Double container and exterior sleeve used in double container

1. A double container comprising:

a paper inner container having a cylindrical barrel portion formed to have a curled portion on an upper circumferential edge thereof, and a bottom portion provided on a lower end of the barrel portion so as to close a lower face thereof; and

a paper exterior sleeve which covers the barrel portion so as to form a thermal insulating space between itself and an outer surface of the barrel portion;

wherein the circumferential edge portion of the upper end portion of the exterior sleeve enters a gap on the inner side of the curled portion of the circumferential edge portion at the upper end of the inner container, and the thermal insulating space between the exterior sleeve and the inner container expands as the lower end is approached; and

wherein at least one of the outer surface of the barrel portion of the inner container and an inner surface of the exterior sleeve is provided over the entire circumference thereof with a plurality of elongated projections, which consist of thermoplastic resin, arranged in a row and spaced apart in a circumferential direction, and the projections extend in an elongated fashion circumferentially and each has a projection amount of 1.0 to 2.0 mm,

and the row of the plurality of elongated projections is situated at a location that is above half of the height of the double container.

2. A double container according to claim 1 , wherein the exterior sleeve covers substantially the entirety of the barrel portion of the inner container and is secured to the barrel portion.

3. A double container according to claim 1 , wherein the exterior sleeve has a height that is smaller than that of the inner container, and the exterior sleeve extends partway from the curled portion of the inner container toward the lower end of the inner container; and

wherein the plurality of elongated projections are provided on at least one of the outer surface of the barrel portion of the inner container and the inner surface of the exterior sleeve in an area covered by the exterior sleeve.

4. A double container according to claim 3 , wherein the exterior sleeve has a height that is 40 to 65% of that of the inner container.

5. A double container according to claim 3 , wherein the exterior sleeve is freely attached to and detached from the inner container.

6. A double container according to claim 3 , wherein the exterior sleeve is secured to the inner container.

7. A double container according to claim 1 , wherein the barrel portion has a paper basis weight that is smaller than that of the exterior sleeve.

8. A double container according to claim 1 , wherein the row of the plurality of elongated projections arranged in a row and spaced apart in the circumferential direction is situated on the double container at a location that is above half of the height thereof.

9. A double container according to claim 1 , wherein spacing between mutually adjacent elongated projections in the circumferential direction is 5.0 to 15 mm.

10. A double container according to claim 1 , wherein each elongated projection has a length of 5.0 to 20 mm in a longitudinal direction and a width, in a direction that is perpendicular to the longitudinal direction, of 1.0 to 2.0 mm.

11. A double container according to claim 1 , wherein multiple rows of the plurality of elongated projections, arranged in a row and spaced apart in the circumferential direction, are provided in a spaced-apart relation in a vertical direction.

12. A double container according to claim 11 , wherein the pluralities of elongated projections included in respective ones of the spaced-apart mutually adjacent rows of elongated projections are provided at positions that are staggered in such a manner that they do not completely overlap each other in the vertical direction.

13. A double container according to claim 11 , wherein spacing between the rows of elongated projections is 25 mm or less.

14. An external sleeve covering a barrel portion of a paper inner container having a cylindrical barrel portion formed to have a curled portion on an upper circumferential edge thereof, and a bottom portion provided on a lower end of the barrel portion so as to close a lower face thereof, the exterior sleeve forming a thermal insulating space between itself and an outer surface of the barrel portion;

wherein the circumferential edge portion of the upper end portion of the exterior sleeve enters a gap on the inner side of the curled portion of the circumferential edge portion at the upper end of the inner container, and the thermal insulating space between the exterior sleeve and the inner container expands as the lower end is approached;

wherein the exterior sleeve has a height that is smaller than that of the inner container and covers the inner container over an area extending partway from the curled portion of the inner container toward a lower edge of the inner container; and

wherein the inner surface of the exterior sleeve is provided over the entire circumference thereof with a plurality of elongated projections, which consist of thermoplastic resin, arranged in a row and spaced apart in a circumferential direction, and the projections extend in an elongated fashion circumferentially and each has a projection amount of 1.0 to 2.0 mm,

and the row of the plurality of elongated projections is situated at a location that is above half of the height of the inner container.

15. The exterior sleeve according to claim 14 , wherein spacing between mutually adjacent elongated projections in the circumferential direction is 5.0 to 15 mm.

16. The exterior sleeve according to claim 14 , wherein each elongated projection has a length of 5.0 to 20 mm in a longitudinal direction and a width, in a direction perpendicular to the longitudinal direction, of 1.0 to 2.0 mm.

17. The exterior sleeve according to claim 14 , wherein multiple rows of the plurality of elongated projections, arranged in a row and spaced apart in the circumferential direction, are provided in a spaced-apart relation in a vertical direction.

18. The exterior sleeve according to claim 17 , wherein the pluralities of elongated projections included in respective ones of the spaced-apart mutually adjacent rows of elongated projections are provided at positions that are staggered in such a manner that they do not completely overlap each other in the vertical direction.

19. The exterior sleeve according to claim 17 , wherein spacing between rows of elongated projections is 25 mm or less.