JPS63142518A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the affinity of a binder to magnetic powder, durability and the viscosity characteristic of the binder by using a polyurethane/urea resin into the molecule of which -COOM group and quaternary ammonium salt are introduced as the binder. CONSTITUTION:The polyurethane/urea resin having -COOM (M is an H atom or alkali metal atom) and quaternary ammonium salt is incorporated into the binder of a magnetic recording medium. The binder, therefore, exhibits the high affinity to the magnetic powder and has the good dispersibility even in the magnetic powder which is pulverized to hyper-fine particles or the magnetic powder having a large quantity of magnetization. Since the polyurethane/urea resin used for the binder has excellent heat resistance and tackiness, the thermal characteristics, blocking resistance and durability of the magnetic layer are greatly improved. The properties of the coated film when formed as a magnetic layer are, therefore, improved and the magnetic recording medium having the extremely high durability, surface characteristic and electromagnetic conversion characteristic is obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium such as a magnetic tape, and more particularly to a binder contained in a magnetic layer formed on a non-magnetic support. This is related to the improvement of.

[Summary of the invention]

The present invention has disclosed that -COO is present in the molecules of polyurethane-urea resin used as a binder for coated magnetic recording media.
By introducing an M group (where M represents a hydrogen atom or an alkali metal atom) and a quaternary ammonium salt, the dispersibility in magnetic powder, properties of the coating film when formed as a magnetic layer, and coating film formation are improved. The present invention aims to provide a binder having excellent properties in terms of workability during processing, etc. 7, and to provide a magnetic recording medium with excellent surface properties and durability, and good magnetic properties and electromagnetic conversion properties.

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), have improved their magnetic properties and electromagnetic conversion properties so that high playback output can be obtained even when recording at short wavelengths. It is requested. As a countermeasure, efforts have been made to make the magnetic powder particles finer and to increase the magnetic force, and there is a strong tendency to increase the packing density of the magnetic powder in the magnetic layer, the so-called backing density.

On the other hand, conventionally used binders for magnetic recording media include binders mainly composed of vinyl chloride-vinyl acetate copolymers and polyurethane resins, but these binders have the disadvantage of increasing backing density as described above.

Furthermore, with the demand for improvements in durability and physical properties of coating films, various problems have arisen with these binders and binders using polyurethane resins, and it is currently difficult to adequately address these problems.

For example, as the specific surface area increases due to finer particles of magnetic powder and the cohesive force increases due to high magnetizing force, satisfactory dispersibility and surface area cannot be obtained with the above-mentioned binders, and the backing density of the magnetic powder increases. It has also become difficult. Therefore, the durability, magnetic properties, and electromagnetic conversion properties were also insufficient. In particular, performance has been insufficient for magnetic powders made into ultrafine particles or magnetic powders with a high amount of magnetization in order to meet higher recording densities.

In this case, for example, a method such as using a surfactant as a dispersant may be considered, but since the surfactant is a low molecular weight, powder falling off and blooming due to changes over time may occur.
Problems arise in mechanical strength, durability, etc.

Therefore, for example, in Japanese Patent Publication No. 58-41565, etc.,
A binder in which a sulfonic acid metal base is introduced into a polyurethane resin has been proposed, and attempts have been made to improve the dispersibility of magnetic powder, but it is still far from satisfactory, and for example, when used as a magnetic recording medium. Powder fell off, and there was still room for improvement in terms of durability.

In addition, from the viewpoint of physical properties of the coating film, for example, polyurethane resins are suitable in terms of abrasion resistance, etc. However, since conventionally used polyurethane resins have a low softening point and poor heat resistance, If the medium is wound onto a reel and stored at high temperatures or for a long period of time, it will stick to the non-magnetic material that overlaps this magnetic layer, causing the magnetic layer to peel off and reduce its performance as a magnetic recording medium. The problem is that they are unable to perform.

[Problem that the invention seeks to solve]

In this way, conventionally widely used binders containing vinyl chloride copolymers, polyurethane resins, and sulfonic acid metal bases have problems in terms of dispersibility for magnetic powder, physical properties of coatings, handling during manufacturing, etc. There are many issues that need to be resolved,
It was difficult to ensure desired durability, magnetic properties, and electromagnetic conversion properties.

Therefore, the present invention has been proposed to solve the above-mentioned drawbacks in the technical field, and is aimed at improving the dispersibility of magnetic powder, the properties of the coating film when formed as a magnetic layer, and the workability when forming the coating film. We provide a binder with excellent properties such as
The object of the present invention is to provide a magnetic recording medium with excellent surface properties and durability, and good magnetic properties and electromagnetic conversion properties.

[Means for solving problems]

The present inventors have discovered that polyurethane-urea resin exhibits excellent properties in terms of coating film properties such as adhesiveness, and that by introducing a carboxylic acid metal base into the side chain as a polar group, the polyurethane-urea resin has higher properties than magnetic powder. showing affinity and improving dispersibility;
Furthermore, the present invention was completed by focusing on the fact that introducing a quaternary ammonium salt as a polar group into the side chain is effective in improving workability. In a magnetic recording medium on which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed, the binder has a -COOM group in its molecule (where M represents a hydrogen atom or an alkali metal atom). and a polyurethane-urea resin having a quaternary ammonium salt.

The polyurethane-urea resin used in the present invention has urethane bonds and urea bonds in its molecules.
It is characterized by having a hydrophilic polar group as a side chain.

In addition, the urethane bond and urea bond described above play an important role in improving the thermal properties of the binder resin, and can increase the softening point temperature, which is a measure of heat resistance, and lower the glass transition point temperature, allowing a wide range of Stable physical properties of the magnetic layer are maintained over a temperature range, which is extremely effective in improving blocking resistance.

That is, the introduction of urea bonds can significantly improve the thermal properties of the resin, similar to urethane bonds. More importantly, the introduction of this urea bond makes it possible to obtain resins that are soluble when used in combination with ketone, alcohol, ester, aromatic hydrocarbon, and aliphatic hydrocarbon solvents. . In addition, since the concentration of polar parts (urethane bonds, urea bonds) in the polyurethane-urea resin molecules can be made higher than in general polyurethane resins, the interaction between molecules becomes stronger, and the resulting magnetic layer is coated. The physical properties of the film are improved and the durability is also improved. That is, by using a polyurethane-urea resin as a binder for a magnetic recording medium, a magnetic recording medium with excellent blocking resistance and durability can be provided.

The total concentration of urethane bonds and urea bonds in the polyurethane-urea resin was 1.8 mm.

+/g to 3.0 mmol/g is preferred. If the concentration is less than 1.8 mmol/g, the softening point of the resin will be lowered and the blocking resistance will not be improved, and if the concentration exceeds 3.0 mmol/g, the resin will become insoluble in general-purpose solvents. Further, the ratio of urea bond concentration/urethane bond concentration is preferably 0.3 to 1.6. The ratio of urea bond concentration/urethane bond concentration is 0.
If it is less than 3, it will become insoluble in general-purpose solvents, and if the ratio of urea bond concentration/urethane bond concentration exceeds 6, the glass transition point of the resin will become high.

Next, a method for producing polyurethane-urea resin will be described.

Polyurethane-urea resins are obtained by addition polymerizing long-chain diols, short-chain diols, organic diamines, and organic diisocyanates. In this addition polymerization, a mixture of a long-chain diol and a short-chain diol is reacted with an organic diisocyanate in advance to prepare a prepolymer with an isocyanate group terminal, and then an organic diamine is added to extend the chain and introduce a urea bond. It is carried out by the prepolymer method.

That is, according to this prepolymer method, the urethane chain is extended by the reaction between the OH group of the long-chain diol or short-chain diol and the NGO group of the organic diisocyanate.

The long-chain diols have a molecular weight of about 500 to 5,000, and are roughly classified into, for example, polyester diols, polyether diols, polyether ester glycols, and the like. Specific examples of polyester diols 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, ethylene glycol, Polyester diols obtained by reacting with 1.3-propylene glycol, 1.4-butylene glycol, 6-hexane glycol, diethylene glycol, neopentyl glycol, or an ethylene oxide adduct of bisphenol A, or a mixture thereof. Alternatively, lactone-based polyester diols obtained by ring-opening polymerization of lactones such as ε-caprolactone may be mentioned. Examples of polyether diols include polyethylene glycol, polypropylene ether glycol, polytetramethylene ether glycols, and copolymerized polyether glycols thereof. Examples of polyether ester glycols 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 urethane bond concentration of the resulting polyurethane-urea resin will become too large, resulting in poor flexibility of the resin and poor solubility in solvents, resulting in a binder for magnetic recording media. It is not very suitable for use as In addition, when the molecular weight of the long chain diol is too large, the long chain diol content in the resin becomes too large and the urethane bond concentration becomes relatively small, resulting in a decrease in the abrasion resistance and heat resistance of the resin. do.

The short chain diol has a molecular weight of about 50 to 500,
For example, ethylene glycol, propylene glycol, I
+ Aliphatic glycols such as 4-butylene glycol, 1,6-hexane glycol, and neopentyl glycol; aromatic diols such as ethylene oxide or propylene oxide adducts of bisphenol A; and ethylene oxide adducts of hydroquinone; - Depending on the properties of the urea resin, these can be used alone or in combination in various quantitative ratios.

In addition, examples of the organic diamine include aliphatic diamines such as tetramethylene diamine and hexamethylene diamine, tophenylene diamine, p-phenylene diamine, 2.
4-) lylenediamine, 2,6. -) lylenediamine, m-xylenediamine, p-xylenediamine, diphenylmethanediamine, 3.3'-dimethoxy-4,4'-biphenylenediamine, 3.3'-dimethyl-4,4'-biphenylenediamine, 4.4 '−
Aromatic diamines such as diaminodiphenyl ether, 1,5-naphthalenediamine, 2,4-naphthalenediamine, 1,3-diaminomethylcyclohexane, 4,4°-
Examples include alicyclic diamines such as diaminocyclohexylmethane and isophorone diamine.

Examples of the organic diisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, and 2.4-)lylene diisocyanate. , 2.6-dolylene diisocyanate, diphenylmethane diisocyanate, 3.3-dimethoxy-4,4''-biphenylene diisocyanate,
3,3°-dimethyl-4,4′-biphenylene diisocyanate, 4,4′-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, 2.4-
Aromatic diisocyanates such as naphthalene diisocyanate, 1,3-diisocyanatomethylcyclohexane,
1.4-Diisocyanatomethylcyclohexane, 4,
Examples include alicyclic diisocyanates such as 4'-diisocyanate dicyclohexylmethane and isophorone diisocyanate.

Furthermore, 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 bond concentration will become too high, and the produced polyurethane-urea resin will have
It cannot be dissolved in the above-mentioned general-purpose solvents used for producing magnetic paints, so it is not very suitable. Ethylene glycol, 1,4-butylene glycol, 1,6- as short chain diols
When using a straight chain diol such as hexane glycol,
The above molar ratio is desirably 1 or less, preferably 0.5 or less, and if a branched short chain diol such as neopentyl glycol or an ethylene oxide or propylene oxide adduct of bisphenol A is used, the solubility of the resin is good. The above-mentioned molar ratio can be increased compared to chain diols. However, even in this case, if the above-mentioned molar ratio is too large, exceeding 3, the solubility deteriorates, which is not preferable. Furthermore, depending on the molecular weight of the long-chain diol or short-chain diol, it is also possible to use them alone.

In producing the polyurethane-urea resin used in the present invention, the long-chain diols having a molecular weight of approximately 500 to 5,000 are selected from among the above-mentioned examples, particularly polyester diols,
Among them, it is preferable to use polybutylene adipate, polyhexamethylene adipate, and polycaprolactone diol. Further, as the short chain diol having a molecular weight of about 50 to 500, among the above-mentioned examples, it is particularly preferable to use a branched short chain diol, especially neopentyl glycol.

Further, as the organic diamine, it is particularly preferable to use isophorone diamine among the above-mentioned examples. Among the organic diisocyanates mentioned above, it is particularly preferable to use 4,4-diphenylmethane diisocyanate and isophorone diisocyanate.

In addition, the reaction method adopted in the production of the polyurethane-urea resin according to the present invention includes melt polymerization in which the reaction is carried out in a molten state, and inert solvents such as ethyl acetate, methyl ethyl ketone, acetone, toluene, etc., alone or in combination, as described above. However, solution polymerization is preferable for the production of polyurethane-urea resins, which are often dissolved in solvents such as binders for magnetic recording media. In some cases, it is more preferable to carry out melt polymerization and then add the above-mentioned inert solvent to carry out solution polymerization before carrying out the chain extension reaction.

In the reaction, an organometallic compound such as an organotin compound such as stannous octylate or diptyltin dilaurate, or a tertiary amine such as N-methylmorpholine or triethylamine may be added as a catalyst. Further, in order to increase the stability of the product, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, etc. may be added in an amount of about 5% or less based on the solid content.

Furthermore, a -COOM group (where M represents a hydrogen atom or an alkali metal atom) and a quaternary ammonium salt are introduced into the polyurethane-urea resin as hydrophilic polar groups. Here, the -C00M group is very effective in improving the dispersibility of magnetic powder, and when used as a magnetic recording medium, the effect of reducing powder dropout is particularly large, but a binder into which -C00M group is introduced alone When made into a paint, the viscosity becomes extremely high, making it impractical, so a quaternary ammonium salt is used in combination.

According to experiments conducted by the present inventors, the use of a polyurethane-urea resin that has a -COOM group in its molecule and a quaternary ammonium salt produces good results without impairing the powder fall reducing effect of the -C00M group. It was found that it was possible to obtain a coating material having excellent viscosity characteristics, and to obtain a magnetic recording medium with better dispersibility than when the -C00M group was contained alone.

By the way, the following method may be used to introduce these -C00M groups and quaternary ammonium salts into the polyurethane-urea resin.

(1) A method in which the -C00M group or quaternary ammonium salt is previously introduced into a part of diisocyanate, polyol, diamine, etc., which are raw materials for polyurethane-urea resin.

(2) A method in which an OH group is left at the end or side chain of a polyurethane-urea resin, and this OH group is modified with a 100 Go-containing compound and a quaternary ammonium salt-containing compound.

One COO used in method (1) above? -C00 as a diisocyanate or polyol into which one group or a quaternary ammonium salt is introduced as a hydrophilic polar group.
Examples include diol containing M group, diol containing quaternary ammonium salt, organic diisocyanate containing -C00M group, organic diisocyanate containing quaternary ammonium salt, organic diamine containing -C00M group, and organic diamine containing quaternary ammonium salt. It will be done. These compounds are polymerized with other raw materials to form part of the polymer molecular chain of the polyurethane-urea resin, and as a result, hydrophilic polar groups are introduced into the polyurethane-urea resin.

-COOM group-containing diols include, for example, dimethylolpropionic acid and compounds in which these -COOH groups are neutralized using a methanol solution of NaOH, a methanol solution of KOH, or the like. By synthesizing a polyurethane-urea resin using the above compound as a chain extender, a -COOM group is introduced into the molecule.

The quaternary ammonium salt-containing diol is obtained by reacting a carboxylic acid component not having a quaternary ammonium salt, a glycol component, and a dicarboxylic acid component having a quaternary ammonium salt.

Examples of the carboxylic acid component not having a quaternary ammonium salt include terephthalic acid and isophthalic acid.

Aromatic dicarboxylic acids such as orthophthalic acid and 1,5-naphthalic acid, aromatic oxycarboxylic acids such as p-oxybenzoic acid and p-(hydroxyethoxy)benzoic acid, succinic acid,
Examples include aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid, and tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid.

The glycol components include ethylene glycol, propylene glycol, 1.3-propanediol, 1.
4-butanediol, 1,5-bentanediol, 1,
6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2.
4-) Limethyl-1,3-pentanediol, 1,4
- cyclohexane dimetatool, ethylene oxide adduct and propylene oxide adduct of bisphenol A,
polyethylene glycol, polypropylene glycol,
Examples include polytetramethylene glycol. Also,
Tri- and tetraols such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol may be used in combination.

Examples of the dicarboxylic acid component having the quaternary ammonium salt include those shown below.

(However, R+ + R21R2+ each represents an alkyl group having 1 to 6 carbon atoms.) Therefore, a part of the above long chain diol is replaced with this quaternary ammonium salt-containing diol to synthesize a polyurethane-urea resin. A quaternary ammonium salt is introduced into the molecule.

In addition, the above -COOM group-containing organic diisocyanate or quaternary ammonium salt-containing organic diisocyanate can be obtained by reacting a trifunctional or higher functional polyisocyanate compound with a compound having -COOM group or a quaternary ammonium salt. Obtainable.

As the above-mentioned polyisocyanate compounds, trifunctional products such as Desmodur (trade name, manufactured by Bayer) and Coronat (trade name, manufactured by Nippon Polyurethane Co., Ltd.) are known, but in general, polyfunctional polyisocyanate compounds are Obtained by addition reaction with isocyanate.

Polyols include propylene glycol, glycerol, trimethylolpropane, pentaerythritol,
Examples include sorbitol. Examples of the polyisocyanate include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, and lysine diisocyanate. It will be done.

-C00 to the above trifunctional or higher functional polyisocyanate compound
To introduce the M group, a compound having a -COO1'l group in one molecule and an active hydrogen that can react with the -NCO group is reacted with a trifunctional or higher functional polyisocyanate compound. Just let it happen. As a result, 2
A compound (-COOM group-containing organic diisosilanate) having at least 1 -NGO group and a -COOM group is obtained.

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

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

(In the reaction formula, R-NGO represents a trifunctional or more functional polyisocyanate compound.) In order to introduce a quaternary ammonium salt,
A compound having a class ammonium salt and an active hydrogen capable of reacting with an -NGO group may be reacted with a trifunctional or higher functional polyisocyanate compound. As a result, a compound having two or more -NCO groups in one molecule and a quaternary ammonium salt (a quaternary ammonium salt-containing organic diisocyanate) is obtained.

has a quaternary ammonium salt in one molecule, and -N
Examples of compounds having active hydrogen that can react with GO groups include the following.

■((CH3)J”CHzCHJH)) X-■[(C
H3)3N'CH2CH200CN)12)) X -
■((CH3)J”CHzCH(CH3)OH)
−■ HzNChNaN”(C)13)3X-・)IC
I■ (IOC)Igc)IJ"(CJs)z) X-
(However, X represents Cβ, Br or I.) These compounds undergo an addition reaction with a trifunctional or higher functional polyisocyanate compound, for example, as shown in the following reaction formula.

R-NGO+ ((CHs)J”CHzCHzOH)
) X-=R-NHCOO-CHzCHJ"(CH
z) J- (In the reaction formula, R-NGO represents a trifunctional or higher functional polyisocyanate compound.) Furthermore, the C00M group can also be introduced by using a C00M group-containing organic diamine as a raw material. This C00M group-containing organic diamine includes an aliphatic or alicyclic diamine represented by the general formula % (in the formula, R6 and R6 represent a hydrocarbon group having 2 to 12 carbon atoms) and an acid anhydride. Examples include equimolar reactants of compounds and their alkali metal salts. Examples of the aliphatic or alicyclic diamines used include tetramethylene diamine, hexamethylene diamine, 3-diaminomethylcyclohexane, 1,4-diaminomethylcyclohexane, 4,4-diaminodicyclohexylmethane, and isophorone diamine. It is particularly preferable to use isophorone diamine. In addition, examples of the acid anhydride include succinic anhydride, maleic anhydride, fuco-methyl-1,2,3,6-tetrahydrophthalic anhydride, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride. Examples include acids.

On the other hand, in the method (2) above, a compound having a -C00M group or a quaternary ammonium salt is added to the OH group present at the end or side chain of a polyurethane-urea resin whose chain has been extended to a predetermined molecular weight by a polymerization reaction. It causes a reaction. In this case, a compound having a 0■ group and a -COOM group, or a compound having an OH group and a quaternary ammonium salt is synthesized, and is reacted with an equimolar amount of a cyisocyanate compound to form one -NCO group of the diisocyanate. -CO group or quaternary ammonium salt is introduced, and the remaining -NG
By reacting the O group with the 10H group of a polyurethane-urea resin, a polyurethane-urea resin into which a -C00M group or a quaternary ammonium salt has been introduced can be obtained. The reaction formula is as follows.

OCN-R-NCO+ HOCHzCOOM→OCN-
R-NHCOOCHzCOOMRPIII-OH+
OCN-R-NHCOOCH2COOMRpuu-OC
ONH-R-NHCOOCHzCOOM (wherein R
represents a divalent hydrocarbon group, and R and UU represent polyurethane-
Represents urea resin. ) CI-R"-CI + KOH-
→ C1-R'-0Hp" pl+ (However, in the formula, R and R' represent a divalent hydrocarbon group, and R
” represents a monovalent hydrocarbon group such as an alkyl group, and RPLltl represents a polyurethane-urea resin.) As described above, the -COOM group and the quaternary ammonium salt can be respectively introduced into the polyurethane-urea resin. can.

The magnetic recording medium according to the present invention is made by introducing a -COOM group and a quaternary ammonium salt into a polyurethane-urea resin used as a binder for magnetic paint. Therefore, in order to introduce two types of hydrophilic polar groups consisting of -Co and quaternary ammonium salt, the following procedure may be used.

(1) 10OOH in the raw material of polyurethane-urea resin
A method of containing a compound having a group and a compound having a quaternary ammonium salt, and introducing these -COOM groups and the quaternary ammonium salt simultaneously with the production of a polyurethane-urea resin.

(II) By modifying the monoOH group present in the side chain or terminal of the polyurethane-urea resin that has already been synthesized, -
Method of introducing COOM group and quaternary ammonium salt.

(I [[) 100% in the raw material of polyurethane-urea resin
contains a compound having a 0M group, thereby -C
A method of introducing a quaternary ammonium salt by modifying the terminal or side chain 10H group of an OOM group-containing polyurethane-urea resin.

(IV) A compound having a quaternary ammonium salt is contained in the raw material of the polyurethane-urea resin, and the terminal or side chain 10H group of the resulting quaternary ammonium salt-containing polyurethane-urea resin is modified. Te-CO
Method of introducing OM group.

For example, in the case of method (I), a long chain polyester diol containing a quaternary ammonium salt is used as a part of the long chain diol, and a short chain diol containing a -C00M group (e.g. dimethylolpropionic acid) is used as a part of the long chain diol. A polyurethane-urea resin may be synthesized by reacting the mixture with an organic diisocyanate in advance to prepare an isocyanate group-terminated prepolymer, and then adding an organic diamine to carry out chain extension and introduction of urea groups.

In addition, in the case of method (II), -COOM groups are first introduced into a part of the 1OH groups existing in the side chains or terminals of the polyurethane-urea resin that has already been synthesized, and then the remaining 10H A quaternary ammonium salt may be introduced into the group.

By the method described above, the -cooFI group and the quaternary ammonium salt can be easily introduced into the polyurethane-urea resin.

The amount of hydrophilic polar groups introduced into the polyurethane-urea resin used as a binder is preferably such that the sum of the -CO quaternary ammonium salt is 0.01 to 1.5 mmo#/g, More preferably 0.01 to 0.5
m moC/g range. The amount of -C00M group introduced is preferably 0.01 to 0.5 mmof/g. If it is less than 0.01 mmol/g, the dispersibility effect will be insufficient, and 0.5 mmol/g is preferable. If it is exceeded, the viscosity of the paint increases, resulting in deterioration of workability and deterioration of the surface properties of the resulting magnetic recording medium. On the other hand, the amount of introduced quaternary ammonium salt is O,OO1m m
It is preferable that it is 017g or more, and 0,001m
If mai is less than 17 g, the effect of preventing increase in paint viscosity will be insufficient. Furthermore, the sum of the introduced amounts of the above-mentioned CO surrounding group and the hydrophilic polar group consisting of the quaternary ammonium salt is 0.
If it is less than 0.01 mmon/g, no sufficient effect will be observed on the dispersibility of the ferromagnetic powder, and if the amount of the hydrophilic polar group introduced exceeds 1.0 mmon/g, intermolecular or intramolecular aggregation is likely to occur. This not only adversely affects the dispersibility, but also causes selectivity to the solvent, and there is a possibility that ordinary general-purpose solvents may no longer be usable.

Further, the number average molecular weight of the above-mentioned polyurethane-urea resin is 2000 to 60000, more preferably 5000 to 4.
Preferably, it is in the range of 0000. If the number average molecular weight is less than 2,000, the coating film-forming ability of the resin will be insufficient, and if the number average molecular weight exceeds 60,000, problems may occur during paint manufacturing processes such as mixing, transferring, and coating. be.

The aforementioned polyurethane-urea resin can be used with other thermoplastic resins,
It can be used in combination with thermosetting resins or reactive resins.

The thermoplastic resin has a softening temperature of 150°C or less,
The average molecular weight is 10,000 to 200,000 and the degree of polymerization is approximately 2.
00 to about 20,000, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer.

Vinyl chloride-vinyl acetate-maleic acid copolymer.

Vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester - styrene copolymer,
Thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyamide resin.

Polyvinyl butyral, cellulose derivatives, styrene
Synthetic rubber resins such as butadiene copolymers and polyester resins include polybutadiene.

Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, silicone resins, acrylic reactive resins, and epoxy resins. Polyamide resin, nitrocellulose-melamine resin.

Mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanate.

Examples include polyamine resins and mixtures thereof. Among these, it is desirable to use in combination with those that have good dispersibility in ferromagnetic powder.

In the magnetic recording medium of the present invention, the magnetic layer is formed by coating the surface of the non-magnetic support with a magnetic paint prepared by, for example, dispersing ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent.

Here, as the ferromagnetic powder used in the present invention, any ordinary magnetic powder can be used. Therefore, usable ferromagnetic powders include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powders, macrogonal barium ferrite particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those having a value of X in the range of 33≦X≦1.50 when expressed by the general formula FeOx, that is, magnetite Cr Fezo.

X = 1.50>, magnetite (Fe, O,, X =
1.33) and their isosolutes (FeOx, 1.33
<X<1.50). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.

As the above-mentioned ferromagnetic chromium dioxide, CrO□A3 Ru is added to these for the purpose of improving coercive force.

A material to which at least one of Sn, Te, Sb, Fe, Ti, V, Mn, etc. is added can be used.

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fe-Ni, Fe-Co-Ni, C.

-Ni, Fe-Co-B, Fe-Co-Cr-B.

Mn-B1. Mn-Aj! , Fe-Co-V, etc. can be used, and Aj! ,
Metal components such as St, Ti, Cr, Mn, Cu, and Zn may be added.

In addition to the binder and ferromagnetic powder, the magnetic layer also contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent,
Rust inhibitors and the like may also be added.

The above dispersants (pigment wetting agents) 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 (RlCOOH, R1 is an alkyl or alkenyl group having 11 to 17 carbon atoms) such as lyrinnic acid and stearolic acid, alkali metal salts of the above-mentioned fatty acids (Li, Na).

etc.) or alkaline earth metal salts (Mg+ Ca, B
Metal soaps consisting of a), amides of the aforementioned fatty acids, polyalkylene oxide alkyl phosphates, trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefins include ethylene, propylene, etc.) are used. Ru. In addition, higher alcohols having 12 or more carbon atoms, sulfuric esters, etc. can also be used. These dispersants are used in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.
It is added in a range of parts by weight.

Examples of the lubricant include dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms) and dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms).

Silicone oil such as monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has 1 to 4 carbon atoms), phenylpolysiloxane, fluoroalkyl polysiloxane (alkyl has 1 to 5 carbon atoms), graphite Conductive fine powder such as molybdenum disulfide, tungsten disulfide, etc., inorganic fine powder such as polyethylene, polypropylene.

Polyethylene vinyl chloride copolymers, fine plastic powders such as polytetrafluoroethylene, α-olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature (compounds in which an n-olefin double bond is bonded to the terminal carbon, carbon number about 2
0), fatty acid esters consisting of a fatty acid having 12 to 22 carbon atoms and an alcohol having 3 to 22 carbon atoms (either a monoester or a diester triester may be used, or a polyester having a higher polyfunctionality may be used). ), fatty acids or their metal salts, fatty acid amides, fatty alcohols or their alkoxides, aliphatic amines, polyhydric alcohols, sorbitan esters, manniratan esters, sulfurized fatty acids, aliphatic mercaptans, perfluoroalkyl ethylene oxides, perfluoropolyethers , higher alkylsulfonic acids or metal salts thereof, perfluoroalkylsulfonic acids or ammonium salts thereof or metal salts thereof, perfluoroalkylcarboxylic acids or metal salts thereof, fluorocarbons, etc. can be used. These lubricants are added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.

As the abrasive, commonly used materials such as fused alumina, silicon carbide, chromium oxide (Crz03), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite) are used. Ru. These abrasives have a Mohs hardness of 5 or more and an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are used in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.
It is added in a range of parts by weight.

As the antistatic agent, carbon blank is used.

Conductive fine powder such as carbon black graft polymer,
Natural surfactants such as saponin, nonionic surfactants such as alkylene oxide, glycerin, and glycidol, and higher alkylamines.

Quaternary ammonium salts, pyridine and other heterocycles,
Cationic surfactants such as phosphoniums, carboxylic acids,
Anionic surfactants containing acidic groups such as sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups, amino acids,
Ampholytic activators such as aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, etc. are used. The above conductive fine powder is 0.2 to 2 parts by weight per 100 parts by weight of the binder.
In the range of 0 parts by weight, surfactants are added in the range of 0.1 to 10 parts by weight. These surfactants may be added alone or in combination. These are used as antistatic agents but are sometimes used for other purposes, such as dispersion,
It may also be used to improve magnetic properties, improve lubricity, and as a coating aid.

As the rust preventive agent, phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used, but in particular, dicyclohexylamine nitrite,
Volatile rust inhibitors (amine, When an inorganic acid salt or an organic acid salt such as amide or imide is used, the rust prevention effect is improved. These rust inhibitors are used in amounts of 0.01 to 20 parts by weight per 100 parts by weight of ferromagnetic fine powder.
Used in parts by weight range.

The constituent materials of the magnetic layer described above are prepared as a magnetic paint by dissolving it in an organic solvent, and are applied onto a non-magnetic support.
Solvents for the magnetic paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl acetate, glycol dimethyl ether, and glycol monoethyl ether. Glycol ethers such as ether and dioxane, aromatic hydrocarbons such as benzene, toluene, and xylene,
Aliphatic hydrocarbons such as hexane and heptane, methylene chloride, and ethylene chloride.

Tetracarbonized carbon L chloroform, ethylene chlorohydrin,
Examples include chlorinated hydrocarbons such as dichlorobenzene.

The material of the non-magnetic support to which these constituent materials are coated may be any material that is normally used in this type of magnetic recording medium, such as polyethylene terephthalate, polyethylene-2,6-naphthalate, etc. polyesters such as polyethylene, polyolefins such as polypropylene, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate,
Cellulose derivatives such as cellulose acetate propionate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, and polyimide.

Plastics such as polyamide and polyamide-imide, non-magnetic metals such as aluminum, copper, tin, zinc or non-magnetic alloys containing these, light alloys such as aluminum alloys and titanium alloys, ceramics, and pottery.

Ceramics such as porcelain, single crystal silicon, and paper.

Baryta or polyethylene, polypropylene.

Paper such as paper coated with or laminated with an α-polyolefin having 2 to 10 carbon atoms such as an ethylene-butene copolymer can be used. The forms of these non-magnetic supports are as follows:
Film, tape, sheet.

It may be a disk, card, drum, etc.

[Effect]

As mentioned above, by using a polyurethane-urea resin with a -COOM group and a quaternary ammonium salt introduced into the molecule as a binder, the affinity for magnetic powder is greatly improved, resulting in ultrafine magnetization. Even large amounts of magnetic powder are well dispersed.

In particular, by introducing a quaternary ammonium salt together with the -C00M group, durability and viscosity characteristics of the binder can be improved.

Furthermore, by using polyurethane-urea resin as a binder, the thermal properties of the magnetic layer, blocking resistance,
This makes it possible to significantly improve durability, which has great benefits in the manufacturing process.

〔Example〕

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

First, a polyurethane-urea resin into which a C00M group and a quaternary ammonium salt were introduced was synthesized by the method described herein. Table 1 shows the properties of the synthesized polyurethane-urea resin.

(Leaving space below) S]l Coarse 1 Magnetic paint composition Ferromagnetic powder 100 parts by weight (specific surface area 35%/g, Co-adhered Fezes) Vinyl chloride-vinyl acetate copolymer 10 parts by weight Binder 1
10 parts by weight Lubricant (silicone oil) 0.5 parts by weight Dispersant (lecithin) 0.5 parts by weight Abrasive agent (CRZO*) 2 parts by weight Antistatic agent (carbon) 2 parts by weight Rust inhibitor (butyl stearate) 0.5 parts by weight Methyl ethyl ketone 110 parts by weight Methyl isobutyl ketone 50 parts by weight Toluene
50 parts by weight The above composition was mixed in a ball mill for 48 hours, filtered, and then added with 3 parts of a curing agent (manufactured by Nippon Polyurethane Co., Ltd., trade name: Coronet L).
Add part by weight, mix for another 30 minutes, and add 16 μm
It was coated so that the poly thickness was 6 μm. Next, after performing a magnetic field orientation treatment, it was dried and wound up. This was calendered and then cut into 1/2 inch width to produce sample tapes.

Examples 2 to 8 Sample tapes were prepared in the same manner as in Example 1 except that Binder 2 to Binder 8 were used in place of Binder 1 in the composition of Example 1.

$+ 1 to 8 Sample tapes were prepared in the same manner as in Example 1 except that Binder 9 to Binder 16 were used in place of Binder 1 in the composition of Example 1.

Surface gloss, powder removal, paint viscosity, and adhesion were measured for each sample tape obtained.

The above surface gloss was measured using a gloss meter (GLO3S METE).
R) under the conditions of an incident angle of 60'' and a reflection angle of 60°.In addition, the amount of powder falling on the head drum, guide, etc. was visually observed after running the shuttle 100 times for 60 minutes. The viscosity of the paint was determined by the point deduction method (-5 to 0).
The values shown are those measured using a No. 4 rotor at 30 rotations using a type rotational viscometer. Adhesive properties were determined by wrapping a sample tape around a reel and leaving it for 24 hours at a temperature of 40°C and a humidity of 80%, and visually evaluating the degree of peeling of the sample tape.
It was scored on a 10-point scale, and the better the adhesive properties, the lower the score.

The measurement results are shown in Table 2.

(Left below) Table 2 As is clear from the results in Table 2, each example according to the present invention not only has excellent surface gloss, powder removal, and adhesive properties, but also has low paint viscosity and is easy to work with. It can be seen that the paint has excellent properties.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
A -COOM group is introduced into the polyurethane-urea resin molecule and a quaternary ammonium salt is introduced, which is used as a binder, so it shows a high affinity for magnetic powder, even if it is made into ultra-fine particles. Even if the magnetic powder has a large amount of magnetization, the dispersibility is good.

Furthermore, the polyurethane-urea resin used as the binder has excellent heat resistance and adhesive properties, so it is possible to significantly improve the thermal properties, blocking resistance, and durability of the magnetic layer.

Therefore, the properties of the coating film when formed as a magnetic layer are improved, resulting in a magnetic recording medium with extremely excellent durability, surface properties, and electromagnetic conversion characteristics.

In addition, polyurethane-urea resin is easily dissolved in general-purpose solvents, and paints containing this binder have low viscosity and are easy to handle, so they have excellent properties in terms of workability when forming coatings. has.

Patent applicant: Sony Corporation Agent Patent Attorney Akira Koba Same Enso Sakae Procedural master's letter (spontaneous) May 8, 1986

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer mainly consisting of ferromagnetic powder and a binder is formed on a non-magnetic support, the binder has a --COOM group (where M is A magnetic recording medium comprising a polyurethane-urea resin having a hydrogen atom or an alkali metal atom) and a quaternary ammonium salt.