Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymerizing in tubular or loop reactor
Reexamination Certificate
2002-03-22
2003-08-05
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymerizing in tubular or loop reactor
C526S206000, C526S329200, C526S346000, C526S348700, C526S065000
Reexamination Certificate
active
06602965
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of continuous cationic living polymerization. More particularly, it relates to a method comprising continuously feeding raw materials to thereby cause the polymerization reaction to proceed and continuously discharging the product.
BACKGROUND ART
Living polymerization is a mode of polymerization in which the polymerization reaction initiated at a starting point(s) on an initiator can proceed without being disturbed by such side reactions as termination and chain transfer reactions and thus allows the molecular chain to grow. If, in such living polymerization, the polymerization reactions from all initiation sites are started simultaneously, a polymer uniform in molecular weight can be obtained and, further, it is possible to introduce a specific functional group terminally or otherwise into the polymer or synthesize a block copolymer by adding a different monomer species near the end point of the polymerization reaction. According to the monomer species to be polymerized, there are known cationic living polymerization (e.g. Japanese Kokai Publication Hei-07-292038, Japanese Kokai Publication Hei-08-53514), anionic living polymerization (e.g. Japanese Kokai Publication Hei-05-247199) or living radical polymerization (e.g. Japanese Kokai Publication Hei-10-306106).
The growing terminus in cationic living polymerization need not be always a carbocation but may be in a nonionic state as a result of binding of the carbocation to a counter anion during the polymerization reaction. In a cationic living polymerization system, termini in the ionic state (i.e. carbocation) and termini in the nonionic state are in equilibrium in many cases and, in such cases, the active carbocation termini react with the monomer. Thus, the term “cationic living polymerization” includes the one strictly classifiable under pseudo-living polymerization. Such cationic living polymerization is carried out at relatively low temperatures in many cases and, as regards the catalyst and additive, ideas proper to respective polymerization systems have been given. Concerning the cationic living polymerization of isobutylene, the result of the evaluation of the distribution (Mw/Mn), which is the ratio of weight based average molecular weight (Mw) to number based average molecular weight (Mn), was 1.09 to 1.38 in Japanese Kokai Publication Hei-07-292038, or in Japanese Kokai Publication Hei-08-53514, the distribution was 1.07 to 1.33, for instance, and, in these systems, polymers uniform in molecular weight are obtainable.
While most of the reports made about conventional cationic living polymerization reactions deal with batchwise polymerization processes in which a stirring vessel reactor is charged with raw reactant materials, attempts have also been made about the continuous polymerization process in which raw materials are continuously fed to a reactor in order to improve the productivity. Thus, in U.S. Pat. No. 4,568,732 and Nagy et al. (Polymer Bulletin, 13, pp. 97-102, 1985; Polymer Bulletin, 14, pp. 251-257, 1985), for instance, attempts were made to carry out cationic living polymerization by continuously feeding a polymerization initiator and a Lewis acid catalyst and isobutylene to one stirring vessel reactor. Majoros et al. (Polymer Bulletin, 31, pp. 255-261, 1993) connected three stirring vessel reactors in series and fed isobutylene continuously thereto to thereby effect polymerization. Further, Nagy et al. (Polymer Bulletin, 15, pp. 411-416, 1986) carried out cationic living polymerization of isobutylene by means of continuous polymerization in a tubular reactor. In Japanese Kokai Publication Hei-06-298843, there is proposed a method which comprises carrying out cationic living polymerization of isobutylene by means of continuous polymerization using a shell and tube heat exchanger and then introducing a vinyl group into the polymer terminus in a tubular reactor.
Whereas, in the conventional batchwise polymerization process, it is necessary to perform a cycle of raw materials charging, reaction and discharging process repeatedly, it can be expected, in the continuous polymerization process, that the productivity will be improved and the heat of reaction will be removed more efficiently since the steady operation can be carried out.
However, there still remain some problems in employing the continuous polymerization process for improving the productivity. Thus, as a result of carrying out continuous polymerization using one stirring vessel reactor, an isobutylene polymer with a distribution of 1.4 to 1.8 was obtained in U.S. Pat. No. 4,568,732, in Nagy et al. (Polymer Bulletin, 13, pp. 97-102, 1985), a polymer with a distribution of 1.6 to 2.7 and in Nagy et al. (Polymer Bulletin, 14, pp. 251-257, 1985), a polymer with a distribution of 1.4 to 1.8 were obtained, and these distribution values are higher than those obtainable in the above-mentioned batchwise polymerization processes of Japanese Kokai Publication Hei-07-292038, Japanese Kokai Publication Hei-08-53514, etc. Such tendency is presumably subject to the influence of the fact that when the reaction is carried out in the continuous flow-through mode using one stirring vessel, the residence time of the reaction solution has a wide distribution (i.e. polymer molecules differ in the residence time in the vessel one another), hence molecular chains growing by living polymerization during different residence times hardly become uniform in length. For anionic living polymerization as well, attempts have been made to carry out the reaction in a continuous flow-through stirring vessel. Reportedly, the polymers obtained show a molecular weight distribution value of 1.8 to 2.6 and this is attributable to the residence time distribution in the stirring vessel (Japanese Kokai Publication Hei-05-339326).
In the continuous polymerization method of Majoros et al. (Polymer Bulletin, 31, pp. 255-261, 1993) in which three stirring vessels are used in series, the residence time distribution is presumed to be improved as narrowed to give polymers with a molecular weight distribution of 1.35 to 1.37. Thus, a tendency that the distribution becomes uniform is manifested as compared with the use of one stirring vessel. However, the uniformity in molecular weight is inferior as compared with the batchwise polymerization process. In Japanese Kokai Publication Hei-06-298843, a shell and tube heat exchanger is used as a reactor in continuous polymerization of isobutylene using a trifunctional initiator, with the result that the molecular weight distribution of the polymer obtained is as high as 3.1. In the polymerization using a tubular reactor reported by Nagy et al. (Polymer Bulletin, 15, pp. 411-416, 1986), the distribution is 1.5 to 2.8. In a report on anionic living polymerization (Japanese Kokai Publication Hei-11-286520), polymers with a molecular weight distribution of 1.3 to 1.8 are obtained using a flow-through tubular reactor and, although the molecular weight distribution is rather smaller as compared with cationic living polymerization, the uniformity is not yet satisfactory. It is considered that when these tubular reactors were used, the mixing just after feeding of the raw materials to the reactor was insufficient and, as a result, the reaction did not occur adequately but side reactions concurred.
According to the method of Japanese Kokai Publication Hei-06-298843, polymers are synthesized using a trifunctional initiator and a vinyl group is further introduced into a polymer terminus. While, in this case, theoretically, the number of terminal vinyl groups based on the initiator should be 3, the reported number of terminal vinyl groups is 6.14. A reason therefor is supposedly that vinyl group termini were generated by side reactions in addition to the polymers having 3 vinyl groups resulting from the reaction as expected.
As discussed above, when cationic living polymerization is carried out by the continuous flow-through process, the residence time distribution of the reaction solution becomes wide
Furukawa Naoki
Terazawa Hiromu
Wachi Shun
Cheung William
Kaneka Corporation
Wu David W.
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