JPH0465451B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a magnetic recording medium, particularly a magnetic recording medium with excellent running stability and durability, which uses a magnetic layer with improved surface smoothness, lubricity, and wear resistance. It is related to. (Prior Art) In recent years, with the spread of home video, the demand for magnetic tapes such as video tapes has increased significantly. There is a demand for long-term recording, high-level sound quality, and image quality, and progress is being made to make it smaller and lighter and add a variety of functions. Therefore, improvements in image quality and stability during long-distance driving are required by improving electrical conversion characteristics. , there is a need for improved durability. For this reason, the magnetic powder used in this magnetic tape is made into even finer particles, but because it has a very large magnetic moment, the particles tend to aggregate, so the resin used as a binder The disadvantage is that uniform dispersion becomes difficult, and to overcome this disadvantage, attempts have been made to introduce carboxyl groups, hydroxyl groups, sulfonic acid groups, etc. into the molecular structure of the binding resin. However, the dispersibility of ferromagnetic powder is still insufficient,
The problem with magnetic tapes using this method is that they have poor surface smoothness and unsatisfactory electromagnetic characteristics and runnability. On the other hand, to improve the surface smoothness and running properties of this magnetic tape, silicone oil, long-chain hydrocarbon compounds, fatty acid esters, and lubricants are used as lubricants.
Some methods have been used to lower the friction coefficient of the magnetic layer by adding glycerides, fatty acid metal soaps, fatty acid amides, etc. to improve running stability and wear resistance, but this method does not improve the friction characteristics at low speeds. It has the disadvantage that it does not fully satisfy the durability and running stability based on the friction and wear characteristics with the video head that rotates at high speed. (Structure of the Invention) The present invention relates to a magnetic recording medium that solves the above-mentioned disadvantages.
vinyl alcohol unit, amine-modified vinyl unit,
and the following general formula (Here, V is 1 having a polymerizable olefin bond.
valent organic group, l is 0 to 10, m and n are 0<m<
1000, an integer where 0<n<1000 and 0<m+n<1000) The layer is formed on a support. That is, as a result of various studies by the present inventors regarding the production of magnetic recording media with excellent running stability and durability, the above-mentioned vinyl chloride units, vinyl alcohol units, amine-modified vinyl units and the above general formulas (), ( ) is used as a binding resin, and ferromagnetic powder is dispersed in this copolymer and coated on a support to form a magnetic layer. If formed, the magnetic powder will be dispersed well and the lubricity of the magnetic coating layer will be improved, so this magnetic recording medium will maintain its lubricity effect for a long time even under high temperature, high humidity or low temperature environments. They discovered that the copolymer exhibits high performance without deteriorating, and conducted research on the composition of this copolymer, the amount of magnetic material to be distributed, etc., and completed the present invention. As described above, the copolymer as a binder constituting the magnetic recording medium of the present invention is a vinyl chloride unit, a vinyl alcohol unit, an amine-modified vinyl unit, or an organosilicon selected from the above general formulas () and (). It is assumed that the four components of the compound are essential components. Among the components that make up this copolymer,
Vinyl chloride has traditionally been used as a vinyl chloride-vinyl acetate copolymer, alone or in combination with polyurethane resin, as a binder for ferromagnetic powder and as a key component for maintaining the physical strength of magnetic coatings. , vinyl alcohol improves the dispersibility of magnetic powder, and its OH groups are crosslinked with isocyanate, which improves the physical strength of the coating film and adhesion to non-magnetic supports, and also improves compatibility with polyurethane resins. It is intended to improve. In addition, the amine-modified vinyl unit improves the dispersibility of the magnetic powder together with vinyl alcohol, and also shows the effect of improving the reactivity with isocyanate. The elementary compound lowers the coefficient of friction of the magnetic layer, but because it is bonded to the copolymer, it does not bleed and keeps the surface slipperiness constant over a long period of time. As the monomer used here, lower fatty acid vinyl esters such as vinyl acetate and vinyl propionate are preferred as starting constituents for obtaining vinyl alcohol units by saponification of vinyl chloride units. However, this amine-modified vinyl unit constituent is not added as a monomer, but is copolymerized with vinyl chloride, lower fatty acid vinyl ester, and an organosilicon compound to be described later.
It is often the case that the saponified polymer is reacted with an amine compound, or that saponification and amination are performed simultaneously to partially produce amine-modified vinyl units. Amines, aromatic amines, alkanolamines, specifically ethylamine, propylamine, butylamine, cyclohexylamine, ethanolamine, naphthylamine, aniline, O-
Toluidine, diethylamine, dioctylamine, diisobutylamine, diethanolamine,
Methylethanolamine, N,N-dimethylethanolamine, methyldiethanolamine, 2-
Methoxyethylamine, N-methylaniline, trimethylamine, N-methylbutylamine, N-
Methyl diphenylamine, hexamethylenetetramine, triethanolamine, dimethylbenzylamine, tetramethylethylenediamine, tetramethyl-1,3-diaminopropane, pentamethyldiethylenetriamine, pyridine, picoline,
Examples include quinoline and morpholine. The organosilicon compound used here is selected from the general formulas () and () above, and is a monovalent organic group having a polymerizable olefin bond represented by V in the general formula. Examples include acryloxy group, methacryloxy group, vinyl group, allyl group,
Examples include 4-vinylphenyl groups, and the following are exemplified, but in terms of reactivity and ease of polymerization, this V may be an acryloxy group or a methacryloxy group. good. This copolymer is produced by copolymerizing vinyl chloride, lower fatty acid vinyl ester, and a polymerizable organosilicon compound by known suspension polymerization, emulsion polymerization, solution polymerization, or bulk polymerization. A suitable solvent such as methanol, toluene, xylene,
After adding acetone, etc., this is saponified using an alkali such as caustic potash, caustic soda, or sodium alcoholate, or an acid such as hydrochloric acid or sulfuric acid as a catalyst, and then refined according to a conventional method.
In this case, some amount of saponified lower fatty acid vinyl esters may be present in the copolymer, which may also include vinyl versatate, acrylic acid, methacrylic acid or their esters, maleic acid,
It may be one in which a small amount of itaconic acid ester, vinylidene chloride, various vinyl ethers, etc. are copolymerized. This saponified copolymer is then aminated, but this amination may be carried out simultaneously with the saponification. Therefore, this amination can be carried out, for example, by adding the above-mentioned solvent, an alkali as a saponification catalyst, and the above-mentioned amine compound to the copolymer obtained above, and stirring the mixture at 10 to 80°C for a certain period of time to convert vinyl ester units into vinyl alcohol units. At the same time, the amine is introduced into the side chain by a reaction between the chlorine atom of the vinyl chloride unit and the amine. On the other hand, in the method of performing silicification and amination in two steps, methanol is added to the saponified copolymer,
An organic solvent such as toluene, xylene, acetone, etc. and an amine compound are added and stirred for a certain period of time at 10 to 80°C to perform amination and introduce the amine into the side chain. The composition of the copolymer only needs to contain four components: vinyl chloride units, vinyl alcohol, amine-modified vinyl units, and organosilicon compounds, but the component ratio of each component is 60% by weight of vinyl chloride units. If it is less than 90% by weight, the physical strength will decrease, and if it is more than 90% by weight, the solubility in organic solvents such as MEK and MIBK will decrease.
It is best to keep the vinyl alcohol unit in the range of ~90% by weight. If the vinyl alcohol unit is too small, the dispersibility of the ferromagnetic powder will decrease, and if it is too large, the compatibility with the polyurethane resin used in combination will decrease. is preferably 2 to 20% by weight. In addition, if the amount of this amine-modified vinyl unit is too small or too large, the dispersibility or smoothness of the ferromagnetic powder will decrease, so it is necessary to set it at 0.05 to 20% by weight, and this organosilicon compound about
If it is less than 0.1% by weight, the lubricity improvement effect on the surface of the magnetic coating will be poor, and if it is more than 20% by weight, the dispersibility of the magnetic powder will decrease, the solubility in organic solvents will also decrease, and the strength of the coating will decrease. Because it decreases
The content is preferably 0.1 to 20% by weight. This copolymer is used as a binder for ferromagnetic powder, but if its average degree of polymerization is too low, the magnetic coating becomes brittle and its physical strength decreases. Magnetic tapes with this coating film will have poor durability, and conversely, if the average degree of polymerization is too high, the viscosity of the paint at a given concentration will become high, making workability poor and handling difficult. It is preferable that the degree is in the range of 200 to 800. The magnetic recording medium of the present invention has a magnetic layer formed by coating a support with ferromagnetic powder dispersed therein using the above copolymer as a binder, and this support is known in the art. Therefore, it may be a film, tape, sheet, or plate made of synthetic resins such as polyester, polyolefin, cellulose acetate, and polycarbonate, nonmagnetic metals, and ceramics. Further, this ferromagnetic powder may also be of a known type, such as γ-Fe ₂ O ₃ , Fe ₃ O ₄ and those obtained by adsorbing or doping cobalt ions thereto, or
Examples include various magnetic powders such as acicular fine particle materials containing Cr, O ₂ , Fe, Co, Fe-Co, or Ni. This magnetic layer is made by dispersing the ferromagnetic powder in the above copolymer as a binder, and the mixing ratio is 8 to 50 parts by weight of the binder per 100 parts by weight of the ferromagnetic powder. However, when forming this magnetic layer, it is necessary to add abrasives, antistatic agents, dispersion aids, rust preventives, etc. to the system, or use methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene as a coating medium. It is optional to add an organic solvent such as. In the formation of this magnetic layer, polyurethane resins conventionally known as this type of binder, such as Nitsuporan N-2304,
N-3022 [trade name manufactured by Nippon Polyurethane Co., Ltd.], Estan 5701-F1 [USA B. F. [product name manufactured by Gutsudoritsuchi Co., Ltd.], Moltan CA-276, CA-280 [product name manufactured by Monton Chemical Company, USA], and isocyanate compounds such as Coronate L [product name manufactured by Nippon Polyurethane Co., Ltd.], Desmodyur L [product name manufactured by Bayer AG, West Germany] It is also optional to add the required amount of product name. Next, synthesis examples and examples of copolymers used to produce the magnetic recording medium of the present invention will be given. This shows the measured values. [Various characteristics measurement conditions] Γ gloss: Gloss meter (manufactured by Murakami Color Giken)
The 60℃ reflectance was compared with that of a standard glass plate. Γ magnetic properties: Measured using a vibrating sample magnetometer (manufactured by Toei Kogyo). Γ friction coefficient: Measured using a tape friction measuring machine (manufactured by Toyo Seiki). Synthesis Example 1 (Synthesis of Polymer) In an autoclave equipped with a stirring device, after purging with nitrogen, 400 parts of deionized water, 83 parts of vinyl chloride, 30 parts of vinyl acetate, and the formula A polymerizable organosilicon compound represented by (hereinafter referred to as S-1)
), 6 parts of trichlorethylene, 0.6 parts of di(2-ethylhexyl) peroxydicarbonate, and 2 parts of partially saponified polyvinyl alcohol were charged, and the temperature was raised to 60°C with stirring to start the reaction. 83 parts of vinyl chloride was continuously fed under pressure over a period of 8 hours to cause a polymerization reaction. Autoclave internal pressure is 0.5Kg/cm ² G after 12 hours
When the residual pressure reached 100%, the residual pressure was released, cooled, washed three times with 1000 parts of deionized water, filtered, and dried at 50℃. 160 parts of a copolymer containing 1.4% by weight of silicon units and having an average degree of polymerization of 410 was obtained. Next, 160 parts of the copolymer obtained in this way,
336 parts of methanol, 114 parts of toluene, 16 parts of sodium hydroxide, 8 parts of N,N-dimethylethanolamine
After 6 hours of reaction at 60°C, the mixture was washed three times with 1,000 parts of methanol, twice with 1,000 parts of deionized water, and overdried. . The obtained polymer was further dissolved in 800 parts of methyl ethyl ketone,
Add 3000 parts of methanol while stirring to re-precipitate,
Separate the polymer, repeat this dissolution and precipitation twice, and wash twice with 1000 parts of deionized water.
After over-drying, 136 g of copolymer powder (hereinafter abbreviated as Polymer A) was obtained, which contained 91.4% by weight of vinyl chloride units, 1.2% by weight of vinyl acetate units, 5.1% by weight of vinyl alcohol units,
It was a copolymer with an average degree of polymerization of 410, consisting of 1.2% by weight of N,N-dimethylethanolamine-modified vinyl units and 1.1% by weight of organosilicon units. Polymer A was confirmed to have a polydimethylsiloxane structure in the copolymer chain by infrared absorption spectroscopy and NMR analysis, and the Si content was determined using elemental analysis and a high-frequency argon plasma spectrometer (Japan JARRELL-ASH). Co.LTD). The amount of amine-modified vinyl units is calculated from the nitrogen atom analysis value by the thermiurene method, assuming that one molecule of the amine compound is added to one molecule of vinyl chloride. Synthesis Example 2 (Synthesis of Polymer B) In an autoclave equipped with a stirring device, after purging with nitrogen, 400 parts of deionized water, 83 parts of vinyl chloride, 30 parts of vinyl propionate, and the formula A polymerizable organosilicon compound (hereinafter referred to as S-2) represented by
), 1 part of ammonium persulfate, and 4 parts of polyoxyethylene nonyl phenyl ether were charged, and the reaction was started by heating to 55°C with stirring, and then 83 parts of vinyl chloride was added over a period of 8 hours. It was added continuously to cause a copolymerization reaction. Subsequently, an emulsion was prepared by aging for 6 hours, and 50 parts of sodium chloride and 20 parts of 5% diluted hydrochloric acid were added to this emulsion.
500 parts of hot water was added and the resulting slurry was filtered to form a cake. This cake was dispersed and washed in 1200 parts of deionized water, filtered, and this water washing operation was repeated 5 times, followed by drying. A copolymer having an average degree of polymerization of 450 was obtained, consisting of 83.0% by weight of vinyl chloride units, 15.5% by weight of vinyl propionate units, and 1.5% by weight of organosilicon units. Next, 150 parts of the copolymer thus obtained was
The mixture was charged with 400 parts of methanol, 50 parts of xylene, 15 parts of sodium hydroxide, and 5 parts of n-butylamine into a reactor equipped with a stirrer and a diket, and reacted at 40°C for 6 hours. Washed twice with deionized water, overdried,
The obtained polymer was further dissolved in methyl ethyl ketone and re-precipitated with methanol, and this dissolution and precipitation was repeated twice, further washed twice with deionized water, and overdried, resulting in a copolymer powder (hereinafter referred to as polymer B). 125 parts (abbreviated) were obtained, the composition of which was as shown in Table 1 below. Synthesis Example 3 (Synthesis of Polymer C) In Synthesis Example 1, 69 parts of vinyl chloride, 60 parts of vinyl acetate, Polymer C was obtained in the same manner as in Synthesis Example 1, except that 2 parts of the polymerizable organic compound shown by (hereinafter abbreviated as S-3), 69 parts of additional vinyl chloride, and morpholine was used as the amine compound. Ta. The polymer composition is shown in Table 1. Synthesis Example 4 (Synthesis of Polymer D) In Synthesis Example 1, 74 parts of vinyl chloride, 32 parts of vinyl acetate, A polymerizable organosilicon compound (hereinafter referred to as S-4) represented by
Polymer D was obtained in the same manner as in Synthesis Example 1 except that 16 parts of N,N-dimethylethanolamine was used. The polymer composition is shown in Table 1. Comparative Synthesis Example 1 (Synthesis of Polymer E) In Synthesis Example 1, a polymeric organosilicon compound (S
A copolymer was prepared by copolymerization in the same manner as in Synthesis Example 1, except that -1) was not added, and this was saponified, but N,N-dimethylethanolamine was not added.
Therefore, Polymer E was prepared without amination (composition and degree of polymerization are listed in Table 1). Comparative Synthesis Example 2 (Synthesis of Polymer F) In Synthesis Example 1, a polymerizable organosilicon compound (S
Polymer F was prepared by copolymerization, saponification, and amination in the same manner as in Synthesis Example 1, except that -1) was not added (composition and degree of polymerization are listed in Table 1). Comparative Synthesis Example 3 (Synthesis of Polymer G) A copolymer with the same composition as in Synthesis Example 1 was filtered, washed three times with deionized water without saponification or amination, and dried at 50°C to form a polymer. G was prepared (composition and degree of polymerization are listed in Table 1). Comparative Synthesis Example 4 (Synthesis of Polymer H) A copolymer was prepared in the same manner as in Synthesis Example 3 above, except that the copolymer was not aminated with morpholine. Polymer H was prepared (composition and degree of polymerization are listed in Table 1).

【table】

[Table] Examples 1 to 4, Comparative Examples 1 to 4 (Synthesis of magnetic paint) γ-Fe ₂ O ₃ powder adsorbed with cobalt ions
100 parts, 2 parts of lecithin, 3 parts of surfactant/nonion #NS-230 (product name manufactured by NOF Corporation), 60 parts of methyl isobutyl ketone, 60 parts of methyl ethyl ketone.
1 part and 60 parts of cyclohexanone and mixed for 30 minutes in an Eiger mill to prepare solution A. Add 7 parts of polyurethane resin N-2304 (described above) to 23 parts of polymers A to H obtained in the above synthesis examples and comparative synthesis examples. , 65 parts of methyl isobutyl ketone, 65 parts of methyl ethyl ketone
1 part and 65 parts of cyclohexanone were added and dissolved and mixed for 30 minutes in a lab mixer to make solution B. After adding solution B to solution A in the Eiger mill and kneading for 1 hour, to this was added an isocyanate compound Coronate L (formerly prepared). 6 parts of the mixture were added, kneaded for 30 minutes, and suctioned through a 5 μm filter to make a magnetic paint. (Magnetic tape production and testing) The above magnetic paint was applied to a thickness of 6 μm on a polyester film with a thickness of 16 μm, subjected to magnetic field orientation treatment, dried, surface treated with a super calender, and heated to 60°C for 24 hours. The coating film was cured by holding for a period of time and cut into 3.8 mm width to create a magnetic tape. Next, the magnetic properties of the magnetic tape obtained in this way were measured, the surface smoothness of the magnetic coating was measured in terms of gloss (%), and the lubricity of the magnetic layer was determined by the coefficient of friction between the tape and the head. The durability test was performed by running each magnetic tape at a head load of 10 g and a running speed of 4.8 cm/sec under conditions of 40°C and 80% RH, and measuring the number of runs until the output decreased by 3 dB from the initial output. As a measure of running stability, we ran a magnetic tape under the same conditions as the durability test and measured the friction coefficient with the magnetic head after running 200 times.
The results shown in the table were obtained. As is clear from this table, Examples 1 to 4 obtained by this invention have better magnetic properties than Comparative Examples 1 to 4, superior surface smoothness of the magnetic layer, small coefficient of friction, and durability. This confirms that the magnetic recording medium obtained by the present invention has excellent magnetic properties, running stability, and durability.

【table】

Claims (1)

[Claims] 1 Vinyl chloride unit, vinyl alcohol unit, amine-modified vinyl unit, and the following general formula (Here, V is 1 having a polymerizable olefin bond.
valent organic group, l is 0 to 10, m and n are 0<m<
1000, an integer where 0<n<1000 and 0<m+n<1000) A magnetic recording medium comprising: formed on a support. 2. The copolymer is composed of 60 to 90% by weight of vinyl chloride units, 2 to 20% by weight of vinyl alcohol units, 0.05 to 20% by weight of amine-modified vinyl units, and 0.1 to 20% by weight of the above-mentioned organosilicon compound. A magnetic recording medium according to claim 1.