KR910006579B1 - Producing method for magnetic recording medium - Google Patents

Abstract

A magnetic recording medium is produced by coating a magnetic pigment on the polyester base film. The pigment is produced by mixing a magnetic powder with a binder vinyl chloride vinyl acetate copolymer and polyurethane resin, and mixing the mixt. with an isocyanate-hardening agent and a hardeing-promoting agent in a solvent. The hardeing-promoting agent is pref. a mixt. of alkyltin carboxylate and tri-amine cpd. The magnetic powder is pref. gamma-Fe2O3 powder, Fe3O4 powder Co-contg. gamma-Fe2O3 powder or CrO2 powder. The recording medium has a good durability.

Description

Method of manufacturing magnetic recording medium

The present invention relates to a method of manufacturing a magnetic recording medium having excellent durability.

Magnetic recording media are usually made by applying and drying a magnetic coating made of magnetic powder, a binder component, an organic solvent and other necessary components on a support such as a polyester film. At this time, the binder component to be used must disperse the magnetic powder well and have good wear resistance and durability.

For this reason, many studies have been made on binder resin conventionally, for example, isocyanate is a binder resin made by combining a vinyl chloride-vinyl acetate copolymer having excellent dispersibility of magnetic powder or a fiber-based resin with a polyurethane resin having excellent abrasion resistance. The method of improving the wear resistance and durability of a magnetic layer has been performed by crosslinking with a compound.

However, the isocyanate compound used at this time has a relatively late crosslinking reaction since the pot life of the magnetic paint is shortened when the one having a fast crosslinking reaction is used, which causes problems in the application of the magnetic paint. As a result, a long time is required until the crosslinking reaction is completed after the magnetic coating is applied to a support such as a polyester film and dried, and an isotropic reaction occurs in which water in the air reacts with an isocyanate compound. This has not been done sufficiently, and has been a problem. In order to solve this problem, organic tin-based compounds such as dibutyl tin dilaurate, dibutyl tin 2-ethylhexylate, ferric acetylacetonate, triethylamine, etc. A method for improving the wear resistance and durability of a magnetic layer by promoting the crosslinking reaction without shortening the pot life of the magnetic coating by adding the catalyst to promote the magnetic coating is used.

In the conventional method as described above, that is, a method in which a relatively slow isocyanate compound and a curing accelerator or the like described above are used together, most of the accelerator is adsorbed to a filler such as magnetic powder or carbon black when the addition amount of the accelerator is small. Since the effect of promoting the curing reaction is not exerted, a relatively large amount should be added. In this case, the curing accelerators sufficiently promote the crosslinking reaction, but additionally, the surface filming phenomenon during the application or the role of the plasticizer may be used. It may be weakened to inhibit the formation of a strong magnetic layer or to form low molecular weight head contaminants. Even for example, amine-based curing accelerators have caused various problems such as causing a bad smell in the final product.

The present inventors have diligently studied to improve all such drawbacks. As a result, a mixture of alkyltin carboxylate and a tertiary amine compound is added to a magnetic paint containing binder resins and a curing agent of an isocyanate compound crosslinked with such binder resins. By adding as a hardening accelerator, it discovered that the wear resistance and durability of a magnetic layer fully improved by the formation of the strong magnetic layer by hardening without the above-mentioned trouble, and came to complete this invention.

That is, the present invention is a mixture of alkyltin carboxylate and tertiary amine compound in a magnetic paint added with a vinyl chloride-vinyl acetate copolymer having excellent dispersibility of magnetic powder and a curing agent of an isocyanate compound crosslinked with a fibrin resin. Is added to the curing accelerator, and it effectively gives the curing accelerator function of the binder resin and the curing agent, which is extremely small amount, without any problems such as surface bulging phenomenon, head contamination formation phenomenon and odor causing during application. Formation is to provide sufficient wear resistance and durability of the magnetic layer.

The alkyltin carboxylate used in the present invention is a chitin compound having an alkyl group and a carboxyl group as four ligands, for example, dimethyltin dilaurate dibutyl tin dilaurate, dioctyl tin dilaurate dibutyl tin succinate, dibutyl Tinmalate, and the like. These compounds are manufactured and marketed by TOKYO Kasei, Goodrich Company-Gaiyi Co., Am & Chemicals, and others. In addition, the tertiary amine-based associations used in the present invention include, for example, triethylamine, triethanolamine, triethylenediamine, and the like, and these compounds are used in various companies such as Goodrich Company, Tokyo Kasei, Air Products & Chemicals, etc. Manufacture.

Alkaline carboxylate and the tertiary amine mixed curing catalyst used in the present invention are preferably 10 ppm to 500 ppm, preferably 50 ppm to 200 ppm, based on the binder resin to be added. If the addition amount is less than 10ppm, the hardening promoting effect is not exhibited greatly, and if it exceeds 500ppm, surface bruising, head contaminant formation, odor generation and the like are not good. In addition, the composition of such a mixed curing catalyst is 20:80 to 80:20, preferably 40:60 to 60:40, in a molar ratio of alkyltincarboxylate to tertiary amine, most suitable for the purpose of the present invention. This is because the alkyl tin carboxylate and the tertiary amine react with each other in an appropriate molar ratio to form a new complex, thereby exhibiting a hardening promoting effect in an extremely small amount than when used alone.

In addition, the mixed curing catalyst is preferably dissolved in an organic solvent such as cyclohexanone, toluene, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, methyl ethyl ketone, and the like. It may be any time before and after introduction. If the magnetic powder is dispersed at the time of dispersing the magnetic powder before the curing agent is added, the mixing state becomes very good. In the case of some binders such as vinyl chloride-vinyl acetate-based copolymers, the copolymer may be decomposed due to the temperature rise due to dispersion. There is also a thermal stabilizer effect on this copolymer binder is also exhibited better.

In the present invention, as the vinyl chloride-vinyl acetate copolymer used as the binder resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate maleic acid copolymer, vinyl chloride- Vinyl propionate copolymer and the like are suitable. This kind of vinyl chloride-vinyl acetate-based copolymer has good affinity with the magnetic powder, so the dispersibility of the magnetic powder is excellent and the electron conversion characteristics are improved. In addition, when used together with a curing agent such as a polyurethane-based resin and an isocyanate compound having a hydroxyl group and a carboxyl group in the molecule, a strong magnetic layer is crosslinked in a three-dimensional network structure by a rapid crosslinking reaction with an alkyltin carboxylate and a tertiary amine curing catalyst. It is formed to improve the wear resistance and durability of the magnetic layer. Examples of such vinyl chloride acetate copolymers include U. C., VYHH, VAGH, VMCH, VYLF, and Denkavinyl, which are manufactured by U.C. and C.

As the fibrin resin used as the binder resin, nitrocellulose, acetyl cellulose, acetyl butyl cellulose, methyl cellulose, ethyl cellulose, benzyl cellulose, carboxymethyl cellulose, and the like are suitable. Nitrocellulose L1 / 2, L1 / 4, L1, H1 / 4, H1 / 2, H1, H5, Daicel Corporation made of Nitrocellulose Cellulose RS1 / 16, RS1 / 2, RS1 , RS2, and so on. Like this type of vinyl chloride vinyl acetate copolymer as described above, since the affinity with the magnetic powder is excellent, the dispersibility of the magnetic powder is excellent, thereby improving the electron conversion characteristics and the hydroxyl group in the molecular chain. When used together with a curing agent such as a polyurethane resin and an isocyanate compound, a crosslinking reaction is carried out very quickly by the action of an electroalkyltin carboxylate and a tertiary amine compound mixed curing catalyst to form a three-dimensional network structure, thereby forming a robust magnetic layer, and Abrasion resistance and durability are improved.

Moreover, as a polyurethane resin used with a vinyl chloride acetate copolymer or a fibrin type resin, urethane elastomer and urethane prepolymer which have been used together conventionally are the most suitable. Urethane resin is also good. In particular, containing hydroxyl groups at both ends or in the molecular chain is more suitable because it improves the dispersibility of the magnetic body. Specific examples of such a polyurethane-based resin (trade name) Pandex T-5201, Pandex T- 5250, Estane 5703 made by Goodrich Co., Ltd., Estan 5706, N-2301, N-2303 made by Nippon Polyurethane Co., and the like. This type of polyurethane-based resin also has good affinity with the magnetic powder and excellent dispersibility of the magnetic powder. When such a polyurethane resin is used together, the dispersibility of the magnetic powder is improved, the surface smoothness of the magnetic layer is also improved, and the electron conversion characteristics are further improved.

When such a vinyl chloride acetate copolymer or fibrin resin is used together with a polyurethane resin, the compounding ratio varies depending on the type of binder resin to be used, but the vinyl chloride vinyl acetate copolymer or fibrin resin in terms of weight ratio It is preferable to use a large polyurethane resin within the range of 10 to 90 to 80 to 20. If the vinyl chloride acetate copolymer or the fibrin resin is too small, the dispersibility of the magnetic powder is not good and the polyurethane resin is too small. Good wear resistance is not obtained.

In addition, an isocyanate compound, which is a curing agent used together with a binder resin such as vinyl vinyl acetate-based copolymer fibrin resin or polyurethane resin, is usually a phase obtained by reacting 1 mol of triol and 3 mol of diisocyanate. Reactive isocyanates are preferred. Isocyanate compounds of this kind cross-react with isocyanate groups in the molecule, such as the vinyl chloride acetate copolymer or the hydroxyl group and carboxyl group in the fibrous resin, or the urethane bonds and hydroxyl groups in the polyurethane-based resin. Since the crosslinking reaction is promoted by the alkyltin carboxylate and the tertiary amine mixed curing catalyst added to the mixture, the magnetic layer is rapidly crosslinked into a three-dimensional network to form a strong magnetic layer, thereby further improving wear resistance and durability of the magnetic layer. The amount of use varies depending on the type of binder resin to be added, but it is preferable to use it in the range of 1 to 40% by weight based on the total amount of the binder component. If the amount is less than 1% by weight, the wear resistance of the magnetic layer is not sufficiently improved. There are too many of these, and the magnetic layer becomes too hard and brittle. As a specific example (brand name) of such a trifunctional isocyanate compound, Colonnet L by the Japanese Polyurethanes company, Mondur CB-50, CB-60, etc. by Momica Chemical Co., Ltd. are mentioned.

When forming the magnetic layer containing such a binder resin, the magnetic powder used is, for example, γ-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing, γ-Fe ₂ O ₃ powder, Co-containing Fe ₃ In addition to O ₄ powder, CrO ₂ powder, CO ferrite powder and Ba ferrite powder, conventionally known various magnetic powders such as Fe powder, Co powder, and metal powder are contained. Furan, methyl isobutyl ketone, toluene ethyl acetate, dioxane, dimethylformamide, and the like may be used to dissolve the binder resin. Any conventionally known organic solvent may be used alone or in combination.

In the following Examples and Comparative Examples will be described the present invention in more detail. Evaluation method of the product produced in each embodiment is as follows and is not limited to the embodiment of the present invention.

1.Elastic modulus in 2% elongation (2% elastic modulus)

Measured using Instron in accordance with ASTM D 882, this value increases in proportion to the degree of cure.

2. Stiffness

Tape stiffness was measured using a Toyoseki Stiffness Tester, and this value increases in proportion to the degree of cure.

3. Friction Coefficient

It was measured by the method according to ASTM D 1984-73, and generally decreased with increasing stiffness and elastic modulus at 2% elongation.

4. Steel duration

A magnetic recording medium is used as a video tape to first record an image and to make it a still image at the time of reproduction. At this time, the time from the stop time until the image is distorted is measured, and the longer the time is, the better the driving performance and the excellent durability.

5. Head contamination

The resulting magnetic tape was assembled into a VHS cassette, and 100 heads of T-120 were tested using a video tape recorder to classify the head contamination into five stages: extremely good (◎), good (○), normal (△), Slightly bad (×), extremely bad (××)

6, tetrahydrofuran (THF) test

The number of times that the magnetic layer starts to rub off with a cotton swab moistened with THF is recorded, and as the number of times is increased, the magnetic layer has excellent solvent resistance and hardening.

7. Odor Condition

The finished product was judged by the sense of smell and divided into three levels: Odorless (○), Normal (△), Poor (×)

Example 1

100 parts by weight of Co-containing γ-Fe ₂ O ₃ powder

Vinyl chloride vinyl acetate vinyl alcohol copolymer (UCC, VAGH) 10 parts by weight

15 parts by weight of polyurethane (Goodrich, Estan 5703)

1 part by weight of stearic acid

1 part by weight of myristic acid

250 parts by weight of tetrahydrofuran

After dispersing the composition in a ball powder for 100 hours, the following curing agent and curing accelerator are dissolved in a solvent and kneaded.

5 parts by weight of curing agent (colonate el)

Dibutyl tin dilaurate 2.0 × 10 ^-3 parts by weight

Triethylenediamine 0.5 × 10 ^-3 parts by weight

The mixed curing catalyst is a system wherein the molar ratio of dibutyltindilaurate to triethylenediamine is 4 to 6. The amount added corresponds to 100 ppm with respect to the total binder resin. The magnetic coating prepared as described above was coated and dried on a 15 µ polyester film substrate to a thickness of about 5 µ, and then the surface of the magnetic layer was calendered with calendered rolls under pressure and cured at 60 ° C. for 18 hours. The product thus produced is cut into suitable widths to produce a magnetic recording medium.

Example 2

Prepared in the same manner as in Example 1 except that the amount of the curing catalyst of 0.26 × 10 ⁻³ parts by weight (molar ratio 6 to 4) of 2.24 × 10 ⁻³ parts by weight of dibutyltin dilaurate trimethylenediamine was changed.

Example 3

Prepared in the same manner as in Example 1, 0.99 × 10 ⁻³ parts by weight of dibutyl tin dilaurate and 0.27 × 10 ⁻³ parts by weight of triethyldiamine (molar ratio 4: 6) such that the amount of the curing catalyst was 50 ppm with respect to the total binder. Was added.

Comparative Example 1

Prepared in the same manner as in Example 1, but did not add any curing catalyst.

Comparative Example 2

Prepared in the same manner as in Example 1, but only 1.5 × 10 ^-2 parts by weight of dibutyl tin dilaurate was added as a curing catalyst instead of the curing catalyst of Example 1.

Comparative Example 3

Prepared in the same manner as in Example 1, but only 1.25 × 10 ^-3 parts by weight of triethylenediamine was added as a curing catalyst instead of the curing catalyst of Example 1.

[Comparative Example 4]

Prepared in the same manner as in Example 1, but only 2.5 × 10 ^-3 parts by weight of dibutyl tin dilaurate was added as a curing catalyst instead of the curing catalyst of Example 1.

Table 1 shows the progress of the evaluation test on the samples obtained in the above Examples and Comparative Examples.

TABLE 1

As can be seen from Table 1, the magnetic recording medium prepared according to the present invention has a strong magnetic layer formation by completing the curing of the magnetic layer even with the addition of a very small amount of curing catalyst, without the formation of head contaminants and odor-causing phenomena compared to the conventional one. It was confirmed that the wear resistance and the durability were extremely excellent.

Claims (1)

A curing accelerator comprising a mixture of alkyltin carboxylate and a tertiary amine compound in a magnetic paint in which a vinyl chloride acetate copolymer or a fibrin resin and a polyurethane resin are used as a binder resin, and a crosslinked isocyanate curing agent is mixed. Method of manufacturing a magnetic recording medium, characterized in that used as.