63

3

Ashless Phosphorus–

Containing Lubricating

Oil Additives

W. David Phillips

CONTENTS

3.1 Introduction and Scope ........................................................................................................... 64
3.2 Historical Background ............................................................................................................ 65
3.3 Manufacture of Phosphorus-Containing Lubricating Oil Additives ...................................... 68
3.3.1 Neutral Alkyl and Aryl Phosphate Esters .................................................................... 68
3.3.1.1 Natural Phosphates.......................................................................................... 69
3.3.1.2 Synthetic Phosphates from Isopropylphenols ................................................. 70
3.3.1.3 Synthetic Phosphates from Tertiarybutylphenols ........................................... 70
3.3.2 Acid Phosphate Esters .................................................................................................. 7 1
3.3.2.1 Alkyl and Aryl Acid Phosphates (Non-ethoxylated) ...................................... 71
3.3.2.2 Alkyl- and Alkylarylpolyethleneoxy Acid Phosphates ................................... 72
3.3.3 Amine Salts of Acid Phosphates and of Polyethyleneoxy Acid Phosphates ................ 72
3.3.4 Neutral Phosphite Esters ............................................................................................... 7 3
3.3.5 Alkyl and Aryl Acid Phosphites ................................................................................... 73
3.3.6 Dialkyl Alkyl Phosphonates ......................................................................................... 74
3.4 The Function of Lubricity Additives ....................................................................................... 74
3.4.1 The Basic Mechanism of Lubrication and Wear and the Infl uence of Additives ......... 75
3.5 Investigations into the Mechanism and Activity of Phosphorus-Containing Additives ......... 79
3.5.1 Early Investigations into Antiwear and Extreme Additives ......................................... 80
3.5.2 Neutral Alkyl and Aryl Phosphates .............................................................................. 80
3.5.2.1 Historical Background .................................................................................... 80
3.5.2.2 Recent Technical Developments ..................................................................... 86
3.5.2.3 Recent Commercial Developments ................................................................. 89
3.5.3 Alkyl and Aryl Acid Phosphates .................................................................................. 91
3.5.3.1 Non-ethoxylated .............................................................................................. 91
3.5.3.2 Alkyl and Alkarylpolyethleneoxy Acid Phosphates ....................................... 92
3.5.3.3 Amine Salts of Acid Phosphates ..................................................................... 95
3.5.4 Neutral Alkyl and Aryl Phosphites .............................................................................. 98
3.5.4.1 Use as Antiwear/Extreme-Pressure Additives ................................................ 98
3.5.4.2 Use as Antioxidants for Lubricating Oils ....................................................... 99
3.5.5 Alkyl and Aryl Acid Phosphites ................................................................................. 100
3.5.5.1 Amine Salts of Acid Phosphites.................................................................... 102
3.5.6 Phosphonate and Phosphinate Esters.......................................................................... 103
3.5.7 A Summary of the Proposed Mechanism for Antiwear and Extreme-Pressure
Activity of Phosphorus-Based Additives .................................................................... 104
3.6 Market Size and Commercial Availability............................................................................ 105