Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – Support per se
Reexamination Certificate
1999-02-03
2002-05-14
Wu, David W. (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
Support per se
C502S160000, C502S167000, C502S168000, C526S126000, C526S218100, C526S219400, C526S219600, C526S224000, C526S227000, C585S943000, C585S422000, C585S435000
Reexamination Certificate
active
06387837
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the free-radical polymerization of monomers in gas phase or suspension processes using a supported, polymerization-initiating system.
BACKGROUND OF THE INVENTION
The homo- and copolymerization of mono- or polyunsaturated, also conjugated dienes using ionic or free-radical initiators is of great industrial significance. For environmental reasons and due to economic considerations, there is a desire to optimize the processes used, in many cases solution processes, or to replace them with novel processes. There is a desire in this connection to polymerize the monomers in the gas phase or in suspension processes as, on the one hand, no solvents need to be used in the gas phase and emissions and waste water contamination may be reduced and, on the other, in suspension and gas phase processes, the polymers are produced in an advantageous form.
These processes may additionally be used to produce novel rubbers having particular product properties. Specifically, particularly well-dispersed fillers are obtained if these are present during polymerization as supports for the active catalyst component.
It is known (
Encyclopedia of Polymer Science
&
Engineering,
volume 2, pp. 1 et seq., volume 2, pp. 729 et seq. and volume 13, pp. 708 et seq.) to convert mono- or polyunsaturated monomers into polymers using cationic, anionic or free-radical initiators or using systems capable of forming such initiators. These processes are preferably performed as solution processes, in which the initiators are soluble and consequently act as efficiently as possible.
It is also known (
Ullmanns Enzyklopacdie der technischen Chemie,
volume 13, pp. 611 et seq.) that, for example, butadiene and acrylonitrile, may be converted into polymeric products using free-radical initiators or substances, which form free-radical initiators.
It is known from EP-A-0798339 that the copolymerization of butadiene and styrene may be initiated and controlled, for example, by a system comprising organolithium compound, potassium alkoxide and ether or amino-functional compound in aliphatic solvents.
The described systems have the disadvantage that they may be used for suspension processes only if relatively elaborate arrangements are made and they cannot be used for gas phase processes.
It is already known from EP-B-0647657 that conjugated dienes, in particular butadiene, may be polymerized in the gas phase without addition of solvents by using a catalyst system based on rare earth compounds and an organoaluminium compound on a particulate, inert, inorganic solid having a specific surface area of greater than 10 m
2
/g (BET) and a pore volume of 0.3 to 15 ml/g.
EP-A-0419951 describes processes for the solid phase polymerization of acrylonitrile from the gas phase using free-radical initiators in the presence of solids, which act as seed substrates and into which the monomer is introduced in liquid form. The process may also be performed in the presence of mediator substances, which act as solvents or swelling agents for the resultant polymers and prevent a fall in reaction rate.
The described catalyst systems are, on the one hand, conventional Ziegler systems, for which numerous heterogenization methods are generally described in the literature and, on the other, gas phase polymerization processes requiring both special seed substrates and mediator substances.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention was to provide a generally applicable process for the free-radical polymerization of monomers in gas phase or suspension processes in order to avoid in this manner, the specific disadvantages of solution or emulsion processes.
This object is achieved according to the present invention by the use of a supported, polymerization-initiating system comprising
a) one or more polymerization-initiation components which initiate and start free-radical polymerization,
b) a support, onto which the polymerization-initiating component is applied, and
c) optionally, one or more modifiers which have an influence upon reaction kinetics and/or product properties.
DETAILED DESCRIPTION OF THE INVENTION
Supporting of the polymerization-initiating substances, hereinafter referred to as initiators, preferably proceeds by applying these substances or two or more initiator components dissolved in a liquid phase onto a porous support material.
Another preferred embodiment relates to the simultaneous immobilization of initiators together with polymerization-influencing and product-modifying substances, hereinafter referred to as modifying agents.
Supporting, preferably proceeds by bringing a solvent or solvent mixture containing the initiator or initiator components in dissolved form into contact with a porous support material. The support material is inert toward the initiator or initiator components and wherein the solvent or solvent mixture may be preferably completely removed from the support or particularly preferably, the volume of the solvent or solvent mixture remaining on the support material is less than or equal to the pore volume of the support material used. In another preferred embodiment, the initiator or initiator components are applied in dissolved form onto a support and precipitated onto the support by the addition of suitable precipitating agents and are consequently, simultaneously deposited in solid form on the support.
The solid is preferably kept in motion before, during and optionally after application of the initiator solution, for example in a stirred tank with a conventional stirrer unit, such as, for example, a cross-arm stirrer or a helical stirrer or in another preferred form, in a plough bar mixer.
In another preferred embodiment, the support material is impregnated with initiator solution in a fluidized bed. In this case, the active substance solution is applied, for example by atomization by means of a nozzle, onto the support material, which is fluidized by a stream of inert gas. The inert gas, once any entrained solvent has been removed, may be returned to the reactor via an internal circuit. The inert solvent is preferably reused to prepare the active substance solution. The process according to the invention may also be advantageously performed continuously. Furthermore, it is advantageous to purposefully control the level of activity of the initiator system by varying the apportioned quantity of initiator solution and optionally, the modifying agent solution.
The supported initiator system may be produced within a wide temperature range. The temperature is preferably between the melting and boiling point of the inert solvent or solvents and below the decomposition temperature of the initiator or the initiators. Temperatures of −20 to 100° C. are preferably used, particularly preferably of 20 to 40° C.
In a preferred embodiment, after the support material has been impregnated with active substance solution, the inert solvent or solvents are removed by distillation completely or to such an extent that the volume of the remaining solvent or solvents is less than or equal to the pore volume of the support material used.
Distillation may be performed both in the same vessel in which impregnation was performed and in a separate apparatus, for example a fluidized bed drier. Depending upon the solvent used, distillation is performed at temperatures of 0 to 150° C., preferably at 10 to 70° C., and pressures of 0.001 mbar to 20 bar absolute, preferably of 0.001 mbar to standard pressure. Distillation may also be performed continuously. The condensate collected may be advantageously reused without further working up as a solvent for the active substances used in the impregnation.
Any porous support materials which are dimensionally stable and inert in the solvent or solvent mixtures being used and have a sufficiently high pore volume, surface area and particle size may be used in the process according to the present invention. Suitable support materials are particular organic or inorganic solids, the pore volume of which is bet
Dauben Michael
Hoch Martin
Oppenheimer-Stix Christiane
Schertl Peter
Bayer Aktiengesellschaft
Cheung Noland J.
Choi Ling-Siu
Gil Joseph C.
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