JP2000212279A - Production of semi-aromatic polyimide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for stably producing polyimides having an extremely high degree of polymerization and containing an aliphatic diamine as the diamine component. SOLUTION: In the process for producing polyimides by heating an aromatic tetracarboxylic dianhydride and an aliphatic diamine in the presence of a catalyst in a solvent to effect addition condensation, the first reaction process which accompanies a temperature rise by initial exothermic heat is carried out by using crotonic acid as the catalyst, and subsequently the second reaction process to heat at a temperature of not lower than the temperature reached by the initial exothermic heat is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a semi-aromatic polyimide comprising tetracarboxylic dianhydride and an aliphatic diamine.

[0002]

2. Description of the Related Art Polyimide resins have high heat resistance, which is not found in other resins, and also have excellent mechanical properties and electrical insulation properties. Therefore, it is very useful as a material used at high temperatures. However, many of the polyimides used so far are wholly aromatic and usually require the use of a solvent for molding.

On the other hand, most of crystalline polyimides containing an aliphatic diamine as a diamine component have a melting point of about 300 ° C. and are heat-resistant materials which can be melt-molded. A polymer having a high degree of polymerization that is difficult to increase and is practically usable is not currently provided.

[0004] Known methods for producing polyimide include (a) reacting tetracarboxylic dianhydride and diamine at a low temperature in a polar solvent under anhydrous conditions to obtain a uniform high molecular weight polyamic acid. A method of forming a solution and cyclizing it by heating, (a) a method of adding acetic anhydride and a monoamine to a polyamic acid to precipitate a polyimide by chemical cyclization, and (c) a method of forming a tetracarboxylic dianhydride and a diisocyanate. There are known a method of reacting, (d) a method of heating and dehydrating a salt of a carboxylic acid and a diamine derived from a tetracarboxylic anhydride, and a method via a polyamic acid. It has low stability and it is difficult to produce high molecular weight polyimide. In the method using diisocyanate, it is difficult to synthesize a target polymer with a high degree of polymerization because the diisocyanate is expensive and very unstable.

In a method for producing a solvent-soluble polyimide from tetracarboxylic dianhydride and aromatic diamine, use of a catalyst has been proposed. For example, JP-A-6-1
No. 92420 reports that a polyimide is directly produced without using a polyamic acid by using an acid catalyst, but the effect is known only when an aromatic diamine is used as an amine. It does not dramatically increase the degree of polymerization.

[0006] Therefore, in a method for synthesizing a semi-aromatic polyimide containing an aliphatic diamine as a diamine component, a method for producing the semi-aromatic polyimide with a high degree of polymerization is not known.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for stably producing a polyimide having an extremely high degree of polymerization containing an aliphatic diamine as a diamine component.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a process for producing a polyimide in which an aromatic tetracarboxylic dianhydride and an aliphatic diamine are heated and addition-condensed in a solvent in the presence of a catalyst. And the reaction of the aromatic tetracarboxylic dianhydride and the aliphatic diamine to produce a polyamic acid sufficiently, and then the reaction of dehydrating and cyclizing the polyamic acid by heating is carried out, whereby the degree of polymerization is reduced. It has been found that it gives high semi-aromatic polyimides.

That is, the present invention relates to a process for producing a polyimide, which comprises subjecting an aromatic tetracarboxylic dianhydride and an aliphatic diamine to addition condensation by heating in a solvent in the presence of a catalyst.
Using crotonic acid as a catalyst, performing a first reaction process with a temperature rise due to initial heat generation, and then performing a second reaction process to heat at a temperature equal to or higher than the attained temperature due to the initial heat generation; It is a manufacturing method.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details will be described below based on embodiments. Since crotonic acid used in the present invention acts as a catalyst, the amount of crotonic acid added may be a catalytic amount, but is preferably between 10 mol and 0.01 mol per 1 mol of the acid anhydride used.

When crotonic acid is excessively added, it is difficult to wash and remove the crotonic acid, and the process cost is increased. On the other hand, if the amount is too small, the effect of accelerating the reaction is reduced, so that it is difficult to increase the degree of polymerization in an appropriate time.

In the present invention, pyridine can be used as a co-catalyst in accordance with crotonic acid. Pyridine is
Although it can be used in an appropriate amount, it is preferably added in an equimolar amount with crotonic acid. This lowers the reaction start temperature,
A polyimide having a high degree of polymerization can be obtained without gelation.

The aromatic tetracarboxylic dianhydride to be subjected to the reaction is not particularly limited, but is preferably one having 1 carbon atom.
0 to 30 aromatic tetracarboxylic dianhydrides can be used. For example, pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, bis (dicarboxyphenyl) propane dianhydride, 4,4 '-[2,2,2-trifluoro -1- (trifluoromethyl) ethylidene] bis (1,2
-Benzenedicarboxylic acid) dianhydride, bis (dicarboxyphenyl) sulfonic dianhydride, bis (dicarboxyphenyl) ether dianhydride, thiophenetetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride,
And so on. These may be used alone or in combination of two or more.

The aliphatic diamine used in the present invention is an aliphatic diamine having an amino group directly bonded to an aliphatic carbon having 2 to 30 carbon atoms. For example, ethylene diamine, propylene diamine, butane diamine, pentane diamine, hexane diamine, octane diamine, nonane diamine, decane diamine, undecane diamine, dodecane diamine,
Alkylenediamines such as tetramethylhexanediamine, 1,12- (4,9-dioxa) dodecanediamine, 1,8- (3,6-dioxa) octanediamine,
Examples thereof include diaminoethers such as Jeffamine, diamines containing alicyclic hydrocarbons such as cyclohexanediamine and isophoronediamine, and diamines represented by the following general formula.

[0015]

Embedded image NH ₂ — (CR ₁ R ₂ ) — (R ₃ ) — (CR ₄ R ₅ )
-NH ₂

Here, R ₁ , R ₂ , R ₄ and R ₅ each independently represent a hydrogen atom, an alkyl group or a phenyl group, and R ₃ represents an alkylene group or an arylene group. These may be used alone or in combination of two or more to form a composition.

In the present invention, it is preferable to use a mixture of a solvent for dissolving the substrate to advance the reaction and a solvent azeotropic for dehydration. Examples of the solvent for dissolving such a substrate include dimethylformamide, dimethylimidazolidinone, dimethylsulfoxide, acetonitrile, N-
Methyl-2-pyrrolidone (hereinafter referred to as NMP). Examples of the azeotropic solvent include toluene, xylene, and benzene. In particular, NMP
And a combination of toluene. NMP is a solvent that is known to effectively act to properly advance the dehydration condensation reaction. Toluene is an effective solvent for removing generated water out of the system by azeotropic distillation. In order to remove water generated by azeotropic distillation, it is necessary to mix a sufficient amount of toluene with NMP. Although the composition is not limited to this, it is preferable to use 20 parts by volume or more of toluene per 100 parts by volume of NMP for efficient azeotropic dehydration.

In the present invention, a first reaction process in which an aromatic tetracarboxylic dianhydride reacts with an aliphatic diamine to produce a polyamic acid, and a heating process for performing a dehydration-cyclization reaction of the polyamic acid. A semi-aromatic polyimide is produced by sequentially passing through two reaction processes consisting of a second reaction process.

In the first reaction process, the aromatic tetracarboxylic dianhydride and the aliphatic diamine self-heat during the reaction, so that the reaction temperature rises without heating.
When the polyamic acid generation is completed and the temperature rise due to self-heating is stopped, heating is performed to continue the second reaction process. If the process is shifted to the second reaction process without sufficiently ending the first reaction process, a polyimide having a high degree of polymerization cannot be obtained because the degree of polymerization of the polyamic acid does not sufficiently increase, and the molecular weight of the polyimide is low. It fluctuates constantly, making commercial production difficult.

The reaction in the second reaction process is carried out at a temperature not lower than the temperature reached by the initial heat generation in the first reaction process, preferably at 130 ° C. or higher. For example, NM
When a solvent in which P and toluene are combined is used, the reaction is performed at a temperature equal to or higher than the boiling point of toluene, which is an azeotropic solvent, and the preferable range is 135 ° C to 160 ° C. At temperatures above 160 ° C., gelation occurs.

The end point of the above reaction can be confirmed by the amount of water removed. At the end of the reaction, a terminal capping material such as an acid anhydride or a monoamine can be added for terminal capping. By adding this, it is possible to improve the stability of the polymer.

The semi-aromatic polyimide thus obtained is
A polyimide having a solution viscosity of usually 3 or more as measured by a solution viscosity (ηsp / c; 50 mg / 10 ml) in a mixed solvent of tetrachloroethane / phenol (volume ratio 6/4) and an aliphatic diamine as a diamine component Has a very high degree of polymerization, and can be stably produced according to the present invention without variation in the degree of polymerization.

[0023]

According to the present invention, crotonic acid is used as a catalyst in producing a semi-aromatic polyimide containing an aromatic tetracarboxylic dianhydride as an acid component and an aliphatic diamine as a diamine component. By going through the first reaction process and the second reaction process, a product having a very high degree of polymerization can be stably obtained without variation in the degree of polymerization.

[0024]

Examples are described below.

Example 1 2250 ml of dry NMP
In a 5 l separable flask fitted with a Dean Stark trap.
g, 108.4787 g of dodecamethylenediamine, 6.472 g of crotonic acid and 5.939 of pyridine.
g was added and the diamine was dissolved in warm water at 45 ° C. After the diamine is dissolved, pyromellitic dianhydride 131.
When 2153 g was added followed by 500 ml of toluene, the temperature increased to 60 ° C. and the increase in viscosity was observed with the formation of polyamic acid. Thereafter, the rise in temperature was stopped, and the first reaction was terminated when the temperature dropped to 45 ° C.

Thereafter, in order to shift to the second reaction, the mixture was gradually heated to 160 ° C. in an oil bath with stirring. Around the reaction temperature exceeding 135 ° C., azeotrope of toluene and water started, and the reaction temperature reached 160 ° C. at the end of the azeotrope. Thereafter, the heating was stopped, and when the internal temperature reached 100 ° C., acetic anhydride and pyridine were added to cap the amino terminal.

After cooling to room temperature, the precipitated polymer was collected by filtration, washed with acetone to remove toluene, and washed twice with warm water of 70 ° C. or more.

The resulting polymer tetrachloroethane /
The solution viscosity (ηsp / c; 50 mg / 10 ml) in a mixed solvent of phenol (volume ratio 6/4) was 7.7.

[Comparative Example 1] 2250 ml of dry NMP
In a 5 l separable flask fitted with a Dean Stark trap.
g, 108.4787 g of dodecamethylenediamine, 6.472 g of crotonic acid and 5.939 of pyridine.
g was added and the diamine was dissolved in warm water at 45 ° C. After the diamine is dissolved, pyromellitic dianhydride 131.
2153 g was added, followed by 500 ml of toluene, and the mixture was gradually heated to 160 ° C. in an oil bath with stirring directly without performing the first reaction process. Around the reaction temperature exceeding 135 ° C., azeotrope of toluene and water started, and the reaction temperature reached 160 ° C. at the end of the azeotrope. Thereafter, the heating was stopped, and when the internal temperature reached 100 ° C., acetic anhydride and pyridine were added to cap the amino terminal.

After further cooling to room temperature, the precipitated polymer was collected by filtration, washed with acetone to remove toluene, and washed twice with warm water at 70 ° C. or higher.

The resulting polymer tetrachloroethane /
The solution viscosity (ηsp / c; 50 mg / 10 ml) in a mixed solvent of phenol (volume ratio 6/4) was 2.9, indicating a low degree of polymerization.

Comparative Example 2 The polyimide obtained by the same operation as in Comparative Example 1 had a solution viscosity of 5.5, a lower polymerization degree than that of the Example, and a reproducibility higher than that of Comparative Example 1. I couldn't.

Claims (3)

[Claims] 1. A method for producing a polyimide, in which an aromatic tetracarboxylic dianhydride and an aliphatic diamine are heated and addition-condensed in a solvent in the presence of a catalyst, wherein crotonic acid is used as a catalyst, and the temperature rises due to initial heat generation. A method of producing a semi-aromatic polyimide, wherein a first reaction process is carried out at a temperature equal to or higher than the temperature reached by the initial heat generation. 2. The heating temperature in the second reaction process is 1
The method for producing a semi-aromatic polyimide according to claim 1, which is at least 30 ° C. 3. The method for producing a semi-aromatic polyimide according to claim 1, wherein a mixture of N-methylpyrrolidone and toluene is used as a solvent.