Laminate quality of continuous press


It has been proposed to feed the laminate directly to a continuous post-forming process. At this point, as the web exits the continuous press, the heat present in the web can be utilized to assist in obtaining the temperature required for post forming. The heat in the post-forming process will promote further curing of the resin. Due to the limited length of the heating and pressing zone between the steel strips, the laminate faces a trade-off between production speed and curing time. In fact, the curing time is only used a few times. minute. This requires a specially formulated fast curing resin. The melamine-formaldehyde resin was originally used in both the decorative layer and the core layer of the laminate. Recently, a fast curing phenolic resin used in a core layer has been developed. Initially, the Hymmen continuous press was only used to produce sidebands. It is very difficult to manufacture a general-purpose veneer with a width of 0.9-1.2 m. In general, it has been found that more resin must be used in a continuous process to produce a qualified laminate. Pankokea believes that for continuous processes, phenolic resins use 42.3% more, while conventional laws use 28.5% more. Considering the low pressure of the continuous process and the short curing time, it is not allowed to have sufficient flow resin to fill the entire pores. The high resin content improves the flowability of the resin and ensures complete penetration of the resin.
Initially, the quality of laminates in continuous presses was not comparable to that of flat presses. Laminate producers seem to be in a difficult situation. If they make the press run fast and produce enough products to pay for the depreciation of the equipment, the quality will suffer. If they lower the speed and make the quality of the laminates acceptable, they would not be able to produce enough laminates to cover the depreciation costs, but further process development improved the situation. With the success of the Hymmen press, Grecon, Sandvik, Held, Siempelkamp and many others have started to develop a range of other types of continuous presses. One type is to bypass the heating cylinder in a single continuous strip. The layers of the laminate are pressed in the nip between the steel strip and the cylinder. The tension is then maintained by the tension of the steel strip which exerts a compressive force perpendicular to the cylinder. This versatile construction has been used for continuous rubber vulcanization and for the curing of polyester-impregnated paper used as sidebands. This continuous press has a very short distance to the laminate for compression and solidification, mainly due to the circumferential portion of the tact. They also require high strip tension to achieve the pressures necessary for the laminate industry. This puts high demands on the material of the steel strip and the bearing of the cylinder. Others have tried to improve it by increasing the pressurization capacity of the double belt press. One method is to use oil pressure instead of air pressure. Another method is to transfer the pressure through the fluid-lubricated hydraulic shoe. The effective pressure is 5.2 MPa. This is equivalent to the operating pressure of the flat press (the new technology of the (5.5-10.3 MPa) continuous laminate process and the flat press process. The competition between mature technologies will continue. But obviously, hundreds of millions of square meters of surface must be decorated and protected every year. Continuous production of laminates will find their place in the fiercely competitive market.

  • 25/01/2019
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