JPH0624059B2 - Binder and magnetic recording material - Google Patents

Description

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

[Conventional technology]

Conventionally, as a binder for a magnetic recording material, there is one composed of a polyurethane resin composed of polycaprolactone polyol, a trifunctional or higher functional low molecular weight polyol, and an organic polyisocyanate (Japanese Patent Laid-Open Nos. 57-60529 and 57-60530). .

[Problems to be solved by the invention]

However, this product has insufficient calendering property, and therefore workability is insufficient because work cannot be performed unless the calendering temperature is raised or the calendering speed is slowed.

[Means for solving problems]

The present inventors have arrived at the present invention as a result of intensive studies to obtain a binder for a magnetic recording material and a magnetic recording material which have excellent calendering properties and dispersibility of a magnetic material.

That is, the present invention relates to a magnetic recording comprising a polyurethane resin (C) made of a polyol (A) consisting of a high molecular weight polyol (A ₁ ) and a low molecular weight polyol (A ₂ ) having an equivalent weight of 200 to 2000 and an organic polyisocyanate (B). In the binder for materials, the polyurene resin (C) comprises (1) at least 50% by weight of (A ₁ ) of a polyvalerolactone polyol (a ₁ ) or (a ₁ ) and a polycaprolactone polyol (a ₂ ). , And (a ₁ ):
The weight ratio of (a ₂ ) is (10: 0) to (1: 9), and the total equivalent weight of (2) (A ₁ ) and (A ₂ ) is 100 to 175.
0, and the NCO / OH equivalent ratio of (3) (B) and (A) is 0.6 to
A binder for magnetic recording materials (first invention) characterized by being 1.5; and a magnetic recording material (second invention) characterized by containing the binder and a magnetic material.

As the polyvalerolactone polyol (a ₁ ) in the present invention, an initiator [glycol (such as ethylene glycol) or triol] is used as a base (substitution).
Valerolactone ( -Valerolactone, β-methyl- And (valerolactone) and the like in the presence of a catalyst (organic metal compound, metal chelate compound, fatty acid metal acylate, etc.).

Among these, polyvalerolactone diol is preferable.

The equivalent of polyvalerolactone polyol is usually 200 to 2000
It is preferably 400 to 1500.

If necessary, other polymer polyol can be used in combination with (a ₁ ). As this polymer polyol,
The polycaprolactone polyol described in JP-A-57-60529 is included.

Also, polyether polyols [low-molecular-weight glycols (ethylene glycol, propylene glycol, 1.4-butanediol, etc .; low-molecular-weight triols (glycerin, trimethylolpropane, hexanetriol, etc.); tetra-functional or higher-low-molecular-weight polyols (sorbitol, sucrose, etc. Closed) or alkylene oxide of aminos (alkanolamine, aliphatic polyamine, etc.) (C2-C2)
4 alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide) adducts and ring-opening polymerization products of the above alkylene oxides. Specifically, polyethylene glycol, polypropylene glycol and polytetramethylene ether glycol are included.

Also, a polyester polyol [a polycarboxylic acid (aliphatic polycarboxylic acid such as adipic acid, maleic acid and dimerized linoleic acid; aromatic polycarboxylic acid such as phthalic acid) and a low molecular weight polyol or polyether polyol less than a hydroxyl group-containing polyester polyol ], Polymer polyols and polybutanediene polyols can also be used. Of these, polyester polyol is preferable.

The total content of the polyvalerolactone polyol (a ₁ ) and the polycaprolactone polyol in the polymer polyol (A ₁ ) is usually 50% by weight or more, preferably 90 to 100% by weight, particularly preferably 100% by weight. Content is 5
If it is less than 0% by weight, the dispersibility of the magnetic material is deteriorated.

The weight ratio of polyvalerolactone to polycaprolactone is usually 10: 0 to 1: 9, preferably 9: 1 to 2: 8, particularly preferably 8: 2 to 5: 5.

The equivalent weight of the polymer polyol (A ₁ ) containing (a ₁ ) is usually
It is 200 to 2500, preferably 400 to 1500. Equivalent to 200
When it is less than 1, the dispersibility of the obtained urethane resin magnetic material is deteriorated, and the scratch resistance is also deteriorated. Also, the equivalent is 2500
If it exceeds, the dispersibility, abrasion resistance, scratch resistance, hydrolysis resistance and the like of the obtained polyurethane resin with respect to the magnetic material are deteriorated.

The low molecular weight polyol (A ₂ ) in the present invention is a low molecular weight glycol (ethylene glycol, propylene glycol, 1.
4 butanediol, bisphenol A, etc., low-molecular glycol or bisphenols (diphenol,
Low molar adducts of alkylene oxides such as bisphenol A).

Further, trifunctional or higher functional low molecular weight polyols described in JP-A-57-60529 are also included.

Further, glycol ester of monohydroxymonocarboxylic acid described in JP-A-61-177627 can also be used. When this product is used, a large amount of polycaprolactone polyol may be used.

The equivalent of the low molecular weight polyol (A ₂ ) is usually 30 to less than ₂₀₀ ,
It is preferably 45 to 150.

In the polyol (A), the low molecular weight polyol (A ₂ ) is 20 to 95.
It is equivalent%, preferably 30 to 80 equivalent%. (A ₂ ) is 2
If it is less than 0 equivalent%, the film properties of the urethane resin produced are likely to deteriorate and the dispersibility of the magnetic powder also becomes poor. Meanwhile (A ₂ )
When it exceeds 95 equivalent%, the dispersibility of the magnetic material of the urethane resin produced is reduced.

The total equivalent weight of the polyol (A) consisting of the high molecular weight polyol (A ₁ ) and the low molecular weight polyol (A ₂ ) is usually 100 to 1750.
When the equivalent weight of (A) is less than 100, the produced polyurethane resin becomes a brittle resin having a poor film forming property and is not sufficient as a binder for magnetic recording materials. On the other hand, if the equivalent weight exceeds 1750, the dispersibility of the magnetic material of the generated urethane resin decreases,
The film strength becomes insufficient, and abrasion resistance, scratch resistance, hydrolysis resistance, etc. decrease.

In the present invention, the organic polyisocyanate (B) is an aromatic polyisocyanate, for example, an aromatic polyisocyanate, [tolylene diisocyanate (TDI); 4.4 '
-Diphenylmethane diisocyanate (MDI); modified MDI;
1.5-naphthylene diisocyanate; m- or / and p-xylylene diisocyanate and 2.2'-dimethyldiphenylmethane-4.4'-diisocyanate, etc.], multimers of aromatic polyisocyanates (dimers and trimers such as TDI and MDI) Etc.) and NCO-terminated urethane prepolymer of polyol and aromatic polyisocyanate [reaction product of low-molecular-weight polyol and excess aromatic polyisocyanate, such as trimethylolpropane (1 mol)
And TDI (3 mol) reaction product; , Hydrogenated MDI (hydrogenated 4.4'-diphenylmethane diisocyanate), isopropylidene bis (4-cyclohexyl isocyanate), isophorone diisocyanate (IPDI) and bis (2-isocyanatoethyl) fumarate]; non-aromatic polyisocyanate Examples thereof include trimer and a non-NCO urethane prepolymer of a polyol and a non-aromatic polyisocyanate (a reaction product of a polyol such as a low molecular weight polyol and an excess of a non-aromatic polyisocyanate).

Two or more of the above organic polyisocyanates can be used in combination.

Among the organic polyisocyanates, preferred ones are aromatic diisocyanates as aromatic polyisocyanates, especially MDI and TDI, and non-aromatic polyisocyanates are aliphatic diisocyanates, especially hexamethylene diisocyanate and alicyclic diisocyanates, especially IPDI. . Especially preferred is MDI.

In the polyurethane resin from the polyol (A) and the organic polyisocyanate (B), the NCO / OH equivalent ratio is usually 0.6
~ 1.5, preferably 0.9-1.2. NCO / OH equivalent ratio is 0.6
If it is less than 1.5 or more than 1.5, the molecular weight of the polyurethane resin obtained by the reaction of (A) and (B) becomes low and the dispersibility decreases, and the scratch resistance, abrasion resistance, hydrolysis resistance, etc. of the magnetic recording material are also reduced. Is easy to decrease.

The polyurethane resin (C) can be produced by reacting (A) and (B) in the presence or absence of a solvent inert to the isocyanate group. As this solvent, ester solvents (ethyl acetate, butyl acetate, etc.), ether solvents (dioxane tetrahydrofuran, etc.), ketone solvents (cyclohexanone, methyl ethyl ketone, etc.)
Examples thereof include methyl isoptyl ketone), aromatic hydrocarbon solvents (toluene, xylene, etc.), and mixed solvents thereof.

As the reaction method, a method in which the polyol (A) and the aromatic polyisocyanate (B) are collectively charged in a reaction vessel, a reaction is performed, a method in which (A) and (B) are divided and a multistage reaction is performed, and in advance There is a method in which the mixed (A) and (B) are passed through a heated continuous kneader to react.

The reaction temperature is usually 40 to 130 ° C., preferably 60 to 80
℃. 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, stannas octoate, etc.), a lead-based catalyst (red oleate, Red 2-
Ethyl hexoate, etc.) and the like can also be used.

The number average molecular weight of the polyurethane resin (C) in the present invention is usually 10,000 to 200,000, preferably 50,000 to 100,000, the OH value is usually 15 or less, preferably 10 or less, and the NCO content is usually 8%.
It is the following.

Polyurethane resin (C) from polyol (A) and aromatic polyisocyanate (B) is used as a binder for magnetic recording materials, but if necessary, other polymeric materials usually used for magnetic recording materials. Can be used together. Examples of the polymer material include polyvinyl chloride-based [vinyl chloride-vinyl acetate copolymer (VYHH, UCC; Slek C, Sekisui Chemical Co., etc.), vinyl chloride-vinyl acetate-vinyl alcohol copolymer (VAGH; S-REC A) Etc.), vinyl chloride-vinylidene chloride-acrylonitrile (Saran, manufactured by Asahi Dow, etc.), polyurethane-based [urethane resin (made by Esten, Goodrich, etc.), butadiene-based [acrylonitrile-butadiene copolymer (Hika-143
2, manufactured by Nippon Zeon Co., Ltd.), acrylonitrile-butanediene-styrene copolymer (ABC), etc.], acrylics (various acrylic acid 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 also referred to as a magnetic paint) by containing this and a magnetic material.

Examples of this magnetic material include Fe (pure iron), γ-Fe ₂ O ₃ (γ-hematite), Cro ₃ (chromium trioxide) and alloy-based magnetic materials such as Co-γ-Fe ₂ O ₃ (cobalt ferrite or cobalt). And doped Fe-Co-Cr.

The magnetic substance is magnetic powder, and its shape is generally granular or acicular. If an example of the size (μ) of the magnetic material is shown, the major axis is 0.2 to 1.0 and the minor axis is 0.02 to 0.1.

A cross-linking agent for cross-linking the polyurethane resin can be used in the magnetic paint. 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'-diisocyanate, etc.] and NCO-terminated prepolymers [polyisocyanate (TDI / MDI, etc.) and polyols (low-molecular-weight polyols, polyether polyols, polyester polyols, etc.), such as Desmodur L (manufactured by Bayer), Colonuto L
(Made by Nippon Polyurethane) and the like]. As the active hydrogen-containing compound, polyamine [tolylenediamine
(TDA), 4.4'-diaminediphenylmethane (MDA), 4.4 '
-Diamino3.3'-dichlorodiphenylmethane etc.) and polyols (low molecular weight polyols, polyether polyols, polyester polyols etc.).

The addition amount of the crosslinking agent is usually 0 to 25 relative to the polyurethane resin.
%, Preferably 2 to 15% by weight. 25% by weight
If it exceeds the range, the flexibility of the film tends to be lowered.

If necessary, 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.

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 solvents (dioxane, tetrahydrofuran, etc.), ketone solvents (cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.)
And these mixed solvents can be used. Among these, preferred are mixed solvents of ketone type and aromatic hydrocarbon type.

The content of polyurethane resin (C) in the magnetic paint is usually 5% by weight or more, preferably 10 to 40, based on the weight of the paint.
% By weight. 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 magnetic substance in the magnetic paint is usually 30 to 80% 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 preliminarily mixed if necessary with a premixer or the like, and then dispersed with 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). Examples of the support film include paper, cellophane, acetate, polyester (PET), reinforced polyester, and polyimide films. Of these films, a polyester film is often used.

When the magnetic paint 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 paint is then subjected to steps such as orientation, drying, calendering, cutting and winding to obtain a magnetic recording medium.

The calendering conditions are, for example, in the case of a paper coating agent, the temperature is usually 70 to 120 ° C., preferably 80 to 90.
℃. The pressure is usually 100 to 400 kg / cm ² , preferably 150.
~ 250 kg / cm ² . The calender speed is, for example, usually 10 to 100 m / min, preferably 20 to 6 in the case of a paper coating agent.
It is 0 m / min.

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, a support film There are also those having a magnetic layer on both sides, those having magnetic layers with different magnetic properties stacked, and those having a protective layer provided on the magnetic layer (protective card).

〔Example〕

The present invention will be further described below with reference to examples, but the present invention is not limited thereto. Parts in the examples indicate parts by weight.

Example 1 1 mol equivalent of 425 polyvalerolactone diol and
A mixture of 4 mol of 1.4-butanediol and 5 mol of TDI was reacted to obtain a polyurethane resin (OHV10) having a slight hydroxyl group end. This is referred to as polyurethane resin (C ₁ ).

Using this (C ₁ ) as a binder, a mixture having the following composition was mixed in advance with a premixer and mixed with a ball mill,
A magnetic paint (D ₁ ) was prepared by dispersing.

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.

This was passed through a pressing machine at a linear pressure of 200 kg at a speed of 30 m for 1 to 3 times, and the film was calendered.
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 2 moles of polyvalerolactone diol with 1000 equivalents, 1 mole of polytetramethylene glycol with 500 equivalents and
Polyurethane resin having hydroxyl groups (OHV) by reacting a mixture of 7 mol of 1.4-butanediol and 10 mol of TDI.
8) was obtained. This is referred to as polyurethane resin (C ₂ ).

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, a magnetic coating material (D ₂ ) was obtained and a magnetic tape was prepared. . This is a magnetic tape (E ₂ ).

Example 3 Polyurethane resin having a slight NCO group obtained by reacting 3 mol of MDI with a mixture of 1000 mol of polyvalerolactone diol (1 mol), 200 mol of polypropylene glycol (1 mol) and ethylene glycol (1 mol) (NCO content of 5 %) Is the polyurethane resin (C ₃ ).

A magnetic coating material (D ₃ ) was prepared 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 to prepare a magnetic tape. did. This is a magnetic tape (E ₃ ).

Example 4 0.5 mol of an equivalent 425 polyvalerolactone diol,
4.5 mol of an equivalent weight of 425 polycaprolactone diol,
MDI 1 with a mixture of 5 moles of polybutylene adipate diol with an equivalent weight of 850 and 4 moles of 1.4-butane diol.
A polyurethane resin (OHV 8) having a slight hydroxyl end was obtained by reacting 4 mol. This is referred to as a polyurethane resin (C ₄ ).

In the composition of Example 1, the polyurethane resin (C ₁ ) 2
Example 1 except that 20 parts of (C ₄ ) was used instead of 0 part.
A magnetic paint (D ₄ ) was obtained in the same manner as in 1. to prepare a magnetic tape. This is a magnetic tape (E ₄ ).

Comparative Example 1 1 mol of polycaprolactone diol having an equivalent weight of 425, 1.4
2 mol of butanediol and trimethylolpropane
A polyurethane resin (OHV 9) having a slight hydroxyl end was obtained by reacting 0.4 mol of the mixture with 3.4 mol of TDI. This polyurethane resin is referred to as Comparative Example (C ₁ ′).

A magnetic paint (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 The magnetic tapes obtained in Examples 1 to 4 and Comparative Example 1 were each subjected to calendering treatment 3 times under the conditions of a linear pressure of 200 Kg / cm and a roll temperature of 60 ° C., and the surface condition of each time was observed with a microscope. The results of observation are shown in Table 1. The microscope magnification at this time was 1000 times, and the degree of smoothness of the tape surface was visually observed to evaluate the calendering property. The smoother the surface, the better the calendering property.

[Advantages of the Invention] The binder for a magnetic recording material and the magnetic recording material of the present invention are the same as the conventional binders (see JP-A-57-60529, JP-A-57-60529).
-60530 gazette) is superior in calendar property. Therefore, it is not necessary to raise the calender temperature or slow the calender speed. Therefore, workability is good.

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

Since the binder and material of the present invention exhibit the above effects, they are, for example, audio tapes, video tapes, computer tapes, data recorder tapes, video sheets,
It is useful as a metallic recording material, a binder for magnetic recording materials for magnetic cards, and magnetic recording materials.

Claims (3)

[Claims] 1. A magnetic recording comprising a polyurethane resin (C) comprising a polyol (A) comprising a high molecular weight polyol (A ₁ ) and a low molecular weight polyol (A ₂ ) having an equivalent weight of 200 to 2000 and an organic polyisocyanate (B). In a binder for materials, the polyurethane resin (C) comprises (1) at least 50% by weight of (A ₁ ) of polyvalerolactone polyol (a ₁ ) or (a ₁ ) and polycaprolactone polyol (a ₂ ) , And (a ₁ ):
The weight ratio of (a ₂ ) is (10: 0) to (1: 9), and the total equivalent weight of (2) (A ₁ ) and (A ₂ ) is 100 to 175.
0, and the NCO / OH equivalent ratio of (3) (B) and (A) is 0.6 to
A binder for a magnetic recording material, which is 1.5. 2. The binder according to claim 1, wherein (A ₂ ) in (A) is 20 to 95 equivalent%. 3. A magnetic recording comprising a polyurethane resin (C) made from a polyol (A) consisting of a high molecular weight polyol (A ₁ ) and a low molecular weight polyol (A ₂ ) having an equivalent weight of 200 to 2000 and an organic polyisocyanate (B). In a binder for materials, the polyurethane resin (C) comprises (1) at least 50% by weight of (A ₁ ) of polyvalerolactone polyol (a ₁ ) or (a ₁ ) and polycaprolactone polyol (a ₂ ) , And (a ₁ ):
The weight ratio of (a ₂ ) is (10: 0) to (1: 9), and the total equivalent weight of (2) (A ₁ ) and (A ₂ ) is 100 to 175.
0, and the NCO / OH equivalent ratio of (3) (B) and (A) is 0.6 to
A magnetic recording material comprising a binder for magnetic recording material and a magnetic material, which is 1.5.