Lubricant Additives

Olefi n Copolymer Viscosity Modifi ers 303

type and concentration of PPD that will be effective in keeping wax crystals small so that they do

not form network structures and lead to high viscosity and yield stress. Both the feedstocks and de-

waxing steps used in the manufacture of a given base oil determine wax composition and, in turn,

PPD response.

Certain types of viscosity modifi ers can interact with base oils and PPDs at low temperatures

and can lead to excessively high MRV viscosities in some situations (see, for example, OCP9 in

Table 10.8). Formulating with amorphous OCPs has not, in the author’s experience, posed many

diffi culties. Conversely, LTOCPs possess longer ethylene sequences that have the potential to

interact with wax crystals at low temperatures. Several reports in the literature [66,76] suggest that

high-ethylene OCPs can, under certain circumstances, interact negatively on MRV viscosity and

yield stress and may be more sensitive to the type of PPDs that will be effective in some formulat-

ing systems.

A previously unpublished study of low-temperature interactions among base oils, OCP visco-

sity modifi ers, and PPDs was carried out in the author’s laboratory using components listed in

Tables 10.9 through 10.11.

Fully formulated SAE 5W-30 and 15W-40 engine oils were blended using performance additive

packages DI-1 (at 11 wt%) and DI-2 (at 13 wt%); API SJ quality and CH-4 quality, respectively; and

all combinations of base oil, VM, and PPD.

TABLE 10.9

Base Oils Used in Low-Temperature Viscosity Modifi er/Pour Point Depressant

Interaction Study

Base Oil Code

(API Group) Saturates (wt%)

Kinematic Viscosity

(cSt) at 100°C Sulfur (wt%) Viscosity Index

CCS Viscosity

(cP) at –25°C

B1-L (I) 73.6 3.88 0.276 104 1170

B1-M (I) 71.8 5.15 0.553 102 4060

B1-H (I) 61.8 12.10 0.381 97 —

B2-L (I) 75.2 4.18 0.193 105 1510

B2-M (I) 75.0 4.91 0.544 106 3060

B2-H (I) 72.3 12.73 0.412 99 —

B3-L (II) 100 4.20 0.006 100 1570

B3-M (II) 100 5.49 0.011 117 2430

B3-H (II) 100 10.72 0.016 98 —

B4-L (III) 100 4.50 0.007 123 1120

B4-H (III) 100 6.49 0.006 131 2710

TABLE 10.10

Viscosity Modifi ers Used In

Low-Temperature Viscosity

Modifi er/Pour Point Depressant

Interaction Study

VM Code OCP Type

SSI (ASTM

D6278)

VM-1 Amorphous 37

VM-2 LTOCP 35

VM-3 LTOCP 37

TABLE 10.11

Pour Point Depressants Used In

Low-Temperature Viscosity Modifi er/Pour

Point Depressant Interaction Study

Pour Point Depressant Code Chemistry

PPD-1 Poly(styrene-maleate ester)

PPD-2 Poly(alkylmethacrylate)

PPD-3 Poly(styrene-maleate ester)

PPD-4 Poly(alkylmethacrylate)

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