process oils

INTRODUCTION TO PROCESS OILS
Krisda SUCHIVA
Research and Development Centre for Thai Rubber Industry,
Mahidol University

INTRODUCTION TO PROCESS OILS
Process oils are used in the rubber industry to,
• improve the processability of rubbers and rubber
compounds
process aids
• increase the bulk of rubber in order to lower cost
oil-extended rubbers
Main application is process aid.
2

INTRODUCTION TO PROCESS OILS
Process aids are increasingly important for the rubber
industry due to the following needs,
- improve efficiency and productivity
- lower energy consumption
In total,
- reduce production cost
- improve product quality
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INTRODUCTION TO PROCESS OILS
Functions of process aids,
1. reduce viscosity
2. reduce elasticity
3. aid dispersion of fillers
4. reduce power consumption
Additional requirement
1. do not affect intended properties of finished products
2. act at low dosage level
3. non-toxic
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INTRODUCTION TO PROCESS OILS
Materials used as process aids,
1. chemical peptizers
2. fatty acid soaps
3. fatty acid ester
4. petroleum oils
5. factice
6. resins
7. partially vulcanised rubber
8. liquid polymers
9. waxes
Process oil is just one of the process aids.
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INTRODUCTION TO PROCESS OILS
How do process aids work ?
For reduction of viscosity and elasticity
2 Mechanisms,
1. Lowering molecular weight of polymer
peptizer
• molecular entanglement reduced
• easier flow of molecules
Chemical processing aids
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INTRODUCTION TO PROCESS OILS
2. Lowering of intermolecular interactions
process aid
• flow of molecules become easier
Most process aids work on this principle
e.g. fatty acid soaps, fatty acid ester, oils, liquid polymers.
No reduction in MW, hence the final properties not affected
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INTRODUCTION TO PROCESS OILS
Efficiency of physical process aids depend on degree of miscibility
with polymer or solubility in polymers.
most efficient
completely miscible
or
completely soluble
partially miscible
or
partially soluble
most effective in reducing
viscosity
only small amount is required.
less efficient
less effective in reducing
viscosity
Higher amount is required.
immiscible
or
insoluble
least efficient
least effective in reducing
viscosity
large amount is required. 8

PROCESS OILS
9

PROCESS OILS
Origin and Composition of Process Oils
• PROCESS OILS are derived from petroleum (crude oil) after the
more volatile petrol and heating oil fractions have been removed by
distillation.
• PROCESS OILS are MIXTURES of paraffinic, naphthenic and
aromatic compounds of wide distribution of molecular weight.
Paraffinic oils
CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 CHCH 2 CHCH 2 CH 3 CH 2
paraffins
isoparaffins
CH 3 CH 3
Naphthenic oils
Aromatic oils
derivatives of cyclohexane or decalin
derivatives naphthalene, debenzothiophene,
carbazole, etc.
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PROCESS OILS
Type of Process Oils
Type
%
paraffinic
%
naphthenic
%
aromatic
VGC
Paraffinic oil 60-74 20-35 0-10 0.790-0.819
Naphthenic oil 35-45 30-45 10-30 0.850-0.899
Aromatic oil 20-35 20-40 35-50 0.950-0.999
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PROCESS OILS
Important Properties of Process Oils
1. solubility or miscibility or compatibility with rubbers
• Determine efficiency in reducing viscosity/flow characteristics
• Depends on,
- % Aromaticity : the higher, the more efficient
- molecular weights (viscosity) : the smaller, the more
efficient
• High solubility means more oil can be incorporated into the
rubber
higher loading of oil possible.
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PROCESS OILS
Important Properties of Process Oils
• Level of aromaticity measured by
1) VISCOSITY GRAVITY CONSTANT (VGC)
G
= 1.0752-a
a
specific gravity
VGC
10
log(V+38)
Viscosity (saybolt)
High VGC = high aromaticity
2) ANILINE POINT
Aniline point = temperature at which equal volumes
oil and aniline are mutually soluble.
Low Aniline Point = high aromaticity
note : ● Aniline point can be influenced by MW of oil.
● Can be difficult to determine with very dark and opaque oils.
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PROCESS OILS
Important Properties of Process Oils
Compatibility of process oils with various rubbers
Oil Type
Rubbers
NR SBR BR NBR CR EPDM IIR
Paraffinic + + + - - + +
Naphthenic + + + 0 0 + 0
Aromatic + + + + + 0 -
+
0
-
compatible
partially compatible
incompatible
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PROCESS OILS
Important Properties of Process Oils
2. Colour stability/Contact staining
Colour stability (increasing darkness) decreases with
increasing % aromaticity.
paraffinic oils > naphthenic oils > aromatic oils
3. Ageing resistance
Ageing resistance decrease with increasing % aromaticity.
paraffinic oils > naphthenic oils > aromatic oils
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PROCESS OILS
4. Loss of oil during high temperature service of rubber
product containing oil.
• Determined by FLASH POINT
5. Toxicity
Important Properties of Process Oils
• Become increasingly important
• Process oils contain Polycyclic Aromatic Hydrocarbons (PAHs)
or Polycyclic Aromatic (PCA) which are carcinogen and can
cause mutation.
• Regulations (European Directive 2005/69/EC) imposed ban of
process oils containing ≥ 10mg/kg (ppm) of PAH since
2010.
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PROCESS OILS
Important Properties of Process Oils
• Trend towards low PAH (

PROCESS OILS
Polycyclic Aromatic Hydrocarbons
PAH S Chemical Formulas MW (g.mol -1 ) Chemical Structures
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PROCESS OILS
Polycyclic Aromatic Hydrocarbons
PAH S Chemical Formulas MW (g.mol -1 ) Chemical Structures
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PROCESS OILS
Comparison of Different Process Oils
Effects on properties of rubber compounds and vulcanisates
Process Oils Compared
Aromatic
Naphthenic
Paraffinic
Sample number Saybolt viscosity VGC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
38°C 100°C
4360
3500
-
2520
2206
760
156
-
110
104
2642
500
-
110
-
210
96
81
85.9
84.7
60
41.0
43.5
38.2
38.0
155
63.5
42.3
40.4
38.0
0.991
0.954
0.981
0.883
0.882
0.869
0.878
0.830
0.886
0.871
0.800
0.803
0.805
0.807
0.832
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PROCESS OILS
Comparison of Different Process Oils
FORMULATION FOR OIL EVALUATION
NR
Zinc oxide
Stearic acid
N-330 carbon black
N- Isopropyl-N’ -phenyl-p-phenylenediamine
Oil
N- Oxydiethylenebenzothiazole-2-sulphenamide
Sulphur
Part by weight
100
5
2.5
45
1.5
10 or 20
0.8
2.5
MIX CYCLE : BR BANBURY
Time (min)
0
0.5
1.0
2.0
3.5
Action
Add rubber.
Add small powders.
Add half black.
Half black plus oil.
Dump.
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PROCESS OILS
Comparison of Different Process Oils
Effects on Mooney Viscosity
Mooney viscosity, ML 1+4, 100 ° C
Mooney viscosity, ML 1+4, 100 ° C
60
50
50
40
30
20
10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Aromatic Oils Naphthenic Oils Paraffinic Oils
10 phr
Naphthenic oils tend to give lower
mooney viscosity
40
30
20
10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Aromatic Oils Naphthenic Oils Paraffinic Oils
20 phr
Paraffinic oils tend to give lower
mooney viscosity
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PROCESS OILS
Comparison of Different Process Oils
Vulcanisation Characteristics (ODR 100°C)
Oil Type Sample 10 phr oil 20 phr oil
Aromatic
Naphthenic
Paraffinic
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
t s5
(min)
4.12
3.42
4.16
3.58
3.53
5.16
3.52
3.47
3.48
4.15
4.07
3.57
4.04
4.00
4.21
T c (90)
(min)
14.33
13.13
13.47
14.31
13.40
14.51
14.43
14.28
14.21
13.56
14.20
14.22
14.45
13.45
14.06
M HR
(torque
33.0
35.6
32.9
32.5
35.5
30.2
33.5
32.1
35.5
32.7
34.6
33.4
33.9
32.5
35.5
M L
units)
7.35
7.45
8.25
7.39
7.36
9.25
7.41
8.16
7.37
7.58
7.44
7.52
7.57
7.13
7.28
t s5
(min)
4.51
3.58
4.25
4.39
4.28
5.00
4.17
4.25
4.17
4.31
4.26
4.35
4.35
4.29
4.39
T c (90)
(min)
16.00
14.32
14.28
15.18
15.11
16.05
14.50
15.24
16.02
15.18
15.13
14.32
16.28
14.58
15.00
M HR
(torque
24.3
27.2
30.3
28.7
27.4
25.4
30.5
27.8
27.2
27.6
28.0
28.8
26.3
27.2
26.4
M L
units)
8.46
7.08
9.00
8.16
8.25
8.53
7.50
8.42
8.22
7.58
8.07
8.16
8.56
8.28
8.14
Little difference was observed for various oil types at 10 and 20 phr. 23

PROCESS OILS
Hardness, IRHD
70
Comparison of Different Process Oils
Effect on Hardness
60
50
40
30
20
Average Values of Hardness for
the Three Oil Types
Dosage
(phr)
A N P
10 62 61.5 62
20 56.5 56 54.5
10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Aromatic Naphthenic Paraffinic
20 phr
Some effects on hardness
• Almost no effect on hardness at
10 phr.
• At 20 phr. paraffinic oils show
slightly greater softening effect.
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PROCESS OILS
Comparison of Different Process Oils
Tensile strength, MPa
Effect on Tensile Strength
30
8
25 2
6 7 9
3
11
10
12 13 14 15
1
4 5
20
unaged
15
10
5
aged 28 days 70 ° C
aged 3 days 100 ° C
Aromatic Naphthenic Paraffinic
20 phr of oil
aged 7 days 100 ° C
• Individual oils gave widely different values of T.S
• Effect of different types of oils on unaged, 70 ° C aged or
100 ° C aged are slight. 25

PROCESS OILS
Comparison of Different Process Oils
Compression set, %
60
Effect on Compression Set
50
1 day 100 ° C
40
30
7 days 70 ° C
20
10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Aromatic Naphthenic Paraffinic
20 phr of oil/25% initial compression
Paraffinic and naphthenic oils tend to give lower
compression set values than aromatic oil. 26

PROCESS OILS
Comparison of Different Process Oils
Effect on Dunlop Resilience
Dunlop resilience, 23 ° C, %
80
70
60
50
40
30
20
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Aromatic Naphthenic Paraffinic
20 phr of oil
• Aromatic oil gave lower resilience
• Higher viscosity oils gave lower resilience
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PROCESS OILS
Performance of Low PAH/PCA Oils
Rolling Resistance
110
108
106
104
102
Wet Grip
+
TDAE
MES
NAP
RAE
100
98
96
94
92
90
DAE TDAE MES NAP RAE
-
-
Rolling Resistance
+
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PROCESS OILS
SUMMARY
1. Process oils are used to improve the processability of rubber
compounds or to increase the bulk of rubber in order to lower cost.
2. Although process oils are classified as paraffinic (CP) naphthenic
(CN) or aromatic (CA), they are mixtures of CP/CN/CA.
3. The efficiency of oil in reducing viscosity and elasticity depends on
its compatibility with rubber or its solubility in rubber.
- good compatibility/solubility efficient
- smaller quantity may be used.
4. Compatibility or efficiency depends on
- % aromaticity : the higher, the more efficient
- MW or viscosity : the smaller, the more efficient
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PROCESS OILS
SUMMARY
5. Study on NR compounds showed that the vulcanisation properties
and vulcanisate properties, unaged and aged, are not greatly
affected by type of process oil.
6. Toxicity of process oils is of major concern at present.
- Polycyclic Aromatic Hydrocarbon (PAH) is carcinogen and
may cause mutation.
7. European Directive 2005/69/EC imposed ban on process oils
containing ≥10 ppm of PAH since 2010.
8. The developing trend in process oil is towards low PAH oils.
- TDAE
- MES
- NAP
- RAE
- Vegetable oils 30

Q & A
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