Modern industrial practice shows that continuous methods have many advantages, including improved product uniformity, reduced labor required, simplified management, and reduced process waste. It is therefore natural to develop a continuous process for the production of laminates.
In the 1960s, Hoover Ball and Bearing Company developed press equipment for continuous production of laminates. The company recommends moving a stack of resin-impregnated paper sheets under a heated forming rod. The passage under the forming rod will heat the paper to polymerize the resin. At the same time, as the pile passes under the rod, it will be subjected to extremely high compression forces. Several laminate manufacturers have experimented with small pilot plants and believe that the process has a certain future, although a lot of development work is still needed. A prototype for the production of special red wood products was produced. But after being installed in California for a short time, it was washed away by the flood. Since then the company has lost interest in this project.
In the early 1970s, another continuous press was developed in Germany using different principles, and by 1975, Hymmen had prepared to use the press in the industry. In this press, a continuous web of resin impregnated paper is fed into the nip between two continuous stainless steel strips. As the web passes through the nip, the web will be subjected to compression and heating and then solidified under the heat and pressure between the steel strips until the strip passes over the deflection rolls before they leave the press. Between the nip inlets, the steel strip and the resin impregnated paper are pressurized by the compressed air in the upper and lower compressed air chambers of the steel strip. Compressed air is also used as a medium for exchanging heat. The laminate is heated throughout the stroke. Immediately after exiting the press section, it is cooled in a separate process. The pressure of the early prototype is about 1. 7MPa. The temperature is below 200 °C. Devices that were later developed are said to have higher pressures.
In this type of continuous press, the layers of the laminate are fed from individual rolls on a multi-roller. The textured paper is also supplied from the paper roll like f-core paper. After use, the textured paper is rolled up on the outlet side of the press for reuse. The pressed laminate can be subjected to a series of processes while still maintaining the form of the web. These processes include trimming, sanding the back of the laminate, slitting according to user specifications, and sanding the decorative surface. The laminate can be rolled into a loose roll or cut to the length required by the user. Since the web is continuous, the cut strip is not wasted. This is a great advantage of continuous operation.
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