JPH0731799B2 - Magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium such as a magnetic tape or a magnetic disk, and more specifically, it is included in a magnetic layer formed on a non-magnetic support. It relates to the improvement of binders.

[Outline of Invention]

The present invention provides a magnetic recording medium comprising a magnetic layer mainly composed of a ferromagnetic powder and a binder formed on a non-magnetic support, and a siloxane bond in the molecular chain of the binder constituting the magnetic layer. It has, -SO ₃ M group, -OSO ₃ M group, -C in the molecular side chain
OOM group, A thermoplastic polyurethane-urea resin or at least one thermoplastic polyurethane-urea resin having a group (where M is hydrogen or an alkali metal, M'is hydrogen, an alcar metal or a hydrocarbon group) and a polyisocyanate curing agent. Using the cured product obtained by the reaction of, the dispersibility of the magnetic powder and the surface property of the magnetic layer are improved, and the thermal characteristics, blocking resistance, durability, running stability, magnetic characteristics of the obtained magnetic recording medium, It is intended to improve the electromagnetic conversion characteristics and the like.

[Conventional technology]

Conventionally, vinyl chloride-vinyl acetate copolymers, cellulose derivatives, polyester resins, etc. have been widely used as binders in magnetic recording media. Furthermore, in order to improve the wear resistance of the magnetic layer or to coat the magnetic layer. In order to improve the physical properties of the film,
A thermoplastic polyurethane resin is used.

On the other hand, high density recording is demanded for magnetic recording media, and as a result, fine particles of ferromagnetic powder filled in the magnetic layer of the magnetic recording medium and smoothing of the surface of the magnetic layer are being advanced.

However, when the smoothness of the surface of the magnetic layer is improved as described above, the contact area increases, which not only adversely affects the running property and durability of the magnetic recording medium but also significantly deteriorates the blocking resistance. In particular, since the conventionally used binder has a low softening point and poor heat resistance, for example, when a tape-shaped magnetic recording medium is wound around a reel and stored at high temperature or for a long time, the non-magnetic support in which the magnetic layers overlap with each other. There is a problem in that the magnetic layer adheres to the body and peels off the magnetic layer, so that the performance as a magnetic recording medium cannot be fully exhibited. In addition, the increase in the specific surface area of the ferromagnetic powder due to its fine particles not only deteriorates the dispersibility of the ferromagnetic powder in the binder, but also deteriorates the filling property and surface glossiness, and is an important characteristic of the magnetic recording medium. It is also difficult to obtain sufficient performance in terms of certain electromagnetic conversion characteristics and running durability such as powder falling and scratches.

Therefore, in order to improve the heat resistance of the thermoplastic polyurethane resin and improve the blocking resistance of the magnetic recording medium, the proportion of the low molecular weight diol, which is a component of the thermoplastic polyurethane resin, is increased to increase the urethane group concentration in the molecule. It has been considered to use a thermoplastic polyurethane resin having increased content as a binder for the magnetic layer of a magnetic recording medium.

Generally, increasing the urethane group concentration can improve the thermal properties of the thermoplastic polyurethane resin. That is, a thermoplastic polyurethane resin having a high softening point and a low glass transition point can be obtained as the concentration of urethane groups in the molecule increases. However, when the urethane group concentration of the thermoplastic polyurethane resin increases, it becomes insoluble in general-purpose solvent systems used in the production of ketone-based, alcohol-based, ester-based, aromatic hydrocarbon-based, aliphatic hydrocarbon-based, etc. magnetic recording media. However, it has the drawback that it is only slightly soluble in highly toxic solvents such as dimethylformamide and tetrahydrofuran. Furthermore, when a solvent such as dimethylformamide or tetrahydrofuran is used as a solvent for the magnetic coating material for forming the magnetic layer, it will attack the material surface that is in contact with the solvent, such as the coating surface of the non-magnetic support on which this magnetic coating material is coated. However, there is a possibility that wrinkles or unevenness may be partially generated, or they may be dissolved in some cases. Therefore, there is a limit to improvement by increasing the urethane group concentration of the thermoplastic polyurethane resin.

Further, even if the above-mentioned thermoplastic polyurethane resin having an increased urethane group concentration is used as a binder for the magnetic layer,
Little effect can be expected to improve the dispersibility of the finely divided ferromagnetic powder.

Further, when the above-mentioned thermoplastic polyurethane resin is used as the binder of the magnetic layer, the resin itself lacks in lubricity, and thus there is a problem in success stability.

[Problems to be solved by the invention]

The present invention has been proposed in order to solve the above problems, greatly improving the dispersibility of the magnetic powder and the surface property of the magnetic layer, and improving the thermal characteristics, blocking resistance, durability, and running stability. It is an object of the present invention to provide a magnetic recording medium having excellent magnetic characteristics and electromagnetic conversion characteristics.

[Means for solving problems]

The present inventors have earnestly studied that they would not achieve the above object, and as a result, have a siloxane bond in the molecular chain and
SO ₃ M group, -OSO ₃ M group, -COOM group, (Wherein M is hydrogen or an alkali metal, M'is hydrogen, an alkali metal or a hydrocarbon group), and a thermoplastic polyurethane-urea resin or a thermoplastic polyurethane-urea resin and a polyisocyanate curing agent The cured product obtained by the reaction is useful for improving the blocking resistance and running stability of the magnetic layer of the magnetic recording medium, improving the dispersibility of the ferromagnetic powder, and is easily dissolved in a general-purpose solvent system and easy to handle. The present invention has been completed and the present invention has been completed. In a magnetic recording medium comprising a non-magnetic support, on which a magnetic layer mainly comprising a ferromagnetic powder and a binder is formed, the magnetic layer is a molecule. Having a siloxane bond in the chain, -SO ₃ M, -OSO ₃ M, -COOM in the molecular side chain, (Wherein M is hydrogen or an alkali metal, M'is hydrogen, an alkali metal or a hydrocarbon group), and contains a thermoplastic polyurethane-urea resin having at least one of them as a binder. A cured product obtained by reacting the above-mentioned thermoplastic polyurethane-urea resin with a polyisocyanate curing agent is contained as a binder.

Thermoplastic polyurethane used in the present invention - urea resin is a feature that has a urethane bond and urea bond (urea bond) in the molecule, further siloxane bond and -SO ₃ M group, -OSO ₃ M group, -COOM group, (However, M is hydrogen or an alkali metal, M'is hydrogen, an alkali metal or a hydrocarbon group) and the like is characterized in that a hydrophilic polar group is introduced.

And, the urethane bond and the urea bond play an important role in improving the thermal properties of the binder resin, the curing point temperature, which is a measure of heat resistance, can be increased, and the glass transition temperature can be decreased, and the temperature can be wide. The stable physical properties of the magnetic layer are maintained over the temperature range, and the blocking resistance is significantly improved. That is, the introduction of the urea group can greatly improve the thermal properties of the resin, like the urethane group.
More importantly, by introducing the urea group, a soluble resin can be obtained by using a combination of the above-mentioned ketone-based, alcohol-based, ester-based, aromatic hydrocarbon-based, and aliphatic hydrocarbon-based solvents. Is. Further, since the concentration of the urethane group and the urea group in the thermoplastic polyurethane-urea resin molecule can be made larger than that of a general thermoplastic polyurethane resin, the interaction between the molecule and the molecule is strengthened, and the physical properties of the coating film of the obtained magnetic layer are improved. Improves and exerts an effect on durability. That is, by using the thermoplastic polyurethane-urea resin as a binder for a magnetic recording medium, it is possible to provide a magnetic recording medium having excellent blocking resistance and durability.

The total concentration of the urethane group and urea group of the thermoplastic polyurethane-urea resin is 1.8 mmol / g to 3.0 mmol
It is preferably / g. When the concentration is less than 1.8 mmol / g, the softening point of the resin is lowered and the blocking resistance is not improved, and when the concentration exceeds 3.0 mmol / g, the resin becomes insoluble in a general-purpose solvent and only dissolves in dimethylformamide or the like. It's gone. The ratio of urea group concentration / urethane group concentration is preferably 0.3 to 1.6. If the urea group concentration / urethane group concentration ratio is less than 0.3, it becomes insoluble in a general-purpose solvent, and if the urea group / urethane group concentration ratio exceeds 1.6, the glass transition point of the resin becomes high.

On the other hand, the hydrophilic polar group introduced as a side chain of the thermoplastic polyurethane-urea resin has an extremely good affinity with the ferromagnetic powder mixed in the magnetic layer, and therefore the binding of these ferromagnetic powders. It is very effective in dispersing in the agent and exhibits a performance capable of sufficiently dealing with an increase in the specific surface area of the ferromagnetic powder. Furthermore, the introduction of the hydrophilic polar group into the thermoplastic polyurethane-urea resin contributes not only to improving the dispersibility of the ferromagnetic powder but also to improving the physical properties of the magnetic layer. That is, by introducing the hydrophilic polar group, the ferromagnetic powder and the binder can directly interact with each other, and a tough magnetic layer having excellent durability can be formed.

The introduction amount of the hydrophilic polar group of the thermoplastic polyurethane-urea resin is preferably 0.01 to 1.0 mmol / g,
The range is more preferably 0.05 to 0.5 mmol / g. When the amount of the hydrophilic polar group is 0.01 mmol / g or less, a sufficient effect on the dispersibility of the ferromagnetic powder cannot be recognized. Further, when the amount of the hydrophilic polar group exceeds 1.0 mmol / g, intermolecular or intramolecular aggregation is likely to occur, which not only adversely affects dispersibility, but also causes selectivity to the solvent and can be used as a general-purpose solvent. There is also a risk that it will disappear.

The siloxane bond introduced into the molecular chain of the thermoplastic polyurethane-urea resin imparts lubricity to the resin itself and can provide a magnetic recording medium having excellent running stability.

The siloxane group concentration of the thermoplastic polyurethane-urea resin is preferably 0.03 mmol / g to 3 mmol / g, more preferably 0.1 mmol / g to 0.7 mmol / g. If the siloxane group concentration is less than 0.03 mmol / g, lubricity cannot be imparted, and the siloxane group concentration is 3 m
When it exceeds mol / g, not only the solubility with a solvent and the compatibility with other binder resins deteriorate, but also the breaking strength of the magnetic coating film,
Physical properties such as Young's modulus deteriorate.

By the way, the thermoplastic polyurethane used in the present invention
The urea resin preferably has a number average molecular weight in the range of 10,000 to 100,000, more preferably 10,000 to 60,000. When the number average molecular weight is less than 10,000, the coating film forming ability of the resin becomes insufficient, and when the number average molecular weight exceeds 60,000 in the production of coating material, there is a possibility that problems may occur in steps such as mixing, transfer and coating. Occurs.

Further, the softening point temperature of the thermoplastic polyurethane-urea resin is preferably 80 ° C or higher, more preferably 100 ° C or higher. If the softening point temperature is lower than this, the properties of the conventional thermoplastic polyurethane resin are approximated, and it is impossible to improve the blocking resistance and the physical properties.

The glass transition temperature of the thermoplastic polyurethane-urea resin is preferably 0 ° C or lower, more preferably -10 ° C or lower. When the glass transition temperature is higher than this, the transition region of physical properties approaches room temperature, which is not preferable.

Next, a method for producing the thermoplastic polyurethane-urea resin used in the magnetic recording medium of the present invention will be described.

Thermoplastic polyurethane-urea resins are long chain diols,
It is obtained by subjecting a short chain diol, an organic diamine and an organic diisocyanate to a polyaddition reaction. This polyaddition reaction is
A mixture of a long-chain diol and a short-chain diol is previously reacted with an organic diisocyanate to prepare a prepolymer having an isocyanate group terminal, and then an organic diamine is added to carry out chain extension and urea group introduction by a prepolymer method. Be done.

The long-chain diol used for producing the thermoplastic polyurethane-urea resin has a molecular weight of about 500 to about 5000 and is roughly classified into polyester diol, polyether diol, polyether ester glycol and the like. Specific examples of the polyester diol include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid or lower alcohol esters thereof, and ethylene glycol, Polyester diols obtained by reacting with 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexane glycol, diethylene glycol, neopentyl glycol, bisphenol A ethylene oxide adduct or the like or a mixture thereof Alternatively, a lactone-based polyester diol obtained by ring-opening polymerization of a lactone such as ε-caprolactone may be used. Examples of the polyether diol include polyalkylene ether glycols such as polyethylene glycol, polypropylene ether glycol, polytetramethylene ether glycol, and copolymerized polyether glycols thereof. Further, as the polyether ester glycol,
Examples thereof include polyester glycols obtained by reacting the above polyalkylene ether glycol as a polyol component with an aliphatic or aromatic dicarboxylic acid. If the molecular weight of this long-chain diol is too small, the concentration of urethane groups in the resulting thermoplastic polyurethane-urea resin will be too high and the flexibility of the resin will be poor, and the solubility in the solvent will be poor, and the magnetic recording medium Less preferred for use as a binder. Also, when the molecular weight of the long chain diol is too large, the content of the long chain diol in the resin becomes too large and the urethane group concentration becomes relatively small, so the abrasion resistance and heat resistance of the resin decrease. To do.

The short chain diol used in the production of the thermoplastic polyurethane-urea resin has a molecular weight of about 50 to about 500,
For example, ethylene glycol, propylene glycol,
1,4-butylene glycol, 1,6-hexane glycol,
There are aromatic glycols such as neopentyl glycol and the like, ethylene oxide adducts of bisphenol A or propylene oxide adducts, and aromatic diols such as ethylene oxide adducts of hydroquinone. These are selected according to the desired properties of the polyurethane-urea resin. They can be used alone or mixed in various quantitative ratios.

As the organic diamine, tetramethylenediamine, aliphatic diamine such as hexamethylenediamine,
m-phenylenediamine, p-phenylenediamine, 2,
4-tolylenediamine, 2,6-tolylenediamine, m-xylylenediamine, p-xylylenediamine, diphenylmethanediamine, 3,3'-dimethoxy-4,4'-biphenylenediamine, 3,3'-dimethyl -4,4'-biphenylenediamine, 4,4'-diaminodiphenyl ether, 1,5
-Aromatic diamines such as naphthalenediamine and 2,4-naphthalenediamine, alicyclic diamines such as 1,3-diaminomethylcyclohexane, 1,4-diaminomethylcyclohexane, 4,4'-diaminodicyclohexylmethane and isophoronediamine Is mentioned.

Examples of the organic diisocyanate include tetramethylene diisocyanate, aliphatic diisocyanate such as hexamethylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-Tolylene diisocyanate, diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3 '
-Dimethyl-4,4'-biphenylene diisocyanate,
Aromatic diisocyanates such as 4,4'-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate and 2,4-naphthalene diisocyanate, 1,3-diisocyanatomethyl cyclohexane, 1,4-di Examples thereof include alicyclic diisocyanates such as isocyanate methylcyclohexane, 4,4'-diisocyanate dicyclohexylmethane, and isophorone diisocyanate.

Further, when the above-mentioned thermoplastic polyurethane-urea resin is used in combination with a polyisocyanate curing agent, a magnetic recording medium having excellent wear resistance can be obtained. As the polyisocyanate curing agent, for example, a polyisocyanate curing agent such as Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.) and Desmodur L (manufactured by Bayer Co., Ltd.), which are conventionally usable as curing agents, can be used. Any of them can be used. Also, the polyisocyanate curing agent may be used in an amount that is normally used.

Further, in the above reaction, the molar ratio of the short chain diol to the long chain diol is preferably 3 or less.
If this molar ratio is too large, the urethane group concentration becomes too high, and the produced polyurethane-urea resin cannot be dissolved in the above-mentioned general-purpose solvent used when preparing a magnetic coating, which is not suitable. When a straight chain diol such as ethylene glycol, 1,4-butylene glycol or 1,6-hexane glycol is used as the short chain diol, the above-mentioned molar ratio is preferably 1 or less, preferably 0.5 or less, such as neopentyl glycol or the like. When a branched short-chain diol or an ethylene oxide or propylene oxide adduct of bisphenol A is used, the solubility of the resin is good, so that the above-mentioned molar ratio can be increased as compared with the linear diol. However, even in this case, if the above-mentioned molar ratio exceeds 3 and is too large, the solubility is deteriorated, which is not preferable.

In the production of the thermoplastic polyurethane-urea resin used in the present invention, the long-chain diol having a molecular weight of about 500 to about 5000 is a polyester diol among the above-mentioned examples, especially polybutylene adipate, polyhexamethylene adipate, polycaprolactone. It is preferable to use a diol. As the short chain diol having a molecular weight of about 50 to about 500, it is particularly preferable to use a branched short chain diol among the above-mentioned examples, and neopentyl glycol is used. Further, as the organic diamine, it is particularly preferable to use isophoronediamine in the above-mentioned examples. As the organic diisocyanate, it is particularly preferable to use 4,4-diphenylmethane diisocyanate and isophorone diisocyanate among the above-mentioned examples.

Further, as the method of the polyaddition reaction employed in the production of the thermoplastic polyurethane-urea resin used in the present invention, melt polymerization in which the reaction is carried out in a molten state, ethyl acetate, methyl ethyl ketone, acetone, toluene alone or a mixed solvent such as Although there is solution polymerization or the like which is carried out by dissolving the above-mentioned raw materials in an inert solvent, solution polymerization is preferable for the production of a resin often used by being dissolved in a solvent such as a binder of a magnetic recording medium, and particularly It is more preferable that melt polymerization is carried out during preparation of the prepolymer, and solution polymerization is carried out by adding the above-mentioned inert solvent before carrying out the chain extension reaction.

During the reaction, an organometallic compound such as stannous octylate or an organotin compound such as dibutyltin dilaurate, or a tertiary amine such as N-methylmolarurine or triethylamine may be added as a catalyst. Also, to increase the stability of the product, antioxidants, UV absorbers,
A hydrolysis inhibitor or the like may be added.

Further, a hydrophilic polar group is introduced into the thermoplastic polyurethane-urea resin. As this hydrophilic polar group, --SO
₃ M, −OSO ₃ M, −COOM, (In the formula, M represents a hydrogen atom or an alkali metal,
M'represents a hydrogen atom, an alkali metal or a hydrocarbon group. ) Is mentioned.

As a method of introducing these hydrophilic polar groups into the thermoplastic polyurethane-urea resin, (1) a method of mixing a hydrophilic polar group-containing compound as a raw material of the thermoplastic polyurethane-urea resin (2) bifunctional or Examples thereof include a method of modifying a thermoplastic polyurethane-urea resin having a trifunctional or higher -OH group with a compound having a hydrophilic polar group.

Examples of the hydrophilic polar group-containing compound used in the above method (1) include a hydrophilic polar group-containing diol, a hydrophilic polar group-containing organic diisocyanate, and a hydrophilic polar group-containing organic diamine. These compounds polymerize with other raw materials to form a part of the polymer molecular chain of the thermoplastic polyurethane-urea resin, and as a result, a hydrophilic polar group is introduced into the thermoplastic polyurethane-urea resin.

The hydrophilic polar group-containing diol has the general formula (In the formula, R ₁ is an alkylene group having 2 to 6 carbon atoms or a substituted product thereof, R ₂ is an alkylene group having 1 to 6 carbon atoms or a substituted product thereof, and R ₃ and R ₄ are alkyl groups having 1 to 6 carbon atoms. Represents a phosphoric acid ester group-containing diol.

Alternatively, it may be a diol having a —SO ₃ M group (wherein M represents a hydrogen atom or an alkali metal). Diols having the -SO ₃ M groups, a carboxylic acid component having no -SO ₃ M group, obtained by reacting a dicarboxylic acid component having a glycol component and -SO ₃ M groups.

Examples of the carboxylic acid component having no —SO ₃ M group include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid, p-oxobenzoic acid, p- (hydroxyethoxy) benzoic acid. Acids such as aromatic oxycarboxylic acids, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and other aliphatic dicarboxylic acids, trimellitic acid, trimesic acid, pyromellitic acid and other tri- and tetracarboxylic acids, etc. Can be mentioned.

As the glycol component, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-
1,3-Pentanediol, 1,4-Cyclohexanedimethanol, bisphenol A ethylene oxide adduct and propylene oxide adduct, hydrogenated bisphenol A
Ethylene oxide adduct and propylene oxide adduct, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.
Further, tri- and tetraols such as trimethylolethane, trimethylolpropane, glycerin and pentaerythritol may be used in combination.

Examples of the dicarboxylic acid component having a —SO ₃ M group include 5-
Sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, 2-
Examples include potassium sulfoterephthalic acid.

The hydrophilic group-containing organic diisocyanate can be obtained by reacting a trifunctional or higher functional polyisocyanate compound with a compound having a hydrophilic polar group.

As the above-mentioned polyisocyanate compound, trifunctional trade name Desmodur L (manufactured by Bayer), trade name Coronate L (manufactured by Nippon Polyurethane Co.), etc. are known.
Generally, a polyfunctional polyisocyanate compound is obtained by subjecting a polyol and a polyisocyanate to an addition reaction.

Examples of the polyol include propylene glycol, glycerol, trimethylolpropane, pentaerythritol, sorbitol and the like. Further, as the polyisocyanate, tolylene diisocyanate, 4,4-
Examples thereof include diphenylmethane diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate and lysine diisocyanate.

Next, a method for introducing the hydrophilic polar group into a tri- or higher functional polyisocyanate compound will be schematically shown.

It has a -SO ₃ M group in the method in one molecule to introduce a -SO ₃ M group, and is reacted with compound 3 or more functional polyisocyanate compound having an active hydrogen capable of reacting against -NCO groups As a result, a compound having two or more —NCO groups and a —SO ₃ M group in one molecule can be obtained.

Examples of the compound having an —SO ₃ M group in one molecule and an active hydrogen capable of reacting with the —NCO group include the following: These compounds undergo an addition reaction with a tri- or higher functional polyisocyanate compound, for example, as shown in the following reaction formula.

(In the reaction formula, R-NCO represents a polyisocyanate compound having three or more functional groups.) Method for introducing -COOM group Active hydrogen having a -COOM group in one molecule and capable of reacting with the -NCO group. By reacting a compound having a with a tri- or higher functional polyisocyanate compound, a compound having two or more -NCO groups and a -COOM group in one molecule can be obtained.

Examples of the compound having a -COOM group and an active hydrogen capable of reacting with an -NCO group in the molecule include the following.

These compounds are trifunctional or higher functional polyisocyanate compounds, for example, undergo an addition reaction as shown in the following reaction formula.

(In the reaction formula, R-NCO represents a tri- or more functional polyisocyanate compound.) NaOH to the reaction product of a -OSO ₃ methods for introducing the M group trifunctional or higher polyisocyanate compounds and H ₂ SO ₄ Then, by neutralizing with KOH or the like, a compound having two or more —NCO groups and —OSO ₃ M groups in one molecule can be obtained, for example, as shown in the following reaction formula.

In _{R-NCO + H 2 SO 4} → R-NHCO-OSO 3 H R-NHCO-OSO 3 H + NaOH → R-NHCO-OSO 3 Na + H 2 O ( Reaction Scheme, the R-NCO are trifunctional or more polyisocyanate compound Represent) It can be obtained, for example, as shown by the following reaction formula, by neutralizing a reaction product of a tri- or higher functional polyisocyanate compound and H ₃ PO ₃ with NaOH, KOH or the like.

(In the above reaction formula, R-NCO represents a tri- or more functional polyisocyanate compound.) Further, as the hydrophilic polar group-containing organic diamine,
General formula (In the formula, R ₅ and R ₆ represent a hydrocarbon group having 2 to 12 carbon atoms.) As shown by the following formula, an equimolar reaction product of an aliphatic or alicyclic diamine and an acid anhydride and an alkali metal salt thereof are Can be mentioned. Examples of the aliphatic or alicyclic diamine include tetramethylenediamine, hexamethylenediamine, 1,3-diaminomethylcyclohexane, 1,4-diaminomethylcyclohexane, 4,4-diaminodicyclohexylmethane and isophoronediamine. It is particularly preferable to use isophoronediamine. The acid anhydrides include succinic anhydride, maleic anhydride, phthalic anhydride, and hexahydrophthalic anhydride. 3-methyl-1,2,3,6-tetrahydrophthalic anhydride, 4
-Methyl-1,2,3,6-tetrahydrophthalic anhydride and the like can be mentioned.

On the other hand, as a specific example of the above method (2), for example, (A) ClCH ₂ CH ₂ SO ₃ M, ClCH ₂ CH ₂ SO ₃ M, ClCH ₂ COOM, (However, M is a hydrogen atom or an alkali metal, M'is a hydrogen atom, an alkali metal or a hydrocarbon group), a compound containing a hydrophilic polar group and chlorine in the molecule, a polyfunctional
OH group-containing thermoplastic polyurethane-urea resin,
Both components are soluble in soluble solvents such as dimethylformamide, dimethylsulfoxide, pyridine, picoline,
Amine such as triethylamine: There is a method of introducing a hydrophilic polar group by a dehydrochlorination reaction of -OH group and chlorine in the presence of a dehydrochlorination agent such as an epoxy compound such as ethylene oxide and propylene oxide. The reaction equation is shown below.

(A-1) R'-OH + ClCH ₂ CH ₂ SO ₃ M → R'-OCH ₂ CH ₂ SO ₃ M + HCl (A-2) R'-OH + ClCH ₂ CH ₂ OSO ₃ M → R'-OCH ₂ CH ₂ OSO ₃ M + HCl (A-3) R'-OH + ClCH ₂ COOM → R'-OCH ₂ COOM + HCl (However, R represents a thermoplastic polyurethane-urea resin.) Although some by-products are produced, it can also be synthesized by the following method. That is, (B) HOCH ₂ CH ₂ SO ₃ M, HOCH ₂ CH ₂ OSO ₃ M, HOCH ₂ COOM, And a diisocyanate compound, for example, 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate and hexamethylene diisocyanate are reacted in an equimolar manner, and one NCO group of the diisocyanate and OH in the molecule.
Reaction with a group gives the reaction product. Next, the -OH group of the thermoplastic polyurethane-urea resin is reacted with the remaining -NCO group to obtain a thermoplastic polyurethane-urea resin having a hydrophilic polar group introduced therein.

(B-1) OCN-R "-NCO + HOCH ₂ CH ₂ SO ₃ M → OCN-R" -NHCOOCH ₂ CH ₂ SO ₃ M R'-OH + OCN-R "-NHCOOCH ₂ CH ₂ SO ₃ M → R'-OCONH -R "-NHCOOCH ₂ CH ₂ SO ₃ M (B-2) OCN-R" -NCO + HOCH ₂ CH ₂ OSO ₃ M → OCN-R "-NHCOOCH ₂ CH ₂ OSO ₃ M R'-OH + OCN-R" -NHCOOCH ₂ CH ₂ OSO ₃ M → R'-OCONH-R "-NHCOOCH ₂ CH ₂ OSO ₃ M (B-3) OCN-R" -NCO + HOCH ₂ COOM → OCN-R "-NHCOOCH ₂ COOM R'-OH + OCN-R "-NHCOOCH ₂ COOM → R'-OCONH-R" -NHCOOCH ₂ COOM (However, R'represents a thermoplastic polyurethane-urea resin and R "represents a divalent hydrocarbon group.) Further, a siloxane bond is introduced into the main chain of the thermoplastic polyurethane-urea resin. As an introduction method, the starting material of the thermoplastic polyurethane-urea resin,
A method of mixing a compound having a siloxane bond is mentioned. Specifically, a diol having a siloxane bond or a diamine having a siloxane bond is used as the compound having the siloxane bond, and the diol having the siloxane bond is mixed in a part of the long chain diol, or the siloxane is mixed in a part of the organic diamine. A diamine having a bond may be mixed.

Examples of the diol having a siloxane bond include compounds represented by the following general formula.

(However, R represents a divalent hydrocarbon group.) Examples of the diamine having a siloxane bond include compounds represented by the following general formula.

The compound having a molecular weight of 300 to 10,000 can be used.

It is also possible to use a long-chain diol in which a siloxane bond is previously introduced. For example, when synthesizing a long-chain diol such as polyester diol or polyether ester glycol, the diol having a siloxane bond may be used.

The thermoplastic polyurethane-urea resin synthesized as described above can be used in combination with other thermoplastic resin, thermosetting resin or reactive resin. In this case, the blending ratio of the above-mentioned thermoplastic polyurethane-urea resin to all binders in the magnetic layer is preferably 10% by weight or more.
If the blending ratio of the thermoplastic polyurethane-urea resin to the total binder is less than 10% by weight, improvement in blocking resistance of the magnetic recording medium can hardly be expected. More preferably, it is 40% by weight or more. As the above-mentioned thermoplastic resin, the softening temperature is 150 ° C. or less, and the average molecular weight is 10,000 to 2000.
A polymer having a degree of polymerization of about 200 to about 2000 at 00, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer ,
Thermoplastic polyurethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin,
Examples thereof include synthetic rubber type thermoplastic resins such as polyvinyl butyral, cellulose derivatives, polyester resins, and polybutadiene. As the thermosetting resin or the reactive resin, for example, phenol resin, epoxy resin, polyurethane curable resin, melamine resin, alkyd resin,
Silicone resin, acrylic reaction resin, epoxy-polyamide resin, nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of methacrylate copolymer and diisocyanate prepolymer, polyester polyol and poly Examples include mixtures of isocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols / high molecular weight diols / triphenylmethane triisocyanates, polyamine resins and mixtures thereof. Of these, it is desirable to use them in combination with those having good dispersibility in the ferromagnetic powder.

The magnetic layer can be formed by dispersing the ferromagnetic powder in the above-mentioned binder, dissolving it in an organic solvent and coating it on a non-magnetic support.

Examples of the ferromagnetic powder used in the present invention include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite fine particles, iron nitride and the like.

As the above-mentioned ferromagnetic iron oxide particles, when represented by the general formula FeOx, those having an X value in the range of 1.33 ≦ X ≦ 1.50, that is, maghemite (γ-Fe ₂ O ₃ , X = 1.50), magnetite (Fe ₃
O ₄ , X = 1.33) and their solid solutions (FeOx, 1.33 <X <1.5
0). Further, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. Cobalt-containing iron oxide is roughly classified into two types: a doped type and an adhered type.

As the above-mentioned ferromagnetic chromium dioxide, it is possible to use CrO ₂ or those to which at least one kind of Ru, Sn, Te, Sb, Fe, Ti, V, Mn or the like is added for the purpose of improving coercive force.

As the ferromagnetic alloy powder, Fe, Co, Ni, Fe-Co, Fe-Ni, Fe
-Co-Ni, Co-Ni, Fe-Co-B, Fe-Co-Cr-B, Mn-Bi, Mn
-Al, Fe-Co-V and the like can be used, and metal components such as Al, Si, Ti, Cr, Mn, Cu and Zn may be added to these for the purpose of improving various characteristics.

Further, in addition to the binder and the ferromagnetic fine powder, a dispersant, a lubricant, an abrasive, an antistatic agent, an anticorrosive agent, etc. may be added to the magnetic layer.

Examples of the dispersant (pigment wetting agent) include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid,
Fatty acids having 12 to 18 carbon atoms such as linolenic acid and stearolic acid (R ₇ COOH, R ₇ is an alkyl or alkenyl group having 11 to 17 carbon atoms), alkali metals (Li, Na, K) of the above fatty acids.
Etc.) or a metal soap consisting of an alkaline earth metal (Mg, Ca, Ba), a fluorine-containing compound of the above fatty acid ester,
The fatty acid amides, polyalkylene oxide alkyl phosphates, trialkyl polyolefin oxyquaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefins such as ethylene and propylene), and the like are used. In addition to these, higher alcohols having 12 or more carbon atoms, and other than these, sulfate esters and the like can also be used. These dispersants are added in the range of 0.5 to 20 parts by weight based on 100 parts by weight of the binder.

Examples of the lubricant include dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxy polysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkyl monoalkoxy polysiloxane (alkyl has 1 to 5 carbon atoms). ,
Alkoxy has 1 to 4 carbons), phenyl polysiloxane, fluoroalkyl polysiloxane (alkyl has 1 to 5 carbons), silicon oil, conductive fine powder such as graphite, molybdenum disulfide, tungsten disulfide, etc. Inorganic fine powder, polyethylene, polypropylene, polyethylene vinyl chloride copolymer, plastic fine powder such as polytetrafluoroethylene, α-olefin polymer, unsaturated aliphatic hydrocarbon liquid at room temperature (n-olefin double bond is a terminal Compound bound to carbon of carbon, carbon number about 2
0), monobasic fatty acids with 12 to 20 carbon atoms and 3 to 12 carbon atoms
Fatty acid esters, fluorocarbons, etc., each consisting of a monohydric alcohol can be used. These lubricants are added in the range of 0.2 to 20 parts by weight based on 100 parts by weight of the binder.

The above-mentioned abrasives are commonly used materials such as fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: corundum and magnetite), etc. Is used. These abrasives have a Mohs hardness of 5
The average particle size is in the range of 0.05 to 5 μ, and particularly preferably 0.1 to 2 μ. These abrasives are added in the range of 0.5 to 20 parts by weight with respect to 100 parts by weight of the binder.

The antistatic agent, carbon black, conductive fine powder such as carbon black graft polymer, natural surfactants such as saponin, alkylene oxide-based, glycerin-based, nonionic surfactants such as glycidol-based, higher alkyl amines, Quaternary ammonium salts,
Pyridine and other heterocyclics, cationic surfactants such as phosphoniums, carboxylic acid, sulfonic acid, phosphoric acid, anionic surfactants containing acidic groups such as sulfate ester group and phosphate ester group, amino acids, aminosulfonic acids An amphoteric activator such as sulfuric acid or phosphoric acid ester of amino alcohol is used. The above conductive fine powder is a binder
0.2 to 20 parts by weight per 100 parts by weight, the surfactant is 0.1
It is added in the range of up to 10 parts by weight. You may add these surfactant individually or in mixture. Since these are used as antistatic agents, they are sometimes used for other purposes such as dispersion, improvement of magnetic properties, improvement of lubricity, and coating aid.

As the rust inhibitor, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate and the like can be used, but especially dicyclohexylamine nitrite, cyclohexylamine chromate, diisopropylamine nitrite, diethanolamine Evaporative rust inhibitors such as phosphate, cyclohexyl ammonium carbonate, hexamethylene diamine carbonate, propylene diamine stearate, guanidine carbonate, triethanolamine nitrite, morpholine stearate (amine, amide or imide inorganic or organic acid salts) ) Improves the anticorrosion effect. These rust preventives are 0.01 to 2 per 100 parts by weight of ferromagnetic fine powder.
Used in the range of 0 parts by weight.

Further, the constituent material of the magnetic layer is dissolved in an organic solvent to prepare a magnetic paint, which is applied on a non-magnetic support. The solvent of the magnetic paint is a ketone-based solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone. , Ester type such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol monoethyl ether acetate, glycol dimethyl ether, glycol monoethyl ether, glycol ether type such as dioxane, aromatic hydrocarbon such as benzene, toluene, xylene, Hexane, heptane and other aliphatic hydrocarbons, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform,
Examples thereof include chlorinated hydrocarbons such as ethylene chlorohydrin and dichlorobenzene. The material of the non-magnetic support is polyethylene terephthalate, polyethylene-2,6-
Polyesters such as naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose derivatives such as cellulose acetate propionate, polyvinyl resins such as polyvinyl chloride and polyvinylidene chloride, and polycarbonate. In addition to plastics such as polyimide and polyamide-imide, non-magnetic metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, ceramics such as glass, pottery and porcelain, paper, baryta or polyethylene,
Papers such as paper coated or laminated with α-polyolefins having 2 to 10 carbon atoms such as polypropylene and ethylene-butene copolymer can also be used. The form of the non-magnetic support may be any of film, tape, sheet, disk, card, drum and the like.

[Action]

Due to the action of the urethane group, the urea group and the hydrophilic polar group in the thermoplastic polyurethane-urea resin, the affinity for the magnetic powder is significantly improved. Therefore, by using this as a binder, even finely divided magnetic powder and magnetic powder having a large amount of magnetization are well dispersed.

At the same time, the siloxane bond has a lubricating effect, which reduces the coefficient of friction and imparts good runnability.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Resin Synthesis Example A thermoplastic polyurethane-urea resin containing a siloxane bond and a hydrophilic polar group in the molecule was synthesized according to the above-mentioned synthesis method. Table 1 shows the characteristics of the synthesized resin.

Example 1 Co Coated γ-Fe ₂ O ₃ 100 parts by weight Vinyl chloride-vinyl acetate copolymer 10 〃 (UCC VAGH) Thermoplastic polyurethane-urea resin 15 〃 (resin A) Dispersant (lecithin) 0.5 〃 Lubricant (silicone oil) 1 〃 Abrasive (Cr ₂ O ₃ ) 2 〃 Methyl ethyl ketone 100 〃 Methyl isobutyl ketone 50 〃 Toluene 50 〃 The above composition was mixed in a ball mill for 48 hours, filtered through a 3μ filter, and then cured. Add 2.5 parts by weight of the agent (Death Module L, manufactured by Bayer Co.) and mix for another 30 minutes.
It was coated on a 6 μm thick polyethylene terephthalate film so that the thickness after drying would be 6 μm, subjected to a magnetic field orientation treatment, dried and wound up. This was calendered and then cut into a 1/2 inch width to prepare a sample tape.

Example 2 In the composition of Example 1, a thermoplastic polyurethane-urea resin (resin B) was used in place of the thermoplastic polyurethane-urea resin (resin A), and a sample tape was prepared in the same manner as in example 1. .

Example 3 A sample tape was prepared in the same manner as in Example 1 except that in the composition of Example 1, a thermoplastic polyurethane-urea resin (resin A) was used instead of the thermoplastic polyurethane-urea resin (resin A). .

Example 4 In the composition of Example 1, a thermoplastic polyurethane-urea resin (resin A) was used in place of the thermoplastic polyurethane-urea resin (resin A), and a sample tape was prepared in the same manner as in example 1. .

Example 5 In the composition of Example 1, a thermoplastic polyurethane-urea resin (Resin A) was used in place of the thermoplastic polyurethane-urea resin (Resin A), and a sample tape was prepared in the same manner as in Example 1. .

Example 6 In the composition of Example 1, a thermoplastic polyurethane-urea resin (Resin F) was used in place of the thermoplastic polyurethane-urea resin (Resin A), and a sample tape was prepared in the same manner as in Example 1. .

Example 7 A sample tape was prepared in the same manner as in Example 1, except that the thermoplastic polyurethane-urea resin (resin A) was replaced by the thermoplastic polyurethane-urea resin (resin G) in the composition of Example 1. .

Example 8 A sample tape was prepared in the same manner as in Example 1, except that the thermoplastic polyurethane-urea resin (resin A) was replaced with the thermoplastic polyurethane-urea resin (resin H) in the composition of Example 1. .

Comparative Example 1 In the composition of Example 1, a thermoplastic polyurethane-urea resin (Resin I) was used in place of the thermoplastic polyurethane-urea resin (Resin A), and a sample tape was prepared in the same manner as in Example 1. .

Comparative Example 2 In the composition of Example 1, a thermoplastic polyurethane-urea resin (Resin J) was used in place of the thermoplastic polyurethane-urea resin (Resin J), and a sample tape was prepared in the same manner as in Example 1. .

Comparative Example 3 A sample tape was prepared in the same manner as in Example 1 except that in the composition of Example 1, a thermoplastic polyurethane-urea resin (resin A) was used in place of the thermoplastic polyurethane-urea resin (resin K). .

Comparative Example 4 A sample tape was prepared in the same manner as in Example 1 except that in the composition of Example 1, a thermoplastic polyurethane-urea resin (resin A) was used in place of the thermoplastic polyurethane-urea resin (resin L). .

Table 2 shows the measurement results of the dynamic friction coefficient, surface gloss, amount of powder drop, adhesive property, and still property of the above sample tape.

The dynamic friction coefficient is the coefficient of friction between the magnetic layer surface and IS stainless at a low tape speed (0.4 mm / sec) (load 50
It was measured as g). The amount of powder falling was evaluated by visually observing the amount of powder falling onto the head drum, guides, etc. after 100 times of shuttle travel for 60 minutes, and the maximum was 0 and the minimum was -5. The adhesive property is that the sample tape is wound on a reel and the temperature is 40
After being left for 24 hours at a temperature of 80 ° C. and a humidity of 80%, the degree of peeling of the sample tape was visually evaluated and scored by a 10-point method. The better the adhesive property, the lower the score. As for still characteristics, a 4.2MHz video signal was recorded on a sample tape, and the time until the reproduction output was attenuated to 50% was measured.

For the surface gloss, the reflectance at an incident angle of 75 ° and a reflection angle of 75 ° was measured using a gloss meter.

As is clear from the results shown in Table 2, by using a thermoplastic polyurethane-urea resin containing a siloxane bond and a hydrophilic polar group as the binder of the magnetic layer, the running stability and thermal characteristics of the magnetic recording medium, Blocking resistance, durability, magnetic powder dispersibility, etc. are significantly improved.

〔The invention's effect〕

As is clear from the above description, in the present invention,
Thermoplastic polyurethane-urea resin having a siloxane bond and a hydrophilic polar group in the molecule, or a cured product obtained by the reaction of this with a polyisocyanate curing agent is used as the binder of the magnetic layer, and therefore higher than the magnetic powder. It exhibits affinity and even if it is made into ultrafine magnetic powder or magnetic powder having a large amount of magnetization, good dispersibility is obtained.
Therefore, the durability and surface property of the obtained magnetic recording medium are improved, and the electromagnetic conversion characteristics are also extremely excellent.

Further, the addition of the siloxane bond provides the lubricity, so that the friction coefficient is reduced and the running property is improved.

Further, the thermoplastic polyurethane-urea resin used in the present invention is soluble in a general-purpose solvent system and easy to handle,
It is also advantageous in terms of productivity and workability.

Continuation of the front page (56) Reference JP-A-60-76017 (JP, A) JP-A-58-218034 (JP, A) JP-A-59-5421 (JP, A) JP-A-59-96534 (JP , A)

Claims (2)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer comprising a ferromagnetic powder and a binder as main components, wherein the magnetic layer has a siloxane bond in the molecular chain, and the molecular side is present. -SO ₃ M group, -OSO ₃ group, -COOM group in the chain, A magnetic recording medium containing, as a binder, a thermoplastic polyurethane-urea resin having at least one of (wherein M is hydrogen or an alkali metal, M'is hydrogen, an alkali metal or a hydrocarbon group). 2. A magnetic recording medium comprising a non-magnetic support and a magnetic layer mainly composed of a ferromagnetic powder and a binder, wherein the magnetic layer has a siloxane bond in the molecular chain and the molecular side -SO ₃ M group, -OSO ₃ M group, -COOM group in the chain, (Wherein M is hydrogen or an alkali metal, M'is hydrogen, an alkali metal or a hydrocarbon group) and a cured product obtained by reacting a thermoplastic polyurethane-urea resin having at least one of them with a polyisocyanate curing agent is bonded. A magnetic recording medium characterized by being contained as an agent.