JPH06318318A - Binder resin composition for magnetic recording and magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic, heat resistant and durability characteristics by incorporating respective polymers of a vinyl monomer contg. a sulfobetaine group and >=1 kinds among many vinyl monomers contg. SO3M<1> groups or hydroxyl groups, etc., and vinyl chloride monomer at respectively specific weight % into the binder resin compsn. CONSTITUTION:A copolymer A of the vinyl monomer contg. sulfobetaine group, such as N-(3-sulfopropyl)-N-methacrylamide propyl-N and vinyl chloride monomer is obtd. A copolymer B is obtd. from >=1 kinds among vinyl monomer group contg. SO3M<1> group, PO2(OM<2>) group or hydroxyl group, etc., and vinyl chloride monomer. These copolymers A, B are incorporated respectively at <=95wt.% ratios into the binder resin compsn., to obtain the binder resin compsn. C. The one surface of a base is provided with a magnetic layer consisting of magnetic powder and a compsn. C and the other surface is provided with a nonmagnetic layer consisting of the compsn. C to obtain the magnetic recording medium. As a result, the excellent affinity to magnetic powder is obtd. and the packing of the magnetic powder at a high density with high orientation is made possible. The electromagnetic characteristics, heat resistance, durability and wear resistance are thus improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl chloride-based binder resin composition for a magnetic recording medium and a magnetic recording medium using the same.

[0002]

2. Description of the Related Art A coating type magnetic recording medium such as a magnetic tape or a magnetic card is generally manufactured by coating a polyester film with a magnetic coating material containing a magnetic powder and a binder resin to form a magnetic layer. The quality required for this magnetic recording medium includes electromagnetic conversion characteristics obtained by filling magnetic powder with high density and high orientation, and durability that can withstand friction with a magnetic head and the like. To be

Therefore, in the binder resin used in the magnetic recording medium, magnetic powder is highly dispersed in the magnetic paint to give the magnetic coating film excellent electromagnetic conversion characteristics, and at the same time, it is combined with a crosslinking agent such as an isocyanate compound. By doing so, strength is given to the magnetic coating film. Further, in order to maintain the quality of the magnetic recording medium and the magnetic characteristics for a long period of time, it is necessary not to deteriorate the magnetic powder in the magnetic coating film.

In recent years, with the development of AV equipment and the like, high quality is required for magnetic recording media, and magnetic powder particles are more and more required for filling magnetic powder with higher density in a magnetic coating film. It tends to be atomized. Therefore, there has been a demand for a binder resin having more excellent dispersibility than ever.

Conventionally, as a vinyl chloride-based binder resin having excellent dispersibility, a vinyl chloride-based binder resin having a highly hydrophilic functional group and a hydroxyl group capable of undergoing a crosslinking reaction with an isocyanate compound or the like in order to obtain an affinity with the magnetic powder. Copolymers are commonly used. Particularly, as the hydrophilic functional group having a strong affinity with the magnetic powder, for example, -COOH, -SO
₃ Na, -PO (OH) _2, etc. [Japan Adhesion Association Magazine 17,
155 (1981)] has been reported, and Japanese Patent Publication No. 1-2.
In Japanese Patent No. 6625, as a vinyl chloride-based binder resin having high dispersibility and excellent reactivity with a crosslinking agent, for example,
A vinyl chloride-based copolymer comprising an unsaturated monomer having a strong acid group containing vinyl chloride, sulfur or phosphorus and an -X-OH group (X is an organic residue) is disclosed.

[0006] Japanese Patent Publication No. 3-97764 discloses that
In order to obtain similar performance, a vinyl chloride-based binder resin containing a sulfonic acid group, a carboxyl group, and a phosphoric acid group is disclosed. JP-B-1-26627 discloses an epoxy group-containing monomer and sulfur. Alternatively, a resin for a magnetic coating is disclosed in which an unsaturated monomer having a strong acid radical containing phosphorus and a vinyl chloride monomer are copolymerized.

Further, a resin having sulfobetaine as a binder capable of favorably dispersing the atomized magnetic powder is disclosed in JP-A-2-56719.

However, when one kind of vinyl chloride binder is used as in the conventional case, when the amount of hydroxyl groups in the resin is increased, the crosslinkability with the isocyanate compound is improved and the abrasion resistance of the magnetic coating film is improved. However, there is a problem in that the viscosity of the magnetic coating increases due to the interaction between the hydroxyl groups or the interaction between the hydroxyl group and other functional groups, and the dispersion stability of the coating decreases. However, there is a problem in that the crosslink density is reduced and the durability of the magnetic coating film is reduced. Therefore, the resin must be designed and manufactured according to the required quality, a variety of products are required, and it is difficult to obtain a binder resin having the required performance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object thereof is to have an excellent affinity with magnetic powder and to be able to fill the magnetic powder with high density and high orientation, Vinyl chloride-based binder resin composition for magnetic recording which can be easily manufactured to meet these required qualities, and a magnetic recording medium having a magnetic coating film excellent in electromagnetic characteristics, heat resistance, durability and abrasion resistance To provide.

[0009]

The copolymer (I) used in the present invention comprises a vinyl monomer containing sulfobetaine and a vinyl chloride monomer.

Examples of the vinyl monomer containing sulfobetaine include N- (3-sulfopropyl) -N-methacrylamidopropyl-N, N-dimethylammonium betaine and N- (3-sulfopropyl) -N-methacryloxy. Ru-N, N-dimethylammonium betaine, 1
Examples include-(3-sulfopropyl) -2-vinylpyridinium betaine. A reaction product of a vinyl monomer containing a tertiary amine group such as N, N-dimethylaminoethyl acrylate and a sultone derivative such as 1,3-propanesultone can also be used.

In the copolymer (I), when the content of the vinyl monomer containing sulfobetaine is small, the affinity between the magnetic powder and the binder resin becomes insufficient, so that it becomes difficult to highly disperse the magnetic powder. When the amount of the vinyl monomer increases, the viscosity of the magnetic coating material increases and the dispersibility of the magnetic powder decreases due to the interaction between the functional groups.
1 to 40% by weight is preferable, and 0.4 to 9 is more preferable.
% By weight.

Further, the above-mentioned copolymer (I) includes a vinyl monomer containing a hydroxyl group, a vinyl monomer containing an epoxy group, a vinyl monomer containing a sulfone group, a vinyl monomer containing a phosphoric acid group, and A vinyl monomer having a tertiary amine group, a vinyl monomer having a quaternary ammonium salt group, a vinyl monomer having a carboxyl group and the like may be copolymerized.

The copolymer (II) used in the present invention is S
Vinyl monomer containing O ₃ M ¹ group (M ¹ represents hydrogen, NH ₄ ⁺ or alkali metal), PO ₂ (OM ² ) ₂ group (M ² represents hydrogen, alkali metal or hydrocarbon group)
Containing vinyl monomer, tertiary amine group containing vinyl monomer, quaternary ammonium salt group containing vinyl monomer, carboxyl group containing vinyl monomer, hydroxyl group containing vinyl monomer and epoxy group containing vinyl monomer It comprises a vinyl chloride monomer containing at least one functional group selected from the group consisting of and a vinyl chloride monomer.

Examples of the vinyl monomer containing SO ₃ M ¹ group include sodium ethylene sulfonate, potassium ethylene sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid. Examples thereof include ammonium, sodium sulfonic acid ethyl methacrylate, allyl sulfonic acid, methacrylic sulfonic acid, and styrene sulfonic acid.

Examples of the vinyl monomer containing the PO ₂ (OM ² ) ₂ group include acid phosphoxyethyl methacrylate, acid phosphoxypropyl (meth) acrylate, 3-chloro-2-acid phosphoxypropyl (meth). Examples thereof include acrylate and methacryloyloxyethyl acid phosphate monoethanolamine half salt.

Examples of the vinyl monomer containing a tertiary amine group include dimethylaminopropyl methacrylamide, N, N-dimethylaminopropyl acrylamide and the like.

Examples of the vinyl monomer containing a quaternary ammonium salt group include 2-hydroxy-3-
Methacryloyloxypropyl trimethylammonium chloride, methacryloyloxyethyl trimethylammonium chloride, trimethyl-3-methacrylamido-propylammonium chloride and the like can be mentioned.

Examples of the vinyl monomer having a carboxyl group include (meth) acrylic acid, succinic acid mono (meth) acryloyloxyethyl ester, phthalic acid mono (meth) acryloyloxyethyl ester,
Examples thereof include one having one carboxyl group in a molecule such as succinic acid monomethacryloyloxyethyl ester, and one having a plurality of carboxyl groups in a molecule such as maleic acid and fumaric acid.

When the content of the vinyl monomer containing the functional group in the copolymer (II) is small, the affinity between the magnetic powder and the binder resin becomes insufficient, and the magnetic powder can be highly dispersed. Since it becomes difficult, and when the number increases, the viscosity of the magnetic coating material increases and the dispersibility of the magnetic powder decreases due to the interaction between the functional groups, the content of the vinyl monomer is 0.1 to 4
0 wt% is preferable, more preferably 0.4 to 9 wt%
Is.

Examples of the vinyl monomer having a hydroxyl group include a reaction product of (meth) acrylic acid and a polyhydric alcohol, a (meth) acrylic acid amide, and the like.

Examples of the reaction product of the (meth) acrylic acid and the polyhydric alcohol include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and 3 - chloro-2-hydroxypropyl (meth) acrylate, CH ₂ = CR ¹ -COO- [CH ₂
CH (CH ₃ ) -O] ₁ -H (R ¹ is hydrogen or a methyl group,
1 represents an integer of 2 to 6) polypropylene glycol mono (meth) acrylate represented by CH ₂ ═CR ² —
_{COO- (CH 2 CH 2 O)} m -H (R 2 is hydrogen or a methyl group, m is an integer of 2-9) polyethylene glycol mono (meth) acrylate represented by 2-hydroxyethyl-2 ' -Acryloyloxyphthalate, C
^{_{H 2 = C (R 3)}} -COOCH 2 CH 2 -O- (CO-C
₅ H ₁₀ O) _n —H (R ³ is hydrogen or a methyl group, n is 1 to
A lactone (meth) acrylate represented by (denoting an integer of 5).

Examples of the (meth) acrylic acid amide include N-methylol (meth) acrylamide.

In the above copolymer (II), when the content of the vinyl monomer containing a hydroxyl group is small, the reactivity with isocyanate is insufficient and durability is deteriorated. Since the viscosity of the magnetic coating material increases due to the interaction of 1), 1 to 50% by weight is preferable, and 2 to 20% by weight is more preferable.

Examples of the epoxy group-containing vinyl monomer include glycidyl methacrylate and allyl glycidyl ether.

In the above copolymer (II), when the content of the vinyl monomer having an epoxy group is small, the effect of suppressing dehydrochlorination from vinyl chloride decreases, and when the content is large, the vinyl chloride component is relatively contained. The content of the vinyl monomer is 0.5 to 30% by weight because the amount of the vinyl monomer decreases and the durability of the magnetic coating decreases.
Is preferable, and more preferably 1 to 16% by weight.

When the degree of polymerization of the above copolymers (I) and (II) is low, the mechanical strength of the magnetic coating film is low, and when it is high, the viscosity is high and the solvent solubility is low.
00 to 900 is preferable, and 150 to 60 is more preferable.
It is 0.

If desired, the copolymers (I) and (II) may be copolymerized with a monomer having a copolymerizable unsaturated group.

Examples of such a monomer include α-olefins such as ethylene, propylene and 1-hexene; vinyl esters such as vinyl acetate and vinyl propionate; butyl vinyl ether, cetyl vinyl ether,
Vinyl ethers such as phenyl vinyl ether; aromatic vinyls such as styrene and α-methylstyrene; (meth)
Vinyl cyanides such as acrylonitrile; vinyl halides such as vinylidene chloride and vinyl fluoride; unsaturated dicarboxylic acid esters such as dimethyl maleate and dimethyl fumarate; unsaturated dicarboxylic acid anhydrides such as maleic anhydride; N -N-substituted maleimides such as phenylmaleimide and N-cyclohexylmaleimide; Formula CH ₂ typified by methyl methacrylate, n-butyl acrylate, etc.
_{^{= CR 4 -COO- (CH 2)}} p -CH 3 (R 4 is hydrogen or methyl, p is an integer of 0 or 1 to 10) alkyl (meth) acrylates represented by; 1,7, 7-trimethylbicyclo [2.2.1] hept-2-yl acrylate and the like can be mentioned.

Particularly, 1,7,7-trimethylbicyclo [2.2.1] hept-2-yl acrylate is preferable in order to improve the solvent solubility of the copolymer and to reduce the viscosity.

In the vinyl chloride resin-based binder resin composition for magnetic recording of the present invention, when the proportion of the copolymer (II) decreases, the effect of suppressing dehydrochlorination from vinyl chloride decreases and the durability of the magnetic coating film decreases. When the ratio of the copolymer (I) is low and the dispersibility of the magnetic powder is low, any one selected from the copolymers (I) and (II) is less than 95% by weight. It is contained in a ratio that does not increase.

As a method for producing the above-mentioned copolymer, a conventional method may be employed. For example, after charging a dispersion medium such as methanol, a polymerization initiator is charged and the inside of the polymerization vessel is evacuated to remove vinyl chloride monomer. Introduce and heat from the jacket to raise the temperature to the polymerization temperature, start the polymerization, and after reaching the target polymerization rate, stop the polymerization by cooling with the jacket and remove the residual vinyl chloride monomer and open it. , Dehydration and drying.

Examples of the dispersion medium include solvents such as methanol, toluene, methyl ethyl ketone, n-hexane, cyclohexane and cyclohexanone. These solvents may be used alone or in combination of two or more, and may be used as a mixed solvent with ion-exchanged water, depending on the application.

As the above-mentioned polymerization initiator, a radical generator which is generally used for the polymerization of vinyl chloride can be used, and specifically, t-butylperoxy neodecanoate, isobutyryl peroxide, benzoyl peroxide can be used. And the like, and azobis-based ones such as azobisisobutyronitrile.

In the production of the above copolymer, when the comonomer has a reaction rate faster than that of vinyl chloride, a method of dividing or continuously adding the comonomer from the initial stage of the polymerization to the middle of the polymerization or the end of the polymerization is preferable. When the reaction rate is slower than that of vinyl chloride, it is generally added all at once at the beginning of polymerization. As the polymerization conditions, a temperature of 30 to 80 ° C. and a polymerization time of 2 to 20 hours are generally used.

In the production of the above copolymer, when the vinyl chloride monomer remains in the polymerization system, a phosphite stabilizer, an organic tin stabilizer, an organic antioxidant and an epoxy compound (hereinafter stabilizer) It is preferable to add any one of the above) because the thermal stability is improved.

The above-mentioned stabilizers may be added before the polymerization, during the polymerization or at the end of the polymerization as long as the vinyl chloride monomer remains in the polymerization system. Depending on the type, it may adversely affect the polymerization and the resin scale may adhere to the polymerization vessel. In such a case, it is preferable to add it at the end of the polymerization. When it is added at the end of the polymerization, it is preferable that the vinyl chloride monomer remains in the polymerization system in an amount of 5% by weight or more of the charged amount.

Examples of the method of adding the above stabilizers and the like to the polymerization system include a method of adding them together with a dispersant or the like before polymerization;
A method of diluting or dispersing in a solvent such as water or methanol during the polymerization or the completion of the polymerization and then adding it by pressurizing with nitrogen; When it is added at the end of the polymerization, it may be at the polymerization temperature or after cooling.

Next, the second aspect of the present invention will be described. In the magnetic recording medium of the present invention 2, a magnetic layer is formed on one surface of the support and a non-magnetic layer is formed on the other surface of the support, the magnetic layer is composed of magnetic powder and a binder resin composition, and the non-magnetic layer is a binder. It consists of a resin composition. At least one of the binder resin compositions uses the vinyl chloride-based binder resin composition for magnetic recording of the present invention.

Examples of the support include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyolefin resins, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins, polyimide resins and polyamide resins. Or sheet; further aluminum,
Non-magnetic metal foil such as copper; paper, ceramic sheet and the like.

The magnetic layer is formed by applying magnetic powder and a magnetic paint obtained from a vinyl chloride resin-based binder resin composition for magnetic recording and drying, and the non-magnetic layer is a vinyl chloride resin-based magnetic recording. It is formed by applying and drying a non-magnetic coating material obtained from the binder resin composition for use in the present invention.

The above magnetic paint is produced from a vinyl chloride resin-based binder resin composition for magnetic recording, magnetic powder and a solvent.

Examples of the magnetic powder include γ-Fe ₂
O ₃ , Co-containing γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , CrO ₂ , Co-Ni-P alloy, Fe
-Co-Ni alloy, Ba ferrite, Sr ferrite,
Known ferromagnetic powders such as Fe alloys, Co alloys, and Ni alloys can be used.

Examples of the solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate and glycol monoethyl ether acetate; glycol. Glycol ethers such as dimethyl ether and dioxane; aromatic hydrocarbons such as benzene, toluene and xylene; methylene chloride, ethylene chloride, carbon tetrachloride,
Examples thereof include chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene, which may be used alone or in combination of two or more.

If desired, various additives such as a curing agent, an abrasive, a lubricant, a dispersant, an antistatic agent and a stabilizer may be added to the magnetic paint.

As the above-mentioned curing agent, known ones such as polyisocyanate compounds are used, and as the lubricant, for example, dialkyl polysiloxane, phenyl polysiloxane, fluoroalkyl polysiloxane (alkyl group having 1 to 5 carbon atoms) and the like. Inorganic powders such as silicone oil, molybdenum disulfide and tungsten disulfide, unsaturated aliphatic hydrocarbons and the like.

Examples of the dispersant include fatty acids having 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid and linoleic acid.

Examples of the antistatic agent include conductive powders such as carbon black, alkylene oxide-based compounds,
Glycerin-based nonionic surfactants; cationic surfactants such as higher alkyl amines and quaternary ammonium salts; anionic surfactants containing acidic groups such as carboxyl groups, phosphate groups, sulfone groups; amino acids, amino sulfones Examples thereof include amphoteric surfactants such as acids.

Examples of the above stabilizers include those represented by the general formula C ₁₇
H ₃₅ COOM ⁵ (wherein M ⁵ is Pb, Cd, Ba, Ca,
Zn, Mg or Al); organic tin compounds such as organic tin malate, organic tin laurate, organic tin mercapto, methyl tin, butyl tin and octyl tin.

In order to produce a magnetic paint using the above binder resin composition, magnetic powder is kneaded with a binder resin solution (a binder resin dissolved in a solvent),
A method of pre-dispersing with a two-roll mill, a three-roll mill, an open kneader, a pressure kneader, a continuous kneader or the like, and then post-dispersing with a sand grinder, a ball mill or the like is generally used.

In order to obtain a magnetic recording medium, it is preferable to form a magnetic layer on a support and then orient the magnetic layer through an electromagnet (solenoid).

The non-magnetic coating material is produced from a vinyl chloride resin-based binder resin composition for magnetic recording and a solvent.

The magnetic coating material and non-magnetic coating material can be applied to the support by air doctor coating, blade coating, rod coating, extrusion coating, air knife coating,
Squeeze coat, impregnation coat, reverse roll coat,
Examples include transfer roll coat, gravure coat, kiss coat, cast coat, spray coat, spin coat and the like.

The above magnetic layers are the first magnetic layer (upper layer) and the second magnetic layer.
When it is composed of two magnetic layers (lower layers), the binder resin composition of the present invention may be used as the second magnetic layer in order to disperse the non-ferromagnetic powder.

Examples of the non-ferromagnetic powder include carbon black, graphite, titanium oxide, barium sulfate and Zn.
S, MgCO ₃ , ZnO, CaO, γ-iron oxide, molybdenum disulfide, boron nitride, MgO, SnO ₂ , Si
O ₂ , CrO ₃ , Cr ₂ O ₃ , α-Al ₂ O ₃ , Si
C, cerium oxide, corundum, artificial diamond, α
-Iron oxide, garnet, garnet, silica, silicon nitride, silicon carbide, molybdenum carbide, tungsten carbide,
Examples include titanium carbide, tripoli, diatomaceous earth, dolomite, and the like.

The magnetic recording medium is used, for example, as a magnetic tape such as an audio cassette tape, a VTR tape, a magnetic disk such as a floppy disk, and a magnetic card.

[0056]

EXAMPLES Examples of the present invention will be described below. (1) Polymerization of Copolymer A of Vinyl Monomer Containing Sulfobetaine and Vinyl Chloride Monomer [Initial Charge] Methanol 6800 was placed in a stainless steel autoclave having an internal volume of 18 liters equipped with a stirrer.
Parts by weight and t-butylperoxy neodecanoate 35
After charging parts by weight, exhaust the air for 5 minutes with an aspirator to remove the remaining air, and then add vinyl chloride monomer 3000.
Part by weight was charged.

[Preparation of Post-Addition] After removing air from a 3 liter suspendable stainless steel container (hereinafter referred to as an addition container), 400 parts by weight of n-butyl acrylate and N were added.
30 parts by weight of-(3-sulfopropyl) -N-methacryloxyethyl-N, N-dimethylammonium betaine,
1000 parts by weight of methanol was suctioned, and 1400 parts by weight of vinyl chloride monomer was further injected. The addition container was shaken to sufficiently mix and dissolve the contents and hung on a spring balance, and was connected to an addition nozzle provided in the polymerization reaction container from a valve at the bottom of the container using a flexible tube.

[Polymerization reaction operation] The rotation speed of the stirrer of the polymerization reactor was set to 250 rpm, 52 parts by weight of the mixed solution was added from the addition container to the polymerization reactor, and warm water was passed through the jacket to bring the internal temperature of the reactor to 53 ° C. The temperature was raised to. Inner temperature is 5
When the temperature reached 3 ° C., 52 parts by weight of the mixed solution was added from the addition container to the polymerization reaction container, and then 50 parts by weight × 3 times, 63 parts by weight × 10 times, every 5 minutes depending on the progress of the polymerization reaction. 6
0 parts by weight × 13 times, 53 parts by weight × 22 times, 48 times in total, were added in portions. Further, the internal temperature of the polymerization reactor was raised and the temperature was adjusted from the time when it reached 53 ° C., so that it was kept constant at 53 ° C. during the reaction. Five minutes after the last addition was completed, the internal temperature was cooled to 25 ° C. to stop the polymerization reaction. After cooling, the vinyl chloride monomer remaining inside the polymerization reactor was discharged, and nitrogen gas was further aerated to sufficiently remove the vinyl chloride monomer. Then, the slurry was taken out from the lower part of the polymerization reactor, filtered, and vacuum dried at 50 ° C. for 10 hours to obtain 1800 parts by weight of white powder of copolymer A. The degree of polymerization and the composition of the obtained copolymer A are shown in Table 1.

(2) Polymerization of copolymer B of vinyl monomer containing sulfobetaine and vinyl chloride monomer n-butyl acrylate, N- (3-sulfopropyl)
Instead of -N-methacryloxyethyl-N, N-dimethylammonium betaine and methanol, 260 parts by weight of n-butyl acrylate, N- (3-sulfopropyl)
40 parts by weight of -N-methacryloxyethyl-N, N-dimethylammonium betaine, 1,7,7-trimethylbicyclo [2.2.1] hept-2-yl acrylate 1
A copolymer B was obtained in the same manner as in (1) except that 20 parts by weight and 990 parts by weight of methanol were used. The polymerization degree and composition of the resulting copolymer B are shown in Table 1.

(3) Polymerization of Copolymer C of Sulfonyl-Containing Vinyl Monomer and Vinyl Chloride Monomer [Initial Charge] Methanol 8000 was placed in a stainless steel autoclave having an internal volume of 18 liters equipped with a stirrer.
Parts by weight, 50 parts by weight of sodium ethylene sulfonate and t-
After charging 35 parts by weight of butyl peroxyneodecanoate, the mixture was evacuated with an aspirator for 5 minutes to eliminate residual air, and then 2300 parts by weight of vinyl chloride monomer were charged.

[Preparation of Post-Addition] After removing air from a 3 liter addition container, 400 parts by weight of n-butyl acrylate and 980 parts by weight of methanol were suctioned, and 1450 parts by weight of vinyl chloride monomer was further press-fitted. Then, polymerization was carried out in the same manner as in (1) to obtain 1800 parts by weight of a white powder copolymer C. The polymerization degree and composition of the obtained copolymer C are shown in Table 2.
It was shown to.

(4) Polymerization of Copolymer D of Vinyl Monomer Containing Tertiary Amine Group and Vinyl Chloride Monomer n-butyl acrylate, N- (3-sulfopropyl)
Instead of -N-methacryloxyethyl-N, N-dimethylammonium betaine and methanol, 360 parts by weight of n-butyl acrylate, 40 parts by weight of N, N-dimethylaminopropylacrylamide and 1030 of methanol were used.
A copolymer D was obtained in the same manner as in (1) except that the parts by weight were used. The degree of polymerization and the composition of the obtained copolymer D are shown in Table 2.

(5) Polymerization of Copolymer E of Epoxy Group-Containing Vinyl Monomer, Hydroxyl Group-Containing Vinyl Monomer, and Vinyl Chloride Monomer [Initial Charge] 18 liter internal volume stainless steel equipped with a stirrer Methanol 7500 in the autoclave
Parts by weight and t-butylperoxy neodecanoate 35
After charging parts by weight, the aspirator was evacuated for 5 minutes to eliminate the remaining air, and then the vinyl chloride monomer 26
00 parts by weight were charged.

[Post-addition preparation] After removing air from a 3 liter addition container, 280 parts by weight of glycidyl methacrylate, 100 parts by weight of 2-hydroxypropyl acrylate and 1000 parts by weight of methanol were sucked in, and 1450 parts by weight of vinyl chloride monomer. Was pressed in. Below (1)
Polymerized in the same manner as described above to obtain white powder copolymer E1500
Parts by weight were obtained. The polymerization degree and composition of the obtained copolymer E are shown in Table 2.

(6) Polymerization of Copolymer F of Vinyl Monomer Containing Hydroxyl Group and Vinyl Chloride Monomer Instead of glycidyl methacrylate and 2-hydroxypropyl acrylate, lactone methacrylate 400 is used.
A copolymer F was obtained in the same manner as in (5) except that the parts by weight were used. The polymerization degree and composition of the obtained copolymer F are shown in Table 2.

(7) Polymerization of Copolymer G of Epoxy Group-Containing Vinyl Monomer and Vinyl Chloride Monomer Instead of glycidyl methacrylate, 2-hydroxypropyl acrylate and methanol, 300 parts by weight of glycidyl methacrylate and 1130 parts by weight of methanol are used. A copolymer G was obtained in the same manner as in (5) except that was used. The polymerization degree and composition of the obtained copolymer G are shown in Table 2.

(8) Polymerization of Copolymer H of Vinyl Monomer Containing Epoxy Group, Vinyl Monomer Containing Quaternary Ammonium Base, and Vinyl Chloride Monomer [Initial Charge] Internal Volume equipped with Stirrer 18 In a liter stainless steel autoclave, add methanol 7500
Parts by weight, 400 parts by weight of allyl glycidyl ether and t
After charging 35 parts by weight of butyl peroxyneodecanoate, the mixture was evacuated with an aspirator for 5 minutes to remove residual air, and then 2600 parts by weight of vinyl chloride monomer were charged.

[Post-addition preparation] After removing air from a 3 liter addition container, 15 parts by weight of methacryloyloxyethyltrimethylammonium chloride, 100 parts by weight of n-butyl acrylate and 1015 parts by weight of methanol were sucked in, and vinyl chloride monomer was further added. 1700 parts by weight was press-fitted. Polymerization is carried out in the same manner as in (1) below,
1600 parts by weight of white powder of copolymer H was obtained. The degree of polymerization and the composition of the obtained copolymer H are shown in Table 3.

(9) Polymerization of Copolymer I of Vinyl Monomer Containing Carboxyl Group, Vinyl Monomer Containing Hydroxyl Group, and Vinyl Chloride Monomer Instead of glycidyl methacrylate, 2-hydroxypropyl acrylate and methanol, maleic acid is used. Copolymer I was obtained in the same manner as in (5) except that 12 parts by weight, 360 parts by weight of 2-hydroxypropyl acrylate and 1008 parts by weight of methanol were used. The polymerization degree and composition of the obtained copolymer I are shown in Table 3.

(10) Polymerization of Copolymer J of Epoxy Group-Containing Vinyl Monomer, Phosphoric Acid Group-Containing Vinyl Monomer, Hydroxyl Group-Containing Vinyl Monomer, and Vinyl Chloride Monomer Glycidyl methacrylate, 2-hydroxy Instead of propyl acrylate and methanol, 100 parts by weight of glycidyl methacrylate, 220 parts by weight of 2-hydroxypropyl acrylate, 20 parts by weight of acid phosphoxyethyl methacrylate and 1040 parts by weight of methanol were used in the same manner as in (5). Polymer J was obtained. The polymerization degree and composition of the obtained copolymer J are shown in Table 3.

(11) Polymer of copolymer K of a vinyl monomer having an epoxy group, a vinyl monomer having a hydroxyl group, a vinyl monomer having a tertiary amine group, and a vinyl chloride monomer, glycidyl methacrylate, (5 except that 100 parts by weight of glycidyl methacrylate, 220 parts by weight of 2-hydroxypropyl acrylate, 20 parts by weight of N, N-dimethylaminopropylacrylamide and 1040 parts by weight of methanol were used instead of 2-hydroxypropyl acrylate and methanol. ) And copolymer K
Got The polymerization degree and composition of the obtained copolymer K are shown in Table 3.

(12) A vinyl monomer containing a sulfone group and a vinyl monomer containing a carboxyl group,
Polymer of copolymer L of a vinyl monomer having a hydroxyl group and a vinyl chloride monomer, the amount of sodium ethylene sulfonate initially charged was changed to 80 parts by weight, and n-butyl acrylate and methanol were added afterwards, A copolymer L was obtained in the same manner as in (3) except that 20 parts by weight of maleic acid, 300 parts by weight of 2-hydroxypropyl acrylate and 1060 parts by weight of methanol were used. The polymerization degree and composition of the obtained copolymer L are shown in Table 3.

(13) Polymer of Copolymer M of Vinyl Monomer Containing Sulfobetaine Group, Vinyl Monomer Containing Hydroxyl Group, and Vinyl Chloride Monomer Instead of glycidyl methacrylate, 2-hydroxypropyl acrylate and methanol, 30 parts by weight of N- (3-sulfopropyl) -N-methacryloxyethyl-N, N-dimethylammonium betaine, 350 parts by weight of 2-hydroxypropyl acrylate and 10 parts of methanol
A copolymer M was obtained in the same manner as in (5) except that 50 parts by weight was used. The polymerization degree and composition of the resulting copolymer M are shown in Table 1.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

(Examples 1 to 15 and Comparative Examples 1 to 9) [Preparation of magnetic paint] Copolymers A, B, C, D, E, F,
G, H, J, K, L and M were mixed in the ratios shown in Tables 4 to 8 and dissolved in a mixed solvent of toluene / methyl ethyl ketone (weight ratio 1: 1) so that the copolymer became 15% by weight. Into the prepared solution, four times (weight) of the metal powder (BET) as compared with the copolymer.
Value of 55 m ² / g) and 6.5 parts by weight of an isocyanate compound (“Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd.) were added to paint conditioner (manufactured by Red Devil Co.) to give 6
It was shaken and dispersed for a time to prepare a magnetic paint. Also,
In addition to the above magnetic paint, a paint having the same composition as the above magnetic paint was separately prepared except that no metal powder was added. [Measurement of Physical Properties of Magnetic Paint] The following physical properties of the obtained magnetic paint were measured and the results are shown in Tables 4 to 8. (1) Glossiness The above magnetic paint is applied on a polyester film, oriented,
A magnetic coating film was prepared by drying and allowing sufficient crosslinking reaction. With respect to this magnetic coating film, the glossiness at an incident angle and a reflection angle of 60 degrees was measured using a digital variable angle gloss meter (“VG-1G” manufactured by Nippon Denshoku Industries Co., Ltd.). (2) Squareness Ratio The magnetic coating film prepared by the above glossiness measurement was cut into a rectangle of 4.5 × 7 cm, and measured with a DC magnetization characteristic recording device (“T / 3256-30” manufactured by Yokogawa Electric Co., Ltd.). (3) Powder falling test The magnetic coating film prepared in (1) was brought into contact with a steel rod (surface roughness Ra = 0.6 μm) rotating at 960 rpm for 1 hour under a constant load (100 g), and the weight at that time The amount of the weight loss was measured as the amount of powder falling and the strength of the magnetic coating film was compared. (4) Viscosity measurement The magnetic paint was measured with an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., for high viscosity). (5) Gel Fraction A coating material containing no metal powder is applied onto a polyester film, dried, and then the polyester film is peeled off.
A paint film was prepared. The gel fraction was calculated from the weight of the film after being immersed in a mixed solvent of toluene / methyl isobutyl ketone at 50 ° C. for one day and the weight of the film before being immersed. (6) Tensile strength Using the paint film prepared in (5), the tensile strength was measured by a tensile tester ("AUTOGRAPH" manufactured by Shimadzu Corporation). (7) Dehydrochlorination amount 1% of the vinyl chloride resin binder resin prepared above
The amount of hydrochloric acid generated at the time of thermal decomposition under the condition of 80 ° C. was measured.

[0078]

[Table 4]

[0079]

[Table 5]

[0080]

[Table 6]

[0081]

[Table 7]

[0082]

[Table 8]

[0083]

The constitution of the binder resin composition for vinyl chloride-based magnetic recording of the present invention is as described above, has an excellent affinity with magnetic powder, and can be filled with magnetic powder in high density and high orientation, It is easy to design various resins according to the required quality, and it is possible to provide a wide variety of magnetic paints. 2 of the present invention
Since the magnetic recording medium of (1) has a magnetic coating film having excellent electromagnetic characteristics, heat resistance, durability and abrasion resistance, it is preferably used for magnetic tapes, magnetic disks, magnetic cards and the like.

Claims (2)

[Claims] 1. A copolymer comprising at least two kinds selected from the following copolymers (I) and (II), and one of the copolymers is contained in a proportion not exceeding 95% by weight. A vinyl chloride-based binder resin composition for magnetic recording, comprising: (I) A copolymer of a sulfobetaine group-containing vinyl monomer and a vinyl chloride monomer. (II) Vinyl monomer containing SO ₃ M ¹ group (M ¹ represents hydrogen, NH ₄ ⁺ or an alkali metal), PO ₂ (OM
² ) a vinyl monomer containing ₂ groups (M ² represents hydrogen, an alkali metal or a hydrocarbon group), a vinyl monomer containing a tertiary amine group, a vinyl monomer containing a quaternary ammonium salt group, a carboxyl group A copolymer of a vinyl chloride monomer and a vinyl monomer containing at least one functional group selected from the group consisting of a vinyl monomer containing, a vinyl monomer containing a hydroxyl group and a vinyl monomer containing an epoxy group. 2. A magnetic recording medium in which a magnetic layer made of magnetic powder and a binder resin composition is formed on one surface of a support, and a non-magnetic layer made of a binder resin composition is formed on the other surface of the support. At least one of the resin composition,
A magnetic recording medium comprising the vinyl chloride-based binder resin composition for magnetic recording according to claim 1.