JP3237715B2 - Method for producing thermoplastic polyimide resin tubular film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermoplastic polyimide-based tubular film.

[0002]

2. Description of the Related Art Hitherto, a polyimide film has been used as a heat-resistant film for various uses. This polyimide film is mainly cast from a solution of a polyimide acid, a precursor of polyimide, by a casting method. In general, a thin film was formed by drying, followed by drying, dehydration, and ring closure to form a film.

[0003]

Problems to be Solved by the Invention Polyimide films formed by the casting method are inferior in productivity during production, and have problems in environmental pollution and hygiene due to the use of solvents, and are expensive. Was something.

In order to solve the above-mentioned problems, the present inventors have attempted to obtain a tubular film having extremely high dimensional accuracy and film thickness accuracy by a melt extrusion method using a material mainly composed of a thermoplastic polyimide resin. After various studies, the present invention has been finally reached.

[0005]

SUMMARY OF THE INVENTION The present invention provides a dimensional accuracy of a melt-extruded film containing a thermoplastic polyimide resin as a main component.
The present invention relates to a method for producing a thermoplastic polyimide tubular film having excellent film thickness accuracy.

[0006] The thermoplastic polyimide resin according to the present invention is a completely new type of thermoplastic polyimide resin different from both conventional thermosetting and non-thermosetting imide resins. As such a resin, for example, using a Koka type flow tester (die 10 mm × 0.1 mm, preheating time 5 min), it is 380 to 420 ° C. near the melting point.
And those having a melt viscosity of 1,000 to 4,000 poise measured in the above. Since a melt-extruded film is formed using such a thermoplastic polyimide resin having a low melt viscosity, a thermoplastic polyimide-based tubular film having excellent dimensional accuracy and film thickness accuracy can be easily formed. At this time, the thermoplastic polyimide resin having a melt viscosity other than the above range may be melt-extruded to form a film, but the dimensional accuracy and the film thickness accuracy tend to decrease, which is not preferable in many cases. There are many cases. However, a thermoplastic polyimide resin having a melt viscosity outside the above range can be used depending on the application, and is not necessarily limited to the above range.

The thermoplastic polyimide resin of the present invention may be formed by melt extrusion film formation alone, but may be mixed with an inorganic filler in order to improve the thermal conductivity. Absent. In this case, examples of the inorganic filler include conductive carbon, talc, fissure titanate, boron nitride, and the like, but are not limited thereto. Further, a stabilizer, a lubricant, a surfactant, a pigment, a resin other than the polyimide-based resin, and the like may be added as long as the performance of the thermoplastic polyimide-based resin is not remarkably reduced, and this is not particularly limited.

When the thermoplastic polyimide resin according to the present invention is supplied to an extruder, it is preferable that the thermoplastic polyimide resin is dehumidified and dried so that the water content is 30 ppm or less.
When the content exceeds ppm, the polyimide resin is easily decomposed, the thermoplastic fluidity is deteriorated, and a bubble or the like is generated in the film, etc., thereby forming a thermoplastic polyimide tubular film having excellent dimensional accuracy and film thickness accuracy. In many cases, it is not preferable.

The thermoplastic polyimide tubular film of the present invention is generally formed into a tubular shape by melt extrusion using an extruder equipped with an annular die. In the case of steel, metal oxides and the like are often oxidized and metal oxides are mixed into the film, and there is a tendency that the excellent performance of the thermoplastic polyimide film is deteriorated. It is often undesirable to use an extruder that has However, if necessary, a cylinder made of nitrided steel may be used without any particular limitation.

[0010] The cylinder of the extruder used to form the thermoplastic polyimide film of the present invention is preferably lined uniformly with a special alloy layer on the inner peripheral surface of the cylinder. Examples of a lining material in which one or two or more of carbon, manganese, silicon, boron, nickel, cobalt, chromium, tungsten, and carbide are uniformly dispersed in a hard corrosion-resistant alloy matrix, but are not necessarily limited thereto Any other material that can prevent oxidation of the nitrided steel may be used.

The screw used in the extruder is preferably a rapid compression type, and examples thereof include those having an L / D of 24 to 29. The screw is generally provided with hard chrome plating, but this is not particularly limited.

If necessary, a filter for gel filtration may be attached to the extruder, for example, near the tip of the cylinder or near the head in order to prevent gel molecules from being mixed into the film. At this time, as such a filter for filtration, for example, a laminate of a nonwoven fabric of a metal fiber having a large fiber diameter and a nonwoven fabric of a metal fiber having a small fiber diameter is laminated with a protective layer having a mesh shape (for example, made of stainless steel) and a mesh shape. (Stainless steel) is preferably sandwiched between support layers, then sintered and integrated to form a fine-grained material having a mesh of about 5 μm, but this value is not particularly limited. Examples of such a filter include a leaf-type filter. However, the filter is not limited thereto, and any other filter may be used as long as it can filter gel molecules of the resin.

To form the thermoplastic polyimide tubular film of the present invention, an annular die is attached to the above extruder, and a gas such as air is blown into the inside of the tube extruded from the annular die to a predetermined diameter ( (It may be smaller than the extrusion diameter of the die). At this time, the annular die is preferably of a spiral mandrel type.

The cooling method is not particularly limited, and any suitable method such as an inside mandrel method or an external cooling method may be adopted. A particularly preferred example is a vacuum water tank. The vacuum water tank is a structure having a sizing sleeve and a cooling water tank whose inside is depressurized by a vacuum pump or the like, and the inner ring surface of the sizing sleeve, that is, the surface in contact with the tube, is made of a material having good smoothness (for example, a mirror finish) Coated metal or fluororesin), and is provided with pores. Due to these pores, the surface in contact with the tubular film is always in a reduced pressure state, whereby the outer diameter of the tubular film is regulated to a constant diameter along the inner ring surface of the sleeve,
At this time, if necessary, a small amount of water or the like may be supplied to the inner ring surface of the sleeve to form a thin water film between the inner ring of the sleeve and the outer surface of the tubular film. With such a vacuum water tank, the outer diameter of the tubular film is accurately regulated and cooled, and the surface condition is also good, and the dimensional accuracy is excellent.

At this time, the cooling water tank is a general one and has a structure in which the outer surface of the tubular film is in direct contact with water. There may be no cyclic structure, and there is no particular limitation.

The extrusion conditions for forming the thermoplastic polyimide tubular film according to the present invention with the above-described extruder are not particularly limited as long as it is appropriately determined. Specifically, the supply units 310 to 360 are provided. ° C, compression part 360-400
° C, melting part 370-410 ° C, die temperature 370-41
A value of about 0 ° C. can be exemplified. However, these values are not particularly limited. The number of spirals of the screw can be exemplified as suitable for the supply units 9 to 15, the compression units 3 to 8, and the fusion units 7 to 8, but this value is merely an example and is not necessarily limited thereto.

In order to improve the mechanical strength at high temperatures, the thermoplastic polyimide tubular film of the present invention is stretched biaxially or uniaxially and, if necessary, crystallized by heat setting. Is desirable. The crystallinity at the time of crystallization is not particularly limited, but the crystallinity is 10
It is preferable to set it to 35%. In this case, when the degree of crystallinity is 10% or less, thermal deformation occurs at 200 ° C. or more, which is not preferable in many cases. When the degree of crystallinity exceeds 35%, the film becomes brittle and cracks occur in the film, which is not preferable. Depending on the application, a value outside this range can be used. At this time, it is needless to say that the above-mentioned stretching and heat setting are not included in the scope of the present invention.

The stretching method is not particularly limited, and may be carried out by an appropriate method. The stretching conditions are not particularly limited, but the stretching temperature is preferably 250 to 350 ° C., and the stretching ratio is preferably 1.2 to 3 times. When the stretching temperature is 250 ° C. or less, uniform stretching tends to be difficult, and the stretching temperature is 350 ° C. or more. In many cases, stretching effects such as increased strength are not recognized, and when the stretching ratio is 1.2 times or less, crystallization is not enough, strength, improvement in rigidity cannot be expected, and when stretched to 3 times or more, The accuracy of the film thickness tends to decrease, and the decrease in the accuracy of the film thickness is often not preferable as the stretching ratio is large. Of course, these values are merely examples, and if necessary, the values may exceed the above range, and are not particularly limited.

The heat setting that is performed as necessary is generally performed continuously as it is after the completion of stretching, but is not limited thereto, and may be performed by any other appropriate method. The heat setting temperature is not particularly limited, but may be 30.
The temperature is preferably 0 to 350 ° C., and if the temperature is 300 ° C. or lower, the heat fixation is insufficient and the dimensional accuracy is often reduced.
Although the heat setting time varies depending on the heat setting temperature, it is usually preferably 10 to 30 minutes, and if it is less than 10 minutes, the heat fixation is not sufficient and the dimensional stability often decreases.
When the length is more than minutes, the film thickness accuracy tends to decrease, but depending on the application, the film can be formed with a value outside these ranges, and such a value is not particularly limited.

The above-mentioned thermoplastic polyimide film is preferably formed in a clean room in order to prevent foreign substances and the like from being mixed in the film, but is not particularly limited thereto. At this time, the cleanness of the clean room is preferably such that the number of particles of 0.1 μm or more contained in one cubic foot of air is 10,000 or less, and the smaller the number, the higher the yield can be expected. Needless to say, it is not always necessary to perform the film formation in a clean room as in the related art.

The thermoplastic polyimide tubular film formed as described above is excellent in heat resistance, mechanical properties, dimensional stability, film thickness accuracy, flame resistance, friction resistance, abrasion, electrical properties, etc., and is flexible. Printed circuit boards, insulating films for electric parts, seat belts, food trays, medical parts,
Applications such as optical parts and materials can be expected to expand, and there is no particular limitation on the use.

Hereinafter, the present invention will be described with reference to examples.

[0023]

EXAMPLE A thermoplastic polyimide resin pellet (glass transition temperature: 250 ° C., melting point: 388 ° C., melt viscosity: 2927 poises measured by a Koka type flow tester at 420 ° C.) was circulated by a tray dryer at a circulating hot air temperature of 300 ° C. for 2 hours. After drying to crystallize only the surface of the pellet, the pellet was dried at 250 ° C. for 10 hours with a sealed dehumidifying hopper drier to obtain a water content of 1
It was set to 0 ppm. Subsequently, the pellet temperature was supplied to a hopper and replaced with nitrogen.
The inner surface of the heated cylinder was fed into an extruder lined with X-alloy 800 (manufactured by Fuji Industries), melted, and passed through the above-mentioned leaf-type filter of 5 μm attached between the tip of the cylinder and a die.
Melt extrusion was performed from an annular die having an outer diameter of 32φ, an inner diameter of 30φ, and a temperature of 390 ° C. The melt-extruded molten film was sucked into a sizing sleeve having an inner diameter of 245 in a vacuum water tank system and cooled to form a thermoplastic polyimide film. This film has a thickness of 50μ ± 5μ and a circumference of 7
It was 5.4 ± 0.5 mm. The tubular film thus obtained was stretched at 290 ° C. twice in the circumferential direction and 1.2 times in the longitudinal direction, and then heat-set at 310 ° C., and the obtained film had a thickness of 20 ± 2 μm. Circumference 15
0.8 ± 0.2 mm. This thermoplastic polyimide tube-like film was formed with a cleanness of 10,000.
No foreign matter was found in the film formed in the clean room.

[0024]

[Comparative Example] Extruded film could not be formed with a thermosetting polyimide resin.

[0025]

The present invention is as described above. The thermoplastic polyimide-based tubular film of the present invention is particularly preferable because it has excellent dimensional accuracy and film thickness accuracy.
(Flexible printed circuit board), insulation film for electric wires, precision electric and electronic parts utilizing heat resistance, such as copying machines,
It is suitable for various belts of a printer, for example, a fixing belt, and has good dimensional accuracy, so that it can be used as a driving belt for precision equipment and the like. Further, it can be expected to have various uses in food, medical, optical parts and other fields.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Wakinaka 1-cho, Hirano, Oku-murakuno, Konan-shi, Aichi Examiner in the Konan factory of Gunze Co., Ltd. Shogo Oshima (56) Reference JP-A-61-143547 (JP, A) JP-A-2-107424 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 47/00-47/96

Claims (2)

(57) [Claims] 1. When feeding to an extruder, the water content is 30
Using a thermoplastic polyimide resin that is not more than ppm,
A cylinder in which the inner surface is coated with a lining layer in which a particulate material is uniformly dispersed in a corrosion-resistant alloy matrix, a screw of a rapid compression type having an L / D of 24 to 29, and a metal fiber having a large fiber diameter Extruder equipped with a filter that is formed by sintering a composite nonwoven fabric obtained by laminating a composite nonwoven fabric and a nonwoven fabric made of a metal fiber having a small fiber diameter between a protective layer and a support layer, and a spiral mandrel type annular die Melt extrusion, followed by cooling in a vacuum water bath, characterized in that the film thickness accuracy is within ± 10% and the perimeter accuracy is within ± 0.66%. 2. The film is formed by melt extrusion in a clean room of 10,000 class or less.
The method for producing a thermoplastic polyimide-based tubular film according to item 1.