Credential Automotive Newsletter

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Isocynates (Paint Spraying) are you following the HSE guidelines?

Isocynates, or di-isocynates, are basic constituents in the production of polyurethane. Methods of use vary but the essential process is that they combine with polyester or polyether resins causing a reaction which creates durable polyurethane foams, elastomers, paints or adhesives. Whilst isocynates are extremely useful, they are known to have a number of ill health effects which are serious and in some cases permanent.

A number of different forms of isocynates are used in industry with
• MDI (diphenyl methane di-isocynate
• TDI (Toluene di-isocynate)
the above being the most common, however other less common forms are:-
• HDI (hexamethylene di-isocynate)
• IPDI (Isophorone di-isocyante)
• NDI (1,5 naphthalene –di-isocynate)
• TMDI (timethyl-hexamethyle di-isocynate)

TDI is used in the production of flexible foams but is the most volatile of the common isocynates, and gives off vapours at room temperatures which are likely to cause harm to health.

MDI, in various grades, is used to make foams, tough elastomers and flexible foams. It is considerably less volatile than TDI, so when used at room temperature, is regarded as less hazardous. However, significant exposure can cause asthma, particularly where it is sprayed or heated.

Paint Spraying Two pack polyurethane paints (one containing an isocynate and the other containing polyol), are mixed together and applied before the mixture begins to cure. Often the paint is applied by spraying and heat curing may be used. These processes are probably responsible for the majority of cases of isocynate induced asthma.

Health Effects

Isocynates are irritants and highly potent sensitising agents affecting the skin and the upper respitory tract.
Very high doses arising from inhalation can cause death due to acute pulmonary oedema.

However it is the allergic reactions which are the main cause for concern. Inhaling very low levels of vapour can cause asthma attacks of varying severity, the worst being potentially fatal.

Isocynates have no detectable odour , except at very high concentrations, and they are not visible as a vapour, Measurements can be made using personal dose badges attached to individuals for the duration or part of a shift. These give reasonable accurate assessments of long term exposure and are useful for checking compliance, but they are not capable of assessing the peak exposures which are likley to be the critical cause of sensitisation.

Health

Where employees are likely to be exposed to free isocynates, appropriate health surveillance should be provided by the employer. This should include pre-employment examination and on going monitoring. The pre-employment examination should include a respiratory questionnaire plus a lung function tests followed by further tests after two weeks, six weeks, six months and thereafter at six monthly intervals.

Further guidance available HSE Guidance note EH16

Precautions
Where possible replace TDI & HDI with MDI.

All areas where isocynates are poured weighed, or dispensed must be well ventilated which in most cases will require local exhaust ventilation (LEV) to be installed

Where spraying takes place. LEV plus suitable personal protective equipment (PPE) will be required

Where assessment shows that exposures are within acceptable limits, the PPE such as overalls, gloves and eye protection should be used.

From Experience

(www.HSE.gov.uk)
When workers in a large body shop complained of paint smells and tight chests, HSE measured their isocyanate exposure by biological monitoring. It was found that everyone

· the body shop was exposed to isocyanate. The most highly exposed person being the receptionist. The downdraft spray booth filters were clogged and the over-pressure sensor had failed. The booths were becoming pressurised, especially during baking, and were leaking badly. They had never been thoroughly examined or tested.

An MVR paint sprayer worked for 10 years painting commercial vehicle bodies. He worked in a spray space and wore air-fed breathing apparatus. However, after spraying he would routinely flip up his visor to check on paint coverage, quality etc allowing no time for the fine (invisible) overspray mist to clear. The first indications that something was wrong were tight chests at night. Neither the sprayer nor his GP made the connection between his asthma and exposure to isocyanates at work. He soldiered on until he could work no longer. By this time, he was unable to walk more than 20 yards

For further information visit :-
http://www.hse.gov.uk/mvr/experience/isocyanates.htm

Note

While cleaning spray guns by passing solvent through the gun under pressure, air supplied respirators must be worn since unreacted isocyanate may be released into the work environment.

Air Booth filter Disposal

Air booth filters contaminated with iscocynates pose a potential threat to the environment if landfilled through the leaching of this material into water table. However it should be noted that this depends on the percentage of isocynates as a whole that is likely to occur within the airbooth filter. This can only be reliably calculated using the Material data safety sheets supplied for your paints and 2 packs plus the weight of the air booth filter before and after its final use.

If it is difficult to establish a precedent based on the above then there are only two alternatives:
1. You class it as Hazardous waste and dispose of it accordingly.

(EWC 15.02.02*)

2. You class it as non-hazardous and dispose of it in the general waste.

(EWC 15.02.03)

We of course would urge you to take the precautionary route.