DESC:FIELD OF THE INVENTION
The present invention relates to a sugar coating composition for coating various substrates.

BACKGROUND OF THE INVENTION
Sugar coating and film coating are the two major types of coating processes widely used in the coating of tablets and other solid dosage forms. Sugar coating is a time-consuming process and requires skilled, experienced operators for the application of visually suitable coatings. Sugar coatings are generally thick, with a high build-up of coating material on edges of tablets. Film coating, whilst usually more rapid in comparison to sugar coating, generally requires more expensive ingredients and employs organic solvents such as alcohols and halogenated hydrocarbons, the vapors of which must be removed from the tablet coating facility to prevent hazards to personnel and equipment. Also, some coatings mask embossing or score marks on tablets, thereby making the tablets too tacky during drying, not forming a smooth, adherent coat on the tablets or are too soft and abrade away under the friction of the load in a drying pan.

The use of the sugar or sugar alcohol and polymer as a sugar coating has been previously suggested in various patents. However, practical usage has been inhibited by the stickiness of the sugar or sugar alcohol and polymer such as cellulosic derivative or polyvinyl alcohol or methacrylic acid co-polymer or vinyl derivatives, due to which continuous spraying on the substrate becomes impossible. Alternatively, the method of ladling and intermediate spraying and drying process for coating a substrate is used at present. However, in the aforementioned method the coating cycle consumes more time. In addition, utilizing the above-mentioned method for coating a substrate has other disadvantages like non-uniformity of coating resulting in weight gain of the tablet and requires expertise to produce excellent quality of the tablets.

Therefore, there is a need in the art for providing an alternative sugar coating composition capable of solving at least one of the aforementioned problems. The present invention addresses this need, among others.

SUMMARY OF THE INVENTION

The present invention relates to a sugar coating composition for coating various substrates comprising of:
at least one sugar or sugar alcohol;
at least one polymer;
at least one plasticizer, and
talc.

Further, the present invention also discloses method for preparing the sugar coating composition, wherein at least one sugar or sugar alcohol, at least one polymer, at least one plasticizer and talc are blended together.

DESCRIPTION OF THE INVENTION

Accordingly, the present invention provides in one aspect a sugar coating composition comprising at least one sugar or sugar alcohol, at least one polymer, at least one plasticizer and talc. The sugar coating composition further comprises pigments and filler.

According to an embodiment of the present invention, the sugar is selected from sucrose. The sugar alcohol is selected from sorbitol, mannitol, xylitol, isomalt. The sugar or sugar alcohol is present in an amount of 20 - 60% wt/wt; preferably 30 -50% wt/wt. The particle size of the sugar or sugar alcohol used in the present invention is between 37 - 595 microns. Preferably, a fine powder of sugar or sugar alcohol is preferred to facilitate dissolving the sugar into hot water when forming the aqueous coating solution.

According to an embodiment of the present invention, the polymer is selected from a group of cellulosic derivatives, poly-vinyl alcohol (PVA), and vinyl derivative, methacrylic acid co-polymer or hydroxypropyl methylcellulose (HPMC). The polymer is present in an amount of 10- 40% wt/wt; preferably 15 -30% wt/wt. The polymer acts as a film former and binder and has a viscosity of 3-1,00,000 cps.

According to an embodiment of the present invention, the plasticizer is selected from polyethylene glycol (PEG) or glycerin. The plasticizer is present in an amount of 1- 20% wt/wt; preferably, the 1- 5% wt/wt. Adding the plasticizer in the above- mentioned amount to the sugar coating composition makes the sugar coating composition smooth and reduces the tackiness of the sugar coating composition

In the present invention, polyethylene glycol of a molecular weight of greater than 400 is preferably used as a plasticizer. The polyethylene glycol acting as a plasticizer has a molecular weight in the range of 400- 8000. Preferably, the molecular weight of polyethylene glycol is 6000. The addition of polyethylene glycol to the sugar coating composition makes the surface of the tablet smooth and also acts as a detackifier, reducing the tackiness of the sugar coating composition.

According to an embodiment of the present invention, glycerin when used as a plasticizer act as a detackifier thereby reducing the tackiness of the sugar coating composition and also improves the smoothness of the final coating.

According to an embodiment of the present invention, the talc used in the sugar coating composition is present in an amount of 5-40% wt/wt; preferably, 8- 30% wt/wt. The use of talc in the aforementioned amount in the sugar coating composition improves smoothness of the final coating since talc facilitates the tumbling of the pharmaceutical tablets over each other during the coating process.

According to an embodiment of the present invention, the filler is selected from a group of calcium carbonate, Dicalcium Phosphate (DCP), microcrystalline cellulose (MCC), lactose.

According to an embodiment of the present invention, the pigment/opacifier is selected from a group of aluminum lakes, iron oxides, titanium dioxide, natural colors. The pigment/opacifier in the dry sugar composition may be present in the amount of 1 -50% wt/wt; preferably 1 -20%.

In another aspect, the present invention provides a method of preparing the sugar coating composition wherein at least one sugar or sugar alcohol, at least one polymer, at least one plasticizer and talc are blended together in a dry powder mixture. The sugar or sugar alcohol, polymer, plasticizer and talc are blended together to form a homogenous mixture. The composition formed is dispersed in hot water to form a homogenous mixture followed by granulating the composition and drying the granules. The granules are screened through 1-2 mm screen.

The sugar coating composition obtained is sprayed on to the substrate such as tablets to be coated, rotating the tablets and passing hot air to evaporate the water thereby obtaining coated substrates. The said composition is continuously sprayed onto the substrate at a spray rate of 60 grams per minute.

According to a further embodiment of the present invention, the method includes repeating the steps from dispersing to drying to obtain coated substrate and polishing the coated substrate using a polishing agent, such as Carnauba wax to obtain a smooth and shiny surface of the coated substrate having a substantially good strength.

The sugar coating composition of the present invention is used to coat substrates, such as pharmaceutical tablets, nutritional supplements, foods, confectionery forms, agriculture seeds, and the like.

The sugar coating composition obtained by using the present invention has a fast disintegration time. Further the additional step of seal coating is avoided and uniform weight gain is achieved. Furthermore, the sugar coating composition of the present invention when coated onto a substrate like pharmaceutical tablets, nutritional supplements, foods, confectionery forms, agriculture seeds, has a smooth surface, a shiny gloss, minimal tackiness, good adhesion and good strength to the substrate.

The sugar coating composition of the present invention exhibits good adhesion properties when coated onto the substrate. Further, the said composition when coated onto the substrate gives it a smooth surface. In addition, the sugar coating composition of the present invention when coated onto a substrate gives it a shiny gloss and minimal tackiness.

The following examples illustrate the invention but are not limiting thereof. All units and percentages in the examples are by weight.
Example 1

The dry ingredients of the following formulation are blended together in a dry power mixer such as Kenwood mixer for 10 mins or until a homogenous mixture was achieved, resulting in one formulation of the dry sugar coating composition.
Component Percentage Grams (gms)
HPMC E6 30% 300
Sucrose, Mannitol, Xylitol, Isomalt, Sorbitol 42% 420
PEG 6000 2% 20
Talc 12% 120
Iron Oxide 4% 40
Calcium Carbonate 10% 100

The dry sugar coating composition was then granulated using a planetary mixer. The granulation process was carried out by loading the dry sugar coating composition into the mixer and slowly adding sufficient hot water until the dry sugar composition forms slightly adherent granules. These granules were then passed through a 1-2 mm screen and then dried at 300C in an oven until loss on drying below 5%. The composition was then sieved again through 1-2 mm screen to obtain a non-dusting, granular form. If not granulated, the composition may be milled such as in a multi mill for example. Other methods of granulation, which may be used, are spraying granulation or roller compaction.

500 grams of granulated dry sugar coating composition was dispersed into 1286 grams of distilled hot water to form an aqueous coating dispersion (28% solids) and 1786 grams of this dispersion was sprayed on to 1000 grams of the pharmaceutical tablets using a coater to form the coating on the pharmaceutical tablets having theoretical weight gain of 40%. The pharmaceutical tablets were rotated in the coater at a rotation speed of 40 rpm. Hot air at 650C was used to evaporate the water in the sprayed coating dispersion by maintaining the temperature of the pharmaceutical tablets at 400C . The spraying rate of the coating dispersion during the coating was 60 grams per minute.

Upon completion of the coating process, the coated pharmaceutical tablets were again coated with 50 grams of the sugar coating composition by dispersing in 335 grams of distilled hot water to form the coating dispersion for smoothness (13% solids) and 385 grams of this dispersion was sprayed on the 1400 grams of the coated tablets using a coater to form the coating on the tablets having theoretical weight gain of 40%. The tablets were then rotated in the coater at a rotation speed of 40 rpm. Hot air at 650C was used to evaporate the water in the sprayed coating dispersion by maintaining the tablets at 400C. The spraying rate of the coating dispersion during the coating was 60 grams per minute.

Upon completion of the coating process, the tablets were subjected for the polishing using polishing agent in the pan to achieve smooth and shiny surface with rounding of the pharmaceutical tablets with good strength.

In the following examples 2-6, the components of each formulation were mixed together, formed into a coating solution, and applied to tablets, as in Example 1, to obtain sugar coating possessing a smooth surface, an excellent long lasting shiny gloss tablets were obtained.

Example 2

The components of the following formulation were mixed together, to form a sugar coating composition, and applied to tablets, as in Example 1. The sugar coating composition obtained from the above – mentioned process when coated onto a tablet gives the tablet a smooth surface and an excellent long lasting shiny gloss.

Component Percentage Grams (gms)
HPMC E6 28.4% 284
Sucrose, Mannitol, Xylitol, Isomalt, Sorbitol 39.6% 396
PEG 6000 2% 20
Talc 14% 140
Titanium dioxide 4% 40
Calcium Carbonate 12% 120

Example 3

The components of the following formulation were mixed together, to form a sugar coating composition, and applied to tablets, as in Example 1. The sugar coating compositions obtained possessed a smooth surface, minimal tackiness, good adhesion and excellent long lasting shiny gloss tablets were obtained.

Component Percentage Grams (gms)
HPMC E6 23% 230
Sucrose, Mannitol, Xylitol, Isomalt, Sorbitol 32% 320
PEG 6000 2% 20
Talc 21.5% 215
Iron oxide 4% 40
Calcium Carbonate 17.5% 175

Example 4

The components of the following formulation were mixed together, to form a sugar coating composition, and applied to tablets, as in Example 1, to obtain sugar coating possessing a smooth surface, an excellent long lasting shiny gloss tablets were obtained.
Component Percentage Grams (gms)
HPMC E6 30% 300
Xylitol 42% 420
PEG 6000 2% 20
Talc 14% 140
Iron Oxide 1% 10
Calcium Carbonate 11% 110

Example 5

The ingredients of the following formulation are loaded onto a suitable mixer after mixing it for 10 minutes, after 10 minutes, the liquid portion of the formulation (Glycerin, a plasticizer), is added to the processor and blending continues for an additional 5 minutes to create a coating composition of the invention. 500 grams of this formulation is then dispersed into 1286 grams of water and stirred for 45 minutes to form an aqueous coating dispersion of 26% solids that is ready for continuous spray coating.

Component Percentage Grams
HPMC E6 30% 300
Isomalt 20% 200
Glycerin 2% 20
Talc 25% 250
Titanium Oxide 1% 410
Calcium Carbonate 22% 220

The sugar coating composition obtained from the above – mentioned process when coated onto a tablet gives the tablet a smooth surface and an excellent long lasting shiny gloss.

Example 6
The sugar coating composition was prepared as shown in Table 1. The prepared sugar coating compositions of Examples 1-2 of the present invention and comparative Examples 1-2 were compared and evaluated for spray ability, adhesion and smoothness of the tablet surface. The results are also shown in the Table.

Table 1:
Ingredients Comparative Example 1 (%) Comparative Example 2 (%) Example 1 (%) Example 2 (%)
HPMC 5 5 30% 28.4%
Sucrose, Mannitol, Xylitol, Isomalt, Sorbitol 70 69.5 20% 39.6%
Talc 20 20 25% 14%
Polyethylene glycol
(PEG 6000) - - 2% 2%
Iron Oxide 5 5 1% 4%
CaCO3 - - 22% 12%
Tablet Surface Rough Rough Smooth Smooth
Spray ability Discontinuous Discontinuous Continuous Continuous
Adhesion Weak Weak Strong Strong

As it can be seen from Table 1, the sugar coating compositions of the present invention i.e. Example 1 and Example 2 contained a plasticizer such as polyethylene glycol (PEG 6000) , glycerin which resulted in improving the smoothness of the final coating thereby giving the table a smooth surface as compared with the sugar coating compositions of comparative Examples 1 and 2, wherein a plasticizer was absent. The addition of the plasticizer reduces the Tg (glass transition temperature of HPMC) to give smoothness to the tablet surface.
Further, the amount of polymer such as HPMC present in the sugar coating compositions of comparative Examples 1-2 is much lower than that of the sugar coating compositions of the present invention. Polymer such as HPMC acts as a binder and helps in improving the adhesive properties of the sugar coating composition. Thus, a high amount of HPMC in the sugar coating compositions is desirable. The sugar coating compositions of Comparative Examples 1-2 contain 5% HPMC which is lower than the content of HPMC present in the sugar coating compositions of Examples 1- 2 of the present invention containing 20-30% of HPMC. Hence, the sugar coating compositions of the present invention having a high quantity of HPMC shows a better binding ability resulting in good adhesion in contrast to the coating compositions of the comparative examples.
From the above, it can be inferred that the sugar coating compositions of the present invention containing the plasticizers polyethylene glycol, glycerin and the polymer such as HPMC when coated on a substrate give it a smooth surface enabling the sugar coating composition to be sprayed smoothly. In addition, the presence of a high quantity of polymer such as HPMC i.e. 20-30% provides a good adhesion to the sugar coating substrate, thereby increasing the tablet strength. Further, there is also a uniform distribution of the coating materials onto the substrate.

Moreover, in the present invention the seal coating is not required as compared to traditional sugar coating methods, where without performing the step of seal coating the sugar coating composition cannot be coated onto a substrate.
,CLAIMS:

1. A sugar coating composition comprising of:
at least one sugar or sugar alcohol;
at least one polymer;
at least one plasticizer; and
talc.

2. The sugar coating composition as claimed in claim 1, wherein the polymer is selected from a group of cellulosic derivative including poly-vinyl alcohol (PVA), vinyl derivative, methacrylic acid co-polymer and hydroxypropyl methylcellulose (HPMC).

3. The sugar coating composition as claimed in claim 2, wherein the polymer has a viscosity of 3cps-100000 cps.

4. The sugar coating composition as claimed in claim 1, wherein the sugar is sucrose in an amount of 20 - 60% wt/wt.

5. The sugar coating composition as claimed in claim 1, wherein the sugar alcohol is sorbitol, mannitol, xylitol, isomalt in an amount of 20 - 60% wt/wt.

6. The sugar coating composition as claimed in claim 1, wherein the sugar or sugar alcohol has a particle size of 37-595 microns.

7. The sugar coating composition as claimed in claim 1, wherein the plasticizer is polyethylene glycol, glycerin or combinations therof.

8. The sugar coating composition as claimed in claim 7, wherein the plasticizer is present in an amount of 1-20% wt/wt.

9. The sugar coating composition as claimed in claim 7, wherein the plasticizer has a molecular weight of 400-8000.

10. A method for preparing the sugar coating composition as claimed in claim 1, wherein at least one sugar or sugar alcohol, at least one polymer, at least one plasticizer and talc are blended together.

11. A method of coating the sugar coating composition as claimed in claim 1 onto a substrate selected from pharmaceutical tablets, nutritional supplements, foods, confectionery forms, agriculture seeds, and the like.