JPS61222028A - Binder for magnetic recording material - Google Patents

Abstract

PURPOSE:To improve wear resistance and durability by constituting a binder for magnetic recording of an urethane oligomer contg. a polyol active hydrogen- contg. (meth) acrylate of a specific component and a prescribed ratio or above of a specific (meth) acryloyl group. CONSTITUTION:The polyol A consisting of a high molecular polyol A1 of, for example, >=250 equiv. a low molecular polyol A2 of <250 equiv. and, for example, 150 equiv. carboxyl group-contg. diol A3 is prepd. The active hydrogen- contg. (meth) acrylate B is added thereto to effect a reaction. The urethane oligomer having, for example, >=2.5 (meth) acryloyl groups from polyisocyanate C in one molecule is obtd., by which the binder for the magnetic recording material having excellent wear resistance and durability is obtd.

Description

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

[Conventional technology]

The present inventors have discovered a thermosetting carboxyl group-containing polyurethane resin as a binder for magnetic recording materials (Japanese Unexamined Patent Publication No. 59-148127). Durability was insufficient.

[Problem that the invention seeks to solve]

The present inventors have arrived at the present invention as a result of studying binders for magnetic recording materials aimed at improving wear resistance and durability.

[Means for solving problems]

The present invention provides a polymeric polyol (A2) having an equivalent weight of 250 or more.
, a polyol (A) consisting of a low-molecular-weight polyol (AI) with an equivalent weight of less than 250 and a carboxyl group-containing diol (N) with an equivalent weight of 150 or less, an active hydrogen-containing (meth)acrylate (B), and a polyisocyanate (C) (
The present invention is a radiation-curable binder for magnetic recording materials, characterized by comprising a meta)acrylolibomer.

Examples of the polymer polyol (81) used in the present invention include polyether polyols and polyester polyols.

Examples of polyether polyols include low molecular weight glycols (ethylene glycol, fluoropylene glycol: =y-l, l, 4
-butanediol, etc.); low-molecular triols (glycerin, trimethylolpropane, hexane, IJ-ol, etc.), tetrafunctional or higher-functional low-molecular polyols (sorbitol, sucrose, etc.), or amines (alkanolamines, aliphatic polyamines, etc.) alkylene oxide (alkylene oxide having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide, butylene oxide)
Examples include adducts and ring-opening polymers of alkylene oxide, and specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Examples of polyester polyols include polyester polyols containing terminal hydroxyl groups of polycarboxylic acid, maleic acid, di-digitated linoleic acid; aromatic polycarboxylic acids such as phthalic acid) and low molecular weight polyols or polyether polyols, polycaprolactone polyols such as initiators [glycol (ethylene glycol nat), triol, etc.] and (substituted) caprolactone (substituted)
ξ-caprolactone, α-methyl-e-caprolactone, C-methyl-ε-caprolactone, etc.) in the presence of a catalyst (organometallic compound, metal chelate compound, fatty acid metal acylate, etc.) to form a polyol. It will be done. Also, polymer polyols and polybutadiene polyols can be used.

Among these, preferred are polymeric polyols containing 50% by weight or more of a compound selected from the group consisting of polycaprolactone polyol, polyester polyol made from polycarboxylic acid and low-molecular polyol, and polytetramethylene glycol.

The equivalent weight of the high molecular weight polyol (N) is 250 or more, preferably 400 to 2,000. If the equivalent weight is less than 250, the resin of the obtained urethane oligomer after radiation curing becomes brittle, and when used as a magnetic recording material, wear resistance and durability are reduced.

In the present invention, low-molecular polyols having an equivalent weight of less than 250 include low-molecular glycols (ethylene glycol,
propylene glycol, 1.4-7” tanediol, neopentyl glycol, 1.6-hexanediol, etc.), low-molecular triols (glycerin, trimethylolpropane, hexanetriol, etc.), low-molecular-weight polyols with four or more functional functions (sorbitol, sucrose, etc.) ), low molar adducts of these fullkylene oxides (diethylene glycol, etc.), and low molar adducts of fullkylene oxide (bishydroxyethylbenzene, etc.) of phenols (such as bisphenol). Preferred among these are low molecular weight triols. and/or a combination of low-molecular diols and low-molecular triols.

Containing diols include 4,4-bis(hydroxyphenyl)butyric acid, 4,4-bis°(hydroxyphenyl)valeric acid, and dimethylolpropionic acid (DMPA).
), the preferred one is DMPA.
It is.

The amount of (A1) in (A) is usually 5 to 70 equivalent%,
Preferably it is 10 to 50 equivalent %. When (A2)' is less than 5 equivalent %, the resin of the produced urethane oligomer after radiation curing becomes brittle, resulting in decreased wear resistance and durability when used as a magnetic recording material. If (A2) exceeds 70 equivalent %, wear resistance and durability will decrease when used as a magnetic recording material.

The amount of (A2) in (A) is usually 20 to 90 equivalent %, preferably 40 to 85 equivalent %.

When (A2) is 20 equivalent% ungrooved, the resin strength of the produced urethane oligomer after radiation curing decreases, and when used as a magnetic recording material, wear resistance and durability decrease. On the other hand (A
When the amount of (A2) in (A) exceeds 90 equivalent %, the resin of the produced urethane oligomer after radiation curing becomes hard, and when used as a magnetic recording material, the abrasion resistance increases.
It is 30 equivalent %, preferably 0.5 to 20 equivalent %. If (n) is less than 0.5 equivalent %, the dispersibility of the magnetic powder will be poor, and if it is more than 20 equivalent %, the viscosity of the magnetic paint will become too high, making application difficult.

Active hydrogen-containing (meth)acrylate (B
) as hydroxyalkyl (the number of carbon atoms in the alkyl group is usually 2 to 4) (meth)acrylate [hydroxyethyl (meth)acrylate, hydroxypropyl (meth)
acrylate], alkylene oxide of hydroxyalkyl (meth)acrylate [alkylene having 2 to 4 carbon atoms, e.g. ethylene oxide (hereinafter abbreviated as EO),
propylene oxide (hereinafter abbreviated as PO) and butylene oxide] and/or adducts of lactones (usually 3 to 7 carbon atoms) (usually 1 to 20 moles added, preferably 1 to 10), (meth) Acrylamide, (meth)
Examples include acrylic acid. Hydroxyalkyl (meth)acrylate is preferred, and 2-hydroxyethyl is particularly preferred.The polyisocyanate (C) in the present invention is aromatic polyisocyanate such as aromatic polyisocyanate (tolylene diisocyanate (TDI)), 4. 4'-diphenylmethane diisocyanate (MDI), modified MDI, 1.5-naphthylene diisocyanate, m- and/or p-xylylene diisocyanate and 2,2-dimethyldiphenylmethane-4,4-diisocyanate), aromatic polyisocyanates (dimers and trimers such as TDI, MDI, etc.) and NCO-terminated urethane prepolymers of polyols and aromatic polyisocyanates [reactants of low-molecular-weight polyols and excess aromatic polyisocyanates, such as trimethylolpropane] (1 mol) and TDI (3
moles) of reactants]. Among the aromatic polyisocyanates, preferred are TDI and MDI.

In addition, non-aromatic polyisocyanates such as aliphatic diisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, etc.) and alicyclic diisocyanates [hydrogenated TDI
(hydrogenated tolylene diisocyanate), hydrogenated MDI (
4.4'-diphenylmethane diisocyanate)
, isopropylidene bis(4-cyclohexyl isocyanate), isophorone diisocyanate (IPDI')
etc.] NG of trimer of non-aromatic polyisocyanate and polyol and non-aromatic polyisocyanate
O-terminated urethane prepolymers (reactants of polyols such as low molecular weight polyols and excess non-aromatic polyisocyanate) can also be used. Among the non-aromatic polyisocyanates, preferred are IPDI and hydrogenated MDI.

Urethane oligomers from (A), (B) and (C) are obtained by reacting (A), (B) and (C). (A), (B) and (C) are reacted, (A) is usually 30 to 70 equivalent %, preferably 40 to 60 equivalent %, and (B) is equivalent %. C) is usually 20 to 70 equivalent%, preferably 30 to 6
It is 0 equivalent%.

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

The reaction method includes a method of charging (A), (B) and (C) in a reaction container at once and reacting them, (A), (B)
) and (C) in a multistage reaction by dividing them, and a method in which (A2), (n), and a part of (A2) are reacted with (C3), and then the remainder of (A2) is reacted, and then (B) Examples include methods for reacting.

The reaction temperature is usually 40-130°C, preferably 60-90°C.
℃, the reaction is catalyzed using a tin-based catalyst such as trimethyltin laurate, trimethyltin hydroxide, dimethyltin dilaurate, dibutyltin dilaurate (red oleate, red 2-ethylhexoate, etc.). You can also do that.

The resulting urethane oligomer has 2.5 or more (meth)acroyl groups in one molecule, preferably 2.6 to 10, particularly preferably 2.8 to 5. There are 2.(meth)acroyl groups in one molecule. , less than 5, the resin strength after radiation curing decreases, and when used as a magnetic recording material, wear resistance and durability decrease. The urethane oligomer usually has a number average molecular weight of 1,500 to soooo, preferably 2,000.
~30000, acid # (KOH-9IP)
is usually 0.5-50, preferably 1-30.

In addition to the carboxyl group-containing urethane oligomer, other polymer materials can be used in combination with the binder of the present invention. This polymeric material is polyvinyl chloride [vinyl chloride-ff] vinyl copolymer (VYHH, U (made by C;
S-LEC C1 manufactured by Sekisui Chemical, etc.), vinyl chloride-vinyl acetate-viny 7L/flucol copolymer (VAG
H, Esrec A, etc.), vinyl chloride-vinylidene chloride-acrylonitrile (Saran, manufactured by Asahi Dow), etc.
Polyurethane type [urethane resin (manufactured by Nisten, Guttrich, etc.)], butadiene type [acrylonitrile-phtadiene copolymer (Hiker 1432, manufactured by Nippon Zeon, etc.), acrylonitrile-butanediene-styrene copolymer, etc.], acrylic type (various acrylic Examples include acid ester polymers, nitrocellulose, phenoxy resins, and epoxy resins.

The content of the carboxyl group-containing urethane oligomer in the binder is usually 20% or more, preferably 30% 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.

As this magnetic material, iron oxide such as r-F etos
(1-hematite), CrO- (chromium trioxide) and alloy-based magnetic materials such as Cr4-r Fex
es (cobalt ferrite or cobalt-doped l-iron oxide), Fe Co-Cr, pure iron Fe, and barium ferrite. In the present invention, especially the recent more finely powdered Co-r-Fetu
s (eg, particles with a major diameter of about 0.3 μm) and pure iron (eg, particles with a major diameter of about 0.2 μm).

Magnetic materials are magnetic powders that are usually granular or acicular in shape. An example of the size (μm) of a magnetic material is when the diameter is 0.
02~0. 70, for example, major axis 0.2 to 0,7,
The short axis is 0.02 to 0.1.

Other dispersants (lecithin, anionic, nonionic, or cationic surfactants such as dodecylbenzenesulfone lubricants (higher fatty acid esters such as butyl stearate) may also be added if necessary.

Solvents are used in magnetic paints to adjust their viscosity. Examples of this solvent include the same solvents as those described in the urethane oligomer production reaction, such as ester solvents (ethyl acetate, butyl acetate, 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 urethane oligomer in the magnetic paint is usually 3% by weight or more, preferably 5 to 30% by weight, based on the weight of the paint. By including urethane oligomer in an amount of 3% by weight or more, the object of the present invention can be fully achieved.

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

A method for producing magnetic paint is to mix the binder, solvent, and magnetic material in advance using a blender, etc., if necessary, then disperse them using a mixing/dispersing machine (ball mill, etc.), and filter. A support film for air recording media can be created. The support film may be made of paper, cellophane, acetate, polyester (PET), reinforced polyester, polyimide, etc. 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 doctor blade method and 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 generally consist of a support film and a magnetic layer (magnetic binder), but there are also media with an intermediate layer (undercoat layer) between the support film and magnetic layer, and media with a support film and a magnetic layer (magnetic binder). Some have Q magnetic layers on both sides, some have stacked magnetic layers with different magnetic properties, and some have a protective layer on the magnetic layer.

It is hardened by Examples of this radiation include electron beams, neutron beams, l-rays, etc., and preferably electron beams.

Examples of electron beam accelerators include a scanning method, a curtain beam method, and a broad beam curtain method. The accelerating voltage of the electron beam is usually 100 to 10 U OKV, preferably 100 to 3 U UKV. The absorbed dose is usually 0.5 to 20 megarads, preferably 3 to 15 megarads. If the accelerating voltage is less than 100KV, the thickness of the electron beam transmission film is insufficient, and the
If the absorbed dose exceeds 12-0 megarads, the energy efficiency used for curing decreases, making it uneconomical.If the absorbed dose exceeds 12-0 megarads, 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 the examples indicate parts by weight.

Example 1 Polytetramethylene glycol (hereinafter referred to as
PTMG) 48.0 parts, ethylene glycol (abbreviated as PTMG)
Hereinafter, abbreviated as EG) 11.0 s, 2.0 parts of DMPA, 75.5 parts of IPDI, 162.9 parts of cyclohexanone, and 0.005 parts of digyltin dilaure) were taken and reacted at 75 to 85°C for 4 hours. After that, 13.6 parts of trimethylolpropane (hereinafter abbreviated as TMP) was added, and the mixture was further reacted for 6 hours. Thereafter, 2-hydroxyethyl acrylate (hereinafter abbreviated as HEA '112.
8 parts and 0.15 parts of 7-methylhydroquinone (hereinafter abbreviated as MQ) were added, and the mixture was further reacted for 200 hours.
A urethane oligomer CD-1) having three acryloyl groups in one molecule was obtained and bound with the binder of the present invention.

This product has a number average molecular weight of 5650. The acid value was 5.1.

Example 2 In the same manner as in Example 1, 1-48.5 parts of 1-tylene adipate having an average molecular weight of 1000 and neopentyl glycol (hereinafter referred to as
19.0 parts of NPG (abbreviated as NPG) and 134.0 parts of DM Sanon were reacted at 65 to 75°C for 3 hours. Then TMP0.
45 parts 2) (3 g of 'EAt and 13 parts of MQo were added and the reaction was further carried out for 6 hours to obtain a urethane oligomer CD-2 having 3 acryloyl groups in one molecule), which was used as the binder of the present invention. This material has a number average molecular weight of 27,800. The acid value was 5.0.

Example 3゜Similarly to Example 1, 28.2 parts of polycaprolactone diol (hereinafter referred to as PCL) with an average molecular weight of 1250, 1
．． 4-butanediol (hereinafter abbreviated as 1.48G)6.
9 parts, DMPA 2.0 parts, TMP 4.4 parts, H
gAl 2.8 parts, IPDI 47.5 parts, toluene s 0.9 parts, methyl ethyl ketone 50.9 parts, dibutyltin dilaurate 0. OU 3rd Division and MQo
, and reacted at 75 to 85° C. for 25 hours to obtain a urethane oligomer (D-, 3) having three acryloyl groups in one molecule, which was used as the binder of the present invention.

This product has a number average molecular weight of 3050. The acid value was 8.2.

Example 4゜Similar to Example 3, PCL 51 with an average molecular weight of 4000
．． 6 parts, NG 1.5 parts, DMP A 6.0 parts, TMP 6.7 parts, HE A 6.4 parts, I P
DI 19.7 parts, cyclohexanone 91.9 parts,
Dibutyltin dilaure-1-0,003 parts and MQo
, 09 parts were reacted for 15 hours to obtain a urethane oligomer CD-4) having three acryloyl groups in one molecule, which was used as the binder of the present invention. This product has a number average molecular weight of 6700. The acid value was 273. Example 5゜Same as Example 3, PTMG28 with an average molecular weight of 2000
．． 9 parts, EG 2.0 parts, 1.4 B G 3.9 parts, tetraol with an average molecular weight of 400 (manufactured by Sanyo Chemical Industries, Ltd.)
Product name Sannix EP-400) 12.0 copies, DMP
5 parts of Al, 13.9 parts of HEA, 32.8 parts of MDI, 95 parts of cyclohexanone and 1 part of MQo were reacted for 8 hours to obtain a urethane oligomer CD-5) having 4 acryloyl groups in one molecule, This was used as the binder of the present invention.

This product had a number average molecular weight of 11,800 and an acid value of 6.6.

Comparative Example 1゜Similar to Example 1, 48.5 parts of butylene adipate with an average molecular weight of 1000, 19.0 parts of NPG, DMP A
1.6 parts of MDI, 63.2 parts of MDI, and 134.0 parts of cyclohexanone were reacted at 65 to 75°C for 3 hours. After that, 0.36 parts of TMP and 74 parts of BGo were added and reacted for 6 hours to form a urethane oligomer (E
-1) was obtained, and this was used as a comparative binder. This product had a number average molecular weight of 26,200 and an acid value of 5.1.

Comparative Example 2゜Similar to Example 1, PTMG48 with an average molecular weight of 1000
．． 0 parts, E G 11.9 parts, I P D I 75.
5 parts, 161.8 parts of cyclohexanone and 0.005 parts of dibutyltin dilaurate were heated at 75-85°C.
After reacting for an hour, 13.6 parts of TMP was added, and the reaction was further continued for 6 hours. Then, 12.8 parts of HEA and 15 parts of MQo were added, and the reaction was further carried out for 200 hours.
A urethane oligomer (E-2) having three acryloyl groups in one molecule was obtained and used as a comparative binder. This product had a number average molecular weight of 5420 and an acid value of 0.

Test Example 1 The urethane oligomers obtained in Examples 1 to 5 and Comparative Example 2 were blended in the following proportions and conditioned with paint conditioner (manufactured by Red Devil Co., Ltd.) for 4 hours to create a magnetic paint. Urethane oligomer (Solid content) 18 parts Cor-
FetOs (major axis 0.28 μm 1 minor axis 0.04 μm) 7'2 Toluene 105 Cyclohexanone
105 The obtained magnetic paint was coated onto a 15 μm polyester film using a doctor blade so that the coating thickness of the solid content was 5 to 6 μm, and immediately after it was passed through a parallel magnetic field of 6000 oersted for magnetic field orientation. , the solvent was dried (100°C, 1 minute), then calendered, surface speed voltage 150KV, absorbed dose 5
A magnetic film was obtained by irradiating an electron beam under megarad conditions in a nitrogen gas atmosphere.

In addition, the urethane oligomer obtained in Comparative Example 1 was added to the magnetic paint composition and 0.9 part of Coronae 1-L (manufactured by Nippon Polyurethane, solid content) to prepare a magnetic paint. The obtained magnetic paint was applied to a polyester film in the same manner as above, and after magnetic field orientation, the solvent was dried. After that, the surface was smoothed by calendering, and then placed in a thermostatic oven at 70℃ for 2 hours.
A magnetic film was obtained by leaving it for 4 hours to harden the magnetic layer.1
Table 1 shows the test results.

Table-1 [*l] A magnetic film was shaped into a disc and applied to a commercially available taper set scratch tester (manufactured by Toyo Seiki Co., Ltd.) to relatively evaluate the degree of wear of each magnetic film. The value was set as Δ.

*2) A test magnetic tape with a length of 50 m was used as a simulated head.
The tape surface was repeatedly slid back and forth at a speed of m/sec and then measured visually and with a microscope. A coating film with no scratches or powder falling off was considered good.

*3) Measured by visual inspection and 60 degree specular reflectance.

*4) Using a B-H curve tracer, the saturation magnetic flux density Bm and residual magnetic flux density Br in the orientation direction of the magnetic film were measured, and the ratio Br/Bm of the two was determined.

Effects of the Invention] The binder for magnetic recording materials of the present invention has improved abrasion resistance and durability of magnetic recording materials compared to conventional binders. In addition to the above-mentioned effects, the binder of the present invention has good dispersibility of magnetic powder, and the resulting magnetic recording material has excellent electromagnetic conversion characteristics.

The binder of the present invention is useful as a binder for magnetic recording materials, such as audio tapes, video tapes, computer tapes, data recorder tapes, video sheets, magnetic disks, and magnetic cards.

Claims (1)

[Claims] 1. High molecular polyol (A_1) having an equivalent weight of 250 or more;
Low molecular polyol (A_2) with an equivalent weight of less than 250 and carboxyl group-containing diol (A_3) with an equivalent weight of 150 or less
A polyol (A) consisting of an active hydrogen-containing (meth)acrylate (B), and a urethane oligomer having 2 to 5 or more (meth)acryloyl groups in one molecule from a polyisocyanate (C). Binder for radiation-curable magnetic recording materials. 2. A patent in which (B) is a compound selected from the group consisting of hydroxyalkyl (meth)acrylate, adduct of hydroxyalkyl (meth)acrylate with alkylene oxide and/or lactone, (meth)acrylamide, and (meth)acrylic acid. The binder according to claim 1.