JPH035302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method of making substantially dense aromatic polyimide tubing.

Aromatic polyimides have excellent heat resistance, mechanical properties, and chemical properties, so they are also used in various molded products such as films and tubular products.

The method for producing aromatic polyimide tubular products is as follows:
Conventionally, it has been known to manufacture a polyimide film by cutting it into a tape shape, winding it spirally around a mandrel, etc., and bonding it with an adhesive, but the resulting tubular product has poor thermal and mechanical properties. This cannot be said to be satisfactory. This method also involves film production, slitting,
The manufacturing process is complicated because it requires a manufacturing process such as applying an adhesive medium, and the reliability of the product is also likely to decrease.

Furthermore, there is a method in which a paint containing an aromatic imide ring is applied onto a metal wire, the process of drying and solidifying is repeated, and then the metal wire is stretched beyond its descending point to separate the wire (Japanese Patent Application Laid-open No. 51-50378). A dry method such as a method in which a biphenyl-based compound is mixed into a paint containing a group imide ring and applied onto a metal wire, and after drying and solidification, the metal wire is stretched and separated (Japanese Unexamined Patent Publication No. 152923/1983). is also known.

However, it is difficult to obtain thick-walled tubular products using these methods. In other words, if the thickness of the coating on the metal wire is increased in order to manufacture a thick tubular object using these methods, the paint will flow and cause thickness unevenness, so in reality the coating thickness is 50 μm.
To obtain a thick-walled tube, 6 to 12 applications are required.
It requires repeated drying and solidification, and is not suitable as an industrial manufacturing method. Furthermore, since both methods utilize the operation of stretching and separating metal wires, large forces are required in the stretching process to obtain tubular objects with large inner diameters, which leads to disadvantages such as expensive manufacturing equipment. There is.

On the other hand, in the wet manufacturing method, a dope solution containing polyimide is extruded into a coagulation solution in the form of hollow fibers, and the solvent used in the dope solution is substantially removed from the coagulation solution made of a polar solvent. A method of extraction and removal (Japanese Unexamined Patent Publication No. 167414/1983) is known. However, this method is not suitable for obtaining a so-called pipe-like or tube-like polyimide molded product having a large diameter because it is difficult to make the wall thickness and shape uniform. Furthermore, it is difficult to manufacture tubular objects with irregular shapes such as square cross sections. A further problem is that the internal structure of the side wall of a polyimide molded body obtained by substantially extracting and removing the solvent in the dope solution is not dense, but rather porous, making it opaque and The problem is that mechanical properties such as tensile strength are not sufficient.

Accordingly, the present invention provides a method for producing aromatic polyimide tubular articles that overcomes the drawbacks of the prior art as described above.

The present invention is a step of extruding a polyimide precursor dope liquid in which one or more aromatic polyimide precursors are dissolved in an organic polar solvent into a tubular shape: By contacting a coagulating liquid that is compatible with the organic polar solvent, 5% of the organic polar solvent in the tubular dope liquid is
Step of extracting and removing ~80% by weight to form a tubular dope liquid coagulate: Inserting a core material with a larger coefficient of thermal expansion than the polyimide obtained from the polyimide precursor into the pores of this tubular dope liquid coagulate. From a method for producing an aromatic polyimide tubular article, comprising: a step of drying and solidifying it by heating and imidizing the polyimide precursor; and a step of separating and removing the core material after drying and solidifying. It is what it is.

According to the present invention, it is possible to obtain an aromatic polyimide tubular article having a dense internal structure of the side wall and excellent mechanical properties such as tensile strength while taking advantage of the inherent excellent heat resistance of aromatic polyimide.

Further, according to the present invention, it is possible to obtain a uniform polyimide molded body having a large diameter and having a so-called pipe shape or a tube shape, and also has the advantage that it is also possible to manufacture a polyimide tubular body having an irregular shape such as a square cross section. There is.

The polyimide precursor dope solution used in the present invention is one in which one or more aromatic polyimide precursors are dissolved in an organic polar solvent. It can be obtained by reacting an anhydride with an aromatic diamine or by dissolving a polyimide precursor powder in an organic polar solvent.

The aromatic tetracarboxylic dianhydride includes 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzohyenonetetracarboxylic dianhydride, pyromellitic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxylic dianhydride) (phenyl) ether dianhydride and the like. These aromatic tetracarboxylic dianhydrides are 1
Only the seeds may be used, or two or more types may be used together. Further, a part of it may be replaced with an aromatic tetracarboxylic acid.

Aromatic diamines include p-phenylene diamine, m-hyenylene diamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenylmethane, 4, Examples include 4'-diaminodiphenyl sulfone. These aromatic diamines may be used alone or in combination of two or more.

In the present invention, as a polyimide precursor, 3,
3',4,4'-biphenyltetracarboxylic dianhydride and/or pyromellitic dianhydride and 4,4'-
Aromatic polyimide precursors obtained from diaminodiphenyl ether and/or p-phenylenediamine are preferred.

Examples of the organic polar solvent include solvents capable of dissolving polyamic acid such as N-methylpyrrolidone, pyridine, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, tetramethylurea, cresol, and phenol. can be preferably mentioned. It is also possible to use organic solvents such as aromatic hydrocarbons in combination with these organic polar solvents.

Known additives such as mold release agents, organic/inorganic fillers, pigments, solution viscosity stabilizers, etc. may be blended into the raw material dope.

The concentration of the polyimide precursor in the raw material dope is preferably selected from 5 to 40% by weight, particularly preferably from 10 to 25% by weight. In addition, the viscosity of the dope liquid is 0~
Temperature of 130℃ (temperature used for manufacturing tubular products)
10 to 100,000 poise, particularly preferably 2,000 to 50,000 poise.

In the present invention, the polyimide precursor dope solution is extruded into a tubular shape using an extrusion device or the like. The extrusion device is capable of extruding the polyimide precursor dope liquid into a tubular shape, and supplies a coagulating liquid as a core liquid to the inner circumferential side of the polyimide precursor dope liquid forming the tubular shape and brings it into contact with the polyimide precursor dope liquid. There are no special restrictions as long as it is possible.

For example, a tube-in-orifice type extrusion device having a tip consisting of a dope liquid extrusion reorifice and a coagulation liquid (core liquid) injection tube can be used. In this case, the polyimide precursor liquid is extruded into the coagulation bath through the dope liquid extrusion reel fixture, and the coagulation liquid (core liquid) for coagulating the inner peripheral surface is extruded from the coagulation liquid injection pipe. The coagulation bath is appropriately equipped with guide yowl, etsuprol, and the like. The cross-sectional shape of the tip of the extrusion device is not particularly limited, and can take various cross-sectional shapes such as circular, elliptical, triangular, quadrangular, and hexagonal. In addition, the extrusion device has the inner diameter of the tubular body,
It is best to use a type that allows you to easily change the outer diameter.

Through the above steps, the polyimide precursor dope liquid extruded into a tubular shape is immediately brought into contact with the coagulation liquid on its inner and outer circumferential sides.

As the coagulating liquid, a liquid that is compatible with the organic polar solvent used as the solvent of the dope liquid is used.

Examples of such coagulating liquids include lower alcohols (methanol, ethanol, η-propanol, isopropanol, etc.), ketones (acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, etc.), ethers, amides,
Examples include lower carboxylic acids, sulfoxides, and mixed solvents of each of these compounds and water.

When the polyimide precursor dope liquid extruded into a tube comes into contact with the coagulation liquid on its inner and outer peripheral surfaces, the organic polar solvent in the dope liquid quickly migrates into the coagulation liquid, and as a result, The organic polar solvent in the tubular dope liquid is sequentially extracted and removed.
As extraction and removal of the organic polar solvent progresses, the inner peripheral surface of the tubular dope begins to solidify.
A flexible tubular dope liquid coagulate is obtained.

In the production method of the present invention, it is necessary to extract and remove 5 to 80% by weight, preferably 10 to 70% by weight, particularly preferably 20 to 60% by weight of the organic polar solvent in the dope solution. As a result, a tubular dope liquid coagulation body having self-supporting properties is obtained.

In this step, a flexible tubular dope liquid solidified body whose inner and outer walls are solidified to the extent that the next core material insertion operation is possible is obtained. The solidified surface becomes cloudy and opaque. This is because a part of the organic polar solvent in the dope is extracted from the surface by the coagulation liquid, and the concentration of the polyimide precursor in the vicinity exceeds the saturated dissolution amount. This is thought to be due to the structure. After a certain period of time, this cloudiness becomes redissolved and disappears due to the diffusion of the organic polar solvent remaining inside. If an excessive amount of the organic polar solvent remains in the dope, it becomes difficult to obtain a tubular dope solidified body having the strength required for the next core material insertion step. In addition, if the remaining amount of the organic polar solvent is too small, the coagulation of the dope liquid coagulation has progressed excessively, and even if the coagulate is subjected to the drying process after inserting the core material, it will not be possible to achieve the desired density and strength. It is difficult to obtain large polyimide tubular products.

The dope liquid coagulate prepared as described above so that an appropriate amount of organic polar solvent remains has a cloudy opaque layer on the surface at the initial stage, but as time passes, the cloudy opaque layer becomes Since it is redissolved in a polar solvent, it becomes an almost transparent solidified body as a whole.

A core material having a larger coefficient of thermal expansion than the polyimide obtained from the polyimide precursor is inserted into the hole of this liquid solidified body. The core material inserted into the pores of the coagulated body also serves to maintain a constant diameter of the pores of the coagulated body, thereby easily producing a tubular article having a desired inner diameter. Note that it is preferable that the core material is inserted in a state in which an opaque cloudy layer remains in the solidified body after a predetermined amount of the organic polar solvent has been extracted and removed.

It is desirable that the core material used in the above method has a coefficient of thermal expansion larger than that of the polyimide obtained from the polyimide precursor. In other words, in order to insert the core material into the pores of the solidified body, the outer diameter of the core material must be smaller than the diameter of the pores of the solidified body (inner diameter of the solidified body) at room temperature or a temperature close to that temperature. It is. In addition, considering that it is necessary to be able to separate and remove the formed tubular material when the temperature is returned to room temperature after completing the drying and solidification process, the thermal expansion coefficient of the core material is the same as that of the aromatic polyimide. (2
×10 ^-5 /°C to 5 × 10 ^-5 /°C) is desirable. This core material must not be easily attacked by organic polar solvents, etc., and must have a high melting point ( For example, it is natural that it is desirable to have a temperature of 100°C or higher, especially 200°C or higher. Examples of the core material include tetrafluoroethylene resin, silicone resin, trifluoroethylene resin, low density crosslinked polyethylene resin, and high density crosslinked polyethylene resin. These resins can be used in the form of hollow pipes, or solid rods. The materials described above can also be used in the form of coatings on pipes, rods, and wires made of other expensive materials, such as iron, copper, aluminum, various alloys, and the like.

The core material does not need to be straight, and may be curved, for example, in an S-shape or a ring shape with a portion open. Further, there is no particular limitation on the cross section of the core material, and it can take various cross-sectional shapes such as circular, elliptical, triangular, circular, hexagonal, etc., for example.

In the method of the present invention, the coagulated body into which the core material has been inserted is dried and solidified by heating, and the polyimide precursor is imidized.

In this step, the cloudiness and non-dense structure of the coagulated layer are destroyed by the diffusion of the organic polar solvent, the evaporation of the organic polar solvent through the coagulated layer, and the accompanying shrinkage, resulting in a dense and transparent structure. Furthermore, volumetric contraction is difficult to occur in the axial direction of the tubular body, probably due to the resistance of the contact part with the core material, but it contracts in the radial direction and inner thickness direction, so it is relatively easy to determine the tube diameter when extruding the dope. It is.

The heating drying method described above may be a method such as hot air drying or heating vacuum drying, but it is initially carried out at a relatively low temperature (60 to 120 ° C.) for about 10 minutes to 5 hours,
It is preferred that the organic polar solvent is sufficiently uniformly diffused into the coagulated layer.

In this step, drying and solidification (removal of the organic polar solvent) and imidization of the polyimide precursor are performed.
The imidization reaction occurs at a temperature of about 120°C, but complete imidization requires heating at a temperature of 300°C or higher for 20 minutes or more. Therefore, in the final stage of drying, it is preferable to store at a temperature of 300° C. or higher for 20 minutes or more to complete imidization. Core materials that can withstand this temperature are tetrafluoroethylene resin and silicone resin, and it is preferable to use these.
If another material is used as the core material, it is preferable to dry it at a temperature below the heat resistant temperature of the core material, and after cooling and separation, further fit into a heat resistant support to complete imidization.

After completion of drying and solidification, the core material is separated and removed to obtain an aromatic polyimide tubular product.

After drying and solidifying the coagulated material, the core material is usually separated and removed after the coagulated material is returned to room temperature. Since the thermal expansion coefficients of the dried solidified solidified body, that is, the aromatic polyimide tubular material and the core material are different as described above,
The core material can be easily extracted from the tubular article.
The core material separated in this way can be used repeatedly.

The method of the present invention has a wide tolerance range for the diameter, thickness, and shape of the tubular product that can be formed, and has dense mechanical properties.
This is a molding method that enables the molding of aromatic polyimide tubular products with excellent electrical and thermal properties.

Examples and comparative examples are shown below.

Example 1 200 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 202 mmol of 4,4'-diaminodiphenyl ether are combined with 400 g of N-methylpyrrolidone and 0.79 g of ethyl alcohol. Place in a separable flask equipped with a stirrer.
Polyimide precursor solution was obtained by polymerization at a polymerization temperature of 30° C. and a polymerization time of 20 hours. The rotational viscosity of this solution was 10,600 poise.

This solution was used as a molding dope, and the outer diameter was 13 mm.
Using an extrusion die having a ring-shaped slit with an inner diameter of 12.5 mm, the dope solution was extruded into a tube from the slit at a rate of 6.6 ml/min while acetone was injected from the injection port at the center of the slit. Next, the tubular body was introduced into an acetone coagulation bath placed 15 mm below the die and allowed to pass through it for 4 minutes.
A soft and opaque tube with solidified inner and outer surfaces was obtained.

At this time, the amount of N-methylpyrrolidone extracted by acetone in the dope was 22.1% by weight.

This tube was cut into a length of 280 mm, passed through a core made of stainless steel wire with an outer diameter of 5 mm through a tetrafluoroethylene resin pipe with an outer diameter of 7 mm and an inner diameter of 5 mm, and heated in a hot air dryer at a temperature of 80°C. It was dried for 1 hour. Furthermore, drying and imidization of the polyimide precursor were carried out while holding each temperature at 150°C, 200°C, 270°C, and 300°C for 30 minutes.

After cooling, the core material is separated and the inner diameter is 7.2mm and the wall thickness is 150μ.
A polyimide pipe with a length of 277 mm was obtained.

This pipe was transparent and brown in color and had a tensile strength of 17.3 kg/mm ² using a conventional Instron type tensile tester.

Example 2 223.1 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 0.6 mmol of 3,3',4,4'-biphetatetracarboxylic acid, and 223.7 mmol of paraphenylenediamine. millimoles and 410 g of dimethylacetamide were placed in a separable flask equipped with a stirrer and heated at a polymerization temperature of 30°C for 15 minutes.
Polyimide precursor solution was obtained by polymerizing while stirring for a period of time. The rotational viscosity of this solution was 8800 poise.

Using this solution as a dope for molding, use an extrusion die with a ring-shaped slit with an outer diameter of 13 mm and an inner diameter of 12.5 mm. While injecting methanol from the injection port in the center of the slit, the dope is made into a tube.
It was extruded at a rate of 6.6 ml/min. Then 15 from the dice
The tubular body was introduced into a methanol coagulation bath provided below the tube and passed through it for 5 minutes, and the inner diameter was 9.2 mm and the wall thickness was 290 μm.
A flexible and opaque tube with solidified inner and outer surfaces was obtained.

At this time, the amount of dimethylacetamide in the dope solution extracted by titanol was 43.6% by weight.

Next, a core material was passed through it in the same manner as in Example 1, followed by drying in a hot air dryer and imidization of the polyimide precursor. After cooling, the core material is separated and the inner diameter is 25.5mm.
A polyimide pipe with a wall thickness of 125 μm and a length of 278 mm was obtained.

This pipe was transparent and brown in color and had a tensile strength of 30.3 Kg/mm ² using a conventional Instron type tensile tester.

Claims (1)

[Claims] 1. Step of extruding into a tube a polyimide precursor dope liquid in which one or more aromatic polyimide precursors are dissolved in an organic polar solvent: Inner and outer circumferential surfaces of the extruded dope liquid into a tube shape. By contacting a coagulating liquid that is compatible with the organic polar solvent, 5 of the organic polar solvent in the tubular dope liquid is
Step of extracting and removing ~80% by weight to form a tubular dope liquid coagulate: Inserting a core material having a larger coefficient of thermal expansion than the polyimide obtained from the polyimide precursor into the pores of the tubular dope liquid coagulate. A method for producing an aromatic polyimide tubular article, comprising: a step of drying and solidifying it by heating to imidize the polyimide precursor; and a step of separating and removing a core material after completion of drying and solidification.