Reverse roll-coater

Kiss-Roll Colters. In kiss-roU coating, the web passes over a roU wet with the coating fluid, and has no backing roU. There are many types of kiss-roU coaters. The kiss roU can turn in the dkection of the web or in the reverse dkection but usually operates in the web dkection. Kiss-roU coaters are tension sensitive and are often used to apply excess coating prior to a metering device. 

Reverse pluronics, 24 151 Reverse-roll coaters, 7 12—13 method summarized, 7 5t shear rates, 7 32t... 

Recently, hot melt PSA systems have been introduced and radiation curable PSA systems are at the commercial development stage. High solids (50%-70% by wt.) nonaqueous dispersion acrylic PSA systems have also been reported(1). Unlike the hot melt and radiation cured systems which require new capital outlay in coating head and/or curing (drying) equipment, BFG has developed PSA systems, based on Hycar 2100R reactive acrylic liquid polymers and isocyanate terminated prepolymer, which can be processed at 80% solids (by wt.) with equipment presently used in the PSA industry, namely, the reverse roll and knife-over-roll coater. 

Figures VI and VII illustrate the initial viscosity of both the Hycar 2103 and Hycar 2106 systems as well as the viscosity increase with time due to the reactive nature of the 2-component system. These figures will help in determining the percent solids necessary for processing on a given piece of equipment depending upon its viscosity handling capability. Since the 100% solids PSA systems have high initial viscosities of over 100 Pa s (100,000 cps), the conventional knife-over-roll and reverse roll coaters can not process them.

Lund M.A. 1990. Nonhomogenous Behavior of Barium Ferrite Dispersions. [CWM, LES] Fukuzawa K. 1992. Reverse Roll Coater Model. [LES]... 

Latex adhesives are made from natural rubber latex by adding stabilizers, wetting agents, and other components. They are applied to the substrate by brush, spray, doctor knife, or reverse roll coater. The adhesive is dried to film near room temperature. The adhesive strength can be improved by vulcanizing the system. The applications of latex adhesives are to porous substances such as paper, leather, and textiles. 

Solution adhesives are applied at 10-25% total solids content by spray, doctor knife, reverse roll coater, roller, or by spatula or trowel. The adhesive is dried at room temperature or in air ovens, care being taken to eliminate the fire and health hazards associated with some solvents. 

Although virtually any type of roll coater may be used, reverse roll coating is the most common. This may incorporate a doctor roll, doctor blade, or Mayer bar to meter the spread rate. With tapes, adhesive is usually applied directly to the tape, which then passes through a drying station incorporating countercurrent air, usually warm. The dried tape is then rolled and slit. With label stock, adhesive is normally applied to the release paper, dried, and then transferred to the label when the label stock is united with the release paper in a nip roll. 

Adhesives for reverse roll application will typically have viscosities in the range of 1000 to 10,000 cP. While coating speeds in excess of 200m/min are possible, machine speeds are normally limited by the speed at which the film can be dried. A simple reverse roll coater is shown in Fig. 3. 

Flooring coated by reverse-roll-coater with monolithic particles. [Data from Piacente, A. N. Papp, G. J. Whitehouse, R. E. Mansolillo, R. D., US Patent 5,178,912, Jan. 12,1993.]... 

Also possible is a 100%-solids heat-curable foam which can be direct- or transfer-coated with the standard knife or reverse roll coaters. By incorporation of a blowing agent, the urethane coating is foamed during the oven curing. It is normally used with a conventional top coat. 

Figure 15. Standard coating equipment for PSAs A) Knife over roU B) Reverse roll coater... 

Standard equipment for solution based PSAs are knife over roll and reverse roll coaters (Fig. 15) [255, p. 13 ff]. For high-speed application, a closed reservoir or a slot die is preferred for better control of air bubbles [260]. Especially the knife over roll coater allows for an easy change of the coating material. 

This flexibility has proven invaluable in the design of coater-ready aqueous adhesives which are specifically designed for a wide range of application techniques. These techniques include reverse roll coating, curtain coating, gravure coating, and spray application. Key characteristics built into the aqueous adhesives to permit such a wide variety of application techniques include ... 

Solvent cements are usually supplied at concentrations of 10-25% solids, with viscosities in the range of 1,000-30,000 cPs. They may be applied by brush, spray, doctor blade, reverse-roll coater, hand roller, trowel, and many other application methods. The proper coating of the adhesive is obtained by establishing the correct viscosity for the particular application method. After application, the solvent is removed by ambient drying or by forced drying in heated ovens or tunnels. 

Drying Lines. Oven drying lines represent large capital investments, of the order of several million dollars, and the same line is frequently used to handle both solutions and latices. The metering equipment may be either reverse roll coaters, which offer maximum flexibility, or knife-over-roll coaters, which are less expensive. For thin films a wire-wound rod to remove excess material can be used. Because of coating difficulties encountered with latex vehicles such devices as an air knife or flexible blade are sometimes used with these products. 

Reverse Roll Coater Reverse Roll Coater with Direct Roll Coating... 

---