JPS62179521A - Urethane resin for magnetic tape - Google Patents

Abstract

PURPOSE:To obtain a urethane resin excellent in dispersion of magnetic iron oxide and capable of forming a cured resin excellent in moisture resistance and heat resistance, by using a thermoplastic urethane resin formed by reacting a specified lactone polymer with an isocyanate compound as a component. CONSTITUTION:A thermoplastic urethane resin formed by reacting a lactone polymer synthesized by using 3-metylpentane-1,2,5-triol as a olymerization initiator. with an isocyanate compound. Examples of the lactones include those represented by the formula and having five or more carbon atoms in the ring or a mixture thereof. In the formula, n>=3, (n+2) R groups are H atoms and the rest are each H, alkyl, cycloalkyl, alkoxy or a monocyclic aromatic hydrocarbon. epsilon-caprolactone is particularly desirable. It is necessary that the catalyst used is a compound free of an active hydrogen group, and a tin compound such as a tetraalkyltin is suitable as the catalyst.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to urethane resin for magnetic tape.

For details, see 3-methylpentane-1,3,5-triol t? as a component of thermoplastic 7f IJ urethane resin.
By using the synthesized lactone polymer as a polymerization initiator, the dispersibility of magnetic iron oxide is excellent, and when it is thermally cured in combination with a low molecular weight compound having three or more incyanate groups, the strength of the cured resin and its moisture content are improved. The present invention provides a urethane resin for magnetic tapes that has excellent heat resistance.

[Prior art]

When manufacturing magnetic tape using r -Fe2O3-based magnetic iron oxide, there are many difficulties in uniformly dispersing the magnetic iron oxide in the magnetic paint. The dispersion effect of magnetic iron oxide was enhanced by methods such as the use of cellulose derivatives esterified with nitric acid. Recent magnetic tape manufacturing methods are required to reduce the number of processes to reduce costs, and as the quality increases, magnetic iron oxide has become more finely powdered, and the packing density of magnetic iron oxide per unit area has increased. There is a need to reduce the amount of resin in magnetic coating liquids. Therefore, conventionally, in order to increase the dispersion effect of magnetic iron oxide by urethane resin, a method has been used to copolymerize a hydrophilic raw material, such as a raw material containing a sulfonic acid metal base or a carboxylic acid metal base, and iris gellicol alone or in combination. It has been known. These urethane resins have excellent dispersibility with magnetic iron oxide, but cured resins that are heat-cured with a low molecular weight compound having three or more incyanate groups suffer from deterioration in moisture resistance and heat resistance. It had the disadvantage of being large.

[Purpose of the invention]

The present inventors have found that a resin cured product that has excellent dispersibility with magnetic iron oxide and is thermosetted using a combination of low-molecular compounds having three or more incyanate groups has excellent moisture resistance and heat resistance. As a result of intensive research aimed at obtaining a thermoplastic urethane resin, it was discovered that a lactone polymer synthesized using 3-methylpentane-1,3,5-)liol as a polymerization initiator has a tertiary hydroxyl group in its molecular structure. It was discovered that a thermoplastic polyurethane using this as an IF reol satisfies the above object, and the present invention was completed.

[Structure of the invention]

The present invention relates to a urethane resin for magnetic tapes made of a thermoplastic urethane resin prepared by reacting a lactone polymer synthesized using 3-methylpentane-IF3,5-triol as a polymerization initiator and an incyanate compound.

When producing the lactone polymer used in the present invention,
It is essential that the polymerization initiator is 3-methylpentane-1,3,5-)liol represented by formula (1).

Examples of the lactone raw material include substituted or unsubstituted lactones represented by the general formula (II) and having 5 or more carbon atoms in the ring, and mixtures thereof.

In the formula, n is at least 3, (n+2) of R are hydrogen, and the remainder is hydrogen, alkyl, cycloalkyl, alkoxy, or a monocyclic aromatic hydrocarbon group, but the total number of substituted carbon atoms is 12 The following is desirable. Examples include ε-caprolactone, dimethylcaprolactone, γ-methyl-ε-casirolactone, β-ethyl-δ-parerolactone, and ε-caprolactone is particularly preferred. The catalyst used must preferably be a compound having no active hydrogen group, and tin-based compounds such as acetic acid and tetraalkyltin are suitable.

The lactone polymer can be produced using the above-mentioned lactone, catalyst, and polymerization initiator CI) by any known method, but since the obtained lactone polymer is preferably colorless, the reaction is carried out using nitrogen gas. The reaction temperature is preferably in the range of 150 to 200°C. Although it is possible to freely adjust the molecular weight of the lactone polymer produced by changing the ratio of the polymerization initiator (1) to the lactone, the tertiary hydroxyl group of [I] remains unreacted. That is, it is an essential condition for obtaining the lactone polymer used in the present invention that [1] acts as a bifunctional polymerization initiator. In addition, the molecular weight of the lactone polymer is 500 to I
QOOO is particularly preferably in the range of 500 to 3000.

The thermoplastic urethane resin of the present invention is produced by combining the lactone polymer, a compound having a polyfunctional active hydrogen, and a compound having a diisocyanate group. Examples of compounds having polyfunctional active hydrogen include polyfunctional glycols, polybasic acid and maryester compounds, d13-ester compounds, and the like, but chilester compounds are most suitable from the mechanical properties of urethane resins.

Examples of compounds having a diisocyanate group include 2.4-tolylene diisocyanate, 2.6-)lylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, etc. alone or in mixtures. Among these, 2,4-tolylene diisocyanate and 414'-diphenylmethane diisocyanate alone or as a mixture are preferred. In addition, thermoplastic N
A catalyst can be used if necessary in producing the urethane resin, and known methods can be employed as the production method.

For example, each raw material is heated and melted, thoroughly stirred and mixed, poured into a heated vat to proceed with the resin reaction, and after cooling is processed into an islet shape with a kneader etc. to obtain a resin, and aromatic hydrocarbons such as toluene and xylene, etc. Examples include a solvent reaction method in which a ketone group such as methyl ethyl ketone and methyl imbutyl ketone is reacted in a single or mixed solvent.

The molecular weight of the obtained urethane resin is preferably in the range of 10,000 to 200,000, particularly 30,000 to 60,000. Examples of the low molecular weight compound having three or more incyanate groups used for curing the urethane resin of the present invention include compounds having the following structures or compounds derived from adducts of monomers having diisocyanate groups. can be mentioned.

Commercially available products of such compounds include Coronat (Nippon Pyriurethane) and Desmod (Sumitomo Bayer).
etc.

〔Effect of the invention〕

The urethane resin for magnetic tape of the present invention has the following features.

■Excellent dispersibility with magnetic iron fluoride.

(2) A cured resin product thermally cured with a low molecular weight compound having three or more isocyanate groups has excellent moisture resistance and heat resistance.

(2) A cured resin product thermally cured with a low molecular weight compound having three or more incyanate groups has excellent tensile modulus.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the scope of these Examples.

In addition, parts in Examples and Comparative Examples indicate parts by weight.

Example-1 A molecule [2000 (hydroxyl value: 56 Molecule i consisting of 100 parts of the lactone polymer of .5), 1,6-hexamethylene glycol and adipic acid (hydroxyl value 55.0)
) were heated and dissolved at 110° C., and then dehydrated for 1 hour under reduced pressure vacuum.

Thereafter, under normal pressure and at 60°C, triethylenediamine o,
24.8 parts of 4.4'-diphenylmethane diisocyanate were added and mixed for about 10 minutes.

This mixed solution was poured into a vat heated to 120°C, left for about 5 hours, and then cured for 3 days in a heating furnace at 100°C to complete the reaction. The mixture was taken out from the vat at room temperature and crushed in a hammer mill to obtain a lump of urethane resin.

Example-2 A molecule [1000 (hydroxyl value 112. 100 parts of the lactone polymer of 0) and 12,000 l of molecules (hydroxyl value 55.2) consisting of 1,4-butanediol and adipic acid.
After heating and dissolving 310 parts of each lyester jeliol at 110° C., dehydration treatment was performed under reduced pressure vacuum for 1 hour. Thereafter, at 60°C under normal pressure, 70.005 parts of triethylenediami and 63 parts of 4,4'-diphenylmethane diisocyanate were added.
．． A bulk urethane resin was obtained in the same manner as in Example-1.

Comparative Example-1 Molecule 112,000 synthesized using ethylene glycol as a polymerization initiator and ε-caprolactone as a lactone raw material
(hydroxyl value 56.0) lactone polymer 100 parts and 1,
A bulk urethane resin was obtained from 100 parts of hylyester hyliol having a molecular weight of 12,000 (hydroxyl value: 55.0) consisting of 6-hexamethylene glycol and adipic acid in the same manner as in Example-1.

Comparative Example-2 Molecule 11200 synthesized using 1,4-butanediol as a polymerization initiator and ε-caprolactone as a lactone raw material
0 (hydroxyl value 55.0) lactone polymer and 100 parts
．． Molecule consisting of 4-butanediol and adipine [2
000 (hydroxyl value 55.2) 4? After heating and dissolving 100 parts of each reprocessed sterhyliol at 110° C., dehydration treatment was performed under reduced pressure vacuum for 1 hour. Thereafter, 0.001 part of dibutyldendilaurate and 16.5 parts of hexamethylene diinocyanate were added, and a lump-like urethane resin was obtained in the same manner as in Example-1.

Comparative Example-3 1,6-hexamethine/glycol and adipic acid, 5-
Sodium sulfodimethyl inphthal #1 (adipic acid 9
Molecule H2000 (hydroxyl value 5 to 7 parts)
A lumpy urethane resin was obtained from 100 parts of the polyester N IJ-all (5.0) in the same manner as in Example-1.

Regarding the urethane resins obtained in Examples and Comparative Examples, the dispersibility of magnetic iron oxide and the performance over time of moisture resistance, heat resistance, and tensile modulus of cured resin products were measured.

The results were as shown in Table-11 Table-2 Table-1 Table-2 () Retention rate when the normal value is 100 The surface and measurement method are as follows.

1) 25 parts of urethane resin in the form of dispersible lumps of magnetic iron oxide are mixed with 1 part of methyl isobutyl ketone.
After confirming complete dissolution, 100 parts of magnetic iron oxide (manufactured by Titan Kogyo, AX-3000) was added and sand ground for 10 minutes at room temperature. The mixture was mixed in a mill and further mixed in a ball mill for 10 hours to obtain a magnetic coating liquid.

The obtained magnetic coating liquid was applied onto the ester film using an applicator so that the film thickness after drying (70°C, 1 hour) was approximately 7μ, and the gloss of the film surface was measured. The dispersibility of magnetic iron oxide was evaluated.

2) Moisture resistance and heat resistance of cured resin product In a resin solution, 30 parts of bulk urethane resin is dissolved in a mixed solvent of 40 parts of methyl ethyl ketone and 30 parts of toluene.
7 parts of the mixture was added to the coronate at room temperature, and the mixture was stirred and mixed for 30 minutes.

The obtained liquid mixture was applied onto a polypropylene film using a percoater so that the coating thickness after drying (80° C., 1 hour) was 40 to 50 μm.

The obtained film-shaped cured resin product was treated in a constant temperature and humidity chamber at 60°C and 90% conditions, and tensile strength, elongation, and tensile modulus were measured in accordance with JISK-6301 (dumbbell No. 2).

From the above results, the thermoplastic urethane resin containing a lactone polymer synthesized using 3-methylinteryL3*5-triol as a polymerization initiator has excellent dispersibility of magnetic iron oxide, and the cured resin product has moisture resistance and heat resistance. It was confirmed that the properties and tensile modulus of elasticity were improved.

Claims (1)

[Claims] A urethane resin for magnetic tapes made of a thermoplastic urethane resin obtained by reacting a lactone polymer synthesized using 3-methylpentane-1,3,5-triol as a polymerization initiator and an isocyanate compound.