JPS582940B2 - Production method of new isocyanate compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a water-soluble and stabilized incyanate compound, and more particularly, it is heat-curable and anionized to form a water-soluble or aqueous emulsion. The present invention relates to a method for producing an isocyanate compound that can be converted into an isocyanate compound.

More specifically, by anionizing with a potentially reactive incyanate group blocked by an imidazole compound having at least one active hydrogen in one molecule, a carboxyl group sufficient to make the isocyanate compound aqueous is formed. The present invention relates to a method for producing a water-soluble and stabilized isocyanate compound having the property of regenerating free isocyanate groups when heated.

It is well known that block polyisocyanate compounds (hereinafter abbreviated as block compounds) have been used instead of free polyisocyanate compounds.

Although the block does not react even when it comes into contact with an active hydrogen compound at room temperature, it has the property of regenerating free polyincyanate groups and undergoing a crosslinking reaction at relatively high temperatures.

These blocks are generally used as a thermosetting resin solution in which the blocks are mixed and dissolved in a resin solution.

However, in most of these prior art solvents other than water are used, and the main reason for this is that the internal skeleton of the block body is hydrophobic, and the blocking agent itself that blocks isocyanate groups is This is thought to be due to the fact that the skeleton after forming the block body is hydrophobic.

In addition, many examples have been reported in which water is used as a medium, but in all of them, blocks are dispersed by emulsifying or suspending them in water, and a completely dissolved and uniform aqueous solution is formed. I have yet to find an example of this.

In addition, a major feature of an aqueous dispersion of blocks is that water can be used as a medium, but it is difficult to form a homogeneous system between the aqueous dispersion of blocks and an emulsified or suspended aqueous solution of a resin. When the mixed resin solution is used as a paint, the resulting paint film may have low gloss due to the non-uniformity of the block body and resin, or the curing reaction may not take place sufficiently, resulting in poor film performance. There are drawbacks.

On the other hand, for example, there are methods in which blocks are dissolved in resin dispersed in water, or methods in which blocks are mixed into a part of the resin composition in advance and dispersed in water. It is difficult to obtain a homogeneous system in the method of dispersion.

The object of the present invention is to provide a completely new process for the production of thermosetting, potentially water-soluble, stabilized incyanate compounds which overcomes the drawbacks mentioned above.

That is, in the present invention, (b) about 1 mol of imidazole or 2-alkyl-imidazole is reacted with 1 mol of (a) organic diisocyanate to produce a blocked isocyanate intermediate having a free isocyanate group at one end. I got it, and then...
(c) About 1 mol of aliphatic dihydroxycarboxylic acid having 3 to 8 carbon atoms having two hydroxyl groups or hydroxyalkyl groups at the α- or β-position is reacted with 2 mol of the intermediate. The present invention relates to a method for producing a novel isocyanate compound having a blocked isocyanate group.

The novel isocyanate compound produced by the present invention has a free carboxyl group in its molecular skeleton that is a salty substance (
It can be made aqueous by neutralizing it with an alkaline substance such as caustic soda or caustic potash.

The fact that the novel isocyanate compound produced by the present invention is completely soluble in water as mentioned above is extremely characteristic, but it is also because it has a free carboxyl group in its molecular skeleton that can be easily made water-soluble, and also because it has a free carboxyl group that can be easily made water-soluble. This is achieved only by the mutual effect of the hydrophilicity of the skeletons of the imidazole blocks at both ends connected via bonds, and is the most characteristic factor of the present invention.

The purpose of the new substance of the present invention is to have properties that are stable at room temperature, regenerate free isocyanate groups when heated, and become completely water-soluble when anionized. .

The production method of the present invention is obtained by first reacting a diisocyanate compound and an imidazole compound in equimolar or approximately equimolar amounts, which has a free incyanate group at one end via a urethane bond, and the other end is formed by imidazole. This is also carried out by preparing an intermediate of the blocked diisocyanate compound, and then reacting this intermediate with a dioxycarboxylic acid, preferably in equimolar or approximately equimolar amounts.

The carboxy block isocyanate compound produced by the present invention contains one dioxycarboxylic acid component in one molecule.

Although the order in which the components are reacted can be modified in this way, the process does not need to be particularly limited depending on the purpose of use and the convenience of the reaction equipment, and it is possible to manufacture using a more appropriate method. .

Examples of the diisocyanate compound in the present invention include 1,6-hexamethylene diisocyanate, 4,4'
-Sophenylmethane diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate,
Examples include 1,10-decamethylene diisocyanate, 1,4-cyclofuxylene, diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,5-tetrahydronaphthylene diisocyanate.

As the dioxycarboxylic acid in the present invention, for example, α
, α'-dioxymethylpropionic acid, α,α'-dioxymethylpropionic acid, tartaric acid, dihydroxymalonic acid, and the like.

Examples of the imidazole compound in the present invention include imidazole, 2-alkylimidazole such as 2-methylimidazole, 2-ethylimidazole, 2-n-butylimidazole, and 2-n-amylimidazole.

In order to more clearly show the structure of the carboxy block isocyanate compound produced by the present invention, 1,6 hexamethylene diisocyanate is used as the diisocyanate compound, α,α'-dioxymethylpropionic acid is used as the dioxycarboxylic acid, and imidazole compound is used. 2-
The specific basic components when methylimidazole is used are as follows.

Furthermore, since the novel incyanate compound obtained by the present invention is often solid at room temperature, it is preferable to use an appropriate reaction solvent.

The solvent may be any solvent as long as it is inert to the reactive inocyanate group and is compatible with the blocked isocyanate compound intermediate and the new isocyanate compound finally obtained.In particular, methyl ethyl ketone, dimethyl Formamide, dimethylsulfoximide and the like are preferred.

The reaction temperature is generally from room temperature to about 120°C, particularly preferably about 50 to 80°C.

Further, the reaction can be carried out without a catalyst or in the presence of a catalyst.

If particularly necessary, urethanization catalysts commonly used in the reaction of dioxycarboxylic acids and diisocyanate compounds are effective.

For example, tertiary amines such as triethylamine, triethylenediamine, pyridine, N-methylpyridine, dibutyltin dilaurate, 2-ethylcaproic acid, chloride (I
I) Metal salts such as iron, zinc chloride, etc.

However, tertiary amines have the effect of accelerating the reaction between carboxylic acid and incyanate group, and are not so preferred.

The new isocyanate compound produced by the present invention is water-soluble, stabilized, and has a latent functional group, and the functional group (isocyanate group) is easily regenerated by heating to 80 to 180°C. can do.

The present invention will be explained below with reference to examples, but the technical scope of the present invention is not limited by these examples.

Example 1 348 g (2 mol) of 2,4-tolylene diisocyanate, 192 g (2 mol) of 2-ethylimidazole, and 192 g (2 mol) of 2,4-tolylene diisocyanate are introduced into a four-loaf flask equipped with a stirrer, a thermometer, a condensing tube with a gas blowing tube and a calcium chloride tube, while passing dry nitrogen into the flask. 2 mol), dimethylformamide 224g, methyl ethyl ketone 2
24 g was added, heated to 60°C, and reacted for 2 hours to obtain a monoblocked diisocyanate compound intermediate.

Next, 1.7 g of diptyltin dilaurate was added as a catalyst to this reaction product, and a solution of 134 g (1 mol) of α,α'-dioxymethylpropionic acid dissolved in 226 g of dimethylformamide was heated at the same temperature for about 2 hours. After the addition was completed, the mixture was further reacted at the same temperature for 4 hours to obtain a carboxyprotutatiisocyanate compound.

This was added to ether, taken out as a viscous liquid, and dried and solidified under reduced pressure.

The acid value of the product was 81.

Further, in the infrared absorption spectrum, no absorption of isocyanate groups was observed at 2,260 cm-1.

This product was neutralized with a 1N aqueous potassium solution and water was added so that the concentration of solids in the aqueous solution was about 30%, which completely dissolved at room temperature.

Furthermore, this aqueous solution was preheated at 80°C for 30 minutes to volatilize the water, and then further heated at 150°C for 30 minutes and measured by infrared absorption spectrum.
A remarkable absorption of isocyanate groups was observed at 260 cm-1.

Conventionally known isocyanate blocking agents such as phenols, oximes, alcohols, lactams, etc. have mostly hydrophobic skeletons forming blocks and do not contribute to water solubility.

On the other hand, even if the skeleton of the block is hydrophilic, the water-solubility effect will be significantly impaired unless some kind of hydrophilic group is introduced into the internal skeleton of the constituent molecules.

The carboxy block isocyanate compound prepared according to the present invention can be easily made water-soluble by anionizing the free carboxy group introduced into the molecular skeleton using an alkaline substance, or in some cases a basic substance.

It still has the property of regenerating free isocyanate groups at heating temperatures in the range of 80-180°C, and can be reacted with compounds having various reactive functional groups.

For example, it can be applied to water-solubilized alkyd resins, polyester resins, acrylic resins, epoxy resins, and butadiene-modified resins, in which hydroxyl groups, carboxyl groups, methylol groups, epoxy groups, etc. are used singly or in combination to adjust the reactivity. be.

The carboxy block isocyanate compound produced according to the present invention has the above-mentioned features, such as being water-soluble and having a latent functional group, which makes the isocyanate group highly reactive for paints (hydrogen, solvent-based, powder type), etc. It is useful as a curing agent (crosslinking agent) and emulsifier in fields where it can be applied.

Claims (1)

[Scope of Claims] 1 (a) 1 mol of organic diisocyanate is reacted with (b) about 1 mol of imidazole or 2-alkyl-imidazole to produce an adduct having a free incyanate group at one end, Blocking characterized by reacting (C) about 1 mole of a C3-8 aliphatic dihydroxycarboxylic acid having two hydroxyl groups or hydroxyalkyl groups at the α-position or β-position with respect to 2 moles of the adduct. A method for producing a novel isocyanate compound having an isocyanate group.