JPH0264135A - Heat-adhesive polyamide film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a polyamide film, particularly a film made of a para-oriented aromatic polyamide, and more specifically, in the longitudinal direction of the film (hereinafter referred to as MD force direction) and The present invention relates to a polyamide film that exhibits excellent mechanical properties in both the width direction (TD force direction) and has thermal adhesive properties.

[Prior Art] Para-oriented aromatic polyamides have particularly excellent crystallinity and high melting points, and due to their rigid molecular structure, they have heat resistance and high mechanical strength, and have attracted particular attention in recent years. It is a polymer material that has been used for many years. It has also been reported that fibers spun from a thick solution exhibiting optical anisotropy exhibit high strength and modulus, and have already been implemented industrially. There are few proposals, and there are still no known examples of practical use.

Problems with para-oriented aromatic polyamides include:
The useful high molecular weight polymers are poorly soluble in organic solvents, necessitating the use of strong inorganic acids such as concentrated sulfuric acid as the solvent.

Several methods have been disclosed for obtaining a film by extruding and coagulating an optically anisotropic dope of aromatic polyamide having a disorienting property (Japanese Patent Publication No. 5914567,
Special Publication No. 57-35088, Special Publication No. 59-5407
(Japanese Patent Application Laid-open No. 54132674). However, these methods are difficult to use as a practical industrial method for producing films because the anisotropy of the physical properties of the obtained film is too large and the production method is complicated.

Japanese Patent Publication No. 57-i7886 discloses that by heating an optically anisotropic dope of para-oriented aromatic polyamide until it becomes optically isotropic immediately before solidifying it, and then solidifying it, it is transparent and has equal mechanical properties. It is described to obtain films that are symmetrical. This method is an original method that goes against the conventional concept of achieving high performance by utilizing optically anisotropic doping. At the same time, it has been successfully avoided that the liquid crystal domain structure of the optically anisotropic dope remains even after the dope is extruded and solidifies as it is, resulting in an opaque film.

The aramid film produced by this method has excellent mechanical properties, heat resistance, chemical resistance, dimensional stability, etc.
magnetic tape, photographic film, capacitor film,
Electrical insulation film 1. It is expected to be used as a material for ink ribbons for thermal printers, films for flexible printed wiring boards, etc.

However, para-oriented aromatic polyamide has very high heat resistance and does not have a softening temperature, so it is inconvenient to use because it does not have the thermal adhesive properties of films made of ordinary thermoplastic or thermosoftening polymers. may occur. For example, heat fixation after winding up a film in the production of film capacitors, heat fixation after coating in wire coating, etc. cannot be performed.

(Problems to be Solved by the Invention) An object of the present invention is to provide a high-performance film using a para-oriented aromatic polyamide, and a heat-fusible polyamide film.

[Means for Solving the Problems] As a result of extensive research to obtain a polyamide film that meets the above objectives, the present inventors have discovered, for example, Japanese Patent Publication No. 57-1
The technique disclosed in '7886, that is, an optically anisotropic dope of para-oriented aromatic polyamide is first made;
In a specific para-oriented aromatic polyamide film obtained by a method of coagulating this by optical isostatic ratio, by containing a thermoplastic fluoropolymer on the surface or inside of the film, para-oriented aromatic polyamide It was discovered that heat fusion properties can be imparted without impairing the high performance of the film, and after further research, the present invention was completed.

That is, the present invention is made essentially of a para-oriented aromatic polyamide with a logarithmic viscosity of 3.5 or more, a tensile elongation in the direction parallel to the film surface of 8% or more, and The present invention is a heat-fusible polyamide film characterized by having a thermoplastic fluorine-based polymer.

The para-coordinating aromatic polyamide used in the present invention (where R is a hydrocarbon group such as methyl, ethyl, phenyl, etc. or a halogen such as C1, Br, etc., and A is 0-1-3
It is a polyamide consisting essentially of a component in which an amide group is bonded to the para position of a benzene ring forming the main chain, such as S GHz).

Among these, aromatic polyamide films containing halogen atoms may cause corrosion to the metal layer of the conductor after long-term use, so aromatic polyamide films that do not substantially contain halogen atoms are preferably used. . Particularly preferably used is poly-p-phenylene terephthalamide (abbreviated as PPTA).

The degree of polymerization of the polymer of the present invention is 3.5 or more, since if it is too low, a film with good mechanical properties cannot be obtained.
Logarithmic viscosity η1nh (sulfuric acid 10(
Poly on 1+1? -0.5 g-t-value measured at 30°C when dissolved) is selected.

The film of the present invention can achieve its purpose only if it satisfies the following two requirements.

First of all, the film of the present invention needs to have a tensile elongation of 8% or more in the direction parallel to the film surface. Films with an elongation less than 8% tend to tear easily and are not practical.

A preferable tensile elongation is 10% or more. The high elongation of the film of the present invention is related to the process of casting an optically anisotropic dope onto a support surface and then making it optically isotropic.

Second, the film of the present invention needs to have a thermoplastic fluoropolymer on its surface and/or inside.

Here, thermoplastic fluoropolymers include, for example, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, trifluorochloride ethylene fluoropolymer, etc. It needs to exist in a layer on the surface or be dispersed in the form of fine particles inside the film, and it is possible to have both states.

If it exists in a layer on the surface of the film, the thickness is 0.1μ
m to 25 μm, preferably 0.1 μm to 5 μm
m is more preferred. On the other hand, when dispersed inside in the form of fine particles, the size of the dispersed particles is preferably 2 μm or less, and 1 μm or less.
The following are more preferable. The content of the fluorine-based polymer is preferably 0.1% to 20% based on the para-coordinating aromatic polyamide.

The film of the invention preferably also has the following properties:

For example, the film of the present invention has a Young's modulus in at least one direction of 800 kg/mm 2 or more.

This condition is closely related to the deformation resistance of the film, and more preferably the Young's modulus in at least one direction is 1.
300 kg/nun” or more, most preferably 15
00 kg/In1ll" or more. There are two aspects of the film of the present invention. One is a balanced type with vertical and horizontal Young's modulus of 800 kg/mm" or more, which are almost equal, and the other is a balanced type. One is the tensilized type, which has a large Young's modulus in either the vertical or horizontal direction, and is 1000 kg/threshold 2 or more.

Further, it is preferable that the film of the present invention is substantially free of voids.

Furthermore, the film of the present invention typically has a density of 1.3
It is in the range of 70-1.420 g/cffl. This density value was determined at 30°C by density gradient tube method using carbon tetrachloride-toluene.

This density range is 1.4% higher than that of known PPTA fibers.
This value is considerably smaller than the range of 3 g/ctl to 1.46 g/c+fl. The density is 1.37
When it is less than 0 g/cff1, mechanical properties deteriorate;
If it exceeds 420 g/cffl, the film will have poor planar orientation and thus poor isotropy in mechanical properties. In any case, this low density results in a light and high-strength film.

The film of the present invention preferably has plane orientation defined by the crystal orientation angle determined by X-ray diffraction described below. In other words, the crystal orientation angle with respect to the peak of 2θζ23° caused by X-rays incident at right angles to the film surface is 30° or more, and the 2θ angle caused by X-rays incident parallel to the film surface is 30° or more.
It is preferable that the crystal orientation angle regarding the ζ18' peak is 60° or less.

There are two types of incident X-rays: when they are incident at right angles to the film surface (hereinafter referred to as the TV direction), and when they are incident parallel to the surface (hereinafter referred to as the TV direction).
(hereinafter referred to as SV force direction). The film of the present invention has a large diffraction peak at 2θL=23° due to X-rays from the TV direction, but the crystal orientation angle at 2θ-23° is preferably 30° or more, more preferably 50° or more. It is more preferable. Furthermore, a large diffraction peak at 2θ', 18° appears on the equator line due to incidence in the S force direction, and it is preferable that the crystal orientation angle at 2θ', 18° is 60° or less. When both of these crystal orientation angles are satisfied, it can be said that the film of the present invention has a so-called plane-oriented structure, and has high mechanical properties both in the direction in which the film is taken and in the direction perpendicular thereto. It is highly preferred since it has high tear strength.

A known method can be used to measure the crystal orientation angle.
For example, the following method is used. Predetermined 2θ
A diffraction intensity curve is obtained by placing the counter at an angle of and rotating the film 180°. In addition, in the case of a TV, the maximum intensity is the center and the rotation is made between 90 degrees in front and back.

The value of the arc length in degrees in the diffraction photograph corresponding to the point indicating half the intensity of the highest intensity of this curve with respect to the Haese line drawn between the lowest intensity points (i.e., the value of the arc length in degrees for the point that is 50% of the Haese line of maximum intensity) angle) and use it as the crystal orientation angle of the sample. During the measurement, the diffraction intensity can be measured by stacking several films if necessary.

Next, a method for obtaining such a film will be explained using an example in which PPTA is used as the polymer.

To obtain a PPTA film, it is first necessary to adjust the optical anisotropy dope.

A suitable solvent for preparing the dope used for casting PPTA films is sulfuric acid at a concentration of 95% by weight or more. 9
If the sulfuric acid content is less than 5%, dissolution may be difficult or the dope after dissolution will have an abnormally high viscosity.

Dope contains chlorosulfuric acid, fluorosulfuric acid, phosphorus pentoxide,
A small amount of trihalogenated acetic acid or the like may be mixed.

Sulfuric acid can be used in a concentration of 100% by weight or more, but from the viewpoint of stability and solubility of the polymer, a concentration of 98 to 100% by weight is preferably used.

The polymer concentration in the dope is at room temperature (approximately 20 to 3°C)
or more than a concentration that exhibits optical anisotropy at a temperature higher than that, specifically about 10% by weight or more,
Preferably, a concentration of about 12% by weight or more is used. At polymer concentrations below this, ie, polymer concentrations that do not exhibit optical anisotropy at ambient or higher temperatures, the cast PPTA film often does not have favorable mechanical properties. The upper limit of the polymer concentration of the dope is not particularly limited, but is usually 20% by weight or less,
Particularly for PPTA with high ηinh, the amount is preferably 16% by weight or less, and more preferably 13% by weight or less.

When a thermoplastic fluoropolymer is contained inside the film, it is necessary to add fine particles of the fluoropolymer to the dope. Examples of the addition method include dispersing the fluoropolymer in a solvent such as sulfuric acid and then dissolving PPTA;
A method such as mixing PPTA and a fluoropolymer in powder form and then melting the mixture in a solvent can be used.

The dope used in the present invention includes, for example, an extender, a light remover,
Additives such as ultraviolet stabilizers, heat stabilizers, antioxidants, pigments, solubilizing agents, and lubricants may be mixed.

Whether the dope is optically anisotropic or optically isotropic can be determined by a known method, such as the method described in Japanese Patent Publication No. 50-8474, but the critical point depends on the type of solvent, temperature, polymer Since it depends on the concentration, polymerization degree of polymer, content of specific solvent, etc., by investigating these relationships in advance, optically anisotropic dope can be created, and by changing the conditions for optically isotropic dope, optically anisotropic It is possible to change from tropic to optically isotropic.

The dope thus prepared is cast onto a support surface from a slit die, for example, while maintaining its optical anisotropy. In addition, in the laboratory, it can also be cast onto a glass plate using a doctor knife.

In the present invention, even if steps such as casting and subsequent conversion to optical isotropy, solidification, washing, stretching, and drying are performed continuously, all or part of these steps may be performed intermittently, that is, batchwise. You may do so. A preferred method is one in which the casting step is carried out continuously, and the moving speed of the support surface on which the dope is cast is at least twice the linear speed at which the dope is discharged from the die.

The supporting surface used in the present invention can be shaped like a belt or drum,
The material is not particularly limited as long as it is acid-resistant and can be surface-finished; for example, it may be plated with glass, Hastelloy, tantalum, gold, platinum, titanium nitride, etc. Metals and the like are preferably used, and those with a so-called mirror finish are particularly preferred.

In the method for obtaining the film of the present invention, after the dope is cast onto a support surface, the dope is converted from optically anisotropic to optically isotropic prior to solidification.

Specifically, in order to convert optical anisotropy to optical isotropy, the optically anisotropic dope cast on the support surface is allowed to absorb moisture prior to solidification to reduce the concentration of the solvent that forms the dope. The dope can be transformed into an optically isotropic region by changing the solubility and polymer concentration, or the temperature of the dope can be increased by heating to transform the dope phase into an optically isotropic region, or the phase of the dope can be transformed into an optically isotropic region by changing the solubility and polymer concentration, or by simultaneous or simultaneous absorption of moisture and heating. This can be achieved by sequential combination use. Among the above methods, the method using moisture absorption, including the method using heating in combination, is useful because the optical isotropic ratio of optical anisotropy can be achieved efficiently and without causing decomposition of PPTA.

To make the dope absorb moisture, air at normal temperature and humidity may be used, but humidified or heated and humidified air is preferably used. The humidified air may contain atomized moisture exceeding the saturated vapor pressure, and may be so-called water vapor. However, 1. Supersaturated steam at temperatures below about 45° C. is undesirable because it often contains large particles of condensed water. Moisture absorption is usually carried out by humidified air at room temperature to about 180°C, preferably 50 to 150°C.

In the case of a heating method, the heating means is not particularly limited;
Examples include a method of applying humidified air to the casting dope as described above, a method of irradiating with an infrared lamp, and a method of using dielectric heating.

The optically isotropically cast dope on the support surface is then solidified. In the present invention, a 30% by weight or more sulfuric acid aqueous solution is preferable as the dope coagulation liquid.

If the sulfuric acid aqueous solution is less than 30%, it becomes difficult to obtain a film with excellent surface precision, probably because the coagulation rate of the dope including water is too high. The coagulation bath is preferably a 40 to 70% by weight aqueous sulfuric acid solution.

In the present invention, the temperature of the coagulating liquid is preferably 10'C or less. This is because it has been found that the lower the temperature, the lower the solidification rate and the tendency for the film to contain fewer voids, thus improving the surface precision of the film.

The coagulation bath temperature is preferably 5°C or less, more preferably 0 to -40°C.

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. 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 washing with water. Cleaning is carried out, for example, by running the film in a cleaning liquid or by spraying the cleaning liquid.

The washed film may then be stretched in the wet state if desired before being subjected to drying. Stretching is performed in one direction or two directions at a stretching ratio of 1.05 times or more. At this time, it is often observed that the moisture contained in the film comes out like sweat. In the case of stretching in the (2) direction, it may be in the MD force direction or in a direction perpendicular thereto, and the stretching ratio is preferably about 1.1 to 1.7 times.

Stretching in two directions may involve simultaneous biaxial stretching, or sequential stretching in one direction.
It may be stretched axis by axis. In the case of bidirectional stretching, the stretching ratio is preferably about 1.07 to 1.5 times. Since the PPTA molecular chains can be oriented in the stretching direction by stretching,
Mechanical properties are improved.

Drying must be carried out under tension, at a constant length, or with slight stretching to limit shrinkage of the film. If a film that has a tendency to shrink upon removal of the cleaning liquid (e.g. water) is dried without any shrinkage restriction, micro-inhomogeneous structure formation (crystallization, etc.) may occur.
Perhaps because of this, the light transmittance of the resulting film becomes low. Furthermore, the flatness of the film may be impaired or the film may curl. To dry while limiting shrinkage, for example, a tenter dryer or drying between metal frames can be used.

Other conditions related to drying are not particularly limited, and may include methods using heated gas (air, nitrogen, argon, etc.) or room temperature gas, methods using radiant heat such as electric heaters or infrared lamps, dielectric heating methods, etc. It can be freely selected, and the drying temperature is not particularly limited as long as it is room temperature or higher. However, in order to increase mechanical strength,
A high temperature is preferred, with temperatures of 100°C or higher, more preferably 200°C or higher. The maximum drying temperature is
Although not particularly limited, it is preferably 50 (L'C or less) in consideration of drying energy and decomposability of the polymer.

In the present invention, when the fluoropolymer is present in a layered form on the surface of the film, when producing the film, after the film is formed by coagulation, it is dried and/or heat treated and then rolled up. Methods such as coating with an aqueous dispersion containing a fluoropolymer at a certain point and then drying it, or laminating a fluoropolymer melt-extruded from a slit die onto a homogeneous aromatic polyamide film are employed.

Appropriate times for coating the dispersion containing a fluoropolymer are after the coagulated film has been washed with water, in a wet film state before drying, or in a dry film state after drying, but from the viewpoint of process simplicity. Therefore, it is more preferable to contact in the form of a wet film. Methods for bringing the processing liquid into contact with the film include a method of running the film in a tank containing the processing liquid, or a method of applying the processing liquid to the surface of the film while it is running, such as reverse coating (
(bottom feed 3 reverse, bottom feed 4 reverse, 2 roll reverse, top feed 3 reverse, etc.), Kismayer coating, gravure coating (direct gravure or offset gravure), slot die coating, curtain coating, etc. .

In the present invention, the concentration of the treatment liquid is usually 60 int% or less, and the viscosity is preferably 50 cps or less.

When laminating melt-extruded fluoropolymers, the film obtained by drying and heat treatment can be used as is, or
After pre-treatments such as corona discharge treatment, plasma treatment, primer treatment, adhesive application, and drying, the fluoropolymer melt is superimposed and pressed using a laminator.

Two or more methods of applying the fluoropolymer described above can be used in combination, and the thermal fusion properties can be strengthened by performing both dispersion into the film and formation of a surface layer.

(Examples) Examples of the present invention are shown below, but these Examples are for explaining the present invention, and are not intended to limit the present invention. In the examples, parts by weight or weight % are shown unless otherwise specified.

Logarithmic viscosity ηinh is 98% sulfuric acid 100d and polymer 0.5
This value was measured using a conventional method at 30°C.

The viscosity of the dope was measured using a B-type viscometer at a rotation speed of 1 rpm.

The thickness of the film was measured using a dial gauge with a measuring surface of two cylinders in diameter.

The strength and elongation and Young's modulus were determined by cutting a film sample into a rectangle of 100 mm x 10 mm using a constant speed extension type strength and elongation measuring machine, and running the load-elongation curve 5 times at an initial grip length of 30 fflff+ and a tensile speed of 30 ■/min. This is what we drew and calculated from this.

The 180° peel force was measured by cutting the heat-sealed film into a rectangle with a width of 10 marks, and using a constant-speed elongation type strength and elongation measuring machine at a tensile speed of 30 mm/min.

Example 1 A PPTA polymer having an ηinh of 5.5 was dissolved in 99.7% sulfuric acid at a polymer concentration of 11.5% to obtain a dope with optical anisotropy at 60°C. The viscosity of this dope was measured at room temperature and was found to be 10,600 poise.

The dope was heated to about 70°C and degassed under vacuum. This case also has the same optical anisotropy as above, and the viscosity is 44
It was 00 poise. The 1.5 m long blood vessel from the tank through the static mixer to the gear pump to the die is heated to approximately 70°C.
The cast dope was cast onto a mirror-polished tank belt through a gouie with a slit of 0.15 + an With the belt, -
The mixture was introduced into a 30% by weight aqueous sulfuric acid solution at 20°C and coagulated. The coagulated film was then peeled off from the belt and washed by running it in warm water at about 40°C. After washing the film, the water adhering to the surface is removed using a drain roll, and then dispersion of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) (solid content 55-58%) is applied.
) was applied, and then dried with hot air at 240° C. while being stretched 1.1 times in the transverse direction using a tenter, and then wound up to obtain a film with a thickness of 7.8 μm.

The thickness of FEP is 2.5μ, and the strength is 20kg/mm2.
The elongation was 24% and the elastic modulus was 900 kg/vgn 2. After stacking two layers of this film and press-bonding them at 300°C, the 180° peeling force was measured, and the result was 0.4 kg/cm.
Met.

Example 2 In Example 1, 2% by weight of PPTA polymer
A dope was prepared by adding fine powder FEP (average particle size: 1 μm), and a film was produced in the same manner as in Example 1 except for the following. This film had a strength of 18 kg/nun'', an elongation of 22%, an elastic modulus of 900 kg/mm2, and a 180° peel force after pressure bonding of 0.8 kg/cm.

Example 3 In Example 2, a film was produced without FEP dispersion coating.

The strength of this film is 20 kg/mm2, the elongation is 24%,
The modulus of elasticity is 940 kg/mm2, and it is 18° after crimping.

The peeling force was 0.2 kg/cm.

C. Effects of the Invention As shown in the examples, the film of the present invention has good mechanical properties, such as high strength and high Young's modulus, which are not found in commercially available films, and also has good heat resistance. and has excellent heat fusion properties. In addition to these properties, it also has excellent electrical insulation, oil resistance, pressure resistance, chemical resistance other than strong acids, and dense structure.

Therefore, the film of the present invention is useful for electrical insulation of motors, coils, etc., for covering electric wires, for capacitor dielectrics, for insulating cover films for flexible printed wiring board coverlays, etc.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] It is substantially made of para-oriented aromatic polyamide with a logarithmic viscosity of 3.5 or more, a tensile elongation in the direction parallel to the film surface of 8% or more, and thermoplastic fluorine on the surface and/or inside of the film. A heat-fusible polyamide film characterized by having a polyamide-based polymer