- Email: [email protected]
Plasma polymerised polysiloxanes
Patents Slit-shaped pores for membranes This rare e x a m p l e of a E u r o p e a n p a t e n t g r a n t e d to a J a p a n e s e c o m p a n y covers the u s e of noncrystalline polymers mixed with 10-60 wt% fine p a r t i c l e s a n d their e x t r u s i o n a n d s u b s e q u e n t c o n s i d e r a b l e s t r e t c h i n g to form a sheet or hollow fibre m e m b r a n e . The fine p a r t i c l e s m a y s u b s e quently be removed by elution or dissolution to leave a m e m b r a n e with s l i t - s h a p e d pores. The process defined in the p a t e n t h a s general application to a n y n o n - c r y s t a l l i n e polymer, so t h a t super-engineering plastics (polysulphone, polyimide a n d polyarylate), engineering p l a s t i c s (polycarbonate, p o l y p h e n y l e n e oxide) a n d g e n e r a l - p u r p o s e plastics s u c h as polystyrene a n d p o l y m e t h a c r y l a t e can all be treated in this way. The pore d i m e n s i o n s of the finished m e m b r a n e are: width 0.1-5 microns, length 0 . 5 - 5 0 microns. The ratio of average length to width is preferably more t h a n 3, a n d m o s t preferably not less t h a n 8 in order to give a m e m b r a n e t h a t has adequate mechanical strength. The finished m e m b r a n e m a y or m a y not c o n t a i n fine particles: if they are present, the h e a t r e s i s t a n c e of the m e m b r a n e is improved. The p a r t i c l e s can be of talc, calcium c a r b o n a t e or m a n y other inorganic c o m p o u n d s , or of organic polymers s u c h as melamine, silicones or rubber; the s u r f a c e of the particles can be treated to improve their even d i s p e r s i o n t h r o u g h the body of the m e m b r a n e . The p o l y m e r - p a r t i c l e m i x t u r e is e x t r u d e d to give a p r e c u r s o r form. This is t h e n s t r e t c h e d by not less t h a n 2 0 0 % / m i n to give a finished p r o d u c t with a s t r e t c h i n g ratio - c o m p a r e d to the p r e c u r s o r of 300-800%. The e x t r u s i o n a n d s t r e t c h i n g t e m p e r a t u r e s h o u l d be 5-30°C. above the glass t r a n s i t i o n t e m p e r a t u r e (Tg) of the polymer.
10
The p a t e n t also provides for p o s t - s t r e t c h t r e a t m e n t of the polymer. In one example a hydrophilic polymer coating was applied to e n h a n c e the flux properties of the polymer on filtration of hydrophilic liquids.
Patent number: EP 665049 Date: 2nd A u g u s t 1995 Inventors: J. Kamo, S. Koyanagi, M. Kawai Applicant: Mitsubishi Rayon Co. Ltd
Plasma polymerised polysiloxanes The object of this p a t e n t is to combine the good intrinsic p e r m e a b i l i t y a n d selectivity to oxygen of polysiloxane-based m a t e r i a l s with a m e c h a n i c a l support to give a d e q u a t e m e c h a n i c a l strength. To this end, a low-temp e r a t u r e p l a s m a polymerisation process h a s been developed. The u s e of a glow-discharge p l a s m a process to form polymerised memb r a n e s is not itself novel. Prior a r t is cited requiring long p l a s m a exp o s u r e times of the order of 30 m i n u t e s in order to deposit sufficient polymer to cover fully pores in a p o r o u s s u b s t r a t e . In this process, it h a s been found t h a t the u s e of a fully alkylated disiloxane mixed with oxygen permits a c o n s i d e r a b l y s h o r t e n e d p l a s m a exposure time. The process operates at 0.05-0.2 torr a n d close to a m b i e n t t e m p e r a t u r e .
Patent number: WO 9519837 Date: 27th J u l y 1995 Inventor: H. N o m u r a Applicant: Neomecs Inc.
Hydrolytically stable nylon membrane The m e m b r a n e is c a p a b l e of w i t h s t a n d i n g autoclaving a n d hot water sterilisation without polymeric dissociation occurring,
r e g a r d l e s s of the pore size, m e m b r a n e t h i c k n e s s , nylon solids c o n t e n t of the dope, or the t e m p e r a t u r e at which the dope is p r e p a r e d . In conventional nylon products, antioxidant compounds s u c h as alkylated phenols, polyphenolics, a r o m a t i c a m i n e s or organic p h o s p h a t e s are i n c o r p o r a t e d to improve the m a t e r i a l ' s r e s i s t a n c e to b o t h photo-oxidation and thermal degradation. Some t h e r m a l l y m o u l d e d nylon p r o d u c t s containing a n t i o x i d a n t s are h y d r o l y s i s - r e s i s t a n t g r a d e s which can be s u b j e c t e d to w a t e r at 70-800C with less d e g r a d a t i o n t h a n the plain nylon material. These additives can leach from the surface a n d body of the material, a p r o b l e m in a r e a s s u c h as food or p h a r m a c e u t i c a l manufacture. This p a t e n t b u i l d s on r e s e a r c h which shows t h a t the c h a n g e s which take place in nylon polymer d i s s o c i a t i o n m a y be related not only to the t e m p e r a t u r e of the water, b u t also to its dissolved oxygen content. A n t i o x i d a n t s are of little lasting value in nylon m e m b r a n e s s u b j e c t e d to this environment: the surface a r e a to volume ratio is too unfavourable. In this case, it h a s been found t h a t the n a t u r e a n d n u m b e r of end g r o u p s in nylon polymers effectively controls the chemical stability of the polymer, p a r t i c u l a r l y towards h e a t a n d light damage. If the nylon h a s at least 0.9 moles of a m i n o end g r o u p s per mole of nylon, more preferably at least 1.3 moles per mole of nylon a n d optimally at least 1.6 moles of amino end g r o u p s per mole of nylon, then the t e m p e r a t u r e , hydrolysis a n d light stability are improved several times over c o m p a r e d to conventional nylon having a low n u m b e r of amino end groups.
Patent number: WO 9518673 Date: 13th J u l y 1995 Inventors: K.C. Hou, J.C. Disbrow, R.V. Repetti, C.T. Badenhop Applicant: Cuno Inc.
M e m b r a n e T e c h n o l o g y No. 70
10
The p a t e n t also provides for p o s t - s t r e t c h t r e a t m e n t of the polymer. In one example a hydrophilic polymer coating was applied to e n h a n c e the flux properties of the polymer on filtration of hydrophilic liquids.
Patent number: EP 665049 Date: 2nd A u g u s t 1995 Inventors: J. Kamo, S. Koyanagi, M. Kawai Applicant: Mitsubishi Rayon Co. Ltd
Plasma polymerised polysiloxanes The object of this p a t e n t is to combine the good intrinsic p e r m e a b i l i t y a n d selectivity to oxygen of polysiloxane-based m a t e r i a l s with a m e c h a n i c a l support to give a d e q u a t e m e c h a n i c a l strength. To this end, a low-temp e r a t u r e p l a s m a polymerisation process h a s been developed. The u s e of a glow-discharge p l a s m a process to form polymerised memb r a n e s is not itself novel. Prior a r t is cited requiring long p l a s m a exp o s u r e times of the order of 30 m i n u t e s in order to deposit sufficient polymer to cover fully pores in a p o r o u s s u b s t r a t e . In this process, it h a s been found t h a t the u s e of a fully alkylated disiloxane mixed with oxygen permits a c o n s i d e r a b l y s h o r t e n e d p l a s m a exposure time. The process operates at 0.05-0.2 torr a n d close to a m b i e n t t e m p e r a t u r e .
Patent number: WO 9519837 Date: 27th J u l y 1995 Inventor: H. N o m u r a Applicant: Neomecs Inc.
Hydrolytically stable nylon membrane The m e m b r a n e is c a p a b l e of w i t h s t a n d i n g autoclaving a n d hot water sterilisation without polymeric dissociation occurring,
r e g a r d l e s s of the pore size, m e m b r a n e t h i c k n e s s , nylon solids c o n t e n t of the dope, or the t e m p e r a t u r e at which the dope is p r e p a r e d . In conventional nylon products, antioxidant compounds s u c h as alkylated phenols, polyphenolics, a r o m a t i c a m i n e s or organic p h o s p h a t e s are i n c o r p o r a t e d to improve the m a t e r i a l ' s r e s i s t a n c e to b o t h photo-oxidation and thermal degradation. Some t h e r m a l l y m o u l d e d nylon p r o d u c t s containing a n t i o x i d a n t s are h y d r o l y s i s - r e s i s t a n t g r a d e s which can be s u b j e c t e d to w a t e r at 70-800C with less d e g r a d a t i o n t h a n the plain nylon material. These additives can leach from the surface a n d body of the material, a p r o b l e m in a r e a s s u c h as food or p h a r m a c e u t i c a l manufacture. This p a t e n t b u i l d s on r e s e a r c h which shows t h a t the c h a n g e s which take place in nylon polymer d i s s o c i a t i o n m a y be related not only to the t e m p e r a t u r e of the water, b u t also to its dissolved oxygen content. A n t i o x i d a n t s are of little lasting value in nylon m e m b r a n e s s u b j e c t e d to this environment: the surface a r e a to volume ratio is too unfavourable. In this case, it h a s been found t h a t the n a t u r e a n d n u m b e r of end g r o u p s in nylon polymers effectively controls the chemical stability of the polymer, p a r t i c u l a r l y towards h e a t a n d light damage. If the nylon h a s at least 0.9 moles of a m i n o end g r o u p s per mole of nylon, more preferably at least 1.3 moles per mole of nylon a n d optimally at least 1.6 moles of amino end g r o u p s per mole of nylon, then the t e m p e r a t u r e , hydrolysis a n d light stability are improved several times over c o m p a r e d to conventional nylon having a low n u m b e r of amino end groups.
Patent number: WO 9518673 Date: 13th J u l y 1995 Inventors: K.C. Hou, J.C. Disbrow, R.V. Repetti, C.T. Badenhop Applicant: Cuno Inc.
M e m b r a n e T e c h n o l o g y No. 70