JP2000109537A - Radiation curable resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radiation curable resin having excellent pigment-dispersing and coating material-stabilizing properties when used as a binder resin for various coating materials including magnetic recording media. SOLUTION: This radiation curable resin is obtained by reacting (A) a vinyl chloride-based copolymer having hydroxyl groups and other polar groups with (B) a monomer which has one or more ethylene-based unsaturated double bonds and an isocyanate group but does not have any urethane bond in its molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radiation-curable resin useful as a binder for various pigments such as a magnetic recording medium binder.

[0002]

2. Description of the Related Art In recent years, in a magnetic recording medium, a radiation curable resin is mixed and dispersed with a magnetic powder and other essential components to prepare a magnetic paint, and the obtained magnetic paint is coated on a support and dried. Thereafter, radiation curing is performed to form a magnetic layer. And, as these radiation-curable resins, a vinyl chloride copolymer having a hydroxyl group such as a vinyl chloride-vinyl acetate-vinyl alcohol copolymer is added to a monoisocyanate compound having an ethylenically unsaturated group, for example, 1 mol of tolylene diisocyanate. 2-
A radiation-curable resin is obtained by reacting an adduct with 1 mol of hydroxyethyl acrylate, or a vinyl chloride copolymer having a hydroxyl group is reacted with an acid anhydride and then a glycidyl acrylate compound is reacted to cure the radiation. Or obtain a resin. However, when such a radiation-curable resin is used as a binder, a dispersant having no polar group must be used, and the physical properties of the coating film deteriorate. In addition, since the ethylenically unsaturated compound is bonded using a long side chain from the polymer chain, the dispersibility and orientation of the magnetic powder are insufficient, which is insufficient for high recording density. Have.

[0003]

SUMMARY OF THE INVENTION The present invention is an improvement over the above-mentioned various drawbacks. When used as a binder resin for various kinds of paints such as a magnetic recording medium, the pigment dispersibility and the stability of the paints are improved. It is intended to provide a resin having excellent properties.

[0004]

The present invention provides a vinyl chloride copolymer (A) having a hydroxyl group and a polar group other than a hydroxyl group, at least one ethylenically unsaturated double bond and an isocyanate group, It is a radiation-curable resin obtained by reacting a monomer (B) having no urethane bond in the molecule.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a hydroxyl group and a polar group
The base of the vinyl chloride copolymer (A) having a functional group
Vinyl chloride-vinyl acetate-vinyl alcohol
Cole copolymer, vinyl chloride-vinyl alcohol copolymer
Body, vinyl chloride-hydroxydialkyl (meth) acryle
Copolymer, vinyl chloride-vinyl acetate-vinyl alcohol
Il-chrysidyl (meth) acrylate copolymer and the like
Yes, the number of hydroxyl groups is preferably 3 to 60 per molecule.
And the polar group is -OSO
_ThreeM group, -OSO_ThreeGroup, -OPO_ThreeM group, -PO_ThreeM group,-
COOM group (M atom is H, Li, Na, K,
Ba, Ca, etc. are shown. ).

[0006] One or more of these polar groups can be contained. In the present invention, one or more ethylenically unsaturated double bonds and one isocyanate group
Examples of the monomer (B) having a molecule and having no urethane bond in the molecule include 2-isocyanatoethyl (meth) acrylate. Like this molecule, the distance between the isocyanate group and the acrylic group must be short.

An ethylenically unsaturated double bond is introduced by a urethane bond by a reaction between a vinyl chloride copolymer (A) having a hydroxyl group and a polar group and a monomer (B). The radiation curability can be freely designed by the molar ratio of the vinyl chloride copolymer (A) and the monomer (B). However, if the urethane bond concentration is too high, the dispersibility decreases. Therefore, when a balance between the dispersibility and the curability is taken, 1 to 20, preferably 2 to 10 monomers (B) are reacted per molecule of the vinyl chloride copolymer (A) having a hydroxyl group and other polar groups. By doing so, a radiation-curable resin excellent in both dispersibility and curability can be obtained.

In the present invention, the reaction between the vinyl chloride copolymer (A) having a hydroxyl group and another polar group and the monomer (B) may be carried out, if necessary, with a known organic solvent which does not participate in the reaction. A vinyl chloride copolymer having a polar group is dissolved, and the reaction is carried out at a reaction temperature of 60 ° C. or lower using a known urethanization reaction catalyst and a known radical polymerization inhibitor, for example, hydroquinone.

When the resin of the present invention is used as a coating material for a magnetic recording medium, the resin of the present invention may contain a magnetic powder, a radiation-curable resin such as polyester acrylate, polyurethane acrylate and epoxy acrylate, a diluent monomer such as styrene, and a lubricant. Then, an abrasive, an antistatic agent and the like are added, provided as a magnetic layer on the support by a method such as coating, dried if necessary, and then cured by irradiation with radiation to obtain a magnetic recording medium.

The radiation used for curing the resin of the present invention includes an electron beam using an electron beam accelerator or the like, a gamma ray using Co60 as a source, and an X-ray using an X-ray generator as a source. Rays, ultraviolet rays and the like.

[0011]

The present invention will be described below with reference to examples. The middle part in Examples means parts by weight. Example 1 Vinyl chloride copolymer containing a hydroxyl group and a sulfonate group “MR110” (trade name, manufactured by Zeon Corporation) 10
0 parts were dissolved in 200 parts of methyl ethyl ketone and 50 parts of toluene, and then phenothiazine and hydroquinone were mixed at 200 ppm with respect to the acrylic compound. Thereafter, 2-isocyanatoethyl methacrylate (MO
I, manufactured by Showa Denko KK) 5 parts, di-n of urethanization reaction catalyst
-Butyltin laurate (DBTL) was mixed at 1000 ppm with respect to the MOI, and the mixture was stirred at a reaction temperature of 60 ° C. for 8 hours. It was confirmed by IR spectrum that there was no absorption of isocyanate groups.

Comparative Example 1 After adding 0.13 part of hydroquinone to 174 parts of tolylene diisocyanate heated to 80 ° C., 130 parts of 2-hydroxyethyl methacrylate was gradually added dropwise, and reacted at 80 ° C. for 2 hours. Thus, an adduct was obtained. Vinyl chloride copolymer "VROH" (trade name, manufactured by Union Carbide) having no polar group other than hydroxyl group 2
00 parts are methyl ethyl ketone 400 parts, toluene 180
At 60 ° C., and the resulting adduct body 50
And 0.1 part of DBTL as a urethanization reaction catalyst was added. The mixture was stirred at 60 ° C. for 8 hours, and it was confirmed from the IR spectrum that no isocyanate group was absorbed.

Comparative Example 2 200 parts of a vinyl chloride copolymer "VROH" having no polar group other than a hydroxyl group was dissolved in 290 parts of methyl ethyl ketone at 60 ° C., and then 25 parts of phthalic anhydride, 25 parts of glycidyl methacrylate, and hydroquinone 0.02
Parts and 0.12 parts of triethanolamine,
The reaction was carried out at 20 ° C. for 20 hours, and it was confirmed that the acid value was less than 10.

A magnetic recording medium was prepared using the resins of Example 1 and Comparative Examples 1 and 2, and their characteristics were evaluated. Table 1 shows the results. The evaluation was performed by the following method.

[0015]

[Table 1] Manufacture of magnetic paint Ingredients Cobalt-doped acicular γ-Fe ₂ O ₃ (specific surface area 21 m ² / g) 100 parts Carbon black (antistatic agent) 4 parts Alumina powder (polishing agent) 8 parts Lecithin 3 parts Methyl ethyl ketone 50 parts Toluene 50 parts Component Solvent solution of the resin obtained in Example 1 or Comparative Example 1 or 3 60 parts Urethane acrylate “Aronix M-1200” (trade name, manufactured by Toa Gosei Chemical Industry Co., Ltd.) 7 parts Butyl stearate 2 Parts methyl ethyl ketone 90 parts toluene 90 parts The above components were mixed and dispersed in a ball mill for 3 hours, and then the above components were added and mixed and dispersed for 5 hours to obtain a magnetic paint. A magnetic layer was provided by applying the obtained magnetic paint to a 15-μm-thick polyester film support, oriented in a magnetic field, and cured by irradiating an electron beam at 5 Mrad. The surface gloss (gloss 6) of the obtained magnetic film was evaluated in order to evaluate the performance of the magnetic recording medium.
0 degree) and the squareness ratio (Rs) were measured.

[0016]

As is clear from Table 1, when the radiation-curable resin of the present invention is used as a binder for a magnetic recording medium, the dispersibility and orientation of magnetic powder can be remarkably improved. A magnetic recording medium suitable for increasing the recording density can be provided. Furthermore, by utilizing the high dispersibility of various pigments, it can be usefully used as a binder resin for paints and inks.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor: Shinichi Kodera 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (1)

[Claims] 1. A vinyl chloride copolymer (A) having a hydroxyl group and a polar group other than a hydroxyl group, having at least one ethylenically unsaturated double bond and an isocyanate group, and having no urethane bond in the molecule. Radiation curable resin obtained by reacting with monomer (B)