Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1995-07-25
1999-05-18
Shippen, Michael L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562513, 562523, 562526, C07C55/00
Patent
active
059051680
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for treating a material comprising a polymer to recover at least partially the monomers forming the polymer.
It relates more particularly to a process for treating a material comprising a polymer containing amide functional groups by oxidative hydrolysis of these amide functional groups to regenerate monomers which can be employed for the synthesis of identical or different polymers.
Synthetic materials and, among these, polymers containing amide functional groups, such as polyamides and more particularly polyamide 6.6 or polyamide 6 are increasingly employed for the production of varied articles such as textile fibres, technical industrial yarns, filaments or moulded articles such as components for electricity, electronics or motor vehicles. These synthetic materials are generally employed in the form of compositions containing various additives in addition to the synthetic material in order, for example, to increase their stability to heat or to radiations, to improve their mechanical, electrical or electrostatic properties, colorants and pigments. These additives are of very varied nature and may be organic as well as inorganic compounds.
In addition, especially in the case of the production of moulded articles, the compositions include fillers, frequently inorganic, such as glass fibres, talc, clay and the like.
The materials thus produced may be destroyed after use. One of the means for conventional destruction is incineration, which enables energy to be recovered. However, it is also proposed to recycle these materials. One of the means of recycling consists in depolymerizing the polymer or synthetic material into compounds of lower degree of condensation and, if possible, regenerating the initial monomers to enable them to be recycled into the polymerization processes. One of the processes proposed for recycling polyamide is a process consisting in hydrolysing the polymer in basic medium. However, this process does not make it possible to regenerate the monomers and generally requires a preliminary separation between the polymer and the fillers. Moreover, the additives present in the polymer, especially when they are organic in nature, may contaminate the products recovered after the hydrolysis, it being possible for this contamination to prevent their being recycled.
One of the objectives of the present invention is especially to propose a process making it possible to treat materials which may comprise fillers and/or additives, to hydrolyse the amide functional groups of the polymer present in the material in order to regenerate, on the one hand, the original dicarboxylic acid and, on the other hand, to produce one or more carboxylic acids whose chemical structure corresponds substantially to that of the original diamine or amino acid monomers.
To this end, the invention proposes a process for treating a material comprising a polymer containing at least amide functional groups. This process is characterized in that it consists in subjecting the material to a hydrolysis in the presence of nitrous groups dissolved in the hydrolysis medium and to an oxidation.
According to a preferred embodiment the hydrolysis medium is an oxidizing medium.
According to a characteristic of the invention the nitrous groups are obtained by chemical or thermal decomposition of at least one compound containing these groups.
Thus, compounds generating nitrous groups which may be mentioned by way of example are nitric acid, alkali metal and metal nitrites, nitrous vapours (NO.sub.x) or the like.
The hydrolysis medium is an aqueous medium exhibiting an acid pH preferably lower than 1.
In a preferred embodiment the H.sup.+ concentration in the medium is at least 1 mole/l (1N).
The process of the invention is advantageously carried out by maintaining the hydrolysis medium at a temperature lower than 100.degree. C., preferably between 40 and 100.degree. C. However, the process of the invention may be carried out under pressure at a temperature above 100.degree. C., for example at a te
Dos Santos Emmanuel
Gubelmann Michel
Mettvier Pascal
Rhone-Poulenc Chimie
Shippen Michael L.
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