JPH0289214A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium which is excellent in the dispersibility of magnetic powder and has the excellent wear resistance, heat resistance and hot water resistance of a magnetic layer by using a polyurethane resin having >=1 COOH groups in one molecule and an arom. polycarbonate structure and polyglycidyl amine as a binder for the magnetic recording medium. CONSTITUTION:The polyurethane resin having >=1 COOH groups per 1 molecule and the arom. polycarbonate structure and the polyglycidyl amine are used as the binder component for the recording layer. Namely, the polyurethane resin having the arom. polycarbonate structure in the main chain having excellent strength and heat resistance is crosslinked by using the polyglycidyl amine which is not affected by moisture. The polyurethane resin having the COOH groups is used in order to assure the crosslinking reaction at this time. The COOH groups in the polyurethane resin constitute the crosslinking points and constitute the powerful adsorption point to the magnetic powder and, therefore, the binder obtd. therefrom is excellent in the adhesiveness to the powder and the dispersibility of the magnetic powder as well. The heat resistance, hot water resistance, strength, and dispersibility are improved in this way, by which the magnetic recording medium having the excellent durability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of use with millet) The present invention relates to magnetic recording media, and more particularly to improvements in binders thereof.

[Conventional technology]

In recent years, there has been an increasing demand for magnetic recording media such as video tapes and floppy disks to have higher densities and faster recording and reproducing speeds.

Because the magnetic wire comes into sliding contact with the magnetic head etc. at a high speed during recording and reproduction, the binder for magnetic recording media must be highly reliable.Note: The binder for magnetic recording media is 411 wear resistant, heat resistant, and hot water resistant.

It is required to have excellent strength and adhesion to magnetic powder. On the other hand, to support high-density recording.

It is also important that the magnetic powder has excellent dispersibility and is a strong binder.

Conventionally, in order to meet these requirements, a polyester polyurethane resin crosslinked with a polyisocyanate has been used. However, polyester polyurethane resin has the drawbacks of insufficient heat resistance and strength, and poor blocking properties. In order to overcome this drawback, there has been a proposal to use aliphatic polycarbonate polyurethane resin as a binder (Japanese Patent Application Laid-open No. 60430/1983).

One reason for this is the use of polyisocyanate as a crosslinking agent. Polyiso7anate reacts quickly with water, so a significant portion of the added polyisocyanate is consumed by reaction with atmospheric moisture, and the crosslinking reaction with the binder does not occur sufficiently.

Also, since the crosslinking rate changes depending on the crosslinking atmosphere, especially humidity, this has also been a cause of variations in properties.

In order to improve the drawbacks of the binders used as polyinocyanate t-crosslinking agents, polyglycidyl compounds, especially polyglycidyl amines, are used to bind CO which is reactive with Epoxy 7 groups.
A method has been proposed for crosslinking polyurethane resins containing functional groups such as O groups in their molecules.
However, even in this case, weakness due to the polyester polyurethane main chain remained, so the improvement was still poor.

[Four problems that the invention attempts to solve]

This invention improves the heat resistance of conventional polyurethane binders:
The object of the present invention is to provide a magnetic recording medium with improved hot water resistance, two-strength, one-component properties, etc., and excellent durability.

[Friendly means of solving problems]

In the present invention, as a binder for magnetic recording media, 1
By using polyurethane resin and polyglycylamine having at least 100 C0OH groups, an aromatic polycarbonate structure, and t-, the magnetic powder has excellent dispersibility.
No wear resistance l1f5 Note, heat resistance.

A magnetic recording medium with excellent hot water resistance was obtained.

That is, a polyurethane resin having an aromatic polycarbonate structure in its main chain, which has excellent strength and heat resistance, is crosslinked using polyglycidylamine, which is not affected by moisture. In order to ensure the crosslinking reaction at this time, a polyurethane masking having COOH&T- is used. Like this rJ! II
i. The strength of the bonding agent, which was concerned about wear resistance, has been increased by adding an 11n structure to the frame.

The heat resistance is higher than that of the binder.

In addition, the C00)I group in polyurethane resin serves as a crosslinking point and a strong adsorption point for magnetic powder, so the obtained binder has good adhesion with magnetic powder and p It also has excellent properties as a magnetic powder, making it a good companion.

Aromatic polycarbonate base and COO group used in the present invention
The manufacturing method is similar to the generally known manufacturing method.

(a) Organic diisocyanate; (b) aromatic polycarbonate diol; (c) chain extender having a COOH group; (d) chain extender having no COOH group.

It is produced by reacting each of the components. The blending ratio of (a), (b) and (e) is adjusted as necessary.

Examples of the organic diisocyanate (a) include toluidine diisocyanate, 4,4 diphenylmethane diinocyanate, hextemethylene diisocyanate), 4,4-dicyclohexylmethane diisocyanate, and inophorone diisocyanate.

The aromatic polycarbonate diol (b) is
It has a main chain with an aromatic polycarbonate structure, and an aliphatic OH group is introduced at the end.

(c) co oH 熾? :As a chain extender.

Dimethylolpropionic acid, dihydroxytartaric acid.

Diols such as tartaric acid, or l,3-cyano-2-carboxypropane, DL-αC diaminopimelic acid, 3,5-diannobenzoic acid, 2,5-diaminopentanoic acid, 2,3-diaminopropionic acid, etc. Diamines can be mentioned.

(d) Cool (as a chain extender that does not have a t-group).

1, 3-7'ropanediol l, 2-propanediol l, 4-butanediol, 1,3-butanediol l, 2-butanediol, l, 5-bentanediol, neopentyl glycol l.

Polyhydric alcohols such as 7-hebutanediol, l,8-octanol, ethylene glycol, diethylene glycol triethylene glycol, l,4-cyclohexanediol, diamines such as ethylene thiamine, tolylene diamine, and water. be.

To synthesize polyurethane resin, ((transfer), (b) 9
Each of the compounds listed as examples of (c) and (c) may be used alone or in combination of two or more. (The nine compounds listed in dl may be used or not. When used, they may be used alone or in combination of two or more.

The polyurethane resin containing aromatic polycarbonate used in the present invention has a number average molecular weight of 1 O, COO~20
1J, COO. Preferably 15,COO~l 00,0
One in the range of 0 U is good.

Polyglycylylaquine is used as a crosslinking agent.

It is a compound with a structure represented by the general formula (%). Generally synthesized from the corresponding amine and epihalohydrin.

The 1-mino group of the intermediate may be further reacted with an epoxy group to form a polymer. Examples include nat-2-glycidyl metaxylene diamine, nat-2-glycidyl anophenylmethane, triglycidyl-p-aminophenol, and the like.

In the present invention, a polyurethane resin having aromatic polycarbonate chains and other binder resins may be used in combination. Examples of the monomer used in combination include nitrocellulose, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, polyvinyl butyral, and phenoxy 7 resin.

The amount of aromatic polycarbonate-containing polyurethane resin fat is preferably 5 to 30 parts per 1 part of ferromagnetic material.

It is desirable to use 0.5 to 30 parts per 100 parts of the polycrethane resin for 1 part of the polyglycyl aban. It may also be used in combination with conventional polyisocyanate compounds as a jAllll agent.

di1 conveniently used in the present invention! +: For the first time, you can use anything that is used for one-way service. That is, γ
-Fe10s, Cot[γ-Foxes, FesO
These include a, Baliuemu ferrite, Fe, Fe-Ni alloy, co-Ni alloy, etc. Also, dialect vJ1so, 71 fatpo ester,! #tS base oil, silicone oil, etc. lubricant, AJzOs,
6 lessons can be applied to t-magnetic materials such as CrzOs abrasive agents, #I inhibitors such as carbon black, and dispersants such as lecithin. [Examples] Examples of the present invention are described below. .

Example 1 Synthesis of polyurethane resin containing aromatic polycarbonate 22.5 parts of phenol, 6 parts of 7-chlorohessanone, and 2.5 parts of -hydrochloric acid were mixed and reacted at 40°C for 48 hours. The precipitated reaction product t-fs was separated and recrystallized using a 20% acetic acid water bath to obtain a diochitin compound.

27 parts of this dioxic acid compound, 18 parts of pyridine, and 200 parts of methylene chloride were mixed.

12 parts of phosgene are introduced with stirring at 20-35°C. Next 1. Add 20 parts of 4-benzenedethanol,
Stir for 2 hours. The obtained reaction f# liquid t is poured into methanol to precipitate the reaction product 1. The precipitate separated from P was heated to 50°C.
After drying under reduced pressure for 48 hours, polycarbonate diol At
? Obtained. This material has a number average molecular weight of 2.0 in terms of GPC polystyrene. lX1O, OH radical is 9.3XlOmol
I got it at /g.

Polycarbonate diol At-210 obtained by reaction with
part and 4.5 parts of dimethylolpropionic acid, 4.5 g of diphenylmethane diisocyanate, 6 parts of l,4-butanoneol, 0.05 parts of octylic acid, r7 clohexanone/
Dissolved in a toluene mixed solution of 200 f5 and reacted with stirring at 80°C to form polycarbonate-containing polyurethane Bf,
Obtained. The number average molecular weight of the obtained polycarbonate-containing polyurethane resin was 4.0 in terms of GPC polystyrene. UX
Metsuyuki in lO.

<Manufacture of magnetic recording media> Co-containing K r-Fe Os 100
tfffl polycarbonate-containing polyurethane resin 820 ton carbon black 4 parts alumina 5 Iffi Dobe 2-ethylhexyl oleate 1 uaiis methyl ethyl ketone 120 t 17 parts) Le! 7
120 tons/1g was processed for 70 hours using the above composition St-ball mill.

Next, 1 part of tetraglycidylmetaquinene diamine was added and mixed and dispersed for an additional 30 minutes to prepare a magnetic paint. This magnetic paint is applied onto a polyester film with a thickness of 14 μm, and the thickness after drying is 1.1 μm! Apply it so that it is F,
After drying, a magnetic 1-total structure was formed. Then, it was calendered and punched out into a disk shape to produce a magnetic disk.
Example 2 In the <Manufacture of magnetic recording medium> of Example 1, at 2°C, before using the polycarbonate WA-rich polyurethane-fat, 21) 1 part of filtration was changed to 15 parts of salt, and 51 parts of nitrocellulose was added.
A magnetic disk was produced in the same manner as in Example 1 'A' except that a filter section was added.

Example 3 Example 4 See 2 in Example 1 <Manufacture of magnetic recording media>.

Initial temperature and 60°C of magnetic disks obtained in Examples and Comparative Examples using tetraglycidyl metaglycide/diyl as a structural agent.
, Durability test after storage for 4 weeks in an environment of 90% RH was conducted as follows.

A magnetic disk was loaded into a recording/reproducing apparatus, and while a magnetic head was brought into sliding contact with the disk at a pad pressure of 309/c4, the running time until the reproduction output reached 70% of the initial output was measured. This time was defined as the durability time.

A magnetic disk was prepared in the same manner as in Example 1. , 1 Comparative Example 4 Example 1 Manufacture of Magnetic Recording Media> Tetraglycidyl metaj? 7 instead of diamine.

A magnetic disk was produced in the same manner as *4 Example 1 except that trimethylolpropane toluene diincyanate 4 was used.

〔Effect of the invention〕

As explained above, in the present invention, a polyurethane resin having one or more C0OH groups in one molecule and having an aromatic polycarbonate structure and a polyglycidylamine are used as binder components for magnetic recording media. As a result, it was possible to obtain an excellent magnetic recording medium that has superior durability and less product variation.

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer formed by dispersing ferromagnetic fine powder on a non-magnetic support, a polyurethane having one or more COO groups per molecule and an aromatic polycarbonate structure is used as a binder component for the magnetic layer. A magnetic recording medium characterized by using a resin and polyglycidylamine.