JPH0136787B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a fully aromatic polyimide laminate that has extremely high mechanical properties, particularly flexural modulus, and excellent heat resistance and chemical resistance. be.

[Prior Art] Fiber-reinforced composite materials are known and are already widely used as materials that have mechanical properties similar to those of metals such as aluminum, are lightweight, and are useful as structural materials. The disadvantage was that it was quite complicated.

[Problems to be Solved by the Invention] As a result of intensive research aimed at creating a material that can be produced through a simple process, is lightweight, and has excellent mechanical properties, the present inventors have discovered that a laminate of a specific wholly aromatic imide polymer has been developed. The present invention has been achieved based on the discovery that it is suitable for this purpose.

[Means for Solving the Problems] The present invention involves thinly applying a solution of polyamic acid, which is a precursor polymer of the same polymer, to both sides of a uniaxially stretched film of a wholly aromatic imide polymer having a tensile modulus of 80 GPa or more. Once dry, multiple sheets are laminated and approximately
This is a method for producing a polyimide laminate, characterized by thermocompression bonding at a temperature of 390 to 450°C.

The present invention will be explained in detail below.

Polyimide laminates are often laminated with uniaxially stretched films aligned in the stretching direction, and the flexural modulus of such laminates in that direction is usually 60 GPa or more, comparable to that of aluminum. However, the mechanical properties in the width direction are not excellent. For molded products that require a certain degree of elasticity not only in the longitudinal direction but also in the transverse direction, cut a section at an appropriate angle from the stretching direction and laminate the appropriate number of pieces of film in the original stretching direction. This makes it possible to improve the modulus of elasticity in the transverse direction. In addition, the polyamic acid applied to both sides of the uniaxially stretched film acts as an adhesive.
During thermocompression bonding, it is thermally ring-closed to the same polyimide.

In the present invention, the tensile modulus in the stretching direction
First, we will explain the fully aromatic imide-based polymer that provides a uniaxially stretched film of 0 GPa or higher. Such polymers are so-called rigid and rigid wholly aromatic imide-based polymers, and are made into films using a dry or wet method from a solution of polyamic acid, which is a precursor polymer, and are then uniaxially stretched and thermally ring-closed to improve tensile elasticity in the stretching direction. A film with a rate of 80 GPa or higher can be obtained. As such a rigid polymer, a polymer whose crystallinity has been appropriately reduced by nuclear halogen substitution or the like is preferable. Specific examples include poly(2,2'-dichloro-4,4'-biphenylenepyromellitimide), poly(2,6'-dichloro-4,4'-biphenylenepyromellitimide),
Poly(2,2'-dibrome-4,4'-biphenylenepyromellitimide) and the like. Furthermore, the material is not limited to polyimide, but may be a rigid polymer having bonds other than imide bonds. Such polymers include: That is, 4′,4″-diamino-2′,
2″-Dichloroterephthalalinide (Di-Cl-
PTP) and pyromellitic anhydride (PMDA), polyamideimide, 4′,4″-diamino-2′,2″-
Examples include a polymer made of dibromoterephthalalinide and PMDA, or a polyamide ester imide made of Di-Cl-PTP and p-phenylene bistrimethate dianhydride. Although homopolymers and regular copolymers have been exemplified above, random copolymers obtained by adding a small amount of a third component, preferably 20 mol % or less, to the above polymer may also be used. Such copolymer components include diamine such as 2-chloro-p-phenylenediamine, and acid hydrate such as 3,
3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyl ether tetracarboxylic dianhydride, 3,3',
Examples include 4,4'-biphenyltetracarboxylic dianhydride. A solution of polyamic acid, which is a copolymer of these imide-based polymers, can be easily obtained by polymerizing the above-mentioned monomers using an amic acid-based solvent such as N-methylpyrrolidone (NMP) by a known method.

Next, a film is made using the above polyamic acid solution. A dry method is usually used as a film forming method, which can be broadly classified into the following two methods.

In the first method, the polyamic acid solution is cast directly onto a flat plate or extruded through a slit die onto a belt or drum to form a film, and then the solvent is evaporated to impart shape retention.

The second method is to add a chemical cyclizing agent such as acetic anhydride to a polyamic acid solution at a temperature that does not substantially cause ring closure (below 10°C), then form it into a film, and then cyclize it. The temperature is raised to a certain temperature to partially promote imidization, resulting in gelation and shape retention. Its temperature is usually 50-150°C. The solvent content obtained by the first or second method in this way
The 10-40% by weight film is then hot stretched in one direction. The temperature is 150 to 350°C, and the stretching may be performed by increasing the temperature stepwise. The hot stretched film is further heat treated at a higher temperature to promote cyclization and completely evaporate the solvent. In this way, a uniaxially stretched film having a tensile modulus in the stretching direction of 80 GPa or more can be obtained.

Next, a solution of polyamic acid, which is a precursor of the same polymer, is thinly coated on both sides of the uniaxially stretched film, and then once dried. There is no particular restriction on the thickness of the coating layer, but although the polyamic acid in the coating layer is ultimately thermally ring-closed to the same polyimide, it is non-oriented and therefore hardly contributes to mechanical properties. Therefore, it is preferable to make it as thin as possible within a range that can ensure adhesiveness. For this purpose, the polyamic acid solution may be appropriately diluted and applied. Moreover, the drying temperature is 50 to 200°C.

Next, a plurality of uniaxially stretched films coated with polyamic acid on both sides are laminated and bonded under heat to form a molded product. In this case, the materials are usually laminated aligned in the stretching direction, and the flexural modulus of such a laminated product in that direction is 60 GPa or more. Furthermore, by cutting a section at an appropriate angle from the stretching direction and laminating it with an appropriate number of films in the original stretching direction, it is possible to improve the bending modulus not only in the longitudinal direction but also in the lateral direction to some extent. Thermocompression bonding is ultimately performed at a temperature of approximately 390 to 450°C, but lower temperatures,
For example, the temperature may be increased stepwise from about 150°C. Adhesion will not be sufficient if the final temperature is below approximately 390°C. Furthermore, temperatures of about 450° C. or higher are undesirable because the polymer undergoes thermal decomposition and its mechanical properties deteriorate.

[Effects of the Invention] The polyimide laminate of the present invention has extremely high mechanical properties, particularly flexural modulus, and is lightweight with a density of about 1.5. Furthermore, it has excellent heat resistance and chemical resistance. Therefore, it is extremely effective as a structural material in place of metal.

[Example] The present invention will be explained in further detail by the following example.

The intrinsic viscosity (η _ioh ) of the polyamic acid in the example was measured at 25° C. after diluting the polymer solution with NMP to a ratio of 0.5 g of polymer/100 ml of NMP.

In addition, the tensile properties of the uniaxially stretched film were measured using Tensilon manufactured by Toyo Baldwin Co., Ltd., with a sample length of 100 mm.
Measurement was performed at a tensile speed of 20 mm/min. In addition, the elastic modulus was measured by changing the sample length in the range of 50 to 100 mm.
The compliance of the equipment system was corrected by extrapolating the sample length to infinity.

The flexural modulus of the laminate was measured by the simple beam deflection method. That is, the distance between the supporting points was set to 100 mm, a load was applied to the center of the test piece, and the bending elastic modulus was calculated from the amount of deformation (deflection) read with a cassette meter.

Example In this example, the diamine component is 4′,4″-diamino-
2′,2″-dichloroterephthalarinide (Di−Cl−
PTP), and an example of creating a uniaxially stretched film of a copolymer whose acid anhydride components are PMDA (85 mol%) and BTDA (15 mol%), and after coating the film with a polyamic acid solution of the same polymer and drying. The results of lamination and thermocompression bonding are shown.

The above monomers were reacted in NMP solvent to obtain a polyamic acid solution with an intrinsic viscosity of 2.13 and a polymer concentration of 11%. This solution was cast onto a glass plate to a thickness of approximately 200 μm and heated in an oven at 90° C. for 20 minutes to obtain a film with a polymer concentration of 65%. Peel this film from the glass plate, cut it into 10mm wide pieces, and heat it at 200℃.
After stretching 1.70 times in air using a manual stretcher,
The mixture was heated in an oven at 210°C for 10 minutes and then at 280°C for 30 minutes to promote thermal ring closure and evaporate NMP.
Furthermore, it was subjected to tension heat treatment using a hot plate at 330°C.

A portion of the film was taken and heat treated in an oven at 400°C for 3 minutes. This film (5.4mm width,
The tensile properties of 20μ thick) were as follows.

Strength 0.91GPa, elongation 1.0% Apparent elastic modulus 99GPa, corrected elastic modulus 127GPa.

The same polyamic acid solution used for film formation was applied to both sides of the film, which had been tension-treated using the 330℃ hot plate described above, to a thickness of about 15μ, and then heated in an oven at 90℃.
It was heated and dried for 10 minutes. These 13 films were stacked in the stretching direction, pressed at 150℃ and 50Kg/cm ² , and then pressed at the same pressure for about 17 minutes.
The temperature was raised to 250℃. Then, the pressure was increased to 250 Kg/cm ² and the temperature was raised to 400° C. over 28 minutes. The obtained laminated sheet (6.3mm width, 290μ thickness) had good adhesion between the films, and the bending elastic modulus in the stretching direction was
It was 98GPa.

Claims (1)

[Claims] 1. A solution of polyamic acid, which is a precursor polymer of the same polymer, is applied thinly to both sides of a uniaxially stretched film of a wholly aromatic imide-based polymer with a tensile modulus of 80 GPa or more, and after drying, multiple sheets are laminated to form a film with a tensile modulus of about 390 GPa or more. ~450
A method for producing a polyimide laminate, characterized by thermocompression bonding at a temperature of °C.