The present invention relates to a method of manufacturing food containers or covers formed of vegetable fiber material, more specifically, to a method of manufacturing the food container or covers formed of the vegetable fiber material commercially at low cost.
Conventional food containers for containing food, such as lunch boxes or trays, are made of plastic materials like foamed polyurethane and so on. However, since the plastic materials have a problem in disposing them after use, vegetable-fiber-made food containers are strongly required in view of environmental conservation.
However, there has been a problem in manufacturing the vegetable-fiber-made food containers by die molding process in that only shallow containers with insufficient strength could be manufactured. Further, in the case of the containers made from pulp board, there has been a problem of costly manufacturing, since the containers are so manufactured that cuts are formed at four corners, sidewall pieces are erected, edges of the sidewall pieces are brought into superposition to each other to apply bonding agent, and the bonded portions are manually fixed. As a consequence thereof, the vegetable-fiber-made food containers are not widely distributed comparing to the other food containers, e.g., cheap trays as presently sold in supermarkets.
In addition, paper-made containers that have a number of bellows-like wrinkles formed at the corner portions and the surface is coated with film have also been known. However there has been a problem of extremely expensive cost.
Meanwhile, with regard to paper as vegetable-fiber-made material, the natural forest including the virgin forest is to be deforested for raw material of paper. However, it is a current issue to deforest the natural or virgin forest not only from view point of natural ecosystem where various animals inhabit but also from local environmental disruption view point.