JPH01137428A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics and durability by using a polyurea/urethane resin contg. >=2 hydroxyl groups in one molecule as a binder component. CONSTITUTION:The polyurea/urethane resin formed by using the diisocyanate contg. the hydroxyl groups in the molecule at the quantity larger by 2 pieces on one molecule in average and having a cyclic structure as a material as well a polyisocyanate compd. and at least one kind of a vinyl chloride resin and nitrocellulose are used as the binder component of a magnetic recording medium contg. the polyurea/urethane resin having the hydroxyl groups in the molecule as the binder component. The crosslinkability in a coated film is poor and, therefore, the durability is poor if the quantity of the hydroxyl group in one molecule is <=2 pieces in average. The quantity of the hydroxyl groups in one molecule larger than 2 pieces is more preferable in terms of electromagnetic conversion characteristics. The recording medium having the excellent electromagnetic conversion characteristics and durability is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a coated magnetic recording medium composed of a magnetic layer and a support, and more particularly to improvements in the binder thereof.

[Conventional technology]

Traditionally 1? The binder of the β-certified magnetic recording medium includes, for example, vinyl chloride, vinegar, vinyl alcohol copolymer, nitrocellulose, etc.
Polyester resins, polybutyral resins, polyester resins, polyurethane resins, etc. were used singly or as a mixture.

In response to the world's needs for higher recording densities and improved durability of magnetic recording media, the use of ternary binders such as vinyl chloride resin or nitrocellulose, polycrethane resin, and polyisocyanate compounds was adopted. There is a lot of screaming. As for magnetic powder, we need to make it finer and move from iron oxide to metal or perpendicular magnetic recording.
It is transitioning to the A-7 Elite series. Under these current circumstances, the above combination of binder and magnetic powder
In order to improve the electromagnetic conversion characteristics and durability, which did not meet the required performance.

The use of a polyurea-urethane resin containing -CO*Mt-505M (M:H or alkali gold r14) has been proposed (JP-A-61-107531). When such polyflare urethane resin containing -C01M and -805M is used, the electromagnetic conversion characteristics are satisfied, but the durability cannot be said to be sufficiently improved.

[Problem that the invention seeks to solve]

This invention is possessed by the above-mentioned conventional binder.

The object of the present invention is to solve the problem that the dispersibility and mechanical strength of magnetic powder cannot be satisfied at the same time, and thereby provide a magnetic recording medium with excellent electromagnetic conversion characteristics and durability.

[Means to solve the problem]

As a result of intensive study, the present inventors found that -COsM* -8
It has been found that the reason why the durability is insufficient when a polyflare urethane resin containing 05M is used is that its crosslinkability is lower than that of a polyurethane resin. The reason for this is thought to be that urea bonds have higher cohesive force than urethane bonds, making it difficult for the molecular chain to move. To improve the crosslinking properties of such motion-averse molecular chains.

Although it is possible to introduce into the molecule a functional MM group that reacts with the incyanate group, such as a hydroxyl group or an amino group, it has been found that amino groups are not preferred in view of the pot life of the paint. In addition, -CO*AIL-805M contributes to improving the dispersibility or dispersion stability of paints, and is said to be effective in improving the electromagnetic conversion characteristics of final products and magnetic recording media. It was found that even when flare urethane resin is used, effects similar to those of -C05M and -805M can be obtained depending on the amount of the resin, and a medium having electromagnetic conversion characteristics equivalent to or better than that of -C05M and -805M can be obtained.

That is, one aspect of the present invention is a magnetic recording medium containing a polyurea-urethane resin having hydroxyl groups in its molecules as a binder component. More specifically, polyurea-urethane resins and polyisocyanate compounds using diisocyanates with a ring structure, which have an average of more than two hydroxyl groups f in their molecules, and polyisocyanate compounds, vinyl chloride resins, and nitrocellulose. This is a magnetic recording medium using at least xtm* as a binder component.

If the average amount of hydroxyl groups per molecule is less than 2, the crosslinkability in the coating film will be poor, resulting in poor durability. From the viewpoint of electromagnetic conversion characteristics, it is preferable that the amount of hydroxyl groups in one molecule is greater than two.

The urea bond of such a polyurea-urethane resin is generated by a reaction between a diisocyanate and a polyamine or water, and the urethane bond is generated by a reaction between a polyol and a diisocyanate.

Among these materials, diisocyanates have a ring structure t-M from the viewpoint of ms durability.
I), diphenylmethane diisocyanate (MDI)
), inphorone diisocyanate (IPDI), and 7tale diisocyanate are preferred, and from the viewpoint of electromagnetic conversion characteristics, HtsMDI, MDI, and IPDI are preferred.

From the point of view of a rare bond conductor material, polyamines are much more preferable. This is because when polyamine is used, urea bonds are formed adjacent to each other, which may be the reason why the coating has good durability. Boliankin like this.

Examples include ethylenediamine, tetramethylenecyamine, hexamethylenecyane, 2.2.4-)limethylhexamethylenecyphene, methylcyclohexyldiamine,
Examples include 4.4'-dicyclohexyldiamine and isophoronediamine.

The polyol of the urethane bonded material includes conventionally known polyols, such as polyester diols such as polybutylene adipate, polyethylene adipate, and polyhexamethylene adipate, polycarbonate diols such as polykab a2 chton diol, polynato 2 methylene glycol, and polypropylene glycol. Examples include ether diols, polycarbonate diols, ethylene glycol, 1,4-butanediol, hexamethylene diol, and octanediol, and these may be used alone or in combination.

By the way, regarding the introduction of hydroxyl groups, for example, triols having alcohol groups of different series in the polyol of the urethane bonded material, such as glycerin and an ethylene oxide adduct of glycerin.

2-Methylpropane-1,2,3-triol.

4-[bis(2-hydroxyethyl 3)-2hydroxypentane, 3-methylpentane-1,3゜5-triol, 1,2,6-hexanetriol, N-impCl
There is a method of introducing alcohol using halogen diethanol alcohol, taking advantage of the difference in reaction rate between an isocyanate group and a primary alcohol, an isocyanate group and a secondary alcohol, or an acidic tertiary alcohol. It may be possible to use a polyamine having an alcohol group in the flare-bonded Hijin material and introduce it by utilizing the difference in reaction rate between the amino group and the incyanate group of the alcohol group.

Synthesized hydroxyl group-containing polyurea
Regarding magnetic powder for magnetic recording media having a magnetic layer containing urethane resin as a binder component, conventionally known 7-Fez
es, Co-coated 7-FelOs, iron oxides such as Fax04, Fe, Fe-Ni, Fe-Co, Co-
Ni.

Metal-based powders such as Fe-Co-Ni, Cr(h and Ba-7 elite powders) can be used.Especially when iron oxide based magnetic powders are used, the BET specific surface area is 40.
rr1711 or higher, #1BE when using metal-based materials
T specific surface area 45 dl1 or more, Cro! When using BET specific surface area of 30rr//I or more, the durability was improved as reported in #t1 by iA.

In addition to magnetic powder and binder, magnetic J- contains, for example,
Alumina powder, Cr! Abrasives such as Os powder and red iron oxide, antistatic agents such as carpump 2, conductive curved lead flower, and lubricants such as fatty acids, fatty acid esters, and silicones may be added as necessary.

An example of synthesis of polyurea-urethane resin is shown. Synthesis example 1~
4L, polyurea-urethane resin with a large amount of hydroxyl groups, Example 5.6 is a synthesis example of a polyflare urethane resin with a small amount of hydroxyl groups.

[Synthesis Example 1] 524 parts of methylene bis(4-7 chlorohexyl isocyanate) and 2-butanone SOO parts were placed in a 81-sized Loftusco equipped with a thermometer, stirrer, 2 condensers, and heated to a temperature in an N8 gas stream. After heating to 60°C, add 1000 parts % of polybutylene adipate diol (molecular weight 1000) while stirring.
A mixed solution of 22.5 parts of 1.4-butanediol, 40.75 M of N-inglovir diethanolamine, 0.05 part of tin 1-refk acid, and 771,500 parts of 2-butane was heated to a temperature of 60°C in the reaction system. It was dripped in a controlled manner. After the dropwise addition was completed, the mixture was heated to 70°C for 30 minutes, and then 34.8 parts of hexamethylene diamine was added dropwise while controlling the temperature in the entire reaction system to be 70°C. After reacting at a temperature of 75° C. for 3 hours, 10 parts of ethanolamine was added and the reaction was further continued for 2 hours. Add 1,810 parts of 2-butanone to this, and the solid content is 3
Diluted to 0%. The hydroxyl value of the resulting resin was 15 parts gK.
It was OH/I.

[Synthesis Example 2] 5 methylene bis(4-cyclohexyl isocyanate) was placed in 87!04 flasks similar to those used in Synthesis Example 1.
Add 24 parts and 2-butanone SOO parts.

After heating to a temperature of 50°C in a Ns stream, polybutylene adipate diol (molecular fi 1000) 100
A mixture of 0 parts, 11.3 parts of 1,4-butanediol, 61.2 parts of N-ingulovir diethanolamine, 0.05 parts of tin octylate, and 1500 parts of 2-butanone was heated to 50°C in the reaction system. Control the ttC and drip so that After the addition was completed, stir at 60°C for 1 hour.

Subsequently, 34.8 parts of hexamethylene cyanide was added while controlling the temperature in the reaction system to be ≠60°C.

After heating at 65°C for 30 minutes, the mixture was reacted at 75°C for 3 hours, and 11 parts of ethanolamine was added thereto, followed by further reaction for 2 hours. To this was added 1810 parts of 2-butanone to dilute the solid content to 30%. The hydroxyl value of the obtained resin was 20m9KOH/
It was g.

[Synthesis Example 3] Methylene bis(4-7 chlorohexyl incyanate)) 52 was added to the four strands of 81 used in Synthesis Example 1 and the open collar.
Add 4 parts and 2-butanone SOO parts.

After heating to 65°C in an air stream for 1 hour, 1000 parts of polybutylene adipate diol (molecular weight 1000), 33.8 parts of 1,4-butanediol, and 20 parts of N-ingropanol diethanolamine were added while stirring. A mixture of 3 parts of tin octylate, 0.05 parts of tin octylate, and 1500 parts of 2-butanone was added dropwise to the reaction system while controlling the temperature at 65°C.

After completion of the dropwise addition, the mixture was heated at 70°C for 30 minutes, and then 34.8 parts of hexamethylene diamine was added dropwise while controlling the temperature inside the reaction system to be 70°C. After reacting at 75°C for 3 hours, 1° of ethanol was added and the reaction was further continued for 2 hours. Add 181 (l) of 2-butanone to this to obtain a solid content of 3
Diluted to 0%. The hydroxyl value of the obtained resin was 10■KO
It was H/11.

[Synthesis Example 4] 52 methylene bis(4-cyclohexyl isocyanate) was placed in a 81 4-bottle flask similar to that used in Synthesis Example 1.
4 parts, 5 oost of 2-butanone.

Mff1. Polybutylene adipate diol (molecular weight 1000) 1000 while stirring
parts, 40.5 parts of 1.4-p7 diamine, 8.1 parts of N-ingropanol, and 0.05 parts of tin octylate.

A mixed solution of 1,500 parts of 2-butanone was heated to t'65°C in the reaction system.
It was dripped in a controlled manner. After completion of the dropwise addition, the mixture was heated to 70'C for 15 minutes, and then 34.8 parts of hexamethylene diamine was added dropwise while controlling the temperature inside the reaction system to be 70C. After reacting at 75°C for 2 hours, 11 parts of ethanolamine was added, and the reaction was further continued for 3 hours.
1 (diluted to a solid content of 30% by adding 1 liter). The hydroxyl group of the obtained chili paste was 8.5?KOH/F [Synthesis Example 5] 4th 7th; methylene bis(4-cyclohexyl inocyanate) 524
500 parts of 2-butanone and heated at 75°C in a Nl stream.
After heating, 1000 parts of polybutylene adipate diol (molecular weight 1000) was added while stirring.

1.4-butanediol 45 parts, tin octylate 0.0
A mixed solution of 5 parts of 2-butanone and 1500 parts of 2-butanone was added dropwise while controlling the temperature in the reaction system to be 75°C.

After the addition was completed, the mixture was stirred at 75°C for 1 hour, and then 34.8 parts of hexamethylene diamine was added dropwise while controlling the temperature inside the reaction system to be 75°C. After reacting at 75° C. for 3 hours, 79 parts of ethanolic acid was added and the reaction was further continued for 3 hours.

1,810 parts of 2-butanone was added to this to dilute it to a solid content of 30%. The hydroxyl value of the obtained resin is a9WgKOH/
It was II.

[Synthesis Example 6] 524 parts of methylene bis(4-cyclohexyl inocyanate) was placed in a four-bottle flask similar to that used in Synthesis Example 1.
Add 500 parts of 2-butanone, heat to 75°C in a Nl stream, and add polybutylene adipate diol (
Molecule 1i1000) 1000 parts, 1,4-butanediol 33.8 parts, 2,2-bis(hydroxymethyl)p-tetrabionic acid 16.7 parts, tin octylate 0.0
A mixed solution of 1,500 parts of 2-butanone was added dropwise while controlling the temperature inside the reaction system to be 75°C. After the dripping is finished,
After stirring at 75°C for 1 hour, 34.8 parts of hexamethylene diamine was added dropwise while controlling the temperature inside the reaction system to be 75°C. After reacting at 75° C. for 3 hours, 711 parts of ethanol was added and the reaction was further continued for 2 hours. To this was added 1810 parts of 2-butanone to dilute the solid content to 30%. Obtained. The hydroxyl value of the sugar beet was 6.8 #KOH/#.

〔Example〕

Examples 1 to 4 Co deposited 7-F@sOs (BET specific surface area 4sm"/
JF) 80 parts chloride, vinyl vinegar, vinyl alcohol copolymer (V manufactured by UCC)
AGH) 10 parts polyurea urethane resin 6 parts Arunna
4 parts carbon black
4-part stearic acid
4 parts n-butyl stearate 8 parts 2-butanone 50 parts cyclohexanone 60 parts toluene
50 parts where polyurea
The urethane ladle obtained in Synthesis Examples 1 to 4 is used. Examples 1 to 4 were given according to the compositions using the resins obtained in Synthesis Examples 1 to 4.

The mixture having the above composition was placed in a ball mill and subjected to mixing and dispersion treatment for 72 hours. and polyisocyanate compounds (
After adding 4 parts of Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) and further stirring for 1 hour, the mixture was filtered to obtain a magnetic paint. This paint was applied onto a polyester film with a thickness of 14 μm and dried while oriented in a magnetic field so that the dry film thickness was 4.5 μm.
Surface smoothing treatment, 5! ! After that, the tape was cut to @l/2 inch to obtain a videotape.

[Comparative Example 1.2] The polyflare urethane resin obtained in Synthesis Example 5.6 was used as the polyflare urethane resin in the compositions in Examples 1 to 4.

Comparative Example 1 was made using the resin of Synthesis Example 5, and Comparative Example 2 was made using the resin of Synthesis Example 6.

Video tapes were obtained in the same manner as in Examples 1 to 4, including the coating manufacturing method and the video tape manufacturing method.

Example 5 BET of Co-coated 7-FesOs in Examples 1 to 4
A videotape was obtained in the same manner as in Examples 1 to 4, except that the specific surface area was changed to 20 to 55 ry,''/I, and the polyurea-urethane resin obtained in Synthesis Example 1 was used. .

Comparative Example 3 Synthesis Example 5 was added to the polyurea-urethane resin in Example 5.
A videotape was obtained in the same manner as in Example 5, except that the same procedure as in Example 5 was used.

Table 1 shows the properties of the polyurea-urethane resins used in Examples and Comparative Examples.

Table 1 [Effects of the Invention] Carrier output, C/N and steal durability of the videotapes obtained in Examples 1 to 4 and Comparative Examples 1.2 were evaluated and compared. For evaluation, a video tape recorder manufactured by Matsushita Electric Industrial Co., Ltd., AC-2000, was used.

Stell durability was evaluated by the time required for the output to drop by 2 dB from the initial output at a temperature of 25° C. and a humidity of 40% RH.

Table 2 shows the results.

Table 2 Carrier output was evaluated as OdB for the videotape obtained in Example 4. From this result, using polyflare urethane resin containing more than two hydroxyl groups in one molecule had better electromagnetic conversion characteristics and durability. It can be seen that it is good.

Furthermore, the running durability of the video tapes obtained in Example 5 and Comparative Example 3 was evaluated. For the evaluation, a video tape recorder AG-2000 manufactured by Matsushita Electric Industrial Co., Ltd. was used, and the evaluation was performed based on the number of runs until the reproduction output decreased by 2 dB from the initial output at a temperature of 25 degrees Celsius, 1M degrees, and 40% RH.

FIG. 1 shows the relationship between the BET specific surface area and running durability of magnetic powder using polyflare urethane resins with different amounts of hydroxyl groups as parameters. According to this, a magnetic powder using a polyurea-urethane resin containing more than two hydroxyl groups in one molecule has good durability, and in particular, when the BET specific surface area of the magnetic powder is 40r1711 or more, the durability is improved. It can be seen that the effect is large.

As explained above, in the present invention, hydroxyl group @
: By using polyurea-urethane resin containing more than 2 parts as a binder component.

A magnetic recording medium with good electromagnetic characteristics and durability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the BET specific surface area and running durability of magnetic powder using different polyurea-urethane resins. Patent applicant: Hitachi Maxell, Ltd. Representative Atsushi Nagai Procedural amendment (method) March 23, 1988

Claims (2)

[Claims] (1) In a magnetic recording medium consisting of a magnetic layer and a support,
The magnetic layer is synthesized from a polyol, an aliphatic amine or water, and a diisocyanate having a ring structure;
A magnetic recording medium comprising a reaction product of a polyurea-urethane resin having two or more hydroxyl groups in its molecule and a polyisocyanate compound. (2) Magnetic recording according to claim (1), characterized in that the diisocyanate of the polyurea-urethane resin synthetic material is at least one of methylene bis(4-cyclohexyl diisocyanate), diphenylmethane diisocyanate, and isophorone diisocyanate. Medium.