JPS5910897B2 - Polyamide film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aromatic polyamide film having excellent strength, electrical properties, and heat resistance.

In recent years, improvements in the materials used as electrical insulating materials and the development of new materials have led to higher performance, smaller size, and lighter weight devices using these materials.

Among these, polyethylene terephthalate film is widely used as a general electrical insulating material due to its excellent strength and electrical properties. On the other hand, electrical insulating materials for high-speed motors such as Shinkansen trains and covering ultra-high voltage wires require heat resistance in addition to mechanical and electrical properties, so aromatic polyimide is used in this field. Films and aromatic polyamide papers have been developed and some products are now commercially available.

However, the former requires very expensive raw materials and a complicated manufacturing process, and the latter has inferior strength and electrical properties to polyethylene terephthalate film, so aromatic polyamide is used as a high-performance electrical insulating material. The film is expected to be put into practical use. In order to meet the needs of the industry, the present inventors have arrived at the present invention as a result of intensive research into a method for producing an aromatic polyamide film that can be put to practical use as an excellent electrical insulating material.

That is, the present invention has an intrinsic viscosity (F00.
(measured at 5y/100ml) has at least 1, 2 or more, and at least 50% of the repeating structural units are -HN
A substantially unoriented film made of an aromatic polyamide represented by HCO□Co- is first stretched 1.1 times or more in one direction at a temperature of 200° C. or higher, and then at a temperature higher than the temperature of the first stretching. This is a method for producing an aromatic polyamide film having excellent strength, electrical properties, and heat resistance, characterized in that the film is secondly stretched by 1.1 times or more in a direction substantially perpendicular to the direction of the first stretching.

As a preferable example of the aromatic polyamide used in the present invention, at least 50% of the repeating structural units are composed of m-phenylene isophthalamide units, and less than 5035% of the repeating structural units are composed of P-phenylene isophthalamide units, P-phenylene isophthalamide units, and P-phenylene isophthalamide units. Examples include those consisting of units such as nylentephthalamide, and these are:
It may be a regular, random or block copolymer, or it may be a blend polymer. The aromatic polyamide applied to the present invention was prepared at 25°C in a sulfuric acid solvent.
It is necessary that the intrinsic viscosity measured at a concentration of 0.5t/100ml is at least 1.1 or more, preferably 1.3 or more; if it is less than 1.1, the high performance film targeted by the present invention cannot be obtained. do not have.

An aromatic polyamide having an intrinsic viscosity of 1.1 or more can be obtained by reacting a corresponding diamine with a diacid chloride in an amide solvent using, for example, a conventional reactor equipped with a stirrer. In order to produce the substantially unoriented film used in the present invention from the aromatic polyamide thus obtained, for example, a thin film is formed from the aromatic polyamide and an amide solvent alone or a solution containing a salt such as calcium chloride. The formed thin film may be dried or coagulated in a suitable medium, washed with water, and then dried.

Among these, the formed thin film has a residual solvent amount of 50% by weight or less,
The method of drying to preferably 30% by weight or less, washing with water, and then drying is preferred in order to obtain a transparent film with excellent electrical insulation properties. As the amide solvent, any solvent that dissolves the above polyamide can be used, but examples include N-N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylpiperidone, N-methylcaprolactam, and N-methylacetamide. N-
N'・N'-tetramethylurea, N・N-N'・N-V
・N-hexamethylphosphoramide and the like are preferred. The substantially unoriented aromatic polyamide film used in the present invention is a highly non-crystallized film obtained by a dry method or a wet method, and the film is coated with a suitable agent such as an ultraviolet deterioration inhibitor. Also included are aromatic polyamide films mixed with antistatic agents, plasticizers, etc.

In the present invention, the film obtained in this way is first
．． Stretch 1 times or more.

In this case, stretching in the longitudinal direction using a roll or the like or in the lateral direction using a tenter is preferred since it is easy to operate, but the invention is not limited thereto. The stretching ratio needs to be 1.1 times or more, preferably 1.3 times or more. Heating methods during stretching include roll heating, atmosphere heating,
Any method such as infrared heating or microwave heating may be used, but a stretching temperature of 200° C. or higher, particularly preferably 250° C. or higher, is appropriate because the stress required for stretching is small. Further, when heat treatment is performed at a high temperature of 300° C. or higher, it is desirable to perform the stretching in an inert gas such as nitrogen to prevent thermal deterioration. Then, the film is secondly stretched by a factor of 1.1 times or more in a direction substantially perpendicular to the direction of the first stretching at a temperature higher than the temperature of the first stretching, preferably at least 5° C. higher than the temperature of the first stretching.

The reason why a higher temperature is required during the secondary stretching than during the primary stretching is to avoid cutting in the secondary stretching, where alignment occurs in one direction due to the primary stretching and stretching is performed in a direction perpendicular to the alignment direction. This is to reduce the stress required for stretching.

In the primary stretching of the present invention, it is desirable to perform uniaxial stretching of 1.3 times or more, but if the stretching ratio of the primary stretching is 2 times or more, for example, 2.5 times or more, the subsequent secondary stretching becomes difficult. becomes. However, even if the primary stretching is doubled or more,
If the film before stretching is stretched with at least 10% by weight of an aqueous solution containing less than 10% by weight of an amide solvent, even if the stretching ratio of the primary stretching is dramatically increased,
The next secondary stretching becomes easy. In addition, each stretching ratio is 1 unless balance in both directions is required.

If it is 1 times or more, the film will have sufficiently excellent performance.

Further, the aromatic polyamide film according to the present invention exhibits good properties as it is, but if dimensional stability is required, it may be further subjected to heat treatment.

The heat treatment may be carried out at a temperature of 280° C. or higher, preferably 300° C. or higher, thereby imparting a high degree of dimensional stability to the aromatic polyamide film of the present invention. Further, it is also possible to perform a hard tin processing before or after stretching.

Electrical articles using the aromatic polyamide film obtained as described above have excellent strength, electrical properties, and heat resistance.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 20% by weight of polymetaphenylene isophthalamide with an intrinsic viscosity of 1.60 (measured in sulfuric acid at 25°C and a concentration of 0.5t/100ml) and 4% by weight of calcium chloride were dissolved in N-N-dimethylacetamide. The solution was cast onto a casting roller, dried under a nitrogen stream heated to 150°C until the residual solvent amount was 40% by weight, washed with water for 30 minutes, dried, and then formed into an unoriented film with a thickness of 50μ. Obtained.

This unoriented film was stretched 1.5 times in the longitudinal direction between rolls heated at 250° C. at different circumferential speeds. Next, hold this vertically stretched film with a tenter, and
It was stretched 1.4 times in the transverse direction in an atmosphere at 70°C. Table 1 shows the performance of the obtained film. For comparison, the performance of a film obtained by heat-treating the film at 270° C. before stretching is shown. Examples 2, 3, 4, 5, 6 and comparative example 1
The substantially unoriented film obtained in Example 1 was stretched according to the method of the present invention under various stretching conditions.

Table 2 shows the stretching conditions and the performance of the obtained film. Furthermore, the results obtained when the stretching conditions were outside the range of the present invention are also shown as Comparative Example 1 for reference. Example 7 and Comparative Example 2 Intrinsic viscosity consisting of 70% metaphenylene isophthalamide units and 30% paraphenylene isophthalamide units 1.
84 (measured at 25°C in sulfuric acid at 0.57/100ml) and comparative example 2 with an intrinsic viscosity of 0.85 (measured at 25°C in sulfuric acid at 0,
An unoriented film of an aromatic polyamide copolymer (measured at 57/100 m1) was first stretched 1.4 times in the warp direction at 260°C, and then stretched 1.2 times in the cross direction at 270°C. .

The obtained film was placed in an oven maintained at 220° C., and changes in dielectric breakdown voltage over time were measured. Table 3 shows the results.
Shown below. It is clear from Table 3 that the film according to the present invention has a high dielectric breakdown voltage and excellent heat resistance.

Comparative Example 3 A film stretched 1.5 times in the vertical direction as in Example 1 was held in the same tenter as used in Example 1, and heated at 250°C.
When stretching was attempted in the horizontal direction in an atmosphere of

Claims (1)

[Scope of Claims] 1. Has an intrinsic viscosity (measured in sulfuric acid at 25°C at 0.5 g/100 ml) of at least 1.1, and at least 50% of the repeating structural units have a ▲ mathematical formula, chemical formula, table, etc. A substantially unoriented film made of aromatic polyamide shown by ▼ is first stretched 1.1 times or more in one direction at a temperature of 200°C or higher, and then at a temperature higher than the temperature of the first stretching. 1.1 times or more in a direction substantially perpendicular to the direction of primary stretching,
A method for producing an aromatic polyamide film, which comprises second stretching.