P a t e n t s

In one example of the cell 's opera t ion , the feed to the midd le c o m p a r t m e n t of the cell c o n t a i n e d 32 wt.% s o d i u m s u l p h a t e to which h a d b e e n added .05 wt. % a m m o n i a . The a n o d e compar t - m e n t was p r i m e d wi th 2.5 wt. % s u l p h u r i c acid, the ca thode c o m p a r t m e n t wi th 2.5 wt % s o d i u m hydrox ide so lu t ion . C u r r e n t d e n s i t y was 3 k A / m 2 a n d the ope ra t ing t e m p e r a t u r e was 82--85°C. The ca thode a n d a n o d e c o m p a r t m e n t s were kep t u n d e r par t ia l v a c u u m to al low h e a t f rom the ce11's ope ra t i on to c o n c e n t r a t e the acid a n d a lka l i so lu t ions . The f inal c o n c e n t r a t i o n of the ac id a n d alkal i var ied acco rd ing to the c u r r e n t eff iciency of the ceLl.

Patent number: EP 449071 Date: 2 October 1991 Inventors: W. H a b e r m a n n , W. Bochn i t sch , J. F r i t z m a n n , P. H a m m e s , T. Proll, W. Weisbrodt Applicant: BASF AG

Cyclodextrin polymer membrane syntheses This se t of four p a t e n t s desc r ibes different m e t h o d s of f unc t i ona l - izing cyclodextr in , wh ich pos se s se s the a d v a n t a g e o u s proper t ies for s e p a r a t i o n or d ia lys is m e m b r a n e s of be ing bo th hydrophi l ic in cha rac t e r a n d phys ica l ly s e l f - suppor t i ng in m e m b r a n e o u s form. Each p a t e n t gives a compound- spec i f i c example.

In JP 3 2 2 1 5 0 2 , be ta - cyclodextr in is first reac ted wi th a n allyl ether, specifically al lyl-3- ch lo ro-2-hydroxypropy l ether, to give th is c o m p o u n d

CH2=CH

I CH2

I O CH2 I CH-OH

I C H 2 - - O - - - [ - ~

where ~ r e p r e s e n t s the cyclodextrin. This is copoly- mer ized with vinyl acetate , t h e n saponif ied wi th a m e t h a n o l / s o d i u m hydroxide mix ture . A cyclodextrin polymer of 50 0 0 0 - 60 000 molecu la r weight is ob ta ined . The reac t ion c a n also be carr ied ou t with a s imi lar e ther to give

CH3

I CH2= C

I C=O

I O

I CH2 I CH-OH

1 C H 2 - O - - [ - ~

The c o m p o u n d ob t a ined by reac t ing polyvinyl alcohol (molecular weight I0 000) wi th a ca rbony l c o m p o u n d , specifically 3 -p ropr iona ldehyde is the func t iona l i z ing agen t in JP 3221503 . It is reac ted with cyclodextr in in the p ropor t ions of 1 : 10-1 :100 (PVA:cyclodextrin).

A s imi lar s p a n of ra t ios is avai lable for the final reac t ion in JP 3221504 , which covers the reac t ion of polya l ly lamine hydrochlor ide

-(CH2-CH)n- l

CH2 I NH2

HC1

of 10 000 molecu la r weight with the cyclodextr in derivative mono-6-deoxy- 6- iodo-beta- cyclodextrin.

Final ly, in JP 3221505 a n a m i n e or carboxylic acid derivative, specifically d i amino beta-cyclodextr in , is reac ted with adipic acid dichloride, ph tha l i c acid chloride or hexame thy l ene - d i a m i n e in a 1 : 1 mola r rat io so t ha t each a m i n o or carboxyl group on the cyclodextr in is func t iona l i sed .

Patent numbers: JP 3 2 2 1 5 0 2 - 3 2 2 1 5 0 5 Date: 30 Sep tember 1991 Inventor: M. Yoshinaga Applicant: T o p p a n Pr in t ing Co. Ltd

Hydrophilic polypropylene- based membranes The process allows the proper t ies of a conven t iona l m i c r opo rous polypropylene m e m b r a n e to be modified by the u s e of a s imple po lymer iza t ion process . The modif ied m e m b r a n e is s tab le to large p r e s s u r e g rad ien t s a n d to v igorous agi ta t ion, a n d is pa r t i cu la r ly s u i t e d to u se in b io reac tors a n d a s the m e m b r a n e sepa ra to r in rechargeab le bat ter ies .

The base m e m b r a n e mate r i a l h a s a n average t h i c k n e s s of 0 .25 ~m a n d pore d i m e n s i o n s of 0 .04 x 0.4 ~ma. It is soaked in a so lu t ion of a m o n o f u n c t i o n a l vinyl m o n o m e r , typical ly a so lu t ion of acrylic acid in to luene , wi th a s m a L l a m o u n t of benzoyl peroxide wh ich ac ts as a po lymer iza t ion ini t iator . Once t h e po lymer iza t ion h a s s tar ted , the m e m b r a n e is hea ted u n d e r n i t rogen for a per iod of 4 - 7 hours . The cond i t i ons are c h o s e n in order to form polyacrylic acid with a molecu la r weight of a t leas t 60 000 wi th in the pores of the po lypropylene base :

It was f ound that , for complete a n d p e r m a n e n t wet tabi l i ty to be achieved, the c o n c e n t r a t i o n of acrylic ac id in the so lu t ion h a d to be 50% or greater, wi th a benzoyl peroxide c o n c e n t r a t i o n of 0.5 mol %. A modif ica t ion of this p r o c e s s a d d s 5 - 1 0 mol % tr imethylol- p r o p a n e t r iacrylate to the acrylic acid solut ion. ' It ac t s as a cross- l i nk ing agent , b e c a u s e it is a t r f func t iona l vinyl monomer .

In a fur ther e m b o d i m e n t the incorpora ted polymer forms a gel wi th a l iquid which is p r e s e n t as a solvent d u r i n g po lymer iza t ion or is added later, so g iv ing a we l l - suppor ted l iquid m e m b r a n e in which the l iquid is he ld f irmly in the pores by the gel. The gel is composed pr imar i ly of the l iquid c o m p o n e n t a n d the t r a n s p o r t p roper t i es a re e s sen t i a l ly those of the liquid. In this case, s ince the polyacrylic acid is hydrophflic, the l iquid is water.

8 M e m b r a n e Techno logy