JPS6015820A - Copolymer for magnetic paint and magnetic paint for magnetic recording medium containing said copolymer - Google Patents

Abstract

PURPOSE:To improve dispersibility and pot life of magnetic powder by copolymerizing at random a vinyl ester of carboxylic acid, vinyl alcohol monomer and further the specific 4th component with a vinyl chloride. CONSTITUTION:A titled copolymer is formed of a copolymer consisting of >=0.1wt% and <5wt% vinyl ester of carboxylic acid, 3-9.9wt% vinyl alcohol and 0.1-5wt% unsatd. dicarboxylic acid and/or unsatd. dicarboxylic acid anhydride as the 4th component copolymerized with >=90wt% and <=9wt% vinyl chloride. A long pot life is obtd. while the high dispersibility of magnetic powder is maintained by using the unsatd. dicarboxylic acid and unsatd. dicarboxylic anhydride in combination. If such coating is applied on a base body consisting of a polyester sheet, the smooth magnetic coated film having high brightness is obtd. When such film is further dried and pressed to make a magnetic tape, the tape has such an excellent characteristic that the tape is free from blocking even when exposed to adverse conditions under high humidity.

Description

Detailed Description of the Invention The present invention relates to a copolymer for magnetic coatings comprising vinyl chloride, vinyl carboxylic acid ester, vinyl alcohol, unsaturated dicarboxylic acid and/or unsaturated dicarboxylic acid anhydride, and a magnetic recording medium using the same. Regarding magnetic paint for use.

Generally, magnetic recording media such as magnetic tapes and magnetic cards are manufactured by applying a magnetic paint containing magnetic powder, thermoplastic resin, and thermosetting resin dissolved and dispersed in an organic solvent onto a substrate such as polyester film or C1-. ing.

As thermoplastic resins that are raw materials for this magnetic paint, vinyl chloride copolymers, vinylidene chloride copolymers, acrylic ester copolymers, methacrylic acid copolymers, etc. have been proposed.
Specific examples of these resins include vinyl chloride-vinyl acetate copolymer, vinyl chloride-PJ [vinyl-vinyl alcohol ternary copolymer], and vinyl chloride-vinyl acetate-maleic acid ternary copolymer. However, when manufacturing magnetic coatings using these resins, there are issues with the mixability of magnetic powder and thermoplastic resin, the mixability when thermosetting resins such as urethane resins are added, and the substrate to be coated. There are advantages and disadvantages such as affinity with magnetic coatings, the state of the magnetic coating film obtained, and physical properties as a magnetic coating material, and it is difficult to simultaneously satisfy the necessary physical properties with one type of resin.

For example, vinyl chloride-vinyl acetate copolymer has poor reactivity with urethane resins, and when a magnetic paint using this copolymer is applied to a substrate, the paint film peels off, making it impractical for use in magnetic recording media. In addition, vinyl chloride-vinyl acetate-vinyl alcohol terpolymer has good dispersibility of magnetic powder and good reactivity with urethane resin, so if it is used to make a magnetic paint, it can be used as a paint with a short bot life. This results in poor workability, and when applying this to a substrate such as a polyester sheet or film, the viscosity of the paint increases over time, so it is necessary to increase the amount of organic solvent added when preparing the paint. It is necessary to lower the viscosity of the paint from the beginning, and it is impossible to prepare a large amount of paint at once.

In addition, although the general vinyl chloride-vinyl acetate-maleic acid terpolymer has a relatively hard dispersibility of magnetic powder, it has no reactivity with urethane resin, and it is difficult to strengthen the coating film by crosslinking. I can't wait.

The thermoplastic resin according to the present invention contains (a) more than 90% by weight of vinyl chloride, (b) carboxylic acid vinyl ester, (C
) vinyl alcohol monomer, and a fourth component (d
) component, that is, a polymer in which an unsaturated dicarboxylic acid and an unsaturated dicarboxylic anhydride, an unsaturated dicarboxylic acid, or an unsaturated dicarboxylic anhydride are randomly copolymerized,
By using the thermoplastic resin according to the present invention, the dispersibility of magnetic powder, pot life, etc. are significantly improved, and when used in a magnetic coating for magnetic recording media, the required properties are better than those of conventional thermoplastic resins. It is possible to obtain a magnetic coating material that is significantly improved and excellent in comparison with the composition of the present invention.

However, if only unsaturated dicarboxylic acid is used as the fourth component, the dispersibility of the magnetic powder will be better compared to conventional resins, and if only unsaturated dicarboxylic acid anhydride is used, the dispersibility of magnetic powder will be better compared to conventional resins. In addition to improving dispersibility, the reaction with the thermosetting resin is suppressed, and the so-called pot life becomes longer. Furthermore, when an unsaturated dicarboxylic acid and an unsaturated dicarboxylic acid anhydride are used together, the bot life is long while maintaining the high dispersibility of the magnetic powder, and when this is applied to a substrate made of polyester sheet, a smooth, high-gloss magnetic material is created. When a coating film is obtained, which is further dried and pressed to form a magnetic tape, it has excellent properties such as no blocking even when left under adverse conditions such as high temperature and high humidity. These characteristics are vinyl chloride, vinyl ester, vinyl alcohol ternary-ITi combination and vinyl chloride, vinyl ester, non-tl
Sum: h 71/ Contains more than 90% by weight of vinyl chloride, cannot be obtained as a mixture with a fonic acid copolymer, and is copolymerized with an unsaturated dicarboxylic acid and/or an unsaturated dicarboxylic acid anhydride as the fourth component. The present inventors have discovered that the present invention, which consists of coalescence, can be obtained in a concise manner, and have completed the present invention.

The present invention will be explained in more detail below.

The present invention is a resin solution having an average degree of polymerization of 100 to 900, which is obtained by copolymerizing the monomers of each of the above components.

As the vinyl chloride of the present invention, ordinary commercially available products can be used. As the carboxylic acid vinyl ester of the fbl component to be copolymerized with vinyl chloride, vinyl acetate, vinyl propionate, vinyl hazathysocate (manufactured by Shell, trade name),
Examples include vinyl stearate, among which vinyl acetate is preferred.

(The unsaturated dicarboxylic acid of the dl component is selected from maleic acid, itaconic acid, fumaric acid, etc., of which maleic acid is preferable. As the unsaturated dicarboxylic acid anhydride, maleic anhydride and itaconic anhydride are preferable. Other examples include fumaric anhydride, himic anhydride (trade name of Hitachi Chemical Co., Ltd.), etc.The vinyl alcohol of the component (C) can be obtained by saponification of the polymerized carboxylic acid vinyl ester of the component +b). As saponifying agents, acids such as hydrochloric acid, sulfuric acid and nitric acid, and alkalis such as caustic soda and caustic potash are used, but hydrochloric acid is generally most preferred. For example, (a
), fbl, and (dl) are copolymerized and then partially saponified using hydrochloric acid in the presence of alcohol to obtain a vinyl alcohol copolymer component.

Next, the monomer composition of the copolymer will be explained.

In the thermoplastic resin composition according to the present invention (al component vinyl chloride is more than 90% by weight and 95% by weight of the total components)
It is as follows. If vinyl chloride exceeds 95% by weight, the viscosity of the solution increases when mixed with magnetic powder, so the viscosity of the paint must be lowered when applied to a substrate, which requires the use of a large amount of solvent.

Furthermore, the amount of vinyl alcohol as the component (C) is 3 to 9 J weight %, and if the amount of the component (C) is 3 weight % or less, the compatibility with the urethane resin decreases and the dispersibility of the magnetic powder does not improve.

In addition, component fd) may be obtained by copolymerizing either an unsaturated dicarboxylic acid or an unsaturated dicarboxylic acid anhydride, or a mixture thereof.

The (cl) component is 0.1 to 5% by weight, preferably 0.1 to 5% by weight.
It is 5 to 3% by weight. If it is less than 0.1% by weight, the reaction with the urethane resin is not sufficiently suppressed. On the other hand, if it exceeds 5% by weight, the amount of insoluble substances increases and it cannot be put to practical use. The average degree of polymerization of the vinyl chloride copolymer of the present invention is 100 to 900. When applied to a substrate as a magnetic paint, if it is less than 100, the coating film will be weak and it is not practical. On the other hand, if it exceeds 900, the viscosity of the paint is high and workability is poor. Average degree of polymerization is 150
-75o, preferably 150-550.

It is desirable that the vinyl chloride resin according to the present invention has each monomer arranged as evenly as possible. To explain the general manufacturing method, first, vinyl chloride is added to the polymerization end in a proportion that will give the above copolymer composition. and carboxylic acid vinyl ester, an oil-soluble polymerization initiator such as hendyl peroxide, and a solvent are charged, and the mixture is heated and polymerized under pressure. Next, the unsaturated dicarboxylic anhydride and/or the unsaturated dicarboxylic anhydride may be added all at once at the beginning of the polymerization, or a portion is added at the beginning of the polymerization and the remainder is added in portions as the polymerization progresses; This method is more preferable in terms of dispersibility when forming a magnetic coating material and reactivity with a thermosetting resin, since a copolymer resin having a uniform composition can be obtained. The vinyl chloride copolymer resin thus obtained is saponified into vinyl alcohol in a predetermined amount using hydrochloric acid as a catalyst in the presence of alcohol, and the organic solvent is removed to form a powder. Alternatively, only the alcohol can be removed from the organic solvent after saponification by evaporation under reduced pressure, and the product can be used as a solution in an organic solvent suitable for the intended use. An equivalent copolymer cannot be obtained by a method in which at least the polymers of components (a) and (b) are partially saponified (copolymerizing the dl component).

When the vinyl chloride copolymer resin according to the present invention is used as a magnetic coating, as the thermosetting resin, polyisocyanates such as aromatic polyisocyanates and aliphatic polyisocyanates or urethane prepolymers are mainly used, and phenol resins, Epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reactive resins, epoxy polyamide resins, nitrocellulose melamine resins and mixtures thereof are used, among which urethane resins, epoxy resins and phenolic resins are suitable. .

To produce a magnetic paint using vinyl chloride copolymer resin, 200 to 600 parts by weight, preferably 300 to 50 parts by weight of ferromagnetic iron oxide is added to 100 parts by weight of vinyl chloride copolymer resin.
0 parts by weight, 600 to 1,200 parts by weight of the organic solvent, preferably 800 to 1,000 parts by weight, and 5 to 50 parts by weight, or 4 parts or 10 to 30 parts by weight of the thermosetting resin.

The magnetic paint according to the present invention may contain other thermoplastic resins, dispersants, lubricants, antistatic agents, abrasives, and the like.

Other thermoplastic resins include vinyl chloride copolymers such as vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, and vinyl chloride acrylic acid ester copolymer; vinylidene chloride acrylonitrile copolymer, vinylidene chloride methacrylate Vinylidene chloride copolymers such as acid ester copolymers; cellulose derivatives such as nitrocellulose and cellulose acetate; thermoplastic polyurecne elastomers, butadiene-acrylonitrile copolymers, polyester resins, styrene-butadiene copolymers, amino resins, Saturated polyester resin, thermoplastic acrylic ester resin,
Thermoplastic methacrylic acid ester resins, synthetic rubber-based thermoplastic resins, and mixtures thereof are used.

As a dispersant, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linuric acid, carboxylic acid having 11 to 17 carbon atoms, or Li, Nas K, etc. Mg
, Ca-, Ba salts, or lecithin, alcohols with 12 or more carbon atoms, sulfuric esters of alcohols with 12 or more carbon atoms are used.Lubricants include silicone oil, graphite, molybdenum disulfide, and disulfide. Tungsten, carbon number 12-16
Fatty acid esters of higher fatty acids and monohydric alcohols having 3 to 12 carbon atoms are used.

Antistatic agents include natural surfactants such as saponin, nonionic surfactants (alkylene oxide, glycerin, glycidol), cationic surfactants (phosphonium, sulfonium), and anionic surfactants. (Carboxylic acid type 5. Sulfonic acid type, phosphoric acid type, sulfuric acid ester type, phosphoric acid ester type), amphoteric surfactant (ester of amino acids or aminosulfonic acids or amino alcohols and sulfuric acid or phosphoric acid), etc. are used. .

As the polishing agent, fused alumina, silicon carbide, chromium oxide, corundum, etc. are used.

The present invention will be specifically described below with reference to Examples.

Example 1 170 parts by weight of vinyl chloride, 30 parts by weight of vinyl acetate, 180 parts by weight of acetone, and 2 parts by weight of Nzoyl peroxide were charged into an autoclave, and polymerization was started at a temperature of 50°C.

When the polymerization rate of vinyl chloride-vinyl acetate reached 10%, 1/6 of a mixed solution consisting of 1.8 parts by weight of maleic acid and 20 parts by weight of acetone was added.

The remaining 5/6 was added in portions until the polymerization rate reached 60%.

The mixture was polymerized and cooled until the polymerization rate reached 90%, and 1200 parts by weight of methanol and 14 parts by weight of 38% hydrochloric acid were added thereto for saponification at a temperature of 60°C. When the saponification rate of vinyl acetate reached 70%, it was cooled and methanol was removed. Furthermore, 1200 parts by weight of methanol was added to wash the vinyl chloride copolymer resin, and methanol was removed again and the mixture was dried.

Using this copolymer, a magnetic paint was prepared according to the gloss measurement method described below, and a coating film was formed.

This copolymer and magnetic paint were tested according to the measurement method and criteria described below, and Table 1 shows the results.

Measurement method and criteria (1) Compatibility Copolymers obtained in Examples and Comparative Examples (solid content equivalent) 100 parts by weight (Product name: Coronate urethane resin) 20 parts by weight Methyl ethyl ketone 300 iR [parts] ○ for transparent items, △ for semi-transparent items,
Opaque products were marked as ×.

(2) Glossiness Copolymers obtained in Examples and Comparative Examples (solid content equivalent) 100 parts by weight Magnetic iron oxide powder
400 parts by weight Methyl ethyl ketone 300 parts by weight Methyl isobutyl ketone 300 parts by weight Toluene 30
0 parts by weight (trade name: Coronate urethane resin) 20 parts by weight (trade name: Lecithin (soybean oil)) A magnetic paint obtained by thoroughly kneading a mixture consisting of 2 parts by weight is applied to a polyester film substrate to a dry film thickness. Apply to a thickness of 10μ and dry at 100°C for 1 minute. Furthermore, the magnetic coating 9
Smoothness is imparted by pressing under the conditions of 0° C. x 30 seconds x 2 kg/cffl. The magnetic coating film was measured at 60% using a gloss meter.
Measure the reflectance at the reflection angle.

(3) Bond life of magnetic paint The same magnetic paint used for the above gloss measurement was
The bot life was determined by measuring the time until the paint loses its fluidity (gelling) in a constant temperature bath at 25°C.

(4) Blocking property The same magnetic paint used in the above gloss measurement was applied to a polyester film base so that the film thickness after drying was 10 μm, dried at 100°C for 1 minute, and then stacked to give 2 kg/
24 at a temperature of 60°C and a humidity of 90% with a load of cnl.
After leaving it for a while, remove the film. Those that were easily peeled off were rated ○, those that were slightly sticky were rated △, and those that were sticky were rated ×.

(5) Adhesion The same magnetic paint used in the above gloss measurement was applied to a polyester film substrate so that the film thickness after drying was 10 μm, and dried at 100°c for 1 minute. Apply Sellotape (trade name) on top of this coating, rub it strongly with your fingers, and then peel it off. At this time, the adhesiveness was rated as ○ if the magnetic coating film did not adhere to the cellotape, Δ if the coating film slightly adhered, and × if the coating film adhered and peeled off.

Note that the following Examples and Comparative Examples were also tested in accordance with the above method.

Examples 2 to 6 Thermoplastic copolymers and magnetic paints were obtained in the same manner as in Example 1, except that the types of monomers, the charging ratio, and the saponification rate were varied. These conditions and test results are shown in Table 1.

Comparative Example 1 Denkavinyl #1 was used instead of the copolymer resin according to the present invention.
Using 000GKT (Denki Kagaku Kogyo Co., Ltd. (trade name, composition shown in Table 2)), a magnetic paint was produced in the same manner as the gloss test method described above7, and applied to a polyester film.The measurement method described above. Each physical property was measured according to the following, and the results are shown in Table 2.

Comparative Example 2 A magnetic paint was obtained in the same manner as in Comparative Example 1, except that Denkavinyl #1000CK (Denka Kagaku Kogyo@: trade name, composition shown in Table 2) was used instead of Denkavinyl #1000GKT. This was applied to a polyester film.

Each physical property was measured and the results are shown in Table 2.

Comparative Example 3 A copolymer resin was obtained in the same manner as in Example 1, except that the type of monomer, the charging ratio, and the saponification rate were changed as shown in Table 2. Using this, a magnetic paint was manufactured by the method of Example 1, and each physical property was measured, and the results are shown in Table 2.

Comparative Example 4 Denkavinyl #1000 used in Comparative Example 1 and Comparative Example 2
GKT and Denkavinyl #1000GK were mixed in the proportions shown in Table 3, a magnetic paint was obtained in the same manner as in Comparative Example 1, it was applied to a polyester film, and each physical property was measured. The results are shown in Table 3.

Comparative Example 5 Polymerization was carried out in the same manner as in Example 1 except that the polymerization initiation temperature was 32°C. The obtained resin composition is vinyl chloride 90
It was a copolymer containing 5 parts by weight of vinyl acetate, 5 parts by weight of vinyl alcohol, 0.5 parts by weight of maleic anhydride, and 1 part by weight of maleic acid, and had a degree of polymerization of 930. The compatibility test result of this copolymer was that it was translucent, and the pot life of the magnetic paint using this copolymer was 290 hours. Furthermore, the coating film obtained from this magnetic paint had a glossiness of 40%, good printability, and good adhesion.

Table 1 Note: *1 Itaconic acid was used.

Table 2 Table 3

Claims (1)

[Scope of Claims] fl) component fa), more than 90% by weight and not more than 95% by weight of vinyl chloride, component (b), 0.1% by weight or more and less than 5% by weight of carboxylic acid vinyl ester, (C1 Ingredients, 3-9.9% by weight vinyl alcohol, (
A copolymer for magnetic paint, which is a random copolymer consisting of a dl component and 0.1 to 5% by weight of an unsaturated dicarboxylic acid and/or an unsaturated dicarboxylic anhydride, and has an average degree of polymerization of 100 to 900. (2) (Al component, more than 90% by weight and not more than 95% by weight of vinyl chloride, (b) component, 0.1% by weight or more and less than 5% by weight of carboxylic acid vinyl ester, (C) component, 3- 9.9% by weight vinyl alcohol,
(di component, a random copolymer consisting of 0.1 to 5% of unsaturated dicarboxylic acid and/or unsaturated dicarboxylic acid anhydride, and having an average degree of polymerization of 100 to 900. A magnetic paint for magnetic recording media containing a thermosetting resin, magnetic powder, and an organic solvent.