NOVEL IMMEDIATE RELEASE FILM COATING COMPOSITIONS

FIELD OF INVENTION

The present invention relates to novel immediate release film coating compositions having enhanced adhesion and tensile strength. The invention relates to the field of coating compositions for substrates like pharmaceutical tablets, nutritional supplements, food products, confectionery, agricultural seeds and the like.

BACKGROUND OF INVENTION

Film coating is a process in which substrate like tablet, confectionary or a seed is enveloped by a thin layer of polymeric material. Most pharmaceutical materials, food products, confectionery, nutritional supplements, agricultural seeds and the like, need coating on their surface. The reasons for coating may be various and include protection of unstable compositions, protection in the stomach with enteric coating, improving the appearance of the tablet, separation of the ingredients of a tablet if they are incompatible, and masking objectionable odors and taste.

One of the polymers frequently used in coating is polyvinyl alcohol (PVA). Polyvinyl alcohol is very sticky in nature and renders tackiness to the final composition. Hence, there have been several attempts in prior art to use PVA in film coating without the resultant tackiness.

WO20061 11980discloses a dry /liquid film coating composition having polyvinyl alcohol and self-emulsifying glyceryl monostearate (GMS)as an anti-tack agent. This application, however utilizes hot water for the reconstitution of the anti-tack agent toprovide final film coating. This may not be suitable for heat sensitive ingredients/drugs. Moreover, maintaining a high temperature during spraying is cumbersome in an Industrial set up.Notwithstanding, the viscosity of the final film coating composition resulting from the disclosure in this application is very high which may lead to spray related problems.

WO2003/GB03195 also attempts to eliminate tackiness by combiningEudragit with GMS along with surface active agent. Herein again, the composition needs to be solubilized at a high temperature to provide working film coating formulationand hence not suitable at several instances.

US 2010/0291 159 provides a method of using waxy detackifier such as glyceryl monostearate (GMS) through micronization, further thispublication exemplifies the use of micronized GMS to yield coating compositions.However, Glycerol monostearate is a waxy substance and micronization process of waxy substances is not uniform and yields variable particle sizes, which interfere with spraying process. Additionally to get micronized GMS pre-processing is required. Since pre-processing step is required for processing every batch, which includes steps such as sieving (material wastage), manual processing, time consuming selection, equipment dependent piucess, etc., Lhere is a huge wastage of time and material. It also draws serious limitation of applicability to small sized industries and research and development laboratories requiring lower amount of micronized GMS. Further, such composition retains its hydrophobic property and is difficult to disperse during reconstitution.

Hence, there is a need to have an alternative process and/or composition that eliminates the problems of prior art and simultaneously reduces the tackiness of film coating compositions based on PVA.

OBJECT OF INVENTION

An object of the present invention is to provide a novel immediate release, non-tacky film coating composition of PVA that is completely dispersed at ambient temperature and the process for producing the same.

SUMMARY OF THE INVENTION

It has been surprisingly found that the use of plasticizer in combination withwaxy emulsifierwetting agent and the polymer results in a composition which is non-tacky and disperses easily in ambient temperature, which also results in a smooth coating. Further the resultant film exhibits good adhesion and tensile strength. DETAILED DESCRIPTION

Unless otherwise stated all terms used in the following description, shall constitute the same meaning as understood by a person skilled in the art. All terms used here in the specification carry the same meaning as in common scientific parlance.

Film coating is the process whereby a tablet, capsule, or pellet is surrounded by a thin layer of polymeric material. Coating tablet with a thin polymeric film is commonly performed to modify drug release, mask the taste of therapeutic agents, to enhance the stability of the drug within the gastrointestinal fluids or may be used for pure aesthetic reasons.

For the purpose of present invention, 'polymer composite base' comprises the dry mass obtained by mixing the polymer in heated plasticizer, emulsifier and wetting agent.

For the purpose of present invention,'ambient temperature' shall be understood to mean temperatures generally in the range ol ^' irom about 20°C (68°F) to about 30°C (86°F) +/-3°C.

An immediate release film coating composition of the present invention comprises a dry polymer composite base along with pharmaceutically acceptable excipients.

The dry polymer composite base of present invention comprises a polymer, awaxy emulsifier, a plasticizer and a wetting agent.

The present invention provides a novel immediate release film coating composition comprising a polymer, awaxy emulsifier, a plasticizer,a wetting agent and optionally an opacifier, a pigment,a diluent, lubricant or other pharmaceutically acceptable excipients.

The novel immediate release film coating composition of the present invention includes a polymer which forms a good filmlacks toxicity and has a suitable solubility profile upon ingestion. The film must provide a tough, yet elastic film even in the presence of powdered additives such as pigments. The film must be stable to heat, light, moisture and be free from undesirable taste and odor.

The polymer may be selected fromthe group comprising polyvinyl alcohol (PVA), copolymers of PVA, polyvinylpyrrolidone-vinyl acetate copolymer (copovidone), polyvinylacetate phthalate, methacrylic acid copolymers, hypromellose (hydroxypropylmethyl cellulose), hydroxypropylcellulose, sodium carboxymethyl cellulose, ethyl cellulose. The polymer may be preferably polyvinyl alcohol.

Polyvinyl alcohol is an odorless and tasteless, translucent, white or cream colored granular powder. All grades of polyvinyl alcohol may be used in the present invention.

The amount of polymer used in the composition of the present invention may be range of 50- 90%, preferably 55to 85% w/w, more preferably 60-80% by weight of the polymer composite base.

Plasticizer of the present invention may be selected from the groupcomprising phthalate esters, phosphate esters, and other esters like citrates, stearates, sebacate, oleate, oils, glycerols, glycols etc. Preferably, the plasticizer of the present invention is selected from the group comprising polyethylene glycol, ethyl phthalate, methyl phthalate, propylene glycol, fractionated coconut oil, lecithin, castor oil, dibutylsebacate, diethyl phthalate, dipropyl phthalate, dibutyl phthalate, triacetin, liquid paraffin, triethyl citrate, and combinations thereof. More preferably, the plasticizer is dibutylsebacate, diethyl phthalate, and dibutyl phthalate.

The amount of plasticizer used in the composition of the present invention may be range of 2 to 30% w/w, preferably 5-25% by weight of the polymer composite base.

The composition of the present invention comprises a waxy emulsifier. A non-limiting list of materials that may be used as 'waxy emulsifier' includes glyceryl monostearate, glycerylbehenate (e.g. Compritol 888 ATO), glycerylpalmitostearate (e.g. Precirol ATO 05), sorbitan ester (e.g. sorbitan monopalmitate— Span 40), palmitic acid, polyoxyethylene alkyl ether (e.g. Cremophor AG; Brij 52; Brij 72; Volpo S2; and Ethylan 2512), lauroylpolyoxylglyceride (e.g. Gelucire 44/14) and stearoylpolyoxylglyceride (e.g. Gelucire 50/13), ceresin, cetostearyl alcohol, cetyl alcohol, docusate sodium, ethyl maltol, ethylene glycol stearates, glycerylmonooleate, lanolin, myristic acid, petrolatum/lanolin alcohol, polyoxyl 6 stearate, polyoxyl 8 stearate, propylene glycol monostearate, sorbitan tristearate, sodium stearylfumarate, stearyl alcohol, hydrogenated vegetable oil, carnauba wax, microcrystalline wax and zinc stearate, and the like. Preferably the wetting agent is polysorbate 80.

The amount of waxy emulsifier used in the composition may be in the range of 1 % w/w to 20 % w/w, preferably in the range of 3% w/w to 15% by weight of the polymer composite base.

Wetting agents of the present invention may be selected from the group comprising Tween 20(polysorbate 20 or poloxyethylene (20) sorbitan monolaurate), Tween 40 (polysorbate 40 or polyoxyethylene (20) sorbitan monopalmitate), Tween 60 (polysorbate 60 or polyoxyethylene (20) sorbitan monostearate), Tween 80 (polysorbate 80 or polyoxyethylene (20) sorbitan monoleate), sodium lauryl sulphate and combinations thereof.

The amount of wetting agent used in the composition of the present inventionmay be in the range of 0, 1% w/w to! 5% w/w, preferably in the range of 0.5% w/w to 10% by weight of the polymer composite base

The composition of the present invention may additionally comprise other ingredients such as an opacifier, a colorant, adiluent, a lubricant, a flavoring agent and/or a sweetening agent etc.

Opacifiers of the present invention may be selected from the group comprising titanium dioxide, zinc oxide, calcium carbonate, magnesium oxide and the like.

A pigment may be used to provide color to the film coating. For instance, pigments of the present invention may include iron oxide colors, Lake or soluble colors, natural colors, candurin colors and the like or any food approved colors or dyes or combinations thereof. Diluent of the present invention may include Tri basic calcium phosphate, Micro-crystalline cellulose, calcium phosphate and the like.

Lubricants of the present invention may be selected from the group comprisingmagnesium stearate, calcium stearate, zinc stearate, stearic acid, mineral oil, and combinations thereof.

Sweeteners of the present invention may be selected from the group comprising glucose, fructose, sorbitol, aspartame, glycerol, saccharin, xylitol and the like.

Flavoring agents of the present invention may be selected from the group comprising powder, liquid, encapsulated flavors either natural or syntheticorigin.

Substrates of the present invention comprise but are not limited to pharmaceutical materials, nutritional supplements, food, confectionery forms, agricultural seeds, and the like.

The present invention provides a coating composition, wherein the dry polymer composite base present may be present in the range of 50 to 90%, preferably in the range of 60 % w/w to 80%, with other pharmaceutical excipients. The pharmaceutical excipients may include anopacifier in the range of 0.1-25% w/w, a pigment in the range of 0.1-25% w/w, a diluent in the range ofO.1- 15% w/w, a lubricant in the range of 0.1-5% w/w or combinations thereof. The coating composition may additionally comprise other pharmaceutically acceptable excipients.

In another aspect the composition of the present invention may be, prepared by a process comprising the steps of:

1. combining the liquefied plasticizer with the waxy emulsifier and wetting agent;

2. heating the above said mixture to obtain a homogenous liquid dispersion;

3. adding the polymer to the heated mixture of step 1 to obtain the polymer composite base in dry powder form;

4. Optionally adding other pharmaceutical excipients to obtain the composition of the present invention. The process of preparing the composition of the present invention includes combining the waxy emulsifier, wetting agent and liquefied plasticizer. The combination may be achieved by several processes such as mixing, stirring etc. The resultant mixture obtained, on combining the liquefied plasticizer with the waxy emulsifierand wetting agent may be heated in the temperature range of about 60-90 °C (degree Celsius), more preferably about 70-80°C, for a period of 5-10 min to obtain a homogenous liquid dispersion.

The polymer of the present invention may be added to the homogenous liquid dispersion to obtain the polymer composite base. In addition other components of the composition as described abovemay be added to the polymer composite base.

In another embodiment, the present invention provides a method for coating substrates comprising reconstituting the film coating composition and applying the coating solution onto the substrates to form a film coating on the substrates, and drying the film coating on said substrates.

In another aspect of the invention, the polymer composite base of the present invention is reconstituted in purified water, de-mineralized water, and Iike.The amount of solid present after reconstitution may be in the range of 5-20% w/v, preferably 5 to 15% w/v.

In another aspect of the invention, the composition of the present invention is reconstituted in solvents selected from the group comprising aqueous solutions, purified water, de-mineralized water, and Iike.The amount of solidpresent after reconstitution may be in the range of 10-40% w/v, preferably 1 to 30% w/v.

The polymer composite baseor the composition of the present invention may be coated by methods such as simple pan coating, fluidized bed coating, pans with one-way air flow through the tablet bed and the like. The film coating process may be carried out in conventional pan. Operation variables such as speed of pan, rotation, angle of pan axis, and temperature and humidity control, optimum spray rate may beadjusted whichhelp in increasing the efficiency of the process and to obtain the desired coating effect. Surprisingly,the composition of the present invention, displayed good spray delivery rates even at such high solids contents in the coating suspension.

For instance, the composite base or the composition of the present invention may be sprayed by adapting the following coating parameters, such as Inlet air temperature in the range of 50-70 degree Celsius, Tablet bed temperature in the range of 30-50 degree Celsius, suitable pump •speed, pan speed, an atomizing air pressure in the range of 1.4-3.0KG/cm sq. as per requirement of lot size to be coated.

Without being limited by theory, the composition of the present invention uses aliydrophobic plasticizer in combination with other ingredients and PVA, which results in a composition which provides a smooth coating, which is non-tacky and disperses easily in ambient temperature. Further the resultant film exhibits good adhesion and tensile strength. Moreover, the process of preparing the composition of the present invention, using a combination of heating and marinating the mixture at appropriate temperatures and addition of the composition in sequence. It is postulated that the plasticizer interacts with the waxy emulsifier thereby surprisingly reducing the relative size of GMS and hydrophobicity of mixture. Such a mixture is easily dispersed in the polymer, thereby easing reconstitution.

Hence, the composition of the present invention is synergistic, is easily dispersible, readily reconstitutable and eliminates the problems of prior art.

In another aspect, the present invention relates to the intimate mixture obtained by heating the plasticizer and wetting agent to a temperature of about 60-85°C and subsequent addition of waxy emulsifier with continuous mixing of 10-15 minutes. The intimate mixture thus obtained has a desirable particle size. This intimate mixture is capable of freely passing through #120 mesh to #325 mesh, 38 micron, 28 micron sieves. Subsequently addition of polymer to this intimate mixture provides granules having ranges of #100 mesh to #120 mesh. FC U0t)U4HA

When the composition of the present invention is coated over a 100 kg batch of substrate, at weight gain of 2.5 % w/w,time period for spraying reconstituted solution is about2 Hours.The composition of the present invention provides uniform film formation.

ADVANTAGES

1. The present invention uses a wetting agent with a waxy emulsifier and a liquefied plasticizer in raised temperature, thereby dissolving the waxy emulsifier easilyand hence eliminating the problem of prior art.

2. The composition of the present invention may be adapted to provide colorless and transparent film coat to the materialswith the enhanced film properties like finish, aesthetics, moisture barrier and luster.

3. The composition of the present invention has minimum tackiness, good adhesion, good tensile strength, high stability and high percentage of reconstitution.

4. The reconstitution of composition of the present invention is simple and the high solid content does not lead to any viscosity problem for spray and does not dry at the orifice of the spray gun.

5. The reconstitution of the composition of the present invention may be carried out in water, and thereby eliminates the use of harmful organic solvents.

6. The composition of the present invention provides a uniform and nearly perfect coat in relatively less time.

7. High solid content of the present composition helps to build up necessary weight and coating thickness quicker than other compositions thus increasing the speed of the process and thereby decreases the time consumed and is more economic.

8. During reconstitution of the composition, there is no sedimentation or floating of the particles thereby eliminating continuous stirring. Thus the compositions of the present invention are highly stable with respect to storing after reconstitution for long hours. 9. The formulation of the present invention solves the problems of prior art, with regards to the use of glycerol monostearate in a composition.

10. The composition of the present invention reduces the dispersion time of the composition and renders ease of constitution. The composition of the present invention is reconstituted within a time period of 20-25 minutes, whereas the compositions of prior art are reconstituted only in about 35-40 minutes.

11. The solid content of the composition of the present invention is much higher than that of prior art.

The invention illustratively disclosed herein suitably may be practiced in the absence of any component, ingredient, or step which is not specifically disclosed herein. Several examples are set forth below to further illustrate the nature of the invention and the manner of carrying it out. However, the invention should not be considered as being limited to the details thereof.

EXAMPLES

The present invention will next be described in further detail based on examples and comparative examples, although the present invention shall not be limited by the following examples. All units and percentages in the examples are by weight.

Example 1: Preparation of the composition of present invention

Process of preparation of Polymer compositebase comprises of heating 59.09% w/w of Diethyl phthalate to 80 degree Celsius and adding 29.23% w/w of Glyceryl monostearate, 1 1.68% w/wof Polysorbate 80 to form a homogenous liquid dispersion.

Take 28% w/w of the above liquid dispersion (at a temperature 70-80°C) and mix with 72% w/w poly vinyl alcohol to prepare the desired polymer composite base. The same is gradually cooled to room temperature to obtain a dry powder base. The powder obtained is sifted through sieve of 40 mesh to ensure the absence of lumps or agglomerates. The final composition of the dry polymer composite base thus obtained is given in table 1.

Table 1 Component Percentage in

Polymer composite

base

Diethyl phthalate 16.5452

Glyceryl Monostearate 8.1844

Polysorbate 80 3.2704

Poly vinyl alcohol 72

Total 100

This polymer composite base is reconstituted in water at ambient temperature and the suspension thus obtained is used as film coating to coat various substrates.The film coating can be applied as part of a pan coating or spray coating process commonly used to coat such articles. The amount of coating applied will depend upon several factors, including the nature and functionality of the film coating, the substrate to be coated and the apparatus employed to apply the coating, etc.

In this case types of tablet used were medium sized, round, plane on both sides with sharp edges with diameter 10 mm, thickness mm and hardness of core 4.2 kg/cm sq.

Example 2

Process of preparation of Polymer compositebase comprises of heating 59.09% w/w of Dibutyl sebacate to 80 degree Celsius and adding 29.23% w/w of Glyceryl monostearate, 1 1.68% w/wof Polysorbate 80 to form a homogenous liquid dispersion.

Take 25% w/w of the above liquid dispersion (at a temperature 70-80°C) and mix with 75% w/w poly vinyl alcohol to prepare the desired polymer composite base. The same is gradually cooled to room temperature to obtain a dry powder base. The powder obtained is sifted through sieve of 40 mesh to ensure the absence of lumps or agglomerates. The final composition of the dry polymer composite base thus obtained is given in table 2 Table 2

Powder is sifted, reconstituted, sprayed on tablet as explained in example 1 Example 3

Process of preparation of Polymer compositebase comprises of heating 85.09% w/w of Diethyl phthalate to 80 degree Celsius and adding 12.68% w/w of Glyceryl monostearate, 2.23% w/wof Polysorbate 80 to form a homogenous liquid dispersion.

Take 35% w/w of the above liquid dispersion (at a temperature 70-80°C) and mix with 65% w/w poly vinyl alcohol to prepare the desired polymer composite base. The same is gradually cooled to room temperature to obtain a dry powder base. The powder obtained is sifted through sieve of 40 mesh to ensure the absence of lumps or agglomerates. The final composition of the dry polymer composite base thus obtained is given in table 3.

Table 3

Component Percentage in

Polymer composite

base

dibutyl phthalate 29.7815

Glyceryl Monostearate 4.438

Polysorbate 80 0.7805 Poly vinyl alcohol 65

Total 100

Powder is sifted, reconstituted, sprayed on tablet as explained in example 1 Example 4

Process of preparation of Polymer compositebase comprises of heating 38.09% w/w of Diethyl phthalate to 80 degree Celsius and adding 32.23% w/w of Glyceryl monostearate, 29.68% w/wof Polysorbate 80 to form a homogenous liquid dispersion.

Take 28% w/w of the above liquid dispersion (at a temperature 70-80°C) and mix with 72% w/w poly vinyl alcohol to prepare the desired polymer composite base. The same is gradually cooled to room temperature to obtain a dry powder base. The powder obtained is sifted through sieve of 40 mesh to ensure the absence of lumps or agglomerates. The final composition of the dry polymer composite base thus obtained is given in table 4.

Table 4

Powder is sifted, reconstituted, sprayed on tablet as explained in example 1 Example 5:

The polymer composite base is taken from any of the preceding examples andblended with Other pharmaceutical ingredients.

Table 5

Ingredient Percentage by weight Weight in grams

Polymer composite 57% 570 base

Polyethylene glycol 8% 80

6000

Magnesium Stearate 3% 30

Titanium Dioxide 15% 150

Pigment 17% 170

Total 100% 1000

The Polymer composite baseis taken in amounts of 57% w/w, PEG 6000 in amounts of 8% w/w,magnesium stearate in amounts of 3% w/w, Titanium dioxide in amounts of 15% w/w, and pigment in amounts of 17% w/w.

The powder mixtures are prepared using standard dry blending or mixing techniques. The ingredients are individually weighed, added to high speed mixer, blended for a sufficient time until a substantially uniform mixture of the ingredients is obtained. The time required to achieve such substantial uniformity will, of course, depend upon the batch size. This mixture is then passed through a 40 mm sieve to ensure smoothness of the mixture.

If any of the powder composition'singredients are liquids, they are added only after all of the dry ingredients have been sufficiently blended, and the combination of wet and dry ingredients is blended for an additional amount of time to ensure homogeneity once all of the liquid is introduced. As will be described below, the methods in accordance with the present invention include applying the film coating compositions as described herein as aqueous suspensions to the surfaces of orally ingestible substrates.

The film coating can be applied as part of a pancoating or spray coating process commonly used to coat such articles. The amount of coatingapplied will depend upon several factors, including the nature and functionality of the filmcoating, the substrate to be coated and the apparatus employed to apply the coating, etc. In this case types of tablet used were medium sized, round, plane on both sides with sharpedges with diameter 10 mm,thickness 5mm and hardness of core 4.2 kg/cm sq.

Example 6:

The polymer composite base is taken from any of the preceding examples and blended with other pharmaceutical ingredients.

Table 6

The Polymer composite base is taken in amounts of 57 % w/w, PEG 6000 in amounts of 4% w/w, calcium carbonate 4% w/w, magnesium stearate in amounts of 3% w/w, Titanium dioxide in amounts of 15% w/w, and pigment in amounts of 17% w/w.

The powder mixtures are blended, sifted, reconstituted, sprayed on tablet as explained in example 5.

Example 7:

The polymer composite base is taken from any of the preceding examples and blended with other pharmaceutical ingredients.

Table 7

Ingredient Percentage by weight Weight in grams Polymer composite 80% 800

base

Polyethylene glycol 10% 100

6000

Micro-crystalline 7% 70

cellulose

Titanium Dioxide 3% 30

Total 100% 1000

The Polymer composite base is taken in amounts of 80% w/w, PEG 6000 in amounts of 1U% w/w, calcium carbonate 7% w/w, Titanium dioxide in amounts of 3% w/w.

The powder mixtures are blended, sifted, reconstituted, sprayed on tablet as explained in example 5.

Example 8:

Process of preparation of Polymer compositebase comprises of heating 59.09% w/w of Diethyl phthalate to 80 degree Celsius and adding 29.23% w/w of Glyceryl monostearate, 1 1.68% w/wof Polysorbate 80 to form a homogenous liquid dispersion.

Take 28% w/w of the above liquid dispersion (at a temperature 70-80"C) and mix with 72% w/w poly vinyl alcohol to prepare the desired polymer composite base. The same is gradually cooled to room temperature to obtain a dry powder base. The powder obtained is sifted through sieve of 40 mesh to ensure the absence of lumps or agglomerates. The final composition of the dry polymer composite base thus obtained is given in table 8.

Table 8

Component Percentage in

Polymer composite

base

Diethyl phthalate 16.5452

Glyceryl. Monostearate 8.1844

Polysorbate 80 3.2704 Poly vinyl alcohol 72

Total 100

The above composite base is used as a ready mix to be blended with color, lake colors, titanium dioxide and Magnesium stearate to produce the desired product.

Table 9

The Polymer composite base of step-II is then taken in amounts of 55 % w/w, PEG 6000 in amounts of 10% w/w,magnesium stearate in amounts of 3% w/w, Titanium dioxide in amounts of 15% w/w, and pigment in amounts of 17% w/w.

The powder mixtures are prepared using standard dry blending or mixing techniques. The ingredients are individually weighed, added to high speed mixer, blended for a sufficient time until a substantially uniform mixture of the ingredients is obtained. The time required to achieve such substantial uniformity will, of course, depend upon the batch size. This mixture is then passed through a 40mm sieve to ensure smoothness of the mixture.

The film coating can be applied as part of a pan coating or spray coating process commonly used to coat such articles. The amount of coating applied will depend upon several factors, including the nature and functionality of the film coating, the substrate to be coated and the apparatus employed to apply the coating, etc. In this case types of tablet used were medium sized, round, plane on both sides with sharp edges with diameter 10mm, thickness 5mm and hardness of core 4.2 kg/cm sq.

Example 9:

Process of preparation of Polymer composite base comprises heating of Diethyl phthalate to 80 degree Celsius and Glyceryl monostearate in amounts as given in table no 10. Heat the mixture to 70-80 °C for 5-10 min.

Table no 10

When mixtcire obtained from above is taken in amounts of 28% w/w and mixed with 72% w/wpolyvinyl alcoholit results in the formation of a powder.Powder thus obtained is re-dispersed in water, however homogenous dispersion is not achieved.The properties expected to result that were not comparable to those of earlier compositions suggesting that presence of each component is necessary to obtain the desired properties.

Example 10:Preparation of the Aqueous Dispersion:

The dry film coating composition (25grams) is dispersed into 75grams of water at ambienttemperature to make an aqueous coating suspension having 25% w/w non-water ingredients.

The water is weighed into a vessel with a diameter approximately equal to the depth of thefinal dispersion. A low shear mixer is lowered into the water and turned on to create a vortexfrom the edge of the vessel down to just above the mixing blade to prevent entrapment of air. The 25grams of dry film coating composition is added to the vortex at a rate where there is noexcessive buildup of dry powder. The speed and depth of the mixing blade is adjusted to avoidair being drawn into the suspension so as to avoid foaming. The suspension is stirred to form ahomogeneous aqueous dispersion suitable for coating.

The average coating parameters were: Inlet air temperature 55-60 degree Celsius, tablet bed temperature 40-43 degree Celsius, pump RPMlrpm, pan speed 35-38 rpm,atomizing air pressure 1.4-2.0KG/cm sq.