PPDs address changes in industry formulations and technological developments.
By: Katherine Bui
Low-temperature-performance technology has been challenged these past few years. In many ways, it is a wonder that research in pour point depressant (PPD) and viscosity index improver (VII) technology has been able to keep up. Consider for a moment the number and magnitude of the changes: (1) the move from API Group I to Group II/III base oils, (2) the improvement of additives, (3) changes in the system/engine, and (4) continuous changes in industry specifications and customer needs (i.e., hydraulics, automotive).
Much of the focus has been on improving the efficiency and low-temperature properties of VI in base oils, but very little has been said about PPDs. The PPD market makes up about $20 million of the estimated consumption of lubricant additives in the U.S., said Kline & Co. (Little Falls, NJ) in 1998.
How PPDs Work
Though PPDs make up only 0.10%-0.50% of most lubricants (gear oils tend to require more), even with this relatively small presence, the technology helps prevent wax from crystallizing at low temperatures. PPDs are generally added to lubricant formulations to subdue the wax still in the base oil following the refining process. PPDs are added to both industrial and automotive lubricants; the changes in industrial applications have not been as severe as those in the automotive segment. The Society of Automotive Engineers (SAE), for example, which sets a standard for low- and high-temperature viscosity called SAE J300, has revised the standard in the recent past and may create similar new challenges in the future.
The biggest challenge to research in this technology has lately come from the move to hydrocracked refining of base oils (Group II/III) and changes in the engine or lubricant formulation. Specifically, SAE J300 has reduced the low-temperature viscosity measurement temperatures by 5šC. This applies to viscosity under both cold starting (measured by cold-cranking simulation [CCS]) and pumping (measured by the mini-rotary viscometer [MRV]). Although the former is not affected by PPDs, the latter is significantly impacted by PPD choice and concentration. Today, PPDs also have to contend with a multitude of low-temperature oil pumpability tests such as the MRV (ASTM Standard D4684), Scanning Brookfield Gelation Index (ASTM D5133), Pour Point (ASTM D5985), and Brookfield (ASTM D2983).
PPDs have come a long way since 1931, when Standard Oil first filed a patent for the technology. At the time, Garland H.B. Davis of Standard Oil wrote, "I have discovered, methods by which paraffin containing oils...may be greatly improved with respect to their pour or solidification points without detriment to quality." His alkylated naphthalene was the first synthetic PPD to reach the marketplace.
Shortly afterward, in 1937, Rohm and Haas first patented the use of polymeric compounds as PPDs in recognition of the fact that wax causes fluidity problems in oil at low temperatures. Up to that time, alkylated naphthelene had been used to treat the paraffinic wax.
Sixty years later, "flowability" continues to be a key measure of lubricant quality and applicability. Tom Weyenberg, regional business manager of Lubrizol's Viscosity Modifiers Group, says "originally one of the key measures of a lubricant's quality and applicability has been the lowest temperature at which the lubricant will flow when poured out of its container. A pour point test, which has evolved over the years, measures this flowability. Modern techniques for measuring the ability of lubricants to protect engines during low-temperature startup have since been adopted by the industry. No longer do we need to rely upon pour points to predict low-temperature engine oil performance in our engines."
Additive suppliers currently offer a variety of PPDs, such as methacrylates, paraffinic phenol phthalates, tetraparaffinic phenols, fumarates, and alkylated styrenes. PPD selection is generally performed at the end of the lubricant formulation process in order to optimize low-temperature performance.
Starting at the Base
Changes in the base oil industry in the next few years may have significant impact on the technology of PPDs. Driven by a desire for lower volatility and improved fuel economy, the industry is imposing tighter control on these parameters by incorporating new limits in ILSAC GF-3 and ACEA categories.
One debate surrounding low-temperature performance is whether PPDs are needed in warm climates. "If you stay in the same region ... where the weather is consistently warm," says Bernard G. Kinker, product research manager for RohMax USA Inc., "temperature is not a factor. But most of us don't stay in one area. We might drive from Houston to St. Louis, and then the weather conditions play a very important factor."
Subtle changes in base oils may be on the horizon for other reasons. Mike Covitch, senior research scientist, viscosity modifiers, for Lubrizol, says, "Several years ago, SAE J300 was modified to change low-temperature pumping requirements (MRV) justified by data supplied by ASTM (ASTM Research Report RR-D02-1442). Considering the same set of data, SAE J300 was recently updated to change cold-starting requirements, as well" (see sidebar). Covitch says the changes may indirectly lead to the reformulation of PPDs. Besides reducing the cold-cranking limits 5šC lower for modern engines, maximum viscosity limits were also roughly doubled. The PPD technology may have to be adjusted to accommodate the resulting changes in base oil formulations.
Volatility and fuel economy are the drivers leading to the increased utilization of API Group II/III base oils in the new GF-3 gasoline engine oil category. In the past, the solvent-refining technology used for Group I base oils led to development of a certain PPD design. Ultimately this design depended on crude source, dewaxing technology used, and amount of wax removed.
The crude source concerns remain relevant in finding the appropriate PPD for Group II-plus oils. In addition, as isodewaxing technology changes the wax structure in lubricant base oils, PPD design has been changed and will continue to change to effectively perform in these base oils.
"In the 1980s, part of the challenge involved developing PPDs that would prevent these new wax structures from congealing at cold temperatures," Kinker says. "As more and more refineries practice hydrodewaxing and conditions change in refineries, the challenge has been and will continue to be to develop compounds that are suitable for these modified systems."
"There are many Group II systems, commonly made by hydrocracking technology, that are out there today," says Dianne Carmody, business development manager for RohMax. "Our PPD product line in North America, and to some extent in Europe, has evolved since 1990, and this newer technology is definitely up to the challenge of these Group II systems."
To make matters worse, refiners who blend with both Group I and II base oils are requiring more flexibility in the PPD. "They don't want to purchase several different products if they don't have to," Kinker says. "They prefer to purchase just one PPD. A product now has to work effectively with both the Group I base oils and the Group II base oils."
This is especially true in cases where refiners request a PPD that can be carried across Group I and Group II applications. "Logistically, many marketers find it attractive to stock one PPD for all of their lubricant formulations, from engine oils to gear lubricants," Weyenberg says. "Lubricant blenders always need to balance the added complexity of carrying multiple PPDs versus accepting technical compromises that are often experienced when choosing one PPD for their entire product line."
Other Factors Impacting PPDs
Changes in base oil technology have been but one issue impacting developments in pour point technology. An evolution toward improved low-temperature properties of olefin copolymer (OCP) VIs (copolymers of ethylene and propylene) used in passenger-car and heavy-duty lubricants has resulted in more ethylene. The inclusion of more ethylene creates more wax in the base oil. "The pour point depressant needs to encompass all the waxes in the system," Kinker emphasizes.
Extracting more miles out of a quart of oil may or may not create new opportunities for PPDs. On the one hand, the move to longer drain intervals has little or no impact on PPDs. The additive is relatively inert. "It is difficult to chemically destroy or shear them," Kinker says. Alternately, Covitch suggests that "Little is known about the low-temperature cranking and pumping properties of used engine oils. There is a lot of current work in this area, and the industry will learn more in the near future about the role that PPDs may play with used oils."
"Changes in pour point depressant will probably be subtle," Weyenberg says, "relative to the changes in additive packages."
Profit Margins: Keeping Up with Investments in R&D
With the constant balancing act forced by shifting industry specifications and technological developments, investments in PPD technology may have to gradually increase. Additive suppliers agree that they would not be in the business if returns were not profitable, and they freely admit that keeping up with the trends has been a costly challenge. Though the amount of PPD is small compared to the other components that go into the lubricant, Weyenberg says, "If you take the global volume of lubricants and multiply that by 0.10%, it adds up to a fairly sizable market."
One factor that has increased PPD marketability is the fact that they do a lot more than lower the pour point. Weyenberg says, "PPDs were originally used to reduce the solidification temperature of the oil. That has become less important as the sophistication of our ability to measure low-temperature viscosity increases. Perhaps an appropriate name might be 'cold-flow modifiers.'"
A factor that has helped in cost reduction is the type of tests required for PPDs. Current standards require PPDs to be tested using bench testing rather than engine testing.
"Our goal is rheology," Kinker explains. "The CMA code is quite clear. Variations in pour point depressant type or treatment level in a formulation are acceptable with Level 1 support. This support includes analytical and rheological testing, such as physical and chemical characterization, ASTM D4684 and ASTM D5133."
"The bottom line for us is we have to invest in people, time, and effort," Kinker adds. "But at the same time, we don't have expensive engine tests to conduct."
Carmody notes the percentage of PPDs used in most formulations is minor compared to the percentage of base oil and additive packages. Even within the area of bench testing, many in the industry question the necessity of running multiple tests and their potential for redundancy. Kinker says, "To blend an SAE 5W-30 oil on a rheological basis, you need to worry about the 100šC kinematic viscosity, low-temperature viscosity (CCS and MRV), high-temperature kinematic viscosity, and high-temperature/high-shear-rate viscosity. None of these are necessarily related to the function of pour point depressants."
However, tests such as ASTM D97, ASTM D4684, ASTM D5133, and Stable Pour Points are relevant and no single test is sufficient, given the potential for numerous different cooling cycles, says Kinker. "One cannot mimic all the cooling cycles of nature, but the more [tests] you do, the better you feel," he says.
"The Scanning Brookfield method slowly shears the oil as it cools, and this has been shown to perturb the wax structure that sets up at low temperature," points out Covitch.
The Future for PPDs
Despite the consistent changes in technology and formulations, the technological outlook for PPDs, many feel, is quite good. "We have extensive knowledge of Group III stocks," Kinker says. "Our goal is to be sure we are on top of things. I think we've kept up over the years, and we are pleased with the product offerings we bring to the marketplace today and those that we will provide for our customers in the future."
Technological advancements in PPDs, as they have in the past, will depend on developments in other product formulations. When higher-ethylene OCP VIIs appeared on the market, combined with the different waxes from the newer basestocks, several years ago, PPD technology seemed to take a step backward.
Yet Kinker says he has confidence that PPDs will meet the challenge of future developments.
However, the technology is not strictly dependent on the trends of other markets. For base oils, Kinker contends, it makes little difference whether the world moves to Group II, Group II-plus, or Group III. The technology has already kept up with the changes and remains strong, he says. "Though we need to prepare ourselves, the [PPD] technology is already there," Kinker says. "We are flexible. It doesn't matter; we'll be there."
By: Katherine Bui
Low-temperature-performance technology has been challenged these past few years. In many ways, it is a wonder that research in pour point depressant (PPD) and viscosity index improver (VII) technology has been able to keep up. Consider for a moment the number and magnitude of the changes: (1) the move from API Group I to Group II/III base oils, (2) the improvement of additives, (3) changes in the system/engine, and (4) continuous changes in industry specifications and customer needs (i.e., hydraulics, automotive).
Much of the focus has been on improving the efficiency and low-temperature properties of VI in base oils, but very little has been said about PPDs. The PPD market makes up about $20 million of the estimated consumption of lubricant additives in the U.S., said Kline & Co. (Little Falls, NJ) in 1998.
How PPDs Work
Though PPDs make up only 0.10%-0.50% of most lubricants (gear oils tend to require more), even with this relatively small presence, the technology helps prevent wax from crystallizing at low temperatures. PPDs are generally added to lubricant formulations to subdue the wax still in the base oil following the refining process. PPDs are added to both industrial and automotive lubricants; the changes in industrial applications have not been as severe as those in the automotive segment. The Society of Automotive Engineers (SAE), for example, which sets a standard for low- and high-temperature viscosity called SAE J300, has revised the standard in the recent past and may create similar new challenges in the future.
The biggest challenge to research in this technology has lately come from the move to hydrocracked refining of base oils (Group II/III) and changes in the engine or lubricant formulation. Specifically, SAE J300 has reduced the low-temperature viscosity measurement temperatures by 5šC. This applies to viscosity under both cold starting (measured by cold-cranking simulation [CCS]) and pumping (measured by the mini-rotary viscometer [MRV]). Although the former is not affected by PPDs, the latter is significantly impacted by PPD choice and concentration. Today, PPDs also have to contend with a multitude of low-temperature oil pumpability tests such as the MRV (ASTM Standard D4684), Scanning Brookfield Gelation Index (ASTM D5133), Pour Point (ASTM D5985), and Brookfield (ASTM D2983).
PPDs have come a long way since 1931, when Standard Oil first filed a patent for the technology. At the time, Garland H.B. Davis of Standard Oil wrote, "I have discovered, methods by which paraffin containing oils...may be greatly improved with respect to their pour or solidification points without detriment to quality." His alkylated naphthalene was the first synthetic PPD to reach the marketplace.
Shortly afterward, in 1937, Rohm and Haas first patented the use of polymeric compounds as PPDs in recognition of the fact that wax causes fluidity problems in oil at low temperatures. Up to that time, alkylated naphthelene had been used to treat the paraffinic wax.
Sixty years later, "flowability" continues to be a key measure of lubricant quality and applicability. Tom Weyenberg, regional business manager of Lubrizol's Viscosity Modifiers Group, says "originally one of the key measures of a lubricant's quality and applicability has been the lowest temperature at which the lubricant will flow when poured out of its container. A pour point test, which has evolved over the years, measures this flowability. Modern techniques for measuring the ability of lubricants to protect engines during low-temperature startup have since been adopted by the industry. No longer do we need to rely upon pour points to predict low-temperature engine oil performance in our engines."
Additive suppliers currently offer a variety of PPDs, such as methacrylates, paraffinic phenol phthalates, tetraparaffinic phenols, fumarates, and alkylated styrenes. PPD selection is generally performed at the end of the lubricant formulation process in order to optimize low-temperature performance.
Starting at the Base
Changes in the base oil industry in the next few years may have significant impact on the technology of PPDs. Driven by a desire for lower volatility and improved fuel economy, the industry is imposing tighter control on these parameters by incorporating new limits in ILSAC GF-3 and ACEA categories.
One debate surrounding low-temperature performance is whether PPDs are needed in warm climates. "If you stay in the same region ... where the weather is consistently warm," says Bernard G. Kinker, product research manager for RohMax USA Inc., "temperature is not a factor. But most of us don't stay in one area. We might drive from Houston to St. Louis, and then the weather conditions play a very important factor."
Subtle changes in base oils may be on the horizon for other reasons. Mike Covitch, senior research scientist, viscosity modifiers, for Lubrizol, says, "Several years ago, SAE J300 was modified to change low-temperature pumping requirements (MRV) justified by data supplied by ASTM (ASTM Research Report RR-D02-1442). Considering the same set of data, SAE J300 was recently updated to change cold-starting requirements, as well" (see sidebar). Covitch says the changes may indirectly lead to the reformulation of PPDs. Besides reducing the cold-cranking limits 5šC lower for modern engines, maximum viscosity limits were also roughly doubled. The PPD technology may have to be adjusted to accommodate the resulting changes in base oil formulations.
Volatility and fuel economy are the drivers leading to the increased utilization of API Group II/III base oils in the new GF-3 gasoline engine oil category. In the past, the solvent-refining technology used for Group I base oils led to development of a certain PPD design. Ultimately this design depended on crude source, dewaxing technology used, and amount of wax removed.
The crude source concerns remain relevant in finding the appropriate PPD for Group II-plus oils. In addition, as isodewaxing technology changes the wax structure in lubricant base oils, PPD design has been changed and will continue to change to effectively perform in these base oils.
"In the 1980s, part of the challenge involved developing PPDs that would prevent these new wax structures from congealing at cold temperatures," Kinker says. "As more and more refineries practice hydrodewaxing and conditions change in refineries, the challenge has been and will continue to be to develop compounds that are suitable for these modified systems."
"There are many Group II systems, commonly made by hydrocracking technology, that are out there today," says Dianne Carmody, business development manager for RohMax. "Our PPD product line in North America, and to some extent in Europe, has evolved since 1990, and this newer technology is definitely up to the challenge of these Group II systems."
To make matters worse, refiners who blend with both Group I and II base oils are requiring more flexibility in the PPD. "They don't want to purchase several different products if they don't have to," Kinker says. "They prefer to purchase just one PPD. A product now has to work effectively with both the Group I base oils and the Group II base oils."
This is especially true in cases where refiners request a PPD that can be carried across Group I and Group II applications. "Logistically, many marketers find it attractive to stock one PPD for all of their lubricant formulations, from engine oils to gear lubricants," Weyenberg says. "Lubricant blenders always need to balance the added complexity of carrying multiple PPDs versus accepting technical compromises that are often experienced when choosing one PPD for their entire product line."
Other Factors Impacting PPDs
Changes in base oil technology have been but one issue impacting developments in pour point technology. An evolution toward improved low-temperature properties of olefin copolymer (OCP) VIs (copolymers of ethylene and propylene) used in passenger-car and heavy-duty lubricants has resulted in more ethylene. The inclusion of more ethylene creates more wax in the base oil. "The pour point depressant needs to encompass all the waxes in the system," Kinker emphasizes.
Extracting more miles out of a quart of oil may or may not create new opportunities for PPDs. On the one hand, the move to longer drain intervals has little or no impact on PPDs. The additive is relatively inert. "It is difficult to chemically destroy or shear them," Kinker says. Alternately, Covitch suggests that "Little is known about the low-temperature cranking and pumping properties of used engine oils. There is a lot of current work in this area, and the industry will learn more in the near future about the role that PPDs may play with used oils."
"Changes in pour point depressant will probably be subtle," Weyenberg says, "relative to the changes in additive packages."
Profit Margins: Keeping Up with Investments in R&D
With the constant balancing act forced by shifting industry specifications and technological developments, investments in PPD technology may have to gradually increase. Additive suppliers agree that they would not be in the business if returns were not profitable, and they freely admit that keeping up with the trends has been a costly challenge. Though the amount of PPD is small compared to the other components that go into the lubricant, Weyenberg says, "If you take the global volume of lubricants and multiply that by 0.10%, it adds up to a fairly sizable market."
One factor that has increased PPD marketability is the fact that they do a lot more than lower the pour point. Weyenberg says, "PPDs were originally used to reduce the solidification temperature of the oil. That has become less important as the sophistication of our ability to measure low-temperature viscosity increases. Perhaps an appropriate name might be 'cold-flow modifiers.'"
A factor that has helped in cost reduction is the type of tests required for PPDs. Current standards require PPDs to be tested using bench testing rather than engine testing.
"Our goal is rheology," Kinker explains. "The CMA code is quite clear. Variations in pour point depressant type or treatment level in a formulation are acceptable with Level 1 support. This support includes analytical and rheological testing, such as physical and chemical characterization, ASTM D4684 and ASTM D5133."
"The bottom line for us is we have to invest in people, time, and effort," Kinker adds. "But at the same time, we don't have expensive engine tests to conduct."
Carmody notes the percentage of PPDs used in most formulations is minor compared to the percentage of base oil and additive packages. Even within the area of bench testing, many in the industry question the necessity of running multiple tests and their potential for redundancy. Kinker says, "To blend an SAE 5W-30 oil on a rheological basis, you need to worry about the 100šC kinematic viscosity, low-temperature viscosity (CCS and MRV), high-temperature kinematic viscosity, and high-temperature/high-shear-rate viscosity. None of these are necessarily related to the function of pour point depressants."
However, tests such as ASTM D97, ASTM D4684, ASTM D5133, and Stable Pour Points are relevant and no single test is sufficient, given the potential for numerous different cooling cycles, says Kinker. "One cannot mimic all the cooling cycles of nature, but the more [tests] you do, the better you feel," he says.
"The Scanning Brookfield method slowly shears the oil as it cools, and this has been shown to perturb the wax structure that sets up at low temperature," points out Covitch.
The Future for PPDs
Despite the consistent changes in technology and formulations, the technological outlook for PPDs, many feel, is quite good. "We have extensive knowledge of Group III stocks," Kinker says. "Our goal is to be sure we are on top of things. I think we've kept up over the years, and we are pleased with the product offerings we bring to the marketplace today and those that we will provide for our customers in the future."
Technological advancements in PPDs, as they have in the past, will depend on developments in other product formulations. When higher-ethylene OCP VIIs appeared on the market, combined with the different waxes from the newer basestocks, several years ago, PPD technology seemed to take a step backward.
Yet Kinker says he has confidence that PPDs will meet the challenge of future developments.
However, the technology is not strictly dependent on the trends of other markets. For base oils, Kinker contends, it makes little difference whether the world moves to Group II, Group II-plus, or Group III. The technology has already kept up with the changes and remains strong, he says. "Though we need to prepare ourselves, the [PPD] technology is already there," Kinker says. "We are flexible. It doesn't matter; we'll be there."
