Zinc Dialkyl Dithiophosphate Lubricant Additives

Introduction

Lubrizol's lubricant additives are comprehensively designed to protect all types of engines and to meet the needs of specific applications.  Lubrizol's unique understanding of chemistry, technology and the additives market, along with decades of experience enable us to provide broad product offerings ranging from basic technology to novel, cutting-edge - performance chemistry.  

Lubrizol ZDDPs control oxidation and corrosion, keeping engines running longer and more smoothly by preventing valve train wear and bearing corrosion.  The antioxidant properties of ZDDPs increase the life of engine oil by reducing breakdown that can result from the formation of sludge and soot deposits on pistons and other engine components.  They protect metal from corrosion by forming protective chemical films on metal surfaces. 

Applications

These additives are used by companies that manufacture lubricants and greases for use in industrial, professional and consumer applications. Formulated products containing ZDDP have a wide range of uses including initial-fill by original equipment manufacturers and service-fill for on-road and off-road vehicles. They are also used in industrial gear applications.   

Physical and Chemical Properties

Physical and chemical properties vary somewhat depending on the specific alkyl group(s). ZDDP additives are viscous liquids with molecular weights in the 400 to 2000 Dalton range. Their vapor pressures and fugacity are low. They are slightly-to-moderately soluble in water. Thermal stability, anti-wear protection, hydrolytic stability and cost performance vary depending on the type of ZDDP. Aryl type ZDDPs provide excellent thermal stability but are less effective in terms of antiwear protection and hydrolytic stability The secondary alkyl type provides the best antiwear protection and hydrolytic stability, but does not provide good thermal stability. 

Health Effects

The health hazards of ZDDP additives have been well-studied in animals. The primary occupational concern during manufacture or formulation is eye and/or skin irritation or corrosion. ZDDPs exhibit low acute toxicity via oral, dermal, and inhalation routes of exposure and are not skin sensitizers. In oral gavage repeat dose studies, ZDDP causes effects only at high doses, primarily due to irritation. They do not cause effects on fertility or development at doses that are not maternally toxic. The weight-of- evidence of genotoxicity testing indicates that ZDDPs are not mutagenic and do not cause larger chromosomal effects. While ZDDPs have not been tested in carcinogenicity studies, genotoxicity studies and studies of formulated products indicate that they are not carcinogenic.

Environmental Effects

The environmental hazards of ZDDP additives have been well-studied in vertebrate and invertebrate species. Based on available environmental fate and ecotoxicological data for daphnids, fish, and algae, they are considered to be toxic to aquatic wildlife with long lasting effects. ZDDPs are not readily biodegradable.

Regulatory Information

ZDDP additives currently are subject to the European Commission REACH (Registration, Evaluation, Authorisation and Restriction of Chemical substances) regulation. The registration and Chemical Safety Reports for ZDDP substances subject to 2010 reporting have been submitted to the European Chemicals Agency (ECHA) by Lubrizol. As noted in Lubrizol safety data sheets, ZDDPs have gained acceptance in major industrialized countries through global notifications.

Exposure Potential

Lubrizol ZDDPs are sold to industrial customers who formulate lubricants and greases. Workers in these industrial exposure scenarios can be exposed to ZDDP via dermal and inhalation routes. Some operations are conducted under elevated temperatures that increase the potential for inhalation exposure. Because formulated products contain low levels of ZDDP, the exposure potential for professional workers and consumers generally is much lower. The extent of exposure varies depending on use conditions such as closed systems and the duration and frequency of use.

Risk Management

Information on the safe handling of these products is disseminated through material safety data sheets provided to workers who make the products and who formulate lubricants and greases. These documents provide a broad range of safety information including hazard warnings and risk management measures. They note engineering controls, work practices and personal protective equipment that are needed during manufacture and formulation to control exposures. Good industrial hygiene practices, training and gloves are used to avoid skin contact. Half mask respirators are recommended for certain operations. Control of spills and environmental releases is important.

Conclusion

Lubrizol ZDDP's are designed to meet a wide range of performance needs. Their excellent physical and functional properties make them ideal for use in lubricants and greases where controlling oxidation and corrosion is important.

Exposure of workers to ZDDP can cause irritation or corrosion to the eyes and/or skin; release to the environment is toxic to aquatic organisms with potential long-lasting effects. However, the use of appropriate engineering controls, work practices, personal protective equipment, and environmental release controls and practices provides effective risk management.