Raw base paper is a kind of special industrial paper, which is processed with raw materials of high quality wood pulp and titanium dioxide under special technology. After printing, then melamine impregnation, it is widely laminated as top layer of wood based panels like fiberboard, particleboard and plywood, etc. Due to the requirements on special use, base paper has to perform well in opacity, impregnation and print. Its surface should be smooth and has good absorption on melamine resin and water base ink.
Base paper has to be impregnated with melamine resin before lamination. There is only a few seconds in contact with melamine resin during impregnation. In this short time, base paper is required to quickly absorb a specified amount of resin, and the amount is several times to itself weight. So the base paper must have a fast, stable and uniform absorption. Otherwise it will affect the speed of impregnation, and may cause quality problem during lamination. Absorption performance is an important indicator need strict control.
We can improve the absorption of base paper by selecting high quality wood pulp and improving production. Hardwood pulp is the preferred to produce base paper. Quality hardwood pulp fiber is short in average length and uniform, and has good strength, good dimensional stability, high light scattering coefficient, high whiteness. It not only can ensure good absorption, but also can guarantee the good stability, uniformity, printability and opacity of base paper. In the production process, mixing degree, PH value have great influence on base paper absorption. Under the premise of uniformity and strength, try to low down the mixing degree, ensure the PH value between 6.5 to 7.5, and increase the swelling properties of pulp fibers. In addition, the tension of paper could be lowed by reducing the pressure, lower tension on net. Soft roll can make the base paper good in printability and absorption. By fast warming to dry the paper will increase its porosity and permeability, and to improve the absorption properties of base paper.
The base paper requires to have good wet strength. During impregnation, it has to bear self weight and absorbed resin weight, overcome the tensile force, pass through impregnating machine without break.
Same with absorption, the strength of base paper is close related with wood pulp and production process. Coniferous wood pulp fiber is better in strength, and the strength could also be increased by using technology to improve the tightness of base paper. In addition, the application of reinforcing agent can also improve the strength index of base paper. But too much reinforcing agent has sizing function, can reduce permeability of pulp fiber, thus affecting the base paper absorption performance. Weigh the relationship between absorption and strength, in the premise of no harm on absorption, try to improve production technology, and get a strength of base paper.
After printing and impregnation, the substrate could not be seen during lamination. So the base paper requires good opacity. In order to get the quality print, the brightness of base paper should be more than 90%. To improve its whiteness and opacity, we usually fill high whiteness agent, such as titanium dioxide, lithopone, potassium titanate crystal fiber. But too much agent is bad for absorption of base paper. The absorption performs well when the agent content is lower, when the agent content is too high, the absorption capacity decreased. So, try to ensure the paper absorption, strength and opacity by improving production process.
4. Smoothness and uniformity
Smoothness of raw base paper is an important indicator which will affect quality printing, and uniformity will also affect the absorption performance. These two indicators must be paid more attention during the production of base paper. Smoothness can be improved by adjusting press operation, but it must be noted the interaction with absorption performance.
The uniformity of base paper is related with many factors. Long pulp fiber means poor uniformity, and we should reduce their length by free beating. When fill pulp onto dry nets, it should reduce the concentration and ensure the full dispersion of fiber. In addition, the use of various kinds of agent should be appropriate, try to prevent the bad effects on uniformity of base paper because of high agent content.
In a words, all indicators of raw base paper are mutual restraint and mutual influenced. Among the wood pulp, agent and production process, we have to comprehensively consider the actual use requirements, effectively improve the base paper properties, while ensure various performance indicators.
Hangzhou fimo Decorative Material Co., Ltd., selects the high quality raw base paper, and guarantee the printing quality of decor paper and applicability of subsequent melamine impregnation and lamination. Technical index of raw base paper from FIMO DECOR is as below.
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