Coating manufacturing processes: Yesterday, today and tomorrow Jan 5, 2005

Transcription

1 Provided by t Coating manufacturing processes: Yesterday, today and tomorrow Jan 5, 2005 Girish MALHOTRA, Member of SpecialChem Technical Expert Team. Introduction How did the processes develop? Current Methods New business environment Equipment related Process control related Raw materials related New opportunities Equipment Technology Process Controls Raw materials Future Introduction Coatings are applied to many substrates from metal (hard) to skin (soft). Application surfaces define the performance and quality of the products. Substrate performance needs demand that different raw materials be used to deliver the needed product. This article is a general review of the development of coating manufacturing processes, but also discusses and outlines how to simplify and improve manufacturing processes. A review reveals that processing methods are similar for most of the coatings even for different processed components. It is interesting to follow the path of how the coating manufacturing processes developed. Powder Coatings have been excluded. In general there are two types of liquid coatings. 1. Water based 2. Solvent based Coatings components that are needed to meet specific performance can be classified in the following general categories. Solvent (water or organic) Pigments/Fillers Resins Additives such as Thickeners/ Surfactants/Dispersants/Preservatives/Flavors Colorants

2 How did the processes develop? If one steps back in time to the B.C. era, it is possible to speculate on the development of coatings manufacturing processes. Though the sequence of events may be up for discussion, one can visualize such a development process. I would guess that the initial process involved mixing colored pigments in water or oils from plants. Initially pigment particles were probably large, but would settle. Mixing was necessary before application to suspend the pigments in the solvent. Since repeated mixing was needed, applicators realized that the finer particles stayed suspended to a higher degree, and thus less re-mixing was required to produce a better product. Since uniformity of particles was necessary for improved coatings it led to the pigment grinding steps. With time, different grinding equipment and methods developed. Development and use of particle size measurement occurred, ensuring product consistency. Coatings first used naturally occurring pigments and materials, subsequently shifting to synthesized materials as they became commercially available. Similarly, other organic solvents were used as they became available. Additives were developed and used to prevent settling of solids, give homogeneity and wet the surfaces for better suspension in liquids. With time many other additives were developed and their use led to better coatings. Continuous development of new and improved components has led to better products. Since customers needed uniform and variety of consistent colors, different test methods were developed for color measurement. Continuous evolution and adoption of test methods used in other businesses improved the coating manufacture and product quality. Current Methods The current manufacturing processes replicate how coatings are developed and tested in the laboratory. In the simplest form, the manufacture of coatings can be called the blending of various chemicals to produce a product that can be easily applied on the desired substrate. Components are weighed and added to a process container of suitable size and dispersed using equipment appropriate for the coating to achieve desired characteristics followed by testing. In the laboratory, testing is done off-line - an acceptable method as the development chemist is working on one recipe at a time. The chemist uses the test results to make changes to the recipe to achieve the performance objectives. Since the laboratory batch size is small, inline testing would be considered cumbersome due to subsequent manual cleaning. The laboratory processing and testing is simple. These methods are used on a larger scale to produce commercial quantities, ensuring that lab and plant test results are similar. "Off line" testing is easy for an experienced person and has allowed businesses to meet customer needs. Upon reviewing different coating applications we realize that their fundamental test methods are similar but have been modified to account for the nuances of coating application. They also have different names; in the paint companies one calls the formulation area a "lab" but in the paper companies it is a "coating kitchen". Coating companies have to do draw downs for hiding and color measurements. Ink companies also do draw downs but "bleach" their products to facilitate testing. Colorants are also mixed with a standard white to facilitate testing. The basic premise is same but the methods have been altered for applications. Recognizing that the manufacturing methodologies were simple, easy and profitable, many individuals entered the business. Entrepreneurs offered their specialties and the coating businesses grew. We all know that in the 20th century, many local paint coating companies served their respective markets. Businesses adapted to the laboratory product development and manufacturing methods. Since

3 the testing has been done "off line" and it takes time to add components and re-test, it became necessary for a manufacturing facility to have sufficient process tank capacity along with necessary raw materials so that customer needs can be met when they need the product. Companies are continuously making efforts to improve their asset utilization by adapting to "large batch", "medium batch" and "small batch" methods to improve the total business process. These work for some companies but are temporary solutions to meet customer needs. Companies are also constantly evaluating and optimizing supply chain methods and processes to maximize profits. Just in time, Six Sigma and ISO methods have improved the business processes. New business environment With recent consolidations, many smaller paint companies are being assimilated as part of larger entities. Each company develops and implements methods that allow it to better serve its customer and maximize its profits. Economies of scale ask: is the current process technology the right technology and what can be done to improve it? Manufacturing methods need to be reevaluated through "Process Innovation". One has to look at the pinch points in the manufacturing process. Once these pinch points are identified, solutions follow. Pinch points may vary by the size of the operations and coating products. Solutions may be similar but of a different scale. An overall assessment and solution of combined pinch points is necessary. In a coating operation one can consider the following as classic pinch points: Equipment related. Process control related. Raw materials related. Equipment related 1. Do we have the correct equipment? 2. Is the equipment being used correctly? 3. Should one consider different or newer technologies to produce coatings? 4. Are we using the best unit operations to simplify processing? Individual operations have to answer these questions. Equipment evaluation is a continuous process improvement process and cannot be ignored. A process review can and will answer these questions. Vendors and others can assist in the process but a critical review of equipment performance and benefit is necessary. These are investment and processing related issues. They all need to be addressed. Process control related The following can be considered as pinch points. 1. Have we added the right amount of each component? 2. Is dispersion done? 3. Is the viscosity and density right? 4. Does the coating cover the substrate per customer's needs? 5. Is the color correct?

4 All of the above are addressed by "off-line" testing and making additions and re-testing until the product specifications are met. "Off-line" testing and adjustments take time. Each operation has to implement technologies that control the addition of coating components and allow specification matching in minimum amount of time (preferably the first time) after all components are mixed. Raw materials related Each raw material has its own physical and handling characteristics. Can the raw material specifications be narrowed so that when all of the components are together a final product of narrower specification range can be produced? Organic solvents have individual or unique boiling points. As energy is put in the coating manufacture it converts into heat and can lead to evaporation of solvents. One has to adopt and implement necessary process unit operations for a safe and healthy work environment. As we progress in time, new information is being learned about the health effects of chemicals used. We are finding that what was safe yesterday may not be safe tomorrow, leading to new use control regulations. All of the safety, health and environmental related regulations must be met. This is beneficial for the consumer as well as the producers. New opportunities A manufacturing operation would benefit if it can produce quality products meeting customer needs in the minimum amount of time (preferably the first time) using the least cost raw materials. These opportunities come by combining the following: 1. Equipment technology. 2. Process controls. 3. Raw materials. Raw material suppliers are being squeezed by the coating producers who in turn are being squeezed by their customers. This will go on forever. IT implementation can improve many segments of the business, but "out of the box" thinking is needed to improve manufacturing methods. Effort is being made to reduce process time. However, the "off line" test methods are not able to make a significant reduction in process time. Since the equipment in place has traditionally worked and delivered little effort is invested in consideration of newer technologies. Since operations are being consolidated, it is an opportune time for both small and large coating producers to consider the "combined" implementation of the above three factors to reduce processing time. Equipment Technology High speed dispersers and mills have been the work horse of coatings businesses, but new equipment is being developed to assist in reducing processing time. In-line rotor-stator machines and in-line eductors are relatively lower cost and should be considered to reduce process time. Are heat exchangers needed to control the temperature of the dispersion process? We have to make sure that we do not evaporate solvents (money) during processing. Automation may be necessary to reduce costs. Process Controls The basic reason for the use of process controls is to produce a quality product either the first time or in the least time. Coating manufacturers have not had the luxury of using process controls similar to those being used in the manufacture of many chemicals. As stated above, test

5 methods used in the lab have delivered on a commercial scale, driving a perceived lack of need to automate. If process controls can allow a producer to manufacture small to large quantities with minimum changeover time, it is possible that an "in-line" technology will change the way coatings are produced. Sometimes use of process controls and automation are linked to continuous processing. If one considers a continuous process running for a finite time it becomes a batch process. Such perspective will allow use of "in-line" controls to produce coatings. "Inline" process control technologies are available and significant in-house development is also taking place. Raw materials If a company manufactures different price point products then by using similar raw materials it may be possible for the company to produce such products by varying ratio of different formulation components. If this is possible, it may give the coating producer an opportunity for raw material consolidation and volume purchasing. Processing finesse can allow reduced processing time. Future Recent consolidation of companies (larger volume of similar products and need to reduce costs) demands that we consider "in-line" process controls and equipment technologies. New equipment and process control technologies are being introduced and they are economical. Return on investment is high. One has to look at these technologies and methods as they are non-traditional but give excellent results. Use of these technologies will result in further consolidation of significant raw materials and operations. Some of the newer, "in-line" process control technologies may also reduce product development time as well as improve product quality, customer service and higher profitability. The coating industry, like any other industry is effectively using IT and other technologies to improve profitability. The time has come to review and optimize coating manufacturing processes. Imagination and creativity will produce very beneficial results. This document was provided by SpecialChem's editor. If you want to share your technical expertise in a specific area related to paints, coatings and inks or publish your press releases on please send it to e ditor@specialchem.com. SpecialChem reserves the right to refuse any article or news item.