Lubricant Additives

150 Lubricant Additives: Chemistry and Applications

anhydride copolymer or styrene–maleic anhydride–alkyl acrylate terpolymer with alcohols, usually
in the presence of a protic acid, such as sulfuric or methanesulfonic acid, catalyst. Since complete
esterifi cation of the anhydride is hard to achieve, the neutralization of the residual carboxylic acid
anhydride is carried out by alternative means [38–40].

FIGURE 5.3 Polyisobutylene structures and the mode of their formation.

R

H 3 C CH (^3) CH 3
CH 2
Terminal olefin (vinylidene)
I
IV
V
IX VIII III
Trisubstituted olefin
Tetrasubstituted olefin
IV
V
VI VII
Trisubstituted olefin
Tetrasubstituted olefin Carbocation intermediate
Trisubstituted olefin
R = polyisobutyl
II III
R
H
H 3 C CH 3 CH 3
CH 3
R
H 3 C CH 3 CH 3
CH 3
H
R
H
R H
H
H H
H
1
1
2
(^43)
CH 3 CH (^3) H 3 C
CH 3
CH 3
CH 3 CH 3
C

• R + + +
  CH 3
  CH 3
  H
  H 3 C CH 3
  H
  (^43)
  2
  1
  1


• 
  


• 
  

  CH 3 CH 3
  CH 3
  CH 3
  CH 3
  CH 3 CH 3
  CH 3
  CH 3
  CH 3 CH 3
  (^4322432)
  1 CH 3
  1
  1 1
  3
  R 4
  1
  1
  1
  2
  (^43)
  R
  H
  R
  H H
  H
  H
  1
  1
  3
  2
  3 2
  1
  H
  4 4
  C 3 to C 2
  hydride
  transfer
  C 2 to C 3
  methide
  transfer
  C 4 to C 3
  methide
  transfer
  C 3 to C 4
  hydride
  transfer
  C 3 proton
  loss
  R
  H
  CH (^3) CH
  3
  H 3 C CH 3 CH^3 CH 3
  H
  H 3 C
  H 3 C
  R
  H
  Not shown
  by arrow
  C 2 proton
  loss
  R
  H 3 C CH 3 CH 3
  CH 3
  H