Effect of Blank Holding Force on the Gas Tightness of Paperboard Trays Manufactured by the Press Forming Process

Abstract

Although several authors have studied 3D forming using the press forming process, the gas tightness of polymer-coated paperboard trays has not been widely researched. In this paper, the effect of blank holding force on the surface quality and tightness of press-formed paperboard trays was researched. The press-formed trays were heat-sealed with a multilayer polymer lid. The tightness of the trays was analyzed by following the oxygen content of the packages over the course of 14 d and by using a penetrant coloring solution to locate possible leaks. The results indicate that the blank holding force had a great effect on the quality and tightness of the trays, especially in the case of a rectangular geometry. The geometry of the formed trays played a significant role in process parameter selection, and more demanding geometries emphasize the importance of parameter optimization. However, with the correctly selected parameters, the use of modified atmospheric packaging (MAP) in polymer coated paperboard trays was shown to be possible. The oxygen content of both analyzed geometries was found to be less than 1% 14 d after sealing. It was also demonstrated that the gas tightness of a seal cannot be confirmed using a penetrant solution test exclusively.

Process cycle optimization in press forming of paperboard

“…The effect of BHF on the quality of formed products has been previously discussed in. 3 The BHF values and calculated surface pressure values presented in Figure 5 show that this commonly used setup is not restricting increase in these values during the pressing phase. This is due to the latency of the pressure regulator and indicates that the cylinder pressure has to be controlled with a more elaborate way.…”

“…The flattening force is a part of the pressing force that is conducted mechanically through the structure of the mould set, as illustrated in Figure 6. The importance of the quality of the tray flange is well known, 3 and the effect of manufacturing process on this quality has also been investigated. [2][3][4] The movement of the male mould in relation to the rim tool is mechanically limited to enable the set distribution of pressing force between the tray flange and the lower part of the tray.…”

“…Three-dimensional (3D) forming of paperboard by press forming and deep drawing processes has been studied by several authors. Previous articles describe the effect of process parameters, tooling technology, the adjustability of the processes, [1][2][3][4] and material behavior in the forming processes. [5][6][7][8] The requirements set by the forming process, such as the dwell time and the tool heating, have been previously studied by Tanninen et al, 9 and the optimization and design of forming tools have also been investigated extensively.…”

Influence of pulp type on the three-dimensional thermomechanical convertibility of paperboard

“…In press-forming, which is one method for producing packages from paperboard, the rigidity of trays is controlled by feeding the blank into the press so that the longer side of the blank is parallel to the machine direction (MD) (Leminen et al 2013). Either the female or male tool is heated, or in some cases both tools, which aids plastic deformation.…”

Characterization of Influences on the Wall Stability of Deep Drawn Paperboard Shapes

“…Hauptmann et al (2013) showed that deep drawn structures can be sealed tightly without creating pinholes that are likely to occur in wrinkled areas at the sealing rim. These pinholes are also known to prevent gas leaks in press molded trays; however, Leminen et al (2015) found that the optimized blank holder force can lead to gas-tight sealed trays made from press molding.…”