JP3267731B2 - Thermoplastic polyurethane resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is useful as a binder for a magnetic recording medium which has no blocking property, is excellent in solvent solubility and PVC compatibility, and is excellent in dispersibility and electromagnetic conversion characteristics of fine magnetic particles. And a thermoplastic polyurethane resin composition.

[0002]

2. Description of the Related Art Conventional binders for magnetic recording media include:
Cellulol resin, polyvinyl chloride resin, vinyl chloride-vinyl acetate resin, styrene-butadiene resin, polymethacrylic acid resin, vinylidene chloride-methacrylic acid resin,
Polyurethane resins, epoxy resins, polyester resins and the like have been used. However, when the above-mentioned binder is used, satisfactory performance has not been obtained in applications requiring high performance such as data tapes for computers, audio tapes, video tapes and the like.

In particular, in recent years, a magnetic recording medium having high functionality and high reliability has been demanded. For example, high grade video tapes are being accelerated, and a magnetic recording medium capable of high recording density for recording and reproducing clear sound and images is demanded.

[0004] As measures for increasing the recording density, finer magnetic powder and higher magnetic force have been achieved, and the tendency to increase the packing density of the magnetic powder in the magnetic layer has been increasing. However, the dispersing ability of the magnetic powder was not sufficient with the conventional binder as in the foreground, and the dispersing function was left to the dispersing agent such as a phosphoric acid compound. In the case of long-term use, the durability of the magnetic layer is adversely affected, such as generation of blades.

[0005] In order to solve the above-mentioned problems, a hydrophilic substituent such as a sulfonic acid metal base, a hydroxy metal base, a carboxylic acid metal base, or a phosphate group is introduced into the binder to improve the affinity with the magnetic powder. Binders with improved high dispersing function have been proposed. (Japanese Patent Publication No. 58-41565,
JP-A-57-92422, JP-A-59-30235, JP-A-59-154633, and JP-A-60-1547.
No. 3, No. 60-20315, No. 62-111
No. 0, etc.) Among these, a binder containing a metal sulfonate group is the most excellent in dispersibility of magnetic powder and is promising.

[0006]

However, the above-mentioned binder containing a metal salt of sulfonic acid is expensive, and is generally produced by solution polymerization using a known organic solvent as a reaction medium. Therefore, the product is in a liquid form (varnish form), and the solid content as an active ingredient is only a part thereof. Therefore, there are the following problems. In the case of product transportation, transportation costs are high. It lacks safety because it is transported in the presence of flammable organic solvents. Since the reaction solvent used for the solution polymerization is the solvent for the magnetic paint, a solvent that is compatible with the solvent recovery device used when manufacturing magnetic recording media must be used as the reaction solvent, and the solvent must be changed for each device. It is difficult to make a binder.

[0007] For these reasons, it is soluble in various solvents, has excellent solubility in various vinyl chloride resins (PVC compatibility), and has good dispersibility and electromagnetic conversion characteristics of magnetic powder. An excellent solid binder has been desired.

For the above reasons, binders for solid magnetic recording media have been desired, and are disclosed in JP-B-58-8053, JP-B-61-231050 and JP-B-3-1364.
No. 8, which discloses a binder for a solid magnetic recording medium that satisfies the uniform dispersibility of magnetic powder, high filling ratio (low porosity), and high surface smoothness during coating. Not

As a result of intensive studies on a thermoplastic polyurethane resin composition having a specific binder composition, the present inventors have found that it has no blocking property at 70 ° C. or less, has excellent solvent solubility and PVC compatibility, and has a magnetic powder. A thermoplastic polyurethane resin composition having excellent dispersibility and electromagnetic conversion characteristics was found, and the present invention was achieved.

[0010]

That is, according to the present invention, the sulfonic acid metal base concentration and the urethane group concentration are each 10 to 1000 equivalent / 10 ⁶ g, 2500 to 390 per polymer.
A thermoplastic polyurethane having 0 equivalent / 10 ⁶ g,
(1) An acid component mainly composed of at least one aliphatic carboxylic acid having 2 to 12 carbon atoms and a sulfonic acid metal base-containing carboxylic acid, and at least one glycol component having a molecular weight of 500 or less, and a molecular weight of 500 to (2) at least one aliphatic or aromatic diisocyanate and (3) a thermoplastic polyurethane obtained by reacting at least one short-chain glycol having a molecular weight of 500 or less; and (4) at least one polyester polyol. 0.01 to 1.0% by weight of higher fatty acid metal salt per polymer
A thermoplastic polyurethane resin composition characterized by containing:

The thermoplastic polyurethane resin composition of the present invention has a metal sulfonate group concentration and a urethane group concentration of 10 to 1000 equivalent / 10 per polymer.
⁶ g, are those having from 2500 to 3900 equivalent weight / 10 ⁶ g, and a molecular weight is obtained by appropriately using the polyester polyol and the molecular weight of 500 or less short chain glycol is 500 to 1,200, polymerization step after the resin after cutting In the case where the post-polymerization temperature is 40 ° C. or lower, the blocking property is suppressed, but the post-polymerization must be carried out for a long time, which tends to reduce continuous productivity and is not industrial. The resin obtained by post-polymerization is 40
Above ° C, the blocking properties are remarkable, and the shape of the pellet cannot be maintained due to the environmental temperature during transportation, which is not practical.

The present inventors have conducted intensive studies to solve the above-described blocking properties, and as a result, have found that a good resin having no blocking properties can be obtained at 80 ° C. or lower by using an additive. This additive is a higher fatty acid metal salt, and may be added in an amount of 0.01 to 1.0% by weight, preferably 0.02 to 0.1% by weight, based on the polymer. It may be filled in the post-polymerization process. With this formula, 80
Even if post-polymerization is carried out at a temperature of 0 ° C., there is no blocking property and the polymerization can be completed in a short time, so that continuous production is possible and productivity is greatly improved. Further, the resin obtained under the above conditions can be a solid binder for a magnetic recording medium having excellent solvent solubility, PVC compatibility, and excellent dispersibility and electromagnetic conversion characteristics.

On the other hand, in the composition of the present invention, the higher fatty acid metal salt is not contained or the content is higher than 0.1% per polymer.
In a resin composition manufactured with an addition amount of 01% by weight or less, 40%
In the post-polymerization process at a temperature of not less than ℃, the blocking property is remarkable and handling becomes difficult. Further, if the temperature is lower than 40 ° C., the productivity becomes very poor.

When the higher fatty acid metal salt is prepared in an amount of 1.0% by weight or more per polymer in the composition of the present invention, the aggregate in the final preparation paint (binder, magnetic powder, additive) In the process of removing impurities and the like using a filter, problems such as clogging of the filter occur.

The higher fatty acid metal salt used in the present invention is a metal salt of a saturated fatty acid having 14 to 30 carbon atoms. Preferred higher fatty acid metal salts are calcium stearate, magnesium stearate, zinc stearate, magnesium lignocerate, Examples include zinc lignocerate, calcium montanate, magnesium montanate, zinc montanate, and the like.

The thermoplastic polyurethane resin in the present invention is obtained by reacting with a high molecular diol, a low molecular diol and a polyisocyanate, and preferably a resin in which part or all of the high molecular diol has a metal sulfonate group. Good.

As the polymer diol containing a metal sulfonate, a polyester polyol having a metal sulfonate is particularly desirable. The polyester polyol having a sulfonic acid metal base comprises a carboxylic acid component having no sulfonic acid metal base and a carboxylic acid component having a sulfonic acid metal base.

Examples of the carboxylic acid component having no sulfonic acid metal base include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid.

Examples of the carboxylic acid containing a sulfonic acid metal base include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoisophthalic acid, and 2-potassium isophthalic acid. The copolymerization amount of the dicarboxylic acid component containing these sulfonic acid metal bases is 0.5 mol% or more, preferably 1 to 50 mol%, based on all carboxylic acid components.

The glycol components used in the high molecular diol include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-
Propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, 2,2,4 -Trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, trimethyl-1,6-hexanediol, 1,12-dodecanediol and the like are used.

The above-mentioned polymer diol containing a metal sulfonate group may be used alone or in combination of two or more. Further, it may be used in combination with a polymer diol having no sulfonic acid metal base, for example, ordinary polyester polyols, polyether diols, polycarbonate diols, castor oil derivatives, tall oil derivatives, and other compounds containing a hydroxyl group.

As the chain extender (3), ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-
Butanediol, neopentyl glycol, 1,5-
Pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, trimethyl For example, -1,6-hexanediol, 1,12-dodecanediol and the like are used.

The polyisocyanate (2) used in the thermoplastic polyurethane resin of the present invention includes 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, tetramethylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate, 4,4 ′ diisocyanate-diphenyl ether, 1,5-naphthalenediisocyanate, p
Aromatic isocyanates such as -xylene diisocyanate and m-xylene diisocyanate, 1,3-diisocyanatomethylcyclohexane, 1,4-diisocyanatomethylcyclohexane, 4,4'-diisocyanatodicyclohexane, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, Examples thereof include aliphatic isocyanates such as hexamethylene diisocyanate, and 2,4,4'-triisocyanate-diphenyl, benzene triisocyanate, and the like can be used in small amounts as necessary.

In the present invention, the thermoplastic polyurethane resin may be produced by a known method, for example, a method in which all the raw materials are rapidly mixed, and the mixture is heated and polymerized in a conveyer belt. A melt polymerization method in which polymerization is performed while kneading can be used. In this case, the desirable compounding ratio is NCO group of polyisocyanate /
Total OH groups of high molecular diol and low molecular diol = 0.5 to
1.5, preferably 0.9 to 1.1.

In the production of the thermoplastic polyurethane resin according to the present invention, a catalyst can be used if necessary. Examples of commonly used catalysts include nitrogen-containing compounds such as triethylamine and triethylenediamine, and organometallic compounds such as dibutyltin diurarate and tin octylate. These catalysts can be used alone or in a mixed system. Other catalysts can also be used.
Further, the polyurethane resin in the present invention has a pellet shape,
Although it can be used in the form of a flake, a sheet, or the like, in consideration of the solubility in a solvent in the paint production process, a pellet having a large specific surface area of the resin and being easily dissolved is desirable.

The thermoplastic polyurethane resin in the present invention may be, if necessary, a plasticizer such as dibutyl phthalate or triphenyl phosphate, dioctyl sulfo sodium succinate, t-butyl phenol-polyethylene ether, ethyl naphthalene-soda dilauryl succinate. Lubricants such as zinc stearate, soybean oil lecithin, silicone oil, various antistatic agents, ultraviolet absorbers such as substituted benzotriazoles, antioxidants such as phenol derivatives, and hydrolysis inhibitors such as carbodiimitods. Can be added.

As the binder for the magnetic recording medium according to the present invention, urethane resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, nitrocellulose and the like which are usually used together with the thermoplastic polyurethane resin of the present invention. Cellulose resins, polyester resins, epoxy resins, phenoxy resins, acrylonitrile-butadiene copolymers, thermosetting resins or reactive resins, and unsaturated prepolymers, such as electron beam or ultraviolet curing resins such as urethane acrylic type and aryl type Can be used in combination.

The fine magnetic particles used in the present invention include γ-Fe ₂ O ₃ , C having a spinel structure.
o-containing iron oxide magnetic powder such as γ-Fe ₂ O ₃ , CrO ₂ , hexagonal barium ferrite fine particles, and Fe, Co, N
i, Fe-Co-Ni-based alloys, Fe-Mn-Zn-based alloys, and other ferromagnetic powders such as Fe, Co, and Ni-containing metal magnetic powders and iron nitride.

The thermoplastic polyurethane resin according to the present invention includes, in addition to the binder for magnetic recording media, paints, adhesives, sealing agents, waterproofing agents, dispersants, artificial leather, fiber treatment agents, elastic fibers, cushioning agents, sheets, It can be used for belts, films, rolls, gears, solid tires, vibration insulators, tubes, packing agents, shoe soles, and the like.

[0030]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, “parts” are “parts by weight” unless otherwise specified. The reduced viscosity of the thermoplastic polyurethane resin was measured at 30 ° C. with a phenol / tetrachloroethane (6: 4 weight ratio) mixed solvent. The urethane group concentration (U: equivalent weight / 10 ⁶ g) in the present invention is represented by the following formula when 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as MDI) is used as the organic diisocyanate. U = {(MDI charged amount / total raw material charged amount)} 125} ×
10 ⁶

(1) Synthesis of a polyester polyol containing a sulfonic acid metal base. In a reaction vessel equipped with a thermometer, a stirrer, and a condenser for distilling, 49700 parts of adipic acid, 2000 parts of 5-sodium isophthalic acid, 1,4-butanediol 4410
0 part, 21800 parts of neopentyl glycol, and 4 parts of tetrabutyl titanate were charged, and the esterification reaction was carried out at 180 ° C. to 220 ° C. for 5 hours. did. Further, a polycondensation reaction was performed at 230 ° C. at 0.3 mmHg for 10 minutes. The OH value of the obtained polyester is 10
The number average molecular weight was 2.73 at 2.7 mgKOH / g. The composition obtained from NMR analysis and the like was adipic acid 98.
5%, 1.5 mol% of 5-sodium isophthalic acid, 1,
The content was 75 mol% of 4-butanediol and 25 mol% of neopentyl glycol. By the same production method, polyester polyols (B) to (E) shown in Table 1 were synthesized.

[Table 1] In addition, ISN in Table 1 shows 5-sodium sulfoisophthalic acid.

(2) Evaluation of dispersibility of magnetic powder 12 parts of thermoplastic polyurethane resin 18 parts of vinylite (manufactured by UCC) 120 parts of γ-Fe ₂ O ₃ containing Co 135 parts of methyl ethyl ketone 135 parts of toluene 135 parts

After the mixture having the above composition was kneaded for 5 hours using a paint shaker, 12 parts of Coronate-L (manufactured by Nippon Polyurethane) was further added, and the mixture was further mixed for 30 minutes. The obtained magnetic paint was applied on a polyethylene terephthalate film having a thickness of 50 μm using a doctor blade having a gap of 50 μm, and the solvent was removed by drying. The uniform dispersibility, packing ratio and surface smoothness of the magnetic powder of the obtained magnetic coating film were evaluated as follows.

Uniform dispersibility: The surface gloss of the magnetic coating film was measured with a gloss meter. Filling rate: The magnetic coating film was immersed in silicone oil, and the porosity of the magnetic coating film was determined and evaluated from the amount of silicone oil impregnated. Surface smoothness: The surface roughness of the magnetic coating film was measured with a stylus meter and evaluated.

Example 1 A 1: 2 mixed solution of the polyester polyol (A), MDI and neopentyl glycol (NPG) / 3-methylpentanediol (MPD) shown in Table 1 was used at 80 ° C., 50 ° C. and 25 ° C., respectively. , Using a gear pump to feed the following amount of liquid, and a twin screw extruder with a screw diameter of 30 mm (L / D =
40), and the thermoplastic polyurethane resin was continuously melt-polymerized while kneading under a temperature condition of a final resin temperature of 230 ° C. Polyester polyol (A); 65.3 parts / minute Mixed glycol; 13.6 parts / minute MDI: 44.8 parts / minute

The thermoplastic polyurethane resin in the molten state
Cooling by discharging in the form of a strand from the die of the screw extruder
Water cooled by g bath and pelletized by strand cutter
After that, the pellets are delivered by air to Nauta
ー Continuously charged into a mixer (manufactured by Hosokawa Micron)
After filling 50,000 parts of pellets,
Added 10 parts of Cium (0.02% by weight per polymer)
After 30 hours while stirring at 70 ° C. under a nitrogen stream, dry
Dried, cured and pelletized thermoplastic polyurethane tree
A fat composition was obtained. The obtained thermoplastic polyurethane resin set
The content of the sulfonic acid metal base in the product is 40 equivalent / 10⁶
g, urethane group concentration is 2900 equivalent / 10 ⁶g
The reduced viscosity (ηsp / c) was 1.22. Also gain
Drying and curing of the obtained thermoplastic polyurethane resin composition
There was no blocking property at the time of storage. Solvent dissolution
(Methyl ethyl ketone / toluene = 1/1 mixed solution, solid
25%), and good compatibility with PVC. This resin
The surface gloss, porosity and surface roughness of the magnetic coating used
Table 2: 88, 22.5 respectively as shown in Table 3.
%, A good value of 0.022 μm.

[Table 2]

[0037]

[Table 3] In Tables 2 and 3, MPG is 2-methyl-1,3-propanediol, PG is propylene glycol, St-
Ca indicates calcium stearate, and St-Mg indicates magnesium stearate. [Examples 2 to 7] A thermoplastic polyurethane resin was obtained in the same manner as in Example 1 except that the composition of the raw material, the urethane group concentration, and the type and content of the higher fatty acid metal base were changed as shown in Table 2. . The resulting thermoplastic polyurethane resin is 70
There was no blocking property even in an atmosphere of ° C, and the surface gloss, porosity and surface roughness of the magnetic coating film using these resins were good values as shown in Table 2.

Comparative Example 1 A thermoplastic polyurethane resin was prepared under the same synthesis conditions as in Example 1 except that only the composition ratio was changed so that the urethane group concentration became 2490 equivalent / 10 ⁶ g. Obtained. The surface gloss, porosity, and surface roughness of the magnetic coating film using this resin are good as shown in Table 3, but pellets of the thermoplastic polyurethane resin obtained are 7 particles.
It was extremely blocked in an atmosphere of 0 ° C., and handling was difficult.

Comparative Example 2 A thermoplastic polyurethane resin was prepared under the same synthesis conditions as in Example 1 except that only the composition ratio was changed so that the urethane group concentration was 3990 equivalent / 10 ⁶ g. Obtained. The resulting thermoplastic polyurethane resin pellets are good without blocking properties,
The solvent solubility (methyl ethyl ketone / toluene = 1/1 mixed solution) was very poor, and evaluation of the magnetic coating film was impossible.

Comparative Example 3 A thermoplastic polyurethane resin having the same composition as in Example 1 was obtained by using the same method as in Example 1 without adding calcium stearate. Although the surface gloss, porosity, and surface roughness of the magnetic coating film using the obtained resin are good as shown in Table 3, the obtained thermoplastic polyurethane resin pellets are significantly blocked at 70 ° C. atmosphere. And it was difficult to handle.

Comparative Example 4 A thermoplastic polyurethane resin was obtained in the same manner as in Example 1 except that the amount of calcium stearate added was 1.20% by weight, and the same method as in Example 1 was used. The obtained resin pellets have no blocking property, good solvent solubility, and the surface gloss, porosity, and the like of a magnetic coating film using the obtained thermoplastic polyurethane resin.
The surface roughness was also good as shown in Table 3. However, clogging during filtration of the magnetic coating film was remarkable.

Comparative Example 5 Example 1 was repeated except that the polyester polyol (D) and the chain extender shown in Table 1 were replaced with MPG.
A thermoplastic polyurethane resin was obtained by using the same method as described above. As shown in Table 3, the obtained resin pellets had remarkable blocking properties and good surface roughness values could not be obtained.

Comparative Example 6 Using the polyester polyol (E) of Table 1 containing no sulfonic acid metal base, Table 3 was used.
In the same manner as in Example 1, a thermoplastic polyurethane resin having the composition shown in (1) was obtained. The obtained thermoplastic polyurethane resin pellets do not have blocking properties and are soluble in solvents.
Although the PVC compatibility was good, the surface gloss, porosity, and surface roughness of the magnetic coating film were not good as shown in Table 3.

[0044]

By using the thermoplastic polyurethane resin of the present invention, it is possible to obtain a binder for a magnetic recording medium which is low in cost and excellent in dispersibility of magnetic particles. A medium can be obtained, which greatly contributes to industry.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G11B5 / 702 G11B5 / 702 (56) References JP-A-59-6210 (JP, A) JP-A-3-166277 (JP) JP-A-4-356722 (JP, A) JP-A-63-206910 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 75/04-75/12 C08G 18/00-18/87 C08K 5/09 C09D 5 / 23,175 / 06 G11B 5/702

Claims (1)

(57) [Claims] 2. The method according to claim 1, wherein the concentration of the metal sulfonate group and the concentration of the urethane group are 10 to 1000 equivalents / 1 polymer.
0 ⁶ g, a thermoplastic polyurethane is 2,500 to 3,900 equivalent / 10 ⁶ g, (1) an acid component having at least one aliphatic carboxylic acid and sulfonic acid metal salt group-containing carboxylic acids having 2 to 12 carbon atoms And at least one glycol component having a molecular weight of 500 or less, a polyester polyol having a molecular weight of 500 to 1200, (2) at least one aliphatic or aromatic isocyanate, and (3) at least one short molecule having a molecular weight of 500 or less. At least (1) with a chain glycol,
(2) A thermoplastic polyurethane obtained by reacting (3) with (4) at least one higher fatty acid metal salt in an amount of 0.01 to 1.0% by weight per polymer. Polyurethane resin composition.