JPH0345732B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyamide-imide molded product having high elastic modulus and excellent heat resistance.

Fully aromatic polyimide has the highest heat resistance among organic polymers, and taking advantage of this characteristic, it has already been put to practical use in films and molded products. However, their tensile properties are very common, and their strength and modulus are not high. In recent years, it has been used for applications such as base films for magnetic tapes.
There is an increasing demand for films that have both high elastic modulus and heat resistance. In order to meet this demand, films of poly(2-chloro-P-phenylene terephthalamide) or wholly aromatic polyamides containing poly(2-chloro-P-phenylene terephthalamide) as a main component have been proposed in the past. These films do have high modulus,
Also, although it is not as good as polyimide in heat resistance, it is considerably superior. However, it cannot be said that these polyamide films are necessarily advantageous from the viewpoint of manufacturing process. In other words, while polyimide film can generally be formed using a dry method,
Polyamide film must undergo a wet process. This is because dibasic acid chloride is used in solution polymerization of polyamide, and therefore an inorganic base such as lithium carbonate or calcium hydroxide is usually added to neutralize hydrogen chloride produced as a by-product. Therefore, inorganic salts such as lithium chloride and calcium chloride are generated in the solution, and these cannot be removed by dry film forming, but must be removed by washing with water at an early stage of the film forming process. One possibility is to isolate the polymer, dry it, and then redissolve it in an amide solvent.
In the case of the above-mentioned polyamide, the result is the same because it will never dissolve unless an inorganic salt such as lithium chloride is present.

In the above-mentioned wet film formation of polyamide, there are the following problems. First, the solvent must be separated and recovered from the inorganic salt aqueous solution. Additionally, a portion of the neutralizing agent remains unreacted, increasing the burden of filtration. Furthermore, if washing with water is insufficient, inorganic salts remain in the film, which not only impairs the homogeneity of the film but also deteriorates its mechanical and electrical properties. Therefore, a polymer solution that does not contain an inorganic salt and is capable of forming a dry film is highly desirable from a process standpoint.

The inventors of the present invention have conducted extensive research with the aim of creating molded products such as in-plane isotropic or uniaxially oriented films that can be dry molded and have both high elastic modulus and heat resistance. It has been discovered that polyamideimide and its precursor polymer are suitable for this purpose, and the present invention has been achieved.

The molded product of the present invention consists essentially of the structural unit of the following formula, and 0.5 g of polyamic acid polymer as a precursor polymer/100 ml of solvent N-methylpyrrolidone (25
It is a polyamide-imide molded product with an intrinsic viscosity of 1.5 or more when measured under conditions of (℃).

As mentioned above, in the present invention, it is important that the polyamic acid, which is the precursor polymer, has an intrinsic viscosity of 1.5 or more. If it is less than 1.5, the mechanical properties of the final polyamide-imide molded product will be poor. Taking a film as an example, the molded product of the present invention has a strength of 20 Kg/mm ² or more and an elastic modulus of 800 Kg/mm ² or more when it is in-plane isotropic, and a strength in the stretching direction of 30 Kg/mm 2 when it is uniaxially oriented. ² or higher, and has an elastic modulus of 2,500 Kg/mm ² or higher, and has extremely high heat resistance and chemical resistance, making it useful for many applications.

The present invention will be explained in more detail below. The polyamide-imide molded product of the present invention is produced by polymerizing polyamic acid, which is a precursor polymer soluble in organic solvents, and then molding it into a film or the like, and then using an appropriate method to cyclize the amic acid units into imide groups. able to make. Therefore, first, a method for producing polyamic acid will be explained. The monomer used in the present invention has a diamine component of N,N'bis(2-chloro-4-aminophenyl).
It is terephthalamide (Di-CI-PTP), and the acid anhydride component is pyromellitic anhydride. Although some examples of the polymerization of aromatic diamines containing amide bonds and pyromellitic anhydride are known from USP 3, 179635, the above combination of polymers is new.
Di-CI-PTP is easily soluble in the amide solvent used for polymerization at room temperature and is easy to handle. On the other hand, monomers with the above structure without nuclear chlorine substitution, i.e., N,N'-
Bis(4-aminophenyl) terephthalamide is extremely poorly soluble and will not dissolve in an amide solvent at room temperature unless an inorganic salt such as lithium chloride is present. Therefore, polymerization in the presence of inorganic salts is inevitable, and therefore dry molding is not possible.

A polyamic acid solution is obtained by polymerizing the above Di-CI-PTP and pyromellitic anhydride in an amide solvent. Examples of the amide solvent used include N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and N,N-dimethylformamide.

In order to obtain the polymer of the present invention, a small amount of other monomers other than the above-mentioned monomers may be copolymerized. Such comonomers include p-phenylenediamine, m-phenylenediamine, benzidine, 2,2'-dichlorobenzidine, 2,7-
Diaminofluorene, 4,4'-diaminodiphenylmethane, 4,4'diaminodiphenyl ether,
Examples include 3,3'-diaminodiphenyl sulfone. In addition, acid anhydride components include 3, 3', 4,
4'-diphenyltetracarboxylic dianhydride, 3,
Examples include 3',4,4'-benzophenonetetracarboxylic dianhydride and 2,3,6,7-naphthalenetetracarboxylic dianhydride. The amount of these copolymer components used is within about 30 mol%.

Dry molding is performed using the polyamic acid solution thus obtained. The methods can be broadly classified into three types. The first method is to cast a solution of polyamic acid directly onto a flat plate, or extrude it through a slit die onto a belt or drum to form a film, etc., and then raise the temperature to evaporate the solvent and thermally cycle it. We will continue to develop In the second method, after molding into a film or the like using the above-mentioned means, a part of the solvent is evaporated, and then the molded product is immersed in a chemical cyclizing agent to chemically imidize it. As such a chemical cyclizing agent, aliphatic acid anhydrides such as acetic anhydride and propionic anhydride are suitable. An organic base such as pyridine, 3-methylpyridine, 3,5-lutidine, or quinoline may be used as a catalyst for this chemical cyclization. Further, other organic solvents can be used as diluents during chemical cyclization. Such diluents include dioxane, benzene, toluene, chloroform, carbon tetrachloride, acetonitrile, and the like. The processing conditions for chemical cyclization are a temperature of 15 to 50℃, and
Processing time is 10 minutes to 1 day.

In the third method, a chemical cyclizing agent is added to a polyamic acid solution at a temperature that does not substantially cause cyclization (below 10°C), and then after being molded into a film etc., the temperature is raised to a temperature at which cyclization occurs. to gel it and give it shape retention properties. The chemical cyclizing agent used is the same as that described above, and the amount added is preferably 1 to 4 equivalents relative to the amic acid unit. The temperature of the gelled molded product is further raised to evaporate the solvent and complete cyclization.

Although in-plane isotropic films do not require any particular hot stretching operation at any stage of the above process, biaxial stretching may be performed if higher tensile properties are desired. This stretching can be applied either simultaneously or sequentially, and the magnification is 1.05 to 1.4 times. If particularly high tensile properties are required in only one direction, uniaxial stretching is required. Its magnification is 1.3-2.5
It's double. The above-mentioned uniaxial or biaxial stretching may be carried out with a portion of the solvent remaining, or may be carried out after the solvent has been completely evaporated. In general, the former method can be stretched at a lower temperature and is preferable from the viewpoint of the process. Further, this hot stretching may be carried out by raising the temperature stepwise. The hot-stretched or non-hot-stretched molded product is finally heat treated at a higher temperature. The temperature is preferably 350°C or higher, and the atmosphere is air or an inert gas such as nitrogen.

The polyamide-imide molded article of the present invention can also be made by wet molding. In this case, the polyamic acid solution is extruded through a slit die into an aqueous coagulation bath and molded. The recipe for subsequent cyclization, hot stretching or heat treatment is almost the same as for dry molding.

For example, the polyamide-imide molded product of the present invention has a strength of 20 Kg/mm or more when it is in-plane isotropic, and a modulus of elasticity of 800 Kg/mm ² or more when it is uniaxially oriented, and a strength of 30 Kg/mm in the stretching direction when it is uniaxially oriented. ^mm2 or more, elastic modulus 2500
It has a high performance of Kg/mm ² or more, and also has extremely high heat resistance and chemical resistance, making it useful for many applications. For example, it is used as a base film for magnetic tapes, heat-resistant electrical insulation, etc. Moreover, laminated films can also be used as a structural material.

The present invention will be explained in further detail by the following Examples and Comparative Examples.

The intrinsic viscosity in the example is calculated by diluting the polymer solution with NMP to obtain a ratio of 0.5 g of polymer/100 ml of solvent.
Measured in °C.

Further, the tensile properties were measured using Tensilon manufactured by Toyo Saiki Co., Ltd. under conditions of a sample length of 25 mm and a tensile speed of 10 mm/min. In addition, in the case of an in-plane isotropic film, the sample width is 5 mm.

Example This example shows an example of the polymerization of polyamic acid from Di-CI-PTP and pyromellitic anhydride, and the results of forming a polyamide-imide film having the structural unit of the following formula by a dry process using the solution.

9.553 g of Di-CI-PTP was dissolved in 106 ml of dehydrated NMP, cooled in a 20°C water bath, and 5.017 g of pyromellitic anhydride was added with vigorous stirring. Polymerization was continued for another 5 hours at room temperature, and the polymer concentration was 12.1.
%, an intrinsic viscosity of 2.70, and a solution viscosity of 4450 poise (25°C).

Take 34.8g of the above solution and dilute it with 11ml of NMP, then -10
Cool in a dry ice-acetone bath at ℃, add 1.32 g of acetic anhydride (twice the equivalent of the amic acid unit), and pyridine.
A mixture consisting of 0.51 g (equivalent to an amic acid unit) and 5 ml of NMP was added dropwise over 5 minutes, and stirring was continued for an additional 10 minutes (polymer concentration 7.9%). This solution was cast onto a glass plate and heated in an oven at 70°C for 1 hour to obtain a chemically cyclized film with a polymer concentration of 85%.
Peel off this film from the glass plate, fix it on an 8cm square aluminum frame, and leave it in the air at 250℃ for 30 minutes.
Heat treatment was performed at 450°C for 4 minutes. The tensile properties of the obtained in-plane isotropic film (thickness 12.1μ) are 32
Kg/mm2, elongation 4.6%, and elastic modulus 1300 Kg/ ^mm2 .

The tensile properties of commercially available Kapton film made of poly(4,4'-oxydiphenylene pyromellitimide) are strength 20 Kg/mm ² , elongation 72%, and elastic modulus.
300Kg/mm ² , and compared to this, the film of this example has 1.6 times higher strength and 4.3 times higher elastic modulus.

On the other hand, the chemically cyclized dry film obtained by the above method and having a polymer concentration of 85% was cut into 5 mm widths and stretched 1.7 times using a hot plate at 190°C. Then in the air, 250
After treatment at ℃ for 30 minutes, use a hot plate at 400℃ for 5 seconds.
A tension heat treatment was performed, and a relaxation heat treatment was further performed at 450° C. for 1 minute in air. The resulting uniaxially stretched film (width 2.1
The tensile properties of the material (thickness: 112.5 μm) were strength: 52 Kg/mm ² , elongation: 0.8%, and elastic modulus: 4900 Kg/mm ² . The first part of the SS curve of this film was a slightly downwardly convex curve, and the elastic modulus determined from the slope of the straight part was 7400 Kg/mm ² .

Comparative Example This comparative example shows the results of film formation using a chemical cyclization dry method of poly(p-phenylenepyromellitimide).

p-phenylenediamine and pyromellitic anhydride were reacted in NMP using almost the same recipe as in Example 1,
A polyamic acid solution with a polymer concentration of 10.0% and an intrinsic viscosity of 2.75 was obtained.

Take a portion of this solution and dilute it with NMP, then -10
It was cooled to ℃, and acetic anhydride equivalent to twice the amic acid unit and pyridine equivalent were added dropwise (polymer concentration 6.9
%). This solution was cast onto a glass plate, treated in an oven at 70°C for 1 hour, fixed on an 8 cm square aluminum frame, and treated in an oven at 300°C for 30 minutes. The film I took out was torn, and the pieces were so fragile that I could barely touch them.

The polyimide of this comparative example has a sufficiently rigid structure suitable for a high modulus film, and even though the polyamic acid precursor polymer has a high intrinsic viscosity, a high-performance film could not be obtained. .

Claims (1)

[Scope of Claims] Consisting essentially of structural units of the primary formula, and having an intrinsic viscosity of 1.5 when measured under the conditions of 0.5 g of polyamic acid as a precursor polymer/100 ml of solvent N-methylpyrrolidone (25°C) Polyamide-imide molded product as described above.