JPH0674313B2 - Binder and magnetic recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a binder and a magnetic recording material.

[Conventional technology]

A polyurethane resin obtained by reacting a polyol component composed of a high-molecular polyol, a low-molecular polyol and dimethylolpropionic acid with an organic polyisocyanate is known as a binder for magnetic recording materials (for example, JP-A-59-148127). Gazette).

[Problems to be solved by the invention]

However, with the demand for high image quality and long-term recording, high recording density and high durability are required for video tapes.
A binder having excellent dispersibility and adhesiveness to the polyester film of the base material is required.

[Means for solving problems]

The present inventors have arrived at the present invention as a result of extensive studies on a binder for a magnetic recording material and a recording material having improved adhesiveness.

That is, the present invention relates to a polyol (A) and an organic polyisocyanate (B) each having an equivalent weight of 200 to 2000, a high molecular weight polyol (A ₁ ), a low molecular weight polyol (A ₂ ) and a carboxyl group-containing urethane modified diol (A ₃ ). Binder for magnetic recording material (first invention) characterized by comprising a polyurethane resin (C) from ( ₁ ), high molecular weight polyol (A ₁ ) having an equivalent weight of 200 to 2000, low molecular weight polyol (A ₂ ) and carboxyl group-containing Polyol (A) consisting of urethane-modified diol (A ₃ ) and organic polyisocyanate (B)
A magnetic recording material (second invention), characterized by containing a binder for a magnetic recording material comprising a polyurethane resin (C) and a magnetic material.

Examples of the carboxyl group-containing urethane modified diol in the present invention include an OH-terminated prepolymer of a carboxyl group-containing diol and an organic polyisocyanate.

As the carboxyl group-containing diol, aliphatic diols such as dimethylolpropionic acid (abbreviated as DMPA) and aromatic diols such as 4.4-bis (hydroxyphenyl) butyric acid, 4.4-bis (hydroxyphenyl) valeric acid and Mixtures of two or more of these may be mentioned. Of these, preferred is DMPA.

Examples of the organic polyisocyanate include aromatic polyisocyanates such as aromatic polyisocyanates [tolylene diisocyanate (TDI), 4.4'-diphenylmethane diisocyanate (MDI), modified MDI, 1.5-naphthylene diisocyanate, m- and / or p -Xylylene diisocyanate (XDI), 2.2'-dimethyldiphenylmethane-4.4'-diisocyanate, etc.]; Non-aromatic polyisocyanates such as aliphatic diisocyanates [tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, etc.], alicyclic Diisocyanate [hydrogenated TDI (hydrogenated tolylene diisocyanate), hydrogenated MDI (hydrogenated 4.4'-diphenylmethane diisocyanate), isopropylidene bis (4-cyclohexyl isocyanate), isophor Diisocyanate (IPDI), etc.], multimers of aromatic polyisocyanates (such as dimers and trimers of TDI, MDI, etc.), trimers of non-aromatic polyisocyanates and polyols with aromatic polyisocyanates. NCO-terminated urethane prepolymer [reaction product of low-molecular-weight polyol and excess aromatic polyisocyanate, such as trimethylolpropane (1 mol)
And a reaction product of TDI (3 mol)] An NCO-terminated urethane prepolymer of a polyol and a non-aromatic polyisocyanate (a reaction product of a polyol such as a low-molecular polyol and an excess of an aromatic polyisocyanate).

Of these, preferred are IPDI, MDI, and XDI, and particularly preferred are IPDI and MDI.

The carboxyl group-containing urethane-modified diol has the general formula (In the formula, X is an organic polyisocyanate residue, n is 1 to 10
Is. ).

If n is less than 1 in the above, the adhesion is insufficient and
If it exceeds 10, the dryness of the binder will deteriorate.

In producing the carboxyl group-containing urethane modified diol, the NCO / OH equivalent ratio of the carboxyl group-containing diol and the organic polyisocyanate is usually 0.4 to 0.99, preferably 0.5 to 0.95.

The above reaction can be carried out in the presence or absence of a solvent inert to the isocyanate group. As this solvent, ester type solvents (ethyl acetate, butyl acetate, etc.),
Examples thereof 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 thereof.

The reaction temperature is generally 40 to 130 ° C, preferably 60 to 110 ° C.

In the reaction, a catalyst used in a usual urethane reaction for promoting the reaction, for example, a tin-based catalyst (trimethyltin laurate, trimethyltin hydroxide,
It is also possible to use dimethyltin dilaurate, dibutyltin dilaurate, stannas octoate, etc.), a lead-based catalyst (such as lead oleate, red 2-ethylhexoate).

Examples of the polymer polyol (A) include polyether polyol and polyester polyol. As polyether polyols, low molecular weight glycols (ethylene glycol, propylene glycol, 1.4-butanediol, etc.), low molecular weight triols (glycerin, trimethylolpropane, hexanetriol, etc.), tetrafunctional or higher functional low molecular weight polyols (sorbitol, sucrose) Etc.) or amines (alkanolamines, aliphatic polyamines, etc.), alkylene oxide (alkylene oxides having 2 to 4 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide) adducts, and ring-opening polymerization products of alkylene oxides. Specifically, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol are included.

As the polyester polyol, polycarboxylic acid (aliphatic polycarboxylic acid such as adipic acid, maleic acid, dimerized linoleic acid; aromatic polycarboxylic acid such as phthalic acid) and a low molecular weight polyol or polyether polyol are condensed with a terminal hydroxyl group. Polyester polyol; Polycaprolactone polyol, for example, (substitution) caprolactone, (ε-caprolactone, α-methyl-ε-caprolactone, ε-methyl-ε-caprolactone) based on an initiator [glycol (ethylene glycol, etc.), triol, etc.] And the like) were subjected to addition polymerization in the presence of a catalyst (organic metal compound, metal chelate compound, fatty acid metal acylate, etc.) and cyclic dicarboxylic acid modified polycaprolactone polyol (Japanese Patent Application No. 61-78920). Those described.), And the like. Also, polymer polyols, polycarbonate polyols and polybutadiene polyols can be used.

Among these, preferred is a compound selected from the group consisting of polycaprolactone polyol, condensed polyester polyol, cyclic dicarboxylic acid modified polycaprolactone polyol and polytetramethylene glycol.
It is a high molecular weight polyol containing at least wt.

The polymer polyol (A ₁ ) has an equivalent weight of 200 to 2000, preferably 250 to 1500.

The low molecular weight polyol (A ₂ ) in the present invention includes low molecular weight glycols (ethylene glycol, propylene glycol, 1.4 butanediol, etc.), low molecular weight triols (glycerin, trimethylolpropane, hexanetriol, etc.), tetrafunctional or higher functional low molecular weight polyols. Examples thereof include polyols (sorbitol, sucrose, etc.), alkylene oxide low-molar adducts thereof (diethylene glycol, etc.), and alkylene oxide low-molar adducts of phenols (phenol, bisphenol etc.) (bishydroxyethylbenzene etc.). Of these, preferred are low molecular weight glycols.

The amount of (A ₃ ) is usually 0, based on the weight of polyol (A).
It is 1 to 60%, preferably 0.1 to 50%. (A ₃ ) amount
If it is less than 0.1%, the adhesiveness is not sufficient, and if it exceeds 60%, the drying property of the binder is deteriorated.

In the polyol (A ₃₎ is usually 0.1 to 70 equivalent%, preferably 0.1 to 60 equivalent percent, (A ₂₎ is 5 to 80 equivalent%, preferably 10 to 50 equivalent%. If the content of (A ₂ ) is less than 5 equivalent%, the film characteristics of the urethane resin produced are likely to deteriorate and the dispersibility of the magnetic powder also becomes poor. On the other hand, when A ₂ exceeds 80 equivalent%, the dispersibility of the magnetic material of the generated urethane resin deteriorates.

The equivalent weight of the polyol (A) is usually 100 to 1,600.
When the equivalent of (A) is less than 100, the polyurethane resin produced becomes a brittle resin having poor film-forming properties and is not sufficient as a binder for magnetic recording materials. On the other hand, when the equivalent weight exceeds 1600, the dispersibility of the magnetic material of the generated urethane resin decreases and the film strength becomes insufficient, resulting in abrasion resistance, scratch resistance,
Hydrolysis resistance is reduced.

Examples of the organic polyisocyanate (B) in the present invention include those similar to the organic polyisocyanates described in the section of the carboxyl group-containing urethane modified diol. Preferred are MDI, IPDI and TDI.

In reacting (A) and (B), (B) and (A)
The equivalent ratio is usually 0.6 to 1.5, preferably 0.8 to 1.2.
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 and the dispersibility will be low, and the scratch resistance, abrasion resistance and resistance of the magnetic recording material will be reduced. Hydrolyzability is likely to decrease.

The above reaction can be carried out in the presence or absence of a solvent inert to the isocyanate group. As this solvent, ester type solvents (ethyl acetate, butyl acetate, etc.),
Examples thereof 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 thereof.

As a reaction method, (A) and (B) are put together in a reaction vessel and reacted, a method of dividing (A) and (B) into a multistage reaction and premixing (A)
And (B) are passed through a heated container kneader to react.

The reaction temperature is generally 40 to 130 ° C, preferably 60 to 80 ° C. In the reaction, a catalyst used in a usual urethane reaction for promoting the reaction, for example, a tin-based catalyst (trimethyltin laurate, trimethyltin hydroxide, dimethyltin dilaurate, dibutyltin dilaurate, stannas octoate, etc.), a lead-based catalyst (Led oleate, red 2-ethylhexoate, etc.) can also be used.

The number average molecular weight of the obtained polyurethane resin (C) is usually 3,000 to 200,000, preferably 5,000 to 150,000.

The molecular weight per carboxyl group is usually 1,000 to 200,00
It is 0, preferably 5,000 to 150,000. If the molecular weight per carboxyl group is less than 1,000, the hydrolysis resistance is reduced.

The polyurethane resin (C) obtained by reacting (A) and (B) is used as a binder for a magnetic recording material, but if necessary, it may be used in combination with another polymer material usually used for a magnetic recording material. You can Examples of the polymer material include polyvinyl chloride-based [vinyl chloride-vinyl acetate copolymer (VYHH, UCC; manufactured by ESLEC C, Sekisui Chemical Co., Ltd.), vinyl chloride-vinyl acetate-vinyl alcohol copolymer (VACH, ESLEC A) Etc.), vinyl chloride-vinylidene chloride-acrylonitrile (Saran, made by Asahi Dow, etc.), polyurethane-based [urethane resin (made of Esten, Guttrich, etc.)], butadiene-based [acrylonitrile-butadiene copolymer (Hiker 1432, Nippon Zeon Etc.), acrylonitrile-butanediene-styrene copolymer (A135), etc.], acrylic (various acrylic ester-based polymers, etc.), nitrocellulose, phenoxy resin, epoxy resin and the like.

The binder for a magnetic recording material of the present invention can be made into a magnetic recording material (hereinafter sometimes referred to as a magnetic paint) by containing this and a magnetic material.

Examples of the magnetic substance include iron oxides such as γ-Fe ₂ O ₃ (γ-hematite), CrO ₃ (chromium trioxide) and alloy-based magnetic substances such as Co-γ-Fe ₂ O ₃ (cobalt ferrite or cobalt-doped). (γ-iron oxide), Fe-Co-Cr, and pure iron Fe
Can be given. In the present invention, it is particularly useful for recent finer γ-Fe ₂ O ₃ particles (for example, particles having a BET specific surface area of 40 m ² / g or more).

The magnetic substance is magnetic powder and its shape is usually granular or acicular. If you show an example of the size (μm) of the magnetic substance, the diameter is 0.
02 to 0.70, for example, the major axis is 0.2 to 0.7 and the minor axis is 0.02 to 0.1.

A cross-linking agent can be used in the magnetic paint to cross-link the polyurethane resin. Examples of this cross-linking agent include NCO-containing compounds and active hydrogen-containing compounds. As the NCO-containing compound, polyisocyanate [modified MDI (Millionate ME, Hodogaya Chemical Co., Ltd.), 3.3'-dimethoxy-4.4 '
-NCO-terminated prepolymers such as diisocyanates) and NCO-terminated prepolymers [polyisocyanates (TDI, MDI, etc.) and polyols (low-molecular-weight polyols, polyether polyols, polyester polyols, etc.) such as Desmodur L (made by Bayer), Coronate L
(Made by Nippon Polyurethane) and the like]. As the active hydrogen-containing compound, polyamine [tolylenediamine (TDA), 4.4'-diaminodiphenylmethane (MDA), 4.4 '
-Diamino-3.3'dichlorodiphenylmethane) and polyols (low molecular weight polyols, polyether polyols, polyester polyols, etc.).

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

In addition, a dispersant (lecithin, anion, nonion, cationic surfactant such as sodium dodecylbenzenesulfonate) and a lubricant (higher fatty acid ester such as butyl stearate) can be added, if necessary.

A solvent is used for the magnetic paint to adjust the viscosity. As this solvent, the same solvent as described in the polyurethane resin formation reaction, that is, an ester solvent (ethyl acetate,
Butyl acetate etc.), ether solvent (dioxane, tetrahydrofuran etc.) Ketone solvent (cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone etc.), aromatic hydrocarbon solvent (toluene, xylene etc.)
And a mixed solvent of two or more of these can be used. Among these, preferred are mixed solvents of ketone type and aromatic hydrocarbon type.

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

The amount of the magnetic substance 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 the other polymer material is usually 0 to 20% by weight, preferably 2
~ 15% by weight.

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

As a method for producing a magnetic coating material, there is a method in which a binder, a solvent and a magnetic material are mixed beforehand by a premixer, if necessary, and then dispersed by a mixing / dispersing machine (ball mill etc.).

This magnetic paint can be applied to a support film for a magnetic recording medium to prepare a magnetic recording medium (such as a magnetic tape). This support film includes paper, cellophane, acetate, polyester (PET), reinforced polyester,
Films such as polyimide can be used. Of these films, polyester film is often used.

When the magnetic coating material is applied to the support film, the coating thickness is usually several μ to several tens μ. Examples of applicable methods include doctor blade method and transfer printing method (gravure method, reverse roll method, etc.) and the like.

The film coated with the magnetic coating material is then subjected to processes such as orientation, drying, surface processing, cutting and winding to obtain a magnetic recording medium.

A magnetic recording medium is generally composed of a support film and a magnetic layer (magnetic binder), but one having an intermediate layer (undercoat layer) provided between the support film and the magnetic layer, or a support film. There are also those having magnetic layers on both sides, those having magnetic layers having different magnetic characteristics stacked, and those having a protective layer provided on the magnetic layer.

〔Example〕

The present invention will be further described by the following examples, but the present invention is
It is not limited to this. Parts in the examples indicate parts by weight.

Example 1 1 mol of a cyclic dicarboxylic acid-modified polycaprolactone diol having an equivalent of 1000, 1 mol of polytetramethylene glycol having an equivalent of 500, 3 mol of neopentyl glycol, and 0.1 mol of a carboxyl group-containing urethane-modified diol 1 and 1.4.
-A polyurethane with a slight hydroxyl end (OHV1
0) was obtained. This is referred to as polyurethane resin (C ₁ ).

(Note) Carboxyl group-containing urethane modified diol 1 is DM
It is a urethane-modified diol composed of 2 mol of PA and 1 mol of IPDI.

Using this (C ₁ ) as a binder, a mixture having the following composition was mixed in advance with a premixer, mixed with a ball mill and dispersed to prepare a magnetic coating material (D ₁ ).

γ-Fe ₂ O ₃ fine powder 100 parts Polyurethane resin (C ₁ ) 20 parts Vinyl chloride-vinyl acetate (88:12) copolymer 10 parts Desmodur L 2 parts Lecithin 1 part Methyl ethyl ketone 75 parts Toluene 75 parts This magnetic paint Was coated on a polyester film so that the coating thickness after drying was 5 μm and dried.

The film was passed through a pressing machine at a linear pressure of 200 kg at a speed of 30 m for 1 to 3 times to calender the film. The temperature at this time is 80 ° C. After calendering, the tape was cut to a width of 12.65 mm. This is a magnetic tape (E ₁ ).

Example 2 MDI (5.3 mol) was reacted with a mixture of 1 mol of cyclic dicarboxylic acid-modified polycaprolactone diol (1000 mol), neopentyl glycol (2.5 mol), carboxyl group-containing urethane modified diol (1) (0.066 mol) and ethylene glycol (1.734 mol), and MDI (5.3 mol) was reacted. A polyurethane resin (OHV4.3) having This is referred to as polyurethane resin (C ₂ ).

A magnetic coating (D ₂ ) was obtained in the same manner as in Example 1 except that 20 parts of the polyurethane resin (C ₂ ) was used instead of 20 parts of the polyurethane resin (C ₁ ) in the composition of Example 1 to prepare a magnetic tape. did. This is a magnetic tape (E ₂ ).

Example 3 1 mol of polycaprolactone polyol of 1000 equivalents, equivalent
A polyurethane resin (OHV3.7) having slightly terminal OH groups was obtained by reacting a mixture of 200 mol of polypropylene glycol, 0.0375 mol of urethane modified diol containing carboxyl group 1 and 0.9625 mol of ethylene glycol with 3 mol of MDI. It was This is called polyurethane resin (C ₃ ).

A magnetic paint (D ₃ ) was obtained in the same manner as in Example 1 except that 20 parts of the polyurethane resin (C ₃ ) was used instead of 20 parts of the polyurethane resin (C ₁ ) in the composition of Example 1, and the magnetic tape was used. Created. This is a magnetic tape (E ₃ ).

Comparative Example 1 Polytetramethylene glycol having an equivalent weight of 500, 2 mol, 1.6-
A mixture of 3 mol of hexanediol, 0.6 mol of DMPA and 1 mol of trimethylolpropane was reacted with 7 mol of TDI to obtain a polyurethane resin (OHV7.2) having a small amount of terminal OH groups and COOH groups. This polyurethane resin is referred to as Comparative Example (C ′ ₃ ).

A magnetic coating material (D ′ ₁ ) was obtained in the same manner as in Example 1 except that 20 parts of the polyurethane resin (C ′ ₁ ) was used instead of 20 parts of the polyurethane resin (C ₁ ) in the composition of Example 1. I made a tape. This is a magnetic tape (E ′ ₁ ).

Test Example 1 With respect to the magnetic tapes obtained in Examples 1 to 3 and Comparative Example 1, test pieces were prepared in accordance with the blind eye test method (JIS K5400-79) and subjected to cellophane tape peeling. The results are shown in Table-1. The numerical value indicates the number of peeled pieces. The smaller the value, the better the adhesion.

[Advantages of the Invention] The binder for magnetic recording material and the magnetic recording material of the present invention have excellent adhesion to the polyester film as compared with the conventional binder (as disclosed in JP-A-59-148127). Therefore, even if the magnetic tape is repeatedly used, the acoustic characteristics and recording characteristics of the magnetic tape do not deteriorate.

Moreover, the binder and material of the present invention have extremely good dispersibility of the magnetic material. It also has a good calendar. Therefore, it has excellent effects as a binder for a magnetic recording material and a magnetic recording material.

Because of the above effects, the binder and material of the present invention are useful as a binder and a magnetic recording material for magnetic recording materials for audio tapes, video tapes, computer tapes, data recorder tapes, video sheets, metal disks, magnetic cards. is there.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 61-192775 (JP, A) JP 60-166316 (JP, A) JP 59-148127 (JP, A) JP 58- 145722 (JP, A) JP-A-57-113420 (JP, A)

Claims (6)

[Claims] 1. A polyol (A) and an organic polyisocyanate (B) comprising a high molecular weight polyol (A ₁ ) having an equivalent weight of 200 to 2000, a low molecular weight polyol (A ₂ ) and a carboxyl group-containing urethane modified diol (A ₃ ). A binder for a magnetic recording material comprising a polyurethane resin (C) from 2. The binder according to claim 1, wherein (A ₃ ) is an OH-terminated prepolymer of a carboxyl group-containing diol and an organic polyisocyanate. 3. (A ₃ ) is a general formula (In the formula, X is a residue of an organic polyisocyanate, and n is 1 to
Is 10. The binder according to claim 1 or 2, which is a compound represented by the formula (1). 4. The content of (A ₃ ) is based on the weight of (A).
The binder according to any one of claims 1 to 3, which is 1 to 60%. 5. The binder according to any one of claims 1 to 4, wherein the number average molecular weight of (C) is 3000 to 200.000. 6. A polyol (A) consisting of a high molecular weight polyol (A ₁ ) having an equivalent weight of 200 to 2.000, a low molecular weight polyol (A ₂ ) and a carboxyl group-containing urethane modified diol (A ₃ ) and an organic polyisocyanate (B). A magnetic recording material comprising a binder for a magnetic recording material comprising a polyurethane resin (C) and a magnetic material.