Paper and paperboard webs are used in a myriad of applications as packaging materials such as wrappings and boxes. When formed into these packaging materials, it is often desirable to reinforce certain areas of the paper web, particularly critical areas where tears and damage are most likely to occur such as the corners of a box. However, it is normally wasteful to reinforce the entire web including both high and low stress points.
Typically, the solution in the past has been to bond reinforcement strips to the substrate or web in areas which need reinforcement by means of an adhesive or glue placed between the surface of the substrate and the reinforcement strip. The substrate and reinforcement are thus directly bonded to one another.
This solution has disadvantages. In particular, because the substrate and reinforcement are directly bonded to one another, the two have no freedom to move or deform independently of each other. The substrate and reinforcement are in effect combined into a single unit. This in turn leads to a tendency for the substrate and reinforcement to tear and fail together rather than individually and to generally exhibit a lower combined strength than would be expected from the sum of the strengths of the two acting in opposition to a force independently of one another.
Accordingly, it is an object of the invention to provide a method for making a reinforced substrate having improved strength properties.
Another object of the invention is to provide a reinforced substrate wherein the reinforcement is not directly bonded to the substrate.
Still another object of the invention is to provide a reinforced packaging materials have selectively applied reinforcements.