JP3301500B2 - Thermoplastic polyurethane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic useful as a binder for a magnetic recording medium, which has no blocking property, is excellent in solvent solubility and PVC compatibility, and has excellent fine particle dispersibility and electromagnetic conversion characteristics. Regarding polyurethane.

[0002]

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

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 against the increase in density, magnetic powder has been made finer and higher in magnetic force, and the packing density of the magnetic powder in the magnetic layer has tended to increase. However, with the increase in the specific surface area due to the micronization of the magnetic powder and the increase in the cohesive force due to the high magnetic force, the dispersing power of the magnetic powder is not sufficient with the conventional binder as described above, and the dispersion function Has been entrusted to a dispersant such as a phosphoric acid compound. However, in a system in which a dispersant is blended with a binder, the durability of the magnetic layer such as generation of a blade in a long-term use appears.

[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-60-15473.
Gazette, JP-A-60-20315, and JP-A-62-1110
Among these, a binder containing a metal sulfonate group is most promising because it has the best magnetic powder dispersibility.

[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 shape is liquid (varnish-like), and the solid content as an active ingredient is only a part of the product. Therefore, there are the following problems. When transporting products, transportation costs increase.Possible organic solvent is transported in the form of coexistence.Insecure.Reaction solvent used for solution polymerization is a solvent for magnetic paint. Therefore, it is difficult to produce a binder by changing the solvent for each individual apparatus.

[0007] For these reasons, it is soluble in various solvents, is excellent in solubility in various vinyl chloride resins (PVC compatibility) in the solvent system, and has good dispersibility and electromagnetic conversion characteristics of magnetic powder. An excellent solid binder has been desired. In addition, when such a solid binder for a magnetic recording medium is produced by melt polymerization or bulk polymerization, good cutting properties and non-blocking properties in the process of post-polymerizing the resin after cutting are required. However, a solid binder having no blocking property tends to have poor solvent solubility and PVC compatibility. Conversely, those having excellent solvent solubility and PVC compatibility had remarkable blocking properties between resins, and it was very difficult to maintain the shape of the product. That is, the blocking property, the solvent solubility, and the PVC compatibility have a trade-off relationship, and a thermoplastic polyurethane having a metal sulfonate group that satisfies both of these properties and is excellent in dispersibility and electromagnetic conversion of magnetic powder. Had not been obtained.

The inventors of the present invention have conducted intensive studies on the binder composition and have found that a thermoplastic polyurethane having excellent blocking properties, solvent solubility and PVC compatibility, and excellent magnetic powder dispersibility and magnetic conversion properties can be obtained. And found the present invention.

[0009]

That is, according to the present invention, the sulfonic acid metal base concentration and the urethane group concentration are 10 to 1000 equivalent / 10 ⁶ g, 2700 to 390, respectively, per polymer.
A thermoplastic polyurethane having 0 equivalent / 10 ⁶ g,
(1) a molecular weight of an acid component containing at least one aliphatic carboxylic acid having 2 to 12 carbon atoms and a sulfonic acid metal base-containing carboxylic acid and a glycol component consisting of at least one glycol having 2 to 20 carbon atoms; 500 ~
A polyester polyol which is 1200 and (2) at least one aliphatic or aromatic diisocyanate;
(3) A thermoplastic polyurethane obtained by reacting at least one glycol having 2 to 20 carbon atoms.

The thermoplastic polyurethane (resin) of the present invention has a metal sulfonate concentration and a urethane group concentration of 10 to 1000 equivalent / 10 ⁶ g per polymer, respectively.
If a polyester polyol having a molecular weight of 700 to 3900 equivalents / 10 ⁶ g and a molecular weight of 500 to 1200 and an appropriate chain extender are used, blocking in the polymer cutting step and the post-polymerization step of the resin after cutting is performed. The properties are suppressed and a good resin can be obtained. 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.
Further, the thermoplastic polyurethane resin in the present invention is NCO
/ OH ratio, that is, the number of moles of the diisocyanate component / the total number of moles of the polyester polyol and the chain extender can be appropriately changed. For example, NCO may be used in consideration of post-crosslinking for imparting mechanical strength to the magnetic layer.
The / OH ratio may be appropriately used. On the other hand, when a thermoplastic polyurethane resin having a urethane group concentration of less than 2500 is used, the obtained thermoplastic polyurethane resin has good solvent solubility and good PVC compatibility, but has remarkable blocking properties and is difficult to handle. Become. When a urethane group having a concentration of 3900 or more is used, the blocking property is lost, but the solvent solubility and the PVC compatibility are significantly reduced. When the polyester polyol having an average molecular weight of less than 500 is used, the flexibility is not practical. When the average molecular weight is more than 1200, aggregation of the hard segment becomes remarkable (in the worst case, gelation) or crystallinity in the soft segment increases, and the solvent solubility and PVC compatibility (two-phase separation or cloudiness) occur. State), which adversely affects the dispersibility of the magnetic powder and the electromagnetic conversion characteristics, resulting in lack of practicality.

The thermoplastic polyurethane resin in the present invention is obtained by reacting with a high molecular diol, a low molecular diol and a polyisocyanate.

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 sulfoisophthalic acid.
The copolymerization amount of the dicarboxylic acid component containing these sulfonic acid metal bases is 0.5 mol% based on the total carboxylic acid component.
As described above, the content is preferably 1 to 50 mol%.

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 high molecular weight diol having no sulfonic acid metal base, for example, ordinary polyester diol, polyether diol, polycarbonate diol, a derivative of castor oil, a derivative of tall oil, or other compounds containing a hydroxyl group.

(3) As a chain extender, 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 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,
aromatic diisocyanates such as p-xylene diisocyanate, m-xylene diisocyanate, 1,3-diisocyanatomethylcyclohexane, 1,4-diisocyanatomethylcyclohexane, 4,4′-diisocyanatedicyclohexane, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene Examples thereof include aliphatic diisocyanates such as methylene diisocyanate, and a small amount of 2,2,4′-triisocyanate-diphenyl, benzene triisocyanate and the like can be used as needed.

In the present invention, the thermoplastic polyurethane may be produced by a known method, for example, by rapidly mixing all the raw materials, heating the mixture in a conveyor belt, and polymerizing the mixture, kneading with a single-screw or multi-screw extruder. For example, a melt polymerization method in which polymerization is carried out while being used 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 of 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 organic metal compounds such as dibutyltin dilaurate and tin octylate. These catalysts can be used alone or in a mixed yarn. 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 triphenyl phosphate, dioctyl sulfo sodium succinate, t-butyl phenol-polyethylene ether, ethyl naphthalene-sodium dilauryl succinate stearin. Adds lubricants such as zinc acid, soybean oil lecithin, silicone oil, various antistatic agents, ultraviolet absorbers such as substituted benzotriazoles, antioxidants such as phenol derivatives, and hydrolysis inhibitors such as carbodiimides. can do.

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 resin, polyester resin, epoxy resin, phenoxy resin, acrylonitrile-butanediene copolymer, thermosetting resin or reactive resin and unsaturated prepolymer such as urethane acrylic type, phosphate acrylic type, aryl type, etc. An electron beam or ultraviolet curing resin 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 , fine particles of hexagonal barium ferrite, Fe, Co, N
i, ferromagnetic Fe-Co-Ni alloy, Fe-Mn-Zn
Examples include various magnetic powders such as metal magnetic powders containing Fe, Co, and Ni such as alloys and iron nitride.

The thermoplastic polyurethane resin according to the present invention may be used in addition to binders for magnetic recording media, such as paints, adhesives, sealing agents, waterproofing agents, flooring agents, 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.

[0025]

EXAMPLES Hereinafter, the present invention will be described specifically 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, and the urethane group concentration (U: equivalent / 10 ⁶ g) in the present invention was determined by using an organic diisocyanate. When 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as MDI) is used, the following formula is used. U = {(MDI charged amount / total raw material charged amount)} 125} × 1
0 ⁶

(1) Synthesis of Polyester Holol Containing Sulfonate 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 2.64 at 2.6 mgKOH / g. The composition obtained from NMR analysis and the like was adipic acid 98.
5 mol%, 1.5 mol% of 5-sodium isophthalic acid,
1,4-butanediol was 75 mol% and neopentyl glycol was 25 mol%. By the same production method, polyester polyols (B) to (E) shown in Table 1 were synthesized.

[Table 1] In Table 1, ISN indicates 5-sodium sulfoisophthalic acid.

(2) Evaluation of magnetic powder dispersibility 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 kneading the mixture of the above composition for 5 hours using a paint shaker, 12 parts of Coronate-L (manufactured by Nippon Polyurethane) were 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 evaluated based on 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 The polyester polyol (A), MDI and neopentyl glycol /
Using a gear pump, a 1: 2 mixed solution of 3-methylpentanediol was sent at a temperature of 80 ° C., 50 ° C., and 25 ° C., respectively, using a gear pump.
It was charged into a 0 mm twin-screw extruder (L / D = 40), and the thermoplastic polyurethane resin was continuously melt-polymerized while being kneaded under a temperature condition of a final resin temperature of 230 ° C. Polyester polyol (A); 65.3 parts / min. Mixed glycol; 13.6 parts / min. MDI; 44.8 parts / min.

The thermoplastic polyurethane resin in a molten state is discharged in a strand form from a die of a twin-screw extruder, cooled with water in a cooling bath, pelletized by a strand cutter, dried at 50 ° C. under a nitrogen stream for 40 hours, and dried and cured. Thus, a pellet-shaped thermoplastic polyurethane resin was obtained. The obtained thermoplastic polyurethane resin had a sulfonic acid metal base content of 40 equivalents / 10 ⁶ g and a urethane group concentration of 290.
0 equivalent / 10 ⁶ g, and reduced viscosity (η _{SP / C} ) is 1.22
Met. Further, the obtained thermoplastic polyurethane resin had no blocking property, and also had good solvent solubility (methyl ethyl ketone / toluene = 1/1 mixed solution, solid content 25%) and vinyl chloride compatibility (using vinylite).

The surface gloss, porosity and surface roughness of the magnetic coating film using this resin were 88 and 2 respectively as shown in Table 2.
2.5% and 0.022 μm, which are good values.

[Table 2] In Table 2, NPG is neopentyl glycol,
MPD indicates 3-methylpentanediol, MPG indicates 2-methylpropanediol, and PG indicates propylene glycol.

Examples 2 to 5 A thermoplastic polyurethane resin was obtained by the same synthesis method as in Example 1 except that the composition of the raw materials and the urethane group concentration were changed as shown in Table 2. The obtained thermoplastic polyurethane resin was not blocking, and the surface gloss, porosity, and surface roughness of the magnetic coating film using these resins obtained good values as shown in Table 2.

Comparative Example 1 A thermoplastic polyurethane resin was obtained under the same synthesis conditions as in Example 1 except that the composition was the same as that of Example 1 and the urethane group concentration was changed to 2426 equivalents / 10 ⁶ g. The surface gloss, porosity, and surface roughness of the magnetic coating film using this resin are good as shown in Table 2, but the pellets of the obtained thermoplastic polyurethane resin are extremely blocked and are very difficult to handle. Met.

Comparative Example 2 A thermoplastic polyurethane resin was obtained under the same synthesis conditions as in Example 1 except that the composition was the same as that of Example 1 and the urethane group concentration was changed to 3900 equivalent / 10 ⁶ g. The pellets of the obtained thermoplastic polyurethane resin have good blocking properties, but have very poor solvent solubility (gelled state).
Evaluation of surface roughness and the like was impossible.

Comparative Example 3 Using a polyester polyol (D) having the same composition as the polyester polyol (A) but having a molecular weight changed to 2156, using the composition shown in Table 2 and thermoplasticity under the same synthesis conditions as in Example 1 A polyurethane resin was obtained. The surface gloss, porosity, and surface roughness of the magnetic coating film using the obtained thermoplastic polyurethane resin are good as shown in Table 2, but the obtained thermoplastic polyurethane resin pellets are significantly blocked, Handling was very difficult.

Comparative Example 4 Using the polyester polyol (E) of Table 1 containing no sulfonic acid metal base, Table 2
A thermoplastic polyurethane resin having the composition shown in Table 2 was obtained under the same synthesis conditions as in Example 1. The surface gloss, porosity, and surface roughness of the magnetic coating film using the obtained thermoplastic polyurethane resin were poor as shown in Table 2.

[0038]

By using the thermoplastic polyurethane resin of the present invention, it is possible to provide a high-performance magnetic recording medium excellent in dispersibility in various magnetic powders at low cost.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-206910 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 18/00-18/87 C09D 5 / 23 C09D 175/04-175/12

Claims (1)

(57) [Claims] 1. The concentration of a metal sulfonate group and the concentration of a urethane group are each 10 to 1000 equivalent / 10 per polymer.
⁶ g, 2700-3900 equivalent / 10 ⁶ g of a thermoplastic polyurethane, comprising: (1) an acid component comprising at least one aliphatic carboxylic acid having 2 to 12 carbon atoms and a carboxylic acid containing a sulfonic acid metal base, and carbon A polyester polyol having a molecular weight of 500 to 1200 from a glycol component comprising at least one glycol of Formulas 2 to 20;
(2) at least one kind of aliphatic or aromatic diisocyanate and (3) at least one kind of glycol having 2 to 20 carbon atoms, which is obtained by at least reacting (1) (2) (3). Thermoplastic polyurethane.