JPS6080122A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with high packing density.

Introducing polar groups such as sodium sulfonate □ groups into the binder of magnetic recording media has the effect of reinforcing the interface between the magnetic powder and the binder, and improves the dispersion and orientation of the magnetic powder, wear resistance, and durability. . However, with such a binder, even if a technique such as kneader crosstalk is used, it is not effective in densely packing the magnetic layer, and therefore the sensitivity, especially in the low frequency region, is not improved. In order to achieve high-density packing, materials that alleviate the intermolecular forces of the binder, such as dispersants, have been added, but this has resulted in serious drawbacks in powder shedding and durability.

The present invention overcomes these drawbacks and provides a highly densely packed magnetic recording medium.

That is, this invention has a polar group and a carbon number of 8 to 8 in one molecule.
20 monovalent aliphatic hydrocarbon groups, and the monovalent aliphatic hydrocarbon group equivalent is i,ooo~20. It is characterized by using a binder that is ODD.

(In the formula, M represents a hydrogen atom, lithium, sodium, or potassium.) One or more types represented by the following are preferred.

This polar group adsorbs to the magnetic powder in the magnetic coating material used in manufacturing the magnetic recording medium to prevent agglomeration and promote dispersion. If the amount of this polar group is too small, such a dispersion effect cannot be fully expected, and if it is too large, the solubility in general-purpose solvents will be reduced, which will be disadvantageous for preparing magnetic paints, etc. Therefore, the polar group equivalent (molecular weight per polar group) of the binder of the present invention is 3. OD D~2 [1, [O which is advantageously in the range of 100] The binders of the invention also contain monovalent aliphatic hydrocarbon radicals with a return number of 8 to 20. This hydrocarbon group may be linear or branched and may be saturated or unsaturated. The number of unsaturated bonds (double bonds and triple bonds) is also not limited to one, and may be two or more. This hydrocarbon group is effective in relaxing the intermolecular forces of the binder and achieving dense packing; to fully obtain this effect, the hydrocarbon group equivalent [one hydrocarbon group The molecular weight of the binder per unit] is 20
．． 000 or less is better. However, if there are too many hydrocarbon groups, plasticity increases within or between molecules of the binder, which may reduce the mechanical strength of the binder.

Therefore, the hydrocarbon group equivalent is preferably i,ooo or more.

In addition, the number average molecular weight of the binder is 5.000 to 60.00.
Preferably, it is in the range of 0. This is because if the molecular weight is too small, the physical properties of the paint film that can be formed will deteriorate, and if the molecular weight is too large, the viscosity of the paint will become too high. Furthermore, the ratio of the weight average molecular weight to the number average molecular weight of the binder Mw/M
It is preferable that n is 1.5 to 65.

The binder used in the present invention can be obtained by introducing a polar group and a monovalent aliphatic hydrocarbon group as described above into a resin such as a polyester resin, a polyurethane resin, or a vinyl chloride resin. Methods for introducing it include (I), a method in which a monomer containing the above-mentioned polar group or the above-mentioned hydrocarbon group is used in part as a starting material monomer for polyester resin or polyurethane resin (2), and active hydrogen A compound containing a halogen atom and the above polar group, and a compound containing a halogen atom and the above hydrocarbon group are added to a polyester resin, a polyurethane resin, a vinyl chloride resin, etc. containing the above in the presence of a dehydrohalogenation agent. Methods such as reacting with each other can be applied.

In the invention, the carboxylic acid component of the polyester resin that can be used as a binder includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid, p-oxybenzoic acid, p-( aromatic oxycarboxylic acids such as (hydroxyethoxy) benzoic acid,
Examples include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid, and tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid. Particularly preferred are terephthalic acid, isophthalic acid, adipic acid, and sebacic acid.

Polyhydric alcohol components of the polyester resin include ethylene glycol, propylene glycol, 1,6-propanediol, 1,4-butanediol, 1,5-bentanediol, 1,6-hexanediol, neopentyl glycol, and diethylene glycol. Recall, dipropylene glycol, 2.2.4-) IJ methyl-1,6-bentanediol, 1,4-cyclohexane dimetatool, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A and propylene Examples include oxide adducts, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Further, tri- and tetraols such as trimethylolethane, trimethylolethane, glycerin, and pentaerythritol may be used in combination.

Among the carboxylic acid components containing the polar group that can be used to introduce the polar group into the polyester resin, -505M
Containing carboxylic acids include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-sulfoisophthalic acid, 2-sodium sulfoisophthalic acid, and 2-sodium sulfoisophthalic acid.
- Potassium sulfoterephthalic acid, 2-sulfoterephthalic acid, etc.; ■ li -COOM-containing carboxylic acids, such as sodium dihydrogen 1,3.5-benzenetricarboxylate, potassium dihydrogen 1,3.5-benzenetricarboxylate; - Examples of the 0M-containing carboxylic acid include sodium-6,5-dicarboxyphenolate, potassium-3,5-dicarboxyphenolate, 6,5-dicarboxyphenol, and mixtures thereof. In addition to these representative compounds, any of the organic acids exemplified above as the carboxylic acid component and having the aforementioned polar group can be used. It is also possible to use a polyhydric alcohol component with a polar group introduced, for example, di-β-hydroxyethyl hydrogen phosphate, di-β-hydroxyethyl sodium phosphate, di-β-hydroxy potassium phosphate. Diesters of phosphoric acid such as ethyl and diols (including phenol) and their alkali metal salts can be used.

The side aliphatic hydrocarbon group is also synthesized by using a carboxylic acid or polyhydric alcohol containing this monovalent aliphatic hydrocarbon group as a part of the carboxylic acid component or polyhydric alcohol component. can be introduced into the polyester resin.

As such a hydrocarbon group-containing carboxylic acid, an ester of a dicarboxylic acid containing a hydroxyl group such as malic acid or tartaric acid and a fatty acid having 9 to 21 carbon atoms or a halide thereof can be used.

Further, as the hydrocarbon group-containing polyhydric alcohol, glycerin, trimethylolpropane, tri, etc. can be used. Fatty acids with 9 to 21 carbon atoms include saturated fatty acids such as nonanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid, as well as oleic acid, liluic acid, linoleic acid, elaidic acid, stearolic acid, and krillin. Examples include unsaturated fatty acids such as acids, and halides of these include chlorides and bromides.

The polyurethane resin containing the above-mentioned polar group and the above-mentioned aliphatic hydrocarbon group, which can be used as a binder according to the present invention, is synthesized by using diisocyanate in addition to the compounds of each component of the polyester resin as described above. You can get it by doing this. Examples of the diisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate;
m-phenylene diisocyanate, p-phenylene diisocyanate, 2.4-tolylene diisocyanate, 2
．． 6-) lylene diisocyanate, 111-xylylene diisocyanate, p-xylylene diisocyanate, diphenylmethane diisocyanate, 3,6'-dimethoxy-4,4'-biphenylene diisocyanate, 3
．． Aromatic diisocyanates such as 3'-dimethyl-4,4-biphenylene diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, 2,4-naphthalene diisocyanate, 1,6-diisocyanate Dotanso to Le S Noka mouth
1-a-S polysoyanatomethylcyclohexane, 4
．． Examples include alicyclic diiso and cyanates such as 4'-diisocyanate dicyclohexylmethane and inphorone diisocyanate.

Polyester resins and polyurethane resins made of such components may be of electron beam curing type.

Electron beam-curable polyurethane resin is obtained by introducing a double bond by reacting a (meth)acrylic monomer with a hydroxyl group such as 2-hydroxyethyl (methacrylate) with the isocyanate groups at both ends. In addition, electron beam curable polyester resins or polyurethane resins can be cured by using diols with double bonds such as glycerin nanano (methacrylate) as part of the polyhydric alcohol component of polyester resins and polyurethane resins. Obtainable.

When modifying a vinyl chloride resin to introduce the polar group, the vinyl chloride resin that can be used must contain at least vinyl alcohol as a copolymerization component, and further contain fatty acid vinyl such as vinyl acetate or vinyl propionate. , unsaturated fatty acids such as acrylic acid, methacrylic acid, and maleic acid may be included in the copolymerization component. Specifically, the vinyl chloride resin method includes vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl propionate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid-vinyl alcohol copolymer, etc. It is. As a compound to be reacted to introduce the rod group into these vinyl chloride resins, for example, general formula 201 X-A-803M%X-A-O803M%X-A-01
'0)(,.

0M X-A-COOM% Compounds containing a halogen atom and a polar group in one molecule such as
In order to introduce the monovalent aliphatic hydrocarbon group, the vinyl chloride resin to be modified may be reacted with a halide of a fatty acid having 9 to 21 carbon atoms as described above. All of these reactions can be carried out in a solvent such as dimethylformamide or dimethyl sulfoxide in the presence of an amine such as pyridine, picoline or triethylamine, or a dehydrohalogenating agent such as ethylene oxide or propylene oxide. This method of modifying a resin can be applied to any resin having active hydrogen, such as polyester resins and polyurethane resins, in addition to vinyl chloride resins.

In this invention, it is preferable that the binder made of the resin containing the polar group and the monovalent aliphatic hydrocarbon group having 8 to 20 carbon atoms is used in an amount of 30% by weight or more of the total binder component. A sufficient effect on dispersion and relaxation of intermolecular forces cannot be expected. Other binders that can be used in combination include vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylic ester-acrylonitrile copolymers; thermoplastic polyurethane elastomers. , polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative,
Thermoplastic resins such as polyester resins and polybutadiene, phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, epoxy resins IJ7 mid resin, nitrocellulose melamine resins , mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of poly and high molecular weight diols and triphenylmethane triisocyanate, and thermosetting resins such as polyamine resins. and mixtures thereof.

It is also possible to further improve the abrasion resistance of the magnetic layer by using polyisocyanate as a crosslinking agent in the binder.

Further, as the magnetic powder constituting the magnetic layer together with the above-mentioned binder, strong C (ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, etc.) can be used.

Strong al[2 and '1 particles have the general formula Fe0x(1,33
≦X≦1.50), that is, maghemite (r-Fe203X=1.50), magnephyte (l
i'e304X=1.33), and Hikolerano solid solution (F
eOx 1.33<X<1.50) can be used.

These ferromagnetic iron oxides may be doped with or coated with cobalt for the purpose of increasing coercive force. Ferromagnetic chromium dioxide is Cr02 or chromium dioxide.
%Fe, Ti, V, 4n, etc. can be used. Ferromagnetic alloy powders include Fe%Co%IJ, Fe-Co%Ii'e
-Ni or Fe-Co-Ni, etc. can be used, and in order to improve various properties, A4 %Si %Ti
, Cr % Mn , Cu , Zn, or other metal components may be added.

The magnetic layer further contains abrasives such as aluminum oxide, chromium oxide, and silicon oxide; antistatic agents such as carbon black; lubricants such as molybdenum disulfide, graphite, silicone oil, olive oil, and fatty acid ester; and dispersants such as lecithin and A fatty acid having 12 to 18 carbon atoms (for example, palmitic acid, stearic acid), etc. may be added.

The constituent materials of these magnetic layers are dissolved in an organic solvent during manufacture of the magnetic recording medium. Examples of this specific solvent include ketones such as acetone, methyl ethyl ketone, methyl imbutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol acetate monoethyl ether; Glycol ethers such as recall dimethyl ether, glycol monoethyl ether, and dioxane; Tars (aromatic hydrocarbons) such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and Chlorinated hydrocarbons such as chlorobenzene can be selected and used.

A magnetic paint made of these materials is applied to a non-magnetic carrier according to a conventional method. Materials for this non-magnetic carrier include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, etc. Cellulose derivatives; vinyl resins such as polyvinyl chloride and polyhynyritene chloride; polycarbonate, polyimide,
In addition to plastics such as polyamide-imide, non-magnetic metals such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these; ceramics such as glass, earthenware, and porcelain; paper, glue Paper such as lighter or paper coated with or laminated with α-polyolefin having 2 to 1 U of carbon atoms such as polyethylene, polypropylene, or ethylene-butene copolymer can also be used. These nonmagnetic carriers may be transparent or opaque depending on the intended use.

Further, the form of the nonmagnetic carrier may be any film, tape, sheet, disk, card, drum, etc., and various materials are selected as necessary depending on the form. The thickness of these nonmagnetic carriers is about 1 to 50 μm, preferably 1 to 60 μm when they are in the form of a film, tape, or sheet. Further, in the case of a disk or card shape, it is about 0.5 to 10 mm, and in the case of a drum shape, it is cylindrical, and the shape is determined depending on the recorder used.

Examples of this invention will be described below.

Synthesis Example 1 A polyester resin (-) consisting of the following composition (jl) was synthesized by melt polycondensation according to a conventional method.The number average molecular weight (Mn) of this polyester resin was 40,000 (measured by vapor pressure osmosis method), and the weight average molecular weight The ratio between Mw and number average molecular weight (Mw/Mn) was 1.

Composition (1) Dibasic acid components: Terephthalic acid 20 mol thiisophthalic acid 20 mol 5-sodium sulfoisophthalic acid 2.5 mol thiadipic acid 57.5 mol Tidiols Components: Ethylene glycol 47.5 mol tineopentyl glycol 50 mol titrimethylol Propane monooleate 2.5 molty Synthesis Example 2 A polyester resin (B+) consisting of the following composition (...) was synthesized under the same conditions as Synthesis Example 1. The Mn of this polyester resin was 37,000, and the M%v/Mn was It was 2.1.

Composition (Ill Dibasic acid component: Terephthalic acid 2q mol Isophthalic acid 20 mol Chetylene glycol 50 mol Thipropylene glycol 50 mol Synthesis example 3 A polyester diol consisting of the following composition (B) was synthesized. The Mn of this polyester diol was 2,000 , the hydroxyl number was 900 equivalents/10 g.

Composition (ml) Dibasic acid components: Terephthalic acid 20 mol Thiisophthalic acid 20 mol 5-Sodium sulfoisophthalic acid 2.5 mol Thiadipic acid 57.5 mol Tidiol component: Ethylene glycol 50 mol Tineopentyl glycol 50 mol Next, this polyester 100 parts by weight of diol, 4.47 parts by weight of neopentyl glycol, 1-1.04 parts by weight of chrycerin monooleate, 230 parts by weight of diphenylmethane diisocyanate, and 0.5 parts by weight of dibutyltin dilaurate.
8 parts by weight of methyl ethyl ketone and toluene in a 1:1 ratio
After dissolving it in a mixed solvent of about 30% concentration,
Under nitrogen flow in a reaction vessel equipped with a residual condenser,
When the polyurethane resin is synthesized by reacting with C for 6 to 8 hours, the reduced viscosity ηsp/c of the polyurethane resin is 0.
．． 60dll/9, Mn is 25.0 [10 tatsuta.

Synthesis Example 4 Synthesis Example 6 was prepared using 100 parts by weight of the polyester diol of Synthesis Example B, 11-4.78 parts by weight of neopentyl glyco', 2 parts by weight of diphenylmethane diisocyanate, 0 parts by weight of dibutyltin dilaurate, and 058 parts by weight of dibutyltin dilaurate. Synthesize polyurethane resin (131) in the same manner as
1.

Mn is 24. It was O.D.O.

Synthesis Examples 5 and 6 Some of the hydroxyl groups of the vinyl alcohol component were
The specially modified vinyl-vinyl acetate-vinyl alcohol copolymer (B) had Mn=24.000 and -0805Na equivalent=5.000 (Synthesis Example 5). Next, this vinyl chloride-vinyl acetate-vinyl alcohol copolymer (B11
00g was dissolved in 300g of a 1:1 mixed solvent of methyl ethyl ketone and toluene, and 1.64 # of pyridine was mixed therein. On the other hand, 6.59 oleic acid chloride was dissolved in 10 g of a 1:1 mixed solvent of methyl ethyl ketone and toluene, and gradually added to the previously prepared mixture with stirring under a nitrogen stream.

After the addition, the mixture was allowed to react for 4 hours under distillation, and the generated pyridine hydrochloride was removed by filtration. In this way, the copolymer (
A vinyl chloride-vinyl acetate-vinyl alcohol copolymer (Al) was synthesized, in which the remaining hydroxyl group of No. was replaced with an oleic acid ester residue.

Examples Using the resins of Synthesis Examples 1 to 6 as a binder, a magnetic paint with the following composition QV) was prepared through kneading, dissolving, and mixing steps, and then coated on a 10 μm polyethylene terephthalate film to give a mirror surface. The tape was processed and cut into audio tapes.

Composition (IV) 180:ffi Noble toluene 180 parts by weight The audio tape thus obtained had a residual magnetic flux density Br and a squareness ratio of 111. s, and 31511z Fbule
The results of measuring II'' 315 are shown in the table below.
Br and Rs are 20000e g! From the results shown in the table above, we found that polyester resin (A), polyurethane resin (...) and vinyl chloride-vinyl acetate-vinyl alcohol copolymer (7!) were used as binders. It can be seen that the audio tape according to the present invention has improved sensitivity in the low frequency range and increased packing density.

Agent Katsu Ueya Yoshio always Toshiki Sugiura

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer mainly composed of magnetic powder and a binder is provided on a non-magnetic support, the binder comprises 1
It has a polar group and a monovalent aliphatic hydrocarbon group having 8 to 20 carbon atoms in the molecule, and the equivalent weight of the monovalent aliphatic hydrocarbon group is i, ooo
A magnetic recording medium characterized by a Kokichi of ~20,000.