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Are wood effect powder coatings viable?
FOCUS ON P O W D E R C O AT I N G S A MONTHLY REPORT FROM SID HARRIS
ARE WOOD EFFECT POWDER COATINGS VIABLE?
MARCH 2006 In this issue
TECHNICAL
2-3
Wood effect powder coatings
INDUSTRY NEWS
3-5
New powder paint covers edges evenly Bejing Red Lion buys back equity Paints: Barloworld aiming to become leading producer in Australia Neopentyl glycol in short supply Rohm and Haas Powder Coatings reinforces Tikkurila’s service in North and East Europe
NEW PRODUCTS
5-6
Nanoceramic-based Conversion Coating
MARKETS
AN INTERNATIONAL NEWSLETTER MONITORING TECHNICAL AND COMMERCIAL DEVELOPMENTS IN POWDER COATINGS ISSN 1364–5439
6-8
China paint additives growing strong High prices for raw materials and strong competition promote flexibility Powder coating prospects in the Middle East
One of the most remarkable features of powder coatings is their ability to produce unique structural and effect finishes that cannot be matched by liquid coatings. The first abstracted paper in this issue deals with wood effect powder coatings, which are available from Rohm & Haas Powder Coatings Division. An article by Eugenio Gomez describes three different qualities all of which require a somewhat tedious procedure involving either inks, silk screening or patterning with a roller. This is in contrast to one coat applications, which are commercially available, and provide an acceptable wood grain simulated effect. I have seen examples of wood effect finish applied as one coat applications to shop shelving which have given an attractive wood grain effect. The lengthy and costly processes outlined in the article may well give a more precise wood finish effect, but I doubt that it will receive widespread acceptance. The key factor in all effect powder coating finishes is the uniformity of pattern obtained in a one coat application. I am enthusiastic about the new nanoceramic structured pretreatment developed by Henkel. The complete absence of troublesome compounds in the effluent coupled with the
extremely low film thickness is a remarkable advance in pretreatment technology. Adhesion of powder coatings to metallic substrates is excellent and I have always found that pretreatments applied prior to powder coating perform best when the film thickness of the pretreatment is kept low. This is especially true when applying zinc phosphate pretreatment to hot dipped galvanized surfaces. Nano films bond more effectively to clean metal surfaces than micron layers of conventional pretreatments and their combination with powder coatings should give a new meaning to reduced under film corrosion creep. An interesting new product from Dai Nippon Toryo is its new V-PET EC range of powder coatings that are claimed to give improved cut edge covering to metal substrates. It is claimed that the improvements are due to optimising the formulation and adjusting the cure speed during stoving. The same problem is found in the coating of MDF board with UV curable powders. Perhaps the answer lies in both formulating and preheating? In separate reports, Tikkurila is said to be handling the distribution of Rohm and Haas powder coatings in North and East Europe and is also planning
POWDER COATINGS POWDER COATINGS POWDER COATINGS POWDER COATINGS
F O C U S to act as distributor of Oxyplast for its range of powder coatings. In-house distribution of company products is a difficult operation, particularly in those areas that are remote from the manufacturing base and it is good commercial sense to utilise the services of companies who are familiar with those areas. I expect to see a greater use of such services in the highly competitive future growth of powder coatings. The growth of additives business in China is reported and a number of the major European suppliers are locating subsidiaries in mainland China. A cautionary note can be found on the internet, where a number of Chinese companies are now offering a wide range of low cost additives based on their equivalents to western products. The whole range of powder coating additives can now be supplied by Chinese duplicated technology. The Chinese have already captured a major part of the powder coatings production machinery market with competent low cost equivalents to the established European and US producers. The future of the Western coatings industries is dependent upon the continual improvement of products and processes and there are still sufficient technical barriers to be overcome, which will sustain the enthusiasm of formulators. Their efforts could provide the profitability to enable the industry to survive, and maintain the lead in the quality and performance of coatings. Sid Harris
TECHNICAL Wood effect powder coatings Wood effect powder coatings have seen growth over the years, particularly in Europe, as a real alternative to typical architectural materials such as wood, marble
2
ON
POWDER
and granite. The powder coated finish provides the high weathering performance of aluminium coupled with the decorative effect of real wood. Decorative wood effects available from Rohm & Haas, Powder Coatings division, can be achieved in three ways: Sublichromy, Naturall, and Effecta. The Sublichromy Process produces a wood effect pattern onto aluminium profiles using a transferable media coated with special inks in a three-step process. When placed under a combination of heat and low pressure, the pattern is transferred onto a surface that has previously been coated with a specially formulated powder coating. The procedure for Sublichromy is: substrate pretreatment, basecoat powder application, and sublimation process. The pretreatment process is the key to ensuring that the initial powder coating layer achieves good adhesion to the surface and ensures good corrosion resistance. Pretreatments can include: hexavalent chrome systems and the more environmentally friendly, trivalent and chrome-free methods. A Qualicoat approved polyurethane, polyester/TGIC or polyester/TGIC free powder coating is applied to the substrate at a coating thickness of up to 60µm and then cured at 180°C to 200°C for approximately 20 minutes. This provides the base for the transfer of the ink design onto the surface in the next stage. In the sublimation process the coated aluminium profile is wrapped into a bag that has the transfer ink coated on one side and this is sealed at one end and along the topside. A vacuum is applied to the open end of the bag and the transfer ink is pulled into contact with the powder base coat. Sublimation, or ink transfer occurs in the oven at 150°C to 160°C, after which the bag is
C O AT I N G S removed and the profile is allowed to cool. There are several ways of assessing the quality of the process. One technique is to verify the degree of ink penetration into the powder coated base layer. This test can be performed using a metallographic microscope and inspecting the cross-section of a coated profile. It monitors the amount of ink that has penetrated into and through the base powder coating and good penetration improves the final performance of the coated product. Coating glass plates and inspecting the reverse side of the glass plate to determine the penetration of the transfer ink through the base coat is another method of visually inspecting ink penetration through the base coat. In order to achieve a high quality decorative finish, the base coat must have low opacity and conversion marks from the pretreatment should not be visible through the base coating. Film thickness should be even since a variable thickness will alter the hiding effect of the base coat and alter the appearance due to the uneven distribution of the ink through the film. Curing parameters of the basecoat should be strictly adhered to, and the transfer process must be performed in accordance with the manufacturers instructions. Basecoats that are the same colour, but formulated with powders of different chemical composition, will have similar weathering performance but may show different solvent resistant properties. The Naturall process is also known as the powder-on-powder coating system as it is a fivestage process using two applications of powder coatings. This is a patented process to obtain a wood effect finish on aluminium profiles and can be achieved by using TGIC-free polyester powder coatings. The first stage is surface pretreatment
MARCH 2006
ARE WOOD EFFECT POWDER COATINGS VIABLE?
MARCH 2006 In this issue
TECHNICAL
2-3
Wood effect powder coatings
INDUSTRY NEWS
3-5
New powder paint covers edges evenly Bejing Red Lion buys back equity Paints: Barloworld aiming to become leading producer in Australia Neopentyl glycol in short supply Rohm and Haas Powder Coatings reinforces Tikkurila’s service in North and East Europe
NEW PRODUCTS
5-6
Nanoceramic-based Conversion Coating
MARKETS
AN INTERNATIONAL NEWSLETTER MONITORING TECHNICAL AND COMMERCIAL DEVELOPMENTS IN POWDER COATINGS ISSN 1364–5439
6-8
China paint additives growing strong High prices for raw materials and strong competition promote flexibility Powder coating prospects in the Middle East
One of the most remarkable features of powder coatings is their ability to produce unique structural and effect finishes that cannot be matched by liquid coatings. The first abstracted paper in this issue deals with wood effect powder coatings, which are available from Rohm & Haas Powder Coatings Division. An article by Eugenio Gomez describes three different qualities all of which require a somewhat tedious procedure involving either inks, silk screening or patterning with a roller. This is in contrast to one coat applications, which are commercially available, and provide an acceptable wood grain simulated effect. I have seen examples of wood effect finish applied as one coat applications to shop shelving which have given an attractive wood grain effect. The lengthy and costly processes outlined in the article may well give a more precise wood finish effect, but I doubt that it will receive widespread acceptance. The key factor in all effect powder coating finishes is the uniformity of pattern obtained in a one coat application. I am enthusiastic about the new nanoceramic structured pretreatment developed by Henkel. The complete absence of troublesome compounds in the effluent coupled with the
extremely low film thickness is a remarkable advance in pretreatment technology. Adhesion of powder coatings to metallic substrates is excellent and I have always found that pretreatments applied prior to powder coating perform best when the film thickness of the pretreatment is kept low. This is especially true when applying zinc phosphate pretreatment to hot dipped galvanized surfaces. Nano films bond more effectively to clean metal surfaces than micron layers of conventional pretreatments and their combination with powder coatings should give a new meaning to reduced under film corrosion creep. An interesting new product from Dai Nippon Toryo is its new V-PET EC range of powder coatings that are claimed to give improved cut edge covering to metal substrates. It is claimed that the improvements are due to optimising the formulation and adjusting the cure speed during stoving. The same problem is found in the coating of MDF board with UV curable powders. Perhaps the answer lies in both formulating and preheating? In separate reports, Tikkurila is said to be handling the distribution of Rohm and Haas powder coatings in North and East Europe and is also planning
POWDER COATINGS POWDER COATINGS POWDER COATINGS POWDER COATINGS
F O C U S to act as distributor of Oxyplast for its range of powder coatings. In-house distribution of company products is a difficult operation, particularly in those areas that are remote from the manufacturing base and it is good commercial sense to utilise the services of companies who are familiar with those areas. I expect to see a greater use of such services in the highly competitive future growth of powder coatings. The growth of additives business in China is reported and a number of the major European suppliers are locating subsidiaries in mainland China. A cautionary note can be found on the internet, where a number of Chinese companies are now offering a wide range of low cost additives based on their equivalents to western products. The whole range of powder coating additives can now be supplied by Chinese duplicated technology. The Chinese have already captured a major part of the powder coatings production machinery market with competent low cost equivalents to the established European and US producers. The future of the Western coatings industries is dependent upon the continual improvement of products and processes and there are still sufficient technical barriers to be overcome, which will sustain the enthusiasm of formulators. Their efforts could provide the profitability to enable the industry to survive, and maintain the lead in the quality and performance of coatings. Sid Harris
TECHNICAL Wood effect powder coatings Wood effect powder coatings have seen growth over the years, particularly in Europe, as a real alternative to typical architectural materials such as wood, marble
2
ON
POWDER
and granite. The powder coated finish provides the high weathering performance of aluminium coupled with the decorative effect of real wood. Decorative wood effects available from Rohm & Haas, Powder Coatings division, can be achieved in three ways: Sublichromy, Naturall, and Effecta. The Sublichromy Process produces a wood effect pattern onto aluminium profiles using a transferable media coated with special inks in a three-step process. When placed under a combination of heat and low pressure, the pattern is transferred onto a surface that has previously been coated with a specially formulated powder coating. The procedure for Sublichromy is: substrate pretreatment, basecoat powder application, and sublimation process. The pretreatment process is the key to ensuring that the initial powder coating layer achieves good adhesion to the surface and ensures good corrosion resistance. Pretreatments can include: hexavalent chrome systems and the more environmentally friendly, trivalent and chrome-free methods. A Qualicoat approved polyurethane, polyester/TGIC or polyester/TGIC free powder coating is applied to the substrate at a coating thickness of up to 60µm and then cured at 180°C to 200°C for approximately 20 minutes. This provides the base for the transfer of the ink design onto the surface in the next stage. In the sublimation process the coated aluminium profile is wrapped into a bag that has the transfer ink coated on one side and this is sealed at one end and along the topside. A vacuum is applied to the open end of the bag and the transfer ink is pulled into contact with the powder base coat. Sublimation, or ink transfer occurs in the oven at 150°C to 160°C, after which the bag is
C O AT I N G S removed and the profile is allowed to cool. There are several ways of assessing the quality of the process. One technique is to verify the degree of ink penetration into the powder coated base layer. This test can be performed using a metallographic microscope and inspecting the cross-section of a coated profile. It monitors the amount of ink that has penetrated into and through the base powder coating and good penetration improves the final performance of the coated product. Coating glass plates and inspecting the reverse side of the glass plate to determine the penetration of the transfer ink through the base coat is another method of visually inspecting ink penetration through the base coat. In order to achieve a high quality decorative finish, the base coat must have low opacity and conversion marks from the pretreatment should not be visible through the base coating. Film thickness should be even since a variable thickness will alter the hiding effect of the base coat and alter the appearance due to the uneven distribution of the ink through the film. Curing parameters of the basecoat should be strictly adhered to, and the transfer process must be performed in accordance with the manufacturers instructions. Basecoats that are the same colour, but formulated with powders of different chemical composition, will have similar weathering performance but may show different solvent resistant properties. The Naturall process is also known as the powder-on-powder coating system as it is a fivestage process using two applications of powder coatings. This is a patented process to obtain a wood effect finish on aluminium profiles and can be achieved by using TGIC-free polyester powder coatings. The first stage is surface pretreatment
MARCH 2006