Deep drawn paperboard container and process for making it

Claim 1

A deep drawn paperboard container for food comprising a coated paperboard substrate deep drawn into the shape of a container, said paperboard substrate comprising bleached virgin sulphate or sulphite pulp or mixtures thereof and having a thickness of at least about 15 caliper, a basis weight of about 50 lbs/1000sq. ft. to 110 lbs/1000 sq. ft.; a tensile strength of about 70 to 190 lbs/in. in the machine direction and about 40 to 100 lbs/in. in the cross direction, and a Taber V-5 stiffness of from about 100 to 780 Taber units in the machine direction and about 50 to 350 Taber units in the cross direction, said paperboard substrate having affixed thereto a water impermeable layer, said water impermeable layer forming the inside surface of said container, said container comprising a bottom and side walls with rounded corners, said rounded corners containing folded pleats, said container having a depth greater than about 1.375", the rounded corners of the bottom having a radius of less than about 7/8", and the angle of inclination of the side walls being less than about 20 degrees from vertical.

Claim 9

The method of deep drawing a container for food which comprises: (a) providing a female mold; (b) providing a male mandrel arranged and constructed so that it may engage the female mold; (c) providing a paperboard blank, said blank having rounded corners and comprising a paperboard substrate with a water impermeable layer affixed thereto, said paperboard substrate having a thickness of at least about 15 caliper, a basis weight of about 50 lbs/1000 sq. ft. to 110 lbs/1000 sq. ft., a tensile strength of about 70 to 190 lbs/in. in the machine direction and about 40 to 100 lbs/in. in the cross direction, and a Taber V-5 stiffness of about 100 to 780 Taber units in the machine direction and about 40 to 100 lbs/in. in the cross direction, the rounded corners of said blank containing spaced radial score lines on the surface of the blank coated with said water impermeable layer; (d) positioning said blank between said female mold and said male mandrel so that the scored surface coated with said impermeable layer faces said male mandrel; (e) drawing said blank into said female mold by engaging said female mold with said male mandrel; (f) exposing the drawn container while in said female mold to a temperature greater than about 200° F., said male mandrel, paperboard blank and female mold constructed so that a container with a depth greater than about 1.375", rounded bottom corners of a radius of less than about 7/8", and side walls with an angle of inclination of less than about 20 degrees from vertical is thereby produced.

Claim 10

The method of deep drawing a container for food which comprises: (a) providing a female mold; (b) providing a male mandrel arranged and constructed so that it may engage the female mold; (c) providing a paperboard blank, said blank having rounded corners and comprising a paperboard substrate with a water impermeable layer affixed thereto, said paperboard substrate having a thickness of at least about 15 caliper, a basis weight of about 50 lbs/1000 sq. ft. to 110 lbs/1000 sq. ft., a tensile strength of about 70 to 190 lbs/in. in the machine direction and about 40 to 100 lbs/in. in the cross direction, and a Taber V-5 stiffness of about 100 to 780 Taber units in the machine direction and about 40 to 100 lbs/in. in the cross direction, the rounded corners of said blank containing spaced radial score lines on the surface of the blank coated with said water impermeable layer; (d) positioning said blank between said female mold and said male mandrel so that the scored surface coated with said impermeable layer faces said male mandrel; (e) drawing said blank into said female mold by engaging said female mold with said male mandrel; (f) exposing the drawn container while in said female mold to a temperature greater than about 200° F., said male mandrel, paperboard blank and female mold constructed so that a container with a depth greater than about 1.375", rounded bottom corners of a radius of less than about 7/8", and side walls with an angle of inclination of less than about 20 degrees from vertical is thereby produced.