JPS6311386B2 - - 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.
It is described that it is suitable for high-density recording. 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, maintaining adhesion between the binder and the magnetic powder and between the binder and the base film, which is mainly made of polyester resin, as well as heat resistance and abrasion resistance, are essential properties. Traditionally, binders for paints containing magnetic powder include those using thermoplastic resins such as vinyl chloride copolymers, polyurethane, nitrocellulose, polyvinyl butyral, and saturated polyester, and thermosetting resins such as phenol, urea, melamine, and epoxy. It is common to use plastic resins, and additives such as dispersants, lubricants, abrasives, antistatic agents, etc. are added 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 using thermosetting resin,
Although the above drawbacks can be made relatively satisfactory,
On the other hand, curing by heating for a long time is necessary to obtain the desired physical properties, and at this time, defects such as a decrease in the surface smoothness of the magnetic layer and thermal deformation of the base film are likely to occur, and furthermore, thermal energy This will also have a negative impact on the total cost due to longer manufacturing times. 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. There are, but
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. or more, and part or all of the chain extender component has two or more active hydrogen atoms and at least one
The present invention relates to a magnetic paint characterized in that it is a polyhydroxycarboxylic acid having 2 carboxyl groups and/or a polyhydroxysulfonic acid metal salt having two or more active hydrogens and at least one sulfonic acid metal base. In the present invention, by using the above-mentioned specific unsaturated polyurethane resin, a large number of hydrophilic carboxyl groups and/or sulfonic acid metal bases are present in the molecular chain. It has excellent adsorption properties to magnetic powders such as γ-Fe ₂ O ₃ doped with ₂ O ₃ and cobalt, and ferromagnetic powders such as metal powders such as iron, chromium, nickel, and cobalt, or alloys thereof, and as a result, This results in a significant improvement in dispersibility. The unsaturated polyurethane resin of the present invention is, for example, a polyurethane obtained using an organic polyisocyanate (A), a polyol (B), an ethylenically unsaturated compound having active hydrogen (C), and a chain extender. A polyhydroxycarboxylic acid (D) having two or more active hydrogens and at least one carboxyl group and/or a polyhydroxycarboxylic acid (D) having two or more active hydrogens and at least one sulfonic acid metal base It can be obtained by substitution with a sulfonic acid metal salt (E). 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 adivic 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 (C) having active hydrogen can be used, but representative examples include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, Dihydric alcohols such as 1,4-butanediol, diethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol as well as mono and di(meth)acrylates, trihydric alcohols such as trimethylolethane, trimethylolpropane, and glycerin. ) acrylates, di- and tri(meth)acrylates of tetrahydric or higher alcohols such as pentaerythritol, etc., and these can be used alone or in combination of two or more. In the present invention, various known compounds can be used as the polyhydroxycarboxylic acid (D) used as the chain extender, but typical examples include 2,3-dihydroxypropionic acid,
2,3-dihydroxy-2-methylpropionic acid, 2,2-dihydroxymethylpropionic acid,
2,3-dihydroxy-2-(1-methylethyl)butanoic acid, 3,11-dihydroxytetradecanoic acid, 9,10-dihydroxyoctadecanoic acid,
Dihydroxymonocarboxylic acids such as 1,2-dihydro-6-hydroxy-2-oxy-4-pyridinecarboxylic acid, 2,3-dihydroxybutanedioic acid, 2,3-dihydroxy-2-methylbutanedioic acid, 2,4 -dihydroxypentanedioic acid, 2,4
-dihydroxy-3-methylpentanedioic acid, 2,
Dihydroxydicarboxylic acids such as 5-dihydroxyhexanedioic acid, 9,10-dihydroxyoctadecanedioic acid, 2,3-dihydroxy-2-butenedioic acid, 1,2-dihydroxy-1,2,2-tricarboxylic acid, 1, 3-dihydroxypropane-
Examples include dihydroxytricarboxylic acids such as 1,1,3-tricarboxylic acid. In addition, various known compounds can be used as the polyhydroxysulfonic acid metal salt (E), and representative ones include those of the general formula (R ¹ is an alkylene group having 2 to 6 carbon atoms, R ² is hydrogen or an alkyl group having 1 to 5 carbon atoms, R ³ is an organic residue, M is an alkali metal, and m is a number from 1 to 3)
Compounds represented by can be mentioned. ^R3
Preferred examples of organic residues include alkylene groups having 1 to 10 carbon atoms, phenylene groups, etc.
Examples thereof include a valent aromatic group, a group in which an alkylene group and an aromatic group are bonded to each other, and the like. Examples of preferred compounds among these are as follows. The molecular weight of these compounds (D) and (E) is preferably 600 or less. In the synthesis of the unsaturated polyurethane resin of the present invention, it is optional to use a normal chain extender (F) (having no carboxyl group and/or sulfonic acid metal group) in addition to the above-mentioned components. As a chain extender, for example, a chain extender having a molecular weight of 600 or less is used.
Examples include hexafunctional polyols and diamines having a molecular weight of 600 or less and 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, Examples include polyols with a molecular weight of 600 or less obtained by adding propylene oxide and/or ethylene oxide to alkanolamines in any order. The unsaturated polyurethane resin of the present invention is synthesized by various methods using the above-mentioned components. For example, a method in which an NCO-terminated prepolymer is synthesized from an organic polyisocyanate (A), a polyol (B), and a compound (C), and then a chain extender (D) and/or (E) is reacted;
A method of synthesizing an NCO-terminated prepolymer from (A) and (B), and (D) and/or (E), and then reacting (C),
Examples include a method in which NCO-terminated prepolymers are synthesized from (A) and (B), and (A) and (C), respectively, and then (D) and/or (E) are added and reacted. Furthermore, a chain extender (F) can optionally be added at the same time as (D) and/or (E), if necessary. In the present invention, the ratio of each component can be appropriately determined from a wide range depending on the desired polyurethane, but it is usually within a range where the chemical equivalent ratio of NCO groups to active hydrogen groups is about 0.9 to 1.4, preferably about 0.95 to 1.2. The reaction is usually about 30 to 130
℃, preferably about 40 to 120℃. In the unsaturated polyurethane resin of the present invention, the concentration of carboxyl groups is 0.25 meq/g or more, and the concentration of sulfonic acid metal bases is 0.05 meq/g or more, especially in order to sufficiently disperse the ferromagnetic powder. If the concentration is less than this, aggregated magnetic powder tends to remain in the magnetic paint, and when formed into a magnetic paint film, it has poor smoothness and cannot exhibit sufficient magnetic properties. 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 blended is preferably about 50 to 2000 parts by weight per 100 parts by weight of the unsaturated polyurethane resin. 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. 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 copolymers or their esters, poly(meth)acrylates, C _5-9 petroleum resins, hydrogenated petroleum resins, polybutadiene, natural or synthetic rubber, polyethylene,
Examples include polypropylene, ethylene-vinyl acetate copolymer resin, polyvinyl alcohol, and wax. 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 the ethylenically unsaturated compound, but representative examples include styrene, vinyltoluene, chlorostyrene, t-butylstyrene, α-methylstyrene, divinylbenzene, acrylic acid, and methacrylic acid. , methyl, ethyl, isopropyl, n-butyl, t-butyl, α-ethylhexyl, n-nonyl, n-decyl, lauryl, stearyl ester of acrylic acid or methacrylate, n-butoxyethyl acrylic acid or methacrylate, Cyclohexyl, phenoxyethyl, tetrahydrofurfuryl, glycidyl, allyl, benzyl, tribromophenyl, 2,3-dichloropropyl, 3-chloro-2
-Hydroxypropyl, N,N-dimethylaminoethyl, N,N-diethylaminoethyl, N-t
-butylaminoethyl ester, etc., ethylene glycol mono(meth)acrylate, propylene glycol mono(meth)acrylate, diethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, with a molecular weight (hereinafter referred to as MW) of 200 to 1000 Polyethylene glycol mono(meth)acrylate, MW200
~1000 polyethylene glycol monomethyl ether mono(meth)acrylate, MW200~1000
polypropylene glycol mono(meth)acrylate, polypropylene glycol monomethyl ether mono(meth)acrylate with MW200-1000, 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, when present during the urethanization reaction, the ethylenically unsaturated compounds having active hydrogen among the above should be excluded. Among the above-mentioned crosslinking agents, particularly preferred compounds have the general formula (In the formula, A represents an alkylene group or haloalkylene group having 2 to 4 carbon atoms), and specific examples include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, Examples include monomethacrylates such as 1,3-butanediol and 1,4-butanediol, and 3-chloro-2-hydroxypropyl methacrylate. In the present invention, the ratio of the unsaturated polyurethane resin and the ethylenically unsaturated compound is from 30:70 to 95:5 by weight.
is preferred, and 50:50 to 80:20 is more preferred. For the purpose of stably storing the magnetic paint of the present invention, a known thermal polymerization inhibitor can be added. 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 based on the total amount of the unsaturated polyurethane resin and crosslinking agent. It is desirable that the amount is in the range of 0.001 to 2.5% by weight, preferably 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 coating may be treated to orient the magnetic powder 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 methods using thermal energy such as infrared rays, high frequency waves, or microwaves, i.e., 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 and 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 as a binder an unsaturated polyurethane resin containing a hydrophilic carboxyl group and/or a sulfonic acid metal base in its molecular chain, and magnetic powder is added to the resin. The resulting magnetic paint has significantly improved heat resistance, hydrolysis resistance, and abrasion resistance, and is a magnetic material for magnetic recording with excellent magnetic 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 Place TDI (95.5g) in a reactor equipped with a stirring device and
Warmed to °C, Byron RV200L (molecular weight 1860)
A mixed solution of 510.0g, dioxane 325.7g, and dibutyltin dilaurate 0.2g was gradually added dropwise to the solution at 90°C.
The mixture solution of 24.8 g of 2-hydroxyethyl acrylate (HEA) and 1.4 g of hydroquinone was gradually added dropwise to react for about 3 hours.
After reacting for 2.5 hours, a mixed solution of 21.0 g of 2,2-dihydroxymethylpropionic acid (DMPA) and 325.8 g of cyclohexanone is gradually added.
After reacting for about 3 and a half hours, the solid content was 50%, and the solid content was reduced to 50%.
An unsaturated polyurethane resin solution () with a COOH group concentration of 0.24 meq/g was obtained. Synthesis Example 2 An unsaturated polyurethane resin solution () was obtained in the same manner as in Synthesis Example 1 except that 16.6 g of diethylene glycol (DEG) was used instead of DMPA. Examples 1-2 and Comparative Examples 1-2 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 addition, in the table (including Table 2)
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, including 2-methacryloxyethyl phosphate and di(2-methacryloxyethyl).
A mixture of phosphates, THF-A is tetrahydrofurfuryl acrylate, TMP-tA is trimethylolpropane triacrylate, and MEK is methyl ethyl ketone. In addition, magnetic powder A has a specific surface area of 48 m ² /g Fe-
Co alloy, B is Co-coated γ-Fe ₂ O ₃ of 32 m ² /g,
C indicates γ-Fe ₂ O ₃ of 22 m ² /g. In the adhesion test, cellophane tape was adhered to the magnetic coating under a load of 5 kg and then 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 weight loss (mg) was measured when the magnetic coating was moved back and forth 100 times.

[Table] Synthesis Example 3 Put MDI (125.0g) into a reactor equipped with a stirring device,
Byron RUX (molecular weight
2000) 375g, Plaxel 210 (molecular weight 1000) 123.7
A mixed solution of g, 0.22 g of dibutyltin dilaurate, and 324.4 g of dioxane was gradually added dropwise and allowed to react at 90°C for about 3 hours. Next, a mixed solution of 28.2 g of HEA and 1.4 g of hydroquinone was added dropwise and allowed to react for about 2.5 hours. Ta. A mixed solution of 15.9 g of DMPA and 345.0 g of cyclohexanone was gradually added dropwise to this, and the mixture was reacted for about 3.5 hours to achieve a solid content of 50% and COOH in the solid content.
An unsaturated polyurethane resin () with a group concentration of 0.17 meq/g was obtained. Synthesis Example 4 Put MDI (145.2g) into a reactor equipped with a stirring device,
Byron RV200L (molecular weight
1860) 312.3 g, Plaxel 220 (245.0 g), cyclohexanone 689.3 g, MEK 353.55 g, and dibutyltin dilaurate 0.14 g were gradually added dropwise and reacted at 90°C for about 3 hours to produce 32.7 g of HEA,
Add 1.46g of hydroquinone in the same way and add about 2.5g
After reacting for about 2 hours, a solution of DEIS (48.9 g) and dimethylformamide 135.7 g was gradually added.
The reaction was carried out for a period of time to obtain an unsaturated polyurethane resin solution () having a solid content of 40% and a concentration of sodium sulfonate base in the solid content of 0.17 meq/g. Synthesis Example 5 In Synthesis Example 3, DEG (12.6
An unsaturated polyurethane resin solution () was obtained in the same manner except that g) was used. Examples 3 to 5 and Comparative Examples 3 to 5 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.

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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. A polyhydroxycarboxylic acid having two or more terminal groups, and a part or all of its chain extender component has two or more active hydrogens and at least one carboxyl group and/or two or more active hydrogens. and at least 1
A magnetic paint characterized in that it is a polyhydroxysulfonic acid metal salt having sulfonic acid metal bases. 2. The magnetic paint according to claim 1, wherein the polyhydroxycarboxylic acid has two active hydrogens and one carboxyl group. 3 Polyhydroxysulfonic acid metal salt has the general formula (R ¹ is an alkylene group having 2 to 6 carbon atoms, R ² is hydrogen or an alkyl group having 1 to 5 carbon atoms, R ³ is an organic residue, M is an alkali metal, and m is a number from 1 to 3)
The magnetic paint according to claim 1, which is a compound represented by: 4. The magnetic paint according to claim 1 or 2, wherein the unsaturated polyurethane resin has carboxyl groups of 0.025 meq/g or more. 5. The magnetic paint according to claim 1 or 3, wherein the unsaturated polyurethane resin has a sulfonic acid metal base content of 0.05 meq/g or more. 6 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). 7. The magnetic paint according to claim 1, wherein the magnetic paint is cured by radiation.