Crosslinked organic polyamide or polyhydrazine permselective polymeric membranes

Claim 1

A permselective polymeric membrane consisting essentially of a synthetic organic polyamide or polyhydrazide represented by the following formula: ##STR8## wherein (a) a, b, c, d, e, f, g, h and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 ,R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic, and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO--, --CO-- and --CONHNHCO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 or R 6 , (d) X 2 is a group selected from the class consisting of --CONH--, and --CO--, and --CONHNHCO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 or R 6 , (e) Y is a group selected from the class consisting of CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating units being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio; ##EQU3## said polyamide or polyhydrazide being ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 8

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, and rinsing the protomembrane with a rinse medium containing a salt of metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals, with or without a neutralization reagent, said dope comprising a synthetic organic polyamide or polyhydrazide, represented by the following formula: ##STR9## wherein (a) a, b, c, d, e, f, g, h, and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic, and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO--, --CO--, and --CONHNHCO, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (d) X 2 is a group selected from the class consisting of --CONH--, --CO--, and --CONHNHCO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU4## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 9

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, and rinsing the protomembrane with a rinse medium containing a salt of metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals, with or without a neutralization reagent, said dope comprising a synthetic organic polyamide or polyhydrazide, represented by the following formula: ##STR9## wherein (a) a, b, c, d, e, f, g, h, and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic, and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO--, --CO--, and --CONHNHCO, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (d) X 2 is a group selected from the class consisting of --CONH--, --CO--, and --CONHNHCO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU4## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 11

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20% to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium containing a neutralization reagent and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals, said dope comprising a synthetic organic polyamide or polyhydrazide represented by the following formula: ##STR10## wherein (a) a, b, c, d, e, f, g, h and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO--, --CO-- and --CONHNHCO--, wherein in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 . (d) X 2 is a group selected from the class consisting of --COHN--, --CO--, and --CONHNHOC--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 . (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H. (f) The polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 , and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer replating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU5## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 12

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20% to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium containing a neutralization reagent and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals, said dope comprising a synthetic organic polyamide or polyhydrazide represented by the following formula: ##STR10## wherein (a) a, b, c, d, e, f, g, h and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO--, --CO-- and --CONHNHCO--, wherein in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 . (d) X 2 is a group selected from the class consisting of --COHN--, --CO--, and --CONHNHOC--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 . (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H. (f) The polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 , and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer replating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU5## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 14

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20% to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium, and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals with or without a neutralization reagent, said dope comprising a synthetic organic polyamide or polyhydrazide represented by the following formula: ##STR11## wherein (a) a, b, c, d, e, f, g, h and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > (b) R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO--, --CO--, and --CONHNHCO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 ,

Claim 15

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20% to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium, and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals with or without a neutralization reagent, said dope comprising a synthetic organic polyamide or polyhydrazide represented by the following formula: ##STR11## wherein (a) a, b, c, d, e, f, g, h and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > (b) R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO--, --CO--, and --CONHNHCO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 ,

Claim 27

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, and rinsing the protomembrane with a rinse medium containing a salt of metal selected from the class consisting of alkaline earth metals, with or without a neutralization reagent, said dope comprising a synthetic organic polyamide, represented by the following formula: ##STR13## wherein (a) a, b, c, d, e, f, g, h, and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic, and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (d) X 2 is a group selected from the class consisting of --CONH-- and --CO--, wherein in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU8## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 28

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, and rinsing the protomembrane with a rinse medium containing a salt of metal selected from the class consisting of alkaline earth metals, with or without a neutralization reagent, said dope comprising a synthetic organic polyamide, represented by the following formula: ##STR13## wherein (a) a, b, c, d, e, f, g, h, and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic, and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (d) X 2 is a group selected from the class consisting of --CONH-- and --CO--, wherein in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU8## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 29

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium containing a neutralization reagent and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals said dope comprising a synthetic organic polyamide represented by the following forumla: ##STR14## wherein (a) a, b, c, d, e, f, g, h, and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in their heterocycle in R 1 , R 5 , or R 6 , (d) X 2 is a group selected from the class consisting of --CONH-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 , and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 where P.I. represents the following ratio: ##EQU9## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 30

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium containing a neutralization reagent and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals said dope comprising a synthetic organic polyamide represented by the following forumla: ##STR14## wherein (a) a, b, c, d, e, f, g, h, and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in their heterocycle in R 1 , R 5 , or R 6 , (d) X 2 is a group selected from the class consisting of --CONH-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 , or R 6 , (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 , and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating unit being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 where P.I. represents the following ratio: ##EQU9## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 31

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium, and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals with or without a neutralization reagent, said dope comprising a synthetic organic polyamide, represented by the following formula: ##STR15## wherein (a) a, b, c, d, e, f, g, h and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO-- and --CO--, wherein in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 or R 6 , (d) X 2 is a group selected from the class consisting of --CONH-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 or R 6 ; (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating end being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU10## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.

Claim 32

A method of preparing a permselective polymeric membrane which comprises the steps of casting a dope on a supporting material, removing about 20 to 80% of the solvent contained in the dope to obtain a protomembrane, rinsing the protomembrane with a rinse medium, and treating the rinsed membrane with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals with or without a neutralization reagent, said dope comprising a synthetic organic polyamide, represented by the following formula: ##STR15## wherein (a) a, b, c, d, e, f, g, h and i represent the molar fraction (%) of each component, each being larger than zero or equal to zero, and satisfying the following relations: a + b + c + d + e + f + g + h + i = 100 a + b + c + d + e + f + g + h > 0 (b) R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members selected from the group consisting of carbocyclic aromatic, heterocyclic and alicyclic groups having 4 to 30 carbon atoms, (c) X 1 is a group selected from the class consisting of --NHCO-- and --CO--, wherein in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 or R 6 , (d) X 2 is a group selected from the class consisting of --CONH-- and --CO--, wherein, in the case of --CO--, it is bonded directly to a nitrogen atom in the heterocycle in R 1 , R 5 or R 6 ; (e) Y is a group selected from the class consisting of --CO 2 H and --SO 3 H, and (f) the polymer has a molecular weight high enough to provide a film, a solvent for the polymer, and an inorganic salt selected from the class consisting of LiCl, LiBr, LiNO 3 , CaCl 2 and MgCl 2 , the total number of cross-linked groups for divalent metal ions in the polymer repeating end being in the range of 7.0 × 10 -5 - 7.0 × 10 -3 , the concentration of said ionic groups in the polymer, expressed as P.I., is in the range of 3.5 × 10 -4 - 1.4 × 10 -2 , where P.I. represents the following ratio: ##EQU10## whereby said polyamide or polyhydrazide is ionically cross-linked with a salt of a metal selected from the class consisting of alkaline earth metals, transition metals, aluminum group metals and lead group metals.