JPH04222919A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To form a magnetic recording medium excellent in durability by forming a magnetic later containing an amino group-contg. silane coupling agent, a compd. comprising anhydride of specified carbon number and alkylketene dimers, and a binder comprising polyurethane resin. CONSTITUTION:This magnetic recording medium consists of a magnetic layer formed on a nonmagnetic supporting body. This magnetic layer consists of an amino group-contg. silane coupling agent and a magnetic powder coated with a reaction product of acid anhydride having 6-22 carbon number and one or more kinds of alkylketene dimers. The magnetic layer also contains a binder comprising polyvinyl chloride containing hydroxyl group, epoxy group and metal sulfonate group in one molecule and polyurethane resin containing 0.1-100 equiv./10<4>g metal sulfonate group. Thereby, the obtd. magnetic recording medium has excellent durability.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic recording media, and more particularly to magnetic recording media with improved durability.

0002

[Prior Art and its Problems] Magnetic recording media slide violently against magnetic heads, pads, etc. during recording and reproduction, and the magnetic layer is likely to be abraded. Therefore, it is desired that the magnetic layer has less abrasion and is highly durable. ing.

Therefore, as a measure to improve the durability of the magnetic layer, various lubricants are mixed into the magnetic layer to reduce the wear of the magnetic layer, or an appropriate binder is selected to increase the strength of the magnetic layer. The following methods have been adopted.

However, it is currently difficult to say that these methods are fully satisfactory in terms of performance.

[0005]

[Means for Solving the Problems] As a result of intensive research, the present inventors found that a magnetic recording medium having a magnetic layer made of a specific treated powder and a binder has significantly improved durability of the magnetic layer. , arrived at the present invention.

That is, the present invention provides a magnetic recording medium having a magnetic layer on a non-magnetic support, in which the magnetic layer comprises an amino group-containing silane coupling agent, an acid anhydride (I) having 6 to 22 carbon atoms, and Magnetic powder coated with a reaction product with one or more compounds selected from the group consisting of alkyl ketene dimer (II), polyvinyl chloride having a hydroxyl group, an epoxy group, and a sulfonic acid metal base in one molecule , and a polyurethane resin containing a sulfonic acid metal base at a concentration of 0.1 to 100 equivalents/10 6 g.

[0007] As the amino group-containing silane coupling agent according to the present invention, for example, H2NC2H4NHC3H
6Si(OCH3)3, H2NC2H4NHC3H6S
i(CH3)(OCH3)2, H2NC3H6Si(O
C2H5)3, H2NCONHC3H6Si(OC2H
5)3,

[0008]

[Chemical formula 1]

Compounds such as the following can be mentioned.

The acid anhydride having 6 to 22 carbon atoms according to the present invention is preferably an acid anhydride having an alkyl group or an alkenyl group, and the alkyl ketene dimer according to the present invention is preferably one having 12 to 44 carbon atoms. preferable.

The magnetic powder according to the present invention includes fine needle-shaped metal oxides such as γ-Fe2O3, Fe3O4, and CrO2, as well as Co-coated γ-Fe2O3 and Co
γ processed such as doped γ-Fe2O3
-Fe2O3, iron metal powder, etc. Among these, iron metal powder, barium ferrite in the form of microplates, and some of its Fe atoms are Ti, Co, Zn,
Magnetic powders substituted with one or more of V, Nb, etc., and ultrafine powders of metals or alloys such as Co, Fe-Co, Fe-Ni, etc. have particularly poor chemical stability. Cobalt, titanium, silicon, aluminum, etc. may be added in small amounts or surface treated in the form of metal atoms, salts, and oxides, and these may also be used. In order to stabilize iron metal powder, a thin oxide film is sometimes formed on the surface in a weakly oxidizing atmosphere, and metal powder treated in this way can also be used.

In the present invention, the method for obtaining the magnetic powder coated with the reaction product of the amino group-containing silane coupling agent and the compound selected from the group consisting of (I) and (II) is not particularly limited. For example, the method shown below is exemplified. (a) first heat-treating the amino group-containing silane coupling agent (ii) to the magnetic powder (i) in an inert organic solvent;
A method in which one or more compounds (iii) selected from the group consisting of (I) and (II) are then heat-treated. (b) The above (i) and (ii) and (
iii) A method in which the ingredients are mixed together and heat treated. C. First, in an inert organic solvent, the above (ii) and (iii)
) is reacted, and then (i) is added and heat treated.

The magnetic recording medium of the present invention can be obtained by adding a binder and a solvent to the magnetic powder treated by the above-mentioned treatment method to form a paint, and applying it to a polyester film, etc., but the details thereof are as follows. will be explained in Examples together with a method for treating magnetic powder.

The amount of the amino group-containing silane coupling agent according to the present invention used is about 0.2 to 3% by weight, preferably 0.5 to 2% by weight, based on the magnetic powder. Further, the amount of one or more compounds selected from the group consisting of (I) and (II) is about 1.5 to 3 times the weight of the amino group-containing silane coupling agent. It is preferable to use

Inert solvents that can be used in the treatment of magnetic powder include methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, cyclohexanone,
Examples include benzene, xylene, and toluene.

In the present invention, as a binder, (a) polyvinyl chloride having a hydroxyl group, an epoxy group and a sulfonic acid metal group in one molecule, and (b) 0.1 to 100
A polyurethane resin containing a concentration of sulfonic acid metal bases of equivalent weight/106 g is used.

The concentration of hydroxyl groups in the polyvinyl chloride (a) is 100 to 500 equivalents/106 g, the concentration of epoxy groups is 100 to 1000 equivalents/106 g, and the concentration of sulfonic acid metal bases is 10 to 100 equivalents/106 g
It is preferable that Polyvinyl chloride having such characteristic groups can be synthesized by emulsion polymerization using, for example, vinyl chloride, 2-hydroxylethyl methacrylate, styrene sulfonic acid, and glycidyl methacrylate.

The concentration of the sulfonate metal base in the polyurethane resin containing the sulfonate metal base (b) is 0.1 to 100 equivalents/106 g, preferably 1 to 106 g.
10 equivalents/106 g. If the sulfonic acid metal base concentration is less than 0.1 equivalent/106 g, the magnetic powder will not be sufficiently dispersed;
If the amount is more than equivalent/106 g, the thixotropy of the paint tends to increase, making it difficult to handle. Furthermore, problems may arise in terms of hydrolysis of the polyurethane resin.

The polyurethane resin containing a sulfonic acid metal base used in the present invention can be produced by the following method. 5-sodium sulfoisophthalic acid,
A polyhydroxy compound having a sulfonic acid metal group is synthesized from a polyol compound and a dicarboxylic acid having a sulfonic acid metal group such as 5-potassium sulfoisophthalic acid, 2-sodium sulfoisophthalic acid, and 2-potassium sulfoisophthalic acid. A polyurethane resin having a sulfonic acid metal group is obtained by reacting the compound with a polyisocyanate compound.

The polyurethane resin containing (a) polyvinyl chloride and (b) sulfonic acid metal base is (a)
)>(b) It is preferable to use it in an amount that satisfies the following. (a)
The total amount of +(b) is 15 to 30 per 100 parts by weight of magnetic powder.
Preferably, parts by weight are used.

Furthermore, polyvinyl chloride of (a) above and (
In addition to the polyurethane resin containing a sulfonic acid metal group b), polyurethane resins synthesized using ordinary diols and polyisocyanates can also be used in combination. In this case, the polyurethane resin has a molecular weight of 70
It is preferably in the range of 00 to 70,000, and the amount used is preferably 10 to 50 parts by weight per 100 parts by weight of the polyurethane resin containing the metal sulfonic acid base (b). Diols that are raw materials for such polyurethane resins include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, dodecanediol, tridecanediol, Tetradecanediol, pentadecanediol, hexadecanediol, heptadecanediol, octadecanediol, nonadecanediol, eicosanediol, heneicosanediol, docosanediol, tricosanediol, tetracosanediol, pentacosanediol, hexacosanediol, heptadecanediol Cosanediol, octacosanediol, nonacosanediol, triacontanediol, hentriacontanediol, dotriacontanediol, tritriacontanediol, tetratriacontanediol, pentatriacontanediol,
Examples include hexatriacontanediol, heptatriacontanediol, octatriacontanediol, neopentyl glycol, 2,2-dimethyl-1,3-propanediol, and the like.

Further, as the diisocyanate which is a raw material for polyurethane, aromatic diisocyanates such as m-phenylene diisocyanate, ethane diisocyanate, propane diate, p-phenylene diisocyanate, l-phenylene diisocyanate, etc. -Chloro-2,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3 Aromatic diisocyanates such as '-dimethyl-4,4'-biphenylene diisocyanate, ethane diisocyanate, propane diisocyanate, butane diisocyanate, pentane diisocyanate, hexane diisocyanate, heptane diisocyanate , aliphatic diisocyanates such as octane diisocyanate, nonane diisocyanate, and decane diisocyanate, and isophorone diisocyanate. Among them, 4,4'-diphenylmethane diisocyanate, 2
, 4-tolylene diisocyanate and isophorone diisocyanate are preferred.

As the binder, the above (a) and (b) are used.
) can also be used together. Banders that can be used in combination include polyvinyl chloride other than (a), vinyl chloride vinyl acetate copolymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin, polyamide, polyacrylic ester, polymethacrylic ester, polyacetic acid Examples include vinyl, polyvinyl butyral, vinylidene chloride, nitrified cotton, maleic acid-modified vinyl chloride/vinyl acetate copolymer, and ethyl cellulose. These may be used alone or in combination of two or more. When using other binders together, the total amount of (a) polyvinyl chloride and (b) polyurethane resin containing a sulfonic acid metal base is preferably 50% by weight or more based on the total amount of the binder, and 100% by weight. But that's fine. Further, the total amount of the binder is preferably 15 to 30% by weight of anti-magnetic powder.

[0024] The non-magnetic supports used in producing the magnetic recording medium of the present invention include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; Polycarbonate; polyvinyl chloride; polyimide; plastics such as aromatic polyamide; metals such as Al and Cu; paper, etc. are used. The form may be a film, tape, sheet, disk, card, drum, etc. Further, the surface of the support may be treated with corona discharge, radiation, ultraviolet light, etc., or may be precoated with a suitable resin.

[0025]

According to the present invention, a magnetic recording medium with improved durability is provided.

[0026]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but it goes without saying that the present invention is not limited to these Examples.

Example 1 (Preparation of magnetic powder) A four-necked flask with a cooling tube was prepared with a major axis diameter of 0.
．． Take 100 g of metal powder with a diameter of 35μ and an axial ratio of 1/10, 300 g of toluene, and 1.6 g of γ-aminopropyltriethoxysilane (A-1100 manufactured by Nippon Unicar Co., Ltd.).
The mixture was stirred at 80°C for 1 hour, and then 4 g of dodecenylsuccinic anhydride was added and further stirred at 80°C for 1 hour to obtain treated magnetic powder. (Creation of magnetic recording medium) Magnetic powder obtained above 105
Weight part MR 110 *1
16.0〃uR8200
*2
4.8 Polyurethane resin *3
1.4 2-ethylhexyl palmitate 8.0 Cr2O3 (abrasive) 15.0
〃Methyl ethyl ketone
83 Cyclohexanone
83 Toluene
126
Note) *1 Polyvinyl chloride resin with hydroxyl group, epoxy group, and sulfonic acid metal base manufactured by Nippon Zeon Co., Ltd. *2
Toyobo Co., Ltd.'s sodium sulfonate-containing polyurethane*3 Polybutylene adipate diol, 1,4-butanediol, neopentyl glycol, and 4,4'-
Synthesized from diphenylmethane diisocyanate. The end of the molecule is a hydroxyl group. Number average molecular weight 20,000. After mixing the above composition in a sand mill for 10 hours, it was taken out through a filter, and a curing agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industries, Ltd.) was added immediately before application.7.
7 parts by weight were added and stirred. This paint was applied to both sides of a 32μ thick polyethylene terephthalate film so that the magnetic layer thickness after drying would be 4μ, dried and rolled up. This was calendered and cured, then punched out into a disk shape and housed in a case to produce a sample disk. This disk was loaded into a recording/reproducing device, and the head was continuously run on the same track. The circumferential speed at this time is 7m/
sec, 20°C, 65% RH and 40°C, 80
Tested under an environment of %RH. After a certain number of passes, the damage to the magnetic layer of the sample disk was visually evaluated. A state with no scratches was rated as ◎, and ratings were given as ○, △, and × in descending order of the number of scratches. The results are shown in Table 3.

Example 2 (Preparation of magnetic powder) The procedure was repeated in the same manner as in Example 1 except that 4 g of octadecanyl succinic anhydride was used instead of the dodecenyl succinic anhydride used in the preparation of the magnetic powder in Example 1. A treated magnetic powder was obtained. (Creation of magnetic recording medium) Magnetic powder obtained above 105
Weight part MR 110 *1
16.0〃uR8200
*2
4.8 2-ethylhexyl palmitate
8.0 〃Cr2O3 (abrasive)
15.0 Methyl ethyl ketone 83
〃Cyclohexanone
83 Toluene
126 Note) *1 Polyvinyl chloride resin having hydroxyl group, epoxy group and sulfonic acid metal base manufactured by Nippon Zeon Co., Ltd. *2 Polyurethane containing sodium sulfonate manufactured by Toyobo Co., Ltd. From the above composition, in the same manner as in Example 1 A sample disk was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 3.

Example 3 In producing the magnetic recording medium of Example 1, a polyurethane resin containing sodium sulfonate obtained using the raw materials shown below was used as the polyurethane resin containing sodium sulfonate. (Manufacture of polyester) Isophthalic acid-based condensed polyester A was manufactured by a conventional method using the raw materials shown in Table 1 below.

[0030]

[Table 1]

(Production of polyurethane resin) A polyurethane containing sodium sulfonate was produced by a conventional method using the polyester A obtained above, the chain extender shown in Table 2, polyisocyanate, etc. as raw materials. A sample disk was prepared in the same manner as in Example 1, except that 4.8 parts by weight of this polyurethane resin was used, and the same evaluation as in Example 1 was performed. The results are shown in Table 3.

[0032]

[Table 2]

Comparative Example 1 In Example 1, the magnetic powder was used for preparing magnetic powder without surface treatment, and sample disks were prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. . The results are shown in Table 3.

Comparative Example 2 In Example 1, a normal polyurethane resin was used in place of uR8200 (therefore, a total of 6.2 parts by weight of polyurethane resin was used). Example 1 below
A sample disk was prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. The results are shown in Table 3.

Comparative Example 3 In Example 1, “VAGH” was used instead of MR 110.
(Vinyl chloride/vinyl acetate manufactured by Union Carbide/
A sample disk was prepared in the same manner as in Example 1 using a polyvinyl alcohol copolymer resin) and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0036]

[Table 3]

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer on a non-magnetic support, wherein the magnetic layer comprises an amino group-containing silane coupling agent, an acid anhydride (I) having 6 to 22 carbon atoms, and an alkyl ketene dimer. Magnetic powder coated with a reaction product with one or more compounds selected from the group consisting of (II), polyvinyl chloride having a hydroxyl group, an epoxy group, and a sulfonic acid metal base in one molecule, and
．． A magnetic recording medium comprising a polyurethane resin containing a sulfonic acid metal base at a concentration of 1 to 100 equivalents/106 g.