JPS59129267A - Ionizing radiation-curing magnetic coating - Google Patents

Abstract

PURPOSE:To provide the titled magnetic coating consisting mainly of magnetic powder and a binder prepared from a specified thermoplastic resin, which is excellent in dispersion of magnetic powder and coatability and produces magnetic recording media having good magnetic properties and durability. CONSTITUTION:An ionizing radiation-curing magnetic coating consists mainly of magnetic power and a binder. The binder is a thermosetting resin obtained by adding a (meth)acryloyl group-containing monomer to a resin prepared by polymerizing 100pts.wt. vinyl chloride and/or vinylidene chloride monomer or its blend with a copolymerizable monomer having hydroxyl, carboxyl or epoxy group in the presence of 3-100pts.wt. thermoplastic polyurethane elastomer having a softening point of 20 deg.C or higher and containing a terminal hydroxyl group to introduce a hydroxyl and/or carboxyl group and/or epoxy group in the molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ionizing radiation-curable magnetic coating that has excellent dispersibility of magnetic powder and coating properties, as well as excellent magnetic properties, durability, and heat resistance of the resulting magnetic recording medium. .

Generally, magnetic recording media such as magnetic tapes, magnetic cards, or magnetic disks are made by using a plastic film such as polyester or a non-magnetic metal disk such as aluminum alloy as a support, coating the surface with magnetic paint, drying it, and fixing magnetic powder with a binder. It is something. Various binders have been used heretofore, but vinyl chloride-vinyl acetate copolymer is widely used because it has excellent dispersibility of magnetic powder and is easily immersed in solvents. In order to give vinyl chloride-vinyl acetate copolymer flexibility, plasticizers such as dioctyl phthalate (DOP) and soft resins such as polyurethane disstomer are usually used in combination, or are there various problems? be. In a magnetic recording medium mixed with a plasticizer such as DOP, the plasticizer migrates to the surface of the magnetic coating during use, which not only contaminates the magnetic head but also reduces the durability of the magnetic recording medium.

On the other hand, when polyurethane elastomer is mixed and used, polyisocyanate is also used as a crosslinking agent, so the pot life of the magnetic recording paint is short. -Depending on the degree of compatibility between the vinyl acetate copolymer and the polyurethane elastomer, the dispersibility of the magnetic powder and the surface smoothness and durability of the resulting magnetic recording medium often become poor.

The present inventors have completed the present invention as a result of intensive studies aimed at providing a magnetic paint that improves these drawbacks.

That is, the present invention provides an ionizing radiation-curable magnetic paint containing magnetic powder and a binder as main components, in which the binder has the following M V
C or MVC monomer 100! Softening point 2 for f amount part
A thermoplastic polyurethane disstomer (hereinafter referred to as TPO) having a hydroxyl group at the end was combined at 0°C or higher in the presence of 6 to 100 parts by weight, and a hydroxyl group and/or a carboxyl group and/or an epoxy group were introduced into the molecule. An ionizing radiation-curable magnetic paint characterized by being a curable resin obtained by adding a (meth)acryloyl group-containing monomer to a resin (hereinafter referred to as resin A).

MVC: vinyl chloride monomer and/or vinylidene chloride monomer.

MVC monomer: Contains a hydroxyl group, a carboxyl group, or an epoxy group that can be copolymerized with vinyl chloride monomer and/or vinylidene chloride monomer and vinyl chloride monomer or vinyl chloride de/monomer. A mixture of monomers and other monomers.

In the present invention, an acryloyl group and a methacryloyl group (
Collectively called meth)acryloyl group.

Resin A is substantially TPU as MVC or MVC.
MVC or M in a state dissolved in the system monomer or organic solvent
It is produced by polymerizing VC monomers. Although the nature of this reaction is not clear, MVC-soluble T
It is presumed that a certain type of chemical bond (ie, a reaction called sweet graft copolymerization) occurs between the PU and the MVC monomer.

That is, compared to the blend of TPU and PVC used in the formulation of magnetic paint, the produced polymer of the present invention has significant improvements in terms of magnetic powder dispersibility, heat resistance, durability, surface smoothness, etc. It is inferred that it is excellent.

TPU in the present invention has a hydroxyl group at the end, is substantially soluble in MVC or MVC monomers, or organic solvents under the polymerization conditions of the present invention, and has a softening point of 20"C. above, preferably 20 to 100°C
, more preferably 3° to 60°C. Softening point 1
If the temperature exceeds 00°C, it becomes difficult to dissolve in the MVC monomer, and if the temperature exceeds 20°C, the resulting polymer will have poor tensile strength, heat resistance, and oil resistance.

In general, TPU refers to an elastomer that has urethane bonds in the molecule, and has a linear block copolymer structure of polyurethane as a noft segment and polyurethane as a hard segment, and has a hydroxyl group at the end. There is. Generally, soft segments are obtained by reacting a polymer diol having hydroxyl groups at both ends with a diisocyanate, and hard segments are obtained by reacting a glycol or diamine with a diincyanate.

T)) tJ used in the present invention has a hydroxyl group at the end, is soluble in (~1■C or MVC monomer or organic solvent, and has a softening point of 20"C or more, In order to have such physical properties, it is necessary to select soft segments and hard segments.If there are too many hard segments and the molecular weight becomes large, solubility will be poor, and TP
Since the softening point of O exceeds 100"C, it is necessary to limit the amount of hard segments used. Therefore, the amount of hard segments used in the present invention is mostly soft segments, with a small amount of hard segments as necessary. can include.

The polymer diol constituting the soft segment of TPU has a number average molecular weight of 500 to io, oo.

A range of polyester diols, polyether diols, polyolefin diols, polylactone diols, etc. are used.

Polyester diols include geltaric acid, adipic acid, cohelic acid, speric acid, separtenic acid, oxalic acid,
Dibasic acids such as methyladipic acid, pimelic acid, azelaic acid, fucuric acid, terephthalic acid, isophthalic acid, maleic acid, and fumaric acid, and ethylene glycol, 1.4-butanediol, 1.6-hexanediol, Those obtained by an esterification reaction with a diol such as lengelicol, diethylene glycol, or neopentyl glycol are used.

As the polyether diol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. are used.

As the polyolefin diol, polybutadiene diol and the like are used, and as the polylactone diol, polycaprolactone diol and the like are used.

In the present invention, in order for the curable resin to have excellent performance, TPO using polyester diol, particularly adipic acid-based polyester diol, is preferable.

As the glycols and diamines constituting the hard segment of TPU, the diols shown as the raw materials for polyester diols and aliphatic and aromatic diamines such as ethylene diamine, propylene diamine, and xylene diamine are used.

Examples of diisocyanates constituting the soft segment and hard segment of TPU include 4,4'-diphenylmethane diisocyanate, 4,41-diphenyl diisocyanate, 2,4-) lylene diisocyanate, and 2-
6-) Lylene diisocyanate, 1,5-naphthalene diisocyanate, xylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate, influorone diisocyanate, etc. are used alone or in combination of two or more.

The TPU used in the present invention is as described above, but in order to further obtain the desired curable resin, it is preferable to dissolve it in MVC or an MVC monomer or an organic solvent. Therefore, TPU has a weight average molecular weight of 180.000 as measured by gel permeation chromatography.
In the following, a bismetron type rotational viscometer (60-ter,
6 Or, p, m, .

The viscosity of a 20% methyl ethyl ketone solution of the resin (hereinafter abbreviated as 20% M E K viscosity) measured at 60 seconds at 25"C) is 2,000 cps or less.

In the present invention, the high viscosity TPU is MVC or MVC
It takes a long time to dissolve in the system monomer, and low viscosity TP
U indicates that the performance of the resulting curable resin is poor. Therefore, 20%
MEK viscosity is 60-ioo.

cps range is preferable, more preferably 50 to 40
0 cps, more preferably 100 to 000 cps
s range.

MVC soluble type T having a hydroxyl group at the end that is effective for the present invention
1) One suitable type of TJ is Bandex 'I'-526 manufactured by Dainippon Ink and Chemicals.
5C Polyurethane mainly composed of adipic acid polyester diol and aliphatic diisocyanate; Softening point, 5
6°C; 20% MEK viscosity.

800 cpsA: weight average molecular weight, 120,000),
Bandex T-525 (softening point, 47°C), etc.

In addition, when producing resin A by solution polymerization, M
It is also possible to use TPU, such as Vandex T-5000, which does not dissolve in VC or MVC monomers but dissolves in organic solvents such as dimethylformamide and tetrahydrofuran.

In the present invention, TPU is MVC or MVC at the time of preparation.
Polymerization is initiated at 3 to 100 parts by weight, preferably from 5 to 60 mr, per 100 parts by weight of the system monomer.

Based on 1003 parts of MVC or MVC monomer,
If the amount of TPU is less than 3 parts by weight, the resulting magnetic coating using the resulting polymer will not have satisfactory flexibility;
If the amount exceeds 0 parts by weight, the resulting magnetic paint using the resulting polymer will not have satisfactory tensile strength.

In the present invention, the MVC-soluble TPU content in the produced polymer is preferably 4 to 40% by weight, more preferably 8 to 60% by weight.
Good weight percentage. This is because if the amount is less than 4% by weight, it is difficult to obtain satisfactory flexibility in the resulting magnetic paint. On the other hand, if it exceeds 40% by weight, it is not preferable because the dispersibility of the magnetic powder becomes poor and the magnetic paint used cannot obtain a satisfactory tensile strength.

In the present invention, monomers that can be copolymerized with MVC include olefins such as ethylene and globyrenato, vinyl esters such as vinyl acetate, vinyl ethers such as ■-butyl vinyl ether, butyl acrylate, and 2-ethylhexyl acrylate. Acrylic esters such as
Examples include Nisder methacrylates such as 2-ethylhexyl methacrylate.

In the coexistence of TPU having a hydroxyl group at the end, MVC or M,
Resin A having a hydroxyl group in the molecule can be obtained by polymerizing a V C monomer, but it can be copolymerized with MVC to further introduce a hydroxyl group and/or a carboxyl group and/or an epoxy group. It is preferable that part or all of the monomer be a polymerizable monomer having a hydroxyl group, a carboxyl group, or an epoxy group in the molecule.

Examples of such copolymerizable monomers include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyglobylacrin-1., 2-
Hydroxyethyl acrylate, ro-chloro-2-hydroxypropyl methacrylate, ro-hydroxybutyl acrylate, hydroxybutyl vinyl ether, methacrylic acid, acrylic acid, monobutylmaleic acid, undecylenic acid, glycidyl (meth)acrylate, and the like.

In addition, in order to obtain the resin A having a hydroxyl group or a carboxyl group in the molecule used in the present invention, a monomer capable of producing a hydroxyl group or a carboxyl group in the molecule is co-coated with MVC by chemical treatment. It is also possible to polymerize as part of a monomer and chemically treat it.This method includes, for example, a method of hydrolyzing a polymer using vinyl ester,
Method for hydrolyzing polymers using acrylic esters, N
Examples include a method of hydrolyzing a polymer using -alkoxymethylacrylamide.

The amount of the monomer copolymerizable with MVC is preferably 50% or less, more preferably 6% by weight or less, based on the MVC monomers.
The ON amount is % or less. This is because if the amount exceeds 50 M%, the resulting polymer will have poor magnetic powder dispersibility, durability, etc.

On the other hand, the amount of the polymerizable monomer having a hydroxyl group, carboxyl group or epoxy group in the molecule is preferably 20% by weight or less, more preferably 10i% by weight or less based on the MVC monomer. This is for resin holes that exceed 20% by weight (meta)
When obtaining a curable resin by adding an acryloyl group-containing monomer, the curable resin to which (meth)acryloyl groups are added to most of the hydroxyl groups or carboxyl groups is hard and lacks toughness. This is because a curable resin in which (meth)acryloyl groups are attached to only a portion of the hydroxyl or carboxyl groups and most of the acryloyl groups remain as they are will have high water absorption and will have poor moisture resistance and durability.

The amount of hydroxyl or carboxyl groups produced in the molecule by chemical treatment is preferably 20% by weight or less, more preferably 10% by weight or less, based on the MVC monomer.

For the production of resin A, methods such as solution polymerization using an organic solvent as a medium, suspension polymerization using water as a medium, and emulsion polymerization are adopted.

The solvent used in solution polymerization may be any known solvent. For example, aromatic hydrocarbons such as toluene and xylene, ketone compounds such as methyl ethyl ketone and methyl imbutyl ketone, and ester compounds such as butyl acetate and ethyl acetate are used, and these may be used alone or in combination.

The suspending agent used in suspension polymerization may be any known suspending agent. For example, partially cured polyvinyl alcohol,
Methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, polyacrylic acid, vinyl erthyl maleic anhydride, gelatin, calcium phosphate, etc. are used, and these may be used alone or in combination.

In addition, the amount of these used is 0.01 to 2T for the aqueous medium.
EM; approximately %.

Known emulsifiers are used in emulsion polymerization. For example, nonionic surfactants such as polyoxyethylene alkyl phenol ether, polyoxyethylene sorbitan fatty acid ester, fatty acid salt,
Anionic surfactants such as higher alcohol f17c 19 ester salts, alkylbenzene sulfonates, alkylnaphthalene sulfonates, and argyl phosphate salts, cations such as alkyl amines, quaternary ammonium salts, and polyoxyethylene alkyl amines. surfactants are used.

In the production of resin A, the charging ratio of organic medium or aqueous medium/(MVC-type TPU + MVC monomer) is 1/1 to 3/
1 is good. This is because if the nucleation ratio is less than 1/1, the polymerization becomes unstable, and if the nucleation ratio exceeds 5/1, it is not economically advantageous.

The oil-soluble polymerization initiator used in the production of the resin may be any known polymerization initiator. For example, azo compounds such as azobisisobutylvaleronitrile, lauryl peroxide, di-2ethylhexyl oxydicarbonate, etc.
There are organic peroxides such as 1.,t\butyl peroxybiparate. The amount used is about 1.about.2% of OL based on the MVC monomer at the time of preparation.

The polymerization temperature is preferably 60 to 70°C, preferably 40 to 60°C. If the temperature is lower than 60°C, the polymerization rate tends to be slow, which is not industrially advantageous. If the temperature exceeds 70°C, the resulting polymer tends to have poor heat resistance, which is undesirable.

In the present invention, known chain transfer agents such as trichlorethylene and mercaptoethanol may be used.

The curable resin of the present invention is obtained by adding a monomer having a (meth)acryl group to the tree 711A,
Typical methods include V and methods (1) to (3) shown below.

(1) A method in which one molecule of resin A having one or more hydroxyl groups in the molecule is reacted with one molecule or more of an additive of 1 mol/1 mol of diisocyanate and hydroxyalkyl (meth)acrylate.

As the diisocyanate used in this method, the above-mentioned TP
The diincyanates mentioned in the UO section can be used. As the hydroxyalkyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc. can be used.

(2) A method in which one molecule of resin A having one or more carboxyl groups in the molecule is reacted with one or more molecules of glycidyl (meth)acrylate.

(3) Resin A having one or more epoxy groups in the molecule
A method in which one or more molecules of (meth)acrylic acid are reacted with one molecule.

It is also preferable to use a small amount of a stabilizer to prevent the curable resin from gelling during synthesis or storage, thereby increasing storage stability.

Suitable stabilizers include, for example, phenols such as hydroquinone, t-butylhydroginone, catechol, t-butylcatechol, hydroquinone monomethyl ether, and benzoquinone.

Examples include quinones such as naphthoginone and diphenylbenzoquinone, phenothiazines, and copper salts.

The amount of these stabilizers used is 0,0001 per curable resin.
It may be in the range of ~6% by weight.

Although the binder constituting the present invention has the above-mentioned curable resin as its main component, other crosslinkable monomers and resins may be mixed therein if necessary.

Crosslinkable monomers that can be used in combination are those having two or more acryloyl groups and/or methacryloyl groups in the molecule [hereinafter (
meth)acryloyl group], and the number of molecular groups per methanoacryloyl group is 1000.
Below, it is more preferably 700 or less. Note that the lower limit value is inevitably determined from the structure of the crosslinkable monomer, the raw materials during synthesis, etc., and is usually a value within the range of about 9D to about 200.

In addition, if the boiling point of the crosslinkable monomer, 4, is too low, it tends to cause loss due to evaporation and odor pollution.
0''C or higher is used.

Specific examples of crosslinkable monomers that can be used in the present invention include:
For example, the (meth)acrylates (a general term for acrylates and methacrylates) listed in (a) to (j) of Item-17 can be cited.

(,I) Poly(meth) of aliphatic, alicyclic, araliphatic di- to hexavalent polyhydric alcohol and polyalkylene glycol
Acrylate; e.g. ethylene glycol, globylene glycol, 1
．． or polyhydric alcohols such as 1,4-butanediol, hexanediol, neopentyl glycol, cyclohexyldiol, trimethylolethane, trimethylolpropane, glycerin, sorbitol, pentaerythritol, dipentaerythritol, hydrogenated bisphenol A; Examples include poly(meth)acrylates of polyhydric alcohols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, diethylene glycol, and polypropylene glycol. Specific examples of these are shown in, for example, Japanese Unexamined Patent Publication No. 12098/1983.

(bl aliphatic, alicyclic, araliphatic, aromatic 2-6
Poly(meth)acrylates of polyhydric alcohols with alkylene oxide added to them; Examples include evabisphenol A dioxyethyl ether, trimethylolpropane, pentaerythritol, glycerin, bisphenol A, etc. Examples include poly(meth)acrylates of polyhydric alcohols obtained by adding ethylene oxide or propylene oxide to polyhydric alcohols.

(C) Poly(meth)acryloyloxyalkyl phosphate; obtained by reaction of hydroxyl group-containing (meth)acrylate with phosphorus pentoxide, such as poly(meth)acryloyloxyethyl phosphate, poly(meth)acryloyloxy Examples include ethyl phosphate ester.

(d) Polyester poly(meth)acrylate; Polyester poly(meth)acrylate is usually synthesized by esterifying (meth)acrylic acid (acrylic acid and methacrylic acid collectively), polyhydric alcohol, and polyhydric carboxylic acid. be done. It is assumed that the main component is polyester-type polyhydric alcohol poly(meth)acrylate,
Synthesis examples and specific examples thereof include, for example, JP-A No. 49-12894.
Publication No. 4 and other published patent publications (49-128 (188
,49-120981,49-9ro476.49-28
692.48-96515.48-66679.48-
25790, etc.).

For example, di(meth)acrylate of polyester diol of succinic acid and ethylene glycol, di(meth)acrylate of polyester diol of maleic acid and ethylene glycol
acrylate, di(meth)acrylate of polyester diol of heptatalic acid and diethylene glycol, di(meth)acrylate of polyester diol of tetrahydrophthalic acid and diethylene glycol, poly(meth)acrylate of polyester diol of adipic acid and triethylene glycol. ) acrylate, polyester polyol with tetrahydrophthalic acid and trimethylolpropane (poly(
Examples include meth)acrylate, and poly(meth)acrylate of polyester polyol of tetrahydrophthalic acid and pentaerythritol.

Among these polyester poly(meth)acrylates, aliphatic or alicyclic polycarboxylic acid-based polyester poly(meth)acrylates were used rather than aromatic polycarboxylic acid-based ones such as 7-talic acid. This has the advantage that the crosslinked cured product has better physical properties such as weather resistance and toughness.

(e) Epoxy poly(meth)acrylate: An epoxy resin having two or more epoxy groups in the molecule, (meth)acrylic acid approximately equivalent to the epoxy group, (meth)acrylate having a carboxyl group, or (meth)acrylate having a carboxyl group. It is synthesized by reacting a mixture of acrylic acid or (meth)acrylate with a carboxyl group and a polybasic acid. Alternatively, there is also a method of reacting an epoxy group-containing (meth)acrylate with a polyhydric carboxylic acid.

Synthesis examples and specific examples of epoxy poly(meth)acrylates can be found in, for example, JP-A-49-28692 and other published patent publications (48-16182, 14849-1209).
1.49-12090, etc.).

For example, the addition reaction between various epoxy resins such as bisphenol A diglycidyl ether type, glycerin diglycidyl ether type, polyalkylene glycol diglycidyl ether type, polybasic acid diglycidyl ester type, and cyclohexene oxide type, and (meth)acrylic acid. Things can be given.

(f) Polyurethane poly(meth)acrylate; polyhydric alcohol having a polyurethane bonding unit in the main chain (
It has a meth)acrylate structure and is usually synthesized by reacting a hydroxyl group-containing (meth)acrylate with a polyisocyanate and, if necessary, a polyhydric alcohol.

For example, an addition reaction product of 2-hydroxyethyl (meth)acrylate or 2-hydroxypropy(meth)acrylate and a diisocyanate, an addition reaction product of 2-hydroxyethyl (meth)acrylate, a diisocyanate, and a dihydric alcohol. An example of this would be

(g) Polyamide poly(meth)acrylate: It has the structure of polyhydric alcohol (meth)acrylate having a polyamide bonding unit in the main chain, and is usually a polyamide-type polycarboxylic acid containing hydroxy group-containing (meth)acrylate or epoxy It is synthesized by reacting a group-containing (meth)acrylate or by reacting a polyamide-type polyhydric alcohol with (meth)acrylic acid.

Synthesis examples and specific examples are described in, for example, JP-A-48-37246.

For example, a reaction product of a polyamide-type polycarboxylic acid obtained by the reaction of ethylenediamine and heptatalic acid and 2-hydroxyethyl (meth)acrylate or glycidyl (meth)acrylate corresponds to this example.

(Member polysiloxane poly(meth)acrylate; It has the structure of (meth)acrylate of polyhydric alcohol with polyurethane bonding units in the main chain, and usually polyhydric alcohol with polysiloxane bonding units has (meth)acrylic acid or hydroxyl. It is synthesized by a method such as reacting a group-containing (meth)acrylate.

Synthesis examples and specific examples are described in, for example, Japanese Patent Publication No. 49-4296.

(i) Vinyl-based or diene-based low polymer having (meth)acryloyloxy groups in the side chain and/or terminal; Ester bond, urethane bond, amide bond in the side chain or terminal of the vinyl-based or diene-based low polymer , has an Ml structure in which a (meth)acryloyloxy group is bonded via an ether bond or the like.

Low polymers usually have hydroxyl groups, carboxyl groups, epoxy groups, etc. in their side chains or terminals, and (meth)acrylic acid, which is reactive with these groups, and carboxyl group-containing (meth)
It is synthesized by reacting acrylate, hydroxyl group-containing (meth)acrylate, epoxy group-containing (meth)acrylate, incyanate group-containing (meth)acrylate, amino group-containing (meth)acrylate, etc. Synthesis examples and specific examples can be found, for example, in JP-A No. 50-9687, JP-A-45-15629, and JP-A-45-1.
It is described in Publication No. 5630, etc.

An example is a reaction product obtained by reacting a copolymer of (meth)acrylic acid and another vinyl monomer with glycidyl (meth)acrylate.

Note that crosslinkable monomers belonging to this system generally tend to become highly viscous or solid as their molecular weight increases, so they should be used after being dissolved in a liquid low viscosity crosslinking monomer as described below, or It is preferable to use a liquid with a low molecular weight (usually a 4-fold average molecular weight of 3000 or less).

(j) Modified crosslinkable monomers described in (a) to (2) above; reacting a small amount (or a part) of the hydroxyl groups or carboxyl groups remaining in each of the above crosslinkable monomers with these groups. It is a modified product that is modified by reacting with a chemical acid chloride, acid anhydride, incyanate, or ebogishi compound.
This method is disclosed in Japanese Patent Application Laid-Open No. 8994, Japanese Unexamined Patent Publication No. 128088/1988, and the like.

In addition, resins that can be used in combination include ethyl cellulose,
Nitrocellulose, polyvinylidene chloride resin, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, polymethyl methacrylate resin, vinylidene chloride-methyl methacrylate copolymer, polyurethane resin, epoxy resin, polyester resin, etc. I can give you something.

Furthermore, polyisocyanate can be used as a cross-linking agent if necessary.

The magnetic powder constituting the magnetic paint of the present invention is made of acicular r-Fe
, 03, Co-containing r-Pc20. , CrO2, Fe-
(Known materials such as 20 alloy, Fe-Co-Ni alloy, metal magnetic powder, etc. can be used.

In the magnetic paint of the present invention, the blending ratio of the binder and the magnetic powder is 250 to 250 parts by weight per 100 parts by weight of the binder.
It is in the range of 500 parts by weight, preferably from OO to 40 parts by weight.

In the magnetic paint of the present invention, a bath agent can be used if desired, and known bath agents such as methyl ethyl ketone, methyl isobutyl ketone, noclohexanone, toluene, and cellosolve acetate can be used alone or in combination. Ru. The amount of solvent to be used is determined to provide the most suitable viscosity depending on the type of dispersing machine and coating machine.

Furthermore, the magnetic paint of the present invention may contain conventionally known additive components such as a dispersant, a lubricant, and an antistatic agent.

The magnetic paint of the present invention is prepared by dispersing and mixing the above-mentioned components and then passing the mixture through the mixture. Mixing and dispersing machines include ball mills and vibration mills (sand mills, etc. are used).

The ionizing radiation used in the present invention is an electron beam, a gamma gland, an alpha
High-energy radiation such as green and β-rays are used, but electron beams and r-rays are practically preferred.

The magnetic paint of the present invention does not have the problem of plasticizer migration, has good dispersibility of magnetic powder, and is coated on a plastic film or non-magnetic metal disk and cross-linked by irradiation with ionizing radiation, resulting in durability and A magnetic recording medium with excellent heat resistance, tensile strength, and surface smoothness is produced.

The present invention will now be specifically explained with reference to Reference Examples, Examples, and Comparative Examples.

In addition, on each side, parts represent parts by weight, and % represents weight %.

Reference Examples 1 to 4 Resin A was obtained by polymerization using the polymerization procedure shown in Table 1. That is, in a stainless steel autoclave having an internal capacity of 10 liters, the raw materials other than MVC shown in Table 1 were replaced with air inside the autoclave, and then MVC was charged. 5
After reacting at 8°C for 15 hours, unreacted monomers were removed, and this was dehydrated and dried to obtain a powdery 11-surface aggregate.

Reference example 5 The force shown below (polymerization was carried out with a combination decision, that is, darkness V'j
tf-, into a 10 l stainless steel autoclave (V
Raw materials other than C were charged, the air inside was replaced with nitrogen, and then vinyl chloride was charged. The reaction was carried out at 60° C. for 200 hours to obtain a methyl ethyl ketone solution of resin A. Reaction rate 98
%, T P N content +H4°2D wt% in the co-aggregate
, co-merged hydroxyl value 24 qKOH/, p.

Composition at time of preparation (part) MVC town mold Tl)U (Pantex T-5265)
20 (terminal OH type) Vinyl chloride 752-Ethylhexyl acrylate 5 Methyl ethyl ketone 200 Di-2-ethylhexylhexyl oxydicarpho'+ -to 0.05 Azobisin butyronitrile 0.05 Reference examples 6 to 9 The curable resin was prepared by reacting as shown in Table 2. Part 1j: The resin having a hydroxyl group in the molecule obtained in Reference Example 1.2.4.5 and cyclohexanone as a solvent
1! Pour into the fourth flask, heat and dissolve, and after raising the temperature to 80°C, tolylene diisocyanate (hereinafter referred to as TDI)
/2-hydroxyethyl acrylate (hereinafter referred to as HEA) = 1/1 adduct was added, dibutyltinlaurate and methylhydroquinone were added, and the mixture was reacted at 80°C for 8 hours in a nitrogen stream to react the incyanate group. The rate was set at 95% or higher.

The method for producing the TDI/HEA=1/1 adduct is as follows.

1160g of cyclohexanone in 6774 flasks
, TDI696.9. Dibutyltin laurate 07g,
Charge methylhydroquinone 007I and replace with nitrogen, 8
After heating to 0° C., 464 g of HE A was added dropwise over 2 hours, and the mixture was further reacted at 80° C. for 6 hours to obtain an adduct.

Table 3 Reference Example 10 Glycidyl group-containing resin A-500 obtained in Reference Example 3,
? and cyclohexanone 102'5# 3I! Pour 4 into a flask, heat and dissolve, and after raising the temperature to 80℃, add acrylic acid 7
．． 7 g and 2.5.9 g of choline chloride were added thereto, and the mixture was reacted at 80° C. for 5 hours to obtain a curable resin.

Examples 1 to 5 The curable resins obtained in Reference Examples 6 to 10 were made into magnetic paints with the following compositions.

γ-Fe2O312o heavy-i part carbon black 5 α-alumina 2 soybean lecithin
6r curable resin solution (6r wt%) 90
#Fatty acid-modified silicone 6 #Cyclohexanone 90 N Methyl ethyl ketone 150 I This composition was mixed for 8 hours in a horizontal motion type, fully closed ball mill (Dyno Mill KDL type manufactured by Wiley Kou Batskoufen),
It was filtered to remove the solvent-based magnetic paint.

These paints were coated on a polyethylene terephthalate base (25μ
m thickness) so that the coating thickness after drying is 10 μm, left to stand in a parallel magnetic field of 2000 Gauss for 1 second for orientation treatment, dried, and irradiated with an electron beam of 5 megarads at an accelerating voltage of 170 KeV. , a cathode current of 6 mA, and an atmospheric oxygen concentration of 300 ppm), a magnetic recording medium was obtained.

The obtained magnetic recording medium was tested and its performance was evaluated in the following manner. The results are shown in Table 3.

Square type Vibrating sample type magnetometer VSMP- manufactured by Hijitsu Ei Kogyo ■
Measured using type B.

Dispersibility: Shown as the ratio of the squareness ratio in the direction parallel to the orientation treatment and the squareness ratio in the perpendicular direction.

Surface flattening 1'-1': The presence or absence of gloss was visually determined.

A load of 1 kg was applied to one end of the tube, and the tube was wound around a glass tube having a diameter of 36 mrrt, and after being left at 60° C. and 80% humidity for one week, it was determined whether there was any resistance when the tube was unwound.

Comparative Example 1 Instead of the thermoplastic resin of Examples 1 to 4, vinyl chloride
Vinyl acetate copolymer (Union CarbideCo)
rp, product name vinyl light V rvf CH) 60
A magnetic coating was prepared in the same manner except that the N content was changed to 1.10 parts by weight of dioctyl fucray, and a magnetic recording medium was prepared and evaluated. The results are shown in Table 3.

/

Claims (1)

[Claims] 1. An ionizing radiation-curable magnetic paint containing magnetic powder and a binder as main components, wherein the binder is the following M V C or M
100 parts by weight of a VC monomer is polymerized with a thermoplastic polyurethane elastomer having a softening point of 20C or more and a hydroxyl group at the end in the coexistence of 6 to 100 double stitches to form a hydroxyl group and/or carboxyl group and/or in the molecule. or an iL ionizing radiation-curable magnetic coating MVC characterized by being a curable resin obtained by adding a (meth)acryloyl group-containing monomer to a resin into which an epoxy group has been introduced: vinyl chloride monomer and/or
or vinyl chloride/monomer. MVC monomer Vinyl dichloride monomer and/or vinylidene chloride monomer and fibrillated vinyl monomer or salt, hydroxyl group-, carboxyl- or ebony group-containing monomer copolymerizable with vinylidene chloride monomer A mixture of monomers containing monomers.