JPH06287268A - Thermoplastic polyurethane - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic polyurethane resin useful as a binder for a magnetic recording medium, having excellent uniform dispersibility of finely divided magnetic particles and highly packing properties. CONSTITUTION:A thermoplastic polyurethane has 10-1,000 equivalents/10<6>g sulfonic acid metal base concentration per polymer and 2,700-3,900 equivalents/10<6>g urethane group concentration per polymer and is obtained by reacting (1) a polyester polyol which comprises an acid component composed of an aliphatic carboxylic acid and a sulfonic acid metal base-containing carboxylic acid and at least one glycol and has 500-1,200 molecular weight with (2) a diisocyanate and (3) at least one 2-20C glycol.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermoplastic resin which has no blocking property, is excellent in solvent solubility and vinyl chloride compatibility, and is excellent in the dispersibility of fine particles and electromagnetic conversion characteristics and is useful as a binder for magnetic recording media. Regarding polyurethane.

[0002]

2. Description of the Related Art As a conventional binder for magnetic recording media,
Cellulose resin, polyvinyl chloride resin, vinyl chloride-vinyl acetate resin, styrene-butadiene resin, polymethacrylic acid resin, vinylidene chloride-methacrylic acid resin,
Polyurethane resin, epoxy resin, polyester resin, etc. 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 and video tapes.

Particularly, in recent years, a magnetic recording medium having high functionality and high reliability has been demanded. For example, in video tapes, the high grade is accelerating, and there is a demand for a magnetic recording medium capable of high recording density for recording and reproducing clear sound and images.

As a measure for increasing the density, magnetic particles have been made finer and the magnetic force has been increased, and there has been a strong tendency to increase the packing density of the magnetic powder in the magnetic layer. However, with the increase in the specific surface area due to the fine particles of the magnetic powder and the increase in the cohesive force due to the increase in the magnetic force as described above, the conventional binder as described above does not have sufficient dispersing power for the magnetic powder, and its dispersing function However, in a system in which a binder is mixed with a dispersant, adverse effects are exerted on the durability of the magnetic layer such as the occurrence of blades when used for a long period of time.

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 phosphoric acid group is introduced into the binder to improve the affinity with the magnetic powder. Binders with improved high dispersancy 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.
No. 60-20315, No. 62-1110
Among these, a binder containing a metal sulfonate group has the most excellent dispersibility of magnetic powder and is promising.

[0006]

However, the above-mentioned binder containing a metal sulfonate group 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), 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 are high. It is insecure because it transports likely organic solvents in the form of coexistence. The reaction solvent used for solution polymerization becomes the solvent for the magnetic paint, so when manufacturing magnetic recording media. The solvent suitable for the solvent recovery device of the above must be used as the reaction solvent, and it is difficult to change the solvent for each individual device to produce the binder.

For these reasons, it is soluble in various solvents, has excellent solubility (vinyl chloride compatibility) in various vinyl chloride resins in the solvent system, and has excellent dispersibility of the magnetic powder and electromagnetic conversion characteristics. A good solid binder was desired. Further, when such a solid binder for a magnetic recording medium is produced by melt polymerization or bulk polymerization, good cutting property and non-blocking property 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 vinyl chloride compatibility. On the contrary, those having excellent solvent solubility and vinyl chloride compatibility had a remarkable blocking property between resins, and it was very difficult to maintain the shape of the product. That is, the blocking property, the solvent solubility and the vinyl chloride compatibility are in an antinomic relationship, and a thermoplastic polyurethane having a metal sulfonate group that satisfies both of these characteristics and is excellent in the dispersibility of the magnetic powder and the electromagnetic conversion is It was not obtained.

As a result of diligent studies on the binder composition, the present inventors have obtained a thermoplastic polyurethane excellent in blocking property, solvent solubility and vinyl chloride compatibility, as well as magnetic powder dispersibility and magnetic conversion properties. The present invention has been completed and the present invention has been achieved.

[0009]

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

The thermoplastic polyurethane (resin) according to the present invention has a metal sulfonate group concentration and a urethane group concentration of 10 to 1000 equivalents / 10 ⁶ g, 2 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 a suitable chain extender are used, blocking occurs in the cutting step of the polymer and the post polymerization step of the resin after cutting. The property is suppressed and a good resin can be obtained. Furthermore, the resin obtained under the above conditions can be a solid binder for a magnetic recording medium, which is excellent in solvent solubility, vinyl chloride compatibility, and dispersibility and electromagnetic conversion characteristics.
The thermoplastic polyurethane resin used in the present invention is NCO.
/ OH ratio, that is, the number of moles of diisocyanate component / the total number of moles of polyester polyol and chain extender can be appropriately changed and used, for example, NCO in consideration of post-crosslinking for imparting mechanical strength in 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 2,500 is used, the resulting thermoplastic polyurethane resin has good solvent solubility and vinyl chloride compatibility, but has a marked blocking property, which makes handling difficult. Become. Further, when a urethane group having a concentration of 3900 or more is used, the blocking property is lost, but the solvent solubility and the vinyl chloride compatibility are remarkably lowered. Further, when a polyester polyol having an average molecular weight of less than 500 is used, the flexibility is lost and it is not practical. Further, when the average molecular weight exceeds 1200, aggregation of the hard segment becomes remarkable (in the worst case, gelation) or crystallinity in the soft segment increases, and solvent solubility and vinyl chloride compatibility (two-phase separation or cloudiness). The state) is deteriorated and the dispersibility of the magnetic powder and the electromagnetic conversion characteristics are adversely affected, resulting in a lack of practicality.

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

As the polymer diol containing a metal sulfonate group, a polyester polyol having a metal sulfonate group is particularly desirable. The polyester polyol having a metal sulfonate base is composed of a carboxylic acid component having no metal sulfonate base and a carboxylic acid component having a metal sulfonate 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 metal sulfonate group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoisophthalic acid and 2-potassium sulfoisophthalic acid.
The copolymerization amount of these dicarboxylic acid components containing a metal sulfonate group is 0.5 mol% based on the total carboxylic acid components.
As described above, it is preferably 1 to 50 mol%.

The glycol component used in the polymer diol includes 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 polymeric 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 metal sulfonate group, for example, ordinary polyester diols, polyether diols, polycarbonate diols, castor oil derivatives, tall oil derivatives, and other hydroxyl group-containing compounds.

The chain extender (3) is 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-naphthalene diisocyanate,
Aromatic diisocyanates such as p-xylene diisocyanate and m-xylene diisocyanate, 1,3-diisocyanate methylcyclohexane, 1,4-diisocyanate methylcyclohexane, 4,4′-diisocyanate dicyclohexane, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexa Aliphatic diisocyanates such as methylene diisocyanate can be mentioned, but if necessary, a small amount of 2,2,4′-triisocyanate-diphenyl, benzenetriisocyanate or the like can be used.

As the method for producing the thermoplastic polyurethane in the present invention, a known method, for example, all raw materials are rapidly mixed, and the mixture is heated in a conveyor belt to perform polymerization, bulk polymerization, kneading by a single-screw or multi-screw extruder It is possible to use a melt polymerization method or the like in which the polymerization is performed. The desirable blending ratio in this case is NCO group of polyisocyanate /
All OH groups of high-molecular diol and low-molecular diol = 0.5-
It is 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 organometallic 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 is in the form of pellets,
Although it can be used in the form of flakes, sheets, etc., considering the solubility in a solvent in the paint manufacturing process, it is desirable to use pellets that have a large specific surface area of the resin and are easily dissolved.

The thermoplastic polyurethane resin in the present invention may be a plasticizer such as dibutyl phthalate triphenyl phosphate, dioctyl sulfo sodium succinate, t-butyl phenol-polyethylene ether, ethyl naphthalene sulfonic acid sodium dilauryl succinate stearin if necessary. Lubricants such as zinc acid, soybean oil lecithin and silicone oil, various antistatic agents, UV absorbers such as substituted benztriazoles, antioxidants such as phenol derivatives, and hydrolysis inhibitors such as carbodiimides are added. can do.

As a binder for the magnetic recording medium according to the present invention, urethane resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, ethyl cellulose, nitrocellulose, etc., which are usually used together with the thermoplastic polyurethane resin of the present invention, can be used. Fibrin 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 curable resin can be used together.

The fine magnetic powder 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, and Fe, Co, N
i, ferromagnetic Fe-Co-Ni alloy, Fe-Mn-Zn
Examples thereof include metal magnetic powders containing Fe, Co, Ni such as alloys, and various ferromagnetic powders such as iron nitride.

The thermoplastic polyurethane resin according to the present invention includes paints, adhesives, sealing agents, waterproofing agents, flooring agents, artificial leather, fiber treating agents, elastic fibers, cushioning agents, sheets, in addition to binders for magnetic recording media. It can be used for belts, films, rolls, gears, solid tires, anti-vibration agents, tubes, packing agents, shoe soles, etc.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. The "parts" in the examples and comparative examples 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 is the organic diisocyanate. When 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as MDI) is used as, it is represented by the following formula. U = {(MDI charge amount / total raw material charge amount) ÷ 125} × 1
0 ⁶

(1) Synthesis of Polyester Foliol Containing Metal Sulfonate Base In a reaction vessel equipped with a thermometer, a stirrer, and a condenser for distillation, 49700 parts of adipic acid, 2000 parts of 5-sodium isophthalic acid, 1,4- Butanediol 4410
Charge 0 parts, neopentyl glycol 21800 parts, and tetrabutyl titanate 4 parts to carry out an esterification reaction at 180 ° C to 220 ° C for 5 hours, then depressurize the reaction system to 5 mmHg over 30 minutes and raise the temperature to 230 ° C during this time. did. Further, a polycondensation reaction was carried out at 230 ° C. for 10 minutes at 0.3 mmHg. The OH number of the obtained polyester is 10.
The number average molecular weight was 1094 at 2.6 mgKOH / g. The composition obtained from NMR analysis and the like is adipic acid 98.
5 mol%, 5-sodium isophthalic acid 1.5 mol%,
It was 75 mol% of 1,4-butanediol and 25 mol% of neopentyl glycol. Polyester polyols (B) to (E) shown in Table 1 were synthesized by the same manufacturing method.

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

(2) Evaluation of magnetic powder dispersibility Thermoplastic polyurethane resin 12 parts Vinylite (manufactured by UCC) 18 parts Co-containing γ-Fe ₂ O ₃ 120 parts Methyl ethyl ketone 135 parts Toluene 135 parts

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 coating material was applied onto 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 of the magnetic powder, the filling factor and the surface smoothness 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 ratio: The magnetic coating film was dipped 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 by a stylus meter and evaluated.

Example 1 Polyester polyol (A), MDI and neopentyl glycol in Table 1 /
A 1: 2 mixed solution of 3-methylpentanediol was stored at 80 ° C., 50 ° C., and 25 ° C. from a storage tank, and a gear pump was used to deliver the solution at the following volume, and the screw diameter was 3
It was charged into a 0 mm twin-screw extruder (L / D = 40), and the thermoplastic polyurethane resin was continuously melt-polymerized while kneading under the temperature condition of 230 ° C. at the final resin temperature. Polyester polyol (A); 65.3 parts / min Mixed glycol; 13.6 parts / min MDI; 44.8 parts / min

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

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

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

[Examples 2 to 5] Thermoplastic polyurethane resins were obtained by the same synthetic method as in Example 1 except that the composition of raw materials and the concentration of urethane groups were changed as shown in Table 2. The resulting thermoplastic polyurethane resin was not blocking-resistant, and the magnetic coatings using these resins had good surface gloss, porosity, and surface roughness as shown in Table 2.

Comparative Example 1 A thermoplastic polyurethane resin was obtained under the same synthetic conditions as in Example 1, except that the composition was the same as in Example 1 but 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 block significantly and are very difficult to handle. Met.

[Comparative Example 2] A thermoplastic polyurethane resin was obtained under the same synthetic conditions as in Example 1 except that the composition of Example 1 was changed to a urethane group concentration of 3900 equivalent / 10 ⁶ g. The pellets of the obtained thermoplastic polyurethane resin have good blocking properties, but have very poor solvent solubility (gel state), surface gloss of the magnetic coating film, porosity,
It was impossible to evaluate the surface roughness.

Comparative Example 3 A polyester polyol (D) having the same composition as the polyester polyol (A) but having a molecular weight of 2156 was used, and the composition was as shown in Table 2 and the thermoplastic conditions were the same as those in Example 1 except that the thermoplastic resin was thermoplastic. 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 pellets of the obtained thermoplastic polyurethane resin block significantly, It was very difficult to handle.

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

[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.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yo Imagawa 2-1-1 Katata, Otsu City, Shiga Toyobo Co., Ltd.

Claims (1)

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