Laminate structure to stabilize a dimensionally unstable layer

A seal laminate having dimensional stability in high humidity and for closing a mouth of a container, the dimensionally stable seal laminate comprising:

• a heat seal layer having an upper surface thereof, the heat seal layer for bonding the seal laminate to a rim surrounding the container's mouth;
• a structural support layer having upper and lower surfaces thereof and positioned above and extending across the entire upper surface of the heat seal layer, the structural support layer including materials selected from the group consisting of pulp, paper, cardboard, chipboard, paperboard, cellulose based material, and mixtures thereof and including one of softwood fibers, hardwood fibers, and blends thereof with a moisture content of about 3 to about 6 percent at about 50 to about 55 percent relative humidity;
• upper and lower dimensionally stable layers directly bonded to the structural support layer on the upper and lower surfaces thereof, the upper and lower dimensionally stable layers each having a water vapor transmission rate of no more than about 1.5 g/100 in2/24 hours, the upper dimensionally stable layer being a polymer layer comprising at least one polymer in the form of a coating that is applied at about 6 to about 30 pounds per 3000 square feet;
• and
• a ratio of a total thickness of the sum of the upper and lower dimensionally stable layers to a thickness of the structural support layer from about 1:2 to about 1:10 such that the upper and lower dimensionally stable layers directed bonded to the structural support layer balance the vertical forces internal to the structural support layer upon exposure to about 60 percent or greater relative humidity so that the seal laminate has a curl of less than about 9.5 mm upon exposure to humidity of about 60 percent or greater.