Method for coating a hollow container comprising molded pulp
The present disclosure generally relates to a method for providing a barrier coating on a hollow container ( 100 ) comprising molded pulp. The method comprises providing a polymeric powder coating onto the interior surface ( 105 a ) and at least a portion of the exterior surface of the container ( 100 ) prior to curing and/or melting the powder coatings. The present disclosure also relates to a hollow container ( 100 ) formed by the method.
1 . A method for providing a barrier coating on a hollow container ( 100 ) comprising molded pulp; said method comprising:
a) providing a hollow container ( 100 ) comprising molded pulp, wherein said hollow container ( 100 ) comprises a main portion ( 101 ) and an upper portion ( 102 ); said hollow container extending along a longitudinal center line ( 103 ), wherein the longitudinal extension of said upper portion ( 102 ) corresponds to 5-30% of the maximum longitudinal extension of said hollow container ( 100 ), and wherein the longitudinal extension of said main portion ( 101 ) corresponds to 70-95% of the maximum longitudinal extension of said hollow container ( 100 ), wherein said hollow container comprises a bottom surface ( 104 ) and sidewalls ( 105 ) extending from said bottom surface ( 104 ) to an opening ( 106 ) of said hollow container; said sidewalls ( 105 ) and said bottom surface ( 104 ) defining an exterior surface and an interior surface ( 105 a ) of said hollow container;
b) depositing a polymeric powder onto the interior surface ( 105 a ) of said hollow container ( 100 ) by means of a spraying device ( 107 ) capable of charging the polymeric powder prior to or during deposition of said polymeric powder, wherein at least said main portion ( 101 ) of said hollow container ( 100 ) is grounded during said polymeric powder deposition, wherein said polymeric powder deposition step b) is carried out in a molding device ( 108 ) comprising an electrically conductive material, and wherein said molding device ( 108 ) comprises at least a first ( 108 a ) and a second ( 108 b ) removable portion, wherein said first removable portion ( 108 a ) is configured to enclose said upper portion ( 102 ) of said hollow container ( 100 ) and wherein said second removable portion ( 108 b ) is configured to enclose said main portion ( 101 ) of said hollow container ( 100 );
c) depositing a polymeric powder onto the exterior surface of at least a portion of said upper portion ( 102 ) of said hollow container ( 100 ) by means of said spraying device ( 107 ), wherein the exterior surface of said main portion ( 101 ) is void of a barrier coating comprising polymeric powder, wherein said polymeric powder deposition step c) is performed by arranging said spraying device ( 107 ) at a distance, d 1 , of from 10 mm to 250 mm from said opening ( 106 ) of said container, wherein said first removable portion ( 108 a ) is removed from said molding device ( 108 ) during said polymeric powder deposition step c); and
d) treating said hollow container with heat or irradiation under conditions that melt and/or cure said polymeric powder after said steps b) and c).
2 . The method according to claim 1 , wherein said hollow container has a moisture content of from 3 to 15% during said steps of polymeric powder deposition.
3 . The method according to claim 1 , wherein said molding device comprises a formable electrically conductive material.
4 . The method according to claim 1 , further comprising the step of:
a′) conditioning the hollow container at an ambient relative humidity of from 30 to 100%, after step a) of providing said hollow container comprising molded pulp.
5 . The method according to claim 1 , wherein said polymeric powder deposition steps b) and c) are performed simultaneously.
6 . The method according to claim 1 , wherein said hollow container is a bottle, wherein said upper portion ( 102 ) comprises a shoulder portion ( 102 a ) and a neck portion ( 102 b ), wherein said neck portion has a smaller cross-sectional area than said main portion and is configured to circumferent at least said opening ( 106 ) of said bottle, and wherein said shoulder portion ( 102 a ) is arranged to taper between said main portion ( 101 ) and said neck portion ( 102 b ).
7 . The method according to claim 6 , wherein at least said neck portion ( 102 b ) of said upper portion ( 102 ) is coated in said polymeric powder deposition step c).
8 . The method according to claim 6 , wherein the entire upper portion ( 102 ) of said hollow container ( 100 ) is coated in said polymeric powder deposition step c).
9 . The method according to claim 1 , wherein said step d) is performed by heating said hollow container ( 100 ) at a temperature of from 120° C. to 220° C., for 1 to 30 minutes.
10 . A hollow container ( 100 ) formed by the method according to claim 1 , wherein the hollow container comprises a main portion ( 101 ) and an upper portion ( 102 ); said hollow container extending along a longitudinal center line ( 103 ), wherein the longitudinal extension of said upper portion ( 102 ) corresponds to 5-30% of the maximum longitudinal extension of said hollow container ( 100 ), and wherein the longitudinal extension of said main portion ( 101 ) corresponds to 70-95% of the maximum longitudinal extension of said hollow container ( 100 ), wherein said hollow container comprises a bottom surface ( 104 ) and sidewalls ( 105 ) extending from said bottom surface ( 104 ) to an opening ( 106 ) of said hollow container; said sidewalls ( 105 ) and said bottom surface ( 104 ) defining an exterior surface and an interior surface ( 105 a ) of said hollow container, wherein said hollow container comprises a barrier coating comprising polymeric powder on said interior surface ( 105 a ) of said hollow container and on the exterior surface of at least a portion of said upper portion ( 102 ) of said hollow container, wherein the exterior surface of said main portion ( 101 ) is void of a barrier coating comprising polymeric powder.
11 . A hollow container according to claim 10 , wherein said hollow container is a bottle; said upper portion ( 102 ) comprising a shoulder portion ( 102 a ) and a neck portion ( 102 b ), wherein said neck portion has a smaller cross-sectional area than said main portion and is configured to circumferent at least said opening ( 106 ) of said bottle, and wherein said shoulder portion is arranged to taper between said main portion and said neck portion, wherein said bottle comprises a barrier coating comprising polymeric powder on the interior surface ( 105 a ) of said bottle and on at least the exterior surface of said neck portion ( 102 b ) of said bottle.
12 . A hollow container according to claim 10 , wherein the thickness of the barrier coating is in the range of from 5 to 300 μm.
13 . The method according to claim 4 , wherein said step a′) comprises conditioning the hollow container at an ambient relative humidity of from 60 to 100% after step a) of providing said hollow container comprising molded pulp.
14 . The container according to claim 12 , wherein the thickness of the barrier coating is in the range of from 20 to 100 μm.