JPH02143828A - Manufacture of film - Google Patents

Abstract

PURPOSE:To obtain film, which has high surface accuracy and Young's modulus and is excellent in heat resistance by a method wherein the means shearing speed of solution at its passing through a slit is specified and the mixture of two or more para-aramids is used. CONSTITUTION:The film concerned is produced on wet method or dry method by extruding para-aramid solution through a slit die on a supporting surface. At that time, the solution is extruded at the means shearing speed of 50/sec at its passing through a slit. In addition, the mixture of two or more para- aramids, the logarithmic viscosity numbers of which are different from each other by 0.2 or more and the major para-aramid of which does not exceed 90% of the total weight is used. As the above-mentioned para-aramids, the polymers represented by formulae I and II or their copolymer is used. The obtained film has favorable slipperiness between films, between film and metal and between film and ceramics in addition to its good surface accuracy and consequently is useful as base film for magnetic tape, electrical insulating material, dielectric for capacitor, base film for printed wiring board and self-adhering tape printed with bar code.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a film made of para-aramid. More specifically, the present invention relates to a method for producing a film that exhibits excellent mechanical properties and excellent surface properties.

(Prior art) An example of forming a film from para-aramid was published in 1983.
-14567 Publication, Publication No. 57-35088, Publication No. 5
It is disclosed in Publication No. 9-5407, Publication No. 57-17886, etc.

Among these, the technique disclosed in Japanese Patent Publication No. 57-17886 is particularly noteworthy because it provides an essentially isotropic film that is transparent and has excellent mechanical properties. However, the films obtained by the methods disclosed in these publications do not necessarily have a satisfactory level of surface roughness, and are unsatisfactory, for example, in magnetic tape applications that require severe surface precision. For this reason, for example, in Japanese Patent Application Laid-open No. 104714/1982, there are
A proposal has been made based on Technique 4Xr of Publication No. 6 to improve the surface precision of the film.

With the further increase in recording density, the demand for improving the surface precision of base films for magnetic recording media is becoming stronger.

On the other hand, JP-A-51-132265 describes a method for producing molded articles, especially fibers, using a mixture of two or more types of poly(p-phenylene terephthalamide) having different degrees of polymerization. In this publication, it is said that the effects are solely on the mechanical performance and economic efficiency of the obtained fibers, and there is no specific explanation of film production. There is no description or suggestion regarding the effect of using the above (It) together.

Furthermore, in JP-A-62-70450, poly(p-phenylene terephthalamide) is substituted with poly(p-phenylene terephthalamide).
Although it is disclosed that a film with a high elastic modulus is obtained by blending a small amount with p-phenylene terephthalamide), there is no mention or suggestion of surface precision at all. There is no disclosure as to whether the surface precision is improved.

(Issue 8 to be solved by the invention) An object of the present invention is to produce a para-aramid film with excellent surface precision, high Young's modulus, and excellent heat resistance, which is particularly useful as a base film for high-density magnetic recording media. The present invention provides a method for manufacturing.

(Means for Solving the Problems) As a result of intensive research in order to obtain a film that meets the purpose described above, the present inventors have discovered that it is possible to manufacture a film from a para-aramid solution by placing it on a supporting surface from a slit die. extruded into,
When a wet or dry method is used and a mixture of two or more para-aramids with substantially different viscosity behavior is used, an unexpected effect of reducing the surface roughness of the resulting film may occur. Based on this knowledge, we conducted further research and arrived at the present invention.

That is, in the present invention, a solution of para-aramid is extruded from a slit die onto a supporting surface to produce a film in a wet or dry process, so that the average shear rate when passing through the slit is at least 50 seconds four times. Extruding a solution, and two or more types of para-aramids having logarithmic viscosities different by 0.2 or more,
Moreover, this is a method for producing a film characterized in that para-aramid, which is the most abundant, is used in a mixture such that it does not exceed 90% of the total amount.

As the rose-based aramid I' used in the present invention, polymers of the following general formula (1), -JilQ formula (II), or copolymers thereof are selected.

(In the formula, 11., R, and R, 3 are selected from, and these hydrogen atoms are halogen, methyl, ethyl,
It may be substituted with functional groups such as methoxy, nitro, and sulfone. m and n are the average degree of polymerization, approximately 50 to 100
It is 0. ) The para-aramid used in the present invention may be copolymerized or blended with polymers other than the above-mentioned components, as long as the amount is about 20 mol % or less. Particularly preferred para-aramids are poly(p-phenylene terephthalamide) or poly(p-benzamide).

When producing a film from these polymers, a medium such as dimethylacetamide F, N-methylpyrrolidone, hexamethylphosphoramide, tetramethylurea, or a mixture thereof, or lithium chloride, calcium chloride, It can be carried out using a solvent to which an inorganic salt such as lithium carbonate or lithium bromide is added, and by a conventional wet or dry method, or a combination of these methods. Alternatively, the polymer can be produced from a dope dissolved in sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, or the like. These dopes may form what is called an optically anisotropic dope, but once this dope is discharged from the die, it is converted into an optically isotropic dope by heating or humidification, then wet solidified, and then washed. By carrying out biaxial stretching in a wet state, a film with an extremely high Young's modulus can be conveniently produced.

The method of the present invention is applicable to processes of extrusion from a slit die onto a support surface, whether dry or wet. The slit die may be a so-called T die or a ring die. Film forming methods using these dies are described in Japanese Patent Publication Nos. 56-45421 and 57.
-35088, 59-5407, JP-A-54-132674, JP-A-57-17886, J, ^pp1. Polym, Sci, (Journal of Applied Polymer Science)
Vol. 27°NαB, P, 2965 (1982) etc.

In the present invention, it is extremely important to use a mixture of two or more types of para-aramids having logarithmic viscosities different by O12 or more. The difference in logarithmic viscosity is more preferably 0.5 or more. In the present invention, constant viscosity is defined as the value measured at 30° C. by dissolving 0.5 g of polymer in 100 d of 98.5% concentrated sulfuric acid.

There are several ways to prepare two or more types of rose aramid having logarithmic viscosities different by 0.2 or more, and examples of the two types will be described next.

(A) Polymers of the same or almost the same chemical species but with different degrees of polymerization. In this case, there are cases in which polymers with different degrees of polymerization are prepared in the polymerization process, and so-called leak polymers, which have previously gone through the same or similar film manufacturing process, are combined with so-called virgin polymers, which are freshly obtained from polymerization. There is a case.

(B) When using polymers of different chemical species. In this case, a polymer selected from the above-mentioned polymer group is used.

The mixing of two or more types of polymers is carried out prior to or during the preparation of the stock solution (dope), but the mixing ratio is
The maximum amount of component polymer is used so that it does not exceed 90% of the total, since mixing becomes ineffective if a particular component polymer occupies too large a portion.

In the present invention, the effect of mixing is to improve the surface precision of the film. This is a rose aramid dope (
Concentrated solutions) have unique rheological properties, such as large flow orientation and thixotropy, so when a single polymer is used for film forming, even though it itself has a degree of polymerization distribution, the surface precision is not very good. However, when a film is formed using the method of the present invention, the flow behavior across the slit die width and the discharge behavior from the die change slightly due to the mixture of polymers with different rheological properties. It is estimated that this improves the surface precision of the obtained film.

In the present invention, extrusion from the slit portion of the die is
The surface properties of the film are further improved by adjusting the average shear rate to be at least 1 sec-1, preferably 100 sec-1.

In addition, in the present invention, it is preferable to perform the film forming process as slowly as possible in order to improve the surface area of the film. It is desirable to adjust the degree of pressure reduction, and in the case of a wet method, use a low coagulation bath temperature and high coagulation bath concentration to reduce the coagulation rate.

Further, in the present invention, it is preferable to stretch the film after film formation in an arbitrary step in order to improve the surface precision of the film.

(Example) Examples will be shown below to explain the present invention in more detail.

In the examples, the logarithmic viscosity ηtnh is 98% sulfuric acid 100
0.5 g of polymer was dissolved in d 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 1 rpm. The thickness of the film was measured using a dial gauge with a measuring surface of 2 mm in diameter. The strength elongation and modulus are determined by cutting a film sample into a rectangle of 10,100 mm x 10 using a constant speed extension type strength elongation measuring machine, drawing a load extension curve 5 times at an initial grip length of 30 fflIm and a tensile speed of 30 mm/min. This is the calculated value. To evaluate the surface accuracy of the film, we used the all-purpose surface profile measuring machine Surfcom 3B manufactured by Tokyo Seimitsu Co., Ltd.
Center line average roughness (Ra) according to JIS B-0601 and J
This was done by measuring according to IS B-0651.

Reference Example (Manufacture of Polymer) Poly(p-phenylene terephthalamide) was produced by reacting terephthalic acid chloride and phenylene diamine in a solvent in which lithium chloride was dissolved in N-methylpyrrolidone.
(hereinafter referred to as 11PTA) was obtained. At this time, by changing the ratio of 7-mer and solvent, η1nh6.1.5
．． 0.3.8 were obtained respectively. In addition, as diamine monomers, 4,4'-diaminodiphenyl ether and phenylene diamine were used at a molar ratio of 377, and η
A copolymer of 1nh3.2 was obtained.

Example 1 P of 77 inl+ 6.1.3.8 obtained in Reference Example
A film was made using P 1'A.

Approximately equal amounts of two PPTAs with different ηinh were 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 tope was measured at room temperature and was found to be 9100 poise. To make it easier to imitate the product, add about 70% of this dope.
It was degassed under vacuum while being held at 'C. This case also had optical anisotropy as above, and the viscosity was 3900 poise. The 1.5m curved pipe from the tank through the filter to the gear pump to the die is maintained at approximately 70°C, and the discharge linear velocity from the slit die is 3.5m/min (average shear rate of 950 sec-1). A mirror-polished tantalum bell) (
The cast dope was made optically anisotropic by blowing air at about 90'C with a relative humidity of about 65% onto a caster (moving at a speed of 12 m/min), and then placed in a 30 wt% aqueous sulfuric acid solution at -20'C. and coagulated. Next, the coagulated film was peeled off from the belt and washed by running it in hot water at about 40"C.The washed film was stretched to about 1.1 times in the length direction with a rower without drying, and then Using a tenter, first stretch it to about 1.3 times in the width direction, then stretch it by 2 times.
It was dried with hot air at 40"C and further heat-treated at 350°C under constant length.

The ηinh of the mixed polymer before dope preparation was 4.9, and the ηinh of the obtained film was 4.4. The properties of the obtained film are shown in Table 1.

Comparative Example 1 Using PPTA with η1nh5.0 alone "C1 Example 1"
repeated.

The properties of the obtained film are shown in Table 1. It can be seen that the mechanical performance is the same or higher than that of the film of Example 1, but the Ra is large (the surface is rough).

Example 2 PPTA with η1nh5.0 and copolymer polymer with η1nh3.2 (reference example) were mixed at a weight ratio of 2:1,
Example 1 was repeated using a dope dissolved in concentrated sulfuric acid to form 133 dopes.

The properties of the obtained film are shown in Table 1. The film of this example had high tear strength.

Example 3 This example illustrates the effect of mixing so-called reworked polymers.

The film obtained in Comparative Example 1 (ηinh 4.5 ) was shredded, and the film obtained in Reference Example 1 (η1nh5. About 4 for o's PI'T 8
Polymer (ηinh 4.0
) was prepared. The film obtained in Comparative Example 1 had almost the same infrared absorption spectrum as PPTA, but there was a slight difference in the so-called shoulder peak.

The blended polymer was dissolved at 10% in 99.5% sulfuric acid to obtain an optically anisotropic 7900-void l-p at 45°C. After degassing and filtration, the dope was cast onto a tantalum belt through a slit die. At this time,
The linear velocity of the tope discharged from the die was 3.5 m/min, the average discharge shear velocity was 670 sec-1), and the moving speed of the heald was 10 m/min. The cast tope was converted to a clear optically isotropic dope by blowing air at about 75° C. with about 80% relative humidity and then coagulated with a 45% aqueous sulfuric acid solution at 1'C. After peeling off the coagulated film from the belt, soak it in room temperature water, 2% caustic soda aqueous solution, about 30-40°C.
It was washed with water in the order of C.

The washed T-temperature film containing approximately 250-350% water was stretched 1.2 times in the length direction (9) in the width direction using a tenter, and then stretched by another 1.2 times in the width direction with circulation of hot air at 150°C. The film was dried in a tenter while being stretched to 1.05 times only in the width direction.

The properties of the obtained film are shown in Table 1.

Margin below (Effects of the invention) In addition to the original characteristics of para-aramid films such as high rigidity, heat resistance, high strength, and chemical resistance, the film obtained by the method of the present invention has extremely high surface precision. In good condition. It was also found that the film has the unexpected property of having good slipperiness between films, between films and metals, and between films and ceramics, despite having a good surface In degree.

Due to these characteristics, the film obtained by the method of the present invention is particularly useful as a base film for magnetic tapes, a base film for printers, etc., and can also be used as an electrical insulating material, a capacitor dielectric material, a base film for printed circuit boards, etc. It is useful as a film, carrier tape, barcode printed adhesive tape, etc.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] In producing a film by extruding a para-aramid solution from a slit die onto a supporting surface using a wet or dry process,
The average shear rate when passing through the slit is at least 50 seconds^-^
extruding the solution such that the logarithmic viscosity is 1 and the logarithmic viscosity is 0
．． A method for producing a film characterized in that two or more different para-aramids are used in a mixture such that the largest amount of para-aramid does not exceed 90% by weight of the total.