JPH0544732B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks. More specifically, as a binder component of a magnetic layer provided on a non-magnetic support,
The present invention relates to a magnetic recording medium using polyester resin or polyurethane resin having excellent properties. (Prior art) Magnetic tape, which is a general-purpose magnetic recording medium, has a long axis.
Acicular magnetic particles of 1 μm or less are dispersed in a binder solution with appropriate additives (dispersants, lubricants, antistatic agents, etc.) to create a magnetic paint, and this is applied to polyethylene terephthalate film. There is. The properties required of binders for magnetic recording media include dispersibility, filling properties, and orientation of magnetic particles, durability, abrasion resistance, heat resistance, smoothness, and adhesion to nonmagnetic supports of the magnetic layer. The binder plays a very important role. Conventionally used binders include vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinylidene chloride copolymer, polyurethane resin, polyester resin, acrylonitrile/butadiene. copolymer, nitrocellulose, cellulose acetate butyrate,
Epoxy resin or acrylic resin is used. Among these resins, polyurethane resin has superior properties such as toughness and abrasion resistance compared to other resins due to intermolecular hydrogen bonding caused by urethane bonds, but conventional adipate-type or caprolactone-type polyurethane resin alone cannot , poor properties such as blocking resistance, heat resistance, and running stability. For this reason, mixed systems of polyurethane resin and nitrocellulose or vinyl chloride/vinyl acetate copolymers are particularly used. However, properties such as durability, abrasion resistance, and running stability are still insufficient in fields that require high performance, such as video tapes, computer tapes, and floppy disks. Further, polyester resin has excellent adhesion to polyethylene terephthalate film, which is a general-purpose non-magnetic support, and has good heat resistance, but is inferior in properties such as durability and abrasion resistance. (Problems to be Solved by the Invention) In magnetic recording media, smoothness of the surface of the magnetic layer is required in order to increase the recording density, improve the S/N (signal/noise) ratio, etc. As smoothness is improved, properties such as durability, abrasion resistance, and running stability become more important, but conventional magnetic recording media still have the problem of being insufficient in these properties. (Means for Solving the Problems) In order to achieve the objective of the present invention, which is to provide a magnetic recording medium with excellent durability, abrasion resistance, and running stability, as a result of intensive studies on polyester resins and polyurethane resins, We have discovered that this can be achieved by introducing imide groups into polyester resins and polyurethane resins. That is, the present invention provides a magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, and a polyester resin having an imide group in the molecule and/or a polyester resin having an imide group in the molecule as a component of the binder.
Or a magnetic recording medium characterized by containing a polyurethane resin. In the present invention, the imide group is represented by the following general formula (A) or
The one expressed as (B) is preferable. In the production of the polyester resin used in the present invention, the dicarboxylic acid component and diol component used contain an imide group as an essential component, and are represented by, for example, the following general formula. (In the formula, R ₁ , R ₂ , R ₃ , R ₅ , R ₆ , R ₇ , R ₈ : Hydrocarbon group having an ester bond-forming functional group R ₄ : Divalent hydrocarbon group) Imide group-containing dicarboxylic acid Alternatively, imide group-containing diols include acid anhydrides such as trimellitic anhydride and pyromellitic anhydride, aminobenzoic acid, phenylenediamine, monoethanolamine, 4,
It is obtained by the reaction of an aminocarboxylic acid containing a primary amino group, such as 4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl ether, an aminoalcohol, and a diamine compound. Further, an imide group-containing diol can be obtained by esterifying an imide group-containing dicarboxylic acid with a glycol. Other carboxylic acid components of the polyester resin include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid; aromatic acids such as p-oxybenzoic acid and p-(hydroxyethoxy)benzoic acid; group oxycarboxylic acids,
Examples include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. In addition, the glycol components of the polyester resin include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-
hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol,
2,2,4-trimethyl-1,3-pentanediol, cyclohexanedimethanol, ethylene oxide adduct and propylene oxide adduct of bisphenol A, hydrogenated bisphenol A
Examples include ethylene oxide adducts, propylene oxide adducts, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. Raw materials other than the above include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid,
Ester group-forming sulfonic acid metal salt-containing compounds such as sodium sulfoterephthalic acid, 2-sodium sulfo-1,4-butanediol, and 3-sodium sulfo-1,2-butanediol, with the following general formulas [] and [] Mention may be made of the neighbor-containing compounds shown. (In the formula, R ₁ is a monovalent ester-forming functional group. _{R 2} and R ₃ are the same or different groups,
It is selected from the group consisting of a monovalent hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, and a monovalent ester-forming functional group. A represents a divalent or trivalent organic residue. Further, n ₁ is 1 or 2, and n ₂ and n ₃ each represent an integer of 0 to 4. ) (In the formula, R ₄ is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms that may contain an ester-forming functional group, or M _1p , and R ₆ is a divalent or trivalent group having 1 to 6 carbon atoms.
valent hydrocarbon group. R ₂ is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms that may contain a hydroxyl group, or
M ₁ and M ₁ are alkali metal atoms. m is 0 or 1,
l represents an integer of 1 or 2. ) Sulfonic acid metal base-containing compound, general formula [],
When the compound represented by [ ] is used as at least one component of the raw material, it is effective in greatly improving the drawback of low dispersibility of inorganic pigments and fillers found in conventional polyester resins,
When the magnetic layer of a coated magnetic recording medium is used as a binder, the dispersibility of the magnetic particles is improved, and the properties caused by the dispersibility of the magnetic particles, such as the electromagnetic conversion properties of the magnetic recording medium, are greatly improved. . The polyurethane resin used in the present invention is obtained by the reaction of a diol component and an organic diisocyanate, and contains an imide group in the molecule. Examples of methods for introducing imide groups include a method using an imide group-containing polyester diol among the aforementioned polyester resins as a component of the raw material, or a method using another imide group-containing diol. Other imide group-containing diols include general formulas (1), (2), (4),
In (5), those containing hydroxyl groups in R ₁ , R ₂ , R ₃ , R ₅ , R ₆ , R ₇ and R ₈ are preferred. The polyurethane resin used in the present invention may be a raw material component that does not contain an imide group. For example, long chain diol components include polyester diol,
Examples include polyether diols and polycarbonate diols, and examples of chain extenders include glycols, amino alcohols, diamines, and water. The organic diisocyanate used in the production of the polyurethane resin used in the present invention includes:
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, 3,3'-dimethoxy-4, 4'-biphenylene diisocyanate, 2,4-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-
Biphenylene diisocyanate, 4,4'-diphenylene diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 1,3-
Diisocyanate methylcyclohexane, 1,4
-diisocyanate methylcyclohexane, 4,
Examples include 4'-diisocyanate cyclohexane, 4,4' diisocyanate cyclohexylmethane, and isophorone diisocyanate. The content of imide groups in the polyester resin or polyurethane resin used in the present invention is from 0.05 to 0.05 when expressed as the content of nitrogen in the imide group in the resin.
It is preferably in the range of 5%; if it exceeds 5%, the solubility in the solvent may deteriorate, and if it is less than 0.05%, the effect of containing the imide group is not observed. In the magnetic recording medium of the present invention, in addition to the polyester resin or polyurethane resin used in the present invention, other resins may be added for the purpose of adjusting flexibility, improving cold resistance, heat resistance, etc. It is desirable to mix a compound that crosslinks by reacting with the polyurethane resin. Other resins include vinyl chloride resin, polyester resin, cellulose resin, epoxy resin, phenoxy resin, polyvinyl butyral, acrylonitrile,
Examples include butadiene copolymers. On the other hand, compounds that crosslink with polyurethane resins include polyisocyanate compounds, epoxy resins, melamine resins, urea resins, etc. Among these, polyisocyanate compounds are particularly desirable. The ferromagnetic particles used in the magnetic layer of the magnetic recording medium of the present invention include γ-Fe ₂ O ₃ , γ-Fe ₂ O ₃ and
Fe ₃ O ₄ crystal, CrO ₂ , cobalt doped γ-
Fe ₂ O ₃ or Fe ₃ O ₄ , barium ferrite and Fe
Examples include ferromagnetic alloy powders such as -Co and Fe-Co-Ni. The magnetic recording medium of the present invention may optionally contain plasticizers such as dibutyl phthalate and triphenyl phosphate, dioctyl sulfonodium succinate, t-butylphenol polyethylene ether, ethylnaphthalene sodium sulfonate, and dilauryl succinate. Lubricants such as , zinc stearate, soybean oil lecithin, silicone oil, and various antistatic agents may also be added. (Function) The polyester resin or polyurethane resin used in the present invention contains an imide group having a rigid molecular chain, and is different from conventional polyester resins,
Compared to polyurethane resins, it has better lubricity and even greater toughness. By using a polyester resin or a polyurethane resin having such characteristics as a binder for the magnetic layer of a magnetic recording medium, the magnetic recording medium of the present invention has excellent durability and
It is considered to have excellent wear resistance and running stability. (Example) Hereinafter, the present invention will be specifically explained with reference to Examples. In the examples, parts simply indicate parts by weight. Each measurement item follows the method below. Running stability: We ran the magnetic tape over a video deck and observed unevenness during running. ○: Runs stably. △: Slightly uneven running. ×: There is uneven running and squeaks. Still characteristics: Time for a still image to disappear. The longer this time, the better the durability and wear resistance. Polyester resin synthesis examples 1 to 3 291 parts of dimethyl terephthalate, 272 parts of dimethyl isophthalate, 29.6 parts of dimethyl 5-sodium sulfoisophthalate, ethylene glycol
372 parts of neopentyl glycol, 416 parts of neopentyl glycol, 1088 parts of the imide group-containing dicarboxylic acid listed in Table 1, and 0.5 parts of tetrabutoxytitanium were placed in an autoclave, and esterification and transesterification reactions were carried out at 200 to 230°C for 4 hours. Summer. Next, the temperature was raised to 250℃ over 30 minutes, and at the same time the pressure was gradually reduced.
Excess glycol was distilled off at 250°C and 10 mmHg, and finally a polycondensation reaction was carried out at 260° and 0.1 to 0.3 mmHg for 90 minutes to obtain a yellowish brown polyester resin with a reduced viscosity of 0.58. The composition of the resin was as shown in Table 1 by analysis such as NMR. Similarly, an imide group-containing polyester resin was obtained using the raw materials listed in Table 1. The composition is shown in Table 1.

【table】

[Table] Polyurethane resin synthesis examples 1 to 6 After thoroughly drying the imide group-containing diol listed in Table 2 in a reaction vessel equipped with a thermometer, a stirrer, and a reflux type condenser, charge it with cyclohexanone.
After adding 231 parts of toluene, 231 parts of toluene, and 82 parts of 4,4'-diphenylmethane diisocyanate and raising the temperature to 80°C, 0.08 parts of dibutyltin dilaurate was added as a reaction catalyst.
1 part was added and reacted for 2 hours. Then molecular weight 2000
100 parts of polybutylene adipate were added thereto, and after 1 hour, 15 parts of neopentyl glycol was further added, and the mixture was reacted at 80 to 90°C for 10 hours. After the reaction was completed, it was diluted with 231 parts of methyl ethyl ketone to obtain a brown polyurethane resin solution with a solid content concentration of 30%. The solution viscosity was 85 poise (25°C), and the molecular weight of the polyurethane resin was 25,000 in terms of polystyrene as measured by gel permeation chromatography. Similarly, an imide group-containing polyurethane resin was obtained using the raw materials listed in Table 2. The imide group-containing diol used in polyurethane resin synthesis example 6 was heated at 250℃0.5 mm.
Obtained by deglycolization in Hg for 60 min.

【table】

[Table] Example 1 The polyester resin listed in Table 1 (Synthesis Example 1) was mixed with methyl ethyl ketone/toluene/cyclohexane (=1/1/1 weight ratio) at a solid content concentration of 30%.
Using the resulting solution, put the composition in the following blending ratio in a ball mill and disperse for 48 hours, then add 5 parts of the isocyanate compound Coronate 2030 (manufactured by Nippon Polyurethane Industries Co., Ltd.) as a curing agent. In addition, the mixture was kneaded for an additional hour to obtain a magnetic paint. This was applied onto a 12μ thick polyethylene terephthalate film while applying a magnetic field of 2000 Gauss so that the thickness after drying would be 5μ. After being left at 50°C for 2 days, it was slit into 1/2 inch width to obtain a magnetic tape. Polyester resin solution (solid content 30%) 100 parts Cobalt-coated γ-Fe ₂ O ₃ 120 parts Olive oil 1 part Methyl ethyl ketone 50 parts Toluene 100 parts Examples 2 to 7, Comparative Examples 1 to 5 Same as Example 1 , magnetic recording media of Examples 2 to 7 were obtained using the resins listed in Table 3. In addition, the magnetic recording media of Comparative Examples 1 to 5 were prepared in the same manner as in Example 1 using polyester resins 4 and 5 that do not contain imide groups, adipate type polyurethane resin, nitrified cotton, and a vinyl chloride/vinyl acetate copolymer. I got it. Table 3 shows the properties of the obtained magnetic tape.

[Table] Example 8 Conducted using a solution of the polyurethane resin listed in Table 2 obtained in Synthesis Example 1 (solvent: cyclohexanone/toluene/methyl ethyl ketone = 1/1/1 weight ratio, solid content concentration 30%). A magnetic tape was obtained in the same manner as in Example 1. Examples 9 to 15, Comparative Examples 6 to 12 Magnetic tapes were obtained in the same manner as in Example 8 using the imide group-containing polyurethane resins listed in Table 4. Table 4 shows the properties of the magnetic tape obtained. Further, magnetic tapes of Comparative Examples 6 to 12 were obtained in the same manner as in Example 8 using a polyurethane resin containing no imide group. The characteristics are shown in Table 4.

[Table] (Effects of the invention) Polyester resins or polyurethane resins containing imide groups in their molecules have increased toughness and improved lubricity compared to those that do not contain imide groups. The magnetic recording medium of the present invention using these resins as a binder for the magnetic layer has excellent running stability, abrasion resistance, and durability, as is clear from the examples.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, a polyester resin and/or polyurethane resin having an imide group in the molecule is used as a component of the binder. A magnetic recording medium comprising: