JP2611194B2 - Aromatic polyamide film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aromatic polyamide film having excellent mechanical properties.

[Conventional technology]

Conventionally, aromatic polyamide has been used as a fiber having extremely high strength and elastic modulus without being subjected to drawing or heat treatment while air-jetting wet spinning of optically anisotropic dope, poly-p-phenylene terephthalamide, Poly p-
Compositions such as benzamide are known. However, they exhibit liquid crystal anisotropy and are practically useful as fibers which are one-dimensionally formed. However, in the case of films which are two-dimensionally formed, especially those mainly containing p-bonds have poor solubility. It was difficult to obtain a film having excellent two-dimensional properties from an organic solvent-based solution.

In view of these drawbacks, the addition of a copolymer component having a chlorine substituent as the main component in an aromatic polyamide mainly composed of p-bonding and further adding a copolymer component having no substituent in the nucleus makes it easier to dissolve in an organic solvent. It is known that a film forming method can be applied to obtain a film having a high elastic modulus to some extent.

[Problems to be solved by the invention]

However, in recent years, miniaturization of various recording and information devices,
Along with the demand for a large capacity, a film having much improved mechanical properties, especially elastic modulus, is desired. On the other hand, the polyamide-based film has an amide bond in its molecule, and has a disadvantage that its physical properties vary considerably with respect to moisture.
For example, water absorption of several percent to several ten percent may be shown.
It causes dimensional changes due to water absorption, decreases in strength and Young's modulus, and fluctuations in electrical characteristics (such as dielectric constant and dielectric power factor). Also, the dimensional change due to heat was large. Due to these drawbacks, no film has been provided which has both high rigidity, heat resistance, and dimensional stability against temperature and humidity, which can be used as a support film in recording / information materials.

An object of the present invention is to provide an aromatic polyamide film useful in recording material applications, information-related applications, electric / electronic material applications, etc. by solving the above-mentioned drawbacks.

[Means for solving the problem]

The present invention has substantially the general formula As a constituent unit (where m and n are integers from 0 to 3 and not simultaneously 0), and the remainder is an amide bond component having no substituent on the aromatic nucleus. A film composed of an aromatic copolymer polyamide having a unit as a constituent unit, wherein the film is formed through a process including multi-stage stretching, and in at least one direction in a stretched film state. Tensile modulus is 1800kg / mm ²
As described above, the present invention provides a high elastic modulus aromatic polyamide film having a humidity expansion coefficient of 8 × 10 ⁻⁶ mm / mm ·% RH or less.

Next, a method for producing the film of the present invention will be described. Conventionally, by selecting a specific composition of aromatic polyamide, even if the solution film is formed, that is, without stretching or heat treatment, the tensile strength and elastic modulus are unusually higher than the plastic film by the melt film forming method. It is known that a film can be obtained. As described above, the aromatic polyamide film is characterized by high tensile strength, elastic modulus, and excellent heat resistance as expected due to its molecular structure, intermolecular attractive force, and the like. Further, in order to improve the elastic modulus, a method of stretching at a relatively low temperature and a low magnification, and a one-step heat treatment or a multi-step heat treatment at a relatively high temperature are taught. However, aluminum foil has a significant disadvantage compared to an elastic modulus of about 7000 kg / mm ^2, and has a serious disadvantage that its dimensions change with changes in humidity.

As a result of intensive studies, the present inventors have adopted a multi-stage stretching process including a process of stretching a polyamide film having a selected composition in a wet state at a relatively low temperature and a process of stretching at a high temperature of 300 to 600 ° C. The film of the present invention has no problem of high elastic modulus and good humidity dimensional stability.

That is, the aromatic polyamide film of the present invention selects a specific composition containing a para-oriented chlorine nucleus-substituted polyamide as a main component, further discharges an isotropic dope dissolved in a solvent into air once, forms a sheet, and runs. After drying, multi-stage stretching including a step of stretching in a wet state and a step of stretching in a temperature range of at least 300 to 600 ° C., preferably 350 to 550 ° C. is performed, and the total stretching area ratio is 2.5 to 40 times, preferably Is obtained by stretching vertically and horizontally so that the magnification becomes 3 to 30 times.

In the prior art, stretching of a film at a high temperature of 300 ° C. or higher has not been adopted in terms of mechanical equipment, but equipment has been improved to obtain the film of the present invention.
In addition to performing multi-stage stretching at a temperature of 00 ° C. or higher, the inventors have found that high-magnification stretching can be performed in combination with wet stretching, and have obtained the film of the present invention. The transition point of the aromatic polyamide film of the present invention is inherently high (250 ° C. or higher). Therefore, when the film is drawn at a low temperature of 300 ° C. or lower, even if it is combined with wet drawing, the film enters the film at the time of drawing, and the draw ratio is low. It will break.

The above general formula of the present invention (Where m and n are integers from 0 to 3 and are not 0 at the same time). The unit is a main component containing 40 mol% or more and less than 90 mol%, and the monomer constituting such a structure is terephthalic acid. Acid chloride, 2-chloroterephthalic acid chloride, 2,5-
Dichloroterephthalic acid chloride, 2,6-dichloroterephthalic acid chloride, p-phenylenediamine, 2-chloro-
Examples include p-phenylenediamine, 2,5-dichloro-p-phenylenediamine, and 2,6-dichloro-p-phenylenediamine. When the chlorine content of the monomer is low or when the symmetry is good, and in the case of a homopolymer containing only the above-mentioned components, a high concentration of the organic solvent solution shows anisotropy. It becomes difficult. The monomer represented by the above general formula is used in the polymer used in the present invention.
The object of the present invention cannot be achieved unless it is 40 mol% or more and less than 90 mol%. That is, if the amount of the monomer is less than 40 mol%, a mechanically high-strength film cannot be obtained, and if it is more than 90 mol%, it becomes very difficult to prevent the precipitation.

However, even when such a component is used as a main component, a copolymer having uniform properties can be obtained by forming a copolymer as in the present invention and providing an isotropic solution.
Copolymer components selected for such purposes include:
An amide bond component unit having no substituent in the nucleus is defined as the above-mentioned copolymer component. The copolymer component unit includes, for example, the following structural units.

It is important that such copolymerized units be contained in the range of 10 mol% or more and less than 60 mol% in the whole polymer. That is, when such a unit is less than 10 mol%, it is difficult to dissolve in an organic solvent as described above, and the solution lacks stability,
It is not possible to form a film safely, and if it is more than 60 mol%, the strength and heat resistance are extremely poor.

In order to obtain a film with practical strength, the polymer must have an intrinsic viscosity of 1.0 or more (measured in a 0.5 g / 100 ml concentrated sulfuric acid solution at 30 ° C). If such a polymer is used The polymer concentration in the solution is preferably about 2 to 40%.

Copolymers comprising such components can be produced by ordinary low-temperature solution polymerization, interfacial polymerization, and the like, but polymerization in an organic solvent is more advantageous in that the polymerization solution can be used as it is for film formation. It is convenient.

The polymer composed of the above-mentioned components of the present invention alone forms a solution capable of forming a film. However, from the viewpoint of the stability of the solution, the addition of an inorganic salt can significantly improve the solution stability. Can be safely achieved.

The inorganic salt is suitably used in an amount of 20 to 150% by weight per polymer. If the amount is too small, gel-like substances increase, and if it is too large, undesired problems such as precipitation of undissolved inorganic salts occur.

Suitable inorganic salts include halides and hydroxides of alkali or alkaline earth metals, such as LiCl, CaCl ₂ , and MgCl ₂ .

As the organic solvent used in the present invention, polar aprotic solvents, particularly amide solvents, are excellent, such as N-methylpyrrolidone, N-ethylpyrrolidone, hexamethylphosphoramide, dimethylacetamide, dimethylformamide, and tetramethyl. Urea, γ-butyrolactone and the like can be mentioned, but a mixed solvent system can of course be used.

The film of the present invention may be blended with fine particles such as a lubricant, an antistatic agent, carbon black, titanium oxide, and alumina to such an extent that physical properties are not impaired.

The stock solution prepared as described above is discharged into an air layer, then dried by running, and then introduced into a coagulation solution to form a film by a so-called dry-wet method in which coagulation is extracted, or the stock solution is directly used. The film is formed by a so-called wet method of extruding into a coagulating liquid.

This liquid is generally composed of an aqueous medium, and may contain other organic solvents or inorganic salts other than water. However, in general, the water content is 30% by weight or more, preferably 50% by weight or more, and the bath temperature is usually used at 0 to 100 ° C to extract salts and organic solvents contained in the film. .

The dry-wet film forming method has the advantages of suppressing the generation of voids in the film and reducing unevenness in thickness, and is more preferably used.

To describe in more detail the case of film formation by the dry-wet method,
The stock solution is extruded from an orifice onto a suitable support such as a roll, belt, drum or the like to form a coating film.

Such a support is preferable from the viewpoint of film-forming properties when it is heated and maintained at a temperature of not higher than the solvent boiling point + 100 ° C. and at a temperature not lower than the stock solution temperature. In addition, as a method of forming a film, other than the above-mentioned orifice, a roll coating method, a knife coating method,
There are a method using an applicator and a method combining these methods.

In the dry process, the solvent is scattered from the coating layer on the support and concentrated to make the coating self-supporting. In this case, it is necessary to adjust the solvent so that the solvent does not suddenly scatter from the film surface. Usually, the treatment is carried out at a temperature above room temperature and below the boiling point of the solvent + 100 ° C, but it is sufficient that the treatment is carried out in an atmosphere from reduced pressure to normal pressure and in a temperature range not exceeding the boiling point of the solvent. . A homogeneous film becomes more difficult as the film thickness increases, but in such a case, it can be improved by reducing the solvent scattering speed. That is, it is dried at a low temperature for a long time.

The film after the dry process is peeled from the support and introduced into the wet process. Here, the inorganic salt contained in the film is removed. The wet bath has the same composition as that of the wet film forming bath, and a water-soluble organic solvent or inorganic salt is added in the same manner as described above in order to adjust the desalting rate in the desalting operation. is there. The desalination rate depends on the bath temperature, the higher the temperature, the faster it usually operates between room temperature and 100 ° C.

In order to obtain the film of the present invention, in the wet process, the film is stretched to 1.02 times or more and less than 1.5 times in the wet state in the bath. Stretching 1.05 times or more in this state facilitates stretching in the subsequent high-temperature stretching step.
However, stretching in the bath cannot be performed at a high magnification because of stretching at a low temperature.

Subsequent to the stretching in the wet state, stretching in an inert gas including a high-temperature stretching step is performed. This high area stretching ratio can be achieved by taking a multi-stage stretching process.
At least one of the stretching steps includes a high-temperature stretching step at 300 to 600 ° C, preferably 350 to 550 ° C.
As the stretching process, for example, vertical-horizontal, horizontal-vertical, vertical-horizontal-
Vertical, multi-stage vertical-horizontal, multi-stage vertical-horizontal-vertical, vertical-simultaneous biaxial, simultaneous biaxial-vertical, simultaneous biaxial-simultaneous biaxial, vertical-horizontal-simultaneous biaxial, vertical-horizontal-vertical-horizontal process And so on. Preferably, a high-temperature stretching step is incorporated in the last step of these multi-step steps. The high-rigidity film of the present invention cannot be obtained simply by casting or solidifying the polymer solution of the present invention. In addition, if only the stretching orientation at a temperature of 300 ° C. or less, which is usually adopted, the film is broken at the time of stretching, the stretching ratio does not increase, and a high-rigidity film cannot be obtained. In addition, in a single-stage high-temperature stretching step, uneven stretching occurs, tearing frequently occurs, and even if stretching can be performed, the elastic modulus does not improve. For stretching below 300 ° C,
The area stretching ratio does not reach 2.5 times or more.

Heating is performed in an atmosphere of an inert gas such as air, nitrogen, argon, or helium. The heating method uses a method in which these inert gases are heated and circulated through a circulating gas oven. In an inert gas atmosphere of
A method of heating by a hot wire such as a hot plate, a hot pin, an infrared lamp, and a condensing infrared heater, or various means such as high frequency heating and electromagnetic induction heating may be used. Preferably, in a high-temperature hot blast stove, it is good to make a short section stretch by contacting with a heating roll.

By adopting a multi-stage stretching process to achieve a high stretching ratio so that the total area stretching ratio is 2.5 to 40 times, preferably 3 to 30 times, the tensile elastic modulus in at least one direction in the film state is 1800 kg / mm ² or more can be expressed. For example, the first
1.3 times for longitudinal stretching in the first stage, 1.6 times for horizontal stretching in the second stage, 3rd
At the stage, the vertical stretching at 350 ° C or more is 6.0 times, and the total area stretching ratio is 12.5 times. Alternatively, in the above, in the third stage, high-temperature stretching at 350 ° C. or more, 3.0
If simultaneous biaxial stretching is adopted twice, the total area magnification is 18.7.
Double. The upper limit of the tensile modulus is not particularly limited, but is preferably about 9000 kg / mm ² .

In the present invention, the coefficient of humidity expansion in at least one direction is 8
The reduction to × 10 ⁻⁶ mm / mm ·% RH or less can be achieved by performing multi-stage stretching at a high temperature and increasing the stretching ratio much more than before. The lower limit of the humidity expansion coefficient is not particularly limited, but is preferably -1 × 10 ⁻⁵ mm / mm ·% RH.

The thickness of the film is not particularly limited, but if it is less than 0.5 μm, it is difficult to handle the film alone. If it is 250 μm or more, it takes time to evaporate the solvent, which is not preferable in terms of productivity. A more preferred thickness is 1 to 100 μ.

(Effect of the present invention)

The above-mentioned aromatic polyamide film of the present invention exhibits a high elastic modulus comparable to aluminum foil and good dimensional stability. Therefore, the film can be effectively used in the fields of information recording materials such as recording material supports, capacitor dielectrics, printed boards, and thermal transfer ribbons, and industrial materials.

 Hereinafter, the present invention will be further described with reference to examples.

Example 1 2-Chloro- was added to 500 ml of dried N-methylpyrrolidone.
9.72 g of p-phenylenediamine, 1.98 g of 4,4'-diaminodiphenylsulfone and 10 g of anhydrous lithium chloride are stirred and dissolved under a nitrogen stream. 15.45 g of terephthalic acid chloride is added at once to this solution cooled to 0 ° C., and the contents gradually become viscous when stirring is continued. After the addition, stirring was continued for 2 hours, and then the temperature was raised to room temperature, and 4.8 g of solid lithium hydroxide was added to neutralize the generated hydrogen chloride. This stock solution was stirred with a large amount of water in a mixer to reprecipitate the polymer and dried under reduced pressure. The polymer had an intrinsic viscosity of 3.5 in concentrated sulfuric acid at 25 ° C.

5 g of polymer, 5 g of lithium chloride and 95 g of N-methylpyrrolidone were stirred at room temperature to obtain a homogeneous solution. When this solution was heated at 150 ° C. for 2 hours, the change in turbidity was not noticeable. Next, this solution was uniformly cast on a glass plate to a thickness of 200 μm, and heated at 120 ° C. for 30 minutes to obtain N-methylpyrrolidone 8
Even after 5% of the film had been scattered, no significant clouding was observed in the film as measured by turbidity. This film was peeled off from the glass plate, immersed in running water at room temperature for 10 minutes, and stretched 1.2 times in the longitudinal direction in a wet state. Subsequently, the film is stretched 1.2 times in the transverse direction in a hot air oven at 280 ° C.
Hold under tension for minutes. The thickness of the obtained film is 17μ
The tensile modulus in the longitudinal and transverse directions is 1310 kg each.
/ mm ² , 1200 kg / mm ² . The longitudinal humidity expansion coefficient is 12.
It was 5 × 10 ⁻⁶ mm / mm ·% RH.

The sample film was cut to a width of 5 mm, and the polyamide film was brought into contact with a heating bar heated to 420 ° C. by using both hot air and a focused infrared heater. Was. The longitudinal stretching ratio was up to 6 times. The resulting film had a thickness of 9-11 μm.

The tensile modulus was determined from the gradient of the tangent line at the position of 2% elongation of the strain / stress curve at 25 ° C. and 65% RH using “Tensilon” manufactured by Toyo Sokki Co., Ltd. The sample was 10 mm in width and 100 mm in length (clamp interval), and the tensile speed was 500 mm / min.

As a method for measuring the humidity expansion coefficient, a film sample with a width of 10 mm and a length of about 400 mm with a mark near the upper and lower ends was subjected to a gravity of 100 g / mm ^{2 in} a cell with a glass window capable of adjusting the temperature and humidity. 50% R for 24 hours at a constant temperature of 25 ° C
After adjusting the humidity to H, track the increase in gauge length when the humidity inside the cell gradually increases from 50% RH to 80% RH at an average rate of 0.5% RH / min using a cassette meter or differential transformer. Then, the ratio of the increment to the initial length of the sample was obtained for the change in relative humidity.

As shown in Table 1, it can be seen that the elastic modulus is scatteredly improved by the high temperature re-longitudinal stretching, and the humidity expansion coefficient is sufficiently reduced by the high temperature re-longitudinal stretching.

Example 2 In Example 1, the stretching ratio in the machine direction under wet conditions was changed to 1.05.
A film was prepared in the same manner except that the transverse stretching ratio in hot air at 280 ° C. was changed to 1.05 times. The tensile modulus in the machine direction of the obtained film was 820 kg / mm ² .
Next, a strip sample having a width of 5 mm was subjected to high-temperature vertical re-stretching. At a stretching temperature of 400 ° C, stretching can be performed up to 4.7 times the stretching ratio.
The tensile elastic modulus in the machine direction of the obtained film was 4790 kg / mm ² . When the stretching temperature is raised to 410 ° C, the film can be stretched up to a stretching ratio of 5.2, and the tensile modulus in the machine direction of the film is 4860 kg / m.
Atsuta in m ^2. When the stretching temperature is further increased to 420 ° C, the film can be stretched to a stretch ratio of 6.0 times, and the tensile modulus of the film is 8780k.
It was dramatically improved with the g / mm ^2.

The figure shows the dynamic elastic modulus and ta of the film before hot stretching and the film stretched at 420 ° C by 6 times the stretching ratio.
nδ is displayed. The dynamic viscoelasticity was measured using a RHEOVIBRON DDV-II-EA manufactured by Toyo Boldouin Co., Ltd. at a frequency of 110 Hz and a heating rate of 2 ° C./min. It can be seen that the elastic modulus of the film is sufficiently improved by the high-temperature re-longitudinal stretching. When the dynamic elastic modulus at 200 ° C of the high-temperature re-stretched film is E (200 ° C) and the dynamic elastic modulus at 25 ° C is E (25 ° C), the retention of the dynamic elastic modulus at 200 ° C and 25 ° C h (however, Is calculated as 57.1% by reading each value from the figure. In addition, it can be seen from the figure that even at a high temperature side of 300 ° C. or higher, the elastic modulus retention rate is high and the heat resistance is excellent.

Comparative Example 1 This example is an example of a polyamide of the same bond type as in Example 1, but a non-nucleated polyamide. Example 1
8.64 g of p-phenylenediamine, 3.96 g of 4,4'-diaminodiphenylmethane and 10 g of anhydrous lithium chloride were dissolved in 500 ml of N-methylpyrrolidone dried in the same manner as described above, and 20.30 g of terephthalic acid chloride was added at 0 ° C. Stirred.

Simultaneously with the addition of the acid chloride, the system becomes cloudy and a polymer precipitates. Therefore, it cannot be used as it is as a stock solution for film formation. 5 g of the polymer is reprecipitated and dried with water.
g and 95 g of hexamethylphosphoramide were mixed and stirred at room temperature. However, the polymer was mostly insoluble, and film formation from this mixture was not possible. The polymer obtained had an intrinsic viscosity of 2.3 at 0.5 g / 100 ml in concentrated sulfuric acid.

Comparative Example 2 This example shows an example in which a nucleus has a chlorine substituent but is a homopolymer and is very easily precipitated.

17.70 g of 2,6-dichloro-p-phenylenediamine and 15 g of lithium chloride are dissolved in 500 ml of dried N-methylpyrrolidone, and 20.30 g of terephthalic acid chloride is added at -5 ° C. at once, followed by stirring for 1.5 hours. Was continued to obtain a uniform viscous solution. This solution is then applied to a glass plate for 200
When the film was uniformly cast into μ and placed in an oven at 80 ° C. for 2 minutes, the film became cloudy and showed 6.5 times that of the stock solution which had not received a heat history in terms of haze. The cloudy film was immersed in a large amount of water at 5 ° C. for 5 minutes, and further immersed in running water at room temperature for 10 minutes to perform desalting. Next, the film was heated at 300 ° C. for 5 minutes under a constant length to obtain a 11.5 μm film, which was a cloudy film. This film showed a tensile modulus of 450 kg / mm ² , but was a brittle film.

[Brief description of the drawings]

The figure shows the longitudinal dynamic modulus and tan δ of the aromatic polyamide film. In the figure, ●●●●● indicates a film before high-temperature stretching, and XXXXX indicates a film which was subjected to high-temperature re-longitudinal stretching at 420 ° C. and 6.0 times.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Reference number in the agency FI Technical display location C08L 77:10

Claims (1)

(57) [Claims] (1) a substantially general formula An amide bond component containing 40 mol% or more and less than 90 mol% as a constituent unit (where m and n are integers of 0 to 3 and not simultaneously 0), and having no substituent in the remaining aromatic nucleus. A film composed of an aromatic copolymer polyamide having a unit as a constituent component unit, wherein the film is formed through a process including multi-stage stretching, and in at least one direction in a stretched film state. Tensile modulus is 1800kg / mm ²
An aromatic polyamide film having a humidity expansion coefficient of 8 × 10 ⁻⁶ mm / mm ·% RH or less.