A PROCESS FOR FORMING A MOULDED PULP FIBRE PRODUCT

A process for forming a moulded pulp fibre product involves creating a slurry deposit, reducing the liquid content of the slurry deposit to form a pulp fibre pre-form having an initial form, and pressing the pulp fibre pre-form in a tool set to further reduce the liquid content of the pulp fibre pre-form and deform the pulp fibre pre-form from the initial form to a secondary form. A first mould tool has a surface that includes primary regions to apply a first reduction in material thickness, and secondary regions in which the surface is shaped to cause a change in the material thickness of the pulp fibre pre-form that is less than the first reduction. Portions that are formed between the primary regions and a second mould tool have higher density, compared with portions that are formed by the secondary region and the second mould tool.

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Description
FIELD OF THE INVENTION

The present invention relates to a process for forming moulded pulp fibre product. The present invention also relates to moulded pulp fibre products.

BACKGROUND

Moulded pulp fibre is well known for use in packaging products, and single use food and beverage service trays/containers, and transport products. When made from materials that can be recycled or otherwise composted after the product's useful life, moulded pulp fibre products can be “sustainable”, which is a highly desirable characteristic. In addition, moulded pulp fibre products can be less expensive to produce than equivalent products made of plastics materials.

A widely-utilized process (hereinafter referred to as the “basic process”) for forming moulded pulp fibre products involves:

    • a. creating a slurry of fibrous material and liquid in an open tank;
    • b. immersing a forming head into the slurry, the forming head having a shaped mesh mould;
    • c. applying suction to the forming head, so as to draw the slurry onto the mesh mould, whereby a wet pulp pre-form of the final moulded pulp fibre product is formed on the mesh mould;
    • d. removing the forming head from the open tank, while maintaining a suction pressure to hold the pre-form on the mesh mould;
    • e. releasing the wet pulp pre-form from the forming head, and
    • f. baking the wet pulp pre-form to remove water from the pulp, and thus form the final product shape.

The basic process can form moulded pulp fibre products relatively quickly. However, the basic process has limited control over the shape of the final product; the surface of the final product that is against the mesh mould has a debossed surface that is defined by the mesh mould, and the opposing surface form is defined by the characteristics of the fibrous material and the suction pressures. Further, internally within the pulp fibre matrix of the final product, the assembly of fibres is also defined by the characteristics of the fibrous material and the suction pressures. Inter-fibre bonds are formed primarily where individual pulp fibres are brought into contact with other fibres in the matrix during the suction stage. As such, the final product has low rigidity, and relatively poor surface qualities.

To address deficiencies in the basic process, a modified process for forming moulded pulp fibre products, known as “thermoforming”, involves applying heat and pressure to the wet pulp pre-form instead of the baking step of the basic process. The application of heat and pressure is achieved using a toolset of two (or more) complementary moulds that are heated, and pushed together with the pre-form disposed in the moulds to compress the wet pulp pre-form. The mould pressure drives liquid out of the wet pulp pre-form, which increases the contact of fibres. Consequently, there is greater contact between fibres throughout the matrix, and the final product having tighter geometric tolerance and improved rigidity, when compared with the final product produced by the basic process. In addition, contact of the complementary moulds can facilitate smoother surfaces of the final product, which improves the appearance of the final product.

It is known that increasing the production rate of moulded pulp fibre products using thermoforming processes compromises both the precision of the geometry, and the ability to control material density in the moulded pulp fibre products. To this end, where greater precision in final product geometry is sought, there is a decrease in the control in material density. Conversely, where greater control in material density is sought, there is a decrease in the precision in final product geometry. Moulded pulp fibre products that have complex geometries and/or high tolerances can be particularly difficult to produce at commercially viable volumes.

It is known to form products from plastic materials (including at least synthetic plastic materials) that have sections with mechanically different characteristics, incorporated within the product form and/or by the forming process. These different characteristics can be exploited to create products with sections that perform different functions in service.

Pulp fibre products with sections having mechanically different characteristics can be achieved using post forming operations on the initial material. By way of example, it is known to form creases, score lines, and perforations in paperboard sheet when forming boxes, to facilitate box folding and opening. As will be appreciated, these post-forming operations require addition equipment, labour and processing time on the products.

Post forming operations can also be used to form decorative elements in pulp fibre products. Decorative elements can be created in finishing processes, for example by embossing and debossing. These decorative elements are generally not intended to alter the mechanical characteristics in any meaningful way. It is also known to design mould tools such that formed pulp fibre products have logos/indicia incorporated in the material during the forming process, to create either a debossed-type form or an embossed-type form.

There is a need to address the above, and/or at least provide a useful alternative.

SUMMARY

There is provided a process for forming a moulded pulp fibre product, the process involving:

    • creating a slurry deposit from a suspension of pulp fibres in liquid,
    • reducing the liquid content of the slurry deposit to a liquid fraction within a predefined range to thereby form a pulp fibre pre-form having an initial form; and
    • pressing the pulp fibre pre-form in a tool set to further reduce the liquid content of the pulp fibre pre-form and thereby deform the pulp fibre pre-form from the initial form to a secondary form, the tool set including at least first and second mould tools that are arranged to move relative to one another between a retracted position in which the separation of the mould tools is a maximum, and a forward position in which the separation of the mould tools is a minimum, at least the first mould tool having a non-planar mould tool surface that includes:
    • one or more primary regions in which the non-planar mould tool surface is shaped to apply a first reduction in the material thickness of the pulp fibre pre-form in the parts of the pulp fibre pre-form that are between each of the primary regions and the second mould tool at the completion of the step of pressing the pulp fibre pre-form; and
    • at least one secondary region in which the non-planar mould tool surface is shaped to cause a change in the material thickness of the pulp fibre pre-form in the part of the pulp fibre pre-form that is between the secondary region and the second mould tool that is less than the first reduction at the completion of the step of pressing the pulp fibre pre-form,
    • whereby within the secondary form, portions that are formed between the primary regions of the first mould tool and the second mould tool have a higher density, compared with the portion that is formed by the secondary region of the first mould tool, and the second mould tool.

Alternatively or more particularly, within the secondary form, portions that are immediately adjacent the secondary region, and are formed between the primary regions of the first mould tool and the second mould tool have a higher density, compared with the portion that is formed by the secondary region of the first mould tool and the second mould tool.

Preferably, the first mould tool is configured such that at least part of the non-planar mould tool surface that is within the at least one secondary region is to be spaced from the secondary form when the first and second mould tools are at the forward position.

In some embodiments, the first mould tool is configured such that the entire part of the non-planar mould tool surface that is within the at least one secondary region is to be spaced from the secondary form when the first and second mould tools are at the forward position.

Alternatively or additionally, there is provided a process for forming a moulded pulp fibre product, the process involving:

    • creating a slurry deposit from a suspension of pulp fibres in liquid,
    • reducing the liquid content of the slurry deposit to a liquid fraction within a predefined range to thereby form a pulp fibre pre-form having an initial form; and
    • pressing the pulp fibre pre-form in a tool set to further reduce the liquid content of the pulp fibre pre-form and thereby deform the pulp fibre pre-form from the initial form to a secondary form, the tool set including at least first and second mould tools that are arranged to move relative to one another between a retracted position in which the separation of the mould tools is a maximum, and a forward position in which the separation of the mould tools is a minimum, at least the first mould tool having a non-planar mould tool surface that includes:
    • one or more primary regions in which the non-planar mould tool surface is to engage the surface of the pulp fibre pre-form while the tool set is pressing the pulp fibre pre-form; and
    • at least one secondary region in which the non-planar mould tool surface is recessed relative to immediately adjacent the primary regions and with respect to movement of the mould tools towards the forward position,
    • whereby compression of the pulp fibre pre-form in the tool set induces propagation of liquid that is within the pulp fibre pre-form in the initial form and is between the primary regions of the first mould tool and the second mould tool, towards the part of the pulp fibre pre-form that is between the secondary region of the first mould tool and the second mould tool.

Preferably, the propagation of liquid occurs substantially transversely with respect to movement of the mould tools towards the forward position. Alternatively or additionally, the propagation of liquid occurs substantially transversely with respect to non-planar mould tool surface of the first mould tool.

In some examples, during the step of pressing the pulp fibre pre-form in the tool set, the tool set generates a pressure differential within the pulp fibre pre-form, causing propagation of liquid within the pulp fibre pre-form towards the part of the pulp fibre pre-form that is between the secondary region of the first mould tool and the second mould tool.

During the step of pressing the pulp fibre pre-form, the propagation of liquid causes an at least temporary relative increase in the liquid fraction of the part of the pulp fibre pre-form that is between the secondary region of the first mould tool and the second mould tool, compared to part of the pulp fibre pre-form that is between the primary regions of the first mould tool and the second mould tool, to thereby facilitate a varied material density transversely within the second form of the pulp fibre pre-form.

Preferably, the step of pressing the pulp fibre pre-form further involves maintaining the pulp fibre pre-form under compression between the tool set until pulp fibre pre-form has attained a substantially homogenous distribution of the liquid fraction.

Alternatively or additionally, there is provided a process for forming a moulded pulp fibre product, the process involving:

    • creating a slurry deposit from a suspension of pulp fibres in liquid,
    • reducing the liquid content of the slurry deposit to a liquid fraction within a predefined range to thereby form a pulp fibre pre-form; and
    • pressing the pulp fibre pre-form in a tool set to further reduce the liquid content of the pulp fibre pre-form and thereby deform the pulp fibre pre-form from an initial form to a secondary form, the tool set including at least first and second mould tools that are arranged to move relative to one another between a retracted position in which the separation of the mould tools is a maximum, and a forward position in which the separation of the mould tools is a minimum, at least the first mould tool having a non-planar mould tool surface that includes:
    • one or more primary regions in which the non-planar mould tool surface is to engage the surface of the pulp fibre pre-form while the tool set is pressing the pulp fibre pre-form; and
    • at least one secondary region in which the non-planar mould tool surface is recessed relative to immediately adjacent the primary regions and with respect to movement of the mould tools towards the forward position, the secondary region being surrounded by the primary regions,
    • whereby pressing the pulp fibre pre-form in the tool set involves:
    • progressing the mould tools towards the forward position to an initial contact position, in which the primary regions that surround the secondary region are in contact with the pulp fibre pre-form and a cavity is formed between at least part of the non-planar mould tool surface within the secondary region and the pulp fibre pre-form, and then
    • at least partially maintaining the cavity as the mould tools continue from the initial contact position towards the forward position such that the portion of the surface of the pulp fibre pre-form that is adjacent the secondary region is unconstrained by the first mould tool.

In some embodiments, the method involves maintaining the cavity between the mould tool surface within the entire secondary region and the pulp fibre pre-form, such that the surface of the pulp fibre pre-form that is adjacent the secondary region is unconstrained by the first mould tool throughout the step of pressing the pulp fibre pre-form.

In some alternative embodiments, the method involves maintaining the cavity between only a part of the mould tool surface within the secondary region and the pulp fibre pre-form, such that only a portion of the surface of the pulp fibre pre-form that is adjacent the secondary region is unconstrained by the first mould tool throughout the step of pressing the pulp fibre pre-form.

Maintaining the cavity can involve controlling at least one of the rate of movement of the mould tools towards the forward position, and the force applied to at least one of the mould tools.

Controlling the rate of movement of the mould tools towards the forward position, may involve limiting the maximum rate of movement to a predefined upper limit.

Controlling the force applied to at least one of the mould tools may involve limiting the maximum force that is applied to a predefined maximum.

Preferably, the lateral diameter of the secondary region of the first mould tool is selected such that a diameter-to-material thickness ratio that is equal to or less than 2:1, the diameter-to-material thickness ratio being the ratio of the lateral diameter of the secondary region to the minimum thickness of the pulp fibre pre-form in its initial form. Preferably, the diameter-to-material thickness ratio is less than 1.5:1. In some examples, the diameter-to-material thickness ratio is less than approximately 1.3:1.

In some implementations of the process, the non-planar mould tool surface is configured such that, after the step of pressing the pulp fibre pre-form, the lowest density of the portion that is formed by the secondary region of the first mould tool and the second mould tool is between 50% and 98% of the maximum density of the portions that are formed between the primary regions of the first mould tool and the second mould tool.

In some further implementations of the process, the non-planar mould tool surface is configured such that, after the step of pressing the pulp fibre pre-form, the lowest density of the portion that is formed by the secondary region of the first mould tool and the second mould tool is between 60% and 95% of the maximum density of the portions that are formed between the primary regions of the first mould tool and the second mould tool.

In some further implementations of the process, the non-planar mould tool surface is configured such that, after the step of pressing the pulp fibre pre-form, the lowest density of the portion that is formed by the secondary region of the first mould tool and the second mould tool is approximately 75% to 95% of the maximum density of the portions that are formed between the primary regions of the first mould tool and the second mould tool.

In at least some implementations of the process, after the step of pressing the pulp fibre pre-form, the density of the portion that is formed by the secondary region of the first mould tool and the second mould tool decreases with distance from portions that are formed between the primary regions of the first mould tool and the second mould tool.

Preferably, the second mould tool includes extraction passageways that extend from openings in the mould tool surface of the second mould tool through the second mould tool, and the step of pressing the pulp fibre pre-form can involve applying suction to the extraction passageways to draw liquid from the pulp fibre pre-form through the openings and into the extraction passageways.

The method can further involve heating one or both of the first and second mould tools, whereby during the step of pressing the pulp fibre pre-form heat is transferred from the respective mould tool to the pulp fibre pre-form to facilitate the reduction in liquid content.

The first mould tool can include venting passageways that extend from openings in the second region of the mould tool surface of the second mould tool through the second mould tool, and the method can further involve allowing gas to discharge from the cavity through the venting passageways during the step of pressing the pulp fibre pre-form. In some examples, the method can further involve applying suction to the venting passageways to draw gas from the cavity through the venting passageways during the step of pressing the pulp fibre pre-form.

In at least some examples, in the step of reducing the liquid content of the slurry deposit, the predefined range is a liquid fraction of approximately 33% to 60% by weight of the pulp fibre pre-form. Preferably, in the step of reducing the liquid content of the slurry deposit, the predefined range is a liquid fraction of approximately 45% to 55% by weight of the pulp fibre pre-form. In certain examples, in the step of reducing the liquid content of the slurry deposit, the predefined range is a liquid fraction of approximately 50%±V1 by weight of the pulp fibre pre-form, where V1 is a first nominal process variation percentage.

In at least some examples, the step of pressing the pulp fibre further reduces the liquid fraction such that in the second form of the pulp fibre pre-form has a liquid content of less than approximately 10% by weight of the pulp fibre pre-form. In at least some examples, the step of pressing the pulp fibre further reduces the liquid fraction such that in the second form of the pulp fibre pre-form has a liquid content of approximately 5%±V2 by weight of the pulp fibre pre-form, where V2 is a second nominal process variation percentage.

The method can further involve refining the pulp fibre prior to the step of creating the slurry. In some embodiments, refining the pulp fibre can involve refining the pulp fibre to a Canadian Standard Freeness of less than approximately 300 mL CSF. In certain embodiments, refining the pulp fibre can involve refining the pulp fibre to a Canadian Standard Freeness of 130 to 200 mL CSF.

In some examples, the secondary form of the pulp fibre pre-form is the moulded pulp fibre product. In some other examples, the secondary form of the pulp fibre pre-form is an intermediate product in the production of the moulded pulp fibre product.

In some embodiments, the step of reducing the liquid content of the slurry deposit to a liquid fraction within a predefined range involves at least one intermediate pressing step in which the liquid fraction is removed from the pulp fibre material by application of pressure in preceding press tool sets.

In at least some embodiments, the process is arranged to have a material compression ratio that is at least 2:1, wherein the material compression ratio is the ratio of the thickness of the slurry deposit to the minimum thickness of the secondary form of the pulp fibre pre-form, measured in a direction that is parallel to the relative movement of the tool set and at the same relative location of the pulp fibre material.

Preferably, the material compression ratio is at least 2.5:1. Even more preferably, the material compression ratio is in excess of 3:1.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more easily understood, embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1: is a schematic vertical cross-section view of a tool set for use in a process for forming a moulded pulp fibre product, the tool set being in accordance with a first example;

FIG. 2: is a schematic vertical cross-section view of the tool set shown in FIG. 1 together with a pulp fibre pre-form in its initial form, and illustrating a first stage in the forming process;

FIG. 3: is a schematic vertical cross-section view of the tool set shown in FIG. 1 together with a pulp fibre pre-form, and illustrating a second stage in the forming process, with the tool set in its retracted position;

FIG. 4: is a schematic vertical cross-section view of the tool set shown in FIG. 1 together with a pulp fibre pre-form, and illustrating a third stage in the forming process, with the tool set in its forward position;

FIG. 5: is an enlarged view of Region A in FIG. 4;

FIG. 6: is a schematic perspective view of the pulp fibre pre-form in its secondary form;

FIG. 7a: is a schematic vertical cross-section view of the pulp fibre pre-form in its secondary form;

FIG. 7b: is a chart showing schematically relative density of the secondary form as shown in FIG. 7a, and the surface height displacement of the pulp fibre pre-form between the initial and secondary forms;

FIG. 8: is a perspective view of a pulp fibre pre-form in its secondary form according to a second example;

FIG. 9: is a vertical cross-section view of the pulp fibre pre-form of FIG. 8;

FIG. 10: is a perspective view of a moulded pulp fibre product, derived from the pulp fibre pre-form of FIG. 8;

FIG. 11: is a vertical cross-section view of the moulded pulp fibre product of FIG. 10;

FIG. 12: is a schematic vertical cross-section view of a tool set for use in a process for forming a moulded pulp fibre product, the tool set being in accordance with a third example;

FIG. 13: is a schematic vertical cross-section view of the tool set shown in FIG. 12 together with a pulp fibre pre-form, and illustrating a stage in the forming process, with the tool set in its forward position;

FIG. 14: is a schematic vertical cross-section view of the pulp fibre pre-form after pressing in the tool set of FIG. 12;

FIG. 15: is a schematic vertical cross-section view of a tool set for use in a process for forming a moulded pulp fibre product, the tool set being in accordance with a fourth example;

FIG. 16: is a schematic vertical cross-section view of the tool set shown in FIG. 15 together with a pulp fibre pre-form, and illustrating a stage in the forming process, with the tool set in its forward position;

FIG. 17: is a schematic vertical cross-section view of the pulp fibre pre-form after pressing in the tool set of FIG. 15;

FIG. 18: is a schematic vertical cross-section view of a tool set for use in a process for forming a moulded pulp fibre product, the tool set being in accordance with a fifth example;

FIG. 19: is a schematic vertical cross-section view of the tool set shown in FIG. 18 together with a pulp fibre pre-form, and illustrating a stage in the forming process, with the tool set in its forward position;

FIG. 20: is a schematic vertical cross-section view of a tool set for use in a process for forming a moulded pulp fibre product, the tool set being in accordance with a sixth example;

FIG. 21: is a schematic vertical cross-section view of the tool set shown in FIG. 20 together with a pulp fibre pre-form, and illustrating a stage in the forming process, with the tool set in its retracted position;

FIG. 22: is a schematic vertical cross-section view of a tool set for use in a process for forming a moulded pulp fibre product together with a pulp fibre pre-form, the tool set being in accordance with a seventh example;

FIG. 23: is a schematic vertical cross-section view of the tool set shown in FIG. 22 together with a pulp fibre pre-form, and illustrating a stage in the forming process, with the tool set between the retracted and forward positions;

FIG. 24: is a schematic vertical cross-section view of the tool set shown in FIG. 22 together with a pulp fibre pre-form, and illustrating a stage in the forming process, with the tool set in its forward position;

FIG. 25: is a schematic vertical cross-section view of the pulp fibre pre-form after pressing in the tool set of FIG. 22;

FIG. 26: is a chart showing schematically relative density of the secondary form as shown in FIG. 25;

FIG. 27: is a schematic vertical cross section view of moulded pulp fibre product that is formed by a process according to an example;

FIG. 28: is a schematic vertical cross-section view of a tool set for use in a process for forming a moulded pulp fibre product, the tool set being in accordance with an eighth example;

FIG. 29: is a schematic vertical cross-section view of the pulp fibre pre-form after pressing in the tool set of FIG. 28;

FIGS. 30a to 30c: are schematic vertical cross-section view of the tool set shown in FIG. 28 together with a pulp fibre pre-form, and illustrating sequential stages in the forming process;

FIGS. 31a to 31c: are schematic diagrams illustrating the contact of the pulp fibre pre-form with the non-planar mould tool surface of the first mould tool shown FIG. 28 at sequential stages in the forming process;

FIG. 32: is a schematic vertical cross-section view of a first mould tool of a tool set in accordance with a ninth example;

FIG. 33: is an enlarged view of Region B in FIG. 32; and

FIGS. 34 to 36: are enhanced micro CT images of sample moulded pulp fibre products produced in accordance with forming processes described herein.

 DETAILED DESCRIPTION

The following description provides further elaboration on aspects of processes for forming a moulded pulp fibre product. This elaboration is provided in the context of schematic examples.

First Example

FIGS. 1 to 7b relate to a first example of a process for forming a moulded pulp fibre product. The process involves:

    • a. creating a slurry deposit from a suspension of pulp fibres in liquid; and
    • b. reducing the liquid content of the slurry deposit to a liquid fraction that is within a predefined range, thus forming a pulp fibre pre-form having an initial form; and
    • c. pressing the pulp fibre pre-form in a tool set to further reduce the liquid content of the pulp fibre pre-form.

The pressing step that is performed in step (c) above causes the pulp fibre pre-form to be deformed from the initial form to a secondary form. For clarity, the initial form of the pulp fibre pre-form is the shape of the pulp fibre pre-form prior to the pressing step (c) commencing, and the secondary form of the pulp fibre pre-form is the shape of the pulp fibre pre-form after completion of the pressing step (c).

The above steps (a) and (b) can be achieved by known means, an illustrative example of which is described in further detail below.

FIG. 1 shows a tool set 10 for use in the process of this first example. The tool set 10 includes a first mould tool 12, and a second mould tool 14. The mould tools are shown in a vertical cross section to more clearly illustrate interaction of the tool set 10 on the pulp fibre pre-form during the pressing step (c).

FIG. 2 illustrates the tool set 10 together with a pulp fibre pre-form in its initial form 50; that is, after liquid is removed from the slurry deposit in step (b), such that in its initial form 50, the pulp fibre material has a liquid fraction that is within the predefined range. (FIG. 2 is a vertical cross section through the tool set 10 and the initial form of the pulp fibre pre-form.) In this example, initial form 50 of the pulp fibre pre-form is a sheet of uniform thickness T1.

As will be appreciated, the tool set 10 are component parts of a press that is arranged to move the first mould tool 12 and second mould tool 14 relative to one another between a retracted position and a forward position. FIGS. 1 and 2 show the first mould tool 12 and second mould tool 14 in the retracted position, in which the separation of the mould tools is a maximum. FIG. 4 shows the first mould tool 12 and second mould tool 14 in the forward position, in which the separation of the mould tools is a minimum. As indicated in FIG. 1, the press applies a force F on the first mould tool 12 to drive the first mould tool 12 towards the forward position.

The first mould tool 12 has a non-planar mould tool surface. In this example, the first mould tool 12 has a primary region 16, and a secondary region 18; the primary region 16 is a continuous planar part of the non-planar mould tool surface that surrounds the secondary region 18. Further, as particularly shown in FIGS. 1 and 2, the secondary region 18 of the non-planar mould tool surface is recessed relative to immediately adjacent the primary region 16 (and with respect to movement of the mould tools 12, 14 towards the forward position).

In this example, the second mould tool 14 has a substantially planar tool surface 20. The second mould tool 14 is formed with fluid extraction pathways 22 that extend from the substantially planar tool surface 20 through the tool. As shown in FIG. 1, the second mould tool 14 is connected to a plenum chamber 24, such that rearward ends of the fluid extraction pathways 22 open into the plenum chamber 24. In use, a vacuum V is applied to the plenum chamber 24 to generate a suction pressure that draws fluid through the fluid extraction pathways 22 for discharge. The plenum chamber 24 is omitted from other figures in the drawings for clarity.

FIG. 3 illustrates the tool set 10 and initial form of the pulp fibre pre-form, with the first mould tool 12 displaced from the retracted position, partially towards the forward position. In FIG. 3, the primary region 16 of the non-planar mould tool surface of the first mould tool 12 has made initial contact with the upper surface of the initial form 50.

FIGS. 4 and 5 illustrate the tool set 10 and the secondary form 52 of the pulp fibre pre-form, with the first mould tool 12 in the forward position (in other words, with the minimum separation of the mould tools). The displacement of the first mould tool 12 from the position illustrated in FIG. 3 to that in FIG. 4 corresponds with the pressing step that is performed in step (c) above. FIG. 6 shows the secondary form 52 of the pulp fibre pre-form, and FIG. 7a shows a schematic vertical cross section through the middle of the secondary form 52.

FIG. 4 includes a dashed line I that indicates the position of the upper surface of the initial form 50. FIG. 4 also indicates the vertical displacement h1 of the upper surface of part of the pulp fibre pre-form that is located between the primary region 16 and the second mould tool 14, and also the minimum vertical displacement h2 of the upper surface of part of the pulp fibre pre-form that is located between the secondary region 18 and the second mould tool 14.

After step (c), the first mould tool 12 is then retracted to release the pulp fibre pre-form in its secondary form 52.

The secondary form 52 is illustrated in FIGS. 6 and 7a. An outer region 54 of the secondary form 52 has a shape that is defined by the primary region of the tool set 10. An inner region 56 of the secondary form 52 has a shape that is defined by the secondary region of the tool set 10.

As will be apparent from FIGS. 4 to 7b, the primary region 16 of the first mould tool 12 applies a first reduction in the material thickness of the pulp fibre pre-form, corresponding with the surface height displacement h1 indicated in FIG. 4. The thickness of the outer region 54 is equal to the sheet thickness T1 minus the first reduction h1. The secondary region 18 of the first mould tool 12 causes a change in the material thickness of the pulp fibre pre-form that less than the first reduction at the completion of the pressing step (c). Hence, the outer region 54 has a higher density compared with the inner region 56.

FIG. 7a is a schematic vertical cross section through the secondary form 52 of the pulp fibre pre-form produced by the process described in reference to FIGS. 1 to 5, and as illustrated in FIG. 6. As indicated in FIG. 7a, the outer region 54 is formed to a first portion 58 of pulp fibre material has a relatively high level of compression (in other words, reduction in material thickness), and has relatively high density. The inner region 56 of this example has a second portion 60 of pulp fibre material that has a relatively low level of compression, and has relatively low density. Between the first portion 58 and the second portion 60 is a third portion 62 of pulp fibre material in which the density transitions between the different densities of the first and second portions 58, 60. Similarly, the extent of compression also transitions in the third portion 62, between the different levels of compression in the first and second portions 58, 60.

FIG. 7b is a chart showing the relative material density across the width of the secondary form 52 of the pulp fibre pre-form as shown in FIG. 7a; width direction shown on the horizontal axis. In the chart, the left hand vertical axis shows the density of the pulp fibre material relative to that in the first portion 58. Hence, the relative density of the first portion 58 is equal to 1. The relative density of the material is shown by a dotted line. In this particular example, the relative density of the pulp fibre material within the second portion 60 is approximately 0.9. The relative density transition within the third portion 62 is evident from the chart. As indicated in the chart, the relative density within the second portion 60 is approximately constant.

The chart of FIG. 7b also shows the surface height displacement of the pulp fibre pre-form between the initial form 50 and the secondary form 52. In the chart, the right hand vertical axis shows the surface height displacement, and shown by a dash-dot line. The largest surface height displacement h1 being for the first portion 58, and the least surface height displacement h2 being for the second portion 60. Again, there is a transition in the surface height displacement within the third portion 62, which is representative of the transition in the level of material compression during the pressing step (c).

The correlation of material density and surface height displacement is apparent from FIG. 7b. Further, by comparing the vertical cross section of FIG. 7a with the surface height displacement in the chart of FIG. 7b, the correlation between material thickness, and material density is also apparent.

By virtue of the differing densities between the outer region 54 and the inner region 56, the mechanical properties of the secondary form 52 of the pulp fibre pre-form is not uniform. By way of example, the compressive strain of the inner region 56, in response to a point load that acts substantially transverse to the width direction of the secondary form 52, is greater than for the outer region 54 (in response to the same point load). This is because the material has a lower density within the inner region 56, compared to the outer region 54. It will be appreciated that this difference in compressive strain is due the part of the secondary form 52 that is within the inner region 56 having a lower Young's Modulus in Compression, compared with the part of the secondary form 52 that is within outer region 54.

It will be appreciated that additional and/or alternative differing mechanical properties within a moulded pulp fibre product can be achieved by the process. By way of example only, it will be recognised that the material response to bending stresses (by application of local forces, and/or distributed forces) will differ between higher density primary regions and the lower density secondary regions.

As will be apparent from FIGS. 3 and 4, the primary region 16 of the non-planar mould tool surface is to engage the surface of the pulp fibre pre-form while the tool set 10 is pressing the pulp fibre pre-form. The recessed surface form defined by the secondary region 18 of the non-planar mould tool surface is such that, in this example, there is little or no contact between the pulp fibre pre-form and the secondary region 18.

Pressing step (c) involves progressing the mould tools 12, 14 towards the forward position to an initial contact position (illustrated in FIG. 3), in which the primary region 16 is in contact with the initial form 50 of the pulp fibre pre-form. Further, a cavity 26 is formed between the non-planar mould tool surface within the secondary region 18 and the initial form 50. As will be apparent from FIG. 4, the cavity 26 is at least partially maintained as the mould tools 12, 14 continue from the initial contact position (as illustrated in FIG. 3) towards the forward position (as illustrated in FIG. 4). Accordingly, the portion of the upper surface of the pulp fibre pre-form that is adjacent the secondary region 18 is unconstrained by the first mould tool 12 during the pressing step (c).

In some embodiments, the suspension of pulp fibres in liquid, from which the slurry deposit is created, has a low pulp fibre fraction. In some examples, the suspension has a liquid fraction of the order of 99.2% (and a solid fraction of the order of 0.8%).

Step (a) typically involves accumulating pulp fibre on a forming tool. This may involve immersing a forming head (of a forming tool) into the suspension, applying suction to the forming head, so as to draw liquid component from the suspension through the forming tool, with pulp fibre component being retained on the forming head. Hence, the slurry deposit is formed on the forming head. Alternatively, this may involve passing a quantity of the suspension through a screen of a forming tool, such that pulp fibre is retained on the screen and liquid component passing therethrough.

The forming head can have a shaped mesh mould such that the slurry deposit has a predefined shape. Similarly, the screen can be shaped.

The properties of the slurry deposit that is formed in step (a) is influenced by several factors, including the forces acting on the suspension, and the fluid properties of the suspension. In at least some embodiments, these factors cause the pulp fibre within the slurry deposit to take on a loose layer-like arrangement, in which there is a degree of bonding between pulp fibres in each layer.

In some embodiments, the slurry deposit has a liquid fraction of the order of 95% (and a solid fraction of the order of 5%).

Step (b) can involve using heat and pressure on the slurry deposit to reduce the liquid content. This can occur in a single stage, or in multiple stages that progressively reduce the liquid content. The predefined range can be a liquid fraction of approximately 33% to 60% by weight of the pulp fibre pre-form in its initial form 50. In certain examples, the predefined range is a liquid fraction of approximately 50%±V1 by weight of the pulp fibre pre-form in its initial form 50, where V1 is a first nominal process variation percentage.

In some examples, the liquid content of the pulp fibre pre-form after step (c) (that is, in its secondary form 52) is of the order of approximately 5%±V2 by weight, where V2 is a second nominal process variation percentage.

As is known in the art, a pulp fibre product is a matrix of individual pulp fibres that are held together by bonds between the contacting fibres. The degree of bonding between pulp fibres within a pulp fibre matrix is inversely proportional to the liquid content. Similarly, the strength of bonds between pulp fibres within a pulp fibre matrix is also inversely proportional to the liquid content.

The slurry deposit has a sufficiently high liquid content that the individual pulp fibres within the material can be moved relatively easily, and somewhat independently of the immediately adjacent fibres within the matrix. The pulp fibre pre-form in its initial form 50 (that is, after step (b)) has sufficient inter-fibre bonds that the fibres are still movable, but the cohesion is such that movement of a fibre (or group of fibres) within the matrix effects the position of other fibres in the near vicinity.

During step (c), liquid within the pulp fibre pre-form is removed via the fluid extraction pathways 22, as previously described. However, during at least part of the pressing step (c), compression of the pulp fibre pre-form in the tool set 10 induces propagation of liquid that is within the pulp fibre pre-form in the initial form and is between the primary region 16 of the first mould tool 12 and the second mould tool 14, towards the part of the pulp fibre pre-form that is between the secondary region 18 of the first mould tool 12 and the second mould 14. This propagation of liquid is illustrated in FIG. 5 by dashed arrows P.

Without wishing to be bound to a particular mechanism or theory, it is understood that during at least an initial phase of the pressing step (c), a pressure differential is generated internally within the pulp fibre pre-form material; that is, in the portion of the pulp fibre pre-form material that is between the primary region 16 and the second mould tool 14 and is under a higher compressive load, relative to the portion of the pulp fibre pre-form material that is between the secondary region 18 and the second mould tool 14. This pressure differential causes the above described propagation P of liquid, whilst simultaneously the suction pressure draws liquid into the fluid extraction pathways 22. Hence, liquid that is extracted from the secondary region 18 during the initial phase or pressing step (c) is partially replenished by liquid propagating from the primary region 16.

As noted above, part of the upper surface of the initial form 50 that is adjacent the secondary region 18 of the first mould tool 12 is unconstrained by first mould tool 12 during the pressing step (c). However, the cohesion of the pulp fibres means that the deformation of the pulp fibre material that is in contact with the primary region 16 of the first mould tool 12 induces deformation of the adjacent pulp fibre material that is unconstrained by the first mould tool 12.

The Applicant's observations of various trials of the process described in reference to FIGS. 1 to 7b indicates that the liquid content of the initial form 50 of the pulp fibre pre-form and the establishment of the cavity 26 during the pressing step (c) contribute to the above described propagation of liquid, and the unconstrained upper surface of the pulp fibre pre-form material facing the secondary region 18. Hence, the varied density in the outer region 54 and inner region 56 in the secondary form 52 of the pulp fibre pre-form being attained.

As will be apparent from FIG. 5, the above described propagation P of liquid occurs substantially transversely with respect to movement of the first mould tool 12 towards the forward position.

Pressing step (c) can involve maintaining the pulp fibre pre-form under compression with the tool set 10 at its minimum separation (for example, with the first mould tool 12 at its forward position) until pulp fibre pre-form has attained a substantially homogenous distribution of the liquid fraction. In this way, the liquid content within the pulp fibre material in the secondary form 52 is substantially constant.

The tool set 10 can be heated such that heat is transferred from the tool set 10 to the pulp fibre pre-form. As will be appreciated, the addition of heat can facilitate the release of liquid water from the pulp fibres during the pressing step (c).

The method can further involve refining the pulp fibre prior to step (a) of creating the slurry. The Applicant's trials have used bagasse fibre that has been refined to a Canadian Standard Freeness of the order of 150 to 200 mL CSF.

Analysis of pulp fibre pre-form products that have been produced by the Applicant in trials of the process have indicated that the difference in density between the pulp fibre material of outer region 54 and inner region 56 is due, at least in part, to the formation of interlayer cavities within the second portion 60 of the pulp fibre material. These interlayer cavities 66 are indicated schematically in FIG. 7a. As will be appreciated, lateral extremities of some of the interlayer cavities 66 extend into the third portion 62 of the pulp fibre material.

Again without wishing to be bound to a particular mechanism or theory, it is understood that the formation of these interlayer cavities 66 occurring due to:

    • the slurry deposit is formed with the pulp fibre material in a loose layer-like arrangement, with the layers retaining a higher degree of internal fibre bonding (contrasted with the degree of “cross-layer bonds”) through step (b) of the process;
    • the propagation of liquid from the first portion 58 of pulp fibre material into the second and third portions 60, 62 of the pulp fibre material during the pressing step (c); and/or
    • the lower surface height displacement of the second and third portions 60, 62 of the pulp fibre material during the pressing step (c).

The Applicant's initial trials indicated that above described processes are workable at least in instances in which the lateral gap diameter of the secondary region 18 of the first mould tool 12 is selected to have a ratio to the thickness of the pulp fibre pre-form in its initial form 50 that is equal to or less than 2:1. Preferably, this ratio is less than 1.5:1. In some examples, this ratio is less than approximately 1.3:1.

As shown in the cross section of FIG. 7a, the surfaces of the secondary form 52 of the pulp fibre pre-form that are in contact with both the surfaces of the first mould tool 12 and second mould tool 14 are exposed to a higher heat transfer rate during the pressing step (c). Consequently, the secondary form 52 has surface boundary layers 68 in which the pulp fibres are locally more densely packed, and are smoothed by the contact with the mould tool surface.

Trial Example

The following part of the description relates to a trial example of the process that has been conducted by the Applicant.

A first mould tool was formed with a secondary region similar to that illustrated in FIG. 1. The secondary region had a lateral diameter of approximately 2.19 mm. The depth of the recess of the secondary region, relative to the first region, was sufficient to ensure no contact occurred between the surfaces of the pulp fibre pre-form and the secondary region of the first mould tool. The second mould tool had a substantially planar surface.

Steps (a) and (b), and the refinement of a bagasse pulp fibre were completed substantially as described in reference to FIGS. 1 to 7b.

The initial form of the pulp fibre pre-form (after step (b)) had a thickness of approximately 0.850 mm. At the conclusion of step (c) the secondary form of the pulp fibre pre-form was measured. For each of the first and second portions of the secondary form of the pulp fibre pre-form, the material thickness, calculated surface height displacement (during step (c)), and calculated relative density was as follows:

Thickness Displacement Material portion (mm) (mm) Relative density First (54) 0.570 0.280 Second (56) 0.627 0.223 0.909

The relative density calculation is based on an assumption that the initial form of the pulp fibre pre-form had a substantially uniform distribution of pulp fibre in the initial accumulation of pulp fibre to create the slurry deposit. Further, that any deviation in liquid fraction within the secondary form of the pulp fibre pre-form was negligible.

In some implementations of the process, the secondary form 52 of the pulp fibre pre-form may be a fully formed moulded pulp fibre product. In some alternative implementations of the process, the secondary form 52 of the pulp fibre pre-form is an intermediate product that is subjected to subsequent processing to complete the formation of the final moulded pulp fibre product.

The pulp fibre used to make the slurry was refined to a Canadian Standard Freeness within the range of 50 to 200 mL CSF.

In this trial example, the slurry deposit had a material thickness (measured in the direction parallel to the tool set displacement) of approximately 1.81 mm. Hence, the material compression ratio of the first portion is approximately 3.18:1.

The primary regions of the pulp fibre pre-form was subjected to an additional “dry” pressing step (that is, after the pressing step (c) was completed). This caused a further reduction in material thickness.

The resulting moulded pulp fibre product was deemed to have beneficial barrier properties with regard to an oxygen transmission rate (OTR) and water vapour transmission rate (WVTR).

Second Example

FIGS. 8 and 9 show a pulp fibre pre-form 152 corresponding with a secondary form of a pulp fibre pre-form at the conclusion of pressing step (c). The pulp fibre pre-form 152 has an outer region 154a, and a central circular region 154b. Between the outer region 154a and the circular region 154b is an annular region 156.

The tool set used in the process to form the pulp fibre pre-form 152 has a first mould tool with two primary regions that respectively form each of the outer region 154a and the circular region 154b. The secondary region of the first mould tool is an annulus that is recessed relative to the primary regions.

The pulp fibre pre-form 152 is an intermediate product in the formation of a final pulp fibre product. To this end, the pulp fibre pre-form 152 is subjected to subsequent processing after the pressing step (c). A circular cut is made through the annular region 156; the cut line being indicated in FIG. 9 by dashed lines C.

FIGS. 10 and 11 show a moulded pulp fibre product 170 that is formed from the pulp fibre pre-form 152 as described above in reference to FIGS. 8 and 9. The moulded pulp fibre product 170 has a central circular region 174 that is surrounded by an annular region 176. The radial outer edge 178 of the annular region 176 defines the peripheral edge of the moulded pulp fibre product 170.

Third Example

FIGS. 12 to 14 relate to a third example of a process for forming a moulded pulp fibre product. The process is substantially similar to the first example. Elements of the tool set 210 and secondary form 252 of the pulp fibre pre-form shown in FIGS. 12 to 14 that are similar to those shown in FIGS. 1 to 7b have the same reference numerals with the prefix “2”. These elements are not described herein for the sake of brevity.

The third example differs in respect of the geometric characteristics of the non-planar mould tool surface. To this end, the recess depth of the secondary region 218 with respect to the primary region 216 is less, compared with that of the tool set 10 in the first example. In particular, the recess depth of the secondary region 218 is such that the cavity 226 that is formed between the non-planar mould tool surface within the secondary region 218 and the initial form of the pulp fibre pre-form (not shown) is only partially maintained. In other words, as the mould tools 212, 214 continue from the initial contact position towards the forward position, a central part of the surface in the second portion 260 contacts the substantially planar tool surface 220.

As will be apparent from FIG. 13, the cavity 226 is only partially maintained once the mould tools 212, 214 are in the forward position; in this position the cavity 226 is reduced to an annular cavity. In this example, only an outer annular portion of the upper surface of the pulp fibre pre-form that is adjacent the secondary region 218 is unconstrained by the first mould tool 212 during the pressing step (c). Conversely, a central portion of the upper surface of the pulp fibre pre-form that is adjacent the secondary region 218 is in brought into contact with the mould tools 212 between the initial point of contact and the forward position of the tool set 210; that central portion being only partially unconstrained by the first mould tool 212 during the pressing step (c).

It will be appreciated that the density of the inner region 256 of the secondary form 252 will be higher than the inner region 56 of the secondary form 52. In addition, the central portion of the upper surface of the secondary form 252 within the inner region 256 has includes part of the surface boundary layers 268 in which the pulp fibres are locally more densely packed, and are smoothed by the contact with the mould tool surface.

Fourth Example

FIGS. 15 to 17 relate to a fourth example of a process for forming a moulded pulp fibre product. The process is substantially similar to the first example. Elements of the tool set 310 and secondary form 352 of the pulp fibre pre-form shown in FIGS. 15 to 18 that are similar to those shown in FIGS. 1 to 7b have the same reference numerals with the prefix “3”. These elements are not described herein for the sake of brevity.

The fourth example differs in respect of the geometric characteristics of the non-planar mould tool surface. To this end, the lateral gap diameter of the secondary region 318 of the first mould tool 312 is less than that of the secondary region 18 in the tool set 10 of the first example.

Referring to FIG. 17, it may be observed that within the inner region 356 of the secondary form 352 of the pulp fibre pre-form has an upper surface shape that is, in its entirety, influenced by the compression of the pulp fibre material by the primary region 316 during pressing step (b). Consequently, the density of the pulp fibre material within the inner region 356 varies continuously in the lateral directions.

Fifth Example

FIGS. 18 and 19 relate to a fifth example of a process for forming a moulded pulp fibre product. The process is substantially similar to the first example. Elements of the tool set 410 and secondary form 452 of the pulp fibre pre-form shown in FIGS. 18 and 19 that are similar to those shown in FIGS. 1 to 7b have the same reference numerals with the prefix “4”. These elements are not described herein for the sake of brevity.

The fifth example differs in respect of the form of the first mould tool 412. To this end, the first mould tool 412 includes vent ports 428 that extend from the non-planar mould tool surface within the secondary region 418, through the first mould tool 412. In this way, the cavity 426 that is formed between the non-planar mould tool surface within the secondary region 418 and the pulp fibre pre-form is vented to atmosphere. Hence, the internal pressure within the cavity 426 is at atmospheric pressure throughout the pressing step (c).

By virtue of the venting of cavity 426 to atmosphere, the minimum vertical displacement h2 of the upper surface of part of the pulp fibre pre-form that is located between the secondary region 418 and the second mould tool 414 is negative. In other words, part of the upper surface of the pulp fibre pre-form is displaced away from the second mould tool 414, as shown in FIG. 19.

Sixth Example

FIGS. 20 and 21 relate to a sixth example of a process for forming a moulded pulp fibre product. The process is substantially similar to the fifth example. Elements of the tool set 510 and secondary form 552 of the pulp fibre pre-form shown in FIGS. 20 and 21 that are similar to those shown in FIGS. 18 and 20 have the same reference numerals with the prefix “5” replacing the prefix “4”. These elements are not described herein for the sake of brevity.

In the sixth example, the first mould tool 512 includes vacuum lines 530 that are interconnected with the vent ports 528 that extend from the non-planar mould tool surface within the secondary region 518, through the first mould tool 512. The vacuum lines 530 are also interconnected with a vacuum source. During the pressing step (c), a suction pressure is induced in the vacuum lines 530. Once the cavity 526 between the non-planar mould tool surface within the secondary region 518 and the pulp fibre pre-form is formed, that cavity 526 has a negative pressure with respect to atmosphere. The negative pressure within the cavity 526 can further facilitate displacement of part of the upper surface of the pulp fibre pre-form away from the second mould tool 514, as shown in FIG. 21.

Seventh Example

FIGS. 22 to 26 relate to a seventh example of a process for forming a moulded pulp fibre product. The process is substantially similar to the first example. Elements of the tool set 610, initial form 650 and secondary form 652 of the pulp fibre pre-form shown in FIGS. 22 to 26 that are similar to those shown in FIGS. 1 to 7b have the same reference numerals with the prefix “6”. These elements are not described herein for the sake of brevity.

As will be immediately apparent in comparing FIG. 22 with FIG. 2, the initial form 650 has a taper, such that the upper surface of the initial form 650 whilst planar is oblique to the plane of the bottom surface. The primary region 616 likewise is planar, but is not parallel with the substantially planar tool surface 620 of the second mould tool 614.

As shown in FIG. 23, at the initial point of contact between the second mould tool 614 and the initial form 650, substantially the entirety of the primary region 616 comes into contact with the pulp fibre material.

It will be apparent that in this example, the surface height displacement of the first portion 658 (between the initial form 650 and the secondary form 652) is substantially constant. However, due to the tapered form of the initial form 650, the material compression within the first portion 658 is not constant across the width direction of the cross section, as viewed in FIGS. 24 and 26b. Hence, in this example, the parts of the outer region 654 that are immediately adjacent the inner region 656, and are formed between the primary region 616 of the first mould tool 612 and the second mould tool 614 have a higher density, compared with the inner region 656, as shown in FIG. 25.

Further, because the material compression between primary region 616 of the first mould tool 612 and the second mould tool 614 is not even, there pressure differential also varies. The result being that the part of the upper surface in the inner region 656 adopts an asymmetrical shape, as shown in FIG. 25.

FIG. 27 is a schematic vertical cross section view of a moulded pulp fibre product 780 that is formed by a process such as the first described example. The upper surface 782 of the moulded pulp fibre product 780, whilst illustrated schematically, is shown in a form to be representative of profilometry measurements obtained by the Applicant from a moulded pulp fibre product produced in a trial example of the process.

For ease of explanation, FIG. 27 includes an illustrative mould tool 712 with a form that would be suitable for forming the moulded pulp fibre product 780. The mould tool 712 has a primary region 716, and a secondary region 718. Further, the secondary region 718 of the non-planar mould tool surface is recessed relative to immediately adjacent the primary region 716. The secondary region 718 is surrounded by the primary region 716.

Laterally outer region 784 of the moulded pulp fibre product 780 are formed between the primary region 716 and the second mould tool (not shown). The central region 786 of the moulded pulp fibre product 780 are formed between the secondary region 718 and the second mould tool.

It will be apparent from the preceding description that the pulp fibre within the central region 786 has a lower density than the pulp fibre within the laterally outer region 784. As shown in FIG. 27, the upper surface 782 in the laterally outer region 784 is smooth, compared to the upper surface 782 in the central region 786. This difference in surface texture is at least partially due to the absence of contact between the part of the upper surface 782 in the central region 786 with the mould tool during the pressing step (c). To this end, exposed pulp fibres in this part of the upper surface 782 are not pressed flat as the pulp fibre pre-form is dried during the pressing step (c).

A dashed line in FIG. 27 indicates the mean position of the upper surface 782.

FIG. 27 also illustrates schematically the interlayer cavities 766 that are formed within the central region 786.

Eighth Example

FIGS. 28 and 29 relate to an eighth example of a process for forming a moulded pulp fibre product. The process is substantially similar to the first example. Elements of the tool set 810 and secondary form 852 of the pulp fibre pre-form shown in FIGS. 28 and 29 that are similar to those shown in FIGS. 1 to 7b have the same reference numerals with the prefix “8”. These elements are not described herein for the sake of brevity.

The eighth example differs in respect of the form of the first mould tool 812. To this end, the primary region of the first mould tool 812 is non-planar. To this end and in this example, a first side section 816a of the primary region is planar and parallel to the substantially planar tool surface 820 of the second mould tool 814. A second side section 816b of the primary region is planar and parallel to the substantially planar tool surface 820 of the second mould tool 814. However, section 816b is offset rearwardly with respect to movement of the first mould tool 812 towards its forward position. Between the first and second side sections 816a, 816b are curved sections 816c (one of which is visible in FIG. 28), in which the non-planar tool surface transitions across the offset. As with the first example, the primary region surrounds a secondary region 818.

FIGS. 30a to 30c show stages of engagement of the primary region with the pulp fibre pre-form 850, during the pressing step (c) of the forming process. FIGS. 31a to 31c are schematic diagrams illustrating the contact between the first mould tool 812 and the pulp fibre pre-form 850. In particular:

    • FIGS. 30a and 31a:
    • illustrate a stage in which the first side section 816a is in contact with the upper surface of the pulp fibre pre-form 850 (and there is no contact between the pulp fibre pre-form 850 and the second side section 816b and curved sections 816c);
    • FIGS. 30b and 31b:
    • illustrate a stage in which the first side section 816a and the curved sections 816c are in contact with the upper surface of the pulp fibre pre-form (and there is no contact between the pulp fibre pre-form 850 and the second side section 816b); and
    • FIGS. 30c and 31c:
    • illustrate a stage in which the entire primary region is in contact with the upper surface of the pulp fibre pre-form 850.

Further, the stage illustrated in FIGS. 30c and 31c is representative of the point in the forming process at which the first mould tool 812 has advanced to the initial contact position. Hence, all sections (816a, 816b, 816c) of the primary region that surrounds the secondary region 818 are in contact with the pulp fibre pre-form, and the cavity 826 is formed between the secondary region 818 and the pulp fibre pre-form 850.

For clarity, the second to eighth examples are illustrative of various implementations of the forming processes disclosed herein.

Further Trial Examples

The following part of the description relates to further trial examples of the process that have been conducted by the Applicant.

A set of first and second mould tools were used to create pulp fibre pre-forms having a shape similar to that shown in FIGS. 8 and 9. FIGS. 32 and 33 are schematic views of a first mould tool 912 of the set. FIG. 32 is a vertical cross section through the first mould tool 912, showing the non-planar mould tool surface. In these examples, each first mould tool 912 has an inner primary region 916a, and an outer primary region 916b. The surface of the first mould tool 912 in the inner and outer primary regions 916a, 916b are co-planar. Between the inner and outer primary regions 916a, 916b is a secondary region 918. The secondary region 918 is a generally annular recess, with respect to the inner and outer primary regions 916a, 916b.

The second mould tool (not shown) is substantially in accordance with second mould tool 14 described and illustrated in FIGS. 1 to 5. To this end, the second mould tool has a substantially planar tool surface, and is formed with fluid extraction pathways that extend from the substantially planar tool surface through the tool.

As shown particularly in FIG. 33, the secondary region 918 has a base 918a, and a pair of inclined side walls 918b, 918c. The base 918a is generally planar, and parallel to the plane of the inner and outer primary regions 916a, 916b. The side walls 918b, 918c each had a draft angle of approximately 30°.

Indicated in FIG. 33 are the main geometric attributes of the secondary region 918, as follows:

    • W1: the width of the secondary region 918, at the intersections with the inner and outer primary regions 916a, 916b,
    • W2: the width of the base 918a of the secondary region 918, and
    • d: the depth of the base 918a.

In the further trial examples, three different first mould tools 912 were used, with secondary regions having the geometric attributes as listed in the table below.

W1 (mm) W2 (mm) d (mm) Tool Set A 2.74 1 1.5 Tool Set B 4.88 2 2.5 Tool Set C 7.04 3 3.5

In all three tool sets, the annular recess formed by the secondary region 918 had a nominal pitch circle diameter of 46.5 mm.

As illustrated in FIGS. 32 and 33, each first mould tool 912 has vent ports 928 that extend from the non-planar mould tool surface within the secondary region 918, through the first mould tool 912. In this way, the cavity that is formed during the pressing step (c), between the non-planar mould tool surface within the secondary region 918 and the pulp fibre pre-form, is vented to atmosphere. Each first mould tool 912 had twenty four vent ports 928.

    • In these further trial examples, steps (a) and (b) were completed substantially as described in reference to FIGS. 1 to 7b. A bagasse pulp fibre was used to form the suspension of pulp fibres in water from which the slurry deposit was created (step (a)). The bagasse pulp fibre was refined to three different levels. Samples of the refined bagasse pulp fibre was analysed according to the Canadian Standard Freeness (CSF) test, and using a MORFI NEO, manufactured by Techpap, of Gières, France, to determine morphological characteristics of the pulp fibre.

With respect to the morphological characteristics of the samples of the refined bagasse pulp fibre, the following morphological characteristics* were recorded, and assigned abbreviations as indicated below:

Characteristic Description Unit Abbreviation Fibre length length weighted fibre length μm FLL Fibre length mean arithmetic length μm FLM Fibre width mean fibre width μm FW Aspect ratio mean arithmetic length to mean N/A AR fibre width (=FLM/FW) Fines content percentage in length of fibre % FC within the suspension
    • Detail of the analysis procedures and techniques, terminology, and calculation methodology of the above characteristics is explained in the MORFI NEO User's Manual Release 1.0.55, dated 7 Jun. 2021.

The results of the analyses of the refined pulp fibre are as follows:

CSF FLL FLM FW AR FC Pulp A 320 mL 982 625 22.9 27.3 47.8 Pulp B 197 mL 923 599 22.8 26.3 52.2 Pulp C 131 mL 886 585 23.1 25.3 52.2

It should be appreciated from the above described results that Pulp A was the least refined pulp fibre, and Pulp C was the highest refined pulp fibre.

Nine sample pulp fibre products were produced, using combinations of suspensions with the above three-described refined pulp fibre, and the above three described tool sets.

In the formation of each sample pulp fibre product, a slurry deposit was formed having a material thickness (measured in the direction parallel to the tool set displacement) of approximately 1.81 mm. In these further trial examples, the slurry deposit was formed by passing a quantity of the suspension through a substantially flat screen of a forming tool. It should be appreciated that the nature of the pulp fibre accumulation on the screen during this process naturally results in varied thickness in the slurry deposit.

The water content of the slurry deposit was reduced in multiple stages to form the pulp fibre pre-form. The multiple stages included application of pressure, and then application of both heat and pressure to the slurry deposit material. The multiple stages were performed such that the initial form of the pulp fibre pre-forms had a water fraction within the range of 42% to 53% by weight. The target water fraction for the initial form of the pulp fibre pre-forms (in other words, prior to the pressing step (c) of the process) being approximately 48% to 50% by weight.

Geometric and mass characteristics of each of the nine sample pulp fibre products were recorded. The average material density of each sample was determined on the basis of the sample mass and total area (which was uniform for all the samples, at 16 cm2). As each sample has a general sheet-like form, it is appropriate for the density to be expressed in grams/m2 (or GSM).

In addition, each sample was analysed using micro computed tomography (micro CT) x-ray scanning techniques. The images generated via the micro CT analysis facilitate non-destructive assessment and analysis of each sample. In particular and referencing FIG. 7a, the pulp fibre material within each of the first, second and third portions 58, 60, 62 of the secondary form 52 of the pulp fibre pre-form were accessible for assessment. To this end, thickness measurements of the first and second portions 58, 60 could be obtained from the images. These thickness measurements facilitate calculation of the minimum relative density of the second portion 60, with respect to the average density for the sample, and thus also of the minimum material density of the second portion 60.

The results of the above described mass and geometric observations for each sample are presented in the following table.

Relative Sample Pulp Tool Set Average GSM Min GSM density 1 A A 303 181 0.597 2 A C 311 176 0.567 3 A B 292 163 0.557 4 B C 309 203 0.656 5 B A 314 213 0.677 6 B B 313 170 0.545 7 C B 316 198 0.627 8 C A 320 161 0.503 9 C B 319 189 0.592

FIGS. 34 to 36 are enhanced images taken from the micro CT scans in respect of Samples 5, 3 and 4, respectively. The image enhancement primarily involves colour inversion for clarity. In FIGS. 34 to 36, the first, second and third portions 58, 60, 62 are identified, where visible.

In FIGS. 34 to 36, the presence of interlayer cavities within the second portions 60 of the pulp fibre material are clearly evident, as are the emergence of the interlayer cavities within the third portions 62. Further, the substantial absence of interlayer cavities within the first portions 58 of the pulp fibre material are also clearly evident.

Further observations in respect of the information contained in FIGS. 34 to 36 are as follows.

In respect of Sample 5 (FIG. 34), the interlayer cavities within the second portion 60 are concentrated closer to the upper surface of Sample 5, which was unconstrained by secondary region 918 of the first mould tool 912 during pressing step (c). In other words, the pulp fibre material adjacent to the lower surface of Sample 5 has a higher density compared to the pulp fibre material adjacent to the upper surface.

In respect of Samples 5, 3 and 4, the upper surfaces within the respective third portions 62 have a shallower angle compared with the draft angle of the first mould tools 912. To this end, the upper surfaces within these third portions 62 have an angle of the order of 12° to 25° to a horizontal datum.

None of the Samples showed any indication of the pulp fibre material that was in contact with the secondary region 918 of the first mould tool 912 during pressing step (c). To this end, visual inspection of the upper surface of the Samples showed a visually different surface texture between parts of the upper surface, due to contact, and absence of contact, with the first mould tool 912 surface. Further, the visual differences in surface texture are indicative of a cavity being formed between the secondary region 918 and the pulp fibre pre-form during the pressing step (c).

Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

1-41. (canceled)

42. A process for forming a moulded pulp fibre product, the process comprising:

creating a slurry deposit from a suspension of pulp fibres in liquid,
reducing the liquid content of the slurry deposit to a liquid fraction within a predefined range to thereby form a pulp fibre pre-form; and
pressing the pulp fibre pre-form in a tool set to further reduce the liquid content of the pulp fibre pre-form and thereby deform the pulp fibre pre-form from an initial form to a secondary form, the tool set including at least first and second mould tools that are arranged to move relative to one another between a retracted position in which the separation of the mould tools is a maximum, and a forward position in which the separation of the mould tools is a minimum, at least the first mould tool having a non-planar mould tool surface that includes:
one or more primary regions in which the non-planar mould tool surface is to engage the surface of the pulp fibre pre-form while the tool set is pressing the pulp fibre pre-form; and
at least one secondary region in which the non-planar mould tool surface is recessed relative to immediately adjacent the primary regions and with respect to movement of the mould tools towards the forward position, the secondary region being surrounded by the primary regions,
wherein pressing the pulp fibre pre-form in the tool set comprises:
progressing the mould tools towards the forward position to an initial contact position, in which the primary regions that surround the secondary region are in contact with the pulp fibre pre-form and a cavity is formed between at least part of the non-planar mould tool surface within the secondary region and the pulp fibre pre-form, and then
at least partially maintaining the cavity as the mould tools continue from the initial contact position towards the forward position such that the portion of the surface of the pulp fibre pre-form that is adjacent the secondary region is unconstrained by the first mould tool.

43. The process of claim 42, further comprising maintaining the cavity between the mould tool surface within the entire secondary region and the pulp fibre pre form, such that the surface of the pulp fibre pre-form that is adjacent the secondary region is unconstrained by the first mould tool throughout the step of pressing the pulp fibre pre-form.

44. The process of claim 42, further comprising maintaining the cavity between only a part of the mould tool surface within the secondary region and the pulp fibre pre form, such that only a portion of the surface of the pulp fibre pre-form that is adjacent the secondary region is unconstrained by the first mould tool throughout the step of pressing the pulp fibre pre-form.

45. The process of claim 43, wherein maintaining the cavity comprises controlling at least one of the rate of movement of the mould tools towards the forward position, and the force applied to at least one of the mould tools.

46. The process of claim 45, wherein controlling the rate of movement of the mould tools towards the forward position comprises limiting the maximum rate of movement to a predefined upper limit.

47. The process of claim 45, wherein controlling the force applied to at least one of the mould tools comprises limiting the maximum force that is applied to a predefined maximum.

48. The process of claim 42, wherein the lateral diameter of the secondary region of the first mould tool is selected such that a diameter-to-material thickness ratio that is equal to or less than 2:1, the diameter-to-material thickness ratio being the ratio of the lateral diameter of the secondary region to the minimum thickness of the pulp fibre pre-form in its initial form.

49. The process of claim 42, wherein the non-planar mould tool surface is configured such that, after the step of pressing the pulp fibre pre-form, the lowest density of the portion that is formed by the secondary region of the first mould tool and the second mould tool is between 50% and 98% of the maximum density of the portions that are formed between the primary regions of the first mould tool and the second mould tool.

50. The process of claim 42, wherein after the step of pressing the pulp fibre pre-form, the density of the portion that is formed by the secondary region of the first mould tool and the second mould tool decreases with distance from portions that are formed between the primary regions of the first mould tool and the second mould tool.

51. The process of claim 42, wherein the second mould tool includes extraction passageways that extend from openings in the mould tool surface of the second mould tool through the second mould tool, and the step of pressing the pulp fibre pre-form comprises applying suction to the extraction passageways to draw liquid from the pulp fibre pre-form through the openings and into the extraction passageways.

52. The process of claim 42, wherein the first mould tool includes venting passageways that extend from openings in the second region of the mould tool surface of the second mould tool through the second mould tool, and the method further comprises allowing gas to discharge from the cavity through the venting passageways during the step of pressing the pulp fibre pre-form.

53. The process of claim 52, further comprising applying suction to the venting passageways to draw gas from the cavity through the venting passageways during the step of pressing the pulp fibre pre-form.

54. The process of claim 42, wherein, in the step of reducing the liquid content of the slurry deposit, the predefined range is a liquid fraction of approximately 33% to 60% by weight of the pulp fibre pre-form.

55. The process of claim 42, wherein the step of pressing the pulp fibre further reduces the liquid fraction such that in the second form of the pulp fibre pre-form has a liquid content of less than approximately 10% by weight of the pulp fibre pre-form.

56. The process of claim 42, further comprising refining the pulp fibre prior to the step of creating the slurry.

57. The process of claim 56, wherein refining the pulp fibre comprises refining the pulp fibre to a Canadian Standard Freeness of less than approximately 300 mL CSF.

58. The process of claim 42, wherein the secondary form of the pulp fibre pre-form is the moulded pulp fibre product.

59. The process of claim 42, wherein the secondary form of the pulp fibre pre-form is an intermediate product in the production of the moulded pulp fibre product.

60. The process of claim 42, wherein the process is arranged to have a material compression ratio that is at least 2:1,

wherein the material compression ratio is the ratio of the thickness of the slurry deposit to the minimum thickness of the secondary form of the pulp fibre pre-form, measured in a direction that is parallel to the relative movement of the tool set and at the same relative location of the pulp fibre material.

61. The process of claim 42, wherein pressing the pulp fibre pre-form in the tool set induces propagation of liquid that is within the pulp fibre pre-form in the initial form and is between the primary regions of the first mould tool and the second mould tool, towards the part of the pulp fibre pre-form that is between the secondary region of the first mould tool and the second mould tool.

Patent History
Publication number: 20260348103
Type: Application
Filed: Oct 10, 2023
Publication Date: Nov 5, 2026
Inventors: Mark APPLEFORD (Braeside, Victoria), Stuart GORDON (Braeside, Victoria), Liam METHVEN (Braeside, Victoria), Dion SANTOSO (Braeside, Victoria), Rico TABOR (Braeside, Victoria)
Application Number: 19/119,984
Classifications
International Classification: D21J 3/00 (20060101);