JPH05186516A - Production of radiation-curable vinyl chloride resin - Google Patents

Abstract

PURPOSE:To obtain the title resin which suffers little discoloration and enables the production of a magnetic recording medium excellent in magnetic properties and durability by reacting a hydroxylated vinyl chloride resin with a compound having a specific group in the presence of a compound having a glycidyl group. CONSTITUTION:A hydroxylated vinyl chloride resin is reacted with a compound having at least one ethylenic group and one NCO group per molecule in the presence of a glycidyl compound having a mol.wt. of 500 or lower. The glycidyl compound is used in such an amount that the glycidyl group amount is 1-1,000 equivalents per ton of the all reactants. Thus, a radiation-curable vinyl chloride resin which suffers neither discoloration nor a decrease in physical property can be produced at a temp. not lower than 60 deg.C. This resin enables the production of a magnetic recording medium excellent in mechanical and electrical properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a radiation-curable vinyl chloride resin useful as a binder for magnetic recording media.

[0002]

2. Description of the Related Art Vinyl chloride resins are used as binders for magnetic recording media because of their excellent mechanical properties such as toughness. In recent years, radiation-curable vinyl chloride resins have been investigated because they do not require treatment such as curing. As a method for producing a radiation-curable vinyl chloride resin, JP-A-61-59621 discloses a vinyl chloride resin having a hydroxyl group in the molecule, one or more ethylenically unsaturated groups and one group in the molecule. It is disclosed that the compound having an isocyanate group of 1 is reacted, but when the temperature is raised to 60 ° C. or higher to shorten the reaction time, the vinyl chloride resin is unstable and releases chlorine to decompose, thereby coloring and coating. This is a problem because the physical properties of the film are deteriorated.

[0003]

In view of the above-mentioned circumstances, the present inventors have made it possible to produce a magnetic recording at a reaction temperature of 60 ° C. or higher without deterioration of physical properties and to obtain magnetic recording excellent in mechanical properties and electrical properties. As a result of extensive studies aimed at obtaining a radiation-curable vinyl chloride resin capable of producing a medium, the present invention has been accomplished.

[0004]

That is, the present invention provides a vinyl chloride resin having a hydroxyl group in the molecule and a compound having one or more ethylenically unsaturated groups and one isocyanate group in the molecule. When reacting 500 or less glycidyl group-containing compounds, the glycidyl groups are converted into all reactive components 1
It is a method for producing a radiation-curable vinyl chloride resin, which comprises reacting by allowing it to exist in an amount of 1 to 1000 equivalents per ton.

As a method for producing a radiation-curable vinyl chloride resin, the present inventors have made a vinyl chloride resin by adding 1 to 1000 equivalents of a glycidyl group-containing compound in the system per ton of all reactive components. Vinyl chloride resin having hydroxyl groups in the molecule and at least one ethylenically unsaturated group and one isocyanate group in the molecule at a temperature of 60 ° C or higher, which is practically sufficient for urethanization without decomposing It has been found that a compound having a can be reacted.

As the vinyl chloride resin having a hydroxyl group in the present invention, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a vinyl chloride-vinyl alcohol copolymer,
There are vinyl chloride-hydroxyalkyl (meth) acrylate copolymers, vinyl chloride-vinyl acetate-vinyl alcohol-glycidyl (meth) acrylate copolymers, and the like, and the number of hydroxyl groups is 3 to 60 in one molecule, preferably It is 5 to 30 pieces. In addition, one or more polar groups may be contained in the molecule, and as the polar group, —OSO ₃ M group,
Group -SO ₃ M, -OPO ₃ M group, -PO ₃ M group, -CO
For example, OM group (M atom represents H, amine, alkali metal, etc.).

In the present invention, the compound having at least one ethylenically unsaturated double bond and one isocyanate group in one molecule and having no urethane bond in the molecule includes (meth) acroyl isocyanate, 2-isocyanate ethyl (meth) acrylate, a reaction product of polyisocyanate and hydroxy (meth) acrylate, and the like. The amount of the above compound added is from 2 to 6 of the main chain polymer.
The range of 20 wt% is good, and if it is less than 2 wt%, the curability is insufficient, and if it is added in excess of 20 wt%, the curability is not improved, and the physical properties of the coating film are adversely affected.

As the glycidyl group-containing compound having a molecular weight of 500 or less, glycidyl esters and glycidyl ethers having no active hydrogen group are preferable, and glycidyl (meth) acrylate is particularly preferable from the viewpoint of curability. The addition amount of the glycidyl group is less than 1 equivalent per ton of the total reactive resin component, and the addition amount exceeds 1000 equivalents, which adversely affects the physical properties of the coating film. On the other hand, when the molecular weight exceeds 500, not only the physical properties of the cured film are adversely affected, but also the stabilizing effect during polymerization of the vinyl chloride resin is deteriorated.

The reaction conditions are a reaction temperature of 60 to 90 ° C.
Is preferred. As the solvent, those having no active hydrogen can be used, and examples thereof include aromatic hydrocarbons such as toluene and xylene, and ketones such as methyl ethyl ketone and cyclohexanone. As the catalyst, an ordinary isocyanate reaction catalyst is used, and for example, a metal compound such as dibutyltin dilaurylate or dibutyltin oxide or an amine compound such as triethylamine can be used. Further, a polymerization inhibitor or the like may be used for stabilizing the ethylenically unsaturated double bond during the reaction.

As the electron beam irradiator, a scanning system or a curtain beam system can be adopted, and the absorbed dose is 1 to 20 Mrad, preferably 2 to 15 Mrad. If the absorbed dose is less than 1 Mrad, the curing reaction will be insufficient, and if it exceeds 20 Mrad, the energy efficiency used for curing will decrease, and excessive crosslinking will proceed, such being undesirable.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 In a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, VAGH, which is a vinyl chloride resin containing a hydroxyl group, is used.
(Union Carbide Co., Ltd.) 100 parts and methyl ethyl ketone 250 parts were charged, and after dissolution, 10 parts of 2-methacryloyloxyethyl isocyanate, 0.1 part of glycidyl methacrylate, 0.02 part of dibutyltin dilaurate and 0.003 part of hydroquinone were charged. , 70-80 ℃
The reaction was carried out for 6 hours to obtain a radiation-curable vinyl chloride resin A. Similarly, radiation-curable vinyl chloride resins B and C having the compositions shown in Table 1 were obtained.

Comparative Example 1 100 parts of the above-mentioned VAGH and 250 parts of methyl ethyl ketone were charged into a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, and after dissolution, 10 parts of 2-methacryloyloxyethyl isocyanate and dibutyltin. Dilaurate 0.02
Part and hydroquinone 0.003 part were charged, and 70 to 8
Radiation-curable vinyl chloride resin D was obtained by reacting at 0 ° C. for 6 hours. Similarly, radiation-curable vinyl chloride resins E and F were obtained. The results are shown in Table 1.

Method for producing magnetic paint Magnetic powder (cobalt-coated γ-iron oxide) 60 parts Polyurethane acrylate resin (BK4102: manufactured by Toyobo Co., Ltd.) (solid content concentration 35 wt%) 15 parts Radiation curable vinyl chloride resin solution A ( Solid content concentration 30.6 wt%) 15 parts Toluene 25 parts Methyl isobutyl ketone 25 parts

After mixing the above composition in a ball mill for 24 hours, this magnetic coating material was applied onto a 25 μm polyethylene terephthalate film so that the thickness after drying would be 6 μm. Then, a magnetic field orientation treatment was carried out in the length direction of the film by a direct current magnetic field of 2500 gauss for 0.05 seconds, followed by hot air drying at 100 ° C. for 1 minute, followed by calendering treatment and radiation treatment of 5 Mrad. Then, this film was cut into a width of 1.5 cm to prepare a magnetic tape.

A radiation-curable vinyl chloride resin B to F shown in Table 1 was used to form a magnetizable layer on a polyethylene terephthalate film by the same method, and a width of 1.
A 5 cm magnetic tape was made. The measurement results of the characteristics of each magnetizable layer are shown in Table 2.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

As is clear from Tables 1 and 2, the radiation-curable vinyl chloride resin produced according to the present invention has little coloring, and the magnetic recording medium obtained using this resin has magnetic characteristics and durability. Excellent in

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Claims (1)

[Claims] 1. When reacting a vinyl chloride resin having a hydroxyl group in the molecule with a compound having one or more ethylenically unsaturated groups and one isocyanate group in the molecule,
A method for producing a radiation-curable vinyl chloride-based resin, which comprises reacting a glycidyl group-containing compound having a molecular weight of 500 or less so that the glycidyl group is present in an amount of 1 to 1000 equivalents per ton of all reactive components and reacting.