Scavenging oxygen
View Patent ↗A food container ( 2 ) includes a rigid thermoformed plastics carton ( 4 ) which holds a dry food 6 and is closed by a removable film closure ( 8 ). The film ( 8 ) incorporates a hydride which is arranged to generate hydrogen on contact with moisture. Additionally, the film ( 8 ) is arranged to have relatively high water vapour permeability and relatively low hydrogen gas permeability. In use, water vapour from air surrounding the container ( 2 ) passes into the film ( 8 ) and reacts with the hydride to generate hydrogen. Due to the relatively low hydrogen permeability of the film ( 8 ), the hydrogen is restricted from escaping from the container. Instead, the hydrogen then reacts with any oxygen within the container in a reaction catalysed by a catalyst also associated with the film closure ( 8 ), thereby to scavenge oxygen within the container ( 2 ) and protect the food ( 6 ) from oxidation.
1. An assembly comprising a film closure, the film closure comprising: a high water permeability region comprised of a first thin layer having a relatively high water vapour permeability and being arranged to allow water to pass through in a direction towards a hydrogen generating means, wherein said hydrogen generating means comprises a second thin layer which is arranged downstream of the first thin layer, the second thin layer being arranged to generate hydrogen after contact with water which has passed through said high water permeability region, said assembly further comprising a catalyst disposed in a third thin layer downstream of the second thin layer for catalyzing a reaction between said hydrogen and molecular oxygen, and wherein said assembly contains a relatively dry packaged material.
2. An assembly according to claim 1 , wherein said dry material is a material which, when in equilibrium in a sealed environment, exhibits a relative humidity measured at 25° C. and 1 atm, of less than 40%.
3. An assembly according to claim 1 , wherein said assembly defines an enclosed space, downstream of the high water permeability region, and the atmosphere in the space has a mixing ratio at Standard Ambient Temperature and Pressure of less than 2 g/Kg.
4. An assembly according to claim 1 , wherein said high water permeability region suitably has a water vapour permeability of more than 0.02 g-mm/m 2 -day and less than 5 g-mm/m 2 -day.
5. An assembly according to claim 1 , wherein said high water permeability region has a hydrogen permeability of less than 50 cc-mm/m 2 -atm-day.
6. An assembly according to claim 1 , wherein the Water Permeability Ratio (WPA) is defined as
WPA
=
outer
surface
area
(
m
2
)
of
assembly
defined
by
said
high
water
permeability
region
total
outer
surface
area
(
m
2
)
of
assembly
and said WPA is in the range of 0.9 to 0.001.
7. An assembly according to claim 1 , wherein said hydrogen generating means comprises an active material arranged to generate molecular hydrogen on reaction with moisture.
8. An assembly according to claim 7 , wherein said hydrogen generating means comprises a matrix with which said active material is dispersed, wherein said matrix comprises a polymeric matrix material.
9. An assembly according to claim 8 , wherein said polymeric matrix material is selected from the group comprising ethylene vinyl acetate, styrene-ethylene-butylene (SEBS) copolymers, Nylon 6, styrene, styrene-acrylate copolymers, polybutylene terephthalate, polyethylene terephthalate, polyethylene, and polypropylene.
10. An assembly according to claim 7 , wherein said active material comprises a metal and/or a hydride.
11. An assembly according to claim 1 , wherein the first and second thin layers are part of a fluid control structure and wherein said thin layers are secured relative to one another, optionally with an intermediate layer positioned therebetween.
12. An assembly according to claim 11 , wherein at least part of said fluid control structure is removable to provide access to the dry material.
13. An assembly according to claim 11 , wherein said fluid control structure is a component of a lidding foil of a package defined by said assembly.
14. An assembly according to claim 1 , wherein said high water permeability region is movable to provide access to the dry material.
15. A method of protecting a relatively dry packaged material from damage caused by contact with oxygen, the method comprising:
(i) selecting a relatively dry material;
(ii) arranging said relatively dry material within a confined and/or enclosed space thereby to define an assembly;
(iii) wherein said assembly comprises a film closure, the film closure comprising: a high water permeability region comprised of a first thin layer having a relatively high water vapour permeability and being arranged to allow water to pass through in a direction towards a hydrogen generating means, wherein said hydrogen generating means comprises a second thin layer which is arranged downstream of the first thin layer, the second thin layer being arranged to generate hydrogen after contact with water which has passed through said high water permeability region, said assembly further comprising a catalyst disposed in a third thin layer downstream of the second thin layer for catalyzing a reaction between said hydrogen and molecular oxygen.
16. A method of making the assembly described in claim 1 , the method comprising:
(i) selecting a relatively dry material;
(ii) arranging said relatively dry material within a confined and/or enclosed space thereby to define an assembly;
(iii) wherein said assembly comprises a film closure, the film closure comprising: a high water permeability region comprised of a first thin layer having a relatively high water vapour permeability and being arranged to allow water to pass through in a direction towards a hydrogen generating means, wherein said hydrogen generating means comprises a second thin layer which is arranged downstream of the first thin layer, the second thin layer being arranged to generate hydrogen after contact with water which has passed through said high water permeability region, said assembly further comprising a catalyst disposed in a third thin layer downstream of the second thin layer for catalyzing a reaction between said hydrogen and molecular oxygen.