JP2001146637A - Polyimide fiber for binder and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyimide fiber for a binder excellent in heat, chemical and radiation resistances, flame retardance and mechanical characteristics and good in dispersibility and handleability and to provide a method for producing the polyimide fiber. SOLUTION: This polyimide fiber for the binder has <=30 μm fiber diameter and >=1.8 cN/dtex strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in heat resistance, flame retardancy, chemical resistance and radiation resistance which can be used as a binder for so-called super fibers having extremely high performance such as aramid fibers and carbon fibers. And a method for producing the same.

[0002]

2. Description of the Related Art Polyamide, polyester, polyacetal, polycarbonate and the like are called engineering plastics, while polyimide is called a super engineering plastic because of its excellent heat resistance, flame retardancy, chemical resistance, radiation resistance and the like. Have been done.

[0003] Polyimides that are generally known are thermosetting resins, and among the polyimides, there are resins that exhibit thermoplasticity, and their fiberization is being studied. In addition, various studies have been made to produce a high-performance composite material by mixing a fibrous polyimide with a so-called super fiber, heating the mixture, and using the thermoplastic polyimide as a binder of the super fiber.

[0004] The required performance as a binder is that it has good dispersibility with other materials, that it is easy to handle during processing and handling of the fiber, and that it plays a role in heat fusion between fibers during heat molding (binder). And so on. Therefore, the binder in the form of fiber is often excellent in performance.

[0005] As a method for producing a fiber of polyimide, there is a method of spinning by dissolving or dispersing in a solvent or a plasticizer. However, this method requires cost for dissolution, solvent removal, and solvent recovery.
It was not practical in terms of cost from an industrial point of view.

[0006] In some cases, melt spinning using thermoplastic polyimide as a raw material cannot be produced because of its high melting point, high melt viscosity, and easy occurrence of melt fracture. As a countermeasure, for example, Japanese Unexamined Patent Publication No. Hei 6-33316 discloses a method of performing stable spinning by limiting spinning conditions of thermoplastic polyimide.

However, the polymer melt viscosity range in which stable spinning can be performed by this method is limited to 700 Pa · s or less, and heat resistance, flame retardancy, and chemical resistance are obtained from high molecular weight polyimides. It was difficult to produce a polyimide fiber having excellent radiation resistance.

The present applicant has proposed a method for producing polyimide fibers in Japanese Patent Application No. 10-301892. Thereby, it has become possible to stably produce high-strength polyimide fibers having excellent yarn properties, but it is difficult to obtain a polyimide fiber having a small fiber diameter with performance suitable for binder fibers even in this method. was there.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and is excellent in heat resistance, flame retardancy, chemical resistance and radiation resistance, and has good dispersibility and handleability. An object of the present invention is to provide a polyimide fiber for a binder and a production method capable of stably producing the fiber for a long time.

[0010]

Means for Solving the Problems The present inventor has conducted studies on melt spinning of polyimide in order to solve the above-mentioned problems. As a result, the raw materials, melt spinning conditions and the production process thereof are important for the fiberization of polyimide. Having found that fact, they arrived at the present invention.

That is, the present invention has the following configuration. (1) A polyimide fiber for a binder, wherein the fiber diameter is 30 μm or less and the strength is 1.8 cN / dtex or more. (2) In producing the polyimide fiber according to the above (1),
Polyimide with a melt viscosity of 700 to 3,000 Pas 370 to 410
Melting at a temperature of 5 ° C for 5 to 30 minutes, extruding from a nozzle hole, and collecting and collecting a filament at a position of 10 to 100 cm from the nozzle surface, a filament having a fiber diameter of 50 μm or less,
A method for producing a polyimide fiber for a binder, which comprises performing a 5.0-fold stretching treatment and winding up.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the polyimide may contain a copolymer, a blend, or an inorganic additive, but is required to be a polyimide exhibiting thermoplasticity. By exhibiting thermoplasticity, melt spinning becomes possible, and there is an industrial merit in terms of cost.

The polyimide fiber of the present invention has a fiber diameter of 30 μm.
m or less, and particularly preferably 20 μm or less. When the fiber diameter is 30 μm or less, when mixed as a composite material, its dispersibility is improved,
Since it is uniformly dispersed, it becomes possible to sufficiently exhibit the role as a binder when subsequently hot-molded. If the fiber diameter exceeds 30 μm, the dispersibility when mixed as a composite material is undesirably reduced.

Further, the polyimide fiber of the present invention has a high strength.
It is necessary to be at least 1.8 cN / dtex, preferably at least 2.0 cN / dtex. As a binder, because it is finally melt molded, the fibers do not have to be high strength, but when cutting or mixing polyimide fibers, 1.8 c
When it is N / dtex or more, the handling becomes extremely good and the handling becomes easy.

The polyimide fiber of the present invention can be used as a binder fiber while dispersing uniformly when compounded with a super fiber, making use of the inherent properties of the fiber such as flame retardancy, heat resistance and chemical resistance. It can be used in an extremely wide range of applications such as composite materials such as fiber reinforced plastics and electric applications such as printed circuit boards.

Next, the method for producing the polyimide fiber of the present invention will be described. In the present invention, the polyimide used as a raw material of the polyimide fiber needs to be a polymer exhibiting thermoplasticity.For example, it is possible to use a polyimide formed from tetracarboxylic acid and its derivative and diamine and its derivative. it can.

This polymer needs to have a melt viscosity of 700 to 3,000 PaS measured at 400 ° C. and 100 s ⁻¹ , particularly preferably 1,000 to 2,000 PaS. If the melt viscosity is less than 700 PaS, the speed of extrusion from the nozzle hole in the molten state is too high, causing unevenness in fiber diameter and the like, and poor spinning properties. On the other hand, if it exceeds 3,000 PaS, the flowability of the molten polymer is poor, so that the spinning properties may be reduced, and the workability may be deteriorated when used as a binder fiber.

In order to melt the polyimide and extrude it from the spinneret, the spinning temperature is preferably from 370 ° C to 410 ° C. When the spinning temperature is lower than 370 ° C., the distribution of the molten polymer stream in the spinneret becomes extremely poor due to the high melt viscosity of the molten polymer, and stable spinning becomes extremely difficult. On the other hand, when the melting temperature exceeds 410 ° C., voids are formed in the filament due to decomposition of the polymer and the contained oligomer, and stable spinning becomes difficult.

The melting time of the polymer needs to be 5 to 30 minutes, preferably 10 to 20 minutes. If the residence time is less than 5 minutes, it is difficult to make the temperature of the polymer uniform, and it is difficult to stably produce thin fibers due to unevenness in melt viscosity. On the other hand, when the time exceeds 30 minutes, the polymer is liable to cause thermal deterioration, and stable spinning becomes difficult.

The melt spun fiber is extruded from a spinneret, cooled and solidified, and then converged.
It needs to be 10 to 100 cm from the spinneret. If this distance is shorter than 10 cm, the fibers extruded from the spinneret will be sharply bundled, resulting in insufficient cooling and solidification and increased resistance to the guide, causing tension fluctuations and thread breakage. May be. On the other hand, if the length is longer than 100 cm, the fiber is susceptible to the effect of air resistance. As a result, a large tension is applied to the fiber, and the number of thread breakage increases.

By satisfying the above conditions, the polyimide fiber discharged from the spinneret is preferably reduced to 100%.
It is wound up at a speed of up to 2,000 m / min, particularly preferably 200 to 1,500 m / min. If the winding speed is less than 100 m / min, not only the productivity is low but also the fiber diameter may be non-uniform. Conversely, if the winding speed exceeds 2,000 m / min, the morphological change of the filament at the time of take-up becomes large, and yarn breakage is likely to be induced.
Further, it is preferable to apply an oil agent to the polyimide fiber at the stage when the fiber is cooled and solidified.

The filament that has been cooled and solidified is
It is necessary that the fiber diameter is 50 μm or less. Fiber diameter
If it exceeds 50 μm, the deformation of the filament will not be able to cope with the plastic deformation in the stretching step, and thread breakage will occur.
In addition, it is necessary to perform a high-magnification stretching process on a filament having a large fiber diameter, which tends to cause a problem in operability.

In the present invention, a fiber having a fiber diameter of 50 μm or less which has been cooled, solidified and drawn is subjected to a 1.2- to 5.0-fold drawing treatment to obtain a desired polyimide fiber. The stretching process is
The fiber once wound may be processed in another step, or may be wound immediately after winding without winding. If the draw ratio is less than 1.2 times, it will be difficult to obtain a filament having a uniform fiber diameter due to drawing unevenness, and if it exceeds 5.0 times, the plastic deformation of the filament due to drawing cannot be applied, causing thread breakage, and It becomes impossible to obtain a polyimide fiber.

[0024]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples. In addition, each physical property in an Example was measured by the following method. a) Melt viscosity Using a Shimadzu flow tester, sample 2 g, die diameter
The melt viscosity was measured under the conditions of 1.0 mm × 10.0 mm and a melting temperature of 340 ° C. The melt viscosity at a shear rate of 100 sec ^-1 was determined from the relationship between the melt viscosity and the shear rate. b) High elongation Using a Shimadzu Autograph DSS-500, sample length 30
cm, gripping distance 5 cm, and tensile speed 30 cm / min. c) Good spinning quality Continuous spinning is performed for 24 hours.During this time, evaluation is made in the following two stages according to the situation of thread breakage, single yarn winding on rollers, etc. 、: Poor yarn-making properties with broken yarns and the like were indicated by x. d) Performance evaluation of binder fiber The filament is cut to a length of 5 mm, mixed with carbon fiber (BESFIGHTHTA-3K manufactured by Toho Rayon Co., Ltd.), and then made into a composite sheet. The sheet is pressed at a temperature of 300 ° C. Molded. The surface of the obtained sample was observed with a microscope, the state of dispersion of the fibers was visually judged, and those uniformly dispersed were indicated by と し て as the effect of the binder was large, and those that were uneven were indicated by ×. . e) Handling When the obtained fiber is rewound, cut or processed, it causes filament breakage or thread breakage, etc. Was.

Example 1 Polyimide having a melt viscosity of 1,200 PaS (Ultem manufactured by GE Plastics)
1010) was used as a raw material and melted. 0.3m diameter of molten polymer
A fixed amount was extruded from a spinneret having 24 m 2 nozzle holes, and was wound at a speed of 500 m / min. An oil agent was applied to the filament when it was cooled and solidified. Thereafter, the fibers were passed through a heater plate heated to 250 ° C. and subjected to a 2.2-fold heat drawing treatment to obtain a 130 dtex / 24f multifilament.

Example 2 Using oxydiphthalic anhydride and 3,4'-oxydianiline as raw materials, a polyimide resin having a melt viscosity of 1,500 PaS was obtained.
This was treated under the same conditions as in Example 1 to obtain a fiber.

Examples 3 and 4 Fibers were obtained in the same manner as in Example 2 under the conditions described in Table 1.

Examples 5 to 6 Fibers were obtained in the same manner as described in Example 1 under the conditions described in Table 1.

Comparative Examples 1 and 2 Fibers were obtained in the same manner as in Example 2 under the conditions described in Table 1.

Comparative Examples 3 to 11 Fibers were obtained in the same manner as in Example 1 under the conditions described in Table 1. Table 1 shows the melt viscosity, the melting temperature, the melting time, the convergence position, the yarn formability and the yarn strength of the polymers in Examples 1 to 6 and Comparative Examples 1 to 11.

[0031]

[Table 1]

As is apparent from Table 1, in Examples 1 to 6, polyimide fibers having a fiber diameter of 30 μm or less and a strength of 1.8 cN / dtex or more were obtained stably. The dispersibility was good.

[0033]

The polyimide fiber for a binder of the present invention has good dispersibility and handleability in addition to the original physical properties of being excellent in heat resistance, flame retardancy, chemical resistance and radiation resistance.
By the method of mixing with the reinforcing fiber, woven with the reinforcing fiber to make a woven fabric, or winding with the reinforcing fiber, etc.
It can be suitably used as a binder for a fiber reinforced composite. Further, according to the production method of the present invention, it is possible to stably produce polyimide fibers for a binder having the above advantages for a long time.

Claims (2)

[Claims] 1. A fiber having a fiber diameter of 30 μm or less and a strength of 1.8 c
A polyimide fiber for a binder, which has a N / dtex or more. 2. A polyimide having a melt viscosity of 700 to 3,000 Pa · s when producing the polyimide fiber according to claim 1.
Melting is performed at a temperature of 370 to 410 ° C for 5 to 30 minutes, extruded from a nozzle hole, bundled and taken up at a position of 10 to 100 cm from the nozzle surface, and a filament having a fiber diameter of 50 μm or less, A method for producing a polyimide fiber for a binder, which comprises performing a double stretching treatment and winding the resultant.