JPH0317849B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a curable resin that can be freely cured at room temperature or under heating and is useful for various uses. [Prior Art] There are various types of resins that can be cured, especially those that cure by radical polymerization reactions, such as unsaturated polyester resins, vinyl ester resins (epoxy-acrylates), various oligoacrylates, and diallyl phthalate prepolymers, each of which has its own application. It is widely used because of its features in the field. However, with the diversification and sophistication of required performance in each field of application, these existing resins may not be able to fully satisfy the required performance. For example, it is extremely difficult to uniformly coat a metal surface in microns and cure it to form a smooth protective coating layer using the existing radical-curing resins, which have molecular weights that belong to oligomers. It is. [Problems to be Solved by the Invention] In view of the above situation, the present inventors have conducted various studies on the synthesis of radical-curable resins that can be used in applications where existing resins are unsatisfactory. The present invention was completed based on the knowledge that a curable resin obtained by reacting with a saturated isocyanate can satisfy a portion of the diversification and sophistication of performance required. [Means for Solving the Problems] That is, the present invention has a polymerization degree of 20 or more (a molecular weight of 5000
(preferably equivalent to 10,000 or more), the phenoxy resin has one isocyanate group and at least one unsaturated bond in one molecule, which is obtained by reacting a polyvalent isocyanate and an unsaturated monoalcohol. It consists of reacting an unsaturated isocyanate having 0.01 equivalent or more of the isocyanate group of the unsaturated isocyanate with respect to 1 equivalent of the hydroxyl group of the phenoxy resin. [Function] For reference, a typical method of the present invention will be illustrated by a chemical formula. As mentioned above, the hydroxyl group of the phenoxy group is bonded to the methacryloyl group via two urethane bonds, resulting in an unsaturated bond added to the polymer side chain. Since the side chain acryloyl group introduced by such an operation can be cross-linked, it is possible to convert phenoxy resin, which is originally a thermoplastic polymer, into a thermosetting type, which imparts heat resistance and chemical resistance. This will be useful for improving your skills, etc. The phenoxy resin used in the present invention is a polymer represented by the following general formula, and has a degree of polymerization of 20 or more (average molecular weight of 5,000 or more, preferably 10,000 or more). However, R=-H or

【formula】

【formula】

In general, compounds in the range of 30,000 to 100,000 are commercially available, and in the present invention, these can be dissolved as they are in a necessary solvent and used for the reaction with the unsaturated isocyanate. If the molecular weight is less than 5000, the film forming properties before curing are not necessarily sufficient. In principle, 1 mole of unsaturated monoalcohol is used for 1 mole of diisocyanate in the production of unsaturated isocyanate, but 2,4
- Even in cases where there is a significant difference in reactivity between two isocyanate groups, such as tolylene diisocyanate, the unsaturated isocyanate depicted in the model cannot be obtained alone, but usually the following three types of diisocyanates, unsaturated isocyanates,
A mixture of oligoacrylates is formed. Among these components, undesirable is free diisocyanate, which if left behind may cause gelation or abnormally increase in viscosity, making handling difficult. When phenoxy resin is used as a component, the residual amount of diisocyanate must be 0.1 (wt%) or less. In order to remove free diisocyanate, it is necessary to increase the amount of the unsaturated monoalcohol component to more than a specified number of moles, or to remove the diisocyanate by distillation under reduced pressure after the reaction is completed. However, if the unsaturated monoalcohol has a (meth)acryloyl group, reduced pressure at high temperature will polymerize the (meth)acryloyl group, resulting in gelation. Measures such as depressurization are required. Oligoacrylates, which are another so-called by-product, do not impede the invention. If its abundance is fixed, it will be useful for improving physical properties, for example, increasing heat distortion temperature. Therefore, a practically easy method for producing unsaturated isocyanate is to use 1 mol or more of unsaturated monoalcohol per 1 mol of diisocyanate, and the most appropriate molar ratio is 1.2 mol or more and 1.5 mol or less. be. For example, when 1.2 mol of unsaturated monoalcohol is used per 1 mol of diisocyanate, the following mixture is obtained. This can be used as is for reaction with phenoxy resin. Examples of diisocyanates for forming unsaturated isocyanates include the following types. 2,4-tolylene diisocyanate, 2,4-
Mixture of tolylene diisocyanate and 2,6-tolylene diisocyanate, paraphenylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate , hexamethylene diisocyanate, isophorone diisocyanate. Desirable types are those in which two isocyanate groups differ in reactivity, such as 2,4-tolylene diisocyanate and isophorone diisocyanate. Furthermore, examples of the unsaturated monoalcohols used include those having a (meth)acryloyl group and a hydroxyl group in one molecule, which are obtained by reacting acrylic acid or methacrylic acid with an alkylene monoepoxide. In addition, it is also possible to use allyl alcohol. The reaction ratio of the phenoxy resin and the unsaturated isocyanate is 0.01 equivalent or more of isocyanate groups (i.e. unsaturated isocyanate) per equivalent of hydroxyl group of the phenoxy resin, but preferably
It is 0.1 equivalent or more and 1 equivalent or less. If the amount is less than 0.01 equivalent, it is difficult to make it thermosetting. During the reaction, it is necessary to use a polymerization inhibitor to prevent gelation, and it is advantageous to use a reaction accelerator such as a tertiary amine or an organic tin compound to shorten the reaction time. The curable resin composition obtained by the method of the present invention can be cured by using a radical generating catalyst such as an organic peroxide and, if necessary, a curing accelerator. It goes without saying that the curable resin according to the present invention may be used in combination with a colorant, a reinforcing material, a filler, a mold release agent, etc., as necessary. [Example] Next, in order to assist in understanding the present invention, examples are shown below. Example 1 Production of unsaturated isocyanate (A) 174 g of 2,4-tolylene diisocyanate was placed in a separable flask equipped with a stirrer, a gas inlet tube with a thermometer, a reflux condenser, and a dropping funnel.
(1 mol) was charged, and 130 g (1 mol) of 2-hydroxyethyl methacrylate containing 200 ppm of benzoquinone was added dropwise from around 40°C. Since the temperature will rise, cool as necessary so that the reaction occurs at around 60°C. After reacting at 60°C for 8 hours, it was determined that free hydroxyl groups had disappeared as a result of infrared analysis. Change the reflux condenser to a fractionation condenser,
Add 0.1g of phenothiazine and add ≒2~ in oxygen stream
Reduce pressure to 3 mmHg and 90°C. After 3 hours, gas chromatography analysis revealed that free diisocyanate was approximately 0.06 (%), and the treatment was discontinued. Pale reddish brown unsaturated isocyanate A was obtained in the form of a viscous liquid. Production of curable resin (B) As a phenoxy resin, 60 g of unsaturated isocyanate (A) (phenoxy resin isocyanate group per equivalent of hydroxyl group in
0.2 equivalents) and 0.5 g of dibutyltin dilaurate were added and reacted at 60° C. for 5 hours. As a result of infrared analysis, it was confirmed that free isocyanate groups had disappeared. A methyl ethyl ketone solution of a phenoxy resin having a (meth)acryloyl group in its side chain (abbreviated as resin B) was obtained with a reddish brown color and a viscosity of about 200 poise. 100 parts by weight or less of Resin B, 0.5 parts of 328E from Kayaku Nouri Co., Ltd. and 0.2 parts of cobalt naphthenate were added as hardening agents, and 50 parts of methyl ethyl ketone were coated on a Bonderite steel plate to a thickness of 0.1 mm using a bar coater. After curing in an oven at 60°C for 12 hours and at 120°C for 2 hours, the film was smooth, had a pencil hardness of 3H, and had an excellent goblin adhesion test of 100/100. Furthermore, even when the coating film was immersed in methyl ethyl ketone, no peeling due to dissolution or swelling was observed, and it was confirmed that the coating film had hardened. Example 2 Production of unsaturated isocyanate (C) Into a two-separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, 512 g of methyl ethyl ketone, 225 g (about 1 mol) of isophorone diisocyanate, and 0.1 g of benzoquinone. , 1 g of dibutyltin dilaurate was charged, and the adduct of phenyl glycidyl ether and acrylic acid was prepared at a temperature of 60°C in a ratio of 1 mole to 1 mole. 270 g (equivalent to 1.2 mol per 1 mol of isocyanate) is added dropwise. After the dropwise addition was completed, the reaction was carried out at 60°C for 6 hours, and as a result of infrared analysis, it was determined that the free hydroxyl groups had disappeared. A pale yellowish brown unsaturated isocyanate (C) (approximately 50% solution in methyl ethyl ketone) was obtained. Production of curable resin (D) 2 equipped with stirrer, reflux condenser and thermometer
In a three-neck flask, as a phenoxy resin, Epicote 53HB35 (Methyl ethyl ketone solution 34-36% solids, molecular weight approx.
55000), 800g, unsaturated isocyanate (C), 400g
(approx. 0.3 equivalent of isocyanate group per equivalent of hydroxyl group of phenoxy resin), 0.1 g of hydroquinone, and 0.5 g of dibutyltin dilaurate were added, and the mixture was reacted at 60° C. for 8 hours. As a result of infrared analysis, it was confirmed that the isocyanate groups had completely disappeared. The resulting curable resin (D) has a yellowish brown color and a viscosity of approx.
It was 130 poise. 30 parts of methyl ethyl ketone, 1 part of cumene hydroperoxide, and 0.2 parts of cobalt naphthenate were added to 100 parts of resin (D), and the mixture was coated onto a bonderite steel plate to a thickness of 0.1 mm. After heating at 60℃ for 12 hours and 120℃ for 2 hours, the coating film was smooth, hard 3-4H, and had a goblin adhesion test of 100/100.
Even after being immersed in methyl ethyl ketone for one day, no abnormalities were observed, and no dissolution or swelling was observed, confirming that it had hardened. [Effects of the Invention] The curable resin produced by the method of the present invention can be freely cured at room temperature or under heating, and is useful for various uses. In particular, the ability to form a smooth protective coating layer by coating and curing metal surfaces in micron units is an effect that has not been observed with conventionally known curable resins.

Claims (1)

[Claims] 1. A phenoxy resin with a degree of polymerization of 20 or more, a polyvalent isocyanate having at least 2 isocyanate groups in one molecule, which has 0.01 equivalent or more of isocyanate groups per 1 equivalent of hydroxyl group of the phenoxy resin, and 1. having at least one isocyanate group and at least one unsaturated group in the molecule obtained by reaction with an unsaturated alcohol having at least one unsaturated group and a hydroxyl group in the molecule. A method for producing a curable resin by reacting it with an unsaturated isocyanate.