JP3103084B2 - Manufacturing method for tubular objects - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a tubular article made of a polyimide precursor solution resin.

(Prior art) Polyimide resin has excellent heat resistance, dimensional stability, mechanical properties, and chemical properties, and its applications are flexible, printed circuit boards, heat-resistant wire coating materials, and magnetic tapes. It is used for various applications.
Commercially available polyimide film, for example, a polyamic acid is made from an acid anhydride such as biphenyltetracarboxylic dianhydride and a diamine, and then made into a film by a method such as casting at this stage, and then into a polyimide by dehydration cyclization. The method has been taken.

Further, for example, as a method for producing a tubular article made of a polyimide resin, a surface of a tetrafluoroethylene-hexafluoroethylene copolymer film is subjected to a corona discharge treatment, then thermally laminated with a polyimide film, and a tape of the two-layer structure is formed. Provide a fixed wrap width, wind it around the core metal, heat it again to the melting temperature of the ethylene tetrafluoride-ethylene hexafluoride copolymer,
There is a method in which a wrap portion wound around a metal core is adhered with an ethylene tetrafluoride-propylene hexafluoride copolymer, and the metal core is extracted to form a tubular material.

In addition, as a method for producing a tubular product from a polyimide precursor, a polyamic acid solution is poured into the inner surface of a molded tube such as a glass tube or a stainless steel tube having a smooth inner surface to form the tube to a constant thickness. A method is also known in which the film is dried and imidized by heating to form a film, and then the film is extracted from a molded tube.

Further, as disclosed in JP-A-64-22514, a polyimide precursor is uniformly applied to the outer surface of a heat-shrinkable tube and then imidized by heating to obtain a polyimide tube. After that, there is also a method in which heating is performed to shrink the heat-shrinkable tube to reduce its outer diameter, and then the polyimide tube is removed.

(Problems to be Solved by the Invention) However, the tubular article produced by the above-described first method cannot be used in a temperature range exceeding the heat resistance of the ethylene tetrafluoride-hexafluoroethylene copolymer. Not only is the excellent heat resistance of the polyimide not fully utilized, but also due to its structure, a spiral wrap portion remains, and the tubular article is composed of thick and thin portions.

Further, the tubular article manufactured by the second method is composed of a single polyimide resin, but it is very difficult to extract the polyimide tubular article from the inner surface of a molded pipe such as a glass or stainless steel pipe. In addition, it is difficult to produce a small-diameter tubular article in order to take out the polyimide tubular article from the inner surface of the molded tube, and it is extremely difficult to produce a long article.

Further, the polyimide tubular article manufactured by the third method is a tubular article obtained from a polyimide resin alone as in the above-described second method. However, the heat-shrinkable tube for applying the polyimide precursor to the outer surface must be insoluble in N-methyl-2-pyrrolidone contained in the polyimide precursor at the reaction temperature for imidization of the polyimide precursor. Then, a heat-shrinkable tube made of a fluorine resin must be used. In addition, the same quantity of the heat-shrinkable tube made of fluororesin is consumed for manufacturing the polyimide tubular article, which is very expensive. Furthermore, since the processing temperature of the fluorinated resin heat-shrinkable tube is high, the uneven thickness and the variation of the outer diameter are large, and the variation in the performance of the heat-shrinkable tube directly adversely affects the polyimide tube.

Incidentally, a problem in manufacturing a polyimide tubular article is that extrusion molding, inflation or vacuum molding cannot be performed unlike a tubular article made of a thermoplastic resin. Therefore, as a method for producing a polyimide tubular article, a method of applying the polyamic acid solution, which is a precursor thereof, to a mold or the like and removing the mold at the stage of imidization by heating is inevitable.

However, polyimide resin is a resin used also as an adhesive, and when a polyamic acid solution is applied to a mold and imidized by heating, the polyimide tubular article adheres to the mold and it is impossible to remove the polyimide tubular article from the mold. Near possible.

The present invention solves the above-mentioned conventional problems, and provides a method for producing a tubular article using a polyimide precursor solution that can be easily produced and can be reduced in cost.

(Means for Solving the Problems) The inventors of the present invention have conducted various studies on the problems of the prior art and the problems in processing of the polyimide resin. The present inventors have invented a method for producing a new polyimide tubular article using a mold-releasing resin or using a core coated with a mold-releasing resin. That is, the present invention applies a polyimide precursor solution,
The core resin to be molded or the release resin covering the core body withstands a temperature of 180 ° C, and in the wettability of the resin,
A resin having a contact angle with water of 48 degrees or more, preferably 72 to 120 degrees, such as polyvinyl fluoride, polyvinylidene fluoride, polychlorinated trifluoride, polytetrafluoroethylene, and tetrafluoroethylene. Hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-
Use or coat a resin such as ethylene chloride trifluoride, ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer, silicone polyimide, polyamide, phenol, polypropylene, epoxy, etc. The applied polyimide precursor is heated to a state where the applied polyimide precursor can maintain strength at least as a tubular material, and a tubular material having an inner diameter corresponding to the outer diameter of the thermally expanded core body is formed and cooled. Thereafter, the tubular article is taken out from the core body and further subjected to a heat treatment.

(Action) In the heating step, the release resin or the core coated with the release resin expands and the outer diameter increases. A tubular object having an inner diameter corresponding to the outer diameter is formed. Then, the diameter of the tubular material core which has been imide-converted by partial heating slightly decreases due to a temperature decrease. However, the tubular body and the core body are separated due to the relationship between the coefficient of thermal expansion and the release effect of the release resin, and are reduced in diameter, so that both can be easily separated.

(Example) An example of the manufacturing method of the present invention will be described step by step.
However, the present embodiment does not limit the scope of the present invention.

First, the core used in the present invention is molded or cut out of the above-mentioned releasable resin as it is, subjected to a cutting process, etc., and used after finishing to the inner dimensions of the tubular article, or After applying or applying the resin on the surface of the core material made of metal or heat-resistant resin, it is baked and cured, and a method of providing a coating layer of the releasable resin on the surface of the core material or extruding and press-molding the releasable resin. Various processing methods are conceivable, such as a method of molding on a core material or a method of covering a tube made of a release resin on the core material.

However, in general, it is desirable to mold the releasable resin in some form on the surface of the metal core material in view of the dimensional accuracy of the tubular article itself. Also, when a release resin is molded on the surface of a core material such as a metal, the adhesion between the core material and the release resin is extremely important, and only the release layer is peeled off from the core material by heating. Otherwise, the accuracy of the tubular object will not be obtained at all.

The materials used for the releasable core material and the releasable resin layer greatly affect the viscosity of the polyimide precursor solution for molding the tubular article, and the present inventors have been concerned about this.

According to the experimental results of the present inventors, it is suitable that the higher the viscosity of the polyimide precursor solution, the larger the contact angle of the releasable material. In other words, the lower the viscosity of the polyimide precursor solution, the lower the contact angle of the releasable material is required. This is because the polyimide precursor solution is slightly imidized by applying heat and is separated from the core material. The larger the contact angle of the conductive material, the more difficult it is to apply the polyimide precursor solution uniformly to the release material. In the case of increasing the solute concentration by heating), the uniformity of the applied liquid is lost, and it becomes impossible to form a precise tubular object. From the experimental results so far, when the viscosity of the polyimide precursor solution is about 1 to 100 poise, the contact angle of the release material is 48 to 9
0 degree is suitable, 60-120 degree for 100-500 poise, and 80 degree or more for 500 or more poise.

However, it has been recognized that when the viscosity is high, there is no major problem as long as the release material has a contact angle of 48 degrees or more.

Subsequently, a tubular article using the polyimide precursor solution is produced using the releasable core.

For example, the releasable core is immersed in a container containing a polyimide solution or a polyimide precursor solution. And
When the core is pulled up between the outer diameter of the core and a drawing ring having a predetermined gap, a resin film having a predetermined thickness is formed on the core.

As a method of forming the polyimide precursor solution on the outer peripheral surface of the core body, it is possible to mold using a scraper or to mold by an extrusion method.

Then, the core body is placed in a heating furnace and heated at a predetermined temperature to reduce the solvent concentration in the polyimide or polyimide precursor solution, thereby maintaining the strength as a tubular body. In addition, the heating causes some imide conversion of the polyimide precursor solution itself, and the resin is cured. At this time, the core body is thermally expanded by being heated, and the outer diameter increases.
As the solvent in the polyimide precursor solution is gradually removed, imidization occurs little by little, and a state is maintained in which the strength of the tubular material is maintained.

Finally, the core is cooled. By this cooling, the core body and the tubular object shrink. However, due to the difference in shrinkage between the core and the tubular body and the release effect of the core, the tubular body is separated from the core,
A predetermined tubular object is obtained.

In addition, since the release layer is still firmly formed on the core body, the first step may be performed to form the tubular article again.

The tubular material obtained in this way removes a little of the solvent contained in the tubular material or performs a little imidization, rather than completely imidizing on the core, and has a strength as a tubular material. It is desirable to cool and separate it from the core at the stage where the holding is performed. This is because if the imidization of the tubular material is completely performed on the releasable core, the polyimide precursor solution will become completely imidized and will become more viscous. And it cannot be separated. Further, it is desirable that the tubular material separated in a state where the imidization has begun a little is put into the core again, or only the tubular material is reheated and completely imidized to be used as the tubular material.

 Next, specific examples of the present invention will be described.

(Example 1) A stainless steel core having an outer diameter of 50 mm and a length of 500 mm was coated with polytetrafluoroethylene (hereinafter, referred to as PTFE) resin.
A smooth PTFE resin-coated core was prepared.

The contact angle of PTFE was 115 degrees. This core is immersed in a polyimide precursor solution having a viscosity of 1000 poise,
The polyimide precursor solution was applied to the outer surface of the core with a thickness of 210 μm by pulling up between the outer diameter of the core and a ring-shaped outer mold having a gap of 1000 μm.

This core was heated in an oven at 140 ° C. for 90 minutes to remove the solvent, and further heated at 200 ° C. for 10 minutes to perform imide conversion.
At this time, the core expands and the outer diameter increases. A tubular object having an inner diameter corresponding to the outer diameter is formed. Thereafter, when the tube is taken out of the oven and cooled to lower the temperature of the imide-converted tubular material and the metal core, the two are easily separated due to the difference in coefficient of thermal expansion and the releasability of the fluorine resin.

Then, after cooling to room temperature, remove from core and remove inner diameter 50.1mm
A polyimide tube having a thickness of 100 μm and a length of 450 mm was obtained. Further, after that, the tubular body was inserted again into the metal core, and the core was put into an oven, and heated at 250 ° C. for 20 minutes and at 400 ° C. for 20 minutes. Then, the mixture was cooled again to obtain a completely imidized tubular material. In this case, there was no adhesion between the metal core and the tubular object, and the tube could be easily separated. The tensile strength was 28 kg / mm ² .

(Example 2) An aluminum core having an outer diameter of 90 mm and a length of 1000 mm was coated with polyvinylidene fluoride (hereinafter, referred to as PVdF) to obtain a smooth PV.
A dF resin-coated core was prepared.

The core was immersed in a polyimide precursor solution having a viscosity of 100 poise, and the polyimide precursor solution was uniformly applied to a thickness of 200 μm on the outer diameter of the core.

This core was heated in an oven at 250 ° C. for 10 minutes to remove the solvent, further heated at 120 ° C. for 90 minutes, and then heated at 160 ° C. for 20 minutes to perform imide conversion. At this time, the core expands and the outer diameter increases. A tubular object having an inner diameter corresponding to the outer diameter is formed.

Then, after cooling to room temperature, the core was released from the core, and the tube was heated at 350 ° C. for 1 hour to obtain an inner diameter of 90.1 mm 2
A polyimide tube having a length of 0 μm and a length of 900 mm was obtained. Its tensile strength was 27 kg / mm ² .

(Example 3) The surface of a core made of an extruded polyamide resin having an outer diameter of 30 mm and a length of 100 mm was immersed in a polyimide precursor solution having a viscosity of 10 poise and slowly pulled up to the outer diameter of the core.
The polyimide precursor solution was uniformly applied to a thickness of 50 μm.

The contact angle of the polyamide resin was 77 degrees. Leave this core in a 60 ° C oven while rotating it for 60 minutes, then heat dry at 100 ° C for 30 minutes and 150 ° C for 10 minutes,
Removed from oven and cooled.

Since the polyimide precursor completely maintained the strength as a tubular material, the core body and the tubular material separated when slowly pulled out.

Thereafter, the tubular object is further fitted into the glass core,
After heating at 30 ° C., 250 ° C., and 360 ° C. for 30 minutes each, the mixture was cooled, and the tube was pulled out to obtain a polyimide tube. This tubular article had a thickness of 5 μm and a tensile strength of 27 kg / mm ² , confirming that it was a complete polyimide tubular article.

(Comparative Example 1) The surface of a stainless steel core having an outer diameter of 47 mm and a length of 500 mm was mirror-finished to a surface roughness of 0.5 μm or less by puff polishing, and a polyimide precursor was applied to this core in the same manner as in Example 2. It was applied to the outer surface of the core with a thickness of 200 μm by the method.

The coated core of the polyimide precursor solution was heated in an oven at 250 ° C. for 10 minutes to remove the solvent, further heated at 120 ° C. for 90 minutes, and then heated at 160 ° C. for 20 minutes to perform imide conversion.

Tried to remove the polyimide tube after cooling, the polyimide tube is tightly adhered to the stainless steel core,
It was not possible to remove it from the core while keeping the tubular shape.
In addition, the tubular object attached to the stainless steel core
After heating at 0 ° C. for 1 hour, an attempt was made to remove it, but it could not be removed at all.

(Comparative Example 2) In the same manner as in Example 1, a polyimide tubular article was manufactured, and separation of the tubular article from the releasable core was performed by final heating 400.
Performed after heating at 20 ° C. for 20 minutes.

In this case, although the core was coated with PTFE, which is a release resin, separation was difficult, and the shape of the tubular material could hardly be maintained. An accurate tubular object could not be obtained.

In the above-described embodiments of the present invention, various polyimide precursor solutions were used as the thermosetting resin. These solutions are, for example, Japanese Patent Publication No. 37-97, Japanese Patent Publication No. 60-362, or No. 38324 discloses a production method thereof, and is not limited to the material of the tubular article of the present invention.

Further, as the thermosetting resin, an epoxy resin or the like can be used in addition to the polyimide precursor.

In addition, as for the fluorine resin coated on the surface of the metallic core, in addition to the PTFE resin, an ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer (PFA) or an ethylene tetrafluoride-hexafluoroethylene copolymer ( FEP) or ethylene tetrafluoride copolymer (ETFE) can also be used.

Further, as the releasable resin, in addition to the above-mentioned fluorine resin, silicon or polypropylene resin can be used.

The polyimide tubular article produced by the present invention is expected to be used in a very wide range of applications such as a conveyor belt requiring dimensional stability or heat resistance or a tubular film for fixing a hot-melt toner such as a copying machine or a laser beam printer. .

As described above, the present invention can easily obtain a polyimide precursor solution or a tubular material by selecting the viscosity of the polyimide precursor solution and the contact angle of the surface material of the core to be molded. A tubular article can be formed on the outside of the core so that the tubular article can be separated from the core. In other words, the polyimide precursor solution is applied to the surface of the core coated with the release resin or the release resin, heated, and easily separated by separating the tubular material from a state in which the strength is maintained as a tubular material. It shows a method by which a tubular article can be obtained.

(Effect of the Invention) The present invention provides a good combination of the difference in thermal expansion coefficient between the polyimide precursor solution and the releasable core and the surface tension of the releasable resin. By the combination, a polyimide tubular article, which could not be obtained conventionally, can be molded on the outer surface of the core body. That is, the present invention
When a tubular material having an inner diameter corresponding to the outer diameter of the core expanded in the heating step is formed, and the temperature of the imide-converted tubular and the releasable core decreases, the difference between the coefficient of thermal expansion and the releasable resin is reduced. Are easily separated from each other due to the releasing effect of. Therefore, the tubular article can be produced very easily, and the core can be used repeatedly, so that the production cost can be reduced.

Furthermore, the polyimide tubular article obtained by the production method of the present invention has a uniform thickness, and the difference in inner diameter in the length direction of the tubular article is 0.
It was less than 05 mm, and it was possible to easily obtain a highly accurate tubular object.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hitoshi Fujiwara 5-13-13 Ichiriyama, Otsu City, Shiga Prefecture Ai. S. Teiuchi (72) Inventor Yoji Tani 5- 13-13 Ichiriyama, Otsu City, Shiga Pref. S. (56) References JP-A-60-203427 (JP, A) JP-A-64-22514 (JP, A) JP-A-1-141100 (JP, A) (58) Fields investigated (Int. . ^7, DB name) B29C 41/00 - 41/52

Claims (8)

(57) [Claims] 1. A tubular molding solution comprising a polyimide precursor solution is applied to the outer surface of a core comprising a release resin, and the applied polyimide precursor solution is heated until at least the strength of the tubular material can be maintained. And forming a tubular article having an inner diameter corresponding to the outer diameter of the thermally expanded core body, cooling, removing the tubular article from the core body, and performing a heat treatment thereon. 2. A tubular molding solution comprising a polyimide precursor solution is applied to the outer surface of a core obtained by coating a surface of a metal core material with a release resin, and the applied polyimide precursor solution comprises at least a tubular material. Heat until the strength can be maintained as it is, and form a tubular body with an inner diameter corresponding to the outer diameter of the thermally expanded core,
A method for producing a tubular article, comprising taking out the tubular article from the core after cooling, and further performing a heat treatment. 3. The method for manufacturing a tubular article according to claim 1, wherein the thickness of the tubular article is in the range of 5 to 5000 μm. 4. A core made of a release resin or a release resin coated on the core withstands a temperature of at least 180 ° C. and has a contact angle with water of 48 ° or more in wettability of the resin. Item 4. The method for producing a tubular article according to any one of Items 1 to 3, wherein a core made of a polymer material is used. 5. The method according to claim 1, wherein the core or the release resin covering the core withstands a temperature of at least 180 ° C. and the viscosity of the polyimide precursor solution is 1 to 100 poise. The tubular article according to any one of claims 1 to 3, wherein a core made of a polymer material having a contact angle with water of 48 to 90 degrees is used in the wettability of the resin. Manufacturing method. 6. When the core of the release resin or the release resin covering the core withstands a temperature of at least 180 ° C. and the viscosity of the polyimide precursor solution is 100 to 500 poise. The tubular article according to any one of claims 1 to 3, wherein a core made of a polymer material having a contact angle with water of 60 to 120 degrees in terms of wettability of the resin is used. Manufacturing method. 7. When the core made of a release resin or the release resin coated on the core withstands a temperature of at least 180 ° C. and the viscosity of the polyimide precursor solution is 500 poise or more, In the wettability of the resin, the contact angle with water is 80
Item 4. The method for producing a tubular article according to any one of Items 1 to 3, wherein a core made of a polymer material having a degree of degree or higher is used. 8. The tubular article according to any one of claims 4 to 7, wherein the release resin comprises a fluororesin or a release resin obtained by mixing a filler with the fluororesin. Production method.