Process for producing high vinylidene polyisobutylene

Details Process for producing high vinylidene polyisobutylene Process for producing high vinylidene polyisobutylene

2002-12-31

2004-01-27

Teskin, Fred (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S064000, C526S237000, C526S212000, C526S348700, C585S521000, C585S525000

Reexamination Certificate

active

06683138

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the preparation of polyisobutylene (PIB). In particular the present invention relates to the preparation of highly reactive PIB having a relatively high degree of terminal unsaturation. In this latter regard, the invention provides a novel liquid phase process for the polymerization of isobutylene to prepare highly reactive PIB using a modified BF
3
catalyst.
2. The Prior Art Background
The polymerization of isobutylene using Friedel-Crafts type catalysts, including BF
3
, is a generally known procedure which is disclosed, for example, in “HIGH POLYMERS”, Vol. XXIV (J. Wiley & Sons, Inc., New York, 1971), pp. 713 ff. The degree of polymerization of the products obtained varies according to which of the various known polymerization techniques is used. In this latter connection, it is to be understood that the molecular weight of the polymeric product is directly related to the degree of polymerization.
It is also known that PIB may be manufactured in at least two different grades—regular and high vinylidene. Conventionally, these two product grades have been made by different processes, but both often and commonly use a diluted isobutylene feedstock in which the isobutylene concentration may range from 40-60% by weight. More recently it has been noted that at least the high vinylidene PIB may be produced using a concentrated feedstock having an isobutylene content of 90% by weight or more. Non-reactive hydrocarbons, such as isobutane, n-butane and/or other lower alkanes commonly present in petroleum fractions, may also be included in the feedstock as diluents. The feedstock often may also contain small quantities of other unsaturated hydrocarbons such as 1-butene and 2-butene.
Regular grade PIB may range in molecular weight from 500 to 1,000,000 or higher, and is generally prepared in a batch process at low temperature, sometimes as low as −50 to −70° C. AlCl
3
, RAlCl
2
or R
2
AlCl are used as catalysts. The catalyst is not totally removed from the final PIB product. Molecular weight may be controlled by temperature since the molecular weight of the product varies inversely with temperature. That is to say, higher temperatures give lower molecular weights. Reaction times are often in the order of hours. The desired polymeric product has a single double bond per molecule, and the double bonds are mostly internal. Generally speaking, at least about 90% of the double bonds are internal and less than 10% of the double bonds are in a terminal position. Even though the formation of terminal double bonds is believed to be kinetically favored, the long reaction times and the fact that the catalyst is not totally removed, both favor the rearrangement of the molecule so that the more thermodynamically favored internal double bond isomers are formed. Regular PIB may be used as a viscosity modifier, particularly in lube oils, as a thickener, and as a tackifier for plastic films and adhesives. PIB can also be functionalized to produce intermediates for the manufacture of detergents and dispersants for fuels and lube oils.
High vinylidene PIB, a relatively new product in the marketplace, is characterized by a large percentage of terminal double bonds, typically greater than 70% and preferentially greater than 80%. This provides a more reactive product, compared to regular PIB, and hence this product is also referred to as highly reactive PIB. The terms highly reactive (HR-PIB) and high vinylidene (HV-PIB) are synonymous. The basic processes for producing HV-PIB all include a reactor system, employing BF
3
and/or modified BF
3
catalysts, such that the reaction time can be closely controlled and the catalyst can be immediately neutralized once the desired product has been formed. Since formation of terminal double bonds is kinetically favored, short reactions times favor high vinylidene levels. The reaction is quenched, usually with an aqueous base solution, such as, for example, NH
4
OH, before significant isomerization to internal double bonds can take place. Molecular weights are relatively low. HV-PIB having a number average molecular weight (M
N
) of about 950-1050 is the most common product. Conversions, based on isobutylene, are kept at 75-85%, since attempting to drive the reaction to higher conversions reduces the vinylidene content through isomerization. Prior U.S. Pat. Nos. 4,152,499 dated May 1, 1979, 4,605,808 dated Aug. 12, 1986, 5,068,490 dated Nov. 26, 1991, 5,191,044 dated Mar. 2, 1993, 5,286,823 dated Jun. 22, 1992, 5,408,018 dated Apr. 18, 1995 and 5,962,604 dated Oct. 5, 1999 are directed to related subject matter.
U.S. Pat. No. 4,152,499 describes a process for the preparation of PIBs from isobutylene under a blanket of gaseous BF
3
acting as a polymerization catalyst. The process results in the production of a PIB wherein 60 to 90% of the double bonds are in a terminal (vinylidene) position.
U.S. Pat. No. 4,605,808 discloses a process for preparing PIB wherein a catalyst consisting of a complex of BF
3
and an alcohol is employed. It is suggested that the use of such a catalyst complex enables more effective control of the reaction parameters. Reaction contact times of at least 8 minutes are required to obtain a PIB product wherein at least about 70% of the double bonds are in a terminal position.
U.S. Pat. No. 5,191,044 discloses a PIB production process requiring careful pretreatment of a BF
3
/alcohol complex to insure that all free BF
3
is absent from the reactor. The complex must contain a surplus of the complexing agent in order to obtain a product wherein at least about 70% of the double bonds are in a terminal position. The specification broadly suggests that reaction times ranging from 10 seconds to several hours are within the contemplation of the disclosure; however, none of the specific examples reveals the residence time employed. Moreover, there is absolutely no disclosure whatsoever in the '044 patent which correlates reaction time with either the choice of catalyst complexing agent or the formation of terminal double bonds. Additionally, while the '044 patent reference broadly suggests that reaction temperatures may generally be below 0° C., in each of the specific examples, the reaction temperature is −10° C. or lower. And once again there is no disclosure whatsoever in the '044 patent which correlates reaction temperature with either the choice of catalyst complexing agent or the formation of terminal double bonds.
In addition to close control of reaction time, the key to obtaining high vinylidene levels seems to be control of catalyst reactivity. This has been done in the past by complexing BF
3
with various oxygenates including sec-butanol and MTBE. One theory is that these complexes are actually less reactive than BF
3
itself, disproportionately slowing the isomerization reaction and thus allowing for greater differentiation between the vinylidene forming reaction (polymerization) and the isomerization reaction rates. Mechanisms have also been proposed that suggest the BF
3
complexes are non-protonated and thus are not capable of isomerizing the terminal double bond. This further suggests that water (which can preferentially protonate BF
3
) must generally be excluded from these reaction systems. In fact, prior publications describing preparation of PIB using BF
3
complexes teach low water feed (less than 20 ppm) is critical to formation of the high vinylidene product.
HV-PIB is increasingly replacing regular grade PIB for the manufacture of intermediates, not only because of higher reactivity, but also because of developing requirements for “chloride free” materials in the final product applications. Important PIB derivatives are PIB amines, PIB alkylates and PIB maleic anhydride adducts.
PIB amines can be produced using a variety of procedures involving different PIB intermediates which provide a reactive site for subsequent amination. These intermediates may include, for example, epoxides, halides, maleic anhydride add

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