CA1288560C - Substituted aliphatic polyamide porous membranes - Google Patents
Substituted aliphatic polyamide porous membranesInfo
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- CA1288560C CA1288560C CA000507895A CA507895A CA1288560C CA 1288560 C CA1288560 C CA 1288560C CA 000507895 A CA000507895 A CA 000507895A CA 507895 A CA507895 A CA 507895A CA 1288560 C CA1288560 C CA 1288560C
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- acid halide
- crystalline
- acid
- crystalline portions
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Abstract
ABSTRACT
Polymeric porous membranes comprising aliphatic polyamide membrane matrices having both relatively non-crystalline and relatively crystalline portions are described.
The method of preparing the porous membranes includes dissolution of an aliphatic thermoplastic polyamide (having crystalline and non-crystalline portions) into an acidic hydrolytic solvent such that the crystalline portions form a colloidal dispersion which is further formed into a film. The non-crystalline portions are precipitated in the film to form a porous membrane matrix which is reacted with an acid halide of basicity above one to provide acid radicals within the membrane. The acid halide may be derived from an aromatic carboxylic acid or an aromatic derivative of a chlorosilane. The substituted aliphatic polyamide porous membranes lend themselves to the preparation of chemical derivatives of the membrane which are not readily available by aqueous synthesis and to increased density of derivatives which otherwise may be prepared in water.
Polymeric porous membranes comprising aliphatic polyamide membrane matrices having both relatively non-crystalline and relatively crystalline portions are described.
The method of preparing the porous membranes includes dissolution of an aliphatic thermoplastic polyamide (having crystalline and non-crystalline portions) into an acidic hydrolytic solvent such that the crystalline portions form a colloidal dispersion which is further formed into a film. The non-crystalline portions are precipitated in the film to form a porous membrane matrix which is reacted with an acid halide of basicity above one to provide acid radicals within the membrane. The acid halide may be derived from an aromatic carboxylic acid or an aromatic derivative of a chlorosilane. The substituted aliphatic polyamide porous membranes lend themselves to the preparation of chemical derivatives of the membrane which are not readily available by aqueous synthesis and to increased density of derivatives which otherwise may be prepared in water.
Description
~L2~3~6a~
This invention relates to porous membranes made from aliphatic thermoplastic polyamide materials.
Synthetic polymeric membranes are used for separation of species by dialysis, electrodialysis, ultrafiltration, cross flow filtration, reverse osmosis and other similar techniques. One such synthetic polymeric membrane is disclosed in Australian Patent Specification No. 505,494 of Unisearch Limited.
The membrane forming technique disclosed in the ~nisearch Patent is broadly described as being the controlled uni-directional coagulation of the polymeric material from a solution which is coated onto a suitable inert surface. The first step in the process is the prieparation of a "dope" by dissolution of a polymer. This is said to be achieved by cutting the hydrogen bonds (which link the molecular chains of the polymer together) with a solvent. After a period of maturation, the dope is then cast onto a glass plate and coagulated by immersion in a coagulation bath which is capable of diluting the solvent and annealing the depolymerised polymer which has been used. According to the one example given in this specification, the Rdop~ consisted of a polyamide dissolved in a solvent which comprised hydrochloric acid and ethanol.
In another membrane forming technique, the liquid material out of which the membrane is cast is a colloidal suspension which gives a surface pore density that is significantly increased over the surface pore density of prior membranes.
, ', . ~ ',, - ', ' ' , . . :
~Z~3~356V
According to that technique, a thermoplastic material having both relatively non-crystalline and relatively crystalline portions i5 dissolved in a suitable solvent under conditions of temperature and time which cause the relatively non-crystalline portions of the thermoplastic material to dissolve whilst at least a portion of the relatively crystalline portion does not dissolve but forms a colloidal dispersion in the solvent. The colloidal dispersion and solvent (i.e. the "dope") is then coated onto a surface as a film and thereafter precipitation of the dissolved thermoplastic portion is effected to form a porous membrane.
Such aliphatic polyamide membranes suffer from disadvantages which limit their commercial usefulness and applicability. For example, they exhibit dimensional instability when drying and may shrink by up to 7%0 Thus, it is essential that they be kept moist prior to and after use. Furthermore, it has not been possible to generate chemical derivatives of the membrane matrix which restricts the situations to which the membrane may be applied.
Another disadvantage is that such polyamide membranes are fundamentally unstable and eventually become brittle on storage. The instability has been carefully investigated by I.R. Susantor of the Faculty of Science, Universitas Andala~, Padang, Indonesia with his colleague Bjulia~ Their investigations were reported at tha ~Second A.S.E.A.N. Food Wàste Project Conference", Bangkok, Thailand 11982) and included the following comments regarding brittleness:
"To anneal a membrane, the thus prepared membrane (according to ~ustralian Patent ~o. 505,494 using Nylon 6 yarn) is immersed in water at a given temperature, known as the annealing temperature, T in degrees Kelvin. It is allowed to stay in the water a certain length of time, called the annealing time. For a given annealing temperature, there is a m~ximum annealing time, t~b) in minutes, beyond which further ann~aling makes the membrane brittle. Plotting lN l/t~b) versus l/T gives a straight line. From the slope of this line it can be concluded that becoming brittle on prolonged annealing is a pro~ess requiring an activation ener~y of approximately 10.4 kilocalories/mole. From the ma~nitude of this ~ctivation energy, which is of the order of van der Waals forces, the various polymer fragments are probably held together by rather strong van der Waals forces or hydrogen bond(s)."
We have confirmed that the brittleness is due to a recrystallization of water-solvated amorphous polyamide. In some cases (such as polyamide 6) brittleness occurs within 48 hours of immersion in distilled water (pH7) at 80C.
Colorimetric -NH2 end group analysis has shown that there is no significant hydrolysis of the amide groups during this time. As would be expected, the rate of embrittlement is catalysed by dilute acids teg: pH of 1.0) due to nitrogen protonation and subsequent solvation. This effect explains the apparently low a~id resistance of the polyamide membranes. However colorimetric determination of both -NH2 end groups and -COOH end groups has shown that the effect is due to crystallization rather than acid catalysed hydrolysis.
That most of the brittleness is due to physical effects rather than chemical decomposition or chemical solvation (at least for dilute acids) is shown by the extreme embrittlement caused on standing 5 minutes in absolute ethanol.
The problem of crystallization of the aliphatic polyamide material can be overcome by cro~s-linking portions of he polyamide through the rea~tion of a bis-aldehyde with the membrane matrix as is described in our Canadian Patent Application 507,896, filed April 29, 1986 "Cross Linked Porous Me~branes .
~ owever, the chemical derivatives of such cross-linked polyamide membranes are limited to those which can be prepared in water and thus those membranes can not be used to provilde derivatives which do not lend themselve~ to agueous syn~hesis su~h as the ester of ~-hydroxybenzaldehyde.
Furthermore, the density of derivatives prepared in water " , , ' ' ", "' '. .. ' :
.
' ' ' :, ' ' ' . "' , ' , , ' . ,' ' ~81~:i61) may not be as large as desired. For example, the up-take of resorcinol in the glutaraldehyde ~ro~s-l inked membrane of example 2 of our above m~rltioned Cana~.an Patent Appli~:ztion was only 0.2~ ~f the dry weight of the membrane.
S It i~ an ob~ec~ of this invention 'co provide aliphatic polyamide porou~ membranes whi~h lend them~elve to the preparation of chemical d0rivatives which ~re not readily ~v~ilable by agyeou~ ~ynthe~i~ and to increa~ea density of derivatives which o~herwi~e may be prepare~ ln water.
According to the invention there i~ provided a polymeric porous membrane compri~inq a ~e~brane matrix made from an ~liph~ti~ thermoplastic polyamide ~aterial which has both relatively non-~ry~talline and relatively ~ry~talline portion~ ~oined together by relatively non-erystalline portions charac~eri3ed ln that at least some of the relatively non-erys~alline portions of ghe masnbrane are reacted with an a~id halide of ba~i~ity above one to provide within the membrane the following type of ~tructures:
X
--C~2 ~ CH2 --o where X i3 the a~id radical of the Acid halide of ba~icity abo~e one.
Preferably, th~ acid halide i~ deriYed from an ~romatic carboxylic a~id or an aromatic derivative of a chloro~ ne. ~ar~eu~rly preerred acid h~lld~ are terephth~loylchlori~e, isophthaloyl~hloride, ~nd the reaction product of an exc~s~ o a dichloro~ilane with a diph~nol.
The utll:ity of the acid halide tre~t~d polyamide membrane~ of l:he invention may be further improved by :i ~
, . .
.
reacting the free end of the terminal acid halide chain with a phenol of basicity above one (such as resorcinol) so that the free end of the acid halide becomes a phenol ester as follows:
~ { 3 R
where R is a substituent consisting of or containing at least one phenolic group.
Apart from resorcinol, the phenolic component may be a phenol derivative such as 2,2-bis(4-hydroxyphenyl)propane.
The resultant phenolic ester may be cross-linked by reaction with an aldehyde such as with glutaraldehyde. A
small amount of formaldehyde may be additionally used as the final aldehyde link particularly if free ends are further reacted with resorcinol. The original polyamide membrane thus becomes a block co-polymer of polyamide/aromatic polyester/phenol-aldehyde, all with little effect on the ori~inal porosity3 The terminal aromatic acid chloride intermediate membranes are particularly useful to foxm derivatives so that the membranes can react with bioloyical products such as -NH2 or -COOH terminated proteins. The resulting products may be used to isolate pure products by affinity c~romatography.
The invention also provides a method of preparing a porous membrane which comprises the steps of:-(i~ dissolving an aliphatic thermoplastic polyamide which has both relatively non-crystalline and relatively crystalline portions into an acidic, hydrolytic solvent under conditions of temperature and time which cause the relatively non~crystalline portions of the polyamide to dissolve while at least a part of the relatively crystalline portions of the ~: .
. , . . , ' . .
3S6~
polyamide do not dissolve, but, Eorm a colloidal dispersion in said solvent, (ii) forming said colloidal dispersion and an acidic hydrolytic solvent into a film and thereafter causing precipitation of at least part of the dissolved non-crystalline portions in the film to form a porous membrane matrix, and, (iii) reacting the membranes matrix with an acid halide of basicity above one to provide within the membrane the following types of structures:-CH2 N _ Cl CH2 -O
where X is the acid radical of the acid halide of basicity above one.
An acidic~ hydrolytic solvent (A) was prepared by mixing 225 ml of 6.67N hydrochloric acid with 15 ml of anhydrous ethanol. 90 grams of 50 dtex 17 filament polyamide 6 with lO9S twists per metre (which constitutes the thermoplastic starting material) was added to solvent (A) held at a temperature of 22C over a period of less than 15 minutes~
The dope of the poiyamide 6 and solvant (~) was then left to mature for 24 hours at a temperature of 22C during which the relatiYely non crystalline portions of the polyamide 6 dissolved as did no more than ~0~ oE the relatively crystalline portions of the polyamide 6 with the remaining relatively crystalline portion dispersing in the solvent.
After mat:uration, the dope was then spread as a film of about 120 micron thick on a clean glass plate. The coated plate was placed in a water bath where precipitation `:;
-: ~, ,, . . , :
:: , ~ '' ': ' '' ' ' ', , ' .
s~
of the dissolved portions of the polyamide was effected within 3 minutes. The membrane had a water permeation rate of 330L/M2.h at 100 kPa pressure. It shrank 7~ on drying and crystallized to a brittle sheet on heating at pE17 for 48 h~urs at 80C. It dissolved readily and completely in 7N
hydrochloric acid.
A sheet ~B) of the above membrane was dried at 60C to constant weight. A portion of the sheet tB) weighing 144 g was soaked in 1 L of petroleum spirit containing 20 g of isophthaloylchloride as the acid halide and S0 g of powdered potassium carbonate for 20 hours at 22C. Three independent analyses (chloride ion formed, weight increase of the sheet and loss from the petroleum spirit) showed that 18 g to 19 g of isophthaloylchloride had reacted. This ~heet (C) was washed with petroleum spirit and dried at 60C in dry aix.
A 35 g portion of membrane (C) was reacted with 0.lM
sodium carbonate for 15 minutes and 60C giving copious carbon dioxide and chloride ion. The membrane was then washed with water and gave a water permeation rate at 100 kPa pressure of 313L/M~h. After soaking in 2N hydrochloric acid and washing the rate was 303 L/M2h and the membrane - stained blue with methylene blue showing abundant free carboxylic acid groups.
The rest of the sheet - membrane (C) - was reacted with 2L of aqueous solution containing 20 g resorcinol at p~ 9.0 with sodium carbonate to become membrane (D). Analysis showed the up-take of 5.6 g of resorcinol. The membrane (D) was washed and showed a water permeation rate of 150L/M2h at 100 kPa pressure. Membrane (D) was much more resistant than the original membrane to 5N hydrochloric acid. A portion of membrane (D) was stained deep orange by a solution of p-nitro-benzenediazonium tetrafluoroborate showing the presence of large amounts of resorcinol derivative.
An 88 g portion of membrane ~D) was heated for 4 days at 60C with a 2.2~ w/v solution of glutaraldehyde at pH 4.0 and then washed to give a membrane (E). Mem~rane (E) showed a 2.5% change in length when dried, then wetted. The ~8 permeation rate was now 272L/M2h. The ra~istance to acid was improved. The presence of free -C~0 group~ ~a~ proven by t~e inten~e violet formed with fuch~in - NaHS03 reagent. The latter te~t i8 due to the combination of the -CH0 group~ in mrmbrane (E) with Na~S03 to form a hydroxysulphonic acid derivative. A further indication of copious -CH0 group~ wa~ the up-take of 2,4 -dinitrophenylhydrazine from 3N hydrochlorie acid to form the deep yellow 2,4 - dinitrophenyl-hydrazone.
1~ Each 100 g of dry original membran~ had ~equentially ta~cen up 12.6 g isophthaloylchloride, ~4 g r~sorcinol aDd 4 . 0 g glutaraldehyde.
13XA~PLE 2 The procedures of EXAMPL~ 1 were ~epe~ted using terephthaloylchloride ~8 the acid halide instead of i~ophthaloylchloride and gav~ very ~imllar result3 e~cept that at that ~tage (C) in ~XAMPI.l~ 1 th~ mambrane was relatively ~tif f .
A solution of 2.97 g of 2,2 - b~s(4-hydro~cyphenyl) propane in 10 ml of d~ pyridine was poured onto 3 . 22 g of stirred dimethyldichlorosilane thereffl precipitating pyrid1ne hydrochloride as wa~te.
Th~ acia chlorid~ ~o ~orm~d wa~, in effec~, a ~ilicon analogua of an aromatic bis(acid chloride) a~ chemical con~iderations ~ugge~t that it had the following ~tructure:
~l~Ma2)~i-o-c6 ~4~ctMe)2 C6~4 ~ 2 A port~on o~ the dry starting membrane (8) as in EX~MPLE 1 was added to the resultant solution and heated 1 hour at 60C. The resultant sheet was washad ~n pyridine, then ethanol, then methylenechlorlde and dried. The permaation rate of N/10 caustic soda at 100 kPa prsssure both before and after treatment wa 169L/MZh. One unexpected difference was that ' .
. ~ , ~ ;" . .
' ' 1~9~1~356~
the treatment doubled tannic acid ad~orption. The explanation is that the treatment conferred silicic acid derivative end-group8 on the membrane.
. . ., ~, ,1 ~ .
, .' '-: ., ' ' ' ~
.
This invention relates to porous membranes made from aliphatic thermoplastic polyamide materials.
Synthetic polymeric membranes are used for separation of species by dialysis, electrodialysis, ultrafiltration, cross flow filtration, reverse osmosis and other similar techniques. One such synthetic polymeric membrane is disclosed in Australian Patent Specification No. 505,494 of Unisearch Limited.
The membrane forming technique disclosed in the ~nisearch Patent is broadly described as being the controlled uni-directional coagulation of the polymeric material from a solution which is coated onto a suitable inert surface. The first step in the process is the prieparation of a "dope" by dissolution of a polymer. This is said to be achieved by cutting the hydrogen bonds (which link the molecular chains of the polymer together) with a solvent. After a period of maturation, the dope is then cast onto a glass plate and coagulated by immersion in a coagulation bath which is capable of diluting the solvent and annealing the depolymerised polymer which has been used. According to the one example given in this specification, the Rdop~ consisted of a polyamide dissolved in a solvent which comprised hydrochloric acid and ethanol.
In another membrane forming technique, the liquid material out of which the membrane is cast is a colloidal suspension which gives a surface pore density that is significantly increased over the surface pore density of prior membranes.
, ', . ~ ',, - ', ' ' , . . :
~Z~3~356V
According to that technique, a thermoplastic material having both relatively non-crystalline and relatively crystalline portions i5 dissolved in a suitable solvent under conditions of temperature and time which cause the relatively non-crystalline portions of the thermoplastic material to dissolve whilst at least a portion of the relatively crystalline portion does not dissolve but forms a colloidal dispersion in the solvent. The colloidal dispersion and solvent (i.e. the "dope") is then coated onto a surface as a film and thereafter precipitation of the dissolved thermoplastic portion is effected to form a porous membrane.
Such aliphatic polyamide membranes suffer from disadvantages which limit their commercial usefulness and applicability. For example, they exhibit dimensional instability when drying and may shrink by up to 7%0 Thus, it is essential that they be kept moist prior to and after use. Furthermore, it has not been possible to generate chemical derivatives of the membrane matrix which restricts the situations to which the membrane may be applied.
Another disadvantage is that such polyamide membranes are fundamentally unstable and eventually become brittle on storage. The instability has been carefully investigated by I.R. Susantor of the Faculty of Science, Universitas Andala~, Padang, Indonesia with his colleague Bjulia~ Their investigations were reported at tha ~Second A.S.E.A.N. Food Wàste Project Conference", Bangkok, Thailand 11982) and included the following comments regarding brittleness:
"To anneal a membrane, the thus prepared membrane (according to ~ustralian Patent ~o. 505,494 using Nylon 6 yarn) is immersed in water at a given temperature, known as the annealing temperature, T in degrees Kelvin. It is allowed to stay in the water a certain length of time, called the annealing time. For a given annealing temperature, there is a m~ximum annealing time, t~b) in minutes, beyond which further ann~aling makes the membrane brittle. Plotting lN l/t~b) versus l/T gives a straight line. From the slope of this line it can be concluded that becoming brittle on prolonged annealing is a pro~ess requiring an activation ener~y of approximately 10.4 kilocalories/mole. From the ma~nitude of this ~ctivation energy, which is of the order of van der Waals forces, the various polymer fragments are probably held together by rather strong van der Waals forces or hydrogen bond(s)."
We have confirmed that the brittleness is due to a recrystallization of water-solvated amorphous polyamide. In some cases (such as polyamide 6) brittleness occurs within 48 hours of immersion in distilled water (pH7) at 80C.
Colorimetric -NH2 end group analysis has shown that there is no significant hydrolysis of the amide groups during this time. As would be expected, the rate of embrittlement is catalysed by dilute acids teg: pH of 1.0) due to nitrogen protonation and subsequent solvation. This effect explains the apparently low a~id resistance of the polyamide membranes. However colorimetric determination of both -NH2 end groups and -COOH end groups has shown that the effect is due to crystallization rather than acid catalysed hydrolysis.
That most of the brittleness is due to physical effects rather than chemical decomposition or chemical solvation (at least for dilute acids) is shown by the extreme embrittlement caused on standing 5 minutes in absolute ethanol.
The problem of crystallization of the aliphatic polyamide material can be overcome by cro~s-linking portions of he polyamide through the rea~tion of a bis-aldehyde with the membrane matrix as is described in our Canadian Patent Application 507,896, filed April 29, 1986 "Cross Linked Porous Me~branes .
~ owever, the chemical derivatives of such cross-linked polyamide membranes are limited to those which can be prepared in water and thus those membranes can not be used to provilde derivatives which do not lend themselve~ to agueous syn~hesis su~h as the ester of ~-hydroxybenzaldehyde.
Furthermore, the density of derivatives prepared in water " , , ' ' ", "' '. .. ' :
.
' ' ' :, ' ' ' . "' , ' , , ' . ,' ' ~81~:i61) may not be as large as desired. For example, the up-take of resorcinol in the glutaraldehyde ~ro~s-l inked membrane of example 2 of our above m~rltioned Cana~.an Patent Appli~:ztion was only 0.2~ ~f the dry weight of the membrane.
S It i~ an ob~ec~ of this invention 'co provide aliphatic polyamide porou~ membranes whi~h lend them~elve to the preparation of chemical d0rivatives which ~re not readily ~v~ilable by agyeou~ ~ynthe~i~ and to increa~ea density of derivatives which o~herwi~e may be prepare~ ln water.
According to the invention there i~ provided a polymeric porous membrane compri~inq a ~e~brane matrix made from an ~liph~ti~ thermoplastic polyamide ~aterial which has both relatively non-~ry~talline and relatively ~ry~talline portion~ ~oined together by relatively non-erystalline portions charac~eri3ed ln that at least some of the relatively non-erys~alline portions of ghe masnbrane are reacted with an a~id halide of ba~i~ity above one to provide within the membrane the following type of ~tructures:
X
--C~2 ~ CH2 --o where X i3 the a~id radical of the Acid halide of ba~icity abo~e one.
Preferably, th~ acid halide i~ deriYed from an ~romatic carboxylic a~id or an aromatic derivative of a chloro~ ne. ~ar~eu~rly preerred acid h~lld~ are terephth~loylchlori~e, isophthaloyl~hloride, ~nd the reaction product of an exc~s~ o a dichloro~ilane with a diph~nol.
The utll:ity of the acid halide tre~t~d polyamide membrane~ of l:he invention may be further improved by :i ~
, . .
.
reacting the free end of the terminal acid halide chain with a phenol of basicity above one (such as resorcinol) so that the free end of the acid halide becomes a phenol ester as follows:
~ { 3 R
where R is a substituent consisting of or containing at least one phenolic group.
Apart from resorcinol, the phenolic component may be a phenol derivative such as 2,2-bis(4-hydroxyphenyl)propane.
The resultant phenolic ester may be cross-linked by reaction with an aldehyde such as with glutaraldehyde. A
small amount of formaldehyde may be additionally used as the final aldehyde link particularly if free ends are further reacted with resorcinol. The original polyamide membrane thus becomes a block co-polymer of polyamide/aromatic polyester/phenol-aldehyde, all with little effect on the ori~inal porosity3 The terminal aromatic acid chloride intermediate membranes are particularly useful to foxm derivatives so that the membranes can react with bioloyical products such as -NH2 or -COOH terminated proteins. The resulting products may be used to isolate pure products by affinity c~romatography.
The invention also provides a method of preparing a porous membrane which comprises the steps of:-(i~ dissolving an aliphatic thermoplastic polyamide which has both relatively non-crystalline and relatively crystalline portions into an acidic, hydrolytic solvent under conditions of temperature and time which cause the relatively non~crystalline portions of the polyamide to dissolve while at least a part of the relatively crystalline portions of the ~: .
. , . . , ' . .
3S6~
polyamide do not dissolve, but, Eorm a colloidal dispersion in said solvent, (ii) forming said colloidal dispersion and an acidic hydrolytic solvent into a film and thereafter causing precipitation of at least part of the dissolved non-crystalline portions in the film to form a porous membrane matrix, and, (iii) reacting the membranes matrix with an acid halide of basicity above one to provide within the membrane the following types of structures:-CH2 N _ Cl CH2 -O
where X is the acid radical of the acid halide of basicity above one.
An acidic~ hydrolytic solvent (A) was prepared by mixing 225 ml of 6.67N hydrochloric acid with 15 ml of anhydrous ethanol. 90 grams of 50 dtex 17 filament polyamide 6 with lO9S twists per metre (which constitutes the thermoplastic starting material) was added to solvent (A) held at a temperature of 22C over a period of less than 15 minutes~
The dope of the poiyamide 6 and solvant (~) was then left to mature for 24 hours at a temperature of 22C during which the relatiYely non crystalline portions of the polyamide 6 dissolved as did no more than ~0~ oE the relatively crystalline portions of the polyamide 6 with the remaining relatively crystalline portion dispersing in the solvent.
After mat:uration, the dope was then spread as a film of about 120 micron thick on a clean glass plate. The coated plate was placed in a water bath where precipitation `:;
-: ~, ,, . . , :
:: , ~ '' ': ' '' ' ' ', , ' .
s~
of the dissolved portions of the polyamide was effected within 3 minutes. The membrane had a water permeation rate of 330L/M2.h at 100 kPa pressure. It shrank 7~ on drying and crystallized to a brittle sheet on heating at pE17 for 48 h~urs at 80C. It dissolved readily and completely in 7N
hydrochloric acid.
A sheet ~B) of the above membrane was dried at 60C to constant weight. A portion of the sheet tB) weighing 144 g was soaked in 1 L of petroleum spirit containing 20 g of isophthaloylchloride as the acid halide and S0 g of powdered potassium carbonate for 20 hours at 22C. Three independent analyses (chloride ion formed, weight increase of the sheet and loss from the petroleum spirit) showed that 18 g to 19 g of isophthaloylchloride had reacted. This ~heet (C) was washed with petroleum spirit and dried at 60C in dry aix.
A 35 g portion of membrane (C) was reacted with 0.lM
sodium carbonate for 15 minutes and 60C giving copious carbon dioxide and chloride ion. The membrane was then washed with water and gave a water permeation rate at 100 kPa pressure of 313L/M~h. After soaking in 2N hydrochloric acid and washing the rate was 303 L/M2h and the membrane - stained blue with methylene blue showing abundant free carboxylic acid groups.
The rest of the sheet - membrane (C) - was reacted with 2L of aqueous solution containing 20 g resorcinol at p~ 9.0 with sodium carbonate to become membrane (D). Analysis showed the up-take of 5.6 g of resorcinol. The membrane (D) was washed and showed a water permeation rate of 150L/M2h at 100 kPa pressure. Membrane (D) was much more resistant than the original membrane to 5N hydrochloric acid. A portion of membrane (D) was stained deep orange by a solution of p-nitro-benzenediazonium tetrafluoroborate showing the presence of large amounts of resorcinol derivative.
An 88 g portion of membrane ~D) was heated for 4 days at 60C with a 2.2~ w/v solution of glutaraldehyde at pH 4.0 and then washed to give a membrane (E). Mem~rane (E) showed a 2.5% change in length when dried, then wetted. The ~8 permeation rate was now 272L/M2h. The ra~istance to acid was improved. The presence of free -C~0 group~ ~a~ proven by t~e inten~e violet formed with fuch~in - NaHS03 reagent. The latter te~t i8 due to the combination of the -CH0 group~ in mrmbrane (E) with Na~S03 to form a hydroxysulphonic acid derivative. A further indication of copious -CH0 group~ wa~ the up-take of 2,4 -dinitrophenylhydrazine from 3N hydrochlorie acid to form the deep yellow 2,4 - dinitrophenyl-hydrazone.
1~ Each 100 g of dry original membran~ had ~equentially ta~cen up 12.6 g isophthaloylchloride, ~4 g r~sorcinol aDd 4 . 0 g glutaraldehyde.
13XA~PLE 2 The procedures of EXAMPL~ 1 were ~epe~ted using terephthaloylchloride ~8 the acid halide instead of i~ophthaloylchloride and gav~ very ~imllar result3 e~cept that at that ~tage (C) in ~XAMPI.l~ 1 th~ mambrane was relatively ~tif f .
A solution of 2.97 g of 2,2 - b~s(4-hydro~cyphenyl) propane in 10 ml of d~ pyridine was poured onto 3 . 22 g of stirred dimethyldichlorosilane thereffl precipitating pyrid1ne hydrochloride as wa~te.
Th~ acia chlorid~ ~o ~orm~d wa~, in effec~, a ~ilicon analogua of an aromatic bis(acid chloride) a~ chemical con~iderations ~ugge~t that it had the following ~tructure:
~l~Ma2)~i-o-c6 ~4~ctMe)2 C6~4 ~ 2 A port~on o~ the dry starting membrane (8) as in EX~MPLE 1 was added to the resultant solution and heated 1 hour at 60C. The resultant sheet was washad ~n pyridine, then ethanol, then methylenechlorlde and dried. The permaation rate of N/10 caustic soda at 100 kPa prsssure both before and after treatment wa 169L/MZh. One unexpected difference was that ' .
. ~ , ~ ;" . .
' ' 1~9~1~356~
the treatment doubled tannic acid ad~orption. The explanation is that the treatment conferred silicic acid derivative end-group8 on the membrane.
. . ., ~, ,1 ~ .
, .' '-: ., ' ' ' ~
.
Claims (18)
1. A polymeric porous membrane comprising a membrane matrix made from an aliphatic polyamide material which has both relatively non-crystalline and relatively crystalline portions joined together by relatively non-crystalline portions characterised in that at least some of the relatively non-crystalline portions of the membrane have been reacted with an acid halide of basicity above one to provide within the membrane the following type of structures: --CH2-?-?CH2-where X is the acid radical of the acid halide of basicity above one.
2. A membrane according to claim 1 wherein the acid halide is derived from an aromatic carboxylic acid or an aromatic derivative of a chlorosilane.
3. A membrane according to claim 1 or claim 2 wherein the acid halide is either terephthaloylohloride, or isophthaloylchloride.
4. A membrane according to claim 1 or claim 2 wherein the acid halide is the reaction product of an excess of a dichlorosilane with a diphenol.
5. A membrane according to claim 1 wherein the free end of the terminal acid halide chain has been reacted with a phenol of basicity above one so that the free end of the acid halide becomes a phenol ester as follows:
where R is a substituent consisting of or containing at least one phenolic group.
where R is a substituent consisting of or containing at least one phenolic group.
6. A membrane according to claim 5 wherein the phenol is resorcinol.
7. A membrane according to claim 6 wherein the membrane has been crosslinked by reaction with an aldehyde.
8. A membrane according to claim 7 wherein the aldehyde is glutaraldehyde.
9. A membrane according to claim 8 modified in that formaldehyde has been used as an additional linking reagent.
10. A method of preparing a porous membrane comprising the steps of:
(i) dissolving an aliphatic thermoplastic polyamide which has both relatively non-crystalline and relatively crystalline portions into an acidic hydrolytic solvent under conditions of temperature and time which cause the relatively non-crystalline portions of the polyamide to dissolve while at least a part of the relatively crystalline portions of the polyamide do not dissolve, but, form a colloidal dispersion in said solvent, (ii) forming said colloidal dispersion into a film and thereafter causing precipitation of at least part of the dissolved non-crystalline portions in the film to form a porous membrane matrix, and, (iii) reacting the membranes matrix with an acid halide of basicity above one to provide within the membrane the following types of structures:
where X is the acid radical of the acid halide of basicity above one.
(i) dissolving an aliphatic thermoplastic polyamide which has both relatively non-crystalline and relatively crystalline portions into an acidic hydrolytic solvent under conditions of temperature and time which cause the relatively non-crystalline portions of the polyamide to dissolve while at least a part of the relatively crystalline portions of the polyamide do not dissolve, but, form a colloidal dispersion in said solvent, (ii) forming said colloidal dispersion into a film and thereafter causing precipitation of at least part of the dissolved non-crystalline portions in the film to form a porous membrane matrix, and, (iii) reacting the membranes matrix with an acid halide of basicity above one to provide within the membrane the following types of structures:
where X is the acid radical of the acid halide of basicity above one.
11. A method according to claim 10 wherein the acid halide is derived from an aromatic carboxylic acid or an aromatic derivative of a chlorosilane.
12. A method according to claim 10 wherein the acid halide is either terephthaloylchloride or isophthaloylchloride.
13. A method according to claim 10 wherein the acid halide is the reaction product of an excess of a dichlorosilane with a diphenol.
14. A method according to claim 10 wherein the free end of the terminal acid halide chain is further reacted with a phenol of basicity above one so that the free end of the acid halide becomes a phenol ester as follows:
where R is a substituent consisting of or containing at least one phenolic group.
where R is a substituent consisting of or containing at least one phenolic group.
15. A method according to claim 14 wherein the phenol is resorcinol.
16. A method according to claim 15 wherein the membrane is reacted with an aldehyde.
17. A method according to claim 16 wherein the aldehyde is glutaraldehyde.
18. A method according to claim 17 modified in that formaldehyde is used as an additional reagent.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000507895A CA1288560C (en) | 1983-10-18 | 1986-04-29 | Substituted aliphatic polyamide porous membranes |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPG190283 | 1983-10-18 | ||
| CA000507895A CA1288560C (en) | 1983-10-18 | 1986-04-29 | Substituted aliphatic polyamide porous membranes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1288560C true CA1288560C (en) | 1991-09-10 |
Family
ID=25642722
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000507895A Expired - Fee Related CA1288560C (en) | 1983-10-18 | 1986-04-29 | Substituted aliphatic polyamide porous membranes |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1288560C (en) |
-
1986
- 1986-04-29 CA CA000507895A patent/CA1288560C/en not_active Expired - Fee Related
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