Use proper composition with improved mechanical strength. Insufficient film strength to provide resistance to edge damage. recessed area in a coating film with a raised area in the middle , is nothing but Fish eyes. Appearance is similar to that of an orange. Decrease the spray rate and use optimum drying conditions. Application of higher rate of the coating solution. Required fields are marked *. Coating and core have different thermal expansion properties. This is a typical defect when adhesive is sprayed , or coated by pickup rollers. Fish-eyes can be caused by oily spots or silicone particles and/or by air-borne droplets that are deposited on the coated surface. Use coating formulation which is less tacky. Another approach being most often used to prevent crawling is lowering the surface tension of the liquid adhesive by adding wetting agent. We are all aware of these Coating Methods and we know how to use them to the best to produce an Adhesive Coated Product. The most common ionizers used in film transport systems are static bars and ionized air blowers. 2. Reduce the amount of hygroscopic excipient such as disintegrant. In other words, it is the fading or dulling of a coated tablet color after a prolonged period of storage at a high temperature. Formulation of paracetamol suspension seems very easy to formulate. Tablet picking results when two adjacent tablets stick together and subsequently break apart (as a result of the constant motion within the coating equipment) leaving defects in the surface of the coating where pieces of coating have been removed. In some cases the substrate must be modified in such a way that the surface energy of the substrate is raised, i.e. Surface modifying additives, especially surfactants, will reduce the surface tension, and help entrapped bubbles to move to the surface. Use coating formulation which is less tacky. Use high molecular weight of plasticizer. Penetration of coating solution at the surface of the tablet, often at the crown where the surface is more porous causing localized disintegration of the core. Inadequate distribution of the coating suspension. Adhesive might be too viscous ( high viscosity ) Or The coating nip is too tight solvent evaporation too fast Origin and Potential Causes: Improper gun adjustment and techniques. It occurs when the internal stress (that develops within the film as it dries) exceeds the tensile strength of the film. Academia.edu no longer supports Internet Explorer. If using a primer, allow it to dry completely before applying top coat. Mottle typically occurs when metallic flake pigment is used in a coating. In other words, it is a haziness or appearance of white specks in the film coated tablet. Adhesive Oozing / Bleeding Blistering Setting appropriate drying temp is a key to get raid of Blisters. It can also be introduced during the application process. Pharmaceutics: The science of dosage form design. Because of the catastrophic nature of film cracking, the most effective approaches involve designing tablet core formulations that minimize or eliminate the risk of significant expansion behaviour occurring and creating film-coating formulations that are flexible enough to withstand any tablet core expansion that might occur. Adjusting the type and concentration of plasticizer. It is a coating defect that involves variation in color of the film. It is a coating defect where tablets stick together especially when two tablets stick together. Adhesive Film defects can ruin protective and aesthetical properties of coatings. The plasticizers that make films soft, also make them very impressionable. A lot of hustle can be prevented by using available knowledge that is simple and easy. Inappropriate drying (inlet air) temperature. Adhesive Oozing / Bleeding Blistering Possible Causes: Applying highly plasticizer loaded or softer adhesive . Higher internal stresses in the film than the tensile strength of the film. Lachman, L., & Liebermann, H. A. Exposure of uncured adhesive to high humidity levels. Increase the hardness of the film by increasing the molecular weight of the coating polymer. A charged film of either polarity will attract to uncharged surfaces of insulators or conductors. After finding the tablet coating defects and their remedies, you will successfully complete the tablet production cycle. Refurbishing or replacement of damaged/worn tooling. 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. At first, the use of surfactants should be minimized. Melting or dissolution of lubricant on tablet surface or melting of core ingredient due to high core temperature. Adjust the Adhesive viscosity or the nip replace the solvent Peeling. In other words, it is a defect in the films coating results in craters appearing on the tablet which in turn results in the exposure of the tablets surface. 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. Unmodified plastics, for example, are a group of materials having low surface energy. Coating droplets are over-dried before contacting tablet surface, increasing tablet surface roughness and filling the logo. Use of a low-grade, highly pigmented paint. In other words, pitting is the deformation of the core of the tablet without any visible signs of disruption of the film coating. Reduction of the surface tension is required to avoid fish-eyes. Enter the email address you signed up with and we'll email you a reset link. This occurs when the coating fills in the lettering or logo on the tablet and is typically caused by improper application of the solution, poor design of the tablet embossing, high coating viscosity, high percentage of solids in the solution, or improper atomization pressure. Adhesive Oozing / Bleeding a squeezing out of the adhesive from between layers of tape so that the sides of the roll are very tacky. For a proper coating on tablets, a formulator must know about the following tablet coating defects and their remedies. Foam and Bubble formation because of air spraying of a polymer solution. Learn how your comment data is processed. The strong electrostatic fields associated with these charges attract dust particles, fibers, bugs and hair resulting in surface contamination. However, poor operator techniques, or too much adhesive coating thickness , will also produce a rough finish. Uneven coatings and "wicking" of adhesive are often the result of static charges. 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. It is a coating defect where tablet surfaces erode as tablets tumble during the coating process. Larger the tablets and the denser the core formulation. They may be electrically operated, passive, or may use radioactive materials as the ion generation source. Insufficient film strength to provide resistance to edge damage. use granulation process instead of direct compaction). Separation or pulling apart of wet film to Expose underlying Finish or substrate. Tiny deep holes exposing substrate A small , sunken area that forms on a coating film after a bubble ruptures. Two aspects strongly dominate the formation, stabilization and release of foam. Entrapment of gases in or underneath the film due to overheating either during spraying or at the end of the coating run. Why Pharmacists are not Dispense Prescription Order? This problem is experienced most strongly in water based adhesives. Static electricity is the cause of many problems encountered in the transporting and converting of film webs in today's modem machinery. High molecular weight polymeric blends or polymers. Entrapment of gases or vapor in or under the film due to overheating either during spraying or at the end of the coating. As a matter of fact a temp gradient setting is essential. Adhesive Coating is a simple process There are various methods available for the same. A neutral material will have no electric field so induction charging, particle attraction and most ESD events will not occur. It is a coating defect where tablets stick together especially when two tablets stick together. The coating solution penetrates the surface of the tablet, often at the crown where the surface is more porous, causing localized disintegration of the core and disruption of the coating. The resultant coating is rough with numerous areas of localized thick coatings. Factors that influence delamination include: 1. Inadequate distribution of the coating suspension. The incorrect thickness of the coating where not enough coating is deposited so that there is insufficient conformal coating to self level. Causes and Remedies of Chipping/ Edge Erosion. This condition relates to inadequate spreading of coating solution before drying thereby causing a bumpy or orange peel effects on the coating. Add alcohol or use spray nozzle capable of finer atomization. Exposure of the Adhesive film to high temperature , humidity or moisture shortly after adhesive is coated , especially if there was inadequate exhaust. Decrease in viscosity of coating suspension. Apply a sufficient amount of coating suspension. 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. Foam and Bubble formation because of air spraying of a polymer solution. Your email address will not be published. A typical sample is shown in . During drying, the film may shrink and pull away from the sharp corners of an intagliation or bisect, resulting in a bridging of the surface. The drying Air temp and the velocity is critical. Chipping/ Edge Erosion: a common tablet coating defect, 11. Select a more flexible coating Contamination Dirt Pickup: NEUTRALIZING CHARGES ON THE FILM WEB If static charges on the film web can be controlled to a low level, most electrostatic related problems can be eliminated. PEOPLE ALSO READ:Working Principle of Vibratory Sifter. Peeling from undercoat or substrate Delamination in adhesive coating is where the coating lifts from the surface , leaving the area below exposed. Details discussion on the tablet coating problems and remedies: It is local detachment of film from the substrate forming blister. Adjusting the speed of the coating pan to reduce dwell time in the spray zone. The attritional effects in the typical film-coating process cannot be overemphasized. Where there is a primer and top coat of adhesive, peeling may involve some or all coats. Reducetheamountofhygroscopicexcipient such asdisintegrant. Use optimized suspension preparation to avoid aeration. Pan loading with insufficient amount of core tablets. All Rights Reserved. Aulton, M. E. (2004). London: Pharmaceutical Press. Selecting coating formulations with increased mechanical strength and/or increased film flexibility. Film webs tend to develop high charges; 30 kV to 40 kV is common. Increase the hardness of the film by increasing the molecular weight of the coating polymer. Low the viscosity of the coating solution. Less protection by film from moisture during storage. Use lower molecular weight polymeric blends or polymers. This causes obvious quality problems in printing, coating and laminating and cleanliness problems with food, medical and pharmaceutical packaging films. A pre-condition that has to be met in order to obtain complete wetting is that the substrate is clean. After being flattened in temper rolling, these areas reflect light differently, appearing as either dark or bright spots depending on the lighting condition. It is a coating defect where the engraved logo or break line filled with either particle of dried polymer or solidified foam. 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. In your post, your discuss 18 tablet coating defects and their remedies, it is most resourceful that i ever seen in online. Unlike conductors, charges on insulative materials cannot be neutralized by simply grounding. Peeling refers to the formation of uneven or rough irregularities on the surface of a coating film applied on a core tablet surface. Meltingordissolutionoflubricantontabletsurfaceormeltingofcore ingredientduetohighcoretemperature. It frequently extends entirely through the coating film. Reduce coating solids to facilitated equal coating distribution. It is a coating defect where pits appear on the surface of a tablet core without any visible disruption of the film coating. It is a coating defect where coating bridges formed across a logo or break line. It's a promise from my side to guide you , in terms of selection of a suitable additive or a process. 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. Depending on whether the defect occurs early or late in the coating process, the affected area may be partially obscured as coating proceeds. High degree of attrition related to the coating process. As a result of such detachment, the film is able to shorten and thus partially relieve the stress within the film. Higher internal stresses in the film than the tensile strength of the film. It is defect of film coating whereby volcanic-like craters appears exposing the tablet surface. 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). Finally, the rheology of the system should be such that the air that was introduced can escape in a short period of time during the first stage of film formation. It is defect whereby pits occur in the surface of a tablet core without any visible disruption of the film coating. Increase viscosity of coating solution to decrease spray application rate. Edinburgh: Churchill Livingstone. 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. Use coating formulation with increased hiding power. Use high molecular weight of plasticizer. Improper dry. Working & Principle of Tablet Compression Machine. Insufficient plasticization or too much pigmentation. Scuffing is appeared when tablets are more sliding rather than trembling. To reduce tablet edge chipping, coating process adjustments that might be considered include: Logo bridging of pharmaceutical tablets occurs when a component of the internal stress becomes sufficiently high so as to cause partial or complete detachment of the coating from the tablet surface within the region of the logo. Orange Peel is Uneven , rough irregularities in the surface of a coated film. It is a coating defect where peels off the tablet during or after the coating process. Scuffing is appeared when tablets are more sliding rather than trembling. Blisters will occur as a result of humidity testing on test panels, indicating moisture penetration through the film. Low molecular plasticized coating system. Secondly, introduction of air in the adhesive during production, handling and application should be prevented as much as possible. But a pharmacist make it less . Low molecular plasticized coating system. Use appropriate drying (inlet air) temperature. So much so that when vinyl films and overlaminates are rolled up on a roll, the films can pick the impression of backside of the release liner. However, the resulting hole possibly can not level out when the viscosity of the film is too high. Static charges are generated on the surface of the film as it unwinds from the roll and as it contacts and separates from surfaces such as idler rolls, nip rolls and printing or coating rolls. Causes and Remedies of Cracking/Splitting. Use of sorbitol in coating formulation which causes major fall in the thermal gelation temperature of the HPMC (Hydroxy Propyl Methyl Cellulose), HPC (Hydroxy Propyl Cellulose), Cellulose ethers, and Methyl Cellulose. This problem is caused by the high surface tension of the adhesive applied on a polymer surface, such as a plastic films. Pan fill with sufficient amount of core tablets. A wide variety of coating defects occur and the same are discussed. This allows the entire thickness of the wet adhesive film warm up uniformly. Use high quality adhesive which will allow good flow and appearance coat an appropriate primer before using such Adhesive over the surface. Decrease the spray rate and use optimum drying conditions. It is a coating defect where whitish specks or haziness in the film appear. 50-58. In general following methods are used Gravure Gravure with Myer Bar Kiss Coating Floating Knife Comma Coating Or Reverse Roll coating. A small , dome like bulge in the coated film or a small recess in a coating film. Adhesive coated film should never be exposed to very high temp in the first zone. Cure temperature too high Conformal coating heat cured too quickly without allowing enough time for room temperature (RT) drying Film thickness too great causing coefficient of thermal expansion (CTE) mismatch and cracks occurring in the coating Operating temperature too high or too low causing the conformal coating to flex too much & crack. Use of low quality adhesive or very old adhesive. Improper flash or recoat time between coats. Especially this problem has happened with the presence of inappropriate logo. Internal stress in the film exceeds tensile strength of the film. 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. Tablet Coating techniques: Concepts and recent trends. Migration and melting of ingredients in the core. Orange peel often occurs when a binder fails to flow uniformly across an object's surface. (2013). A coating defect characterized by a small. The use of air ionizers is the most common, cost effective method of controlling static charges on the film web. First, foam bubbles can be stabilized by additives having a surfactant (soap) structure. To high processing temperaturelow molecular weight of Plasticiser. Excessive foaming of the coating solution. 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. The ions are made available to the charged web where the electric field attracts the necessary ions of opposite polarity to its surface, thus balancing the charge on the web. 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.
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