Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Including surface treatment of porous body
Patent
1992-05-01
1993-06-01
Sever, Frank
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Including surface treatment of porous body
210639, 21050037, 264DIG48, 264DIG62, 427244, E01D 7156
Patent
active
052156923
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the surface grafting of formed bodies, in particular also microporous membranes made from nitrogen-containing polymers.
State of the Art
According to a widespread grafting process, radical groups are introduced into the chain of the base polymer, e.g. by means of high-energy radiation, on which radical groups the grafting can take place by means of radical chain polymerization.
The generation of the activated, e.g. radical groups which effect the starting point of the grafting takes place in these grafting processes in an untargeted fashion, that is, the grafting does not take place exclusively, on a certain grouping of the chain of the base polymer, such as e.g. on the nitrogen atom, but rather on all positions of the polymer chain which can be activated by means of high-energy radiation, e.g. also on methylene groups. A more or less strong degradation of polymer chains takes place at the same time by means of high-energy radiation and a damaging of the mechanical strength of the base polymer occurs as a consequence of the lowering of the degree of polymerization occasioned therewith. Likewise undesired side reactions in radiation-induced grafting are cross-linking reactions, which result in an embrittlement of the material.
Other processes of graft copolymerization are based on activation under radical formation by means of strong oxidizing agents such as e.g. Ce.sup.IV salts. This process can only be used in the case of very low pH'es, namely below pH 2, because otherwise a hydrolytic precipitation of the Ce.sup.IV salt occurs. The use of this process in the case of the polymers intended for the process of the invention results in a hydrolytic damaging of these polymers and a diminution of the mechanical strength due to a reduction in the degree of polymerization can also be observed. In addition, no purposeful grafting for increasing the chemical resistance of the base polymer is possible even according to this process.
Other processes for graft polymerization are based on chain transfer in that a homopolymerization of the monomer is induced by a radical initiator in the presence of the base polymer to be grafted, for which high temperatures must generally be employed (70.degree.-80.degree. C.). The grafting takes place in this instance by means of interaction of the growing polymer radical with the base polymer. The grafting site can also not be influenced in a purposeful manner in this instance A further disadvantage of this grafting process resides in the fact that only a slight portion of the monomer used is consumed for the grafting whereas at the same time a considerable amount of homopolymer is produced The formation of homopolymer is undesired because this increases the amount of the required monomer, which adversely affects the economy of the process and, moreover, a specific method step for removing the homopolymer becomes necessary.
The previously named grafting processes have the fact in common that the grafting does not take place at any sharply defined position of the base polymer, especially not with preference on the nitrogen atom. The chemical nature of the corresponding bonds such as the peptide group and of the carbamic acid group is therefore not changed and a positive influence on the chemical stability of these bonds can therefore not take place.
It is also known that polyamides can be grafted with acrylamide or acrylonitrile in such a manner that in a first method step the hydrogen atoms on the nitrogen atoms are replaced by chlorine atoms. The halogen-substituted polyamides are then converted back into the initial polymer by means of hydrazine or iron-II-salts, during which time a radical transitional state of nitrogen appears. A radical chain polymerization on the nitrogen takes place in the presence of the named monomers as well as in the case of other redox-initiated polymerization processes. This reaction is described e.g. by K. V. Phung and R. C. Schulz in "Makromolekulare Chemie", 180, 1825 (1979). It was used in this paper to demo
REFERENCES:
patent: 4277344 (1981-07-01), Cadotte
Horl Hans-Heinrich
Nussbaumer Dietmar
Wunn Eberhard
Sartorius AG
Schellin Eric P.
Sever Frank
LandOfFree
Process for the surface grafting of formed bodies, in particulat does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the surface grafting of formed bodies, in particulat, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the surface grafting of formed bodies, in particulat will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1812509