JPS5952660B2 - Polymaleimide manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to relate to a method for producing a polymaleimide having excellent polymerization activity in high yield.

Polymaleimide is a relatively low-molecular compound containing two or more maleimide groups in the molecule, a so-called oligomer.
Either alone or in combination with other suitable monomers, a polymerization reaction is caused by heat or a catalyst to form a cured thermosetting resin mainly having a so-called three-dimensional structure.

Cured products of thermosetting resins containing this polymaleimide have excellent heat resistance and are used as varnishes, powder coatings, laminates, molded products, etc. in electrical and mechanical fields where heat resistance is required. When using a thermosetting resin containing polymaleimide for such applications, it is important that the polymerization and curing reaction proceed quickly and sufficiently to increase the productivity of manufacturing the cured product, and also to ensure that the cured product has good heat resistance. In order to satisfy this condition, the polymerization activity of the polymaleimide used as a raw material is required to be high. Since polymaleimide is useful in this way, there is a desire to develop a method for producing polymaleimide with higher polymerization activity at a higher yield and at a lower cost than ever before. Regarding the production method of bismaleimide, which is a type of polymaleimide, for example, Nat
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8284-291 (1973), for example, 1 mol of a primary diamine such as 4,4'-diaminodiphenylmethane and 2 mol of maleic anhydride are mixed in 1.1 mol in an organic solvent such as dimethylformamide. In the presence of sodium acetate, N,N
'-(methylene di-P-phenylene) bismaleamic acid was prepared, and then 2 moles of acetic anhydride was added as a dehydrating agent to dehydrate and cyclize it as shown in formula 2 to form N,N'-(methylene di-P-phenylene) bis. It is known that bismaleimides such as maleimide can be obtained.

By this known method, for example, N,N''-(methylenedi-1P-phenylene)bismaleamic acid obtained by reacting 4,4''-diaminodiphenylmethane with maleic anhydride is converted into N,N''-(methylenedi-1P-phenylene)bismaleamic acid. P-phenylene)
When bismaleimide is produced, the bismaleimide is obtained as a pale yellow powder with high polymerization activity.

However, according to this known method, the yield of the bismaleimide obtained with respect to the raw material bismaleamic acid (hereinafter simply referred to as yield) is as low as 75 to 80%, and it lacks industrial practicality. For this reason, various studies were conducted on methods for producing bismaleimide, and subsequently, a method for producing the corresponding bismaleimide by reacting bismaleamic acid and carboxylic acid anhydride in the presence of a soluble nickel compound as a catalyst became known. ing. By this known method, for example, N,N''-(methylenedi-P) is obtained by adding maleic anhydride to 4,4''-diaminodiphenylmethane.
- Phoenix. ) from bismaleamic acid to N,N''-
When (methylenedi-P-phenylene) bismaleimide is produced, the yield is relatively high at about 85%, but the obtained bismaleimide has a marked brownish color, and the bismaleimide produced by the sodium acetate catalyst has a relatively high yield of about 85%. Polymerization activity is low compared to that of Further, a method for producing bismaleimide characterized by using an alkaline earth metal compound as a catalyst is disclosed in JP-A-50-83368.

The present inventors obtained N,
When N'-(methylenedi-1P-phenylene)bismaleamic acid was reacted with acetic anhydride as a dehydrating agent and calcium acetate as a catalyst, N,
N''-(methylenedi-P-phenylene) bismaleimide was obtained. However, the obtained bismaleimide had a blackish brown color and had very low polymerization activity.
In general, cured products of thermosetting resins, including cured products of curable resins obtained from bismaleimide, are cured products that have sufficiently undergone crosslinking and curing reactions, so-called cured products with a high crosslinking density, and cured products that are insufficiently cured. It is a well-known fact that the curable resin obtained from bismaleimide, which has low polymerization activity, has superior mechanical strength, chemical resistance, and heat resistance. Perhaps this is because the curing reaction does not proceed sufficiently even after heat curing, but the resulting cured product has poorer mechanical strength, chemical resistance, and heat resistance than when bismaleimide, which has high polymerization activity, is used. I found out.

In addition, in order to sufficiently cure the curable resin obtained from bismaleimide, which has low polymerization activity, we performed heat treatment at a higher temperature for a longer time, but the resulting cured product still did not polymerize, perhaps due to thermal deterioration. It was found that mechanical strength, chemical resistance, and heat resistance were inferior to those using highly active bismaleimide. That is, if a production method capable of producing bismaleimide with excellent polymerization activity at a yield of at least 85%, preferably 90% or more, as described above, could be found, it would be of great industrial value.

The present inventors have conducted intensive research on a method for producing polymaleimide with excellent polymerization activity and high yield, and have found that by using a cobalt compound as a catalyst, polymaleimide with excellent polymerization activity can be obtained in high yield. They discovered this and achieved the present invention.

The present invention is a method for producing polymaleimide, which is characterized by reacting polymaleamide acid in the presence of a dehydrating agent, a cobalt compound, and a tertiary amine. The cobalt compound used as a catalyst for the cyclodehydration reaction in the present invention means a divalent or trivalent cobalt compound soluble in the reaction medium, such as a divalent cobalt compound optionally in hydrated form. Cobalt salts such as chloride, bromide, iodide, fluoride, formate, acetate, propionate, butyrate, stearate, linoleate, naphthenate, benzoate, framate,
trivalent cobalt salts such as carbonates, sulphates, nitrates, phosphates, hydroxides, perchlorates, and optionally in hydrated form, such as chlorides, bromides, iodides, fluorides, formates, acetic acid salts, propionates, sulfates, etc., as well as divalent cobalt complex salts, such as cobalt-bisacetylacetonate, tetrakiz(pyridine)cobalt chloride, etc., and trivalent cobalt complex salts, such as cobalt trisacetylacetonate, tris( Dipyridyl) cobalt chloride, etc.

From the viewpoint of ease of purification after the reaction, it is preferable to use divalent cobalt acetate, cobalt naphthenate, or cobalt benzoate. The amount of catalyst used is in the range of 2 x 10-5 to 0.2 equivalents per equivalent of maleamic acid group, preferably 2 x 10
A very small amount in the range of −4 to 2×10 −2 equivalents is sufficient. In the present invention, the dehydrating agent is one that acts on maleamic acid groups to dehydrate and cyclize them to convert them into maleimide groups, and itself becomes a hydrate, such as acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride. , etc. lower monocarboxylic acid anhydrides. Also, dicarboxylic acid anhydrides such as succinic anhydride, glutaric anhydride, and phthalic anhydride. Further, oxides such as calcium oxide and barium oxide can be mentioned. Generally, acetic anhydride is preferred as the dehydrating agent because of its economical efficiency and ease of purification of the polymaleimide after reaction. The amount of the dehydrating agent used is in the range of 1 to 5 mol, preferably 1.1 to 2.2 mol, of the dehydrating agent per equivalent of maleamic acid group. Examples of the tertiary amine used in the present invention include trialkylamines having an alkyl group having 1 to 10 carbon atoms, such as trimethylamine, triethylamine, and tri-n-butylamine, and N,N''-dimethylbenzylamine. , N,N-dialkylbenzylamines such as N,N-diethylbenzylamine, and 1,
8-diazabicyclo[5,4,0] 7-undecene,
Cyclic amines such as N-methylmorpholine and N-ethylmorpholine can be used. A particularly preferred tertiary amine is triethylamine. The amount of tertiary amine used is 0.01 to 2.0 per equivalent of maleamic acid group.
It is in the molar range, preferably in the range of 0.1 to 0.5 molar. The dehydration cyclization reaction in the present invention is carried out at 20 to 100
The reaction is carried out at a temperature in the range of 0.degree. C., preferably in the range of 40 to 60.degree. C., under a pressure such that the reaction system is in a liquid phase.

Examples of organic solvents used as necessary in the present invention include dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylepyrrolidone, N-
- Polar solvents, such as methynolecaprolactam, and also cyclic ether compounds, such as tetrahydrofuran, dioxane, and particularly preferred solvents are dialkyl ketones, such as acetone, methyl ethyl ketone. The amount of organic solvent used is preferably 1.0 to 4.0 times the weight of the polymaleamic acid. Further, lower carboxylic acids such as acetic anhydride and butyric anhydride, which are dehydrating agents, have a function as a solvent, so that it is possible to proceed the reaction without particularly using an organic solvent. The present invention thus also includes methods that do not use organic diluents. The polymaleamic acid that can be used as a starting material in the method of the present invention refers to a compound containing two or more maleamic acid groups in the molecule, such as N-N''-(m-phenylene)bismaleamic acid. , N-N″-(methylenedi-P-phenylene) bismaleamic acid, N,N″-(oxydi-P-phenylene)
Bismaleamic acid, N,N′-(sulfonyldi-1m-phenylene)bismaleamic acid, N,N″-(sulfonyldi-1P-phenylene)bismaleamic acid, N,N″(isopropylidenedi-1P-phenylene)bismaleamic acid,
N,N″-[methylenedi-(3-chloro-1,4-phenylene)]bismaleamic acid, N,N″-(4-methyl-1
,3-phenylenebisnomaleamic acid, N,N''-(2
-Methyl-1,3phenylene) bismaleamic acid, and polyvalent maleamic acids with a higher valence than the divalent one represented by the formula (1) can be mentioned.

Polymaleamic acid, which is the starting material of the present invention, can be produced in approximately the theoretical yield by reacting a polyamine corresponding to maleic anhydride in the presence of a suitable organic solvent according to a known method.

In order to advantageously carry out the production method of the present invention, the polymaleamic acid obtained by the addition reaction of maleic anhydride and a polyamine in an organic solvent can be subjected to the dehydration cyclization reaction, which is the production method of the present invention, without separating it. It is to be used directly. According to the production method of the present invention, polymaleimide can be produced at a high yield of 90% or more, and the obtained polymaleimide is pale yellow in color and has high polymerization activity, and is especially curable when bismaleimide is blended. The resin could be cured in a short time, and the cured product obtained had excellent mechanical properties, electrical properties, and heat resistance.

Hereinafter, aspects of the present invention will be specifically explained with reference to Examples. However, the present invention is not limited thereto. In the examples, the gelation time of polymaleimide was measured as follows, and this was used as an index of polymerization activity.

It can be said that the shorter the gelation time, the higher the polymerization activity. That is, 1 g of a sample of polymaleimide was placed on a stainless steel plate adjusted to 200° C.±1° C., and kneaded once per second with a stainless steel spatula, and the time until the sample became gel-like was defined as the gelation time. Practically speaking, it is desirable that the gelation time be 3 minutes or less. More preferably, it is 1 minute or less. Example
1 N,N″-(methylenedi-P-phenylene) bismaleamic acid (98.5 g (4).25 mol) was dissolved in acetone 250 g.
It was dissolved in g.

To this was added 0.63 g (2.0 mmol) of cobalt naphthenate and 10 g (4) of triethylamine. 1 mol), acetic anhydride 71.4 g (a). After adding 7 mol), the reaction temperature was raised to 55°C, and the reaction was continued for 2 hours while maintaining the temperature below 60°C.

Next, the solution was cooled to 20° C., and 250 g of water was added dropwise to this solution, and the precipitated solid was filtered off. This precipitate was washed with water, then with an aqueous sodium carbonate solution, further washed with water, and finally washed with methanol and dried to obtain 81.5 g of N,N''-(methylenedi-P-phenylene)bismaleimide (yield 91%). A pale yellow powder was obtained.The gelation time of this pale yellow powder was measured.
It gelated in 0 seconds. Example 2 The same method and scale as in Example 1 were used except that 0.6 g (2.0 mmol) of cobalt benzoate was used as a catalyst.

80.6 g (yield 90%) of pale yellow powder of N,N''-(methylenedi-P-phenylene) bismaleimide was obtained,
The gelation time was measured and gelation occurred in 45 seconds. Example
3 Example 1 except that 0.72 g (2.0 mmol) of cobalt (auto)tris acetylacetonate was used as a catalyst.
It was carried out using exactly the same method and scale.

81.0 g (yield 90.5%) of pale yellow powder of N,N''-4,4''-diphenylmethane bismaleimide was obtained,
The gelation time was measured and gelation occurred in 35 seconds. Example
97g (4) of polymaleamic acid having 4 structures. 1 mol) was dissolved in 350 g of acetone, and in this was dissolved 0.63 g (2.0 mmol) of cobalt naphthenate, 10 g (0.1 mol) of triethylamine, and 71.4 g (0.7 mol) of acetic anhydride.
After adding mol), the reaction temperature was raised to 55°C, and the reaction was continued for 2.5 hours while maintaining the temperature below 60°C.

Next, the solution was cooled to 20° C., 300 g of water was added dropwise to this solution, and the precipitated solid was separated by furnace. This precipitate was washed with water, then with an aqueous sodium carbonate solution, then with water, and finally with methanol, and dried to give 77.8 g of a yellowish brown solid (yield: 88%).
) was obtained. The presence of a maleimide ring was confirmed by infrared absorption spectrum measurement. The gelation time of this product was measured and it gelled in 32 seconds. Example 5 98.9 g (a).25 moles of N,N''-(oxydi-P-phenylene) bismaleamic acid was added to 300 g of acetone.
0.5 g of cobalt acetate tetrahydrate (2
．． 0 mmol), triethylamine 10 g (4). 1,
After adding 71.4 g (0.7 mol) of acetic anhydride, the reaction temperature was raised to 55°C and the reaction was continued for 2 hours while maintaining the temperature at 60°C or lower.

Next, the solution was cooled to 20° C., 250 g of water was added dropwise to this solution, and the precipitated solid was filtered off. This precipitate was washed with water, then with an aqueous sodium carbonate solution, further washed with water, finally washed with methanol, and dried to obtain 82.0 g of N,N''-(oxydi-1P-phenylene)bismaleimide (yield 91%). ) was obtained, and gelation occurred in 43 seconds when gelation time was measured. Example 6 98.5 g (0.25 mol) of N,N''-(methylene di-1P-phenylene) bismaleamic acid, acetone 250 g, cobalt acetate tetrahydrate 0.5 g (2.
0 mmol), triethylamine 10g (0.1 mol)
and acetic anhydride 71.4 g (4). After mixing 7 mol), stirring was continued for 2.5 hours while maintaining the reaction temperature at 62°C.

Next, 250 g of water was added dropwise to the reaction solution cooled to 25° C., and the precipitated solid was filtered out. This precipitate was washed with water, neutralized with sodium carbonate, further washed with water and methanol, and then dried. 80.3 g of pale yellow powder of N,N″-(methylenedi-P-phenylene) bismaleimide (yield: 89
．． 6%) was obtained, and the gelation time of this product was 42 seconds. Example 7 98.5 g of N,N'-(methylenedi-P-phenylene)bismaleamic acid (a). 25 mol), cobalt acetate tetrahydrate 0.5 g (2.0 mmol), triethylamine 2 g (4). 02 mol) and acetic anhydride 21.5 g (2
．． 1 mol) was mixed and heated to 65°C with stirring, and further 8 g of triethylamine (a). 08 mol) plus 7
Upon heating to 2°C, a dark brown homogeneous solution was obtained.

After continuing stirring at 72° C. for 1 hour, the reaction solution was cooled to room temperature, and unreacted acetic anhydride and produced acetic acid were distilled off under reduced pressure.

Add 300 g of water to the distillation residue, filter the resulting precipitate,
After washing with water, it was further neutralized with a sodium carbonate solution, washed with water and methanol, and then dried. 64.5 g (yield 72%) of pale yellow powder of N,N''-(methylenedi-P-phenylene) bismaleimide was obtained.Gelation time was 4.
It was hot in 5 seconds. Examples 8 to 11 The reaction was carried out in the same manner as in Example 1, except that the compounds shown in Table 1 were used instead of N,N''-(methylenedi-P-phenylene) bismaleamic acid used in Example 1. do the
The results shown in Table 1 were obtained.

Claims (1)

[Scope of Claims] 1. A method for producing polymaleimide, which comprises reacting polymaleamic acid in the presence of a dehydrating agent, a cobalt compound, and a tertiary amine. 2. The method according to claim 1, wherein a divalent cobalt salt is used as the cobalt compound. 3. The method according to claim 1, wherein the cobalt compound is one or more selected from cobalt acetate, cobalt naphthenate, and cobalt benzoate.