JPH0619018B2 - Aramid extrudate and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) Polymetaphenylene isophthalamide aromatic polyamide (hereinafter abbreviated as PMIA) has a glass transition temperature of about 280.
℃, melting point is about 430 ℃, limiting oxygen index is about 30,
It has little temperature dependence of mechanical properties and is excellent in heat resistance and flame retardancy, so it is widely used as various molded products such as fibers, films and compression molded products. by the way,
In the production of these molded products, since the melting point of PMIA and the thermal decomposition point are extremely close to each other, it is generally impossible to carry out melt molding, and conventionally, solution molding or compression molding below the melting point has been adopted. However, in the solution molding method, since it is necessary to remove the solvent, only fibers having a thickness of several tens of denier and films having a thickness of approximately 100 microns can be molded. On the contrary, it is practically impossible to produce a fiber or film-like material by the compression molding method. On the other hand, the present inventors succeeded in instantaneous thermoplastic molding as a result of various studies for molding the bristles of PMIA.
57-192436, 58-109618, 58-109619, 59-144607, 61-245
In the publications of No. 305, these methods have enabled bristle molding of PMIA, which has been impossible in the past.

Since then, the present inventors have conducted various studies to develop new applications for PMIA bristles, and one of them is a heat-resistant brush with less foreign matter adhesion. To simply reduce the adhesion of foreign matter, the surface of the bristles may be processed with a silicone-based or fluorine-based treatment agent, but in applications such as brushes, the durability is insufficient and it is not practical. Therefore, the present inventors made a plate-shaped molded product by powder-mixing tetrafluoroethylene resin (PTFE) powder and PMIA powder and then compression-molding the mixture. Attempting to mold bristles by the method, it was extremely difficult to mold the bristles with 5% or more of PTFE mixed, and the bristles molded with 5% or less had irregularities on the surface and mechanical properties such as strength were markedly deteriorated. Not only that, but the effect of preventing foreign matter from adhering was also small, and this attempt ended in failure. The causes are as follows.

(1) The PTFE powder easily causes secondary agglomeration, and it is difficult to uniformly mix it with the PMIA powder.

(2) Since the melt viscosity of PTFE is extremely high (about 10 ^{11 to 12} poise at the molding temperature of PMIA bristles at 340 to 380 ° C) and the spinnability is low, PTFE particles dispersed in PMIA during the bristle molding process are It does not flow and remains almost as isolated particles.

(Means for Solving the Problems) Then, the present inventors have conducted extensive studies to solve the above problems, and as a result, have found a method for obtaining PMIA bristles having extremely remarkable advantages and arrived at the present invention.

That is, the present invention is an aramid extruded product characterized by comprising a fibrillar tetrafluoroethylene resin (PTFE) dispersed in an aromatic polyamide resin, and a method for producing the same.

The aromatic polyamide (PMIA) in the present invention is a homopolyamide or copolyamide in which 85 mol% or more of all repeating units are metaphenylene isophthalamide units. This PMIA is obtained by polycondensing metaphenylenediamine as an amine component or an aromatic diamine with it and isophthalic acid or an aromatic dibasic acid or its derivative as an acid component. is there.

As a specific method for producing PMIA, the interfacial polymerization method described in JP-B-47-10863 is preferable. This is because by this method, a PMIA powder extremely suitable as one of the raw materials for the aramid extruded product of the present invention can be obtained. That is,
The powder obtained by this method has a primary particle diameter of 1
It is as fine and uniform as about μ, and its primary particles aggregate to form a porous powder of about 30 to 100 μ.

The shape of the aramid extruded product of the present invention may be any of fibrous, film-like, rod-like, pipe-like, plate-like, etc., but in any case, the fibril-like P is contained in the PMIA resin.
The TFE resin is dispersed in a mesh shape. Since the fibrils in the dispersion state are extremely fine and uniform, it is difficult to distinguish them by direct observation of the molded product itself, but the molded product is a solvent of PMIA (concentrated sulfuric acid, N-methylpyrrolidone, N, N dimethylformamide, N, N dimethylacetamide), etc. to dissolve and remove PMIA, then remove the solvent, then scoop out the insoluble matter in the solvent, place it on the preparation, drop the solvent on it, and place the slide glass. By observing with a microscope of up to 100 times, the dispersion state can be clearly identified. The dispersed state of fibrillar PTFE observed by such means has the appearance of a capillary tube in a living body. FIG. 1 is a micrograph showing an example thereof. This is a monofilament-shaped extruded product of the present invention (2% mixture of PTFE) dipped in N-methylpyrrolidone to dissolve PMIA, and then gently take out a white thread-like insoluble matter, followed by a micrograph by the above method. It was taken (150 times).

The aramid extruded product of the present invention may have a multi-phase structure of a dispersed phase in which fibrillar PTFE is spread like a mesh in PMIA and a single phase of PMIA only. In such a multi-phase structure molded product, it is practically preferable to use the dispersed phase as the surface layer of the molded product as shown in FIG. That is, FIG. 2 is a schematic cross-sectional view of the above-mentioned multi-phase structure molded article, and 1 is fibrillar PTFE.
2 is a single phase of PMIA only.

Fibril-like PT in the aramid extruded product of the present invention
The content of FE is preferably 0.01 to 10% by weight. 0.01% by weight
If it is less than 10% by weight, the effect of the present invention is not exhibited, and if it exceeds 10% by weight, mechanical properties are rather deteriorated. Fibril PTFE
The preferred content of PTFE in the dispersed phase is 0.1-5% by weight.

Fibril-like PT in the aramid extruded product of the present invention
The dispersion amount (dispersion density) of the FE may be gradually changed from the surface layer to the inner layer of the molded product. Such a dense structure can be utilized when the difference in physical properties between the surface layer and the inner layer of the molded product is remarkably exhibited.

The aramid extruded product of the present invention may be mixed with a third component other than PTFE and PMIA, for example, dye, pigment, carbon, ceramic powder, metal powder and the like.

The fibrillarly dispersed PTFE of the present invention is highly oriented and crystallized. This contributes to the excellent mechanical properties of the extrudates according to the invention. The oriented crystallization of PTFE in the molded product can be clearly identified by wide-angle X-ray photography. FIG. 3 is a wide-angle X-ray photograph of the monofilament extrudate, and the clear spots on the photograph are reflections of the (1,0,0) plane in the PTFE crystal.

The aramid extruded product of the present invention is obtained by mixing an aqueous suspension of PTFE and a powder of PMIA and then drying the mixture to obtain a tetrafluoroethylene resin-coated aromatic polyamide powder (hereinafter referred to as PTFE-coated PMIA powder). Aromatic polyamide powder (PMIA powder) containing a) is thermally compressed and then extruded from a heat molding die.

The aqueous suspension of PTFE used in the method of the present invention may be an aqueous colloidal suspension that is generally commercially available. For example, first, a commercially available aqueous suspension having a resin content of 60% by weight is diluted with water to prepare a desired aqueous suspension for mixing, which is mixed with a PMIA powder in a mixer, and then dried in a dryer. And mold PTFE coated PMIA powder. The mixing ratio (weight ratio) of the aqueous suspension for mixing and PMIA powder is preferably in the range of 1: 2 to 2: 1. If the former is too small, the mixing will be non-uniform, and if too large, not only will the drying take longer, but the uniformity of the mixing will be lost.
The preferred concentration of PTFE in the mixed aqueous suspension of PTFE is in the range of 0.1 to 20%, more preferably 0.5.
It is in the range of ~ 10%.

The dry powder thus formed has a PTFE surface.
It is covered with a thin film. In particular, the above Japanese Patent Publication No. 47-10863
The PMIA powder obtained by the interfacial polymerization method described in Japanese Patent Publication No. JP-A-2003-13853 is an agglomerated particle of primary particles having a diameter of about 1 μm, and is easily penetrated by an aqueous PTFE suspension, which is preferable for producing the aramid extruded product of the present invention.

The aramid extrusion-molded product of the present invention is obtained by thermally compressing the PMIA powder containing the PTFE-coated PMIA powder obtained as described above, and then extruding it from a heat-molding die. Here, the PMIA powder containing the PTFE-coated PMIA powder (coating powder) is a mixed powder in which the coating powder and the original uncoated PMIA powder (original powder) are substantially uniformly mixed by a mixer or the like, or It means a composite powder in which a coating powder and an original powder are mixed in a phase, respectively, or a coating powder 100%, or a powder obtained by combining these three.

In the method of the present invention, the PMI containing the coating powder as described above is used.
After the powder A is hot-pressed, it is extruded from the heat-molding die to form the aramid extruded product of the present invention. The heat-compression operation and the extrusion operation from the heating die may be either discontinuous or continuous.

For example, in the case of discontinuity, the means described in JP-A-61-293818 is used to form a molded product having a certain shape, for example, a plate shape, and then the means described in JP-A-61-245305 is used. Then, the aramid extruded product of the present invention can be extruded. On the other hand, in the case of continuous operation, a plunger type extrusion device in which a heat compression zone and a heat extrusion zone are separated is used. Whichever means is used to produce the aramid extrudates of the invention, the method of the invention has enormous manufacturing utility. That is, since the PTFE-coated PMIA powder is included in the PMIA powder used in the present invention, it becomes difficult for the PMIA to adhere to the inner wall of the molding machine at the time of thermal compression and at the time of extrusion molding from the heating die. Not only can it be performed smoothly, but continuous production for a long time becomes possible.

Next, the method of the present invention will be described in more detail with an example using the apparatus shown in FIG.

FIG. 4 is a schematic diagram showing a plunger type extrusion device for forming a rod-shaped aramid extrudate using the method of the present invention. In order to mold the rod-shaped aramid extruded product of the present invention using this apparatus, first, the PT
FE-coated PMIA powder is prepared, and the powder obtained by mixing the powder with the original powder at a constant ratio or, preferably, only the coated powder is charged as the raw material 7 into the thermal compression zone in the extruder.
The thermal compression zone is divided into a cylindrical part 3 and a conical part 4 as shown in the figure,
The cylindrical portion 3 is set to a temperature (about 260 ° C.) slightly lower than the glass transition temperature of PMIA (about 280 ° C.), and the conical portion 4 is set to a temperature 30 to 70 ° C. higher than the glass transition temperature. The extrusion zone 5 composed of a thermoforming die having a thermoforming nozzle having a nozzle having a conical portion and a cylindrical portion is set at a temperature 20 to 80 ° C. lower than the melting point (about 430 ° C.). Thus, when the plunger 8 directly connected to the hydraulic cylinder is lowered and pressurized, the powder in the cylindrical portion of the thermal compression zone is heated and compressed while transmitting the pressure while maintaining the porous state. On the other hand, the powder in the cone portion is softened by being heated to the above temperature and is compressed while pushing out the air inside, and finally reaches the filling rate of 100%. The important thing here is
This means that the pressure loss of the plunger is transmitted to the lower side and the friction coefficient between the powder and the inner wall of the molding machine must be minimized. In the method of the present invention,
The use of the PMIA powder coated with PTFE is extremely advantageous in that respect.

The heat-compressed aramid that has gone through the heat-compression zone reaches the extrusion zone 5 composed of a heat-molding die, where it is further heat-thinned and extruded as a rod-shaped resin having a constant diameter,
The aramid extruded product 9 of the present invention is introduced into the cooling bath 6.

In the above steps, focusing on the behavior of the PTFE coating the aromatic polyamide powder, it becomes more apparent that the aramid extruded product of the present invention is formed by the method of the present invention. In the present invention, PT coating with PMIA powder
FE is made from an aqueous suspension as described above,
It is not a continuous film but an aggregate of fine particles, and it is unstable enough to be dispersed in water again without any treatment.
When the PMIA powder coated with such a resin is thermally compressed at the above temperature (310 to 350 ° C), the melting point is about 330 ° C.
The fine particles of No. 2 are softened, and the fine particles adjacent to each other are in close contact with each other and are continuously connected in a mesh shape. The mesh-like PTFE thus formed is further heated and stretched in the next heat-extruding step to become a fibril shape.

In this way, in order to improve the mechanical properties of the extruded rod-shaped aramid extruded product, it is desirable to draw it near the glass transition temperature of the aromatic polyamide. This is because not only the molecules of the aromatic polyamide itself are oriented but also the fibrillar ethylene tetrafluoride is oriented and crystallized by this stretching operation.

(Effect of the Invention) The aramid extruded product of the present invention has the following effects.

(1) The surface is non-adhesive, and it is difficult for foreign matter to adhere.

(2) The coefficient of friction is low.

(3) Static electricity is hard to generate.

(4) Chemical resistance is improved.

(5) Bending fatigue is improved.

Of the above effects, (1) and (2) can be inferred from the mixture of the present invention, but (3), (4) and (5) are unexpected and unexpected effects. According to the inference by the present inventor, the cause of (3) is that the charge trains of the aromatic polyamide and PTFE are almost opposite to each other, and the electrostatic charge is caused by the structure in which the fibrillar PTFE is dispersed in the aromatic polyamide. The reason for (4) is presumed to be that PTFE having extremely strong chemical resistance covers the surface of the aromatic polyamide in fibril units. Also,
It is speculated that the cause of (5) is that the oriented and crystallized fibrillar PTFE resin is dispersed in the aromatic polyamide resin in a mesh shape to cover the brittleness of the aromatic polyamide resin.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples.

Example 1 A rod-shaped aramid extruded product was molded by the following method.

(1) Preparation of PTFE-coated PMIA powder 100 parts by weight of meta-type aromatic polyamide (PMIA) powder (secondary particle average diameter 70 μm) obtained by the interfacial polymerization method described in JP-B-47-10863, and 150 parts by weight of a 4% by weight aqueous suspension of ethylene oxide resin (PTFE) was prepared, mixed with a V-type mixer for 30 minutes, and then dried with a drier to substantially remove water. Coated PMIA
A powder (coating powder) was prepared.

(2) Molding of Rod-Shaped Aramid Extruded Product Using the above coated powder as a raw material, a rod-shaped aramid extruded product having a diameter of 5 mm was molded under the following conditions using the apparatus shown in FIG.

Thermal compression zone Cylindrical part: Diameter 50 mm, temperature 260 ° C Cone: Bottom diameter 20 mm, temperature 340 ° C Extrusion zone Cylinder: Diameter 5 mm, temperature 370 ° C Finishing at the point where the lowest point is reached, the next molding is a discontinuous molding method in which the plunger is raised and the powder is charged, and the same operation is repeated, but in this example, no matter how many times the molding is repeated, A good extruded product was obtained without foreign matter adhering to the inside of the molding machine.

When a part of the obtained extruded product was dipped in dimethylacetamide, PMIA was dissolved and removed, and microscopic observation was carried out by the above-mentioned method. As a result, a PTFE fibril-like substance having an appearance like a capillary tube was observed.

Comparative Example 1 Using the same PMIA powder as in Example 1 as a raw material as it was, an apparatus and a molding method were the same, and an attempt was made to mold an extruded product having the same shape.

As a result, the first molding was successful, but after the second molding, PMIA was formed on the conical portion of the heat compression zone and the inner wall of the extrusion zone.
Adhered, which made molding difficult. Further, the surface of the obtained rod-shaped extruded product was extremely rough as compared with the surface of the smooth extruded product obtained in Example 1.

Comparative Example 2 100 parts by weight of the same PMIA powder as in Example 1 and 6 parts by weight of fine PTFE powder (polyflon molding powder manufactured by Daikin Industries, Ltd., M-12, average particle size 25 μ) were mixed in a V-type mixer for 30 minutes. A mixed powder was prepared, and using this as a raw material, a rod-shaped extruded product was molded in the same manner as in Example 1. As a result, adhesion to the inside of the molding machine was reduced as compared with Comparative Example 1, but as the number of moldings was increased, the adhesion started gradually and the moldability deteriorated.

The surface of the obtained extrudate was not as smooth as in Example 1.

Furthermore, when the dispersion state of the tetrafluoroethylene resin contained in the extruded product was examined, it was found that the short fibrous substances, scale-like substances and other complicated shapes were nonuniformly gathered. It was confirmed by infrared analysis that these insolubles were tetrafluoroethylene resin.

Example 2 Five types of fibrous aramid extrudates were molded by the following method.

(1) Preparation of PTFE-coated PMIA powder Five types of aqueous suspensions containing 0.5, 1, 3, 5, 10 wt% PTFE were prepared, and the PMIA powder of Example 1 and the respective aqueous suspensions were prepared. After mixing at a ratio of 1: 1 and drying, 5 kinds of coating powders were prepared.

(2) Molding of fibrous aramid extruded product In order to produce a fibrous aramid extruded product from the above-mentioned coated powder as a raw material, first, the above-mentioned coated powder is heated at 320 ° C. using an apparatus described in JP-A-61-293818. , 50 kgf / cm ² were heat-compressed to form a plate-shaped extrudate having a thickness of 8 mm. At this time, surprisingly, it was possible to form a plate-like material having a filling rate of 100% at a low pressure without containing a small amount of water in the powder. It is presumed that this is because the ethylene tetrafluoride resin reduced the internal friction of the powder and filled the spaces between the particles.

Next, using this plate-shaped extruded product as a raw material, the method disclosed in JP-A-61-24530
The fibrous aramid extruded product of the present invention was molded in the following manner using the method described in Japanese Patent Publication No. 5 and using the apparatus shown in FIG. That is, the plate-shaped extruded product is pushed into a box-shaped preheating zone to be preheated to 255 ° C., and then is softened by heating to 350 ° C. by a heating molding die (die) forming a softening zone and extruded from a nozzle, and further to 340 ° C. It is drawn in a heated box-shaped heat retaining zone while stretching it 10 times, and it is further stretched 3 times on a stretching plate at 280 ° C.
A 0 denier fibrous aramid extrudate was molded.
For comparison, a plate-like extruded product formed by using the original PMIA powder not coated with the tetrafluoroethylene resin at all was formed, and a 1200-denier fibrous aramid extruded product was formed under the same conditions.

When these fibrous aramid extrudates were compared and evaluated, the results shown in the table below were obtained, and it was found that a mixture of 2.9 wt% was comprehensively superior in terms of both production method and physical properties.

The extruded product mixed with the tetrafluoroethylene resin was treated with N, N ′ dimethylformamide solution to obtain PMIA.
After the components were dissolved and removed, the residue was observed under a microscope.
It was confirmed that FE was dispersed in a fibril form. In addition, wide-angle X-ray photography revealed a pattern in which the tetrafluoroethylene resin component was highly oriented and crystallized, as shown in FIG.

Example 3 2.9 wt% PTFE coated PMIA powder used in Example 2 3
A plate-like extruded product was molded in the same manner as in Example 2 with 0 part as the upper layer and the lower layer and 40 parts of the original powder of PMIA placed in the middle layer part.

This is extruded from the same device as in Example 2 in which the die part is replaced with a slit nozzle of 1 mm (temperature conditions are the same), thickness 0.3 m
A m-shaped film extrudate was formed. Next, this film was stretched 1.5 times in the width direction.

When this film was dipped in dimethylacetamide and the white paper-like insoluble matter was taken out and observed under a microscope, fibrils like a nonwoven fabric structure were observed.

[Brief description of drawings]

FIG. 1 is a micrograph showing the shape of fibrillar fibers of polytetrafluoroethylene contained in an aramid extruded product, FIG. 2 is a schematic cross-sectional view of a multiphase structure molded product, and FIG. 3 is an aramid extruded product. A wide-angle X-ray photograph, FIG. 4 is a schematic view of an aramid extrusion molded article forming apparatus.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI technical display location // B29K 77:00 4F (C08L 77/10 27:14) (72) Inventor Akira Kobayashi Osaka Prefecture 3-4-1 Mihara, Ibaraki City, Textile Processing Laboratory, Teijin Limited (56) Reference JP-A-55-131024 (JP, A) JP-A-55-127461 (JP, A) JP-A-61-7353 (JP, A) JP-A-1-152042 (JP, A)

Claims (4)

[Claims] 1. An aramid extruded product comprising a fibrillar tetrafluoroethylene resin dispersed in an aromatic polyamide resin. 2. The aramid extruded product according to claim 1, wherein the extruded product is fibrous. 3. The aramid extruded product according to claim 1, wherein the extruded product is in the form of a film. 4. An aromatic polyamide powder containing an aromatic polyamide powder coated with a tetrafluoroethylene resin, which is obtained by mixing an aqueous suspension of an ethylene tetrafluoride resin with an aromatic polyamide powder and then drying the mixture. A method for producing an aramid extruded product, which comprises extruding from a heat-forming die after heat-compressing.