- May 01, 2010, By Edward D. Cohen, Edward D. Cohen Consulting Inc.
The converting industry and some of its processes are 100 years old or more. Despite that, the industry has remained dynamic and competitive by continuously incorporating new process and product technology to improve quality, reduce costs, and develop new products.
Examples of technology advances in the past decade include the following:
- Increased use of in-line instruments to control quality and reduce costs, replacing off-line evaluation methods
- Development of fundamental process engineering science concepts, which have been used to improve the design of equipment coating applicators and the behavior of materials during handling and processing
- The development of flame, electrical-discharge, and plasma technology to modify substrate properties, leading to improvements in adhesion, product performance, and coating quality by improving surface wettability
- The widespread use of the Internet in all aspects of the business
- The development and increased use of pre-metered coating methods
Evolutionary advances will be made in the above technologies during the next ten years, leading to improved quality and productivity at lower purchase prices. In addition, there is the potential for breakthrough technologies in the following areas:
- Low-energy drying systems
- Coating technologies for coating uniform thin layers and low-solvent-level coating solutions
- Low-cost, reliable alternative energy sources
- New processes to reduce environmental contaminants
- Cloud computing via the Internet
- New raw materials based on renewable resources and not on fossil fuels
- Automated coater lines
Computer gains continue
There will be significant advances in computer and information technology. Computer data processing rates and data storage capability will continue to increase, hardware purchase costs will be reduced, and more processes will be automated.
“Cloud computing” is an emerging technology that utilizes remote servers and the Internet to maintain all data and applications. All processing is done via a browser on a pay-as-you-go basis. As a result, users do not have to buy the servers or software for their applications and do not have to maintain their own systems. This also will increase the technical capability of companies that do not have resources for their own system.
Large amounts of process data can be stored and analyzed with sophisticated software. Engineers and R&D can have access to programs that calculate and optimize energy consumption, model dryers, and web transport systems.
This should improve quality at a low cost, but in order to successfully achieve this goal, all personnel will have to be proficient in utilizing computer and information technology.
On-line QC, measurement
The current use of on-line defect inspection systems is relatively low — 20% in the US — but its use will expand in the coming decade. These systems are needed to determine defects rapidly and accurately on the product as it is coated. It is a necessary technology to improve quality and reduce scrap losses.
The next generation's on-line inspectors will have improved optics and systems to detect smaller defects at higher line speeds. They may be able to check for additional properties such as color, surface roughness, etc. Artificial intelligence systems will be included to characterize defects and control process variables that influence defects. Cloud computing will give on-line inspection system units increased computational power, large data storage capability, and powerful analytical capability.
On-line coating weight measurement is another critical system that can improve product uniformity and lower costs by reducing the amount of out-of-limits product that must be scrapped. The use of this system will expand from the current 50% to a much higher level. Improvements in computer and electronics technology will lead to lower costs and improved precision. Nuclear gauging devices will be eliminated due to safety and environmental concerns, replaced by advances in infrared (IR) and laser technology.
There is also a need to characterize the coating solution before coating application with in-line sensors to determine if there are any contaminants, bubbles, dirt, or particles in the solution. The coating application would not start until the coating is free of defects. In-line viscosity measurement and control also is needed to ensure uniform coating weight and coating quality.
Continue to page 2
On the topic of measurement, there are a number of new markets and technologies in which coatings are getting very thin, sometimes in the nanometer range. Breakthrough measurement technology will be required to meet the gauging needs of the new low-coating-weight products under development.
While current measurement systems do not function in this range, potential methods could be ellipsometers, interferometers, and combination detectors.
The energy factor
Because of high energy costs and concern about reliable supplies, reduced energy consumption is mandatory in the converting industry. Many programs in this area will be required for success; a single technology application will not be sufficient.
Below are technologies that will need to be implemented to achieve energy reductions:
- Change the approach to product formulation and manufacturing to consider energy costs. The energy cost of cents per square foot will be a critical evaluation parameter as well as performance properties, yield, and quality. New software will be needed to calculate energy consumption rapidly along with a database for costs.
- Reduce drying load by using solvents with low heat of evaporation and concentrating the percent solids of coating solution.
- Eliminate solvents for lower drying load and utilize hot melt coating. New application methods to apply thinner layers will be needed.
- Reduce solution preparation energy by minimizing time and temperature of mixing.
- Reduce solution delivery system energy by holding solution at low temperature and heat immediately prior to coating application.
- Recycle all scrap material to create energy.
- Reduce energy consumption during coating stops. This will require rapid-acting control systems to reduce dryer temperature quickly when the coater stops and to attain equilibrium rapidly when the coater starts.
- Use of software programs to optimize drying profiles for lowest energy costs.
- Increase energy efficiency, which is a must for all coating line components.
What about low volumes?
There are several new products under development, including smart labels, RFID labels, and other forms of printable electronics, that will have a high value in use but will be produced at much lower volumes than the majority of the current products. In addition, volumes of current product lines will drop as the use of the Internet for communication increases.
In order to accommodate these small-volume products, new technology will be needed. Startup time on the coating line must be minimized, or startup losses will be too high for a competitive cost. Technologies to reduce startup times will include hardware for rapid change of coating methods; improved solution processing to reduce bubbles and contamination defects on startup; and new process control instruments and control logic to arrive at equilibrium conditions rapidly.
Another approach is to develop automated coating lines specifically designed for low-volume products. It may be cheaper to use a new machine than to modify existing hardware.
The focus on the coating applicator system in the near future will be to provide defect-free product for both short and long coating campaigns and to develop technology for coating high quality, thin coating layers and wet layers
What will accomplish this will be new hardware systems to minimize bubbles and reduce streaks and discrete defects. Narrow gaps between the coating applicator and backup roll are critical to good coating quality and are required to optimize coating quality for thinner products.
However, existing applicators and support hardware cannot maintain the low gaps needed. What will be required to meet this need are improved precision of applicator and coater roll tolerances and an upgraded coating station to hold the tighter tolerances.
Improved measurement techniques to monitor gap continuously will be developed and will be used for control loop. Fundamental engineering studies will be needed to define key process parameters for both thin liquids and 100% solids coating so improved hardware can be designed and built.
Methods of the future
In regard to coating methods, slot die usage will increase and the use of roll coatings will decrease. The advantages of the slot die over roll coating are improved coverage uniformity; excellent coating quality; reduced solvent emission due to minimal exposure of coating solution to atmosphere; multilayer capability; and the ability to produce discrete coatings.
Continue to page 3
In addition, the development of improved coating technology for 100% nonvolatile systems will continue. Not having to remove solvent will considerably reduce process energy requirements.
New product structures will require discrete coating and multiple layers, as well as continuous coating. To meet these needs, improved digital and inkjet coating methods will be needed along with multiple layer slot dies.
One area that probably will not see any significant technology advances is drying. That is because, due to past developments, there already are several systems in use: hot air impingement, single side, floater, festoon, IR, and microwave. Drying configurations are available to meet current needs; there also are models to simulate drying conditions so drying profiles can be optimized.
The drying process is the largest consumer of energy in the coating process. Because of this, hardware technology developments have been implemented to reduce coater energy requirements, and extensive use of this technology will continue.
In summary, converting technology developments over the past decade have paved the way for the future. In the next ten years, we will see the industry build on those developments, as well as find new solutions to problems we may not yet foresee.
Edward D. Cohen is a technical consultant for AIMCAL. He has 40+ years of experience in research and manufacturing technology. Contact him at 480-836-9452; firstname.lastname@example.org.
The following people provided input for this article, Tim Potts, Dark Field Technologies; Hector Marchand, NDC Infrared Engineering; Ed Gutoff, consultant; Ted Lightfoot, DuPont; Tom Giles, Aspect Automation.
|Coater performance capabilities||Line speed 29-1,000 fpm|
|Quality yields >90%||Improved process control|
|Energy costs >5% of total cost||Coating runs 0.5-2,000,000 sq ft|
|Coating thickness 0.48-4 mils||Product change time 10 ft|
|Yield & productivity are Independent of volume|
|Quick change coating station: Roll premetered and 100% solids|
|Coater enabling technologies in 2010|
|Reduced energy consumption||Dryer optimization|
|Minimum energy mix and dry||Heat recovery drying and scrap|
|Reduced solvent loads: Concentrated solutions, Low latent heat of vaporization, 100% solids coating|
|On-line quality measurement|
|Dryer: Defect inspection, Coating weight, Performance properties|
|Coating solutions: Bubbles and dirt, Particle size|
|Viscosity and surface tensions: Undercoating|
|Artificial intelligence systems:
Controls loops to reduce defects & optimize process
|Coating application||Discontinuous coatings|
|Rapid change||Custom design|
|Increased fabrication precision||Multi-temperature|
|Sensors for gap, roundness||Automated|
|Multiple methods: Solution, hot melt, inkjet|
|Optimize for low energy consumption:
Recycle air; Continuous optimization-Additional sensors
Rapid acting control systems; Model-based control loops
|Computer & information technology|
|Monitor & control entire process||Simplified analysis capability|
|Increased process rate & storage||Automated control, all systems|
|Internet computing, “cloud”||Advanced modeling|
|Substrate||Surface treatment: Adhesion wettability clean surface|
|On-line testing||Non-oil-based compositions|
|Safety & environmental|
|Solvent recovery||Automated coater|
|Scrap recovery||Environmentally on standards|