Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1993-02-25
1994-12-13
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
521 405, 5253303, C08F 806
Patent
active
053730674
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process for the treatment of polymeric materials based on cross-linked E.V.A (vulcanized ethylene vinyl acetate) in order to obtain polymeric fragments with a lower molecular mass. The process of the invention applies in particular to the treatment of waste based on E.V.A (waste from the boot and shoe industry etc) with the object of using it profitably, notably as a modifying agent, a coating binder or as a raw material.
Polymers based on cross-linked E.V.A are very specific compounds by virtue of their three-dimensional non-linear structure and strong covalent bonds which ensure cohesion in the three-dimensional network. These compounds are insoluble in an aqueous medium and in all organic solvents.
At the present time, in many industries, notably the boot and shoe industry, considerable quantities of waste are produced based on the cross-linked compounds referred to above and no process exists which enables them to be de-crosslinked in order to :render them soluble for the purpose of recycling. Consequently, taking into account the nuisance problems associated with these compounds (they are very difficult to degrade) they are currently destroyed essentially by pyrolysis or combustion.
The difficulty of de-crosslinking these compounds results from the existence of strong covalent bonds in the three-dimensional network; these bonds are difficult to break without totally destroying the molecule with the production of a diversity of small unusable molecules.
In another connection, ozone has already been used for converting certain pure polymers, for example polyethylene or polyolefines, by oxidizing them. Such ozonization processes are described in the following publications: French patent 1,472,411; B.BOUTEVIN et al., Ozonization of polyethylene. Eur. Polym. J. Vol 20 n.degree.9 pp 875-878, 1984; U.S. Pat. No. 4,118,427; French patent 2,292.715. However such processes are aimed at pure non cross-linked polymers which are by nature very different from those aimed at by the invention and which are in particular soluble (certain processes work in an aqueous medium) and have as their objective the oxidation of these polymers with a view to utilizing them at a later stage. These previous documents do not provide any information concerning the de-cross linking of polymers based on vulcanized E.V.A. For example, U.S. Pat. No. 4,118,427 describes total depolymerization of a soluble polymer whose molecular mass is 80,000, leading to the production of small molecules with a molecular mass of the order of 1,000 to 2,000 which no longer have the physico-chemical properties of the starting polymer.
The present invention proposes to provide a process for the treatment of polymeric materials based on cross-linked E.V.A. with a view to converting this material into polymeric fragments having a lower molecular mass; the invention thus aims at producing soluble and hence usable fragments of the starting cross-linked polymers.
An essential objective of the invention is to carry out this conversion without totally destroying the polymer, that is to say by limiting it to a controlled cleavage of the molecule by breaking certain bonds without disrupting the functional groups.
For this purpose, the process according to the invention for treating polymeric materials based on cross-linked E.V.A., consists of:
reducing the polymeric materials into a particulate form,
incorporating the polymeric particles obtained into an organic solvent suitable for diffusing into the interior of the polymeric network of the material and for swelling the said network, the said solvent being chosen as being by nature non-degradable or only slightly degradable by ozone,
subjecting the reaction medium consisting of the solvent containing the particles, to a stream of ozone until the desired size of the polymeric fragments is obtained,
separating the solid phase from the solvent.
Experiments have shown that unexpectedly, the process of the invention which operates in the liquid phase enables certain covalent bonds of the cross-
REFERENCES:
patent: 4118427 (1978-10-01), Rhein et al.
patent: 4378998 (1983-04-01), Korbanka et al.
Abdennadher Mohamed
Borredon Elisabeth
Delmas Michel
Fahimi Akbar
Gaset Antoine
Enterprise "Malet"
Lipman Bernard
LandOfFree
Process for the treatment of polymers based on cross-linked E.V. 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 treatment of polymers based on cross-linked E.V., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the treatment of polymers based on cross-linked E.V. will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1194050