Page 131 - Engineering Plastics Handbook

Acrylonitrile-Butadiene-Styrene (ABS) Resin 105

rubber latex, followed by graft polymerization of styrene/acrylonitrile
copolymer.
Water is present in the continuous phase and plays a role of reaction
heat transfer material. The reactants are present in the discontinuous
phase. As the reaction proceeds, particles of ABS resins are produced in
water, and thus the high reaction heat peculiar to ABS polymerization
can be readily removed by water.
Polybutadiene rubber latex is prepared according to trans-1,4, cis-1,4
addition free-radical emulsion polymerization of butadiene. In this reac-
tion, an initiator such as KPS or NaPS can be used.
Oil-soluble initiators such as cumene hydroperoxide are generally used
as the initiator for ABS polymerization. The emulsifier plays a role to
facilitate the formation of discontinuous phase from the reactants, and
the typical example includes rosin, fatty SLS, oleate, etc. See Fig. 6.3.
The emulsifier is composed of a hydrophilic portion and a hydrophobic
portion, and it plays a role in forming the interface between water and
the reactants and in stabilizing the emulsion. The molecular weight reg-
ulator is typically TDDM, and it plays a role to prepare ABS resin having
the desired molecular weight by stopping the polymerization without
influencing the polymerization rate. Upon completion of polymerization,
polymer particles are obtained by adding acids or salts to remove the sta-
bility of emulsion and then are washed and dried to obtain the final ABS
resin.

M M M
BD
B/D M M
TNAK SM
PBL
TANK
AN
Poly PBL Polymerization Recovery PBL
Agglomeration ABS
Polymerization
Coagulant
DP SAN Additive
M
M Dehydrator
Compound
M M
Slurry
Coagulation Dryer LG
tank ABS
Aging NP
Extruder
DP
ABS DP
Dry LG
Figure 6.3 Emulsion polymerization process of ABS.