Method for forming molded slurry product

Abstract

A method for forming a molded pulp fibrous product, comprising: preparing a stock pulp solution; providing a porous mold having pre-forming mold portions, each having a forming surface corresponding to a portion of the outer surface of the final molded pulp fibrous product; accumulating the wet refined slurry fibers on the forming surface of the pre-forming mold portion; and pressing the slurry deposit between opposing molding tool surfaces to expel the liquid. Preparation of the stock slurry includes passing a suspension of slurry fibers and a liquid through a series of refining processes to refine the slurry fibers to have predetermined characteristics. Pressing the pulpy deposit reduces the ratio of liquid to refined pulp fibers and processes accumulated refined pulp fibers from the form of the pulpy deposit into the form of a final molded pulp fiber product.

Description

Technical Field

[0001] This invention relates to a method for forming molded slurry products. The invention also relates to a production line and production plant for forming molded slurry products. Background Technology

[0002] Molded pulp fibers are known for their use in packaging products (such as egg cartons, carton liners, etc.), disposable food and beverage service trays / containers, and transportation products. Compared to many similar plastic materials, the advantage of molded pulp fiber products is that they can be composted after their service life.

[0003] A widely used method for forming molded slurry fiber products (hereinafter referred to as the "basic method") includes: 1. Prepare the pulp stock solution, which is a suspension of pulp fibers and liquid; 2. Immerse the molding head into the slurry stock solution. The molding head has a molding mesh mold. 3. Apply suction to the molding head to pull the slurry fibers onto the mesh mold, thereby forming a preform on the mesh mold (this preform can be regarded as a "slurry deposit"; in other words, a mixture of liquid and slurry fibers that forms the final molded slurry fiber product). 4. Remove the molding head from the open can while maintaining suction pressure to hold the preform on the mesh mold; and 5. Dry the preform to solidify the slurry fiber material.

[0004] The drying step of the basic method typically involves placing the preform in a drying oven to bake it, thereby fixing the bonds between the structures and giving the final product the desired structural integrity.

[0005] An improved method for forming molded slurry fiber products is termed "thermoforming" or "precision molding." This method uses a tooling set of two (or more) complementary dies that are heated and compress the wet slurry preform during a drying step. Compared to the basic method, this method offers the advantage of forming products with thinner walls, higher structural integrity, and smoother surfaces.

[0006] Typically, manufacturers of molded pulp fiber products receive pulp materials from pulp mills, such as dried, sheet-like pulp materials. The pulp material produced by the pulp mill is considered virgin pulp fiber. At the manufacturing plant, the virgin pulp fiber material is impregnated in a repulper to prepare a pulp solution. Inside the repulper, the virgin pulp fibers are at least partially pulverized and mixed with water to form a pumpable suspension (typically with a fiber content of about 4% or less), which is the pulp solution. Inhomogeneous and / or non-homogeneous pulp solutions with uneven fiber content can lead to inconsistent performance / characteristics in the final pulp product. To make the pulp solution more homogeneous, the partially pulverized pulp from the repulper suspension can be deflaked to further break down large particles in the pulp. In this part of the process, the size and quantity of fiber bundles, fiber fragments, and fiber chips are reduced.

[0007] The structure and physical properties of the fiber material in the pulp solution can be altered through a finishing process, which is a mechanical processing of the pulp fibers. The purpose of finishing the pulp solution is to adjust the characteristics of the pulp fibers to obtain the properties required for the final product. The characteristics altered during finishing include (but are not limited to) fine content, breakage content, degree of fibrillation, fiber hydration degree (which affects fiber flexibility), fiber length, and fiber crimp / twist. Pulp fiber finishing is used in the production of paper and paperboard products to increase the density of the fiber network in the final product, thereby affecting the elastic modulus and tensile strength of the final product.

[0008] The refining process of pulp fibers consumes a significant amount of energy, which incurs costs. Furthermore, as the degree of refining increases, the rate of pulp fiber dehydration decreases. Therefore, the workload (i.e., the energy required) for the initial dehydration from the suspension to form a slurry deposit, and then for further drying of the pulp fibers, increases with the degree of refining. Since increasing the degree of refining of the pulp fibers in the pulp solution increases energy consumption, the degree of refining should be minimized while still meeting the performance requirements of the final product.

[0009] Although the raw material fibers used in molding pulp products and paper products are fundamentally similar, the forming processes (including the processing of the material fibers) are quite different. A significant difference is that molding pulp products are essentially formed individually (either fully formed or formed in batch operations of a group of products), while paper can be formed in a continuous production process. Continuous production processes for paper and paperboard manufacturing can accommodate increased dewatering times (i.e., drainage and evaporation rates) by using process equipment suitable for continuous production (such as dewatering jets, multi-roll presses, etc.). The "direction" of dewatering during paper and paperboard forming is typically perpendicular to the machine direction (the main plane of the paper), meaning that the pressing operation is highly efficient.

[0010] In contrast, molding methods for (typically three-dimensional) molded pulp fiber products face significant challenges as the degree of pulp fiber refinement increases. Consequently, the molding of molded pulp fiber products is performed in batches, meaning that production efficiency drops rapidly with increasing fiber refinement. This problem is further exacerbated during thermoforming, where the draft angle of the final molded pulp product approaches the closing direction of the molding tooling assembly, the dehydration "direction" is nearly parallel to the main surface of the product, and the material is subjected to shearing forces during dehydration.

[0011] Studies have shown that dehydration time is directly related to commercial viability (Debnath et al., 2022, “A Review of Molded Pulp Packaging”, BioResources 17(2), 3810-3870). Therefore, as mentioned above, the numerous benefits that pulp refining can bring to paper and paperboard products cannot be translated into molded pulp fiber products in a commercial context. For molded pulp fiber products, the obstacles encountered with increasing fiber refining limit the molding process, and consequently limit the functional and structural properties of the final product. Conversely, as mentioned above, these limitations restrict the range of products prepared from molded pulp fibers.

[0012] It is generally accepted that in commercial-scale production of molded pulp fiber products, the process of processing pulp fibers into pulp concentrate involves only a low level of fiber finishing.

[0013] The above problems need to be addressed, or at least useful alternatives need to be provided.

[0014] For the purposes of this specification and the following claims, “discharge” and “emission” of liquid from a suspension should be understood to include removing liquid from a suspension by gravity alone, by applying a vacuum, and by applying pressurized gas. The latter two cases can involve removing liquid by gravity or by overcoming gravity.

[0015] For the purposes of this specification and the following claims, "fiber" should be understood to refer to fibrous material with a length greater than or equal to 200 μm. In the context of slurry fibrous materials, the term "fine particle" should be understood to refer to fibrous material with a length less than 200 μm and at least about 2 μm or greater in any direction. Fiber material smaller than the fine particle is considered cellulose microparticles. The term "percentage of fine particle by length in suspension" refers to the percentage of the total length of all fine particles in the suspension relative to the total length of all fibers. For example, the percentage of fine particle by length in suspension can be determined based on morphological analysis of one or more samples of the suspension.

[0016] For the purposes of this specification and the following claims, “slurry fiber” (including “virgin slurry fiber”, “partially milled slurry fiber” and “milled slurry fiber”) should be understood to include slurry fiber materials containing fibers, and may also include fine particles. Summary of the Invention

[0017] This invention provides a method for forming molded pulp fiber products, the method comprising: Preparation of slurry stock solution includes: Forming a suspension of pulp fibers and liquid, and The suspension is subjected to a series of fine grinding processes, each of which finely grinds the pulp fibers, such that the average fiber length of the finely ground pulp fibers in the pulp stock solution is less than the average length of the original pulp fibers forming the suspension, and the finely ground pulp fibers in the pulp stock solution have a proportion of at least 45% fine material in the pulp fiber component of the suspension by length. Provide a porous mold having one or more pre-forming mold portions, each of the pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By guiding the slurry concentrate toward a porous mold and removing the liquid through the mold, wet, finely ground slurry fibers accumulate on the forming surface of the preforming mold section, forming a slurry-like deposit; and The slurry deposit is pressed between opposing molding tool surfaces to expel the liquid, thereby reducing the ratio of liquid to finely ground slurry fibers and processing the accumulated finely ground slurry fibers from the form of slurry deposit into the form of the final molded slurry fiber product.

[0018] In at least some embodiments, preparing the pulp stock solution includes passing the suspension through a series of fine grinding processes such that the average fiber width of the finely ground pulp fibers in the pulp stock solution is 90% or greater than the average native fiber width. Preferably, preparing the pulp stock solution includes passing the suspension through a series of fine grinding processes such that the average fiber width of the finely ground pulp fibers in the pulp stock solution is 95% or greater than the average native fiber width. More preferably, preparing the pulp stock solution includes passing the suspension through a series of fine grinding processes such that the average fiber width of the finely ground pulp fibers in the pulp stock solution remains substantially unchanged relative to the average native fiber width.

[0019] A method for forming a molded pulp fiber product is provided, the method comprising: Preparation of slurry stock solution includes: Forming a suspension of pulp fibers and liquid, and The suspension is subjected to a series of fine grinding processes, each of which finely grinds the pulp fibers. As a result, the average fiber length of the finely ground pulp fibers in the pulp stock solution is less than the average length of the original pulp fibers forming the suspension, and the average fiber width of the finely ground pulp fibers in the pulp stock solution is 90% or greater than the average original fiber width. Provide a porous mold having one or more pre-forming mold portions, each of the pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By guiding the slurry concentrate toward a porous mold and removing the liquid through the mold, wet, finely ground slurry fibers accumulate on the forming surface of the preforming mold section, forming a slurry-like deposit; and The slurry deposit is pressed between opposing molding tool surfaces to expel the liquid, thereby reducing the ratio of liquid to finely ground slurry fibers and processing the accumulated finely ground slurry fibers from the form of slurry deposit into the form of the final molded slurry fiber product.

[0020] In at least some embodiments, preparing the pulp stock solution includes passing the suspension through a series of fine grinding processes such that the average fiber width of the finely ground pulp fibers in the pulp stock solution is 95% or greater than the average native fiber width. Preferably, preparing the pulp stock solution includes passing the suspension through a series of fine grinding processes such that the average fiber width of the finely ground pulp fibers in the pulp stock solution remains substantially unchanged relative to the average native fiber width.

[0021] In at least some embodiments, preparing the slurry stock solution includes subjecting the suspension to a series of fine grinding processes, such that the finely ground slurry fibers in the slurry stock solution have a proportion of at least 45% fine material in the slurry fiber component of the suspension by length.

[0022] In at least some embodiments, pressing the slurry deposit between opposing molding tool surfaces comprises a series of two or more pressing steps configured to progressively drain liquid from the slurry deposit, wherein, as the series of pressing steps proceeds, the geometry of the accumulated, finely ground slurry fibers changes from the initial form of the slurry deposit to the form of the final molded slurry fiber product.

[0023] In some examples, the geometry of the accumulated, finely ground slurry fibers varies from the initial form of the slurry deposition to the form of the final molded slurry fiber product, including one or more intermediate forms formed by corresponding pressing processes in a series of pressing processes prior to the final pressing process.

[0024] In some examples, the geometry of the accumulated, finely ground pulp fibers varies at each pressing step and includes one or more of the following: The reduction in the thickness of one or more portions of the accumulated finely ground pulp fibers, or the reduction in the thickness of the entire accumulated finely ground pulp fibers; The change in the geometric proportions of the accumulated, finely ground pulp fibers; or The relative displacement of two spaced-apart surface portions in the accumulated, finely ground pulp fibers.

[0025] Preferably, the proportion of fine material by length in the slurry fiber component of the suspension is 50% to 60%. More preferably, the proportion of fine material by length in the slurry fiber component of the suspension is about 55%.

[0026] Alternatively or additionally, the preparation of the pulp stock solution includes: milling the pulp fibers to a Canadian standard freeness of less than about 300 mL CSF.

[0027] A method for forming a molded pulp fiber product is provided, the method comprising: Preparation of slurry stock solution includes: Forming a suspension of pulp fibers and liquid, and The suspension is subjected to a series of fine grinding processes, each of which refines the pulp fibers to achieve a freeness of less than approximately 300 mL CSF according to Canadian standards. Provide a porous mold having one or more pre-forming mold portions, each of the pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By guiding the slurry concentrate toward a porous mold and removing the liquid through the mold, wet, finely ground slurry fibers accumulate on the forming surface of the preforming mold section, forming a slurry-like deposit; and The slurry deposit is pressed between opposing molding tool surfaces to expel the liquid, thereby reducing the ratio of liquid to finely ground slurry fibers and processing the accumulated finely ground slurry fibers from the form of slurry deposit into the form of the final molded slurry fiber product.

[0028] In some embodiments, preparing the pulp stock solution includes: milling the pulp fibers to a Canadian standard freeness of 100 mL CSF to 200 mL CSF. Preferably, preparing the pulp stock solution includes: milling the pulp fibers to a Canadian standard freeness of 100 mL CSF to 150 mL CSF. More preferably, preparing the pulp stock solution includes: milling the pulp fibers to a Canadian standard freeness of 130 mL CSF.

[0029] In some examples, each fine grinding step includes passing the suspension through at least one fine grinding mill having a rotor and a stator with a gap defined between the rotor and the stator, through which the suspension passes, wherein a series of fine grinding steps is configured such that the width of the gap decreases between at least some of the successive steps in the series of fine grinding steps.

[0030] In some embodiments, a series of finishing processes includes an initial finishing process and one or more subsequent finishing processes, and the method includes setting the width of the gap between the rotor and the stator before allowing the suspension to pass through each subsequent finishing process.

[0031] The gap width is set before the suspension passes through each subsequent finishing grinding step by the following steps: According to a pre-established agreement, and / or Based on the analysis of partially finely ground slurry in the suspension, the predetermined suspension characteristics are achieved when the corresponding subsequent fine grinding process is completed.

[0032] In some cases, setting the gap width includes reducing the width of the gap between the rotor and stator relative to the width of the gap in the immediately preceding finishing process. In some cases, setting the gap width includes maintaining the same gap width as used in the immediately preceding finishing process. In some cases, setting the gap width includes increasing the width of the gap between the rotor and stator relative to the width of the gap in the immediately preceding finishing process.

[0033] In some examples, each fine grinding step includes passing the suspension through a fine grinding mill having a rotor and a stator with a gap defined between the rotor and the stator, through which the suspension passes, and wherein passing the suspension through a series of fine grinding steps includes circulating the suspension, and each fine grinding step corresponds to passing the suspension through the gap.

[0034] Circulating a suspension may include: making the suspension flow continuously such that at any given time, a portion of the suspension passes through the gap while another portion of the suspension travels along a flow path extending from the outlet of the gap to the inlet of the gap.

[0035] The pulp fiber used to prepare the pulp stock solution can be sugarcane bagasse.

[0036] In some examples, preparing the pulp stock solution includes: finely grinding the pulp fibers such that the average pulp fiber length in the finely ground pulp stock solution is less than or equal to 1 mm. In some preferred examples, preparing the pulp stock solution includes: finely grinding the finely ground pulp fibers such that the average pulp fiber length in the pulp stock solution is in the range of 0.58 mm to 1 mm.

[0037] In some embodiments, preparing the pulp stock solution includes: finely grinding the pulp fibers such that the average length of the finely ground pulp fibers in the pulp stock solution is less than or equal to 1 mm. In some preferred embodiments, preparing the pulp stock solution includes: finely grinding the pulp fibers such that the average length of the finely ground pulp fibers in the pulp stock solution is in the range of 0.58 mm to 1 mm. In some cases, preparing the pulp stock solution includes: finely grinding the pulp fibers such that the average length of the finely ground pulp fibers in the pulp stock solution is 0.7 mm ± 0.1 mm.

[0038] In some alternative or additional embodiments, preparing the pulp stock solution includes passing the suspension through a series of fine grinding processes such that the average fiber width of the finely ground pulp fibers in the pulp stock solution is in the range of 15 μm to 25 μm. In some cases, preparing the pulp stock solution includes passing the suspension through a series of fine grinding processes such that the average fiber width of the finely ground pulp fibers in the pulp stock solution is 25 μm ± 5 μm.

[0039] In some examples, preparing the pulp stock solution further includes: finely grinding the pulp fibers so that the proportion of fine particles as secondary fine particles in the pulp stock solution is less than one-third. In some applications, preparing the pulp stock solution further includes: finely grinding the pulp fibers so that the proportion of fine particles as secondary fine particles in the pulp stock solution is less than about 25%.

[0040] In some embodiments, the preparation of the pulp stock solution further includes: finely grinding the pulp fibers so that the content of pulp residue in the fiber-forming regions, as measured by imaging technology, is less than 0.5%. In some cases, the preparation of the pulp stock solution further includes: finely grinding the pulp fibers so that the content of pulp residue in the fiber-forming regions, as measured by imaging technology, is about 0.3%.

[0041] In some examples, the preparation of the pulp solution further includes: milling the pulp fibers such that the milled pulp fibers in the pulp solution have a fibrillation index of at least 1%. Alternatively or additionally, the milled pulp fibers in the pulp solution have a fibrillation index between 1.5% and 2%. In some examples, the milled pulp fibers in the pulp solution have a fibrillation index of about 1.8%.

[0042] In some examples, the preparation of the sizing solution further includes: finely milling the sizing fibers so that the sizing solution has a fine content of less than or equal to 65% by length. Alternatively or additionally, the sizing solution has a fine content between 50% and 60% by length. In some examples, the sizing solution has a fine content of approximately 55% by length. The fine content is determined by the percentage of total fine length to total fiber length in the sample.

[0043] A series of fine grinding processes may include two or more fine grinding processes, each having a predetermined gap width. In this process, the gap width of each of the second and subsequent fine grinding processes is in the range of 40% to 95% of the gap width of the immediately preceding fine grinding process.

[0044] The suspension of pulp fibers and liquid may also include: immersing virgin pulp fibers in the liquid.

[0045] The preparation of slurry raw materials may further include: passing the suspension through a dissolving process. Preferably, the suspension is passed through the dissolving process before the fine grinding process.

[0046] The reduction in thickness of one or more portions of the slurry deposit during any pressing step in the pressing process includes: Decrease in the direction parallel to the relative movement of the opposing molding tool surfaces; The decrease in the direction of relative movement transverse to the opposing molding tool surfaces; or The decrease is in the direction parallel to the relative movement of the opposing molding tool surface and in the direction transverse to the relative movement of the opposing molding tool surface.

[0047] Preferably, each pressing step in the pressing process includes reducing the thickness of the slurry deposit by 50% or less in any direction.

[0048] In some embodiments, the series of pressing steps includes three or more pressing steps, at least one of the pressing steps including: reducing the thickness of the slurry deposit only in a direction parallel to the relative movement of the opposing molding tool surfaces.

[0049] In some implementations, in the first pressing step of a series of pressing steps, the forming surface of the preform mold portion is one of the molding tool surfaces relative to the molding tool surface.

[0050] Preferably, in at least some of the pressing steps, the molding tool defining the opposing molding tool surfaces is heated, and the method further includes controlling the temperature of each opposing molding tool surface such that at the end of the respective pressing step, the ratio of finely ground slurry fibers to liquid has a predetermined value.

[0051] Alternatively or additionally, in at least some of the pressing steps, the molding tool defining the opposing molding tool surface has a suction channel communicating with a vacuum source, and the method further includes: controlling the suction applied to the suction channel so that at the end of the respective pressing step, the ratio of finely ground slurry fibers to liquid has a predetermined value.

[0052] A method for forming a molded pulp fiber product is also provided, the method comprising: Preparation of slurry stock solution, which includes forming a suspension of slurry fibers and liquid; Provide a porous mold having one or more pre-forming mold portions, each of the pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By guiding the slurry concentrate toward a porous mold and removing the liquid through the mold, wet slurry fibers accumulate on the molding surface of the pre-forming mold section, forming a slurry-like deposit; and The slurry deposit is pressed between opposing molding tool surfaces to expel liquid, thereby reducing the liquid-to-slurry fiber ratio and processing the slurry fiber from the form of slurry deposit into the form of a final molded slurry fiber product. As a series of pressing processes are carried out, the geometry of the accumulated slurry fiber changes from the initial form of slurry deposit to the form of the final molded slurry fiber product.

[0053] In some examples, the geometry of the accumulated pulp fibers changes at each pressing step by one or more of the following: A reduction in the thickness of one or more portions of the accumulated pulp fibers, or a reduction in the thickness of the entire accumulated pulp fibers; The geometric ratio of the pulp fibers; or The relative displacement of two spaced-apart surface portions in the accumulated pulp fibers.

[0054] The reduction in thickness of one or more portions of the slurry deposit during any pressing step in the pressing process includes: Decrease in the direction parallel to the relative movement of the opposing molding tool surfaces; The decrease in the direction of relative movement transverse to the opposing molding tool surfaces; or Decrease in the direction parallel to the relative movement of the opposing molding tool surface and decrease in the direction transverse to the relative movement of the opposing molding tool surface.

[0055] Preferably, each pressing step in the pressing process includes reducing the thickness of the slurry deposit by 50% or less in any direction.

[0056] In some embodiments, the series of pressing steps includes three or more pressing steps, at least one of the pressing steps including: reducing the thickness of the slurry deposit only in a direction parallel to the relative movement of the opposing molding tool surfaces.

[0057] In some implementations, in the first pressing step of a series of pressing steps, the forming surface of the preform mold portion is one of the molding tool surfaces relative to the molding tool surface.

[0058] Preferably, in at least some of the pressing steps, the molding tool defining the opposing molding tool surfaces is heated, and the method further includes controlling the temperature of each opposing molding tool surface such that at the end of the respective pressing step, the ratio of finely ground slurry fibers to liquid has a predetermined value.

[0059] Alternatively or additionally, in at least some of the pressing steps, the molding tool defining the opposing molding tool surface has a suction channel communicating with a vacuum source, and the method further includes: controlling the suction applied to the suction channel so that at the end of the respective pressing step, the ratio of finely ground slurry fibers to liquid has a predetermined value. Attached Figure Description

[0060] To facilitate a clearer understanding of the invention, embodiments will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 This is a flowchart of a method for forming a molded pulp fiber product according to the first embodiment; Figure 2 : is shown Figure 1 A flowchart showing more details of one or more finishing operations in the method illustrated; Figure 3 : is shown Figure 1 A flowchart showing more details of the pressing operation of the method illustrated; Figures 4a and 4b illustrate the implementation. Figures 1 to 3 The diagram shows a schematic process flow chart of the equipment, operations, and steps for forming molded pulp fiber products; Figures 5a to 5f are schematic cross-sectional views showing the material deformation in each pressing step of the pressing process shown in Figure 4b; Figure 6 This is a flowchart of a method for forming a molded pulp fiber product according to the second embodiment. Detailed Implementation

[0061] Figure 1 This is a flowchart illustrating the operation of a method 100 for forming a molded slurry fiber product. The method 100 includes: Operation 102 – Preparation of slurry stock solution, which comprises finely ground slurry fibers and liquid; Operation 120 – Provides a porous mold having one or more preformed mold portions, each preformed mold portion having a forming surface; Operation 122 – Accumulate wet, finely ground pulp fibers on the molding surface; Operation 124 – Press the slurry deposit between the opposing mold tool surfaces to expel the liquid.

[0062] Figure 2 The preparation of the slurry stock solution is shown in more detail (operation 102). Operation 102 specifically includes: Operation 104 – Forming a suspension of pulp fibers and liquid; and Operation 108 – subjecting the suspension to a series of fine grinding processes.

[0063] Figure 3 The pressing of the slurry deposit between opposing molding tool surfaces to expel the liquid is shown in more detail (operation 124).

[0064] The raw material for pulp fibers can be any desired cellulose material, which can be derived from plants. Therefore, the raw material for pulp fibers can be plant fibers supplied by a pulp mill as dried pulp fiber sheets. The suspension formed at operation 104 can be obtained by mixing these dried pulp fiber sheets with a liquid (e.g., water). It may be necessary to pulverize the pulp fibers through impregnation.

[0065] At operation 108, the suspension undergoes a series of refining processes, each refining the pulp fibers. The refined pulp fibers in the pulp stock solution possess the following characteristics: - An average fiber length smaller than the average length of the virgin pulp fibers used to prepare the suspension, and - The proportion of fine particles by length in the slurry fiber component of the suspension is between 45% and 65%.

[0066] Average fiber length can be determined using morphological analysis techniques / instruments. The proportion of fine fibers by length can also be determined using morphological analysis techniques / instruments. This will be discussed in more detail below.

[0067] like Figure 2 As shown, the suspension formed in operation 104 can undergo a spalling operation 106. As is known, spalling of the suspension separates the fiber bundles (called shives). During spalling, the slurry fiber material is subjected to an abrasive-like action, thereby generating shear forces on the slurry fibers. These shear forces initiate the separation of the shives, with minimal impact on the properties of individual fibers. This operation 106 can reduce the energy required for the finishing process.

[0068] exist Figure 2 In the example shown, there are four fine grinding processes in a series (labeled operations 110, 112, 114, and 116, respectively). The equipment used to perform operation 108 affects certain aspects of method 100. For example... Figure 1 and Figure 2 The flowchart illustrates an example where each fine grinding operation 110, 112, 114, and 116 involves passing a suspension through a common fine grinding mill having a rotor and a stator, through which the suspension travels. The fine grinding mill can be configured to allow adjustment of the width of the gap between the rotor and stator. Furthermore, the slurry operation 106 is achieved by passing the suspension through this fine grinding mill.

[0069] Prior to the slurry operation 106, the gap width of the fine grinding mill is set to an initial gap width. After the slurry operation 106, method 100 includes setting the rotor / stator gap width at operation 106b to the width required for the first slurry fiber fine grinding operation 110. Similarly, after the first fine grinding operation 110, the second fine grinding operation 112, and the third fine grinding operation 114, method 100 includes setting the rotor / stator gap width at operations 110b, 112b, and 114b to the width required for the corresponding subsequent slurry fiber fine grinding operations. In operations 110b, 112b, and 114b, the gap width is set such that the slurry fibers are progressively processed to the target fine grinding level through operation 108.

[0070] Method 100 includes an optional operation 114c, in which the suspension following operation 114 (“third pulp fiber finishing”) is analyzed to evaluate the properties of the partially finished pulp fibers in the suspension. This analysis may be an empirical measurement representing the properties of the partially finished pulp fibers (e.g., Canadian Standard Freeness), and / or may be a quantitative measurement of the actual partially finished pulp fibers (e.g., by morphology analysis). This analysis provides a finishing progress index indicating the degree of finishing achieved in the first finishing step 110, the second finishing step 112, and the third finishing step 114.

[0071] The analysis and evaluation of the degree of refinement of the partially refined pulp fibers at the end of operation 114 provides a refinement progress index. This index allows setting the gap width between the rotor and stator in the final refinement process 116; thus, the pulp concentrate is refined to a degree close to or (ideally) reaching the target refinement level in the pulp concentrate. Based on the analysis in operation 114c, operation 114b may include reducing the gap width or maintaining either the gap width used in the third pulp refinement operation 116.

[0072] After the first fine grinding step 110 or the second fine grinding step 112, the degree of fine grinding of the partially finely ground pulp fibers can be analyzed and evaluated to provide a fine grinding progress indicator. This can serve as an alternative to or supplement to the aforementioned operation 114c. Furthermore, the gap width for one or more fine grinding steps in subsequent fine grinding processes can be set based on the fine grinding progress indicator.

[0073] In some alternatives, method 100 may not require analysis of the suspension prior to the fourth fine grinding step 116. In these alternatives, the gap width between each fine grinding step is set according to an agreement.

[0074] After the fourth pulp fiber refining operation 116, the pulp concentrate is ready for use. For example... Figure 2 As shown, the raw slurry is transferred 118 for accumulation operation 122 as required.

[0075] like Figure 3 As shown, operation 124 mainly comprises a series of two or more pressing steps, which are configured to progressively drain liquid from the slurry deposit. Figure 3In the example shown, there are five pressing steps (labeled operations 126, 128, 130, 132, and 134, respectively). As the slurry deposit progressively passes through a series of pressing steps, the geometry of the accumulated, finely ground slurry fibers transforms from the initial slurry deposit form to the final molded slurry fiber product form. Because each of the five pressing steps in this example (operations 126, 128, 130, 132, and 134) uses a separate molding tool to provide a relative molding tool surface at each pressing step, the accumulated, finely ground slurry fibers are transferred four times between successive pressing steps—see [link to example]. Figure 3 Operations 126b, 128b, 130b, and 132b (“Transfer Preform”) are included.

[0076] The geometric variation of the finely ground slurry fibers accumulated at each pressing step depends at least in part on the shape of the relative molding tool surface of the corresponding pressing step. The geometric variation at each step may include one or more of the following: - The thickness of the finely ground pulp fibers is reduced, either partially or entirely. - The geometric proportions of the accumulated, finely ground pulp fibers; or - The two spaced-apart surface portions in the accumulated finely ground pulp fibers undergo relative displacement.

[0077] These changes will be discussed in more detail below.

[0078] Those skilled in the art will understand from this disclosure that the methods disclosed herein are capable of forming molded pulp fiber products with desired properties, including (but not limited to) high material density (especially in wall sections with draft angles in the range of 10° to 5°), high geometric tolerances, material surface properties (e.g., surface roughness), mechanical properties, and blocking / barrier properties for water vapor and / or oxygen permeation.

[0079] In terms of barrier / blocking properties, it is possible to form molded pulp fiber products in which the molded pulp fiber material itself, even if it does not reach a barrier level, provides at least the same level of resistance to water vapor and / or oxygen permeation as so-called "medium" barrier plastics (e.g., certain PVC and PET). These and other properties of the molded pulp fiber materials formed according to the methods disclosed herein will be discussed in more detail below.

[0080] It should also be noted that the method disclosed herein, which involves repeated pressing of the accumulated pulp fibers, provides a degree of control over the forming method, enabling the formation of molded pulp fiber products that, in addition to possessing one or more of the aforementioned material properties, also have complex geometries. For the purposes of molded pulp fiber products, the term "complex geometry" should be understood to include one or more of the following: - Small draft angle (in other words, a small angle between the surface of the molded slurry fiber product and the pressing direction of the molding tool); for example, less than 7°. - Concave and convex corners with small / compact radii of curvature, and - Products where the sidewall “height” is greater than the lateral / diameter spacing of the sidewall.

[0081] It should be understood that the above list is not exhaustive.

[0082] Each pressing step in pressing processes 126, 128, 130, 132, and 134 can be individually controlled in terms of pressing load (including maximum compressive force and load curve), molding tool temperature, and pressing time. Some pressing processes can also employ suction treatment to assist in extracting liquid from the finely ground slurry fiber material, and in each of these processes, the suction force can also be individually controlled. The work done by each pressing step on the accumulated finely ground slurry fibers can be adjusted according to the liquid content of the material at the start of the pressing process. In this regard, it should be noted that the liquid content of the slurry fiber material is an important factor affecting the material strength, mainly due to the degree of hydrogen bond formation, especially the degree of formation between individual fibers in the material.

[0083] The accumulation of wet slurry fibers on the molding surface (operation 122) includes: conveying the slurry stock solution (prepared in operation 102) toward a porous mold and removing a portion of the liquid component from the suspension through the porous mold. In this manner, the slurry fiber component in the suspension accumulates on the molding surface to form a slurry deposit; therefore, the slurry deposit contains liquid and at least includes fibers and fine particles from the suspension. The liquid content of the slurry deposit (i.e., the ratio of liquid to accumulated finely ground slurry fibers at the end of operation 122) depends on various factors. In one example, operation 122 can be controlled such that the liquid content in the accumulated finely ground slurry fibers reaches a range of 80% to 90% by weight. In this state, the accumulated finely ground slurry fibers in the slurry deposit are particularly soft, making the slurry deposit unable to self-support.

[0084] Refer again Figure 3 For example, operation 124 includes: Operation 126 – “Press the multi-hole mold”: The forming surface of the porous mold provides one of two opposing molding tool surfaces. A slurry deposit is pressed between the forming surface and the molding tool surface of the heated molding tool.

[0085] The advantage of using a porous mold in the first pressing step of the pressing process is that the porous mold provides structural support for the slurry deposits from the accumulation process (operation 122) and the first pressing step (operation 126).

[0086] At the end of operation 126, the shape of the accumulated finely ground slurry fibers has changed, and the liquid content of the material has decreased (compared to the liquid content of the slurry deposit). Therefore, the article can be regarded as a preform (in other words, a partially molded version of the final molded slurry fiber product).

[0087] In one example, operation 126 can be controlled such that the liquid content of the preform at the end of operation 126 reaches 70% to 87% by weight. Therefore, the reduction in liquid content in the preform is approximately 3% to 10%.

[0088] Operation 128 – “Pressing the first preform”: The preform—transferred in operation 126b—is pressed between the two opposing molding tool surfaces of the first pressing molding tool set.

[0089] In one example, operation 128 can be controlled such that at the end of operation 128, the liquid content in the preform is within the range of 55% to 82% by weight. Therefore, the reduction in liquid content in the preform is approximately 5% to 15%.

[0090] Operation 130 – “Second Preform Pressing”: The preform—transferred from the first pressing molding tool set in operation 128b—is pressed between the two opposing molding tool surfaces of the second pressing molding tool set.

[0091] In one example, operation 130 can be controlled such that at the end of operation 130, the liquid content in the preform is within the range of 35% to 67% by weight. Therefore, the reduction in liquid content in the preform is approximately 15% to 35%.

[0092] Operation 132 – “Third Preform Pressing”: The preform is transferred from the second pressing molding tool group in operation 130b and pressed between the two opposing molding tool surfaces of the third pressing molding tool group.

[0093] In one example, operation 132 is controlled such that the liquid content in the preform at the end of operation 130 is within the range of 0% to 10% by weight. Therefore, the reduction in liquid content in the preform is approximately 32% to 67%.

[0094] In this process, the preform is basically dry.

[0095] Operation 134 – “Fourth Preform Press”: The preform—transferred from the second pressing molding tool set in operation 132b—is pressed between the two opposing molding tool surfaces of the third pressing molding tool set.

[0096] Operation 134 can be used in method 100 to structurally modify the slurry fiber mesh within the material of the preform. For this purpose, the structural modification may include reinforcing the bonding portions within the slurry fiber material, hardening and / or smoothing the surface of the slurry fiber material, and sealing any remaining pores within the slurry fiber material by final pressing.

[0097] At the end of operation 134, the molded pulp fiber product is formed and can withstand any secondary processing operations, such as material trimming, application of surface coatings, decoration, etc.

[0098] The accumulation of wet slurry fibers on the molding surface (operation 122) includes: conveying the slurry stock solution (prepared in operation 102) toward a porous mold and removing a portion of the liquid component from the suspension through the porous mold. In this manner, the slurry fiber component in the suspension accumulates on the molding surface to form a slurry deposit.

[0099] The nature of the accumulation operation will depend at least in part on the structure of the plant equipment implementing method 100. In some examples, a porous mold is placed on the surface of a reservoir of suspension. The porous mold is connected to a vacuum source, and suction pulls the liquid components in the suspension through the porous mold. The movement of the liquid components carries the slurry fiber components toward the porous mold, resulting in the accumulation of slurry fibers on the forming surface.

[0100] In some alternative examples, the porous mold closes the bottom of the hopper, and the forming surface faces into the cavity of the hopper. A certain amount of suspension is loaded into the hopper. The liquid components of the suspension are drained and / or drawn through the porous mold, causing the slurry fiber components of the suspension to accumulate on the forming surface to form a slurry deposit.

[0101] Figures 4a and 4b schematically illustrate the process flow diagram of the production line 200 implementing method 100. The process flow diagram schematically illustrates the factory equipment for implementing various parts of method 100.

[0102] As shown in Figure 4a, virgin pulp fibers (“RPF”) and water (H2O) are loaded into a repulper 202. The repulper 202 has a set of blades for pulverizing the virgin pulp fibers. Once the virgin pulp fibers are sufficiently pulverized to form the desired pulp fiber-water suspension, the suspension is pumped to a first holding tank 204 via a flow line 206. The production line 200 also includes a second holding tank 208 and a fine mill 210. The first holding tank 204, the second holding tank 208, and the fine mill 210 are interconnected via a flow line 212 to the inlet of the fine mill 210 and via a flow line 214 to the outlet of the fine mill 210. A group of pumps and valves (not shown) control the flow of the suspension between the first holding tank 204, the fine mill 210, and the second holding tank 208. In fact, for each of the slurry operation 106 and the series of fine grinding operations 108, the suspension travels back and forth between the first holding tank 204 and the second holding tank 208 and through the fine grinding mill 210.

[0103] After the slurry stock solution is prepared, it is transferred (operation 118) to the third holding tank 216 via the flow line 218 branching off from the flow line 214.

[0104] Production line 200 includes a preparation tank 220 that receives the stock solution via a flow line 222. The preparation tank 220 is connected to a storage tank, which in this example is a stock solution tank 224. As shown in Figure 4a, the preparation tank 220 may be provided with an inlet to dilute the stock solution as needed before discharging it into the stock solution tank 224. Any additives used for the stock solution can be added directly to the preparation tank 220 (such as A). X As shown), and / or any additives for the slurry stock solution can be added to the flow line 222 between the preparation tank 220 and the slurry stock solution tank 224 (e.g., A). Y (As shown).

[0105] In the example of Figure 4a, the porous mold 226 is oriented such that the molding surface 228 faces generally downwards. The porous mold 226 is lowered into the slurry stock located in the slurry stock tank 224. A vacuum line (not shown) connected to the porous mold 226 is operated to accumulate finely ground slurry fibers from the slurry stock onto the molding surface 228, as previously described.

[0106] Figure 4b illustrates a series of pressing processes (operation 124). These pressing processes are implemented on the equipment of the production line 200 in this embodiment, as described below: - A complementary molding tool 230, the molding tool surface of which is complementary to and therefore cooperates with the porous mold 226 for use in performing operation 126 ("pressing the porous mold"). - A first press molding tool set 232, which includes a first lower molding tool 234 and a first upper molding tool 236, for performing operation 128 (“first preform press”). - A second press molding tool set 242, which includes a second lower molding tool 244 and a second upper molding tool 246, for performing operation 130 (“second preform press”). - A third press molding tool set 252, which includes a third lower molding tool 254 and a third upper molding tool 256, for performing operation 132 (“third preform press”). - Fourth press molding tool set 262, which includes a fourth lower molding tool 264 and a fourth upper molding tool 266 for performing operation 134 (“fourth preform press”).

[0107] Production line 200 includes transfer equipment (not shown) for sequentially transferring preforms from porous mold 226 to first lower molding tool 234, second lower molding tool 244, third lower molding tool 254, and fourth lower molding tool 264. In one example, the first upper molding tool 236, second upper molding tool 246, third upper molding tool 256, and fourth upper molding tool 266 reciprocate to close their respective molding tool sets and perform each of the pressing operations 128, 130, 132, 134, and 136.

[0108] The complementary molding tool 230 may include a heating element (not shown) to transfer heat to the slurry deposit during operation 126. If desired, suction may be applied via a vacuum line during operation 126 to remove liquid from the slurry deposit.

[0109] Similarly, one or two molding tools in at least some of the molding tool groups 232, 242, 252 and 262 may include heating elements (not shown) to transfer heat to the preform during the corresponding pressing operations 128, 130, 132 and 134.

[0110] Vacuum lines (not shown) may also be connected to selected molding tools in at least the first molding tool group 232, the second molding tool group 242, and the third molding tool group 252. These vacuum lines can be operated as needed to extract liquid from the preform during the corresponding pressing operations 128, 130, 132.

[0111] One or more of the molding tools in the selected molding tool group may have the structure described in the applicant's international patent application No. PCT / AU2020 / 051248. For example, the second lower molding tool 244 of the second press molding tool group 242 may include a first layer and a second layer, the second layer having interconnected internal voids that form part of the fluid extraction path of the second lower molding tool 244.

[0112] As shown in Figure 4b and as previously described, the final molded slurry fiber product M is formed. Figure 5a is an illustrative example showing a vertical cross-section of the slurry deposit accumulated on the porous mold 226, which is region A in Figure 4b.

[0113] Figures 5b to 5f show examples of geometric changes in the preform corresponding to region A. In Figures 5b to 5e, the shapes shown by the solid lines (and the shaded sections) correspond to the corresponding intermediate shapes of the preform at the end of the respective pressing processes. In Figure 5f, the shapes shown by the solid lines (and the shaded sections) correspond to the shape of the molded slurry fiber product M.

[0114] In each of Figures 5b to 5f, the closing direction of the molding tool set is indicated by arrow C. Furthermore, in these figures, dashed lines indicate the locations where the slurry deposit surface (in Figure 5b) and the preform (in Figures 5c to 5f) shift during the corresponding pressing process.

[0115] Specifically, in this particular example, the geometric changes shown are as follows: i. In Figure 5b (Operation 128 / Multi-hole mold pressing): - The thickness of the accumulated finely ground pulp fibers is reduced, and - The geometric proportions of the accumulated finely ground pulp fibers change; ii. In Figure 5c (Operation 130 / First Preform Press), the thickness of the accumulated finely ground slurry fibers decreases in a direction parallel to the relative movement of the opposing molding tool surfaces. In other words, the direction of decrease is parallel to the closing direction C of the molding tool assembly; iii. In Figure 5d (Operation 132 / Second Preform Pressing), the thickness of the accumulated finely ground slurry fibers decreases approximately transversely to the relative movement with respect to the opposing molding tool surfaces. In other words, the direction of decrease is approximately transverse to the closing direction C of the molding tool assembly; iv. In Figure 5e (Operation 134 / Third Preform Press): - The thickness of the accumulated finely ground slurry fibers decreases both in the direction of relative movement parallel to the opposing molding tool surfaces and in the direction transverse to the opposing molding tool surfaces; and - The two spaced-apart surface portions of the accumulated finely ground pulp fibers undergo relative displacement, which in this example forms rib-like portions on the underside of the accumulated pulp fibers; as well as v. In Figure 5f (Operation 136 / Fourth Preform Press), the thickness of the accumulated finely ground slurry fibers decreases both in the direction parallel to the relative movement of the opposing molding tool surfaces and in the direction transverse to the relative movement of the opposing molding tool surfaces. Furthermore, the geometric proportions of the ribs also change. More specifically, both the width and height of the ribs are reduced.

[0116] Experimental process : The following description section relates to the testing of method 100 conducted by the applicant using factory equipment substantially the same as that described and illustrated in Figures 4a and 4b.

[0117] During the experiment, the liquid used for the suspension was drinking water, and the pulp fiber was commercially available dry sugarcane bagasse pulp sheet.

[0118] The suspension was formed in a re-shredder (model: ADP0.5M3) manufactured by Aikawa Iron Works Co., Ltd.

[0119] The suspension undergoes a spalling process, followed by four fine grinding processes using a spalling / fine grinding mill (model SDR-14) manufactured by Aikawa Iron Works Co., Ltd., to prepare the slurry stock. The gap width for each of these operations is listed in Table 1.

[0120] Table 1

[0121] The morphological properties of pulp fibers in samples of slurry that had been loosened but not refined (i.e., after loosening step 106 but before the first refining step 110) were analyzed using MORFI NEO, manufactured by Techpap in Guia, France. Data obtained from MORFI NEO* revealed the following characteristics: Fiber length — Length-weighted fiber length: 1,190 μm (1.190 mm) Mean arithmetic length: 592 μm (0.592 mm) Fiber width (average): 23.2μm (0.0232mm) Fine content— 39.81% (percentage in suspension by length) Slurry residue content (by area): 1.3% The above analytical results of the pulp fibers in the unground pulp liquor are consistent with the characteristics stated in the literature; for example, as stated by Andrade MF, Colodette JL and Jameel H in “Chemical and morphological characterization of sugar cane bagasse” published in Tappi J 13(6):27-33 (2014): Fiber length: 1.44mm, SD=0.5mm.

[0122] Fiber width: 21.3μm, SD=6.5μm.

[0123] The morphological characteristics of pulp fibers in the suspension after the descaling process are considered to directly represent the characteristics of unrefined pulp fibers. This is because the descaling process primarily separates the pulp residue, with minimal impact on individual fibers.

[0124] It should be noted that the refining time in each of the delamination step 106 and the refining steps 110, 112, 114, and 116 affects the morphological properties of the pulp fibers. For disc refiners (such as those used in this example), the flow rate of the suspension through the refiner is related to the refining time. For example, as the refining time increases, the area content of pulp residue decreases in the delamination step.

[0125] The morphological characteristics of the pulp fibers in the pulp stock sample (i.e., the pulp stock after the fourth refining process 116) were also analyzed using MORFI NEO. The data obtained from MORFI NEO* demonstrate the following characteristics: Fiber length — Length-weighted fiber length: 901 μm (0.901 mm) Mean arithmetic length: 592 μm (0.592 mm) Fiber width (average): 22.7μm (0.027mm) Fine content— 53.543% (percentage in suspension by length) Primary and secondary feedstock ratio: 75.89% Secondary fines percentage: 24.11% Slurry residue content (by area): 0.3% *Detailed information on the analysis procedures and techniques, terminology, and calculation methods for the above characteristics is explained in the MORFI NEO User Manual version 1.0.55, released on June 7, 2021, which is incorporated herein by reference.

[0126] For the purposes of this specification and the following claims, the values ​​of the morphological properties of the pulp fibers should be determined with reference to the specifications and parameters of the MORFINEO instrument, as well as the analytical procedures, techniques, terminology, and calculation methods detailed in the MORFINEO User Manual.

[0127] Based on the above morphological analysis of the unground pulp fibers in the suspension and the morphological analysis of the pulp concentrate, the following two observations are presented: 1. The length-weighted fiber length of the pulp fibers was reduced by approximately 189 μm during the finishing process; therefore, the length of the finished pulp fibers was approximately 76% of the length of the unfinished pulp fibers. 2. The fiber width of the pulp fiber is reduced by about 0.5 μm during the finishing process; therefore, the fiber width of the finished pulp fiber is about 98% of the fiber width of the unfinished pulp fiber.

[0128] It should be understood that the above values ​​are statistical representations of the pulp fibers. These values ​​were obtained by averaging a large number of analytical results based on instrument sampling procedures and software image processing methods.

[0129] It should also be noted that different morphology analysis instruments may have different specifications and parameters than the MORFI NEO, and / or use different analytical procedures and techniques, calculation methods, and may even use conflicting terminology. Therefore, evaluating pulp fibers with other equipment may yield results that differ from the symbolic morphological properties described herein.

[0130] The applicant conducted a mass fraction test on the finely milled pulp fibers, which included a sieving and grading process of the pulp liquor to separate the pulp fibers from the fine particles and cellulose microparticles present in the pulp liquor. In this process, the applicant used a Brecht-Holl classifier (manufactured by Rycobel) and sieves designed for separating fiber materials smaller than 74 μm to separate the pulp fiber component from the fine particle and cellulose microparticle components. The separated pulp fiber, fine particle, and cellulose microparticle components were dried and weighed to determine the mass fraction of fine particles and cellulose microparticles in the pulp liquor. The mass fraction test results indicate that, by weight, the fine particle and cellulose microparticle components account for approximately 57% of the fibrous material present in the pulp liquor. Although the characteristics measured by the mass fraction test are not identical to the morphology analysis provided by MORFI NEO, it should be considered that, by weight, cellulose microparticles account for approximately 3% of the pulp liquor. Therefore, the morphology analysis results of the fine particle component, measured by weighted length, provided by MORFI NEO are comparable to the actual fine particle component by weight.

[0131] Regarding the second observation, those skilled in the art should understand that the difference in fiber width between unrefined and refined pulp fibers is negligible.

[0132] Operation 108, performed during these tests, included analyzing a portion of the refined pulp fibers in the suspension following the third pulp fiber refining process (Operation 114c). For this purpose, a sample of the suspension was taken and subjected to a Canadian standard freeness test (according to TAPPI standard test method T 227 om-21). Considering the method and the operating parameters of the equipment, a provisional target freeness for the suspension entering the fourth pulp fiber refining process (Operation 116) was determined. Based on the deviation between the freeness analyzed in Operation 114c (i.e., the refining progress index) and the intermediate target freeness, the gap width of the refining mill in the fourth pulp fiber refining process (Operation 116) was set.

[0133] When the finishing progress index is higher than the intermediate target freeness (indicating insufficient finishing at the end of the third finishing process 114), the gap width should be set to further enhance the finishing of the pulp fibers in the final finishing process (operation 116). Therefore, if the finishing progress index indicates that the suspension is "more free," the gap width in the fourth finishing process 116 should be set to the lower limit of the range in Table 1. Conversely, when the finishing progress index is lower than the intermediate target freeness (indicating a higher degree of finishing at the end of the third finishing process 114), the gap width should be set to reduce the finishing of the pulp fibers in the final finishing process (operation 116). Therefore, if the finishing progress index indicates a suspension with "lower degree of freedom," the gap width in the fourth finishing process 116 should be set to the upper limit of the range in Table 1.

[0134] This pulp stock solution is made with a low pulp fiber fraction. In this example, the liquid fraction of the suspension is approximately 99.2% (and the solid fraction is approximately 0.8%). The Canadian standard freeness of the finely milled pulp fibers in the suspension constituting this pulp stock solution is in the range of approximately 100 mL CSF to 150 mL CSF.

[0135] In the preparation tank 220 / flow line 222, additives are added to the slurry stock. In this example, alkyl ketene dimer (AKD) (up to about 0.3% by volume) and polyamino polyamide-epoxychloropropane (PAE) (up to about 0.6% by volume) are added before the wet, finely ground slurry fibers are deposited onto the molding surface 228 of the porous mold 226 (operation 122). After the wet, finely ground slurry fibers are deposited onto the molding surface 228, the slurry deposit undergoes a series of pressing processes between opposing molding tool surfaces (operation 124). In this example, operation 124 includes five pressing operations 126, 128, 130, 132, and 134, as described above and referenced. Figure 3 As shown in Figure 4b, to drain the liquid.

[0136] Table 2 lists the approximate liquid content of the slurry fiber material as it undergoes a series of pressing processes (operation 124) from the accumulated slurry deposit to the final molded slurry fiber product M.

[0137] Table 2

[0138] As is evident from Table 2, the reduction in liquid content of the preform is non-linear as it undergoes a series of pressing processes (operation 124). The gradual, non-linear reduction in liquid content through the porous mold pressing process 126, the first preform pressing process 128, the second preform pressing process 130, and the third preform pressing process 132 facilitates the transformation of the slurry fiber material from an accumulated slurry deposit into the final molded product form, while simultaneously controlling the continuous enhancement of inter-fiber bonding strength established within the slurry fiber mesh.

[0139] In some examples of method 100, a third preform pressing process 132 may be implemented to reduce the liquid content to 0.0%, or at least to an unmeasurable liquid content.

[0140] Table 3 lists the geometric variations of the accumulated finely ground slurry fibers obtained from the preforms shown in Figures 5a to 5f.

[0141] Table 3

[0142] *The parallel and lateral directions are relative to the closed direction C of their respective tool groups.

[0143] As can be seen from the lateral offsets shown in Table 3, method 100 can achieve a significant lateral offset in the slurry fiber preform during the second preform pressing step 130 and the third preform pressing step 132. The advantage of this process is that the density of the portion of the final molded slurry fiber product with a relatively high draft angle (approximately 10° to 5°) can be at least equal to, or even greater than, the density of the portion of the final molded slurry fiber product whose surface is substantially transverse to the molding tool closing direction C.

[0144] In one example, the applicant used method 100 to produce a final molded pulp fiber product M using a molding tool assembly that forms portions in product M with a draft angle of approximately 8°. The material density of these portions was measured to be in the range of at least approximately 900 kg / m³ and up to approximately 1150 kg / m³. Furthermore, the wall thickness in these portions ranged from approximately 275 μm to 380 μm. In contrast, equivalent molded pulp fiber products formed using previously known thermoforming / precision molding processes and having similar wall thicknesses at this draft angle typically have a material density in the range of 250 kg / m³ to 400 kg / m³.

[0145] For clarity, in this specification and the following claims, any expressions related to "reduction of thickness" expressed as a percentage shall be understood as the proportion of the change in material thickness (in the specified direction) to the material thickness before reduction (in the same specified direction) and expressed as a percentage.

[0146] Furthermore, surface roughness measurements were performed on the outer surface of the portion of product M with a draft angle of approximately 8°. The measured arithmetic mean height surface roughness (Sa) of these portions (i.e., the absolute value of the difference between the height of each point on the surface and the arithmetic mean of the surface) ranged from 6.549 μm to 10.065 μm. In contrast, equivalent molded slurry fiber products formed using previously known thermoforming / precision molding methods typically have an arithmetic mean height surface roughness (Sa) that is at least an order of magnitude higher.

[0147] In certain final applications of the molded pulp fiber products produced by method 100, it may be necessary or required to coat the molded pulp fiber material with one or more materials in a liquid state, and then cure / dry it to a solid state under standard atmospheric conditions. The applicant has observed that molded pulp fiber products with pulp fiber densities of the aforementioned order of magnitude can offer the advantage of limited permeability to liquid coating materials. By way of example only, when liquid wax is applied to the molded pulp fiber material produced using method 100, the liquid wax hardly penetrates into the pulp fiber material. The benefit of this characteristic of molded pulp fibers is a reduction in the amount of coating material required, and / or a reduction in defects in the coated portion itself.

[0148] Figure 6 A method 400 for forming a molded pulp fiber product according to another embodiment is shown. Operations in method 400 that are the same as or similar to those in method 100 have the same reference numerals, except that the prefix "1" is replaced with the prefix "4". For the sake of brevity, these will not be described again.

[0149] The main difference between methods 100 and 400 is that method 400 does not include a pulp refining step. In some cases, the pulp stock is made from a suspension of virgin pulp fibers that has not undergone any refining treatment. In other cases, the virgin pulp fibers may be subjected to one or more dry refining processes before forming a suspension to prepare the pulp stock.

[0150] Figure 6 A series of pressing steps 424 are shown, generally comprising two or more pressing steps configured to progressively remove liquid from the slurry deposit. Figure 6 In the example shown, there is an initial pressing step 424a, followed by one or more subsequent pressing steps 424b.

[0151] As the slurry deposit undergoes a series of pressing steps 424, the geometry of the accumulated, finely ground slurry fibers transforms from the initial slurry deposit form to the final molded slurry fiber product form. In this example, each of the two or more pressing steps 424a, 424b uses a separate molding tool to provide a relative molding tool surface at each pressing step. Therefore, there may be several intermediate forms of geometry from the initial slurry deposit form to the final molded slurry fiber product form, one less than the number of subsequent pressing steps 424b used in process 400.

[0152] In the examples described herein and shown in the figures, bagasse is used as the pulp fiber. It should be understood that the method and the product formed by the method may use other plant-derived fibers and / or cellulose obtained from other materials. Furthermore, the method and the product formed by the method may also use plant fibers from more than one plant class and / or source. By way of non-limiting example, other plant-derived fibers include, but are not limited to: bamboo, cotton, hemp plants, straw (rice straw, wheat straw, pea straw), flax, palm, and wood.

[0153] Sample materials : The applicant prepared comparative samples of pulp fiber materials (for making handmade paper) from each of the pulp liquors of sugarcane bagasse, bamboo, and wheat straw. To ensure consistency and repeatability, each test sample was made into handmade paper from the selected pulp fibers according to the TAPPI standard test method T 205 sp12.

[0154] The slurry fiber raw material used to form the sample is: a. Commercially available dried sugarcane bagasse pulp sheets (“virgin sugarcane bagasse raw material”); b. Commercially available dried bamboo pulp (“raw bamboo material”); and c. Commercially available wheat straw pulp (“raw wheat straw raw material”) obtained from Nafici Environmental Research Ltd.

[0155] The first portion of the bagasse feedstock was reserved for analysis and sample preparation. The second portion of the bagasse feedstock was finely ground using methods essentially identical to the fine grinding steps 110, 112, 114, and 116 in the aforementioned experimental method. This fine grinding method yielded finely ground bagasse feedstock.

[0156] Similarly, the first fraction of each of the raw bamboo and raw wheat straw materials was analyzed and sampled. The second fraction of each of the raw bamboo and raw wheat straw materials was finely ground using a laboratory disc grinder (Bauer type, model MD-3000) manufactured by IDM Instruments Pty Ltd. This grinder was equipped with finebar-type grinding discs with a gap width set to 0.5 mm. Each pulp material was ground for 30 minutes. The results showed that this method was essentially as effective as the method for grinding the pulp fibers as it was for raw bamboo (it should be noted that actual results depend on the characteristics of each grinder and the pulp material itself). This grinding method yielded finely ground bamboo and finely ground wheat straw materials.

[0157] Before being processed into handmade paper, each fraction of the first portion of each pulp solution was subjected to a Canadian standard freeness test (according to TAPPI standard test method T 227 om-21). Similarly, the morphological characteristics of the pulp fibers in each fraction of the first portion of each pulp solution were determined using MORFI NEO. These test and analysis results are listed in Table 4 below. No analysis was performed on the pulp residue content / characteristics of each pulp solution.

[0158] Table 4

[0159] The contents of columns 2 through 6 in Table 4 are as follows: CSF – Canadian Standard Freeness (measured in milliliters / mm); LWFL—Length-weighted fiber length (measured in micrometers / μm); MAL—Mean arithmetic fiber length (measured in micrometers per μm); MFW—Mean fiber width (measured in micrometers per micrometer); and Fine particles – Fine particle content (percentage of the particle in the suspension, measured by length).

[0160] Each refined pulp stock solution is obtained by refining the corresponding virgin pulp stock solution. Therefore, the percentage of the average fiber width of the refined pulp stock solution relative to the average fiber width of the virgin pulp fiber can be directly determined from the data in Table 4. For clarity, the average fiber width of the virgin pulp fiber is also referred to as the "average virgin fiber width" in this specification and subsequent claims. For the three refined pulp stock solutions, the percentage of the average fiber width relative to the average virgin fiber width is as follows: Finely ground sugarcane bagasse: 99.13% Finely ground bamboo: 113.33% Finely ground wheat straw: 94.09% In the recorded fines content, the ratio of primary fines to secondary fines was determined and is shown in Table 5 below.

[0161] Table 5

[0162] The selected material properties and characteristics of the sample handmade paper were obtained through testing or calculation, as described below.

[0163] Thickness – obtained using standard laboratory equipment and according to TAPPI standard test method T551 om-98 “Thickness of paper and paperboard (soft plate method)”, expressed in mm. Quality – obtained using standard laboratory equipment and on a 75mm diameter portion of the handwritten sample paper. Density – calculated using sample thickness and mass results, and expressed in GSM (g / m³). 2 ) and kg / m 3 To indicate, Water vapor transmission rate (WVTR) – obtained using standard laboratory equipment and according to TAPPI standard test method T448om-09, "Water vapor transmission rate of paper and paperboard at 23°C and 50% RH", expressed in g / m³. 2 .day is used to represent, Water vapor permeability (WVP) – calculated using sample WVTR and thickness results, and expressed in g / m³ 2 .day / kPa.m 3 To indicate, Water absorption rate (Cobb 60) – Obtained using standard laboratory equipment and a Cobb tester, and according to TAPPI standard test method T 441 om-09 "Water absorption rate (Cobb test) of (non-absorbent) paper, paperboard and corrugated board with specified dimensions"; test time is 60 seconds, and results are expressed in g / m³. 2 (Absorbed water) is used to represent this. Air permeability (AP) – obtained using an L&W air permeability meter and expressed in mL / min. Edge crush strength (ring crush strength) – obtained using standard laboratory equipment and according to TAPPI standard test method T818 cm-97 "Ring crush strength of paperboard", and expressed in MPa. Maximum shear punching force (shear punching) – obtained by pushing a 9.8 mm diameter pin through a sample clamped between a pair of plates with aligned 10 mm diameter holes using a modified Instron machine, and is denoted by N. Shear strength – calculated using the shear impact force of the sample and expressed in MPa.

[0164] The table below provides a summary of the test and calculation results. If the test was repeated on a single sample of handwritten paper, and / or multiple samples of handwritten paper were tested, the values ​​shown in the table are averages.

[0165] Table 6

[0166] Observations: The data in Table 6 show that, for all tested pulp materials, refining the pulp fibers resulted in thinner raw paper samples than unrefined raw paper samples. This is attributed to the fact that fiber refining causes the pulp fibers to be more tightly packed within the pulp matrix of the refined material compared to the unrefined material.

[0167] It should be noted that the density measurement of handmade paper samples made from refined bamboo raw materials is lower than that of handmade paper samples made from virgin (unrefined) bamboo raw materials. Table 4 shows that the average fiber width (MFW) of bamboo, as determined by morphological data, is increased. This is attributed to the alteration of fiber width distribution caused by the refining process of bamboo pulp fibers. It can be assumed that this characteristic of refined bamboo, combined with the lighter weight of the handmade paper samples, likely contributes to the decrease in material density.

[0168] Table 7

[0169] Observations: The data in Table 7 show that, for all tested pulp materials, the refined pulp fibers resulted in improved material properties in each of the refined pulp paper samples in terms of water vapor transmission rate, water vapor permeability, water absorption rate, and air permeability, compared to the corresponding unrefined pulp paper samples.

[0170] Table 8

[0171] Observations: The data in Table 8 show that, for all tested pulp materials, fine grinding of the pulp fibers improved the maximum shear impact force and shear strength characteristics of the finely ground pulp paper samples compared to the corresponding unground pulp paper samples.

[0172] Table 9

[0173] Observations: The data in Table 9 show that, for all tested pulp materials, refining the pulp fibers improved the edge compressive strength (as measured by ring crush test) of the refined pulp paper samples compared to the corresponding unrefined pulp paper samples.

[0174] Tests conducted on sample handmade paper indicate that finely ground bagasse, bamboo, and wheat straw are all suitable for forming molded pulp products according to the methods described herein. It should be understood that the selection of one or more pulp fibers for forming any molded pulp fiber product takes into account various factors, including the suitability of the materials for the desired application.

[0175] In this specification and the following claims, unless the context otherwise requires, the word “comprising” and its variations, such as “including” and “comprising of”, shall be understood to include the stated feature, integer, operation or step, or group of features, integers, operations or steps, but do not exclude any other feature, integer, operation or step, or group of features, integers, operations or steps.

[0176] The methods and / or processes described herein shall be construed as referring to a sequence or order of operations, procedures, or steps only where the context requires a sequence or order. Otherwise, the methods and / or processes described herein may perform operations, procedures, or steps in any order, and / or include intermediate operations, procedures, or steps.

[0177] Any prior publications (or information obtained from them) or any known matters mentioned in this specification do not constitute and should not be construed as an acknowledgment or endorsement, or as an implication that such prior publications (or information obtained from them) or known matters constitute part of the general knowledge in the field covered by this specification.

Claims

1. A method for forming a molded pulp fiber product, the method comprising: Preparation of slurry stock solution, the preparation of said slurry stock solution includes: Forming a suspension of pulp fibers and liquid, and The suspension is subjected to a series of fine grinding processes, each of which finely grinds the pulp fibers, such that the average fiber length of the finely ground pulp fibers in the pulp stock solution is less than the average length of the original pulp fibers forming the suspension, and the finely ground pulp fibers in the pulp stock solution have a proportion of at least 45% fine material in the pulp fiber component of the suspension by length. A porous mold is provided, the porous mold having one or more pre-forming mold portions, each of the one or more pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By directing the slurry concentrate toward the porous mold and removing the liquid through the porous mold, wet, finely ground slurry fibers accumulate on the molding surface of the preforming mold portion, forming a slurry deposit; and The slurry deposit is pressed between opposing molding tool surfaces to expel liquid, thereby reducing the ratio of liquid to finely ground slurry fibers and processing the accumulated finely ground slurry fibers from the form of the slurry deposit into the form of the final molded slurry fiber product.

2. The method according to claim 1, wherein, The preparation of the slurry stock solution includes: passing the suspension through the series of fine grinding processes, such that the average fiber width of the finely ground slurry fibers in the slurry stock solution is 90% or greater than the average native fiber width.

3. The method according to claim 1, wherein, The preparation of the slurry stock solution includes: passing the suspension through the series of fine grinding processes, such that the average fiber width of the finely ground slurry fibers in the slurry stock solution is 95% or greater than the average native fiber width.

4. A method for forming a molded pulp fiber product, the method comprising: Preparation of slurry stock solution, the preparation of said slurry stock solution includes: Forming a suspension of pulp fibers and liquid, and The suspension is subjected to a series of fine grinding processes, each of which finely grinds the pulp fibers, such that the average fiber length of the finely ground pulp fibers in the pulp stock solution is less than the average length of the original pulp fibers forming the suspension, and the average fiber width of the finely ground pulp fibers in the pulp stock solution is 90% or greater than the average original fiber width. A porous mold is provided, the porous mold having one or more pre-forming mold portions, each of the one or more pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By directing the slurry concentrate toward the porous mold and removing the liquid through the porous mold, wet, finely ground slurry fibers accumulate on the molding surface of the preforming mold portion, forming a slurry deposit; and The slurry deposit is pressed between opposing molding tool surfaces to expel liquid, thereby reducing the ratio of liquid to finely ground slurry fibers and processing the accumulated finely ground slurry fibers from the form of the slurry deposit into the form of the final molded slurry fiber product.

5. The method according to claim 4, wherein, The preparation of the slurry stock solution includes: passing the suspension through the series of fine grinding processes, such that the average fiber width of the finely ground slurry fibers in the slurry stock solution is 95% or greater than the average native fiber width.

6. The method according to any one of claims 1 to 5, wherein, The preparation of the slurry stock solution includes: passing the suspension through the series of fine grinding processes, such that the average fiber width of the finely ground slurry fibers in the slurry stock solution remains substantially unchanged relative to the average native fiber width.

7. The method according to any one of claims 1 to 6, wherein, Pressing the slurry deposit between opposing molding tool surfaces comprises a series of two or more pressing steps configured to progressively drain liquid from the slurry deposit, wherein, with each series of pressing steps, the geometry of the accumulated, finely ground slurry fibers changes from the initial form of the slurry deposit to the form of the final molded slurry fiber product.

8. The method according to claim 7, wherein, The geometry of the accumulated, finely ground slurry fibers varies from the initial form of the slurry deposition to the form of the final molded slurry fiber product, including one or more intermediate forms formed by corresponding pressing processes in a series of pressing processes prior to the final pressing process.

9. The method according to claim 6 or 7, wherein, The variation in the geometry of the accumulated, finely ground pulp fibers at each pressing step includes one or more of the following: The reduction in the thickness of one or more portions of the accumulated finely ground pulp fibers, or the reduction in the thickness of the entire accumulated finely ground pulp fibers; The change in the geometric proportions of the accumulated, finely ground pulp fibers; or The relative displacement of two spaced-apart surface portions in the accumulated finely ground pulp fibers.

10. The method according to any one of claims 1 to 9, wherein, The preparation of the pulp stock solution includes: finely grinding the pulp fibers to have a Canadian standard freeness of less than about 300 mL CSF.

11. A method for forming a molded pulp fiber product, the method comprising: Preparation of slurry stock solution, the preparation of said slurry stock solution includes: Forming a suspension of pulp fibers and liquid, and The suspension is subjected to a series of fine grinding processes, each of which finely grinds the pulp fibers, so that the pulp stock solution has a Canadian standard freeness of less than about 300 mL CSF. A porous mold is provided, the porous mold having one or more pre-forming mold portions, each of the one or more pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By directing the slurry concentrate toward the porous mold and removing the liquid through the porous mold, wet, finely ground slurry fibers accumulate on the molding surface of the preforming mold portion, forming a slurry deposit; and The slurry deposit is pressed between opposing molding tool surfaces to expel liquid, thereby reducing the ratio of liquid to finely ground slurry fibers and processing the accumulated finely ground slurry fibers from the form of the slurry deposit into the form of the final molded slurry fiber product.

12. The method according to claim 10 or 11, wherein, The preparation of the pulp stock solution includes: finely grinding the pulp fibers to a Canadian standard freeness of 100 mL CSF to 150 mL CSF.

13. The method according to any one of claims 1 to 12, wherein, Each fine grinding step includes passing the suspension through at least one fine grinding mill having a rotor and a stator, with a gap defined between the rotor and the stator, through which the suspension passes, wherein the series of fine grinding steps is configured such that the width of the gap decreases between at least some of the successive steps in the series of fine grinding steps.

14. The method according to claim 13, wherein, The series of fine grinding processes includes an initial fine grinding process and one or more subsequent fine grinding processes, and the method includes setting the width of the gap between the rotor and the stator before allowing the suspension to pass through each of the subsequent fine grinding processes.

15. The method according to claim 14, wherein, The width of the gap is set before the suspension passes through each subsequent refining process by the following: -According to a pre-established agreement, and / or -Based on the analysis of the partially finely ground slurry in the suspension, the predetermined suspension characteristics are achieved when the corresponding subsequent fine grinding process is completed.

16. The method according to claim 14 or 15, wherein, Setting the width of the gap includes reducing the width of the gap between the rotor and the stator relative to the width of the gap in the immediately preceding fine grinding process.

17. The method according to any one of claims 1 to 16, wherein, The pulp fiber used to prepare the pulp stock solution is bagasse, and the preparation of the pulp stock solution includes: finely grinding the pulp fiber so that the average pulp fiber length in the finely ground pulp stock solution is less than or equal to 1 mm.

18. The method according to any one of claims 1 to 17, wherein, The preparation of the slurry stock solution includes: passing the suspension through the series of fine grinding processes, so that the average fiber width of the finely ground slurry fibers in the slurry stock solution is in the range of 15 μm to 25 μm.

19. The method according to any one of claims 1 to 18, wherein, The preparation of the slurry stock solution further includes: finely grinding the slurry fibers so that the proportion of fine particles as secondary fine particles in the slurry stock solution is less than one-third.

20. The method according to any one of claims 1 to 19, wherein, The preparation of the pulp stock solution further includes: finely grinding the pulp fibers so that the content of pulp residue constituting the fiber region, as measured by imaging technology, is less than 0.5%.

21. The method according to any one of claims 1 to 20, wherein, The preparation of the pulp stock solution further includes: finely grinding the pulp fibers so that the finely ground pulp fibers in the pulp stock solution have a fibrillation index of at least 1%.

22. The method according to any one of claims 1 to 21, wherein, The preparation of the pulp stock solution further includes: finely grinding the pulp fibers so that the pulp stock solution has a content of less than or equal to 65% fine material based on length.

23. The method according to any one of claims 7 to 9, wherein, The reduction of the thickness of one or more portions of the slurry deposit in any of the pressing steps includes: Decrease in the direction parallel to the relative movement of the opposing molding tool surfaces; The reduction in the direction of relative movement transverse to the opposing surfaces of the molding tool; or The decrease is in the direction parallel to the relative movement of the opposing molding tool surfaces and in the direction transverse to the relative movement of the opposing molding tool surfaces.

24. A method for forming a molded pulp fiber product, the method comprising: The preparation of the slurry stock solution includes forming a suspension of slurry fibers and liquid; A porous mold is provided, the porous mold having one or more pre-forming mold portions, each of the one or more pre-forming mold portions having a forming surface having a shape that substantially corresponds to a portion of the outer surface of the final molded pulp fiber product; By causing the slurry concentrate to travel toward the porous mold and removing the liquid through the porous mold, wet slurry fibers accumulate on the molding surface of the preforming mold portion, and the accumulated slurry fibers form a slurry deposit. as well as The slurry deposit is pressed between opposing molding tool surfaces to expel liquid, thereby reducing the liquid-to-slurry fiber ratio and processing the slurry fiber from the form of the slurry deposit into the form of the final molded slurry fiber product. As a series of pressing processes are performed, the geometry of the accumulated slurry fiber changes from the initial form of the slurry deposit to the form of the final molded slurry fiber product.

25. The method according to claim 24, wherein, The geometry of the accumulated pulp fibers changes at each pressing step by one or more of the following: A reduction in the thickness of one or more portions of the accumulated pulp fibers, or a reduction in the thickness of the entire accumulated pulp fibers; The geometric proportions of the pulp fibers; or The relative displacement of two spaced-apart surface portions in the accumulated pulp fibers.

26. The method of claim 25, wherein, The reduction of the thickness of one or more portions of the slurry deposit in any of the pressing steps includes: Decrease in the direction parallel to the relative movement of the opposing molding tool surfaces; The reduction in the direction of relative movement transverse to the opposing surfaces of the molding tool; or The decrease is in the direction parallel to the relative movement of the opposing molding tool surface and in the direction transverse to the relative movement of the opposing molding tool surface.

27. The method according to claim 25 or 26, wherein, Each pressing step in the pressing process includes reducing the thickness of the slurry deposit by 50% or less in any direction.

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