Containers with improved crease-crack resistance

Abstract

A container with improved crease-crack resistance and a method of making that type of container. The container utilizes a layer of a soft plastic on its exterior to control cracking at outward creases. When the container holds motor oil, the oil itself may plasticize the stiff material on the container's interior to preclude inward crease cracking. In this case, the stiff layer should have a sufficient thickness that an adequate amount of material remains unaffected by the oil and does not lose its rigidity or jeopardize the container's structural integrity. Where the contents do not provide the requisite improvement in inward crease cracking or would completely soften the stiff layer, then the container has a separate, soft, third layer of plastic on the interior of the container. The softness of this layer protects against inward crease cracking. It may also protect the stiff layer from softening by the bottle's contents. Making the container involves forming the substantially stiff layer that gives the container its shape and rigidity. A soft, outer layer should also be formed for protection against outward crease cracking. If the intended contents of the container will either not plasticize the inner surface of the stiff layer or will cause excessive softening, then a third, thin, layer must be formed on the container's interior. This soft layer then guards against inward crease cracking.