KR960009287B1 - Method of manufacturing polyurethane resin for binder of magnetic recording media - Google Patents

Abstract

The polyurethane resin binder is prepared by reacting organic diisocyanate(D) with diol mixture that contains 10-90wt% polycarbonate diol(A-1) of MW 500-3,000 synthesized from glycol and carbonate, 90-10wt% polyester diol of MW 500-5,000 synthesized from cyclic glycol and aliphatic secondary basic acid, diol(B) with COOX group(X is H2 or alkali metal atom), and short chain diol(C) with carbon no. of 2-10.

Description

Polyurethane resin manufacturing method for binder of magnetic recording medium

1 is a graph showing wear resistance of a binder polyurethane resin of a magnetic recording medium,-○-is Example 1,-□-is Example 2,-△-is Example 3,-●-is Comparative Example 1,-■-shows Comparative Example 2,-▲-shows the wear resistance of the magnetic recording medium formed of the resin prepared in Comparative Example 3.

The present invention relates to a method for producing a polyurethane resin for a binder of a magnetic recording medium, and more particularly, to improve the hydrolysis resistance and dispersibility of a magnetic component as a binder component, to cause a curing reaction with a polyisocyanate having two or more isocyanate groups, and a magnetic layer. The present invention relates to a method for producing a polyurethane resin for a binder of a magnetic recording medium which improves durability such as wear resistance and long term storage resistance.

In recent years, the demand performance has also changed in accordance with the demand and use of magnetic recording media, such as audio tapes and home VTR tapes. In particular, high recording density, high speed, high temperature and high humidity, durability improvement under high speed and high humidity conditions, and severe friction with the head when the tape is driven for a long time are raised in the magnetic layer. The need for high reliability, such as the drop-out phenomenon of magnetic components and the drop-out phenomenon due to wear and the occurrence of false signals, and the time required for the dispersion of magnetic components, can be shortened and the hardening of magnetic coating To improve the productivity of the magnetic recording medium obtained by increasing the speed and smoothing the surface of the magnetic recording medium. One is required increases.

In addition, the binder plays an important role in maintaining the properties, physical properties, and productivity of the magnetic layer, which enables the production of excellent magnetic paints and high performance magnetic recording media with uniform dispersion of magnetic components in a shorter time. In addition, good electronic properties such as high signal-to-noise ratio (SN) ratio and high carrier-to-noise ratio (CN) ratio are required, and a binder having excellent durability such as wear resistance is required.

Conventional binders for magnetic recording media include fibrous resins such as nitrocellulose and vinyl chloride-vinyl acetate copolymers. Recently, thermoplastic polyurethane resins have been used to improve the durability of magnetic recording media by providing wear resistance to magnetic layers. A binder consisting of polyisocyanates of is proposed.

That is, the thermoplastic polyurethane resin has various properties such as injection molding, ejection molding, synthetic leather, elastic fiber, paint, adhesive or ABS resin, due to its excellent properties such as high elasticity, flexibility, wear resistance, cold resistance, and strength. It is widely used as a polymer modifier such as AS resin, PVC or derivatives thereof, and fiber acetate, but has weak disadvantages in heat resistance, hydrolysis resistance, and moisture heat resistance, and is used for printing ink, magnetic paint, conductive resin, magnetic rubber, etc. Although the development is active, there is a problem in that the dispersibility of the magnetic component is poor at the time of use, and this causes the satisfactory electronic properties to not be obtained, and it is difficult to smooth the surface of the magnetic recording medium, thereby improving the productivity.

In order to solve the above-mentioned problems, Japanese Unexamined Patent Application No. 58-153230 introduces a tertiary amino group into the molecular chain, while Japanese Unexamined Patent Application No. 61-92422 introduces a tertiary hydroxyl group into the molecular chain to improve dispersibility. Although the method of the present invention is described, there is a problem in that hydrolysis resistance and heat resistance are deteriorated, and US Pat. No. 4,643,949 describes a method of improving hydrolysis resistance using polycarbonate polyol, but the dispersibility and cold resistance are deteriorated. There was a problem.

Accordingly, an object of the present invention is to provide a polyurethane resin for a binder of a magnetic recording medium which is excellent in hydrolysis resistance, heat resistance, and dispersibility of magnetic components and which can improve durability such as wear resistance and long-term storage resistance of the magnetic layer.

In order to achieve the above object, in the present invention, 10 to 90% by weight of polycarbomate diol (A-1) synthesized by acyclic glycol and carbonate and polyester diol (A-) synthesized by aliphatic dibasic acid and cyclic glycol 2) Long-chain diols (A) mixed with 90 to 10% by weight, diols (B) containing COOX groups (where X is a hydrogen atom or an alkali metal atom) in the molecular chain and short-chain diols having 2 to 10 carbon atoms (C) By preparing a polyurethane resin by reacting a diol (A + B + C) composed of) with an organic diisocyanate, a binder for a magnetic recording medium having excellent general physical properties was obtained.

The present invention is described in more detail as follows.

Polyurethane resin of the present invention 90 to 90% by weight of polycarbonate diol (A-1) synthesized by acyclic glycol and carbonate aliphatic dibasic acid and polyester diol (A-2) synthesized by cyclic glycol It consists of a long chain diol (A) mixed with 10% by weight, a diol (B) containing a COOX group (where X is a hydrogen atom or an alkali metal atom) in the molecular chain and a short chain diol (C) having 2 to 10 carbon atoms. It is prepared by reacting diol (A + B + C) with organic diisocyanate.

Among the components of the long-chain diol (A), the polycarbonate diol (A-1) has a molecular weight of 500 to 3,000, particularly preferably 600 to 2,000, and has a solubility problem when the molecular weight is 500 or less, and when the molecular weight is 3,000 or more, There is a problem that wear resistance is lowered.

Acyclic glycols in the polycarbonate diol (A) composition include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 2,2 -C1-C10 glycols such as dimethyl-1,3-propanediol, diethylene glycol, 1,5-pentanediol, and 1,6-hexanediol may be used alone or in combination, and as a carbonate, diaryl carbonate , Dialkyl carbonate and the like can be used.

The molecular weight of the polyester diol (A-2) which is another component of the long-chain diol (A) is preferably 500 to 5,000, particularly 600 to 3,000, and when the molecular weight is 5,000 or more, the magnetic layer has a weak wear resistance and durability. When molecular weight is less than 500, there exists a fault which the dispersibility of a magnetic component falls.

As the aliphatic dibasic acid in the polyester diol (A-2) composition, dibasic acids such as succinic acid, adipic acid, glutaric acid, maleic acid, pimelic acid, azaline acid and sebacic acid may be used alone or in combination. As a cyclic glycol, glycol, such as 1, 4- cyclohexane diol and 1, 4- cyclohexane dimethanol, can be used individually or in mixture.

As the long-chain diol (A) component of the polyurethane resin used in the present invention, polycarbonate diol (A-1) and polyester diol (A-2) in a weight ratio of 10: 90 to 90: 10, in particular 25: 75 to By mixing 75: 25, it improves durability such as hydrolysis resistance, heat resistance, magnetic layer wear resistance and long-term integrity, and when the ratio of polycarbonate diol (A-1) exceeds 90% by weight, solubility and cold resistance There is a drawback that is lowered, if less than 10% by weight problems in hydrolysis resistance and wear resistance.

Polyurethane resin used in the present invention is a powder of the magnetic component by introducing at least 0.5, preferably 0.5 to 2 COOX groups (wherein X is a hydrogen atom or an alkali metal atom) as a hydrophilic polar group in the molecular chain Improve the electronic properties of acidic and magnetic layers. If the number of COOX groups in one molecule of polyurethane is less than 0.5, the concentration is too small, which leads to a problem in improving the dispersibility of the magnetic component, and thus the excellent performance required in the present invention is not obtained.

Generally, pigments contained in coating agents, various binders, and the like, ie, magnetic components have adsorption water and chemical bonding water on their surfaces, and thus exhibit hydrophilicity. Thus, they are compatible with compounds containing -COOX groups, -SO ₃ X groups, etc. This improves the dispersibility and greatly shortens the dispersion time.

As diols having a COOX group in the molecular chain used in the present invention, 2,2-dimethyl propionic acid, 2,2-dimethylolacetic acid, 2,2-dimethylolgilacetic acid and sodium salts thereof can be used, and Aliphatic dibasic acid which is a component of the cyclic or acyclic glycol used in the synthesis of glycol and the polycarbonate diol (A-1) and polyester diol (A-2) and the polyester diol (A-2) Polyester diols having a molecular weight of 300 to 5,000 synthesized from can be used.

As long-chain diols (C) having 2 to 10 carbon atoms used in the present invention, cyclic glycols and acyclic glycols used in the production of long-chain diols (A) may be used alone or in combination. Organic diisocyanates (D) used in the present invention include 4,4'-diphenylmethane diisocyanate, lidine diisocyanate, cyclohexane diisocyanate, 2,4- and 2,6-toluene diisocyanate, isopron diisocyanate, Xylene diisocyanate, p- and m-phenylene diisocyanate, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate and the like can be used alone or in combination.

The molar ratio of the long-chain diol (A) and the diol (B) containing a COOX group in the molecular chain and the short-chain diol (C) is (A) / (C) = 1/0 to 1/5, (C) / (B) = 0/1 to 20/1 are suitable, and NCO: OH molar ratio of total diol (A + B + C) and organic diisocyanate (D) is suitably 0.8: 1 to 1.2: 1, and 0.9: 1 to 1.1. : l is particularly preferred. Outside the above range, the excellent performance required by the present invention is not obtained, and thus it is not suitable as a binder for magnetic recording media.

In addition, catalysts and various stabilizers may be used if necessary. As a catalyst, for example, tertiary amines such as triethylamine and triethylenediamine, nitrogen compounds such as morpholine and N-methylpolporine, metal salts such as potassium acetate and zinc stearate, dibutyl tin dilaurate and dibutyl An organometallic compound such as tinoxaine may be used, and as the stabilizer, ultraviolet ray stabilizers such as substituted benzotriazoles and thermal oxidation stabilizers such as phenol derivatives may be blended to significantly stabilize the performance of the polyurethane resin.

The molecular weight of the polyurethane resin of the present invention is preferably 10,000 to 60,000, especially 15,000 to 50,000, and when the molecular weight is less than 10,000, the magnetic component is excellent in spraying ability, but the magnetic layer has low abrasion resistance, resulting in desorption and adhesiveness of the magnetic component. When the molecular weight is 60,000 or more, the wear resistance of the magnetic component is improved, but the dispersibility, solubility, and solution stability of the magnetic component are lowered, which makes it difficult to paint. The end group of the polyurethane resin is preferably both an isocyanate group or a hydroxyl group at one end of the polyurethane resin, an isocyanate group at one end thereof and a hydroxyl group at the other end thereof, but preferably has a hydroxyl group at the end of the socks.

As a method for preparing the polyurethane resin of the present invention, a known method, for example, a method of sufficiently mixing the reactants in the presence of a catalyst, flowing over a flat plate or flat surface, heated, cooled and pulverized, polymerization by an extruder Pelletization immediately after the reaction in a single or mixed solvent organic solvent such as dimethylformamide, toluene, xylene, benzene, dioxane, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate Conventional production methods such as a solution reaction method can be used.

Finally, the polyurethane resin produced in the present invention needs to be cured with a suitable curing agent, and a low molecular weight polyisocyanate having a molecular weight of 150 to 7,000 is suitable as the curing agent, and is manufactured by DIC Corporation Banok D-750, D-800. , DN-960, DN-950, CL-2, Desmordue L, Desmodour RF, Desmordue R, and other equivalents from Bayer may be used. In addition, as the blocked isocyanate, DIC's Banokku D-500, D-504, D-550 and the like may be used.

By adding 5 to 35 parts by weight of the low molecular weight polyisocyanate to 100 parts by weight of the polyurethane resin of the present invention, the mechanical strength, abrasion resistance, heat resistance, moist heat resistance, solvent resistance, and adhesion to the substrate can be greatly improved. Can be.

In addition, if necessary in the binder component, a thermoplastic polyurethane resin, a vinyl chloride-vinyl acetate copolymer, a fibrin resin, a polyvinylbutylal resin, a thermoplastic polyester resin, and a vinyl chloride-propionic acid, which are usually used as a binder component of a magnetic recording medium, if necessary By using a commercially available product such as a vinyl copolymer, an epoxy resin and a phenoxy resin as it is, the dispersibility of the magnetic component, the smoothness of the surface of the magnetic layer, and the like can be improved.

On the other hand, the magnetic component used as the magnetic layer may be used r-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing r-Fe ₂ O ₃ powder, Co-containing Fe ₃ O ₂ powder, CrO ₂ powder, etc. In addition, various magnetic powders known in the art may be used.

The following Examples and Comparative Examples illustrate the present invention in more detail, but the present invention is not limited to the Examples and Comparative Examples.

(Example 1)

60 parts of polyhexamethylene carbonate diol having a molecular weight of 2,000 synthesized by condensation reaction of 1,6-hexanediol with diphenyl carbonate, polyester diol having a molecular weight of 1,500 synthesized from adipic acid and 1,4-cyclohexane dimethanol 40 1 part of 2,2-dimethylol propionic acid, 3 parts of 1,4-butanediol, 2 parts of 1,6-hexanediol and 0.1 part of dibutyl tin dilaurate were stirred at 80 ° C. under reduced pressure to remove moisture, and then 50 ° C. 30 parts of pre-heated 4,4'-diphenylmethane diisocyanate were added. After mixing these components for 1 minute, the reaction mixture was poured on a glass plate and aged at 100 DEG C for 24 hours, and then the reaction was completed to obtain a polyurethane resin. Hydrolysis resistance, heat resistance and dispersibility of magnetic components and abrasion resistance of the magnetic tape of this resin were evaluated and the results are shown in Table 1 and FIG.

(Example 2)

A polyester having a molecular weight of 1,000 synthesized from 50 parts of a polycarbonate diol having a molecular weight of 1,500 synthesized by condensation reaction of 1,6-hexanediol with diphenyl carbonate as a diol, adipic acid and sebacic acid, and 1,4-cyclohexane diol 50 parts of diol, 2 parts of 2,2-dimethylolpropionic acid, 3 parts of diethylene glycol, 3 parts of 1,4-cyclohexane diol, and 0.1 parts of dibutyltin dilaurate as 4,4'-diphenyl as organic diisocyanate. Except for adding 38 parts of methane diisocyanate to obtain a polyurethane resin in the same manner as in Example 1 to evaluate the physical properties, the results are shown in Table 1 and FIG.

(Example 3)

70 parts of polycarbonate diols having a molecular weight of 1,000 synthesized by condensation of 1,6-hexanediol with diphenyl carbonate as diol, and a polyester diol having a molecular weight of 1,000 synthesized from adipic acid and 1,4-cyclochlorohexane dimethanol 30 parts, 2 parts of ethylene glycol, 3 parts of 1,6-hexanediol, 1 part of 2,2-dimethylolpropionic acid, 0.1 part of dibutyl tin dilaurate, 41 parts of 4,4-diphenylmethane diisocyanate as organic diisocyanate Except for the addition, a polyurethane resin was obtained in the same manner as in Example 1, and physical properties were evaluated. The results are shown in Table 1 and FIG.

Comparative Example 1

5 parts of polycarbonate diols having a molecular weight of 2,000 synthesized from 1,6-hexanediol and diphenylcarbonate as diols, except that only 95 parts of polyester diols having a molecular weight of 2,000 synthesized from adipic acid and 1,4-cyclohexane dimethanol were used. In the same manner as in Example 1 to obtain a polyurethane resin to evaluate the physical properties, the results are shown in Table 1 and FIG.

Comparative Example 2

Only 95 parts of polycarbonate diol of 1,500 molecular weight synthesize | combined from 1, 6- hexanediol and diphenyl carbonate as a diol, and 5 parts of polyester diol of 1,000 molecular weight synthesize | combined from adipic acid and sebacic acid, and 1, 4- cyclohexane dimethanol , Except that 34.3 parts of 4,4'-diphenylmethane diisocyanate was used as the isocyanate, and was obtained in the same manner as in Example 2 to obtain a polyurethane resin and to evaluate physical properties thereof. The results are shown in Table 1 and FIG. Indicated.

Comparative Example 3

Except for using 1 part of 1,4-butanediol and 42 parts of 4,4-diphenylmethane diisocyanate instead of 2,2-dimethylol propionic acid, the same procedure as in Example 3 was carried out to obtain a polyurethane resin and evaluated for physical properties. The results are shown in Table 1 and FIG.

(Assessment Methods )

Hydrolysis and heat resistance

Polyurethane resin was prepared as a 100㎛ film and left for 30 days at 70 ℃, 95% relative humidity conditions and 7 days in 120 ℃ hot air dryer to evaluate the hydrolysis resistance and heat resistance as a change in tensile strength.

· Dispersibility of magnetic ingredients

20 parts of the polyurethane resins obtained in Examples 1 to 3 and Comparative Examples 1 to 3, 40 parts of cyclohexanone, 40 parts of methyl ethyl ketone, and 30 parts of r-Fe ₂ O ₃ magnetic powder were ball milled. After mixing for 24 hours, the obtained magnetic paint was applied and dried on a polyester film having a thickness of 10 µm so as to have a thickness of approximately 15 µm and dried, and the surface state of the magnetic layer was observed under a microscope (40 times) to disperse the magnetic component. Was evaluated.

Wear resistance of magnetic recording media

50 parts of polyurethane resins obtained in Examples 1 to 3 and Comparative Examples 1 to 3, 50 parts of Vinyrite VAGH (United Union Carbide, vinyl chloride-vinyl acetate copolymer), 300 parts of cyclohexanone, methyl ethyl ketone 300 parts, 150 parts of r-Fe ₂ O ₃ , 10 parts of carbon black, 5 parts of lubricant are mixed for 48 hours using a ball mill and 5 hours of 20 parts of Banokku D-750 (DIC, low molecular weight polyisocyanate) added. The magnetic coating obtained after stirring was applied onto a polyester film having a thickness of 10 μm, dried to have a thickness of 16 μm, dried, cut to a predetermined width to make a magnetic recording medium, and then measured for abrasion resistance. Shown. Abrasion resistance was measured by the amount of wear of the thickness by rubbing the magnetic surface of each tape in the rotating desk.

TABLE 1

Claims (3)

10 to 90% by weight of a polycarbonate diol (A-1) having a molecular weight of 500 to 3,000 synthesized by acyclic glycol and carbonate, and a polyester diol having a molecular weight of 500 to 5,000 which is synthesized by aliphatic dibasic acid and cyclic glycol (A -2) consisting of a long chain diol (A) containing 90 to 10% by weight, a COOX group (where X is a hydrogen atom or an alkali metal atom) containing a diol (B) and a C 2 to C 10 short chain diol (C) A method for producing a polyurethane resin for a binder of a magnetic recording medium, which is prepared by reacting diol (A + B + C) with an organic diisocyanate (D). The mixture ratio of the long chain diol (A), the COOX group-containing diol (B), and the short chain diol (C) is (A) / (C) = 1/0 to 1/5, (C) / ( A method for producing a polyurethane resin for a binder of a magnetic recording medium, wherein B / = 0/1 to 20 to 1. The method of manufacturing a polyurethane resin for a binder of a magnetic recording medium according to claim 1, wherein the molar ratio of NCO: OH of all diols (A + B + C) and diisocyanate (D) is 0.8: 1 to 1.2: 1. .