Flashcards in Greco Lecture 5: Mixing and Granulations Deck (16):
What is the aim of mixing?
Obtain a homogenous distribution of two or more components (without physical or chemical changes occurring)
What is a positive, negative, neutral mixture?
1. Postive: materials that mix spontaenously and irreversibly
2. Negative: materials that do not mix and separate
3. Neutral: Materials that separate nor to mix
If there's more particles in a dose, what is that more likely to mean?
Content will mirror ratio in the mixture
What is segregation and what are the factors that affect it?
1. The opposite of mixing (de-mixing)
2. Factors are:
Why can segregation be a problem when forming tablets?
1. First tablet may be 100% API (smaller molecules)
2. Second tablet may be 100% excipients (larger molecules)
What is the process of checking mixture with time?
1. Powder a mixture
2. Take samples from different regions of the mixer
3. Measure the content ratio of the API to the excipients
4. Calculate the standard deviation of the sample and plot it verses time
5. Standard deviation will start decreasing the more the product gets mixed
What are the sorts of equipment you need for mixing?
1. Y-Cone mixer
2. Rotating cube
3. Double cone
4. Oblique cone
5. Agitator mixers
What is granulation?
The process when a homogenous mixture of primary particles form larger still homogenous particles called granules
What are the main reasons behind granulation?
1. Improve particle flow rate (reduced dust generation)
2. Prevent segregation
3. Improve compaction (occupy less volume)
Describe the wet granulation process?
1. The powders are mixed with a granulating fluid that's usually volatile
2. Formation of a damp mass that's dried to form granules
3. The mass is forced through a sieve
4. Add your lubricant and compress and you have your tablet
Describe the dry granulation process?
1. A pressure is applied
2. Intermediate product is broken
3. Sieving- desired particle size
4. Add lubricant and compress it
What are the wet granulation mechanisms?
1. Adhesion and cohesion in immobile films
2. Interfacial forces in mobile films
3. Solid bridges (hardening of binders, or crystallisation of dissolved substances)
4. Attractive forces between particles
What are the steps of forming granules from wet granulation?
1. Nucleation: small particles form balls
3. Ball growth: particles attach to the nucleus to make the ball grow bigger
What are the granulation mechanisms of dry granulation?
1. Attractive forces between solid particles
2. Solid bridges (by partial melting)
How do shear granulators form granules?
2. Formation of damp mass
3. Pushed through a sieve: forms granules