JPH07118595A - Vinyl chloride resin composition and magnetic recording medium made by using it - Google Patents

Abstract

PURPOSE:To obtain the title composition which is excellent in compatibility with a magnetic powder and can be filled with it densely in a highly oriented state by copolymerizing a vinyl chloride monomer with a specified vinyl monomer in the presence of a specified free-radical generator. CONSTITUTION:The composition is obtained by copolymerizing a vinyl chloride monomer with a hydroxylated vinyl monomer (e.g. 2-hydroxypropyl acrylate) in the presence of an organic free-radical generator containing a polar group other than an OH group (e.g. succinic acid peroxide). In a magnetic recording medium having a magnetic layer consisting of a magnetic powder and a binder resin formed on one side of a support and having a nonmagnetic layer consisting of a binder resin and an inorganic powdery pigment on the other side, the resin composition is preferably used at least as one of the hinder resins.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

For this reason, in the binder resin used in the magnetic recording medium, magnetic powder is highly dispersed in the magnetic paint, and the magnetic layer is filled with high density with high orientation to obtain excellent electromagnetic conversion characteristics. The magnetic coating film is provided with strength by combining with a crosslinking agent such as an isocyanate compound. Further, in order to maintain the quality of the magnetic recording medium and the magnetic characteristics for a long time, it is necessary not to deteriorate the magnetic powder in the magnetic coating film. Good thermal stability is required.

Recently, with the development of AV equipment, the quality of magnetic recording media has been improved, and the magnetic powder tends to be more finely divided and to have a higher holding power. Binder resins having excellent dispersibility and stability after dispersion have been demanded.

As a vinyl chloride-based binder resin satisfying these requirements, a monomer containing a carboxylic acid group, a monomer supplying a hydroxyl group, and a magnetic paint containing vinyl chloride as a main component have been disclosed (Japanese Patent Publication No. 4-34578). However, this magnetic paint did not satisfy the above-mentioned required performance.

[0006]

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, It is easy to design various resins according to the required quality and the vinyl chloride resin composition with excellent stability over time of the magnetic coating obtained, as well as excellent electromagnetic conversion characteristics, heat resistance, durability and abrasion resistance. Another object is to provide a magnetic recording medium having a high quality magnetic layer.

[0007]

The vinyl chloride resin composition of the present invention comprises a copolymer of a vinyl monomer having a hydroxyl group and a vinyl chloride monomer.

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, which may be used alone. One or more species may be used in combination.

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 ⁷ -COO- [CH ₂
CH (CH ₃₎ - O] _p -H (R ⁷ is hydrogen or a methyl group,
p represents an integer of 1 to 6), polypropylene glycol mono (meth) acrylate represented by CH ₂ ═CR ⁸ —
_{COO- (CH 2 CH 2 O)} q -H (R 8 is hydrogen or a methyl group, q is an integer of 1 to 6) polyethylene glycol mono (meth) acrylate represented by 2-hydroxyethyl-2 ' -Acryloyloxyphthalate, C
^{_{H 2 = C (R 9)}} -COOCH 2 CH 2 -O- (CO-C
₅ H ₁₀ O) _r —H (R ⁹ is hydrogen or a methyl group, r 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.

When the content of the vinyl monomer having a hydroxyl group in the above-mentioned copolymer becomes small, the reactivity with the isocyanate compound (crosslinking agent) becomes insufficient, so that the durability of the magnetic coating composition deteriorates, and when it becomes large, the solvent solubility becomes high. Decreases and the viscosity of the magnetic paint increases due to the interaction of the hydroxyl groups, so
It is preferably 0% by weight, more preferably 2 to 20% by weight.

The degree of polymerization of the above copolymer is preferably 100 to 700, more preferably 15 since the mechanical strength of the magnetic coating film decreases as the degree of polymerization decreases and the viscosity increases as the degree of polymerization increases.
0 to 600.

If desired, the above-mentioned copolymer may be copolymerized with a monomer having an unsaturated group which is copolymerizable with vinyl chloride.

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; alkyl (meth) acrylates such as methyl methacrylate and n-butyl acrylate, and these may be used alone or in combination of two or more. May be done. The amount of the above monomer used is preferably 20% by weight or less.

The above copolymer is obtained by copolymerizing a vinyl monomer having a hydroxyl group and a vinyl chloride monomer using a radical generator containing a polar group other than a hydroxyl group.

Examples of the polar group other than the above hydroxyl group include polar groups such as a carboxyl group, an amine group and an amidine group. Examples of the radical generator containing a polar group other than the hydroxyl group include organic peroxide-based and azobis-based radical generators. Specific examples include succinic acid peroxide and 2,2′-azobis (2-methyl-N). -Phenylpropionamidine) dihydrochloride, 2,
2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis [N- (4-aminophenyl) -2-methylpropionamidine) tetrahydride, 4,4'-azobis (4-cyano Valerianic acid) and the like are exemplified.

Two or more kinds of the above radical generators may be used in combination, and it is usually preferable to use 0.1 to 5 parts by weight with respect to 100 parts by weight of the vinyl chloride monomer.

As a method for obtaining the above-mentioned copolymer, any of emulsion polymerization, bulk polymerization, solution polymerization and suspension polymerization may be used. Examples of the solvent used in the solution polymerization include n-hexane, lower alcohols such as methanol and ethanol, and other solvents generally used in solution polymerization, and these solvents may be used in combination with water. Two or more kinds may be used in combination.

Next, the present invention 2 will be described. In the magnetic recording medium of the present invention 2, a magnetic layer is formed on one surface of a support,
A non-magnetic layer is formed on the other surface, the magnetic layer is made of magnetic powder and binder resin, and the non-magnetic layer is made of binder resin and non-magnetic powder. Then, the vinyl chloride resin composition of the present invention is used for at least one of the binder resins.

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, films of vinyl resins, polyimide resins, polyamide resins, or the like. Sheets; further, non-magnetic metal foils such as aluminum and copper; paper, ceramic sheets and the like.

The magnetic layer is formed by applying and drying a magnetic coating material obtained from magnetic powder, a binder resin and a solvent, and the nonmagnetic layer is formed from a binder resin, a nonmagnetic powder and a solvent. It is formed by applying a magnetic paint and drying. The vinyl chloride resin composition of the present invention is used for either one of the binder resins used in the above magnetic paint and non-magnetic paint.

Examples of the above 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, Co ferrite, Ba ferrite,
Known ferromagnetic powders such as Sr ferrite, Fe alloy, Co alloy, and Ni alloy can be used.

Examples of the above non-magnetic 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.

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 several kinds.

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.

Known hardeners such as polyisocyanate compounds are used as the above-mentioned curing agent, and examples of the lubricant include dialkylpolysiloxane, phenylpolysiloxane, fluoroalkylpolysiloxane (having 1 to 5 carbon atoms in the alkyl group) 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 caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and other fatty acids having 12 to 18 carbon atoms.

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-mentioned stabilizer 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 vinyl chloride resin composition, magnetic powder is dissolved in the resin composition solution (the resin composition and polyurethane resin or polycarbonate polyurethane resin are dissolved in a solvent). ),
Kneading, dispersing, two roll mill, three roll mill,
A method of pre-dispersing with an open kneader, pressure kneader, continuous kneader, etc., and then post-dispersing with a sand grinder, ball mill, etc. is generally used.

In order to produce a non-magnetic paint using the vinyl chloride resin composition, a method of kneading and dispersing the inorganic powder pigment and a solvent in the same manner as the magnetic paint can be used.

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.

When a non-magnetic layer is laminated between the magnetic layer and the support, the vinyl chloride resin composition of the present invention is used to disperse the non-magnetic powder in the non-magnetic layer. Good.

Examples of the above nonmagnetic 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.

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 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.

[0037]

EXAMPLES Examples of the present invention will be described below. (Example 1) [Initial charging] 230 parts by weight of ion-exchanged water, polyethyleneimine polypropylene oxide block polymer 1.3 was added to a pressure resistant polymerization reactor with a jacket equipped with a stirrer.
By weight, 0.5 parts by weight of succinic acid peroxide as an organic radical generator containing a polar group was charged, and after sealing and exhausting for 5 minutes with an aspirator to remove residual air, vinyl chloride monomer 64 Part by weight was charged.

[Post-addition preparation] After removing air from a suspendable stainless steel container (hereinafter referred to as an addition container),
8.5 parts by weight of 2-hydroxypropyl acrylate as a hydroxyl group-containing monomer and vinyl chloride monomer 3
6 parts by weight were press-fitted. This addition container was shaken to sufficiently mix the mixed monomers and hung on a spring balance, and was connected from a valve at the bottom of the container to an addition nozzle provided in the polymerization reaction container using a flexible tube.

[Polymerization reaction operation] The rotation speed of the stirrer of the pressure resistant polymerization vessel was set to 250 rpm, 10% by weight of the above mixed monomer was added from the addition container to the pressure resistant polymerization vessel, and the inner temperature of the reactor was changed by passing warm water through the jacket. The temperature was raised to 70 ° C. When the internal temperature reached 70 ° C., the remaining mixed monomer was added to the pressure-resistant polymerization vessel from the addition container in 5 minutes every 40 times in total. The internal temperature was increased to 2 minutes 5 minutes after the last addition was completed.
The polymerization reaction was stopped by cooling to 5 ° C. 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, withdraw the slurry from the bottom of the polymerization reactor,
After washing with ion-exchanged water, dehydration and drying were performed to obtain a white powder copolymer.

(Example 2) The same procedure as in Example 1 was repeated except that 0.5 parts by weight of 4,4'-azobis (4-cyanovalerianic acid) was used instead of succinic acid peroxide. Polymerization gave a vinyl chloride copolymer.

(Example 3) Polymerization was carried out in the same manner as in Example 1 except that the addition amount of succinic acid peroxide was 1 part by weight and the divided addition from the addition container was performed every 4 minutes, and vinyl chloride was added. A system copolymer was obtained.

(Example 4) The same procedure as in Example 1 was repeated except that 0.5 parts by weight of 2,2'-azobis (2-methylpropionamidine) dihydride was used instead of succinic acid peroxide. Polymerization gave a vinyl chloride copolymer.

(Example 5) 1.5 parts by weight of 2,2'-azobis [N- (4-aminophenyl) -2-methylpropionamidine] tetrahydride was used in place of succinic acid peroxide. Was polymerized in the same manner as in Example 1 to obtain a vinyl chloride copolymer.

Comparative Example 1 The same as Example 1 except that 0.5 part by weight of t-butylperoxy-2-ethylhexanoate having no polar group was used in place of succinic acid peroxide. And polymerized to obtain a vinyl chloride copolymer.

Comparative Example 2 Polymerization was carried out in the same manner as in Comparative Example 1 except that 1 part by weight of 2-acryloyloxyethylphthalic acid was further added as a post-added monomer to obtain a vinyl chloride copolymer. .

(Comparative Example 3) Polymerization was carried out in the same manner as in Comparative Example 1 except that 1 part by weight of N, N'-dimethylaminopropylacrylamide was further added as a post-added monomer to obtain a vinyl chloride copolymer. Obtained.

Measurement of Component Composition of Vinyl Chloride Copolymer The hydroxyl group-containing component of the vinyl chloride copolymer obtained above was determined by acetic anhydride-pyridine method, and determined by oxygen flask combustion method. The vinyl chloride component was determined by measuring the chlorine content. Further, the carboxyl group-containing component was obtained by titrating the carboxyl group with a methanol / potassium hydroxide solution and quantifying it. The balance of the above three components was the quaternary ammonium salt group-containing component, and the measurement results of each component are shown in Tables 1 and 2.

Measurement of Degree of Polymerization of Vinyl Chloride Copolymer The degree of polymerization of the vinyl chloride copolymer obtained above was measured by JI
The measurement was performed according to SK6721, and the results are shown in Tables 1 and 2.

Preparation of magnetic paint 10 parts by weight of vinyl chloride type copolymer, metal magnetic powder (BE
100 parts by weight of T value 60 m ² / g) and 10 parts by weight of urethane resin (“Takelac E780” manufactured by Takeda Chemical Industries, Ltd.)
175 parts by weight and 1/2 of a mixed solvent of methyl ethyl ketone / toluene / cyclohexane (weight ratio 2: 1: 1)
Fill a glass bottle with 400 parts by weight of an inch SUS ball,
After shaking with a paint shaker (manufactured by Red Devil) for 6 hours to disperse, polyisocyanate (“Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent 1.1
By adding 4 parts by weight and shaking for 30 minutes, a magnetic coating material corresponding to each of the vinyl chloride-based copolymers obtained above was prepared.

Measurement of Physical Properties of Magnetic Paint The following physical properties of the above magnetic paint were measured and the results are shown in Tables 1 and 2. (1) Glossiness A magnetic coating immediately after the above preparation was applied on a polyester film, oriented in a magnetic field, dried and sufficiently crosslinked to obtain a sample having a magnetic coating film with a thickness of 5 μm after drying. It was For this sample, the glossiness at the incident angle and the reflection angle of 60 degrees of the magnetic coating film was measured using a digital variable angle gloss meter (“VG-1G” manufactured by Nippon Denshoku Industries Co., Ltd.).

(2) Squareness Ratio The sample whose glossiness was measured was cut into a size of 4.5 × 7 cm, and a direct current magnetization characteristic recording device (“T / 32” manufactured by Yokogawa Electric Corporation) was cut.
56-30 ").

(3) Stability with time After the magnetic coating material prepared above was allowed to stand for 72 hours,
A sample was prepared in the same manner as in (1), and the glossiness was measured in the same manner as in (1).

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

The composition of the vinyl chloride resin composition of the present invention is as described above, has an excellent affinity with magnetic powder, can be filled with magnetic powder in a high density and in a high orientation, and meets the required quality. Since various resin designs are easy, it is possible to provide a wide variety of magnetic paints with excellent stability over time. Since the magnetic recording medium of the present invention 2 has a high-quality magnetic layer having excellent electromagnetic characteristics and excellent heat resistance, durability and abrasion resistance, it is suitable for use in magnetic tapes, magnetic disks, magnetic cards and the like. It

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G11B 5/702 8721-5D 5/704 8721-5D (72) Inventor Mitsuo Matsumoto 529 Kushigahama Higashi Hamada, Tokuyama City, Yamaguchi −19 (72) Inventor Mitsue Shiga 3-9-19-406 Ogami, Shinnanyo-shi, Yamaguchi Prefecture

Claims (2)

[Claims] 1. A vinyl chloride resin composition characterized in that a vinyl chloride monomer and a vinyl monomer having a hydroxyl group are copolymerized by using an organic radical generator containing a polar group other than a hydroxyl group. 2. A magnetic recording medium in which a magnetic layer made of magnetic powder and a binder resin is formed on one surface of a support, and a nonmagnetic layer made of a binder resin and an inorganic powder pigment is formed on the other surface of the support. At least one of the vinyl chloride resin compositions according to claim 1 is a magnetic recording medium.