CONTAINER FOR LIQUID CONTAINING FOOD PRODUCTS

Abstract

The present invention relates to a container for liquid containing food products, manufactured by press forming of a polymer coated fiber based substrate, said container comprising a bottom portion, a sidewall portion and a top flange portion, wherein said press forming has resulted in the formation a plurality of creases extending in a direction from the bottom portion to the top flange portion and further across the top flange portion. The container comprises an indentation pattern (130, 140, 150, 160, 170, 180, 190a, 190b, 200) formed at a creased inner surface of said sidewall portion and/or at a creased top surface of said top flange portion, said indentation pattern preventing migration of liquid from a liquid containing food product in the container along said creases. The invention relates also to a method for manufacturing such container.

Claims

1. A container for liquid containing food products, manufactured by press forming of a polymer coated fiber based substrate, said container comprising: a bottom portion, a sidewall portion, and a top flange portion, wherein said press forming forms a plurality of creases extending in a direction from the bottom portion to the top flange portion and further across the top flange portion, and wherein the container comprises an indentation pattern formed at a creased inner surface of said sidewall portion, at a creased top surface of said top flange portion, or at both, and said indentation pattern preventing migration of liquid from a liquid containing food product in the container along said creases.

2. The container according to claim 1, wherein said indentation pattern comprises one or more indentations on the creased inner surface.

3. The container according to claim 1, wherein said indentations have a width in the range of 0.1-1 mm.

4. The container according to claim 1, wherein said indentations have a depth in the range of 0.05-1 mm.

5. The container according to claim 1, wherein a distance between two adjacent indentations is in a range of 0.5-5 mm.

6. The container according to claim 1, wherein at least one of said indentations is positioned at a topmost half of the sidewall portion.

7. The container according to claim 1, wherein at least one of said indentations is positioned at a top surface of the top flange portion.

8. The container according to claim 1, wherein said indentation pattern comprises a pattern of discrete indentations having a length of less than 10 mm.

9. The container according to claim 1, wherein said indentation pattern comprises an indentation in the form of a groove traversing said creases.

10. The container according to claim 9, wherein said indentation pattern comprises at least two parallel grooves.

11. The container according to claim 9, wherein said the groove extends entirely around the sidewall portion of the container.

12. The container according to claim 9, wherein the groove extends entirely around the top flange portion.

13. The container according to claim 1 wherein said indentation pattern is formed during or after press forming of the polymer coated fiber based substrate.

14. The container according to claim 1, wherein a polymer coating of the polymer coated fiber based substrate comprises one or more of: polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polylactic acid (PLA).

15. The container according to claim 1, wherein the barrier and sealing properties of the polymer coating is intact after forming of the indentation pattern.

16. A method for manufacturing a container for liquid containing food products, the method comprising the steps: a) press forming a polymer coated fiber based substrate to obtain a container comprising a bottom portion, a sidewall portion, and a top flange portion, wherein said press forming forms a plurality of creases extending in a direction from the bottom portion to the top flange portion and further across the top flange portion; and b) forming an indentation pattern at a creased inner surface of said sidewall portion, at a creased top surface of said top flange portion, or both wherein said indentation pattern prevents migration of liquid from a liquid containing food product in the container along said creases.

17. The method according to claim 16, wherein the indentation pattern in step b) is formed simultaneously with the press forming in step a).

18. The method according to claim 16, wherein the indentation pattern in step b) is formed as a separate step after the press forming in step a).

19. The method according to claim 16, wherein the indentation pattern formed comprises: a width in the range of 0.1-1 mm; or a depth in the range of 0.05-1 mm; or a distance between two adjacent indentations in a range of 0.5-5 mm; or at least one of said indentations is positioned at a topmost half of the sidewall portion; or at least one of said indentations is positioned at a top surface of the top flange portion; or a pattern of discrete indentations having a length of less than 10 mm; or an indentation in the form of a groove traversing said creases; or at least two parallel grooves; or any combination of the foregoing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 depicts a prior art press formed container in the form of a rectangular tray having rounded corners.

[0053] FIG. 2a-2c depict a corner section with discrete indentations according to embodiments of the invention.

[0054] FIG. 3a-3c depict a corner section with indentations in the form of grooves according to embodiments of the invention.

[0055] FIG. 4a-4b depict a corner section with indentations in the form of grooves according to embodiments of the invention.

[0056] FIG. 5 is a diagram of liquid rise times for different embodiments of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0057] The invention will now be described more in detail with reference to specific embodiments, wherein the container is in the form of a rectangular tray having rounded corners. Alternative embodiments of the tray may be circular, or may have a different number of sidewalls, such as a pentagonal, hexagonal or octagonal tray.

[0058] FIG. 1 depicts a prior art press formed container, in the form of a tray 100. The tray 100 is rectangular in shape, has a bottom portion 102, a first and second major sidewall 104a, 104b and a first and second minor sidewall 106a, 106b. In this embodiment, each sidewall is joined to another by a corner 108 that is generally pleated, or folded, as shown in FIG. 1.

[0059] The tray 100 is made from fiber based substrate material, typically a paperboard or a paperboard substitute, such as a bleached, unbleached, or recycled cellulose pulp molded fiber matrix. The fiber based substrate is coated, at least on the surface of the substrate which will form the inside of the container, with a heat sealable thermoplastic polymer. In alternate embodiments, the substrate may further include additional or different materials to form the tray 100, such as metal foil, paper, plastic, and so forth.

[0060] The tray body and top flange are formed from a single piece of substrate material. Within the context of this document, the phrase a “single piece of material” includes a single piece of material that comprises a single layer or multiple layers of the same material or multiple layers of different materials. These multi-layered materials could include, for example, layers of two or more paper and/or paperboard substrates completely bonded together and/or partially bonded together, such as a corrugated board material, with or without any other layer or layers of any other materials such as metal, foil, plastic, and so forth. Thus, laminates formed from two or more differing types of material are nonetheless encompassed by the phrase a “single piece of material”.

[0061] As mentioned, the tray 100 has a top flange 110 protruding outwardly from the sidewalls to mate with a lid or sealing film. Generally, when the material is formed into the flange, no portion of the flange extends into the interior of the tray. Rather, the flange 110 protrudes outwardly from the tray sidewalls as shown in, for example, FIG. 1. Alternative embodiments may have the flange extending at a different angle from the sidewalls, such as at a forty-five degree angle to or flush with the sidewalls.

[0062] In the rectangular tray 100 depicted in FIG. 1, the top flange 110 comprises major sidewall flanges 112a, 112b, minor sidewall flanges 114a, 114b, and corner flanges 116. The term corner flange refers to those portions of the top flange that extend radially outwardly from each corner 108 of the tray 100, while the term sidewall flange refers to the portions of the top flange extending outwardly from each tray sidewall. It should be understood that these terms merely refer to different portions of what is generally a unitary flange. It should be further understood that the press formed top flange 110 and tray 100 are typically formed from a continuous piece of substrate material.

[0063] FIG. 1 shows creases 120 inherently formed by folds and pleats in a press formed tray that result in an uneven surface of the corners 108 and corner flanges 116 of the tray 100. The corners 108 of the tray, 100 and thus the corner flanges 116, are pleated or folded as a byproduct of being press formed, whereas the sidewalls and sidewall flanges are smooth. The pleating or folding of material to form a corner flange typically results in irregular or nonplanar upper and lower surfaces of the corners 108 and corner flanges 116. The folds and pleats result in the formation a plurality of creases 120 extending substantially radially in a direction from a bottom portion 102 of the container to the top flange 110 and further across the top flange. As layers of material often overlap at each corner, the corners 108 typically have a greater cross-sectional thickness than the sidewalls. The same is true for the corner flanges 116 when compared to the sidewall flanges.

[0064] When liquid containing food products are packaged, some of the ingredients of the product may spread or splash on the surfaces of the package for which they are not desired. This is most likely to take place in filling and baking phases of the packaging chain. Oil or grease has also a tendency to rise/climb along the wall of the packages. Especially oil and grease-like food ingredients cause problems in the closure of packages when a lid or sealing film is glued or heat sealed to the top flange.

[0065] The uneven surfaces make it difficult to achieve a hermetic seal around, for example, the corners of the top flange 110. Possible oil or grease contamination of the top flange surfaces makes sealing even more difficult and unpredictable.

[0066] Oil or grease can rise/climb along the wall of the packages due to the capillary phenomenon. This is particularly emphasized in the walls or corners of the packages with creases extending radially in a direction from a bottom portion of the container to the top flange 110 and further across the top flange.

[0067] The irregularities or creases created within the pleated corners and corner flanges are easily seen on the press formed tray. The creases 120 may be of varying widths, depths, and so forth. Each tray is unique in its irregularities.

[0068] The inventive containers comprise an indentation pattern formed at a creased inner surface of said sidewall portion and/or at a creased top surface of said top flange portion. The indentation pattern prevents migration of liquid from a liquid containing food product in the container along said creases.

[0069] The indentation pattern typically comprises one or more indentations on the creased inner surface of the container. The indentations are typically formed by mechanical modification, e.g. molding or debossing, of the surface of the substrate during or after press forming of the polymer coated fiber based substrate.

[0070] The indentation pattern can be provided in many different forms. For example, the indentation pattern can comprise a pattern of discrete indentations interrupting the crease pattern on the inner surface of the container, or it can comprise one or more grooves traversing the creases and causing transport of liquids away from the creases.

[0071] FIG. 2a shows an embodiment of the invention, where the indentation pattern is in the form of a pattern of discrete indentations. The discrete indentations are in the form of short grooves 130 arranged in parallel lines from the bottom to the top of the sidewall portion, parallel to the creases. Each discrete indentation has a length of about 3 mm, a width of about 0.5 mm, and a depth of about 0.1 mm. The distance between two adjacent indentations is about 2 mm.

[0072] FIG. 2b shows another embodiment of the invention, where the indentation pattern is in the form of pattern of discrete indentations. The pattern is similar to the pattern in FIG. 2a, with the difference that the discrete indentations, in the form of short grooves 140, of adjacent parallel lines are displaced. The discrete indentations are in the form of short grooves, each having a length of about 3 mm, a width of about 0.5 mm, and a depth of about 0.1 mm. The distance between two adjacent indentations is about 2 mm.

[0073] FIG. 2c shows another embodiment of the invention, where the indentation pattern is in the form of pattern of discrete indentations. The pattern is similar to the pattern in FIG. 2b, with the difference that the discrete indentations, in the form of short grooves 150, are tilted at an angle of about 45 degrees in relation to the parallel lines. The discrete indentations are in the form of short grooves, each having a length of about 3 mm, a width of about 0.5 mm, and a depth of about 0.1 mm. The distance between two adjacent indentations is about 2 mm.

[0074] In some embodiments of the inventive containers, one or more grooves are formed at an inner surface of the sidewall portion and/or at a top surface of the top flange portion, said grooves extending substantially transversely across the creases formed in the press forming operation. The grooves interrupt the creases, thereby preventing migration of liquid from a liquid containing food product in the container along said creases. This way, the spreading or migration of liquid from a liquid containing food product to a sealing surface of the container can be prevented or reduced.

[0075] FIG. 3a shows an embodiment of the invention, where the indentation pattern is in the form of a groove 160 extending transversely across the creases in the creased inner surface near the top of the sidewall portion. The groove has a length of about 50 mm, a width of about 0.7 mm, and a depth of about 0.2 mm.

[0076] FIG. 3b shows an embodiment of the invention, where the indentation pattern is in the form of a groove 170 extending transversely across the creases in the creased top surface of the top flange portion. The groove has a length of about 50 mm, a width of about 0.7 mm, and a depth of about 0.2 mm.

[0077] FIG. 3c shows an embodiment of the invention, where the indentation pattern is in the form of a plurality of parallel grooves 180 extending transversely across the creases in the creased inner surface of the sidewall portion. The indentation pattern comprises six parallel grooves distributed from the bottom to the top of the sidewall portion, perpendicular to the creases. The grooves have a length of about 50 mm, a width of about 0.7 mm, and a depth of about 0.2 mm. The distance between two adjacent grooves is about 5 mm.

[0078] FIG. 4a shows an embodiment of the invention, where a plurality of grooves 190a is formed at an inner surface of a sidewall portion, and a plurality of grooves 190b is formed at the top surface of the top flange portion. The grooves have a width of about 0.7 mm and a depth of about 0.2 mm. The distance between two adjacent grooves is about 5 mm at the inner surface of the sidewall portion and about 2 mm at the top surface of the top flange portion. The grooves formed at the top surface of the top flange portion extend in parallel around the entire top flange portion of the container. The plurality of grooves prevents the spreading or migration of liquid from a liquid containing food product inside the container across the sealing surface of the top flange. The grooves formed at the inner surface of the sidewall portion extend in parallel around the entire sidewall portion of the container. The plurality of grooves prevents the spreading or migration of liquid from a liquid containing food product inside the container up towards the top flange. FIG. 4b shows an embodiment of the invention, where a plurality of grooves 200 is formed at the top surface of the top flange portion only.

[0079] The grooves extend in parallel around the entire top flange portion of the container. The grooves have a width of about 0.7 mm and a depth of about 0.2 mm. The distance between two adjacent grooves is about 2 mm. The plurality of grooves prevents the spreading or migration of liquid from a liquid containing food product inside the container across the sealing surface of the top flange. Droplets of liquid accidentally spilled on the top flange may also be contained in an area delimited by the grooves, and thereby prevented from spreading further over the top flange surface.

[0080] The indentation pattern, or grooves, are preferably formed by mechanical modification, e.g. molding or debossing, of the surface of the substrate by pressing it with a set of tools used in tray pressing. A negative of the desired pattern is integrated to the tool surface. The patterning tools (in micro- and macroscale) can be manufactured with various methods, including precision machining, electro erosion, laser engraving, etching, and 3D-printing. The transferability of the pattern can be adjusted by pressing force and tool temperatures. The mechanical surface modification can be done in conjunction with the actual press forming process or as a separate process cycle. The patterning method can advantageously be introduced into an existing converting machine by replacement of the forming tool.

[0081] While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention.

[0082] In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

EXAMPLE

[0083] Containers in the form of a rectangular trays having rounded corners (GN¼ trays) were prepared from polyethylene terephthalate (PET) coated paperboard by press forming. Press forming resulted in the formation of a set of creases at each corner of the tray. Different indentations patterns were imprinted in the creased inside surface of the tray using a negative of the desired pattern is integrated in the press forming tool surface. In one case, the pattern was instead imprinted on the finished tray using a sheet metal beading machine. A conventional unimprinted tray was used as reference.

Sample 1:

[0084] Indentation pattern as described with reference to FIG. 2a imprinted in the press forming tool. Discrete indentations with regular intervals in parallel lines.

[0085] Sample 2:

[0086] Indentation pattern as described with reference to FIG. 2b imprinted in the press forming tool. Discrete indentations with regular intervals in parallel lines. Discrete indentations of adjacent parallel lines are displaced.

[0087] Sample 3:

[0088] Indentation pattern as described with reference to FIG. 2c imprinted in the press forming tool. Discrete indentations with regular intervals in parallel lines. Discrete indentations of adjacent parallel lines are displaced. The discrete indentations are tilted at an angle of about 45 degrees in relation to the parallel lines.

[0089] Sample 4:

[0090] Indentation pattern as described with reference to FIG. 3c imprinted in the press forming tool. The indentation pattern comprises six parallel grooves distributed from the bottom to the top of the sidewall portion, perpendicular to the creases.

[0091] Sample 5:

[0092] Same as Sample 4 but imprinted on the finished tray using a sheet metal beading machine.

[0093] Sample 6:

[0094] A conventional unimprinted tray as described with reference to FIG. 1 was used as reference.

[0095] Rise time was evaluated by pouring 250 ml of a test liquid (Caj P original barbeque rapeseed oil) into the bottom of the tray and. The pathways of the liquid rising from the bottom towards the top of the creased sidewall was observed visually and the time at which the liquid reached the flange portion was measured. The results of the measurements are presented in FIG. 5. The results show that an indentation pattern can be used to significantly reduce the liquid rising. In practice, this may allow long enough time between tray filling and sealing to achieve adequate lid sealing without problems caused by contamination of the sealing surface.