Reformulating tablet core to reduce brittleness and increase robustness. Foam and Bubble formation because of air spraying of a polymer solution. Low the viscosity of the coating solution. Insufficient plasticization or too much pigmentation. Adjust the Adhesive viscosity or the nip replace the solvent Peeling. Pan loading with insufficient amount of core tablets. Use appropriate drying (inlet air) temperature. These charges often cause attraction of Dirt , Dust , fibre and hair on to the web material and defects in coating uniformity resulting in quality problems and customer dissatisfaction. the substrate is changed from hydrophobic to hydrophilic. A substrate having low surface energy is called hydrophobic, implying that the surface of the substrate is not able interacting strongly with a material brought on top of it. It's a promise from my side to guide you , in terms of selection of a suitable additive or a process. It is a coating defect where tablet surfaces erode as tablets tumble during the coating process. The improper application of the conformal coating. Insufficient film strength to provide resistance to edge damage. This problem is experienced most strongly in water based adhesives. The incorrect thickness of the coating where not enough coating is deposited so that there is insufficient conformal coating to self level. Lowering the surface tension of the coating by using additives made specifically for this purpose. Be aware that the use of defoamer, being an approach that cannot always be prevented, increases the risk of cratering , as well as reduction in Peel adhesion values. Pan fill with sufficient amount of core tablets. Increasing viscosity of coating solution. Inappropriate drying (inlet air) temperature. Too little air pressure, wide fan patterns or spraying at excessive nozzle distances causes droplets to become too dry during their travel time to the work surface and they remain as formed by gun nozzle. Wrinkling: A rough, crinkled adhesive surface, which occurs when uncured adhesive forms a "skin.". In general following methods are used Gravure Gravure with Myer Bar Kiss Coating Floating Knife Comma Coating Or Reverse Roll coating. As a matter of fact a temp gradient setting is essential. Avoid the use of high density mineral excipient like dicalcium phosphate, calcium carbonate. It occurs when the internal stress (that develops within the film as it dries) exceeds the tensile strength of the film. Picking is primarily an over wetting issue and it occurs when the uid delivery rate exceeds the drying capacity of the process. In addition, appropriate design of tablet punches (especially with respect to the logo) may help to alleviate the problem, whereas adjustment of process conditions may also prove beneficial. Methods such as modifying the surface of the material to give it some degree of conductivity or the use of air ionization must be employed. Unequal distribution of coating suspension. Increasing compaction forces to reduce tablet friability. Application of higher rate of the coating solution. Alteration of the frequency and duration of appearance of tablets in the spray zone or the size/shape of the spray zone. Causes and Remedies of Scuffing of Film-coated Tablets. Your email address will not be published. Sorry, preview is currently unavailable. Inappropriate drying (inlet air) temperature. It is a coating defect where the film becomes chipped or worn away and dented usually at the edges of the tablet as the coating is being applied. Formulation of paracetamol suspension seems very easy to formulate. It is a coating defect where peels off the tablet during or after the coating process. This article will focus on identifying the most common defects in film coating process, along with typical causes and possible solutions. Aulton, M. E. (2004). "Fish-eyes" are areas in a freshly applied surface coat that tends to thin or open up on their own accord. Another approach being most often used to prevent crawling is lowering the surface tension of the liquid adhesive by adding wetting agent. Adjusting the type and concentration of plasticizer. In other words, it is the fading or dulling of a coated tablet color after a prolonged period of storage at a high temperature. Entrapment of gases in or underneath the film due to overheating either during spraying or at the end of the coating run. Decrease spray rate and/or increase processing temperatures. Inadequate coating or migration of soluble dyes-plasticizers and other additives during drying. Excessive foaming of the coating solution. A wide variety of coating defects occur and the same are discussed. Coating droplets are over-dried before contacting tablet surface, increasing tablet surface roughness and filling the logo. This allows the entire thickness of the wet adhesive film warm up uniformly. Adhesive coated during extremely hot weather or cool damp weather, which causes the adhesive film to dry faster on top than on the bottom. Lachman, L., & Liebermann, H. A. Effect of temperature on the adhesion, elasticity, and strength of the film. Cleanliness of the surface for adhesion 2. Low the viscosity of the coating solution. This is a typical defect when adhesive is sprayed , or coated by pickup rollers. These problems can be avoided by increasing the nozzle air pressure (or the atomization air volume), increasing pan speed and optimizing the uniformity of solution delivery through the spray gun respectively. Factors that can cause orange peel effect include: 1. Less protection by film from moisture during storage. In spite of its relative longevity, it remains a complex process in which all technical issues and their impact are not always fully appreciated with the result that potential problems continue to arise with all too frequent regularity. If using a primer, allow it to dry completely before applying top coat. The plasticizers that make films soft, also make them very impressionable. Adhesive Coating is a simple process There are various methods available for the same. Edinburgh: Churchill Livingstone. There are two ways to improve wetting characteristics: Raising the surface energy of the substrate through cleaning -removal of oils and/or other contaminants -or through surface treatment (corona pre-treatment, flaming, acid or caustic wash). Low molecular plasticized coating system. Exposure of uncured adhesive to high humidity levels. We are all aware of these Coating Methods and we know how to use them to the best to produce an Adhesive Coated Product. 2020-22 PharmaEducation, All Rights Reserved. Use high molecular weight of plasticizer. Foam and Bubble formation because of air spraying of a polymer solution. Get the Information Regarding Medicines and Diseases, Operation and Cleaning of Fluidized Bed Dryer, Ten Tips to Prevent an Accidental Overdose. Causes and Remedies of Chipping/ Edge Erosion. Enter the email address you signed up with and we'll email you a reset link. This process-related problem may be resolved by reducing liquid application rate or increasing drying air temperature and air volume. It a defect where tablets break apart during pan loading or while tumbling in the pan or during the coating process, or during unloading of the coating pan. Uneven coatings and "wicking" of adhesive are often the result of static charges. Conditions similar to cratering that produces an overly wet tablet bed where adjacent tablets can stick together and then break apart. Scrape or sand substrate to remove wrinkled coating. Surface modifying additives, especially surfactants, will reduce the surface tension, and help entrapped bubbles to move to the surface. Chipping/ Edge Erosion: a common tablet coating defect, 11. As progressing technology allows faster production speeds, static related problems are also increasing, hampering production and affecting product quality. Decrease the spray rate and use optimum drying conditions. Tablet coating is the application of a coating composition in a moving bed of tablets with the concurrent use of heated air to facilitate the evaporating of the solvent [1] and with the intention of conferring benefits and properties to the dosage form over the uncoated variety. It is a coating defect that involves variation in color of the film. Use proper composition with improved mechanical strength. Reduce the amount of hygroscopic excipient such as disintegrant. The most ideal temps for drying zone wise beginning from First to last zone should be set. However, the resulting hole possibly can not level out when the viscosity of the film is too high. It a defect where tablets break apart during pan loading or while tumbling in the pan or during the coating process, or during unloading of the coating pan. At first, the use of surfactants should be minimized. Causes and Remedies of Sticking and Picking. In other words, it is a haziness or appearance of white specks in the film coated tablet. It is a coating defect in which the film either cracks across the crown of the tablet (cracking) or splits around the edges of the tablet (Splitting). Improper dry. This defect is characterized by pore-like holes of about the size of a pinpoint. Pan fill with sufficient amount of core tablets. Cracking is the term used to describe a condition in which the continuity of the film is disrupted. Secondly, introduction of air in the adhesive during production, handling and application should be prevented as much as possible. PEOPLE ALSO READ:SOP for Operation and Cleaning of Vibrosifter. Peeling from undercoat or substrate Delamination in adhesive coating is where the coating lifts from the surface , leaving the area below exposed. Mottling is a dull, hazy or blotchy appearance on the surface of some vinyl films or over laminates. Reducetheamountofhygroscopicexcipient such asdisintegrant. Although some degree of roughness is always evident with film-coated tablets, coating process adjustments that might allow this characteristic to be kept to a minimum such that it is not readily visible to the naked eye include: Although the adjustments listed above may fall outside compliance with the registered process, they likely should be considered to be part of the original process design process. Examples of suspension (Chemistry, Food & Pharmaceuticals), Difference between Drug Design and Drug Development, Tablet Compression Machine: Types, Functional Parts, List of tablet coating defects and remedies, 7. Other possible cause of picking may include inadequate atomization, poor product movement or poor distribution of spray. Details discussion on the tablet coating problems and remedies: It is local detachment of film from the substrate forming blister. Because the stress increases with increasing coating thickness, logo bridging of pharmaceutical tablets becomes progressively worse as more coating is gradually applied. Solutions to bridging involve improving film adhesion and/or reducing stress within the film, and usually require some reformation of either the tablet core or the film coating solution. Add alcohol or use spray nozzle capable of finer atomization. If first coats of enamel are allowed to become too dry, solvent in the paint droplets of following coats will be absorbed into the first coat before proper flow is achieved. This coating defect is characterized by circular voids or separation in the coating. Pin holing is one of the most common surface issues especially in sprayed application. It is a coating defect where tablets stick together especially when two tablets stick together. This could be that the flash off zone before heat curing is inadequate or the oven profile is incorrect. Permeability to moisture 4. 3. Use lower molecular weight polymeric blends or polymers. It can also be introduced during the application process. London: Pharmaceutical Press. Adjusting the type and concentration of plasticizer. Loading and unloading tablets from the coating pan. Adhesive droplets dry before they can flow out and level smoothly together. Common Tablet Defects:Causes and Remedies, Advantages and Disadvantages of Pharmaceutical Emulsions, Problems Encountered During Trituration and Possible Solutions, Mechanisms Involved in the Mixing of Pharmaceutical Powders, Mixing of Pharmaceutical Powders in Small-Scale Operations, 9 Reasons Why Customers Choose Your Competitors Products Over Yours, Common Medical Abbreviations and Their Meaning, Understanding the Various Types of Hepatitis Virus, Six Reasons for the Importance of Primary Care for the Elderly, National Agency for Food & Drugs Admin & Control, Journal of Pharmaceutical Development and Industrial Pharmacy, Coated product performance and functionality, Processing efficiencies and manufacturing costs, Optimizing spray rate and/or drying air temperatures and volumes to achieve better atomization of the coating liquid and improve drying, Thinning of coating solution with additional solvent to reduce viscosity and thus improve atomization. A rough substrate surface containing iron fines and slivers is prone to the development of outbursts in the coating. Tablet Coating techniques: Concepts and recent trends. The incorrect cure profile when using an accelerated curing mechanism. Spraying coating formulations once the required inlet temperature has been reached instead of prewarming the tablets (a process that usually involves some tablet motion without any coating being applied). coating of top coat of adhesive to insufficiently cured primer. Excessive foaming of the coating solution. Informative and well-decorated articles regarding tablet coating defects. Small to large broken or unbroken bubbles Broken edge craters and small blister-like spots can be caused by oil, grease or contamination on the substrate. A charged film of either polarity will attract to uncharged surfaces of insulators or conductors. It is a coating defect where tablet surfaces erode as tablets tumble during the coating process. Coatingisrubbingoffduetoexcessive attritionaleffects. Static electricity is the cause of many problems encountered in the transporting and converting of film webs in today's modem machinery. How to resolve a defect turns out to be logical as soon as the governing phenomena of that defect are known and understood. Use optimized suspension preparation to avoid aeration. They may be electrically operated, passive, or may use radioactive materials as the ion generation source. The prevention of foam in films can be arranged in a number of ways. In doing so, legibility of the logo can be significantly reduced. During the coating, process tablets pass from many stages during those stages tablet face many problems so for avoiding these problems we use few techniques to solve this type of coating problem, in this article we do a detailed discussion on the tablet coating problems and remedies for their solution. Pan loading with an insufficient amount of core tablet. Applying (especially rolling) paint too rapidly. It is a coating defect where the engraved logo or break line filled with either particle of dried polymer or solidified foam. Meltingordissolutionoflubricantontabletsurfaceormeltingofcore ingredientduetohighcoretemperature. Orange peel often occurs when a binder fails to flow uniformly across an object's surface. Depending on whether the defect occurs early or late in the coating process, the affected area may be partially obscured as coating proceeds. Under static conditions, the contact angle Q of a liquid drop placed on a given substrate determines whether wetting is good or poor. Avoid the use of sorbitol with HPMC (Hydroxy Propyl Methyl Cellulose), HPC (Hydroxy Propyl Cellulose), Cellulose ethers, and Methyl Cellulose. Recoat , (avoiding temperature/humidity extremes) . Trapped solvents can also show up as blisters. Decrease in viscosity of coating suspension. Commonly flat surfaces along the edgesofcapsule-shaped tablets. It is a coating defect where pits appear on the surface of a tablet core without any visible disruption of the film coating.