Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
2001-10-23
2002-12-24
Kifle, Bruck (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
active
06498250
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for nylon depolymerization, in which process a multi-component material, comprising nylon and one or more non-nylon components, is fed to a depolymerization zone in which depolymerization of at least part of said nylon is effected, resulting in a product stream and a residue, said product stream containing monomers of said nylon, said residue containing non-nylon components.
Such a process is known from U.S. Pat. No. 5,681,952. In this publication a continuous process is described, where a multi-component, nylon 6 waste material and steam are fed continuously to a reactor. In the reactor depolymerization of nylon 6 takes place, and caprolactam may be recovered overhead, while a nylon 6 depleted bottom stream (residue) may be discharged from the bottoms. Since the composition of the feed material, in particular if the feed material is a multi-component waste material, is usually not constant, it is difficult to control the depolymerization process.
SUMMARY OF THE INVENTION
In view of the above it is an object of the present invention to provide an effective way to control a process for nylon depolymerization, in which process a multi-component material, comprising nylon and one or more non-nylon components, is fed to a depolymerization zone in which depolymerization of at least part of said nylon is effected, resulting in a product stream and a residue, said product stream containing monomers of said nylon, said residue containing non-nylon components.
According to the invention this object is achieved in that the nylon content in the residue is measured and used to control the depolymerization process. We have found that an efficient production of nylon monomers is possible according to the invention since the nylon content of the residue shows considerable variations with relatively small changes in depolymerization process conditions and with relatively small changes in the composition of the multi-component material which is fed to the depolymerization zone.
It is noted that WO-A-9749652 describes a process in which depolymerization of polyamides is effected in the presence of non-polymer contaminants. In the examples a batch process is described in which depolymerization of a glass-filled nylon 6,6, is effected, resulting in a product stream which contains monomers and in a residue, which contains glass fibers. In the examples the extent of the reaction is monitored by analyzing the product stream. The weight of the reactor residue is determined in order to calculate the polymer conversion. The nylon content in the residue is not used to control the depolymerization process.
DETAILED DESCRIPTION
As used herein, “multi-component material” denotes materials or articles that include at least one type of nylon and at least one non-nylon component. By “non-nylon component” is meant any material, excluding nylons, nylon depolymerization products, depolymerization agents, stripping agents, or depolymerization catalysts. By “depolymerizing agent” is meant a solid, liquid or gas that will react with the amide linkage of the nylon to break the linkage, thus lowering the molecular weight of the nylon. Examples of depolymerizing agents are water, steam, alcohols, ammonia, amines. By “stripping agent” is meant a material which is in the gas phase at reaction temperature and which is able to carry away volatile reaction products of the depolymerization, e.g. monomers. The stripping agent may be the depolymerizing agent itself, such as for instance steam, gaseous ammonia or gaseous alcohol, or an inert gas, such as for instance nitrogen. By “depolymerizing catalyst” is meant a solid, liquid or gaseous material which catalyzes the breaking of amide bonds, such as for instance phosphoric acid, boric acid, phosphate salts, alkali metal oxides and alkali metal hydroxides. By “nylon depolymerization products” is meant monomers or oligomers of nylon. The non-nylon components of the “multi-component material” may for instance be non-hydrolyzable polymers, such as for instance polyethylene, polypropylene, polystyrene, and copolymers thereof with butadiene, inorganic or organic materials, such as for instance fillers, pigments, dyes and/or other additives, or other types of materials. The non-nylon components may for instance constitute from about 2 to about 98, preferably from about 5 to about 95, more preferably from about 10 to about 90, and most preferably from about 20 to about 80 weight percent of the multi-component material which is fed to the depolymerization zone. These weight percentages are given with respect to the total weight of the nylon plus the non-nylon components in the multi-component material. The nylon may be any type of nylon, for instance nylon-6, nylon 6,6, nylon 4,6 as well as mixtures thereof. The nylon may for instance constitute from about 2 to about 98, preferably from about 5 to about 95, more preferably from about 10 to about 90, and most preferably from about 20 to about 80 weight percent of the multi-component material which is fed to the depolymerization zone. These weight percentages are given with respect to the total weight of the nylon plus the non-nylon components in the multi-component material. Preferably, at least 40 wt. %, more preferably at least 50 wt. %, in particular at least 75 wt. % and more in particular at least 90 wt. % of the total amount of nylon in the multi-component material is one type of nylon. Preferably, at least 40 wt. %, more preferably at least 50 wt. %, in particular at least 75 wt. % and more in particular at least 90 wt. % of the total amount of nylon in the multi-component material is nylon 6.
The nylon content of the residue may be measured using any technique that allows the determination of the nylon content in the residue. The nylon content in the residue may be expressed by any characteristic from which the amount of nylon in the residue relative to the amount of other components in the residue, preferably relative to the amount of non-nylon components in the residue can be derived. Examples of suitable measurement techniques are high performance liquid chromatography, density measurements, Raman spectroscopy and near infrared spectroscopy. Preferably, measurements techniques are used in which the analysis time is not too long, preferably less than 1 hour. Most preferably, near-infrared spectroscopy is used. Using this technique a quick and acurate measurement of the nylon content is possible.
According to the invention the content of a specific type of nylon in the residue may be determined, for instance the nylon 6 or the nylon 6,6 content. According to the invention it is also possible to measure the total content of all nylons in the residue.
As used herein, “measuring the nylon content of the residue”, denotes the determination of the nylon content of the residue during the depolymerization process, either continuously or at intervals. If the nylon content is determined at intervals, it is preferred that frequency of the measurements of the nylon content is sufficiently high that adjustments to the process parameters may be made on time. In order to be able to make adjustments to the process parameters as quickly as possible, it is desired that the time, required for the determination of the nylon content is as short as possible. If the process is very stable, the time interval between two measurements may be longer than if the process is less stable.
The value of the nylon content, e.g. expressed in weight percent nylon, is used to control the depolymerization process. Preferably, the control of the depolymerization process is carried out by comparing the measured nylon content in the residue with a desired value, and adjusting at least one process variable in accordance with the difference between the nylon content in the residue and the desired value. Examples of such process variables are the temperature at which depolymerization is conducted, the rate at which the multi-component material is fed to the depolymerization zone, the feed rate of steam, w
Berghmans Antonius C.
Houben Marco J. A.
Huys Michel J. G.
Raets Leonardus J. G.
DSM N.V.
Kifle Bruck
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