Polymerization process

Details Polymerization process Polymerization process

2002-10-09

2004-11-30

Harlan, Robert D. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S115000, C526S117000, C526S171000, C526S172000

Reexamination Certificate

active

06825292

ABSTRACT:

The present invention relates to a process for the polymerisation and copolymerisation of 1-olefins, and particularly to a process for transitioning between different polymerization catalyst systems.
During the production of olefin polymers in a commercial reactor it is often necessary to transition from one type of catalyst system producing polymers having certain properties and characteristics to another catalyst system capable of producing polymers of different chemical and/or physical attributes. Transitioning between similar traditional Ziegler-Natta type catalysts for example, or compatible catalysts, generally takes place easily. However, where the catalysts are incompatible or of different types the process is typically complicated. For example, transitioning between a traditional Ziegler-Natta type catalyst and chromium based catalyst, two incompatible catalysts, it has been found that some of the components of the traditional Ziegler catalyst or the cocatalyst/activator act as poisons to the chromium based catalyst. Consequently, these poisons prevent the chromium catalyst from promoting polymerization. In another example, the extreme different responses to molecular weight regulators, such as hydrogen and comonomer, of traditional Ziegler-Natta catalysts and metallocene catalysts makes these catalysts incompatible. Any traces of active Ziegler-Natta catalyst will produce very high molecular weight product under metallocene catalyst reactor conditions. Furthermore, particularly in a continuous transitioning process, the interaction between the two incompatible catalysts may lead to production of high levels of small particles less than about 100 microns, termed fines. These fines can induce operability problems in the reactor such as fouling and sheeting.
In known transitioning techniques, to accomplish an effective transition between incompatible catalysts, the first catalyzed olefin polymerization process is stopped by various techniques known in the art. For example in reactions involving use of chromium based catalysts, oxygen, CO, water or polar hydrocarbons such as alcohols, ethers, ketones and aldehydes are known to be effective in reaction termination. The reactor is then emptied, recharged and a second catalyst is introduced into a reactor. Such catalyst conversions are time consuming and costly because of the need for a reactor shut-down for an extended period of time during transition.
WO 99/12981 discloses that ethylene and other 1-olefins may be polymerised by contacting it with certain late transition metal complexes of selected 2,6-pyridinecarboxaldehydebis (imines) and 2,6-diacylpyridinebis (imines).
EP-A-751965 discloses methods of transitioning between incompatible catalysts, involving the use of catalyst killers. It defines “incompatible” catalysts as those which satisfy one or more of the following criteria: 1) those catalysts that in each other's presence reduce the activity of at least one of the catalysts by greater than 50%; 2) those catalysts such that under the same reactive conditions one of the catalysts produces polymers having a molecular weight greater than two times higher than any other catalyst in the system; and 3) those catalysts that differ in comonomer incorporation or reactivity ratio under the same conditions by more than about 30%.
According to the above definition, late transition metal catalysts such as the above-mentioned 2,6-pyridinecarboxaldehydebis(imine) type catalysts are incompatible with most known types of catalysts. For example, 2,6-pyridinecarboxaldehydebis(imine) type catalysts typically exhibit a very low comonomer incorporation or reactivity ratio compared with other catalyst types. Accordingly it would be expected that transitioning from one to the other would require procedures such as those described above for incompatible catalysts, with all the attendant disadvantages.
We have surprisingly discovered however that it is possible to transition between late transition metal catalysts and catalysts which are incompatible according to the above definition without the need for such procedures.
Accordingly in a first aspect the present invention provides a process for the polymerisation and copolymerisation of 1-olefins in which a transition is made between two catalysts, comprising the steps of
a) discontinuing the feed of the first catalyst into the polymerization reactor, and then
b) introducing the second catalyst into the reactor,
wherein one of the catalysts comprises a late transition metal catalyst and the other is a catalyst which is incompatible therewith.
Preferably the transition is effected by introducing the second catalyst without first eliminating all activity of the first catalyst and/or without first removing all traces of the first catalyst. More preferably, no deactivating agent (catalyst killer) is used.
In an alternative embodiment, subsequent to step a) a deactivating agent in a sufficient amount to deactivate the first catalyst is introduced into the reactor before the second catalyst is introduced into the reactor.
By “late transition metal catalyst” (hereinafter LTM catalyst) is meant a catalyst comprising a complex of a metal from Groups VIIIb or Ib of the Periodic Table.
By “incompatible” is meant the definition previously given: namely that the two catalysts satisfy at least one of the following conditions: 1) catalysts which in each other's presence reduce the activity of at least one of the catalysts by greater than 50%; 2) under the same reactive conditions one of the catalysts produces polymers having a molecular weight two times or more that of any other catalyst in the system; and 3) catalysts that differ in comonomer incorporation or reactivity ratio under the same conditions by more than 30%.
Catalysts which are incompatible with the LTM catalysts includes Phillips type (chromium) catalysts, metallocene catalysts and Ziegler-Natta catalysts. However this invention also includes within its scope the case where two LTM catalysts are incompatible with each other according to the above definition.
Preferably the LTM catalyst comprises a complex of the formula
wherein M is Fe[II], Fe[III], Co[II], Co[III], Ni[II], Rh[II], Rh[III], Ru[II], Ru[III], Ru[IV] or Pd[II]; X represents an atom or group covalently or ionically bonded to the transition metal M; T is the oxidation state of the transition metal M and b is the valency of the atom or group X; L is a group datively bound to M, and n is from 0 to 5; A
1
to A
3
are each independently N or P or CR, with the proviso that at least one is CR; and R and R
4
to R
7
are each independently selected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl, substituted heterohydrocarbyl or SiR′
3
where each R′ is independently selected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl.
A typical Phillips type catalyst employs a combination of a support material to which has first been added a chromium-containing material wherein at least part of the chromium is in the hexavalent state by heating in the presence of molecular oxygen. The support is generally composed of about 80 to 100 wt. % silica, the remainder, if any, being selected from the group consisting of refractory metal oxides, such as aluminium, boria, magnesia, thoria, zirconia, titania and mixtures of two or more of these refractory metal oxides. Supports can also comprise alumina, aluminium phosphate, boron phosphate and mixtures thereof with each other or with silica.
The chromium compound is typically added to the support as a chromium (III) compound such as the acetate or acetylacetonate in order to avoid the toxicity of chromium (VI). The raw catalyst is then calcined in air at a temperature between 250 and 1000° C. for a period of from a few seconds to several hours. This converts at least part of the chromium to the hexavalent state. Reduction of the

Affiliated with

Also associated with

Rating

Polymerization process does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Polymerization process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymerization process will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3358977