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Web Coating

Blogmaster: Dr. Edward D. Cohen

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Dryers & Drying

26

Increased drying capacity improves quality and productivity

Posted by Edward Cohen on April 26, 2012
Increased drying capacity improves quality and productivity
Ideally, neither the coating process nor the drying process should limit the product quality or the productivity of a coating line. However, often the dryer is rate limiting and this reduces the capability of the coating process. The reason for this is that in any coating process there is an optimu...

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Posted in: Dryers & Drying
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16

The Importance Of Procedures and Training

Posted by Edward Cohen on February 16, 2012
The typical coating line is a complex process that consists of 17 major components, table 1, each of which has many subsystems, that are necessary for the successful operation and can a cause defects if not functioning as specified.  The total number depends on the exact design of the coating l...

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Posted in: Coating Applicator Roll Coating, Coating Applicator, Slot Die, Slide, Curtain, Coating Solution Handling, Coating Solution Measurements & Characterization, Coating Solution Preparation, Defects Characterization Causes & Cures, Dryers & Drying
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29

Web Coating Technology Continuing Education

Posted by Edward Cohen on January 29, 2012
The web coating process is a complicated, technically sophisticated process that has many basic modules, unwind roll, transport roll, prepare coating solution, coating application, dry coated film, online process control, optimize coating solution, and coating line process control. All of these are ...

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Posted in: Coated Product Measurement & Characterization, Coating All Other, Coating Applicator Roll Coating, Coating Applicator, Slot Die, Slide, Curtain, Coating Solution Handling, Coating Solution Measurements & Characterization, Coating Solution Preparation, Defects Characterization Causes & Cures, Dryers & Drying, Laboratory & Pilot Coaters, Laminating, Metallizing, Process Instrumentation & Measurements, Substrate Surface Treatment, Substrates, Web/Tech, Weblogs
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10

Drying Defects: Blisters

Posted by Edward Cohen on December 10, 2011
Drying Defects: Blisters
Blisters are drying defects that are often encountered in the web-coating process. They can either be a small, dome-like protrusions or a small recessed in the dried coating film. They tend to occur all over the surface of the coating. While they appear as two different types, protrusions and depres...

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20

Drying Defects: Drying Rate Variability

Posted by Edward Cohen on September 20, 2011
The goal of the coating process is to maintain a constant drying rate, i.e. the amount of solvent removed per hour by the dryer during all coatings. A uniform reproducible drying rate is required to insure the maximum line speed, maximum productivity, low cost and a reproducible product.  Howev...

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Posted in: Defects Characterization Causes & Cures, Dryers & Drying
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14

AIMCAL Web Coating & Drying Course

Posted by Edward Cohen on September 14, 2011
  This course will present the technologies that are needed to successfully operate a web coating and drying line.  The fundamentals of each operation will be presented along with specific example of the required technologies. The course will be presented on October 37 4  in Phi...

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Posted in: Coating Applicator Roll Coating, Coating Applicator, Slot Die, Slide, Curtain, Coating Solution Handling, Coating Solution Measurements & Characterization, Coating Solution Preparation, Defects Characterization Causes & Cures, Dryers & Drying
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31

Defects Caused by Dryer Contamination

Posted by Edward Cohen on August 31, 2011
Defects Caused by Dryer Contamination
There are several potential contamination sources in the dryer that can result in a variety of spot scratch drying defects being introduced into the wet coating. Condensation Spots Condensation spots are a spot defect with a clear center with high edges, figure 1.  They are caused by solvent...

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Posted in: Defects Characterization Causes & Cures, Dryers & Drying
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22

Drying Flow Induced Defects Post Coating

Posted by Edward Cohen on August 22, 2011
Drying air impinging on the wet coating entering the dryer, can disturb the coating and result in the liquid coating flowing and causing a variety of defects. The specific defects that can be formed depend on the viscosity of the coating, the impinging air velocity, the distance from the nozzle to t...

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Posted in: Defects Characterization Causes & Cures, Dryers & Drying
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15

Preventing dryer defects

Posted by Edward Cohen on July 15, 2011
There are several categories of defects that can be generated in the dryer which need to be eliminated to give good quality and low costs. The first category, are defects such as solvent removal rate variation, dry coating remelt and contamination in the coating that are caused only by the dryer con...

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13

Bubble spot sources

Posted by Edward Cohen on June 13, 2011
After the observed bubble spots in a coating have been identified as due to bubble in the coating, the next step is to determine the source of the bubbles and eliminate them. There are several potential sources for bubbles in a coating machine. Air can be introduced into the coating solution in the ...

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Posted in: Defects Characterization Causes & Cures, Dryers & Drying
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Blogmaster

Edward Cohen photo

Dr. Edward D. Cohen

Dr. Cohen is a technical consultant in all aspects of the web coating process. His expertise includes thin film coating and drying process development, coating application and drying of thin films, polyester base development, film defect mechanisms, formulating coatings, image analysis techniques for characterizing coating films and litigation support.

He has over 45 years experience in coating research and manufacturing technology with the DuPont Company and as a technical consultant to the converting and composites industries

He has extensive publications in the field and has co-authored several books: Modern Coating and Drying Technology, Coating and Drying and Defects: Troubleshooting Operating Problems, and chapters in Kirk-Othmer Encyclopedia of Chemical Technology and Water and Solvent Based Coating Technology. His honors are the John Tallmadge Award for Contributions to Coating technology, the AIMCAL President's award in recognition of Meritorious Service to AIMCAL and the Converting Industry, and the ISCST Founders Award. He was the founding president of the ISCST. He has a Bachelor of Science in Chemical Engineering from Tufts University and a Ph.D. in Physical Chemistry from the University of Delaware.