View source for Polybutene

Polybutene and polyisobutylene are liquid [[oligomer]]s widely used as  [[plasticizer]]s for high molecular weight [[polymer]]s, such as [[polyethylene]]. They are not to be confused with the high [[molecular weight]] polymer [[polybutene-1]].

==Properties==
The liquid is clear and colourless, and is sold in many different grades.  The grades are determined mainly by [[molecular weight]], with the higher molecular weight grades having increasing [[viscosity]]. The [[oligomer]] degrades at high temperature (upwards of 350 C) to form [[monomer]] [[isobutene]] by chains unzipping from the chain ends.

==Production==
Polybutene is similar to but different from polyisobutylene (PIB).  Polybutene is typically made from cat cracker mixed C4s (after the stream is Merox treated to remove sulfur and amines, and contain 1-butene, 2-butene and isobutylene.  Ethylene steam cracker C4s are also used as supplemental feed for polybutene.  On the other hand, PIB is produced from essentially pure isobutylene made in a C4 complex of a major refinery.  The presence of isomers other than isobutylene can have several effects including: 1) lower reactivity due to steric hinderance at the terminal carbon in, e.g., manufacture of polyisobutenyl succinic anhydride (PIBSA) dispersant manufacture; 2) the molecular weight - viscosity relationships of the two materials may also be somewhat different.

The reaction is an acid catalyzed carbocationic polymerization typically using aluminum chloride or hydrogen halide acid such as HF. So called "high reactivity" polybutene or PIB is produced using purified isobutylene feedstock and strong acid catalyst such as HF or HF with promoter.

==Structure==
The [[repeat unit]] is in case of 1-butene:

-[-CH<sub>2</sub>-CH(CH<sub>2</sub>CH<sub>3</sub>)-]<sub>n</sub>-

The [[repeat unit]] in case of 2-butene is:

-[-CH(CH<sub>3</sub>)-CH(CH<sub>3</sub>)-]<sub>n</sub>- 

One of the end units in the polymer chain contains a double bond, allowing reactivity with other compounds to provide functional chemistry mainly for lubricant additives for engine oils, fuels and greases.

==Oxidation==
But the same [[double bond]] makes the molecule sensitive to [[oxidation]] when hot liquid is exposed to air. The [[polymer degradation]] reaction produces [[aldehydes]] and [[ketone]]s, which are the further oxidised to [[carboxylic acid]]s. This causes loss of tack and makes the material soluble in [[water]].

==Applications==
It is used in two broad areas: 1) as a chemical intermediate for additives used in [[engine oil]]s, [[gasoline]] and [[Grease (lubricant)|grease]]s, and 2) formulations based on its physical performance characteristics.  It is used in preparation of polybutenyl succinic anhydride (PIBSA), a dispersant / VI improve in engine oils.  Industrial applications include, sealants, adhesives, extenders for putties used for sealing roofs and windows, coatings, polymer modification, tackified polyethylene films, personal care, polybutene emulsions.  Hydrogenated polybutenes are used in a wide variety of [[Cosmetics|cosmetic]] preparations, such as [[lipstick]] and [[lip gloss]]. It is used in [[adhesive]]s owing to its [[tack]]iness.  In addition it is used as a smoke inhibitor in two stroke engine fuels, where the benefit derives from the polymer decomposing (unzipping) at temperatures below the combustion temperature.

==Also see==
*[[Polybutene-1]]
*[[Oligomers]]

==Bibliography==
* Decroocq, S and Casserino, M, ''Polybutenes'', Chapter 17 in Rudnick (Ed), ''Synthetics, Mineral Oils, and Bio-Based Lubricants: Chemistry and Technology'', CRC Press (2005), Print ISBN: 978-1-57444-723-1, eBook ISBN: 978-1-4200-2718-1.


[[Category:Polymer chemistry]]
[[Category:Polymers]]
[[Category:Plasticizers]]



[[zh:聚丁烯]]
[[Category:2Fix]]