Document w693J3V8xyVE2k8oMrOE5BwJ

ue u. UQIION CARBIDE INTERNAL CORRESPOND MINING AND METALS DIVISIO! To (Namo) Division Location Copy to Mr. W. C. Thurber UCC Metals Division 38th Floor 270 Park Avenue New York, NY 10017 Messrs. R. E. Byrne, Jr. J. L. Myers H. B. Rhodes R. L. Schult File Originating Ntopt. Aniwaring Iattar data Subject fa Ui'h "Calidria" p Versus Cab-O-Sil/fn Paints^ 1 In reference to Mr. T. Ginsberg's letter of September 15, 1975, to you regarding the above subject, there are some misconceptions on the part of Mr. Ginsberg that should be clarified. Mr. Ginsberg's comments concerning RG-244 plugging of in-line filters in airless spray systems were correct at the time of his observations roughly two years ago. However, since then there has been substantial changes in the industry and we have made considerable inroads in the area of airless spray applications. The airless system has become more and more the standard for spray equipment throughout industry in lieu of air support equipment. Inquiries as recent as October 1975 with several major suppliers of spray coating products, including Hooker Chemical (Durez Division), Standard Paint and Varnish, and International Paint have determined that upward of 90% of their customers now use airless spray equipment as opposed to air-supported systems. Of these, a considerable number are using RG-244 containing resins. Airless guns mentioned included Grayco, DeVilbiss, Venus, and Glas-Mate. Typical nozzle size was reported to be in the range of 0.011 to 0.025, depending upon the application. Applications included zinc-rich primers, phenolics and epoxy marine coatings, epoxy coal tar maintenance coatings, and polyester spray applications. During the early introduction of airless spray equipment very small nozzle tips were used and typical in-line filters were in the range of 100200 mesh. However, due to increasing demands for greater throughput and the obvious problems associated with fine mesh screens, the industry began to use larger nozzle tips and filters in the range of 50 to 100 mesh. Most gun manufacturers today supply or recommend 50-60 mesh in-line filters for their spray equipment. This has proved to be adequate protection in the vast majority of applications and RG-244 will pass 60 mesh without bridging. Screens finer than 60 mesh can be used depending upon conditions such as the amount of RG-244 in the resin, surface area of filter, and driving forces. Approximately 0.5-1.5% by weight of RG-244 is used in most applications and the degree to which bridging becomes relevant is within this order of magnitude. Fluted screens in the order of l"x5" have proved most successful with RG-244 containing systems due to more available surface area, however, conical and cylindrical types are commonly used as well. To be on the safe side, we recommend 40-60 mesh screens which rarely pose a problem regardless of the type of filter or spraying conditions. Mr. W. C. Thurber -2- October 17, 1975 One last comment, our own laboratory has investigated the sprayability of RG-244 containing resin at a number of spray gun manufacturers including Glas-Mate, DeVilbiss, Binks, and Venus products. All have attested to the fact that RG-244 containing resins can be used with their equipment. We would be happy to discuss the details of our knowledge in these applications with Mr. Ginsberg or any customer who might have reservations regarding the use of RG-244 in airless spray equipment. We do not suggest that the problem is entirely without foundation, however, it is usually a matter of educating the customer rather than a technical problem. B. L.\Jlngalls BLI:cjb