brush/rolling of two-pack polyurethane ?

[Adam Seychell]

I have got hold of about 10 liters of two pack isocyanate cured
polyurethane paints, and just discovered why it is so popular with
professionals painters. Its incredibly durabe and tough compared to
standard domestic paints.
However, after reading all the nasty things isocyanates can do to your
lungs I will only be applying the paint by brush or roll, but possibly
located in a semi closed garage at home. There is very little
information about necessary protective gear for applying 2 pack
polyurethane with this method. Most of the safety information focuses
on spraying since this is primarily how its applied in industry.
According to the MSDS the hazardous compound is 1,6-Hexamethylene
diisocyanate
wich has an occupational exposure limit is 0.005 ppm, Boiling point of
255°C and vapor pressure 7 pascals at 25°C. This suggest its not very
likely to reach high concentrations in the air due to vaporization
from a surface.

I want to know what filter cartridge I should use for a half mask
respirator since there are a large number of them available including
combination filters that do organic vapor, inorganic vapors and
particulates.

[David Flew]

"Adam Seychell" <asey...@vet.com.au> wrote in message
news:21a524b0.03022...@posting.google.com...

I'd be looking a little further just respiration as a way this can get into
your body ( or your house.)
And I'm not sure if you can predict concentation LIMITS from boiling point
or vapour presssure. And while spraying certainly puts vapours right into
the air, I've seen this type of paint rolled on, and you an use a lot of
paint in a short time with either method.
But let's assume that what is in the paint will ultimately end up in the air
in your "semi-enclosed" garage. Say your garage is 20 ft x 10 ft x 15 ft =
3000 cu ft. Air density 0.0808 lbs per cu ft ( dredged that number out of
somewhere in the past ...) so you have 242 lbs of air in the box. 0.005
ppm equates to ( quick change to metric ) 242 *454* 0.005 /1000000*1000= 5
milligrams.
So if you apply 1 litre of paint in the time it takes for the air in your
garage to change once, the most "nasty" you can have in the paint is 5mg per
litre. Above that and you are relying on the respirator. You could evaluate
the concentration of nasties in the paint against efficiencies of the
cartridge ..... Half mask respirators are renown for issues of leakage,
non-wearing, etc etc.

It's tempting to say that industrial spray application is more hazardous,
but whilst the rate of paint usage may be greater, so is the size of the
space and (more importantly) the rate of air change. I suspect the reality
is that you need a positively ventilated space, and unless you an guarantee
concentrations around the exposure limit, something a little better than a
half face respirator. I think I'll stick to my solvent based industrial
enamel - it's just very flamable and a little narcotic ...

David

[Jim Conlin]

As I understand it, the isocyanates in these paints are not particularly
volatile and are only likely to end up in the air if the product is sprayed.
Certainly the solvents involved are nasty and deserve an organic vapor
cartridge.

[Adam Seychell]

Yes, I did some more research and what you saying agrees with what I
found.
This article best described the answer I was looking for.
http://www.anchem.su.se/isocyanate2000/abstracts/abs_berntsen.html

Basically the report measures the air concentration of several
hazardous compounds when rolling on polyurethane paints. The test
conditions were
"2 litres of product is applied in a 25 minute period in a spray booth
of 3 x 3 x 2,5 metres. There was no ventilation in the spray booth
during the paint application. Sampling time equals working time = 25
minutes"

According to the results, Product #1 (shown in table #2) produced a
air concentrations of Hexamethylene diisocyanate (HDI) of 1/14th of
the Occupational Exposure Limits (0.035mg / mł).
In other words you are completely safe from HDI when rolling/brushin
two-pack polyurethane paints , even in confined spaces. However the
solvents will get you, so an organic vapor respirator will be
absolutely essential, not to mention protective clothing, gloves, ect.

Typically the concentration of HDI monomer is 1.2g/liter in a prepared
polyuthane/isocyante paint. If 2 liters of paint were applied that
makes 2.4g of HDI available for evaporation. The volume of air in the
spray booth is 3x3x2.5 = 22.5mł. If all the HDI monomer evaporates
then it will give a concentration of 2.4/22.5 = 106 mg/mł. this is
106/0.035 = 3028 times the OEL ! However the measured results
reported only 0.07 times the OEL.

This suggest the evaporation of isocyanates are very slow from
applying paints by brush. It would be interesting to know if the
concentrations levels increase after several hours in the confined
space, instead of just the 25 minutes sample period. My guess is water
in the atmosphere reacts with the isocyanates before high
concentrations can be reached.

Adam

Jim Conlin <con...@attbi.com> wrote in message news:<3E5B73D4...@attbi.com>...

[jelle]

I think you are overreacting. The short term dangers from applying paint
with organic solvents with brush/roller will at the most be some headache
if ventilation is insufficient. Just open a window and you'll be fine. The
dangers of organic solvent lie in long time exposure if you do it as a
profession.
some flauwed reasoning:
I assume you are living in the USA, where every customer wrongdoing is
rewarded gigantic compensations in court. Now, if organis solvents where
really that dangerous, how woould you be able to buy that stuff in the
first place?
Just follow the instructions on the can and you'll be fine.

[John Meachen]

If you are truly concerned about your safety,leave the paint to the
professionals who wear air fed respirators while working in sprayshops
with powerful extraction.Anything else has a degree of risk,can you
afford to take the chance with your health for some low cost,durable
paint?

John Meachen