JP2632984B2 - Process for producing unsaturated carboxylic acid isocyanatoalkyl ester - Google Patents

Description

The present invention relates to an improved method for producing an unsaturated isocyanatoalkyl carboxylate represented by the general formula [I], which is useful as various synthetic intermediates. About.

[Wherein, R represents a hydrogen atom, a lower alkyl group, an aryl group,
Or R 'represents a hydrogen atom or a methyl group. A represents a linear or branched alkylene group having 2 to 4 carbon atoms. Since the unsaturated carboxylic acid isocyanatoalkyl ester represented by the general formula [I] has a CＣC double bond and an isocyanato group in one molecule at the same time, (A) alone or in combination with another vinyl monomer This causes the polymer chain to have an isocyanato group as a pendant.

(B) -OH, by addition to the polymer having a functional group having active hydrogen such as -NH _2, to synthesize a so-called macromonomer.

(C) A new functional monomer is synthesized by adding a functional molecule having an active hydrogen to the isocyanato group (for example, a physiologically active substance).

It can be used for such purposes. It is an industrially useful compound. In particular, in the formula [I], R = H, R '= C
Compounds with H ₃ , n = 2 (methacrylic acid-2-isocyanatoethyl ester) are used as raw materials for manufacturing distinctive products in the fields of photoresists, paints, adhesives and the like.

[Conventional technology]

As a method for producing an unsaturated carboxylic acid isocyanatoalkyl ester, the following method has been conventionally proposed.

(1) Ethyl hydroxycarbamate is synthesized from a monoalkanolamine, ethyl chloroformate and a basic compound (K ₂ CO ₃ ), and reacted with an unsaturated carboxylic acid chloride to form a urethane ester, which is then pentachlorinated. A method of converting to isocyanate with phosphorus or thionyl chloride. (U.S. Pat. No. 2,718,516) In this method, phosphorus and sulfur remain as impurities, and side reactions (for example, polymerization and addition of HCl) which are considered to be based on a double bond easily occur. It is difficult to obtain in high yield.

(2) A method in which an unsaturated carboxylic acid aminoalkyl ester hydrochloride is synthesized from an unsaturated carboxylic acid chloride and a monoalkanolamine hydrochloride, and is reacted with phosgene to produce an isocyanate. (U.S. Pat. No. 2,821,544) This method has the disadvantage of low yield.

(3) Reaction of 2-alkenyl oxazoline with phosgene. According to this method, an expensive oxazoline compound is used as a raw material, and the process is long, so that the resulting product must be expensive.

Further, in each of the methods (1) to (3), chlorine is contained as an impurity in the product, and therefore, it is not suitable for use in electronic materials.

(4) Hydroxyurethane is synthesized by the reaction of dimethyl-, diethyl-, or dipyrropropylcarbonate with ethanolamine, and converted to urethane with an unsaturated carboxylic acid or a chloride or ester thereof. how to. In this method, thermal decomposition of uretanoester is difficult, and the decomposition rate is 50 to 60% even at a high temperature of, for example, 400 ° C. However, unsaturated carboxylic acid isocyanatoalkyl esters are extremely easy to polymerize, and thus polymerize when exposed to such a high temperature, and are liable to cause problems such as a decrease in yield, clogging of a thermal decomposition reactor, and industrialization. It is not always easy.

[Problems to be solved]

In view of the circumstances described above, the present inventors have carried out various studies on a method for producing an unsaturated carboxylic acid isocyanatoalkyl ester in a high yield and containing no harmful impurities.

[Means to solve the problem]

As a result, (i) reacting the imidazole derivative with phosgene, (ii) reacting the obtained reaction product with a monoalkanolamine, (iii) converting the reaction product of (ii) into an unsaturated carboxylic acid or its chloride. By performing esterification using a product or an ester, a blocked isocyanatoalkyl ester of an unsaturated carboxylic acid can be synthesized in good yield, and by decomposing and distilling it, chlorine, phosphorus,
The inventors have found that a high-purity product containing almost no harmful impurities such as sulfur can be obtained, and have completed the present invention.

The imidazole derivative used in the first step of the present invention must have a> NH bond since it needs to react with phosgene to generate carbamic acid chloride, and therefore, an N-substituted derivative cannot be used.

In addition, since imidazole derivatives are relatively expensive, it is desirable to recover and reuse them, and therefore, those that can be distilled are preferable.

From these viewpoints, as the imidazole derivative, imidazole (unsubstituted), 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-ethylimidazole and the like are preferable. The phosgene to be reacted with the imidazole derivative is used in an amount equal to or more than that of the imidazole derivative, preferably 1.1 to 1.5 times, in order to completely advance the reaction. Since unreacted imidazole may cause undesired side reactions, the reaction must be allowed to proceed completely.

This reaction is preferably performed in a solvent for smoothing the reaction. The solvent must not react with phosgene, amine, alcohol, acid, isocyanate, etc.
Halogenated hydrocarbons such as dichloromethane and aromatic hydrocarbons such as toluene are used.

After the reaction of the imidazole derivative with phosgene, it is better to drive off excess phosgene and the generated hydrogen chloride. If excess phosgene or hydrogen chloride remains, it reacts with the alkanolamine in the next step of the reaction, giving undesired by-products.

In order to remove phosgene and hydrogen chloride, an inert gas such as nitrogen may be blown under normal pressure to slightly reduced pressure.

Reaction product of phosgene and imidazole derivative (A)
In the second step of reacting the alkanolamine with (A), it is preferable to gradually add (A) to the alkanolamine. In this case, the alkanolamine is preferably dissolved in the same solvent as used in the synthesis of (A).
In addition, in order to remove generated hydrogen chloride, sodium hydride, potassium carbonate, triethylamine, pyridine, etc.
It is desirable that the l-receptor coexist.

The reaction product (B) of (A) and alkanolamine thus obtained can be converted into an ester of unsaturated fatty acid by esterification with an unsaturated fatty acid or an acid chloride thereof in a usual manner. , By transesterification of the acid with an ester. At this time, the reaction temperature is 100 ° C,
Preferably, the reaction is carried out under reduced pressure, if necessary, so as not to exceed 80 ° C. If the temperature is too high, the product may decompose, giving undesired by-products.

After completion of the reaction, the obtained solution can be directly thermally decomposed, but before that, it is preferable to wash with a weakly alkaline solution such as sodium hydrogen carbonate and water to remove inorganic acids and salts.

When the ester of the unsaturated fatty acid thus obtained is thermally decomposed, the desired unsaturated fatty acid isocyanatoester is obtained, which is extremely easily polymerized as described above, so that thermal polymerization does not occur. It is necessary to decompose at a temperature of Further, since this thermal decomposition reaction is an equilibrium reaction, it is preferable to carry out the reaction while constantly removing the product.

From such a viewpoint, the thermal decomposition reaction is desirably performed in the form of reactive distillation. That is, after evaporating the solvent under reduced pressure, a catalytic amount of a tertiary amine or an organotin compound is added,
By distilling at 90 to 120 ° C. under reduced pressure, decomposition and distillation and purification of the target product can be performed simultaneously. The residual solution after the reaction can be used again in the first step.

Thereafter, if necessary, the solvent mixed as an impurity is removed by distillation, so that a product with higher purity can be obtained.

[Examples] Next, the present invention will be described more specifically with reference to examples.

Example 1 200 ml of toluene, 2-ethyl-4-methylimidazole 2
250 g of phosgene was blown into the mixture of 18 g at room temperature (about 1 hour) and then allowed to stand for 18 hours. The reactor was immersed in an oil bath maintained at a temperature of 40 to 50 ° C., and nitrogen gas was blown therein at a rate of 1 / min for 8 hours.

The resulting mixture was added dropwise to a mixture of 122 g of monoethanolamine, 173 g of anhydrous potassium carbonate, and 100 g of toluene over 1 hour with good stirring. After stirring was continued for 8 hours, the mixture was washed twice with 500 g of water.

Next, 5 g of p-toluenesulfonic acid and 150 g of acrylic acid
Was added thereto, and the mixture was refluxed at a reduced pressure of 60 to 70 Torr for 8 hours in a reactor equipped with a Dean-Stark trap to carry out esterification.

After the completion of the reaction, washing is carried out once with 500 ml of a 5% aqueous sodium hydrogen carbonate solution and twice with 500 ml of water.
After distilling off toluene under reduced pressure, 0.5 g of dibutyltin dilaurate was added, the temperature of the heating bath was raised to 100 to 120 ° C., and reactive distillation was carried out while gradually increasing the degree of reduced pressure.

As a result, 187 g of crude 2-isocyanatoethyl acrylate was obtained. About 5% (by weight) of toluene
Was included.

Example 2 In place of 2-ethyl-4-methylimidazole, 136 g of imidazole was used to carry out phosgenation and reaction with monoethanolamine in the same manner as in Example 1. Add 15 g of imidazole, 10 g of 4,4-diazabicyclo [2,2,2] octane, and 710 g of methyl methacrylate, and add 200 to 25.
The reaction was carried out while removing methanol produced under a reduced pressure of 0 Torr as an azeotrope with methyl methacrylate. On the way, add 200g of methyl methacrylate twice every 8 hours,
After reacting for 24 hours, 2-isocyanatomethyl methacrylate blocked with imidazole was formed in a yield of 62%.

Example 3 2-ethyl-4-methylimidazole was replaced by 2-
Phosgenation and reaction with monoethanolamine were carried out in the same manner as in Example 1 using 164 g of methylimidazole. Add 218 g of 96% crotonic acid chloride to this,
The esterification reaction was performed at 80 ° C. for about 2.5 hours.

After completion of the reaction, washing and thermal decomposition were performed in the same manner as in Example 1. As a result, 170 g of crude 2-isocyanatoethyl crotonate was obtained. About 5% of toluene and 3-
Chlorobutyric acid-2'-isocyanatoethyl ester is about 3
% Was included.

Example 4 The esterification reaction was carried out in the same manner as in Example 3, except that 150 g of mono (2-hydroxypropyl) amine was used instead of monoethanolamine, and 351 g of 95% cinnamic acid chloride was used instead of crotonic acid chloride. Done. As a result, 2
-Cinnamic acid-2-blocked with methylimidazole
Isocyanatopropyl ester was formed in 67% yield.

〔The invention's effect〕

According to the present invention, an unsaturated carboxylic acid isocyanatoalkyl ester containing no harmful impurities can be produced in high yield.

Claims (1)

(57) [Claims] (I) reacting an imidazole derivative with phosgene; (ii) reacting the reaction product of (i) with a monoalkanolamine; (iii) converting the reaction product of (ii) with an unsaturated carboxylic acid; Or a method for producing an unsaturated isocyanatoalkyl carboxylate represented by the general formula [I], wherein the esterification is carried out using a chloride or ester thereof. [Wherein, R represents a hydrogen atom, a lower alkyl group, an aryl group,
Or R 'represents a hydrogen atom or a methyl group. A represents a linear or branched alkylene group having 2 to 4 carbon atoms. ]