METHOD AND SYSTEM FOR INTRODUCING MOISTURE IN A MOULDED FIBER PACKAGING UNIT IN A MANUFACTURING PROCESS

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Netherlands Patent Application No. 2038495, filed on Aug. 26, 2024, to Evert Kuiper et al., currently pending, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a method for manufacturing a moulded fiber packaging unit, and more specifically the introduction of moisture in such packaging unit. Such packaging units are made from moulded pulp material and are typically used to contain, store, transport, cover and/or display a range of products, such as food products including beverages. The packaging units may specifically relate to containers, cups, carriers, covers, plates, sip lids, cases, trays et cetera. The moulded fiber packaging unit can be manufactured in a wet moulding process with a pulp matrix optionally involving a foamed pulp matrix, and/or a dry laid process with a “fluffy” pulp matrix.

BACKGROUND OF THE INVENTION

Conventional manufacturing processes of moulded fiber products involve the preparation of mouldable fiber material that is then typically formed in a mould to provide a primary packaging unit. These primary packaging units have an inhomogeneous/unregulated moisture content or moisture distribution within the packaging unit and/or a relatively large variation in moisture content between the individual packaging units. This (unregulated) variation in moisture content influences product characteristics, for example the effects achieved with a (post-moulding) pressing step depend on the moisture content and/or moisture distribution. This results in a variation in product quality of these products.

WO 2020/223943 A1, DE 692 21 442 T2 and U.S. Pat. No. 2,938,582 A disclose conventional methods for manufacturing moulded fiber packaging units.

Conventionally, the primary packaging units are often stored under controlled conditions to homogenize moisture content. Such storage under controlled conditions may reduce the variation in moisture content within a primary packaging unit and/or between different packaging units such that the negative influences on the product characteristics are minimized.

These conventional storage processes are time consuming and require the buffering of the products. Such process step increases manufacturing costs. In addition, there remains are relatively high risk of the presence of an inhomogeneous/unregulated moisture distribution/variation between different products and/or within a product, thereby providing a variation in product characteristics/quality.

SUMMARY OF THE INVENTION

The present invention has for its object to obviate or at least reduce one or more of the above stated problems in conventional manufacturing processes for moulded fiber packaging units and to provide a manufacturing method that is both cost-effective and provides high-quality packaging units.

For this purpose, the present invention provides a method for manufacturing a moulded fiber packaging unit that introduces moisture in a moulded fiber packaging unit, the method comprising the steps of:

• • preparing a mouldable fiber material;
  • forming the mouldable fiber material in a mould into a primary packaging unit with a compartment;
  • providing a moisturized flow to the primary packaging unit and forcing the flow through the fiber material of the primary packaging unit; and
  • controlling the moisturized flow depending on the permeability of the primary packaging unit.

The moulded fiber packaging unit that is manufactured in a method according to the present invention can be manufactured in a wet moulding process with a pulp matrix and/or a dry laid process with a “fluffy” pulp matrix. In a wet moulding process the pulp matrix is provided to the moulds and after moulding the products are dried. Optionally, this may involve a foaming step to provide a foamed material to mould. Alternatively, in a dry laid process, the pulp matrix can be supplied as sheets or reels that can be fed into a hammer mill, or similar device also referred to as defibrator, that separates compressed rolls or sheets of the pulp into individual, loose fibers, which are then transported to the forming system that forms the moulded fiber packaging unit.

Preparing and providing a mouldable fiber material typically involves providing an amount of fiber material. This fiber material may have different origin, such as wood and/or non-wood fiber material, optionally from a recycling process such as from recycled paper material. Alternatively, or in addition to such paper material, the fiber material may also comprise an amount of non-wood fiber material to which is also referred to as natural and/or alternative fibers. Such fibers may involve biomass fibers from plant origin, examples of which are described in WO 2021/145764 A1. After preparing a mouldable fiber material, the primary packaging unit is formed in a mould. Such moulding involves the forming of the material into the desired shape of the primary packaging unit that typically has a compartment capable of carrying or holding a product, such as a food product including beverages. After the forming process the primary packaging units are typically dried, optionally involving an in-mould drying step.

According to the invention a moisturized flow, such as a moisturized air flow, and more specifically an over-saturated moisturized air (“mist”) flow is provided to the primary packaging unit. Forcing such moisturized flow through the primary packaging unit regulates, and may also homogenize, the moisture content of the primary packaging unit within the primary packaging unit itself. Preferably, also the moisture content in a batch of primary packaging units is homogenized such that the variation/distribution of moisture content is significantly reduced, is better regulated, and is more or less constant in a batch of products and preferably also in time. Alternative methods to provide moisture to the primary packaging unit include spraying, brushing and printing. These methods can be applied as alternatives or in combination with each other and/or with providing an over-saturated moisturized air flow. Experiments showed that providing an over-saturated moisturized air flow provided a good regulation of the specific moisture content.

As an example, for small cups having a weight of about 1.25 g, it is often desired to have an increase of the overall moisture content of about 0.1 g/cup and homogenously distributing the moisture over the cup. Total moisture content may vary and may be in a range of 5 wt % to 10 wt % of the total product weight. It will be understood that the desired level of moisture content may depend on product characteristics, material characteristics, intended use et cetera. Temperature of the moisturized flow is typically in the range of 20° C. to 70° C. In some of the embodiments according to the invention the temperature of the moisturized flow is substantially similar to the temperature of the process equipment to minimize temperature differences between the flow and the equipment. It will be understood that temperature(s) and flow rate(s) may depend on the specific circumstances.

According to the invention, the manufacturing method further comprises the step of controlling the afore described moisturized flow depending on the permeability of the primary packaging unit. The permeability of a primary packaging unit is (mainly) defined by the fibers. The influence of “free” moisture inside a primary packaging unit is minimal or even absent. In general, the permeability of a product is the capacity of a porous material of the product for transmitting a fluid, with the product having a certain cross-section and thickness, and being under the influence of pressure (or pressure difference). So-called air permeability is typically defined as a measure of the ability of air to pass through a material measured in a volume of air passing to a certain cross-section of the material at a specific pressure difference in a time interval.

Controlling the moisturized flow depending on the permeability of the primary packaging unit has shown to provide a significant contribution to the regulation, and preferably homogenization, of the moisture content, both within a single primary packaging unit, as between different primary packaging units. Tests have shown that properties/characteristics of the end-products are significantly more constant for packaging units manufactured with the method according to the present invention as compared to conventional manufacturing processes.

Preferably, in one of the presently preferred embodiments of the invention, the method further comprises the step of providing an additive to the moisturized flow. Such additives may involve the application of one or more of additives to change surface tension and/or viscosity, to change the size of the water droplets in the flow and/or the interaction between the moisture the fibers of the packaging unit. Also, additives may relate to colorants and barrier additives. The additives may be provided as dissolved or suspended additives. Tests have shown that adding one or more additives to the moisturized flow is an effective way to change the behavior of the moisturized flow and/or to color the packaging unit and/or to improve barrier properties.

It will be understood that in addition to the aforementioned manufacturing steps also further steps can be performed. For example, a laminate layer can be attached to the packaging unit and a further pressing step can be performed to improve the product characteristics.

Preferably, controlling the moisturized flow involves directly or indirectly taking into account permeability of the primary packaging unit. The controller that steers the moisturized flow through the primary packaging unit is provided with information about the permeability, either directly or indirectly. This may involve the step of measuring the permeability of a primary packaging unit and/or measuring variations between the different primary packaging units in relation to permeability. In case of a different permeability of the primary packaging unit as expected, the settings of the moisturized flow can be adapted accordingly by the controller. For example, in case of a relatively low permeability there is a relatively high flow resistance such that it is more difficult for the moisturized flow to force itself through the fiber material of the primary packaging unit. The controller can then adapt the settings of the moisturized flow, for example by changing the pressure or pressures in the process.

In a presently preferred embodiment of the invention, the method further comprises the step of providing a pressure difference over the primary packaging unit.

The amount of moisturized flow (flow rate) that is provided through the fiber material of the primary packaging unit depends on the pressure difference over the fiber material. Manipulating the pressure on one or both sides of the primary packaging unit may change the pressure difference and thereby influence the moisturized flow through the fiber material of the primary packaging unit. This enables the control of the moisture uptake by the primary packaging unit such that the overall product characteristics of the end-product can be maintained more constant. In tests using the aforementioned small cups, a pressure difference of the primary packaging unit in the range 350 mbar to 900 mbar, more preferably in the range of 450 mbar to 800 mbar, and most preferably about 700 mbar, is applied.

In a presently preferred embodiment of the invention, the providing of a moisturized flow comprises directing the moisturized flow to a first side of the primary packaging unit, and further comprises providing an under-pressure at the other second side of the primary packaging unit, such that the moisturized flow is forced through the primary packaging unit from the first side to the second side. In such embodiment, the first side of the primary packaging unit is upstream of the moisturized flow and the other second side of the primary packaging unit is downstream of the moisturized flow relative to the primary packaging unit. The pressure difference between the first upstream side and second downstream side of the primary packaging unit is relevant for the through flow of the moisturized flow through the primary packaging unit and as a consequence thereof for the moisture uptake and/or moisture homogenization thereof.

In presently preferred embodiments of the invention the controller steers the pressure on the other second side of the primary packaging unit.

Controlling, and when necessary adjusting, the pressure on the second downstream side of the primary packaging unit has shown to be an effective means to introduce moisture in and/or homogenize the moisture content of a moulded fiber packaging unit, and more specifically the primary packaging unit. Preferably, the controller steers the under-pressure on the second side of the primary packaging unit, wherein the under-pressure is typically a pressure below 1.0 bar, to thereby steer the moisturized flow and the moisture uptake/homogenization.

In a further preferred embodiment of the invention, the method comprises the step of measuring a pressure difference over the primary packaging unit.

Performing a measurement of the pressure difference over the primary packaging unit provides direct information of the permeability of the primary packaging unit. Consequently, the controller may adapt the process settings thereby manipulating the moisturized flow such that product characteristics are more uniform, independent of the actual permeability of the primary packaging unit(s). Such pressure difference is typically measured by a sensor or sensor system that provides the measurements to the controller.

In a further preferred embodiment of the present invention the method further comprises the step of providing the moisturized flow to the primary packaging unit in a time interval in the range of 10 milliseconds to 60 seconds, preferably in a range of 2.0 to 20 seconds, and most preferably in a range of 3.0 to 10 seconds.

Tests have shown that providing and/or maintaining the moisturized flow to the primary packaging unit in one of the afore mentioned time intervals provides an effective moisture uptake, regulation and/or homogenization of the moisture content of the primary packaging unit. It will be understood that the actual time interval may depend on the design and weight of the primary packaging unit, for example.

In presently preferred embodiments of the invention the step of providing a moisturized flow involves providing of flow per gram of primary packaging unit in the range of 2.0 to 20 l/min. Test results have shown that the flow in the aforementioned range provides an effective moisture uptake, regulation and/or homogenization of the moisture content of the primary packaging unit.

In a further presently preferred embodiment of the invention, the method comprises the step of providing the moisturized flow simultaneously to two or more primary packaging units.

Providing the moisturized flow simultaneously to multiple primary packaging units, wherein multiple relates to two or more, a higher production capacity can be achieved. In such embodiment, the moisturized flow is prepared and provided to the two or more primary packaging units simultaneously. This is preferably done in-process, meaning that no separate storage or buffering step is required. This results in a cost-effective manufacturing process of the packaging units.

Preferably, when providing the moisturized flow simultaneously to two or more primary packaging units, and in case the moisturized flow in one of the two or more primary packaging units is actually lower, the controller preferably adapts the pressure on the second downstream side of the primary packaging unit that is subjected to the lower moisturized flow. Experiments have shown that this approach is beneficial for the regulation of the moisture content of the different moulded fiber packaging units. Alternatively, the back pressure (the pressure on the other second downstream side) of the other primary packaging units can be adapted accordingly.

In a further preferred embodiment of the invention, the method comprises the step of providing a distribution system configured to provide the moisturized flow simultaneously to a number of primary packaging units.

Providing a distribution system enables a controlled provision of moisturized flow in a simultaneous manner to the two or more primary packaging units. Such distribution system may involve the use of a set of tubes and/or manifolds, for example.

The invention further relates to a system for introducing moisture content in a moulded fiber packaging unit in a manufacturing process, wherein the system is configured for performing the method in an embodiment according to the present invention.

Such system provides the same or similar effects and advantages as described in relation to the method.

The system is specifically triggered to treat the primary packaging unit by providing a moisturized flow. Therefore, the system preferably comprises a controller configured for controlling at least the providing of the moisturized flow to the primary packaging unit. Optionally, this involves the application of one or more so-called pulse width modulation valves.

In a preferred embodiment of the invention the system further comprises a distribution system configured to provide the moisturized flow simultaneously to two or more primary packaging units. This improves the production capacity of the overall production process.

In a further preferred embodiment of the present invention the system further comprises a sensor system configured to determine a pressure difference over the primary packaging unit. Preferably, such pressure difference is used as a measure for the permeability of the primary packaging unit. Preferably, the measure is provided to the controller that steers the moisturized flow to the primary packaging unit, and more preferably to the two or more primary packaging units simultaneously.

With the manufacturing method and/or system in one of the aforementioned embodiments of the invention, the packaging unit can be manufactured from a moulded pulp material. Therefore, the invention also relates to such packaging unit of moulded fiber material. These packaging units may relate to containers, cups, carriers, covers, sip lids, cases, plates, trays et cetera.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

FIG. 1 shows a schematic overview of the manufacturing process involving the method of the present invention;

FIG. 2 schematically shows the components of a system according to an embodiment of the present invention that is capable of performing the method of FIG. 1;

FIG. 3A shows side view of a cup that can be manufactured with the method and/or system of FIGS. 1 and/or 2;

FIG. 3B shows a perspective view of a cup that can be manufactured with the method and/or system of FIGS. 1 and/or 2;

FIG. 4 shows a perspective view of a sip lid that can be manufactured with the method and/or system of FIGS. 1 and/or 2; and

FIG. 5 shows a perspective view of a tray that can be manufactured with the method and/or system of FIGS. 1 and/or 2.

DETAILED DESCRIPTION OF THE INVENTION

The following description is merely exemplary in nature and is in no way intended to limit the invention, its application or users. While the disclosure is described as having exemplary attributes and applications, the present disclosure can be further modified. This application is therefore intended to cover any variations, users, and adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as commonly known or customary practice of those skilled in the art to which this disclosure pertains and which fall within the limits of the appended claims. Accordingly, the following corruption of certain embodiments and examples should be considered merely exemplary and not in any way limiting.

Manufacturing process 2 (FIG. 1) comprises preparation step 4 wherein a pulp material is prepared. This pulp material 6 is then provided to forming step 8 wherein a raw product 10 is moulded. This raw product 10 is then dried in drying step 12 resulting in primary packaging unit 14. Moisture regulation/homogenization step 16 for regulating/homogenizing moisture content of primary packaging unit 14 involves providing a moisturized flow to primary packaging unit 14 and results in (homogenized) packaging unit 18 with a regulated moisture content. This step may include providing one or more additives to the moisturized flow. Packaging unit 18 can be subjected to one or more post-treatment processes 20 such as lamination and/or pressing processes thereby resulting in end-product 22 that is then used in (use) step 24.

Preparation step 4 may involve applying and/or mixing wood fiber material and/or non-wood material such as alternative fibers. Wood material may involve so-called virgin fibers and/or fibers from recycled paper material, for example. This results in a slurry for a wet moulding process, optionally having a foaming agent to enable manufacturing a foamed packaging unit. Alternatively, this results in a fluffy pulp matrix to enable so-called dry laid processing of a moulded fiber packaging unit.

Method step 16 for providing a moisturized flow to primary packaging unit 14 can be performed using system 26 (FIG. 2). System 26 for regulating/homogenizing moisture content of a moulded fiber packaging unit comprises a flow production unit 28 that generates a moisturized flow 30, preferably with oversaturated moisture content thereby providing a “mist” to flow distributor 32. Flow distributor 32 provides moisturized flow 34, which resembles moisturized flow 30, to individual primary packaging unit 14. In the illustrated embodiment sensor system 36 measures properties of primary packaging unit 14 and/or moisturizing flow 34 and/or other suitable conditions to generate measurement signal 38. Measurement signal 38 is provided to controller 40 that generates control signal 42 to set flow distributor 32 and optionally control signal 44 to set flow production unit 28.

Method 2 and system 26 can be used to manufacture a range of packaging units. As an example, cup-shaped packaging unit 102 (FIGS. 3A-3B) can be manufactured comprising cup-shaped container body 104 having bottom 106 and side wall 108. Preferably, flange or rim 110 is configured for optionally receiving seal or lid 112 thereon. The inside of cup 102 defines product compartment 114. Optionally, bottom 106 comprises additional support 116. Also optionally, inner wall 118 of compartment 114 is provided with laminate layer 120.

Sip lid 202 (FIG. 4) comprises top wall 204 and first wall section 206 that in the illustrated embodiment is connected to second wall section 208 having transition region 210. Sip lid 202 is preferably provided with terrace structure 212 with opening 214. Bottom part 216 of sip lip 202 is open to receive a liquid and provide the liquid to opening 214. This part defines compartment 218 wherein liquid can be received to enable a user to drink a liquid from a cup through opening 214 of sip lid 202.

Tray 302 (FIG. 5) comprises bottom 304, rim 306, outer side wall 308 and inner side walls 310. In the illustrated embodiment, bottom 304 and inner side walls 310 are provided with laminate layer 312. Compartment 314 is defined by bottom 304, side walls 310 and rim 306.

Flow distributor 32 can be provided in different embodiments, including an embodiment with a central (mist) creation and a transport system using two or more tubes and/or manifolds to provide the flow to two or more primary packaging units 14. Alternatively, flow distributor 32 involves local (mist) creation for each individual primary packaging unit 14. It will be understood that other embodiments of flow distributor can also be envisaged in accordance with the present invention, including the application of spray nozzles optionally involving pulse width modulation. Tests have been performed with different embodiments including “mist” creation centrally and creation locally. The results show a higher moisture uptake with a higher flow.

In tests, use has been made of one or more pulse width modulation valves to illustrate the effect of the open percentage on the added moisture in gram per individual product. Results show an increase of added moisture when increasing the interval wherein a valve is open.

To illustrate the effect of permeability on the moisture uptake with the use of providing a moisturized flow 30, 34 to primary packaging unit 14, moisture regulation/homogenization step 16 is performed with controller 14. Results show a constant moisture uptake in grams per product independent of the actual permeability of the individual products. This illustrates the functioning and effect of providing a moisturized flow 30, 34 in regulation/homogenization step 16 to primary packaging unit 14.

The present invention is by no means limited to the above-described preferred embodiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged.