The
development over the years of the many different milling technologies
led to the appearance, between the 30's and 40's,
of the first jet mills.
During the post-war period, jet milling technology was used
for a variety of applications, including pesticides and pigments.
The original principles of jet milling are simple.
The powder particles are fed into the flat cylindrical milling
chamber tangentially through a venturi system by pressurized
air or nitrogen.
The particles are accelerated in a spiral movement inside the
milling chamber by a number of nozzles placed around the periphery
of the chamber.
The micronizing effect takes place by the collision between
the incoming particles and those already accelerated into the
spiral path.
Whilst centrifugal force retains the larger particles at the
periphery of the milling chamber, the smaller particles exit
with the exhaust air from the centre of the chamber.
The particle size distribution is controlled by adjusting a
number of parameters, two of the main ones being:
PRESSURE and FEED RATE.
During the early 60's JETPHARMA pioneered the European
development of jet milling technology.
In this important phase the principles of jet milling were
carefully studied and major changes were brought to the original
geometry of both the milling chamber and the product entry.
This produced significant increases in the hourly output considerable
savings in gas consumption, elimination of blow-back and limitation
of "caking" in sticky powders: the MC JETMILL®
were created.
During the 70's JETPHARMA GROUP started its own Contract
Micronization activity offering its services to the international
pharmaceutical industry using its own MC JETMILL® technology.
This enabled further improvements of the MC JETMILL® systems,
like the development of the feeding unit, the primary filtering
unit with its unique cyclone-filter concept (without reverse-jets),
the total control of internal pressure, reduction of contact
surface, homogeneity of micronized powder, the high yields
of production (>99.5%), and the optimization of design
to allow an ease cleaning and cleaning validation operations,
assuring the shortest turnaround times.
The MC JETMILL® systems were optimised to control the
PARTICLE SIZE DISTRIBUTION (PSD), just using the two parameters:
pressure and feed rate.
The growing importance of bioavailability and bioequivalence,
the new forms and means of drug administration, the increasing
pressure of health authorities concerning drug activity and
safety during the 80's have greatly increased the importance
of the specific surface of pharmaceutical activities and consequently
their particle size control.
The consequence of this was a major need for milling technologies
able to reach fine particle size distribution with D50 ranging
between 5 and 15 micron and D100 below 20 or 30 micron. In
some cases D50 below 1 micron and D 100 below 5 microns would
be necessary. The MC JETMILL® systems were the perfect
answer to this necessity.
During the 90's the U.S. FDA started considering the
micronization process as a critical step of pharmaceutical
production. They developed a number of very strict controls
to cover micronization departments of pharmaceutical companies
and contract micronization world-wide in order to prevent
cross-contamination of products. JETPHARMA reacted promptly
to this new requirements and rapidly developed its MC JETMILL®
micronization systems and its special micronization cabins
to meet the most demanding requirement of cGMPs.
With this outstanding know-how, today, JETPHARMA can offer
the most advanced jet mill system for the micronization of
pharmaceutical powders.
The MC JETMILL® system can be adapted to every possible
application: CIP, SIP system, half-suit or glove box, heated,
cooled (cryogenig), or inert (nitrogen) process gas, explosion
proof (10 bar resistant) or with bursting discs, surface hardening
or liners in many different materials (polymers, ceramic and
several metal oxides).
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