JPS63173223A - Binder for magnetic recording material - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder by incorporating the urethane oligomer contg. an amino group and a carboxyl group into the binder as the essential component. CONSTITUTION:The urethane oligomer contg. an amino group and a carboxyl group is incorporated as the essential component. In this case, the urethane oligomer is composed of a polyisocyanate and the hydroxyl component consisting of a mono-ol contg. an amino group and/or a polyol, a mono-ol contg. a carboxyl group and/or a polyol, and, if necessary, a polyol not contg. an amino group and a carboxyl group. As a result, a magnetic powder is excellently dispersed, and the electromagnetic transducing property of the obtained magnetic recording material is remarkably improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to binders for magnetic recording materials.

[Conventional technology]

Conventionally, carboxyl-containing polyurethane resins have been known as binders for magnetic recording materials (Japanese Patent Laid-Open No. 59-1
48127).

[Problem that the invention seeks to solve]

However, with the demand for high-quality video recording over long periods of time, the recording density of video tapes has also increased, and a binder with excellent dispersibility of magnetic powder has become necessary.

[Means to solve the problem]

The present inventor has arrived at the present invention as a result of studying binders for magnetic recording materials with the aim of improving the dispersibility of magnetic powder.

That is, the present invention provides a binder for air recording materials (first invention) characterized by containing a urethane oligomer containing an amino group and a carboxyl group as an essential component, and a (meth)acryloyl binder containing an amino group and a carboxyl group. A binder for magnetic recording materials (second invention) characterized in that the essential component is a urethane oligomer having a group.

Urethane oligomers containing amino groups and carboxyl groups include amino group-containing monools and/or polyols (a), carboxyl group-containing monools and/or polyols rb>, and optionally those containing no diamino groups or carboxyl groups. Polyol (
Hydroxy component from Cl and polyisocyanate (B
) are urethane oligomers.

The oligomer containing an amino group and a carboxyl group and a (meth)acryloyl group includes an amino group-containing monool and/or polyol (a), a carboxyl group-containing monool and/or polyol (b), and optionally a diamino group. and polyisocyanate (B), and urethane oligomer from acrylic monomer (c) containing an active hydrogen atom that is reactive with isocyanate. It will be done.

The alkylene group, R1, Rt is H or an alkyl group having 1 to 10 carbon atoms. ) adducts of alkanolamino and alkanolamino alkylene oxides [alkylene oxides having 2 to 4 carbon atoms, such as ethylene oxide (hereinafter abbreviated as EO) and propylene oxide (hereinafter abbreviated as PO)] (the number of moles added is usually 1) ~20,
1 to 10) are preferred. Among these, preferred are tertiary monoalkanol aminos.

As the amino group-containing polyol, general formula HO-X+-
N-Xt-OH (X+, Xti, carbon i number 1 to 1011
7) -r alkylene group, R is H1 an alkyl group having 1 to 10 carbon atoms or -Y-OH group. Y has 1 to 1 carbon atoms
0 alkylene group. ) Alkanolamino and alkanolamino alkylene oxides (
Examples include adducts of alkylene oxides having 2 to 4 carbon atoms, such as EO and PO (the number of moles added is usually 1 to 20, preferably 1 to 10). Among these, preferred are tertiary polyalkanol aminos.

Examples of carboxyl group-containing monools in the present invention include glycolic acid and hydroxyisobutyric acid monoalkyl (alkyl group has 1 to 10 carbon atoms) esters.

Examples of carboxyl group-containing polyols include dimethylolpropionic acid (hereinafter abbreviated as DMPA), 4,4-bis(hydroxyphenyl)butyric acid, and 4.4-bis(hydroxyphenyl)valeric acid. Among these, preferred is DMPA.

In the present invention, the active hydrogen atom-containing acrylic monomer [C] that is reactive with isocyanate includes hydroxyalkyl (carbon ia of the alkyl group, usually 2 to 4) (
meth)acrylates [such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate], alkylene oxides of hydroxyalkyl (meth)acrylates (carbon & 2-4 alkylene oxides such as EO, PO and butylene oxide) and/or
Or adducts of lactones (usually 3 to 7 carbon atoms) (the number of moles added is usually 1 to 20, preferably 1 to 10), (meth)acrylamide, (meth)acrylic acid, and the like. Preferably, hydroxyalkyl (meth)acrylate is used, particularly preferably 2-hydroxyethyl (
meth)acrylate.

Polyols (c) containing no amino groups or carboxyl groups that may be used as necessary include polymeric diols with a hydroxyl group equivalent of 300 or more and hydroxyl equivalents of 250 or more.
The following low molecular weight diols are mentioned.

Polymer preols include polyether polyols and polyester polyols.

Examples of polyether polyols include low-molecular glycols (ethylene glycol, propylene glycol, 1,4-butanediol), low-molecular triols (glycerin,
trimethylolpropane, hexane), IJ-ol, etc.), tetrafunctional or higher-functional low molecular weight polyols (sorbitol, Shinyrose, etc.), aminos (alkanolamino,
alkylene oxides (alkylene oxides having 2 to 4 carbon atoms, such as EO, PO,
and butylene oxide) adducts and ring-opening polymers of alkylene oxides, and specific examples thereof include polyethylene glycol, polypropylene glycol, f-litewa methylene glycol, and the like.

Polyester polyols include polyesters containing terminal hydroxyl groups of polycarboxylic acids (aliphatic polycarboxylic acids such as adipic acid, maleic acid, and trimerized linoleic acid; aromatic polycarboxylic acids such as phthalic acid) and low-molecular-weight polyols or polyether polyols. Polyol; polycaprolactone polyol such as initiator [
Glycol (ethylene glycol), triol, etc.] is substituted with caprovacton (epsilon).
- Polyol obtained by addition-polymerizing caprovacton, α-metallic acid, epsilon-caprolactone, epsilon-methyl-epsilon-caprovacton, etc.) in the presence of a catalyst (organometallic compound, metal chelate compound, fatty acid metal acylate, etc.) etc. can be mentioned. Also, polymer polyols and polybutadiene polyols can be used.

Among these polymer polyols, preferred are polymers containing a compound selected from the group consisting of polycaprolactone polyol, polyester posiol made from polycarboxylic acid and low-molecular polyol, and polytetramethylene glycol in a weight ratio of 50 or more. It is a polyol.

The hydroxyl equivalent of the polymer polyol is usually 300 or more, preferably 400 to 2,000. When the hydroxyl equivalent is less than 800, the resulting urethane oligomer becomes brittle when cured by radiation, resulting in decreased abrasion resistance and durability when used as a magneto-electric recording material.

Examples of low-molecular polyols having a hydroxyl group of 4250 or less include low-molecular glycols (ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, etc.), low-molecular triols (glycerin, trimethylolpropane, etc.) , hexanetriol), tetrafunctional or higher-functional low-molecular polyols (sorbitol, sucrose, etc.), low-mole alkylene oxide adducts of these (diethylene glycol, etc.), and alkylene oxide low-mole adducts of phenols (bisphenol, etc.) ethylbenzene, etc.)
can be given. Among these, preferred are low-molecular diols and/or a combination of low-molecular diols and low-molecular triols.

The bond of (a) in (A) is usually 0.1 to 804@, preferably 0.2 to 20 ff4. When the amount of (a) is 0.2 equivalent t1, the dispersibility of the magnetic powder is poor, and even if the amount is more than 20 equivalents, the dispersibility is not good.

The element (b) in (A) usually has a molecular weight of 0.2 to 80 kg, preferably 0.5 to 20 kg. If the amount of (b) is less than 0.5 equivalents 4, the dispersibility of the magnetic powder will be poor, and if it is more than 20 equivalents, the viscosity of the magnetic paint will become too high.
Application becomes difficult.

(c) in (A) is usually θ~90 equivalents, preferably 20~70 equivalents (14).If the amount of (c) is more than 90 equivalents, the magnetic powder will be dispersed. Sex gets worse.

The equivalence ratio between (a) and (bl) is usually from V8o to 15/1, preferably from 1/10 to 10/1.

The power of (c) in the total of (A) and (c) usually ranges from 0 to 6 degrees, preferably from 1 to 50 degrees.

As the polyisocyanate [B] in the present invention, aromatic polyisocyanates such as aromatic polyisocyanate (tolylene diisocyanate (TDI), 4
．． 4'-diphenylmethane diisocyanate (MDI)
, modified MD1. t,5-naphthylene diisocyanate,
m- and/or p-xylylene diisocyanate,
2'-dimethyldiphenylmethane-4,4'-diisocyanate, etc.), aromatic polyisocyanate multimers (dimers and trimers such as TDI, MDI, etc.), and N between polyols and aromatic polyisocyanates.
A CO-terminated urethane prepolymer (a reaction product of a low-molecular-weight podiol and an excess of aromatic polyisocyanate, such as a reaction product of trimethylolpropane (1 mol) and TDI (8 mol)) is mentioned. Among the aromatic isocyanates, preferred are TDI and MDI.

Also non-aromatic, ti' IJ isocyanates such as aliphatic diisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, etc.) and alicyclic diisocyanates [hydrogenated TDI (hydrogenated tolylene diisocyanate), hydrogenated MDI (hydrogenated 4.47-cyphenylmethane diisocyanate), isopropylidene pin (4-cyclohexyl isocyanate), isophorone diisocyanate) (I
NCO-terminated urethane prepolymers of trimers and polyols of non-aromatic polyisocyanates and non-aromatic polyinocyanates (reactants of polyols such as low-molecular-weight polyols and excess non-aromatic polyisocyanates) ) can also be used. Among the non-aromatic polyisocyanates, preferred are IPDI and hydrogenated MDI
It is.

Urethane oligomers from (A) and [B] and optionally (c) are obtained by reacting (A) and CB'l and optionally (c). (A
) and CB) and optionally (c)′(
(A) is usually 80 to 80 equivalents, preferably 4
[B] usually has a range of 70 to 20 equivalents, preferably 60 to 80 equivalents, and (c) usually has a range of 0 to 70 equivalents.
~50 equivalents, preferably 1-40 equivalents.

The above reaction can be carried out in the presence or absence of a solvent inert to the isocyanate weir.

Examples of this solvent include aromatic hydrocarbon solvents (toluene, xylene, etc.), ketone solvents (cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, etc.), ester solvents (ethyl acetate, butyl acetate, etc.), and ether solvents (dioxane, tetwahydride, etc.). 7-run, etc.) and mixed solvents of two or more of these.

Reaction methods include (A) and (B) and optionally! 5 A method in which (c) is charged into a reaction vessel all at once and reacted, a method in which (A) and optionally (c) are divided and reacted in multiple stages, for example, a method in which a part of Ia), fb) and (c) Examples include a method of reacting CB), then reacting the main part of Cl, and then reacting (c).

The reaction temperature is usually 40-180°C, preferably 60-9°C. In order to accelerate the reaction, catalysts used in normal urethane reactions, such as tin-based catalysts (trinotyltin laurate, trimethyltin hydroxide, dimethyltin dilaurate, dimethyltin dilaurate, stannath octoate, etc.), and lead-based catalysts are used. (red oleate, red 2-ethylhexoate, etc.), etc. can also be used.

The obtained urethane oligomer has one or more (meth)acroyl groups in one molecule, preferably 1.5 to 10, particularly preferably 2 to 5 in the case of (c) e.

If the number of (meth)acroyl groups is less than one per molecule, the strength of the resin after radiation curing will decrease, and the abrasion resistance and durability will decrease when used as a magnetic recording material. The urethane oligomer usually has a number average molecular weight of 1,500 to 100,000, preferably 2,000 to 50,000.

When [C] is used as the urethane oligomer in the present invention, (1) a group represented by the formula Q-.

(2) Group represented by formula -Y-X- and/or formula -Y
A group represented by -X.

(3) Group represented by formula -Y-Z- and/or formula -Y
- A group represented by ZI.

and, if necessary, (4) a urethane oligomer composed of a group represented by the formula -YL. In the formula, Q is CH, =C-C0
-(Q')p-CR is H or CH3, Q' is -NH-
CO-mata OA (OA)m(0COA), 0C
O-1A is alkylene i, p is O or 1, m +
n is ot or an integer greater than or equal to 1, (OA) unit and (0COA
) Units may be arranged arbitrarily]; Y is -N
H-Y'-NH-<y' is a residue of f-ry'noR'cyanate); X is -Coo (AO)mA-N
-A-(OA), n0CO-CA is an alkylene group, R'
is H, alkyl group or mA (OA )rnOH, r
n is 0 or 1 or more R'' ■ Integer]; X is -Co-0(AO)rhA-N-R'
<A is an alkylene group, R' is an alkyl group, m
is O and OOH (an integer greater than or equal to 1); Z is -CO-0-Z'-0-CO-(
Z' is the remaining percentage of carboxyl group-containing polyol); ZI is -CO-0-A-COOH (A is an alkylene group), L is -CO-0-L'-0-CO- (L' is an amino group and Examples of this oligomer include those having the general formula (1): [where a, b, and c are 0 or 1 or more] (However, a and b cannot be O at the same time), T represents Eagle, (
The X-Y) units, (Y-Z) units, and (Y-L) units may be arranged arbitrarily. ].

Polymer polyols containing amino and carboxyl groups, urethane oligomers from fc) and CB) and optionally xl) ["C:] can also be used as binders according to the invention.

Polymer polyols containing amino groups and carboxyl groups include amino group-containing ethylenically unsaturated monomers [dialkylaminoalkyl (meth)acrylates, such as dimethylaminoethyl (meth)acrylates]
and a carboxyl group-containing unsaturated monomer [(meth)acrylic acid, etc.] is polymerized in a polymer polyol such as f-reather polyol (polypropylene glycol, etc.) or polyether polyol (the ratio used is 100 parts by weight of polymer polyol). The total amount of monomers is usually 2 to 70
(parts by weight, preferably 5 to 40 parts by weight).

The binder of the present invention can contain other polymeric materials in addition to the urethane oligomer containing amino groups and carboxyl groups. This polymer material includes polyvinyl chloride [vinyl chloride-vinyl acetate copolymer (VYHH,
manufactured by UCC; S-LEC C9 manufactured by Sekisui Chemical, etc.), vinyl chloride-vinyl acetate-vinyl flucol copolymer (V
AGH, Eslec A, etc.), vinyl chloride-vinylidene chloride-acrylonitrile (Saran, manufactured by Asahi Dow), etc.
Preurethane-based [urethane resin (Nisten, Guttrich)], butadiene-based [acrylonitrile-butadiene copolymer (Hiker 1482, Nippon Zeon), acrylonitrile-butanediene-styrene copolymer, etc.], acrylic-based ( various acrylic acid ester polymers), nitrocellulose, phenoxy resin,
Examples include engineering fkisi tree 1 effect.

In the binder, the urethane oligomer containing amino groups and carboxyl groups usually has a molecular weight of 204 or more, preferably 801 or more.

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

Examples of this magnetic material include iron oxide such as γ-Fe, O1 (
γ-hematite), CrO2 (chromium trioxide) and alloy-based magnetic materials such as CO-γ-Fe, Q-kame (cobalt ferrite or cobalt-doped γ-iron oxide), Fe
-Co-Cr, pure iron Fe, and barium ferrite. In the present invention, 6-γ-Fe, which is particularly finely powdered in recent years, is used! It is useful for O, (eg, particles with a major diameter of about 0.8 μm) and pure iron (eg, with a particle major diameter of about 0.2 μm).

The magnetic material is magnetic powder, and its shape is usually granular or acicular. Example of the size (μm) of a magnetic material: If shown, the diameter is 0.
．． 02~0.70. For example, the major axis is 0.2 to 0. ? , the short axis is 0.02 to 0.1.

In addition, a dispersant (lecithin, anionic, nonionic, or cationic surfactant such as sodium dotesylbenzenesulfonate) and a wetting agent (higher fatty acid ester such as butyl stearate) may be added if necessary.

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

Examples of this solvent include the same solvents as described in Section 6 of the urethane oligomer product, namely ester solvents (ethyl acetate, butyl acetate, etc.), ether solvents (1-ketone solvents such as dioxane and tetrahydrofuran (cyclohexanone, methyl ethyl ketone, etc.) , methyl isobutyl ketone, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.), and mixed solvents of two or more of these solvents. Among these, preferred are mixed solvents of ketones and aromatic hydrocarbons. It is.

The content of urethane oligomer in the magnetic paint is usually 8 parts by weight or more, preferably 5 to 80 parts by weight, based on the weight of the paint.
I am in charge of L. The object of the present invention can be fully achieved by including urethane oligomers of 8 or more urethane oligomers.

The amount of magnetic material in the magnetic paint usually ranges from 15 to 80% by weight.

A method for producing a magnetic paint includes a method in which the i-binder, solvent, and magnetic material are mixed in advance in a premixer or the like, if necessary, and then dispersed in a mixing/dispersing machine (such as a ball mill) and filtered.

This magnetic paint can be applied to a support film for magnetic recording media to create magnetic recording media (magnetic tape, etc.). Examples of the support film include films made of paper, cellophane, acetate, preester (PET), reinforced ester, 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 μm to several tens of μm. Application methods include coating methods such as doctor blade method and transfer printing method (gravure method, reverse roll method, etc.).

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

Magnetic recording media generally consist of a support film and a magnetic layer (magnetic binder), but there are also media that have an intermediate layer (undercoat layer) between the support film and the magnetic layer, and Some have magnetic layers on both sides, some have stacked magnetic layers with different magnetic properties, and some have a protective layer on the magnetic layer.

The urethane oligomer in the present invention can be cured using a crosslinking agent (first invention). Examples of the crosslinking agent include NGO-containing compounds and active hydrogen atom-containing compounds that are reactive with isocyanates. As the NGO-containing compound, polyisocyanate [modified MDI (Millione) ME.

Hodogaya Chemical), 3,8'-dimethoxy-4,4'-diisocyanate, etc.] and NCO-terminated prepolymers [
Examples include NCO-terminated premarimers of polyisocyanates (TDl, MDI, etc.) and polyols (low-molecular polyols, f-reather polyols, saryester polyols, etc.). In addition, as an active hydrogen-containing atom-containing compound, 4jl riamino [tolylene diamino (TD
A), 4,4'-diaminodiphenylmethane (MDA)
etc.] and polyols, polyether preols, polyester polyols, etc.

The amount of crosslinking agent added to the urethane oligomer is usually O~
25 layers, preferably 2 to 15 layers. If the weight exceeds 25 weights, the flexibility of the cured resin tends to decrease.

The urethane oligomer in the present invention is cured by radiation (second invention). Examples of this radiation include electron beams, neutron beams, gamma rays, etc., and preferably electron beams. Examples of electron beam accelerators include a scanning method, a curtain beam method, and a broad beam method. The acceleration voltage of the electron beam is usually 100 to 1000 Kvte, preferably 100 to 300 Kv.

It is KV. The absorbed dose is usually 0.5 to 20 megawatts, preferably 8 to 15 megawatts. When the accelerating voltage is less than 100 KV, the film thickness through which the electron beam passes is insufficient, and when it exceeds 1000 KV, the energy efficiency used for curing decreases, which is not economical. When the absorbed dose exceeds 20 megauds, the energy efficiency used for curing decreases.

[Example] The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. Parts in Examples indicate parts by weight.

Example 1 67.9 parts of butylene adipate with an average molecular weight of 1000 and 26.6 parts of neopentyl glycol (hereinafter referred to as NPC, !: abbreviation) were placed in a four-loaf flask equipped with a stirrer and a cooling tube.
2.24 parts of DMPA, 88.5 parts of MDI and 188 parts of cyclohexanone were reacted at 65 to 75°C for 4 hours.

Then 0.70 parts of triethanolamino, 1.82 parts of hydroxyethyl acrylate (hereinafter abbreviated as HEA) and hydroquinone monomethyl ether C or less, MQ
0.18 part was added and the reaction was continued for further 6 hours to obtain a urethane oligomer having three acryloyl groups in one molecule, which was used as the binder of the present invention.

Example 2 As in Example 1, 47.9 parts of polycaprolactone diol (hereinafter abbreviated as PCL) with an average molecular weight of 1250,
1,4-butanediol (hereinafter abbreviated as 1.4-BG) 5.87 parts, monomethyljetanol amino 4.
88 parts, DMPA 3.40 parts, trimethylolpropane C (hereinafter abbreviated as TMP) 7.48 parts, HEA 21.8 parts
80.8 parts of IPDI, 86.5 parts of toluene, 86.5 parts of methyl ethyl ketone, 5 parts of dibutyltin dilaurate Q, OO and 1.7 parts of MQ were taken, and 85-95 parts of
The reaction was carried out at °C for 25 hours to obtain a urethane oligomer having 8 acryloyl groups in one molecule, which was used as the binder of the present invention.

Example 8 Similar to Example 1, PCL117 with an average molecular weight of 1250
．． 2 parts, 1.4-BG 2.47 parts, monoethyl jetanolamino 8.07 parts, DMPA 1.52 parts, IPD
54.9 parts of I, 190 parts of cyclohexanone and 0.006 parts of dibutyltin diureth), 80-85
℃ for 6 hours, then 7.08 parts of HEA, 1.9 parts of methanol and 19 parts of MQo were added, and further 20 parts of MQo was added.
The reaction was carried out for 0 hours to obtain a urethane oligomer having one acryloyl group per molecule, which was used as the binder of the present invention.

Practical Example 4 As in Example 1, polytetraethylene glycol (hereinafter abbreviated as PTMG) with an average molecular weight of -@2000 was used.
2 parts, 7.76 parts of triethanolamino, 1.4-BG
6.50 parts, average molecular weight -tii 400 tetraol (
EO adduct of pentaerythritol) 20.0 parts, DM
PA 2.50 parts, HEA 23.2 parts, MDI 54.
7 parts, 160 parts of cyclohexanone, and 17 parts of MQo were reacted for 8 hours to obtain a urethane oligomer having 4 acryloyl groups per molecule, which was used as the binder of the present invention.

Example 5 Same as Example 1, 105 parts of ethylene butylene adipate with an average molecular weight of 2000, 4.78 parts of 1.4-BG,
5.47 parts of NP C, 2.6 parts of MDI δ and 180 parts of cyclohexanone were reacted at 65 to 75°C for 4 hours, 5.26 parts of tetraol (pentaerythritol OEO adduct) having an average molecular weight of 400 was added, and the mixture was further reacted for 5 hours with Vc. Ta. Then 1.17 parts of dimethylethanolamino,
1,00 parts of glycolic acid, 3.05 parts of HEA and MQ
0.18 part was added and reacted for 7 hours to obtain a urethane oligomer having two acryloyl groups in one molecule, which was used as the binder of the present invention.

Example 6 Similar to Example 1, PTMG11 with an average molecular weight of 1000
1 part, monomethyljetanol amino 3.25 parts, D
MPA 3.66 parts, NPC 43.5 parts, MDI 14
5 parts of cyclohexanone and 807 parts of cyclohexanone were reacted at 65 to 75°C for 4 hours at 11t'c. So17) M TMP 0.8
2 parts of EG and 1.69 parts of EG were added and reacted for 6 hours to obtain a urethane oligomer having an OH group at the end, which was used as the binder of the present invention.

Comparative Example 1 Same as Example 1, 67.9 parts of butylene adipate having an average molecular weight of 1000, 26.6 parts of NPC, DMPA 2.
24 parts, MDI 88.5 parts and cyclohexano 218
Eight parts were reacted at 65-75°C. After that TMP0.6
Add 8 parts, HEAl, 82 parts and MQo, 18 parts;
After further reaction for 6 hours, 8 acryloyl groups were added to each molecule.
A unique urethane oligomer was obtained and used as a comparative binder.

Comparative Example 2 Similar to Example 1, 105 parts of ethylene butylene adipate with an average molecular weight of 2000, 4.78 parts of 1.4-BG,
5.47 parts of NP C, 52.6 parts of MDI, and 180 parts of cyclohexanone were reacted at 65 to 75°C for 4 hours, and 5.26 parts of tetraol (EO adduct of pentaerythritol) having an average molecular weight of 400 was added, and the mixture was further reacted for 5 hours. Made it react.

Then add 1.17 parts of dimethylethanolamino,
Le 9.61 part, HEA 3.05 part O! HiMQ 0.
18 parts were added and reacted for 7 hours to obtain a urethane oligomer having two acryloyl groups in one molecule, which was used as a comparative binder.

Use Example 1 The urethane oligomers obtained in Examples 1 to 5 and Comparative Example 1.2 were blended as shown below and shaken for 4 hours with a paint conditioner (manufactured by Red Devil Co., Ltd.) to prepare a magnetic paint.

Urethane oligomer (solid content) 18 parts Pure iron (
Long axis Q, 20 μm, surface area 50 mDino) 72 Toluene 105 Cyclohexanone 105 The obtained magnetic paint was
Coating is performed on a µm polyester film using a doctor blade so that the coating thickness of the solid content is 6 to 6 µm,
Immediately, this was oriented in a parallel magnetic field of 8000 oersteds, and then the solvent was dried (100° C., 1 minute).

After that, it was calendered to make the surface smooth. When the urethane oligomers of Practical Examples 1 to 5 are used, an acceleration voltage of 200 KV is applied using an electron beam accelerator.
A magnetic film was obtained by irradiating the magnetic film with an electron beam in a nitrogen gas atmosphere at a Tokyo laboratory with an absorbed dose of 5 megarads. Also, as a binder, 5X! When the urethane oligomer of Example 6 is used, when preparing the magnetic coating material, the coronation is further improved (NCO-terminated prepolymer manufactured by Nippon Polyurethane)0.
9 parts were added to create magnetic paint. The obtained magnetic paint was applied to a polyether film in the same manner as described above, and after magnetic field orientation, the solvent was dried. Thereafter, it was calendered to smooth the surface and then left to stand in a constant temperature bath at 70°C for 24 hours to harden the magnetic layer and obtain a magnetic film. Table 1 shows the test results.

Table 1 *1) The 60 degree gloss of the magnetic film was measured using a digital female angle gloss meter (manufactured by Nippon Seishoku Kogyo). The larger the value, the better the dispersibility of the magnetic powder.

*2) Using a B-H curve tracer, the saturation magnetic flux densitometer and residual magnetic flux Br in the blending direction of the magnetic film were measured, and the ratio Br/Bm was determined. The larger the value of Br/&n, the better the dispersibility of the @-type powder and the better the electromagnetic conversion characteristics of the magnetic recording material.

〔Effect of the invention〕

The binder for magnetic recording materials of the present invention has excellent dispersibility of magnetic powder compared to conventional binders, and the obtained magnetic recording material also has excellent electromagnetic conversion characteristics.

Claims (1)

[Scope of Claims] 1. A binder for magnetic recording materials, which comprises as an essential component a urethane oligomer containing an amino group and a carboxyl group. 2. The oligomer contains an amino group-containing monool and/or
or a hydroxyl component [A] consisting of a polyol (a), a carboxyl group-containing monool and/or a polyol (b), and optionally a polyol (c) that does not contain an amino group or a carboxyl group, and a polyisocyanate [B]. The binder according to claim 1, which is a urethane oligomer. 3. A binder for a radiation-curable magnetic recording material, which contains as an essential component a urethane oligomer containing an amino group, a carboxyl group, and a (meth)acryloyl group. 4. The oligomer contains an amino group-containing monool and/or
Or a hydroxyl component [A] consisting of a polyol (a), a carboxyl group-containing monool and/or a polyol (b), and optionally a polyol (c) that does not contain an amino group or a carboxyl group, a polyisocyanate [B], and an isocyanate. The binder according to claim 3, which is a urethane oligomer made from a reactive active hydrogen atom-containing acrylic monomer [C]. 5. The oligomer has (1) a group represented by the formula Q-, (2) a group represented by the formula -YX- and/or a group represented by the formula -Y
a group represented by -X_1, (3) a group represented by the formula -Y-Z- and/or a group represented by the formula -Y
The binder according to claim 3 or 4, which is a urethane oligomer composed of a group represented by -Z_1 and, if necessary, a group represented by formula (4) -YL-. In the formula, Q is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [R is H or CH_3,
Q' is -NH-CO- or -OA(OA)_m(OC
OA)_nOCO-, A is an alkylene group, p is 0 or 1, m and n are integers of 0 or 1 or more, (OA) unit and (
OCOA) units may be arranged arbitrarily];Y
is -NH-Y'-NH- (Y' is a polyisocyanate residue); ＿mO
H, m are integers of 0 or 1 or more]; X_1 is -CO-O
(AO)_m-▲There are mathematical formulas, chemical formulas, tables, etc.▼(A
is an alkylene group, R'' is H or an alkyl group, m is an integer of 0 or 1 or more); Z is a ▲ mathematical formula, chemical formula, table, etc. ▼ (Z' is a residue of a carboxyl group-containing polyol); Z_1 is - CO-O-A-COOH
(A is an alkylene group); L is -CO-O-L'-OC
O- (L' is a polyol residue having no amino group or carboxyl group). 6. The oligomer has the general formula (1): Q(Y-X)_a(Y-Z)_b(Y-L)_cY-T
The binder according to claim 5, having a structure represented by [where a, b, and c are integers of 0 or 1 or more (
However, a and b are never 0 at the same time), T is X_1
, Z_1 or Q (however, when a is 0, T is X_1, b
When is 0, T represents Z_1), (Y-X) units,
The (YZ) units and (YL) units may be arranged arbitrarily. ] 7. Claim 3 in which the amino group is a tertiary amino group
The binder according to any one of items 1 to 6. 8. The binder according to any one of claims 1 to 7, wherein the oligomer has a molecular weight of 1,500 to 100,000.