JPH02373B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-resistant polyimide film with excellent strength. That is, this invention uses an aromatic diamine component having a molar ratio (DADE/PPD) of 4,4'-diaminodiphenyl ether (DADE) and p-phenylenediamine (PPD) of 0 to 2.5, and a melting point of 295. ~
The present invention relates to a polyimide film having a tensile strength of at least 25 kg/mm ² and made of a condensation polymer with 3,3',4,4'-biphenyltetracarboxylic dianhydride at 305°C. Conventionally, known polyimides are produced by condensing an aromatic diamine component and an aromatic tetracarboxylic dianhydride component in an organic polar solvent at a temperature of about 80°C or less to produce polyamic acid, and then thermally converting the polyamic acid into polyamic acid. It is also known that it can be chemically imidized and obtained as polyimide. In addition, polyimide film is produced by gradually removing the solvent from a polyamic acid solution obtained by condensation polymerization of pyromellitic dianhydride and an aromatic diamine component in an organic polar solvent at a temperature of about 80°C or less. It is known that a polyimide film can be obtained by molding a polyamic acid film and chemically imidizing the polyamic acid film. The above-mentioned pyromellitic acid and aromatic diamine (especially
The polyimide film obtained from DADE) is
It is said to have the best physical properties (especially tensile strength) among the known polyimide films, and it is also known that the tensile strength of the pyromellitic acid-DADE polyimide film is about 20 kg/mm ² at maximum. . That is, no other polyimide film having a tensile strength superior to that of the pyromellitic acid-DADE polyimide film was known. As a result of intensive research in search of a heat-resistant polyimide film with tensile strength superior to the above-mentioned pyromellitic acid-DADE polyimide film, the inventors found that
Select PPD or a specific mixture of PPD and DADE, as the aromatic tetracarboxylic dianhydride component, 3,3',4,4'-biphenyltetracarboxylic dianhydride with a melting point of 295-305℃ thing (S-
The inventors have discovered that a polyimide film with excellent tensile strength can be obtained by selecting polyamic acid (BPDA), molding the resulting polyamic acid by condensation polymerization of this combination, and then imidizing the resulting polyimide film, thereby achieving the present invention. The polyimide film of the present invention has not only excellent tensile strength but also excellent heat resistance. For example, the polyimide film of the present invention has a tensile strength of at least 25 Kg/mm ² or more. and a tensile strength of about 40 Kg/mm ² is also provided. “Report of the Academy of Sciences of the USSR” 1965, No.
Volume 165, No. 5, pages 1069-1070 contain 3, 3', 4,
A polyamide with an intrinsic viscosity [η] of 0.5 to 0.7 obtained by condensation polymerization of 4'-biphenyltetracarboxylic dianhydride (BPDA...melting point 286°C) and 4,4'-diaminodiphenyl ether (DADE). It is described that polyimide is produced by heating acid, and the production of this polyimide is
In addition to DADE, p-phenylenediamine (PPD)
It has been suggested that this is also possible when benzidine or benzidine is used as the aromatic diamine. According to the description of this known document, a polyimide film made from polyamic acid obtained by condensation polymerization of BPDA and DADE having a melting point of about 286°C was prepared in Comparative Example 4.
The tensile strength is 13.6Kg/mm ² as stated in
It is of a certain degree. Since the BPDA shown in the known examples has a low melting point and appears to be impure, purer BPDA, such as the melting point used in the present invention, is recommended.
It may be predicted that a polyimide film with higher strength could be obtained by using a material with a temperature of about 305°C. However, with a melting point of 305℃
A polyimide film made of polyamic acid obtained by polycondensation of BPDA and DADE has a tensile strength of only 15.3 Kg/mm ² as shown in Comparative Example 2 described below. Therefore, instead of the slightly impure BPDA with a melting point of about 286°C described in the above-mentioned known literature,
It is understood that even if pure polyimide with a melting point of 305° C. is used, the increase in tensile strength of polyimide is on the order of about 1.125 times. In contrast, BPDA and PPD in the present invention
When using BPDA, which has a melting point of about 286°C and is described in a known document, the tensile strength of the polyimide film is 15.7 Kg/mm ² (see Comparative Example 3); When BPDA with a melting point of about 305°C is used, the tensile strength of the polyimide film is 37.8 Kg/mm ² (see Example 1), and the increase in the tensile strength of the polyimide film is on the unexpected order of 2.4 times. It reaches . It is important that the aromatic diamine component has a molar ratio (DADE/PPD) of 2.5 or less, particularly 2.2 or less, and as the molar ratio (DADE/PPD) decreases, the tensile strength of the polyimide film increases. The elongation rate of the polyimide film decreases, and when p-phenylenediamine alone is used as the aromatic diamine component, a polyimide film exhibiting the maximum tensile strength and the minimum elongation rate is obtained. Further, the aromatic diamine component may include other aromatic diamines, such as m-phenylenediamine,
4,4'-diaminodiphenylthioether, 4,
If 4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, etc. is not more than about 20 mol%, especially about 15 mol% or less, based on the total aromatic diamine component, PPD alone or PPD and DADE can be used. It may be used in combination with a mixture of 3,3',4,4'-biphenyltetracarboxylic dianhydride having a melting point of 295 DEG to 305 DEG C. is produced by the method proposed by the present inventors and described in Japanese Patent Publication No. 51-23498. This 3,3',4,4'-biphenyltetracarboxylic dianhydride can be used with other aromatic tetracarboxylic dianhydrides, such as 2,3,3',4'-biphenyltetracarboxylic acid, 3 , 3',4,4'-benzophenonetetracarboxylic acid, pyromellitic acid,
bis(3,4-dicarboxyphenyl)methane,
A dianhydride such as bis(3,4-dicarboxyphenyl) ether may be used in combination as long as it is not more than 10 mol %, particularly not more than 5 mol %, based on the total acid dianhydride. The polyamic acid used in the production of the film of the present invention contains the aromatic diamine component described above and 3.
It is obtained by condensation polymerization of 3',4,4'-biphenyltetracarboxylic dianhydride in an organic polar solvent at a temperature of 0 to 80°C, preferably 0 to 60°C. In the above-mentioned condensation polymerization, all the components of the aromatic diamine and all the components of the aromatic tetracarboxylic dianhydride may be added in approximately equimolar amounts, particularly substantially equimolar amounts, to the solvent at the same time. preferable. That is, in the polycondensation, the difference (mol) between the aromatic diamine component and the aromatic tetracarboxylic dianhydride component is 5 mol% or less based on the total number of moles of the aromatic tetracarboxylic dianhydride component, In particular, it is preferable to add it to the solvent in an amount of 3 mol % or less. When producing the film of this invention, polyamic acid has a logarithmic viscosity (30°C, concentration 0.5 g/100 ml N-
(measured with methylpyrrolidone) is 1.5 or more, especially 1.5
It is preferable to have a high molecular weight of about 6 to 6, more preferably about 2.0 to 5. If the logarithmic viscosity is low, the tensile strength of the resulting polyimide film will be low, which is not preferable. As the logarithmic viscosity of the polyamic acid increases, the tensile strength of the resulting polyimide film increases almost linearly. In order to produce polyamic acid whose logarithmic viscosity (30°C, 0.5 g/100 ml N-methylpyrrolidone) is 2.0 or more, an aromatic diamine component and an aromatic tetracarboxylic dianhydride are Difference between component and amount added to solvent (mol)
is 2 mol% or less, particularly 1 mol% or less, based on the total number of moles of the aromatic tetracarboxylic dianhydride component, and the polycondensation temperature is maintained at about 0 to 60°C, especially 5 to 50°C. Optimal. In producing the film of this invention, the polyamic acid solution may be the aforementioned condensation polymerization solution as it is, or the polyamic acid may be isolated and purified once and dissolved in the same organic polar solvent as used in the condensation polymerization. It may be something that has been done. As the organic polar solvent used for condensation polymerization, N-
Methylpyrrolidone, pyridine, N,N-dimethylacetamide, N,N-dimethylformamide,
Suitable examples include solvents that can dissolve polyamic acid, such as dimethyl sulfoxide, tetramethylurea, cresol, and phenol. In producing the film, the polymer concentration of the polyamic acid solution is preferably about 5 to 20% by weight, particularly about 8 to 15% by weight. The method of molding a polyamic acid film while gradually removing the solvent from a polyamic acid solution may be carried out by any known molding method, for example, molding a polyamic acid film with a thickness of 10 to 100μ. In this case, a solution of polyamic acid is poured onto a flat plate such as a glass plate, a copper plate, an aluminum plate, etc. to form a film, and the solvent is gradually removed from this film by heating. An example of this method is to form a film by pouring a solution of polyamic acid into a rotary drum, forming a film on the surface of the drum, and gradually removing the solvent from this film. In addition, polyamic acid film has a
A polyimide film can be obtained by heating to a temperature of 350° C. to convert the amide-acid bonds of polyamic acid into imide bonds. Note that the removal of the solvent in forming a film from a solution of polyamic acid and the heating for imidization of the polyamic acid film may be performed continuously, or the latter half of solvent removal and the first half of imidization may overlap. and may be performed simultaneously. It is preferable to heat the polyamic acid molded product to about 400°C for a short period of time during the latter half of heating the polyamic acid molded product, or after the imidization by heating is completed, as this will further improve the strength of the resulting polyimide film. be. Examples and comparative examples are shown below. 3 used in Examples 1 to 10 and Comparative Examples 1 to 2,
3',4,4'-biphenyltetracarboxylic dianhydride is synthesized by the method disclosed in Japanese Patent Publication No. 51-23498 and has a melting point of 305°C. Examples 1 to 7 Into 14 cylindrical polymerization vessels, p-phenylene diamine (PPD) and 4,4'-diaminodiphenyl ether (DADE) in the amounts shown in Table 1 as aromatic diamine components, and aromatic 530 g (1.80 mol) of 3,3',4, as tetracarboxylic dianhydride
4'-biphenyltetracarboxylic dianhydride (S-
BPDA) along with N-methylpyrrolidone 6, stirred at room temperature (approximately 30°C) for 6 hours, and
A solution of polyamic acid having the logarithmic viscosity shown in the table (30 DEG C., 0.5 g/100 ml N-methylpyrrolidone) was obtained.
Each of these polyamic acid solutions was poured onto a glass plate to form a film of the polyamic acid solution, the film was maintained under reduced pressure at room temperature for 1 hour, and then
The solvent was evaporated off by maintaining the vacuum at 120° C. for 1.5 hours to form a polyamic acid film (approximately 30 μm). Peel off each polyamic acid film from the glass plate, attach it to a metal frame, and leave it at room temperature.
Raise the temperature to 200℃ in about 30 minutes, then from 200℃ to 300℃
The temperature was raised to 300°C for about 30 minutes, and the temperature was maintained at 300°C for about 1 hour to imidize the polyamic acid film and form a polyimide film. The tensile strength and elongation of each polyimide film were measured at room temperature (about 25°C), and the results are shown in Table 2. The decomposition start temperature of the polyimide films obtained in Example 1 and Example 5 was changed at a heating rate of 10
When determined under the conditions of .degree. C./min, the film of Example 1 had a temperature of 580.degree. C., and the film of Example 5 had a temperature of 520.degree. The film of Example 1 had a coefficient of linear expansion of 1.8 x 10 ^-5 cm/cm/°C within a temperature range of 50 to 300°C. In addition, in a hot air dryer for heat resistance testing,
After holding the polyimide film obtained in Example 1 or Example 5 at 300°C or 350°C for 48 hours, the tensile strength and elongation of each film were measured. The results are shown in Table 1.

[Table] Examples 8 to 10 As aromatic diamine components, p-phenylenediamine (1.62 mol), 4,4'-diaminodiphenylthioether (DADT), and 4,4'-diaminodiphenylmethane (DADM) or 4,4'-diaminodiphenylsulfone (DADS) (0.18 mol)
The second process was carried out in the same manner as in Example 7, except that
Solutions of polyamic acid having the logarithmic viscosity shown in the table were prepared. A polyimide film was molded in the same manner as in Example 1, except that the above-mentioned solutions of each polyamic acid were used. Table 2 shows the tensile strength and elongation of each polyimide film. Comparative Examples 1-2 As the aromatic diamine component, 4,4'-diaminodiphenyl ether (1.80 mol) or 4,4'-diaminodiphenyl ether (1.80 mol),
A solution of polyamic acid having the logarithmic viscosity shown in Table 2 was prepared in the same manner as in Example 1, except that 4'-diaminodiphenyl ether (1.62 mol) and p-phyllenediamine (0.18 mol) were used. Polyimide films were molded in the same manner as in Example 1, except that each polyamic acid solution was used. Table 2 shows the tensile strength and elongation of each polyimide film.

【table】

[Table] Examples 11 to 15 The films imidized at 300°C of Examples 1 to 5 were subsequently heated from 300°C to the temperature shown in Table 3, and heat-treated at that temperature for 10 minutes. The results obtained are shown in Table 3.

[Table] Comparative Example 3 Synthesis of biphenyltetracarboxylic dianhydride “Report of the Academy of Sciences of the USSR” 1965, Vol.
According to the method described in Volume 165, No. 5, pages 1069-1070,
3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) with a melting point of 284-289°C was produced. Production of film 1.00g of this BPDA and 0.367g of p-phenylenediamine (PPD) were mixed with dimethylformamide.
It was placed in a polymerization reaction vessel together with 12.31 g and polymerized at room temperature (20°C) for 6 hours to obtain a polymer solution (polyamic acid solution). The polymer produced in the polymer solution obtained by the above polymerization reaction had a logarithmic viscosity (measurement temperature: 20° C., concentration: 0.5 g/100 ml, solvent: dimethylformamide) of 0.56. Next, the polymer solution obtained by the above polymerization reaction was poured onto a glass plate to form a thin film of the polymer solution, and the film was maintained under reduced pressure at room temperature for 1 hour and heated at 120°C for 20 minutes. to form a self-supporting film, the film is peeled off from the glass plate, the film is then fixed in a mold and placed in a heating oven at 200°C for 30 minutes and then at 400°C. Heat treatment was performed for 10 minutes to form a polyimide film with a thickness of approximately 15 μm. The polyimide film formed as described above had a tensile strength of 15.7 Kg/mm ² and an elongation of 2%. Comparative Example 4 1.00 g of BPDA obtained in Comparative Example 3 and 0.690 g of 4,4'-diaminodiphenyl ether (DADE) were placed in a polymerization reactor together with 12.31 g of dimethylformamide, and the mixture was heated at room temperature (20°C). , Polymerization was carried out for 6 hours to obtain a polymer solution (polyamic acid solution). The polymer produced in the polymer solution obtained by the above polymerization reaction had a logarithmic viscosity (measurement temperature: 20° C., concentration: 0.5 g/100 ml, solvent: dimethylformamide) of 0.52. Next, the polymer solution obtained by the above polymerization reaction was poured onto a glass plate to form a thin film of the polymer solution, and the film was maintained under reduced pressure at room temperature for 1 hour and heated at 120°C for 20 minutes. to form a self-supporting film, the film is peeled off from the glass plate, and then the film is fixed in a mold and placed in a heating oven at 20°C for 30 minutes.
A polyimide film with a thickness of about 30 μm was formed by heat treatment at 300° C. for 30 minutes. The polyimide film formed as described above had a tensile strength of 13.6 Kg/mm ² and an elongation of 26%.

Claims (1)

[Claims] 1 An aromatic diamine component having a molar ratio (DADE/PPD) of 4,4'-diaminodiphenyl ether (DADE) and p-phenylenediamine (PPD) of 0 to 2.5 and a melting point of 295 to 305°C 3,
A polyimide film comprising a condensation polymer with 3',4,4'-biphenyltetracarboxylic dianhydride and having a tensile strength of at least 25 Kg/ ^mm2 .