KR940011780B1 - Process for preparation of magnetic media polyurethane - Google Patents

Abstract

(a) a long chain diol of 500-5000 molecular weight contg. ether coupling gp. and SO3X (X = alkali metal) gp. at the molecular chain; (b) a polyester diol and/or polyether diol of 500-5000 molecular weight having 0.5-10 tertiary anino gps.; and (c) an organic diisocyanate in the presence of a catalyst or in the organic solvent. The organic diisocyanate is pref. 4,4'-diphenylmethane diisocyanate, cyclohexane diisocyanate, hexamethylene diisocyanate and/or xylene diisocyanate. The polyurethane resin has a good adhesiveness and dispersibility, and is used for a magnetic recording medium having an improved abrasion resistance and durability.

Description

Manufacturing method of polyurethane resin for magnetic recording medium

The present invention relates to a method for manufacturing a polyurethane resin for a magnetic recording medium, and more particularly, to a poly for magnetic recording medium having improved wear resistance and durability of a magnetic layer by using a special polyurethane resin having excellent adhesion and dispersibility of magnetic components. To provide a urethane resin.

In recent years, as the use of magnetic recording media such as audio tapes and home TVR tapes has been expanded, the performance of the recording media has also changed. In particular, the demand for high reliability in recording and reproduction has been increased, Improving productivity is also one of the big challenges.

Examples of high reliability include high recording density for reproducing clear images and sounds, high speed, high temperature and humidity conditions, and long-term driving, and magnetic components in the magnetic layer due to severe friction with the head during long-term running of the tape. The drop-out phenomenon and the generation of a signal by a desorption and abrasion powder do not arise, etc. are mentioned.

As an example of productivity improvement, productivity improvement of the magnetic recording medium obtained by shortening the time required for dispersing the magnetic component and smoothing the surface of the magnetic recording medium is mentioned. In other words, improving the properties and physical properties of the magnetic layer and improving the productivity is an important task of the binder, it is possible to produce excellent magnetic paint and high-performance magnetic recording medium by the uniform dispersion of magnetic components in a shorter time, high strength, high While good electronic properties such as SN ratio and high CN ratio are obtained, a binder having excellent durability such as wear resistance is required.

Fiber binders (nitrocellulose, etc.) and vinyl chloride-vinyl acetate copolymers are used as binders for magnetic recording media. Recently, thermoplastic polyurethane resins and polyisocyanates have been used to improve the durability of magnetic recording media by providing wear resistance to magnetic layers. A binder made from is proposed.

Thermoplastic polyurethane resins have excellent properties such as high elasticity, flexibility, abrasion resistance, cold resistance, strength, etc. for various moldings such as injection molding and ejection molding, synthetic leather, elastic fiber, paint adhesive or ABS resin, AS resin and It is widely used as a polymer modifier such as PVC, its derivatives, and cellulose acetate, but has weak disadvantages in heat resistance, hydrolysis resistance, and moist heat resistance, and is actively developing applications for printing ink, magnetic paint, conductive resin, and magnetic rubber. However, in use, the dispersibility of the magnetic powder is poor, and this causes a satisfactory electronic property, and it is difficult to smooth the surface of the magnetic recording medium, thereby improving the productivity.

Therefore, the present invention is a method for improving the above disadvantages, ether groups in the molecular chain of the polyurethane resin A polyurethane resin having a molecular weight of 5,000 to 100,000 was prepared by introducing a diol containing a tertiary amino group and a hydrophilic SO ₃ X group (where X is an alkali metal atom), with excellent adhesion and dispersibility of magnetic components. This resin is used to provide a magnetic recording medium with remarkable wear resistance and durability of a magnetic layer.

The present invention is described in detail as follows.

The present invention is characterized by improving the adhesiveness and dispersibility of the magnetic component by using a long chain diol having an ether bond in the polyurethane resin structure to contain 1 to 25% by weight of the ether bond. When the ether bond concentration is small, the adsorption effect and dispersion effect of the magnetic component is small, and when the ether bond concentration is large, the hydrophilicity is strong and the moisture is adsorbed, thereby causing problems in water resistance and heat and moisture resistance. A long chain diol having an ether bond or a glycol having an ether bond is reacted with a dibasic acid to obtain a polyester polyol, and an active oxygen compound such as ethylene oxide, propylene oxide, butylene oxide is added as an initiator to obtain a polyether polyol. These are used alone or as a mixture thereof to introduce the polyurethane resin into the structure.

Among the components constituting the polyester polyol, glycols having ether bonds include diethylene glycol, triethylene glycol and dioxane glycol. As the dibasic acid, an aliphatic dibasic acid such as adipic acid, sebacic acid, azeline acid, pimeric acid, schweric acid, succinic acid, malonic acid, glutaric acid, and the like, and phthalic acid, terephthalic acid, isophthalic acid, etc. may be used. Aromatic dibasic acids can be used.

The polyurethane resin is a tertiary amino group in the molecular chain The diol containing and the SO ₃ X group which is a hydrophilic polar group are introduced as 0.5 or more suitably 0.5-10 each, respectively, and the dispersibility of a magnetic component and the electronic property of a magnetic layer are improved. Outside the above range, there is a problem such as dispersibility and water resistance of the magnetic component is not suitable as a binder.

As the diol containing the tertiary amino group, the primary amines represented by R-NR ₂ (R: C _n H _{2n + 1} , n = 1 to 30) are ethylene oxide, propylene oxide and butylene oxide. Diols and derivatives thereof made by addition of 60 moles can be used. N-methyl diethanol amine, N-ethyl diethanol amine obtained by adding 2 mol of ethylene oxide to primary amines, such as methylamine, ethylamine, isopropylamine, n-butylamine, and isobutylamine, for example, Ethylene is repeatedly added to N-alkyl diethanol amines such as N-isopropyl diethanol amine and alkyl amines such as polyoxyethylene oleyl amine in which 2 to 60 moles of ethylene oxide is added to lauryl amine, stearyl amine, oleyl amine and the like. Diols to which an oxide, propylene oxide, and the like are added may be used. In addition, a polyester diol prepared by polycondensing an electric dibasic acid, an acid ester thereof, and an acid halide may be used in a mixed system of the N-alkyl diethanol amine with a glycol having an electrical ether bond, and ε-caprolactone Polycaprolactone diols in which the ring opening is polymerized in the presence of a mixture of the above-described lactones in the presence of a mixture with the above N-alkyl diethanol amine and glycol can be used.

The diol having the SO ₃ X group is a mixture of sodium dibasic acid sulfonic acid or esters thereof, such as dimethylisophthalate-5-sulfonic acid sodium or dimethyl succinate sodium sulfonate, and an electrodibasic acid and acid esters thereof. Polyacet diols having a molecular weight of 500 to 5,000 synthesized by polycondensation of glycols having an electrical ether bond with a single or a mixture thereof may be used.

Generally, pigments contained in coating agents, various binders, etc., ie, magnetic components have adsorbed water and chemically bonded water on their surfaces and exhibit hydrophilicity. Therefore, tertiary amino groups, side chain hydroxyl groups, -SO ₃ X groups, and -COOX groups Affinity with the compound to be contained improves dispersibility and greatly shortens the dispersion time. In addition, the tertiary amino group acts as a catalyst for the urethanation reaction, improves durability of the magnetic recording medium, and improves solubility and solution stability.

Organic diisocyanates used in the present invention include 4,4'-diphenylmethane diisocyanate, ridine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, xylene diisocyanate, 2,4- and 2,6-toluene di Isocyanates, p- and m-phenylene diisocyanates, hexa methylene diisocyanates, 1,5-naphthalene diisocyanates and the like or mixtures thereof are used.

In addition, the NCO / OH molar ratio of the polyol and the organic diisocyanate in the polyurethane resin is 0.8 to 1.2 / 1, particularly preferably 0.9 to 1.1 / 1. Outside of this range, the excellent performance required by the present invention is not obtained and therefore not suitable. It is also possible to use catalysts and various stabilizers if necessary.

As a catalyst, for example, tertiary amines such as triethyl amine and triethylene diamine, nitrogen compounds such as morpholine and N-methyl morpholine, metal salts such as potassium acetate and zinc stearate, dibutyltin dilaurate and dibutyl Organometallic compounds such as tin oxide can be used.

As a stabilizer, ultraviolet-ray stabilizers, such as substituted benzotriazoles, and thermal oxidation stabilizers, such as a phenol derivative, can be mix | blended and it can remarkably stabilize the said performance of a polyurethane resin.

The molecular weight of the polyurethane resin is preferably 5,000 to 100,000, particularly 10,000 to 60,000. When the molecular weight is less than 5,000, the dispersibility of the magnetic component is excellent, but the wear resistance of the magnetic layer is weak, resulting in desorption and adhesiveness of the magnetic component. When the molecular weight is 100,000 or more, the abrasion 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, which is not suitable. The end group of the polyurethane resin may be either an isocyanate group or a hydroxyl group at the same time, or one end isocyanate and the other end is a hydroxyl group, but more preferably, it has a hydroxyl group at the sock end.

Conventionally known methods may be used to prepare the polyurethane resins used in the present invention and if necessary, the reactants are sufficiently mixed in the presence of a catalyst, flowed onto a flat or flat surface, heated, cooled and pulverized, dimethyl form. Conventional production methods such as solution reaction methods such as amide, toluene, xylene, benzene, dioxane, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate and the like in a single or mixed solvent-based organic solvent Can be used.

In the present invention, the polyurethane resin needs to be finally used by curing with an appropriate curing agent, and a low molecular weight polyisocyanate having a molecular weight of 150 to 7,000 is suitable as the curing agent. Dano manufactured by DIC Inc. D-750, D-800, DN You can use Desmodure L, Desmodure RF, Desmodure R, or any of the equivalents available from other companies as -960, CL-2, and Bayer.

In addition, as the block isocyanate, Banokku D-500, D-504, D-550, etc. may be used as the DIC company.

By adding 3-50 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 are greatly improved. You can.

In addition, if necessary in the binder component, a thermoplastic polyurethane resin, a vinyl chloride-vinyl acetate copolymer, a fibrous resin, a polyvinyl butylal resin, a thermoplastic polyester resin, and a vinyl chloride-propionate vinyl are commonly used as binder components of magnetic recording media. By using together a commercial item, such as a system copolymer, an epoxy resin, and a phenoxy resin, as it is, the dispersibility of a magnetic component, the smoothness of the surface of a magnetic layer, etc. can be improved.

As the magnetic component used in the present invention, r-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing r-Fe ₂ O ₃ powder, Co-containing Fe ₂ O ₃ powder, CrO ₂ powder, etc. may be used. In addition, various magnetic powders known in the art may be used.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are only one form and the present invention is not limited to the examples.

Example 1

100 parts of polyester diols having a molecular weight of 1,000 synthesized from adipic acid, diethylene glycol, dimethylisophthalate 5-sulfonic acid sodium sulfonate, 2 parts of N-ethyl diethanol amine, and 0.2 parts of dibutyltin dilaurate were stirred under reduced pressure at 80 ° C. After removing water, 28.5 parts of 4,4'- diphenylmethane diisocyanate which were previously heated at 50 degreeC were added.

After mixing these components for 1 minute and aging for 24 hours at 100 degreeC which sent this reaction mixture on the glass plate, reaction was completed and a polyurethane resin was obtained. The dispersibility, adhesion, and wear resistance of the magnetic tape of the resin were evaluated. The results are shown in Tables 1 and 2.

Example 2

100 parts of polyester diol of molecular weight 2,000 synthesized from adipic acid, triethylene glycol, dimethyl succinate sodium sulfonate, 3 parts of N-ethyl diethanolamine, 0.2 parts of dibutyltin dilaurate, 4,4'-diphenyl 18 parts of methane diisocyanates were added to obtain a polyurethane resin in the same manner as in Example 1. The evaluation results are shown in Table 1 and Table 2.

Comparative Example 1

100 parts of polyester diol having a molecular weight of 1,000 synthesized from adipic acid and 1,4-butane diol, 4 parts of 1,4-butane diol, 0.2 parts of dibutyltin dilaurate 0.2 parts of 4,4'-diphenyl methane diisocyanate The polyurethane resin was synthesize | combined by the method similar to Example 1 by addition.

Comparative Example 2

100 parts of molecular weight 2,000 polyester diol synthesized from adipic acid and 2,2-dimethyl-1,3-propane diol, 5 parts of 1,4-butane diol, 0.2 parts of dibutyltin dilaurate, 4,4'- 26 parts of diphenylmethane diisocyanate were added, and the polyurethane resin was synthesize | combined by the method similar to Example 1.

[Assessment Methods]

· Dispersibility of magnetic ingredients

20 parts of each of the polyurethane resins obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were taken and mixed with the following materials.

40 cyclohexanone

40 parts methyl ethyl ketone

40 parts r-Fe ₂ O ₃ magnetic powder

After mixing the above mixture for 20 hours using a ball-mill, the obtained magnetic paint is dried on a 6 μm-thick polyester film so that the thickness after drying is approximately 12 μm, and the surface state of the magnetic layer is observed under a microscope (40 times). Was observed to evaluate the dispersibility of the magnetic component.

Adhesiveness with polyester film

After adding 10 parts of Banokku D-750 to the magnetic paint and mixing for 2 hours, the obtained magnetic paint was applied and dried to a thickness of approximately 20 μm after drying on a polyester film having a thickness of 60 μm to form a magnetic coating film. The adhesiveness with the polyester film was evaluated by the area (peel area) of the magnetic coating film which peeled off when the cellophane tape (50 mm width) 100 mm was adhered on this magnetic coating film, and when the cellophane tape was peeled off.

Wear resistance of magnetic recording media

50 parts of each of the polyurethane resins obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were taken and mixed with the following materials.

Beanie VAGH (U.S. union carbide company vinyl chloride-super 50 parts

Vinyl acid copolymer)

Cyclohexanone 280 parts

Methylethyl ketone 280 parts

r-Fe ₂ O ₃ 150 parts

Carbon black eight

Lubricant Part 5

The mixture was mixed for 48 hours using a ball mill, 20 parts of Banocque D-750 (DIC, low molecular weight polyisocyanate) was added and stirred for 5 hours, and the resulting magnetic paint was dried on a polyester film having a thickness of 6 μm. The coating was dried to a thickness of 12 m, cut into a predetermined width to make a magnetic recording medium, and then the wear resistance was measured. Abrasion resistance was measured by rubbing the magnetic surface of each tape at the rotary desk to measure the wear amount of the thickness.

TABLE 1

●: Very good, 0% of peeling area

▲: Usually, peeling area 10-50%

X: defective or peeled area 50% or more

TABLE 2

○: Example 1 ●: Comparative Example 1

□: Example 2 ■: Comparative Example 2

Claims (2)

A method for producing a polyurethane resin for a magnetic recording medium binder, wherein the resin is prepared by introducing a component consisting of the following components (A), (B) and (C) to the polyurethane resin. Way. (A) a long-chain diol having a molecular weight of 500 to 5,000 having a linear terminal receiver and containing an ether bond and a SO ₃ X (where X is an alkali metal atom) group in the molecular chain (B) Polyester diol and / or polyether diol of molecular weight 500-5,000 which has 0.5-10 tertiary amino groups in a molecular chain using the tertiary amino group containing diol or corresponding diol represented by the following. (C) organic diisocyanate The magnetic recording medium according to claim 1, wherein the NCO / OH molar ratio of the total polyol (A + B) and the organic diisocyanate (C) used in the production of the polyurethane resin is used in the range of 0.8 to 1.2 / 1. Method for producing a polyurethane resin for use.