A2 RCDG Flashcards
How does RCDG works?
consolidation and densification of the material in between two pressure rolls
What are the units of RCDG
Feeding, compaction and granulation unit
The aim of RCDG
increase of particle size decrease amount of fines increase bulk density , better flowability decrease of demixing
what are the main region in RCDG (learn to draw it)
Slip, nip and release region
what happend at the slip region?
Velocity of the feeding material is samller compred to the movement of the rolls
where is a density gradient formed
at the slip region
what does a density gradient mean?
the lower the powder get into th nip region, the higher the density
nip region
Material and roll speed are moving at the same space
decreas of the gap width, which significantly increase the roll pressure
why do densification occur at the nip region?
due to the decrease roll gap (Gap width)
what is the densification factor?
nip width /gap width
what happend when the gap width decrease
the compaction force increases
what influence the ribbons density?
SCF
Gap width
excipients
Release region
Increase of the Gap width
On what does the release depends?
On the stored elastic strains on the compact
What happend when the ribbons are release?
the density decrease due to elastic strain of the compact
What are the roll compaction design
Fixed gap and the flexible gap
Fixed gap
Both rolls have a fixed position
what is the main disad von the fixed gap?
Fluctuation of material during feeding, leading to different solid fraction
How does the SF affect CF in a fixed gap?
a high amount of powder, leads to high SF. the increase of the SF, increases as well the CF, more dense ribbons
How does the Cf affects the granules?
high CF results to larger granules
Probleme in the fixed gap
high fluctuation of feeding–> different solid fraction–> compaction force cannot be kept constant–> ribbons with different density
why it is important to keep the SF constant
due to the direct relation to the CF, if Sf changes, the Cf changes as well
How can the Cf be adjusted in the fixed gap
just by the feeding screw speed
flexible gap
fixed master roll, slave roll (movable)
what is the ad of the flexible gap over the fixed gap
Cf can be kept constant, indenpendly of SF
How is CF kept constant in th flexible gap?
it is kept constant due to constant opening of the moveable rolls
How can the CF be controlled?
by the SFS and RS
How can the solid fraction be controlled
By keeping the RCF Constant
Parameter that influences compaction
specific compaction force
Gap width
Roll speed
What is the specific compaction force?
it is the compaction force per cm of roll width
what should be kept constant during scale up
the SCF and the GW
What is the unit of SCF
CF/RW [KN/cm)
the SFC depends on
Cf and RW
Why should SCF and GW be kept constant?
in order to achieve a uniform ribbons property.
What affect the ribbons density
SCF and GW
What’s the main different between the manual and automatic production mode, regarding the CF and GW
Manual: just the CF is kept constant
automatic: both CF and GW are constant
How is the SCF kept constant in the manaul mode?
by hydraulic cyclinders or by spindel motor
How is the GW kept constant in the manaul mode?
by a control of the circuit varying the speed of tamping augur
what happend to CF, if the GW changes?
GW decrease–> increase of Cf
GW increase–>CF decrease
for what is the roller orientation important
for bypass
Which orientation is possible?
Horizonal, Vertical
inclined
Horizontal feeding?
by gravity, high bypass, material remaining in nip region
vertical alignment?
No gravitational forces, less bypass
inclined alignment
decrease of bypass
Feefing system and their function
feed auger–> defines the FR
tamp auger–> transport to the gap and predensification
how should the ratio temp auger speed to feed auger speed should be?
> 1
Roll surface
smooth, knured
what are roll surface use for?
Use to maintain the back pressure
Back pressue is important for?
to avoid bypass
How can bypass be avoided?
Vertical feeding system or using a rough surface
How does the roll surface influence the ribbons?
smooth roll surfaces–> higher density of the ribbons
rough roll surfaces–> thickness of ribbons
Types of sealing system
Cheek plates
Rim roll
Advantage of rim roll over cheek plates
more homogeneous ribbons density distribution in the RR sealing system than in the cheek plates
Why are rough surface important?
they are important to increase friction for better feeding and so increase of the nip region
what is important during feeding of the material?
Feeding should be uniform to avoid
poor compact quality
generation of excess fines
more un-compacted material
When can the gravity feeding be used?
when the powder is dense and free flowing
Why is the screw feeder better than the gravity feeder?
it provides a pre-compression force
What does the froce in screw feeder does?
it increases the friction between powder and the roll surfaces to improve compaction
what happend when we have a lot of bypass
it causes segregation of blend and consequently content uniformity
the gap size influence?
the density profile of the ribbons
What cause gap size variation?
Nono-free-flowing powder and changes in the powder density
why it is important to have a constanst CF?
to have a uniform ribbon thickness with a uniform distribution of the density
Material properties have impact on?
Compaction properties of ribbons granules PSD flowability, content uniformity compaction properties of the tablets
What influence the porosity of the ribbons
RCDG process (FSS, RS, RP, RG) milling conditions
under feeding or over feeing leads to?
under feeding–> less compaction
over feeding–> over compaction
What happend if there is more entrapped air during feeding?
it results in lower bulk density and higher porosity
the roll speed is characteris by what?
the dwell time of the material between the rolls
high rolls speed results to?
it reduces compaction, therefore the dwell time
what is the consequences of a short dwell time?
short dwell time reduces tome for plastic rearrangemnet and bonding, ribbons with low density
long dwell time is achieve by?
reduction of the roll speed, therefore particle have more tome for rearrangement, ribbons with higher density
how does a high Cf influence the PS of the granules
higher compaction force produces more dense ribbons, larger granules PS
Cf depends on?
FSS and RS
higher Cf is obtained by?
decrease of the RS and increase of the FSS
Decrease of the ribbons porosity is cause by?
decrease RS and higher FSS
increase Ribbons porosity
increase of RS (shiort dwell time) and slow FSS (less powder material)
Granule size enlargementz
larger partciles always resulus in lower tabletability
the quality of the granules are influence by?
by the porosity distribution if the roller compated ribbons
How can the strength of the ribbons been describe?
through the density of the ribbons
how does a variation of the porosity influences the properties of the granules?
it influences the PSD and density of the granules
PSD of the granules depends on?
excipeints and ribbons porosity
What’s the main different between brittel and plastic material?
Brittel material breaks easily and so independ of the compaction force
plastic material depends on the compaction force
what happend to plastic material at high CF
by high CF, longer dwell time –> ribbons with high density
Plastic material at high CF
dense ribbons–> broad PSD granules–> less binding capacity during tableting
Relation between ribbons and tablets?
denser ribbons leads to denser granules, making tablets more porous
Granules size is affect by?
infleunces by the degree of strenght reduction after dry granulation for plastcially deforming material
brittel material are unaffected
granules hardening?
due to precompression to form the granules, the
granules hardening?
due to precompression to form the granules, the crystal can not undergo futher compaction process
tablet behaviour after roll compaction
improved die filling, mass uniformity, less deaeration and capping
which tablet properties are most affect after granulation
lower compressibility, compactability and tabletability
Why do granules products porous tablets?
due to higher bulk density
reduce compactability and compressibility and low tabletability
Tabletability (know how to draw the diagram)
Capacity of a powder to be transformed into tablets of specificed strength under the effect of CF
TS against SF
Compactibility
is ability of a powdered material to be transformed into tablets with strength during densification
TS aginst SF
Compressibility
Reduction of volume wuth applied CP
SF gainst CP
compactibility is related to?
Bulk density and properties of the material
lubrication is important for?
Decrease friction during compression of the powder
Less friction during tabletting is achieve by
external lubrication
Which material is sensitive to lubricant
Plastic materials
Tablets with high TS are obtained when in RCDG
by low CF, leading to porous ribbons, poros granules, high TS due to increase compactibility
Name some dry binder
MC, HPC, HPMC, PVP
How can the RA be divided?
steps to identify, analyse or prevent possible failures or reduce their risk
Risk identification
Systematically uses information to identify possible hazards
Risk analysis?
investigates the likelihood or probability of occurrence, the severtity and the detectability using a Failure Mode and Effects Analysis (FMEA) or Hazard Analysis of critical control points (HACCP)
Why do we used risk control
to keep the risk as low as possible
what is a part of a risk control
mitigation or detection
mitigation?
it reduces the serverity or the lekelihood of occurrence by modification of the process or single process steps
detection
reduces the severity and occurrence probability by additional conctrols
What is the output of a RA
it is either nummerical probability (quantitative estimate) or risk description by precisely definded scores (qualitative exstimte)
Laser diffraction
encountered of the paticles by laser beam, leading to diffraction in a specific angle
What is the Fraunhofer theory?
If the particles are larger than the wevelength of the light, the monochramatic light is scattered forward with a small angle change
Mie theory
if the particles are smaller and reach the dimension of wavelength
what is required to calculted the Mie theory?
optical properties of the disperion medium and the dispered particles (absorbtion refraction index)
How can one divide samples for analysis?
by using a sample divider
what is the mean median diameter?
the size of particles at which 50 % of the sample is smaller and 50 % is larger than this size
what is a ishikawa diagram
a diagram which shows possible causes for an effect or probleme
How can one divide the ishikawa diagram?
Machine, Method, Material, Manpower, Measuremnet and Mother Nature
How is the risk prority number calculted?
RPN= S* P* D
increase milling speed on the granules?
finer granules, due to a higher shear stress during the process
why do the sieve size influence the particle size?
both are directled related, an increase should lead to coarser granules, while lower mesh sizes will results in smaller granules
How ths linear model investigated?
with a leinear regression (Q-q plot of the standardized residuals)
what is used to to describes the fit of the values?
the coefficient of determination
Why do we used the R2 adjust
incases of a low sample size or a high number of coefficient
Which two parameter are most siginicant for the PSD
SS and CF
FFD are used for , whiled CFD are used for?
FFD, for main effects and interactions, whereby CCD are use to define the design space
attributes of excipients to be investigated?
densit, PSD, flowability, porosity
in which order do we run the DoE
in a randomized order , in order to transfer the systematic erre into randm error
what influences most the fraction on fines during granulation
compaction force and not the milling speed, eventhough a higher milling speed results to higher fractions of fines
why do we have a low TS when lubricate external than internal
internaly lubrication leads to the decrease of the bounding strength of the particle, due to the hydrophobic film formed during compression
how do the brittel material affects t he compactability
it increases the compactability, due to their easy breakage during tablet compression
where is the formation of the hydrophobic filmer higher?
by the external lubrication
why do granules product porous tablets?
due to granules entlargment and the granules hardening, it decrease the interlocking of the particles during compression
means, granules have low compactability and compressibility
