ISOCYANATE
In organic chemistry, isocyanate is the functional group with the formula R−N=C=O. Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Di-isocyanates are manufactured for production of polyurethanes, a class of polymers.
Common types of isocyanates are: MDI - methylene diphenyl diisocyanate, TDI - toluene diisocyanate, HDI - hexamethylene diisocyanate, IPDI - isophorone diisocyanate. The 2 main types of isocyanates, MDI and TDI, are found on the market in the proportions of 60% and 35% respectively.
TDI - TOLUENE DI-ISOCYANATE
TDI - TOLUENE DI-ISOCYANATES are a mixture of 2 isomers in various ratios between the two.
Example: TDI80/20 comes in the combination:
Toluene-2, 4-diisocyanate (2,4-TDI) - 80%
Toluene-2, 6-diisocyanate (2,6-TDI) - 20%
TDI 65/35 is still the same type of isocyanate, but with different ratio of isomers. It is used in few cases for making flexible foams.
Possibly used in the synthesis of memory foam, or polyester foam.
Toluene-2, 4-diisocyanate (2,4-TDI) - 65%
Toluene-2, 6-diisocyanate (2,6-TDI) - 35%
TDI is not found naturally in the environment. TDI is a clear liquid with low viscosity at room temperature. TDI is insoluble in water. It is miscible with alcohols, di-glycols, mono-ethyl ether, ethers, acetones, carbon, benzene, chlorobenzene, kerosene and olive oil. TDI is a reactive compound used in combination with polyether polyols and polymer polyols for the production of polyurethane foams.
When combining polyether polyols with TDI – toluene diisocyanate, one can be used in urethane applications, such as flexible foam, in coatings, adhesives, sealants and elastomer systems. As a result, one can be used in a large variety of goods, including furniture, car seatings, bedding, paints and coatings, artificial sport tracks, playground surfaces, ski suits, and other waterproof wear.
IMPORTANT. TDI is a very toxic product. Like other isocyanates, TDI is a highly reactive compound. TDI can react violently with compounds based on active hydrogen atoms (such as alcohol) and can generate enough heat for self-ignition and will result in products toxic combustibles. Other solvents not to be mixed with TDI: water, acids, bases and products strong alkalis, such as sodium hydroxide and tertiary amines.
STORAGE. TDI is sensitive to humidity and heat. Storage is recommended product at temperatures between 15°C-30°C and avoiding humidity. Under appropriate conditions storage in sealed containers, the product will maintain its properties for 6 months from the date of delivery. For longer periods of time, it is recommended to store the product under the nitrogen blanket. At temperatures below 1°C, the product is crystallized.
TDI reacts with water releasing carbon dioxide. During storage, transfer and handling product, contact with water in any form should be avoided.
MDI
MDI - methylene diphenyl diisocyanate is a very versatile molecule that delivers different performance properties for a variety of applications.
Generally used in manufacturing rigid and semi-rigid PU foams. The rigid polyurethane foams are good thermal insulators and used in nearly all freezers and refrigerators worldwide, as well as buildings. It is also used as an industrial strength adhesive, which is available to end consumers as various high-strength bottled glue preparations.
PREPOLYMER MDI
An isocyanate prepolymer is a type of polyurethane prepolymer in which all of the polyol hydroxyl end groups have reacted with isocyanate groups. The end result is a compound with isocyanate functionality at the termini instead of hydroxyls.
It is low functional pre polymer based on monomeric and polymeric MDI suitable for use broad range of flexible, semi-flexible and rebounding applications. When used for making rebond, the foam flocks coming from the shredder are blown into a mixing drum, where stirred and mixed with MDI. With or without use of steam, the adhesive enables the foam flakes to stick together.
MODIFIED MDI
Modified MDI encompasses chemically altered MDI variants, tailored to specific application requirements, and is instrumental in a range of high-performance industries. Properties: Modified MDI is the result of chemical modifications or blending with other compounds to achieve desired properties.
It is low functional pre polymer based on monomeric and polymeric MDI suitable for use broad range of flexible, semi-flexible and rebounding applications. When used for making rebond, the foam flocks coming from the shredder are blown into a mixing drum, where stirred and mixed with MDI. With or without use of steam, the adhesive enables the foam flakes to stick together.
SAFETY. MDI, like the other isocyanates, is an allergen and sensitizer. Persons developing sensitivity to isocyanates may have dangerous systemic reactions to extremely small exposures, including respiratory failure. Handling MDI requires strict engineering controls and personal protective equipment. It is a potentially violently reactive material towards water and other nucleophiles.
STORAGE. Improper MDI disposal contributes to medication wastage and increases the risk of MDI residual propellant release into the atmosphere. HFCs are artificial fluorinated gases that act as potent greenhouse gases (GHGs) when released into the atmosphere.