JPH0249212B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and economically advantageous method for producing heat-resistant aromatic polyamide moldings, and more specifically relates to aromatic polyamide moldings, which were conventionally considered difficult to melt mold. The present invention relates to a means for melt-molding polyamides.

Aromatic polyamides are heat-resistant and flame-retardant polymers that have been widely proposed, especially polymetaphenylene isophthalamide, such as Nomex [DuPont Co., Ltd.
Ltd.] and Conex [manufactured by Teijin Ltd.] in large quantities as fibers. This fiber has a flexibility comparable to that of conventional organic fibers, and is flame retardant with a limiting oxygen index (LoI) of 27, a melting point of 400-410℃, and a decomposition point of approximately 400℃. It has heat resistance and is useful as fireproof clothing, bag filters, and insulation materials. Furthermore, polyparaphenylene terephthalamide is commercially available as a fiber under the name Kevlar (DuPont Co., Ltd.), and this fiber has flame retardancy and heat resistance comparable to the above-mentioned polymethaphenylene isophthalamide fiber. Moreover, it exhibits high strength and high Young's modulus, making it useful for composite materials, ropes, etc. These 2
Various modifications (copolymerization, blending, etc.) have been performed mainly on aromatic polyamides, and the optimal composition for each purpose has been studied.

Generally, aromatic polyamides have a high melting point, which is close to the decomposition initiation temperature, so it is impossible to melt-extrude them using conventional melt-spinning equipment.
Therefore, it is customary to dissolve the polymer in a solvent and perform wet or dry spinning, and the solvents used include dimethylformamide, dimethylacetamide,
Aprotic polar solvents such as N-methylpyrrolidone alone or a mixed solution of them and a halide salt of a metal of a periodic table group or group such as lithium chloride, calcium chloride, sulfuric acid, chlorosulfuric acid, hydrofluoric acid, It is known to use trifluoroacetic acid and the like. For industrial use, equipment to recover or neutralize these solvents is required, and the amount of solvent used per unit weight of the polymer is usually 3 to 20 times the weight of the polymer, so spinning Requires collection or processing equipment that is extremely large compared to the equipment itself. Moreover, the cost of solvents that cannot be recovered is directly added to the cost of fibers.

For these reasons, if the polymer can be melt molded, solution molding (wet or dry) can be used.
It is obvious that it is more advantageous to employ the melt molding method. This also applies if the polymerization of the polymer is carried out in solution. This is because first separating (precipitating) the polymer from a solution and then melt-molding it is a much simpler process than solution-molding.

Conventionally, so-called direct fabrication using a solution molding method has not been put to practical use except in specific cases because the process is very long and production control is too troublesome. If the polymer could be melt-molded, direct fabrication would be possible using an extremely simple process. If an aromatic polyamide having extremely excellent physical properties as described above could be made into a nonwoven fabric by direct fabrication, for example, it would have a great industrial effect.

In addition, in the case of solution molding, it is very difficult to completely extract the solvent when the desired molded product becomes thick, but thick molded products can be easily produced using melt molding.

The present inventors have arrived at the present invention as a result of intensive research on melt molding of aromatic polyamide.

That is, the present invention is based on the following formula as well as [In the formula, (1) and (2), if present, are present in substantially equimolar amounts, and the groups R,
R′ and R″ represent the same or different divalent groups,
At least 70 mole percent of the sum of R, R', and R'' are aromatic groups.] A solid aromatic polyamide consisting essentially of at least one repeating unit selected from the group consisting of A method for producing an aromatic polyamide molded product, characterized in that the aromatic polyamide is extruded through a discharge port within a time period during which the aromatic polyamide does not substantially lose its ability to form a molded product, and is molded while being cooled and solidified; The aromatic polyamide is supplied to a heat-transferable planar body having a large number of slits, the aromatic polyamide is heated and melted in the planar body, and the aromatic polyamide is discharged within a time that does not substantially lose the ability to form a molded article. This is a method for producing an aromatic polyamide molded article, which is characterized by extruding through an outlet and molding while cooling and solidifying.

The aromatic polyamide targeted in the method of the present invention has the following formula: as well as [In the formula, (1) and (2), if present, are present in substantially equimolar amounts, and the groups R,
R′ and R″ represent the same or different divalent groups,
At least 70 mole percent of the sum of R, R' and R'' are aromatic groups.] Polymers consisting essentially of at least one repeating unit selected from the group consisting of It is called aromatic polyamide.

In the above formula, R, R', R'' are the same or different divalent groups, and the total of them is at least 70 mol%, preferably at least 80 mol%, is an aromatic group.Such an aromatic group Examples include paraphenylene group, metaphenylene group, 1.5-naphthylene group, 2,6-naphthylene group, 3,3'-, 4,4'-
or 3,4'-diphenylene group, 3,3'-,4,
Examples include 4'- or 3,4'-diphenyl ether group. Specific examples of aromatic polyamides include polyparaphenylene isophthalamide, polymetaphenylene isophthalamide, polymetaphenylene terephthalamide, poly-1.5-naphthylene isophthalamide, and poly-3,4'-diphenylene terephthalamide. Examples include amides and copolymers thereof.

These polymers are usually tetrahydrofuran/water,
It is prepared by an interfacial polymerization method in a system such as methyl ethyl ketone/water, or a solution polymerization method in a system using an aprotic polar solvent such as dimethylformamide, dimethylacetamide, or N-methylpyrrolidone.
The polymer is generally present in the form of a fine powder in these polymerization solvents. As the separation method, it is usually preferable to extract and remove the solvent by washing, and the solvent contained in the washing liquid is recovered by distillation, freeze separation, or a combination of these and extraction. The size and shape of the fine powder of the polymer are influenced by the temperature, shear rate, coagulation rate of the polymer, etc. when prepared by interfacial polymerization, and when prepared by solution polymerization, the size and shape of the fine powder of the polymer are It is influenced by the temperature, shear rate, coagulation rate of the polymer, etc. when adding the extraction washing liquid to the polymer solution prepared by the polymerization method. The average diameter of easily handled polymer fine powder is 1μ to 1000μ.

In the present invention, the fine polymer powder may be used as it is, or may be compressed into an appropriate shape.

The polymer used in the present invention melts, albeit temporarily. The melting point can be measured by thermally analyzing the polymer using a means such as differential thermal analysis (DTA), differential calorimetry (DSC), or a flow tester. The melting point and decomposition start point of this polymer are close to each other, and it is common for the two to be observed to overlap in DTA and DSC, so in order to clearly determine the melting point, it is necessary to It is preferable to move the starting point of decomposition to a higher temperature and then perform the measurement.
When the temperature rises above the starting point of decomposition, the main chain of the polymer is cleaved, and at the same time, a complex reaction that usually involves crosslinking between the main chains occurs, but all of these reactions impair the ability to form molded objects. The smaller the amount that progresses during molding, the more preferable it is.

The ability to form a molded product as used in the present invention refers to performance when all of the following requirements (1) to (3) are satisfied.

(1) It must be possible to discharge from the discharge port referred to in the present invention. (The viscosity of the polymer can be reduced to a viscosity necessary for passing through the discharge port.) (2) The polymer can be continuously discharged from the discharge port along the discharge direction.

(3) The mechanical strength of the discharged polymer continuum after cooling is within a practical range.

The range of specific physical property values for the requirements (1) to (3) above varies depending on the type of molded product, but in the case of fibers, the viscosity referred to in (1) is 100,000 poise or less, The mechanical strength of (3) is preferably a tensile strength of 0.5 g/de or more. In the case of a film, it is desirable to have a tensile strength and tear strength of 5 g/mm ² or more. 5Kg/cm ² for plate-like objects with a thickness of 1mm or more
It is preferable to have a bending strength equal to or higher than (JIS K6911). In this way, the ability of the polymer to form a molded article varies depending on the type of molded article.
The range can be easily determined by simple experiments.

The solid polymer separated from the polymerization solvent is supplied to a flat body as a fine powder or in the form of a rod or the like obtained by compressing the fine powder, and is preferably heated and melted by heat transfer from the flat body.

Particularly preferred as the planar body is a planar body having a large number of slits as shown in the embodiments of the planar body below. A method of heating the planar body by passing an electric current through it (current heating method), a method of applying high frequency electrolysis and heating by induction heating method, a method of applying high frequency electrolysis and heating by dielectric heating method, as in the seventh planar body embodiment below. A method of heating by flowing a heat medium into a thin tube (thermal fluid heating method) is advantageously employed.

First Planar Body Embodiment A spinneret mold heating body in which orifices with a hole diameter of 0.5 mm are equally spaced at a pitch of 1 mm. Furthermore, a cross section V is formed on the discharge side surface and/or the opposite surface thereof.
Drilling grooves in the shape of a letter (width approx. 0.7 mm, depth approx. 0.7 mm) at angles of approx. 45° and approx. 135° with respect to the orifice arrangement improves heating efficiency and reduces the weight. It also becomes easier for the combined melt to flow into the orifice.

Second planar embodiment For example, a plain woven wire mesh made of stainless steel wire with a diameter of about 0.21 mm and a porosity of about 31% and a number of pores per cm ² of about 590.

Third Planar Body Embodiment For example, for a plain-woven wire mesh made of stainless steel wire with a diameter of about 0.38 mm and a porosity of about 46% and a number of slits of about 96 per ¹ cm2, every other slit is staggered. a tapered pin protruding to a height of approximately 2 mm (situated on the opposite side of the polymer solid feed side).

Fourth Planar Body Embodiment A porous plate-like body in which a large number of minute gold spheres are densely packed and arranged and fixed by sintering.

Fifth Planar Body Embodiment For example, a large number of plain woven wire meshes having a diameter of about 0.2 mm and a porosity of about 30% are vertically and densely arranged and laminated. (The polymer melt is flowed in a direction parallel to the laminated surface of the wire mesh.) Sixth Planar Embodiment A large number of gold layer plates are laminated in the vertical direction at regular minute intervals. (The polymer melt is flowed parallel to the surfaces of the many plates.) Seventh Planar Body Embodiment For example, thin tubes are woven into a weave structure, and one end of the thin tube is used as an inlet and the other side as an outlet, and the heating medium is A method that allows it to flow into a thin tube (hereinafter referred to as the thermal fluid heating method).

Materials that can be used in the current heating method and induction heating method include platinum, gold, silver, copper, titanium, panadium,
Tungsten, iridium, molybdenum, palladium, iron, nickel, chrome, cobalt, lead,
Metals such as zinc, bismuth, tin, aluminum, stainless steel, nichrome, tantalum,
Alloys such as silver, phosphor bronze, and duralumin,
Inorganic compounds that primarily exhibit semiconductor properties such as graphite, silicone, germanium, selenium, tin oxide, indium oxide, iron oxide, and nickel oxide; organic compounds that exhibit semiconductor properties such as polyacetylene and polyphenylene; 10 ^-7 to 10 ⁹ A planar body of the above embodiment made of a material having a specific resistance of approximately Ωcm is advantageously used.

All of the planar bodies described in the above embodiments are conductive and meet the purpose of the present invention. Other examples include a structure in which the surface of a glass sphere bead is coated with silver and brought into contact with pressure to make it conductive; a metal such as aluminum is evaporated onto a ceramic fiber such as alumina or zirconia, and a conductive cap structure is formed by pressure molding; a porous ceramic structure; Examples include a conductive flat plate structure in which a plate is immersed and deposited in a graphite particle dispersion, and other possible structures can be modified and implemented.

In the case of current heating, the conductive flat plate thus obtained is usually applied with an electric field of 0.1 to several hundred V/cm and a current of 0.1 to several hundred A, resulting in a watt density of 0.1 to several thousand W/ ^cm2. However, these values can vary depending on the purpose of use, and the desired performance can be obtained by selecting the material of the flat plate and designing the flat plate structure.

The conductive flat plate for the current heating method is attached to the extruder, and should be installed so that the desired current flows through the conductive flat plate. The conductive flat plate and the extruder may be insulated, or the extruder and the conductive flat plate may be electrically connected to appropriately distribute the current flowing to the extruder and the current flowing to the conductive flat plate to achieve the desired performance. It is also possible.

The insulating material used to insulate the conductive flat plate from the extruder depends on the temperature to which the flat plate is heated. When used at temperatures below 200℃, silicone resin, phenolic resin, etc. are sufficient.
When used at temperatures below 300℃, fluororesin, aromatic polyimide, aromatic polyamide, polyphenylene sulfide, polyarylate, etc. can be used; up to around 1000℃, general ceramic plates, silica, alumina, etc. can be used. A combination of inorganic adhesives such as zirconia can be used.

On the other hand, when heating the surface of a conductive flat plate as described above using the induction heating method, a coil is generally placed approximately parallel to the flat plate surface, and a magnetic field approximately perpendicular to the flat plate surface is applied. Eddy currents are generated and Joule heat is generated. If the heating frequency is selected to be high, the penetration of eddy current becomes shallow due to the skin effect, and local heating of only the surface can be performed. Depending on the thermal properties of the polymer to be molded, the material and shape of the device, the optimum conditions can be obtained by appropriately combining the arrangement of the coils, the strength and frequency of the magnetic field.

The surface material of the flat plate that can be used in the dielectric heating method is generally a substance that causes dielectric loss, and it depends on the frequency of the applied electric field and the nature of the polymer to be molded.
Examples include ceramics with polar groups.

When heating the surface of such a dielectric planar body using a dielectric heating method, electrodes are usually arranged parallel or perpendicular to the surface of the planar body. An alternating electric field parallel or perpendicular to the plane surface is applied, causing dielectric loss and generating heat.

The thin tubes used in the thermal fluid heating method are preferably of high thermal conductivity, such as aluminum, stainless copper, iron, copper, brass, silica, nickel, Inconel, tungsten, tantalum, molybdenum,
Materials such as rhenium, titanium, and niobium are used. The heat medium is selected to be compatible with the operating temperature and the thin tube, such as water, ammonia, methanol,
Acetone, Freon 11, Freon 21, Freon
113, _C6F6 , n-butane, n-pentane, n-heptane, benzene, toluene, Dowsome A, _Dowsome B, DC200, DC209, parachloroethylene,
Dimethyl sulfide, Monsanto CP-9, pyridine,
Monsanto CP-34, lithium, sodium, potassium, cesium, mercury, lead, indium, tin, etc. are used in fluid or gas form.

As a device for supplying the solid polymer to the planar body, a screw or a plunger can be used in the case of a powder, and a plunger can be used in the case of a rod. The solid polymer has a certain extent (~550
It is preferable to press and supply with a pressure of 1 kg/cm ² ). This not only makes heat transfer more efficient, but also causes melting to occur under pressure, resulting in the so-called pressurized defoaming effect. Defoaming is required in order to continuously discharge the melt from the discharge port. However, the length of the zone required for this defoaming may be much shorter. When producing fibers as shown in Example 1 below, the pressure was 30 kg/cm ² and the length of the zone required for defoaming was 5 mm. It is more preferable that the atmosphere in the apparatus for supplying the solid polymer to the planar body be replaced with an inert gas such as nitrogen gas.

As exemplified in the above embodiment, the width of the slit in the planar body depends on the material and the heat transfer efficiency between the polymers, and is preferably 50μ to 1.5mm, preferably 100μ to 1mm.
It is in the range of mm. If the slit is too narrow, it will be difficult for a high viscosity polymer to pass through, and if the slit is too wide, the polymer will not be heated properly or unevenly, which is undesirable.

It is necessary for the polymer to pass through the slits of the planar body within a period of time without losing the ability to form a molded article. If the time for passing through the slits is too long, the ability to form a molded article will be lost, and if the time is too short, the polymer cannot be heated to an appropriate temperature, so there is an optimum range of passing time. This range cannot be specified because it depends on the composition of the polymer and the temperature of the planar body, etc., but if the polymer is polymetaphenylene isophthalamide and the planar body is the same wire mesh as the second planar body embodiment. If the temperature when air-roasted is 600℃,
It is 0.5 seconds to 15 seconds.

The polymer melt must also pass through the discharge port within a period of time without losing its ability to form moldings. The discharge port may be the planar body itself, or another discharge port may be attached to the planar body. When manufacturing fibers, the planar body itself can be used as a discharge port.

The polymer extruded from the discharge port is solidified by cooling gas or cooling liquid. When producing a continuous molded product, it may be rolled up simultaneously with solidification.

EXAMPLES The present invention will be explained below using specific examples, but these are not intended to limit the scope of the present invention.

Example 1 N- obtained by polymerization in tetrahydrofuran/water
Intrinsic viscosity (IV; determined in methylpyrrolidone)
A polymer powder of polymetaphenylene isophthalamide with an average particle size of 500μ and having an inherent viscosity of 1.2 was charged into a plunger-type extruder with a plunger diameter of 1cm as shown in Figure 1, and heated at 340°C for about 15 minutes.
A 30-mesh plain-woven wire mesh is used as the flat plate 5 with a diameter of approximately 1 cm exposed, and approximately
While applying a pressure of about 50 kg/cm ² with the langeer 1 while applying a current of 2 W/cm ² , the polymer was melted and flowed through the narrow gap of the flat plate and discharged, and at the same time cooling air at a speed of about 1 m/sec was applied. Cooling air is blown from the blowing port 8 toward the discharge side of the flat plate, and the discharged material is 0.3 m/
A fiber bundle consisting of fibers with a fiber diameter of about 200 mμ was obtained by pulling the fibers in minutes. The strength and elongation of this fiber bundle were 1.0 g/de and 50%, respectively. Next, this fiber bundle was stretched approximately twice in boiling water at 100°C, and then
The strength of the yarn obtained by stretching it approximately 1.5 times on a hot plate at 310℃,
The elongation was 2.5 g/de and 12%, respectively.

Example 2 A polymer powder of polymetaphenylene terephthalamide with an average particle diameter of 650 μ and an IV of 1.6 obtained in the same manner as in Example 1 was processed using a continuous extruder equipped with two plungers (Special Publication Publication 1973- 19887 Publication Figure 2) and heated the same flat plate as in Example 1 under the condition of 3 W/cm ² to continuously obtain a fiber bundle consisting of fibers with a fiber diameter of approximately 250 mμ. Ta.
The obtained fibers had excellent flexibility, strength and elongation.

Example 3 IV solution polymerized in N-methylpyrrolidone
Polymer particles having an average particle diameter of 330 mμ were obtained from a solution of poly 3,4'-diphenyl ether terephthalamide having an average particle diameter of 2.0 using water as a precipitant and stirring with a propeller. The polymer particles were then heated to 300°C.
Compression molding was performed to obtain cylindrical pellets with an average diameter of 5 mm and a length of 5 mm. After filling the pellets into the cylinder of a plunger extruder and preheating to 330°C,
Approximately 60Kg/cm ² is applied using a plunger.
A current of 1.5 W/cm ² is applied to the flat body of the first flat body embodiment described in the main text, and while melting, it is extruded through the slits of the flat body, and cooling air is blown to separate the fibers and wind them up. After stretching, it was stretched at 400°C. The strength, elongation, and Young's modulus of the obtained yarn were each 7 g/
de, 20%, 200g/de.

Example 4 In order to supply the polymer powder used to the plane plate in a slit-like cross-section, the cross-section on one side (A) was 10 mmφ, and the cross-section on the other side (B) was a continuous slit with a width of 1 mm and a length of 9 mm. Attach a 10 mm long powder supply conduit with a smoothly narrowed conduit to the bottom of the plunger type extruder of Example 1 so that the (A) side is connected.
Attach a 30-mesh plain weave wire mesh similar to that in Example 1 to the (B) side, and add a 1 mm width x 9 mm length to the bottom of the wire mesh.
A slit with a depth of 3 mm was attached so as to match the direction of the slit in the powder supply conduit, and polymetaphenylene isophthalamide was extruded in the same manner as in Example 1 and cooled to obtain a film. The obtained film, which was stretched by about 1.5 times both lengthwise and widthwise, had practical properties.

[Brief explanation of the drawing]

The attached drawings show one example of the apparatus of the present invention, which is an apparatus for producing fibers by applying pressure with a plunger. 1 is a plunger, 2 is a barrel, 3 is a solid polymer powder, 4 is an auxiliary heater, 5 is a flat plate with many slits, 6 is a stopper, 7 is an insulator, 8 is a cooling air outlet, 9 is a power source It is.

Claims (1)

[Claims] 1. The following formula as well as [In the formula, (1) and (2), if present, are present in substantially equimolar amounts, and the groups R,
R′ and R″ represent the same or different divalent groups,
At least 70 mol% of the sum of R, R' and R'' are aromatic groups.] A solid aromatic polyamide consisting essentially of at least one repeating unit selected from the group consisting of A method for producing an aromatic polyamide molded product, characterized in that the aromatic polyamide is extruded through a discharge port within a period of time during which the aromatic polyamide does not substantially lose its ability to form a molded product, and is molded while being cooled and solidified. 2 The following formula as well as [In the formula, (1) and (2), if present, are present in substantially equimolar amounts, and the groups R,
R′ and R″ represent the same or different divalent groups,
At least 70 mole percent of the sum of R, R' and R'' are aromatic groups.] A solid aromatic polyamide consisting essentially of at least one repeating unit selected from the group consisting of: The aromatic polyamide is heated and melted in the planar body, extruded through the discharge port within a time period in which the aromatic polyamide does not substantially lose its ability to form molded articles, and cooled and solidified. A method for producing an aromatic polyamide molded product, which is characterized by molding the product.