JPS6386731A - Production of poly-p-phenylene terephthalamide film - Google Patents

Abstract

PURPOSE:To obtain the titled transparent film having excellent mechanical characteristic in both longitudinal and width directions, by coagulating an isotropic dope consisting of poly-p-phenylene terepthalamide and concentrated sulfuric acid using a spcific coagulation bath and drying the film while limiting the shrinkage in obtaining the film from the dope. CONSTITUTION:An isotropic dope consisting of poly-p-phenylene terephthalamide and concentrated sulfuric acid is cast on a support surface, coagulated, washed and dried to give a film. In the process, the dope is coagulated using a coagulation bath consisting of an aqueous solution of sulfuric acid in 20-70wt% concentration at <=10 deg.C, preferably <=0 deg.C, washed and dried while limiting shrinkage to afford the aimed film. Thereby the ultrathin poly-p-phenylene terephthalamide film, having excellent heat resistance and transparency as well as high dielectric constant and suitable as insulators for capacitors, etc., is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a film consisting essentially of polyparaphenylene terephthalamide (hereinafter referred to as PPTA). More specifically, it is transparent, and the longitudinal direction (hereinafter abbreviated as MD direction) and longitudinal direction (hereinafter referred to as T direction) of the film.
The present invention relates to a manufacturing method for obtaining ultra-thin PPTA films, in particular, exhibiting excellent mechanical properties in both directions (D-force direction).

(Prior art) Linear aromatic polyamides, such as PPTA, have particularly excellent crystallinity and a high melting point, and due to their rigid molecular structure, they have heat resistance and high mechanical strength. It is a polymer material that has received particular attention in recent years. Furthermore, it has been reported that fibers spun from a concentrated solution exhibiting optical anisotropy exhibit high strength and modulus, and although this has already been implemented industrially, there are few proposals for its application to films. Special Publication No. 57-17886 is PPTA
This method shows extremely excellent mechanical properties in both the TD and MD directions by heating an optically anisotropic dope made of polyamide such as polyamide using concentrated sulfuric acid as a solvent, performing optical isotropy, coagulating, washing and drying. Although transparent films have been successfully obtained, it is very difficult to obtain ultra-thin films due to the relatively high concentration of the dope used. On the other hand, this publication discloses obtaining a transparent film from an isotropic dope, but after simply casting the isotropic dope onto a supporting surface,
Simply coagulating and washing the film results in a film that is unsatisfactory in both transparency and mechanical properties as it contains multi-barrel zide.

Furthermore, Japanese Patent Publication No. 57-35088 discloses that an optically anisotropic dope of polyamide such as PPTA using concentrated sulfuric acid as a solvent is extruded into a non-coagulable gas through an annular orifice, and while the dope is present in the non-coagulable gas. , it is stated that a transparent film is obtained by pressurizing gas into the inside of an IT-shaped film, but when the distance from the tubular orifice to the coagulation bath is 150 to 200 mm as described in these examples, the optical anisotropy The dope is never isotropic and only a thick film that is opaque and easy to avoid in one direction is obtained.

(Problems to be Solved by the Invention) The object of the present invention is to create an ultra-thin PPTA film that eliminates these drawbacks, has excellent transparency, and exhibits excellent mechanical properties in both the MD and TD directions. Our goal is to provide the B manufacturing method.

(Means for Solving the Problems) That is, the present invention provides a film in which an isotropic dope consisting essentially of polypara-7-ethylene terephthalamide and concentrated sulfuric acid is cast onto a supporting surface, and then coagulated and washed. In the manufacturing method, the coagulation bath is 20-70! of 106C or less! The present invention provides a method for producing a polyparaphenylene terephthalamide film, which is characterized by using a sulfuric acid water bath solution and drying while limiting shrinkage.

In the manufacturing method of the present invention, it is first necessary to prepare an isotropic dope of PPTA.

PPTA used in the present invention is a polymer substantially represented by, and is conveniently produced from conventionally known paraphenylenecyamine and terephthaloyl chloride by a low @ bath liquid polymerization method.

If the degree of polymerization of the polymer is low, it will not be possible to obtain a film with good mechanical properties, which is an aspect of the present invention.
Logarithmic viscosity ηinh (J
A acid 100! A polymer having a degree of polymerization that gives a value measured at 60° C. by dissolving polymer skin 29 in Ll is selected.

A suitable solvent for preparing the dope used for forming the PPTA film of the present invention is concentrated sulfuric acid, preferably sulfuric acid with a concentration of about 95% by weight or more. The sulfuric acid may have a concentration of 100% by weight or more, that is, fuming sulfuric acid, and may be used in combination with acetic acid such as Torino Roque 9onated acetic acid to the extent that it does not impair the effects of the present invention. .

The polymer concentration in the dope used in the invention is at room temperature (
(approximately 20 to 30'C), and a concentration that exhibits isotropy is preferably used, specifically 1 to 10! Jf Chi, good! Shikke 2 to 6-jyu-chi is used. At a polymer concentration of 10 μm or more, the polymer exhibits anisotropy and the formed film becomes thick, making it difficult to form an ultra-thin film (for example, a thickness of 6 μm or less).

On the other hand, it is difficult to obtain a film with practical @mechanical a performance from doping with too small polymer concentration.

In the present invention, the dope may be mixed with common additives, such as extenders, anti-glare agents, UV stabilizers, heat stabilizers, anti-aging agents, pigments, solubilizing agents, etc.

Whether a dope is anisotropic or isotropic can be determined by a known method, such as the optical method described in Japanese Patent Publication No. 50-8474, but the critical point depends on the type of solvent, temperature, Since it depends on the polymer concentration, polymerization degree of the polymer, amount of non-solvent, etc., it is possible to prepare an isotropic dope by examining these relationships in advance.

The method of the present invention is characterized in that the isotropic dope is cast in the form of a film on the support surface and then solidified at a low solidification rate. Use a sulfuric acid water bath solution. More preferably, it is a coagulation bath at 0°C or lower.

By using such a coagulation bath, the coagulation rate of the film can be reduced, thereby alleviating the formation of a so-called skin solidified layer on the film surface, reducing the difference from the internal solidified layer, and reducing the overall film thickness. It is presumed that the formation of voids due to large solidification shrinkage due to the low polymer concentration can be suppressed. Since the coagulated film as it is contains acid, it is necessary to wash and remove the acid as much as possible in order to produce a film whose mechanical properties are less likely to deteriorate due to heating. Specifically, it is desirable to remove the acid content to about 500 ppm or less, and more preferably to 200 ppm or less. Water is usually used as the cleaning liquid, but if necessary, hot water may be used, or washing may be performed by neutralizing with an alkaline aqueous solution and then using water or the like. Cleaning can be done, for example, by running the film in a cleaning solution,
This is done by spraying a cleaning solution or the like.

In the method of the present invention, the thickness and surface dimensions of the film change significantly before and after drying, and in this respect, special care must be taken during drying in order to obtain a high-quality film. That is, it is necessary to limit the shrinkage of the film under tension to prevent wrinkles. Here, under tension includes six modes: under tension, under constant length, contracted to an extent that wrinkles do not form, and slightly stretched. It is also possible to make the film thinner by stretching during drying or before and after drying.

However, any of the following methods may be used: drying on a heated roll, drying in a heated atmosphere with a tengu, drying in soricone oil, drying while fixed to a metal frame, etc.

The drying temperature is not particularly limited, but is preferably room temperature or above, and in order to effectively improve mechanical strength, a high temperature is preferable, and is preferably 100°C or above, more preferably 200°C.
The above is used. The maximum temperature for drying is not particularly limited, but in consideration of drying energy and decomposability of the polymer, it is preferably 500°C or less.

In producing the film by the method of the present invention, all of the above steps may be performed batchwise or continuously, and the film may be produced while running continuously throughout the entire process. This is one of the preferred embodiments. Further, an oil agent, an identification dye, etc. may be added to the film in any step.

(Example) Examples and reference examples (manufacturing examples of PPTA) are shown below, but these reference examples and examples do not limit the present invention in any way. In the examples, unless otherwise specified, "M parts" or "% by weight" are indicated.

The logarithmic viscosity ηinh is 98% sulfuric acid 100% and polymer 0.
2,! i' was resolved into Fj and measured at 30°C in a conventional manner.

The viscosity of the dope was measured using a B-type viscometer at a rotation speed of i rpm. The thickness of the film is 2Im in diameter.
Measurements were made using a dial gauge with a measuring surface.

The strength and elongation and modulus were determined by cutting a film sample into a rectangle of 100ta x 1 ONm using a constant speed extension type strength and elongation measuring machine, with an initial grasp length of 50m and a tensile speed of 30.
The cargo space-extension curve was drawn five times at a rate of n/min, and the calculation was made based on this. Next, the number of voids is measured as follows.

A film piece of an appropriate size is observed in at least 5 different fields of view at a magnification ranging from 100x to 400x using a normal optical microscope using transmitted light, and the number of voids with a major axis of 1 μ or more is determined. Count and convert it to 11!2 per 6 films.

Reference example (manufacture of PPTA) The following PPTA was obtained by a low temperature bath polymerization method.

In a mixing apparatus shown in Japanese Patent Publication No. 53-43986, 6 parts of anhydrous lithium chloride was added to 1000 parts of N-methylchloride.
Dissolve 5 parts and use paraphenylenecyamine 48.6
part was dissolved. After cooling to 8°C, 91.4 parts of terephthalic acid dichloride were added in powder form all at once. After a few minutes, the polymerization reaction product solidified into a cheese-like shape, so the
According to the method described in Japanese Patent No. 3986, the first reaction product was discharged from the polymerization apparatus, immediately transferred to a two-screw closed kneader, and the first reaction product was pulverized in the same kneader. Transfer the finely pulverized material to a hexiel mixer, add an equal amount of water, further pulverize, pass once, wash several times in hot water, and mix at 110°.
It was dried in hot air at C. Pale yellow P with ηinh of 5.0
95 parts of PTA polymer were obtained.

In addition, the polymer of ηinh can be easily obtained by changing the ratio of N-methylpyrrolidone and monomers (para-phenylenediamine and terephthalic acid dichloride) and/or the ratio between monomers.

Example 1 PPTA having an ηinh of 5.0 was dissolved in qq, 7 wt sulfuric acid at a polymer concentration of 6 h to obtain an isotropic dope at room temperature (60°0). The viscosity of this dope at room temperature is 80
It was 00 boys. This dope is degassed under reduced pressure,
609C was applied onto a glass plate using an applicator having a step difference of 0.01 sn. After application, 0°0150% sulfuric acid water bath solution, 60X amount of sulfuric acid aqueous solution at -10°C, and 40% at -5'C. Each was coagulated in an aqueous solution of IIk thiosulfuric acid, neutralized and washed with water, fixed in a metal frame in an air oven at 250°C, and dried. Above, 6
The properties of the films obtained under the two coagulation conditions are shown in the first example. Note that MD is the direction of the applicator, and TD is
is the direction perpendicular to it.

Comparative Example 1 The dope of Example 1 after degassing under reduced pressure was applied onto a glass plate at 60°C with an applicator having a step of 0.01 fl, and then heated in 15°C water, 30°C water, and 5'C ,10X
Coagulate in aqueous sulfuric acid solution, neutralize and wash with water.2
It was fixed in a metal frame and dried in an air oven at 50°C. The properties of the film obtained under the above conditions are shown in the second example.

(Left below) Example 2 PPTA having a 71nh of 4.0 was dissolved in 99.7wt sulfuric acid at a polymer concentration of 5t to obtain an isotropic dope at room temperature. The viscosity of this dope at room temperature was 12,000 voids. To make it easier to form a film, put it in a beaker,
It was kept at 60°0. Even then, the dope exhibits isotropy70
It was 00 boys. This dope is degassed under reduced pressure,
It was applied onto a glass plate at 30° C. using an applicator with a step height of 0.01. After coating, coagulate in -5°0140% by weight aqueous sulfuric acid solution, neutralize and wash with water.
Drying was performed while performing biaxial stretching in an air oven at 50°C. The properties of the film obtained under the above conditions are shown in the third example.

(Hereinafter referred to as extra color) (Effects of the invention) The film obtained by the method of the present invention is an ultra-thin PPTA film with high strength and high modulus and very few voids.
It is a film, and has high heat resistance, high transparency, and high appeal rate, so it is especially useful for insulators for capacitors, base films for magnetic tapes, tapes for thermal transfer printers, etc. In addition, it can also be used as a color decoration material, a light surface material for model airplanes, a wire covering material, a transparent film, etc.

Claims (1)

[Claims] In a film manufacturing method in which an isotropic dope consisting essentially of polyparaphenylene terephthalamide and concentrated sulfuric acid is cast onto a supporting surface, then coagulated and washed, 1 is used as a coagulating bath.
A method for producing a polyparaphenylene terephthalamide film, which comprises using a 20 to 70% by weight aqueous sulfuric acid solution at 0°C or lower and drying while limiting shrinkage.