n-Propyl bromide (1-bromopropane) is not to be recommended on both
environmental and H&S grounds. There is a task force reporting annually
to the Parties to the Montreal Protocol (I'm a co-chair of it). I quote
below the conclusions verbatim from the 2003 report:
[quote]
Conclusions
i. The forecast global expansion of the nPB market has not yet
occurred, because of the unclear regulatory situation, the current
economic situation and geopolitical tensions.
ii. The bulk price of nPB, both raw and blended, has dropped to a
level that is more competitive for general degreasing operations.
iii. The global production capacity of molecular nPB and blended
solvents has expanded considerably and can meet foreseeable
immediate demands if the regulatory and economic barriers are
removed. Bromine production capacity is sufficient that more nPB
can be produced at fairly short notice, if needed.
iv. nPB manufacturers and blenders are heavily promoting their
products as replacements for non-ozone-depleting chlorinated
solvents, exploiting possible regulatory loopholes.
v. The pharmaceutical, agrochemical and speciality chemical
industries consume about 5,000 tonnes of nPB annually. The
emissions from these are unknown.
vi. There is increased interest in the use of nPB in Article 5(1)
countries, notably in the Peoples’ Republic of China.
vii. Although there is no new information about the reproductive
toxicity and neurotoxicity of nPB, there are grounds for concern
arising from the incomplete toxicity or epidemiological information
already available.
viii. Recommended safety practices regarding the use of nPB are not
always being observed, resulting in excessive emissions and
potential over-exposure of operators. In particular, more attention
must be paid to the risks of dermal uptake, which may be more
rapid in humans than was thought.
ix. In view of the still-unknown toxicology, epidemiology and risk to
the ozone layer, the precautionary principle could discourage use of
nPB in emissive solvents applications, and could require that every
measure be taken to protect the operators from risk of exposure and
to minimise emissions.
[/quote]

In addition, the EU reported that they were proposing an amendment to
the Montreal Protocol this year to introduce nPB as a controlled
substance, meaning that, if this amendment is approved, it will be
rapidly phased out globally. There is therefore a risk that it will no
longer be available within a couple of years or so.

There is no PEL for nPB: OSHA have requested the NTP to conduct a
research programme to determine a suitable PEL. In the meanwhile,
manufacturers recommend an OEL, but this has no mandatory force. OTOH,
if operators fall ill because of exposure, the recommended OELs may be
considered in court hearings. Most of the serious manufacturers and
vendors recommend 25 ppm. One recommends 5 ppm and one 10 ppm. The less
scrupulous vendors may go up to 100 ppm. No serious epidemiological
studies of chronic toxicity have been made and 25 ppm may be too high,
judging from a few anecdotal cases reported of neurotoxicity. It is also
a reprotoxin, sperm count and motility being reported in men and reduced
follicle sizes in women. It is not known to be carcinogenic in either
men or women. The US EPA have a SNAP ruling in consultation and, if this
passes, then its use in some applications will be permitted with a
recommendation of 25 ppm OEL. The EU have a proposed ruling forbidding
its use as a solvent.

If you want more details on either the environmental or toxicological
properties, then I'm at your disposal.

HFEs and HFCs are both a series of niche solvents with a moderately high
global warming potential. They are very expensive and, by themselves,
are very poor solvents. Their main advantage is a very low toxicity.
They are usually blended with chlorinated solvents (e.g.,
1,2-trans-dichloroethylene) and alcohols for defluxing, forming
near-azeotropes. These blends are only moderately effective.

Other possibilities for vapour defluxing include some straight
chlorinated solvent/alcohol blends, such as trichloroethylene/methanol.
These are more toxic and more aggressive to polymeric components, but
low-cost and effective.

Cyclo-hexane or any alkene/alkane blends are totally unsuitable for
vapour degreasing because of their flammability and low vapour density,
making vapour containment almost impossible. They are also strong VOCs.

Hope this helps.

Brian

Stolar, Paul W wrote:

> I have just begun re-evaluating cleaners.
>
> We are presently using an HFE in a degreaser. I want a cleaner I can use
> in the degreaser. Aqueous is not an option.
>
> I am not familiar with the nPB cleaners. Has anyone had bad or good
> experiences?
>
> What about cyclo-hexane?
>
> And other solvents?
>
> Paul Stolar
> Materials/Reliability Engineer
> Manufacturing Reliability Lead Engineer
> Baker Atlas
> 713-625-5376
>
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