JPS62177213A - Production of aromatic copolyester fiber having high molecular weight - Google Patents

Abstract

PURPOSE:To obtain the titled fiber having high strength and high elastic modulus without using heat-treatment process, by using an aromatic polyester, etc., having thermotropic liquid crystal nature as a raw material, melting the polymer at a specific temperature under shearing rate gradient, reacting with a bifunctional compound reactive with terminal carboxyl group and spinning the modified polymer. CONSTITUTION:A thermotropic liquid crystal copolyester having aromatic polyester unit is melted and supplied through a polymer inlet tube 1 to a reaction zone 4 between a rotary cylinder 2 and a main body 3 of e.g. a Couette-type apparatus. A shearing rate gradient is applied to the polymer in the reaction zone 4 by rotating the rotary cylinder 2 while maintaining the polyester to a temperature to get thermotropic liquid crystal nature of the polymer. A bifunctional compound capable of performing addition reaction with terminal caboxyl group is poured through a chemical inlet tube 5 into the reaction zone and made to react with the copolyester keeping the above state. The reaction product is extruded through a spinning nozzle 6 and spun fiber 7 is wound with a winder 8 to obtain the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing polyester fibers with high strength and high elastic modulus by melt-spinning thermotropic liquid crystalline copolyester.

(Prior art) Fibers spun from thermotropic liquid crystalline polyester using the usual melt spinning method have insufficient strength and elastic modulus.In order to obtain fibers with high strength and high elastic modulus, it is necessary to After being rolled up, it had to be heat treated at high temperatures for a long time. (for example.

Special Publication Showa 55-20008. Japanese Patent Publication No. 54-50594. 54-7769L 55-106221, 5B-5
3920, 58-91817. 58-219230
, No. 59-9270, etc.) Furthermore, if the degree of polymerization of the polymer used can be increased to orient the polymer molecules in the fiber axis direction, it is possible to improve the performance, especially the strength, of the resulting fiber. This is well known.

(Problems to be solved by the invention) However, in order to obtain a polymer with a high degree of polymerization, it takes a long time for one polymerization, and as the degree of polymerization increases, the melt viscosity also increases, making stirring impossible. In addition, there arises the problem that the polymer may undergo 2-decomposition and that it becomes difficult to pay out the polymer. In particular, polyester exhibiting liquid crystallinity exhibits extremely high viscosity even with a low degree of polymerization.
Problems such as decreased workability in discharging after polymerization and decreased yield occurred, making it impossible to achieve a high degree of polymerization.

Therefore, it was necessary to perform melt spinning using a liquid crystalline polyester having a relatively low degree of polymerization, and the strength of most of the obtained fibers was as low as 10 g/d or less.

In order to improve the above-mentioned drawbacks, the spun yarn of liquid crystalline polyester fibers is subjected to a long heat treatment as described above. That is, heat treatment improves the orientation of polymer molecules and increases the degree of polymerization of liquid crystalline polyester in the same manner as the solid phase polymerization of ordinary polyethylene terephthalate.
In addition to the above, it can even be improved to 20 g/d or more.

However, when comparing the above-mentioned thermodropink liquid crystalline polyester and lyotropic liquid crystalline aromatic polyamide such as poly P-phenylene terephthalamide, it is possible to obtain high strength and high modulus fibers without long-term heat treatment. Aromatic polyamides that can be used are more advantageous. Although there is a difference in thermotropic liquid crystallinity and otropic liquid crystallinity, the main reason for this is considered to be a difference in the degree of double polymerization.

On the other hand, in the case of thermotropic liquid crystal polyester, compared to lyotropic liquid crystal polyester, it is not necessary to recover the solvent or coagulation solvent of the spinning stock solution, and exhaust equipment etc. are not important problems, so the spinning method, equipment, etc. This is advantageous because the equipment can be simplified.

Therefore, if thermotropic liquid crystalline polyester can be highly polymerized and used for spinning, fibers with high strength and high elastic modulus can be obtained without long-term heat treatment after fiberization, and polyP-phenylene terephthalate fibers can be obtained. They can be produced in a more advantageous manner than amide fibers.

It is well known that 7-way oxazoline compounds react with carboxyl groups.2 For example, when a predetermined amount of an oxazoline compound is added to a polyester such as polyethylene terephthalate and spun, it reacts with the carboxyl groups at the ends of two molecules and blocks the ends of the molecules. As a result, the number of moles of carboxyl groups in the polymer is significantly reduced, and the heat resistance of the fiber is improved. Furthermore, if a bifunctional compound (molecular linking agent) such as a bisoxazoline compound is used, two polymer molecules can react with one molecule of the molecular linking agent.
Not only can the heat resistance of the obtained fibers be improved, but also the mechanical properties can be improved by increasing the degree of 9-polymerization, which is a good result.

However, these matters were only known regarding conventional polyesters, and even when applied to thermotropic liquid crystalline copolyesters, which are significantly different from these polyesters in terms of physical properties, the high solution viscosity makes it difficult to dispense. Polymerization could not be achieved.

The present invention has been developed in view of the above points.

The present invention aims to provide a method for producing high molecular weight aromatic copolyester fibers that can impart high strength and high elastic modulus to thermotropic liquid crystalline copolyester fibers simply by melt spinning.

(Means for Solving the Problems) The present inventors believe that if the degree of polymerization can be increased without increasing the melt viscosity of the thermotropic liquid crystalline copolyester,
Focusing on the fact that it is possible to form fibers with high strength and high elastic modulus, we conducted extensive research and found that applying shear to a molten liquid crystal system destroys the higher-order structure of the liquid crystal. It is known to significantly decrease (J, Polym,
Sci, Polyn+, Physad,, 12.175
3 (1974), J. Polym, Set, Polys.
, Che++, Ed.

14, 2043 (1976), etc.), it was discovered that the above object could be achieved by increasing the degree of polymerization of the copolyester using a bifunctional compound capable of reacting with carboxyl groups under such shear orientation, and the present invention was made based on this finding. Reached.

That is, the present invention melts a thermotropic liquid crystalline copolyester having aromatic polyester units, and melts the copolyester at a temperature at which the copolyester exhibits thermodropink liquid crystallinity and under a shear rate gradient. 0
A high molecular weight aromatic copolyester characterized by reacting with 5 to 10% by weight of a bifunctional compound that can undergo an addition reaction with the terminal carboxyl group in the copolyester, and subsequently extruding the reaction product from a spinneret and spinning it. The gist is the method of manufacturing fibers.

Hereinafter, nine aspects of the present invention will be described in detail.

In the present invention, first, a thermotropic liquid crystalline copolyester (hereinafter referred to as copolyester) having an aromatic polyester unit is melted at a temperature at which the copolyester exhibits thermotropic liquid crystallinity.

and under a shear rate gradient, a bifunctional compound (hereinafter referred to as 2
(referred to as a functional compound). If the copolyester and the bifunctional compound are simply reacted in a molten state, the molecular chains of the copolyester become entangled, and it is impossible to increase the degree of polymerization of the copolyester without increasing the melt viscosity. This is made possible by reacting under a shear rate gradient as in the present invention.

That is, by applying shear, the melt viscosity decreases and the molecular chains of the copolyester are oriented, and furthermore, the shear creates a velocity gradient, which makes it easier for the molecular ends to line up.
Therefore, two molecules of the copolyester and one molecule of the bifunctional compound tend to react linearly, making it possible to achieve a high degree of polymerization with a relatively low melt viscosity.

As a method for imparting a shear rate gradient in the present invention, a method using rotation is suitable from the viewpoint of simplicity of the apparatus.

As a rotary shear imparting device, for example, a cone plate ((
:□n6-Plate) type and the CoueLte type (cylindrical type) shown in Figure 1.
Any device that can produce orientation in the realester can be applied to the present invention.

In order to achieve a high degree of polymerization with a low melt viscosity,
The shear rate of the device is 1 sec-' or more and 1000 sec-
'The following range is preferable, more preferably 105ec
The range is from -' to 1005ec-'.

In the present invention, the reaction between the copolyester and the difunctional compound is carried out within the temperature range in which the copolyester exhibits thermotropic liquid crystallinity, that is, generally the melting point (-p) of the copolyester.
It is necessary to carry out at ~(mp + 50°C). This is because if the copolyester is reacted at a temperature at which it does not exhibit thermotropic liquid crystallinity, the degree of polymerization will increase by 1, but the strength will be poorly improved due to the orientation.

In addition, the bifunctional compound to be reacted with the copolyester must be a compound that can undergo an addition reaction with a carboxyl group, and a condensation reaction in which water, lower alcohols such as methanol or ethanol, or other low-molecular compounds are eliminated and produced is necessary. It must not be a compound that occurs. This is because, in the case of a condensation reaction, the eliminated low-molecular compound causes hydrolysis or alcoholysis of the copolyester, thereby reducing the degree of double polymerization.

The amount of the difunctional compound added should be 0.05 to 10% by weight, preferably 0.2 to 3% by weight, based on the copolyester. The amount of difunctional compound is 0.05% by weight
If it is less than 10%, the performance of the resulting fibers will not be significantly improved. On the other hand, if it exceeds 10% by weight, the degree of polymerization of the copolyester becomes too high, resulting in a marked increase in melt viscosity or inability to spin, which is not preferred.

In addition, when reacting the copolyester and the bifunctional compound, suitable additives may be mixed in for other purposes.

The present invention uses a copolyester and a difunctional compound.

The reaction is carried out at a temperature at which the copolyester exhibits thermotropic liquid crystallinity and under a shear rate gradient.

The copolyester is made to have a high molecular weight without increasing the melt viscosity, and then extruded and spun from one die to obtain a high molecular weight aromatic copolyester fiber.

The direction in which the reaction product obtained by increasing the molecular weight of the copolyester is extruded is not particularly limited.

In order to impart high strength and high elastic modulus to the copolyester fibers, it is advantageous to orient the fibers in the axial direction. Two revolutions of tangential extrusion are most advantageous when applying a shear rate gradient.

In addition, in order to impart high strength and high elastic modulus to the obtained fibers, it is preferable to react the fibers so that the intrinsic viscosity of the fibers becomes 0.4 or more, and then extrude and spin the fibers.

As described above, in the present invention, a thermotropic liquid crystalline copolyester is melted, a shear rate gradient is applied to orient the polymer molecules, and then a bifunctional compound is reacted in the molten state. The molecular chains of the polyester copolyester are linear (Lin) with less entanglement.
ear) state.

Moreover, by reacting a bifunctional compound in a state where one molecule end and another molecule end are adjacent to each other and easily meet each other (nematic state), it is possible to increase the degree of polymerization without almost disturbing the i-high state.

Highly oriented high molecular weight copolyester fibers with improved mechanical properties can be easily obtained.

In this way, the method of applying a velocity gradient by applying shear such as rotation and then reacting the bifunctional compound that is a molecular linking agent is more effective than the conventional method using a static mixing element or the method using forced stirring. It is easy to line up players, which is very advantageous.

The high molecular weight aromatic copolyester fiber obtained in the present invention has a higher molecular weight and a higher molecular weight than conventional thermotropic liquid crystalline fibers obtained without reacting with bifunctional compounds such as bisoxaprine compounds. Because it is oriented, it has high strength and high elastic modulus, and because the concentration of terminal carboxyl groups in the polymer is reduced,
The fiber has improved thermal stability, that is, resistance to hydrolysis and amine decomposition at high temperatures, and can be widely applied to fields that require high strength and high modulus, as well as heat resistance. be.

What is the thermotropic liquid crystalline copolyester having aromatic polyester units used in the present invention?

It is obtained by polymerizing an acid component, a diol component, and an oxycarboxylic acid component.

Specifically, the following components are used.

First, the acid components include terephthalic acid, isophthalic acid,
2,6-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 4,4'-biphenylene dicarboxylic acid,
4.4'-Dicarboxydiphenyl ether, adipic acid, sebacic acid, azelaic acid, etc., and mono- or di-substituted products thereof are preferably used.

The second diol component is hydroquinone.

Resorcinol, 4,4'-biphenol, 2,6-naphthalenediol, 1,5-naphthalenediol.

4.4'-Hydroxydiphenyl ether, ethylene glycol, etc., and mono- or di-substituted products thereof are preferably used.

Third, the oxycarboxylic acid component includes P-oxybenzoic acid, 1m-oxybenzoic acid, 2-oxy-6-carboxynaphthalene, 1-oxy-5-carboxynaphthalene, 4-oxy-4'-carboxybiphenyl, etc. Mono-substituted or di-substituted forms of these are preferably used.

In the present invention, a copolyester exhibiting thermotropic liquid crystallinity may be used among polymers obtained by appropriately selecting and polymerizing the components so that carboxyl groups and hydroxyl groups are equimolar or approximately equimolar.

How to judge thermotropic liquid crystallinity.

The polymer was placed on a hot stage and observed with a polarizing microscope, and if light transmitted through the polymer sample was confirmed in a fluid state, it was determined that the polymer sample had liquid crystallinity.

Note that a polymer without liquid crystallinity has a light transmittance of 0 above its melting point, and the field of view becomes pitch black. The hot stage used in this method was a cooling/heating device for microscopes manufactured by Linkam Tl.
-600RH type (can be used in a temperature range of -180 to 600°C).

In addition, the bifunctional compound that can undergo an addition reaction with the carboxyl terminal group used in the present invention is monoreactive.

From the viewpoint of ease of handling, a bisoxazoline compound represented by the following formula is preferably used.

Specific examples of bisoxazoline compounds include 2,2'-bis(2-oxazoline), 1,3-phenylene-bis(2-oxazoline), and 1,4-phenylene-bis(
2-oxazoline), etc., but such bisoxazoline compounds may be used alone or in combination of two or more types.

Bifunctional compounds other than bisoxazoline compounds include jepoxy compounds having 9 epoxy groups at both ends of the molecule, diglycidyl compounds, bisimidacillin compounds such as tetramethylenebisimidacillin, N, N'
Exoimino compounds such as -P-phenylene-bis(ethyleneiminocarbonate), bislactam compounds such as N,N'-terephthaloylbiscaprolactam, 2.2'
-Bisoxacilone compounds such as -bis(2-oxacylone), bisaziridine compounds, diisocyanate compounds, etc., and these may be used alone or in combination of two or more.

Next, one embodiment of the present invention will be described using a Kueft type device shown in FIG. 1 as a one-rotation shear imparting spinning device. The molten copolyester is supplied from the polymer injection pipe 1 to the reaction section 4 between the rotating cylinder 2 and the main body 3 of the apparatus, and the drug is applied to the copolyester in the reaction section 4 with a shear rate gradient created by the rotation of the cylinder 2. The molten bifunctional compound is injected from the injection tube 5 into the reaction section 4 and reacted with the copolyester.

The reaction product is spun from a spinneret 6 provided tangentially from the bottom of the reaction section 4, and the spun high molecular weight aromatic copolyester fiber 7 is wound into a package using a winding device N8.

9 in the figure is a drive motor.

(Examples) The present invention will be explained in more detail below with reference to Examples. The intrinsic viscosity in each example was measured by dissolving the polymer in pentafluorophenol at 60°C.

Moreover, the strength and initial elastic modulus are values measured under the conditions of a sample length of 200 mm and a tensile speed of 200 mm for 7 minutes.

Example 1 Magnesium acetate (0,1
mol) under nitrogen atmosphere.

Thereafter, polymerization was carried out for 3 hours while raising the temperature from 230°C to 330°C under vacuum. Grind the obtained polymer.

After extracting and removing unreacted substances and oligomers with acetone, the mixture was dried. The intrinsic viscosity value of this dried polymer is 4
．． It was 58 dl/g.

This polymer was melted at 320° C. using a Couette type rotary shearing device as shown in FIG.

1,3-phenylene-bis(2-
After injecting 0.5% by weight of oxazoline into the polymer, it was extruded from a spinneret, turned into fibers, and wound up at a speed of 200 m/min.

The obtained fiber was 70 d/12 f, and the intrinsic viscosity of the fiber was 5.38 dl/g.

On the other hand, as Comparative Example 1, 1.3-phenylene bis(2-
The same operation as in Example 1 was carried out except that oxazoline) was not injected, and as a comparative example 2, the same operation as in Example 1 was carried out except that no rotational shear was applied.
A 2f fiber was obtained.

Table 1 shows Example 1. The physical properties of the fibers obtained in Comparative Example 1 and Comparative Example 2 are shown.

Table 1 Fiber properties Example 2 6-acetoxy-2-naphthoic acid (10 mol), P-oxybenzoic acid (10 mol) and magnesium acetate (0.05 mol) as a catalyst were added and the mixture was heated for 250 min under a nitrogen atmosphere.
Polymerization was carried out while increasing the temperature from °C to 330 °C over 3 hours,
Furthermore, after the temperature reached 330℃, the
Hg) for 30 minutes. After the polymerization was completed, the polymer was pulverized, unreacted substances, oligomers, etc. were extracted and removed with acetone, and then dried.

The intrinsic viscosity value of the polymer was 4.51 dl/g.

The polymer was melted at 335° C. and heated for approximately 40 se
while applying rotational shear at a shear rate of c −′.

After injecting 1,4-phenylene-bis(2-oxazoline) melted at 280°C to the polymer at a concentration of 0.15% by weight, it was extruded from a spinning die for 200 m.
It was rolled up at a speed of / minute. The obtained fiber is 70d/12f
The intrinsic viscosity of the fiber was 5.91 dl/g.

On the other hand, in order to compare with Example 2, Comparative Example 3 was carried out in the same manner as Example 2 except that 1,4-phenylene-bis(2-oxazoline) was not injected, and Comparative Example 3 was carried out in the same manner as in Example 2, and no rotational shear was applied. Table 2 shows the physical properties of each fiber obtained in Comparative Example 4, in which the same operations as in Example 2 were performed except for the following.

Table 2 Fiber physical properties (effects of the invention) As described above, according to the present invention, it is possible to increase the degree of polymerization in the oriented state and reduce the terminal carboxyl groups of the polymer, so that it is possible to improve the fiber properties of conventional thermotropic liquid crystalline copolyester. Copolyester fibers with good heat resistance, high molecular weight, high strength, and high modulus of elasticity with a high degree of orientation can be obtained simply by spinning fiber chips according to the method of the present invention. Not necessary. Note that heat treatment may be performed to further improve the mechanical properties; however, in this case as well, the heat treatment time can be reduced compared to conventional methods. on the other hand,
For applications where the strength required for fibers is sufficient at conventional levels, it is possible to obtain fibers from thermotropic liquid crystalline copolyesters and bifunctional compounds with lower viscosity than conventionally, and therefore it is usually difficult to form fibers. Even if it is a low molecular weight copolyester that is difficult to spin, it can be spun by the method of the present invention, and the yarn properties of the resulting fibers will be sufficient for practical use. This case is extremely advantageous in terms of saving polymerization time and making it easier to discharge the polymer from the reaction tank after polymerization.

[Brief explanation of drawings]

Figure 1 shows a couette used in the present invention.
1 is a schematic diagram of a type of shearing spinning device; FIG.

Claims (4)

[Claims] (1) A thermotropic liquid crystalline copolyester having an aromatic polyester unit is melted, and at a temperature at which the copolyester exhibits thermotropic liquid crystallinity and under a shear rate gradient, 0.05 to 10% of the copolyester is melted. % by weight of a bifunctional compound that can undergo an addition reaction with the terminal carboxyl group in the copolyester, and then the reaction product is extruded from a spinneret and spun. Manufacturing method. (2) Shear is applied by rotation, and the shear rate is 1~
1000 sec^-^1 The method for producing a high molecular weight aromatic copolyester fiber according to claim 1. (3) A method for producing a high molecular weight aromatic copolyester fiber according to claim 2, in which the fiber is extruded in the tangential direction of rotation. (4) The method for producing a high molecular weight aromatic copolyester fiber according to claim 1, 2, or 3, wherein the difunctional compound is a compound represented by the following formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (n is an integer from 0 to 2, and R and R_1 to R_8 each independently represent a hydrogen filament, an alkyl group, an alkoxy group, an aryl group, or a halogen atom.) ( 5) Claims 1 and 2, wherein the spun yarn has an intrinsic viscosity of 0.4 or more.
The method for producing a high molecular weight aromatic copolyester fiber according to item 3 or 4.