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274 Lubricant Additives: Chemistry and Applications

9.5.4.2 Basic Alkali Metal Salts

Sulfurized products show a very strong synergistic effect in combination with basic alkali metal

salts [43], often referred to as overbased sulfonates or carboxylates. Particularly, active sulfur in

combination with overbased calcium or sodium sulfonates exhibits advantageous performance with

regard to improved load-carrying and AW properties. These additive combinations are used in

lubricants for severe metalworking operations.

It is disclosed in International Patent WO 87/06256 [41] that the load-bearing characteristics of a

grease composition and gear lubricant may be unexpectedly improved by formulating these composi-

tions with an additive mixture comprising overbased salts of alkaline earth metals or alkali metals

and at least one sulfurized organic compound. From today’s point of view, the overbased products/

sulfur combination has its advantages in some stainless steel cutting and forming operations. But the

high alkalinity of such formulations shows big compatibility problems when in contact with lubricity

esters and other types of acidic additives. Alkaline washing baths get used up quickly and need much

more frequent changes as calcium soaps built up. Welding without cleaning the metal surface is also

impossible as the high TBN sulfonates are generating high amounts of oxide ash.

9.5.4.3 Antioxidants

Inactive sulfur carriers show a synergism with aminic AOs. This effect is very distinct in low or even

sulfur-free base  uids. Active sulfurized products do not show this synergy. On the contrary, the

active types deteriorate the oxidation stability. Table 9.6 demonstrates the oxidation stability (ASTM

D-2270, RPVOT Test) of active and inactive sulfur carriers based on the same raw materials.

The inactive product improves the oxidation stability (250 min) twice as much as the active type

(120 min). In combination with the aminic AOs, the synergistic effect is obvious. Although the inac-

tive sulfur carrier improves the AO properties of the aminic AO, the active type has a detrimental

effect and reduces the oxidation stability.

9.5.4.4 Esters/Triglycerides

Esters are used either as base  uids or as additives. It is important to coordinate ester type and sulfur

chemistry to achieve optimum performance. Unsaturated esters show strong synergistic effects with

active sulfur, whereas inactive sulfur shows distinct synergies with saturated esters. The perfor-

mance of sulfur carriers in saturated esters is similar to their performance in mineral oil. These

synergies are widely used in the formulation of lubricants.

Combinations of active sulfur and unsaturated esters or triglycerides (mainly vegetable or

animal oils such as canola, rapeseed, tall, sun ower oil, and esters thereof) are very common in all

types of metalworking  uids, in oils, as well as in water-based systems. The combination of these

products shows better EP and AW properties than the single components. This performance is

illustrated in the four-ball test (see Table 9.7).

TABLE 9.6

Synergisitc Effect of ZnDTP on Copper Corrosion

Base Oil

Hydrocracked,

Dewaxed, No

Sulfur (min)

1.0% Inactive

Oleﬁ n, 20%

S, 5% active

S (min)

1.0% Active

Oleﬁ n, 39%

S, 30% active

S (min)

Base oil 40 250 120

0.2% Aminic AO (alkylated

diphenylamine) 400 540 135

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Sulfur Carriers 275

Other applications for the combination of active sulfur and unsaturated ester are heavy-duty

gear oils in agricultural applications and environmentally-friendly chain saw and bar saw lubri-

cants (see Section 9.5.3.5).

If Cu corrosion presents a problem, the use of medium active sulfurized products in combination

with unsaturated esters is of advantage. Some of these sulfur carriers are active enough to create the

synergistic effects, but their Cu corrosion can be controlled with suitable yellow metal inhibitors.

Besides the improvement of EP and AW performance, inactive sulfur carriers can boost the AO

properties.

Saturated esters are used where good oxidation stability is required. The performance of sulfurized

products in saturated esters is comparable to the performance in mineral oil. Inactive sulfurized ole ns

and sulfurized triglycerides, and mixtures thereof, are typically used as additives in lubricants based

on saturated esters.

9.5.5 COST-EFFECTIVENESS

Sulfurized products cover the whole range from relative cheap commodity to high-price specialty.

Depending on the type and treatment level, sulfurized products can be a major cost factor in lubricants.

However, the use of sulfur carriers enables us to run processes and to overcome lubrication problems

that cannot be solved in a cost-ef cient way with other additives. For example, it is possible to increase

machine speeds and thus productivity while using appropriate sulfur carriers instead of esters or

chlorinated paraf ns. Depending on the type of sulfur carrier, other commonly used additives in a

formulation, for example, esters or yellow metal deactivators, can be saved. In comparison with heavy-

metal- or chlorine-containing lubricants, the disposal costs for the used lubricant can be much lower.

Besides direct cost savings, respectively, cost ef ciency due to higher productivity and lower

disposal costs, there are secondary cost factors. In comparison with some traditionally used EP

additives such as chlorinated paraf ns (HCl-formation > rust), overbased sulfonates (dif cult

degreasability, incompatibility with other additives), or heavy-metal-containing additives (residue

formation), sulfurized products show, in general, lower cost-effective side effects.

9.6 MANUFACTURE AND MARKETING ECONOMICS

9.6.1 M

ANUFACTURERS

Afton, United States

Arkema, France

DAI Nippon Inc., Japan

DOG-Chemie, Germany

Dover Chemical Corp., United States

Elco, United States

Harrison Manufacturing Company, Australia

Hornett, United Kingdom

TABLE 9.7

Esters, Synergistic Effect on EP and AW

Sulfurized Oleﬁ n 40%

S, 36% active

TMP

Oleate

Four-Ball Weld Load

DIN 51350 Part 2

(N)

Four-Ball Wear

Scar DIN 51350

Part 3 (mm)

1.5% — 2800 0.8

— 5.0% 800 0.6

1.5% 3.5% 3200 0.55

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276 Lubricant Additives: Chemistry and Applications

Lubrizol, United States

Miracema Nuodex, Brasil

PCAS, France

Rhein Chemie, Germany

Additionally, there are some lubricant manufacturers who still sulfurize dark-colored products for

their own use, and some local sulfurization plants also sulfurize commodity-type products.

9.6.2 MARKETERS

In general, the manufacturers are also marketing the products. Some local manufacturers buy sulfu-

rized products, blend them with esters, mineral oil, etc., and sell them under their own brand name.

Sulfur carriers are intermediate and not consumer products.

9.6.3 ECONOMICS

Market prices vary depending on the raw materials, the production process, and the performance

level of the products. Low-quality, dark sulfurized fats with distinct odor and limited stability sell

for less than U.S.D 1.6/kg. High-performance, top-quality, low-odor, light-color products achieve

prices of more than U.S.D 4.0/kg. Not only the raw materials, but much more the production pro-

cess, determine the price for a sulfurized product. For example, the sulfurization of a typical gear

oil sulfur carrier with di-sulfur-di-chloride and the necessary subsequent washing steps are more

costly than the sulfurization of a fat with  ower of sulfur.

9.6.4 GOVERNMENT REGULATIONS

9.6.4.1 Competitive Pressures

There are no government regulations concerning the use of sulfurized products, but depending on

the location of the manufacturing plant, very stringent regulations and conditions concerning emis-

sion standards can apply. Therefore, there is a competitive distortion in production between more

and less environmentally aware countries. Production technology and in particular low-emission

production are key cost factors.

9.6.4.2 Product Differentiation

Apart from some commodities, there is a clear product differentiation mainly derived from qual-

ity and performance. A  rst criterion for differentiation is color, followed by sulfur content, raw

materials, and odor. A classi cation is hardly possible because many of the products are tailor-made

either to cover a speci c performance pro le or to meet speci cations in various applications. A

simple categorization by sulfur content or raw material bases would be to coarse and would not take

performance into account. Even products based on the same raw materials but manufactured with a

different process can be completely different in performance.

Modern, light-colored, high-performance products with low odor are sulfurized using H

S or

mercaptans. Even the appearance distinguishes these products from conventionally sulfurized dark-

colored, smelly products.

9.7 OUTLOOK

9.7.1 C

RANKCASE/AUTOMOTIVE APPLICATIONS

Steady demands on the reduction of phosphorus levels in motor oils as well as requirements for

increased fuel ef ciency, that is, friction reduction will open new opportunities for sulfur chemistry.

Sulfurized products are already used in this type of application (see Section 9.5.3.6).

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Sulfur Carriers 277

9.7.2 INDUSTRIAL APPLICATIONS

Multifunctional and multipurpose lubricants are on the wish list of many end users. The development

for sulfurized products that can be used in these types of lubricants is in full progress, and the products

have already been commercialized. Mainly light-colored products based on mixed, well- balanced

raw materials to ensure a broad performance range are used for multipurpose applications.

Replacement of heavy metals and chlorinated paraf ns in almost all industrial lubricants is

also an ongoing project that is widely found in the lubricants industry. Sulfur carriers are playing a

predominant role as substitutes for these products.

Increasing demands for environmentally more acceptable lubricants has led many formulators

into the development of lubricants based on natural triglycerides such as canola oil, soybean oil, tall

oil, or esters. Biodegradable sulfur carriers are used as EP and AW additives as well as secondary

AOs in these applications.

9.8 TRENDS

9.8.1 C

URRENT EQUIPMENT/SPECIFICATION

Sulfurized products are single components and not complete performance packages such as hydrau-

lic or crankcase packages. Therefore, sulfur carriers are used in the whole variety of lubricants

rather than in a speci c equipment. Also, no national or international speci cation standards exist

for these products. The manufacturer sets the speci cation in agreement with the user.

9.8.1.1 Types of Equipment

As already mentioned, the biggest use of sulfurized products (excluding SIB) is in industrial appli-

cations. Metalworking and grease applications followed by industrial gear oils are formulated with

sulfur carriers. A lot of old equipment is still in use. Many mid-size and small companies have not

modernized their metalworking machines for more than three decades. This older, robust equip-

ment is very often running at low machining speeds and nonoptimized machining parameters.

Modern machining equipment requires thermally stable  uids, based on highly re ned or synthetic

base  uids. Improved solubility in nonpolar oils and thermal stability of sulfurized products gain

importance.

9.8.1.2 Additives in Use

Today’s additive usage depends very much on regional technological requirements and local legis-

lation. In countries with low, old or standard technology and little environmental concerns, addi-

tives such as chlorinated paraf ns or heavy metals are used for the formulation of lubricants, often

in combination with sulfurized products. In countries where legislation has put some pressure onto

the formulators and users of lubricants (higher disposal costs for chlorine-containing lubricants,

limits on heavy metals in waste water, etc.), sulfurized compounds play an even more impor-

tant role. They are the main EP additives, very often combined with sulfonates, salicilates, phos-

phoric acid esters, dialkyldithiophosphates, or carboxylic esters to complement AW and lubricity

performance.

9.8.1.3 Deﬁ ciencies in Current Additives

All available sulfur carriers are limited in their thermal stability. This is a desired feature, because

reactive sulfur will only be released when the molecule breaks down. However, there are applica-

tions running at a high temperature, where a fast decomposition of the EP product is not desired.

Corrosion toward yellow metals is another de ciency of sulfurized compounds. In high- temperature

applications, the active sulfur will react with copper to form copper sul de.

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278 Lubricant Additives: Chemistry and Applications

9.9 MEDIUM-TERM TRENDS

In general, there is a trend toward higher economy and ecologically and toxicologically safe

lubricants.

9.9.1 METALWORKING

Increased lubricant temperatures are a consequence of higher machine speeds, completely encap-

sulated machines, and reduced process steps. In the future, the thermal stability of metalworking

lubricants and their toxicological safety will be on the focus. Owing to integrated applications (e.g.,

one lubricant for process and machine lubrication), the additives need to cover wide temperature

ranges. The trend to replace multiple cutting steps with forming operations exists. Therefore, the

type of additives will also change.

Minimum amount lubrication requires new lubricant concepts in regard of performance and

marketing. Maintenance of lubricants will further be reduced. Again this trend calls for increased

stability of additives.

Sulfurized products for metalworking application will need improved thermal stability in com-

bination with good solubility in high paraf nic or even synthetic base  uids. Ecological and toxi-

cological safety will be the basic requirements. Improved lubricity and excellent compatibility with

process materials such as cleaners and paints will be essential for the formulation of modern lubri-

cants for deformation processes (e.g., cold forging and deep drawing).

9.9.2 INDUSTRIAL OILS

Synthetic  uids such as PAOs, polyalkyleneglycols (PAGs), extra high VI mineral oils (XHVI),

or synthetic esters are being used in increasing volumes for the formulation of high-performance

industrial lubricants. Smaller lubricant sumps, reduced sizes of components, and increased perfor-

mance will place high demands on the lubricants. Especially in mobile equipment (e.g., excava-

tor and lawn mower), ecologically and toxicologically harmless lubricants will become a demand.

Reduced maintenance and longer lubricant change intervals require high lubricant stability.

Improved thermal stability, low copper corrosion, and excellent solubility in synthetic  uids are

demands on sulfurized products for the new generation of industrial lubricants.

REFERENCES

1. Sellei, H., Sulfurized extreme-pressure lubricants and cutting oils, Part 1, Petroleum Processing, 4,

1003–1008, 1949.

2. Sellei, H., Sulfurized extreme-pressure lubricants and cutting oils, Part 2, Petroleum Processing, 4,

1116–1120, 1949.

3. Base for metal-cutting compounds and process of preparing the same, George W. Pressell, Houghton &

Co. PA, US 1,367,428/GB 129132 (1921).

4. Byers, J.T., Patents show trend in extreme pressure lube technology, National Petroleum News, 28, 79,

1936.

5. van Voorhis, M.G., 200 lubricant additive patents issued in 1938 and 1939, National Petroleum News,

32, R-66, 1940.

6. Miller, F.L., W.C. Winning, and J.F. Kunc, Use of additives in automotive lubrication, Re ner and Natl.

Gas Manuf. 20(2), 53, 1941.

7. Westlake, H.E., Jr., The sulfurization of unsaturated compounds, Chemical Reviews 39(2), 219, 1946.

8. Musgrave, F.F., The development and lubrication of the automotive hypoid gear, Journal of the

Institution of Petroleum 32(265), 32, 1946.

9. Lubricating compound and process of making the same, Leonard A. Churchill, US 1,974,299 (1934).

10. Method of sulphurizing pine oil and data thereof. M.C. Edwards, J. Heights, J.V. Congdon US 2,012,446

(1935).

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Sulfur Carriers 279

11. Method of sulphurizing terpenes, abiethyl compounds, etc. J.W. Borglin, Hercules Powder Company,

Del. US 2,111,882 (1938).

12. Pure compounds as extreme pressure lubricants. E.W. Adams, G.M. McNulty, Standard Oil Company,

IL, US 2,110,281 (1938).

13. Production of mercaptanes, K. Baur, IG Farbenindustry AG, US 2,116,182 (1938).

14. Sulphurized Oils, B.H. Lincoln, W.L. Steiner, Continental Oil, OK, US 2,113,810 (1938).

15. Lubricating Oil, E.A. Evans, C.C. Wake eld & Co Ltd., US 2,164,393 (1939).

16. Extreme Pressure Lubricating Composition, B.B. Farrington, R.L. Humphreys, Standard Oil Company,

CA, US 2,020,021 (1935).

17. Lubricant composition, E.W. Adams, G.M. McNulty, Standard Oil Company, IL, US 2,206,245 (1940).

18. Lubricating Oil, J.F. Werder, US 1,971,243 (1934).

19. Lubricant containing organic sulphides, L.A. Mikeska, F.L. Miller, Standard Oil Development Com-

pany, US 2,205,858 (1940).

20. Compound lubricating oil, C. Winning, West eld, D.T. Rogers, Standard Oil Development Company,

US 2,422,275 (1947).

21. Mougay, H.C., and G.O. Almen, Extreme pressure lubricants, Journal of the Institution of Petroleum,

12, 76, 1931.

22. Baxter, J.P. et. al., Extreme pressure lubricant tests with pretreated test species, Journal of the

Institution of Petroleum, 25(194), 761, 1939.

23. Schallbock et al., Vorträge der Hauptversammlung der deutschen Gesellschaft für Metallkunde, VDI

Verlag, pp. 34–38, 1938.

24. Prutton, C.F. et.al., Mechanism of action of organic chlorine and sulfur compounds in E.P. lubrication,

Journal of the Institution of Petroleum, 32(266), 90.

25. Lubricant, Herschel, G. Smith, Wallingford, Gulf Oil Corporation, PA, US 2,179,067 (1939).

26. Lubricant, E.W. Cook, W.D. Thomas, American Cyanamid Company, NY, US 2,311,931 (1943).

27. Forbes, E.S., Load carrying capacity of organo-sulfur copmpounds—a review, Wear, Lausanne, 15, 341,

1970.

28. Process for producing sulfurized ole ns, A.G. Horodysky, Mobil Oil Corporation, US 3,703,504 (1972).

29. A sulphurised mixture of compounds and a process for ist production, Ingo Kreutzer, Rhein Chemie

Rheinau GmbH, GB 1371949 (1972).

30. Cross-sulfurized ole ns and fatty monoesters in lubricating oils, B.W. Hotten, Chevron Research

Company, CA, US 4,053,427 (1977).

31. Metal working using lubricants containing basic alkali metal salts, J.N. Vinci, The Lubrizol Corpora-

tion, OH, US 4,505,830 (1985).

32. Prof. Hugo, Rhein Chemie Rheinau GmbH internal studies, Freie Universität Berlin, 1980.

33. Korff, J., Additive fuer Kuehlschmierstoffe, Additive fuer Schmierstoffe, Expert Verlag, Renningon

Germany, 1994.

34. ASTM D 1662, Standard Test Method for Active Sulfur in Cutting Oils.

35. Fessenbecker, A., Th. Rossrucker, and E. Broser. Rhein Chemie Rheinau GmbH—performance and

ecology, two inseparable aspects of additives for modern metalworking  uids, TAE, International

Colloquium, 1992.

36. Allum, K.G. and J.F. Ford. The in uence of chemical structure on the load carrying properties of certain

organo-sulfur compounds, Journal of the Institute of Petroleum, 51(497), 53–59, 1965.

37. ASTM D-130, Detection of Copper Corrosion from Petroleum Products by the Copper Strip Tarnish

Test (2000).

38. Roehrs, I. and T. Rossrucker, Performance and ecology—two aspects for modern greases. NLGI Annual

Meeting, 1994.

39. Rossrucker, T. and A. Fessenbecker, Performance and mechanism of metalworking additives: new

results from practical focused studies, Rhein Chemie Rheinau GmbH, STLE Annual Meeting, 1999.

40. Deodhar, J., Steel rolling oils—cold rolling lubrication, the metalworking  uid business, The College of

Petroleum Studies, December, 1989.

41. Vinci, J.N., Grease and gear lubricant compositions comprising at least one metal containig composition

and at least one sulfurized organic compound, The Lubrizol Corporation, OH, International Publication

No. WO 87/06256, 1987.

42. G. Fish. Greases, GKN Technology Limited, WO 94/11470, EP 0668 900 B1, 1994.

43. Vinci, J.N. Metal working using lubricants containing basic alkali metal salts. The Lubrizol Corporation,

OH, US 4,505,830 (1985).

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Part 4

Viscosity Control Additives

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283

Oleﬁ n Copolymer

Viscosity Modiﬁ ers

Michael J. Covitch

CONTENTS

10.1 Introduction .........................................................................................................................283

10.2 Classes of Ole n Copolymers .............................................................................................284

10.3 Chemistry ............................................................................................................................284

10.3.1 Synthesis by Ziegler–Natta Polymerization ...........................................................284

10.3.2 Synthesis by Metallocene Polymerization .............................................................286

10.3.3 Functionalization Chemistry .................................................................................286

10.4 Manufacturing Processes ....................................................................................................287

10.4.1 Solution Process .....................................................................................................288

10.4.2 Suspension Process ................................................................................................289

10.4.3 Postpolymerization Processes ................................................................................289

10.4.4 Making the OCP Liquid Concentrate .................................................................... 290

10.5 Properties and Performance Characteristics .......................................................................290

10.5.1 Effect of Ethylene/Propylene Ratio on Physical Properties of the Solid ...............290

10.5.2 Effect of Copolymer Composition on Rheological Properties in Solution ...........292

10.5.2.1 Low-Temperature Rheology ..................................................................292

10.5.2.2 High-Temperature Rheology .................................................................295

10.5.3 Effect of Diene on Thermal/Oxidative Stability ...................................................299

10.5.4 Comparative Rheological Performance in Engine Oils ........................................300

10.5.4.1 Comparative Study of OCP Viscosity Modi ers in a Fixed

SAE 5W-30 Engine Oil Formulation .....................................................300

10.5.4.2 Comparative Study of 37 SSI OCP Viscosity Modi ers in an

SAE 15W-40 Engine Oil Formulation .................................................. 301

10.5.5 Interaction with Pour Point Depressants ...............................................................302

10.5.6 Field Performance Data .........................................................................................305

10.6 Manufacturers, Marketers, and Other Issues ......................................................................306

10.6.1 EP/EPDM Manufacturers ......................................................................................306

10.6.2 Ole n Copolymer VM Marketers ..........................................................................307

10.6.3 Read Across Guidelines .........................................................................................308

10.6.4 Safety and Health ................................................................................................... 310

References ...................................................................................................................................... 310

10.1 INTRODUCTION

Ole n copolymer (OCP) viscosity modi ers are oil-soluble copolymers comprising ethylene and

propylene and may contain a third monomer, a nonconjugated diene, as well. By virtue of their high

thickening ef ciency and relatively low cost, they enjoy a dominant share of the engine oil viscosity

modi er market [1]. First introduced as a lubricant additive by Exxon in the late 1960s, the chemical

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