JPH04342736A - Production of glass-containing aramid film - Google Patents

Abstract

PURPOSE:To obtain an aramid film suitable for a flexible printed-wiring board and a base film for magnetic recording medium, having excellent dimensional stability and improved strength and modulus of elasticity. CONSTITUTION:An aramid film having >=1wt.% water content is brought into contact with an alkoxysilane, impregnated with the alkoxysilane, dried at >=200 deg.C and 1-30wt.% calculated as glass based on the dried film of the alkoxysilane is added to the film to give a glass-containing aramid film.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has excellent dimensional stability,
The present invention relates to a method for manufacturing an aramid film with improved strength and modulus of elasticity, and is suitable for use in flexible printed wiring boards and magnetic recording media.

0002

[Prior Art] Base films for flexible wiring boards and base films for magnetic recording media are mainly made of polyimide films and polyethylene terephthalate (PE).
T) Film is being used. However, these films have the following drawbacks. Polyimide films are expensive and have a low elastic modulus, so they lack dimensional stability against external forces. On the other hand, PET film lacks heat resistance, making it unsatisfactory for soldering processes and outdoor use, and also has the disadvantage of having a low elastic modulus.

Under these circumstances, para-oriented aramid films having a high elastic modulus have attracted attention, and attempts have been made to apply them to the above-mentioned uses. However, aramid films generally have a high moisture absorption rate, and even aramid, which has halogen groups introduced into the aromatic ring to improve this,
It had the drawbacks of poor heat stability and large heat shrinkage. In addition, in order to further improve dimensional stability, it is desirable to further increase the elastic modulus, but when the elastic modulus is increased, conventional techniques tend to suffer from increased heat shrinkage and shrinkage in the thickness direction of the film (so-called Z direction). There was a drawback that the characteristics of

0004

[Problems to be Solved by the Invention] An object of the present invention is to provide a flexible printed wiring board and a magnetic recording medium, which have excellent dimensional stability and improved strength and modulus of elasticity, and which overcome these drawbacks of the prior art. The purpose of the present invention is to provide a method for manufacturing a film suitable for base films.

[0005]

[Means for Solving the Problems] While researching methods for producing films suitable for such purposes from various viewpoints, the present inventor discovered that aramid films with a specific moisture content were produced using the so-called sol-gel method. They discovered that by dispersing glass in a film, it was possible to obtain a film with excellent dimensional stability and improved strength and modulus of elasticity, which suited the purpose, and after further research, they arrived at the present invention. It is something.

That is, in the present invention, an aramid film having a water content of 1% by weight or more is brought into contact with an alkoxysilane to be impregnated with the alkoxysilane, and then dried at a temperature of 200° C. or more to form a glass into the dry film. 1-30
This is a method for producing a glass-containing aramid film characterized by containing the glass in an amount of % by weight.

The aramid used in the present invention is substantially composed of units selected from the group consisting of the following structural units.

[Chemical formula 1] -NH-Ar1 -NH- ...... (I)
-CO-Ar2 -CO- ………… (II
)-NH-Ar3 -CO- ………… (I
II) Here, Ar1, Ar2 and Ar3 are:
Each is a divalent aromatic group, and (I) and (II) are substantially equimolar when present in the polymer.

In the film of the present invention, Ar1, A
r2 and Ar3 are para-orientated or meta-oriented groups, but to ensure good mechanical performance, Ar
1 , Ar2 and Ar3 are each preferably a so-called para-oriented group.

Here, para-orientation means that the bonds that grow the molecular chain are located coaxially or parallel to the opposite direction of the aromatic nucleus. Specific examples of such divalent aromatic groups include paraphenylene, 4,4'-
Biphenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-naphthylene, 2,5-pyridylene and the like can be mentioned. They are 1 with non-active groups such as halogen, lower alkyl, nitro, methoxy, sulfonic acid, cyano groups, etc.
Alternatively, two or more may be substituted. In addition, as the meta-oriented group, metaphenylene, 4,4'-biphenylene ether, 3,4'-biphenylene ether, 4,4
'-biphenylene sulfone, 1,7-naphthylene, etc., and may be substituted with the above-mentioned inert group.

[0010] Ar1, Ar2 and Ar3 may each be two or more types, and may be the same or different. If the degree of polymerization of the aramid film used in the present invention is too low, it will not be possible to obtain a film with good mechanical properties.
A polymer having a degree of polymerization that gives a value measured at 30° C. by dissolving 0.5 g of polymer is selected.

[0011] The aramid film used in the present invention is
It is necessary to have a moisture content of 1% by weight or more. If the moisture content is less than 1% by weight, the gelling reaction after impregnating the alkoxysilane is often insufficient, and the moisture content is preferably 3% by weight or more. Although the upper limit of the moisture content is not necessarily limited, it is known that aramid films generally have a maximum moisture content of about 300% by weight in an uncrystallized state after film formation, and films in this state may also be used. Can be done. However, if the water content is too high, alkoxysilane and water are not compatible, so it becomes necessary to use a large amount of alcohol, which is a common solvent during the impregnation operation. Moisture content is preferred.

[0012] The aramid film used in the present invention can be produced by various methods. For example, an aramid obtained by polymerizing the corresponding diamine and diacid chloride by the low-temperature solution polymerization method known in Japanese Patent Publication No. 35-14399 etc. can be used as it is or in a solution (doped) after neutralizing the by-product hydrogen chloride. ) or once isolated, an amide solvent,
It can be obtained by wet or dry film formation from a dope dissolved in concentrated sulfuric acid or the like. In addition, the present inventors previously announced (Takayanagi et al. “Polymer Journal Vol. 20 No. 8 No. 639
Electrodeposited films of aramids from dimethyl sulfoxide-sodium hydride solutions can also be used.

The alkoxysilane used in the present invention includes tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, etc., or mixtures thereof. Alkoxysilane is usually used in the form of a solution using the corresponding alcohol as a solvent, and a small amount of other solvent such as water may be mixed therein. Alkoxysilane in alcohol is usually 0.1
It is used at ~60% by weight.

Impregnation of alkoxysilane into the aramid film can be carried out in various ways while bringing the aramid film into contact with the alkoxysilane. A method of simply immersing the aramid film in alkoxysilane or its alcohol solution, a method of using heating, pressurization, depressurization, etc., a method of showering the aramid film with alkoxysilane,
Examples include a method of spraying.

It is also a preferred embodiment to add a small amount of HCl or HNO3 during impregnation in order to accelerate the subsequent gelation reaction (conversion reaction from alkoxysilane to glass). The impregnation time, alkoxysilane concentration, etc. should be selected so that the final glass content will be 1 to 30% by weight (based on dry film), taking into consideration the type of aramid, the thickness of the aramid film, the moisture content, etc. .

[0016] The aramid film impregnated with alkoxysilane is then dried at a temperature of 200°C or higher. here,"
"At 200° C. or higher" means that the final drying or heat treatment temperature is 200° C. or higher, and the temperature may be raised stepwise from room temperature, for example, until that temperature is reached. 20
The reason for setting the drying temperature to 0° C. or higher is that it is necessary for the alkoxysilane to chemically change into glass (SiO2 network structure) at high temperatures. The upper limit of the drying temperature is limited solely by the thermal stability of aramid, and it can be used up to about 500°C instantaneously. The drying temperature is preferably 250 to 450°C.

In the drying process, a gel-like glass is formed due to the evaporation of alcohol and the progress of the hydrolysis reaction of carboxysilane by the coexisting water, but at this time, the aramid film itself often shrinks. For this reason,
It is preferable to dry the film while maintaining a constant length, limiting shrinkage to a certain degree, or while stretching the film. Particularly when producing a film with a high modulus of elasticity, it is desirable to perform a stretching operation (approximately 1.05 to 2 times) before or during drying. Further, drying may be performed at 200° C. or higher in two or more stages at different temperatures. For example, in order to reduce the thermal shrinkage rate, it is effective to dry the material under constant length or stretching, and then further heat treat it under relaxation or low tension.

[0018] In this way, an aramid film containing 1 to 30% by weight of glass, based on the dry film, can be obtained. A glass content of less than 1% by weight does not result in a film with improved dimensional stability, which is a feature of the present invention, while a glass content of more than 30% by weight makes the film brittle and impractical. The glass content can be quantified by the amount of substance remaining even at 600° C. or higher, for example, by thermogravimetric analysis (TGA).

When the cross section of the produced glass-containing aramid film was observed using a scanning electron microscope, it was found that the glass had developed into layers inside the film and was packed tightly together.
This behavior is clearly visible when observed after etching with O)/sodium hydride solution. The obtained glass-impregnated film has a strength of 200 MPa or more and an elastic modulus of 5 GPa or more. These indicate that the degree of planar orientation of the aramid in the film is high, and therefore the film has excellent dimensional stability.

[0020]

[Examples] Examples are shown below, but these reference examples and examples are for illustrating 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.

[0021]Evaluation of each characteristic in the examples was carried out by the following method. ■ Strength and elongation and elastic modulus are determined by cutting a film sample into a rectangle of 0.5 cm x 3 cm using a constant speed extension type strength and elongation measuring machine, and attaching sandpaper cut into a square of 0.5 cm on each side with adhesive. Installed it. This sandpaper portion was gripped by the chuck of the measuring machine and measured by pulling it at 1 cm/min. ■ The amount of glass impregnation is measured using a thermogravimetric analyzer (TGA).
While blowing air into the film, the glass-containing aramid film was heated to 600° C. and held to burn off the organic components, and the remaining amount was determined as glass.

■ The heat shrinkage rate at 250°C is 250°C when a tension of 0.05kg/mm2 is applied to the film.
It was calculated from the dimensional change at room temperature (25°C) before and after the oven treatment after being left in an oven at 30°C for 30 minutes. ■ The coefficient of hygroscopic expansion is determined by setting the film in a thermomechanical analyzer with a tension of 0.05 kg/mm2, feeding air at 23°C, 20% relative humidity, and 60% relative humidity, and measuring the dimensional change during this time. I asked for it from

[0023]

Example 1 A poly(p-phenylene terephthalamide) (PPTA) film was produced by electrodeposition. An electrodeposition solution consisting of 2.5 g of PPTA, 1 L of dimethyl sulfoxide, and 0.84 g of caustic soda was placed between a stainless steel double cylinder in which a polyethylene container was submerged. The rotating cylinder (a well-polished electrodeposition rod) is used as an anode and the outer cylinder is used as a cathode, rotating at a constant speed, and the electrodeposition density is 0.35 mA/cm2.
It lasted 40 minutes. After electrodeposition, it was treated with 1N hydrochloric acid for 10 minutes and washed with water. After drying at room temperature for a while, drying under reduced pressure at 50°C for 2 hours, and further drying at 100°C for 1 hour.
A film with a moisture content of % by weight was obtained.

Next, the film was immersed in an ethanol solution of tetraethoxysilane (approximately 1% by weight) and heated to 1% by weight at 60°C.
It was left undisturbed day and night. After removing the film and rinsing the surface with ethanol, dry it at room temperature, then dry it under reduced pressure at 60°C for 10 minutes.
Dry at normal pressure at 0℃, then dry at 370℃ for 1 minute (heat treatment)
were carried out sequentially over a fixed length. Thus, by polymerizing tetraethoxysilane with water in the PPTA film, glass-containing P
I made PTA film.

[0025] This film was analyzed by infrared absorption spectrum, and a spectrum peculiar to SiO2 was confirmed at a wave number of around 1100 cm-1. Further, the glass content was 13% by weight as a result of thermogravimetric analysis. The PPTA film before impregnating glass has a strength of 170 MPa and an elongation of 4.7%.
, the elastic modulus is 5.56 GPa, and the glass-containing PPTA film has a strength of 205 MPa, an elongation of 5.3%, and an elastic modulus of 6.
．． It was 00 GPa.

[0026]

[Example 2] From a sulfuric acid solution of PPTA,
A film was made by the method disclosed in Japanese Patent No. 7886. 11
The film obtained by drying at 0°C has a thickness of about 25 μm,
The moisture content was 4.8% by weight. Impregnation with tetraethoxysilane and drying were performed in the same manner as in Example 1. However, in this example, the pressure of the film was once reduced, an ethanol solution of tetraethoxysilane was injected and immersed therein, and a pressure of 1 atmosphere was applied to promote impregnation.

The film thus obtained has a thickness of about 29 μm.
The glass content was 8.3% by weight at a thickness of . The PPTA film before glass impregnation has a strength of 160 MPa, an elongation of 53%, a modulus of 3.45 GPa, and a modulus of 2.03
% heat shrinkage rate, 11.6 x 10-5mm/mm/%RH
It had a hygroscopic expansion coefficient of On the other hand, glass-containing PPT
A film has a strength of 220 MPa, an elongation of 35%, and a
．． Elastic modulus of 26GPa, heat shrinkage rate of 0.17%, 8.1
It had a hygroscopic expansion coefficient of x10-5 mm/mm/%RH. Note that a similar glass-containing film was obtained even when no pressure was applied during impregnation.

[0028]

[Effects of the Invention] By the method of the present invention, an aramid film with improved tensile strength and elastic modulus can be obtained, which means that the film has good dimensional stability against external forces. Furthermore, in the film obtained by the method of the present invention,
Since glass is filled inside the film in a layered manner, it can be expected that the compressive strength and compressive modulus of the film, as well as the strength and modulus of elasticity in the thickness direction, are improved.

Furthermore, glass impregnation reduces thermal shrinkage and dimensional changes due to moisture absorption. In other words, thermal dimensional stability and moisture absorption dimensional stability are improved. Due to these characteristics, the film obtained by the method of the present invention is useful as a base film for flexible wiring boards, a base film for magnetic recording media, and the like.

Claims (1)

[Claims] Claim 1: An aramid film with a water content of 1% by weight or more is brought into contact with an alkoxysilane to impregnate it with the alkoxysilane, and then dried at 200°C or higher to form a glass with a moisture content of 1 to 30% by weight based on the dry film. % of glass-containing aramid film.