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What is propylene glycol?

CAS number: MPG: 57-55-6
DPG (CAS 25265-71-8) is a mixture of the isomers 1,1'-oxidi-2-propanol, 2-(2'-hydroxypropoxy)-1-propanol and 2,2'-oxidi-1-propanol
Chemical formula: C3H8O2 (MPG), C6H14O3 (DPG)

Propylene glycol (PG) is the overall name for monopropylene glycol (MPG), dipropylene glycol (DPG) and tripropylene glycol (TPG). Shell chemicals companies are only involved in the manufacture of MPG and DPG. Some heavy glycol (1% of capacity) is produced which could be processed further to DPG and TPG but is instead sold as heavy propylene glycol.   

Propylene glycol is a derivative of propylene oxide (PO) and is produced in a two-step process. The first step is the reaction of PO with water into a mixture of MPG and DPG and the second step is the distillation and purification of the mixture into its two separate components. 

MPG is the largest volume propylene glycol. It is a colourless, viscous, odourless liquid. It is highly hygroscopic and miscible in all ratios with water, alcohols, esters, ketones and amines. It has limited miscibility with halogenated hydrocarbons and is not miscible with aliphatic hydrocarbons. 

DPG is a colourless, hygroscopic liquid. It is miscible with water in any ratio and highly soluble in most organic solvents.

 

 

How is propylene glycol used?

MPG's most important end use is in the production of unsaturated polyester resins which, in turn, are used to make everyday items such as bath tubs, small boats and water/chemical tanks and pipes. Other end use application areas are paints and coatings; aeroplane de-icers/anti-icers; antifreeze and industrial coolants; detergents; hydraulic fluids; and cosmetics. 

Shell chemicals companies also supply United States Pharmacopia (USP) grade monopropylene glycol. 

The end uses of DPG include unsaturated polyester resins, plasticisers, alkyd resins, cosmetics and urethane polyols.

What are our key strengths in the propylene glycol sector?

  • Well-established presence across the globe through a strong supply network.
  • Strong, integrated position in Asia Pacific.   
  • Strong product stewardship commitment.   
Propylene glycols product datasheets and descriptions
Product/Grade Description Download
Dipropylene glycol Dipropylene glycol (C6H14O3) is a mixture of the isomers 1,1'-oxidi-2-propanol (CAS 108-61-2), 2-(2'-hydroxypropoxy)-1-propanol (CAS 106-62-7) and 2,2'-oxidi-1-propanol (CAS 110-98-5). It is a colourless, hygroscopic liquid, miscible in water in any ratio and highly soluble in most organic solvents. Datasheet
Dipropylene glycol-LO

DPG-LO is the Low Odour compliant grade of Dipropylene Glycol (DPG). It is a clear, colourless, odourless, and hygroscopic liquid, completely soluble in water.

DPG-LO is miscible in all proportions with low molecular weight aliphatic alcohols and ketones. It is slightly to moderately soluble in aromatic hydrocarbon solvents and only slightly miscible with aliphatic hydrocarbon solvents.

DPG-LO, as produced, meets the volatile organic compound (VOC) exemption criteria and definition of LVP-VOC as established in CARB's Consumer Products Regulation; in the USEPA's National Volatile Organic Compound Emissions Standards for Consumer Products; and in the Model Rule for Consumer Products as adopted by the Ozone Transport Commission (OTC).

Due to their low volatility and photochemical reactivity, these LVP-VOCs are fully exempt and non-reportable VOCs in calculations of the VOC contents of regulated consumer product categories.

Datasheet
Monopropylene glycol Monopropylene glycol (C3H8O2), also known as 1,2-Propanediol or 1,2-propylen glycol (CAS 57-55-6), is a colourless, viscous, odourless liquid. It is highly hygroscopic and miscible in all ratios with water, alcohols, esters, ketones and amines. It has limited miscibility with halogenated hydrocarbons and is not miscible with aliphatic hydrocarbons. Datasheet
Monopropylene glycol (USP) MPG - USP is the US Pharmacopoeia compliant grade of monopropylene glycol (MPG). It is a clear, colourless and practically odourless, hygroscopic liquid, completely soluble in water. MPG - USP is miscible in all proportions with low molecular weight aliphatic alcohols and ketones. It is slightly to moderately soluble in aromatics hydrocarbon solvents and only slightly miscible with aliphatics hydrocarbon solvents. Datasheet

Currently, Shell Chemicals is among the top four global players in the PO and derivatives sector. This substantial capacity growth has been fuelled by continual developments in our proprietary SMPO technology, and manifested in world-scale, integrated assets that are strategically placed to meet customer needs. It is this same commitment to our customers that drove the establishment of our polyurethanes research and technology centre in Bangalore, India, providing our key clients with practical advice and research findings on the issues that matter to their industries.

Propylene oxide and derivatives: a Shell history
Year Event
1957 First propylene oxide plant acquired in Carrington, UK
1959 First polyether polyols produced in Carrington
1964 New polyol plant starts up in Pernis, The Netherlands
1970
New TDI / MDI joint venture plant starts up in Antwerp, Belgium (halted production in 2003)
1971
Major polyol plant expansion at Pernis, The Netherlands
1980
First SMPO plant starts commercial production in Moerdijk, The Netherlands
1988
New "product" laboratory opened in Louvain-la-Neuve, Belgium
1990
Polyols and SMPO de-bottlenecking in The Netherlands
1997
Shell Seraya Research Laboratory opens in Singapore
1997
SMPO/Polyols/MPG plants start up in Singapore
1998
New rigid polyols facility starts up at Pernis, The Netherlands
1999
New SMPO plant starts up in Moerdijk, The Netherlands
1999
New polymer polyol capacity becomes available
1999
Shell/Huntsman Strategic Alliance on Rigid foam Urethanes
2002
New SMPO/Polyols plant starts up in Singapore
2003
New styrene acrylonitrile (SAN) polymer polyol plant in The Netherlands
2006
SM/PO and derivatives plants come on-stream at CSPCL Nanhai in China
2007
Closure of CARADOL polyether polyols plant at Carrington UK
2008
Opening of new R&D centre in Bangalore, India. Expansion of polyols plant at Pernis, The Netherlands
2009
Shell Chemicals celebrates 50 years of polyols (see link to feature article)
2011 Modifications at Pernis increase capacity of CASE polyols

Bowling alleys, bathrooms and boatyards are all places where we can find things made of unsaturated polyester resins, one of the materials that can be made using propylene glycols.

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