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(11) | EP 4 582 632 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | RECYCLABLE CELLULOSIC STRUCTURE WITH METAL ION TREATMENT |
| (57) A cellulosic structure includes a cellulosic substrate comprises a network of cellulose
fibers having hydroxy moieties and metal ions having a valency of at least three bonded
to the hydroxy moieties of the cellulose fibers proximate at least one surface of
the cellulosic substrate.
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FIELD
[0001] The present invention relates to the field of cellulosic materials and their modification for improved functionality.
BACKGROUND
[0002] Cellulosic materials, derived from natural sources like wood pulp, are used in numerous industries due to their biodegradability, sustainability, and versatility. However, the inherent properties of cellulose, such as high absorbency and susceptibility to moisture, limit its functionality in certain applications, particularly where moisture resistance is essential.
[0003] To address these limitations, various treatments and modifications have been explored in the past. Common approaches include coating or impregnating cellulose fibers with synthetic polymers, applying water-repellent chemicals, or incorporating additives during the papermaking process. While these methods have provided improvements in water resistance and strength, they often compromise the recyclability of the material or involve the use of environmentally harmful chemicals.
[0004] There has been a growing demand for environmentally friendly alternatives that enhance the properties of cellulosic materials without negating their biodegradability or recyclability.
SUMMARY
[0005] The description pertains to a novel cellulosic structure and a method for its manufacture. This cellulosic structure comprises a substrate made from a network of cellulose fibers, which contain hydroxy moieties. Metal ions with a valency of at least three are bonded to these hydroxy moieties proximate (i.e., at or near) at least one surface of the substrate. The hydroxy moieties may include hydroxyl (-OH) and carboxylic acid (-COOH) groups. The metal ions used in this structure can include aluminum (Al3+) and iron (Fe3+), among others.
[0006] The substrate can be a cellulosic sheet, with metal ions applied on one or both major surfaces, on the edges, or distributed throughout the sheet. Additionally, the structure may include barrier layers on at least one major surface.
[0007] The manufacturing method involves preparing the cellulosic substrate and then treating it with metal ions. This treatment can occur at different stages of the process, including during pulp preparation, sheet formation, post sheet formation as a surface treatment, or post-barrier layer application specifically targeting the edges. This approach allows for varied metal ion distributions and properties tailored to different applications.
[0008] As such, according to another aspect of the invention for which protection is sought, there is provided a method for manufacturing a cellulosic structure, the method comprising: preparing a cellulosic substrate comprising a network of cellulose fibers with hydroxy moieties; and treating the cellulosic substrate with metal ions having a valency of at least three.
[0009] Optionally, the hydroxy moieties include hydroxyl (-OH) groups and carboxylic acid (-COOH) groups. The metal ions may include at least one of aluminum (Al3+) and iron (Fe3+),
[0010] Preferably, the cellulosic substrate is a cellulosic sheet substrate. Treating the cellulosic substrate with metal ions having a valency of at least three may include: introducing metal ions during the pulp preparation stage; and/or adding metal ions during the sheet formation stage; and/or applying metal ions as a surface treatment after sheet formation; and/or treating the edges of the cellulosic structure with metal ions post-barrier layer application.
[0012] Other embodiments of the disclosed cellulosic structure and method will become apparent from the following detailed description, the accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
Fig. 1 is a depiction of a cellulosic structure featuring a uniform distribution of metal ions with a valency of at least three throughout the entire cellulosic sheet substrate, bonded to the hydroxy moieties of the cellulose fibers, covering both major surfaces and the edges.
Fig. 2 is an illustration of a cellulosic structure where metal ions are concentrated on one or both of the major surfaces of the cellulosic sheet substrate.
Fig. 3 is a depiction of a cellulosic structure with metal ions applied specifically at one or both edges of the substrate,
Fig. 4 is an illustration of a cellulosic structure similar to Fig. 1, but incorporating an additional first barrier layer on the first major surface, enhancing the barrier properties alongside the uniform metal ion distribution.
Fig. 5 is a depiction of a cellulosic structure akin to Fig. 2, including a first barrier layer on the first major surface, combining the concentrated metal ion treatment on major surfaces with an additional barrier layer.
Fig. 6 is an illustration of a cellulosic structure similar to Fig. 3, featuring a first barrier layer on the first major surface, complementing the edge-concentrated metal ions.
Fig. 7 is a depiction of a cellulosic structure corresponding to Fig. 1, enhanced with dual barrier layers, one on each major surface, to augment the structure's barrier properties in conjunction with the uniform metal ion distribution.
Fig. 8 is an illustration of a cellulosic structure similar to Fig. 2, incorporating dual barrier layers on both major surfaces, thereby enhancing the structure with concentrated metal ion treatment on these surfaces.
Fig. 9 is a depiction of a cellulosic structure analogous to Fig. 3, integrating dual barrier layers on both major surfaces in addition to the edge-concentrated metal ions, providing amplified edge protection and barrier qualities.
DETAILED DESCRIPTION
[0014] This description relates a cellulosic structure comprising a cellulosic substrate. The cellulosic substrate comprises a network of cellulose fibers having hydroxy moieties. Proximate (at or near) at least one surface of the cellulosic substrate, metal ions having a valency of at least three are bonded to the hydroxy moieties of the cellulose fibers.
[0015] The cellulosic structure is composed mainly of cellulose, a common organic polymer in plants. The cellulosic substrate is derived from sources like paper, cotton, and wood pulp, either alone or in combination. These are processed into a network of cellulose fibers, lending structural integrity and flexibility.
[0016] The cellulosic substrate can be a thin, flexible sheet or a rigid board. This allows customization for various applications. Typically produced via papermaking techniques, it can be classified as paper or paperboard.
[0017] Hydroxy moieties in the cellulosic structure include hydroxyl (-OH) and carboxylic acid (-COOH) groups. These are integral to the chemical composition of cellulose fibers. Hydroxyl groups are part of the glucose units in cellulose, while carboxylic acid groups, less common, can be increased through chemical treatments. These groups enable bonding, crucial for attaching metal ions to cellulose. These hydroxy moieties (both OH and COOH groups) are responsible for the ability of cellulose fibers to form chemical bonds.
[0018] Metal ions with a valency of at least three, such as aluminum (Al3+) and iron (Fe3+), bond with the cellulose fibers. These metal ions bond to the cellulose fibers by way of the hydroxy moieties present in the cellulose.
[0019] These metal ions modify the cellulose fibers' interaction with liquids, particularly by reducing capillary action. Capillary action, the process by which liquid moves through a porous material due to the forces of adhesion, cohesion, and surface tension, is a key factor in the absorption of liquids by materials like paper. By altering the surface chemistry of the cellulose fibers, the bonded metal ions can decrease the rate at which liquids are absorbed from the edges. This reduced capillary action can be particularly beneficial in applications where reduced liquid absorption is desired. This alteration decreases liquid absorption, beneficial in moisture-prone environments.
[0020] The use of metal ions with a valency of at least three is not limited to a single type of pulp; rather, it is versatile and can be applied across multiple pulp types used in the creation of cellulosic substrates. These pulp types can include, but are not limited to, virgin softwood and hardwood pulps (with varying amount of lignin residual), specialty pulps derived from non-wood sources such as bamboo, hemp, or agricultural residues, as well the recycled counterparts of these materials.
[0021] The integration of metal ions with a valency of at least three into the cellulosic structure is compatible with other common additives used in the papermaking process. These additives include, but are not limited to, sizing agents that improve the water resistance of paper, strength-enhancing agents like starch, and fillers that enhance the paper's texture and printing properties. The presence of metal ions does not interfere with the efficacy of these additives.
[0022] The metal ions with a valency of at least three are introduced in the form of compounds. Examples of such compounds include chlorides such as iron(III) chloride (FeCl3) and aluminum chloride (AlCl3), sulfates such as aluminum sulfate (Al2(SO4)3) and iron(III) sulfate (Fe2(SO4)3). When applied to the cellulosic substrate, these compounds dissociate, releasing the metal ions, and then the metal ions can form bonds with the hydroxy moieties present in the cellulose, specifically the hydroxyl (-OH) and carboxylic acid (-COOH) groups. The selection of the specific metal ion compound can be tailored based on the desired end properties of the cellulosic structure, taking into account factors such as the type of pulp used, the intended application of the final product, and environmental considerations.
[0023] The cellulosic substrate, despite undergoing chemical modification through the addition of the metal ions, retains its recyclability. This attribute is crucial in today's environmentally conscious landscape. The ability to recycle treated paper products aligns with global efforts to reduce waste and promote sustainable practices. The recyclability of this treated cellulosic substrate can be attributed to several factors:
[0024] Chemical Bonding Nature: The metal ions, such as aluminum or iron, bond with the cellulose fibers. These bonds, while strong, do not fundamentally alter the cellulose's basic structure. This means that the recycling process, which typically involves breaking down the cellulosic substrate into its fibrous components, remains effective.
[0025] Compatibility with Existing Recycling Processes: The treated cellulosic substrate can be processed through standard paper recycling methods. The presence of metal ions does not interfere significantly with the pulping process, where paper is dissolved back into its fibrous state. This compatibility ensures that the treated cellulosic substrate can be integrated into the existing recycling infrastructure without the need for specialized processes.
[0026] Eco-Friendly Metal Ions: The selection of metal ions with a valency of at least three, like aluminum and iron, is also significant. These metals are not only effective in modifying the paper's properties but are also commonly found and handled in recycling operations. Their familiarity in the recycling industry means that the introduction of this treated paper does not pose new challenges or environmental risks.
[0027] Maintaining Fiber Integrity: The treatment process does not significantly degrade the cellulose fibers. Maintaining fiber integrity is significant for recycling, as it ensures the fibers can be reused multiple times, reducing the need for virgin fiber from trees.
[0028] Figures 1-9 demonstrate different designs of a cellulosic structure, focusing on the distribution of metal ions and the presence of barrier layers, which are recyclable.
[0029] Figure 1: Uniform Metal Ion Distribution: This figure shows a cellulosic structure (2) comprising a cellulosic sheet substrate (4) having a first major surface (6), a second major surface (8) opposite the first major surface, and one or more edges (10) between the first and second major surfaces. Metal ions (12) with a valency of at least three are bonded to the hydroxy moieties of the cellulose fibers throughout the entire substrate.
[0030] Figure 2: Major Surface Concentrated Metal Ions: Similar to Figure 1, but here, the metal ions (12) are incorporated only at one or both of the first and second major surfaces (6) and (8) of the substrate.
[0031] Figure 3: Edge Concentrated Metal Ions: Similar to Figure 1, but here, the metal ions (12) are incorporated only at one or both edges (10) of the substrate, between the first and second major surfaces (6) and (8).
[0032] Figure 4-6: Various Metal Ion Distributions with First Barrier Layer: These figures depict cellulosic structures similar to Figures 1-3 but with an additional feature. They include a first barrier layer (14) applied to the first major surface (6).
[0033] Figure 7-9: Various Metal Ion Distributions with Dual Barrier Layers: These figures depict cellulosic structures corresponding to Figures 1-3 but with both a first barrier layer (14) on the first major surface (6) and a second barrier layer (16) on the second major surface (8), further enhancing barrier properties.
[0034] These figures collectively illustrate various designs of the cellulosic structure, emphasizing various metal ion distributions and the inclusion of barrier layers for different applications.
[0035] The integration of metal ion treatment in the manufacturing of this cellulosic structure is a versatile and adaptable process. The metal ion treatment can be incorporated at various stages of the papermaking process, depending on the desired distribution of the metal ions and the specific properties required for the end product. This flexibility in integration allows for a wide range of applications and functionalities to be achieved.
[0036] During Pulp Preparation: Metal ions can be introduced early in the process, during the preparation of the pulp. This involves mixing the metal ions with the cellulose fibers before they are formed into sheets. This method ensures a uniform distribution of the metal ions throughout the cellulose structure, as depicted in Figures 1, 4 and 7. This uniform distribution is particularly beneficial for applications desiring consistent properties across the entire surface of the paper.
[0037] During Sheet Formation: Another potential point of metal ion treatment is during the sheet formation stage. Here, the metal ions can be added to the cellulose fiber slurry as it is being formed into sheets. This method allows for more control over the concentration and distribution of metal ions, enabling designs like those shown in Figures 2, 5 and 8, where the metal ions are concentrated at the first and/or second major surfaces.
[0038] Post Sheet Formation - Surface Treatment: The metal ions can also be applied as a surface treatment after the sheet is formed. This application method is suitable for targeting specific areas of the cellulosic substrate, such as the surfaces as shown in Figures 2, 5 and 8. Surface treatments can involve spraying, brushing, or immersing the paper in a solution containing the metal ions.
[0039] Post Barrier Layer Application - Edge Treatment: In the manufacturing process of the cellulosic structure, the metal ion treatment may occur after the barrier layers have been applied and the edges cut. This step can enhancing edge wicking resistance, a phenomenon where liquid moves along the edges of the cellulosic structure due to capillary action. By treating the metal ions post-edge cutting and post-barrier layer application, the edges, which are more prone to moisture absorption, receive additional fortification. This method is particularly suitable for ensuring that the edges, often the weakest points in terms of moisture resistance in paper products, are effectively protected. This application of metal ions, especially targeting the edges, as depicted in Figures 3, 6, and 9, not only bolsters the functional properties of the cellulose-based material but also significantly extends its usability and effectiveness in various applications.
[0040] Potential commercial areas where the properties of the treated cellulosic structure could be highly beneficial include:
[0041] Liquid Packaging: The invention's use in liquid packaging is particularly promising. Its enhanced resistance to moisture and leakage makes it ideal for packaging beverages like water, juices, and dairy products. These cellulosic containers could offer an environmentally friendly alternative to plastic bottles and containers, aligning with consumer demands for sustainable packaging solutions.
[0042] Food Service Paper Products: In this sector, the invention could improve the production of items like disposable plates, cups, and utensils. These paper products would benefit from increased durability and resistance to moisture and grease, making them more suitable for serving a wide range of foods without compromising on environmental sustainability.
[0043] Food Packaging: The treated cellulosic material can be used for packaging various food items, from snack foods to frozen goods. Its ability to resist moisture and fat infiltration can help maintain the freshness and integrity of the food, making it a viable alternative to traditional plastic and foil packaging. This application would be particularly attractive for eco-conscious brands and consumers.
[0044] Fiber-Based Building Materials: In the construction industry, this invention could be used to create sustainable, fiber-based materials for insulation, wallboard, and even temporary structures. Its moisture-resistant properties would be especially valuable in building materials, potentially increasing the longevity and durability of structures.
[0045] Plastic Replacement: The invention stands as a strong contender in replacing plastics in various applications. This includes not only packaging but also in products like plastic bags, wrapping films, and containers. Its biodegradability and sustainability would be key points in markets increasingly driven by environmental concerns.
[0046] Commercial Printing: For commercial printing applications, this cellulosic material could offer a high-quality, sustainable alternative to traditional paper. Its surface properties could allow for better ink adherence and image quality, making it suitable for high-end printing needs, including advertising, packaging, and graphic design.
Experimental Results
Example 1: Reduction of Water Wicking in FeCl3 Treated Kraft Pulp
[0047] In this experiment, the efficacy of FeCl3 treatment on Kraft pulp in reducing water wicking was evaluated. The sample paper made from FeCl3 treated Kraft pulp demonstrated a water wicking index of 17 kg/m2. In contrast, a control sample made from untreated pulp exhibited a significantly higher water wicking index of 28.8 kg/m2. This represents a 41% reduction in water wicking with the FeCl3 treatment. Notably, the lower the wicking index value, the less liquid is wicked in from an edge, indicating improved resistance to moisture penetration in the treated sample.
Example 2: Reduction of Coffee/Creamer Wicking in Alum Surface Treated Paper
[0048] Another experiment focused on assessing the impact of surface treatment with alum on the wicking of a coffee/creamer mixture. The paper subjected to this surface treatment showed a coffee/creamer wicking index of 10.8 kg/m2. This result was compared to a control sample that had a significantly higher wicking index of 26.6 kg/m2. The treatment resulted in a remarkable 59% reduction in wicking. This substantial decrease highlights the effectiveness of alum surface treatment in enhancing the liquid resistance of paper, making it potentially suitable for applications where exposure to such substances is common.
1. A cellulosic structure comprising:
a cellulosic substrate comprises a network of cellulose fibers having hydroxy moieties; and
metal ions having a valency of at least three bonded to the hydroxy moieties of the cellulose fibers proximate at least one surface of the cellulosic substrate.
2. The cellulosic structure of Claim 1, wherein the hydroxy moieties include hydroxyl
(-OH) groups and carboxylic acid (-COOH) groups.
3. The cellulosic structure of Claim 1 or claim 2, wherein the metal ions include at
least one of aluminum (Al3+) and iron (Fe3+),
4. The cellulosic structure of Claim 1, 2 or 3, wherein the cellulosic substrate is a
cellulosic sheet substrate.
5. The cellulosic structure of Claim 4, wherein the metal ions are applied on at least
one of a first major surface and a second major surface of the cellulosic sheet substrate.
6. The cellulosic structure of Claim 4 or 5, wherein the metal ions are applied on at
least one edge of the cellulosic sheet substrate.
7. The cellulosic structure of Claim 4, 5 or 6, wherein the metal ions are distributed
throughout the cellulosic sheet substrate.
8. The cellulosic structure of any preceding Claim, further comprising one or more barrier
layers applied to at least one major surface of the cellulosic substrate.
9. A method for manufacturing a cellulosic structure, the method comprising:
preparing a cellulosic substrate comprising a network of cellulose fibers with hydroxy moieties; and
treating the cellulosic substrate with metal ions having a valency of at least three.
10. The method of Claim 9, wherein the hydroxy moieties include hydroxyl (-OH) groups
and carboxylic acid (-COOH) groups.
11. The method of Claim 9 or 10, wherein the metal ions include at least one of aluminum
(Al3+) and iron (Fe3+),
12. The method of Claim 9, 10, or 11, wherein the cellulosic substrate is a cellulosic
sheet substrate.
13. The method of Claim 9, 10, 11 or 12, wherein treating the cellulosic substrate with
metal ions having a valency of at least three includes:
introducing metal ions during the pulp preparation stage; or
adding metal ions during the sheet formation stage; or
applying metal ions as a surface treatment after sheet formation.
14. The method of Claim 9, 10, 11, or 12 wherein treating the cellulosic substrate with
metal ions having a valency of at least three includes treating the edges of the cellulosic
structure with metal ions post-barrier layer application.
15. The method of any Claim 9 to 14, or the cellulosic structure of any Claim 1 to 8 wherein
the cellulosic structure is recyclable.