A blank to be folded into a retortable package

Abstract

A blank (100) configured to be folded into a retortable package (200) is disclosed. The blank (100) is made of a multilayer packaging material (101) comprising an outer protective layer (300), a fiber-based mid-layer (302), and an inner protective layer (304). A first set of perforations (102) is provided in a top section (109) as tear- guiding perforations to facilitate opening. A second set of perforations (104a-e) extends through the outer protective layer (300) into or in contact with the fiber-based mid-layer (302) and is provided in at least one of a covering section (110c), a covered section (112c), a second covering section (115c), or a second covered section (116c). A web (702) comprising multiple blanks and a method (600) for producing a package from the blank are also disclosed.

Description

[0001] A BLANK TO BE FOLDED INTO A RETORT ABLE PACKAGE

[0002] Technical Field

[0003] The invention relates to packaging technology, and more particularly to fiberbased, heat-treatable packages, blanks made of multilayer packaging material, and methods for producing such blanks and forming packages therefrom.

[0004] Background

[0005] Carton-based packages are increasingly used as alternatives to tin cans for food packaging. One reason for this shift is the improved environmental profile of carton-based packages. Another advantage is that such packages can be folded flat after use, optimizing waste management and recycling.

[0006] For long shelf life applications (typically exceeding one year), it is common practice to retort the filled packages. By subjecting both the package and the food content to heat treatment, microorganisms that could otherwise spoil the food are eliminated. An example of such a carton-based retortable package is Tetra Recart®, marketed by Tetra Pak®.

[0007] During retorting, the packages may be exposed to steam, hot water, and cold water. To ensure that the package withstands these conditions, the packaging material typically comprises multiple layers with distinct functional properties. For instance, inner and outer polymer-based protective layers shield the fiber-based mid-layer, ensuring structural integrity during the heat treatment.

[0008] While current multilayer packaging materials used for heat-treatable packages (e.g., packages processed in a retort apparatus, also referred to as an autoclave) provide the necessary mechanical and barrier properties, occasional failures may still occur. In some cases, water absorption during the heat treatment process negatively affects the package’s robustness and stiffness.

[0009] Currently, water absorption issues are mitigated by adjusting the heat treatment program to allow sufficient drying time, thereby reducing moisture retention in the packaging material. Additionally, packages may be placed on racks with increased spacing to facilitate water drainage and drying.

[0010] Even though existing solutions help prevent moisture-related degradation, there remains a need to further reduce the risk of packaging failures caused by water absorption. By optimizing the package design, particularly the blank configuration and the arrangement of structural features such as perforations and crease lines, thenumber of faulty packages resulting from retorting or similar heat-treatment processes can be significantly reduced.

[0011] Summary

[0012] It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to reduce the risk of water absorption by the fiber-based mid-layer of the multilayer packaging material, which can otherwise lead to packages failing to meet quality standards due to reduced robustness and stiffness.

[0013] One or more of these objectives, along with additional benefits that will become apparent from the description below, are at least partly achieved by a blank configured to be folded into a retortable package, a web comprising multiple such blanks, and a method for producing a package filled with a food product, as defined by the independent claims, with further embodiments specified in the dependent claims.

[0014] It has been found that by providing two separate, spaced-apart sets of perforations, the risk of water entering the fiber-based mid-layer can be significantly reduced. During processes such as cooling after heat treatment, a pressure difference between the internal pressure of the package and the external pressure in the heat treatment apparatus may cause air to flow through the perforations. If not properly controlled, this airflow can draw water into the fiber-based mid-layer, leading to moisture retention and structural degradation.

[0015] To mitigate this effect, the second set of perforations extends through the outer protective layer into or in contact with the fiber-based mid-layer. These perforations are positioned in covering and / or covered sections of the package, which are formed when the blank is folded and sealed. By locating the second set of perforations in these sections, they are shielded from direct exposure to external moisture, such as water droplets or steam present in the retort environment. Since these sections are typically folded against each other, the perforations remain protected within overlapping material layers, reducing the risk of direct water penetration.

[0016] At the same time, when the package cools after retorting, these protected perforations allow controlled airflow into the fiber-based mid-layer. This equalizes pressure differences between the inside of the package and the external environment, preventing the vacuum effect that could otherwise draw water into the fiber-based structure. As a result, the fiber-based material remains dry and maintains its mechanical properties, ultimately reducing the occurrence of defective packages.Furthermore, the design and placement of the perforations, including their alignment with crease lines, their spacing, and their extension in a straight line or parallel direction, further enhance packaging integrity and prevent excessive moisture penetration.

[0017] Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.

[0018] Drawings

[0019] Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which:

[0020] FIG. 1 illustrates a blank configured to be folded into a retortable package. FIG. 2 is a perspective view of the retortable package.

[0021] FIG. 3 is a cross-sectional view of the multilayer packaging material forming the blank illustrated in FIG. 1.

[0022] FIG. 4 is a side view of a retort apparatus and multiple packages placed on a rack during heat treatment.

[0023] FIG. 5 is a flowchart illustrating a method for producing the blank illustrated in FIG. 1.

[0024] FIG. 6 is a flowchart illustrating a method for producing the package of FIG. 2, filled with a food product.

[0025] FIG. 7 schematically illustrates a system for producing the blank illustrated in FIG. 1.

[0026] FIG. 1 illustrates a blank 100 configured to be folded into a retortable package 200 (see FIG. 2). The blank 100 is made of a multilayer packaging material 101 (see FIG. 3), comprising an outer protective layer 300, a fiber-based mid-layer 302, and an inner protective layer 304. The blank 100 includes a main section 113, a top section 109, and a bottom section 114, which together define the main body 200a, the top portion 200b, and the bottom portion 200c of the package when the blank 100 is folded into the package 200.

[0027] The main section 113 of the blank 100 comprises a front section 122, a back section 118, and two side sections 120a and 120b. Near its edges, the main section 113 includes sealing sections, as is commonly known for the type of blank and package described herein. These sealing sections facilitate the formation of a sealed and structurally stable package when the blank 100 is folded and assembled. Theblank 100 is formed into a package 200 using conventional, known techniques, which may include folding, sealing, and filling processes typically employed in the production of fiber-based, heat-treatable packaging.

[0028] The top section 109 comprises a top panel section 112 and a top fin section 110, which is arranged to be folded towards the top panel section 112 for sealing the package. The top fin section 110 includes a covering section 110c, which is arranged to overlay a covered section 112c of the top panel section 112 when the blank 100 is folded into the package 200.

[0029] The bottom section 114 comprises a bottom panel section 116 and a bottom fin section 115, which is arranged to be folded towards the bottom panel section 116 for sealing the package. The bottom fin section 115 includes a covering section 115c, which is arranged to overlay a covered section 116c of the bottom panel section 116 when the blank 100 is folded into the package.

[0030] A first set of perforations 102 extends through the outer protective layer 300 into the fiber-based mid-layer 302 and is provided in the top section 109. The first set of perforations 102 is configured as tear-guiding perforations, facilitating the opening of the package made from the blank 100.

[0031] A second set of perforations 104a-e extends through the outer protective layer 300 into or in contact with the fiber-based mid-layer 302. The second set of perforations 104a-e is provided in at least one of the covering section 110c of the top fin section 110, the covered section 112c of the top panel section 112, the covering section 115c of the bottom fin section 115, and the covered section 116c of the bottom panel section 116.

[0032] The shadowed sections in FIG. 1 indicate sections of the blank 100 that are either covering sections or covered sections. These shadowed sections correspond to areas of the blank 100 that will not be visible once the blank 100 is folded into the package 200. Since these sections are folded against each other, they protect the perforations from direct exposure to external moisture, such as water droplets or steam during heat treatment. This design reduces the risk of water absorption into the fiberbased mid-layer 302, ensuring that the package maintains its mechanical integrity and barrier properties after retorting.

[0033] The second set of perforations 104a-e may extend in a direction D1 that is substantially parallel to the direction in which the first set of perforations 102 extends. D1 typically extends in a direction that is parallel to the top edge and bottom edge 13. This alignment ensures that tearing and pressure equalization occur in a controlled manner, preventing unintended rupturing of the package.All perforations of the second set 104a-e may extend in a straight line, as shown in FIG. 1. This linear arrangement helps prevent stress concentrations, ensuring that the perforations do not weaken the packaging material unpredictably while still allowing controlled airflow into the fiber-based mid-layer 302 during cooling.

[0034] The second set of perforations 104a-e may be entirely located within the covering section 110c of the top fin section 110, the covered section 112c of the top panel section 112, the covering section 115c of the bottom fin section 115, and / or the covered section 116c of the bottom panel section 116. This placement ensures that the perforations are shielded from direct water exposure during retorting, further reducing the risk of water absorption into the fiber-based mid-layer 302.

[0035] The blank 100 includes four elongated crease lines 113a-d, extending in direction D2 from the bottom edge 13 to the top edge 14. These crease lines 113a-d facilitate folding of the blank 100 to form the side corners of the package 200. The second set of perforations 104a-e extends between two neighboring crease lines 113b and 113c, ensuring that the perforations are positioned in structurally reinforced areas, preventing unintended package deformation. In one embodiment, the second set of perforations 104a-e does not extend outside the two neighboring crease lines 113b and 113c. The direction D2 is typically parallel to the first side edge 11 and the second side edge 12.

[0036] The blank 100 also comprises a bottom edge 13, a top edge 14, a first side edge 11 , and a second side edge 12. It further includes a top fin crease line 15a, a top section crease line 15b, a bottom section crease line 15c, and a bottom fin crease line 15d, all extending in direction D1 from the first side edge 11 to the second side edge 12. These crease lines facilitate the folding process, ensuring proper formation of the top fin, the top portion 200b, the bottom portion 200c, and the bottom fin of the package.

[0037] The package 200 comprises two upper flaps and two lower flaps, which are formed by folding specific sections of the blank 100. The upper flaps are folded down onto the side panels 120a and 120b, providing additional sealing and structural integrity to the top portion 200b of the package. Item 128 in FIG. 1 illustrates the section of the blank 100 that forms one of these upper flaps. When the blank 100 is folded into the package 200, the upper flaps help maintaining the shape of the package and supports secure sealing.

[0038] Similarly, the package 200 includes two lower flaps, which are folded down onto the bottom of the package. These lower flaps contribute to the structural stability of the bottom portion 200c and help ensure that the package remains robust. Item 124 in FIG.1 illustrates the section of the blank 100 that forms one of these lower flaps. When folded, the lower flaps provide help maintaining the shape of the package and supports secure sealing.

[0039] The second set of perforations 104b may be located between the top edge 14 and the first set of perforations 102, allowing for controlled air release during cooling and reducing the risk of water entering the fiber-based mid-layer 302.

[0040] The second set of perforations 104a may be positioned between the first set of perforations 102 and the top fin crease line 15a. This placement may ensure that air can escape before the package is fully sealed, preventing internal pressure buildup that could cause packaging deformation.

[0041] The second set of perforations 104c may be provided between the top fin crease line 15a and the top section crease line 15b. This location may help control airflow during cooling, ensuring that the fiber-based mid-layer 302 is protected from moisture uptake while equalizing pressure differences.

[0042] The second set of perforations 104e may be located between the bottom section crease line 15c and the bottom fin crease line 15d. This placement may allow air trapped near the bottom of the package to escape in a controlled manner, reducing vacuum effects that could lead to moisture ingress.

[0043] Additionally, the second set of perforations 104d may be positioned between the bottom fin crease line 15d and the bottom edge 13. This placement may ensure that air pockets near the bottom fin can be vented, preventing undesired pressure differences during cooling.

[0044] Each of these alternative placements for the second set of perforations may be implemented independently or in any combination with one another, depending on the desired function and the specific requirements of the package design. The second set of perforations may be provided at a single location, at multiple locations, or at all of the locations described above. The use of multiple perforation placements may enhance airflow regulation, facilitate controlled pressure equalization, and further reduce the risk of water ingress into the fiber-based mid-layer 302. By providing flexibility in perforation placement, the design allows for optimized performance based on the specific needs of the packaging material, the food product being packaged, and the heat treatment conditions applied during processing.

[0045] By integrating strategically placed perforations, crease lines, and protected sections, the blank 100 ensures structural integrity, controlled airflow, and protection from moisture ingress during retorting. The covering and covered sections shield the perforations, while the placement of the second set of perforations mitigates vacuumeffects during cooling, reducing the risk of water absorption into the fiber-based midlayer 302. These features collectively enhance package durability, quality, and performance in high-humidity, high-temperature environments.

[0046] In FIG. 1 , the top fin section 110 is further subdivided into four subsections indicated by reference numerals 110a, 110b, 110c, and 110d. These subsections represent respective sections of the fin geometry that form different parts of the package after the blank 100 has been folded and sealed. The subsections 110a— 110d correspond to subsections that are commonly used for similar blanks that are used in the industry. The third section 110c is also referred to as the covering section 110c of the top fin section 110.

[0047] The first section 110a and the second section 110b are separated by the elongated crease line 113a. The second section 110b and the third section 110c are separated by the elongated crease line 113b. The third section 110c and the fourth section 110d are separated by the elongated crease line 113c. When the blank 100 is viewed in direction D1 , the third subsection 110c is located between the second subsection 110b and the fourth subsection 110d.

[0048] When the blank 100 is viewed in direction D2, the subsections 110a-110d of the top fin section 110 are aligned with corresponding regions of the main section 113. More specifically, the first subsection 110a is aligned with the back section 118; the second subsection 110b is aligned with the side section 120a; the third subsection 110c is aligned with the front-panel section 122; and the fourth subsection 110d is aligned with the side section 120b.

[0049] The top panel section 112 is further subdivided into four subsections indicated by reference numerals 112a, 112b, 112c, and 112d. These subsections represent respective sections of the top panel geometry that form different parts of the package after the blank 100 has been folded and sealed. The subsections 112a— 112d also correspond to subsections that are commonly used in the industry for similar types of blanks. The third section 112c is also referred to as the covered section 112c of the top panel section 112.

[0050] The first section 112a and the second section 112b are separated by the elongated crease line 113a. The second section 112b and the third section 112c are separated by the elongated crease line 113b. The third section 112c and the fourth section 112d are separated by the elongated crease line 113c. When the blank 100 is viewed in direction D1 , the third subsection 112c is located between the second subsection 112b and the fourth subsection 112d.When the blank 100 is viewed in direction D2, the subsections 112a-112d of the top panel section 112 are positioned such that they lie intermediate the main section 113 and the top fin section 110. More specifically, subsection 112a is located between the back section 118 and subsection 110a; subsection 112b is located between the side section 120a and subsection 110b; subsection 112c is located between the front-panel section 122 and subsection 110c; and subsection 112d is located between the side section 120b and subsection 110d.

[0051] The bottom fin section 115 is further subdivided into four subsections indicated by reference numerals 115a, 115b, 115c, and 115d. These subsections represent respective sections of the bottom fin geometry that form different parts of the bottom closure of the package after the blank 100 has been folded and sealed. The subsections 115a-115d correspond to subsections commonly used for similar blanks in the industry. The third section 115c is also referred to as the covering section 115c of the bottom fin section 115.

[0052] The first section 115a and the second section 115b are separated by the elongated crease line 113a. The second section 115b and the third section 115c are separated by the elongated crease line 113b. The third section 115c and the fourth section 115d are separated by the elongated crease line 113c.

[0053] When the blank 100 is viewed in direction D1 , the third subsection 115c is located between the second subsection 115b and the fourth subsection 115d, corresponding to the physical sequence of the bottom fin subsections along direction D1.

[0054] When the blank 100 is viewed in direction D2, the subsections 115a-115d of the bottom fin section 115 are aligned with corresponding regions of the main section 113. More specifically, subsection 115a is aligned with the back section 118; subsection 115b is aligned with the side section 120a; subsection 115c is aligned with the lower-panel region that corresponds to the front-panel section 122; and subsection 115d is aligned with the side section 120b.

[0055] The bottom panel section 116 is further subdivided into four subsections indicated by reference numerals 116a, 116b, 116c, and 116d. These subsections represent respective sections of the bottom panel geometry that form the lower wall of the package after the blank 100 has been folded and sealed. The subsections 116a-116d correspond to subsections used in similar industry blanks. The third section 116c is also referred to as the covered section 116c of the bottom panel section 116.

[0056] The first section 116a and the second section 116b are separated by the elongated crease line 113a. The second section 116b and the third section 116c areseparated by the elongated crease line 113b. The third section 116c and the fourth section 116d are separated by the elongated crease line 113c.

[0057] When the blank 100 is viewed in direction D1, the third subsection 116c is located between the second subsection 116b and the fourth subsection 116d, consistent with the arrangement of the corresponding fin subsections.

[0058] When the blank 100 is viewed in direction D2, the subsections 116a-116d of the bottom panel section 116 are positioned such that they lie intermediate the main section 113 and the bottom fin section 115. More specifically, subsection 116a is located between the back section 118 and subsection 115a; subsection 116b is located between the side section 120a and subsection 115b; subsection 116c is located between the lower-panel region corresponding to the front-panel section 122 and subsection 115c; and subsection 116d is located between the side section 120b and subsection 115d.

[0059] In one embodiment, the second set of perforations 104a-104e is arranged as a consecutive pattern of perforations, extending in an uninterrupted sequence along a linear direction, such along direction D1.

[0060] The perforations of the second set may be positioned at regular intervals such that the pattern forms a regular and repeating perforation sequence across the corresponding covering or covered section.

[0061] In some embodiments, the second set of perforations is formed as a substantially uniform row of perforations, wherein the spacing between neighbouring perforations does not vary beyond normal manufacturing tolerances. In such embodiments, the pattern exhibits no irregular interruptions, meaning that there are no gaps, discontinuities, or locally omitted perforations within the sequence that would otherwise disrupt the continuity of the pattern.

[0062] In one embodiment, the second set of perforations 104a-104e does not extend across the full width of the blank 100.

[0063] In one embodiment, the second set of perforations 104a-104e does not have the shape of a consecutive line that extends across the full width of the blank 100.

[0064] In one embodiment, the second set of perforations 104a-104e is limited to extend between the crease lines 113a and 113d.

[0065] In one embodiment, the second set of perforations 104a-104e is limited to extend between the crease lines 113b and 113c.

[0066] In one embodiment, for all these limitations in extensions (the limitations described above), further secondary perforations may still be present outside the perforations 104a-104e, but such perforations do not form a consecutive, uninterruptedset of perforations that aligns with the perforations 104a-104e. As used herein, “aligns with the perforations” may be understood as linearly aligned, i.e., forming a consecutive line of perforations.

[0067] The perforations 104a-104e may be arranged to extend linearly in direction D1. The blank 100 has a width W that extends from the first side edge 11 to the second side edge 12 in direction D1. The width W may be measured parallel to the bottom edge 13 and the top edge 14. The width may be defined as the length of either the bottom edge 13, the top edge 14, or both.

[0068] The second set of perforations may be provided in at least one of four different sections:

[0069] a) the covering section 110c of the top fin section 110, in one embodiment not extending the full width W of the blank 100;

[0070] b) the covered section 112c of the top panel section 112, in one embodiment not extending the full width W of the blank 100;

[0071] c) the covering section 115c of the bottom fin section 115, and not extending the full width W of the blank 100;

[0072] d) the covered section 116c of the bottom panel section 116, in one embodiment not extending the full width W of the blank 100.

[0073] FIG. 2 illustrates the package 200 formed from the blank 100 shown in FIG. 1. Once the blank 100 has been folded, filled with a food product FP, and sealed, a brickshaped package is formed. The brick shape provides multiple advantages, including ease of stacking and optimized space utilization in storage and transportation.

[0074] However, the concepts described herein are not limited to brick-shaped packages. Other package designs, such as pillow-shaped packages, which retain the top fin and bottom fin but lack distinct side, front, and rear panels, may also incorporate the first and second sets of perforations to reduce the risk of water absorption due to pressure differences during heat treatment.

[0075] The main body 200a, the top portion 200b, and the bottom portion 200c of the package 200 correspond to the main section 113, top section 109, and bottom section 114 of the blank 100 in FIG. 1. The top fin section 110 of FIG. 1 is folded and sealed to form the top closure of the package. The first set of perforations 102 is positioned along the top portion 200b, ensuring that the package can be easily opened by the consumer.

[0076] The food product FP, shown inside the main body 200a, indicates that the package 200 is designed for retort processing. After being filled and sealed, the package 200 is subjected to heat treatment in a retort apparatus to ensure sterilization and extended shelf life. The second set of perforations, positioned in the coveringand / or covered sections of the package 200, facilitates controlled airflow during cooling. This reduces the risk of water ingress into the fiber-based mid-layer, thereby preserving the structural integrity and mechanical properties of the package.

[0077] The side panel 120a is visible in FIG. 2, demonstrating how the crease lines in the blank 100 enable the package to retain its shape after folding and sealing. The top flaps 128 confirms that the creased and perforated sections function as intended to form a secure, durable, and easy-to-open package.

[0078] By implementing the first and second sets of perforations, the package 200 achieves pressure equalization during cooling, preventing moisture retention in the fiber-based mid-layer. This design ensures that the package maintains its intended mechanical properties after retorting, regardless of its final shape, whether brickshaped, pillow-shaped, or another form.

[0079] Tests have shown that incorporating a second set of perforations significantly reduces water absorption into the fiber-based mid-layer 302 after retorting. Specifically, in a selected number of packages subjected to particularly harsh retorting conditions, packages equipped with a second set of perforations absorbed an average of only 2.4 grams of water, whereas packages without any second set of perforations absorbed an average of 12.3 grams of water. Additionally, the distribution of water uptake in packages without a second set of perforations was notably uneven, with some packages absorbing significantly more than 12.3 grams of water. This indicates that the absence of a second set of perforations can lead to excessive moisture retention in some cases, increasing the risk of structural degradation and loss of mechanical integrity.

[0080] FIG. 3 schematically illustrates the multilayer packaging material 101 as a cross-sectional view of the blank 100, providing an example of the layered structure of the packaging material and the first and second sets of perforations 102, 104a-e. The blank 100 comprises multiple functional layers, including an outer protective layer 300, a fiber-based mid-layer 302, and an inner protective layer 304. The outer and inner protective layers 300, 304 may be polymer-based, while the fiber-based mid-layer 302 may be a carton layer.

[0081] The first and second sets of perforations 102, 104a-e extend through the outer protective layer 300, which is exposed to the external environment, and into the fiberbased mid-layer 302. In particular, these perforations may extend through at least 75% or more of the fiber-based mid-layer 302, ensuring effective airflow regulation while minimizing the risk of unwanted fiber detachment or weakening of the material. The same depth consideration applies to an optional third set of perforations 126, shouldsuch perforations be added to the blank 100. However, the second set of perforations does not necessarily need to extend into the fiber-based mid-layer 302. Tests have shown that it is sufficient for the second set of perforations to extend to the fiber-based mid-layer 302, meaning they penetrate only through the layers covering the outside of the fiber-based mid-layer 302, without necessarily entering the fiber-based material itself.

[0082] The first set of perforations 102 extends as continuous perforations through the outer protective layer 300 into the fiber-based mid-layer 302, facilitating tear guidance and consumer-friendly opening. Similarly, the second set of perforations 104a,b extends as continuous perforations through the outer protective layer 300 into, or in contact with, the fiber-based mid-layer 302, ensuring controlled airflow and pressure equalization during cooling.

[0083] As used herein, the term “continuous perforations” refers to a series of perforations that extend uninterrupted through all layers positioned between the outer protective layer 300 and the fiber-based mid-layer 302. This continuity ensures that the perforation path remains unbroken, avoiding potential blockages from intermediate layers and guaranteeing consistent airflow regulation and package integrity.

[0084] In the example illustrated, the packaging material may include additional functional barrier layers to enhance food protection and heat resistance. A polyamide layer 306 is provided between the fiber-based mid-layer 302 and the inner protective layer 304, which is in contact with the food product FP. Additionally, an aluminum foil 308 may be included between the fiber-based mid-layer 302 and the inner protective layer 304 to serve as an oxygen and moisture barrier. If both the polyamide layer 306 and aluminum foil 308 are present, the aluminum foil 308 is positioned between the polyamide layer 306 and the inner protective layer 304.

[0085] Further structural enhancements may include:

[0086] A polypropylene adhesive layer 310 between the outer protective layer 300 and an ink layer 312, improving adhesion and print stability.

[0087] The ink layer 312 positioned between the polypropylene adhesive layer 310 and the fiber-based mid-layer 302.

[0088] A polypropylene layer 314 positioned between the fiber-based mid-layer 302 and the polyamide layer 306, enhancing material compatibility and heat resistance.

[0089] A polypropylene adhesive layer 316 provided between the polypropylene layer 314 and the polyamide layer 306.

[0090] A polypropylene adhesive layer 318 between the inner protective layer 304 and the aluminum foil 308, ensuring strong lamination and maintaining barrier properties.To ensure precise perforation depth and uniformity, laser cutting may be used. Laser cutting allows for high precision and well-defined perforations, ensuring that the first set of perforations 102, the second set of perforations 104a,b, and the optional third set of perforations 126 maintain a consistent depth across the material layers. This precision contributes to reliable airflow regulation and controlled opening performance, further enhancing package integrity and retort process efficiency.

[0091] FIG. 4 illustrates, by way of example, a number of packages 200 placed inside a retort apparatus 400 during heat treatment. The packages 200 are positioned on a rack 402, which supports the packages during the retort process. As illustrated, the packages 200 are arranged to rest on their side panels 120a. This orientation reduces the risk that the first set of perforations 102 and the second set of perforations 104a become fully covered by water W, thereby minimizing the risk of water absorption into the fiber-based mid-layer 302.

[0092] Although FIG. 4 illustrates a retort apparatus 400, the concepts described herein are not limited to retort processing and may be applied to other heat treatment apparatuses that involve exposure to hot water, steam, or pressure variations.

[0093] As described earlier, during heat treatment, particularly during cooling, a pressure difference may arise between the outside pressure POUT in the compartment of the retort apparatus 400 and the inside pressure PIN within the packages 200. This pressure difference may cause air or gas to escape through the perforations, into the fiber-based layer, but if the perforations are covered by water W, the pressure differential may result in water being drawn into the fiber-based mid-layer 302. More specifically, the water W, which may form a thin film over the perforations, may be sucked into the fiber-based mid-layer 302 via the first set of perforations 102 or the second set of perforations 104a.

[0094] However, the risk of water absorption is reduced due to the placement and structure of the second set of perforations 104a-e. Specifically, the second set of perforations extends through the outer protective layer 300 into or in contact with the fiber-based mid-layer 302 and is provided in at least one of the covering section 110c of the top fin section 110, the covered section 112c of the top panel section 112, the covering section 115c of the bottom fin section 115, or the covered section 116c of the bottom panel section 116.

[0095] Since these sections are either covering or covered when the blank 100 is folded into the package 200, the perforations remain shielded from direct exposure to external moisture, such as water droplets or steam during heat treatment. This protective placement ensures that even when pressure differentials occur duringcooling, the fiber-based mid-layer 302 is not directly exposed to water. Instead, airflow through the second set of perforations allows for pressure equalization, preventing the vacuum effect that could otherwise draw water into the fiber-based mid-layer 302. By carefully positioning the perforations in sections that are enclosed by other layers of the package structure, the risk of water ingress is significantly minimized while still allowing necessary air exchange to maintain the package's structural integrity after retorting..

[0096] Situation A illustrates a package 200 where the second set of perforations 104a is covered by water W, while the first set of perforations 102 remains uncovered. In this scenario, the pressure difference is compensated by allowing air or gas to escape through the uncovered first set of perforations 102, thereby preventing water W from being absorbed into the fiber-based mid-layer 302.

[0097] Situation B illustrates an opposite case, where the first set of perforations 102 is covered by water W, while the second set of perforations 104a remains uncovered. Similar to Situation A, the pressure difference is compensated through the uncovered second set of perforations 104a, preventing water ingress into the fiber-based midlayer 302.

[0098] FIG. 5 is a flowchart illustrating a method 500 for producing the blank 100, which is the piece of packaging material illustrated in FIG. 1. The method 500 involves forming a multilayer web, perforating the web, and ensuring that each blank 100 is configured with a first set of perforations 102 and a second set of perforations 104a,b.

[0099] The method 500 comprises the following steps:

[0100] Producing 502 a web of consecutive blanks 100 by attaching the outer protective layer 300 and the inner protective layer 304 to the fiber-based mid-layer 302. This results in a continuous web of the multilayer packaging material 101 that can be further processed into individual blanks.

[0101] Feeding 504 the web into a perforation device, which is responsible for introducing perforations at specific locations on each blank 100. The web is transported in a controlled manner to ensure precise alignment with the perforation device.

[0102] Operating 506 the perforation device to form the first set of perforations 102 and the second set of perforations 104a,b, which extend through the outer protective layer 300 into the fiber-based mid-layer 302.

[0103] The first set of perforations 102 is provided in the top fin section 110, ensuring that the package 200, when formed from the blank 100, can be easily opened by the consumer. The second set of perforations 104a,b is positioned as described in connection with one or more of the embodiments illustrated in FIG. 1. This placement ensures that, during heat treatment, if water W is present on the package 200, at leastone set of perforations remains uncovered. By maintaining an unobstructed airflow path, the pressure difference between the internal pressure PIN and the external pressure POUT can be compensated, thereby preventing water from being drawn into the fiber-based mid-layer 302.

[0104] The perforation device used to form the second set of perforations 104a,b may be a laser cutting device or a mechanical perforation device. Laser cutting provides high precision, ensuring that the perforations are consistent in depth and shape, while mechanical perforation may be used for cost-effective and high-speed production.

[0105] By implementing this perforation process, the method 500 ensures that the blank 100 is optimized for retort processing while minimizing the risk of water absorption into the fiber-based mid-layer 302, thereby improving the durability and quality of the final package 200.

[0106] FIG. 6 illustrates a method 600 for producing the package 200 filled with the food product FP. The method 600 comprises multiple sequential steps, including forming, filling, sealing, and retort processing the package to ensure that the food product FP remains sterile and shelf-stable.

[0107] The method 600 includes the following steps:

[0108] Receiving 602 the blank 100, which is made of a multilayer packaging material 101 as described in FIG. 1. The blank 100 includes a first set of perforations 102 and a second set of perforations 104a,b, which are positioned to help regulate airflow during cooling.

[0109] Forming 604 the blank 100 into the package 200, leaving one end open for filling. This step involves folding and sealing various sections of the blank 100, including the top fin section 110 and bottom fin section 115, to create a fully enclosed package with a filling opening.

[0110] Filling 606 the food product FP into the package 200 through the open end. The food product FP may be a liquid, semi-solid, or solid food product that requires sterilization through retort processing.

[0111] Closing 608 the open end of the package 200 to form a sealed package. This step ensures that the package is airtight and ready for heat treatment, preventing contamination and spoilage.

[0112] Loading 610 the package 200 into the retort apparatus 400 for heat treatment. The package 200 may be placed together with other packages 200 onto a rack 402, which includes multiple floors where each floor comprises horizontal rows and columns of packages. The packages 200 are placed to rest on one of their side panels 120a tooptimize heat and cooling efficiency and to reduce the risk of water covering the perforations.

[0113] Heating 612 the package 200 and the food product FP in the retort apparatus 400 to eliminate microorganisms. This step ensures that the food product FP achieves commercial sterility, extending its shelf life. The heating process may involve steam, hot water, or a combination of both.

[0114] Cooling 614 the package 200 in the retort apparatus 400 by applying water W onto the package. During this step, a pressure difference may form between the inside pressure PIN of the package 200 and the outside pressure POUT in the retort apparatus 400.

[0115] The cooling step 614 may create conditions where water W could enter the fiber-based mid-layer 302 if perforations are fully submerged. However, by providing two sets of perforations 102, 104a,b in different sections of the package 200, the likelihood of direct contact between external air and the fiber-based mid-layer 302 is increased. This allows for pressure equalization through uncovered perforations, preventing water from being drawn into the fiber-based mid-layer 302 due to the pressure difference.

[0116] Additionally, when the packages 200 are placed on the rack 402, they may be horizontally spaced 2 cm or less from each other to ensure efficient heat transfer while maintaining proper airflow between packages.

[0117] FIG. 7 schematically illustrates a system 700 for producing the blank 100, which is the piece of packaging material illustrated in FIG. 1. The system 700 is configured to process a web 702 of packaging material and apply perforations 102, 104a,b at designated locations to facilitate controlled airflow, pressure equalization, and consumer-friendly opening.

[0118] As illustrated, the web 702 may comprise a fiber-based mid-layer 302 onto which additional layers are applied. The outer protective layer 300 may be laminated or otherwise attached to one side of the fiber-based mid-layer 302, while the inner protective layer 304 is applied to the opposite side. These layers provide barrier properties, ensuring that the packaging material withstands retort processing while maintaining structural integrity and food safety.

[0119] In addition to the outer protective layer 300, fiber-based mid-layer 302, and inner protective layer 304, further functional layers may be included, such as those illustrated in FIG. 3. These additional layers may be applied at various processing stations before the web 702 reaches the perforation stage.Once the packaging material layers have been combined, the web 702 is fed into a perforation device 704. The perforation device 704 may be a laser cutting device or a mechanical perforation device. The first set of perforations 102 and the second set of perforations 104a,b are applied at specific locations, ensuring that the final blank 100 includes the necessary airflow channels to facilitate pressure equalization and moisture protection.

[0120] Even though FIG. 7 illustrates a single perforation device 704, the system 700 may alternatively include multiple perforation devices operating in parallel or sequentially to improve processing efficiency.

[0121] The invention, including the first and second sets of perforations, is not limited to the specific blank configuration and folding principles described herein. The concept can be applied to other blanks that are folded into retortable packages, even if they utilize a different arrangement of crease lines or an alternative folding principle. For instance, while the described package features a particular alignment of crease lines and folding sequences, the first and second sets of perforations can be incorporated into blanks with varied structural designs, including those with curved, angular, or asymmetrically arranged crease lines. Regardless of the specific shape or folding approach, the perforations provide the same functional benefits, which is reducing the risk of water absorption into the fiber-based mid-layer during heat treatment by allowing controlled airflow and pressure equalization. As such, the invention is applicable to a wide range of retortable packaging formats beyond the example described herein.

[0122] From the description above, it follows that, although various embodiments of the invention have been described and illustrated, the invention is not limited to these specific embodiments. Instead, the invention may be implemented in other ways within the scope of the subject matter defined by the following claims.

Claims

CLAIMS1. A blank (100) configured to be folded into a package (200) that is heat treatable in a retort apparatus (400), the blank (100) being made of a multilayer packaging material (101) comprising an outer protective layer (300), a fiber-based midlayer (302), and an inner protective layer (304), the blank (100) comprisinga main section (113) configured to form a main body (200a) of the package (200), a top section (109) configured to form a top portion (200b) of the package (200), and a bottom section (114) configured to form a bottom portion (200c) of the package (200), whereinthe top section (109) comprises a top panel section (112) and a top fin section (110) that is arranged to be folded towards the top panel section (112) for sealing the package (200), the top fin section (110) having a covering section (110c) that is arranged to overlay a covered section (112c) of the top panel section (112) when the blank (100) is folded into the package (200),the bottom section (114) comprises a bottom panel section (116) and a bottom fin section (115) that is arranged to be folded towards the bottom panel section (116) for sealing the package (200), the bottom fin section (115) having a covering section (115c) that is arranged to overlay a covered section (116c) of the bottom panel section (116) when the blank (100) is folded into the package (200),a first set of perforations (102) extends through the outer protective layer (300) into the fiber-based mid-layer (302), the first set of perforations (102) being provided in the top section (109), and configured as tear-guiding perforations that facilitate opening of the package (200) made from the blank (100), and whereina second set of perforations (104a-e) extends through the outer protective layer (300) into or in contact with the fiber-based mid-layer (302), the second set of perforations (104a-e) being provided in at least one ofa) the covering section (110c) of the top fin section (110),b) the covered section (112c) of the top panel section (112),c) the covering section (115c) of the bottom fin section (115), wherein the second set of perforations (104d) provided in the covering section (115c) of the bottom fin section (115) does not extend the full width (W) of the blank (100), d) the covered section (116c) of the bottom panel section (116).

2. The blank (100) according to claim 1, wherein all perforations of the second set of perforations (104a-e) extend in a direction (D1) that is substantially parallel to the direction in which the first set of perforations (102) extends.

3. The blank (100) according to any preceding claim, wherein all perforations of the second set of perforations (104a-e) extend in a straight line.

4. The blank (100) according to claim 1, wherein all perforations of the second set of perforations (104a-e) are located entirely within the at least one of the covering section (110c) of the top fin section (110),covered section (112c) of the top panel section (112),covering section (115c) of the bottom fin section (115), andcovered section (116c) of the bottom panel section (116).

5. The blank (100) according to any preceding claim, comprising four elongated crease lines (113a-d) that extend in a direction (D2) from a bottom edge (13) to a top edge (14) of the blank (100) and are arranged to facilitate folding of the blank (100) to form the side corners of the package (200), wherein all perforations of the second set of perforations (104a-e) extend between two neighboring crease lines (113b-c) of the four elongated crease lines (113a-d).

6. The blank (100) according to any preceding claim, comprising a bottom edge (13), a top edge (14), a first side edge (11), a second side edge (12), and a top fin crease line (15a), a top section crease line (15b), a bottom section crease line (15c) and a bottom fin crease line (15d) that extend in a direction (D1) from the first side edge (11) to the second side edge (12), said crease lines (15a-d) being arranged to facilitate folding of the blank (100) to form a top fin, the top portion (200b), the bottom portion (200c) and a bottom fin of the package (200).

7. The blank (100) according to claim 6, wherein the second set of perforations (104b) is provided between the top edge (14) and the first set of perforations (102).

8. The blank (100) according to claim 6 or 7, wherein the second set of perforations (104a) is provided between the first set of perforations (102) and the top fin crease line (15a).

9. The blank (100) according to any of claims 6-8, wherein the second set of perforations (104c) is provided between the top fin crease line (15a) and the top section crease line (15b).

10. The blank (100) according to any of claims 6-9, wherein the second set of perforations (104e) is provided between the bottom section crease line (15c) and the bottom fin crease line (15d).

11. The blank (100) according to claims 6-10, wherein the second set of perforations (104d) is provided between the bottom fin crease line (15d) and the bottom edge (13).

12. A web of a multilayer packaging material (12) comprisingmultiple blanks (100) according to any preceding claim, whereinthe blanks (100) are successively arranged and continuously connected at respective side edges.

13. A method (600) for producing a package (200) filled with a food product (FP), said method (600) comprising:receiving (602) a blank (100) according to any one of claims 1 to 12, forming (604) the blank (100) into the package (200) with one end open, filling (606) the food product (FP) into the package (200) via the open end, closing (608) the open end of the package (200) such that a sealed package (200) is formed,loading (610) the package (200) into a retort apparatus (400),heating (612), in the retort apparatus (400), the package (200) and the food product (FP) held in the package (200) such that microorganisms on the package (200) or in the food product (FP) are killed,cooling (614), in the retort apparatus (400), the package (200) and the food product (FP) held in the package (200) by applying water (W) onto the package (200).

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