JPS62209176A - Binding dispersant for magnetic recording material - Google Patents

Abstract

PURPOSE:The titled dispersant providing a magnetic recording material having improved traveling stability, ratio of S/N, etc., eliminating aggregation of magnetic component, improving dispersibility, comprising a salt of a copolymer of a specific monomer such as isobutylene, etc., and maleic acid (anhydride). CONSTITUTION:(A) At least one monomer selected from isobutylene, styrene and acrylic acid ester is reacted with (B) maleic acid (anhydride) and, if necessary, in the presence of a solvent such as ethylbenzene, etc., and a catalyst such as benzoyl peroxide, etc., at 45-200 deg.C for 1-10hr to give a copolymer (salt) having preferably 1,000-200,000 number-average molecular weight. The aimed dispersant comprising the copolymer (salt).

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a binding and dispersing agent for magnetic recording materials, and more specifically, it relates to a binding and dispersing agent for magnetic recording materials, which is applied to a support such as a plastic film to produce a magnetic recording material. A binding dispersion for magnetic recording media that can prevent agglomeration of magnetic components in the composition to improve dispersibility when preparing the composition, and also improve storage stability of the prepared composition. Regarding drugs.

[Prior art and problems to be solved by the invention] Generally, magnetic tapes for video, magnetic tapes for recording, magnetic tapes for computers, and magnetic disks.

Magnetic recording bodies such as magnetic drums and magnetic cards are constructed by applying a composition containing a magnetic material such as γ-iron oxide as a main component to a support such as a plastic film or disk. A binding and dispersing agent is used to bind the magnetic material to the support and to uniformly disperse the magnetic material in the magnetic composition.

This binding and dispersing agent is usually prepared by kneading it with water. Conventionally, casein has been frequently used as this binding and dispersing agent, but this agent causes agglomeration of magnetic substances when preparing the composition. It was easily dispersed and had poor dispersibility. Furthermore, if the composition is left to stand after preparation, the viscosity increases, causing a decrease in storage stability.

The present inventor has conducted extensive research in order to develop a binding and dispersing agent that can solve the above-mentioned problems that occur during the preparation of this magnetic composition.

[Means for solving problems]

As a result, it was found that the purpose could be achieved by using a salt of a copolymer made of a specific monomer as a binding and dispersing agent.

That is, the present invention provides a binding and dispersing agent for a magnetic recording medium comprising a salt of a copolymer of at least one monomer selected from isobutylene, styrene, and acrylic acid ester and maleic acid or its anhydride. It is.

The copolymer in the present invention is as follows. That is, isobutylene units (IB) represented by the following formulas; styrene units (ST) represented by the following formulas; and acrylic units represented by the following formulas (wherein R represents a lower alkyl group, preferably a methyl group). A copolymer whose constituent units are a few (one type of constituent unit) selected from acid ester (AM) units and a maleic acid unit represented by the following formula or a maleic anhydride unit (MA) represented by the following formula. Specifically, IB-MA copolymer, ST-
Binary copolymers such as MA copolymers and AM-MA copolymers; ternary copolymers such as IB-3T-MA copolymers, IB-AM-MA copolymers, and ST-AM-MA copolymers; Examples include polymers and IB-3T-AM-MA quaternary copolymers. These copolymers are block copolymers.

It may be an alternating copolymer, a graft copolymer, or a random copolymer. These copolymers usually have a number average molecular weight of 500 to 4QQ, QQO, and preferably a number average molecular weight of t,ooo to 200.000. Furthermore, the copolymer has a number average molecular weight within the above range, and a content ratio of (anhydride) maleic acid units, which are essential constitutional units, to the copolymer is 5 to 50 mol%.
, particularly preferably 10 to 50 mol%.

The copolymer in the present invention is produced, for example, as follows. That is, when each copolymer component or isobutylene is used, a predetermined amount of each copolymer component except isobutylene is charged into a reaction vessel, and usually cooled and sufficiently degassed. Next, when isobutylene is used, the copolymerization reaction is carried out while stirring after adding isobutylene. At this time, the reaction temperature was 30~200℃,
Preferably, the temperature is set at 45 to 200°C, and the reaction time is set at 0.5 to 20 hours, preferably 1 to 10 hours.

In this copolymerization reaction, ethylbenzene, cumene, n-butylbenzene, etc., a mixture thereof, acetonitrile, nitromethane, etc. are used as necessary.

Nitroethane, methyl ethyl ketone, acetone.

Solvents such as N,N-dimethylformamide, dimethyl sulfoxide, benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tertiary butyl hydroperoxide, dicumyl peroxide.

Catalysts such as azobisisobutyronitrile can be used. When using a catalyst, the amount used is especially ff1i
However, it is usually 0 parts per 100 parts by weight of total monomers.
．． 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight. The catalyst may be used as is or diluted. Further, the catalyst may be added in its entirety at the beginning of the polymerization, or may be added in portions during the polymerization.

Thereafter, the copolymer thus obtained is neutralized with an alkali to produce a copolymer salt. The alkali used at this time is sodium hydroxide,
Preferred are alkali metal compounds such as potassium hydroxide, sodium carbonate, and sodium acetate; ammonia, ammonium hydroxide, urea, thiourea, and organic amines. The reaction temperature of this neutralization reaction is preferably set to 20 to 150°C, and the reaction time is preferably set to 0.5 to 10 hours.

Here, the degree of neutralization preferred for the salt of the copolymer in the present invention is 0.3 to 1.02, particularly 0.4 to 1.0.

The salt of the copolymer in this invention includes a salt that is partially salt and partially ester.

The binding and dispersing agent for magnetic recording bodies of the present invention is used for magnetic recording bodies, but more specifically, it can be applied to supports such as Plus 7AIL/A, Chifugu 1st, Disk≠Water, etc. It is a binding and dispersing agent that is added to prepare a magnetic composition for forming a magnetic layer. This magnetic material composition contains a magnetic material as a main component, and the magnetic material component here is a magnetic tape for video, a magnetic tape for recording, and a magnetic tape for computers.

Any material used in various magnetic recording bodies such as magnetic disks, magnetic drums, and magnetic cards may be used.

For example, iron oxides such as T-iron oxide and triiron tetroxide, nickel, cobalt manganese, titanium, palladium, osmium, etc. are added to these, chromium oxide, pure iron, and various iron-based alloys. ferromagnetic materials can be mentioned.

By mixing and stirring the binding and dispersing agent of the present invention with the above-mentioned magnetic component and other additives, a magnetic composition in which the magnetic component is uniformly dispersed can be obtained.

The proportion of each component in this magnetic composition is not particularly limited and may be determined depending on various situations, but usually the magnetic component is 50 to 99.95% by weight9.9 Binding and dispersing agent of the present invention 0.0
5 to 50% by weight is suitable.

Further, the binder/dispersant may be added in the entire amount mentioned above at once and mixed with the magnetic component, etc. to prepare a composition, or a part of the blended amount may be used as a dispersant to prepare the magnetic component, etc. The mixture may be prepared by mixing and stirring the mixture, and then mixing and stirring the remaining amount as a binder with the mixture. In the latter case, the amount used as a dispersant is usually about 10 to 80% by weight of the magnetic material component.

Furthermore, the binding and dispersing agent of the present invention can also be used as a dispersing agent when other compounds are used as the binding agent.

If this magnetic composition is applied to the surface of a support such as a plastic film and dried, a magnetic recording material having a magnetic layer on the surface can be obtained.

The support to which the magnetic composition is coated may be arbitrarily selected from among the supports used in known magnetic recording bodies. Typically, films, disks, cards, etc. made of polyester, polyamide, polycarbonate, etc. are preferred.

〔Effect of the invention〕

As mentioned above, when the binding and dispersing agent for magnetic recording materials of the present invention is blended with the magnetic component, compared to casein etc. that have been conventionally used as a binding and dispersing agent, it is difficult to prepare the magnetic composition. Since agglomeration of magnetic components is almost eliminated, dispersibility is improved, and therefore, magnetic recording bodies manufactured using this composition have good running stability.

Performance such as S/N ratio is improved.

Further, by using the binder-dispersing agent of the present invention, the upper limit of viscosity over time after the preparation of the composition can be suppressed, so that the composition has high storage stability.

Therefore, the binding and dispersing agent for magnetic recording bodies of the present invention is useful in the field of manufacturing magnetic recording bodies.

〔Example〕

Next, the present invention will be explained in detail with reference to examples.

Examples 1 to 7 Into an autoclave having an internal volume of 11, isobutylene was removed (components shown in Table 1 were charged in predetermined amounts), and the autoclave was cooled to -10°C and the inside of the container was sufficiently degassed.

Next, when using isobutylene, add a predetermined amount of it, add 460 cc of acetonitrile as a solvent, 0.6 g of benzoyl peroxide as a catalyst, and heat at 400 rpm T: FA.
A copolymerization reaction was carried out at 110° C. for 2 hours with stirring, and then the product was poured into water to obtain a copolymer. Number average molecular weight, isobutylene unit amount, and styrene unit amount of the obtained copolymer.

The amount of methyl acrylate units and maleic acid units are the first
Shown in the table.

After that, an amount of thorium hydroxide aqueous solution was added to this copolymer in an amount that would give a neutralization degree of 1, so that the concentration was 20% by weight.
The mixture was closed and neutralized at 90° C. for 6 hours to prepare a copolymer salt.

A magnetic composition was produced using the copolymer salt prepared as described above. That is, 0.5 parts by weight of the salt of the above copolymer as a dispersant and 150 parts by weight of water were added to 100 parts by weight of γ-iron oxide, and the mixture was heated at 25°C using a ball mill for 6 hours.
Kneaded for hours. Next, 30 parts by weight of the salt of the above copolymer was added as a binder to this kneaded product, and the mixture was stirred at 25° C. for 5 minutes to obtain a magnetic composition. γ when preparing this composition
- Aggregation of iron oxide (magnetic material) was visually observed.

In addition, the viscosity of this composition was measured at the time of preparation and after being left for 2 days. Table 1 shows these results and the performance test results of a video magnetic tape (support: polyester film) prepared by applying the composition to a thickness of 8 μm.

Comparative Example A magnetic composition was prepared in the same manner as in the example except that casein was used instead of the copolymer salt prepared in the example. During the preparation of this composition, considerable aggregation of T-iron oxide (magnetic material) was observed.

Further, the viscosity index of this composition was measured in the same manner as in the examples, and was 2.5, which was larger than that in the examples. Further, the performance of a video magnetic tape produced in the same manner as in the example using this composition was tested in the same manner as in the example, and the S/N ratio was +3.8 dB and the running stability was 0. It was 20%.

Claims (2)

[Claims] (1) A binding and dispersing agent for a magnetic recording medium comprising a salt of a copolymer of at least one monomer selected from isobutylene, styrene and acrylic ester and maleic acid or its anhydride. (2) The binding and dispersing agent for a magnetic recording medium according to claim 1, wherein the salt of the copolymer is selected from alkali metal salts, ammonium salts, and amine salts.