reactants with propylene oxide, reactants with caprolactone, reactants with polyisocyanate, etc.).

As the active hydrogen compound (a2) having SO3X+7p, (HOCH2)2c(CH3)SO3Xt 7pH
2NCH2SO3X17P HOCH2CH2SO3X+ /p (HOCH2C1k)2NCH2CH2SO3X+ 7
p(HOCH2CH20CO)2C6H3SO3XI
7p, etc. and derivatives thereof (polyether polyols, polyester polyols, polyurethane prepolymers, etc. derived from these compounds, such as reactants with propylene oxide, reactants with caprolactone, reactants with polyisocyanate, etc.). .

Active hydrogen compound (a3) with PO(OX+7p)2
As, (HOCH2)2C(CH3)PO(OXI zp)2
(HOCH2CH20CO)2C8H3PO(OXI
7P) 2, etc. and their derivatives (polyether polyols, polyester polyols, polyurethane prepolymers, etc. derived from these compounds, such as reaction products with propylene oxide, reaction products with caprolactone, or reaction products with polyisocyanate, etc.) Can be mentioned.

Among these, preferred are dimethylolpropionic acid, phthalic acid glycol diester sulfonic acid, bishydroxyethylamino, ethanesulfonic acid and bishydroxyethylaminoethanephosphoric acid, or metal salts, ammonium salts or amine cations of these acids. It is.

Metals that form salts include alkali metals (lithium,
Examples include sodium, potassium, etc.), alkaline earth metals (calcium, barium, etc.), and the like.

Among these, preferred are sodium and potassium.

Amines that form amine cations include alkylamines (monomethylamine, triethylamine, etc.), alkanolamines (getanolamine, triethanolamine, etc.), heterocyclic amines (piperidine, morpholine, piperazine, etc.), and aromatic amines (aniline, etc.). etc.) etc.

Among these, preferred are triethylalamine and trimethylamine.

In the compound (A5) having a fluorine group and an active hydrogen-containing group in the molecule, examples of the active hydrogen-containing group include an amino group, a carboxyl group, a hydroxyl group, a thioalcohol group, and the like. Such fluorine compounds include those represented by the following general formula.

It may be either an acid group or a thioalcohol group, where q is an integer of 1 to 1O.) Specific compounds include the following.

X-(CF20)q-H (However, or amino group, carboxyl group, water HO-(
CF20)a-H(g) The compounds exemplified above are examples of preferred fluorine compounds in the present invention, and particularly preferred are (d) and (
This is the compound e).

Examples of the organic polyisocyanate (B) in the present invention include the following.

Examples of the aliphatic diisocyanate include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HMDI), dodecamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, lysine diisocyanate, 2,6-dicyanate methyl caproate, bis Examples thereof include (2-isocyanate ethyl) fumarate, bis(2-isocyanate ethyl) carbonate, and tetramethylene xylylene diisocyanate (TMXDI).

Alicyclic diisocyanates include isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (water iMDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), and bis(2-ethyl isocyanate).
Examples include 4-cyclohexene-1,2-dicarboxylate.

Aromatic diisocyanates include 1,3- and/or 1,4-phenylene diisocyanate, 2,4- and/or 2,6-dolylene diisocyanate (TDI
), diphenylmethane-2,4”- and/or 4,
4°-diisocyanate (MDI), naphthylene-1,
5-diisocyanate, m- and/or p-isocyanate phenylsulfonyl isocyanate, etc.).

As polyisocyanates, water-modified products of HDI, IP
Trimerized product of DI, polytolylene diisocyanate (crude TDI), polyphenylmethane polyisocyanate (crude MDI), modified MDI (carposiimide modified MDI)
etc.) and mixtures of two or more thereof.

Among these, preferred are aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates, and particularly preferred are HODI, IPDI, M
DI and TDI.

In the polyol, (A3) is usually 0.1 to 70 equivalents z1, preferably 0.1 to 60 equivalents2. If the amount of (A3) is less than 0.1 equivalent 2, the dispersibility in the magnetic powder will be insufficient and the stability of the paint will be poor, and if it exceeds 60 equivalent 2, the adhesion to the substrate will decrease.

In the polyol, (A4) usually has an equivalent of θ to 70 equivalents2, preferably 0.1 to 60 equivalents2. The amount of (A4) is 6
If the equivalent is more than 0, the viscosity of the magnetic coating material will increase significantly and the coating properties will deteriorate. In addition, (al), (a2) and (
a3) can be used in combination in any proportion as necessary.

(A2) is 5 to 80 equivalents 2, preferably 10 to 50
The equivalent weight is 2. If the amount of (A2) is less than 5z equivalent, the film properties of the produced urethane resin tend to deteriorate, and the dispersibility of the magnetic powder becomes poor. On the other hand, if the amount of (A2) exceeds 80 equivalents 2, the adhesion to the substrate will decrease.

In addition, among the active hydrogen compounds (A), the compound (A5) having a fluorine group and an active hydrogen-containing group in the molecule usually has 0 to 5
0 equivalent %, preferably 0.1 to 40 equivalent %. (A
If 5) is less than 0.1 equivalent %, the running stability of the tape using the produced urethane resin will deteriorate.

On the other hand, if (A5) exceeds 40 equivalent %, the adhesiveness with the polyethylene terephthalate film that is the non-magnetic support will decrease, and the compatibility with other resins used together will deteriorate.

The equivalent weight of the active hydrogen compound is usually 100 to 1,600.

If the equivalent weight of (A) is less than 100, the resulting urethane resin will be a brittle resin with poor film-forming properties and will not be sufficient as a binder for magnetic recording materials. On the other hand, if the equivalent weight exceeds 1,600, the dispersibility of the magnetic powder decreases, film strength becomes insufficient, and abrasion resistance, scratch resistance, and hydrolysis resistance decrease.

When (A) and (B) are reacted, the equivalent ratio of (B) and (A) is usually 0.6 to 1.5, preferably 0.8 to 1.
．． It is 2. If the equivalence ratio is less than 0.6 or more than 1.5, the molecular weight of the polyurethane resin obtained by the reaction of (A) and (B) will be low, the dispersibility will be reduced, and the abrasion resistance and resistance of the magnetic recording material will be reduced. Scratch resistance and hydrolysis resistance tend to decrease.

The above reaction can be carried out in the presence or absence of a solvent inert to isocyanate groups. Examples of this solvent include ester solvents (ethyl acetate, butyl acetate, etc.),
Examples include ether solvents (dioxane, tetrahydrofuran, etc.), ketone solvents (cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.), and mixed solvents of two or more of these solvents. .

The reaction methods include a method in which (A) and (B) are charged together in a reaction vessel and reacted, a method in which (A) and (B) are divided and a multistage reaction is performed, and a method in which (A) is mixed in advance.
and (B) are passed through a heated continuous kneader to react.

The reaction temperature is usually 40-180°C, preferably 60-180°C.
It is 20°C. In order to accelerate the reaction, catalysts used in normal urethane reactions, such as tin-based catalysts (trimethyltin laurate, trimethyltin hydroxide, dimethyltin dilaurate, dibutyltin dilaurate, stannath octoate, etc.), lead-based catalysts are used. Catalysts (red oleate, red 2-ethylhexoate, etc.) and the like can also be used.

The obtained polyurethane resin (C) usually has a number average molecular weight of 3,000 to 200,000, preferably 5,000.
~150.000.

The molecular weight per functional group is usually 1,000 to 200,0
00, preferably s,ooo to 150,000.

When the molecular weight per functional group is less than 1,000, hydrolysis resistance decreases.

Polyurethane resin (C) made by reacting (A) and (B)
) is used as a binder for magnetic recording materials, but if necessary, other polymeric materials commonly used for magnetic recording materials can be used in combination. Examples of this polymer material include polyvinyl chloride-based vinyl chloride-vinyl acetate copolymer (vYHH; manufactured by UCC, S-LEC C; Sekisui Chemical, etc.), vinyl chloride-vinyl acetate-vinyl alkonyl copolymer (VAGH, S-LEC C, etc.), A), vinyl chloride
Vinylidene chloride-acrylonitrile copolymer (Saran;
manufactured by Asahi Dow), etc., polyurethane-based [urethane resin (Nisten; manufactured by Gutdrich, etc.)], butadiene-based [acrylonitrile-butadiene copolymer (Hiker 1482;
Nippon Zeon Co., Ltd.), acrylonitrile-butadiene-styrene copolymer (A-135), etc.], acrylic type (acrylic acid ester copolymer, etc.), nitrocellulose, phenoxy resin, epoxy resin, etc.

The binder for magnetic recording materials of the present invention can be made into a magnetic recording material (hereinafter sometimes referred to as magnetic paint) by incorporating a magnetic substance therein.

As this magnetic material, iron oxide such as γ-F820a (
γ-hematite), Crys (chromium trioxide) and alloy-based magnetic materials such as CO-γ-Fe2O3 (cobalt ferrite or cobalt-doped γ-iron oxide), Fe
-Co-Cr, pure iron Fe (metal powder) and iron carbide. In the present invention, the recent more finely powdered γ-Fe2O3, C is particularly used.

-γ-Fe2O3, metals, iron carbide (e.g. particle BE
It is useful for those with a specific surface area of 40 m2/g or more by the T method.

The magnetic material is magnetic powder, and its shape is usually granular or acicular. An example of the shape of a magnetic material is a diameter of 0.02~
0.7μ, e.g. major axis 0.2 to 0.7μ, minor axis 0.02
~0.1μ.

A crosslinking agent can be used in the magnetic paint to crosslink the polyurethane resin. Examples of the crosslinking agent include NGO-containing compounds and active hydrogen-containing compounds. NG
As the O-containing compound, polyisocyanate [modified MDI
(Millionate ME.

(manufactured by Fukadogaya Chemical), 3,3'-dimethoxy-4,4'-
diisocyanates, etc.] and NCO-terminated prepolymers [
Polyisocyanates (TDI, MDI, etc.) and polyols (low molecular polyols, polyether polyols, polyols)
NCO-terminated prepolymers with NCO-terminated prepolymers such as Desmodur L (manufactured by Bayer), Coronate L (
(manufactured by Nippon Polyurethane) 261]. Examples of active hydrogen-containing compounds include polyamines (tolylene diamine (TDA), 4.4''-diamino-3,3°-dichlorodiphenylmethane, etc.) and polyols (low-molecular polyols, polyether polyols, polyester polyols, etc.). .

The amount of crosslinking agent added is usually 0 to 25% to the polyurethane resin.
Weight%, preferably 2 to 15% by weight. 25% by weight
If it exceeds 50%, the visibility of the film tends to decrease.

Other dispersants (lecithin or anion,
Nonionic, cationic surfactants such as sodium dodecylbenzenesulfonate, etc.) and lubricants (higher fatty acid esters, such as butyl stearate) may also be added.

A solvent is used in magnetic paint to adjust the viscosity.

Examples of this solvent include the same solvents as those described in the polyurethane resin production reaction, ester solvents (ethyl acetate, butyl acetate, etc.), ether solvents (dioxane,
Tetrahydrofuran, etc.), ketone solvents (cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.), and mixed solvents of two or more of these can be used.

Among these, preferred are mixed solvents of ketones and aromatic hydrocarbons.

The content of polyurethane resin (C) in the magnetic paint is usually 5% by weight or more, preferably 6 to 20% by weight based on the weight of the paint.
Weight%. By including (C) in an amount of 5% by weight or more, the objects of the present invention can be fully achieved.

The amount of magnetic material in the magnetic paint is usually 30 to 80% by weight, preferably 32 to 60% by weight.

The amount of solvent in the magnetic paint is usually 30 to 80% by weight, preferably 40 to 70% by weight.

The amount of other polymeric materials is usually 0-20% by weight, preferably 2-15% by weight.

The amount of other (crosslinking agent, dispersant, lubricant, etc.) is usually 0 to 3
% by weight, preferably 0.01-2% by weight.

The method for manufacturing magnetic paint is to mix the binder solvent and the magnetic material in advance with a premixer, etc., if necessary, and then mix and disperse with a ball mill, paint conditioner, etc.
Examples include a method of dispersing with a sand grinder, sand mill, plasto mill, etc.) and filtering.

This magnetic paint can be applied to a support film for a magnetic recording medium to create a magnetic recording medium (magnetic tape, etc.). Examples of the support film include films of fox cellophane, acetate, polyester (PET), reinforced polyester, polyimide, and the like. Among these films, polyester film is often used.

When a magnetic paint is applied to a support film, the coating thickness is usually from several microns to several tens of microns. Application methods include coating methods such as a doctor blade method and a transfer printing method (gravure method, reverse roll method, etc.).

The film coated with the magnetic paint is then subjected to processes such as orientation, drying, surface treatment, cutting, and winding to form a magnetic recording medium.

Magnetic recording media consist of a support film and a magnetic layer (magnetic binder), while those with an intermediate layer (undercoat layer) between the support film and the magnetic layer, and those with a support film There are also those that have magnetic layers on both sides, those that have magnetic layers with different magnetic properties stacked on top of each other, and those that have a protective layer provided on the magnetic layer.

[Examples] Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited thereto. In the following, parts indicate parts by weight.

Example 1 1 mol of polyester diol from adipic acid and butanediol with an equivalent weight of 1000, 1 mol of polytetramethylene glycol with an equivalent weight of 500, 2-methyl-2-nitro-1,
A polyurethane resin (OHV=10) (C1) was obtained by reacting 3 moles of 3-propanediol and a mixture of 0.1 mole of dimethylolpropionic acid and 1 mole of 1,4-butanediol with 6.1 moles of TDI.

Using this (C1) as a binder, a mixture having the following composition was mixed and dispersed with a paint conditioner to prepare a magnetic paint (Dl).

γ-Fe2r3 fine powder 100 parts Polyurethane resin (C1)' 20 parts Vinyl chloride-vinyl acetate copolymer 10 parts Lecithin 1 part Methyl ethyl ketone 75 parts Toluene 75 parts This magnetic paint was applied to a polyester film (dry film thickness 5 μ), 10000 e. A magnetic field was applied to orient the material to obtain a tape (El). Furthermore, this tape was processed with a calendar roll to obtain a magnetic tape.

Example 2 Polyester diol from adipic acid and hexanediol with an equivalent weight of 1000 1 mol 2-methyl-2-nitro-1,3-propanediol 1
Example 1 was carried out using a polyurethane resin (C2) (3l-OHV=3.7) obtained by reacting 0.1 mol of N(C2H5)3 cation of moldimethylolpropionic acid, 1 mol of ethylene glycol, and 3 mol of MDI. A magnetic paint was prepared in the same manner to obtain a tape (E2).

Comparative Example 1 Polyester diol from adipic acid and hexanediol having an equivalent weight of 1000 1 mol neopentyl glycol 1 mol dimethylolpropionic acid 0.1 mol ethylene glycol 1 mol MDI 3 mol Polyurethane resin (C3) obtained by reacting ( OHV=3.7
) was used to prepare a magnetic paint in the same manner as in Example 1 to obtain a tape (E3).

Test Example 1 The tapes obtained in Examples 1 and 2 and Comparative Example 1 (Es~
E3) and the magnetic paint were evaluated for surface gloss, magnetic properties (squareness ratio), and stability of paint viscosity.

Glossiness: Specular reflectance at 60° was measured using a glossy needle.

Squareness ratio: Measured using a vibrating sample magnetometer.

Stability of paint viscosity: rate of increase in viscosity after 7 days (25°C) of paint preparation Example 3 1 mol of polyester diol from adipic acid and butanediol with an equivalent weight of 1000, 1 mol of polytetramethylene glycol with an equivalent weight of 500, 2 -methyl-2-nitro-1
, 3-propanediol 3 mol, fluorine compound (e) 0
．． 1 mol, and a mixture of 0.1 mol of dimethylolpropionic acid and 1 mol of 1,4-butanediol with TDI 6.
React 2 moles to make polyurethane resin (OHV=10)
(C4) was obtained.

Using this (C4) as a binder, a mixture having the following composition was mixed and dispersed with a paint conditioner to prepare a magnetic paint (D4).

γ-Fe2rs fine powder 100 parts Polyurethane resin (Ca) 20 parts Vinyl chloride-vinyl acetate copolymer 10 parts Lecithin 1 part Methyl ethyl ketone 75 parts Toluene 75 parts This magnetic paint was applied to a polyester film (dry film thickness 5 μ), 10000 e. A magnetic field was applied to orient the material to obtain a tape (El). Furthermore, this tape was processed with a calendar roll to obtain a magnetic tape.

Example 4 Polyester diol from adipic acid and hexanediol with an equivalent weight of 1000 1 mole 2-methyl-2-nitro-1,3-propanediol 1
Moldimethylolpropionic acid N(C2H1,)3 cation 0.1 mol Fluorine compound (d) 0.1 mol ethylene glycol 0.9 mol MDI
Polyurethane resin (C6) obtained by reacting 3 moles (
A magnetic paint was prepared in the same manner as in Example 1 using OHV=3.7) to obtain a tape (E5).

Test Example 1 Tapes obtained in Examples 3 to 4 and Comparative Example 1 (E3 to
Es) and the magnetic paint were evaluated for surface gloss, magnetic properties (squareness ratio), and stability of paint viscosity.

Glossiness: Specular reflectance at 60'' was measured using a glossy needle.

Squareness ratio: Measured using a vibrating sample magnetometer.

Stability of paint viscosity: Rate of increase in viscosity after 7 days (25°C) of paint preparation [Effects of the invention] The binder for magnetic recording materials and the magnetic recording material of the present invention are different from conventional binders (Japanese Patent Application Laid-open No. 59-148127
It has the following effects compared to the one in the publication (No. 1).

(1) It has excellent dispersibility for magnetic powder and stability of paint viscosity, eliminates the need to use a dispersant that adversely affects the durability of magnetic paint, and does not deteriorate the physical properties of magnetic paint.

(2) Excellent adhesion to the support film.

Because of the above-mentioned effects, the binder and material of the present invention can be used as a binder for magnetic recording materials for, for example, audio tapes, video tapes, computer tapes, data recorder tapes, video sheets, metal tapes, metal disks, magnetic cards, and magnetic recording materials. Useful as a material.

Claims (1)

[Claims] 1. Active hydrogen compound (A) and organic polyisocyanate (
B) in a binder for a magnetic recording material consisting of a polyurethane resin (C), in which (A) is an active hydrogen-containing compound (A) having a nitro group as a functional group as a part thereof;
A binder for magnetic recording materials, characterized in that it is a compound containing _3). 2. The binder according to claim 1, wherein (A) consists of a high molecular polyol (A_1) and a low molecular polyol (A_2) having an equivalent weight of 200 to 2000. 3. (A) is an active hydrogen-containing compound (A_
4) The binder according to claim 1 or 2, comprising: 4). (a) -COOX_1_/_p (b) -SO_3X_1_/_p (C)-PO(OX_1_/_p)_2 (wherein, X=H, metal, NH_4 or amine cation. p is 1 or 2. ) 4. The binder according to any one of claims 1 to 3, wherein (A) contains a compound (A_5) having a fluorine group and an active hydrogen-containing group in the molecule. 5. A magnetic recording material containing the binder according to any one of claims 1 to 4 and a magnetic material.