Container for hot fill food packaging applications

Abstract

A plastic container suitable for hot-fill food packaging applications is disclosed which is characterized by walls of proportionately decreasing thickness from the mouth of the container to a predetermined collapsible point. The wall thickness is designed such that the container walls will collapse, or deform, only at the collapsible point during cooling after hot-filling of food product or during transportation of the container between locations of varying altitudes and pressures. The container preferably collapses in the base area such that the collapse is not visible to the consumer and also the collapse does not affect stability of the container while in use or during loading and storage. The container of the invention is advantageous in that it requires less plastic material to form than other known hot-fill containers, and also can be formed out of any suitable food-grade plastic material or by any process.

Description

FIELD OF THE INVENTION [0001] The invention relates to a plastic container suitable for hot-fill food packaging applications, and a method of making the container. The container is manufactured in a manner such that the walls have a sufficient strength to withstand collapse upon cooling of the container after sterilization, or during the transport of the filled container between locations of varying altitude. A collapsible point, preferably the bottom of the container, is manufactured to selectively deform to compensate for the pressure differentials experienced between the interior of the container and atmospheric pressure after hot-filling, and during transport of the container between locations of different altitudes. Also disclosed is a method of forming a container having a selectively deformable collapsible point, and walls that do not deform, after hot-filling and during other pressure changes. BACKGROUND OF THE INVENTION [0002] The storage of food products in plastic contain...

AI Technical Summary

Benefits of technology

[0015] The invention relates to a plastic container suitable for the packaging of hot-filled food products that can withstand the pressure changes caused by the cooling of the hot food product in the sealed container, and also during transport of the packed containers between locations having a pressure differential. The invention also relates to a method of manufacture of the container. The container of the invention includes walls designed by their thickness to have a collapsible point, which collapsible point is controllable by the manufacturing process. Preferably, the collapsible point is designed to be located in the base of the container such that it is not visible to the consumer after it collapses, and also is designed such that the stability of the container when standing is not affected.

[0016] Where the collapsible point is designed to be located in the base of the container, the thickness of the container walls are controlled such that the walls can withstand a designed pressure force without deformation, except for the collapsible point. This is done by controlling the manufacturing process to maintain the desired wall and bottom surface thicknesses of the container. In the preferred embodiment, the wall thickness decreases proportionately from the area of the container substantially adjacent to the mouth, to the bottom of the container, and the thickness of the bottom is less than the thickness of the walls. This is accomplished in the preferred forming process of thermoforming by controlling the dimensions of the mold and the counter-mold, and controlling the expulsion (ejection) pressure and the temperature of the plastic sheet during forming. In addition, the desired collapsible point may be further induced by a surface design that will facilitate the collapse of that point at a lesser pressure differential that can be withstood by other components of the container. The collapse of the collapsible point reduces the head space between the food product and the seal in the interior of the container, and then reduces or eliminates the probability that the walls of the container will also collapse, or otherwise deform.

[0017] The container of the invention can be made of any plastic materials that are suitable for food packaging, and any forming method. For example, common plastic materials include polyethylene terephthalate (PET), polyester, ethylene, polystyrene, low density and high density polyethylene and polypropylene, or combinations of these materials. Additives may be included with the plastic materials to enhance properties desired in the final container. For example, additional barrier materials, such as polyvinyldichloride (“PVDC”), polyvinylchloride (“PVC”), or ethylene vinyl acetate-vinyl alcohol resins (“EVOH”) may be added to decrease permeability of the container to such undesirable materials as oxygen and water vapor. Materials may be added to adapt the optical properties. For example, materials may be added to decrease light penetration into the container, or to increase clarity of the container.

Problems solved by technology

This reduction in air volume results in a corresponding reduction in pressure within the container, and can cause the container to collapse due to the head space remaining between the food product and the seal of the container after sealing and cooling.

In addition, any changes in the altitude of the location of the packed container can cause similar expansion and / or contraction of the container due to changing pressure differentials between the interior of the container and the atmospheric pressure at the different locations.

Container deformation typically can occur at any location in the container where the container wall cannot withstand the experienced pressure differential between the inside of the container and the atmospheric pressure.

Although container deformation does not necessarily affect the sterility and stability of the packed food product, consumers tend to shy away from such products based on the appearance that the containers are perhaps damaged or otherwise spoiled.

In addition, container deformation causes the containers to be difficult to load and store due to the nonuniformity of the walls or bases.

Also, container deformation can make a container unstable when used by the consumer, when for example the base is deformed such that the container is not steady when placed on a surface.

Images