JP3353502B2 - Method for producing polyurethane resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a glass transition point (Tg).
High, pigment dispersibility, especially carbon black dispersibility,
The present invention relates to a method for producing a polyurethane resin which has good solubility in a solvent and compatibility with other resins and is suitable as a binder for a magnetic recording medium or the like.

[0002]

2. Description of the Related Art In recent years, with the diversification and high functionality of information devices, high performance has been demanded also for copying machines, electrophotography, magnetic recording media, and the like. With these high performance,
Specifically, it is to increase the density of information typified by an increase in resolution, to improve durability, and the like. In general, magnetic recording media used for these applications are prepared by dispersing a pigment, carbon black, magnetic powder, etc. in a binder, and adding a coating obtained by adding other additives as necessary to a substrate, followed by drying. Manufactured. These properties mainly depend on the properties of the resin used as the binder, and among the resins used, polyurethane resins have been widely used because of their excellent flexibility, abrasion resistance, strength and the like (for example, ,
See JP-B-63-21613).

[0003]

However, in order to further increase the density of information recording, fine particles such as carbon black for improving the dispersibility of the magnetic powder, conductivity, and light shielding properties are added to the binder. It is necessary to improve the dispersibility of the resin, and to improve the durability, it is necessary to increase the Tg and compatibility with other resins to maintain the adhesiveness, and all these properties are simultaneously satisfied. Resin is required. In order to obtain sufficient durability, the glass transition point is desirably 30 ° C. or higher. In order to increase the glass transition point of the polyurethane resin, a method of increasing the urethane group concentration or a method of increasing a hard component such as a benzene ring in the polyurethane resin is generally used. However, simply increasing the glass transition point of the polyurethane resin by these methods alone often has an adverse effect on the dispersibility of magnetic powder, carbon black, and the like,
In addition, solubility in solvents and compatibility with other resins deteriorates, and polyurethane resins with high glass transition point, high dispersibility, and good solubility in solvents and compatibility with other resins can be found until now. It is not at present.

[0004]

The present inventors have made intensive studies in view of the above circumstances, and as a result, have found that the aforementioned problems can be solved by introducing a special structure into the polyurethane resin. Was completed.

That is, in the present invention, a polyester polyol, a chain extender and an organic diisocyanate are reacted at a ratio of 0.5 to 3.0 mol of a chain extender and 0.9 to 6.0 mol of an organic diisocyanate per 1 mol of a polyester polyol. A method for producing a polyurethane resin having a glass transition point of 30 ° C. or higher, wherein 25 to 100 mol% of the polyester polyol uses terephthalic acid and / or isophthalic acid as an acid component and a glycol represented by the following formula 5 as an alcohol component:

[0006]

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(Where a and b are 1 or 2 respectively)
C is an integer of 1 to 4, d is c + 2
It is an integer of c + 4, and a, b and c may be the same or different from each other. ) Is 30-100mo
1% used aromatic polyester polyol,
The chain extender is a glycol having a molecular weight of 50 to 250 and having a tertiary amino group in a molecule represented by the following formulas 6 to 8:

[0008]

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(Wherein, R ₁ and R ₂ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms. , R
₁ and R ₂ may be the same or different from each other,
R ₃ to each other may be different be the same as each other. )

[0010]

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(Wherein, R ₁ , R ₂ and R ₄ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms) R ₁ , R ₂ and R ₄ may be the same or different from each other, and R ₃ may be the same or different from each other.)

[0012]

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(Wherein, R ₁ , R ₂ and R ₄ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms) R ₁ , R ₂ and R ₄ may be the same or different from each other, and R ₃ may be the same or different from each other.) 100mo
The above method, wherein the active hydrogen compound contains 1% of an active hydrogen compound.

The present invention will be described in more detail. The polyurethane resin in the present invention is a resin having a glass transition point of 30 ° C. or higher obtained by reacting a polyester polyol, a chain extender, and an organic diisocyanate.

This polyester polyol uses isophthalic acid and / or terephthalic acid as an acid component, and a glycol represented by the following formula 9 as a part or all of an alcohol component.

[0016]

Embedded image

(Where a and b are each 1 or 2
C is an integer of 1 to 4, d is c + 2
It is an integer of c + 4, and a, b and c may be the same or different from each other. ) Is 30-100mo
1 to 25% by mol of an aromatic polyester polyol produced by using 1%. The use ratio of isophthalic acid to terephthalic acid is preferably in the range of 100/0 to 20/80. That is, for example, an aromatic polyester polyol containing no terephthalic acid, such as polyhexamethylene isophthalate polyol, may be used. Chemical formula 9
Specific examples of the glycol represented by are 2-ethyl-2-butyl-1,3-propanediol, 3-ethyl-3-butyl-1,5-pentanediol, 4,4-
Bis (hydroxymethyl) nonane and the like can be mentioned. In addition to these glycols, commonly used glycols other than these may be used in an amount of less than 70 mol%. Specific examples of such glycols include ethylene glycol,
Diethylene glycol, propylene glycol, 1,4
-Butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol and the like. If the glycol represented by Chemical Formula 9 is less than 30 mol%, sufficient solubility in a solvent and compatibility with other resins cannot be obtained. The number average molecular weight of the aromatic polyester polyol is preferably from 500 to 5,000, particularly preferably from 550 to 3,000. If the number average molecular weight of the aromatic polyester diol is smaller than this, the flexibility of the obtained polyurethane resin is reduced, and if the number average molecular weight is larger than this, the durability is inferior. In addition to the aromatic polyester polyol, an aliphatic polyester polyol such as adipate may be used together with the aromatic polyester polyol in an amount of less than 25 mol% in the total polyester polyol. Specific examples of such aliphatic polyester polyols include polyethylene adipate polyol, polybutylene adipate polyol, polyhexamethylene adipate polyol, and polyneopentyl adipate polyol. The average number of functional groups of the polyester polyol is preferably in the range of 2.0 to 2.5,
The average number of functional groups is particularly preferably 2.0 from the viewpoint that the molecular weight can be increased without gelation.

The chain extender for forming the polyurethane resin may be partially or wholly represented by the following chemical formulas (1) and (2).
1 or a glycol having a tertiary amino group having a special structure in the molecule and having a molecular weight of 50 to 250
The seed or a mixture of two or more is used in an amount of 10 to 100 mol%. If the amount of the tertiary amino group-containing glycol is less than this, the dispersibility of carbon black and the like becomes insufficient.

[0019]

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(Wherein, R ₁ and R ₂ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms. , R
₁ and R ₂ may be the same or different from each other,
R ₃ together also may be different be the same as each other. )

[0021]

Embedded image

(Wherein, R ₁ , R ₂ and R ₄ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms) R ₁ , R ₂ and R ₄ may be the same or different from each other, and R ₃ may be the same or different from each other.)

[0023]

Embedded image

(Wherein, R ₁ , R ₂ and R ₄ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms) R ₁ , R ₂ and R ₄ may be the same or different from each other, and R ₃ may be the same or different from each other.) That is, these special structures Is a glycol having a nitrogen atom in the skeleton branched from the main chain skeleton (when a polyurethane resin is formed), and specifically, 3-dimethylamino-1,2-propanediol, 3-diethylamino-1,2-propanediol, 2- (N, N-dimethylaminomethyl) -1,3-propanediol, N-
(3-dimethylaminopropyl) -N, N-diisopropanolamine and the like. (When polyurethane resin is formed) such as N-alkyldiethanolamine
A glycol containing a nitrogen atom in the main chain skeleton and having no nitrogen atom in the branched skeleton has no effect. Desirable tertiary amino group-containing glycols are those represented by the following formulas, and particularly desirable tertiary amino group-containing glycols are
Diethylamino-1,2-propanediol. Also, as a part of the chain extender, less than 90 mol% thereof is used as an alcohol component for producing the above-mentioned polyester diol, or diamines such as ethylenediamine, hexamethylenediamine, isophoronediamine, and water are used in combination. it can. The amount of the chain extender used is 0.5 to 3.0 with respect to 1 mol of the polyester polyol.
mol ratio. If the amount of the chain extender is smaller than this, the strength of the obtained polyurethane resin is not sufficient, and if it is larger than this, the resin becomes brittle.

As the organic diisocyanate for producing the above polyurethane resin, any organic diisocyanate which can be generally used for producing a polyurethane resin can be used, and specific examples thereof include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like. Is mentioned. It is also possible to use isocyanates obtained by converting some of these organic diisocyanates into uretdione and carbodiimide. In producing the polyurethane resin in the present invention, it is necessary to use the organic diisocyanate in a ratio of 0.9 to 6.0 mol based on 1 mol of the polyester polyol.

The NCO / OH (molar ratio) between the polyester polyol and the chain extender and the organic diisocyanate is preferably from 0.6 / 1.0 to 1.5 / 1.0. Particularly preferably, it is 0.9 / 1.0 to 1.2 / 1.0. If the ratio is out of this range, it is difficult to obtain excellent performances intended in the present invention, which is not preferable.

The above-mentioned polyurethane resins include those having a metal sulfonate group and / or a carboxyl group, and have a concentration of 0.001 to 0.2 per polymer.
mmol / g is desirable. Examples of the sulfonic acid metal base include SO ₃ Na, and examples of the method of introducing SO ₃ Na include a method of introducing into a polyester diol molecule by polycondensation of dicarboxylic acid of 5-sodium sulfoisophthalic acid with glycol. . Examples of the method for introducing a carboxyl group include a method using bis (2,2-hydroxymethyl) propionic acid as a part of a chain extender.

In the production of the polyurethane resin, a catalyst and various stabilizers can be used, if necessary. Examples of the catalyst include tertiary amines such as triethylamine and triethylenediamine; metal salts such as potassium acetate and zinc stearate; and organic metal compounds such as dibutyltin dilaurate and dibutyltin oxide. By blending a stabilizer against ultraviolet rays such as substituted benzotriazoles and a stabilizer against thermal oxidation such as phenol derivatives, various properties of the polyurethane resin can be remarkably stabilized.

In producing the polyurethane resin, a conventionally known method can be used, and a single or a single material such as toluene, xylene, benzene, dioxane, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate or butyl acetate can be used. A solution reaction method in which the reaction is carried out in a mixed solvent system, or a method in which the reactants are thoroughly mixed in the absence of a solvent, heated by flowing the reaction mixture on a flat plate or a flat surface, then cooled, and then pulverized. Ordinary manufacturing methods such as a method of injecting into a substrate can be used.

The polyurethane resin obtained by the method of the present invention is suitable as a binder for various uses, particularly, a binder for a magnetic recording medium. The magnetic recording layer of the magnetic recording medium
For example, it is formed by kneading the binder, the magnetic powder, and each component to be added as necessary with an appropriate organic solvent to prepare a magnetic paint, applying this to the surface of the non-magnetic support, and then drying. You. Similarly, if non-magnetic powder is used instead of magnetic powder, a back coat layer of a magnetic recording medium is formed.

The binder of the magnetic recording layer and / or the back coat layer of the magnetic recording medium according to the present invention may be used in addition to the low molecular weight polyisocyanate compound as a curing agent and the ordinary magnetic recording medium in addition to the polyurethane resin obtained by the present invention. It is also possible to use a mixture of a vinyl chloride-vinyl acetate copolymer, nitrocellulose, an epoxy resin, a phenoxy resin, a thermoplastic polyurethane resin or the like used as a binder. In addition, a resin obtained by introducing a metal salt of sulfonic acid, carboxylic acid, epoxy, amine or the like into these resins can also be used in combination. The low molecular weight polyisocyanate compound is an adduct or isocyanurate of an isocyanate compound having two or more isocyanate groups with a polyhydric alcohol, and specifically, for example, Desmodur L or Desmodur manufactured by Bayer AG N, Coronate L and Coronate HL manufactured by Nippon Polyurethane Industry.

As the magnetic powder used in the magnetic recording layer of the magnetic recording medium according to the present invention, conventionally known magnetic powders can be used, for example, γ-iron oxide,
Cobalt-γ-iron oxide, cobalt-magnetite, barium-ferrite, metal magnetic powder, and the like.

The non-magnetic powder used in the back coat layer of the magnetic recording medium according to the present invention includes carbon black, silicon carbide, titanium oxide, calcium oxide, chromium oxide, silicon carbide, calcium carbide, zinc oxide, α-Fe ₂
Examples include O ₃ , talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide, calcium carbonate, and the like, with carbon black (particularly conductive carbon black) and / or titanium oxide being preferred. When these non-magnetic powders are contained in the back coat layer, the surface of the back coat layer can be moderately roughened to improve the surface properties. In the case of carbon black, the back coat layer is provided with conductivity to provide an antistatic effect. Is obtained. It is preferable to use a combination of carbon black and another non-magnetic powder, since both effects of improving surface properties (stabilization of running properties) and improving conductivity can be obtained.

The magnetic recording layer of the magnetic recording medium and / or
Alternatively, when forming the back coat layer, if necessary, various commonly used additives such as an antistatic agent, a lubricant, and an inorganic pigment such as carbon black can be added. As the non-magnetic support, polyester (for example, polyethylene terephthalate), polyolefin, cellulose derivative, non-magnetic metal, paper and the like are used, and the shape thereof is a film, tape, sheet, card, disk and the like.

[0035]

As described above, according to the present invention,
A method for producing a polyurethane resin having a high glass transition point and excellent in dispersibility of magnetic powder, carbon black, and the like, solubility in a solvent, and compatibility with other resins can be provided. Further, since the polyurethane resin obtained by the present invention has such excellent dispersibility, solubility, and compatibility, various binders such as binders for magnetic recording media, conductive paints such as paints for electromagnetic wave shielding, adhesives, and anchors. It can also be used as a coating agent and the like.

[0036]

The present invention will be described in more detail with reference to the following examples.
However, the present invention is not limited only to the examples.
"Parts" and "%" in Examples and Comparative Examples
Are parts by weight and weight unless otherwise noted.
% ".Example 1  Terephthalic acid in a reaction vessel equipped with stirring blades, thermometer,
262.1 parts of acid, 262.1 parts of isophthalic acid and 2-butyric acid
2-Ethyl-1,3-propanediol 288.4
(Aromatic) Polye having a number average molecular weight of 2,000
Steterdiol A 1000 parts, 2,2-dimethyl-1,
52.1 parts of 3-propanediol, 3-diethylamino
41.7 parts of -1,2-propanediol, toluene 93
After charging 0 parts and mixing at 50 ° C.,
0.6 parts of dioctyltin dilaurate and 4,4'-di
Add 321 parts of phenylmethane diisocyanate and add
The reaction was carried out at ℃. Viscosity increases as the reaction progresses
Timely, toluene, cyclohexanone, methyl
After dilution with ethyl ketone,
After confirming that the absorption peak of the
A good solution was obtained. Polyurethane resin obtained in this way
The solution has a solid content of 30% and is polystyrene by GPC measurement.
The number average molecular weight in terms of len was about 25,000. This
Put the polyurethane resin solution obtained as above on release paper
Using a knife coater, apply to a dry film thickness of 100μ.
Cloth, 60 ° C x 30 minutes + 120 ° C x 2 hours + 25 ° C x 1
Dry for a week to make a clear film, glass transition point
And a sample for measuring solubility. Also got this
Using a polyurethane resin solution, mix
Disperse with a grinding machine (made by Igarashi Kikai) for 3 hours
After 5 hours, each sampled and the resulting paint
On a 15μ thick polyethylene terephthalate film
And dried at 80 ° C for 3 minutes.
After drying, cure at 50 ° C for 24 hours and cut to a predetermined width.
The paint films were cut to obtain glossy films. 5
The higher the gloss after the time, the better the dispersion of the magnetic powder.
The gloss after 3 hours is close to the gloss after 5 hours.
This indicates that the dispersion speed of the magnetic powder is high. Furthermore, this poly
Using a urethane resin and the following formulation 2,
Dispersed for 5 hours with an Indian mill (made by Igarashi Kikai) and obtained
Paint with 15μ thick polyethylene terephthalate fill
And dry film thickness of 5μ at 80 ℃ for 3 minutes
After drying, cure at 50 ° C for 24 hours.
To obtain a paint film and evaluate the glossiness of each
Was. The higher the gloss, the better the dispersibility of the carbon black
It can be said that. Raw materials used in the production of polyurethane resin
Table 1 shows the contents of polyester diol
Polyester diol, chain extension
Types of long agents and organic diisocyanates and their use
Table 2 shows the amounts and the evaluation results of the obtained polyurethane resins.
Shown in

<Formulation 1> Magnetic powder (Co-γ-iron oxide, BET = 38 m ² / g) 85 parts Carbon black (BLACK PEARLS-L manufactured by Cabot Corporation) 15 parts Polyurethane resin (solid content conversion) 30 parts Methyl ethyl ketone 114 Parts Toluene 114 parts Cyclohexanone 76 parts

<Formulation 2> Carbon black (BLACK PEARLS-L manufactured by Cabot Corporation) 100 parts Polyurethane resin (solid content conversion) 30 parts Methyl ethyl ketone 114 parts Toluene 114 parts Cyclohexanone 76 parts

[0039]Examples 2 to 5, Comparative Examples 1 to 3  Instead of the polyurethane resin solution used in Example 1,
Polyurethane obtained from the main raw materials shown in Table 2 or Table 3
Using a resin solution, clear filtration was performed in the same manner as in Example 1.
Creates film and paint film, glass transition point, melting
The properties and glossiness were evaluated. With the results, polyurethane
Polyester diol and chain extender among resin production raw materials
And the type and amount of organic diisocyanate used
The results are shown in Tables 2 and 3. Production of polyurethane resin
Table 1 shows the contents of the polyester diol used in Example 1.

[Evaluation method] Glass transition point: Rheovibro manufactured by Orientec
The viscoelasticity of the clear film was measured at a heating rate of 2 ° C./min using n, and the temperature at which the loss modulus became maximum was defined as the glass transition point. Solubility: The clear film was dissolved in a mixed solvent of cyclohexanone / toluene / methylethylketone = 2/3/3 so as to have a solid content of 30%, and toluene was added dropwise to the solution until turbidity occurred. The dropped amount (ml) of toluene per 1 g of the solution was defined as the solubility index. Gloss: The coated surface of the obtained paint film was measured for reflectance at an incident angle of 45 degrees and a reflection angle of 45 degrees using a gloss meter (manufactured by Suga Test Instruments).

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]Example 6, Comparative Example 4  Polyurethane resin solution used in Example 1 and Comparative Example in Table 3
Polyurethane resin solution obtained from the main raw materials shown in column 4
The same formulation as in Example 1 with the following formulation 3 using each solution
Paint film by the method, the durability of the tape wear
The amount was evaluated.

<Formulation 3> Magnetic powder (Co-γ-iron oxide, BET = 38 m ² / g) 85 parts Carbon black (BLACK PEARLS-L manufactured by Cabot Corporation) 15 parts Polyurethane resin (solid content conversion) 30 parts Coronate L (Nippon Polyurethane Industry isocyanate curing agent, solid content conversion) 3 parts Methyl ethyl ketone 114 parts Toluene 114 parts Cyclohexanone 76 parts

[Evaluation Method and Results] The obtained paint film (10 m in length) was put into a tape recorder, and the abrasion loss of the tape after 10 minutes was measured while being brought into contact with a magnetic head at a speed of 38 cm / sec. The amount of wear of the paint film (Example 6) from the polyurethane resin solution used in Example 1 was 1.3 mg, and Comparative Example 4
The abrasion loss of the paint film was 5.5 mg.

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Claims (1)

(57) [Claims] A polyester polyol, a chain extender, and an organic diisocyanate are combined with 1 mol of a polyester polyol.
A method for producing a polyurethane resin having a glass transition point of 30 ° C. or higher by reacting a chain extender with 0.5 to 3.0 mol and an organic diisocyanate at a ratio of 0.9 to 6.0 mol with respect to 25% of the polyester polyol. ~ 100mol%
Uses terephthalic acid and / or isophthalic acid as an acid component, and a glycol represented by the following formula 1 as an alcohol component: (Where a and b are each an integer of 1 or 2; c is an integer of 1 to 4; d is an integer of c + 2 to c + 4; a, b, and c are the same as each other; And the chain extender has a tertiary amino group in the molecule represented by the following formula (2) to (4). Glycol of the formula (Wherein, R ₁ and R ₂ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group;
₃ is an alkyl group having 1 to 4 carbon atoms, R ₁ and R ₂ may be the same or different, and R ₃ may be the same or different. ) (Wherein, R ₁ , R ₂ and R ₄ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms. , R ₁ and R
₂ and R ₄ may be the same or different from each other, and R ₃ may be the same or different from each other. ) (Wherein, R ₁ , R ₂ and R ₄ are each an alkylene group having 1 to 4 carbon atoms which may have a side chain alkyl group, and R ₃ is an alkyl group having 1 to 4 carbon atoms. , R ₁ and R
₂ and R ₄ may be the same or different from each other, and R ₃ may be the same or different from each other. The above method, characterized in that the active hydrogen compound contains 10 to 100 mol% of at least one of the above.