Drying process characteristics of rotary cutting veneer

The cut veneer contains a large amount of water. If it is not dried, it is directly coated and hot pressed. The water will prolong the hot pressing time, and it is easy to cause bubbling. Some rubber types cannot even be glued. Moreover, the plywood has a large shrinkage stress, is easy to deform and causes cracks in the veneer, which affects the quality. In addition, the wet veneer has a large water content, which is not conducive to stacking and storage, and the edge is prone to cracking or warping, and mildew is likely to occur in summer.

From the drying efficiency of the dryer and the yield of the veneer, the final high water content is beneficial to the dryer, which can improve the production efficiency of the dryer and save energy. However, from the quality of plywood, the water content is lower.

The final moisture content of the veneer should be determined according to the requirements of the tree species, rubber grade and plywood.

Tree species, such as ash, etc., the early tube hole is large, good ventilation, water permeability, high water content has little effect on the bonding strength, and pine, etc., because the veneer contains a lot of turpentine, the gas permeability is poor when hot pressing, if the end contains When the amount of water is high, it is easy to cause defects such as bubbling.

Different types of rubber, the requirements for the final water content of the veneer are also different. Synthetic resin requires that the final water content of the veneer is lower, while the use of protein adhesive is slightly higher.

China's general veneer final water content regulations, phenolic, urea-formaldehyde resin in the range of 8-12%, while soybean gum, blood glue, etc. are controlled in the range of 8-14%.

Veneer drying is similar to wood drying, but the drying method is more complicated. It is characterized by:

The board has a large and thin area, and the water diffuses and evaporates quickly, and can be dried at a high temperature in a few minutes.

When the veneer is dried, the shrinkage of each part is inconsistent and it is easy to warp and crack.

The veneer has a low strength in the transverse direction and is easily broken during drying.

The wood is dry, the moisture moves fast, and the end and longitudinal water movements are 12-13 times faster than the lateral direction. However, since the length of the veneer is hundreds or thousands of times larger than the thickness, the dry moisture movement of the veneer is mainly horizontal.

Mastering the above characteristics, it is necessary to strictly and develop its drying process.

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