Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-01-23
2003-03-11
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S189000, C526S184000, C526S227000, C526S352000, C526S347000, C526S318600, C526S329000, C526S331000, C526S339000
Reexamination Certificate
active
06531556
ABSTRACT:
The present invention relates to a process for the controlled radical polymerization or copolymerization of ethylene under high pressure in the presence both:
of initiating free radicals resulting from initiating compounds; and
of controlling stable free radicals composed of indoline nitroxides,
it being possible for these two types of radicals also to result from the same initiating-controlling compound, as will be described hereinbelow.
The polymerization under high pressure of ethylene or its copolymerization under high pressure with comonomers which can copolymerize by the radical route results in a large variety of products which have numerous applications, among which may be mentioned bases for adhesives, in particular hot melt adhesives, bituminous binders, wrapping films, impact strengtheners, coextrusion binders, moulded items, and the like.
Processes for the polymerization of ethylene at high temperatures and pressures by means of initiating free radicals have been known for a long time. Ethylene polymers are obtained by homopolymerizing ethylene or by copolymerizing it with at least one other comonomer in a polymerization system which operates continuously under pressures of the order of 50 MPa to 500 MPa and at temperatures of between 50 and 300° C. The polymerization is carried out in continuous tubular reactors or stirred autoclaves in the presence of initiators and optionally of transfer agents. The polymers are subsequently separated from the volatile substances after their departure from the reactor in separators.
It is known that the polymerization of ethylene in the presence or in the absence of comonomers can result in reaction runaways (see, for example, Chem. Eng. Proc., 1998, 37, 55-59). These runaways are reflected by a very marked rise in the temperature and in the pressure and thus by bursting of the safety devices of the plant. Consequently, the runaway must result in undesired shutdowns in production. The aim is thus to avoid these shutdowns as far as possible and one means for doing this is to carefully control the flow rates of the reactants entering the reactor, in particular the flow rate of the source of radicals, that is to say of the initiator. This is because the injection of an excessively large amount of radicals results in a localized runaway in one of the regions of the reactor, which runaway subsequently spreads very quickly to the whole of the reactor. There thus exists a content of radicals not to be exceeded in order not to result in the runaway of the polymerization.
However, it is generally known that radical polymerizations can be controlled using stable free radicals, this control making it possible in particular to obtain polymers exhibiting narrow molecular mass distributions. Thus it is that United States Patent U.S. Pat. No. 5,449,724 discloses a radical polymerization process which consists in heating, at a temperature of approximately 40° C. to approximately 500° C. and under a pressure of approximately 50 MPa to 500 MPa, a mixture composed of a free radical initiator, of a stable free radical (conventionally described nitroxides, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and its derivatives) and of ethylene, in order to form a thermoplastic resin which has a molecular mass distribution of approximately 1.0 to approximately 2.0.
In seeking to improve the known process for the controlled radical (co)polymerization of ethylene under high pressure, the Applicant Company has now discovered that, if (co)polymerization involves the participation of a conventional radical initiator and, as agent for controlling radical (co)polymerization, a specific nitroxide not disclosed in United States Patent U.S. Pat. No. 5,449,724 and, in a specific embodiment, an initiator-controller capable of providing at least one initiating radical and at least one stable free radical (stable under the specific temperature conditions deployed in this high pressure (co)polymerization), this (co)polymerization is controlled under particularly favourable conditions while also controlling the reaction stability, an advantage of indoline nitroxides being their high thermal stability, which is important for high pressure processes where the temperatures are generally high.
It was therefore not obvious to thus control the high pressure (co)polymerization of ethylene, with greater effectiveness than with the use of an initiator and of a conventional stable free radical and with the observation, also surprising, that the (co)polymerization of ethylene takes place with a markedly greater rate. Furthermore, with the process of the invention, there is no limitation on the molecular masses of the (co)polymers obtained.
In addition, another consequence of the present invention is that, in the case where the initiator or the initiator-controller chosen is such that it provides an initiating free macroradical, block copolymers are produced in which at least one of the blocks comprises ethylene as constituent. In point of fact, ethylene copolymers prepared under high pressure currently have random structures and it has not been possible to date to obtain such block copolymers having an ethylene-based block. It is well known that the structure of block copolymers can result in markedly better physicochemical properties than random copolymers. The present invention thus makes it possible to achieve the production of novel materials having novel properties.
It may be indicated that United States Patent U.S. Pat. No. 5,872,252 discloses a process for the compression of ethylene monomers, such as ethylene, under a pressure of 20-500 MPa in the absence of a radical polymerization initiator and in the presence of a sterically hindered amine derivative, which can be an N-oxy derivative (stable free radical) . Apart from the fact that this process is not a polymerization process, it may be emphasized that the stable free radicals of the present invention, comprising an indoline nitroxide nucleus, are not at all envisaged in this United States Patent U.S. Pat. No. 5,872,252.
A subject-matter of the present invention is thus firstly a process for the radical polymerization or copolymerization of ethylene under high pressure and in the presence of at least one initiating free radical (Z
•
) and of at least one controlling stable free radical (SFR
•
) which comprises the indoline nitroxide backbone represented by the formula (I):
in which A is a hydrocarbonaceous chain forming an aromatic ring with the two carbon atoms to which it is attached, this ring being able to carry substituents or being able to carry one or more rings placed side by side, which rings are aromatic or aliphatic and optionally substituted, the carbon atoms forming the nitrogenous ring and in the alpha- and beta-position with respect to the nitrogen atom being able to carry hydrogen atoms or substituents.
In particular, the controlling stable free radical or radicals (SFR
•
) are chosen from those which exhibit a decomposition of less than 90%, preferably of less than 95%, after 6 hours at 200° C. in diphenyl ether.
The present invention thus involves the formation of a stable free radical. A stable free radical should not be confused with free radicals with a fleeting lifetime (a few milliseconds), such as the free radicals resulting from the usual polymerization initiators, such as peroxides, hydroperoxides and initiators of the azo type. The free radicals which initiate polymerization tend to accelerate the polymerization. In contrast, stable free radicals generally tend to slow down the polymerization. It may be generally said that a free radical is stable within the meaning of the present invention if it is not a polymerization initiator and if, under the operating conditions of the present invention, the mean lifetime of the radical is at least five minutes. During this mean lifetime, the molecules of the stable free radical continually alternate between the radical state and the state of a group bonded to a polymer chain via a covalent bond resulting from a coupling reaction be
Buback Michael
Carloni Patricia
Damiani Elisabetta
Greci Lucedio
Minaux Eric
Atofina
Choi Ling-Siu
Pennie & Edmonds LLP
Wu David W.
LandOfFree
Process for the controlled radical polymerization or... 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 controlled radical polymerization or..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the controlled radical polymerization or... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3080561