JPS6359433B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic coating material that has not only excellent wear resistance, heat resistance, and hydrolysis resistance, but also particularly excellent dispersibility of magnetic powder, and more particularly relates to a magnetic coating material that is suitable for curing by radiation such as electron beams. In recent years, magnetic materials for magnetic recording are increasingly required to have high performance, and in particular, materials with excellent magnetic properties are strongly required. For this purpose, it is important to improve magnetic powders, and recently, finer powders with a large saturation magnetization per unit volume and a larger coercive force, such as metal powders with a large surface area per unit weight, have recently been developed. Powder attracted attention,
It is being considered as a ferromagnetic material suitable for high-density magnetic recording. For example, according to the catalogs of Pfizer Inc. (USA), when using ferromagnetic powder with a specific surface area of 30 m ² /g or more determined from the amount of nitrogen adsorbed by the BET method, it exhibits particularly excellent magnetic properties and can be used for high-density recording. It is stated that it is suitable for On the other hand, when coating these magnetic powders on a tape support, the binder used is also an important factor. In particular, if the dispersibility of magnetic powder is poor, it often impairs various performances, including magnetic properties, such as generating noise and reducing output. In particular, ferromagnetic powder with a large specific surface area may have adverse effects due to aggregation of particles. Therefore, one of the most important issues in achieving the above objective is to have a property as a binder that can better disperse magnetic powder. In addition, the adhesion between the binder and the magnetic powder and between the binder and the base film mainly made of polyester resin,
Maintaining heat resistance, abrasion resistance, etc. is also an essential property. Conventionally, binders for paints containing magnetic powder have been thermoplastic resins such as vinyl chloride copolymers, polyurethane, nitrolcellulose, polyvinyl butyral, and saturated polyesters, and thermoplastic resins such as phenol, urea, melamine, and epoxy. Those using curable resin are common, and additives such as dispersants, lubricants, abrasives, antistatic agents, etc. are blended as necessary. When thermoplastic resins are used as resins for these binders, heat resistance and abrasion resistance are often not fully satisfied. In addition, when thermosetting resin is used, the above-mentioned drawbacks can be solved relatively satisfactorily, but on the other hand, it requires curing by heating for a long time in order to obtain the desired physical properties, and in that case, magnetic Defects such as a decrease in layer surface smoothness and thermal deformation of the substrate base film are likely to occur, and furthermore, the total cost is adversely affected due to thermal energy cost and prolonged manufacturing time. Furthermore, in order to improve the above-mentioned problems, binders have been provided to improve heat resistance and abrasion resistance by adding compounds that can be cured through chemical reactions, such as isocyanate compounds and epoxy compounds, to thermoplastic resins. However, in this case, the uniformity of the finally obtained magnetic material for magnetic recording is likely to be impaired due to lack of storage stability. In order to solve the various problems mentioned above, recently a new curing method and a method using an unsaturated resin having an ethylenic double bond in the molecule as a binder component and curing with radiation such as an electron beam have been developed. Proposed. As this radiation-curable resin, many resins are used that have a backbone of polyester resin, polyurethane resin, epoxy resin, etc., and have ethylenic double bonds that can be polymerized by radiation. , gamma rays, and X-rays. Many characteristics of these resins and curing methods are listed in known literature, but for example, when used as magnetic paints, they have excellent storage stability, so there is almost no waste during use, and they are easy to handle before and after forming a coating. Easy. Since the amount of solvent in the coating material is unnecessary or small, the base film is not damaged, and it is preferable from the viewpoint of environmental protection. Because it polymerizes and cures instantly with very short irradiation and leaves no unreacted low molecular weight components, the magnetic layer is hardly damaged in the post-curing process. Similarly, thermal deformation, deterioration, etc. of the base film can also be prevented. Since curing occurs through crosslinking, it is advantageous in terms of heat resistance and abrasion resistance, and it is also easy to impart flexibility. In particular, compared to conventional products, it requires almost no thermal energy for heating, and can be manufactured in large quantities in a short period of time, which is very advantageous in terms of cost. However, the currently proposed radiation-curable magnetic paints cannot be said to fully utilize the above-mentioned excellent characteristics, and furthermore, the dispersibility of magnetic powder is significantly inferior to conventional products. The current situation is that there are many. Especially when using the fine ferromagnetic powder mentioned above,
Due to the strong cohesive force between the magnetic powders, the dispersibility becomes worse, the smoothness of the surface of the magnetic layer is impaired, the magnetic properties necessary for high-density magnetic recording cannot be obtained, and the wear resistance is often poor. The purpose of the present invention is to modify the unsaturated polyurethane resin itself as a binder to provide a cured product that has extremely excellent dispersibility of magnetic powder and also has excellent heat resistance, hydrolysis resistance, and abrasion resistance. Our goal is to provide magnetic paints that can. The present invention provides a magnetic paint comprising an unsaturated polyurethane resin, a magnetic powder, and optionally an ethylenically unsaturated compound and/or a solvent, in which the unsaturated polyurethane resin has two terminal groups having a polymerizable double bond. The present invention relates to a magnetic paint characterized by having at least 0.05 meq/g of quaternary ammonium base. In the present invention, by using the above-mentioned specific unsaturated polyurethane resin, a large number of hydrophilic quaternary
Since the grade ammonium base is present in the molecular chain,
Magnetic powders such as γ-Fe ₂ O ₃ with hydrophilic groups on the surface and γ-Fe ₂ O ₃ doped with cobalt, and ferromagnetic powders such as metal powders such as iron, chromium, nickel, and cobalt, or alloys thereof. Excellent adsorption to
As a result, the dispersibility is significantly improved. The unsaturated polyurethane resin of the present invention includes, for example, an organic polyisocyanate (A), a polyol (B), an ethylenically unsaturated compound having active hydrogen (U), two or more active hydrogen atoms and at least one tertiary amino acid. It can also be obtained by treating polyurethane obtained using a chain extender (F) having a molecular weight of 500 or less and, if necessary, a normal chain extender (D), with a quaternizing agent (E). In addition, in the above, the compound (C) or the chain extender (F) can also be treated with the quaternizing agent (E) in advance. Organic polyisocyanate (A) used in the present invention
Examples include diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), tolidine diisocyanate (TODI), xylylene diisocyanate (XDI), naphthylene diisocyanate (NDI), isophorone diisocyanate ( IPDI),
These include diisocyanates such as hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), and lysine diisocyanate (LDI), and polyisocyanates such as triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate (PAPI), and carbodiimide-modified MDI. can be used alone or in combination of two or more. As the polyol (B), various polyester polyols, polyether polyols, and other polyols can be used. Examples of polyester polyols include aliphatic dicarboxylic acids having 4 to 20 carbon atoms such as adipic acid, suberic acid, sebacic acid, and brassylic acid, terephthalic acid, and isophthalic acid as acid components, and ethylene glycol, propylene glycol, neopentyl glycol, Polyester polyols whose polyol components include aliphatic diols having 1 to 6 carbon atoms such as hexamethylene glycol, ether glycols such as diethylene glycol and dipropylene glycol, spiroglycols, and N-alkyl dialkanolamines such as N-methyldiethanolamine; Polycaprolactone polyol etc. can be used,
Specific examples include polyethylene adipate polyol, polybutylene adipate polyol,
Adipate polyols such as polyethylene propylene adipate polyol, terephthalic acid polyols (e.g. Toyobo Co., Ltd., product name Vylon RUX,
Byron RV-200L), polycaprolactone polyol (e.g., Daicel Chemical, trade name Plaxel)
212, Praxel 220), etc. Specific examples of polyether polyols include polyoxyethylene polyol, polyoxypropylene polyol, polyoxytetramethylene polyol, and the like. In addition, other polyols include polycarbonate polyols (e.g., West Germany, Bayer AG, product name Desmofene 2020E), polybutadiene polyols (e.g., Nippon Soda, product names G-1000, G-
2000, G-3000, Idemitsu Petrochemical, product name Poly bd
R-45HT), polypentadiene polyol, castor oil polyol, and the like. These polyols can be used alone or in combination of two or more. In the present invention, various types of ethylenically unsaturated compounds (U) having active hydrogen can be used, but representative examples include ethylene glycol,
Propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, dipropylene glycol, polyethylene glycol, mono(meth)acrylate of dihydric alcohol such as polypropylene glycol, trimethylolethane , mono- and di(meth)acrylates of trihydric alcohols such as trimethylolpropane and glycerin, and di- and tri(meth)acrylates of tetrahydric or higher alcohols such as pentaerythritol. More than one species can be used at the same time. Examples of the compound (C) having two or more active hydrogens and at least one tertiary amino group include N-
Methyldiethanolamine, N-ethyldiethanolamine, N-butyldiethanolamine, bis-hydroxyethylpiperazine, N-phenyldiethanolamine, N,N-dimethylamino-
Examples include polyesters containing N-alkyldiacarnolamines such as 2,2-bishydroxymethylethylamine and N-methyldiethanolamine as a polyol component. In the synthesis of the unsaturated polyurethane resin of the present invention, it is optional to use a chain extender (D) in addition to the above-mentioned components, and such chain extenders include, for example, 2- to 6-functional chain extenders with a molecular weight of 500 or less. Examples include polyols having a molecular weight of 500 or less and diamines having a primary or secondary terminal amino group. Suitable chain extenders include (a) ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, hexanediol,
Polyols such as glycerin, trimethylolpropane, pentaerythritol, sorbitol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylylene glycol (b) Hydrazine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, 1,
Diamines such as 4-cyclohexanediamine (c) Alkanolamines such as ethanolamine, diethanolamine, and triethanolamine (d) Hydroquinone, pyrogallol, 4,4'-isopropylidene diphenol, aniline, and the above polyols, diamines, and alkanols Examples include polyols with a molecular weight of 500 or less obtained by adding propylene oxide and/or ethylene oxide to amines in any order. Examples of the quaternizing agent (E) include dialkyl sulfates such as dimethyl sulfate and diethyl sulfate, halogenated hydrocarbons such as methyl chloride, methyl iodide, ethyl bromide, and benzyl chloride, and organic acids such as acetic acid, propionic acid, and monochloroacetic acid. Various compounds such as acids and various other inorganic acids can be used. Also, a chain extender having a molecular weight of 500 or less and having two or more active hydrogen atoms and at least one tertiary amino group.
As (F), the same compounds as those listed for compound (C) can be used. The unsaturated polyurethane resin of the present invention is synthesized by various methods using the above-mentioned components. For example, a method in which urethane is synthesized from an organic polyisocyanate (A), a polyol (B), an ethylenically unsaturated compound (U), and a compound (C), and then a quaternizing agent (E) is added and reacted; (A) A method of synthesizing a terminal NCO prepolymer from (B) and (U), reacting it with a chain extender (F), and then reacting (E),
A method in which a prepolymer of NCO is synthesized, then (U) is added to contain urethane, and (E) is reacted with this, or (A), (B), and (U) are
Examples include a method in which a prepolymer is synthesized, one (F) and (E) are reacted in advance, and both are reacted. In the unsaturated polyurethane of the present invention obtained by various methods as described above, the quaternized compound (C) and the chain extender (F) may be, for example, [Here, X ₁ and X ₂ are organic polyisocyanate (A)
], the nitrogen atoms contained in the unsaturated polyurethane molecular chain are various 4
It reacts with the grading agent (E) to form a quaternary ammonium base. In the present invention, the proportions of each component can be appropriately determined from a wide range depending on the desired polyurethane, but
Usually, the reaction is carried out in a range where the chemical equivalent ratio of NCO group to active hydrogen group is about 0.9 to 1.4, preferably about 0.95 to 1.2, and the reaction is usually carried out at about 30 to 130°C.
Preferably, it is carried out at about 40 to 120°C. Further, the treatment with the quaternizing agent of the present invention is usually preferably carried out at a temperature in the range of about 40 to 100°C. In the present invention, it is particularly necessary for the concentration of the quaternary ammonium base to be 0.05 meq/g or more in order to sufficiently disperse the ferromagnetic powder. tends to remain, and when used as a magnetic coating, it has poor smoothness and cannot exhibit sufficient electrical properties. Here, for example, when the concentration of quaternary ammonium base is 1meq/g,
If the molecular weight of the polymer is 5000, then 1 × 10 ^-3 × 5000
=5, and there are five quaternary ammonium bases. Various types of magnetic powder can be used in the present invention, including iron, chromium, nickel, cobalt, alloys thereof, oxides thereof, and modified products thereof. Specific examples of oxides include γ-
Fe ₂ O ₃ , ferrite, magnetite, CrO ₂ , etc.
Examples of modified products include cobalt-doped γ-Fe ₂ O ₃ and cobalt-doped Fe ₂ O ₃ .
Examples include a bertholide compound of Fe ₃ O ₄ . It is also possible to use magnetic powders having various surface areas, and particularly when using ferromagnetic powders with a specific surface area of 30 m ² /g or more determined from the amount of nitrogen adsorbed by the BET method, excellent magnetic properties can be obtained. The amount of magnetic powder mixed is unsaturated polyurethane resin.
It is preferable to use about 50 to 200 ωt parts for the 100 ωt parts. In the present invention, the unsaturated polyurethane resin can be synthesized without a solvent, in the presence of an organic solvent, or in the presence of an ethylenically unsaturated compound used as a crosslinking agent, which will be described later. Examples of organic solvents include ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate and methyl propionate, ethers such as dioxane and cellosolve acetate, and dimethylformamide and dimethyl sulfoxide. The ethylenically unsaturated compound is used for dilution and property improvement, and the solvent is used for dilution. Even if it is not used, the intended effect of the present invention is exhibited, but problems may arise in industrial use in terms of viscosity, and ethylenically unsaturated compounds or solvents are used to improve the properties of the cured product. can do. In the present invention, a terminal group having a polymerizable double bond means at least one active hydrogen and (meta)
A compound having an active double bond, represented by an acrylic group, is bonded to the end of a urethane resin with a urethane bond, and it can be cured by radiation such as ultraviolet rays or electron beams, or by adding a thermal polymerization initiator. is hardened by the reaction of double bonds by heat. The ethylenically unsaturated compound is a diluent, and both the terminal double bond and the double bond in the ethylenically unsaturated compound are active double bonds, and they react not only with radiation but also with heat. Start. In the present invention, other compounds can be mixed within a range that does not impair the purpose. Specific examples of these compounds include unsaturated polyester resins, saturated polyester resins, epoxy resins, and (meth)
Esters with acrylic acid, polyurethane resins, diallyl phthalate resins, ketone resins, alkyd resins, phenolic resins, rosin-modified phenolic resins, rosin esters, maleic acid-modified rosin esters, urea resins, melamine resins, polyamide resins, styrene (meth) ) Acrylic acid copolymer or its ester, poly(meth)acrylate, _{C5-9 petroleum} resin, hydrogenated petroleum resin, polybutadiene, natural or synthetic rubber, polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, polyvinyl alcohol , wax, etc. Further, these known compounds can be added before or during the reaction as long as they do not interfere with the synthesis of the unsaturated polyurethane resin of the present invention. In the present invention, an ethylenically unsaturated compound can be used as a crosslinking agent if necessary when curing the unsaturated polyurethane resin. Various known compounds can be used as ethylenically unsaturated compounds, but typical examples include styrene,
Vinyltoluene, chlorostyrene, t-butylstyrene, α-methylstyrene, divinylbenzene, acrylic acid, methacrylic acid, methyl, ethyl, isopropyl, n-butyl, t-butyl, α-ethylhexyl, n -Nonyl, n-decyl, lauryl, stearyl ester, etc., n-butoxyethyl acrylic acid or methacrylic acid, cyclohexyl, phenoxyethyl, tetrahydrofurfuryl, glycidyl, allyl, benzyl, tribromophenyl,
2,3-dichloropropyl, 3-chloro-2-hydroxypropyl, N,N-dimethylaminoethyl, N,N-diethylaminoethyl, Nt-butylaminoethyl ester, etc., ethylene glycol mono(meth)acrylate, propylene Glycol mono(meth)acrylate, diethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate with molecular weight (hereinafter referred to as MW) 200-1000, MW200-
1000 polyethylene glycol monomethyl ether mono(meth)acrylate, MW200~1000 polypropylene glycol (meth)acrylate, NW200~1000 polypropylene glycol monomethyl ether mono(meth)acrylate,
Polyethylene glycol monoethyl ether mono(meth)acrylate with MW200~1000,
MW200-1000 polypropylene glycol monoethyl ether mono(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3
-propanediol di(meth)acrylate,
1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate,
trimethylolethane di(meth)acrylate,
Trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide,
Examples include ethylene bisacrylamide, diallyl phthalate, triallyl isocyanurate, dibutyl fumarate, and vinyl acetate. However, if present during the urethanization reaction, ethylenically unsaturated compounds having active hydrogen should be excluded from the above. Among the above crosslinking agents, particularly preferred compounds have the general formula (In the formula, A represents an alkylene group or a haloalkylene group having 2 to 4 carbon atoms.) Specific examples include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1 , 3-butanediol, monomethacrylates such as 1,4-butanediol, 3-chloro-2-hydroxypropyl methacrylate, and the like. In the present invention, the weight ratio of the unsaturated polyurethane resin to the ethylenically unsaturated compound is preferably 30:70 to 95:5, more preferably 50:50 to 80:20. A known thermal polymerization inhibitor may be added for the purpose of stably storing the magnetic paint of the present invention. For example, hydroquinone, mono-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, hydroquinone monomethyl ether, catechol, p-tert-butylcatechol,
Examples include benzoquinone, 2,5-di-tert-butylbenzoquinone, 2,5-diphenyl-p-benzoquinone, 2,6-di-tert-butyl-p-cresol, and picric acid. It is desirable that these thermal polymerization inhibitors prevent only the thermal polymerization reaction (dark reaction) without inhibiting the photocuring reaction, so the amount added should be adjusted based on the total amount of the unsaturated polyurethane resin and crosslinking agent. It is desirable that the amount ranges from 0.001 to 2.5% by weight, preferably from 0.005 to 1% by weight. Furthermore, in the present invention, commonly used additives such as dispersants, lubricants, abrasives, and antistatic agents can be added as necessary. The magnetic paint of the present invention can be obtained by mixing the above-mentioned components by various known methods, and for example, a mixer, roll mill, ball mill, sand mill, high-speed impeller, etc. can be used. The magnetic paint of the present invention can be applied to tapes, sheets, cards,
It is applied to various types of supports such as disks and drums. The support usually has a thickness of about 5 to 50μ,
It is preferably about 10 to 40μ, and suitable materials include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose acetate, polycarbonate, polyamide, polyimide, polyamideimide, and the like. Various methods can be used to apply the magnetic coating onto the support, such as impregnation coating, air doctor coating, air knife coating, blade coating, reverse roll coating, gravure coating, cast coating, and spray coating. After coating, the magnetic powder may be subjected to treatment to orient it if necessary, or dried if it contains a general organic solvent. The drying temperature is usually approx.
The temperature is about 20 to 120°C, preferably about 50 to 100°C, and the drying time is about 30 seconds to 10 minutes, preferably about 1 to 5 minutes. Furthermore, if necessary, a surface smoothing treatment can be performed before or after curing, or the material can be cut into a desired shape. The magnetic paint of the present invention can be cured by a known method. For example, when curing with an electron beam, the acceleration voltage is 100 to 1000 KeV, preferably 150 to 1000 KeV.
A cured product can be obtained by irradiating in an inert gas atmosphere using a 300 KeV electron beam irradiation device such that the total absorbed dose is 0.5 to 20 Mrad, preferably 2 to 15 Mrad. In addition, in the present invention, other curing means such as those using thermal energy such as infrared rays, high frequency waves, or microwaves, that is, heating curing methods, curing methods using ultraviolet rays obtained from mercury lamps, xenon lamps, etc., or
A method of curing by irradiating with other radiation such as rays or gamma rays can also be used. In the present invention, when using high-energy ionizing radiation such as electron beams, X-rays, and γ-rays, which have the effect of being absorbed by substances and emitting secondary electrons, it is not necessary to add a polymerization initiator. is also good, but
When curing by heating or ultraviolet rays, it is preferable to add a thermal polymerization initiator or a photopolymerization initiator. Examples of these thermal or photopolymerization initiators include ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, hydroperoxides such as cumene hydroperoxide and tert-butyl peroxide, and di-tert-butyl peroxide. Examples include dialkyl peroxides such as oxide, dicumyl peroxide, peroxy esters such as tert-butyl peroxylaurate and tert-butyl peroxybenzoate, and azo compounds such as azobisisobutyronitrile.
Further, polymerization accelerators such as metal soaps such as cobalt and manganese for the above-mentioned ketone peroxides, or reducing amines for the above-mentioned hydroperoxides can also be used. As described above, the magnetic paint of the present invention is characterized by containing an unsaturated polyurethane resin containing a hydrophilic quaternary ammonium base in its molecular chain as a binder, and the dispersibility of the magnetic powder in this resin is improved. Furthermore, the resulting magnetic paint has significantly improved heat resistance, hydrolysis resistance, and abrasion resistance, and is a magnetic material for magnetic recording that has excellent electrical properties and durability. A detailed explanation will be given below with reference to synthesis examples and examples. Note that "parts" or "%" simply means parts by weight or percent by weight. Synthesis example 1 Put IPDI (152.5g) into a reactor equipped with a stirring device and
Warmed to °C, Byron RV200L (molecular weight 1860)
424.9g, Desmofene 2020E (molecular weight 2000) 230.0
A mixed solution of 381.2 g of dioxane, 0.32 g of dibutyltin dilaurate was gradually added dropwise, heated to 90°C and reacted for about 3 hours, and then 39.1 g of 2-hydroxyethyl acrylate (HEA) and 1.74 g of hydroquinone were mixed. After adding the solution dropwise in the same manner and reacting for about 2.5 hours, N-methyldiethanolamine
Add 20.03g. After reacting for about 2 hours, lower the liquid temperature to 60°C, add 21.2 g of dimethyl sulfate little by little, and react for about 30 minutes until the solid content is 70% and the quaternary ammonium base concentration in the solid content is 0.19. meq／
An unsaturated polyurethane resin solution (g) was obtained. Synthesis Example 2 An unsaturated polyurethane resin solution () was obtained in the same manner as Synthesis Example 1 except that the quaternization treatment with dimethyl sulfuric acid was not performed. Examples 1-2 and Comparative Examples 1-3 Using the unsaturated polyurethane resin solutions obtained in the above synthesis examples, the compositions shown in Table 1 were mixed and kneaded in a ball mill for 40 hours to obtain magnetic paints. . Each of the obtained magnetic paints was applied onto a polyester film using a doctor blade, dried in an oven at 80°C for 3 minutes, and then exposed to an accelerating voltage using a curtain beam type electron beam irradiation device.
The coating film was cured by irradiation at 150 KeV and a beam current of 10 mA to give an irradiation dose of 5 Mrad. After curing, the surface gloss of the magnetic coating film was measured using a gloss meter (Toyo Seiki S-60) in order to examine the dispersibility of the magnetic powder. The better the dispersibility, the better the gloss. In the table, PU is an unsaturated polyurethane resin solution, HEMA is hydroxyethyl methacrylate, HPMA is hydroxypropyl methacrylate, and PA is an ester of HEMA and phosphoric acid, 2-methacryloxyethyl phosphate and di(2-methacryloxyethyl) phosphate. , TMP-tA is trimethylolpropane triacrylate, and MEK is methyl ethyl ketone. Magnetic powder A is Fe-Co with a specific surface area of 48 m ² /g.
In the alloy, B indicates γ-Fe ₂ O ₃ coated with Co at 32 m ² /g, and C indicates γ-Fe ₂ O ₃ at 22 m ² /g. In the adhesion test, cellophane tape was applied to the magnetic coating with a load of 5.
After adhesion with Kg, it was suddenly peeled off, and the degree of peeling was evaluated on a three-grade scale. 〇: Peeling area 0% △: 〃 0 to 25% ×: 〃 25% or more The amount of powder falling was measured by using a rubbing tester with only the head of a video deck fixed on the friction surface and making 100 reciprocations over the magnetic coating. The weight loss (mg) was measured.

[Table] Synthesis Example 3 Place TDI (221.5g) in a reactor equipped with a stirring device,
Byron RV200L (molecular weight
1920) 367.0g, Plaxel 210 (molecular weight 1000)
444.8g, dibutyltin dilaurate 0.23g,
A mixed solution of 295.2 g of MEK was gradually added dropwise and reacted for about 3 hours, and then a mixed solution of 71.6 g of HEA and 2.34 g of hydroquinone was added dropwise and reacted for about 2.5 hours. To this, N-methyldiethanolamine
After dropping 35.63 g and reacting for about 2 hours, the solution was lowered to 60°C and 37.7 g of dimethyl sulfate was added little by little until the solid content was 80% and the quaternary ammonium base concentration in the solid content was 0.25 meq. /g of unsaturated polyurethane resin () was obtained. Synthesis Example 4 Put MDI (171.8g) into a reactor equipped with a stirring device,
Byron RUX (molecular weight
2000) A mixed solution of 687.2 g, MEK 400.2 g, and dibutyltin dilaurate 0.17 g was gradually added dropwise and reacted for about 3 hours.
1.87g of N-phenyldiethanolamine was added in the same manner and the reaction was continued for about 3 hours, and then 17.2g of N-phenyldiethanolamine, 1,
After gradually adding 5.8 g of 4-butanediol and reacting for about 2 hours, it was cooled to 60°C and dimethyl sulfate was added.
Add 11.85g little by little until the solid content is 70% and the quaternary ammonium base concentration in the solid content is 0.10meq/
An unsaturated polyurethane resin solution (g) was obtained. Synthesis Example 5 An unsaturated polyurethane resin solution () was obtained in the same manner as in Synthesis Example 3 except that dimethyl sulfate was not added. Synthesis Example 6 An unsaturated polyurethane resin solution (2) was obtained in the same manner as in Synthesis Example 4 except that diethylene glycol was used instead of N-phenyldiethanolamine. Synthesis Example 7 In Synthesis Example 4, the amount of dimethyl sulfate was 3.50g,
Solid content was the same except that the amount of MEK was changed to 396.6g.
70%, quaternary ammonium base concentration in solid content
A 0.03 meq/g unsaturated polyurethane resin solution () was obtained. Examples 3 to 6 and Comparative Examples 4 to 9 Magnetic paints were obtained in the same manner as in Example 1 using the formulations shown in Tables 2 and 3. The properties of the obtained magnetic paint were investigated in the same manner. Furthermore, in the table
EMA is ethyl methacrylate, HDA is 1,6-
Hexanediol diacrylate, SA is HEMA
An ester of succinic acid and 2-methacryloxyethyl succinate.

【table】

【table】

【table】

【table】

Claims (1)

[Claims] 1. A magnetic paint comprising an unsaturated polyurethane resin, a magnetic powder, and optionally an ethylenically unsaturated compound and/or a solvent, in which the unsaturated polyurethane resin has a polymerizable double bond. has two or more terminal groups and a quaternary ammonium base
A magnetic paint characterized by containing 0.05meq/g or more. 2. The magnetic paint according to claim 1, wherein part or all of the polyol component of the unsaturated polyurethane resin is a compound having two or more active hydrogens and at least one tertiary amino group. 3. According to claim 1, the unsaturated polyurethane resin is obtained using a chain extender having a molecular weight of 500 or less and having two or more active hydrogens and at least one tertiary amino group. magnetic paint. 4. The magnetic paint according to claim 3, wherein the chain extender is treated with a quaternizing agent in advance. 5 The ethylenically unsaturated compound has the following general formula 2. The magnetic paint according to claim 1, which contains as a main component a compound represented by the formula (wherein A represents an alkylene group or a haloalkylene group having 2 to 4 carbon atoms). 6. The magnetic paint according to claim 1, wherein the magnetic paint is cured by radiation.