Which country is the patent of milk carton?

Excuse me, are you asking the question "where is the patent of milk box?" The patent of this article is mainly owned by Tetra Pak in Sweden.

Rubin Lausin, the founder of Tetra Pak, saw the huge demand for milk and juice in the late 1920s and conceived a waterproof wrapping paper lined with plastic film. With the help of engineer Vallenborg, this idea came true. To this end, he also applied for a patent for the design and named it "regular tetrahedron", which is what we now call milk box.