KR940004126B1 - Resin used for magnetic recording media and method for the production of the same - Google Patents

Abstract

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Description

Resin for magnetic recording medium and its manufacturing method

The present invention relates to a resin having excellent dispersing properties for a magnetic recording medium, comprising a magnetic powder and having a high wear resistance, and a method of manufacturing the same.

Magnetic recording media used for magnetic recording tapes, magnetic disks, and the like are usually obtained by applying, aligning, and drying a magnetic paint on a medium made of polyester or the like. The medium should have good magnetic and electron conversion properties and durability. This magnetic paint contains a magnetic powder and a resin that adheres the magnetic powder to the medium. Therefore, the resin for the magnetic recording medium is excellent in dispersibility in the magnetic coating, and as a result, it is possible to impart a high square ratio to the magnetic layer, and furthermore, to form a magnetic layer having excellent abrasion resistance and heat resistance on the substrate. Must have In particular, in recent years, it has been desired to develop a resin having excellent dispersibility as well as finer magnetic powder with increasing recording density in magnetic recording media.

As a resin having relatively good characteristics, vinyl chloride-vinyl acetate-vinyl alcohol-based copolymer (for example, disclosed in Japanese Patent Laid-Open No. 61-26132) and the like have been used. When necessary, a resin containing the copolymer and the isocyanate compound is used for the production of the magnetic recording medium. However, these vinyl chloride-vinyl acetate-vinyl alcohol copolymers have poor dispersibility in magnetic paints. Vinyl chloride copolymers generally used in magnetic recording media are usually produced by precipitation polymerization as a modification of solution polymerization. According to this precipitation polymerization method, the produced polymer is precipitated, so that the solvent and the residual monomer are easy to be removed after the polymerization reaction, and there is no need to use a dispersant and / or an emulsifier. However, when the vinyl chloride copolymer is manufactured in a stainless reactor, part of the produced copolymer precipitates and adheres to the inside of the reactor, resulting in uneven composition of the copolymer. It is also not easy to remove the scale from the reaction vessel.

The resin for a magnetic recording medium of the present invention which solves the above problems of the prior art is made of a vinyl chloride copolymer having a hydroxyl group-containing vinyl monomer and a quaternary ammonium base-containing vinyl monomer as structural units.

In a preferred embodiment, the resin further contains an isocyanate compound.

Moreover, in a preferable embodiment, content of the hydroxyl group containing vinyl monomer in a vinyl chloride type copolymer is 1 to 30 weight%.

In a preferred embodiment, the content of the quaternary ammonium base-containing vinyl monomer in the vinyl chloride copolymer is 0.05 to 8% by weight.

In a more preferred embodiment, the vinyl chloride content of the vinyl chloride copolymer is 60 to 95% by weight, the content of the hydroxyl group-containing vinyl monomer is 1 to 30% by weight, and the content of the quaternary ammonium base-containing vinyl monomer is 0.05. To 8% by weight.

In a preferred embodiment, at least one of the quaternary ammonium base containing vinyl monomers is methacryloyloxyethyltri methyl ammonium chloride.

In a preferred embodiment, the vinyl chloride copolymer further contains an acid group-containing vinyl monomer as a structural unit.

In a more preferred embodiment, the content of hydroxyl group-containing vinyl monomer in the vinyl chloride copolymer is 1 to 30% by weight.

In a more preferred embodiment, the content of the quaternary ammonium base-containing vinyl monomer and the acid group-containing vinyl monomer in the vinyl chloride copolymer is 0.05 to 8% by weight, respectively, and their total content is 0.1 to 10% by weight.

In a more preferred embodiment, the content of vinyl chloride in the vinyl chloride copolymer is 60 to 95% by weight, the content of hydroxyl group-containing vinyl monomer is 1 to 30% by weight, and the quaternary ammonium base-containing vinyl monomer and acid group are contained. The content of vinyl monomers is 0.05 to 8% by weight, respectively, and their total content is 0.1 to 10% by weight.

In an even more preferred embodiment, the acid group-containing vinyl monomer is a vinyl monomer having a phosphoric acid group.

The process for producing the resin of the present invention is a reaction in which an organic solvent solution containing vinyl chloride, a hydroxyl group-containing monomer and a quaternary ammonium base-containing vinyl monomer is coated with a fluorine resin on an inner wall which is in contact with the organic solvent solution. It polymerizes in an apparatus and precipitates a vinyl chloride type copolymer.

In a preferred embodiment, the organic solvent solution further contains an acid group-containing monomer. In the method for producing a vinyl chloride-based resin of the present invention, an organic solvent solution containing vinyl chloride, a hydroxyl group-containing vinyl monomer, and a quaternary ammonium base-containing vinyl monomer is coated with a fluorine-based inner wall in contact with the organic solvent solution. And polymerizing in the reactor to precipitate the vinyl chloride copolymer.

In a preferred embodiment, the organic solvent solution further contains an acid group-containing monomer.

Accordingly, the invention described herein can achieve the following objects:

(1) providing a resin having excellent dispersing properties for a magnetic recording medium containing magnetic powder and optionally adding an isocyanate compound to form a magnetic layer excellent in wear resistance and heat resistance;

(2) providing a resin having excellent dispersion characteristics for a magnetic recording medium capable of forming a magnetic layer containing magnetic powder and thereby having a high square ratio;

(3) providing a resin for a magnetic recording medium composed of a vinyl chloride-based copolymer containing vinyl chloride, which together with other components forms a magnetic layer having hardness and flexibility;

(4) A resin for a magnetic recording medium, comprising a copolymer of a hydroxyl group-containing vinyl monomer and a vinyl chloride, and having a quaternary ammonium base-containing vinyl monomer as the component of the polymer, which greatly improves the dispersion characteristics of the magnetic powder. To provide;

(5) When the resin consists of vinyl chloride-based copolymers containing an acid group-containing vinyl monomer and a quaternary ammonium base-containing vinyl monomer in addition to the hydroxyl group, Providing a resin for a magnetic recording medium in which the dispersion of magnetic powder is further improved by a synergistic effect with a vinyl monomer containing an acid group;

(6) When the resin contains an isocyanate compound, the hydroxyl group introduced into the copolymer contributes to the crosslinking reaction between the copolymer and the isocyanate compound to provide a resin for a magnetic recording medium, which forms a magnetic layer having excellent abrasion resistance and heat resistance. that;

(7) Since the scale which precipitates after the polymerization reaction is not produced by performing the precipitation polymerization method using a reaction apparatus coated with a fluorine-based inner wall, there is no risk of producing a copolymer having a non-uniform composition due to the scale. Providing a method for producing a resin for a magnetic recording medium that does not require removal;

(8) Providing a method for producing a vinyl chloride copolymer without generating scale by using precipitation polymerization method.

MEANS TO SOLVE THE PROBLEM The present inventors studied resin for the magnetic recording medium which consists of a copolymer of the vinyl monomer containing a hydroxyl group and vinyl chloride, and when using a quaternary ammonium base containing vinyl monomer as a component of a copolymer, When the dispersibility of the polymer is greatly improved, and the vinyl monomer containing the quaternary ammonium base as the cationic hydrophilic group and the vinyl monomer containing the acid group as the anionic hydrophilic group are used as components of the copolymer, As a result, the present inventors have found that the dispersibility of the magnetic powder is significantly improved as compared with the case of using quaternary ammonium base and acid group alone.

According to the present invention, a vinyl chloride copolymer can be produced by polymerizing an organic solvent solution of a monomer that is a copolymer component in a reaction apparatus in which an inner wall is coated with a fluorine resin, without producing a precipitated scale. This is achieved based on the findings of the inventors.

Vinyl chloride in the vinyl chloride copolymer in the present invention, together with other structural units, imparts suitable hardness and flexibility to the magnetic layer. If the amount of vinyl chloride is too small, the wear resistance of the magnetic recording medium is insufficient, and if the amount of vinyl chloride is too large, the solubility of the solvent is lowered. Therefore, the vinyl chloride content in the vinyl chloride copolymer is preferably 60 to 95% by weight.

As a hydroxyl group containing vinyl monomer used as a structural unit of the said copolymer, it is a compound which has a structural formula as a product of acrylic acid (or methacrylic acid) and polyhydric alcohol. Examples of these compounds, namely (meth) acrylic acid esters (which represent both acrylic and methacrylic acid esters), include 2-hydroxyethyl (meth) acrylate (which is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacryl). Both rates are the same, hereinafter), 2-hydroxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate represented by the following formula

(n is an integer from 2 to 9, R is hydrogen or methyl group),

Polypropylene glycol mono (meth) acrylate represented by the following formula

(n is an integer of 2 to 6, R is hydrogen or a methyl group)

And 2-hydroxyethyl-2'-acryloyloxyethyl phthalate

There is.

N-methylol (meth) acrylamide is mentioned as a hydroxyl group containing vinyl monomer used as a structural unit of said copolymer. These are used alone or in combination as appropriate as structural units of the copolymer, in particular 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate are preferably used.

If the amount of the vinyl monomer containing these hydroxyl groups is too high, the solvent solubility of the copolymer is reduced, and the surface smoothness and moisture resistance of the magnetic recording medium are reduced. On the other hand, when the amount of the vinyl monomer is too small, the dispersibility of the magnetic powder is reduced, moreover, the urethane bonds due to the reaction with the isocyanate compound contained as necessary is insufficient, thereby reducing the strength of the coating film and / or blocking on the magnetic recording medium. (Blocking) phenomenon occurs. Therefore, the vinyl monomer in the copolymer is preferably a case containing 1 to 30% by weight, more preferably 8 to 20% by weight.

The quaternary ammonium base-containing vinyl monomer used in the present invention means a vinyl monomer containing a quaternary ammonium base in the molecule, and a preferred example thereof is 2-hydroxy-3-methacryloyloxyethyltrimethylammonium chloride methacryl. Royloxyethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride and trimethyl-3-methacrylamidepropylammonium chloride. The quaternary ammonium base-containing vinyl monomer greatly contributes to improving the dispersibility of the magnetic powder. When the amount of this vinyl monomer is too large, it is difficult to obtain a transparent solution due to reduced solvent solubility of the copolymer, and side reactions other than a decrease in water resistance, a decrease in thermal stability, and a crosslinking reaction with an isocyanate compound contained as necessary. Since the crosslinking effect such as improvement in wear resistance cannot be obtained, the pot life of the magnetic paint is shortened. On the contrary, when the amount of vinyl monomer is too small, the dispersibility of the magnetic powder is reduced.

Therefore, the quaternary ammonium base-containing vinyl monomer is preferably contained in the copolymer at 0.05 to 8% by weight, more preferably 0.1 to 5% by weight. The quaternary ammonium base can be introduced by polymerization from a polymer having a tertiary amine.

The acid group-containing vinyl monomer in the present invention means, for example, a vinyl monomer containing a phosphoric acid group, a carboxyl group, a sulfone group and metal salts thereof in the molecule. A carboxyl group-containing monomer means a vinyl polymerizable monomer containing a carboxyl group in a molecule, and suitable examples thereof include acrylic acid, methacrylic acid, and succinic acid monoacryloyloxyethyl ester (CH ₂ = CH-COO (CH ₂ ) ₂ OCO ( In compounds and molecules containing one carboxyl group in molecules such as CH ₂ ) ₂ COOH), phthalic acid monoacryloyloxyethyl ester, succinic acid monomethacryloyloxyethyl ester, and phthalic acid monomethacryloyloxyethyl ester There are compounds with several carboxyl groups such as maleic acid and fumaric acid. Phosphoric acid group-containing monomer means a vinyl polymerizable monomer having a phosphoric acid group in a molecule, and suitable examples thereof include acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate and 3-chloro-2-acid phosphoxy. Propyl (meth) acrylate. The sulfone group-containing monomer means a vinyl polymerizable monomer having a sulfone group in a molecule, and suitable examples thereof include 2-acrylamide-2-methylpropane sulfonic acid, acrylic sulfonic acid, methacrylic sulfonic acid, vinyl sulfonic acid and styrene sulfonic acid. Etc. Of the various combinations of functional groups, combinations with quaternary ammonium base groups are particularly suitable in terms of improving the dispersibility of the magnetic powder. The quaternary ammonium base acts synergistically with the acid groups and contributes greatly to the dispersibility of the magnetic powder. The quaternary ammonium base-containing vinyl monomer and the acid group-containing vinyl monomer each contain 0.05 to 8% by weight of the copolymer. The total content of both monomers is preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight.

If necessary, the resin of the present invention may contain monomers such as ethylene, propylene, and vinyl acetate as structural units of the vinyl chloride copolymer, and a homopolymer or copolymer of these monomers may be used together with the vinyl chloride copolymer. have. It is especially preferable to use as a structural unit of an ethylene vinyl chloride type copolymer from the point of solvent solubility improvement.

The vinyl chloride copolymer can be produced by known polymerization methods such as precipitation polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Precipitation polymerization is particularly preferred because it does not require a dispersant or emulsifier and is easy to remove the solvent and / or residual monomer after the polymerization reaction. In this precipitation polymerization method, in order to prevent generation of scale that precipitates on the inner wall of the reactor, a portion which comes into contact with the monomer solution in the reactor is covered with a fluorine resin.

As a solvent used for the polymerization, an organic solvent which dissolves vinyl chloride, the above-mentioned polymerizable monomer and a polymerization initiator but does not dissolve the produced copolymer is used. Such organic solvents include aliphatic alcohols such as methanol, ethanol and butanol; Saturated aliphatic hydrocarbons such as propane, butane, pentane and hexane; Saturated alicyclic hydrocarbons such as cyclobutanone. The aliphatic alcohols preferably have 1 to 5 carbon atoms, saturated aliphatic hydrocarbons and saturated alicyclic hydrocarbons having 3 to 8 carbon atoms in terms of solubility of the monomer. These organic solvents can be used in mixture of 2 or more types, and can also use the liquid mixture of alcohol and water. Their selection is made according to the nature of the monomers used. For example, maleic acid and 2-acrylate-2-methylpropanesulfonic acid cannot be used because they are insoluble in hydrocarbon solvents such as n-hexane, and alcohol solvents such as methanol are used. Methanol is particularly suitable because of its high solubility in quaternary ammonium base-containing vinyl monomers. Among the monomers, as in the case of the suspension polymerization method, chemical reactions are caused by the solvent, and therefore, care should be taken in selecting the monomers.

Unlike water, which has poor solubility of monomers, even when vinyl chloride and / or polymerizable monomers are added to a solution containing a solvent during the polymerization reaction, the monomers can be rapidly dissolved to give a solution having a uniform composition. Therefore, in the case of preparing a copolymer using a polymerizable monomer having a higher monomer reaction ratio than vinyl chloride, for example, (meth) acrylic acid ester, if appropriately added according to the progress of the reaction, each monomer in the reaction system The composition of can be kept constant while the polymerization reaction is in progress. As a result, the copolymer obtained has a uniform composition.

The polymerization reaction is carried out using the monomer, the initiator, and the organic solvent serving as the structural unit of the vinyl chloride copolymer. As the initiator, organic peroxides or azo compounds commonly used in polymerization reactions are used.

As the fluorine resin used for coating the reactor, commercially available products can be used, and examples thereof include polytetrafluoroethylene (Teflon TFE; Dupon Co, Ltd), tetrafluoroethylene-hexafluoropropylene copolymer ( Teflon FEP; Dupon Co., Ltd), ethylene-tetrafluoroethylene copolymer (aflon COP, Asahi Glass Co., Ltd), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA, Mitsui Fluorochemical Co., Ltd.) Ltd), polytrifluoroethylene chloride (CTFE) and polyfluorovinylidene (PVdF). The contact portion with the reaction solution of the reactor is usually coated with these powdered fluorine resins and sintered.

It is preferable that the thickness of a coating film is 0.1-1.0 mm. When using a reaction apparatus coated with a fluorine resin, the precipitated scale hardly adheres to the reaction apparatus, and the resulting copolymer is separated as a powdery precipitate. Thus, the disadvantage of the non-uniform composition of the resulting copolymer or the incorporation of the initiator into the scale and the inability to function as an initiator is eliminated. The separated copolymer can also be easily taken out from the reactor. The inner part of the reaction apparatus can be coated with a fluorine resin as necessary to supplement the strength, and can be applied as a lining and packing material of the reaction apparatus. In particular, the ethylene-tetrafluoroethylene copolymer and the tetrafluoroethylene-perfluoroalkoxy ethylene copolymer can form a thick and tough coating film on the inner wall of the reactor. By the powder coating technique, the coating film of the fluorine-based resin can be easily formed on the inner wall of the reactor even in a complicated form. Since the coating film of such a resin is excellent in organic solvent resistance, acid resistance, alkali resistance, etc., it does not corrode even if any solvent and monomer are used in the method of this invention.

The reaction apparatus coated with such a fluorine resin can effectively prevent the precipitated scale derived from the solution polymerization method, especially the precipitation polymerization method. When the copolymerization reaction is carried out by the suspension polymerization method in this reactor, a large amount of scale is precipitated and attached to the reactor.

According to this precipitation polymerization method, the copolymer can generally be obtained in the form of a fine powder. The average degree of polymerization of the copolymer is preferably in the range of about 159 to about 600 in terms of mechanical strength and magnetic paint properties of the binder. If the average degree of polymerization is less than 150, when the copolymer is applied to the substrate together with the magnetic powder, the obtained copolymer coating film (for example, the magnetic layer) becomes weak, which causes difficulties in practical use. If the average degree of polymerization exceeds 600, the solution viscosity of the copolymer becomes high, thereby reducing the efficiency of the coating operation.

When the abrasion resistance and heat resistance of the magnetic layer to be formed are increased, tolylene diisocyanate, diphenylmethane diisocyanate, dianisidine diisocyanate, hexamethylene diisocyanate, methaxylene diisocyanate as isocyanate compounds to be mixed with the magnetic powder together with the copolymer And 1 mole of trimethylolpropane and 3 moles of tolylene diisocyanate, which are commercially available under the product name "Coronate L" manufactured by Nippon Polyurethane Industries, Ltd., for example.

When the usage-amount of an isocyanate compound is too big | large, a crosslinking density will become high and the coating film obtained finally will harden | cure and break. If the amount of the isocyanate compound is too small, the desired effect cannot be obtained. Therefore, it is normally used in 0.3-30 weight part with respect to 100 weight part of said copolymers.

In producing a magnetic coating by the resin according to the present invention, for example, the vinyl chloride copolymer is dissolved in a mixed solvent of methyl isobutyl ketone and toluene, and a magnetic powder material such as r-iron oxide is interfacing in the solution. Add with additives such as active agents to mix and disperse. When the wear resistance of the magnetic layer is particularly increased, an isocyanate compound is added to this solution to obtain a magnetic paint.

However, the addition order and dispersion method of the said copolymer, an isocyanate compound, and a magnetic powder material in this invention are not limited. The solvent for dissolving the copolymer to produce the resin of the present invention is a solvent selected from toluene, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane or mixtures thereof. The copolymer is usually used in an amount of 10 to 100 parts by weight based on 100 parts by weight of the magnetic powder material, and the magnetic paint is usually prepared to contain the copolymer at a concentration of 5 to 30% by weight.

EXAMPLE

Each cost

If necessary, a magnetic coating containing an isocyanate compound was applied, oriented and dried to a dry thickness of 6 μm on a polyester film having a thickness of 25 μm as a gas to prepare a magnetic recording medium, and a square ratio (Br / Bm, Where Br and Bm represent the residual magnetic flux density and the saturation magnetic flux density, respectively). When the value of the square ratio is around 0.8 or more, powder separation of the magnetic powder is remarkably high.

Glossiness

The reflectance of light incident at 60 degrees is measured for the magnetic coating film provided for the square ratio measurement using a glossmeter, and the glossiness is calculated based on this value. Glossiness not only shows the surface smoothness of the magnetic coating film but also the index of dispersibility of the magnetic powder in the magnetic coating film.

Heat adhesion

The two magnetic recording media are heated at a temperature of 120 DEG C for 15 minutes, and when the magnetic layers overlap each other, it is examined whether or not the magnetic layers adhere to each other to determine the heat adhesion. In Table 1, (circle) shows that it did not adhere | attach (blocking does not occur), and x shows that it adhere | attached.

Gel fraction

The vinyl chloride copolymer film containing no magnetic powder was deposited overnight at 50 ° C. in a toluene-methyl isobutyl ketone (weight ratio 1: 1) mixed solvent. The value obtained by dividing the weight of the deposited film by the film weight before deposition is a gel fraction, which is an index indicating the efficiency of crosslinking reaction between the copolymer and the isocyanate compound.

Example 1

Initial manufacturing

-큐밀퍼옥시네오데카노에이트 25g을 넣은 후, 아스피레이터로 5분간 배기하여 오토클레이브내의 공기를 제거한후, 이 오토클레이브에 염화비닐 2600g을 넣는다.The inner wall of the internal 20-liter autoclave with a stirrer, the surfaces of the stirring blades and the baffle were coated with tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA, Mitsui Chlorochemical Co., Ltd) Form a film. Thus, 8100 g of methanol (primary reagent) and a polymerization initiator were put into an autoclave coated with an inner wall surface with a fluorine resin.

-25 g of cumyl peroxy neodecanoate is added, followed by 5 minutes of exhausting with an aspirator to remove the air in the autoclave, and then 2600 g of vinyl chloride is added to the autoclave.

Post-production

After removing the air in a 3 L suspension suspension vessel (hereinafter referred to as the addition vessel), a mixed solution of 259 g of 2-hydroxypropyl acrylate and 15 g of methacryloyloxyethyltrimethylammonium chloride dissolved in 500 g of methanol was removed. 1045 g of vinyl chloride is injected into the container.

The vessel is shaken to dissolve the contents, suspended on a spring balance, and connected to the nozzle of the autoclave using a flexible tube through the valve at the bottom of the vessel.

Polymerization Treatment

The rotation speed of the stirrer of the autoclave was 380 rpm, and hot water was passed through the jacket to raise the internal temperature of the autoclave to 43 ° C. The polymerization starts as soon as the internal temperature reaches 43 ° C., so that the internal temperature is maintained at 43 ° C. while the polymerization reaction continues.

When the internal temperature reaches 43 ° C, 50 g of a mixed solution of monomers is added to the autoclave from the addition vessel, and 4 g of 46 g at 5 minute intervals and 31 g at 10 minute intervals as the polymerization reaction proceeds. Add 49 parts at 27g intervals for 5 minutes. 10 minutes after the last addition, the autoclave was cooled to 25 ° C. to stop the polymerization. The internal pressure of the autoclave was 2.0 kg / cm 2 G at the start of the reaction and 1.8 kg / cm 2 G at the end of the reaction.

After cooling, unreacted vinyl chloride was degassed, nitrogen gas was introduced to sufficiently remove the vinyl chloride, the methanol slurry of the copolymer was removed from the autoclave, filtered, and dried at 50 ° C. for 24 hours under reduced pressure. 1200 g of white powdery copolymer A is obtained.

The degree of polymerization of the obtained resin was 300, and the composition was 86.5% of vinyl chloride, 13.0% of 2-hydroxypropyl acrylate, and 0.5% of methacryloyloxyethyl trimethylammonium chloride. After the polymerization reaction, the deposited scales on the inner wall surface of the reactor, the stirring blades, and the baffle surface were not observed. As a result of dissolving the obtained resin in a methyl isobutyl ketone-toluene (1: 1) mixed solvent at a ratio of 10% by weight, a transparent solution without an insoluble content was obtained.

-산화철(자성분말)80중량부와 직경 1/8인치의 스테인레스 볼을 자성분말의 8배량으로 가하고 페인트 콘디셔너(Reddevil Co., Ltd)로서 6시간동안 혼합하여 자성도료를 얻은 후, 자기 기록매체를 제조하고 각형비를 측정한 결과, 0.82라는 높은 값을 얻게 되었다. 또 이의 광택도는 96%로 측정되었다.Copolymer A was dissolved in a toluene-methylisobutyl ketone (weight ratio 1: 1) mixture to prepare a copolymer solution containing Copolymer A at a concentration of 15%, and then the copolymer dissolved in the solution in the copolymer solution. Per 20 parts by weight, Co-

After adding 80 parts by weight of iron oxide (magnetic powder) and stainless steel balls 1/8 inch in diameter to 8 times the magnetic powder, and mixing with a paint conditioner (Reddevil Co., Ltd) for 6 hours to obtain a magnetic paint, the magnetic recording medium Was prepared and the square ratio was measured to obtain a high value of 0.82. Its glossiness was measured at 96%.

Example 2

In the same manner as in Example 1, the same monomer as in Example 1 was added to a reactor in which the inner wall surface, the stirring blade, and the baffle surface were coated with ethylene-tetrafluoroethylene copolymer (aflon COP, Asahi Glass Co., Ltd). The polymerization is carried out as in Example 1. The amount of monomer, methanol and initiator is varied here to polymerize. Initially, powder B was obtained, the composition of the copolymer was analyzed, and then a magnetic recording medium was prepared as in Example 1, and its square ratio was measured. The results are shown in the first table. As a fluorine-based resin, tetrafluoroethylene-hexafluoropropylene copolymer (teflon FEP, Dupon Co., Ltd.) was used instead of the ethylene-tetrafluoroethylene copolymer, and the same procedure as in the preparation of copolymer B Copolymers C, D, E, F and G having the compositions shown in Table 1 were obtained, and corresponding magnetic recording media were prepared. Their square ratios exceeded 0.80 as shown in Table 1, and the glossiness was more than 90%.

In either case, hardly any adhered scales were deposited on the inner wall surface of the reactor, the stirring blades, and the baffle surface. The solvent solubility test was carried out similarly to Example 1, and the colorless transparent solution was obtained.

TABLE 1

Example 3

As a continuous manufacturing process, a mixed solution prepared by dissolving 244 g of 2-hydroxypropyl acrylate, 15 g of methacryloyloxyethyltrimethylammonium chlorite and 15 g of acid phosphoxyethyl methacrylate in 500 g of methanol was added to a stainless container. A copolymer H is obtained in the same manner as in Example 1 except that 1045 g of vinyl chloride is injected under reduced pressure.

The degree of polymerization of the obtained resin was 300, and the composition was 86.5% of vinyl chloride, 12.5% of 2-hydroxypropyl acrylate, 0.5% of methacryloyloxyethyltrimethylammonium chloride, and 0.5% of acid phosphoxyethyl methacrylate. After the polymerization reaction, adhesion of scale on the inner wall surface of the reactor, the stirring blades and the baffle surface did not appear. The obtained resin was dissolved in a methyl isobutyl ketone-toluene (1: 1) mixed solvent at a ratio of 10% by weight, and a clear solution without a residue was obtained.

-산화철(자성분말)80중량부와 직경 1/8인치의 스테인레스 볼을 자성분말의 8배량으로 가하고, 페인트 콘디셔너(Reddevil Co., Ltd)로 6시간동안 혼합하여 자성도료를 얻은후, 자기 기록매체를 제조하여 각형비를 측정한 결과, 0.84라는 높은 값을 얻었다. 또 이의 광택도는 108%로 측정되었다.Copolymer H was dissolved in toluene-methyl isobutyl ketone (weight ratio 1: 1) to prepare a copolymer solution containing Copolymer A at a concentration of 15%, and then in this solution, Copolymer 20 dissolved in the solution. Per weight part, Co-

Add 80 parts by weight of iron oxide (magnetic powder) and 1/8 inch diameter stainless ball to 8 times the amount of magnetic powder, and mix with a paint conditioner (Reddevil Co., Ltd) for 6 hours to obtain a magnetic paint. A medium was prepared and the square ratio was measured to obtain a high value of 0.84. Its glossiness was measured at 108%.

Example 4

In the same manner as in Example 3, the same monomer as in Example 3 was added to a reaction apparatus in which the inner wall, the stirring blade, and the baffle surface were coated with ethylene-tetrafluoroethylene copolymer (aflon COP. Asahi Glass Co., Ltd). The polymerization is carried out as in Example 1. The amount of each monomer, methanol and initiator is varied here to polymerize. Table 2 shows the results of analyzing the composition of the powdery copolymer I obtained for the first time, and measuring the square ratio of the magnetic recording medium in the same manner as in Example 1. In addition, as the fluorine-based resin, a tetrafluoro ethylene-hexafluoropropylene copolymer (teflon FEP; Dupon Co., Ltd) was used in place of the ethylene-tetrafluoroethylene copolymer, as in the preparation of copolymer B. Copolymers J, K, L and M having the compositions shown in the table were obtained and corresponding magnetic recording media were prepared. Their square ratios exceeded 0.80 as shown in Table 2, and the glossiness was 100% or more. In either case, the deposited scale did not appear on the inner wall surface, the stirring blade and the baffle surface of the reactor. As a result of the solvent solubility test as in Example 1, a colorless transparent solution was obtained.

TABLE 2

Example 5

Copolymer A obtained in Example 1 and copolymers B to G obtained in Example 2 were dissolved in a toluene-methyl isobutyl ketone (weight ratio 1: 1) mixed solvent, respectively, to prepare a polymer solution having a concentration of 15%.

-산화철 80중량부와 직경 1/8인치의 스테인레스 볼을 자성분말의 8배량으로 가하고 페인트 콘디셔너로 6시간동안 혼합한 다음, 이소시아네이트 화합물(coronate L, Japan Polyurethane Industry Co., Ltd)을 0.65중량부 가하고 교반하여 각 공중합체 A~G에 상응하는 자성도료를 얻는다. 이들 도료를 폴리에스테르필름상에 도포, 배향, 건조하여 가교반응이 충분히 진행된 자기기록매체를 얻는다. 이들 자기기록매체의 각형비, 광택도 및 가열밀착성은 제3표와 같다. 각 공중합체와 이소시아네이트와의 가교반응성을 나타내는 겔분율도 제3표에서 보는 바와 같다.In each copolymer solution, Co- per 20 parts by weight of the copolymer dissolved in the solution

Add 80 parts by weight of iron oxide and 1/8 inch diameter stainless ball to 8 times the amount of magnetic powder, mix for 6 hours with paint conditioner, and then add 0.65 parts by weight of isocyanate compound (coronate L, Japan Polyurethane Industry Co., Ltd). It is added and stirred to obtain a magnetic paint corresponding to each copolymer A to G. These coatings are applied, oriented and dried on a polyester film to obtain a magnetic recording medium having sufficiently crosslinked reaction. The square ratio, glossiness and heat adhesion of these magnetic recording media are shown in Table 3. The gel fraction which shows the crosslinking reaction of each copolymer and isocyanate is also as Table 3 shows.

TABLE 3

Example 6

-산화철(자성분말)80중량부와 직경 1/8인치의 스테인레스볼을 자성분말의 8배량으로 가하고 페인트콘디셔너로 6시간 동안 혼합한 다음, 이소시아네이트 화합물(Coronate L, Japan Polyurethane Industry Co., Ltd)을 0.65중량부 가하고 교반하여 각 공중합체 H~M에 상응하는 자성도료를 얻고, 이들 도료를 폴리에스테르필름상에 도포, 배향, 건조하여 가교반응이 충분히 진행된 자기기록매체를 얻는다. 자기기록매체의 각형비, 광택도 및 가열밀착성은 제4표와 같다. 또 각 공중합체와 이소시아네이트와의 가교반응성을 나타내는 겔 분율도 제4표에서 보는 바와같다.Copolymer H obtained in Example 3 and copolymers I to M obtained in Example 4 were dissolved in a toluene-methyl isobutyl ketone (weight ratio 1: 1) mixed solvent, respectively, to prepare a solution at a concentration of 15%. In each polymer solution, Co- per 20 parts by weight of the copolymer dissolved in this solution

-80 parts by weight of iron oxide (magnetic powder) and 1/8 inch diameter stainless ball are added to 8 times the magnetic powder, and mixed for 6 hours using a paint conditioner, and then an isocyanate compound (Coronate L, Japan Polyurethane Industry Co., Ltd) 0.65 parts by weight of the mixture was stirred to obtain a magnetic coating corresponding to the copolymers H to M, and these coatings were applied, oriented, and dried on a polyester film to obtain a magnetic recording medium having sufficiently undergone a crosslinking reaction. The square ratio, glossiness and heat adhesion of the magnetic recording medium are shown in the fourth table. Moreover, the gel fraction which shows the crosslinking reaction of each copolymer and an isocyanate is also as showing in a 4th table | surface.

TABLE 4

Comparative Example 1

Vinyl chloride / 2-hydroxypropyl acrylate copolymer (containing 13.0 wt% of average polymerization degree 350,2-HPA) a and vinyl chloride / vinyl acetate / vinyl alcohol prepared in the same manner as in the preparation of Resin A of Example 1. A control reference magnetic recording medium was prepared in the same manner as in Example 1 using copolymer b (the composition ratio was 91: 3: 6 in this order), and the square ratios of the magnetic recording medium were measured. 0.75 and 0.76. Their glossiness was low, 52% and 54%, respectively.

Comparative Example 2

As for the copolymer b used in Comparative Example 1, blocking was generated as a result of performing a heat adhesion test after preparing a control reference magnetic recording medium in the same manner as in Example 2.

Comparative Example 3

A vinyl chloride-based copolymer was prepared in the same manner as in Example 1, except that a reaction apparatus in which the inner wall was not covered with a fluorine resin was used. The scale deposited on the inner wall surface of the reactor was about 5 mm thick, and the scale was also attached to the baffle surface and the stirring blade. The precipitated scale was peeled off with a scraper and subjected to a solvent solubility test. As a result, a cloudy solution was produced, indicating that part of the precipitated scale was insoluble in the solvent.

Those skilled in the art will appreciate that various other modifications can be made without departing from the scope of the present invention. Accordingly, the appended claims are not intended to be limited to the contents described herein, but are inherent in the present invention, including all features that may be treated as equivalents by those of ordinary skill in the art. It should be noted that all features of the patentable novelty are inclusive.

Claims (15)

A resin for a magnetic recording medium comprising a vinyl chloride-based copolymer containing a hydroxyl group-containing vinyl monomer and a quaternary ammonium base-containing vinyl monomer as structural units. The resin for magnetic recording medium according to claim 1, further comprising an isocyanate compound. A resin for a magnetic recording medium according to claim 1, wherein the content of the hydroxyl group-containing vinyl monomer in the vinyl chloride copolymer is 1 to 30% by weight. The resin for a magnetic recording medium according to claim 1, wherein the content of the quaternary ammonium base-containing vinyl monomer of the vinyl chloride copolymer is 0.05 to 8% by weight. The content of vinyl chloride in the vinyl chloride copolymer is 60 to 95% by weight, the content of the hydroxyl group-containing vinyl monomer is 1 to 30% by weight, and the content of the quaternary ammonium group-containing vinyl monomer is 0.05. To 8% by weight of a resin for a magnetic recording medium. The resin for magnetic recording medium according to claim 1, which is at least methacryloyloxyethyltrimethylammonium chloride in the quaternary ammonium base-containing vinyl monomer. The resin for magnetic recording media according to claim 1 or 2, wherein the vinyl chloride copolymer further contains an acid group-containing vinyl monomer as a structural unit. 8. The resin for magnetic recording media according to claim 7, wherein the content of the hydroxyl group-containing vinyl monomer in the vinyl chloride copolymer is 1 to 30% by weight. 8. The magnetic recording medium according to claim 7, wherein the content of the quaternary ammonium base-containing vinyl monomer and the acid group-containing vinyl monomer in the vinyl chloride copolymer is 0.05 to 8% by weight, respectively, and their total content is 0.1 to 10% by weight. Suzy. 8. The vinyl chloride 꼐 copolymer has a vinyl chloride content of 60 to 95% by weight, a hydroxyl group-containing vinyl monomer content of 1 to 30% by weight, and a quaternary ammonium base-containing vinyl monomer and an acid group. A resin for a magnetic recording medium having a vinyl monomer content of 0.05 to 8% by weight and a total content of 0.1 to 10% by weight, respectively. 8. The resin for magnetic recording medium according to claim 7, wherein the acid group-containing vinyl monomer is a vinyl monomer having a phosphate group. An organic solvent solution containing vinyl chloride, a hydroxyl group-containing vinyl monomer and a quaternary ammonium base-containing vinyl monomer is polymerized in a reaction apparatus in which an inner wall contacting the organic solvent solution is coated with a fluorine resin to form a vinyl chloride copolymer. A method for producing a resin for a magnetic recording medium which is made to precipitate. The method for producing a resin for a magnetic recording medium according to claim 12, further comprising an acid group-containing monomer in the organic solvent solution. An organic solvent solution containing vinyl chloride, a hydroxyl group-containing vinyl monomer, a quaternary ammonium base, and a vinyl monomer is polymerized in a reaction apparatus in which an inner wall contacting the organic solvent solution is coated with a fluorine-based resin to form a vinyl chloride-based air. A method for producing a vinyl chloride resin comprising precipitation of a copolymer. 15. The method for producing a vinyl chloride resin according to claim 14, wherein the organic solvent solution further contains an acid group-containing monomer.