A sheetlike composite comprising, as layers of a layer sequence in the direction from an outer face of the sheetlike composite to an inner face of the sheetlike composite, a) a first polymer layer, b) a carrier layer which comprises one selected from the group consisting of cardboard, paperboard, and paper, or a combination of at least two of these, and c) an oxygen barrier layer which is selected from a. a plastic barrier layer which comprises at least 70 % by weight of polyamide or polyethylene vinyl alcohol or a mixture thereof, b. a metal layer, c. a metal oxide layer, or d. a combination of at least two of a. to c., wherein the first polymer layer is characterized by a ratio of a proportion of aromatic groups in the first polymer layer to a proportion of carbonyl groups in the first polymer layer in a range from 0.18 to 0.34; wherein the first polymer layer comprises at least one polyurethane and wherein the polyurethane is obtainable by a polyaddition a) of a first di- or polyisocyanate, and b) of a second di- or polyisocyanate with at least one di- or polyol, wherein the first di- or polyisocyanate comprises the aromatic groups and wherein the second di- or polyisocyanate comprises the aliphatic groups. a) a first polymer layer, b) a carrier layer which comprises one selected from the group consisting of cardboard, paperboard, and paper, or a combination of at least two of these, and c) an oxygen barrier layer which is selected from a. a plastic barrier layer which comprises at least 70 % by weight of polyamide or polyethylene vinyl alcohol or a mixture thereof, b. a metal layer, c. a metal oxide layer, or d. a combination of at least two of a. to c., wherein the first polymer layer is characterized by a ratio of a proportion of aromatic groups in the first polymer layer to a proportion of carbonyl groups in the first polymer layer in a range from 0.18 to 0.34; wherein the first polymer layer comprises at least one polyurethane and wherein the polyurethane is obtainable by a polyaddition a) of a first di- or polyisocyanate, and b) of a second di- or polyisocyanate with at least one di- or polyol, wherein the first di- or polyisocyanate comprises the aromatic groups and wherein the second di- or polyisocyanate comprises the aliphatic groups. a. a plastic barrier layer which comprises at least 70 % by weight of polyamide or polyethylene vinyl alcohol or a mixture thereof, b. a metal layer, c. a metal oxide layer, or d. a combination of at least two of a. to c., wherein the first polymer layer is characterized by a ratio of a proportion of aromatic groups in the first polymer layer to a proportion of carbonyl groups in the first polymer layer in a range from 0.18 to 0.34; wherein the first polymer layer comprises at least one polyurethane and wherein the polyurethane is obtainable by a polyaddition a) of a first di- or polyisocyanate, and b) of a second di- or polyisocyanate with at least one di- or polyol, wherein the first di- or polyisocyanate comprises the aromatic groups and wherein the second di- or polyisocyanate comprises the aliphatic groups. wherein the first polymer layer is characterized by a ratio of a proportion of aromatic groups in the first polymer layer to a proportion of carbonyl groups in the first polymer layer in a range from 0.18 to 0.34; wherein the first polymer layer comprises at least one polyurethane and wherein the polyurethane is obtainable by a polyaddition a) of a first di- or polyisocyanate, and b) of a second di- or polyisocyanate a) of a first di- or polyisocyanate, and b) of a second di- or polyisocyanate with at least one di- or polyol, wherein the first di- or polyisocyanate comprises the aromatic groups and wherein the second di- or polyisocyanate comprises the aliphatic groups.