JPS5825371B2 - Anisotropic membrane and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing anisotropic membranes, particularly hollow fiber membranes.

In particular, important aspects of the present invention include anisotropic polysulfone hollow fiber membranes and methods of making polysulfone hollow fiber membranes suitable for the separation of gases such that the material of the hollow fiber membrane achieves separation by selective permeation. .

Compared to other separation operation methods such as absorption, adsorption, and liquefaction, the ability of using membranes for fluid separation is often influenced by the cost and energy consumption of the equipment, the degree of separation selectivity desired, and the performance of the separation operation. It depends on the operation of the equipment, including the allowable total pressure loss experienced by the equipment, the useful life of such equipment, and the size and ease of use of such equipment.

As a result, the desired separation selectivity, flow rate (flux)
There is a need for a membrane that provides strength and strength.

Furthermore, because it is commercially viable on the basis of economics, &L
The membrane should preferably be of a type that can be manufactured in large quantities while achieving reliable product quality and that can be easily and relatively inexpensively assembled into a permeation device.

Particularly advantageous membranes include a relatively thin layer (often a separation layer, barrier layer or It is a single anisotropic hollow fiber membrane with an active layer (referred to as an active layer).

In order to produce these integral anisotropic membranes, a single membrane structure with diametrically opposed structures must be formed.

The separation layer must be formed so that it is thin and has few pores or other defects.

On the other hand, the conditions for manufacturing an integrated anisotropic film are also:
It must provide a highly open support structure to provide low resistance to fluid flow.

Membranes have been manufactured in film and hollow fiber form.

Many proposals have been made regarding the production of integral anisotropic membranes in film form.

Generally, anisotropic film membranes are produced by casting a solution of the membrane-forming polymer in a ζ solvent onto a surface, such as a polished glass surface.

The polymer is at least partially coagulated in air or a gaseous or vaporous atmosphere and then usually immersed in a liquid coagulant.

Considerable flexibility exists in the manufacture of anisotropic film membranes.

For example, because the polymer solution is placed on a support, the membrane precursor structure is small (and does not need to be self-supported until solidification is complete).

Similarly, since one surface of the cast membrane is in contact with the support, each side of the membrane is subjected to different solidification conditions, thereby achieving substantially different structures on each surface of the membrane. make it possible to be

Thus, a membrane is obtained with a relatively thin layer that is substantially free of pores on one side of the film, while the remaining side of the membrane is relatively porous.

Furthermore, since the film membrane precursor is supported,
The coagulation conditions, including the coagulation time, can be varied widely to achieve the desired film structure.

However, in some cases, film membranes need to be supported to better withstand operating conditions, and also because of the overall complexity of devices with film membranes, film membranes are not as effective as other gas separation devices. is not attractive.

Membranes in the form of hollow fibers overcome some of the disadvantages of film membranes for many separation operations.

Hollow fibers are generally self-supporting even under operating conditions and provide a greater amount of membrane surface per unit volume of the separation device than that provided by film membranes.

Separation devices with hollow fibers are thus attractive from the standpoint of convenience, size and reduced complexity of design.

The manufacture of film membranes involves many different considerations than those involved when manufacturing hollow fiber membranes.

For example, in methods of spinning hollow fiber membranes, it is not possible to provide a solid support or interface.

Additionally, in the spinning process, the polymer solution must have sufficient viscosity to provide a self-supporting extrudate before and during coagulation, and coagulation must ensure that the hollow fiber membrane is not adversely affected after extrusion. This must be done promptly to avoid this.

The method for forming an integrated anisotropic membrane must not only meet the criteria for forming an integrated anisotropic hollow fiber membrane, but must also be compatible with hollow fiber spinning capabilities. Must be.

Therefore, there are many limitations to the techniques utilized to produce monolithic anisotropic hollow fiber membranes.

Typically, in hollow fiber membrane spinning operations, a solution of the polymer forming the hollow fiber membrane in a solvent is extruded through a spinneret suitable to form the hollow fiber structure and air is added so that the hollow fiber shape can be maintained. or maintain the liquid in the pores of the hollow fiber extrudate.

Hollow fiber extrudates must be rapidly solidified, for example, by contacting with a non-solvent for the polymer in such a way that the hollow fiber shape can be maintained.

Hollow fiber spinning methods depend on the conditions of the polymer solution as it is extruded from the spinneret, the nature of the fluid maintained within the pores of the hollow fiber membrane extrudate, the environment to which the outer surface of the hollow fiber extrudate is exposed, and the conditions of the polymer solution as it is extruded from the spinneret. There are many variables that affect the structure or morphology of hollow fiber membranes, such as the rate of coagulation of the polymers therein.

Since the hollow fiber formation process is a method of coagulating the polymer from a polymer solution, the nature of the solvent for the polymer has a high impact on determining the morphology of the hollow fiber membrane and its separation properties.

The solvent must have polymorphic properties to be suitable for forming anisotropic membranes, especially anisotropic hollow fiber membranes.

For example, a solvent (or a liquid carrier containing a solvent) can dissolve a polymer to form a hollow fiber membrane;
Furthermore, the polymer must be able to be easily solidified to form an anisotropic structure.

Furthermore, if hollow fiber membranes are desired, the solvent (or liquid carrier containing the solvent) must be one that allows the production of a polymer solution with a suitable viscosity for hollow fiber membrane formation; And advantageously these viscosities can be obtained without using excessively high concentrations of polymer.

Advantageous hollow fiber membranes are often obtained when the extrudate undergoes a significant temperature drop as it exits the spinneret, so that the liquid carrier can provide a suitable viscosity for hollow fiber formation at elevated temperatures. It has to be possible.

This increased temperature facilitates achieving a significant temperature drop.

The solvent or other components of the liquid carrier must not be degraded at such elevated temperatures.

The solvent must be miscible with the non-solvent used to aid in the coagulation of the polymer, and also be removed from the coagulated structure so that the membrane is not unduly plasticized by the solvent and thereby weakened. For example, it must be removed with something that can be removed by washing.

Additionally, the solvent (or liquid carrier containing the solvent) must not exhibit excessive heat of dilution in the non-solvent used to aid coagulation of the polymer.

In order to make the process attractive for producing membranes in commercial quantities, it is desirable that the process be both safe and economical.

Thus, the solvent must not be unduly toxic, so advantageously the solvent exhibits a very low vapor pressure so as to minimize the risk of inhalation and/or air contamination.

Additionally, solvents with very low vapor pressures also minimize the risk of explosion and fire.

The repellent material from the spinning process must be able to be disposed of or recycled economically and also safely.

Solvents are one of the different components used in the spinning process, such as the fluid in the pores of the hollow fiber extrudate, the non-solvent that helps perform coagulation, the washing fluid that removes the solvent from the hollow fiber membrane, etc. The other ingredients must also be economical and safe.

In the past, it has been proposed to use, for example, gasoline, solvent oils or other hydrocarbon materials in the spinning process as a coagulant or to aid in drying, as described in US Pat. No. 4,127,625.

Such materials clearly pose toxicity and fire hazards as well as disposal problems.

Additionally, the cost of the hydrocarbon material, in the amounts required to perform coagulation, washing, etc., is a factor in the economics of the spinning process.

It is therefore desirable to use highly safe and readily available substances in the spinning process, such as water, which can be used particularly as a non-solvent to aid in coagulation and in washes to remove solvent from the hollow fiber membranes.

The possibility of using water depends to some extent on the properties of the solvent for water, such as solubility in water, heat of dilution in water, stability in water, etc.

In accordance with the present invention, a method of making anisotropic membranes is provided that utilizes certain advantageous solvents.

The method of the present invention provides an anisotropic membrane characterized by having a very thin separating layer with relatively few pores on a lower part having an open cell-like structure with little resistance to gas-fluid flow. It is something that can be used.

These membranes are particularly useful for gas separation.

Additionally, polymers that can be utilized by the present invention to provide membranes include polysulfones that exhibit desirable strength and chemical resistance as well as desirable permeability with respect to flux and selectivity.

Advantageously, the method of the present invention may utilize water as a non-solvent to aid in coagulation of the polymer and as a non-solvent to wash solvent from the membrane.

Furthermore, the solvent has a low vapor pressure, does not pose an unreasonable risk of explosion or fire, and can be economically and completely disposed of or recycled.

According to the present invention, an anisotropic membrane is prepared from a solution of a membrane-forming polymer in a liquid carrier consisting of an N-acylated heterocyclic solvent that can be represented by the following structural formula:

In the formula, X is -CH2-3-N(R')- or -0-.

R is hydrogen, methyl or ethyl.

R' is hydrogen or methyl. Polymer solution &i. It is provided in the form of a precursor and then coagulated in a liquid coagulant consisting of water to form an anisotropic film.

The anisotropic membrane may be a film or preferably a hollow fiber.

Representative N-acylated heterocyclic solvents include 1-formylpiperidine, -acetylpiperidine, 1-formylmorpholine, and 1-acetylmorpholine.

A preferred N-acylated heterocyclic solvent consists of 1-formylpiperidine.

Reilly Tar & Chemical Corp.
) In the booklet entitled ``1-Formylpiperidine'', 1-formylpiperidine has a boiling point of about 222°C, 25°C.
It has been reported to have a vapor pressure of 0.111 hg at 0.99 °C, a flash point of about 102 °C, and an LD50 (rat oral) of about 0.88 f/kg body weight.

In the method of the present invention for producing hollow fiber membranes, the polymer solution maintains substantially the fiber-forming polymer in solution and at a fiber-forming viscosity prior to extrusion of the hollow fiber precursor. be at a temperature sufficient to provide a solution.

The polymer solution is extruded through an annular spinneret to form hollow fiber precursors.

While extruding the polymer solution from the spinneret, fluid is injected into the hollow fiber precursor pores at a rate sufficient to maintain the hollow fiber precursor pores open.

The injection fluid is preferably highly miscible with the liquid carrier and therefore often consists of water.

The hollow fiber precursor is then contacted with a liquid coagulant that is a non-solvent for the polymer in the polymer solution.

The liquid coagulant is preferably highly miscible with the liquid carrier and is the injection fluid.

Usually, the temperature of the liquid coagulant is sufficiently low (and the polymer solution at that temperature can be very viscous and even a gel).

The contact of the liquid coagulant with the hollow fiber precursor is for a time sufficient to substantially completely coagulate the polymer in the hollow fiber precursor under the conditions of the liquid coagulant and thereby provide hollow fibers.

The hollow fibers are then washed or contacted with a non-solvent consisting of water for a polymer that is miscible with the liquid carrier to determine the content of liquid carrier in the hollow fibers based on the weight of the polymer in the hollow fibers. The amount is reduced to less than about 5% by weight.

The washed hollow fibers are then dried at a temperature that does not adversely affect the selectivity or flux exhibited by the hollow fibers.

In an aspect of the present invention, the hollow fiber membrane preferably has a relatively circular cross-section with circular concentric holes.

In many cases, hollow fiber membranes. It can be circular and concentric within the tolerances of the machining necessary to create a suitable spinneret.

The external diameter of the hollow fiber membrane (ζ may vary, for example from 100 or 150 to 1000 microns or more).

Often, the external diameter of hollow fiber membranes is about 200 or 30
0 to 800 microns.

The wall thickness/external diameter ratio of the hollow fiber membrane can also vary widely depending on the required collapse pressure that must be exhibited for a given separation operation.

Since the cellular supports are open, the increase in wall thickness is
No undue reduction in flow rate through the membrane wall.

Typical thickness/outer diameter ratios range from about 0.1 or 0.15 to
about 0.45 and often about 0.15 to 0.4
It is.

The void volume of the hollow fiber membrane, ie the portion of the wall of the hollow fiber membrane that is void of material in the hollow fiber membrane, is substantial.

This void volume can be measured by comparing the density with a bulk polymer (or other material for hollow fibers) that corresponds to the same overall physical dimensions and shape of the hollow fibers as the walls of the hollow fiber membrane. can.

Because the cellular support portions of the hollow fibers are open, relatively low void volumes for anisotropic hollow fiber membranes can be achieved without unduly reducing the permeate flux.

Often the void volume is at least about 30-35% by volume.
eg at least 40% by volume, further eg from about 45 or 50% by volume and up to 65 or 7% by volume or more.

The liquid carrier may consist essentially of a solvent or a solvent may be mixed with one or more other ingredients to provide a liquid carrier.

Other ingredients are solid or liquid at room temperature, but are dissolved when in the liquid carrier.

In many cases, the liquid carrier (including any diluent) is relatively non-volatile, especially if the precursor is exposed to the atmosphere before solidification of the polymer.

For example, the liquid carrier advantageously does not have components (solvents or diluents) that have a vapor pressure greater than about 0.8 atmospheres, such as greater than 0.6 atmospheres, at the temperature of the polymer solution during extrusion.

However, if a more volatile component is used in the liquid carrier and the precursor is exposed to an atmosphere prior to contacting the liquid coagulant, the atmosphere may contain such a more volatile component to retard the loss of component from the precursor. Advantageously, it contains a substantial amount of sterile ingredients.

Gaseous components are generally avoided, but may be used, particularly when the precursor is brought into direct contact with the liquid coagulant.

The ingredients are preferably compatible with the solvent and the liquid coagulant.

Often the other components are highly soluble in the N-acylated heterocyclic solvent, e.g., at room temperature (about 25°C) a small amount (about 50 parts by weight, preferably at least about 100 parts by weight) of N-acylated heterocyclic solvents is present.
- acylated heterocyclic solvent, and the other components are preferably miscible in all proportions with the N-acylated heterocyclic solvent and the liquid coagulant.

Preferred components other than the N-acylated heterocyclic solvent in the liquid carrier include dimethylacetamide, dimethylformamide,
These include solvents such as N-methylpyrrolidone, dimethyl sulfoxide and the like, viscosity modifiers such as isopropylamine, surfactants and plasticizers.

A particularly useful component for liquid carriers is a diluent that is a solvent or non-solvent for the polymer.

Preferably, the N-acylated heterocyclic solvent comprises at least about 50%, such as as little as about 60%, by weight of the liquid carrier.

The use of diluents is often used to obtain particularly attractive liquid solutions that exhibit some type of solvent activity with individual polymer molecules such that the polymer coagulates or gels from a polymer solution with little change in energy. A carrier can be provided.

The behavior of polymer molecules in solution is determined not only by interactions between polymer molecules (but also by interactions between polymer molecules and solvent (and liquid carrier)).
It is theorized that it is also influenced by the action of

[Pr1nciples], which is incorporated herein by reference.
of Polymer ChemistryJ (19
According to the theory explained by Mr. Flory in Chapter Mv, pp. 595-639, in a constant solvent monopolymer system at a given temperature, the molecular dimensions of the polymers are close to each other within the molecule. unperturbed by action.

As the temperature increases from this given temperature (theta-temperature), the polymer swells in solution.

The “swelling” of polymer molecules at a reference temperature
g) The higher the J, the better the solvent is for the polymer at that temperature.

If the temperature decreases from the theta temperature, polymer molecules of countless molecular weights gel or precipitate.

That is, the intermolecular forces of the polymer molecules are stronger than the forces between the solvent and the polymer molecules.

A meaningful evaluation of a liquid carrier-polymer system is its intrinsic viscosity (the ability of the polymer to enhance the viscosity of a solution (e.g. at about 25°C for consistency, but other temperatures can be used unless consistent). In order to determine the intrinsic viscosity of the polymer at the and theta temperature (intrinsic theta viscosity), this can be done by making viscosity measurements of very dilute solutions of the polymer in a liquid carrier.

The ratio of intrinsic viscosity/intrinsic theta viscosity (hereinafter referred to as intrinsic viscosity ratio) is an indicator of the effect of the solvent (liquid carrier) on the polymer molecules.

The intrinsic viscosity for a liquid carrier-polymer system is determined by the viscosity of the polymer solution (η
) can be obtained by measuring.

Also. Viscosity of the liquid carrier (η.

) is measured at the same temperature 6η:η.

is the relative viscosity and a plot of the natural logarithm of the relative viscosity divided by the polymer concentration versus the polymer concentration when complemented to zero polymer concentration gives the intrinsic viscosity.

Advantageously, the seed polymer solution used is about 1.1 to 2.5
chosen to give a relative viscosity of

To measure the intrinsic viscosity of a polymer at the theta temperature, several techniques can be used, such as those described by Mr. Flory on pages 612-622 of the reference cited above.

For example, the intrinsic viscosity of a polymer in a theta-solvent at one theta temperature can be measured by viscosity measurements as described above.

Theta-solvents and theta-temperatures for many polymers can be found in the literature.

For example, [Polyme
r Handbook J 2nd edition (1975) 1V
- See the explanation by Brandlamp et al. on page 157.

If necessary, theta solvent and temperature should be adjusted to 1 V-15.
It can be measured by the technique described by Brandlamp et al. on pages 7-IV-159.

The temperature of the polymer solution during viscosity measurements must be maintained precisely as close to the theta temperature as possible.

This is because the intrinsic viscosity of many polymer solutions changes rapidly at temperatures close to the theta temperature.

Alternatively, the intrinsic theta viscosity can be determined by measuring the second virial viscosity of the polymer in solvent at various temperatures.
l) Evaluated by the use of light scattering techniques to measure the coefficients.

A suitable method is rAnalytical Chemis
In the paper entitled "Low Angle Laser Light Scattering" in tryJ Vol. 45 (1973), pp. 221-225, Kay
e) and consists of measuring the amount of light scattering of a laser beam passing through a polymer solution at several temperatures.

For example, the relationship between light scattering and the second virial coefficient was described [Light Scattering 1nPhy
sical Chemistry J (1956)
See Stacy's explanation on pages 117 et seq.

Care must be taken to remove solids from the polymer solution, such as by filtration, that would affect the light scattering data.

The intrinsic viscosity of the polymer is obtained at each temperature.

The second virial coefficient is measured at these temperatures and a plot of intrinsic viscosity and second virial coefficient is made and complemented to the point where the second virial coefficient is O.

The intrinsic viscosity at this point is the intrinsic theta viscosity.

The method of measuring intrinsic theta viscosity is an approximation.

However, such approximations are useful in providing suitable polymer-liquid carrier systems for use in accordance with the present invention to make hollow fiber membranes from polymers.

Generally, suitable polymers in liquid carriers according to the present invention are about 1
．． 05 to 1.7, such as about 1.05 to 1.5, and often even about 1.1 to 1.5.

□ The second virial coefficient of a liquid carrier-polymer system is also useful in determining a suitable liquid carrier-polymer system.

The second virial coefficient exhibited by many useful liquid carrier-polymer systems is often about 15 x 10'
mol-cryt-/? m' (25°C) or less, for example, 12X 10' mol-i77m (25°C) or less, further for example about 10 X 10' mol-cal
/? rrl (25°C) or less.

The second virial coefficient for liquid carrier-polymer systems is often about 0.5 x 10' mol -crit/?
m (25°C) or more, for example I x 10-4 mol
-cyj,/? rri" (25℃) and occasionally 3 X 10' mol-crit/7 m
(25°C or higher, e.g. about 3-8 x 10' mol
-cyyt/ff rt? (at 25°C).

Other useful methods for determining advantageous liquid carrier-polymer systems for hollow fiber membranes according to the method of the invention are described in Harris et al., eds.
structure -8olubi 1ityRel
ationships in Polymers l
(1977), pp. 111-122, in the article by Blanks et al. entitled "Solubility of Styrene-Acrylonitrile Copolymers".
parameter).

The interaction parameter (A12) can be defined as follows.

In the formula, Vm is the molar capacity (=) of the solvent per mole.

R is the gas constant (approximately 12 cal/0K mol)
It is.

T is at temperature 0. δd1. and δd, 8 are the (London) dispersion power components (cal/cc) % of the solubility parameters of the polymer and solvent, respectively.

δp1. and δps 8 are the polar bond terms of the solubility parameters of the polymer and solvent, respectively.
ding terms) (cal/CC)%
It is.

δh1. and δh, 8 are the hydrogen bonding terms of the solubility parameters of the polymer and solvent, respectively.
It is.

The total solubility parameter (δT) is defined as follows.

Solubility parameters are advantageously used to characterize liquid carriers and solutes, and values for solubility parameters and components are often found in the literature.

For example, [J, Applied Polymer Sci
enceJ Vol. 18, pp. 449-472 (1974), "Polymer Using Two-Dimensional Solubility Parameter Approximations - Study of Polymer Solubility" and Mr. Shaw's explanation in (The Polymer Handbook)
2nd Edition, pp. 1V-337-IV-359, Brandrup et al. (Brandrup also describes experimental techniques for obtaining solubility parameters and components).

The components of solubility parameters used to calculate interaction parameters for liquid carriers of one or more components can be evaluated on the basis of volume fraction averages.

In many cases, the volumes of the components of the liquid carrier are not additive, so this estimate is an approximation.

Often, the interaction parameter of the polymer and liquid carrier at 20-30°C is less than about 0.5, such as about 0.
, 3.

Generally the interaction parameter is at least about 0.01;
Preferably at least about 0.02, such as at least about 0.02.
It is 05.

Also, the liquid carrier advantageously has a solubility parameter that is approximately equal to (ie in the range of 5 or 10%) or greater than the solubility parameter of the macromolecule.

In many cases, at least one, and sometimes both, of the polar bond and hydrogen bond terms of the solubility parameter are less than or equal to the corresponding term for the polymer by 0.5 (c
al /CC)% more canine (i.e. no more than 0.5, for example 0-3 (cal /cc) more than 3A).

Advantageous membranes can be made from polymer solutions where the addition of a liquid coagulant, even in very small amounts, does not substantially improve the ability of the solvent to dissolve the polymer.

Often, the polar bond and hydrogen bond terms of the solubility parameter of the liquid carrier are each more significant than the corresponding terms of the solubility parameter of the polymer.

Often, the surface tension of the liquid carrier is about 10 dynes/L of Cr, e.g.
or in the range of 7 dynes/CTL.

Generally, in dilute polymer solutions, if the liquid carrier-polymer system exhibits suitable intrinsic viscosity ratios, second virial coefficients, and interaction parameters, the liquid carrier will also exhibit a surface tension close to that of the polymer. .

Particularly useful liquid carriers are often about 3 or 5 dynes/crfL less than the surface tension of the polymer at room temperature (25°C).
Shows the surface tension at .

Surface tension for polymers can be determined experimentally by any conventional procedure.

One such method of operation is rJ, Applied
Polymer 5science l Volume 18 No. 215
Tanny on pages 3-2154 (1974).
) is explained by Mr.

Often, the liquid carrier used in the method of the invention contains a diluent that is a non-solvent for the polymer.

Non-solvents are generally characterized by little ability to dissolve polymers.

for example. The solubility of the polymer is approximately 1 per 100 TL of non-solvent.
less than 0.01, such as less than 21, often about 0.01. ! l'
It is smaller.

The non-solvent preferably has little swelling effect on the unpolymer.

Nonsolvents, if added in sufficient amounts, can usually cause phase separation of the polymer solution.

Preferably, the non-solvent is not added in such an amount that the polymer solution is unduly unstable under the processing conditions prior to forming the precursor.

Often, the amount of non-solvent in the liquid carrier is 100% of the liquid carrier.
parts by weight (about 2 parts by weight, such as at least about 5 parts by weight).

A suitable non-solvent (ζ liquid coagulant or one or more components of a liquid coagulant) may be included.

Some desirable solvents include at least about 5% by weight liquid coagulant, such as at least about 10% by weight, based on the weight of the solvent.
The polymer can be maintained in solution (for example at 25° C.) in the presence of.

Preferably, however, the addition of a relatively small amount of liquid coagulant to a solution of the polymer in a liquid carrier results in phase separation or gelation of the polymer solution.

Typical diluents, including non-solvents, include formamide, acetamide, ethylene glycol, water, trimethylamine, triethylamine, isopropylamine, isopropanol, methanol, nitromethane, 2-pyrrolidone,
Includes acetic acid, formic acid, aqueous ammonia, methyl ethyl ketone, acetone, glycerol, and the like.

Low molecular weight inorganic salts such as lithium chloride, lithium bromide, zinc chloride, magnesium perchlorate, lithium nitrate, and the like are also useful in liquid carriers.

When producing hollow fiber membranes in which a sufficient amount of polymer is included in the polymer solution to form precursors, the polymer concentration is such that the polymer solution is formed (i.e., extruded) into hollow fiber precursors. The concentration is sufficient so that the polymer is at a fiber-forming viscosity at the temperature of the polymer when it is heated.

An unduly low viscosity results in failure of the hollow fiber precursor and inability to maintain the desired hollow fiber shape.

Although high viscosity is desirable, excessively high viscosity is undesirable due to the pressure required to extrude the polymer solution.

Often the viscosity of the extruded polymer solution is at least about 5000 centipoise, often at least about 100 centipoise.
oo centipoise and may be as high as 500,000 or 1,000,000 centipoise at the temperature of extrusion.

Many attractive hollow fiber membranes are available at extrusion temperatures of approximately 1
It is manufactured using a polymer solution viscosity of 0,000 to 500,000 centipoise.

In some cases, at the temperature of the liquid coagulant, the polymer solution becomes a substantially non-flowing structure, e.g. becomes very viscous or undergoes a physical change, e.g. A sufficient amount of polymer can be included in the polymer solution such that at least some of the polymer is insoluble in the liquid carrier and the liquid carrier forms an interstitially entrapped elastic structure or undergoes phase separation.

The polymer concentration of the polymer solution is advantageously sufficiently high to ensure that the membrane contains a sufficient amount of polymer to give the membrane the desired high strength.

If the polymer concentration of the polymer solution is too low, large voids containing large cells and macrovoids will form in the membrane wall, resulting in a weak wall structure.

At high polymer concentrations, the resulting hollow fiber walls are generally denser and macrovoids are generally more rare, so the hollow fiber membrane can exhibit greater strength.

A macrovoid is a canine void having a major axis dimension of less than about 3 microns.

Preferably, a sufficiently high polymer concentration is used so that under solidification conditions few, if any, macrovoids are formed.

Because the present invention advantageously provides an open cellular structure in the membrane wall, an increase in polymer density can be achieved with little reduction in flux through the membrane wall matrix.

The highest polymer concentration that can be used in a polymer solution is generally determined based on practical practice due to the ability of common equipment to form films from highly viscous polymer solutions.

The highest suitable concentration of polymer in the polymer solution will also depend on the nature of the polymer and the liquid carrier.

For example, higher polymer concentrations may be more desirably used when using low molecular weight polymers than when using high molecular weight polymers.

Often, the polymer concentration is at least about 2% of the polymer solution.
It is 5% by weight.

High polymer concentrations, such as 45 or 50% by weight, are also useful in some cases.

It is often desirable to have a polymer concentration of about 28 or 30 to 38 or 40% by weight.

Often, the viscosity of the polymer solution used according to the present invention '! , which has relatively high activation energy.

Activation energy is the relationship between temperature and viscosity and this relationship is expressed as.

η is the viscosity of the polymer solution. E is activation energy.

R is the gas constant (approximately 2 cal/0K, mole).

T is temperature (0K).

[1fthIntern
ational Symposium on Fres
hWater from the Sea” Volume 4 (1
Please refer to the explanation by Kunst et al. in 976).

The slope of a plot of the logarithm of viscosity (poise) against the reciprocal absolute temperature (0 to -1) is generally linear and from this slope an approximate direct line to the activation energy can be obtained.

Often the activation energy is small (sometimes 8 K c
al 1 mol, for example about 8.5-15Kca 11 mol,
Further, for example, 1 mole of 9-12 Kcal and often at least 11 mole of about 9.5-12 Kcal.

Typically, when using a desirable liquid carrier containing a non-solvent as a diluent, the activation energy increases with increasing concentration of the non-solvent.

Polymer solutions can be prepared in a conventional manner.

For example, the liquid carrier can be added to the polymer, or the polymer can be added to the liquid carrier, or the polymer and liquid carrier can be combined simultaneously.

Of course, if the liquid carrier is composed of more than (2) components, the liquid carrier can be mixed with the polymer for each component.

For example, if the liquid carrier consists of a solvent and a non-solvent, the polymer can advantageously be mixed with the solvent before addition of the non-solvent.

When adding a non-solvent after dissolving the polymer in a solvent, the non-solvent is generally added in a manner that minimizes the concentrated zone of increased non-solvent concentration to avoid coagulation or precipitation of the polymer in the concentrated zone of the non-solvent. Add solvent gradually.

Elevated temperatures can be used to facilitate mixing of the polymer and liquid carrier.

However, the temperature must not be so high as to detrimentally affect the components of the solution formed.

The time required to perform mixing to provide a polymer solution is related to the rate of dissolution of the components, temperature, efficiency of the mixing equipment, viscosity of the polymer solution produced, etc.

Desirably, mixing of the polymer solution should continue until a substantially uniform composition exists throughout the polymer solution.

It has been found that any suitable mixing equipment may be used to prepare the polymer solutions adapted for use in accordance with the present invention.

Preferably, the mixing device & L does not trap excessive air in the polymer solution to facilitate degassing after the polymer solution.

Often, the components of the polymer solution are appreciably volatile under the conditions of mixing.

These volatile components pose an undue risk from a fire and health safety standpoint and the loss of volatile components also changes the composition of the polymer solution.

Therefore, in many cases, mixing of the polymer and liquid carrier is carried out in a substantially closed vessel.

An inert atmosphere may be provided in such a closed container.

Polymer solutions can be adversely affected when exposed to atmospheric conditions (eg, ambient air).

The total pressure of the atmosphere in the mixing vessel is preferably relatively low to minimize dissolution or entrapment of inert atmosphere in the polymer solution during formation of the polymer solution.

In most cases, pressures of about 2 or 3 atmospheres or less are used.

Often, polymer solutions contain trapped or dissolved gases.

These gases cause abnormalities in the membrane, such as the formation of large voids.

Therefore, it is generally desirable to subject the polymer solution to a degassing operation.

Preferably, the polymer solution is substantially free of trapped or melted gas prior to extrusion of the hollow fiber precursor.

Any suitable degassing equipment and conditions are also useful to effect the desired degassing.

For example, sufficient degassing may be achieved by maintaining the polymer solution in a closed container for a sufficient period of time to allow trapped or dissolved gases to escape from the polymer.

It has been found that common degassers such as J-tubes, centrifugal degassers, ultrasonic degassers, etc. can be used to degas the polymer solution.

Since many of the polymer solutions useful for this invention have relatively high viscosities, the polymer solution in the degasser is
It is brought to an elevated temperature in order to reduce its viscosity and facilitate the release of trapped or dissolved gases.

The elevated temperature at which the polymer is subjected and the time that the polymer solution is at such elevated temperature should not be so excessive as to have a deleterious effect on the polymer solution or its components.

Degassing can be carried out at relatively low absolute pressures (ie, vacuum) or at high pressures, such as to prevent undue evaporation of components of the polymer solution.

The pressure must not be so high as to cause excessive dissolution or redissolution of the gas from the degasser.

Generally, degassing is preferably performed at an absolute pressure of less than about 2 atmospheres, and often degassing is performed at a pressure less than atmospheric pressure.

Degassing can be carried out in a closed container.

An inert atmosphere may be used during the degassing operation. The degassed polymer solution can then be used for membrane precursor formation.

When transporting polymer solutions, the piping and pumping equipment is preferably designed to prevent gases (eg air) from entering the transport system and from entering the polymer solution.

The polymer solution may contain solid impurities such as dirt, polymer oligomers, etc. that adversely affect the membrane.

Therefore, the polymer solution is often filtered before entering the spinneret.

Preferably, the filtration is sufficient to remove substantially all solid particles that are, for example, greater than about 50 microns in the longest dimension, and often substantially all that are greater than about 0.5 microns in the longest dimension. Particles are removed by filtration.

Elevated temperatures can be used to facilitate transport and sifting of the polymer solution.

However, such elevated temperatures must not be so high as to have a deleterious effect on the polymer solution or its components. Often, water provides a non-solvent of suitable strength to effect polymer coagulation. constitutes a large proportion of the liquid coagulant sufficient to

For example, the liquid coagulant contains at least about 50% water by weight, such as at least about 75% and often at least about 85% water.

Preferably, the Q gas-liquid coagulant does not cause appreciable swelling of the polymer.

Since water often constitutes a large proportion of the liquid coagulant, it is preferred that the polymer exhibit little swelling in water.

Preferably, the composition of the liquid coagulant is such that the heat of dilution of the liquid carrier in the liquid coagulant is less than about -3.5 kcal per mole.

For example, about -3 kcal for dogs, and for example about -2,
The composition is such that it is less than 5 kcal and often more than about -2 kcal.

The absolute value of the heat of dilution of the liquid carrier in the liquid coagulant is often less than about 3 calories per mole.

In most cases, the heat of dilution is approximately -0.5 per mole.
It is within the range of ~-2 kilocalories.

Heat of dilution can be measured using conventional procedures and is generally measured at about 25°C.

Particularly when producing hollow fiber membranes in a continuous process, the liquid coagulant will contain a liquid carrier which is removed from the precursor.

This liquid carrier reduces the non-solvent strength of the liquid coagulant.

Therefore, it is desirable to replace the liquid coagulant with fresh or recycled liquid coagulant containing substantially no liquid carrier.

Often, the concentration of liquid carrier in the liquid coagulant is less than about 10% by weight, preferably less than about 5% by weight, and for example less than about 2% by weight.

Liquid coagulants include surfactants, substances that increase or decrease the non-solvent strength of the liquid coagulant with respect to the polymer, substances that enhance the solubility of components of the liquid carrier in the liquid coagulant, substances that enhance the solubility of the components of the liquid carrier in the liquid coagulant, Additional ingredients may be included, such as substances that reduce heat of dilution, freezing point depressants, and the like.

Useful additional components to the liquid coagulant that have been found to be useful in membrane preparation include low molecular weight alcohols such as methanol, isopropanol, etc., salts such as sodium chloride, sodium nitrate, lithium chloride, etc. Includes organic acids such as formic acid, acetic acid, and the like.

Desirably, the liquid coagulant is maintained at a temperature at which the polymer solution is substantially non-flowing.

Although suitable temperatures are generally low, some polymer solutions are substantially non-flowing at room temperature or slightly above.

Therefore, it has been found that liquid coagulant temperatures up to about 90°C or slightly higher can be used.

However, often liquid coagulant temperatures are below about 35°C and highly desirable membranes are often produced using liquid coagulant temperatures below about 20°C, such as below about 10°C.

Often, however, the temperature is conveniently above about 0<0>C, such as about 0<0>C to 10<0>C.

However, if a suitable chiller is used and a freezing point depressant is present in the liquid coagulant, temperatures of -15 DEG C. and below can be achieved.

The residence time of the precursor in the liquid coagulant is such that the amount of coagulation at the temperature of the liquid coagulant is sufficient to provide sufficient strength to the membrane to be further processed.

It is often desired that coagulation of the polymer in the precursor occur in a matter of seconds so that the size of the equipment for the coagulation process is not unduly large.

For example, since the exterior of the hollow fiber precursor is in direct contact with the liquid coagulant, it generally coagulates almost immediately.

In some cases, substantially complete coagulation of the polymer in the precursor under liquid coagulant conditions occurs almost immediately.

Even more often. The precursor exhibits an observable change from a clear or translucent structure to an opaque structure in the liquid coagulant.

This change is gradual and the progression of the change can be observed from time to time.

The time of this change under liquid coagulant conditions can vary widely, but in cases of at least about 0.00
1 second, e.g. about 0.01 to 1 second, more e.g. about 0.02
~0.5 seconds.

Generally, even after solidification of the precursor, the membrane still contains a substantial amount of liquid carrier.

This liquid carrier can adversely affect the strength properties of the membrane and even redissolve the coagulated polymer.

Therefore, the membrane is often subjected to at least one washing step to further remove the liquid carrier.

Often, cleaning of the membrane begins under conditions (eg, temperature) that are substantially the same as those under which coagulation occurs.

The temperature used for cleaning is often based on the strength of the membrane containing the liquid carrier, the useful range of temperatures at which it can be subjected to the cleaning liquid, and the convenience of obtaining the cleaning liquid at such temperatures. (.

Generally, temperatures that would result in undesirable annealing of the membrane surface should be avoided during cleaning.

Frequently, the washing temperature will be between about 0 and 50°C, preferably between about 0 and 50°C.
It is in the range of 35°C.

Advantageously, water may be used as the washing fluid, especially if the liquid carrier and liquid coagulant are miscible with water.

The cleaning fluid may contain additives that enhance the removal of liquid carriers, for example.

For example, if water is the wash fluid, water-miscible organic substances (eg, methanol, ingropanol, etc.) can help facilitate removal of the liquid carrier.

Often, the liquid carrier content of the membrane can be easily reduced to less than about 20% by weight of liquid carrier, for example.
(e.g. by passing the hollow fibers through a cleaning liquid for 2-5 minutes).

However, relatively long washing times are required to reduce the liquid carrier content of the membrane to desirable low levels, such as less than about 5% by weight and sometimes less than about 2% by weight of liquid carrier.

This wash is often short (both 3 hours and 2 hours).
It can range up to 0 days or more.

Washing can be carried out by continuously passing a washing liquid substantially free of liquid carrier over the membrane (rinsing) or by immersion or storage in the washing liquid.

The liquid carrier is removed from the membrane, generally using a combination of rinsing and storage.

If the membrane is stored in a wash liquid, it is advantageous to periodically replace the wash liquid if the concentration of liquid carrier in the wash liquid becomes undesirably high.

Although membranes can be stored in the wash liquid for periods longer than 20 days, usually little additional liquid carrier is removed after such long storage periods.

Most often, washing of the membrane is continued until the liquid carrier content of the membrane is less than about 4 or 5% by weight of the membrane.

After washing, the membrane is dried to remove the washing liquid.

The presence of liquid in an anisotropic membrane significantly reduces the flow rate of permeate, such as gas, through the membrane and is therefore generally undesirable.

Adequate drying can be achieved by exposure to a gaseous atmosphere.

Air is usually a suitable gas atmosphere.

Useful drying conditions can vary widely.

For example, suitable drying conditions include temperatures ranging from -15°C or less to 90°C or more and about 0 to 95°C.
% relative humidity in the range of, for example, about 5-60%.

Frequently, the temperature will be in the range of about 0 to 80°C, while the absolute humidity will be less than about 20 or 30 P/i, for example about 5 to 1
In many cases, 5P/i, membrane drying under ambient experimental conditions such as about 20-25° C. and 40-60% relative humidity is used.

Materials useful for making anisotropic membranes are organic polymers or organic polymers mixed with inorganic materials such as fillers, reinforcing agents, and the like.

It has thus been found that the method of the present invention can be advantageously applied to the production of metal hollow fiber membranes according to the teachings of US Pat. No. 4,175,153, which is incorporated herein by reference.

Suitable polymers include N-
6 desirably 25 soluble in the acylated heterocyclic solvent
at least about 50 parts by weight, preferably at least about 10
Even though 0 parts by weight of the polymer is dissolved in 100 parts by weight of the N-acylated heterocyclic solvent, the N-acylated heterocyclic solvent and the polymer are often miscible in all proportions.

However, although N-acylated heterocyclic solvents are good solvents for polymers and are miscible with liquid coagulants, if the solvent cannot be easily removed from the membrane after coagulation, using a polymer Membranes cannot be manufactured.

If the polymer retains solvent, the polymeric structure of the membrane is weakened to the point of excessive densification of the anisotropic structure, thereby undesirably reducing the permeability of the membrane for permeable substances such as gases. cause

Furthermore, if excessive amounts of solvent are retained even after drying, the resulting membrane will not have sufficient structural strength to withstand the operating conditions.

Often, the "intrinsic viscosity ratio" for suitable polymers in dilute solution in N-acylated heterocyclic solvents is small (both about 1.05, preferably at least about 1.3).

Often the "intrinsic viscosity ratio" is up to about 2, e.g. 1.3-1
．． 75 or 1.5 to 1.75.

Often, the second virial coefficient for a polymer solution containing the appropriate polymer in an N-acylated heterocyclic solvent is about 20 x 10-4 mol-cyit/? 2 (25
°C) or less, e.g. about 15 x 10' mol -cr
It/ff2 (25°C) or less.

In the case of many (, the second virial coefficient is small (both about 0.5 × 10' mol -crit/?2 (
25°C), e.g. at least about I x 10' m
ol-crit,/? 2 (25°C), further e.g. at least about 3 x 10-4 mol-crV12 (25°C)
It is.

Often, the interaction parameter for suitable polymers with N-acylated heterocyclic solvents at about 20-30°C is less than about 0.5, such as less than about 0.3,
and most often at least about 0.005, such as at least about 0.01 and sometimes at least about 0.00.
It is 02.

In general, crystalline polymers usually exhibit low permeability coefficients, so that the polymers are substantially amorphous, e.g., less than about 25% crystalline and often less than about 1 or 2% crystalline, by weight. It is preferable that it should be.

However, polymers containing substantial crystallinity are sometimes desirable.

Polymers are also often non-ionic to facilitate the production of anisotropic membranes.

The polymeric material preferably has a high separation capacity, i.e., a polymer that provides the desired separation selectivity at an appropriate permeate effluent strength and chemical resistance with respect to the components of the intended fluid stream. Selected based on the ability of the merging material.

The polymer must have sufficient molecular weight for the formation of hollow fibers, for example.

Generally, for a given type of polymer, the longer the polymer chain, the greater the tensile strength exhibited by the polymer and the higher the glass transition temperature of the polymer.

Increases in these physical properties with increasing molecular weight can often be achieved with little change in the separation ability of the polymer.

Thus, by providing a high molecular weight polymer,
The anisotropic membrane can be made stronger and more tolerant of components of the feed stream that would adversely affect the polymer.

However, increased polymer molecular weight (ζ) generally increases the viscosity of the polymer solution forming the precursor.

Therefore, it is often desirable to utilize polymers that have a narrow molecular weight distribution so that the polymer exhibits a high degree of strength without undue increase in viscosity.

For example, when having a broad molecular weight distribution, the polymer contains significant amounts of low molecular weight polymer molecules in addition to providing high solution viscosity due to the presence of substantially high molecular weight polymer molecules.

An advantageous way of characterizing the molecular weight distribution of a polymer is by the ratio of the weight average molecular weight of the polymer to its number average molecular weight.

A high ratio indicates a broad molecular weight distribution.

Often this ratio is less than about 3.

The strength of the polymer must be sufficient to prevent damage to the separation layer during handling and transportation expected in the manufacture of membranes, the manufacture of permeators containing the membranes, and the installation and use of permeators. No.

The polymer must also exhibit sufficient strength so that the membrane can withstand the glass separation operating conditions.

The strength of a polymer can be expressed, for example, by tensile strength, Young's modulus, and the like.

Although each of these mechanical properties affects the overall strength of the membrane, whether a polymer has sufficient strength can often be determined by considering the tensile strength of the polymer.

Generally, polymers suitable for membranes contain at least about 350 kg/kg
cni, such as at least about 400 kg/cfL, preferably less (both about 500 kg/CfL, and more such as at least about 600 kg/cst).

The tensile strength may be as high as is achievable, but
Some polymers that are advantageous as membrane materials are about 2000
It shows a tensile strength of kg/crtt or more.

The strength of a polymer can be adversely affected, for example by substances that dissolve, plasticize or swell the polymer.

Often, many polymers suitable for membrane production may be dissolved, plasticized, swollen, or otherwise adversely affected by one or more substances. .

In some cases, industrial streams, such as gas streams, that are processed using separation membranes contain one or more components that have an adverse effect on the membrane material.

The use of membrane materials exhibiting a high degree of strength allows for a reduction in membrane strength due to the presence of such deleterious components in the feed mixture.

This is because even weaker membranes can still withstand the separation operating conditions.

Selective permeation of many fluids, including gases, has been reported in many polymers.

In these reported permeations, the separation mechanism clearly involves interaction with membrane materials.

Therefore, a wide variety of separation capacities can be achieved through the use of different polymers.

For example, polyacrylonitrile contains 10 more nitrogen than methane.
Allows for twice as fast penetration.

In contrast, in the case of polysulfone membranes, it permeates slightly more rapidly than methane nitrogen.

The literature is full of information regarding the permeability of polymers.

For example, the explanation by Hwang et al. in ``Gas Transfer Coefficient in Membranes'' in [5eparation 5science I Vol. 9, pp. 461-478 (1974)] and [Polymer Handbook I Vol.
Planned Wrap (Br
Please refer to the explanation by Andrup et al.

For example, the suitability of a polymer for gas separation can be determined by e.g.
Echnlques of Chemistry J No.
In a paper entitled "Membranes in Separations" in Vol. 12, pp. 296-322 (1975), Hw an
g) the transmission constant, as explained by et al.
Permeability and separation factors can be readily determined using common techniques for measuring permeability and separation factors.

Typical polymers suitable for the production of monolithic anisotropic membranes are cetylene-containing copolymers such as polysulfone, acrylonitrile-styrene copolymers, and histyrene-vinylbenzyl-lide copolymers. Including poly(styrene), polycarbonate, cellulose acetate butyrate, cellulose propionate, ethyl cellulose,
Cellulosic polymers such as methylcellulose, nitrocellulose etc., polyamides and polyimides including aryl polyamides and aryl polyimides, poly(arylene oxides) such as polyethers, polyacetals, poly(phenylene oxides) and poly(xylene oxides) , poly(esteramide-diisocyanate)
, polyesters (including polyacrylates) such as polyurethane, poly(ethylene terephthalate), poly(alkyl methacrylate), poly(alkyl acrylate), poly(phenylene terephthalate) etc., polysulfide, polyvinyl e.g. poly(vinyl chloride),
Poly(vinyl fluoride), poly(vinylidene chloride), poly(
vinylidene fluoride), poly(vinyl alcohol), poly(vinylidene fluoride), poly(vinyl alcohol),
vinyl ester) such as poly(vinyl acetate) and poly(vinyl ester)
poly(vinyl propionate), poly(vinyl pyridine), poly(vinyl pyrrolidone), poly(vinyl chytyl), poly(vinyl ketone), poly(vinyl aldehyde) e.g. Evapoly(vinyl formal) and poly(vinyl butyral),
Polymers from monomers with alpha-olefinic unsaturation other than those mentioned above, such as poly(vinylamine), poly(vinyl phosphate) and poly(vinyl sulfate), polyallyl, poly(benzobenzimidazole), polyhydrazide , polyoxadiazole, polytriazole, poly(benzimidazole), polycarbodiimide, polyphosphazine, etc., and terpolymers of acrylonitrile-vinyl bromide-parasulfophenyl methacrylic ether sodium salt. and substituted and unsubstituted polymers selected from interpolymers, including block interpolymers, and grafts and blends containing any of the foregoing.

Typical substituents that provide substituted polymers include halogens such as fluorine, chlorine, and bromine, hydroxy groups, lower alkyl groups, lower alkoxy groups, monocyclic aryl groups, lower acyl groups, and the like.

One class of polymers that is attractive for many gas separations is
It is a copolymer of styrene and acrylonitrile or a terpolymer containing styrene and acrylonitrile.

Often, styrene is up to about 60 or 70 mole percent of the total monomers in the polymer.

For example, about 10 to 50 mol%.

Advantageously, the acrylonitrile monomer is at least about 20 mole% of the polymer, such as about 20 to 90 mole%, often about 30 to 80 mole%.

Other monomers that may be used with styrene and acrylonitrile, for example to provide the terpolymer, include olefinic monomers such as butene, butadiene, methyl acrylate, methyl methacrylate, maleic anhydride, and the like.

Other components that may be used include vinyl chloride.

Copolymers or terpolymers of styrene and acrylonitrile are often used in small amounts (both about 25,000 or 50
000, for example, about 75,000 to 500,000 or more.

One suitable polymer for anisotropic membranes is polysulfone because of its strength, chemical resistance, and relatively good gas separation ability.

Typical polysulfones are characterized by having a polymeric backbone consisting of the following repeating structural units:

where R1 and R2 are the same or different and are aliphatic or aromatic hydrocarbyl-containing moieties having, for example, about 1 to 40 carbon atoms.

The sulfur of the sulfonyl group is attached to an aliphatic or aromatic carbon atom.

Polysulfones often have at least 8000 or 10
000, which is suitable for film or fiber formation.

When the polysulfone is not cross-linked, the molecular weight of the polysulfone is generally less than about 500,000 and often less than about 100,000.

The repeating units may be linked (ie, R1 and R2 may be linked by a carbon-to-carbon bond or through various linking groups, such as or the like).

Particularly preferred polysulfones are those in which at least one of R1 and R2 consists of an aromatic hydrocarbyl-containing moiety and the sulfonyl moiety is bonded to at least one carbon atom.

Aromatic hydrocarbyl-containing moieties include phenylene and substituted phenylene moieties, bisphenyl and arsenic-substituted bisphenyl moieties, bisphenylmethane with a nucleus and substituted bisphenylmethane moieties, substituted and unsubstituted bisphenyl ethers of the formula, and the like.

In the formula, X is oxygen or sulfur. In the bisphenylmethane and hibisphenyl ether moieties mentioned above, R3
-R12 represents a substituent having the same or different structure.

where Xl and X2 are the same or different and are hydrogen or halogen (eg fluorine, chlorine and bromine).

p is 0 or an integer, such as about 1-6.

Z is hydrogen, halogen (eg fluorine, chlorine and bromine), (-YiR13, where q is 0 or 1).

-C- and R13 is hydrogen, such as substituted or unsubstituted alkyl of about 1 to 8 carbon atoms, such as monocyclic or bicyclic substituted or unsubstituted aryl of about 6 to 15 carbon atoms. ), the heteroatom is at least one of nitrogen, oxygen and sulfur, and about 5
Heterocyclic groups that are monocyclic or bicyclic with ~15 ring atoms, sulfato and sulfono, especially lower alkyl-containing or monocyclic or bicyclic aryl-containing sulfato or phosphorus-containing moieties such as sulfono, phosphino and phosphato and phosphono. especially lower alkyl-containing or monocyclic or bicyclic aryl-containing phosphatos or phosphonos,
Amines, including primary, secondary, tertiary and quaternary amines often containing lower alkyl or monocyclic or bicyclic aryl moieties, thioureyl, thioureyl, guanidyl, trialkylsilyl, trialkylsta Nyl, tolualkylbranbyl, sialkylstivinyl, etc.

Often, the substituents on the phenylene group of the bisphenylmethane and bisphenyl ether moieties are
Both are given as one, and R7 to R10 are hydrogen.

Polysulfones with aromatic hydrocarbyl-containing moieties generally have good thermal stability, are resistant to chemical attack, and have an excellent combination of toughness and flexibility.

Useful polysulfones are sold by Union Carbide under trade names such as rP-1700J and "P-3500."

Both commercial products are bisphenolmethane-derived polysulfones (particularly bisphenol A-derived polysulfones) with linear chains of the general formula.

In the formula, n represents the degree of polymerization and is about 50-80.

These commercially available bisphenol A-derived polysulfones often contain crystallized fractions that are believed to be oligomers.

With solvents for polysulfones such as dimethylformamide and dimethylacetamide, this crystallized fraction remains undissolved and there may even be an increase in crystal size and fraction.

This crystallized fraction increases the difficulty in obtaining the desired anisotropic hollow fiber membranes.

The N-acylated heterocyclic solvents used in the process of the present invention appear to give solutions containing polysulfone polymers that have a very small proportion, if any, of these crystals.

Furthermore, the polymer solution exhibits good stability against excessive crystal formation.

Therefore, the polymer solution can even be stored before use.

This stability provides sufficient polymer solution life for sufficient degassing.

For polysulfone polymers such as P-3500, Table A
presents a list of solvents and diluents that are attractive when producing membranes, particularly hollow fiber membranes, according to the present invention.

The method of the invention is particularly advantageous for the production of hollow fiber membranes.

For this aspect of the invention, the polymer solution is extruded through a spinneret to form a hollow fiber membrane.

Although any suitable hollow fiber spinneret may be used to produce the hollow fibers of the present invention, it is preferred that the spinneret be of the tube-in-orifice type.

Tube-in-orifice type spinnerets are characterized by having a continuous annular ring surrounding an internal injection tube.

Most preferably, the injection tube is concentric in the orifice so that the same amount of polymer solution is extruded at all points of the annular ring and the resulting hollow fiber breaker has a substantially uniform wall thickness. It is located in

In most tube-in-orifice type spinnerets, the polymer solution enters a cavity behind the annular ring to aid in distribution of the polymer solution around the annular ring.

Often, at least about four, preferably at least about five, polymer solution inlets are provided and are desirably equally spaced.

When spinning a polymer solution, it is preferred to maintain the polymer solution at an elevated temperature to provide the desired spinning conditions.

In such cases, it may be desirable to provide a heating device to maintain the spinneret at the desired extrusion temperature.

Suitable heating devices include electrical or fluid heating jackets;
Includes embedded electrical heating coils, etc.

Because the residence time of the polymer in the spinneret is relatively short, the polymer solution is often heated to or near the desired extrusion temperature before entering the spinneret.

Often, the temperature of the polymer solution in the spinneret is low (about 20° C.), but not so high that the polymer solution is unduly sensitized during its residence time.

Often, the polymer solution in the spinneret is at about 20-90°C;
For example, at a temperature in the range of about 25-80°C.

The size of the spinneret will vary depending on the desired internal and external diameters of the hollow fiber membranes required.

One class of spinnerets has an orifice diameter (external diameter) of about 300-1000 microns and an internal orifice diameter (often the external diameter of the injection tube) of about 100-500 microns, with an injection capillary in the injection tube. are doing.

The diameter of the injection capillary can vary within limits set by the injection tube.

The injection tube typically projects into the face of the spinneret orifice.

Typically, a spinneret is indicated by the shape of the entrance to the annular ring and the length to width ratio of the annular portion of the spinneret.

The shape of the entrance to the annular portion of the spinneret is, for example, about 80° with respect to the flow direction of the polymer solution in the annular portion of the spinneret.
The annular portion of the spinneret may be truncated at a more dogmatic angle, or be sloped into the annular portion of the spinneret at an angle of less than about 80°, such as from about 75° to 30°, from the direction of polymer solution flow through the annular spinneret. There may be.

The ratio of the length that the annular portion extends from the front of the spinneret to the width of the annular ring at the front of the spinneret may vary over a wide range.

However, the length of the annular ring portion of the spinneret should not be so excessive that an undue pressure drop occurs during passage of the polymer solution through the spinneret.

Often, such length-to-width ratios are about 0.7 to 2.5;
For example, about 1-2.

The dimensions of the hollow fiber precursor are determined by, for example, the dimensions of the spinneret, the flow rate of the polymer solution through the spinneret, the jetstretch of the hollow fiber precursor, and the velocity and pressure of the fluid injected into the holes of the hollow fiber precursor. .

The flow rate of the polymer solution through the spinneret can vary widely depending on the winding speed of the hollow fibers.

However, the flow rate should not be so great as to cause breakage of the hollow fiber precursor.

Frequently, the size of the hollow fibers may vary, for example from about 100 or 150 microns in external diameter to 1000 microns or more (depending on the length of hollow fiber produced per unit time, spinning speed or winding speed). Also, for example, about 5 to 100 m per minute (if the fibers are not unduly stretched and after).

Spinning operations are often described in terms of jet elongation, since higher spinning speeds can be used if sufficient residence time is allowed in the processing step.

The spinning (jet) elongation is defined as (i) the Ca per minute of the polymer solution extruded through the spinneret divided by the cross-sectional area of the annular extrusion zone (c4) and (ii) the hollow extruded per minute. It is defined as the ratio of the length of the fiber precursor crIl, ) (i.e. the winding speed).

The spin elongation is often between about 0.6 and 2, such as between about 0.7 and 2.
1.8, preferably about 0.75 to 1.5.

The injection fluid is introduced into the pores of the hollow fiber precursor in an amount sufficient to maintain the pores of the hollow fiber precursor open.

The injection fluid is gaseous or preferably liquid under the conditions of hollow fiber spinning.

The injection fluid must be miscible (and preferably miscible in all proportions) with the liquid coagulant and the liquid carrier.

Often, the injection fluid is substantially a non-solvent for the polymer.

In many cases, the injection fluid does not need to be a strong non-solvent for the polymer.

The injection fluid can contain one or more components, and often contains at least one component of a liquid coagulant to enhance the miscibility of the liquid coagulant and the injection fluid.

Often, the injection fluid also contains a solvent or weak solvent for the polymer.

The temperature of the injection fluid is generally around the temperature of the extruded polymer solution and the temperature of the spinneret due to heat transfer through the walls of the injection capillary located in the spinneret.

However, with suitable insulation or other preparations to minimize heat transfer by the injection fluid in the spinneret and with the use of cooled injection fluid before being passed through the spinneret, the injection fluid can be removed from the extruded polymer solution. It can be made significantly cooler than the temperature.

The velocity and pressure of the injection fluid introduced into the pores of the hollow fiber precursor must be insufficient to cause a deleterious effect on the separation capacity or structure of the hollow fiber membrane.

Often, the velocity and pressure of the injection fluid is such that the ratio of the internal diameter of the hollow fiber to the internal orifice diameter of the spinneret is less than about 2.5 and preferably this ratio is about 0.5 to 1.5 or 2. It's something like this.

The spinneret may be located below the surface of the liquid coagulant (wet jet) or preferably above the liquid coagulant (dry jet).

When using dry jet spinning techniques, it is preferred that the components of the liquid carrier are substantially non-volatile.

The distance above the liquid coagulant at which the spinneret is positioned can be varied considerably without appreciably affecting the properties of the hollow fiber membrane.

Often, the spinneret is positioned within about 20 or 3 OcrIL.

Desirable hollow fibers have a spinneret face with approximately zero liquid coagulant.
．． 5 crfL or less.

For convenience, the spinneret is often filled with about 0.0% of the liquid coagulant.
It is located within 5 to 15 crrL.

Dry jet spinning techniques are also conveniently preferred when the polymer solution must be extruded at an elevated temperature, and the coagulating liquid is kept at a temperature substantially below the temperature of the polymer at the time of extrusion, such as at least 25°C below. , for example maintained at a temperature of at least 30°C or less.

The method of the invention is particularly characterized in that the anisotropic hollow fibers of polysulfones, in particular containing bisphenylmethane (including substituted bisphenylmethane) and bisphenyl ether (including substituted bisphenyl ether) moieties; Advantageous for producing membranes.

The polysulfone hollow fiber membranes of the present invention exhibit several significant structural properties that enable desirable strength properties combined with advantageous fluid separation.

The polysulfone membranes of the present invention are particularly useful for performing gas separations.

The dry monolithic anisotropic hollow fiber membrane of polysulfone according to the invention has a wall with a thin outer skin over the open cellular support portion.

The outer skin has few, if any, pores (ie, continuous channels for fluid flow through the outer skin).

The cells in the cellular support portion of the hollow fiber wall are preferably relatively small in all dimensions.

Desirably, the cellular support portion is substantially devoid of macrovoids having a maximum length to maximum width ratio of greater than about 10, preferably greater than 5.

Preferred polysulfone hollow fiber membranes of the present invention are substantially free of macrovoids.

Hollow fiber membranes in gas separation vessels are often characterized by their gas separation properties, i.e. their selectivity for passage of one gas compared to at least one other gas in a gas mixture and the selective permeation of gases through the membrane wall. is evaluated by its flow rate and also its intensity.

These properties are determined by the chemical and physical properties of the hollow fiber material and the structure of the hollow fiber.

Because the morphological structures that play an important role in determining the gas separation properties of hollow fiber membranes are on the order of tens of angstroms or less in dimension, such structures can be easily detected using the best available optical microscopy. I can't even visually recognize it.

Such small structures are called submicroscopic structures (submicroscopic structures).
e).

The combination of microscopic techniques (particularly scanning electron microscopy and transmission electron microscopy) and observable properties in characterizing hollow fiber membrane structures on a gross and sub-microscopic basis is very useful.

A particularly useful microscopy technique for characterizing hollow fiber membrane structures is scanning electron microscopy.

To aid in understanding the use of scanning electron microscopy in defining hollow fiber membranes according to the present invention, reference is made to the accompanying drawings.

Figures 1 and 2 are scanning electron micrographs of hollow fiber membranes.

Figures 1a to 1° are polysulfone (p-3500) 3
2% by weight, about 7% by weight formamide, and about 61% by weight 1-formylpiperidine.

Figure 1a shows a cross-section of the hollow fiber at a magnification of approximately 300x.

FIG. 1b shows a portion of the cross-section of the hollow fiber at its outer edge and at a magnification of approximately 20,000 times.

FIG. 1c shows the structure of a cross-section of a hollow fiber in an area approximately in the middle of the fiber wall and at a magnification of approximately 20,000 times.

FIG. 2 shows a cross section of a hollow fiber membrane prepared from a polymer solution containing 36% by weight polysulfone (p-3500) and 64% by weight 1-formylpiperidine and approximately 3% by weight.
00x magnification.

Samples of hollow fiber membranes (as shown in the drawings) for examination by scanning electron microscopy are conveniently prepared by thoroughly drying the hollow fibers, dipping the hollow fibers in hexane, and immediately causing the hollow fibers to rupture. It is prepared by placing it in liquid nitrogen to obtain.

Once a clean piece of hollow fiber is obtained, the sample is mounted and then vapor coated with a gold and palladium mixture (e.g....
(using a vapor deposition coating machine).

The coating operation typically results in a coating of about 50 to 75 angstroms on the hollow fiber sample.

Therefore, very small feature dimensions can be hidden by the coating.

As can be seen in particular from FIG. 1, the structure of the hollow fiber membrane is characterized by a relatively dense structure adjacent to the external surface with an underlying open cellular support portion.

It is observed that the increase in cell size in the hollow fiber wall increases as the distance from the external surface increases to a generally maximum size in the central portion within the hollow fiber wall.

It is observed that the main structure of cells in the central zone of the cross section of the hollow fiber wall is interconnecting cells (cells with open passages for gas flow to neighboring cells), i.e. open cell-like structures. .

However, cell-to-cell interconnections (ζ cells) are very small, e.g. smaller than 0.1 micron in major dimension, and cannot be visually discerned.

This open cellular structure allows fluid to easily pass through the hollow fiber walls with little resistance.

Advantageously, the outer skin (and inner skin, if present) provides the major portion of resistance to fluid flow through the membrane wall.

The dimensions of cells, particularly canine cells, often in the central zone of the hollow fiber wall, can often be assessed using, for example, scanning electron microscopy.

In assessing the gross size and shape of cells, observable passageways between individual cells are considered defects in the cell wall and therefore cell dimensions are not extended through these passageways.

Other characteristics of cells that are important in assessing membrane strength are:
It is the thickness of the cell wall material that regulates the canine cells in the hollow fiber membrane wall.

These evaluations can be performed by visually inspecting photographs of cellular structures or by examining and analyzing the photographs using available computer scanning techniques, such as an image analyzer.

A suitable image analyzer is the American company Quanti.
These include image analyzers useful in the analysis of common textile fibers, such as the MET 720-2 image analyzer available from MET Corporation.

The cell shape of the large cells, which are often present in the central zone of the hollow fiber wall, can vary widely.

An advantageous method of characterizing the shape of a cell is by dividing the cross-sectional cell area by the square of the cell's perimeter in cross-section to give the configuration ratio.

The shape ratio of a perfect circle is about 0.8, that of a square is about 0.06, and that of a rod is 0.01 or less.

When the shape ratio is in the range 0.03-004, the cross section of the cell is often roughly polygonal in appearance.

Such an analysis can be performed by visually inspecting a photograph of the cellular structure of the hollow fiber wall or by examining the photograph using an image analyzer.

Advantageously, the shape ratio can be determined by analyzing any segment of the cross-section of the hollow fiber wall that contains cells of sufficient size to be examined and is free of macrovoids.

The area of the segment examined for representativeness is generally at least about 25 square microns (e.g., at least about 5
segments with minimum dimensions of microns).

In many desirable hollow fiber membranes according to the present invention, the average shape ratio is at least about 0.025, and in many cases less than about 0.03 or at least about 0.
．． Even 035.

Preferably, the segments of the cross-section of the hollow fibers containing even canine cells (excluding macrovoids) are at least about 0.
．． 03, such as having an average shape ratio of at least about 0.035.

If the cell size in the cross-sectional segment of the hollow fiber wall is greater than about 0.1 μm, e.g. more than 0.2 μm, photographic analysis of the cell structure, as recognized e.g. by scanning electron microscopy, also Useful for measuring the ratio of average wall thickness to average cell cross-sectional area.

Generally, the higher the ratio of the thickness of the polymer supporting the cells to the cross-sectional area of the cells, the stronger the hollow fibers.

Frequently, this ratio, particularly in the hollow fiber membrane cross section, will be at least about 0.05, such as at least about 1, and sometimes in the range from 2 to 20 crIl'.

In the photographic analysis of scanning electron micrographs of smaller cells and smaller wall thicknesses, the thickness of the reflective coating becomes significant and must be taken into account.

Often, at least a majority of the cells visible in such photographs also have observable passageways that interconnect with neighboring cells.

Preferably, the bulk (as measured by cross-sectional area) of the hollow fiber wall consists of cells having an average major dimension of less than about 2 microns.

Often, at least about 75% by volume of the wall, such as at least about 90% by volume, is less than or equal to about 2 microns, preferably less than 1.
It consists of cells having a major axis dimension of less than 5 microns and, for example, less than 1 micron.

In certain advantageous hollow fiber membranes, there are substantially no cells having a major axis dimension greater than 2 or 1.5 microns.

As previously mentioned, the size range of cells in the walls of hollow fiber membranes is usually substantial, from sizes too small to be resolved by scanning electron microscopy to cells with major dimensions of 2 microns or more. Change.

In the hollow fibers of the present invention, the major major dimension of the canine cells in the hollow fiber wall is less than about 0.75 microns; Substantially all of the cells in the zone have a major dimension of about 0.1 to 0.7 microns.

Often, this zone of very large cells will occupy at least about 30% by volume of the hollow fiber wall, such as at least about 4%.
0% by volume, for example up to about 50 or 75% by volume.

Often, desirable hollow fiber membranes include segments (e.g., segments of area at least about 25 square microns with a minimum dimension of at least about 5 microns) that are observed in at least a large volume fraction (e.g., at least about 75% by volume) of the hollow fiber walls. (with cells of average major axis dimension that is relatively uniform).

In some cases, hollow fiber membranes can exhibit sufficient resistance to collapse even when large voids are present.

If macrovoids are present in the hollow fibers, the macrovoids can vary widely in shape and location within the hollow fiber wall.

A macrovoid that closely approximates the shape of a circle is generally much more acceptable than a long phase-like macrovoid without undue reduction in resistance to collapse.

Desirably, macrovoids, if present, are present substantially only in the thickness of the hollow fiber membrane up to a distance of about 0.5 or 0.75 from the interior surface to the exterior wall.

Preferably, the hollow fiber membrane is substantially free of macrovoids having a maximum length to maximum width ratio of greater than about 10, such as greater than about 5.

The major dimension of the giant void is preferably about 0.4 times or less, such as about 0.3 times or less, the thickness of the hollow fiber wall.

Scanning electron microscopy is sometimes useful for examining the porosity of the inner (pore side) skin of hollow fiber membranes.

Preferably, the inner skin is highly porous to allow permeable gases to pass through the pores of the hollow fibers with little resistance.

Extremely small structural features such as the external surface of hollow fiber membranes (
A useful microscopy technique for examining porosity (and preferably internal surfaces) is the surface replicate technique.

In this technique, a metal coating, such as a platinum coating, is applied to the surface and then the polymeric hollow fibers are dissolved from the metal coating.

The metal coating is then analyzed using a transmission electron microscope, for example at a magnification of 50,000x or more, to determine the surface properties of the hollow fibers replicated by the metal coating.

Generally, the most preferred hollow fiber membranes of the present invention will have about 10
It provides a smooth surface replica of the external surface that is substantially free of abnormalities or irregularities greater than 0 angstroms, often greater than about 75 angstroms or greater than 50 angstroms (which may indicate pores).

A particularly valuable tool for kinetic evaluation of hollow fiber membranes is the gas permeability through the membrane.

The permeability (1) of a gas through a membrane of a given thickness is the volume of gas at standard temperature and pressure (STP) across the membrane/unit area of the membrane/unit time/unit partial pressure difference.

One way to record permeability is to measure 1 cr/' across the membrane.
The difference in partial pressure of LHg is 1 (STP)/d/sec of membrane area (cut,/crtt-sec-mug).

Unless otherwise noted, all permeabilities are recorded at standard temperature and pressure and measured using pure gas.

The permeability is cwt (S T P ) /crj, ~se
Gas permeation unit (G
PU).

IGPU is I x 10-6CC(STP')/Crl
LSee-CrILHg.

Permeability and permeation constant [e.g. capacity of gas passing through a membrane material of a certain thickness (STP)/unit area/unit time/
Some of the many techniques used to measure unit pressure difference over thickness are described in Techniques of Chemistry, which is incorporated herein by reference.
y” Volume ■ (John Willey and Sons 19
1975) [Membranes in 5eparat
ions l Chapter 12, pages 296-322 has a song (H
Wang et al.

A given gas permeability indicates the permeation of gas through a membrane, regardless of the mechanism by which the gas passes through the membrane.

One useful kinetic relationship, which is an indication of the release from the pores in the separating layer or barrier layer and the range of pore sizes in the barrier layer, is that gases of various molecular weights of substantially different molecular weights, e.g. By measuring the ability of a membrane to separate gases.

Suitable gas pairs for this analysis often include one of molecular hydrogen and helium and one of molecular nitrogen, carbon monoxide or carbon dioxide.

Preferably, the high molecular weight gas of the selected gas pair has a permeation constant (i.e., an intrinsic permeation constant) of the polysulfone that is less than the intrinsic permeation constant of the low molecular weight gas in the polysulfone (both about 10% less).

The analysis is advantageously carried out on the external side of the hollow fiber membrane at approximately 7
．． 8 atm absolute and, for the pore side of the hollow fiber membrane, at a pressure of about 1 atm absolute at ambient temperature (e.g. room temperature of about 25°C).
It can be done with

The polysulfone hollow fiber membranes of the present invention have a permeability (p/1) for high molecular weight gases of at least about 6 and often less than about 7.5 divided by (1) H for at least one pair of gases. Molecular weight gas permeability (P/1 catty/(ji
) The square root of the molecular weight of a high molecular weight gas divided by the square root of the molecular weight of a low molecular weight gas/MW.

The theoretical maximum permeation ratio is the ratio of the intrinsic separation factor for the gas pair to the quotient of the square root of the molecular weight of the low molecular weight gas divided by the square root of the molecular weight of the high molecular weight gas.

Intrinsic separation factors as referred to herein are separation factors for materials that do not have channels for gas flow across the material and are the highest achievable separation factors for materials.

Such materials may be referred to as continuous or non-porous.

The intrinsic separation factor of a substance can be approximated by measuring the molecular factor of a dense membrane of the substance.

However, the presence of pores, the presence of fine particles in the dense membrane,
Several difficulties exist in measuring intrinsic separation factors, including imperfections introduced in the fabrication of dense membranes, such as undefined molecular order due to variations in membrane fabrication.

As a result, the measured intrinsic separation factor is different from the intrinsic separation factor.

Thus, as used herein, "measured intrinsic separation factor" refers to the separation factor of a dry, dense film of materials.

Another useful method of characterizing hollow fiber membranes based on kinetics is that one gas has a permeation constant in polysulfone that is at least about 5 times greater, preferably about 10 times greater than the permeation constant of the other gas. By measuring the permeability of a pair of low molecular weight gases that have approximately the same molecular weight, except that they have the same molecular weight.

Representative gas pairs having approximately the same molecular weight, except for substantially different permeation constants for many polysulfones suitable for hollow fiber membranes, include ammonia and methane, carbon dioxide and propane, and the like.

This relationship is the difference between the permeability of easily permeated gas (P/l) F and the permeability of gas that is not easily permeated (P/1) s divided by CP/l) S It can be expressed as the quotient of the permeation constant Ps for gases that are not easily permeated divided by the gas permeation constant PF.

In many cases, this relationship is at least about 0.00
1, such as at least about 0.01 and preferably less than (
Both are about 0.02.

This relationship is indicative of the material of the hollow fiber membrane that performs at least a portion of the separation.

Another useful kinetic analysis of hollow fiber membranes is the ratio of gas permeability/permeation constant of polysulfone to gas.

The gas used to determine this relationship is preferably one that readily permeates the membrane, such as hydrogen, helium, ammonia, and the like.

Often this ratio is at least 5 x 104 crrL-1
, such as at least about I x 105 CrrL',
Preferably at least about 2 x 105 crrL-1 and up to about 1 x 106 CrfL-1, such as about 1 x 105 to 0
．． It is 6×106CfrL−1.

This relationship is indicative of the low resistance to gas flow through the hollow fiber membrane structure and the resulting high degree of permeation gas permeability that can be achieved.

The structure of the hollow fiber membranes of the present invention can also be observed by other kinetic evaluations.

For example, dry hollow fiber membranes exhibit very low liquid water permeability due to the presence of very few, if any, pores in the separation or barrier layer.

Water permeability is often around 0.5X 10-6 ctA
(liquid) / crii -sec-cIrLHg or about 0.2 x 1o-6c4 (liquid) 7 cm
-see-crIIHg.

For example, about 0. lX10'i (liquid)/cvz -s
smaller than ec-C111Hg and sometimes [room temperature (
Even after soaking in water at 25°C for 4 days] 0.01X1
0”crit (liquid)/crA-8ec-Cr
rLHg.

Water permeability measurements are advantageously carried out at room temperature using a pressure drop of 3.4 atmospheres from the feed side to the permeate side of the membrane at an absolute pressure of about 4.4 atmospheres on the feed side.

Often, the maximum pore size is less than about 250 Angstroms and often less than about 150 Angstroms, such as less than about 100 Angstroms.

A method for evaluating the size and openness of cellular supports is to subject hollow fiber membranes to a conventional Prunauer, Emmett, and Teller (BET) adsorption assay to measure surface area.

In BET analysis, a substantially monolayer of gas, such as nitrogen, is adsorbed onto the effective internal surface of the hollow fiber and the amount of gas adsorbed is measured.

It is believed that the amount of gas adsorbed is proportional to the effective surface area.

In the BET analysis techniques described herein, the analysis is performed such that the internal surfaces of the cells that are not open do not contribute significantly to the measurement of effective surface area.

Smaller cells provide more surface area per polymer 12 than smaller cells.

As a result, BET analysis is an indicator of cellular patency that is too small to be resolved by, for example, scanning electron microscopy.

Poly(hollow fiber membranes according to the invention) preferably have at least about 18 or 20 m' per 12 m'20
The surface area measured by the BET method is shown.

At very high BET measurement surface areas, for example about 50 or 70 m2 per 11, it is often observed that the hollow fibers have a fibrillar structure instead of a cellular structure.

Fibrillar structures are sometimes relatively weak compared to cellular structures.

Typically, the hollow fiber membrane internal surface area, as measured by BET analysis, is in the range of about 18 in 11 or 22 to 30 m2.

Hollow fibers with a predominantly closed cellular structure often exhibit a BET measured surface area of less than about 18 or 20 m2 per 12.

Another useful way to evaluate the surface area measured by BET analysis is the surface area per unit volume of the hollow fiber wall.

Often, the preferred hollow fiber membranes of the present invention have a hollow fiber wall volume of about 10 to 30 m2, such as about 10 to 20 m2 per ICd.
Shows the surface area measured by BET analysis of m'.

The construction of the polysulfone hollow fiber membranes of the present invention allows the hollow fibers to withstand significant external pressure differentials across the pores of the hollow fiber membrane.

That is, hollow fiber membranes exhibit high collapse pressures.

Thus, hollow fiber membranes can be thick while maintaining desirable structural strength, have a relatively small wall/external diameter ratio, and thereby have the advantage of minimizing pressure drop for gas passing within the pores. can be given the dog hole diameter.

The collapse strength from external pressure of a tube with a foam wall structure depends on the strength of the membrane material, the wall thickness of the tube, the nature of the foam wall structure, the external diameter of the tube, the density of the foam, and the hollow fiber shape (i.e., the external and whether the internal shape is concentric and circular.

In general, the collapse pressure of the hollow fiber membranes of the present invention is approximately related to the strength of the material of the hollow fibers and the wall thickness (t/D) divided by the external diameter of the hollow fibers.

This approximate relationship can be expressed by the cube of the hollow fiber material's tensile strength and wall thickness/external diameter ratio.

Similar relationships exist with respect to other strength properties of hollow fiber materials such as modulus of elasticity and the like.

Often the hollowness (kg/crA) of the invention is indicated.

'rs is the tensile strength at yield (or failure, if appropriate) in kg/c4.

A more advantageous hollow fiber membrane according to the invention exhibits a crushing force.

where φ is the volume fraction of hollow fiber membrane material in the wall of the hollow fiber membrane.

Therefore, the volume fraction φ of the hollow fiber membrane material is 1 - amount of void volume (% by volume)/100.

Anisotropic membranes can be produced by the method of the present invention to minimize the thickness of the separation or barrier layer.

Often, the tendency to form pores in the membrane increases when the Qζ barrier layer is reduced.

U.S. Patent Application No. 742, incorporated herein by reference.
No. 157 and Hennis of U.S. Patent Application No. 832,481 (
According to the teachings of Hen1s et al., a coating can be brought into occlusion contact with a gas separation membrane containing pores to enhance the separation selectivity exhibited by the gas separation membrane.

Coating materials do not cause significant separation. Normal, Hennis (H
Membranes suitable for coating according to the invention of E.D. en1s et al.
．． 5 and the transmission ratio as described above.

In many cases, the most advantageously coated uncoated membranes exhibit a transmission ratio of less than about 40, such as less than about 20 or 50.

The ratio of the permeability of the gas (preferably a gas that readily permeates the membrane material)/the permeation constant of the membrane material to the gas is at least about IX I Q"CrrLl, preferably at least about 2×
105 crfL-1, for example up to 1x105 CrrL-1.

For example, polysulfone (for example) hollow fiber membranes (and many other fibrous membranes) which are advantageous for coating are about 100 to 1
It exhibits a hydrogen flow rate of 200 GPUs or more and exhibits a hydrogen permeability/methane permeability ratio of about 1.5 or 2 to about 10, such as about 2-7.

In many cases, the separation selectivity for at least one pair of gases after coating the membrane is demonstrated by an essentially non-porous membrane of the same material, i.e. a non-porous membrane through which the gas passes only by interaction with the membrane material. at least about 4 of it
0%, for example about 50%.

The separation selectivity of the coated membrane is at least about 35%, such as less (both about 50 or 100 % dog.

Moreover, after coating, the flow rates obtainable using the coated membrane are not unduly reduced.

For example, the gas permeability/membrane material permeation constant ratio is preferably small (both about 5 x 104 crn-1, preferably at least about 1 x 105 CrIL-1).

Materials that are particularly advantageous in coatings for enhancing the separation selectivity of the membrane are those that do not unduly reduce the permeation rate (flow rate) of the gas or gases that are desired to be permeated through the membrane wall. It is.

Often the coating material has a relatively high permeation constant.

The coating material must be capable of providing occlusion contact with the external surface of the membrane.

For example, if a coating is applied, the coating must be sufficiently wet and tacky to the hollow fibers to cause occlusion contact.

The wettability of a coating material can be easily measured by contacting the coating material alone or in a solvent with the coating material.

Additionally, a coating material of appropriate molecular size can be selected based on an evaluation of the average pore diameter in the thickness of the separation layer of the membrane.

If the molecular size of the coating material is too large to accommodate the pores, the material is not useful for providing occlusion contacts.

If, on the other hand, the molecular size of the coating material is too small, it will be drawn out through the pores of the membrane during the coating and/or separation operation.

If the pores are of a wide range of different sizes, one can use a polymerizable material for the coating material, which polymerizes after application to the membrane, or two or more, for example by applying the coating materials in order of increasing molecular size. It is desirable to use coating materials of various molecular sizes as described above.6 The coating materials are natural or synthetic and often polymeric and exhibit suitable properties that advantageously provide occlusion contact with the membrane.

This synthetic material includes addition and condensation polymers.

Typical useful materials that can be used in coatings are polymers that are substituted or unsubstituted and are solid or liquid under gas separation conditions and include synthetic rubbers, natural rubbers, relatively high molecular weights and/or high boiling points. liquid, organic prepolymer, poly(siloxane) (silicone polymer), polysilazane,
Polyurethanes, poly(epichlorohydrin), polyamines, polyimines, polyamides, acrylonitrile-containing copolymers such as poly(α-chloroacrylonitrile) copolymers, polyesters (including polylactams and polyacrylates) such as poly(alkyl acrylates) and Poly(alkyl methacrylates) (wherein the alkyl group has, for example, about 1 to 8 carbons), polysebacates, polysuccinates and alkyd resins, tilpinoid resins, linseed oil, cellulose copolymers, polysulfones, especially aliphatic-containing polysulfones, e.g. Polymers from monomers with α-olefinic unsaturation, such as poly(alkylene glycol), poly(alkylene) polysulfate, polypyrrolidone, such as poly(ethylene glycol), poly(propylene glycol), etc. e.g. poly(olefin) ) e.g. poly(ethylene), poly(propylene)
, poly(butadiene), poly(2,3-dichlorobutadiene), poly(isoprene), poly(chloroprene),
Poly(styrene) including poly(styrene) copolymers
For example, styrene-butadiene copolymers, polyvinyl such as poly(vinyl alcohol), poly(vinyl artecht) [e.g. poly(vinyl formal) and poly(vinyl butyral)], poly(vinyl ketone) [e.g. poly(methyl vinyl ketone)] , poly(vinyl ester) [e.g. poly(vinyl benzoate)], poly(vinyl halide) [e.g. poly(vinyl bromide)], poly(vinylidene carbonate), poly(N-vinylmaleimide)
poly(1,5-cyclooctadiene), poly(methyl isopropenyl ketone), fluorinated ethylene copolymers, poly(arylene oxides) such as poly(xylene oxide), polycarbonates, polyphosphates such as poly(ethylene methyl phosphate), etc. ), and interpolymers including block interpolymers containing repeating units from those mentioned above, and polymers including grafts and mixtures containing any of the above may be polymerized after application to the membrane. not polymerized (
It's okay.

Particularly useful materials for coating consist of poly(siloxanes).

Typical poly(siloxanes) consist of aliphatic or aromatic moieties and often have repeating units containing about 1 to 20 carbon atoms.

The molecular weight of the poly(siloxane) can vary widely, but is generally at least about 1000.

Often, poly(siloxanes) have molecular weights of about 1000 to 300000 or more when applied to membranes.

Common aliphatic and aromatic poly(siloxanes) are poly(
mono- and di-substituted siloxanes).

In this case, for example, substituents include lower aliphatic groups such as lower alkyl, including cycloalkyl groups, in particular aryl, including monocyclic or bicyclic aryl, including methyl, ethyl and propyl, lower alkoxy, bisphenylene, naphthalene, etc. , lower monocyclic and bicyclic aryloxy, lower aliphatic and lower aromatic acyl.

Aliphatic and aromatic substituents may be substituted, for example, with halogens such as fluorine, chlorine and bromine, hydroxy groups, lower alkyl groups, lower alkoxy groups, lower acyl groups, glycidyl groups, amine groups, vinyl groups, and the like.

Poly(siloxane) can be cross-linked in the presence of a cross-linking agent to give silicone rubber and poly(siloxane C can be copolymerized with a cross-linkable copolymer such as alpha-methylstyrene to aid in cross-linking. I can do it.

Typical catalysts that promote cross-linking include organic and inorganic peroxides.

Although cross-linking may occur before applying the poly(siloxane) to the membrane, preferably the poly(siloxane) is cross-linked after it has been applied to the membrane.

Often, poly(siloxanes) have about 100
0-1oooo.

It has a molecular weight of

Particularly preferred poly(siloxanes) are poly(dimethylsiloxane), poly(hydrodienemethylsiloxane), poly(phenylmethylsiloxane), poly(trifluoropropylmethylsiloxane), copolymers of α-methylstyrene and dimethylsiloxane, and about 1 before cross-linking
It consists of a post cured poly(dimethylsiloxane) containing silicone rubber having a molecular weight of 000 to 50000 or more.

Some poly(siloxanes) do not wet the hollow fiber material sufficiently to provide the desired degree of occlusion contact.

However, occluding contacts can be easily obtained if the poly(siloxane) is dissolved or dispersed in a solvent that does not substantially affect the membrane material.

Suitable solvents include normally liquid alkanes such as pentane, isopentane, cyclohexane, aliphatic alcohols such as methanol, some halogenated alkanes and dialkyl ethers, dialkyl ethers, etc., and mixtures thereof.

The coating may be in the form of an essentially uninterrupted or essentially non-porous film in contact with the anisotropic membrane, or the coating may be in the form of a discontinuous or interrupted film. good.

Preferably, the coating does not adversely affect the performance of the membrane, for example by causing an undue reduction in flow rate or by creating a resistance to gas flow such that the separation factor of the coated membrane is substantially that of the coating. It's not thick enough to have any impact.

Often the coating has an average thickness of up to about 50 microns.

Of course, if the coating is interrupted, there will be areas without coating material.

The coating often has an average thickness in the range of about 0.001 to 50 microns.

In some cases, the average thickness of the coating is less than about 1 micron and even less than about 5000 Angstroms.

The coating may be one layer or consist of two separate layers, either of the same material or not.

The coating may be applied in any suitable manner, for example by coating operations such as spraying, brushing, or dipping using an essentially liquid substance comprising the coating material.

The coating material, when applied, may be brought into solution using a solvent for the coating material that is contained in an essentially liquid material and is substantially non-solvent for the coating material.

Advantageously, the coating is applied after assembly of the membrane for later installation in the dialysis machine, in order to minimize handling of the coated membrane.
or even after installation in the dialysis machine.

The external surface of the membrane is coated with a densifying agent.
ent) It is often possible to densify the external surface of the membrane by treatment with, for example, plasticizers, swelling agents, non-solvents, solvents for anisotropic membrane materials (preferably weak solvents).

Selection of the appropriate thickening agent depends on the membrane polymer.

Thickening agents found to be applicable include ammonia, hydrogen sulfide, acetone, methyl ethyl ketone, methanol, impencune, cyclohexane, hexane, isopropanol, solvents for the polymer in non-solvents for the polymer (e.g. toluene, benzene, chloride). liquids and gases, such as dilute mixtures of methylene).

Treatment can occur before or after drying the membrane and can occur over a wide range of temperatures.

Temperatures of 0-50°C, for example about 10-35°C, are commonly used.

It is advantageous in some cases to treat the membrane with a thickening agent before coating to increase selectivity.

The membrane of the present invention can be widely applied in gas separation operations, particularly in the separation of low molecular weight gases, due to the interaction of the permeating gas with the membrane material.

Gas mixtures that can be used in gas separation operations include gaseous substances,
or consists of a substance that is liquid or solid under normal conditions but is a gas at the temperature at which the separation is carried out.

Typical gas separation operations that are desirable include, for example, the separation of oxygen from nitrogen, the carbonization of carbon monoxide, carbon dioxide, helium, nitrogen, oxygen, argon, hydrogen sulfide, nitrous oxide, ammonia, and the carbonization of about 1 to 5 carbon atoms. separation of hydrogen, especially from at least one of methane, ethane and ethylene;
Separation of ammonia from nitrogen, argon, and at least one of a hydrocarbon of about 1 to 5 carbon atoms, such as methane, - carbon oxide and at least one of a hydrocarbon of about 1 to 5 carbon atoms, such as methane. Separation of carbon dioxide from species, separation of helium from hydrocarbons of about 1 to 5 carbon atoms, such as methane, separation of hydrogen sulfide from hydrocarbons of about 1 to 5 carbon atoms, such as methane, ethane or ethylene. and separation of carbon monoxide from at least one of hydrogen, helium, nitrogen and hydrocarbons of about 1 to 5 carbon atoms.

The membrane according to the invention can be advantageously applied to separation operations using other gas mixtures.

The following examples are given to aid in understanding the invention and are not given to limit the invention.

Unless otherwise stated, all parts and percentages of gases are parts and percentages by volume and all parts and percentages of liquids are parts and percentages by weight.

'l&' unless otherwise stated! , the gas permeability is all about 7
Measured using substantially pure gas with a shell side pressure of 0 atmospheres absolute and about 1 atmosphere on the hole side of the hollow fiber membrane.

Example 1 68 parts by weight of a liquid carrier consisting of 32 parts by weight of polysulfone (P-3500 obtained from Union Carbide Corporation), 90 parts by weight of 1-formylpiperidine and 10 parts by weight of formamide (reagent grade) were mixed in a dry nitrogen atmosphere. into a heated dope mixer with a

Before entering the dope mixer, the polysulfone polymer is dried under vacuum (eg, less than about 10 or 20 mrnHg absolute pressure) at about 125°C for 5 to 7 days.

Formylpiperidine has a water content of about 0.45 f/100 ml and formamide has a water content of about 0.15 f/100 ml.
It has a water content of f.

To avoid degradation of the formamide, minimize exposure of the formamide to air while filling the heated dope mixer.

The polymer solution is heated in a heated dope mixer for a sufficient time (generally about 8
The temperature is maintained at about 80-100<0>C.

The polymer solution is transferred to a deaerator with a dry nitrogen atmosphere heated to about 80°C.

The deaerator has a conical partition with a cup at the top of the partition.

The polymer solution when fed to the holding tank is introduced into the cup below the level of the polymer solution in the cup.

The polymer solution overflows the rim of the cup and flows down the conical version in the form of a thin film.

The polymer solution passes from the lower edge of the conical version onto the wire mesh and then to the polymer solution in the degasser.

A recycle flow of the polymer solution in the degasser is maintained during degassing.

The deaerator maintains an absolute pressure of approximately 250-300 mmHg.

Satisfactory degassing may also be achieved using substantially atmospheric pressure in the degasser.

Adequate deaeration is generally achieved with a residence time in the deaerator of about 7 hours or less.

The degassed polymer solution was pumped by a Zenith type H pump.
It is pumped at a rate of 8.62 per minute into a tube-in-orifice type spinneret having an orifice diameter of 533 microns, an exit tube diameter of 203 microns, and an exit capillary diameter of 127 microns.

The spinneret has five equidistant polymer solution inlets located behind the annular extrusion zone and is maintained at a temperature of approximately 50-58°C by the use of an external electrical heating jacket, and The temperature of the solution is around this temperature.

Deionized water at about ambient temperature (20-25°C) is fed to the spinneret at a rate of about 1.2 TLl per minute.

While in the spinneret, the deionized water is heated by heat transfer.

The spinneret +'3 is located approximately 10.2 crrL above the coagulation bath.

The hollow fiber precursor is extruded at a rate of about 42.7 meters per minute.

The hollow fiber precursor migrates downwardly from the spinneret into an elongated coagulation bath.

The coagulation bath contains substantially tap water, and sufficient fresh tap water is added to adjust the coagulation bath liquid (liquid coagulant) to bring the concentration of 01-formylpiperidine in the coagulation bath to about 1
Purge to maintain less than % by weight.

The liquid coagulation liquid is maintained at a temperature of about 2-4°C.

The hollow fiber precursor migrates vertically downward into the liquid coagulant over a distance of about 7.8 crn, passes through the liquid coagulant around the rollers in a slightly upwardly sloped path, and then Exit the coagulation bath.

The distance of immersion in the coagulation bath is approximately 1.4 m.

The hollow fibers from the coagulation bath then form three consecutive bodies (
godet) is washed with tap water in a bath.

In the first body bath the hollow fibers are immersed for a distance of approximately 7.3 m.

The first body bath is maintained at a temperature of about 2-4 DEG C. and the concentration of 01-formylpiperidine in the bath is maintained below about 3% by weight by adding fresh water and purging the wash medium.

The second and third body baths are at ambient temperature (e.g., about 15-25 DEG C. depending on the temperature of the tap water and the room temperature of the laboratory) and fresh water is constantly added to the body baths.

The wet hollow fibers have an outer diameter of about 440 microns and an inner diameter of about 155 microns.

While moistened with water, the hollow fibers are wound onto a bobbin using a Leesona winder with the lowest possible tension.

The bobbin contains 3600 m of hollow fiber membrane and the thickness of the hollow fiber wound on the bobbin is less than about 2 cm.

The bobbins are placed in a container containing tap water and the tap water is added and purged from the container at a rate of about 4-51 per hour per bobbin at tap water temperature (10-20° C.) for about 24 hours.

The bobbin is then stored for several days at approximately ambient temperature (20-25°C) in a container containing tap water.

After storage, the hollow fibers, while remaining moist, are wound on a Skyner to form a strand of hollow fibers approximately 3 m long.

Winding of the hollow fibers on a wind machine is done using the minimum tension necessary to effect the winding.

The hollow fiber winds are hung vertically with the hollow fiber holes open at the bottom and allowed to dry at ambient experimental conditions (about 20-25° C. and 50% relative humidity) for at least about 3 days.

The dried hollow fibers have an external diameter of about 390 microns and an internal diameter of about 140 microns and appear similar to the hollow fibers shown in FIG. 1 under a scanning electron microscope.

Ten hollow fiber test loops, each approximately 15 crrL in length, are manufactured.

At one end, the test loop is attached to the tubular sheet.

The pores of the hollow fibers can communicate through this sheet.

The other ends are closed. Vacuum the hollow fiber hole of each test loop for approximately 10 minutes (approximately 50-100 mmHg absolute pressure).
Congratulations.

Polydimethylsiloxane (Sylgard 184, available from Dow Corning) allows each test loop to be post-cured in a vacuum while maintaining vacuum for approximately 10 minutes.
2% by weight of the coating solution and then removed from the coating solution.

After removing the test loop from the coating solution, the vacuum is maintained for about 10 minutes and the test loop is then dried at ambient laboratory conditions (20-25° C. and about 40-60% relative humidity).

The external feed surface side (skin side) of the hollow fiber is at approximately 70 atmospheres absolute and the hole side of the hollow fiber is at approximately 1 atmosphere absolute so that the permeability of the test loop for hydrogen and methane is at ambient experimental temperature (approximately (20-25°C) using essentially pure gas.

The measured permeability generally varied slightly from test loop to test loop, and some variation is believed to be due to leakage in the tubular sheet, damage to the hollow fibers from handling, etc.

Average hydrogen permeability is often around 75-150 GPU (1x
106cc (STP)/crti-see-cr
rLHg] and the average methane permeability is often in the range of about 1-2 GPU.

The ratio of permeability (separation factor) of hydrogen to methane is often about 50-60.

The hollow fiber burst pressure is measured to be greater than 110 kg/crA (1600 pounds per square inch).

Example 2 A degassed polymer solution containing 2 wt. (jet)
A hollow fiber membrane is obtained by spinning through the fiber.

The polymer solution (dope) temperature for Experimental Runs 885-1.533-1-7 and 537-1 was not directly measured and is 60-70°C.

Deionized water is used as a jet fluid and is applied at a velocity sufficient to maintain the inner diameter of the hollow fibers.

The coagulation bath consists of water and the concentration of 1-formylpiperidine in the coagulation bath is maintained below about 1% by weight by purging.

The hollow fibers are immersed in the coagulation bath for a distance of approximately 1 rrL.

The residence time of the hollow fibers in each of the three washing baths (first, second and third Godet baths) is as follows.

The hollow fibers are wound onto a bobbin while kept moist and the bobbin is rinsed in cold running tap water for about 16-24 hours and then stored in a bucket filled with water for 7 days.

The hollow fibers were then heated under ambient experimental conditions (22-25°C and about 40°C).
~60% relative humidity) and then prepared a test loop as described in Example 1, except using 1% by weight Sylgard 184 solution and using 20 hollow fibers in the test loop. coated and then tested.

The observed performance of the hollow fibers is shown in Table 2.

Example 3 The procedure of Example 2 is substantially repeated with the following exceptions.

The degassed polymer solution is essentially polysulfo 7p-35.
0035% by weight and 64% by weight of 1-formylpiperidine
The spinneret has an external diameter of 533 microns, 20
It has an internal diameter of 3 microns and an exit capillary diameter of 127 microns.

The spinneret is approximately 10.2 Cr above the liquid surface in the coagulation bath.
rL, the polymer solution feed rate to the spinneret is about 11.8 cd per minute and the spinning speed is about 42.7 m per minute.

The temperature of the polymer solution extruded from the spinneret is approximately 54°C.

The coagulation bath is at a temperature of about 1-2°C, the first body bath at about 1-2°C and the second and third body baths at about 20°C.

The residence time of the hollow fibers in each body bath is approximately 40.
It is 6 seconds.

The hollow fibers have an external diameter of 445 microns and an internal diameter of 166 microns before drying.

A scanning electron micrograph of dried hollow fibers according to this example is shown in FIG.

The collapse pressure exhibited by the hollow fibers is approximately 170 kg/
It is crrt.

Test loops are made from hollow fibers as in Example 1, coated (using 2% by weight Sylgard 184 solution) and then tested.

The hydrogen and methane permeability of uncoated hollow fibers is approximately 39G.
PU and 2. It is an IGPU.

Hollow fibers made similarly except that the temperature of the coagulation bath was about 5°C had an internal diameter (wet) of about 190 microns and exhibited a collapse pressure of about 100-150 kg/crA, and were coated and Approximately 100 when using a test loop
The hydrogen permeability of GPU and the methane permeability of about 3.3 GPU are shown.

Example 4 The procedure of Example 2 is substantially repeated with the following exceptions.

Polysulfone (P-3500) 36 fc% and 1-
A 64% by weight degassed polymer solution of a mixture of 87 parts by weight of formylpiperidine and 13 parts by weight of formamide was added at a temperature of about 52°C to 5crt! , at a speed of 7 minutes through a spinneret having an external diameter of 457 microns, an internal diameter of 127 microns, and an exit capillary diameter of 76 microns.

The spinneret is located 10.2 crIL from the liquid surface in the coagulation bath.

The spinning speed is approximately 30.5 m per minute.

The coagulation bath and first body bath are at about 3° C. and the second and third body baths are at about room temperature.

The residence time in each of the three body baths is approximately 50.
It is 9 seconds.

Store the hollow fibers in water for 1 day instead of 7 days,
Store for 2 and 24 days.

Hydrogen and methane permeability after storage period of hollow fiber samples,
Analyze for collapse pressure and solvent content.

Hydrogen and methane permeability of test loops containing uncoated hollow fiber samples after one day of storage using a shell side pressure of about 7.8 atmospheres absolute and a pore pressure of about 4.4 atmospheres absolute. Measurements are made on hollow fibers stored at IB, 2 days and 24 days using a shell side pressure of about 70 atmospheres absolute and a pore pressure of about 1 atmosphere absolute.

When dry, the hollow fibers have an external diameter of 456 microns and an internal diameter of 188 microns.

The results are shown in Table ■. Example 5 The procedure of Example 4 is substantially repeated except that the spinning speed is about 45.7 meters per minute and the residence time in each body bath is about 38 seconds.

In one method, a chimney is positioned between the spinneret and the surface of the liquid in the coagulation bath such that a saturated atmosphere exists within the chimney.

The spinneret is 10.2 (1177
It is located at 1.

The other methods are essentially the same except that no chimney is used and the spinneret is positioned 5.1 cIrL above the surface of the liquid in the coagulation bath.

Example 6 The following points substantially repeat the procedure of Example 2.

A degassed polymer solution consisting of 62% by weight of a liquid carrier of i% polysulfone P-350038 and 87 parts by weight of 1-formylpiperidine and 13 parts by weight of formamide was heated to 635 microns at a rate of 6 cJ per minute at about 70°C. The yarn is spun through a spinneret having an external diameter of 228 microns, an internal diameter of 228 microns, and an exit capillary diameter of 152 microns.

The spinneret is located at membrane 2.5 (Z772) above the liquid surface in the coagulation bath, and the spinning speed is approximately 3 per minute.
It is 0.5m.

The coagulation bath and first body bath are at about 3° C. and the second and third body baths are at about room temperature.

The residence time of the hollow fibers in each of the three body baths is approximately 56.9 seconds.

The coagulation bath contains 7.5% by weight acetic acid.

The dry hollow fibers have an external diameter of 444 microns and a
It has an internal diameter of 1 micron.

The hollow fibers exhibit a collapse pressure of approximately 180 kg/cm.

A test loop is constructed from a hollow fiber sample and the hydrogen and methane permeability is measured before and after coating (the permeability of the uncoated membrane is approximately 7.8 atm absolute shell pressure and 1 atm absolute pore pressure). Measured by pressure].

The results are as follows.

Example 7 Example 6 except that the spinneret had an external diameter of 483 microns, an internal diameter of 152 microns and an exit capillary diameter of 76 microns and the hollow fibers were stored in buckets under the various conditions shown in Table 1. substantially implement the operating method.

Example 8 The procedure of Example 2 is substantially repeated with the following exceptions.

The polymer solution contained 32% by weight of polysulfone P-3500 and 68% by weight of a liquid carrier of 85 parts by weight of 1-formylpiperidine and 15 parts by weight of ethylene glycol;
and 63 at a rate of 7.2 cni per minute at approximately 70°C.
The yarn is spun through a spinneret having an external diameter of 5 microns, an internal diameter of 229 microns, and an exit capillary diameter of 152 microns.

The spinning speed is approximately 42.7 m per molecule. The spinneret is approximately 10.2 meters from the liquid surface in the coagulation bath.

The coagulation bath and first body bath are at about 3° C. and the second and third baths are at about room temperature.

The residence time of the hollow fibers in each of the three body baths is approximately 40.6 seconds.

The outer diameter of the hollow fibers is about 456 microns and the inner diameter is about 205 microns.

The hydrogen permeability of the coated hollow fibers is about 64 GPU and the carbon monoxide permeability is about 0.65 GPU.

Example 9 The procedure of Example 2 is substantially repeated, except as follows.

The polymer solution contains 2% by weight of PoIJ sulfone P-35003 and 68% by weight of a liquid carrier having 90 parts by weight of 1-formylpiperidine and 5 parts by weight of ethylene glycol and 5 parts by weight of water.

The polymer solution is spun at 65-70°C through a spinneret having an external diameter of 508 microns, an internal diameter of 152 microns, and an exit capillary diameter of 102 microns.

The spinning speed is 43.5 m per minute.

The spinneret is approximately 17 cIn from the liquid surface in the coagulation bath.

The coagulation bath and first body bath are at about 5°C and the second and third body baths are at about room temperature.

The residence time of the hollow fibers in each of the three body baths is approximately 38 seconds.

The hollow fibers have an external diameter of about 450 microns and an internal diameter of about 236 microns.

The hydrogen permeability of the coated hollow fibers is about 100 GPU and the carbon monoxide permeability is about 2.3 GPU.

Permeability is measured in a gas mixture of about 25 mole percent hydrogen and 75 mole percent carbon monoxide using a shell side pressure of about 150 myrtHg and an experimental vacuum on the hole side of the hollow fiber.

Example 10 The procedure of Example 2 is substantially repeated, except as follows.

32% by weight of polysulfone P-35000 and 80 parts by weight of 1-formylpiperidine.

A polymer solution is prepared from 68% by weight of liquid carrier with 10 parts by weight of ethylene glycol and 10 parts by weight of acetone.

Acetone concentration is not measured after degassing.

The polymer solution has an external diameter of 635 microns at approximately 80°C, 2
28 micron internal diameter and .

The yarn is spun through a spinneret with an exit capillary diameter of 152 microns.

The spinning speed is 26.2 m per minute.

The spinneret is approximately 20.3 crr1 from the liquid surface in the coagulation bath.
．． It is.

The coagulation bath and first body bath are at about 0°C and the second and third body baths are at about 14°C.

The residence time of the hollow fibers in each of the three body baths is approximately 66 seconds.

The pores of the hollow fibers are offset and the outer diameter of the hollow fibers (wet) is about 342 microns and the inner diameter is about 165 microns.

Hydrogen permeability of uncoated hollow fibers is approximately 225GP
U and approximately 82 GPUs after coating.

The methane permeability of uncoated hollow fibers is approximately 50 GP
U and approximately 1.6 GPU after coating.

Example 11 The procedure of Example 2 is substantially repeated, except as follows.

The polymer solution was 40% by weight of polysulfone P-17O0 (similar to P-3500 available from Union Carbide, except that it is a lower molecular weight polysulfone), 87 parts by weight of 1-formylpiperidine, and 13 parts by weight of formamide. Contains 60% by weight of liquid carrier with

The polymer solution is spun at about 70°C at a rate of 9 cril per minute through a spinneret having an external diameter of 635 microns, an internal diameter of 229 microns, and an exit capillary diameter of 152 microns.

The spinneret is approximately 7.6 crfL from the liquid surface in the coagulation bath.

The spinning speed is 30.5 m per minute. The coagulation bath and first body bath are at about 4° C. and the second and third body baths are at about room temperature.

The residence time of the hollow fibers in each of the three body baths is approximately 56.9 seconds.

The outer diameter of the hollow fibers is about 439 microns and the inner diameter is about 154 microns.

The collapse pressure exhibited by the hollow fibers is approximately 175 kg/
It is crtr.

Hollow fiber samples are stored in water for 7 or 23 days, dried and then made into test loops.

Handle test loops in several ways.

Some test loops are flushed with isopentane before coating.

In this method of operation, the pores of the hollow fibers are subjected to a vacuum for about 10 minutes, immersed in inpentane for 10 minutes at room temperature (about 20-25°C), and then soaked in isopentane while maintaining the vacuum on the pore side of the hollow fibers. and then apply vacuum one more time.
Maintain for 0 minutes.

The test loops (coated and uncoated membranes) are also inked in a closed container of gaseous ammonia at room temperature and under a pressure of approximately 18 kL;j/cm.

The coated and uncoated hollow fibers are subjected to this ammonia treatment.

The permeability of hollow fibers to hydrogen and methane is measured using various shell side pressures.

The hole side pressure is about 1 atmosphere absolute.

The results are shown in Table V. Example 12 The procedure of Example 2 is substantially repeated, except as follows.

The polymer solution contains 4% by weight of polysulfone P-350 and 4% by weight of substantially anhydrous lithium chloride per 10,100 O of solution.
It contains 66% by weight of a liquid carrier consisting of a mixture of 2.4f and 1-formylpiperidine.

The polymer solution is spun at about 70-80°C through a spinneret having an external diameter of 635 microns, an internal diameter of 228 microns, and an exit capillary diameter of 152 microns.

The spinneret is 3.5 m above the liquid surface in the coagulation bath.

The spinning speed is approximately 20 m per minute.

The coagulation bath is at 5°C, the first body bath is at 5°C and the second and third body baths are at about room temperature.

The residence time in each of the three body baths is approximately 86 seconds.

The outer diameter of the hollow fibers is about 685 microns and the inner diameter is about 380 microns.

Permeability is measured using the method described in Example 9.

The hydrogen permeability of the coated membrane is about 80 GPU and the carbon monoxide permeability of the coated membrane is about 2.9 GPU.

The hollow fibers have a fine knotty structure as observed from scanning electron micrographs and exhibit an internal surface area of approximately 75 rrl/ff as measured using BET analysis.

Example 13 The procedure of Example 2 is substantially repeated, except as follows.

The degassed polymer solution contained 32% by weight poly(phenylene ether) sulfone and 1% by weight poly(phenylene ether) sulfone available from ICI Ltd.
- 90% by weight of formylpiperidine and 10% formamide
Contains 68% by weight of liquid carrier consisting of grass.

Spinneret dimensions are external diameter 533 microns, internal diameter 20
3E micron and injection capillary diameter 134 micron.

The polymer solution velocity through the spinneret is about 7.1 c4/min and the winding speed is about 42.4 m/min.

The coagulation bath and the first washing bath are at about 1-2°C and the second
and the third washing bath at about 19°C.

The approximate polymer solution concentration varies from about 40-55°C and the dimensions of the hollow fiber membrane before drying are about 435 microns outside diameter and about 150 microns inside diameter.

However, one sample has an oblong pore shape.

The observed performance of the hollow fiber membranes is as given in Table II.

Example 14 The procedure of Example 2 is essentially repeated, except as follows.

The degassed polymer solution is polysulfone (p-3500).
32% by weight and 68% by weight of a liquid carrier consisting of about 90% by weight of 1-acetylpiperidine and 10% by weight of formamide.
Contains.

Spinneret dimensions are external diameter 584 microns, internal diameter 17
8 microns and the injection capillary diameter is 101 microns.

The spinneret is located approximately 5 degrees above the level of the liquid coagulant and is at a temperature of about 57°C.

The winding speed is approximately 42.4 m per minute. The coagulation bath and first wash bath are at about 2°C and the second and third wash baths are at about 16°C.

Details are shown in Table ①.

Example 15 Hollow fibers are prepared by the procedure substantially as set forth in Experimental Run No. 533-1 of Example 2, except that the hollow fibers are stored in water for 7 days.

Hollow fiber samples are dried in a temperature and humidity controlled atmosphere (air) under various conditions and then test loops are produced.

Measure the hydrogen and methane permeability of coated and uncoated hollow fibers.

The results are shown in Table ■.

Example 16 The procedure of Example 1 is essentially repeated, except as follows.

The polysulfone is dried at atmospheric pressure in a forced dry air atmosphere for about 2 days.

Degassing of the polymer is carried out at atmospheric pressure in an atmosphere of dry air.

The polymer solution was extruded through the spinneret at about s, 1 crA per minute and the winding speed was about 42.4 crA per minute.
It is m.

The wet hollow fibers have an external diameter of about 450 microns and an internal diameter of about 155 microns.

When hanging hollow fibers for drying, the hollow fibers are looped.

That is, it is not open at the bottom.

The dried hollow fiber membrane has an outer diameter of about 400 microns and an inner diameter of about 140 microns.

Example 17 The procedure of Example 12 is substantially repeated, except as follows.

The polymer solution was 33% by weight acrylonitrile and 67% by weight styrene in a 66% by weight liquid carrier containing 75% by weight 1-formylpiperidine and 25% by weight formamide.
Contains 34% by weight of suspension polymerized copolymer.

The spinneret is at 0.6 sieve above the liquid coagulant level and the winding speed is about 13-14 meters per minute.

The coagulation bath and the first washing bath are at about 2-3°C and the second
and a third wash bath at about 17°C.

The hollow fibers are dried and soaked in methanol or pentane and then exposed to vaporize at low partial pressures.

Next, the hollow fiber membrane was added to approximately 3% by weight of Siligad in pentane.
Cover with a solution of

The hydrogen permeability of the coating is about 20-40 GPU and the separation factor for hydrogen versus carbon monoxide is about 20-40.

Example 18 The method of Example 12 is substantially repeated, except as follows.

The polymer solution was methylbrominated poly(phenylene oxide) (approximately 45 mol%) in 70% by weight 1-formylpiperidine.
(brominated) 30% by weight.

The spinneret has a liquid coagulant level of 2.6α and the winding speed is about 13-14 meters per minute.

The coagulation bath and first wash bath are at about 46-48C and the second and third wash baths are at about 14C.

When coated, the hollow fiber membrane exhibits a hydrogen permeability of about 90-100 GPU and a hydrogen separation factor of about 13 to carbon monoxide.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1a-c and 2 are scanning electron micrographs of hollow fiber membranes. Figure 1a shows a cross-section of the hollow fiber at a magnification of approximately 300x. FIG. 1b shows a cross section of the outer edge of the hollow fiber at a magnification of approximately 20,000 times. FIG. 1c shows a cross-section of the central part of the hollow fiber at a magnification of approximately 20,000 times. Figure 2 shows a cross section of another hollow fiber at a magnification of about 300x.

Claims (1)

[Scope of Claims] 1. By providing a solution of a film-forming polymer in a liquid carrier containing a solvent for the film-forming polymer in the form of a precursor and then coagulating in a liquid coagulant containing water. Therefore, the liquid carrier has the structural formula (wherein, X is -CH2-l-N(R')- or -0-
, R is hydrogen, methyl or ethyl, and R' is hydrogen or methyl). Production method. 2(a) extruding the polymer solution through an annular spinneret to form a hollow fiber precursor such that the polymer solution during extrusion is at a temperature sufficient to substantially maintain the polymer in solution; b) injecting a fluid that is miscible with the liquid carrier into the pores of the hollow fiber precursor at a rate sufficient to maintain the pores of the hollow fiber precursor open as the hollow fiber precursor is extruded from the spinneret; ) contacting the exterior of the hollow fiber precursor with a liquid coagulant consisting essentially of water and containing less than about 5% by weight of said liquid carrier, and which is miscible with the liquid carrier and the injection fluid; providing the hollow fibers such that the contact is sufficient to coagulate the polymer in the hollow fiber precursor under conditions of the liquid coagulant, and then (d) washing the hollow fibers with a non-solvent for the polymer. to reduce the content of liquid carrier in the hollow fibers to less than about 5% by weight based on the weight of the polymer in the hollow fibers. The method described in paragraph 1. 3. The method according to claim 1 or 2, wherein the N-acylated heterocyclic solvent comprises at least one of 1-formylmorpholine, 1-acetylpiperidine, 1-formylmorpholine, and 1-acetylmorpholine. Method. 4 For the polymer, the liquid carrier and the polymer system are approximately 15
4. A method according to any one of the preceding claims, having a second virial coefficient of up to. 5. A method according to any one of the preceding claims, wherein the liquid carrier has a heat of dilution at 25 DEG C. in the liquid coagulant of less than about -3.5 kilocalories per mole. 6. The method according to any one of the preceding claims, wherein the polymer comprises polysulfone. 7 Polysulfone is a repeating structural unit (wherein R1 and R2 are the same or different and 1
an aliphatic or aromatic hydrocarbyl-containing moiety of ~40 carbon atoms, and the sulfonyl group is attached to the aliphatic or aromatic carbon atom. the method of. s A method according to claim 7 in which R1 and R2 are small (one of which is an aromatic hydrocarbyl-containing moiety). 9 The polysulfone has a structure represented by 10. A method according to any one of claims 1 to 9, wherein the liquid carrier contains a non-solvent. 11. Washed hollow fibers. 11. A method according to any one of the preceding claims, wherein the hollow fiber membrane is dried at a temperature that does not unduly adversely affect the selectivity or flux exhibited by the hollow fiber membrane. 12. A method according to any one of claims 1 to 11, wherein the liquid coagulant has a temperature of about -15°C or above to about 2°C.
The method according to any one of claims 1 to 12, wherein the temperature is 0°C or lower. 14. The method of claim 13, wherein the temperature of the liquid coagulant is about 0 to 10C. 15. Any one of the preceding claims, wherein the annular spinneret is located above the surface of the liquid coagulant.
The method described in. 16 Polymerization of at least about 25% by weight of the polymer solution;
16. A method according to any one of the preceding claims, comprising: 17. A method according to any one of the preceding claims, wherein the polymer solution contains about 28-40% by weight of polymer. 18 The polymer solution has a temperature of about 1000 at the extrusion temperature.
18. A method according to any one of the preceding claims, having a viscosity of 0 to 500,000 centipoise. 19 The liquid carrier contains a non-solvent and the non-solvent comprises at least one of formamide, ethylene glycol and water.
19. A method according to any one of the preceding claims, comprising seeds. 20 consisting of a uniformly formed thin outer separating layer on an open cellular support portion and consisting of polysulfone. Moreover, the bulk of the wall volume of the hollow fiber membrane is comprised of cells having an average major axis dimension of less than about 2 microns, and the open cellular support portion has a major axis dimension of less than about 3 microns and an average major axis dimension of less than about 10 microns. substantially devoid of macroporosity having a maximum length/maximum width ratio of The ratio of the permeability constant of a hollow fiber membrane material to that gas is the ratio of the permeability of low molecular weight gases divided by (1) the permeability of high molecular weight gases divided by (11) the square root of the molecular weight of high molecular weight gases of approximately 6. The permeability ratio of the low molecular weight gases (where the low molecular weight gases are one of hydrogen and helium and the high molecular weight gases are one of nitrogen, carbon monoxide and carbon dioxide and the low molecular weight gas in polysulfone is (Ts) (t/D)3 (where Ts is the tensile strength of the polysulfone and t is the wall thickness). a dry monolithic anisotropic membrane for separating at least one gas of a gas mixture, characterized in that it has a collapse pressure of Hollow fiber membrane. 21. The polysulfone hollow fiber membrane of claim 20, which is substantially free of macrovoids. 22. At least about 90% by volume of the walls of the hollow fiber membrane are larger than about 2 microns. 22. A hollow fiber membrane according to claim 20 or claim 21 consisting of cells having a small major axis dimension. 23. A hollow fiber membrane according to any one of claims 20 to 22, comprising cells having a small major axis dimension. 24. A hollow fiber membrane according to any one of the preceding claims, wherein the average shape ratio of the wall portion of the fiber membrane is at least about 0.03.25. It contains cells with major axis dimensions of more than a micron, and the ratio of average wall thickness/average cell cross-sectional area of the largest cell is small (both about 1 cIrL-
25. The hollow fiber membrane according to any one of claims 20 to 24, which is 1. 26 The hollow fiber membrane wall has a void volume of at least about 40
Hollow fiber membrane according to any one of the preceding claims 20 to 25, wherein the hollow fiber membrane is from % by volume to about 70% by volume. 27. A hollow fiber membrane according to any one of the preceding claims 20 to 26, wherein the void volume of the hollow fiber membrane wall is greater than about 45% by volume and up to about 65% by volume. 28 The collapse pressure of the hollow fiber membrane is approximately 10 (φ) (Ts)
(t/D)3, where φ is the volume fraction of the hollow fiber membrane material in the wall of the hollow fiber membrane. The hollow fiber membrane described in . 29 of at least about 0.01 (1) the quotient of the difference in the permeability of an easily permeable gas and a gas that does not permeate divided by the permeability of a gas that does not permeate x (ii) the permeation of a gas that does not permeate easily; showing the relationship of the ratio of the permeation constant of a gas that does not permeate easily to a constant, and the gas that permeates easily having a permeation constant that is at least about 5 times greater than the permeation constant of a gas that does not permeate easily; and the gas that does not easily permeate has approximately the same molecular weight.
Hollow fiber membrane described in. A hollow fiber membrane according to any one of the preceding claims 20 to 29, wherein the outer skin is less than about 1000 angstroms. 31. A hollow fiber membrane according to any one of the preceding claims, wherein the outer skin is less than about 500 Angstroms. 32. A hollow fiber membrane according to any one of the preceding claims, having a permeability ratio of at least about 7.5. 33. A hollow fiber membrane according to any one of claims 20 to 32 having a maximum pore size of less than about 150 angstroms. Polysulfone is a repeating structural unit (wherein R1 and R2 are the same or different and 1
Claim 20 consisting of a polysulfone having an aliphatic or aromatic hydrocarbyl-containing moiety having ~40 carbon atoms, and the sulfonyl group is attached to the aliphatic or aromatic carbon atom. Hollow fiber membrane according to any one of clause 33. Claims 20 to 3 of Claims 20 to 3, in which a small number of R1 and R2 (one of which is an aromatic hydrocarbyl-containing moiety)
Hollow fiber membrane according to any one of Item 4. 36. A hollow fiber membrane according to any one of claims 20 to 35, wherein the polysulfone comprises a polysulfone having a structure represented by: where n is about 50 to 80. 37 Hollow fiber membrane material weighing at least about 350 kg/
Claims 20 to 3 indicate the tensile strength of CD.
Hollow fiber membrane according to any one of item 6.