JPS61113818A - Melt-spinning method - Google Patents

Abstract

PURPOSE:To produce a fiber having high tenacity and modulus in high spinning workability, by carrying out the melt-spinning of an aromatic polyester exhibiting anisotropy in molten state with an extruder furnished with a screw having a specific structure, thereby finely dividing and dispersing the bubbles in the molten polymer. CONSTITUTION:An aromatic polyester exhibiting anisotropy in molten state is melted with a screw-type extruder furnished with a screw having kneading function, e.g. a screw wherein a part of the screw thread is substituted with a number of protrusions. The bubbles in the molten polymer is finely divided to <=30mum diameter and dispersed in the polymer by the action of the screw, and the molten polymer is extruded and spun. The polyester is preferably a copolymer composed of 20-80mol% p-hydroxybenzoic acid residue and 20-80mol% 2-hydroxynaphthalene-6-carboxylic acid residue, etc., and the melt spinning temperature is preferably 300-400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for spinning aromatic polyester lam having high strength and high modulus of elasticity.

(Prior Art) In recent years, it has become clear that aromatic polyesters that exhibit anisotropy when melted can be made into high-strength, high-modulus fibers by melt-spinning. It has various advantages such as not using a solvent and being able to use known spinning equipment. However, since the spinning temperature is higher than that of ordinary polymers, there is a possibility that reactions such as decomposition, polymerization, and cross-linking may occur during spinning, which may cause problems such as foaming and high viscosity, which are difficult to perform in stable spinning for a long time. There was a problem.

Until now, many patents have been reported for aromatic polyesters that exhibit anisotropy when melted (Japanese Patent Publication No. 55-482, etc.), but most of them are only small-scale examples at the laboratory stage. This could not be a finding from a practical perspective of stable spinning operation.

In addition, in conventional melt spinning of thermoplastic resins such as polyester and nylon, by optimizing the screw structure, it is possible to completely degas during melting, and it is possible to create a melt that does not contain any air bubbles. was created, but
In the aromatic polyester that forms an anisotropic melt as in the present invention, the softening temperature and melting temperature are close to each other, and the viscosity of the melt has a very large temperature dependence. Rapid melting of the resin occurs and the melt has a very low viscosity.

For this reason, even if a screw with an appropriate shape is used, it is difficult to completely degas during melting as with conventional thermoplastic resins, and as a result, bubbles inevitably remain in the melt, and the melting temperature is low. Due to this high concentration, the generation of decomposed gas due to decomposition of the polymer has been a cause of a significant decrease in spinning operability.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the problem of spinning operability due to the inherent difficulty in degassing and the generation of decomposed gas in the aromatic polyester forming an anisotropic melt. (Means for Solving the Problems) An object of the present invention is to overcome the problem of deterioration and thereby provide an industrial manufacturing method for aromatic polyethylene fibers with high physical properties. After melting an aromatic polyester exhibiting the following properties using a screw extruder, a screw with a kneading function is used during spinning to reduce the air bubbles contained in the molten polymer to 80 μm.
This can be achieved industrially advantageously by the following method of finely dispersing, extruding, and spinning.

In the present invention, the IJ ester that exhibits anisotropy when melted is a polyester sample powder that is placed on a heated sample stand between two polarizing plates that are perpendicular to each other at 90° and is heated in a temperature range that allows it to flow. It means something that has the property of transmitting light. Examples of such aromatic polyesters include
Consisting of aromatic dicarboxylic acids, aromatic diols, and/or aromatic hydroxycarboxylic acids and derivatives thereof shown in 008, etc., and in some cases, these and alicyclic dicarboxylic acids, alicyclic diols, and aliphatic diols. Also included are copolymers with these derivatives. Here, the aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4.4-
Dicarboxydiphenyl, 2,6-dicarboxynaphthalene, 1,2-bis(4-carboxyphenoxy)ethane, etc., and nuclear substituted products of these alkyl, aryl, alkoxy, and halogen groups are mentioned. Aromatic diols include hydroquinone, resorcinol, 4.4-dihydroxydiphenyl, 4.4'-dihydroxybenzophenone,
4.4-dihydroxydiphenylmethane, 4゜4'-dihydroxydiphenylethane, 2.2-his(4-hydroxyphenyl)propane, 4.4-dihydroxydiphenyl ether, 4゜4'-dihydroxydiphenyl sulfone, 4,4- Examples include dihydroxydiphenyl sulfide, 2,6-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, and their alkyl, aryl, alkoxy, and halogen-substituted products. Aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid,
m-Hydroxybenzoic acid, 2-hydroxynaphthalene-
6-carboxylic acid, l-hydroxynaphthalene-5-carboxylic acid, etc., and their alkyl, aryl, alkoxy,
Examples include nuclear substitution products of halogen groups. Examples of alicyclic dicarboxylic acids include trans-1e 4-dicarboxycyclohexane, cjs-1,4-dicarboxycyclohexane, and substituted products of these with alkyl, aryl, and halogen groups. Alicyclic and aliphatic diols include trans-1,4-dihydroxycyclohexane,
Examples include cis-1,4-dihydroxycyclohexane, ethylene glycol, 4-butanediol, and xylylene diol. Among these combinations, preferred aromatic polyesters for the present invention include (1) p-hydroxybenzoic acid residues of 40 to 70;
A copolyester consisting of 15 to 8 moles of aromatic dicarboxylic acid residues and 15 to 80 moles of aromatic diol residues, (2) terephthalic acid and/or isophthalic acid, chlorohydroquinone, phenylhydroquinone, and/or or a copolyester consisting of hydroquinone, (3) 20 to 80 moles of P-hydroxybenzoic acid residues and 20 to 20 mols of 2-hydroxynaphthalene-6-carboxylic acid residues.
Examples include copolyesters consisting of 80 moles of polyester. These starting materials can be used as they are or esterified with aliphatic or aromatic monocarboxylic acids or derivatives thereof, aliphatic alcohols, phenols or derivatives thereof, etc. to obtain the polyester that is the object of the present invention. A polycondensation reaction is carried out.

As the polycondensation reaction, known bulk polymerization, solution polymerization, suspension polymerization, etc. can be adopted.
A polymerization catalyst such as a %Ge compound, a stabilizer such as a phosphorus compound, a filler such as TiO2, CaCO3, talc, etc. can be optionally added. The obtained polymer is used as it is or in powder form and heat-treated in an inert gas or under reduced pressure to prepare a sample for spinning. Alternatively, it can also be used after being granulated once using an extruder. It is thought that the aromatic polyester used in the present invention has a molecular weight range suitable for spinning, but depending on the composition and structure, there are problems such as the lack of a solvent that can dissolve it uniformly and the lack of precision in the molecular weight measurement method. Since this cannot be used as a standard for aromatic polyester suitable for the invention, the present inventors introduced "flow temperature" as a physical property value corresponding to the molecular weight suitable for melt spinning conditions.

Using a flow tester OFT-50g manufactured by Takafusa Seisakusho,
A nozzle with a diameter of 1m and a length of 10m, pressure of 100 Ky/c
Exposure of aromatic polyester sample at sR2 at 4℃/exposure
The "flow temperature" was defined as the temperature at which the sample flows through the nozzle and gives a warm viscosity of 48,000 poise. After synthesizing it and changing its flow temperature, we found that it achieved the high strength and
It has been found that the flow temperature of aromatic polyester suitable for spinning high elastic modulus A fibers is 280 to 380°C. If the flow temperature is lower than this temperature, reactions during melting may easily occur, or m! There is a problem that it is difficult to obtain elongation, and if the elongation is high, the processing (spinning) temperature becomes high, which tends to cause decomposition and crosslinking reactions, and also causes problems such as an increase in load on the equipment.

Although an ordinary screw extruder can be used as the melt spinning apparatus of the present invention, the important point in the present invention is to use a screw having a kneading function. By using such a screw, it is possible to promote homogeneous mixing of polyester, and also to make the bubbles in the sample melt that cannot be removed sufficiently even by screw back pressure to be dispersed, thereby making it possible to disperse the melt. This suppresses single yarn breakage when the yarn is discharged from the nozzle, making spinning extremely stable. The bubbles in the melt are thought to be caused by gases between or inside the aromatic polyester powder, granules, and pellets, or by gases generated by decomposition reactions due to retention in a high-temperature section. From the viewpoint of spinning stability and the quality of the obtained fibers, the smaller the gas contained in the sample melt, the better, but if the diameter is 80 μm or less, stable spinning does not seem to be hindered.

Structures that have a kneading function include replacing part of the spiral shape with a combination of several to dozens of disks vertically in the length direction, making cuts in the disks, creating multiple spirals, For example, a portion may be made into a spiral in the opposite direction, or may be made into a structure with many protrusions.

When spinning using the screw according to the present invention, stable spinning operations can be performed, and the air bubbles in the obtained fibers are small and are less likely to cause defects in physical properties, resulting in high quality fibers with small strength dispersion. Obtainable.

Known equipment such as a gear pump can be used.

The temperature suitable for melt spinning of the present invention is 280 to 420 °C,
Preferably it is 300-400°C.

The fibers spun according to the present invention may be used as they are, or may be coated with an oil and then wound or drawn down. The winding or drawing speed is 10 to 7, but
100 to 2,000 m/m in terms of productivity and stable spinning
is preferred. The thickness and cross-sectional shape of the resulting fibers are selected depending on the intended use, but from the viewpoint of strength and elastic modulus, a yarn diameter of 0.5 to 10 deniers is preferable. The obtained fibers can be used as they are, but they can be further increased in strength and elasticity by being subjected to heat treatment, stretching, or a combination of these treatments.

(Function) By employing the technical means of the present invention using a screw having a kneading function, it is possible to finely disperse the gas remaining in the melt and the gas bubbles generated by the decomposition reaction, which can be completely removed. This can lead to problems in spinning operations such as thread breakage,
It is thought that problems such as deterioration in quality and variation due to air bubbles that cause defects in physical properties can be significantly improved (effects of the invention). A noteworthy effect of the present invention is that high-quality aromatic polyester fibers can be industrially advantageously produced without problems with operability or quality. , Cable, FIL'FRTP
Can be used for speaker cones, safety clothing, tension members, etc.

(Examples) Examples and comparative examples are shown below to explain the present invention in detail, but these are merely illustrative and are not intended to limit the invention.

The tensile test of the fibers in the examples was carried out using Instron's universal testing machine Al13C at a sample interval of 20 mm and a tensile speed of 0.5 mm.

The optical anisotropy was measured by placing the sample on heating stage 7, raising the temperature to around 25° C. under polarized light, and observing it with the naked eye.

Reference example 1 p-acetoxybenzoic acid 7.20 Kf (40 mol), terephthalic acid 2.49 Kf (15 mol), isophthalic acid 0
．． 88 KF (5 mol), 4,4-diacetoxydiphenyl 5.45 and 9 (20.2 mol) were charged into a polymerization tank with a comb-shaped stirring blade, and the temperature was raised to 330°C while stirring in a nitrogen gas atmosphere. Polymerization was carried out for 3 hours. During this time, the acetic acid produced was removed and polymerization was carried out with strong stirring, after which it was gradually cooled and the polymer was taken out of the system at 200°C. The yield of polymer was 97.8% of the theoretical yield at io, 88:4.

This was crushed with a hammer mill manufactured by Hoyo Micron Co., Ltd., and
The particles were made smaller than w. When this was treated in a rotary kiln at 280°C under a nitrogen atmosphere for 5 hours, optical anisotropy was observed at temperatures above -850°C, where the "flow temperature" was 826°C.

Reference Example 2 Using the same equipment as in Reference Example 1, a polyester consisting of 2,5-diacetoxybiphenyl and terephthalic acid was synthesized. The "flow temperature" was 820°C, and optical anisotropy was observed at 840°C or higher.

Example 1 Using the polyester of Reference Example 1, melt spinning was performed using a uniaxial screw extruder with a sow diameter. The screw used had an effective length of 990 m and the screw tip (discharge part)
Unlike the spiral structure of the other parts, there is an arc length of 20116. 10 sets of 8 protrusions with a width of 4 baits and a height of IWI# are installed on the same circumference of the screw in the length direction, and one set of 8 protrusions and an adjacent set of protrusions form a spiral. It is designed so that the positions of the protrusions are the same for every other set.

3 pieces of 400 mesh plain weave wire mesh and 1 at the screw tip
The resin is discharged from a C cylinder with a mold having 80 holes with a diameter of 200 to 870℃ at a temperature of
Fibers with a diameter of 0 μm were obtained. When the air bubbles in this fiber were examined, they were all smaller than 30 μm.

Next, using this screw, a gear pump and a nozzle were attached, and melt spinning was performed at 870°C. The nozzle used had a hole diameter Q of 1 ms and 300 holes. No single yarn breakage occurs within one hour, and stable spinning is possible.
A pale yellow transparent fiber was obtained. When this was treated in nitrogen at 820°C for 3 hours, the result was 8.18 denier and a strength of 29.
A fiber with a strength distribution of 10.8 yen, an elongation of 8.0 yen, and an elastic modulus of 1.010 P/d was obtained.

Comparative Example 1 Unlike Example 1, a seven-tipped helical screw without a kneading part was used. Eight pieces of plain woven wire mesh of 400 mesh size and a mold having 80 holes of IMIL diameter were attached to the tip of the screw, and the polyester of Reference Example (2) was discharged at a cylinder temperature of 870°C. When we examined the air bubbles inside a fiber with a diameter of 200 to 300 μm, we found that the maximum size was 50 μm.
Many m-diameter bubbles were observed.

Next, this mold was removed, a gear pump and a nozzle part were attached, and melt spinning was performed at 370°C. Yarn breakage was observed 17 times in about 1 hour, indicating that spinning using the screen 21 having the kneading structure according to the present invention is stable.

Example 2 Using the polyester of Reference Example 2, melt spinning using the screw of Example 1 was performed at 865°C. All bubbles at the screw tip were smaller than 30 μm. Spinning could be carried out for about 1 hour without yarn breakage, and pale yellow transparent fibers were obtained. When this was treated in nitrogen at 320°C for 3.1) hours, it had a denier of 4.26 and a strength of 22.
．． 6 P/d, strength dispersion 11.2 cm, elongation 2.8%
, a fiber with an elastic modulus of 810 P/d was obtained.

Comparative Example 2 Using the polyester of Reference Example 2, spinning was performed at 865° C. using the screw of Comparative Example 1 without a kneading portion.

Many of the bubbles at the tip of the screw had a size of 50 to 60 μm. Although spinning was carried out for about 1 hour, single yarn breakage was observed 14 times, and it could not be said that the spinning was stable.

Claims (3)

[Claims] (1) When an aromatic polyester that exhibits anisotropy when melted is melted using a screw extruder and then spun, a screw with a kneading function is used to reduce the air bubbles contained in the molten polymer to 30 μm. A melt spinning method characterized by carrying out fine dispersion followed by extrusion and spinning. (2) The melt spinning method according to claim 1, which uses an aromatic polyester having a flow temperature of 280 to 380°C. (3) The melt-spinning method according to claim 1, which comprises melt-spinning at a temperature of 280 to 420°C.