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Terpenes
Alcohols and Ketons
Esters
Hydroxyethers
n-Propyl Bromide
Isoparaffinic Solvents
Chlorinated Hydrocarbons
Alkoxy-propanols

Terpenes
Terpenes belong to the family of hydrocarbons. The citrus and pine tree terpene distillates interest the cleaning application industry most.
The terpenes, which have a flash point of 45°C or higher, are often used in combination with hydrocarbons and/or surfactants, making recycling by distillation difficult or impossible.

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Alcohols and Ketons
Cleaning applications with alcohols and ketons are characterized by the low flash point of the solvents, which requires explosion-proof equipment. Their advantages lie in the ease of recycling (distillation) as well as in their ability to dry quickly. Their use is often in specialized applications, such as medical technology.

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Esters
Typical esters include lactates and dibasic (mixtures of abiatic acid and glutamatic acid).
Their properties with regard to flammability, boiling point and evaporation rate are comparable to hydrocarbons. One considerable disadvantage includes instability, namely their tendency to react with water under acidic or alkaline conditions. This limits their use as general cleaning solvents within the industrial cleaning arena.

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Hydroxyethers
Hydroxyethers show good solvency power for oils, fat and resins and also dissolve polar compounds such as salts. Hydroxyethers are stable against hydrolysis (reaction with water) and are not corrosive.
Flash point and evaporation rate show similar behavior to hydrocarbons. Hydroxyethers are defined substances with given boiling point. They are fully recyclable by distillation.

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n-Propyl Bromide (nPB)

This brominated hydrocarbon is deemed to be highly inflammable (flash point below 22°C / R-11) and the stability of the product is rather difficult to control and maintain especially if used in sealed degreasing units with low solvent exchange.

n-propyl bromide is becoming more widely marketed as a drop in replacement for trichloroethylene. Whereas this solvent exhibits good solvency properties for industrial cleaning operations, it has not got the approvals that trichloroethylene has.

The debate causing much confusion in the market is what the legal classification of n-propyl bromide is and whether it is a suitable substitution product for trichloroethylene, or not.

In a recent case between EnviroTech Europe and the Belgium State regarding the classification of n-propyl bromide, EU Courts re-affirm the classification of nPB as already valid in Directive 2004/73/EC of 29 April 2004:

“JUDGMENT OF THE COURT (Second Chamber) of 15 October 2009: the EU Courts concluded:

Examination of the questions referred has shown no factor capable of affecting the validity of Directive 2004/73/EC of 29 April 2004 adapting to technical progress for the 29th time Council Directive 67/548/EEC of 27 June 1967 on the approximation of the laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances, in that it classifies n-propyl bromide as a highly flammable substance (R11) and toxic for reproduction in category 2 (R60)."1

So as detailed in DEFRA AQ-15, Risk phrase substances and the SED (formerly AQ15(07))2, we must now accept that all products containing greater than 0.5% n-propyl bromide must be labelled as above, which means a CMR (carcinogenic, mutagenic, toxic for reproduction) category 2 – being the same category as for trichloroethylene. Thus, n-propyl bromide as a CMR is a potential target for the REACH authorisation.

If we now address the second point whether n-propyl bromide is a suitable substitution product for trichloroethylene we find that the philosophy of substitution is that you only substitute with a substance which is less harmful or less environmentally damaging. As n-propyl bromide is now clearly in the same category as trichloroethylene, it cannot be perceived as less harmful, and as it has a small ODP (ozone depletion potential), hardly less environmentally friendly.

So the only conclusion can be that n-propyl bromide is therefore not an appropriate substitution product for trichloroethylene.

1 Directive 2004/73/EC – Directive 67/548/EEC on Environment and consumer protection – Classification, packaging and labelling of n-propyl bromide as a dangerous substance in Case C–425/08. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:62008J0425:EN:HTML
2 DEFRA (Department for Environment, Food and Rural Affairs), Environmental Permitting, General Guidance Manual on Policy and Procedures for A2 and B Installations (2009), http://www.defra.gov.uk/environment/quality/pollution/ppc/localauth/pubs/guidance/documents/ggm-part-a-sept2009.pdf, page 242-244.

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Isoparaffinic Solvents
Isoparaffins are oil-like solvents and are derived from a petrochemical base using catalytic synthesis. This class of solvent contains pure hydrocarbons. The products most useful for industrial cleaning contain a mixture of fully saturated, linear and/or branched aliphatic hydrocarbons in the range of around C9 to C13. The flash point of these products is typically in the 57 to 65°C range which equals a boiling point of between 180°C and 220°C. Depending on the product, the boiling range may be as narrow as 10 to 15°C.

Isoparaffinic solvents are virtually free of aromatics compounds, are completely saturated and are practically odorless. They are good for the dissolution and removal of oil residues from metal surfaces. Additionally, they are excellent degreasing agents in numerous applications. However, as the solubility of polar substances in hydrocarbon solvents is extremely low, this may result in incomplete cleaning when the contamination contains polar components such as residues of aqueous emulsion and /or polar additives from high performance cutting fluids. Moreover, hydrocarbon solvents can not be stabilized against acidification. Acids brought in as part of contaminations or produced by decompositions may accumulate in the cleaning system and lead to acidification and corrosion.

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Chlorinated Hydrocarbons
Considered very important products in the industry, chlorinated hydrocarbons are produced in large scale operations on all continents. The large majority of these products are chemical intermediates, which means that these products will be used as base stocks to produce other chemical products in the area of fluor chemistry (e.g. fluor polymers, refrigerants), silicon products (e.g. sealing materials) and the construction industry (e.g. production of cellulose ether).

The amount of chlorinated hydrocarbons used as solvents is rather small and decreasing. The main applications include use as extraction solvents in the pharmaceutical industry, finishing and cleaning agent in the textile industry and in metal cleaning.

The use of chlorinated solvents is strictly regulated by different legislations due to potential damage to the environment as well as due to health and safety hazards.

  • Classification
  • Health
  • Transport labels

Chlorinated solvents used in metal cleaning applications are:

Perchloroethylene
Trichloroethylene 
Methylene Chloride

Chlorinated solvents are ideal for high performance metal cleaning applications and are still considered the benchmark in the industry. The advantages provided by chlorinated hydrocarbons are based on their excellent solvency power for typical soils and contamination, no flash point, and easy and efficient recycling through distillation. Furthermore, it has a proven track record in cleaning and the experience gained over decades of use has resulted in vast improvements in the technology and service in the field.

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Alkoxy-propanols
Alkoxy-propanols are synthetic solvents also known as modified alcohols. These solvents show favorable properties for many cleaning applications because of their balanced ability to dissolve polar and unpolar substances. The polarity of the modified alcohols means that stabilizers against acidification and corrosion are very effective within these solvents.

Specially developed formulations based on modified alcohol for different industrial cleaning applications provide excellent cleaning results. All types of products are chemically very stable compounds with a low toxicity and a good environmental profile.

The DOWCLENE™ 16-series offers a viable alternative to chlorinated hydrocarbons, hydrocarbons and aqueous cleaning systems. DOWCLENE™ 1601, 1611 and 1621 are used as degreasing and cleaning media in closed cleaning machines. They are also suited for difficult high-precision applications such as the cleaning of micro-polished parts or small precision parts.

The DOWCLENE™ PX product series offers a comprehensive solution for the electronic and optic industry, and covers many applications in this area.

The DOWCLENE™ 36 series are solvents used successfully in cold cleaning applications.

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