JPS62263318A - Production of hollow polyester fiber - Google Patents

Abstract

PURPOSE:To obtain the titled homogeneous fibers having a high strength and elastic modulus at a low cost, by melt discharging a thermotropic liquid crystalline wholly aromatic polyester through annular slits having a cut opening part and passing the discharged polyester through a heating zone having a heating surface opposite to the cut opening part. CONSTITUTION:A thermotropic liquid crystalline wholly aromatic polyester is melt discharged through a spinneret 1 equipped with spinning holes of a cross-sectional shape having annular slits with one cut opening part each arranged to oppose to a heating surface of a heating zone. The resultant spun filaments 2 are then passed through a heating zone 3 at a higher temperature than the softening point of the polyester provided below the spinneret 1, collected by collecting guides 4 and passed through a chimney 5. After applying an oiling agent with an oiling roller 6, the resultant yarn is taken off with the first godet roll 7 and second godet roll 8 and wound as a package 10 by a winder 9 to afford the aimed hollow fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing polyester hollow fibers made of thermodropink liquid crystalline fully aromatic polyester.

(Prior technology) In recent years, research on separation membranes and permeable membranes using hollow fibers of highly functional polymers has been progressing. It is essential for the development of functional separation membranes.

BACKGROUND ART Conventionally, as a liquid crystalline polymer, fibers using polyester, which has excellent processability and thermotropic liquid crystallinity, have attracted attention and are being actively researched. (For example, Special Publication No. 55-482, etc.). but.

Although fibers made of polyester with thermodropink liquid crystal properties have excellent physical properties such as high strength and high elastic modulus, those with a high degree of polymerization generally have a high melt viscosity and are difficult to melt spin. can be.

When attempting to spin hollow fibers, the joints tend to peel off easily, and the fibers are sufficiently strong as they are spun.

It was difficult to obtain complete hollow fibers.

In addition, Japanese Patent Publication No. 1 Sho 58-4085 discloses that when producing hollow fibers by melt spinning a thermoplastic I main polymer such as polyethylene terephthalate, an annular slit having a cross-sectional shape with one notch opening is used. A method for obtaining uniform hollow fibers with a large hollowness ratio by spinning through a spinneret equipped with spinning holes and arranged such that each notch opening faces the blowing surface of the cooling air flow. is disclosed.

However, even if such a method of blowing a cooling air stream directly under a spinneret is applied to thermotropic liquid crystalline fully aromatic polyester, hollow fibers with good properties cannot be obtained.

(Problems to be Solved by the Invention) The present invention provides a method for producing hollow fibers by melt-spinning thermotropic liquid crystalline fully aromatic polyester.
Maintains a stable spinning state and is uniform.

The present invention aims to provide a method for economically producing hollow fibers with high strength and high modulus.

(Means for solving problems) The gist of the present invention is as follows.

A method for producing polyester hollow fibers, which is characterized in that the following conditions A and B are satisfied when producing hollow fibers by melt-spinning a thermotropic liquid crystalline fully aromatic polyester.

A: Passing the spun yarn through a heating zone at a temperature equal to or higher than the softening point of polyester provided at the bottom of the spinneret.

B; through a spinneret having a spinning hole whose cross-sectional shape is an annular slit with one notch opening and arranged such that each notch opening faces the heating surface of the heating zone; To spin.

The thermotropic liquid crystalline fully aromatic polyester in the present invention is not particularly limited, but particularly preferred are 1
This is the polyester mentioned next.

The method for producing the polyester hollow fiber of the present invention will be explained below by taking this polyester as an example.

That is, in the particularly preferred polyester in the present invention, 5 to 95 mol% of the units constituting the main chain have the following structural formula (
It is a thermotropic liquid crystalline fully aromatic copolyester having units represented by I).

(Ar' represents a trivalent aromatic group. However, the aromatic ring may have a substituent.) 5 to 95 mol% of the unit represented by structural formula (1), preferably 10 to 95 mol% A copolyester having thermotropic liquid crystallinity containing 80 mol%, more preferably 20 to 40 mol%, and having good melt spinnability is suitable.

If there are too many units represented by structural formula (1), the strength will decrease, while if there are too few, the melting point will become too high.

Ar' in structural formula (1) is most preferably a benzene ring or a naphthalene ring. Further, in Structural Formula (1), the hydrogen atom of the aromatic ring may be substituted with an alkyl group having 1 to 20 carbon atoms, an aryl group, an alkoxy group, an allyloxy group, or a halogen atom.

The unit of structural formula (1) is derived from a phosphorus-containing aromatic diol component and an aromatic dicarboxylic acid component.

Specific examples of phosphorus-containing aromatic diols include primary 2(a)
Examples include those represented by ~(dl), but particularly preferred are those represented by formula 1 (al) and formula (bl).

As aromatic dicarboxylic acid, terephthalic acid (TPA)
and isophthalic acid (IPA) are preferred, and the molar ratio of TPA and RP8 is 100:0 to 0:100.
Preferably 100:O to 50:50. Optimally to
It is appropriate to use the ratio of o:o to 80:20.

The second unit that forms a copolyester together with the unit of structural formula (I) may be one that forms a copolyester having thermotropic liquid crystallinity with good spinnability together with the unit of structural formula (1). However, the following structural formula (I[
) A unit consisting of an oxycarboxylic acid residue and an arylate unit represented by the following structural formula (lI[) are preferred, with the former being particularly preferred.

10-Ar2-Co -(II) -O-Ar'-0-QC-Ar'-C○-(II[) where Ar", Ar3. Ar' represents a divalent aromatic group, Specifically, a benzene ring and a naphthalene ring are preferred, and the hydrogen atoms of the benzene ring and naphthalene ring may be substituted with an alkyl group, an aryl group, an alkoxy group, an allyloxy group, or a halogen atom having 1 to 20 carbon atoms. .

Specific examples of these include 4-hydroxybenzoic acid residue and 6-hydroxy-2-naphthoic acid residue.

Examples include hydroquinone terephthalate residue, hydroquinone isophthalate residue, 1,4-naphthohydroquinone terephthalate residue, 2,6-naphthohydroquinone terephthalate residue, resorcinol terephthalate residue, and the most preferred one is 14-hydroxybenzoic acid. It is a residue.

In addition, components other than the above may be copolymerized within the range of forming a thermotropic liquid crystalline copolyester with good 78 melt spinnability, and such copolymerized components include 4.4
'-dihydroxydiphenyl.

Examples include naphthalic acid.

Forming the fiber of the invention. As an example of a preferable copolyester, the unit represented by the structural formula (1) has the above formula 0I
9,10-dihydro-9-oxa-10 represented by I)
-(215'-dihydroxyphenyl)phosphaphenanthrene-10-oxide (pH 1l)) and TPA/
An example of a method for producing a copolyester in which the unit derived from IPA and the unit represented by the structural formula (II) is a unit consisting of a 4-hydroxybenzoic acid (4HBA) residue will be described.

(b) An acid component consisting of TPA/IPA, a diol component consisting of a diacetate of PR[] (PHQ-A), and an oxycarboxylic acid component consisting of an acetate of 411BA (411BA-A) with a hydroxyl group. An amount equivalent to carboxyl groups (and preferably - at the same time, 0.01 to 0.25 times equivalent amount of acetic anhydride to the amount of all hydroxyl groups) or (b) an acid component consisting of TPA/rPA and pH () The diol component and the oxycarboxylic acid component consisting of 4HBA are mixed in an amount such that hydroxyl groups and carboxyl groups are equivalent and 1.05 of the total amount of hydroxyl groups.
~1.25 times the equivalent of acetic anhydride is charged into a reactor, and the esterification reaction is carried out at a temperature not exceeding 1150°C under normal pressure for 0.5 to 4 hours. Then, in an inert atmosphere under normal pressure 11
Acid exchange reaction is carried out for 0.5 to 3 hours at a temperature of 50 to 300°C, and further.

Continue the reaction at a temperature of 230-300°C. At that time 1
Start depressurization using a decompression schedule that will take at least 1 hour to reach full vacuum. After that, the temperature is gradually increased,
By leaking acetic acid and finally carrying out a polycondensation reaction in the melt phase or solid phase under a high vacuum of about 11 torr at a temperature of usually 300 to 350°C for several tens of minutes to several hours, a fiber-forming copolymer is produced. Polyester can be obtained.

Usually, a catalyst is used in the polycondensation reaction, but in the production of the copolyester in the present invention, one or more compounds selected from heavy metal compounds and organic sulfonic acid compounds are used.

Such metal compounds include antimony, titanium, germanium, tin-zinc, and aluminum.

On the other hand, compounds such as magnesium, calcium, manganese, sodium or cobalt are used.

As the organic sulfonic acid compound, compounds such as 1 sulfosalicyl acid and 0-sulfobenzoic anhydride are used.

Particularly preferred are dimethyltin maleate and 0-sulfobenzoic anhydride.

The amount of catalyst added is usually 0.00% per mole of polyester structural unit. I X 10-' to 100 X 10-' mol, preferably 0.5 X 10-' to 50 X 10-' mol, optimally 1x1O-4 to 10XIO-' mol are suitable.

In addition, during the single polycondensation reaction, depending on the type of polyester structural unit, it may become a solid phase.)
In some cases, polycondensation can be carried out in the molten state.

The copolyester in the present invention is made into fibers, and
It is desirable that the intrinsic viscosity [η] is 0.5 or more, preferably 1.0 to 10.0, most preferably 3.0 to 6.0. [η] If it is smaller than the cage range, various physical and mechanical properties such as heat resistance will be inferior; on the other hand, [η]
If it is larger than this range, the melt viscosity becomes too high, impairing fluidity, etc., or the melting point becomes too high, making it necessary to raise the spinning temperature significantly, which is not preferable.

Therefore, [η] of the polyester to be subjected to spinning is usually 0.0% compared to the above value when the moisture content in the polyester is about 1100 pp, taking into account the decrease in [η] during spinning.
．． It is appropriate to use a polyester with a high [η] of 1 or more. When the moisture content in polyester is about 1100 ppm, Luni is heated under reduced pressure at a temperature of 150 to 200'C.
It may be dried for about 8 to 48 hours.

In addition, the thermal properties of the copolyester in the present invention include a melting point of 330° C. or lower and a softening point of 200"C or higher.

Preferably a melting point of 300°C or lower, a softening point of 220'C or higher,
Optimally melting point 280-300°C1 softening point 220-28
A temperature of 0°C is suitable in terms of achieving both heat resistance and various physical and mechanical property values.

The thus obtained copolyester was
Spinning is performed under spinning conditions that satisfy condition B.

That is, first, the melt-spun yarn is passed through a heating zone provided at the bottom of the spinneret. The heating zone of condition A heats the polyester yarn discharged from the spinneret to a temperature higher than its softening point, effectively and uniformly thins the polyester yarn, and forms thermotropic liquid crystalline polyester in the direction of the fiber axis. It is essential to orient the molecules of the fibers and maintain uniformity in the fiber axis direction.

In order to set the ambient temperature of the heating zone within the above-mentioned temperature range, for example, the following procedure may be used. That is, the flow rate is usually 0.1 to 101/min from the outer periphery to the center of the spun yarn,
A heating hood that blows gas at a predetermined temperature range at a flow rate of 0.1 to 10 m/sec may be installed. It is preferable that the ambient temperature be controlled to be as constant as possible within the above-mentioned range.

Next, 1 condition A and 1 condition B, that is, making sure that the position of the notch opening of the spinning hole is opposite to the heating surface of the heating zone is essential for making the hollow fiber perfect. be.

When the position of the notch opening of the spinning hole with respect to the heating surface of the heating zone is different, the orientation of the spun yarn.

This is undesirable because physical properties such as crystallinity and elongation may be different, or the hollow fibers may not be perfect because they have some openings, or the hollow fibers obtained may be brittle.

Note that the spinning speed is preferably about 100 to 1500 m/min.

It is also preferable to use a method of controlling the molecular orientation of the spun yarn by applying a magnetic field in a direction substantially parallel to the flow direction of the polymer in the spinning pack section and/or the heating zone.

Next, the method of the present invention will be specifically explained using nine drawings.

FIG. 1 is a schematic diagram showing an embodiment of a spinning take-off device suitably used in the method of the present invention, in which two focusing guides are used to alternately press these yarns below the spinneret surface. An example of focusing is shown below.

The yarn 2 discharged from the spinneret 1 passes through a heating zone whose atmospheric temperature is adjusted by a heating hood 3, is focused by a focusing guide group 4, passes through a chimney 5, and is oiled by an oiling roller 6. , the first godet roller 7 and the second godet roller 8, and are wound up as a package 10 by a winder 9.

The length of the heating hood 3 is not particularly limited, but it is usually several cm.
-Several tens of cm, preferably about 20 to 80 cm, is appropriate. Further, as long as the length of the heating hood 3 is within this range, the longer the length, the faster the spinning speed can generally be increased.

It is desirable to set the optimum length so that the Worcester spot (U%) of the spun yarn is reduced.

Note that the polyester hollow fiber obtained by the method of the present invention is a hollow fiber in which all threads are completely formed, and exhibits sufficiently high strength in the as-spun state, and can be used in applications that require particularly heat resistance and strength. For example, it is extremely useful as a material for separation membranes and purification of gases and fluids.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

In Examples 4 and 6 to 9, the intrinsic viscosity [η] of the polymer was measured at 60°C in a pentafluorophenol solvent,
In other cases, the viscosity was determined from the solution viscosity measured at 20° C. in a mixed solvent of equal weights of phenol and tetrachloroethane.

Thermotropisoc liquid crystalline Leitz with hot stage
Tri-identification was performed using a polarizing microscope.

The softening point (Ts) of polyester is determined by using an automatic melting point measuring device manufactured by Metmer Co., Ltd., placing two wood fibers in a crosswise manner on a hot stage under a microscope, raising the temperature at a rate of 2°C/min, and then melting the fibers. It was determined as the temperature at which the intersection of the two deforms and fuses.

The glass transition point (Tg) of the polyester was measured using a differential scanning calorimeter (Model DSC2) manufactured by PerkinElmer.

Furthermore, the spinning condition was evaluated on a first-order basis by observing the cross section of the obtained undrawn hollow multifilament yarn.

○; No non-hollow filament in which the notch opening in the multifilament is welded.

Δ; Occurrence rate of non-hollow filaments is 5 to 10%.

×: The incidence of non-hollow filaments is 50% or more.

Example 1 and Comparative Examples PHQ-A, old IBA-A, and acetic anhydride in a molar ratio of 2.5:7.5:2 and PIIQ-8 and equimolar TPA were charged into a reactor.

Dimethyltin maleate was added as a hornworm medium in an amount of 1 x 10-' mol per mol of the polyester structural unit.

Esterification reaction was carried out under a nitrogen atmosphere at normal pressure and a temperature of 145°C for 1 hour. After that, 1 under nitrogen atmosphere, normal pressure, 2
The temperature was raised from 00°C to 275°C at a temperature increase rate of 25°C/hour, and at this time, pressure reduction was started on a pressure reduction schedule such that the pressure reached 1 Torr in 90 minutes. After that, the temperature is gradually increased,
While acetic acid was being distilled off, melt polymerization was finally carried out under reduced pressure of 320'C, 11-l for 1 hour.

The obtained copolyester has a [η) of 4.95. T.S.
It was a liquid crystalline copolyester with three good color tones at 265'C and Tg 186°C.

This copolyester was spun under the conditions shown in Table 1 using a spinneret with a diameter of 90 mm and having 72 spinning holes shaped as shown in FIG.

As the heating hood 3, a cylindrical one was used under the primary conditions.

■Inner diameter of heated air blowing surface 100 mm ■Length of heating hood 3 30 cm ■Heating air volume A preliminary test was conducted for each test, and the amount was determined to minimize U%.

Example 2 In reaction WZ, PIIQ, redulucin (R3), 4HBA and acetic anhydride were added in a molar ratio of 3:1:6:15, and PIIQ and R
Equimolar TPA/IP8 to the sum of 5 (molar ratio 90/10)
and 4×10 −' mol of dimethyltin maleate as a catalyst per mol of the polyester structural unit.
Esterification reaction was carried out at 130°C under nitrogen atmosphere at normal pressure for 2 hours. After that, under nitrogen atmosphere, normal pressure, 1 at 220℃.
The acid exchange reaction was carried out for an hour. Thereafter, the temperature was raised from 220°C to 280°C at a heating rate of 20°C/hour, and at this time,
Depressurization was started on a depressurization schedule to reach 1 Torr in 60 minutes. Thereafter, the mixture was incubated one after another, and the reaction was carried out while distilling acetic acid, and finally melt polymerization was carried out at 310° C. and under a reduced pressure of 11 torr for 2 hours.

The obtained copolyester has [η) 3.06. Ts
It was a liquid crystalline polyester with good two-color tone at 258'C and Tg of 177°C.

This copolyester was spun in the same manner as in Example 1 to obtain polyester hollow fibers.

Example 3 PIQ, hydroquinone (IIQ) and 41
1 B A and acetic anhydride in a molar ratio of 4:1:5:18 and TPA/I in a molar equivalent to the sum of I'lIQ and IIQ? A(
molar ratio 80/20).

Dimethyltin maleate was added as a catalyst in an amount of 1×10 −' mol per mol of the polyester structural unit, and an esterification reaction was carried out at 1 normal pressure and 150° C. for 15 minutes under a nitrogen atmosphere. Thereafter, an acid exchange reaction was carried out under a nitrogen atmosphere at 1 normal pressure and 180°C for 3 hours. Thereafter, the temperature was raised from 180°C to 280°C at a heating rate of 50"C/hour.

Depressurization was started on a depressurization schedule to reach 1 Torr in 90 minutes. Thereafter, the temperature was raised sequentially, and the reaction was carried out while leaking acetic acid, finally reaching 325°C.

Melt polymerization was carried out for 2 hours under a vacuum of 1 torr.

The obtained copolyester has [η) 1.43. Ts
It was a liquid crystalline polyester with good color tone at 273'C and 7g at 190°C.

This copolyester was spun in the same manner as in Example 1 to obtain polyester hollow fibers.

The spinning conditions on each side and the characteristic values of the obtained hollow fibers are shown in Table 1.

In addition, in Comparative Example 41, the strength was low, single fiber breakage occurred during spinning, the U% of the yarn was large, and many non-hollow filaments whose notch openings were not fused were generated, making it difficult to take one winding. was difficult.

Table 1 2) Hollowness ratio was measured using a mercury porosimeter model 221 manufactured by Kalkuchi Elba. This is the ratio of the micropore volume to that of the hollow fiber excluding the hollow part.

Examples 4 to 9 Copolyesters shown in Table 2 were obtained in the same manner as in Example 1 using the raw materials shown in Table 2.

In Table 2, (b), (c), (d)
have the above structural formulas (b), (c), (
d) organophosphorus compound.

The N port indicated 1,4-naphthoquinone, which had a phenolic hydroxyl group converted to a diacetate.

These copolyesters were spun at a speed of 200 m/min.

Spinning temperature Ts + 70°C, heating zone temperature Ts + 1
The temperature was 0° C., and the other conditions were the same as in Example 1 to obtain polyester hollow fibers.

Table 2 shows the characteristic values of the obtained fibers.

(Effect of the invention) According to the present invention, the following effects are achieved.

(1) High strength with excellent heat resistance and physical 3 mechanical strength.

Polyester hollow fibers with high elastic modulus can be obtained.

(2) Polyester hollow fibers with good operability during melt spinning and good uniformity can be economically prepared.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a spinning take-off device suitably used in the method of the present invention, and FIG. 2 is a schematic explanatory diagram showing an example of a spinneret in the present invention. 1 - spinneret, 3 - heating hood, 4 - focusing guide. 5-chimney-16-oiling roller, 7-first godet roller, 8-last godet roller. 9- Wine goo, 1 (1- package.

Claims (1)

[Claims] (1) When producing hollow fibers by melt spinning thermotropic liquid crystalline fully aromatic polyester, the following A and B
A method for producing polyester hollow fibers characterized by satisfying the following conditions. A: Passing the spun yarn through a heating zone above the softening point of polyester provided at the bottom of the spinneret; B: Providing a spinning hole whose cross-sectional shape is an annular slit with one notch opening. , and spinning through a spinneret arranged such that each of the notched openings faces a heating surface of the heating zone.