development of advanced calcium-lithium soap grease with minimum uses of lithium hydroxide

Development of Advanced Calcium-Lithium Soap

Grease with Minimum Uses of Lithium Hydroxide

Dr. Ashok K. Goyal, N.Parameswaran, Dr. B. Ghosh & Ananda Sengupta

Balmer Lawrie & Co Ltd Applications Research Laboratory,

Kolkata

SMART WORLD

Smart Phones

Smart Watches

Smart T.V.

Laptops

Tablets

Electric Vehicles

SMART WORLD OF SMART TECHNOLOGY

Lithium Ion Batteries - Most Popular Lithium has the highest electric output per unit weight. Battery manufacturers across the world are moving to

lithium.

POWER SOURCE FOR SMART TECHNOLOGY

Ceramics and glass Industries - 35%

Rechargeable Batteries - 29%

Lubricating Greases - 8%

Air Treatment - 5%

Polymer Production - 5%

Primary Batteries - 2%

Primary Aluminum Production - 1%

Other Uses - 9%

Above data are taken from U.S. Geological Servey Minerals Yearbook, 2013

Present Uses of Lithium Hydroxide in Different Sectors

Calcium Soap Greases

Calcium Complex Greases

Simple Lithium Soap Greases

Lithium Complex Greases

Aluminium Complex Greases

Sodium Soap Greases

Non-Soap Greases

Polyurea Greases

Sulphonate Complex Greases etc.

Types of Lubricating Greases

76.67%

Global Grease Production Survey NLGI 2012

90.88%

Grease Production Survey NLGI 2012 (India and Indian Subcontinent)

Lesser Availability of Lithium Hydroxide Because of

• Increasing Demand lithium batteries in Smart Devices

• Increasing Demand in Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV)

• Depleting Natural Sources of Lithium

The price of Lithium Hydroxide increasing day by day

Present Scenario for Availability of Lithium Hydroxide for Grease Manufacturing

Project was taken to develop a grease without or lesser uses of lithium hydroxide exhibiting properties near to lithium soap greases.

Calcium hydroxide was chosen as a main base because calcium soap greases are the second largest produced greases.

Calcium hydroxide (Hydrated lime) is easily available every where at cheaper cost.

Knowledge about the properties of conventional calcium soap and calcium complex soap greases alongwith the lithium soap greases is very essential to overcome the drawbacks in newly developed grease.

Development of Advanced Calcium-Lithium Soap Grease

Calcium soap greases are oldest metal soap greases

Dropping points of calcium soap grease are in between 90-120 ⁰C

Water is very much essential to stabilize the structure of grease

Upper temperature limit in any application is only 50-70 ⁰C

At high temperature water evaporates leading to breaking in grease soap structure

Applicable only in less demanding applications

Fair shear stablity

Calcium Soap Greases

Calcium complex greases have the high dropping point

On storage at room temperature these greases will slowly harden when exposed to air.

The hardening begins at the grease/air interface and slowly extend further into the bulk of the grease with time.

This phenomenon is well known as “Case Hardening”

Calcium complex greases also severely harden under sustained high temperatures.

Because of case hardening tendency these greases can not become popular and acceptable for uses.

Poor Shear Stability

Calcium Complex Soap Greases

High Dropping Point (High Heat Resistance)

Excellent Shear Stability

Smooth Texture

No hardening Tendency

Easily Pumpable

Good water resistant property

Very good anti-wear performance

Can be used in Multipurpose applications

Easy Manufacturing Process

Simple Lithium Soap Greases

High Dropping Point (High Heat Resistance)

Very good Shear Stability

Smooth Texture

No significant hardening Tendency

Easily Pumpable

Good water resistant property

Very good anti-wear performance

Easy Manufacturing Process

Can be used in Multipurpose applications


Manufacturing Process

Similar to the process of simple lithium soap greases or lithium complex greases

Fatty Acid / Fat Melting

Saponification

Complexation / Chelation

Cooling

Additive Mixing

Homogenization after cooling

Developed grease offers substantial savings in terms of reduced power and fuel consumption due to lesser processing temperature required for manufacturing


Dropping point of the developed grease was checked as per ASTM D 566 test method

Results were compared with Calcium Soap, Calcium complex and lithium soap greases

Dropping Point of developed grease was found near to the lithium soap greases

Dropping Point


S. No. Type of Grease Dropping

Point, ⁰C

1. Calcium soap grease (Hydration method) 86

2. Calcium soap grease (Anhydrous method) 123

3. Calcium complex Grease (Conventional

Method) 266

4. Advanced calcium-lithium soap grease 195

5. Simple lithium soap grease 199

Dropping Point Test Data of Different Greases with Developed Grease

Dropping Point

Evaluation of the grease soap structure stability was carried out by Two Methods

100,000 Up & Down Strokes (Vertical Shearing) ASTM D 217

Rolling Stability Test at Room Temp. (Rotational Shearing under load)

ASTM D 1831

Stability Against Mechanical Shearing

S.

No. Type of Grease

Penetration

after 60 strokes

@ 25 ⁰C

Penetration after

100000 strokes @

25 ⁰C

Penetration

change after roll

stability test @

rt, 16 hrs.

1. Calcium soap grease

(Hydration method) 287 353 (+70) +63 Units

2. Calcium soap grease

(Anhydrous method) 292 366 (+74) +66 Units

3. Calcium complex Grease

(Conventional Method) 285 376 (+91) +87 Units

4. Advanced calcium-

lithium soap grease 283 316 (+33) +36 Units

5. Simple lithium soap

grease 288 315 (+27) +32 Units

Test Data of Mechanical Shearing Stability of Developed Grease and Other Greases

Stability Against Mechanical Shearing

Case hardening tendency of the developed grease has been checked by

At Room Temperature in Open Air

Wheel Bearing Leakage Test at 105 ⁰C for 6 hours (ASTM D 1263)

Roll Stability Test at 82 ⁰C for 96 hours (modified ASTM D 1831)

Hardening Tendency

S. No. Type of Grease

Unworked

Penetration @

25 ⁰C

Penetration @

25 ⁰C after 60

days storage at

rt

Penetration

@ 25 ⁰C after

90 days

storage at rt

1. Calcium complex Grease 274 187 (-87) 171

2. Advanced calcium-lithium

soap grease 276 273 (-3) 272

3. Simple lithium soap grease 279 277 (-2) 277

Tendency of Case Hardening in Different Greases on Storage at Ambient Temperature

Hardening Tendency

S. No. Test Performed

Test Results

Advanced Ca-Li

soap Grease

Simple lithium

soap grease

1. Change in penetration after roll stability

at 82 ⁰C for 96 hrs. +43 units +54 units

2. Wheel bearing Leakage Test

i Oil leakage in grams 0.73 0.88

ii Change in penetration of grease applied

in bearing hub of the instrument -9 units -8 units

iii Condition of the grease Smooth Smooth

Tendency of Case Hardening in Different Greases on Storage at Elevated Temperature

Hardening Tendency

Anti-wear properties of the grease was testes by Four Ball Wear Scar Diameter Measurement (ASTM D 2266) RPM - 1200 Time - 3600 Sec. Temp. - 75 ⁰C Load - 40 kg.

Coefficient of Friction by SRV Instrument (ASTM D 5707) Temp. - 50 ⁰C Time - 7200 Sec. Amplitude/stroke - 1 Frequency - 50 Hz.

Anti-wear Characteristics

Calcium Soap grease Advanced Ca-Li Soap Grease Simple Lithium Soap Grease

Simple Lithium Soap Grease Advanced Ca-Li Soap Grease Lithium soap grease with AW/EP additive Advanced Ca-Li grease with AW/EP Additive

Frictional Torque with Time During Four Ball Anti-Wear Test with and without Anti-Wear Additive in different greases


S. No. Type of Grease Four Ball Wear

Scar Dia, mm

Coefficient of

Friction by SRV

1. Calcium soap grease 0.71 0.119

2. Advanced calcium-lithium soap

grease 0.57 0.113

3. Advanced calcium-lithium soap

grease with EP/AW additives 0.46 0.106

4. Simple lithium soap grease 0.55 0.111

5. Simple lithium soap grease with

EP/AW additives 0.45 0.104

Anti-Wear Characteristics Data of the Greases Received from Four Ball and SRV Test Methods


Application temperature limit of metallic soap greases are decided by their dropping/melting points.

Maximum application temperature of greases are generally 70-100 ⁰C lesser than their dropping points

Maximum temperature limit for simple lithium greases is kept around 100-120 ⁰C

Similarly Maximum temperature limit for Advanced Calcium -Lithium soap grease should be around 100-120 ⁰C

Anti-wear test at SRV instrument has been performed with ramping of temperature

Heat /Thermal Stability of the Grease Thickener

Frequency - 50 Htz

Amplitude/stroke - 1.0 mm

Temperature - Time

50 ⁰C - 30 minutes

80 ⁰C 30 minutes






Temperature Ramping Anti-wear test at SRV

Temperature Ramping Anti-wear test at SRV

Anti-wear performance of developed calcium-lithium soap grease is very good up to 100 ⁰C and shows similar behavior as shown by simple lithium soap grease.


Calcum Complex Grease

Advanced Calcum –Lithium Soap Grease

Lithium Soap Grease

Advanced calcium-lithium soap grease is substantially non-corrosive (with additive) under prolonged wet conditions

The grease also retains its chemical composition for extended periods of time under operating conditions.

Advanced calcium –lithium soap grease does not suffer from loss of lubricating power due to case hardening

No significant hardening is associated with an improvement in the pumpability of the developed grease

Miscellaneous Characteristics

S.

No. Characteristics

Advanced Ca-Li

Non EP Grease

Advanced Ca-Li

EP Grease

Simple Li Soap

Grease

Simple Li Soap

EP Grease Test Method

1. Appearance Smooth &

Homogenous

Smooth &

Homogenous

Smooth &

Homogenous

Smooth &

Homogenous Visual

2. Worked Penetration, after 60 strokes

(W60) 283 285 288 289 ASTM D 217

3. Worked Penetration after 100000

strokes (change in Units) 316 (+33) 319 (+34) 315 (+27) 318 (+29) ASTM D 217

4. Dropping Point, °C 195 213 199 198 ASTM D 566

5. Wear Scar Dia, mm 0.57 0.46 0.55 0.45 ASTM D 2266

6. Four Ball Weld Load, Kgs. 160 250 160 250 IP 239

7. Roll Stability test 16 Hrs @ room

temp., Change in Penetration +36 Unit +38 Units +35 Units +37 Units

ASTM D 1831

(Modified)

8. Roll Stability test 96 Hrs @ 82 ⁰C,

Change in Penetration +43 Units +47 Units +54 Units +57 Units

ASTM D 1831

(Modified)

9.

Wheal Bearing Leakage Test

ASTM D 1263 (i) Oil Leakage in gms, 0.73 0.86 0.88 0.97

(ii) Evidence of abnormal change in

consistency for structure of the

material

No abnormal

change

No abnormal

change

No abnormal

change

No abnormal

change

10. Hardening on Storage after 3 months,

change in penetration

No significant

hardening

No significant

hardening

No significant

hardening

No significant

hardening ASTM D 1403

Comparison of the Properties of Advanced Calcium-Lithium Soap Greases with Lithium Soap Greases

Advanced calcium-lithium soap grease has been developed by using easily available calcium hydroxide as a main alkaline material with minimal use of lesser abundant lithium hydroxide.

Excellent tribological properties and suitable for use in industrial applications.

Very good mechanical shear stability in both vertical and rotational motion

Very good dropping point results which are comparable with the dropping point of simple lithium soap grease.

Wear characteristics of the developed grease are closer to the simple lithium soap greases.

Conclusions

The case hardening tendency has been overcome in the developed grease

No significant hardening was also observed at elevated temperatures

Equal flexibility to the grease formulators to develop high performance products by using additives as used in lithium soap greases.

Substantial savings in terms of reduced power and fuel consumption due to lesser processing temperature required for manufacturing

Developed grease may be very useful for the grease Industry to reduce the uses of lithium hydroxide in grease making

Conclusions

Acknowledgments

The Authors are sincerely grateful to the Management of M/s. Balmer Lawrie & Co. Ltd. for giving an

opportunity to present the paper at 18th NLGI-IC Conference

T

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