PHOSPHATE ESTERS

CAS NUMBER: 68511-37-5

DESCRIPTION OF PHOSPHATE ESTERS:

Phosphate esters exhibit a variety of properties including emulsification, lubrication, cleaning, and wetting. 
Phosphate esters is offered in an acidic form and is a viscous liquid at room temperature. 
Phosphate esters are characterized by the acid number to the first inflection point ranging from 90 to 110 mg KOH/g and the second inflection point ranging from 150 to 180 mg KOH / g and phosphorus content up to 2%. 
Phosphate esters are water-dispersible.
Phosphate esters are a class of organophosphorus compounds with the general structure O=P(OR)3, a central phosphate molecule with alkyl or aromatic substituents.

Phosphate esters can be considered as esters of phosphoric acid.
Like most functional groups, Phosphate esters occur in a diverse range of forms, with important examples including key biomolecules such as DNA, RNA and ATP, as well as many insecticides, herbicides, nerve agents and flame retardants. 
Phosphate esters have been widely used in various products as flame retardants, plasticizers, and performance additives to engine oil. 
The popularity of Phosphate esters as flame retardants came as a substitution for the highly regulated brominated flame retardants.
The low cost of production and compatibility to diverse polymers made Phosphate esters to be widely used in industry including textile, furniture, electronics as plasticizers and flame retardants. 

Phosphate esters are added to the final product physically rather than by chemical bond.
Phosphate esters leak into the environment more readily through volatilization, leaching, and abrasion.
Phosphate esters have been detected in diverse environmental compartments such as air, dust, water, sediment, soil and biota samples at higher frequency and concentration.
Phosphate esters are the reaction products of ethoxylated, propoxylated, or butoxylated alcohols or phenols with phosphating agents.
Inhibitors for both general corrosion and cracking-type corrosion are obtained by the reaction of a nitrogen base and a phosphate ester.

Phosphate esters are produced by the reaction of ethoxylated, propoxylated, or butoxylated alcohols or phenols with phosphating agents.
Phosphate esters are mainly generated from cleanroom construction materials. 
Phosphate esters are often used as anti fire retardants that are added to HEPA gel such as sealant, foam and other construction materials. 
Phosphate esters are also used as plasticizers or stabilizers. 
Phosphate esters have found numerous industrial applications due to their overall stability, especially in the presence of oxygen.

Phosphate esters have also found application as surfactants and as brighteners in detergents.
The multiple industrial uses have led to the commercial availability of a wide range of phosphate esters with different properties and reactivities. 
The available esters include aromatic phosphate esters such as tricresyl phosphate, alkyl phosphate esters such as tributyl phosphate, thiophosphates and metal containing phosphate esters such as zinc dialkyldithio-phopsphates.
Phosphate esters have been used as lubricant additives for more than 80 years, beginning with the early patents on the use of tricresyl phosphate and tri-n-butyl phosphate in lubricants.
As the temperature, pressure and sheer stress requirements for lubricants have increased, more additives have been developed. 

In addition, environmental requirements have created the need for metal free additives and additives with little or no phosphorus or sulfur content. 
While containing phosphorus, many organic and metal containing phosphate esters have been developed to fill a number of these roles. 
As the allowed phosphorus concentration has decreased, the search for phosphate esters that are effective at lower and lower concentrations and for non phosphorus additives has increased. 
Some studies, however, have indicated that phosphorus concentration in the oil and oil volatility do not predict phosphorus emissions and some additives that contain phosphorus, do not contribute to phosphorus in the exhaust stream depending on their molecular structure.
There are, however concerns about long term toxicity of many of these compounds and their degradation products remain. 
The different aspects of phosphate ester lubricants, including their efficiency as anti-wear/extreme pressure additives with various substrates, mechanisms of action and toxicities of the classes of compounds will be examined in the sections below.

Phosphate esters are based on alcohols, aromatic ethoxylates or alcohol ethoxylates. 
Phosphate esters are 100% active anionic surfactants and show superior stability in acidic or alkaline conditions but also at high temperatures.
Phosphate esters are used as wetting, emulsifying, lubricating and cleaning agents and add corrosion inhibition.
Phosphate Esters are among the most versatile surfactants partly thanks to their stability and solubility in alkali state. 
Phosphate esters are effective coupling agents which display outstanding wetting, emulsification, and low foaming properties.

Their oxidation stability and high ignition temperatures also make them a good choice in applications where fire retardancy is required.
The main advantage of phosphate esters is their inherent fire retarding property which is especially needed in demanding applications to improve the behaviour of plasticised polymers. 
While aromatic phosphate esters are typically used in PVC, TPU, thermosets and rubbers, aliphatic phosphates are mainly used in polyurethane foams. 
In PVC, the phosphate esters offer good gelling behaviour and low temperature performances.
Phosphate esters are used primarily as fire-resistant basestocks in several applications including hydraulic systems, turbines and compressors. 
Phosphate esters were synthesized from coal-tar derivatives and were consequently composed of a mixture of various isomeric aryl phosphates, including the neurotoxic orthotolyl phosphate.

Phosphate esters are the most fire resistant of the non-aqueous synthetic basestocks in common use. 
Their high ignition temperatures, excellent oxidation stability and very low vapor pressures make them difficult to burn, while their low heats of combustion result in self-extinguishing fluids.
The use of phosphate ester-based products in hydraulic applications is still principally dictated by fire-risk considerations. 
Although inhibited phosphate esters possess excellent oxidation stability and inherently good anti-wear properties under critical loading conditions, they suffer from somewhat inferior hydrolytic stability, low viscosity index and extreme chemical aggressiveness toward many conventional seal and coating materials. 

These weaknesses limit the use of phosphate ester to specialized applications where a high degree of fire resistance is required.
Phosphate esters are human-made chemicals added to consumer and industrial products for the purpose of reducing flammability.
Phosphate esters are composed of a group of chemicals with similar properties but slightly different structures. 
Phosphate esters are typically liquids at room temperature; however, some are solids.

Phosphate esters have a multitude of uses including flame retardants, plasticizers, hydraulic fluids, solvents, extraction agents, antifoam agents, and coatings for electronic devices.
Phosphate ester fluids are specialized synthetic lubricants that have unique fire-resistant and self-extinguishing properties.
Phosphate esters are anionic surfactants which are produced by phosphation of fatty alcohols and ethoxylated aliphatic and aromatic alcohols. 
Compared to other anionic surfactants, phosphate esters offer specific advantages, including stability over a broad pH range, good solubility and corrosion inhibiting properties. 
Phosphate esters are highly suitable for use as emulsifying agents, wetting agents, anti-stats, corrosion inhibitors and hydro tropes in cleaning formulations.
Phosphate esters are one of the most popular fire resistant fluids and are used almost extensively in Electro-hydraulic systems. 

Phosphate esters are organic compounds better manufactured from the reaction of alcohol and phosphoric acid. 
Phosphate esters also exhibit high ignition temperature and oxidation stability and are also used as coupling agent. 
Phosphate esters have a wide range of applications in several end-user industries such as polymer & plastics, oil & gas, textile, and others.
Phosphate esters are distinguished from other surfactants by the wide range of structures and compositions that can be created to adapt them to specific applications and also by important functional properties, such as adhesion enhancement, that offer unique advantages beyond those typically offered by anionic surfactants. 
Phosphate esters are ubiquitous in nature and essential to life, where their chemistry reaches a state of near-perfection.

Phosphate esters are 100% active anionic surfactants which are produced as the free acid by either of two chemical routes.
Monoesters are produced by the reaction of either alcohols, alcohol ethoxylates or phenyl ethoxylates with polyphosphoric acid, whereas mixtures of mono and diesters are produced by reaction of the same feedstock with phosphorous pentoxide.
Phosphate esters are highly versatile surfactants offering a wide range of properties and applications. 
Phosphate esters over many other surfactants are their alkali stability and solubility. 
They are excellent hydrotropes and are effective coupling agents which give outstanding wetting, emulsification and detergency. 
As such they are used widely in emulsion polymerisation, textile auxiliaries, maintenance chemicals, metal finishing, and many other applications.

Phosphate esters have a unique range of properties which are exploited in the production of specialised chemical processing aids for industry. 
Being stable in high concentrations of alkali, they are especially useful in household and maintenance cleaning products, where high active heavy duty products are required.
Phosphate esters have a wide range of industrial applications, for example in tribology where they are used as vapour phase lubricants and antiwear additives. 
An atomic-level understanding of phosphate ester tribofilm formation mechanisms is required to improve their tribological performance. 
A process of particular interest is the thermal decomposition of phosphate esters on steel surfaces, since this initiates polyphosphate film formation.

USES OF PHOSPHATE ESTERS:

-Plasticizers 
-Hydraulic fluids 
-Lubricating and anti-static agents 
-Multifunctional (lubrication, corrosion inhibition and anti-wear) additives for metal cutting fluids 
-Emulsifying agents 
-Esterification catalysts and polymerizing agents 
-Heavy duty alkaline cleaners/detergents 
-Curing catalysts and accelerators in resins and coatings 
-Components of rust preventive coatings for metals 
-Pigment dispersion agents 
-Paint driers and viscosity reducers 

FUNCTIONS OF PHOSPHATE ESTERS:

-Emulsifiers
-Extreme pressure additives
-Lubricants

APPLICATIONS OF PHOSPHATE ESTERS:

-Lubricants and metalworking fluids
-base oils
-additives / Metalworking fluids
-Metallurgical industry / Metalworking

ADVANTAGES OF PHOSPHATE ESTERS:

-in preparations for metalworking, Phosphate esters has emulsifying and lubricating properties and very good anti-wear properties,
-resistance to an alkaline environment,
-solubilizing properties,
-solubility, incl. in paraffin, naphthenic, rapeseed, methanol, acetone and gasoline oils.

APPLICATIONS OF PHOSPHATE ESTERS:

-cleaning agents,
-metal processing,
-a dispersant in pigments,
-good softening and antistatic effect in laundries
-an excellent water emulsifier in chlorinated hydrocarbons and white spirit,
-O/W emulsifier in cosmetic preparations.

CHEMISTRY OF PHOSPHATE ESTERS:

-Synthesis:

Various routes exist for the synthesis of organophosphates:

-Esterification of phosphoric acid:

OP(OH)3 + ROH → OP(OH)2(OR) + H2O
OP(OH)2(OR) + R'OH → OP(OH)(OR)(OR') + H2O
OP(OH)(OR)(OR') + R"OH → OP(OR)(OR')(OR") + H2O

Alcohols can be detached from phosphate esters by hydrolysis, which is the reverse of the above reactions. 
For this reason, phosphate esters are common carriers of organic groups in biosynthesis.

-Oxidation of phosphite esters:

P(OR)3 + [O] → OP(OR)3

Phosphate esters can be readily oxidised to give the above organophosphates.

-Alcoholysis of POCl3:

O=PCl3 + 3 ROH → O=P(OR)3 + 3 HCl

PROPERTIES OF PHOSPHATE ESTERS:

The phosphate esters bearing OH groups are acidic and partially deprotonated in aqueous solution. 
For example, DNA and RNA are polymers of the type [PO2(OR)(OR')−]n. 
Phosphate esters have a central phosphate molecular group. 
Phosphate esters are distinct from the triesters as one of the alkyl ester groups is replaced by a hydroxyl group, making OP diesters phosphoric acids.
The wide variety of substitutes used in organophosphate esters results in great variations in physicochemical properties, varying from highly polar to very hydrolysis resistant characteristics.

Phosphate esters exhibit a wide range of octanol water partitioning coefficient where log Kow values range from -0.98 up to 10.6.
The predominant Phosphate esters used as flame retardants and plasticizers have a positive log Kow values ranging between 1.44 and 9.49 signifying hydrophobicity.
Thus, owing to this hydrophobicity OPEs are presumptively bioaccumulated and biomagnified in aquatic ecosystems.
The detection of Phosphate esters in the air as far away as Antarctica at concentrations around 1 ng/m3 suggests their persistence in air, and their potential for long-range transport.
Phosphate esters were measured in high frequency in air and water and widely distributed in northern hemisphere.

PESTICIDES:

Phosphate esters make up about 50% of the killing agents in chemical pesticides.
Phosphate esters like some nerve agents, inhibit acetylcholinesterase, which is broadly essential for normal function in insects, but also in humans and many other animals.
Phosphate esters affect this enzyme in varied ways, a principal one being through irreversible covalent inhibition, and so create potentials for poisoning that vary in degree. 
Phosphate esters degrade rapidly by hydrolysis on exposure to sunlight, air, and soil, although small amounts can be detected in food and drinking water.
Phosphate esters contaminate drinking water by moving through the soil to the ground water.
Phosphate esters is broken down into several chemicals.
Phosphate esters degrade faster than the organochlorides.

STRUCTURAL FEATURES OF PHOSPHATE ESTERS:

Effective Phosphate esters have the following structural features:

-A terminal oxygen connected to phosphorus by a double bond, i.e. a phosphoryl group
-Two lipophilic groups bonded to the phosphorus
-A leaving group bonded to the phosphorus, often a halide

FLAME RETARDANTS OF PHOSPHATE ESTERS:

Flame retardants (FRs) are chemicals that have been used on diverse consumer materials to prevent combustion and to delay the spread of fire after ignition.
he increased demand to satisfy fire safety standards for flammability of plastic materials used in devices and appliances along with the strict regulation of brominated flame retardants has driven the high volume of production and consumption of OPEs.
Most flame retardants used are halogenated Phosphate esters, and the effectiveness of the flame retardant increases with the increased number of halogenated substituents.
Phosphate esters are utilized as additive flame retardants which means the concentration of these flame retardants decreases with time as they readily leak into the environment.

There are several mechanisms flame retardants use to prevent fire, however the most effective ones are the gas phase and the solid phase reactions.
In the solid phase, halogenated flame retardants produce a char layer on burning materials suffocating the combustion, as well as in the gas phase they remove H+ and OH− radicals from the flammable gasses, by reaction with the Br and Cl atoms to further slow down the burning process.
Non-halogenated Phosphate esters are effective mainly in the solid phase of burning materials. Upon exposure to heat the phosphorus compounds react to form a polymeric form of phosphorous acid. 
The acid causes a char layer that covers the burning material, blocking it from contact with oxygen, which in turn slows down the combustion reaction.

STRENGTHS OF PHOSPHATE ESTERS:

-Excellent fire resistance
-Good thermal stability
-Pour point ranges from -25 to -5 °C (-13° to -137.2 °F)
-Excellent boundary lubrication properties

WEAKNESSES OF PHOSPHATE ESTERS:

-Very low viscosity index ranging from 60 to -30
-Degradation products are phosphate soaps; black sludge-like consistency
-Risk of hydrolysis

APPLICATIONS OF PHOSPHATE ESTERS:

-Fire-resistant industrial hydraulic fluids
-Aviation hydraulic fluids (trialkyl or tributyl) (synthetic)
-Electrohydraulic control fluids for steam turbines

FEATURES OF PHOSPHATE ESTERS:

-Anionic character. 
-Anionic surfactants are the preferred choice for use in textile auxiliaries.
-100% active. Economic for shipment, easily incorporated into powder blended products.
-In some cases their emulsifying properties make them ideal for use in oil/water systems.
-Phosphate esters can be neutralised by alkaline earth metals or amines, adding to their versatility.
-Foaming properties of phosphate esters varies, from high to low.
-The variety of wetting, foaming and surface tension reduction properties helps the formulator to develop the required product.
-Very good hydrotroping properties which enable high active products to be produced without the use of additional auxiliary hydrotropes.
-Stability in alkali and builders enabling heavy duty cleaners to be formulated.
-Lubricating properties that enable phosphate esters to be used in metal working fluids and water based lubricants.
-Excellent free rinsing properties leading to smear free surfaces.
-Corrosion inhibition and prevention as well as load carrying properties make phosphate esters ideal for use in metalworking.
-In general low orders of toxicity and relatively low orders of irritation for the potassium salts.
-Some phosphate esters exhibit solvent solubility.

FUNCTIONS OF PHOSPHATE ESTERS:

-Detergency
-Emulsification
-Foaming
-Dispersing
-Wetting
-Antifoaming

SYNONYM:

SCHEMBL2154913
ZINC5287084
AKOS024359733
bis(2,2,2-trifluoroethyl)phosphoric acid
Fluorotelomer (linear) phosphate esters (di)C