JPH02151629A - Preparation of aromatic polyimide - Google Patents

Abstract

PURPOSE:To obtain stably an arom. polyimide useful for impregnating a fibrous material and suitable for making a slurry by preparing an arom. polyimide having partly an arom. acid structure from an arom. polyamic acid in the presence of acetic anhydride by incorporating a specified catalyst. CONSTITUTION:An arom. polyimide having partly an acid structure which has repeating structural units of formula VII and 5-25% polyamic acid structure is obtd. by performing dehydration and ring closure of an arom. polyamic acid with repeating structural units of formula I [wherein Ar is a group of formula II or III (wherein Y is -O-, -CO-, -CH2-, -S-, -SO- or -SO2-); Ar' is a group of formula II or IV (wherein Z is Y or a group of formula V or VI)] in the presence of acetic anhydride by incorporating 1-5mol% tert. amine with a pKa of aq. soln. thereof of 4.9-6.5 (e.g. pyridine) based on the polyamic acid groups.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to the production of an aromatic polyimide partially having an aromatic polyamic acid structure, which is used in an aromatic polyimide resin represented by formula (III). Regarding the method.

(In the formula, Ar and Ar' represent the same residues as in formula (T).

) Polyimide resin of the formula (Iff) is known as a heat-resistant resin used in electronics, composite materials, etc.
Ar represents the same residue as in formula (I)) and an aromatic acid dianhydride represented by the formula CV) Hz N-A r N Hz (V) (wherein Ar' represents the same residue as in formula (1)). Formula (1) obtained by a mixed reaction with an aromatic diamine having a repeating unit represented by It can be obtained by thermal imidization or chemical imidization using a dehydrating agent in the presence of a dehydrating agent.

The polyimide resin represented by formula (III) has Ar in the formula
There are many types depending on the structural formula of Ar' and Ar'1.
Polyimide obtained by the reaction of pyromellitic dianhydride (P?'1DA) and 4,4'-oxydianiline (ODA) is known as Kapton (trademark of Du Pont) and is benzophenonetetracarboxylic dianhydride. thing(
BTDA) and 3,3'-diaminobenzophenone (D
The polyimide obtained by reaction with ABP) is LAR
Known as C-↑PI.

The present invention relates to a method for producing a polyimide partially having a polyamic acid structure, which is used when preparing a polyamic acid slurry solution used in impregnation molding of these polyimide resins.

(Prior art and problems to be solved by the invention) Polyimide resin is sometimes used as a heat-resistant composite material.One step in this manufacturing process is the step of impregnating fibers with polyimide resin. .

Carbon fibers and glass fibers are impregnated with this aromatic polyamic acid solution and subjected to solvent drying and heat dehydration imidization.
At this time, in order to provide the molded product with sufficient material strength, a certain amount of polyimide resin must be maintained relative to the fiber content.

The polyamic acid solution used for this impregnation is difficult to use if it has a solution viscosity that is too high in order to sufficiently impregnate between the fibers, so the solution viscosity is lowered so as not to impede impregnation. The one with the lowest was used. Therefore, due to the lower polymer concentration, less resin adheres to the fibers per impregnation operation, and 5 impregnation and solvent drying must be repeated many times until the desired resin content is achieved, reducing work efficiency. It had gotten extremely bad.

As one useful method for avoiding this, a method has been proposed in which polyimide powder is uniformly dispersed in a polyamic acid solution so that it can penetrate between the fibers, and the powder is impregnated into the fibers. According to Jidojutsu, for example, the process of directly impregnating carbon fiber with a conventional 5% polyamic acid solution and 1 volume of this 5% polyamic acid? A slurry volume in which 5% by weight of polyimide is dispersed in a slurry; using a slurry, the effectiveness can be doubled at once.

However, although impregnation workability is certainly improved, as long as polyimide powder manufactured by conventional methods is used, the dispersibility of polyimide in polyamic acid solution is often insufficient, and after impregnation and drying, Non-uniformity of the resin surface has become a problem.

In addition, although some polyimide powders may be uniformly dispersed in the polyamic acid solution, the viscosity of the slurry solution may become high.
On the contrary, there were drawbacks such as poor fiber impregnation properties.

As a result of studies to solve this problem, the present inventors found that this problem could be solved by using a slurry liquid in which polyimide partially having a polyamic acid structure was dispersed in a polyamic acid solution, and filed an application earlier. However, in the slurry of polyimide powder and polyamic acid solution used here, even if the dispersion conditions are the same, the slurry viscosity changes considerably depending on the amount of polyamic acid in the polyimide. A polyimide with a specific amic acid content must be used.

Conventionally, it has been known to use a catalyst such as triethylamine when heating and imidizing polyamic acid in the presence of a dehydrating agent such as acetic anhydride. However, in the conventional production method, the amic acid content in polyimide is
It was difficult to manufacture while adjusting it to 25%.

[Means to solve problems]

As a result of intensive studies to solve this problem, we decided to specify the PKa and amount in an aqueous solution of a catalyst to be added together with a dehydrating agent when polyimide having a partial polyamic acid structure is produced by a dehydration ring-closing reaction of polyamic acid. It has been found that the amic acid content in a polyimide partially having a polyamic acid structure can be adjusted, and the present invention has been achieved.

That is, in order to not completely imidize the amic acid and leave an unreacted amic acid structure, the type and amount of the catalyst to be used must be determined.

A detailed study of the amount of catalyst used during imidization of polyamic acid and the proportion of the amic acid structure in the resulting polyimide revealed that when imidization is carried out using a specific catalyst for the amic acid group, polyamic acid It has been found that a polyimide having a structure in which the amic acid content in the polyimide has a good dispersibility in an acid solution is 5 to 25% can be obtained.

The method of the present invention is a method in which a solution of a polyamic acid represented by formula (1) in an aprotic organic polar solvent is imidized using acetic anhydride as a dehydrating agent, in which an aqueous solution of PXa is used as a catalyst. A polyimide having a structure having an amic acid content of 5 to 25% is produced by adding 1 to 5 mol % of a 9 to 6.5 tertiary amine to the polyamic acid group and thermally imidizing the polyamic acid group.

The polyamic acid formula (1) used in the present invention is the formula (IV
) and an aromatic diamine represented by formula (V).

Examples of aromatic acid dianhydrides include pyromellitic anhydride, diphenyl ether tetracarboxylic dianhydride, 3.
3',4.4'-diphenylmethanetetracarboxylic dianhydride, 3.3',4.4'-benzophenonetetracarboxylic dianhydride (BTDA), diphenyl sulfoxide tetracarboxylic dianhydride, diphenyl These include sulfide tetracarboxylic dianhydride, diphenylsulfone tetracarboxylic dianhydride, and benzene ring-substituted derivatives thereof, and one or more types can be used.

Examples of aromatic diamines include phenylene diamines, diaminodiphenyl ether, diaminodiphenylmethane, and 3.3'-diaminobenzophenone (abbreviated as 3.3
”-〇ARP), 4.4”-diaminobenzophenone,
Diaminodiphenylsulfide, diaminodiphenylsulfoxide, diaminodiphenylsulfone, 4,4゛-
These include di(doaminophenoxy)biphenyl, bis(4-aminophenoxy-phenyl)dimethylmethane, and benzene ring-substituted derivatives thereof, and one or more of these may be used.

Examples of the aprotic polar solvent include N.

N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N,N'-dimethylimidazolidinone, etc. are used.

Catalysts used in the present invention include, for example, pyridine, quinoline,
A tertiary amine compound having a PKa (logarithm of the reciprocal of the dissolution constant in an aqueous solution) in the range of 4.9 to 6.5, such as inquinoline, α-picoline, etc., is used.

With a tertiary amine compound having a high PKa value, the imidization reaction proceeds too much, and with a tertiary amine compound having a low PKa value, the imidization reaction is slow and the desired compound cannot be obtained.

The amount of the catalyst to be used is 1 to 5 mol % based on the polyaminic acid group. If the amount used is less than 1%, the imidization reaction will be extremely slow, and impurities due to decomposition of the polyamic acid or side reactions will be mixed in during the reaction, resulting in poor thermal stability of the polyimide after molding. If the amount used is 5% or more, the amic acid structure content in the resulting polyimide decreases, causing problems in dispersing it in a polyamic acid solution.

When adjusting the content of the amic acid structure in polyimide, the purpose can be achieved by adjusting the amount of this catalyst added.

An embodiment of the present invention is carried out, for example, by the following method.

The aprotic polyamic acid obtained from diamine and tetracarboxylic dianhydride is heated and imidized by adding acetic anhydride and a tertiary amine catalyst to a solution of a polar polar solvent.

After cooling the reaction solution, the precipitated crystals may be collected by filtration, but in order to increase the recovery rate, alcohol may be added and the precipitated crystals may be filtered. The crystals are washed with alcohol and dried to obtain polyimide.The reaction temperature is 50 to 100°C, preferably 70 to 90°C.

The reaction time may be 0.5 to 20 hours, preferably 1
~5 hours. The alcohol used in the post-treatment may be a commonly used 01-C5 alcohol, preferably methanol. The washed cake is dried by a conventional drying method to obtain a polyimide partially having a polyamic acid structure.

For example, Figure 1 shows that BTDA and DABP are mixed in N,N-dimethylacetamide using a 15% solution of LARC polyamic acid obtained by a known method, in the presence of acetic anhydride, with the addition of pyridine as a catalyst, and heated at 75°C. The reaction was carried out for 8 hours, and the relationship between the addition of pyridine to the amic acid (2) and the amic acid content in the polyimide was determined.

〔Effect of the invention〕

As shown in the figure, the PKa of the aqueous solution added when polyamic acid is dehydrated and ring-closed in the presence of acetic anhydride to form polyimide.
By adjusting the amount of tertiary amine with a value of 4.9 to 6.5, the amic acid content in the polyimide can be adjusted to 5 to 25.
The amount can be adjusted to any value between % and a polyimide suitable for slurry production can be stably produced.

〔Example〕

The specific method of the present invention will be shown in Examples below.

Example-1 N,N-dimethylacetamide (DMAc)/8 liquid (a
Degree 15%i η1nhO, 64dj! /g, 0.5
0g/dj! Measurement of DMAc sample solution at 35°C)1
00g, 5.75g of acetic anhydride and 0.10g of pyridine (2
.

After cooling to room temperature, 100 g of methanol is added dropwise to the reaction slurry while stirring. After the dropwise addition is completed, it is filtered and the resulting wet cake of polyimide powder is washed with 100 g of methanol. Dry at 80'C to obtain 13.94g of polyimide powder. ηinh of polyimide powder is 0.166d
l 7g, composition: imide 84.8χ, amic acid 15
．． 2χ, by-products 0. It was Oz.

Example 2 The same operation as in Example 1 was carried out except that the amount of pyridine added was 0.20 g, and the imide was 92°2χ and the amic acid 7.
Polyimide powder with a by-product of 8χ and a by-product of 0.0χ was obtained.

Example-3 The same operation as Example-1 was carried out except that the amount of pyridine added was 0.05 g, and imide 79.8χ and amic acid 20
．． Polyimide powder with a by-product of 0.1χ and a by-product of 0.1χ was obtained.

Example 4 The polyamic acid solution used was DMAc? The same operation as in Example 1 was performed except that the temperature was changed to night (4 degrees 13.67 χ, η 1 hno, 51 d l 7 g).

Example-5 0.16 parts by weight of isoquinoline (2,
The same operation as in Example-1 was carried out by adding 25 χ mol χ).

Comparative Example-1 The same operation as in Example-1 was performed except that the amount of pyridine added was 0.45 parts by weight (10 mol%). The resulting polyimide powder has an amic acid content of fi0.2! and was outside the target range.

Comparative Example-2 The same operation as in Example-1 was performed without adding any pyridine. The polyimide powder obtained as a result had a high amic acid content of 25.1χ and contained 1.1χ of by-products.

Figure-1 Mol and lysine amino acid hand-written 1r positive 1 death (method) % formula % 1. Indication of the case 1988 Patent Application No. 306088/21 Name of the invention Method for producing aromatic polyimide 3. Amendment Relationship with the case of a person who does
2) The following sentence is inserted between Mitsui Toatsu Kagaku Co., Ltd., Table 1, Section 4, page 15 of the details of the amendment, and the applicant, Mitsui Toatsu Kagaku Co., Ltd.

・、・；　Go to 6

[Brief explanation of the drawing]

Figure 1 shows the relationship between the amount of pyridine added to amic acid and the content of amic acid in polyimide. ”

Claims (1)

[Claims] 1. Formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, Ar is ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲Mathematical formulas, chemical formulas, tables, etc. There is ▼, Y is -O-, ▲ there are mathematical formulas, chemical formulas, tables, etc. ▼
, -CH_2-, -S-, -SO-, -SO_2-. Ar' indicates ▲There are mathematical formulas, chemical formulas, tables, etc.▼, or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and Z is -O
-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -CH_2-, -S-, -SO-, -SO_2-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼▲There are mathematical formulas, chemical formulas, tables, etc.▼ show. ) In the method of dehydrating and ring-closing an aromatic polyamic acid having a repeating structural unit represented by
Formula (II) ▲Mathematical formulas, chemical formulas, tables, etc. are available▼(II) (In the formula, Ar and Ar' are the same residues as in formula (I). )
A method for producing an aromatic polyimide having a repeating structural unit and partially having an amic acid structure, the content of which is 5 to 25%. 2. The manufacturing method according to claim 1, wherein the tertiary amine having a PKa of 4.9 to 6.5 in the aqueous solution is pyridine. 3. The manufacturing method according to claim 1, wherein Ar in formula (II) is ▲ has a mathematical formula, chemical formula, table, etc. ▼ and Ar' is ▲ has a mathematical formula, chemical formula, table, etc. ▼.