JPH04320422A - Polyamic acid, polyimide film prepared therefrom, and their preparation - Google Patents

Abstract

PURPOSE:To prepare a polyimide having an excellent heat resistance, a high elasticity, a low coefficient of thermal expansion, and a low moisture absorptivity selecting a polyimide consisting of tetracarboxylic diimide units combined by both diamine residues having a linear structure and diamine residues having a bendable structure. CONSTITUTION:A polyamic acid of formula I (wherein R2 and R4 are each a diamine residue having a linear structure; R6 is a diamine residue having a bendable structure; and R3 is a tetravalent benzene ring or a deriv. thereof) is prepd. by adding 1 equivalent of pyromellitic dianhydride to 2 equivalents of at least one kind of a diamine having a linear structure (e.g. p- phenylenediamine), then adding 2 equivalents of a tetracarboxylic dianhydride such as of formula II, and adding 1 equivalent of at least 1 kind of a diamine having a bendable structure (e.g. 4,4'-diaminodiphenyl ether). The acid is cyclodehydrated to give a polyimide of formula III, which gives a film having a high elasticity, a low moisture absorptivity, and a suitable flexibility.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a polyamic acid copolymer that provides a polyimide film that has excellent heat resistance, high elasticity, low thermal expansion, and low moisture absorption, a polyimide film made from the copolymer, and a method for producing the same. be.

0002

BACKGROUND OF THE INVENTION Conventionally, polyimide resins have excellent heat resistance and electrical insulation properties, and have been widely used as industrial materials including electrical equipment. As described above, polyimide resin has a variety of superior properties compared to other polymers, but as technology advances, the properties required of polyimide resin also become more sophisticated, and polyimide resins are required to have a combination of various performances depending on the application. is desired.

[0003] When considered for use in electrical equipment, high hygroscopicity is undesirable because it reduces electrical insulation, increases the risk of contamination with ionic impurities, and reduces reliability as a material. Therefore, it is desired that the material has low hygroscopicity. Furthermore, from the viewpoint of strength as a material, it is desirable that the material has high elasticity. Since it is preferable that dimensional changes are small even with temperature changes, low thermal expansion is required.

For example, by using only rigid and straight chains such as pyromellitic anhydride and paraphenylene diamine, a polyimide having high elasticity and low thermal expansion can be synthesized. However, this structure is extremely brittle and inflexible.
Only films with high hygroscopicity can be obtained. Also,
Polyimide is generally a resin with relatively high water absorbency because the carbonyl group and nitrogen atom in the imide ring have large polarization. Thus, there is a need for a polyimide that fully satisfies the physical properties of high elasticity, low moisture absorption, and appropriate flexibility.

[0005]

The present invention relates to a polyamic acid copolymer which provides a polyimide film having excellent properties such as excellent heat resistance, high elasticity, low coefficient of thermal expansion, and low hygroscopicity, and a polyimide film comprising the same. The purpose is to provide a method for manufacturing them.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the present inventors conducted intensive studies on the molecular structure of polyimide, and found that polyimide having a specific structural unit has high elasticity, low thermal expansion, and low moisture absorption. The present invention was completed based on the discovery that the material has a suitable degree of flexibility. That is, the first aspect of the present invention is the following structural formula:

[0007]

[C6]

(However, R2 and R4 are linear diamine residues, R6 is a flexible diamine residue, and R3 is a

00
09]

[C7]

[0010] where R1 and R5 are the following groups.

00
11]

[Chemical formula 8]

It is arbitrarily selected from [0012]. ) A polyamic acid copolymer having a structural unit represented by

The second aspect of the present invention for producing the above polyamic acid copolymer is to add 1 equivalent of pyromellitic dianhydride to 2 equivalents of at least one linear diamine, and then
Structural formula below

[0014]

[Chemical formula 9]

A method for producing a polyamic acid copolymer, characterized in that 2 equivalents of at least one tetracarboxylic dianhydride represented by: are added, and then 1 equivalent of at least one flexible diamine is added, The third aspect of the present invention for producing the polyamic acid copolymer is to add 2 equivalents of at least one tetracarboxylic dianhydride represented by the above structural formula to 1 equivalent of at least one flexible diamine. A fourth aspect of the present invention provides a method for producing a polyamic acid copolymer, which comprises adding 2 equivalents of at least one linear diamine and then 1 equivalent of pyromellitic dianhydride. The polyimide film obtained by dehydrating and ring-closing the polyamic acid copolymer of the first invention is
The sixth aspect of the present invention is a method for producing a polyimide film, which is characterized by subjecting the polyamic acid copolymer obtained in the second invention to dehydration ring closure, and the sixth aspect of the present invention is a method for producing a polyamic acid copolymer obtained in the third invention. Each content is a method for producing a polyimide film characterized by dehydration and ring closure.

The present invention will be explained in detail below. The linear diamine used in the present invention refers to a diamine compound that does not contain a bending group such as an ether bond and has a structure such that the straight line connecting two nitrogen atoms matches the main chain direction of the diamine. for example,

[0017]

[Chemical formula 10]

(However, X is F, Cl, Br, CH3
, CH3O or CF3. ) and the like can be exemplified.

On the other hand, flexible diamine refers to a structure containing a flexible group such as an ether bond or a carbonyl group, for example,

[0020]

[Chemical formula 11]

The following diamines can be exemplified. Further, if a long chain diamine is used as the flexible diamine residue (R6), lower hygroscopicity can be achieved.

In the polyamic acid copolymer and polyimide film of the present invention, it is important that each structural unit is regularly arranged in the order of the above structural units. A synthetic method is used. This polyimide copolymer is obtained from a polyamic acid copolymer solution, which is its precursor, and this polyamic acid copolymer solution is polymerized in an organic polar solvent using substantially equal moles of acid anhydride and diamine components. It can be obtained by

Examples of the organic polar solvent used in the reaction for producing the polyamic acid copolymer include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N,N-dimethylformamide, and N,N-diethylformamide. Formamide solvents such as N,N-
Acetamide solvents such as dimethylacetamide and N,N-diethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone;
Examples include phenolic solvents such as phenol, o-, m-, or p-cresol, hexamethylphosphoramide, γ-butyrolactone, etc., and it is preferable to use these alone or as a mixture of two or more. Furthermore, it is also possible to use some aromatic hydrocarbons such as xylene and toluene.

A specific example of the method for synthesizing the polyamic acid copolymer will be shown below. Synthesis method 1. In a container, 2 equivalents of an organic polar solvent and one or more linear diamines are placed, cooled and stirred. (2) Add 1 equivalent of pyromellitic dianhydride to the above mixture, and stir and cool for preferably 20 minutes or more. (2) Add 2 equivalents of one or more tetracarboxylic dianhydrides selected from the following, and stir and cool for preferably 20 minutes or more.

[0025]

[Chemical formula 12]

(2) One equivalent of one or more flexible diamines is dissolved in an organic polar solvent, and added while gradually cooling and stirring to obtain the polyamic acid copolymer solution.

Synthesis method 2 (1) Place 1 equivalent of an organic polar solvent and one or more flexible diamines in a container, cool and stir. ■1 tetracarboxylic dianhydride selected from the following
Two equivalents of the seeds or two or more species are added, and the mixture is cooled and stirred preferably for 20 minutes or more.

[0028]

[Chemical formula 13]

(2) Two equivalents of one or more linear diamines are added, and the mixture is cooled and stirred preferably for 20 minutes or more. ■
One equivalent of pyromellitic dianhydride is added to the above mixed solution to obtain the polyamic acid copolymer solution. The polyamic acid copolymer obtained as described above is preferably 5 to 40% by weight, more preferably 10 to 40% by weight, in the organic polar solvent.
From the viewpoint of handling, it is desirable that the amount is 30% by weight dissolved.

In order to obtain the polyimide film of the present invention from this aromatic polyamic acid copolymer solution, either a thermal method of thermal dehydration or a chemical method using a dehydrating agent may be used. This method is preferable because the resulting polyimide film has excellent mechanical properties such as elongation and tensile strength. An example of a method for producing a polyimide film will be described below.

A solution prepared by adding a dehydrating agent in a stoichiometric amount or more and a catalytic amount of tertiary amine to the polyamic acid polymer or its solution is cast or coated onto a drum or an endless belt to form a film. 5 at a temperature below 150℃
Dry for ~90 minutes to obtain a self-supporting polyamic acid membrane. Then, it is peeled off from the support and the ends are fixed. Thereafter, it is imidized by gradually heating to about 100 to 500°C, and after cooling, it is removed from a drum or an endless belt to obtain the polyimide film of the present invention. Examples of the dehydrating agent mentioned here include aliphatic acid anhydrides such as acetic anhydride, aromatic acid anhydrides, and the like. Examples of the catalyst include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline, and isoquinoline.

[0032]

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. In the examples, ODA is 4,4'-diaminodiphenyl ether, BAPB is 4,4'-bis(aminophenoxyphenyl)biphenyl, BAPP is 4,4'-bis(aminophenoxyphenyl)propane, and p-PDA is paraphenylene. Diamine, TPE-Q is 1,4-bis(
4-aminophenoxy)benzene, PMDA represents pyromellitic anhydride, BTDA represents benzophenonetetracarboxylic dianhydride, BPDA represents biphenyltetracarboxylic dianhydride, and DMF represents dimethylformamide.

Example 1 DMF and p-PDA were placed in a 2 liter separable flask.
Two equivalents of were taken and mixed well at room temperature until the diamino compound was completely dissolved, and then stirred while cooling with ice. Next, 1 equivalent of PMDA was added, and the mixture was cooled and stirred for 40 minutes. Then, 2 equivalents of BTDA were added at once, and the mixture was cooled and stirred for 40 minutes. One equivalent of ODA was dissolved in DMF and gradually added, followed by cooling and stirring for 1 hour to obtain a DMF solution of polyamic acid. The amount of DMF used was such that the monomer concentration of the diamino compound and aromatic tetracarboxylic acid compound was 18% by weight. A polyamic acid solution was cast onto a glass plate, and after drying at about 100°C for about 30 minutes, the polyamic acid coating was peeled off from the glass plate, the coating was fixed on a support frame, and then heated at about 100°C for about 30 minutes. minutes, approx. 200℃
The mixture was heated for about 60 minutes at about 300°C for about 60 minutes, and dehydrated and ring-closed to obtain a polyimide film of about 25 microns. Table 1 shows the physical properties of the obtained polyimide film.

Example 2 DMF and p-PDA were placed in a 2 liter separable flask.
Two equivalents of were taken and mixed well at room temperature until the diamino compound was completely dissolved, and then stirred while cooling with ice. Next, 1 equivalent of PMDA was added, and the mixture was cooled and stirred for 40 minutes. Then, 2 equivalents of BTDA were added at once, and the mixture was cooled and stirred for 40 minutes. One equivalent of TPE-Q was dissolved in DMF and gradually added, followed by cooling and stirring for 1 hour to obtain a DMF solution of polyamic acid. It was fired in the same manner as in Example 1 to obtain a polyimide film. Table 1 shows the physical properties of the obtained polyimide film.

Example 3 DMF and p-PDA were placed in a 2 liter separable flask.
Two equivalents of were taken and mixed well at room temperature until the diamino compound was completely dissolved, and then stirred while cooling with ice. Next, 1 equivalent of PMDA was added, and the mixture was cooled and stirred for 40 minutes. Then, 2 equivalents of BTDA were added at once, and the mixture was cooled and stirred for 40 minutes. One equivalent of BAPB was dissolved in DMF and gradually added, followed by cooling and stirring for 1 hour to obtain a DMF solution of polyamic acid. It was fired in the same manner as in Example 1 to obtain a polyimide film. Table 1 shows the physical properties of the obtained polyimide film.
It was shown to.

Example 4 DMF and p-PDA were placed in a 2 liter separable flask.
Two equivalents of were taken and mixed well at room temperature until the diamino compound was completely dissolved, and then stirred while cooling with ice. Next, 1 equivalent of PMDA was added, and the mixture was cooled and stirred for 40 minutes. Then, 2 equivalents of BTDA were added at once, and the mixture was cooled and stirred for 40 minutes. One equivalent of BAPP was dissolved in DMF and gradually added, followed by cooling and stirring for 1 hour to obtain a DMF solution of polyamic acid. It was fired in the same manner as in Example 1 to obtain a polyimide film. Table 1 shows the physical properties of the obtained polyimide film.
It was shown to.

Example 5 DMF and p-PDA were placed in a 2 liter separable flask.
Two equivalents of were taken and mixed well at room temperature until the diamino compound was completely dissolved, and then stirred while cooling with ice. Next, 1 equivalent of PMDA was added, and the mixture was cooled and stirred for 40 minutes. Then, 2 equivalents of BPDA were added at once, and the mixture was cooled and stirred for 40 minutes. One equivalent of BAPB was dissolved in DMF and gradually added, followed by cooling and stirring for 1 hour to obtain a DMF solution of polyamic acid. It was fired in the same manner as in Example 1 to obtain a polyimide film. Table 1 shows the physical properties of the obtained polyimide film.
It was shown to.

Example 6 DMF and ODA were added in a 2 liter separable flask.
An equivalent amount of the mixture was taken and mixed well at room temperature until the diamino compound was completely dissolved, and then stirred while cooling with ice. next,
Two equivalents of BTDA were added, and the mixture was cooled and stirred for 40 minutes. and,
Two equivalents of p-PDA were added at once, and the mixture was cooled and stirred for 40 minutes. One equivalent of PMDA was dissolved in DMF and gradually added, followed by cooling and stirring for 1 hour to obtain a DMF solution of polyamic acid. The amount of DMF used was such that the monomer concentration of the diamino compound and aromatic tetracarboxylic acid compound was 18% by weight. A polyamic acid solution was cast onto a glass plate, and after drying at about 100°C for about 30 minutes, the polyamic acid coating was peeled off from the glass plate, the coating was fixed on a support frame, and then heated at about 100°C for about 30 minutes. minutes, approx. 200℃
The mixture was heated for about 60 minutes at about 300°C for about 60 minutes, and dehydrated and ring-closed to obtain a polyimide film of about 25 microns. Table 1 shows the physical properties of the obtained polyimide film.

Comparative Example 1 A polyimide film was obtained in the same manner as in Example 1 using equal moles of PMDA and ODA. Table 1 shows the physical properties of the obtained polyimide film.

Comparative Example 2 DMF and p-PDA were placed in a 2 liter separable flask.
2 equivalents of ODA and 1 equivalent of ODA were mixed well at room temperature until the diamino compound was completely dissolved, and then stirred while cooling with ice. Next, 2 equivalents of BTDA and 1 equivalent of PMDA were gradually added, followed by cooling and stirring for 1 hour to obtain a DMF solution of polyamic acid. It was fired in the same manner as in Example 1 to obtain a polyimide film. Table 1 shows the physical properties of the obtained polyimide film.

[0041]

[Table 1] 1) The weight of the film dried at 150°C for 30 minutes is
, where L1 is the weight of the film after immersion in distilled water for 24 hours at 23°C, water absorption rate (%) = (L1 - L0)/L0 x 100 (according to ASTM-D570). 2) Thermal expansion coefficient of 100-200℃ (manufactured by Rigaku Denki Kogyo)
(measured by TMA8140).

[0042]

As described above, according to the present invention, a polyimide film having excellent heat resistance, high elasticity, low thermal expansion and low moisture absorption can be obtained.

Claims (6)

[Claims] [Claim 1] The following formula [Formula 1] (wherein, R2 and R4 are linear diamine residues, R6
is a flexible diamine residue, R3 is [Formula 2], and R1 and R5 are arbitrarily selected from the following groups [Formula 3]. ) A polyamic acid copolymer having a structural unit represented by: 2. After adding 1 equivalent of pyromellitic dianhydride to 2 equivalents of at least one linear diamine, at least one tetracarboxylic dianhydride represented by the following structural formula: 1. A method for producing a polyamic acid copolymer, which comprises adding 2 equivalents of a polyamic acid copolymer and then adding 1 equivalent of at least one flexible diamine. 3. After adding 2 equivalents of at least one tetracarboxylic dianhydride represented by the following structural formula to 1 equivalent of at least one flexible diamine, at least one straight line is formed. diamine 2
A method for producing a polyamic acid copolymer, which comprises adding an equivalent of pyromellitic dianhydride and then adding 1 equivalent of pyromellitic dianhydride. 4. A polyimide film obtained by dehydrating and ring-closing the polyamic acid copolymer according to claim 1. 5. A method for producing a polyimide film, which comprises dehydrating and ring-closing the polyamic acid copolymer obtained by the method according to claim 2. 6. A method for producing a polyimide film, which comprises dehydrating and ring-closing the polyamic acid copolymer obtained by the method according to claim 3.