JPH0753712B2 - Method for producing polymaleimide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for efficiently producing high-purity polymaleimide.

<Prior Art> Polymaleimide is a compound containing two or more maleimide groups in the molecule, and it causes a polymerization reaction alone or in combination with other monomers to form a cured product of a thermosetting resin. Since this cured product has excellent heat resistance, it has been used as a material for casting, impregnation, lamination, molding, and various electrical insulating materials, structural materials and the like.

Conventionally, the most general method for producing polymaleimide is
After producing polymaleamic acid from polyamine and maleic anhydride in an organic solvent, dehydration cyclization is performed in the presence of a dehydrating agent, a metal salt, and a tertiary amine, and then water or an organic precipitating agent is added to precipitate the polyimide. Methods of separating are known. (For example, JP-A-55-13235) <Problems to be solved by the invention> However, the conventionally known method for separating polymaleimide is not efficient because it requires a large capacity kettle to add a precipitant, It is difficult to recover the reaction solvent from the liquid and recycle it. Further, by adding a precipitant, impurities dissolved in the organic solvent are also broken out, resulting in a decrease in purity. .

<Means for Solving Problems> From such a background, as a result of intensive studies of the present inventors on a method for efficiently producing high-purity polymaleimide, it was found that a specific method is suitable for the above purpose. The invention was completed.

That is, the present invention is a method for producing polymaleimide by reacting a polyamine having two or more amino groups in a molecule with maleic anhydride, and after producing polymaleamic acid in an organic solvent, a dehydrating agent, a metal salt, A method for producing a polymaleimide, which comprises dehydrating and cyclizing an organic solvent while distilling off an organic solvent in the presence of a tertiary amine.

Examples of the polyamine having two or more amino groups in the molecule used in the present invention include diaminodiphenylmethane, phenylenediamine, tolylenediamine, xylylenediamine, diaminodiphenylether, diaminodiphenylsulfone and 2,2-bis (aminophenyl). Examples thereof include propane (each containing isomers), ethylenediamine, hexamethylenediamine, polycondensation product of aniline and formaldehyde, and 4,4'-diaminodiphenylmethane is particularly preferable.

As the organic solvent used in the present invention, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ketones such as acetophenone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2- Aprotic polar solvents such as pyrrolidone, acetonitrile and sulfolane, cyclic ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and butyl acetate, halobenzenes such as chlorobenzene, dichlorobenzene, chloroform, carbon tetrachloride, dichloroethane and trichloroethane. Examples of the solvent include acetone, and particularly acetone is preferably used.

In the method of the present invention, the polymaleamic acid production reaction is
A conventionally known method can be applied. For example, polyamine and maleic anhydride are mixed with 1.0 equivalent of maleic anhydride per 1 equivalent of amino group.
Used in a quantitative ratio of ~ 1.5, in an organic solvent in a weight ratio of 1 to 50 with respect to the total amount of polyamine and maleic anhydride, 10
It can be carried out under a temperature condition of -100 ° C, preferably 20-50 ° C.

As the dehydrating agent used in the present invention, acetic anhydride, propionic anhydride, lower aliphatic carboxylic acid anhydride such as butyric anhydride, phosphorus pentoxide, calcium oxide, oxides such as barium oxide, p-toluenesulfonic acid, Examples thereof include sulfonic acids such as methanesulfonic acid and inorganic acids such as sulfuric acid, and acetic anhydride is particularly preferable.

Examples of the metal salt used in the present invention include nickel, cobalt, sodium, calcium, iron, lithium, manganese and other acetates, chlorides, bromides, sulfates, nitrates and the like, but nickel acetate is particularly preferably used. it can.

Examples of the tertiary amine which can be used in the present invention include triethylamine, tri-n-butylamine, N-methylpiperazine, N, N-dimethylbenzylamine, 1,8-diazabicyclo [5,4,0] 7-undecene and the like. It can be exemplified, but triethylamine is particularly preferable.

The amount of the dehydrating agent, metal salt or tertiary amine used in the dehydration cyclization reaction of the method of the present invention is not particularly limited, but usually 1 to 1 equivalent of the amino group of the polyamine is used as the dehydrating agent. 3 moles, preferably 1-1.5 moles, metal salt 0.000
1 to 1.0, preferably 0.001 to 0.1 mol, and tertiary amine is 0.
The amount is 01 to 1.0 mol, preferably 0.05 to 0.5 mol.

In the present invention, the dehydration cyclization reaction is carried out by using the organic solvent used in the polymaleamic acid formation reaction at 20 to 100 ° C., preferably 30
A major feature is that it is carried out while distilling off under the temperature condition of ~ 80 ° C. If it is less than 20 ° C, the reaction rate is slow, and if it exceeds 100 ° C, impurities accompanying side reactions increase, which is not preferable. In this case, the reaction can be carried out to some extent by maintaining the same temperature before distilling off the organic solvent.

After the reaction solvent is distilled off and the completion of the cyclization reaction is confirmed, if necessary, the temperature is cooled to 10 ° C. or lower, and the mixture is passed to obtain a highly pure polymaleimide.

<Effect of the Invention> According to the method of the present invention, highly pure polymaleimide can be efficiently obtained without adding a precipitating agent.

<Examples> Examples will be described below.

Example 1 In a reactor equipped with a thermometer, stirrer, dropping funnel and reflux condenser, maleic anhydride 108 g (1.1 mol) and acetone 2
52 g was charged and maleic anhydride was dissolved at room temperature.
Next, a solution prepared by dissolving 99 g (0.5 mol) of 4,4′-diaminodiphenylmethane (Sumitomo Chemical Co., Ltd.) in 231 g of acetone was used.
It was added dropwise to the stirred reactor at 4 ° C. for 4 hours. After the completion of dropping, the mixture was stirred at the same temperature for 2 hours, 7.6 g (0.075 mol) of triethylamine and 1.06 g (4.25 mmol) of nickel acetate tetrahydrate were added, and 132.6 g (1.8 mol) of acetic anhydride was added with stirring. The solution was added dropwise at 0 ° C over 1 hour. After completion of the dropping, the reaction mixture was kept at the same temperature for 2 hours, and then acetone was distilled off in about 3 hours under reduced pressure while keeping the same temperature, and the reaction rate reached about 100%. After the acetone was distilled off, the mixture was cooled to 10 ° C. and kept at the same temperature for 1 hour. Then, the crystals were separated, washed with water and dried to obtain N, N′-4 having a GPC purity of 96% and a melting point of 158 to 162 ° C. 4'-Diaminodiphenylmethane bismaleimide was obtained as a pale yellow solid.

Example 2 A bismaleimide having a GPC purity of 97% and a melting point of 159 to 162 ° C. was obtained in the same manner as in Example 1 except that the acetone distillation temperature was 40 ° C. and the distillation time was 5 hours.

Comparative Example 1 In the same manner as in Example 1, after performing the same operation until dropping acetic anhydride, the mixture was kept at 56 ° C. for 7 hours without distilling acetone.
After confirming that the reaction rate reached almost 100%, transfer the reaction solution to a double volume reactor, add water of 1 to precipitate the product, wash with water and dry to obtain a GPC purity of 86%,
Bismaleimide with a melting point of 155-157 ° C was obtained as a brown solid.

Comparative Example 2 In Comparative Example 1, the same operation was performed until the reaction rate was confirmed to be 100%, then acetone was distilled off at a temperature of 55 to 58 ° C., followed by cooling to 10 ° C. and holding at the same temperature for 1 hour. After that, the crystals are separated, washed with water, and dried to obtain GPC purity of 9
2%, melting point 157-160 ° C bismaleimide was obtained as a yellow solid.

Claims (1)

[Claims] 1. A method for producing a polymaleimide by reacting a polyamine having two or more amino groups in the molecule with maleic anhydride, which comprises producing a polymaleamic acid in an organic solvent, and then forming a dehydrating agent, a metal salt, A process for producing polymaleimide, which comprises dehydrating and cyclizing an organic solvent while distilling off an organic solvent in the presence of a tertiary amine.