Heat insulating paper cups
View Patent ↗A heat insulating paper cup having an improved seal. The cup can include a body member having an inside surface and an outside surface, and a bottom panel member having a upper surface and a bottom surface. The body member is coated (or in some instances partially coated) on its outside surface with a foamed low density polyethylene, and on its inside surface with an unfoamed modified low density polyethylene. The bottom panel member is coated on its upper surface with a foamed or an unfoamed low density polyethylene or foamed or unfoamed modified low density polyethylene. The body member and bottom panel member are oriented and joined to form a heat seal at an interface between a portion of the unfoamed modified low density polyethylene coated on the inside surface of the body member and a portion of unfoamed low density polyethylene or unfoamed modified low density polyethylene coated on the upper surface of the bottom panel member.
1. A heat insulating paper cup comprising:
a) a body member having an inside surface and an outside surface, wherein the body member is coated or partially coated on the inside surface with a modified low density polyethylene and on the outside surface with a foamed low density polyethylene; and
b) a bottom panel member having an upper surface and a bottom surface, wherein the bottom panel member is coated or partially coated on the upper surface with a low density polyethylene or a modified low density polyethylene,
wherein the body member and bottom panel member are oriented and joined to form a heat seal at an interface between a coated portion of the inside surface of the body member and a coated portion of the upper surface of the bottom panel member.
2. The heat insulating paper cup of claim 1 , wherein the modified low density polyethylene will not foam under conditions of about 240° F. to about 270° F. and a residence time of about 1.5 to about 2.5 minutes when the cup is subjected to foaming operations in a forced hot-air oven.
3. The heat insulating paper cup of claim 1 , wherein the foamed low density polyethylene entirely covers the outer surface of the body member.
4. The heat insulating paper cup of claim 1 , wherein the modified low density polyethylene on the inside surface of the body member provides a seal to prevent the penetration of liquid contents into the paper during use.
5. The heat insulating paper cup of claim 1 , wherein water is present in the body member prior to foaming of the foamed low density polyethylene, and wherein the modified low density polyethylene on the inside surface of the body member prevents the water present in the paper from evaporating directly into air atmosphere when the cup is heated during a foaming operation.
6. The heat insulating paper cup of claim 1 , wherein the low density polyethylene on the outer surface of the body member is from 25 to 60 μm.
7. The heat insulating paper cup of claim 1 , wherein the low density polyethylene or modified low density polyethylene are present on the inner body member surface and inner bottom panel surface in an amount sufficient to prevent permeation of liquid through the respective members during use.
8. The heat insulating paper cup of claim 1 , prepared from paper sheets comprising from about 3% to about 10% water.
9. The heat insulating paper cup of claim 1 , wherein the heat seal will not peel apart at a 180° angle at a crosshead speed of 1 inch per minute when tested on a Model 4202 Instron Tensile Tester.
10. The heat insulating paper cup of claim 1 , wherein the modified low density polyethylene is present and wherein the polyethylene is modified by blending with a suitable amount of high density polyethylene to prevent the modified low density polyethylene from foaming when the cups are subjected to a foaming operation.
11. The heat insulating paper cup of claim 10 , wherein the modified low density polyethylene comprises from approximately 90% low density polyethylene and 10% high density polyethylene to 10% low density polyethylene and 90% high density polyethylene.
12. The heat insulating paper cup of claim 10 , wherein the modified low density polyethylene comprises from about 2% to about 7% high density polyethylene.