JPS62282602A - Polyester hollow yarn-like separating membrane - Google Patents

Abstract

PURPOSE:To produce a hollow yarn-like separating membrane having high sepn. factor and excellent heat resistance, chemical resistance and mechanical strength with good operability during melt spinning by using a thermotropic mesomorphic copolyester which has a specific temp. or above of the thermal deformation temp. and in which the unit constituting the main chain is expressed by the specific formula. CONSTITUTION:The phosphorus-contg. arom. diol component expressed by formula I, etc., arom. dicarboxylic acid component such as terephthalic acid and isophthalic acid, and component having an oxycarboxylic acid residue are charged together with a catalyst into a reactor and are brought into an ester reaction under the atmospheric pressure in an inert atmosphere and are then brought into an acid exchange reaction; thereafter, the components are subjected to polycondensation while the acetic acid is distilled away under the reduced pressure. The resultant mesomorphic copolyester is melt spun. The hollow yarn-like separating membrane which has >=150 deg.C thermal deformation temp., and in which 5-95mol% of the unit constituting the main chain consists of the unit expressed by formula II (Ar<1> is a trivalent arom. group) and which has >=0.5 intrinsic viscosity is thus obtd.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a hollow fiber separation membrane made of thermotropic liquid crystalline copolyester with excellent heat resistance and moldability. .

(Prior art) Methods for separating specific substances from mixtures such as gas mixtures, solutions, and emulsions include a concentration method, a fractional precipitation method, a centrifugation method, and a filtration method using a separation membrane. has been rapidly developed in recent years due to its advantages such as low cost and high separation efficiency.

For example, the filtration method using a two-separation membrane can: 1) recover hydrogen from waste gas during ammonia synthesis, 2) adjust the composition of water gas,
■Recovery of helium from natural gas.

■Concentration of methane, ■Concentration of oxygen, ■Separation of gases such as hydrogen separation from various synthetic gases, separation of proteins, colloidal substances, microorganisms, etc., industrial use such as wastewater treatment, pharmaceutical use, food use, fuel use, etc. It has been put into practical use in many fields as a method for separating liquids.

Conventionally, such separation membranes have been made of polyalkylene terephthalate or cellulose acetate, but these membranes are heat and chemical resistant.

There were problems with mechanical strength, etc.

As materials with relatively good properties, materials using synthetic polymers such as polysulfone, polyimide, and polytetrafluoroethylene have been proposed (Japanese Unexamined Patent Publication No. 61-42).
307 etc.).

However, even if such a material is used, although it has excellent properties as described above, there remains the problem that the essential separation efficiency is insufficient.

On the other hand, as a heat-resistant polymer, thermotropic liquid crystalline copolyester, which has excellent processability, is attracting attention, and fibers using this are being actively researched. (for example,
(Special Publication No. 55-482, etc.).

Therefore, it is conceivable to use hollow fibers made of thermotropic liquid crystalline copolyester as a separation membrane.
Although fibers made of thermotropic liquid crystalline copolyesters 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 (,
Melt spinning was difficult, and in order to improve the operability during melt spinning, 1) yarns with a relatively low degree of polymerization were used, 1) the obtained yarn was heat treated for a long time to increase its strength (Japanese Patent Publication No.
No. 8), the conditions of melt spinning are devised so that the as-spun fiber has practical strength (Japanese Patent Laid-Open No. 58-9
No. 1811, No. 58-91812, No. 54-1386
No. 21.

No. 52-114723, etc.), which was not practical for obtaining a hollow fiber separation membrane.

(Problems to be Solved by the Invention) The present invention solves the drawbacks of conventional hollow fiber separation membrane manufacturing, and provides a heat-resistant membrane that can be easily manufactured, has a high separation coefficient, and can be used at high temperatures. The purpose of the present invention is to provide a hollow fiber separation membrane made of thermodropink liquid crystalline copolyester with high strength.

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

The heat distortion temperature is 150℃ or higher, and 5 of the units constituting the main chain are
A hollow fiber separation membrane comprising a thermotropic liquid crystalline copolyester in which ~95 mol% is a unit represented by the following structural formula (1), and comprising hollow fibers having an intrinsic viscosity of 0.5 or more.

(Ar' represents a trivalent aromatic group. However, the aromatic ring may have a substituent.) The copolyester in the present invention preferably contains 5 to 95 mol% of the units constituting the main chain. is a thermotropic liquid crystalline copolyester in which 10 to 80 mol%, more preferably 20 to 40 mol%, of units represented by the structural formula (I) is a thermotropic liquid crystalline copolyester having a heat distortion temperature of 150°C or higher, usually 350°C. °
It can be melt-molded at a temperature of C or lower, preferably 300°C or lower.

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 (I) 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.

A specific example of the phosphorus-containing aromatic diol is the 5th order formula (al
-(dl), but particularly preferred are those represented by formula 9 (al and formula (b)).

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

The second unit that forms a copolyester with the unit of structural formula (I) may be any unit that forms a thermotropic liquid crystalline copolyester with good melt spinnability together with the unit of structural formula (1), but the following units may be used. A unit consisting of an oxycarboxylic acid residue represented by the structural formula (n) and the following structural formula (I
The arylate unit represented by [l] is preferred, and the former is particularly preferred.

-0-Ar2-CO -(If) -O-Ar3-0-QC-Ar'-CO -(I[[)
Here, Ar'', Ar', Ar' represent a divalent aromatic group, specifically, a benzene ring and a naphthalene ring are preferable, and the hydrogen atom of the benzene ring and naphthalene ring has 1 to 20 carbon atoms. It may be substituted with an alkyl group, aryl group, alkoxy group, allyloxy group or halogen atom.

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, resorcinte phthalate residue, and the most preferred one is 4-hydroxy It is a benzoic acid residue.

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

naphthalic acid, 2.2-bis(4'-carboxyphenyl)propane, bis(4-carboxyphenyl)methane,
Bis(4-carboxyphenyl) ether and the like can be mentioned.

As an example of a particularly preferred copolyester in the present invention, the unit represented by the structural formula (I) is 9,10-dihydro-9-oxa-10-(2',
A unit derived from 5'-dihydroxyphenyl)phosphaphenanthrene-10-oxide (PHQ) and TPA/IPA, a unit represented by the structural formula (■) consisting of a 4-hydroxybenzoic acid (4HBA) residue. An example of a manufacturing method for the copolyester unit will be explained.

(a) An acid component consisting of TPA/IPA, a diol component consisting of a diacetate of PIIQ (PHQ-A), and an oxycarboxylic acid component consisting of an acetate of 48B^ (4118A-A) are combined with hydroxyl groups and carboxyl groups. (and preferably acetic anhydride equivalent to 0.01 to 0.25 times the amount of all hydroxyl groups at the same time) or (b) an acid component consisting of TPA/IPA and PHQ
The diol component consisting of 4HBA 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 to 1.2 of the total amount of hydroxyl groups.
Five equivalents of acetic anhydride are charged into a reactor, and the esterification reaction is carried out in an inert atmosphere at a temperature not exceeding 150° C. under normal pressure for 0.5 to 4 hours. Then, the acid exchange reaction is carried out in an inert atmosphere at a temperature of 150 to 300"C under normal pressure for 0.5 to 3 hours, and the reaction is continued at a temperature of 230 to 300"C. Start depressurization using a decompression schedule that lasts at least 1 hour.

After that, the temperature is raised sequentially to distill acetic acid, and the final temperature is usually 30
A fiber-forming copolyester can be obtained by carrying out a polycondensation reaction in the melt phase or solid phase at a temperature of 0 to 350° C. under a high vacuum of about 1 Torr for several tens of minutes to several hours.

Although a catalyst is usually used in the 9-polymer condensation reaction, one or more compounds selected from various metal compounds and organic sulfonic acid compounds are used in the production of the copolyester in the present invention.

As the metal compound, compounds such as antimony, titanium, germanium, tin, zinc, aluminum, magnesium, calcium, manganese, sodium or cobalt are used, while as the organic sulfonic acid compound,
Sulfosalicylic acid.

Compounds such as 0-sulfobenzoic anhydride are used. Particularly preferred are dimethyltin maleate and O-sulfobenzoic anhydride.

The amount of catalyst added is usually 0.00% per mole of polyester structural unit. IX10-' to 100X10-' moles, preferably 0.5X10-' to 50X10" moles, optimally 1x10-' to 1.QX10-' moles are suitable.

Depending on the type of constituent units of the polyester, it may solidify into a single solid phase during the single polycondensation reaction, or it may be polycondensed in a molten state.

It is desirable that the copolyester in the present invention has an intrinsic viscosity [η] of 0.5 or more when formed into hollow fibers,
Preferably 1.0 to 10.0. Optimally 3.0-6.0
It is. If [η] is smaller than this range, various physical and mechanical property values including heat resistance will be inferior;
] is larger than this range, the melt viscosity becomes too high and fluidity etc. are impaired.

This is not preferable because the melting point becomes too high and the spinning temperature must be increased significantly.

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. In order to make the moisture content in polyester about 1 ooppm, at a temperature of 150 to 200°C under reduced pressure,
All you have to do is dry it for about 8 hours.

In addition, in order to ensure heat resistance, the copolyester in the present invention has a heat distortion temperature of 150°C or higher, preferably 17°C.
It is necessary that the temperature is 0°C or higher. Preferred thermal properties of the copolyester include a melting point of 330°C or less, a softening point of 200°C or more, preferably a melting point of 300°C or less, and a softening point of 220°C or more. ℃ ones, heat resistance and various physical 1
This is suitable in terms of achieving both mechanical properties.

The copolyester thus obtained is melt-spun into hollow fibers.

It is preferable to carry out the process under conditions that satisfy the following conditions A and B.

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

B: The yarn passed through the first heating zone is passed through the second heating zone at a temperature lower than the softening point of the polyester provided below the first heating zone and higher than the glass transition point.

In the heating zone of condition A, the yarn discharged from the spinneret is heated to above its softening point to effectively and uniformly thin the yarn, and to spread the thermotropic liquid crystalline polyester in the direction of the fiber axis. It is suitable for orienting molecules and maintaining uniformity in the fiber axis direction.

In addition, the second heating zone of 1 condition B heats the yarn that has passed through the first heating zone to a temperature below its softening point and above its glass transition point to uniformly thin it and maintain uniformity in the fiber axis direction. It is suitable for

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 distance from the outer periphery to the center of the spun yarn is usually 0.1 to 107! A heating hood may be installed that blows gas at a temperature within a predetermined range at a flow rate of 10.1 to 10 m/sec. It is preferable that the ambient temperature be controlled to be as constant as possible within the above-mentioned range.

As the spinneret, one for hollow fibers, for example, one having a C-shaped slit nozzle is used.

When using a C-shaped slit nozzle, it is preferable to position the notch opening of the nozzle opposite to the heating surface of the heating zone in order to make the hollow fiber perfect. be.

It is desirable to cool and solidify the melt-spun filament in the form of a hollow fiber so that the inner diameter becomes 70% or less, preferably 50% or less of the inner diameter at the time of spinning.

If this requirement is not met, sufficient strength may not be obtained to maintain the hollow state, the separation coefficient may be insufficient as a 9-separation membrane, and the operability during spinning may be impaired. Undesirable.

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, a method for manufacturing hollow fibers will be specifically explained using nine drawings.

FIG. 1 is a schematic diagram showing an embodiment B of a spinning take-off apparatus suitably used for producing hollow fibers.

An example is shown in which two focusing guides are used below the spinneret surface to alternately press and focus these yarns.

The yarn 2 discharged from the spinneret 1 is passed through the first heating hood 3
After passing through the first heating zone where the ambient temperature is adjusted with the second heating hood 4, the second heating zone where the ambient temperature is adjusted with the second heating hood 4 is focused by the focusing guide group 5, and the chimney
6, it is oiled by an oiling roller 7, and the first
Godets Troller 8. It is taken up by the second godet roller 9 and wound up as a package 11 by the winder IO.

The length of the heating hood 3 is not particularly limited, but 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.

The length of the heating hood 4 is also not particularly limited, and is usually several cm to several tens of cm + preferably about 20 to 80 cm, but it is generally longer than the heating hood 3 and is preferred to avoid Worcester spots ( It is desirable to set the length to an optimum value so that the U%) is small.

Note that the polyester hollow fibers obtained by such a method exhibit sufficient strength for practical use in the as-spun state, especially when high strength is required.

The strength can be further increased by heat treatment.

The separation membrane of the present invention is particularly useful as a separation membrane used in applications requiring heat resistance and strength.

For example, it is preferably used for the separation of helium from natural gas, hydrogen from various synthetic gases, and the like.

In this case, it is not practical unless the ratio of the permeability coefficients of nitrogen and helium or carbon monoxide and hydrogen, that is, the separation coefficient of one separation membrane, is 50 or more, and the separation membrane of the present invention can sufficiently cope with this.

Furthermore, various inorganic salts and organic compounds can be appropriately added to the separation membrane of the present invention in order to improve the separation coefficient and fraction number.

(Function) Although the reason why the separation membrane of the present invention has an excellent separation coefficient is not clear, it is presumed that it is due to the orientation, crystallinity, etc. of the thermotropic liquid crystalline copolyester.

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

The intrinsic viscosity [η] of the polymer was determined from the solution viscosity measured at 20°C in a mixed solvent of equal weights of phenol and tetrachloroethane.

Thermotropic liquid crystal Leitz with hot stage
Confirmed using a polarizing microscope.

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

Further, the glass transition point (Tg) of the polyester was measured using a differential scanning calorimeter (DSCZ type) manufactured by PerkinElmer.

Furthermore, the heat distortion temperature (HDT) of polyester is.

Based on ASTM D 648 standard, high load (18,6 kg/cnl) for 1/8 inch thick molded parts
It was measured with

Example 1 A reaction apparatus was charged with PIIQ-A, 4HBA-A, and acetic anhydride in a molar ratio of 2.5:7.5:2, and TPA in an equimolar amount with PIIQ-A.

Dimethyltin maleate was added as a catalyst in an amount of 4 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. Then under nitrogen atmosphere.

An acid exchange reaction was carried out for 1 hour at normal pressure and a temperature of 200°C.

Then, from 200°C to 275°C at a heating rate of 25°C/hour.
°C, and at this time, depressurization was started using a depressurization schedule that reached 1 Torr in 90 minutes. Next.

While gradually raising the temperature and distilling acetic acid, the temperature reached 320'
C,1) Melt polymerization was carried out for 1 hour under reduced pressure.

The obtained copolyester has a [η) of 4.95. Ts
265'c, Tg 186°C, IIDT 184°
It was a liquid crystalline copolyester with a rating of C and three good color tones.

This copolyester was spun at a spinning temperature of 330° C. using a spinneret with a diameter of 90 mm and having 10 hollow fiber nozzles.
Spinning speed 300 m/min, temperature of the first heating zone 27
Spinning was carried out under spinning conditions of 5° C. and a temperature of 200° C. in the second heating zone.

In addition, as the heating hoods 3 and 4, cylindrical ones were used under the primary conditions.

■Inner diameter of heating air blowing surface: 100 mm ■Length of heating hood 3: 30 cm ■Length of heating hood 4: 60 cm ■Volume of heating air A preliminary test was conducted for each test, and the amount was determined to minimize U%.

Further, the melt-spun yarn was cooled and solidified to have an inner diameter of 40% of the melt-spun yarn.

The obtained hollow fiber has [η) 4.58. Outer diameter 1.6 dragon.

Inner diameter 1. It was ON.

A separation membrane module was prepared by bundling 50 of these hollow fibers with a length of 50 cm.

When the performance of this module was measured, the separation coefficient of hydrogen at 150° C. for a mixed gas of hydrogen and carbon monoxide was 180.

Example 2 A test was conducted in the same manner as in Example 1, except that the melt-spun yarn was cooled and solidified to 70% of the inner diameter at the time of melt-spinning. The separation factor for hydrogen at 150°C was 65.

Example 3 PIIQ, resorcinol (R3) and 411 B in a reactor
A and acetic anhydride in a molar ratio of 3:1:6:15 and PI (
Q and I? Equivalent mole of TPA/IPA to the sum of S (molar ratio 90
/10) and dimethyltin maleate as a catalyst at 4 x 10-
1 mol was added, and an esterification reaction was carried out at 130° C. under nitrogen atmosphere at normal pressure for 2 hours. After that, under nitrogen atmosphere, normal pressure, 2
Acid exchange reaction was carried out at 20°C for 1 hour. After that, 220°C
The temperature was raised from 280°C at a heating rate of 20°C/hour,
At this time, depressurization was started on a depressurization schedule that would reach 1 Torr in 60 minutes. Thereafter, the temperature was raised sequentially to carry out the reaction while distilling acetic acid, and finally melt polymerization was carried out at 310° C. for 2 hours under a reduced pressure of 1 Torr.

The obtained copolyester has [η]3. Q6. Ts 2
It was a liquid crystalline copolyester with two good color tones at 58'C, 7g at 177°C, and ID at 7171°C.

Using this copolyester, one melt-spun yarn was spun in the same manner as in Example 1, except that it was cooled and solidified so that the inner diameter was 21% of the inner diameter at the time of melt-spinning, and a polyester hollow yarn of [η) 2.89 was obtained. Got the thread.

When a separation membrane module was prepared and tested in the same manner as in Example 1 using this hollow fiber, the separation coefficient of hydrogen at 100° C. for a mixed gas of hydrogen and carbon monoxide in the module was 293.

Example 4 PIIQ, hydroquinone (lI[l), 4 II B A, and acetic anhydride were placed in a reactor in a molar ratio of 4:1:5;1
8 and the sum of PIIQ and IIQ and equimolar TPA/IPA
(mole ratio 80/20).

4×10 −' mol of dimethyltin maleate was added as a catalyst per 1 mol of the polyester structural unit, and an esterification reaction was carried out at 150° C. for 45 minutes at normal pressure under a nitrogen atmosphere. Thereafter, an acid exchange reaction was carried out under nitrogen atmosphere at normal pressure and 180° C. for 3 hours. After that, from 180℃, the heating rate was 50℃.
At this time, the temperature was increased to 280°C at a rate of °C/hour.

Depressurization was started on a depressurization schedule to reach 1 Torr in 90 minutes. Thereafter, the temperature was raised sequentially to carry out the reaction while distilling off acetic acid, and finally melt polymerization was carried out at 325° C. under a reduced pressure of 11 torr for 2 hours.

The obtained copolyester has [η) 1.43. Ts
273'C, Tg 190℃, ) 1 at ID7171℃
It was a liquid crystalline copolyester with good color tone.

Using this copolyester, the melt-spun yarn was spun in the same manner as in Example 1, except that it was cooled and solidified so that the inner diameter was 70% of the inner diameter at the time of melt-spinning, and a hollow polyester of [η) 1.38 was obtained. Got the thread.

When a separation membrane module was prepared and tested in the same manner as in Example 1 using this hollow fiber, the separation coefficient of hydrogen at 100° C. for a mixed gas of hydrogen and carbon monoxide in the module was 75.

Examples 5 to 10 The copolyesters shown in Table 1 were obtained in the same manner as in Example 1 using the raw materials shown in Table 1.

In Table 1, (b), (c), (d)
are respectively the above structural formulas (b) +' (c),
(d) The organic phosphorus compound.

NG represents 1,4-naphthohydroquinone, which was obtained by converting the phenolic hydroxyl group into a diacetate form.

These copolyesters were spun into hollow fibers in the same manner as in Example 1, but the ratio d/D of the inner diameter at the time of melt spinning to the inner diameter of the hollow fibers after cooling and solidification is shown in Table 1. value. ), the module was created and tested.

Table 1 shows the separation coefficient of hydrogen at 100° C. for a mixed gas of hydrogen and carbon monoxide in the obtained module.

(Effects of the Invention) According to the present invention, a separation membrane having a high separation coefficient that could not be obtained with the prior art is provided, and at the same time, the following effects are achieved.

(1) Heat resistance and chemical resistance 1 A hollow fiber separation membrane with excellent mechanical strength can be obtained.

(2) Good operability during melt spinning to produce hollow fibers.

Hollow fibers with good uniformity can be obtained economically, and as a result,
Hollow fiber separation membranes with good uniformity can be economically produced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a spinning take-off device suitably used when spinning hollow fibers used in the separation membrane of the present invention. 1--Spinneret, 3--First heating hood. 4.-Second heating hood.

Claims (5)

[Claims] (1) The thermotropic liquid crystalline copolyester has a heat distortion temperature of 150°C or higher, 5 to 95 mol% of the units constituting the main chain are units represented by the following structural formula (I), and the intrinsic viscosity is A hollow fiber separation membrane composed of hollow fibers having a molecular weight of 0.5 or more. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [Ar^1 represents a trivalent aromatic group, however, the aromatic ring may have a substituent. ] (2) Copolyester has 5 to 95 mol% of units represented by structural formula (I) and 95 mol% of units represented by the following structural formula (II)
5 mol % of the hollow fiber separation membrane according to claim 1. -O-Ar^2-CO-(II) [Ar^2 represents a divalent aromatic group. ] (3) The hollow fiber separation membrane according to claim 1 or 2, wherein the unit represented by structural formula (I) is represented by the following structural formula. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (4) The hollow fiber separation membrane according to claim 1 or 2, wherein the unit represented by structural formula (I) is represented by the following structural formula. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (5) Claims 2, 3, or 4, wherein the unit represented by structural formula (II) is a 4-hydroxybenzoic acid residue.
Hollow fiber separation membrane as described in .