JPH0523558A - Production of thin supporting layer film - Google Patents

Abstract

PURPOSE: To prepare a thin film complex membrane for separating an arom. compd. from a satd. compd. by mixing a polymer into a soln. contg. a mixture of a specified solvent having a low surface tension with a specified solvent having a high dissolving power and a surfactant to make a wet soln., and wash- coating a hydrophobic support with the soln. CONSTITUTION: A solvent having a low surface tension of less <35 dyne.1 cm at 20 deg.C, for example, acetone is mixed with a solvent having a high dissolving power such as a highly polar dissolving parameter of <3-1/2 (cal/cc) at 25 deg.C, for example, dimethylamide, at a ratio of 10/90-90/10. The solvent is mixed further with a surfactant, to which >10% of a polymer such as polyurea/ urethane polymer is added, to make a wet soln. Since the soln. has a viscosity of 5-100 cp at 20 deg.C, it wets a surface of a hydrophobic support such as Teflon but does not penetrate into fine holes thereof when wash-coated on the support.

Description

Detailed Description of the Invention

[0001]

SUMMARY OF THE INVENTION A high flux thin layer composite comprising a thin, dense, selective polymer film, preferably of polyurethane, polyurea / urethane, polyurethane / imide or polyurea / polyurethane copolymer, on a microporous hydrophobic support backing. The membrane
It is prepared by washcoating an optimal wetting solution of the polymer in a solvent onto a hydrophobic support. The viscosity of the wetting solution of the polymer in the solvent is 5-100 cp, preferably 10-50 cp, more preferably 20-40 cp. The optimum solution viscosity can be obtained by adding a viscosity modifier, adjusting the polymer concentration / solvent composition, aging the solution, or a combination of these methods.

[0002]

BACKGROUND OF THE INVENTION The use of membranes for the separation of aromatics from saturated compounds has been pursued by the scientific and industrial community and is the subject of many patents. For example, US Pat. No. 3,37
0,102, US Patent 2,958,656, US Patent
See 2,930,754 and U.S. Pat. No. 4,115,465.

US Pat. No. 4,837,054 teaches thin layer composite membranes made by precipitation from solution. A thin film of polyurea / urethane is coated from a multi-component solvent system onto a microporous support material. The solution of polyurea / urethane copolymer is prepared in a solvent system consisting of an aprotic solvent such as dimethylformamide, a third component containing a cyclic ether such as dioxane, cellosolve acetate or methyl cellosolve and a wetting agent such as crotyl alcohol. The polymer in the solvent solution is deposited as a thin film on a support substrate such as polyethylene, polypropylene or Teflon, after which the excess polymer / solvent solution is drained from the support. The solvent is then evaporated, leaving a thin layer of active polyurea / urethane copolymer on the support backing. The solvent system used is (a) an aprotic solvent such as DMF, (b) a cyclic ether such as dioxane, (c).
It consists of a mixture of cellosolve acetate or methyl cellosolve, and (d) a wetting agent such as crotyl alcohol. These solvents are about 3-27 / 94-33 / 2-33.
It is used at a ratio of 100 per part of a / b / c / d within the range of / 1 to 7. The polyurea / urethane copolymer exists in the solvent system as a true complete copolymer and the polymer-solvent system exists as a true solution. Polymer concentration in solution is up to 100 parts solvent per 40 parts polymer, preferably 0.5 to about 20.
It can be within the range of 100 parts solvent solution, more preferably 1-10 parts polymer, most preferably 1-5 parts polymer.

[0004]

DETAILED DESCRIPTION A supported thin layer composite membrane is described that includes a thin active layer deposited on a microporous hydrophobic support. Thin-layer composite membranes are made by depositing a thin film of polymer from solution on a microporous hydrophobic support. The polymer solution can adequately wet the hydrophobic support because the solution contains a low surface tension solvent and a surfactant. The solvent must have optimal wetting properties such that the solution wets the surface of the hydrophobic porous support but does not penetrate into the pores. The low flux membrane occurs when the solution penetrates into the pores. For example, pure (100%) dimethylformamide will bead on Teflon, resulting in discontinuous and incomplete film layers. However, low surface tension solvents such as acetone allow the solvent mixture to wet the Teflon surface. 60/40 D
The MF / acetone mixture, although it coats the surface,
However, it does not penetrate into the pores, resulting in optimum wetting characteristics for a 5 wt% polymer solution. However, DMF / acetone ratios greater than 10/90 will penetrate into the pores.

Although the actual ratio used depends on the concentration of polymer present in the solvent solution, the ratio is between 10/90 and
It will be in the range of 90/10. The viscosity of the wetting solution of the polymer in the solvent is 5-100 cp at 20 ° C., preferably 20
10 to 50 cp at ℃, more preferably 20 to 40 at 20 ℃
cp. Optimal solution viscosities can be obtained, for example, by adding viscosity modifiers (eg Monsanto Modaflow), adjusting polymer concentration / solvent composition, aging the solution or a combination of these methods. The polymer solution should be at least 1 before being coated on the hydrophobic support.
Should be aged for the day. Preferably, the polymer solution is aged for 3 days, more preferably about 7 days, before coating on a hydrophobic support such as Teflon or polypropylene. The polymer solution need not use a particular atmosphere unless it is exposed to the atmosphere in which it chemically reacts. The aging temperature is not critical, but aging at slightly elevated temperatures will result in a reduction of the aging time required for the solution to achieve the desired viscosity in the above range.

The polymer solution used is preferably a solution of polyurea / urethane copolymer, polyurea / polyurethane copolymer alloy, polyurethaneimide or polyurethane in a solvent. The polymer concentration in the polymer solution can be in the range of 0.1-10.0% by weight. The use of a low concentration solution results in a thin active layer. thickness
It is possible to obtain thin active layers in the range of 0.1-10 microns, preferably 0.5-5 microns.

Thin layer composite membranes made by depositing a thin active layer of polyurea / urethane, polyurethane / imide or polyurethane from a polymer solvent solution system onto a microporous support substrate are aromatic carbonized from saturated hydrocarbons. Useful for hydrogen separation and recovery / recovery of aromatic compounds such as benzene, toluene, xylene from chemical streams in the chemical industry.
Particularly useful for concentration and in the oil industry for the recovery of aromatic compounds from saturated compounds in snake-feed streams such as naphtha, catalytic naphtha, snake-cat naphtha, light gas oil, light cat gas oil, reformed gasoline, etc. Is.

Examples of polyurea / urethane copolymers that can be used to produce the thin active layers of the thin layer composite membranes described herein and are effective in accomplishing separation when in the form of a membrane are described in US Pat. No. 064 and Shukker (Robert C. Sc
hucker) in its partially continued application USSN 336,172, filed April 11, 1989.

The polyurea / urethane membranes described in US Pat. No. 4,914,064, which are effective in separating aromatics from saturated compounds, are aromatic in nature and have other constant and specific properties. Are distinguished by having. The aromatic polyurea / urethane polymers used to make the thick dense film membranes of that invention have a urea index of at least about 20% but less than 100%, an aromatic carbon content of at least about 15 mol%, Both are characterized by a functional group density of about 10 per 1000 g polymer and a C = O / NH ratio of less than about 8.

In that disclosure, a dense thick film aromatic polyurea / urethane layer is prepared using an aromatic polyurea / urethane copolymer, which in itself is a dihydroxy or polyhydroxy compound (eg, a molecular weight of about 250-500).
0 polyether or preferably polyester), or polymers of the same type but different molecular weights, ie a component of molecular weight about 500 (polyester or polyether) and a component of molecular weight about 2000 (polyester or polyether).
Is prepared by reacting a mixture of with an aliphatic, alkylaromatic or aromatic diisocyanate or polyisocyanate and a low molecular weight chain extender such as a diamine, polyamine or amino alcohol. The choice of the molecular weight of the polyether or polyester component is a compromise issue. The 500 molecular weight polyether or polyester component provides the most selective but lowest flux membranes. High molecular weight (eg 2000) polyesters or polyethers give low selectivity but high flux membranes. Therefore,
The choice of single molecular weight or blend is a matter of choice and compromise between selectivity and flux. The proportions of these components used in the preparation of polyurea / urethane copolymers are determined by the above properties possessed by the membranes useful for separating aromatics from saturated compounds. The resulting copolymer has a urea index of at least about 20% but less than 100%, preferably at least about 30% but less than 100%, most preferably at least about 40% but less than 100%. By the term urea index is meant the percentage of urea groups with respect to total urea plus urethane groups in the polymer.
The copolymer also contains at least about 15 mole percent aromatic carbon, preferably at least about 20 mole percent, expressed as the percentage of total carbon in the polymer. The copolymer also has a specific density of functional groups (DF ratio) defined as the sum of C = O + NH per 1000 grams of polymer, the density of functional groups being at least about 10, preferably at least about 12.
Or more. Finally, the C = O / NH ratio is less than about 8 to ensure that the functional groups are not predominantly carbonyls,
It is preferably less than about 5.0. This ensures that there are sufficient hydrogen bonds within the polymer to produce strong polymer chain interactions and high selectivity. This polyurea / urethane copolymer blend can be used to form the polymer solution described in this invention for use in making the thin layer composite membranes described herein.

Other polyurethane and polyurea / urethane polymers described in the literature, eg US Pat. No. 4,115,
The one described in No. 465, which can be characterized as an aliphatic polyurethane or polyurea / urethane, can also be used in this solution casting operation to produce the TFC membranes of the present invention. The thin-layer composite membranes produced by the method of the present invention have a heavy feed containing highly complex, polycyclic, highly substituted aromatic species, such as heavy cat, when the constituent components of the feed are small. It is particularly well suited for the separation of aromatic compounds from saturated compounds in naphtha.

As mentioned above, thin layer composite membranes include dihydroxy or polyhydroxy compounds reacted with aliphatic, alkylaromatic or aromatic diisocyanates or polyisocyanates and low molecular weight chain extenders such as diamines, polyamines or aminoalcohols. For example, a molecular weight of 500-
Manufactured from a polyurea / urethane copolymer made from 5000 polyethers or polyesters.

The polyester component is made from an aliphatic or aromatic dicarboxylic acid and an aliphatic or aromatic dialcohol. Aliphatic dicarboxylic acids refer to substances having the general formula HOOCRCOOH, where R has 2 to 10 carbons (and can be a straight chain, branched chain or cyclic structure). Aromatic dicarboxylic acids have the general structure HOOCRCOOH, where R is:

[0014]

[Chemical 1]

[0015]

[Chemical 2]

(Wherein R ', R "and R"' are the same or
Can be different, H and C₁~ C _FiveHydrocarbon group or
 C₆H_Five, And a group consisting of combinations thereof,
And n is 0-4).
In the above formula, each R ′ or R ″ is itself H, C₁~ C_Fiveor
Is C₆H_FiveIt should be understood that a mixture of
It is

The dialcohol has a general structure HOROH [wherein R is
Is

[0018]

[Chemical 3]

[0019]

[Chemical 4]

(In the formula, n is 1 to 10, preferably 4 to 6)
And R'is H, C₁~ C_FiveOr C ₆H_FiveOr)

[0021]

[Chemical 5]

Where R ', R ", R"' and n are defined as for aromatic dicarboxylic acids. An example of a useful dialcohol is bisphenol A. Diisocyanates have the general structure:

[0023]

[Chemical 6]

Wherein R ', R "and R"' are the same or different and are selected from the group consisting of H, C ₁ -C ₅ and C ₆ H ₅ and mixtures thereof, n being 0-4. Aromatic diisocyanate having Aliphatic, cycloaliphatic, aromatic and araliphatic diisocyanates or polyisocyanates can also be used, thus resulting in the formation of aromatic or aliphatic polyurethanes, polyureas / urethanes or polyurethaneimides.

The diamine chain extender has the general formula H ₂ NRNH ₂
[In the formula, R is

[0026]

[Chemical 7]

Wherein n is 1-10, R'can be the same or different and is selected from the group consisting of H, C ₁ -C ₅ hydrocarbon groups and C ₆ H ₅ and mixtures thereof. Including aliphatic and aromatic moieties). formula:

[0028]

[Chemical 8]

(In the formula, R ', R "and R"' are the same or different, and H or Cl or C _{1 to} C ₅ or C ₆ H
₅ and a mixture thereof, and n is 0 to
Diamine chain extenders (in the range of 4) are also included. Examples of polyether polyols useful as polymer precursors in the present invention include polyethylene glycol (PEG) having a molecular weight in the range of about 250-4000,
Polypropylene glycol (PPG), polytrimethylene glycol, PEG / PPG random copolymer, and the like.

Aliphatic diisocyanates which can be used are hexamethylene diisocyanate (HDT), 1,6-diisocyanate-2,2,4,4-tetramethylhexane (TMDI), 1,4-cyclohexanyldiene. Isocyanate (CHDI), Isophorone diisocyanate (IP
DI), while useful alkylaromatic diisocyanates are toluene diisocyanates (TD
I) and vitrylene diisocyanate (TODI). Aromatic diisocyanates are exemplified by 4,4'-diisocyanate diphenylmethane (MDI). Polyisocyanate is a polymer MDI (PMD
I) and carbodiimide modified MDI.
Useful polyamines are polyethyleneimine, 2,2 ',
2 ″ -triaminotriethylamine, 4,4′-diamino-3,3′-dichloro-diphenylmethane (MOC
Illustrated by A). Useful amino alcohols are 6-
Illustrated by aminohexanol, 4-amino-phenol, 4-amino-4'-hydroxyl-diphenylmethane.

The above is provided as an example only. Those skilled in the art, with this teaching to them, will be able to produce polyurea / urethane copolymers with the combinations described herein with the desired properties and then cast them into membranes useful for the separation of aromatics from saturated compounds. The starting material of can be selected from many available materials. Polyurethane is produced using the above reactants and omitting the polyamine or amino alcohol chain extender.

Polyurethaneimides are prepared by endcapping a polyol selected from those mentioned above and a polyisocyanate selected from those mentioned above, while the aliphatic and cycloaliphatic di- and poly-isocyanates are It can also be a mixture of aliphatic, cycloaliphatic, aralkyl and aromatic polyisocyanates, so that it can then be used directly with a polyanhydride to give an imide, or with an amic acid group, condensed to an imide / Chain extension can be achieved by reaction with a cyclizable di- or poly-carboxylic acid. Polyurethane imide is a US patent
It is the subject of 4,929,358.

The polymer, preferably a polyurea / urethane copolymer, polyurethane, or polyurethane / imide, is prepared in a suitable dissolving solvent. Solvent (s) selected
Should be able to dissolve the polymer, preferably a polyurea / urethane copolymer, polyurethane or polyurethane / imide, and also be able to wet the hydrophobic support coating the polymer solution. The solvent (s) must have optimal wetting properties such that the solution wets the surface of the hydrophobic microporous support but does not penetrate into the pores. For example, solvent mixtures of dimethylformamide (high solvency) and acetone (low surface tension) can give complete penetration at high acetone concentrations, while non-wetting conditions occur at high dimethylformamide concentrations. Therefore, the optimum dimethylformamide / acetone solvent ratio is 10/90 and 9
It is between 0/10. The surface tension of the low surface tension solvent at 20 ° C should be less than 35 dynes / cm, preferably less than 30 dynes / cm, more preferably less than 25 dynes / cm. The surface tension of acetone at 20 ° C is 23.
Dyne / cm. Other examples of low surface tension solvents are toluene, heptane and hexane.

A solvent having a high dissolving power (good solvent) is confirmed by a high polar solubility parameter. 25 ° C of good solvent
The polar solubility parameter is 3 (cal / cc) ^1/2 or more,
5 (cal / cc) ^1/2 or more, more preferably 7 (cal)
/ Cc) ^1/2 or more. Dimethylformamide has a polar solubility parameter of 8.07 (cal / cc) ^1/2 . Other examples of good solvents are dimethyl sulfoxide and dimethyl acetamide.

The solvent used in the membrane manufacturing process is about 10/90 of the high-solvent solvent and the low surface tension solvent used.
90/10, preferably about 20/80 to 80/20, most preferably about 40/60 to 60/40 of the mixture. Preferably the solution not only uses a wetting solvent, but also the wetting surfactants present, such as crotyl alcohol or Zonyl FSN, DuPont.
nt) fluorosurfactant. Preferably less than 5% wettable surfactant should be used.

The film coating layer is thin, 0.1-10 μm,
Preferably, the polymer concentration in the solution should be in the range of about 10 wt% polymer and below to ensure that it is in the range of 0.5-5μ, preferably at low concentrations, 0.5. ~ 8 wt%, more preferably 0.5-5 wt% is used. The viscosity of a wetting solution of a polymer in a solvent is
It should be 5-100 cp, preferably 10-50 cp, more preferably 20-40 cp. The optimum solution viscosity can be obtained, for example, by adding a viscosity modifier, adjusting the polymer concentration / solvent composition, aging the solution, or a combination of these methods. Aging of the polymer solution surprisingly results in a composite membrane of high selectivity as compared to a thin layer composite membrane made with a polymer solution of the same composition, but not aged and having a viscosity within the desired range. The polymer solution is aged for at least 1 day, preferably at least 3 days, more preferably at least 7 days. Aging is carried out by leaving the polymer solution at room temperature in a non-reactive atmosphere. The use of temperatures above room temperature will reduce the aging time to achieve comparable viscosities.

The substrate coated with this aged polymer solution is a hydrophobic, microporous substrate such as Teflon or polypropylene. After depositing a layer of polymer solution on the hydrophobic microporous support, the excess solution is drained off and the remaining solvent portion is evaporated. Evaporation of the solvent can be done simply by quenching the solvent into the atmosphere, or evaporation of the solvent can be increased by the addition of heat and / or the application of a vacuum.

Thin-layer composite membranes are useful in the separation of aromatic compounds from saturated compounds in petroleum and chemical streams, and snake-cat
It has been found to be particularly useful in the separation of highly substituted aromatic compounds from saturated compounds such as those encountered in naphtha streams. Other flow intermediate cat naphtha streams a feed stream suitable for the separation of aromatics from saturated compounds, C ₅ -30
A light aromatics content stream boiling in the 0 ° F range (200-320 ° F), a light catalytic cycle oil boiling in the 400-650 ° F range, as well as benzene, toluene,
A stream in a chemical plant containing a recoverable amount of xylene (BTX) or other aromatic compound in combination with a saturated compound. Separation methods that can successfully use the membranes of the invention include perstraction and pervaporation.

Perstraction includes selective dissolution of certain components contained in the mixture into the membrane, diffusion of those components through the membrane, and removal of diffusive components from the downstream side of the membrane by use of a liquid sweep flow. . In the perstraction separation of aromatics from saturated compounds in petroleum or chemical streams (especially snake-cat naphtha streams), the aromatic molecules present in the feed stream are dependent on the membrane dissolution parameters and the aromatic species present in the feed stream. It dissolves in the membrane film due to its similarity to that of. The aromatic compound then permeates (diffuses) through the membrane and is washed away by the low aromatic content sweep liquid. This keeps the concentration of aromatics low on the permeate side of the membrane film and maintains the concentration gradient responsible for permeation of aromatics through the membrane.

The sweep liquid has a low aromatic compound content,
It does not itself reduce the concentration gradient. The sweep liquid is preferably a saturated hydrocarbon liquid with a boiling point that is much lower or much higher than the permeated aromatic compound. This is for example to facilitate separation by simple distillation. Thus, suitable sweep liquid include, for example, C ₃ -C ₆ saturated hydrocarbons and lubricating basestock (C ₁₅ ~C _20).

The perstraction method is preferably carried out at the most convenient temperature. The choice of pressure is not critical since the perstraction method is pressure independent and depends on the ability of the aromatic components in the feed to dissolve and move through the membrane under concentration driving force. Therefore, a convenient pressure can be used, the lower the better to avoid undesired compression if the membrane is supported on a porous backing or otherwise rupture the membrane.

If C ₃ or C ₄ feed liquids are used in the liquid state at 25 ° C. or higher, the pressure must be increased to keep them in the liquid phase. In contrast, pervaporation generally operates at a higher temperature than perstraction, and the vacuum on the permeate side evaporates the permeate from the surface of the membrane, maintaining a concentration gradient that drives the forces driving the separation process. As in perstraction, the aromatic molecules present in the feed dissolve into the membrane film, migrate through said film and reappear on the permeate side under the influence of the temperature gradient. Pervaporation separation of aromatics from saturated compounds can be carried out at a temperature of about 25 ° C. for separation of benzene from hexanes, but heavier aromatic / saturated mixtures such as heavier c
at least 80 ° C and above for separation of naphtha,
Preferably high temperatures of at least 100 ° C and above, more preferably 120 ° C and above should be used.
The maximum upper temperature limit is the temperature at which the membrane is physically damaged or delaminated. A vacuum of about 1/50 mmHg is drawn on the transmission side. The vacuum stream containing the permeate is cooled to condense the highly aromatic permeate. The condensation temperature should be below the permeate dew point at a given vacuum level.

The membrane can itself be in any convenient form using any convenient modular design. Thus, sheets of membrane material can be used in spiral wound or plate and frame permeation cell modules. Membrane tubes and hollow fibers can be used in a bundled construction, with a feed or sweep liquid (or vacuum) maintained in the interior space of the tube or fibers, with a complementary environment apparently maintained on the other side.

The invention will be better understood by reference to the following non-limiting examples, which are provided by way of illustration. Example 1 A solution containing a polyurea-urethane polymer is prepared as follows. Polyethylene adipate (MW = 2,000) 4.
56 g (0.002828 mol), 500 MW polyethylene adipate 2.66 g (0.00532 mol) and 4,4 '
-Diphenylmethane diisocyanate 3.81 g (0.01
52 mol), 250 ml with a stirrer and drying tube
Add to flask. The temperature is raised to 90 ° C. and kept under stirring for 2 hours to form the isocyanate terminated capped prepolymer. 20 g of dimethylformamide are added to this prepolymer and the mixture is stirred until clear. 1.5 g of 4,4'-diamino-diphenylmethane (0.
0076 mol) is dissolved in 10 g of dimethylformamide and then added as chain extender to the prepolymer solution. This mixture was then allowed to react for 20 minutes at room temperature (about 22 ° C). The viscosity of the solution was about 100 cp. Films were cast on glass using a 5 mil casting knife and then dried in an oven at 90 ° C for 2 hours. This method is used as a control for thin layer composites (TFC).
This produced a micron dense film. Example 2 A polymer solution was prepared according to Example 1 and diluted to 5 wt% so that the solution contained a 60/40 wt% blend of dimethylformamide / acetone. The solution was left at room temperature for 7 days. The viscosity of the aged solution was 35 cp. After this time, 1 wt% Zonyl FSN (DuPont) fluorosurfactant was added to the aged solution (note: fluorosurfactant can also be added before aging). Microporous Teflon membrane with nominal 0.1 micron pores [Desalination Systems
K-150) from MS Inc.) was washcoated with the polymer solution. Immediately after washcoating was completed, the coating was dried with a hot air gun. This method resulted in composite membranes with a 3-4 micron thick polyurea / urethane dense phase. Thin coatings can be obtained by reducing the polymer concentration in solution, while thick coatings are obtained at high polymer concentrations.

Table 1 (HCN feed: 52 vol% arom, pervaporation @ 140 ° C / 5 to 10 mbar, <5 LV% yield) Membrane Example 1 Example 2 type dense film TFC coating thickness (μ) 21 3 Permeate quality RI @ 20 ℃ 1.5004 1.5000 Arom,% by volume (1) 86.1 85.7 Permeate flux, kg / m ² -d 40.9 270.0 ───────────────────── ───────────── (1) FIA Analysis (Fluorescent Labeling Analysis, ASTM D131
R developed for specific HCN feeds using 9)
Aromatic compound concentration based on I correlation (Arom = 807.99 × RI-1126.24).

The data in Table 1 show a more than six-fold increase in the flux performance of the thin layer composite over the dense film. Clearly this represents a significant improvement. Example 3 A thin layer composite was prepared from the same solution as in Example 2, but the solution was only aged for 3 days. The solution had a viscosity of only 3 cp.

Table 2 (HCN feed: 52 vol% arom, pervaporation @ 140 ° C / 5-10 mbar, <5 LV% yield) Run M-229R M-228 Membrane Example 2 Example 3 Type TFC TFC Solution Aged , Day 7 3 Coating thickness (μ) 3 1 Permeate quality RI @ 20 ℃ 1.5000 1.4713 Arom, Volume% (1) 85.7 52.0 Permeate flux, kg / m ² -d 270.0> 2000 ──────── ────────────────────────── (1) Aromatic Compound Concentration Based on RI Correlation Developed for Specific HCN Feed Using FIA Analysis (Arom = 807.99 x RI-1126.24).

The data in Table 2 clearly show that aging of the solution improves membrane performance. Example 4 A thin layer composite was prepared as in Example 2 but washcoated with a nylon microporous support (0.1 micron) (same aged solution). Table 3 (HCN feed: 52 vol% arom, pervaporation @ 140 ° C / 5-10 mbar, <5 LV% yield) Run M-229R M-228 Membrane Example 2 Example 4 Type TFC TFC support 0.1 μ Teflon 0.1 μNylon Permeate quality RI @ 20 ℃ 1.5000 1.4953 Arom, volume% (1) 85.7 81.8 Permeate flux, kg / m ² -d 270.0 87.0 ────────────────── ────────────────── (1) Aromatic compound concentration based on RI correlation (Arom = 807.99 × RI-1126.24) developed for a specific HCN feed using FIA analysis. ).

The data in Table 3 clearly show that the use of a high surface tension hydrophilic support such as nylon produces a low flux membrane. The polymer solution penetrated into nylon. Example 5 A solution was prepared as in Example 2, but the polymer solvent was 100% dimethylformamide (DMF) instead of the DMF / acetone 60/40 blend. This solution used 1 wt% Zonyl FSN (DuPont) fluorosurfactant but did not coat the 0.1 micron Teflon support, resulting in an incomplete membrane layer. As a result of poor coverage of the solutions, these membranes showed high flux and aromatic / saturated non-separation. Example 6 A solution containing a polyurea-urethane polymer is prepared as follows. Polyethylene adipate (MW = 2000) 1
0.6 g (0.00532 mol), 500 MW polyethylene adipate 2.66 g (0.00532 mol) and 4,4-
Diphenyl methane diisocyanate 5.33 g (0.212
8 mol) is added to a 250 ml flask equipped with a stirrer and drying tube. Raise the temperature to 90 ° C and stir 2 below
Hold for time to form isocyanate end-capped prepolymer. 20 g of dimethylformamide are added to this prepolymer and the mixture is stirred until clear. 4.2 g of 4,4'-diamino-diphenylmethane (0.
(02128 mol) is dissolved in 2 g of dimethylformamide and then added as chain extender to the prepolymer solution. The mixture is then allowed to react for 20 minutes at room temperature (about 20 ° C). The polymer solution is then diluted with dimethylformamide to 10% by weight. The viscosity of the solution is about 75 cp. 1% by weight of Zonyl FSN fluorosurfactant (DuPont) is added and the solution is washcoated onto a 0.1 micron porous Teflon membrane sample (K-150 from Desalination Systems). Although having a viscosity in the desired range, this solution does not wet the Teflon well so that after drying large cracks are present in the polymer coating. Example 7 A polymer solution is prepared as in Example 1 and then diluted to 10% by weight in a 50/50 dimethylformamide / acetone solvent mixture. The viscosity of the solution was about 75 cp. This solution was used to washcoat 0.1 micron porous Teflon. The solution initially wets the Teflon, but as the acetone evaporates, the residual solution beaded on the surface, producing a discontinuous polymer layer. Example 8 1% by weight of Zonyl FSN fluorosurfactant (DuPont) was added to a solution prepared as in Example 7. This solution was used to coat 0.1 micron porous Teflon. The solution wets the Teflon and after drying produced a continuous dense layer. No aging was necessary as the viscosity was already about 75 cp. The coating thickness after drying was 7μ.

As shown in Table 4, a continuous dense layer was required to achieve separation (ie the membrane of Example 8). Table 4 shows that a continuous dense layer can be formed with a polymer solution in dimethylformamide / acetone solvent mixture and Zonyl FSN fluorosurfactant. These examples are combined with Example 3 to ensure that the polymer solution must have a viscosity within the above range, and that low surface tension solvents such as acetone and fluorosurfactants are used to obtain a thinner continuous dense separation barrier. For example, it indicates that Zonyl FSN is required.

Table 4 Effect of solvent mixture and fluorosurfactant on wetting (model feed; 50% aromatics, perstraction @ 80 ° C, <5LV% yield) Membrane 6 7 8 solvent DMF DMF / acetone DMF / acetone zonyl FSN, weight % 10 1 Coating integrity Discontinuous Discontinuous Continuous permeate Aromatic compound 50 50 86 ─────────────────────────────── ─────

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Burned Alfresz Koenitz Tour             Canada Ontario N 7S 4B             3 Clearwater Ascott Sir             Curu 1368

Claims (7)

[Claims] 1. A wetting solution wets the surface of a hydrophobic microporous support but does not penetrate into the pores, at 5 ° C at 5 ° C.
A low surface tension solvent having a viscosity in the range of 100 cp, wherein the polymer in the solvent solution comprises 10% or less polymer in the solvent, said solvent having a surface tension of less than 35 dynes / cm at 20 ° C .; 3 (cal / cc) ^{1/2 at} 25 ℃
Wettability of the polymer in a solvent comprising a mixture in a low surface tension solvent / high solvent solvent ratio of 10/90 to 90/10 with a high solvent solvent having a high polar solubility parameter of less than and further comprising a surfactant. The solution is washcoated onto the hydrophobic support, the excess solution is drained, and the solution is allowed to evaporate, resulting in a thickness of approximately approx.
A method of manufacturing a thin film composite (TFC) membrane comprising a thin dense selective polymer film of 0.1-10 μm. 2. A thin, dense, selective polymer film of 0.
The method according to claim 1, which has a thickness of 5 to 5.0 μ. 3. The method according to claim 1 or 2, further comprising the step of aging the polymer solution for at least a period of one day before applying the polymer solution as a washcoat to the hydrophobic support. 4. A low surface tension / high solvent power solvent ratio of 20/8.
The method according to claim 1, 2 or 3, which is in the range of 0 to 80/20. 5. The method according to claim 1, 2, 3 or 4, wherein the hydrophobic support is Teflon or polypropylene. 6. The surface active agent is crotyl alcohol or fluorosurfactant, 1, 2, 3, 4.
Or the method according to 5. 7. The polymer in the polymer solution is polyurea /
The method according to claim 1, 2, 3, 4, 5 or 6, which is urethane, polyurethane or polyurethane imide.