Oxazolidone ring-containing epoxy resin

Details Oxazolidone ring-containing epoxy resin Oxazolidone ring-containing epoxy resin

2001-08-16

2003-12-16

Sellers, Robert E. L. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C523S415000, C525S454000

Reexamination Certificate

active

06664345

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a novel oxazolidone ring-containing epoxy resin, more specifically, relates to an oxazolidone ring-containing epoxy resin which is preferred to be used as a resin for an aqueous coating composition.
BACKGROUND OF THE INVENTION
An epoxy resin is the resin which has more than two epoxy groups (—CH(O)CH
2
) in the molecule. An epoxy resin affords a cured resin excellent in dielectric ability, mechanical strength, dimensional stability, and chemical resistance when it is cured by combining a suitable curing agent. An epoxy resin therefore has variety of applications such as a paint for metal, an anticorrosion material, an adhesive, a structural material reinforced by glass fibers, and the like.
J. Polymer Sci. Part A-1, 4, 751 (1966), Iwakura et al, describes an oxazolidone ring-containing epoxy resin. The oxazolidone ring-containing epoxy resin is that obtained by allowing a blocked diisocyanate compound which is obtained by reaction of diisocyanate and monoalcohol, to react with a diepoxy compound. J. Appl. Polymer Sci., 9, 1984 (1966), Sander et al, for example describes an oxazolidone ring-containing epoxy resin which is obtained by allowing a diisocyanate compound to directly react with a diepoxy compound.
The epoxy resins may be employed as a binder resin for an aqueous coating composition. In this instance, an ionic group is introduced in the epoxy resins to provide hydrophilic epoxy resins. Japanese Patent Laid Open Publication No. 306327/1993 describes the method of that a terminal epoxy group of the oxazolidone ring-containing epoxy resin prepared by the above described means, is ring-opened with an active hydrogen compound having an ionic group to prepare an oxazolidone ring-containing aqueous resin having an ionic group such as an amino group, and a carboxyl group therein. This publication also describes an aqueous coating composition which comprises such an oxazolidone ring-containing epoxy resin.
Corrosion resistance, impact resistance, cohesiveness, excellent appearance, and the like are generally required for a resin for use in a coated film. An oxazolidone ring-containing epoxy resin is excellent in heat resistance, and corrosion resistance, and therefore affords a coated film excellent in heat resistance, and corrosion resistance. However, the conventional oxazolidone ring-containing epoxy resin is poor in flexibility. Therefore, impact resistance of a coated film becomes poor when the oxazolidone ring-containing epoxy resin is used as a resin for a coated film.
SUMMARY OF THE INVENTION
The present invention provides a novel oxazolidone ring-containing epoxy resin suitable for use as a resin for a coated film. The oxazolidone ring-containing epoxy resin of the present invention affords a coated film excellent in impact resistance in addition to heat resistance, and corrosion resistance.
The oxazolidone ring-containing epoxy resin has a structure of the formula:
wherein R
3
represents a residue excluding epoxy groups of diepoxide, X represents a residue excluding isocyanate groups of polyurethane diisocyanate, and n represents an integer of 1 to 5; and wherein X has a structure of the formula:
wherein R
1
represents a residue excluding isocyanate groups of diisocyanate, R
2
represents a residue excluding hydroxyl groups of diol, and m represents an integer of 2 to 10.
DETAILED DESCRIPTION OF THE INVENTION
The oxazolidone ring-containing epoxy resin of the present invention is preferably prepared by the process comprising the steps of:
obtaining a blocked polyurethane diisocyanate represented by the formula:
 wherein R
1
represents a residue excluding isocyanate groups of diisocyanate, R
2
represents a residue excluding hydroxyl groups of diol, B represents a residue of a blocking agent, and m represents an integer of 2 to 10, by reacting diisocyanate, diol, and a blocking agent; and
allowing the blocked polyurethane diisocyanate to react with diepoxide.
Diisocyanate means a compound which has two isocyanate groups in the molecule. Specific examples of the diisocyanate include aromatic diisocyanate such as 4,4′-diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), and xylylene diisocyanate (XDI); aliphatic diisocyanate (comprising alicyclic diisocyanate) such as hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), 4,4′-methylenebis(cyclohexylisocyanate), trimethyl hexamethylene diisocyanate.
Preferred diisocyanate is the aromatic diisocyanate. The aromatic diisocyanate is highly reactive with an epoxy group present in an epoxy resin, and an oxazolidone ring may easily be formed.
Diol means a compound which has two hydroxyl groups in the molecule. For example, oligomeric diol or polymeric diol preferably having a molecular weight of from 300 to 9000 is comprised in the diol of the present invention. Throughout the specification and claims, the wording “molecular weight” means number average molecular weight.
Specific examples of the diol include alkylene diol, aromatic diol, polyether diol, polyester diol, polycaprolactone diol, and polycarbonate diol, each having a molecular weight of up to about 9000. More specifically, examples of diol include alkylene diol such as ethylene glycol, 1,2-propylene glycol, 1,3-propane diol, 1,4-butane diol, 1,6-hexane diol; alicyclic diol such as 1,2-cyclohexane diol, 1,4-cyclohexane diol; aromatic diol such as bisphenol A, bisphenol F, resorcinol, hydroquinone; polyester diol prepared by an esterification reaction between polycarboxylic acid or the anhydride thereof, and polyol, polycaprolactone diol prepared by an polymerization reaction of caprolactone by using polyol as an initiator; and polyether diol such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, the random or block copolymer thereof.
The diol is preferably primary diol of which hydroxyl groups are both primary. The reason is that primary diol is conveniently prepared by a simple procedure as described hereinafter. Preferred example of the primary diol is an ethylene oxide adduct of bisphenol A having a structure of the formula:
wherein x represents an integer of 1 to 10. The x in the formula is preferably an integer of 2 to 6 because both flexibility and corrosion resistance of the resulting coated film are easily achieved.
Polyurethane diol is the diol which is prepared by condensing diisocyanate with diol. The polyurethane diol may also be comprised in diol of the present invention. Preferred example of the polyurethane diol is that having a structure of the formula:
wherein R
4
represents a residue excluding hydroxyl groups of diol, R
5
represents a residue excluding isocyanate groups of polyisocyanate, and y represents an integer of 1 to 10.
The diol which corresponds to R
4
is not limited to, but the diol which corresponds to R
4
have to be different from polyurethane diol. Preferred examples of the diol include alkylene diol, aromatic diol, polyether diol, polyester diol, polycaprolactone diol, and polycarbonate diol. It is preferred that primary diol is employed as the diol which corresponds to R
4
because the resulting polyurethane diol also become primary diol. Particularly preferred example of the diol which corresponds to R
4
, is the above described ethylene oxide adduct of bisphenol A.
The diisocyanate which corresponds to R
5
is preferably aliphatic diisocyanate. The reason is that weather resistance of the resulting epoxy resin becomes excellent for use as a coated film. Preferred examples of the diisocyanate which corresponds to R
5
include hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), 4,4′-methylenebis(cyclohexylisocyanate), trimethylhexamethylene diisocyanate.
The polyurethane diol employed herein preferably has a molecular weight of from 300 to 9000, preferably 500 to 5000. If the molecular weight of the polyurethane diol is more than 9000, appearance of the coated film becomes poor, and if it is less than 300, flexibility of the coated film becomes poor.
A blocking agent is th

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