JPH0432112B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to polyamic acid compositions. More specifically, the present invention relates to a novel polyamic acid composition consisting of a polyamic acid precursor and a specific mixed solvent system that provides a polyimide molded product with high strength, high elastic modulus, and extremely high heat resistance.

[Prior Art] The present inventors have previously discovered a material with high strength and high elastic modulus,
Furthermore, poly(2,2'-dichloro-4,4'-
Biphenylene pyromellitimide) was discovered (Japanese Patent Application No. 58-205780). This molded product is produced by a method normally used to obtain a polyimide molded product, that is, a solution of polyamic acid, which is a precursor polymer, in an amide solvent or urea solvent, or a solution containing a chemical cyclizing agent added thereto, such as casting. It is produced by molding using a method and then ring-closing the imide group using thermal or chemical means, but there are still points that need to be improved.

[Problems to be Solved by the Invention] One of the problems is that the amide or urea solvent used is expensive, which increases the manufacturing cost of the molded product. Another problem is that conventional solutions are inappropriate for producing so-called sheets of uniaxially stretched films with a high modulus of elasticity of 0.1 mm or more in thickness. In other words, in order to obtain a uniaxially stretched sheet with a high elastic modulus with a tensile or flexural modulus of 100 GPa, it is necessary to uniaxially stretch a homogeneous partially cyclized polyamic acid gel-like sheet with a polymer concentration of about 25 to 60%. However, when heating and concentrating a cast sheet with such a thick material as described above, concentration unevenness in the thickness direction cannot be avoided, and therefore it is not possible to stretch the sheet to achieve a sufficiently high orientation. The present inventors have made intensive studies to solve the above two problems, and as a result, have found that the use of a specific mixed solvent system is suitable for this purpose, and have arrived at the present invention.

[Means for solving the problem] That is, the present invention has a method in which the repeating unit is substantially 2,
A polymer consisting of 2'-dichloro-4,4'-biphenylenepyromellitamic acid, and at least one selected from amide solvents and urea solvents (A)
and a halogenated hydrocarbon (B), the composition having a polymer concentration of 5 to 20%, and
The present invention provides a polyamic acid composition characterized in that A/B (volume ratio) is 80/20 to 20/80.

That is, by using a halogenated hydrocarbon, which is a relatively inexpensive and highly safe general-purpose solvent, as a part of the solvent component, the manufacturing cost of the polyimide molded product can be reduced. In addition, since halogenated hydrocarbons have a lower boiling point than amide solvents or urea solvents, it is easy to selectively distill off only this solvent component when heating and concentrating a thick cast gel sheet. A homogeneous stretched sheet without uneven polymer concentration in the thickness direction can be obtained.

The present invention will be explained in more detail below.

The polyamic acid of the present invention is obtained by polymerization using 2,2'-dichlorobenzidine as a diamine component and pyromellitic anhydride (PMDA) as an acid anhydride component, but with a small amount of other monomers other than the above monomers, There is no problem even if it is copolymerized. Such copolymerization components include p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,3'-dimethylbenzisdine, and Examples include 3,3'-dichlorobenzidine and 3,3'-diaminodiphenylsulfone. In addition, examples of acid anhydride components include 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, etc. . The amount of these copolymer components used is within about 20 mol%.

As the polymerization solvent system, an amide solvent or a urea solvent alone, or a mixture thereof with a halogenated hydrocarbon is used. As the amide solvent, N,N-dimethylformamide (DMF), N,
N-dimethylacetamide, N,N-dibutylacetamide, N-methylpyrrolidone (NMP),
Examples include N-methylcaprolactam and N-cyclohexylpyrrolidone. In addition, urea-based solvents include N, N, N', N'-tetramethylurea,
1,3-dimethyl-2-imidazolidone (DMI)
There is.

The halogenated hydrocarbons used in the present invention include monochloromethane, dichloromethane, chloroform, 1,2-dichloroethane (DCE), 1,1,
Representative examples thereof include chlorinated hydrocarbons such as 2-trichloroethane, and brominated hydrocarbons such as monobromomethane and dibromomethane. Conventionally, it has been common knowledge that halogenated hydrocarbons are generally poor solvents for aromatic polyamic acids, and therefore it is extremely difficult to obtain moldable polyamic acid solution compositions containing halogenated hydrocarbons. However, in the case of the polyamic acid targeted by the present invention, the present inventors found that it consists of at least one type selected from amide solvents and urea solvents (A) and a halogenated hydrocarbon (B). Add a polymer concentration of 5 to 20 to the mixed solution.
%, and A/B (volume ratio) approximately 80/20 to 20/
They found that it dissolves almost stably within the range of 80%. As mentioned above, polymerization is carried out using an amide solvent or urea solvent (A) alone, or a mixed solvent of A and a halogenated hydrocarbon (B), but it is not necessarily carried out at the A/B ratio of the final composition. You don't have to.

That is, the polymerization may be carried out in a mixed solvent relatively rich in component A, and then diluted with a mixed solvent rich in component B. In this way, the polyamic acid solution composition of the present invention is obtained. In many cases, this polyamic acid composition can be used as it is as a stock solution for molding.
Now, to explain the dry thermal cyclization method as an example, the polyamic acid composition is cast onto a flat plate or extruded through a slit die onto a belt or drum to form a film or the like. The final polyimide molded product can be obtained by raising the temperature to evaporate the solvent and proceed with thermal cyclization. In another molding method, that is, a dry molding method with the addition of a cyclizing agent, the polyamic acid composition of the present invention is subjected to temperature conditions (10
A chemical cyclizing agent is added to the product at a temperature below 30°F (°C or lower), and after forming into a film or sheet, the temperature is raised to a temperature at which cyclization occurs to cause gelation and form retention. As such a cyclizing agent, aliphatic acid anhydrides such as acetic anhydride and propionic anhydride are suitable. The amount added is preferably 0.5 to 3.0 equivalents relative to the amic acid unit. Further, an organic base such as pyridine, 3-methylpyridine, or quinoline may be added as a catalyst together with the cyclizing agent. The temperature of the gelled molded product is further raised to evaporate the solvent and complete cyclization.

In-plane isotropic films do not require any particular stretching operation at any stage of the above process, but if higher tensile properties are desired, a gel film with a relatively low polymer concentration is fixed in a frame and then heated to remove the solvent. It is effective to use a formulation that both removes the heat and promotes thermal cyclization.
When particularly high tensile properties are required in only one direction, uniaxial stretching is required. In this case, it is preferable in terms of the process that a portion of the solvent remains rather than completely distilling off the solvent, since stretching can be performed at a lower temperature. And the final thickness after heat treatment is 0.1
The polyamic acid composition of the present invention is particularly effective when producing a uniaxially stretched sheet with a thickness of up to 1.0 mm. That is, in order to obtain a high modulus uniaxially stretched sheet with a tensile or flexural modulus of about 100 GPa, the gel sheet formed by the above-mentioned cyclizing agent addition method is concentrated to a polymer concentration of 25 to 60% and homogeneous, and then It must be stretched, but if an amide solvent or urea solvent is used alone,
With the above thickness, density unevenness occurs in the thickness direction, and it is not possible to stretch the film to a sufficiently high orientation. If an amide or urea mixed solvent with different boiling points is used, most of the low boiling point components will be distilled off first, and the concentration unevenness in the thickness direction will be considerably eliminated, but this is still not sufficient. On the other hand, in the polyamic acid composition of the present invention, not only the boiling point of the halogenated hydrocarbon is generally significantly lower than that of amide or urea solvents, but also the affinity with the polyamic acid is inferior, so that only this solvent component is used. can be easily selectively distilled off, making it possible to obtain a homogeneous gel sheet with no uneven polymer concentration in the thickness direction. Therefore, high magnification stretching is possible.

The above non-stretched or uniaxially stretched molded product is finally heat-treated at a high temperature to completely advance cyclization. The temperature is preferably 300°C or higher, and the atmosphere is air or an inert gas such as nitrogen.

The polyamic acid composition of the present invention can also be molded using a wet method. In this case, the polyamic acid solution composition is extruded into an aqueous or non-aqueous coagulation bath through a slit die or the like and molded. The recipe for subsequent cyclization, stretching, or heat treatment is almost the same as in the dry molding described above.

The invention will be explained in further detail by the following examples.

[Example] The intrinsic viscosity in the example is 25% of the desired polymer solution in NMP so that the ratio is 0.5g of polymer/100ml of solvent.
Measured in °C.

Further, the tensile properties of the isotropic film were measured using Tensilon manufactured by Toyo Baldwin Co., Ltd. under conditions of a sample width of 5 mm, sample length of 100 mm, and stretching speed of 10 mm/min.

Further, the bending elastic modulus of the uniaxially stretched sheet was measured using the above-mentioned Tensilon at a distance between fulcrums of 40 mm and a crosshead speed of 5 mm/min.

Example 1 In this example, poly(2,2'-dichloro-4,
4′-biphenylenepyromellitamic acid) and DMI/
Example of manufacturing a solution composition consisting of a DCE mixed solvent and poly(2,2'-dichloro-4,
An example of making a uniaxially stretched sheet (4'-biphenylenepyromellitimide) is shown below.

Put 9.366 g (37.0 mmol) of 2,2'-dichlorobenzidine into a 500 ml separable flask,
30 ml of DMI and 55 ml of DCE were added and heated to about 60°C to dissolve. Then cooled in a 20℃ water bath,
7.909 g (36.3 mmol) of PMDA was added and stirred vigorously. After 5 minutes, add 4ml of DMI using a dripping roll.
A mixture consisting of 31 ml of DCE was gradually added dropwise over 25 minutes. Thus, polymer concentration 12%, DMI/DCE
A polyamic acid solution composition having a volume ratio of 28/72 was obtained. Then, this solution was placed on dry ice at -5°C.
The mixture was cooled in an acetone bath, and a mixture consisting of 6.0 g of acetic anhydride (0.8 equivalents of amic acid units) and 0.5 g of pyridine was added dropwise over 5 minutes, followed by defoaming under reduced pressure at a pressure of 65 mmHg. This solution was cast onto a glass plate surrounded by a 4 mm thick aluminum frame and allowed to stand overnight at room temperature in a desiccator to gel. This gel sheet was heated in an air oven at 40°C for 60 minutes to distill off the DCE.
Partially cyclized polyamic acid and DMI with a polymer concentration of 31.5%
A gel sheet consisting of was obtained. 10 of these gel sheets
Cut into mm width and use Tensilon tensile tester.
It was stretched to 1.8 times (after stretching, it partially recovered when removed from the chuck, so the actual magnification was 1.65).
This stretched sheet was heat-treated stepwise in an air oven under the following conditions.

90℃, 30 minutes → 210℃, 1 hour → 230℃, 40 minutes →
250℃, 20 minutes → 275℃, 20 minutes → 300℃, 20 minutes → 340
°C, 20 minutes.

The resulting heat-treated sheet with a width of 4.1 mm and a thickness of 0.50 mm had a bending elastic modulus in the stretching direction of 98 GPa.

Example 2 In this example, poly(2,2'-dichloro-4,
4′-biphenylenepyromellitamic acid) and
An example of the production of a composition consisting of an NMP/DCE mixed solvent and an example of the production of an isotropic polyimide film obtained from the composition by a dry thermal cyclization method will be shown.

Put 6.582 g (26.0 mmol) of 2,2'-dichlorobenzidine into a 300 ml four-necked flask, and then
30 ml each of NMP and DCE were added and dissolved. PMDA5.615 while cooling in a 20 °C water bath and stirring vigorously.
g (25.7 mmol) was added. 2 hours later,
Add a mixture of 15 ml of NMP and 35 ml of DCE to dilute, polymer concentration 10%, intrinsic viscosity 2.13, solution viscosity.
A 990 poise polyamic acid solution was obtained. The NMP/DCE (volume ratio) of this solution was 41/59.

This solution was cast onto a glass plate to a thickness of approximately 300 μm, and heated in an air oven at 90° C. for 20 minutes to concentrate to a polymer concentration of 63%. This film was peeled off from the glass plate and fixed on a 200mm square aluminum frame.
In an air oven, 10 minutes at 210℃, 30 minutes at 280℃,
Further heat treatment was performed at 400°C for 3 minutes. The tensile properties of the obtained isotropic polyimide film with a thickness of 16 μm were as follows.

Strength 0.44GPa, elongation 5.9%, elastic modulus 18GPa.

Example 3 In this example, poly(2,2'-dichloro-4,
4′-biphenylenepyromellitamic acid) and
An example of producing a composition consisting of an NMP/DCE mixed solvent and an example of producing an isotropic polyimide film using a dry method with the addition of a cyclizing agent will be shown.

In a mixed solvent consisting of 25 ml each of NMP and DCE, 2.
2'-dichlorobenzidine 5.569 g (2.20 mmol)
and PMDA4.751g (21.8 mmol) were polymerized,
It was then diluted with a mixture consisting of 27 ml each of NMP and DCE to obtain a polyamic acid solution with a polymer concentration of 9.0% and an intrinsic viscosity of 2.49. In addition, NMP/
DCE (volume ratio) was 50/50. This solution-
Cool to 15°C and add 5.39 g of acetic anhydride (amic acid units).
1.2 equivalents) and 2.1 g of pyridine were added dropwise and defoamed under reduced pressure at a pressure of 50 mmHg.

The above solution was cast onto a glass plate to a thickness of about 350 μm and left in a desiccator at room temperature for 1 hour to gel. This gel film was peeled off from the glass, fixed on a 200 mm square aluminum frame, and then heat treated in an air oven under the following conditions.

70℃, 50 minutes → 210℃, 10 minutes → 280℃, 30 minutes → 400℃
°C, 3 minutes.

Obtained isotropic polyimide film (18μ thickness)
The tensile properties of were as follows.

Strength 0.51GPa, elongation 3.6%, elastic modulus 26GPa.

[Effects of the Invention] Taking a film or sheet as an example, the polyimide molded product obtained from the polyamic acid composition of the present invention has a strength of 0.2 GPa or more when it is in-plane isotropic;
Elastic modulus is 10GPa or more, and strength for uniaxially stretched products
It has extremely excellent mechanical properties, with a tensile or flexural modulus of 40 GPa or more, and a high heat resistance and chemical resistance. Furthermore, it has extremely low thermal shrinkage and thermal expansion coefficients, and has good dimensional stability. Therefore,
Useful for many applications. For example, base film for magnetic tape, semiconductor-related applications such as IC,
Used for heat-resistant insulation applications, etc. Further, the sheet can be used as a structural material as it is or by laminating it.

Claims (1)

[Claims] 1 The repeating unit is essentially 2,2'-dichloro-
Consisting of a polymer consisting of 4,4'-biphenylenepyromellitamic acid and a mixed solvent system of at least one selected from amide solvents and urea solvents (A) and a halogenated hydrocarbon (B) A composition having a polymer concentration of 5 to 20% and A/B (volume ratio)
80/20 to 20/80.