JPH0585642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for spinning aromatic polyester fibers 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, because the processing temperature (spinning temperature) of aromatic polyester, which gives high strength and high elasticity when spun, is high, it may decompose during spinning or foam due to reactions such as polymerization and crosslinking, which allows stable spinning to continue for a long time. It has become an obstacle to the above. In the past, many patents on aromatic polyesters that exhibit anisotropy when melted have been reported (Japanese Patent Publication No. 55-482, etc.), but most of them have only been shown on a small scale at the laboratory stage.
This could not provide knowledge of a practical manufacturing method from the perspective of stable spinning operations.

(Problems to be Solved by the Invention) The purpose of the present invention is to overcome the problems of degassing peculiar to anisotropic aromatic polyester, deterioration of spinning operability due to decomposition gas generation, etc., and to finally achieve high spinning performance. The object of the present invention is to provide a method for industrially producing aromatic polyester fibers having high strength and high modulus.

(Means for Solving the Problems) An object of the present invention is to melt an aromatic polyester that exhibits anisotropy when melted using a screw type extruder, and then spin it using a screw type extruder with a compression ratio of 2.5 to 4.0. Depending on the means used, this can be achieved with industrial advantage.

In the present invention, polyester that exhibits anisotropy when melted means that a polyester sample powder is placed on a heated sample stage between two polarizing plates orthogonal to each other at 90 degrees.
In the temperature range where it can flow when the temperature rises,
It means something that has the property of transmitting light. Such aromatic polyesters include aromatic dicarboxylic acids, aromatic diols and/or aromatic hydroxycarboxylic acids shown in Japanese Patent Publications No. 56-18016 and 55-20008, etc., and derivatives thereof. Optionally, copolymers of these with alicyclic dicarboxylic acids, alicyclic diols, aliphatic diols, and derivatives thereof are also included. here,
Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4'-dicarboxydiphenyl,
Examples include 2,6-dicarboxynaphthalene, 1,2-bis(4-carboxyphenoxy)ethane, etc., and nuclear substituted products of these alkyl, aryl, alkoxy, and halogen groups. Aromatic diols include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylethane,
2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl ether,
4,4'-dihydroxydiphenyl sulfone, 4,
4'-dihydroxydiphenyl sulfide, 2,6
-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, etc. and their alkyl, aryl,
Examples include nuclear substituted products of alkoxy and halogen groups. Aromatic hydroxycarboxylic acids include 4-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxybenzoic acid,
-hydroxynaphthalene-6-carboxylic acid, 1-
Examples thereof include hydroxynaphthalene-5-carboxylic acid and the like, and their alkyl, aryl, alkoxy, and halogen group-substituted products. Examples of alicyclic dicarboxylic acids include trans-1,4-dicarboxycyclohexane, cis-1,4-dicarboxycyclohexane, and substituted products of these with alkyl, aryl, and halogen groups. Examples of alicyclic and aliphatic diols include trans-1,4-dihydroxycyclohexane, cis-1,4-dihydroxycyclohexane, ethylene glycol, 1,4-ditanediol, xylylene diol, and the like.

Among these combinations, preferred aromatic polyesters for the present invention include (1) p
- a copolyester consisting of 40 to 70 mol% of hydroxybenzoic acid residues, 15 to 30 mol% of the above aromatic dicarboxylic acid residues, and 15 to 30 mol% of aromatic diol residues,
(2) Copolyester consisting of terephthalic acid and/or isophthalic acid and chlorohydroquinone, phenylhydroquinone, and/or hydroquinone, (3) p-hydroxybenzoic acid residues 20 to 80 mol%
and 20-80 mol% of 2-hydroxynaphthalene-6-carboxylic acid residues. These starting materials can be used as they are, or by esterification with aliphatic or aromatic monocarboxylic acids or derivatives thereof, aliphatic alcohols, phenols, or derivatives thereof. ,
Carry out a polycondensation reaction. As the polycondensation reaction, known bulk polymerization, solution polymerization, suspension polymerization, etc. can be adopted, and the temperature is 150 to 360°C and normal pressure or 10 to 0.1 torr.
This can be carried out by adding a polymerization catalyst such as Sb, Ti, or Ge compounds, a stabilizer such as a phosphorous compound, a filler such as TiO ₂ , CaCO ₃ , or talc, etc. under reduced pressure. 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 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 uniformly dissolve it, and the lack of accuracy in the molecular weight measurement method. It cannot be used as a standard for aromatic polyesters suitable for the present invention. Therefore, 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 CFT-500 manufactured by Shimadzu Corporation, an aromatic polyester sample was heated at a rate of 4°C/min with a nozzle of diameter 1 mm and length 10 mm at a pressure of 100 Kg/ ^cm2 , and the sample passed through the nozzle. The "flow temperature" was defined as the temperature at which the material flows and gives an apparent viscosity of 48,000 poise.

The present inventors synthesized aromatic polyesters with various compositions and tried changing their flow temperatures. The temperature is
It was found that the temperature was between 280 and 380℃. If the flow temperature is lower than this temperature range, there are problems such as reactions occurring during melting and difficulty in achieving fiber elongation. This poses a problem in that reactions are likely to occur and the load on the equipment becomes large.

A conventional screw type extruder can be used as the melt spinning apparatus of the present invention.

What is important is that the compression ratio is 2.5 as described in the present invention.
The best way to do this is to use a screwdriver of ~4.0. The compression ratio here refers to the ratio of the area of the section of the cylinder where the resin is supplied to the screw, excluding the screw cross section (long resin area), to the minimum resin area of the screw tip, which is most compressed. value).

By using a screw with a compression ratio of 2.5 to 4.0, gas between or inside the aromatic polyester powder, granules, or pellets to be spun is suppressed from being taken into the melt, and the temperature of the cylinder part is reduced. The gas generated by decomposition due to the stagnation is transported back by the back pressure of the resin melt, providing stable spinning properties. If a screw with a compression ratio of less than 2.5 is used, degassing (defoaming) from the melt will not be sufficient, resulting in single fiber breakage during spinning. On the other hand, screws with a compression ratio greater than 4.0 have a large rotational load on the screw, and to prevent this, it is necessary to increase the cylinder temperature or preheat temperature, which is not good for the thermal stability of polyester. . In addition, with aromatic polyester polymers exhibiting such anisotropy, degassing properties also seem to decrease, possibly due to their low melt viscosity, which increases the amount of air bubbles contained in the discharged yarn, causing single yarn breakage. However, the spinning according to the present invention is extremely stable with few single fiber breakages, has fewer air bubbles in the resulting fibers, has a narrow strength distribution, and provides high-strength fibers. Note that known equipment such as a gear pump can be used.

The temperature suitable for melt spinning of the present invention is 280-420℃
The temperature is more preferably 300 to 400°C.

The fibers spun according to the invention can be rolled up or drawn off as is or with an oil applied thereto. Winding,
Or the withdrawal speed is 10~10000m/min,
From the viewpoint of productivity and stable spinning, 100 to 2000 m/min is preferable. 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 thread diameter of 10 denier is preferred. The resulting fibers can be used as is, but they can be processed by heat treatment, stretching, or a combination of these.
Further, higher strength and higher elasticity can be achieved.

(Function) The aromatic polyester according to the present invention has poor deaeration properties, increases the number of bubbles contained in the discharged yarn, and cannot avoid the problem of single yarn breakage. By adopting the technical means of the present invention for spinning, gases contained between or inside polyester powder, granules, and pellets, and decomposed gases generated during melting inside the screw type extruder, are removed by back pressure. It is thought that sufficient defoaming is achieved by feeding the fibers, thereby making it possible to perform stable spinning without the problem of single filament breakage during spinning.

(Effect of the invention) In this way, aromatic polyester fibers having high strength and high elastic modulus can be stably spun without problems such as yarn breakage.
A characteristic advantage of the present invention is that it can be manufactured, and the fibers obtained by the present invention can be used for tire cords, ropes, cables, FRP, FRTP, 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 be limiting.

The tensile test of the fibers in the examples was conducted using Instron Universal Testing Machine No. 1130 at a sample interval of 20 mm and a tensile speed of 0.5 mm/min.

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

Reference example 1 p-acetoxybenzoic acid 7.20Kg (40mol), terephthalic acid 2.49Kg (15mol), isophthalic acid 0.83
Kg (5 mol), 4,4'-diacetoxydiphenyl
5.45 kg (20.2 mol) was charged into a polymerization tank equipped with comb-shaped stirring blades, and the temperature was raised while stirring in a nitrogen gas atmosphere, and polymerization was carried out at 330°C 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 10.88Kg which was 97.8 of the theoretical yield.
It was %. This was pulverized using a hammer mill manufactured by Hosokawa Micron Co., Ltd. to obtain particles of 2.5 mm or less. When this was treated in a rotary kiln at 280°C for 5 hours under a nitrogen atmosphere, the "flow temperature" became 326°C.
Optical anisotropy was observed above 350°C.

Reference Example 2 Using the same equipment as in Reference Example 1, a copolyester consisting of 2,5-diacetoxybiphenyl and terephthalic acid was synthesized. "Flow temperature" is 318℃
Optical anisotropy was observed above 340°C.

Example 1 The polyester of Reference Example 1 was melt-spun using a screw type extruder with a diameter of 30 mm. The screw used had a compression ratio of 3.2 and an effective length of 120 cm. Cylinder tip temperature 370℃, nozzle temperature
It was carried out at 365℃. The nozzle has a hole diameter of 0.12mm and a hole length of 0.12mm.
0.1mm, 150 holes. The molten dope was discharged from all 150 nozzles, and pale yellow transparent fibers could be stably produced. When 150 fibers with a length of 50 mm were examined for air bubbles in the obtained fibers, the result was 5.3
It was ke/m. Also, when this fiber was heat treated (in nitrogen, 320℃, 3 hours), it had a denier of 3.23,
Strength 29.2g/d, strength variance 10.8%, elongation 3.0
%, and the elastic modulus was 990 g/d.

Comparative Example 1 A screw with a compression ratio of 1.7 was used in place of the screw in Example 1, and melt spinning was carried out under the same conditions as above.
There are many air bubbles in the yarn spun from the nozzle,
There were many single thread breaks, and sufficient winding could not be carried out. The spinning temperature was raised and lowered by 5°C, but this had no effect. The number of air bubbles in some of the obtained fibers was investigated and found to be 60 to 70 bubbles/m, indicating that the effect of the screw was significant.

Comparative Example 2 A screw with a compression ratio of 4.5 was used instead of the screw in Example 1, and melt spinning was carried out under the same conditions, but the screw rotational load was large, and although the cylinder temperature was set at 375°C, it did not affect the load much. 380
The load decreased when the temperature was lowered to ℃. However, spinning was unstable and there were many yarn breakages, and the nozzle surface was dirty, so that spinning was far from stable.

Example 2 Melt spinning was carried out under the same conditions except that a screw with a compression ratio of 2.7 was used in place of the screw in Example 1. As in Example 1, stable spinning was possible. The number of bubbles in the obtained fiber was 10.7/m at 320℃ for 3 hours.
When treated in nitrogen, it has a denier of 3.39 and a strength of 27.8.
The dispersion of g/d and intensity was 12.1%.

Example 3 A screw having a compression ratio of 3.7 was used in place of the screw used in Example 1, and melt spinning was carried out under the same conditions as above.
Although the rotational load on the screw was slightly larger than in Example 1, spinning could be performed under the same conditions without yarn breakage. The air bubbles in the fiber obtained are 8.1
It was 6/m. The fibers treated in nitrogen at 320° C. for 3 hours had a denier of 3.36, a strength of 28.8 g/d, and a strength dispersion of 10.3%.

Example 4 The polyester of Reference Example 2 was melt-spun under the same conditions as Example 1. Stable spinning was possible from 150 holes without single yarn breakage. The number of air bubbles in the obtained fiber was 9.2/
4.62 when treated in nitrogen at 320°C for 3 hours
Denier strength: 21.8g/d, strength variance: 10.8%
It was hot.

Comparative Example 3 A screw with a compression ratio of 1.7 was used in place of the screw in Example 4. Spinning was carried out in the same manner as in Example 4, but there were many single fiber breakages, and although the cylinder temperature was raised or lowered by 5° C., there was no effect and stable spinning could not be achieved.

Claims (1)

[Scope of Claims] 1. An aromatic polyester that exhibits anisotropy when melted, which is characterized in that a screw with a compression ratio of 2.5 to 4.0 is used when the aromatic polyester is melted using a screw type extruder and then spun. Spinning method. 2. The spinning method according to claim 1, which uses an aromatic polyester having a flow temperature of 280 to 380°C. 3. The spinning method according to claim 1, which comprises melt spinning at a temperature of 280 to 420°C.