Cellulosic structure and method for manufacturing thereof

Abstract

A cellulosic structure includes a cellulosic substrate and polycaprolactone impregnated within the cellulosic substrate. A method for manufacturing the cellulosic substrate includes providing a cellulosic substrate and impregnating liquid polycaprolactone within the cellulosic substrate. The cellulosic structure may be included in a food package for high grease and / or moisture content food product.

Description

CELLULOSIC STRUCTURE AND METHOD FOR MANUFACTURING THEREOFFIELD

[0001] The present description relates to the field of sustainable materials, specifically to an impregnated cellulosic structure. This cellulosic structure finds its application in areas seeking eco-friendly alternatives to traditional materials used in various industries, including packaging products.B AC KG R O UN D

[0002] Paperboard has long been recognized for its excellent sustainability characteristics. It is a renewable and biodegradable material, making it an environmentally friendly choice for packaging and other applications. However, one of its notable drawbacks is its limited resistance to oil, grease, and moisture, which can compromise its functionality and durability in various applications.

[0003] To address the issue of oil, grease, and moisture resistance, wax-impregnated paperboard is commonly used. This approach enhances the material's resistance to these elements, making it suitable for specific applications where traditional paperboard falls short. However, this improvement comes at the cost of decreased sustainability and compo stability. The wax treatment can make the paperboard less eco-friendly, hindering its ability to degrade naturally or be recycled and potentially causing environmental concerns.

[0004] Given the shortcomings of both traditional paperboard and wax-impregnated paperboard, there is a pressing need for a sustainable and environmentally friendly alternative that can offer improved resistance to oil, grease, and moisture without undermining the material's biodegradability and compostability.S UM M A R Y

[0005] The present description relates to a cellulosic structure comprising a cellulosic substrate and polycaprolactone (PCL) impregnated within the cellulosic substrate and to a food package comprising the cellulosic structure. Polycaprolactonc is a biodegradable and compostable biopolymer.

[0006] The present description further relates to a method for manufacturing a cellulosic substrate. The method includes providing a cellulosic substrate and impregnating liquid polycaprolactone within the cellulosic substrate.

[0007] Other embodiments of the disclosed cellulosic structure and method will become apparent from the following detailed description, the accompanying drawings and the appended claims.B RIEF D ES CRIPTIO N O F THE D RAWIN G S

[0008] FIG. 1 shows a cross-sectional view of a sustainable barrier board featuring a monolayer biopolymer structure coated on both sides of a cellulosic sheet substrate.

[0009] FIG. 2 illustrates another sustainable barrier board but with a multilayer (dual-layer) biopolymer structure on each side of the cellulosic substrate.

[0010] FIG. 3 presents a conceptual representation of roller dynamics used in an exemplary manufacturing process. It shows two counter-rotating rollers creating a 'puddle region' where the laminate material is coated or treated.

[0011] FIG. 4 depicts an exemplary design of the sustainable barrier board used as an L- shaped bacon board, highlighting its protective and eco-friendly features suitable for products like bacon slices.

[0012] FIG. 5 is a bar chart comparing edge wick rates for various different materials.

[0013] FIG. 6 is a bar chart detailing the results of a Corn Oil Immersion Test.D ET A ILED D E S C R IP TIO N

[0014] The present invention pertains to a cellulosic structure comprising a cellulosic sheet substrate and polycaprolactone impregnated within the cellulosic sheet substrate. This structure aims to provide a sustainable, eco-friendly alternative to conventional materials, particularly wax-impregnated cellulosic sheets, which have been widely used due to their resistance to oil, grease, and moisture.

[0015] The foundational element, the cellulosic sheet substrate, is primarily cellulose fibers, sourced from natural materials like wood pulp, cotton, hemp, bamboo, and other plant fibers. These natural sources render it biodegradable and renewable. It may come in various forms, from flexible sheets to stiff boards, and have different properties based on its application, including possible additives or treatments for enhanced performance. It can be a single or multi-ply construction, often made from virgin or recycled fiber through a papermaking process.

[0016] Polycaprolactone (PCL), a biodegradable polyester with a low melting point, is composed of long, flexible chains of repeating caprolactone units, ranging from long-chain polymers with hundreds to millions of caprolactone units to short-chain oligomers comprising a few to several dozen caprolactone units.

[0017] Impregnating the cellulosic substrate with PCL enhances its performance, providing a barrier against oil, grease, moisture, and other environmental agents. This integration creates a composite material that combines the cellulosic substrate's strength and flexibility with the protective qualities of PCL, maintaining overall biodegradability and cco-fricndlincss. The PCL penetrates deeply into the structure of the cellulosic sheet beyond the surface porosity of the cellulosic sheet substrate. This penetration of polycaprolactone can occur throughout the entire thickness of the cellulosic sheet substrate, and the polycaprolactone molecules can infiltrate into the cellulose fibers themselves.

[0018] The process of impregnating the cellulosic substrate with PCL is significantly influenced by the mean molecular weight of PCL, which determines its viscosity and melting temperature. A lower mean molecular weight leads to reduced viscosity, allowing for deeper and more even penetration into the cellulose fibers. Additionally, a lower melting point eases theimpregnation process and reduces the risk of thermal damage to the cellulosic substrate. The effectiveness of impregnation varies with different molecular weight ranges. For instance, PCL with a molecular weight of 10,000 g / mol or less can achieve impregnation, though this might require higher temperatures or additional force for effective substrate penetration. A molecular weight of 5,000 g / mol or less eases some processing challenges, while a weight of 3,500 g / mol or less further simplifies processing and enhances penetration. At a molecular weight of 2,500 g / mol or less, efficient impregnation becomes more feasible under typical processing conditions.

[0019] If the molecular weight of polycaprolactone (PCL) is too low, it may lead to unwanted migration within the cellulosic substrate, especially under environmental stresses such as heat, moisture, or exposure to certain solvents. Conversely, PCL with a high molecular weight offers notable advantages in preventing migration. Higher molecular weight PCL has longer polymer chains, which tend to entangle more effectively with the cellulosic fibers. This entanglement results in stronger adhesion and enhanced stability within the substrate, leading to less migration of PCL. Moreover, the long chains create a denser network, restricting PCL movement within the substrate. This interaction also potentially improves the substrate's resistance to external agents. A mean molecular weight of 200 g / mol or more could yield these benefits, depending on the application and desired properties of the final product. As the molecular weight increases, so does the interaction strength between the PCL and the cellulosic substrate. A mean molecular weight of 300 g / mol or more is likely to enhance PCL retention in the cellulosic structure, leading to more consistent barrier performance and possibly lower sensitivity to environmental changes. Molecular weights exceeding 400 g / mol or 500 g / mol could further amplify these interactions, boosting stability and adhesion between the PCL and the cellulosic substrate.

[0020] In a related aspect, the liquid state of polycaprolactone (PCL) at low or modest temperatures significantly enhances its applicability for impregnation into the cellulosic sheet substrate. This property is linked to the molecular weight of PCL. Generally, PCL with a lower molecular weight tends to have a lower melting point, thus remaining liquid at lower temperatures. Ideally, this PCL should be liquid at 50 degrees Celsius. Lower molecular weight PCL could further improve this property, potentially maintaining a liquid state at even more favorable temperatures such as 40 degrees Celsius, and optimally at 30 degrees Celsius or lower. The most desirable condition would be for the PCL to remain liquid at temperatures as low as 20degrees Celsius. Such a characteristic of remaining liquid at low temperatures, indicative of a lower molecular weight, ensures minimal energy usage during processing. It also reduces the risk of damaging the cellulosic substrate due to high temperatures, and allows greater flexibility in choosing processing equipment and conditions, including impregnation processes at room temperature.

[0021] In this context, the polycaprolactone (PCL) may include or be in the form of polycaprolactone diol, which is a PCL derivative. Polycaprolactone diol is distinguished by two hydroxyl (-OH) groups at its molecular ends, crucial for its chemical reactivity. In cellulosic sheet substrate impregnation, polycaprolactone diol offers significant benefits. It strengthens the bond between the cellulosic fibers and PCL. The diol's terminal hydroxyl groups can establish hydrogen bonds with the cellulosic fibers' hydroxyl groups, resulting in enhanced adhesion and stability of PCL within the cellulosic matrix. This improved bonding is advantageous for maintaining PCL's position in the substrate and avoiding migration, especially under varying environmental conditions.

[0022] Incorporating polycaprolactone diol into the cellulosic sheet substrate notably alters its water absorption resistance. This effect is due to the interaction between the hydroxyl groups of the diol and those in the cellulosic fibers. As polycaprolactone diol integrates into the cellulosic structure, its hydroxyl groups bond with those of the cellulose through hydrogen bonding. This bonding reduces the number of free hydroxyl groups on the surface of the cellulosic fibers, which are typically water-attractive. Consequently, the bonding decreases the substrate's propensity for water absorption, thereby enhancing its water-repellent qualities. The modified structure becomes less hydrophilic, reducing its tendency to absorb moisture.

[0023] The addition of polycaprolactone diol contributes to reducing the swelling of the cellulosic structure upon water absorption. Swelling in cellulosic structures like paper is a cyclic process triggered by moisture exposure. Initially, the hydrophilic cellulose absorbs water, causing the fibers to swell as water molecules enter the spaces between cellulose molecules, pushing them apart. This swelling exposes new cellulosic areas to moisture, leading to further water uptake and increased swelling, potentially compromising the structure's physical properties.

[0024] The effect of polycaprolactone diol on cellulosic structures, particularly in terms of swelling resistance, can be attributed to its chemical structure and interaction with cellulose fibers. Polycaprolactone Diol is characterized by two hydroxyl (OH) end groups connected by a polycaprolactone chain, providing molecular stability and flexibility, essential for interacting with cellulose. Upon introduction to a cellulosic substrate, these hydroxyl groups tend to form hydrogen bonds with the cellulose's hydroxyl groups. Such hydrogen bonding reinforces the cellulosic structure by acting as anchors that maintain the structural integrity of cellulose, even in moist environments. This bonding mechanism helps resist the typical swelling of cellulosic structures when exposed to water by creating a network within the cellulose, making it less prone to water absorption and swelling. The inclusion of polycaprolactone diol in cellulosic substrates results in a more stable, less hydrophilic material.

[0025] The hydroxyl value, typically measured in milligrams of potassium hydroxide per gram (mg KOH / g), serves as an indicator of the reactivity and potential functionality of polycaprolactone diol in the impregnation process. This metric reflects the concentration of hydroxyl groups in a specific weight of polycaprolactone diol, suggesting its ability to engage in chemical reactions. Generally, a higher hydroxyl value may indicate a more substantial presence of hydroxyl groups. This may, for instance, influence the degree of interaction with cellulosic fibers. Within the scope of cellulosic substrate impregnation, increasing hydroxyl values may facilitate enhanced hydrogen bonding with cellulose fibers. This can improve the stability and adhesive characteristics of the impregnated material. Such bonding is thought to support the maintenance of the cellulosic structure's integrity and performance under diverse environmental conditions. By way of example, a hydroxyl value of at least 25 mg KOH / g can offer a baseline reactivity, enhancing the anti-swelling properties of the impregnated cellulosic material. As the hydroxyl value increases, such as at least 50 mg KOH / g or at least 100 mg KOH / g, there can be a progressive enhancement in the potential to mitigate swelling. This is due to the increased density of hydroxyl groups that may enhance hydrogen bonding with cellulose fibers, thus reducing the propensity of the cellulosic structure to absorb water and swell. These values suggest varying degrees of effectiveness in stabilizing the cellulosic matrix against moisture- induced expansion.

[0026] The cellulosic structure may incorporate various additives or components to modify or enhance specific attributes of the impregnated cellulosic substrate. The impregnation material, however, comprises either pure poly caprolactone or a polycaprolactone-based blend. In this blend, the proportion of polycaprolactone is maintained at a high level to ensure the retention of its key properties. Specifically, the polycaprolactone forms at least 50% of the impregnant, with increasing preferences for higher concentrations: at least 60%, further preferably at least 70%, more preferably still at least 80%, and ideally at least 90% or more, optimally reaching at least 95%. These varying concentrations allow for a balance between the benefits of poly caprolactone and the desired modifications introduced by the additives.

[0027] A method of manufacturing the cellulosic substrate includes providing a cellulosic substrate and impregnating liquid polycaprolactone within the cellulosic substrate. The impregnation method involves introducing the liquid polycaprolactone to the cellulosic substrate under various conditions to achieve the desired depth of permeation. This can be achieved through techniques, including, but not limited to, immersion, roll-to-roll coating, spraying, or pressure-driven processes. The method begins with bringing the polycaprolactone to a temperature wherein it maintains a liquid state, which may be room temperature. The cellulosic substrate is then exposed to this liquid polycaprolactone, either by direct application or immersion. If pressure is employed, it aids in ensuring a deeper and more uniform penetration of the polycaprolactone into the substrate. Preferably, the mean molecular weight of the polycaprolactone is selected to provide sufficient penetration into the substrate at room temperature without application of pressure. After impregnation, the final product can then be inspected for uniformity and quality before being further processed. Further processing may include applying a first biopolymer layer applied onto a first major side of the cellulosic substrate and a second biopolymer layer applied onto a second major side of the cellulosic substrate. These biopolymer layers provide further barrier properties for the cellulosic substrate. Further process typically also includes cutting one or more edges of the cellulosic substrate. In the case where one or both major side of the cellulosic substrate are coated, the process of cutting the edges of the cellulosic substrate results in uncoated cut edges. These cut edges are left unprotected by the biopolymer layers applied onto the major sides of the cellulosic substrate. The impregnated polycaprolactone is important for protecting the cut edges and for resisting an edge wicking effect.

[0028] Edge wicking refers to the phenomenon where moisture or other liquid substances are absorbed into the edges of porous materials, such as paper or paperboard. This absorption can lead to significant damage. In cellulosic structures, edge wicking can cause swelling, distortion, and a weakening of the material's integrity. This is particularly problematic in products that require a high degree of moisture resistance, like packaging materials. When the edges of such materials absorb moisture, it can travel inward, affecting the overall structure and potentially damaging the contents. In products like cartons, boxes, or other packaging solutions, edge wicking can compromise the product's strength, stability, and ability to protect its contents. It can also lead to aesthetic issues, such as discoloration or warping, which might diminish the product's visual appeal or perceived quality. The impregnation of polycaprolactone within the cellulosic structure, as described in the patent, aims to mitigate this issue by providing a barrier that resists the absorption of moisture and other substances at the edges, thereby enhancing the material's durability and longevity in challenging environments.

[0029] In an example of the manufacturing process, the step of impregnating the liquid polycaprolactone into the cellulosic substrate is performed using a size press. A size press is a machine commonly used in the paper and board industry to apply surface treatments to the substrate as it passes between two press rolls. As the cellulosic substrate moves through the size press, the liquid polycaprolactone is metered onto the substrate through a nip formed by the two rolls, ensuring a controlled and uniform application. The design of the size press allows for precise control over the amount of polycaprolactone applied, ensuring optimal impregnation depth. As the substrate exits the size press, the liquid polycaprolactone starts to penetrate into the cellulosic fibers, facilitated by its liquid state. The use of a size press for impregnation offers several advantages. Firstly, it ensures a consistent and uniform distribution of the polycaprolactone across the width and length of the substrate. This uniformity is essential for maintaining consistent properties, especially for applications where edge wicking resistance is important. Secondly, the size press process is highly scalable, making it suitable for large-scale production. Furthermore, using polycaprolactone diol in the size press has shown significant promise. When applied to paperboard substrates using this method, the resultant product demonstrated edge wicking resistance comparable to traditional wax-impregnated paperboards, highlighting the effectiveness of the approach. The combination of the size press applicationmethod with the properties of polycaprolactone diol provides a sustainable and efficient solution for enhancing the properties of cellulosic substrates.

[0030] This present description further presents an enhanced sustainable barrier solution. The sustainable barrier board comprises: a cellulosic sheet substrate impregnated with the polycaprolactone, enhancing the intrinsic barrier properties from within the substrate, a first biopolymer coating applied onto a first major side of the cellulosic sheet substrate, and optionally a second biopolymer coating is applied onto the second major side of the cellulosic sheet substrate. The cellulosic sheet substrate may be a cellulosic board substrate, such a paperboard substrate. Notably, all components utilized are environmentally-friendly. This assembly of components presents a viable, eco-friendly alternative to traditional wax- impregnated paperboards, marking a pivotal shift in sustainable barrier board technology.

[0031] The first and second biopolymer coatings are continuous layers of biopolymer material that provide barrier properties to the sustainable barrier board, particularly in terms of resistance to moisture, grease, and oil absorption. The biopolymer coatings also contribute to the compostable and environmentally friendly aspects of the barrier board. The first and second biopolymer coatings are applied onto the respective major sides of the impregnated cellulosic board substrate.

[0032] The first and second biopolymer coatings can incorporate various biodegradable and compostable polymers from renewable sources. These biopolymers provide similar’ barrier qualities to traditional petroleum-based counterparts but with less environmental impact. They can be used alone or combined to optimize specific characteristics. The selection of the biopolymer blend considers aspects like the properties of the cellulosic substrate, the amount and type of impregnated substance, intended use of the barrier board, cost, material availability, and performance needs. In an example, the first and second biopolymer coatings may include biopolyesters. In addition, the first and second biopolymer coatings may also include various additives to further enhance their performance. These additives can include, for example, plasticizers, colorants, fillers, stabilizers, and processing aids.

[0033] The first and second biopolymer coatings may be, for example, heat sealable laminate coatings. The first and second biopolymer coatings may be monolayer or multilayer coatings.

[0034] A first example of a heat-sealable laminate coating is the BioPBS-coated cellulose acetate film. This film uses BioPBS (Polybutylcnc Succinate) as its coating agent. BioPBS is a biodegradable plastic derived from succinic acid and butanediol. When combined with cellulose acetate, a plant-based biopolymer, the resulting film possesses certain functional attributes. BioPBS ensures heat-sealing capabilities with the cellulose acetate substrate. The film is also receptive to printing, allowing for clear graphic representation. In the lamination process, melted BioPBS is spread across the pretreated cellulose acetate substrate at controlled temperatures. The application of heat and pressure allows the BioPBS to bond with the substrate. After lamination, the film is cooled, which solidifies the BioPBS, ensuring its adherence. The film is often used in various packaging applications due to its specific properties.

[0035] A second example of a heat-sealable laminate coating is the heat-sealable flow wrap compostable film. The compostable aspect of this film designates that the film will break down under composting conditions, minimizing environmental impact. The compostable feature arises from the incorporation of biopolymers in the film composition. These biopolymers, when subjected to industrial composting conditions, degrade into harmless byproducts, offering an environmentally conscious alternative to traditional plastic films.

[0036] FIG. 1 illustrates a cross-sectional view of the sustainable barrier board (2) having a monolayer structure on each side. The depiction shows the primary components of the board (2), starting with a central cellulosic sheet substrate (4). This substrate (4) exhibits two major sides: a first major side (6) and a second major side (8). The substrate (4) is impregnated with polycaprolactone (10). Adjacently, a first biopolymer coating (12) is applied onto the first major side (6). Conversely, a second biopolymer coating (14) is applied onto the second major side (8) of the substrate. This configuration ensures that both sides of the cellulosic board substrate (4) are enveloped with a protective biopolymer coat.

[0037] FIG. 2 illustrates a cross-sectional view of the sustainable barrier board (2) having a multilayer structure on each side, specifically a two-layer configuration. Like FIG. 1, a center of the sustainable barrier board (2) is formed by the cellulosic board substrate (4) with a first major side (6) and a second major side (8). However, distinctively in this configuration, the first major side (6) of the substrate (4) is covered with an inner biopolymer coating (16) immediatelyadjacent to the substrate, followed by an outer biopolymer coating (18) forming the exposed surface. Similarly, on the second major side (8) of the substrate, an inner biopolymer coating (20) is initially applied followed by an outer biopolymer coating (22). The inner biopolymer coatings (16 and 20) primarily focus on achieving strong adhesion to the substrate and may contain a higher concentration of specific biopolymers, as previously discussed. In contrast, the outer biopolymer coatings (18 and 22) are designed to provide optimal barrier properties, mechanical strength, and potentially aesthetic appeal. This dual-layered approach on both sides ensures that the cellulosic board substrate (4) benefits from specialized functionalities tailored by each individual layer, optimizing the overall performance of the sustainable barrier board (2).

[0038] Referring to FIG. 3, illustrated is a conceptual representation of roller dynamics. The illustration depicts two adjacent rollers (30 and 32) with a directional arrow indicating the counter-rotation of the rollers. Between the rollers is a puddle region (34) which represent ■ the point where the laminate material gets coated or treated. The arrows indicate that as the substrate enters from the top, it gets pressed between the rollers, and the application process occurs at the puddle region (34), ensuring uniformity in the applied coat.

[0039] FIG. 4 illustrates an exemplary food packaging (50) designed for high grease and / or moisture content food products, such as bacon slices (53). As depicted the food packaging (50) comprises an L-shaped bacon board (51) and a transparent plastic covering (52) that encases both the bacon slices (53) and the bacon board (51). The L-shaped bacon board (51) serves as a rigid backing to support the bacon slices (53) while also providing a surface (54) for graphics, logos, and other relevant product information. The L-shaped bacon board (51) may be folded along fold line (55) to form front and back sides of the bacon board. The plastic covering (52) can be, for example, a vacuum-sealed bag or a shrink-wrapped film, designed to preserve the freshness and extend the shelf life of the bacon (53) by preventing oxygen and moisture from entering the package. Preferably, the plastic covering (52) is compostable to enhance environmental sustainability of the entire food packaging (50). Additionally, this transparent plastic covering (52) allows consumers to visually inspect the quality and appearance of the bacon (53) through a small window (56) located on the back of the package.

[0040] The L-shaped bacon board (51) comprises the sustainable barrier board (2), as described in the present application, with polycaprolactonc impregnated into the cellulosic substrate providing added resistance against the inherent moisture and grease from the bacon slices (53). This ensures the board maintains its structural integrity, even when exposed to prolonged contact with moist or greasy food products. The biopolymer coatings applied on the major sides of the sustainable barrier board (2) also play an essential role in this context, acting as an additional barrier against moisture and grease migration. As a result, the potential for contamination or compromise of the board’s structural and aesthetic qualities is significantly reduced. Various modifications and adaptations can be made to the illustrated packaging design.

[0041] In addition to the protective functionalities, the sustainable barrier board (2) used for the L-shaped bacon board (51) offers another advantage: reduced environmental impact. Given the focus on sustainability, using this barrier board in food packaging applications aligns with current trends towards eco-friendly products. The biopolymer coatings, being derived from renewable sources, along with the compostable plastic covering (52), ensure that the packaging has a reduced carbon footprint and is easier to dispose of in an environmentally friendly manner. The combination of moisture resistance, protection against grease, structural rigidity, and environmentally conscious materials makes the sustainable barrier board (2) a suitable choice for food packaging applications, especially for products with high moisture and grease content like bacon. It offers manufacturers an opportunity to leverage both functional and environmental advantages in their product packaging design.EX PE RIM EN TA L RE S U LTSObjective

[0042] The primary objective of these experiments was to identify an environmentally sustainable substitute for paraffin wax in bacon board barriers. Current barriers, utilizing paraffin wax, present notable challenges in terms of environmental impact and recyclability. These wax- impregnated paperboards also encounter operational difficulties in handling, conversion, and printing. The goal was to develop a material that not only offers effective oil and grease resistance but is also eco-friendly.Materials Assessment

[0043] A range of materials and coatings, both synthetic and natural, were evaluated for their oil and grease resistance capabilities. Among these, liquid polycaprolactone, particularly of low molecular weight, emerged as a standout. This material demonstrated excellent penetration into paperboard substrates and showed superior resistance in oil-grease tests, such as the corn oil vacuum test.Comparative Analysis

[0044] When compared with other materials including water-based polyester (Seycote SF), acrylic dispersion (Michelman X300 AF), and natural biopolymer dispersions (e.g., Paper Greens Bio-Seal-2904 BS 20), polycaprolactone significantly outperformed in terms of resistance to oil and grease absorption.Environmental Advantages

[0045] The proposed material offers significant environmental benefits over traditional wax- impregnated products. Its potential for recyclability, repulpability, biodegradability, and compostability positions it as a highly sustainable alternative.Experimental Procedures

[0046] The experiments included a series of tests to evaluate the effectiveness of the proposed materials. In the Mathis Lab Size Press Trial, we used an 8” x 8” bacon board sheet, manually fed through a coating material puddle between two counter-rotating rolls, at room temperature. The Corn Oil Immersion Test involved immersing a 2”x6” strip into a com oil bath followed by vacuum sealing. The standard for passing the test was set such that the corn oil absorption weight gain should not exceed 15 eg per 100 inches of the perimeter.Data Analysis and Findings

[0047] The analysis, as shown in FIG. 5, revealed that while Paraffin Wax showed the lowest edge wick rate at 29.0 eg / 100", it carried significant known environmental concerns. In contrast, Capa 8015D (mean molecular weight of 1000 g / mol), an eco-friendly and compostable material,exhibited commendable performance with an intermediate edge wick rate of 40.5 cg / 100". Another liquid PCL grade Capa 8025D (mean molecular weight of 2000 g / mol) showed even better performance at a lower edge wick rate of 32.9 cg / 100”. Both compared favorably against Seycote SF, Michelman X300 AF, and Paper Greens BS20, which all showed much higher oil absorption rates. Interestingly, Capa 8025D PCL has a higher molecular weight and viscosity than Capa 8O15D PCL, and imparted more cellulose fiber impregnation and better edge wicking performance than Capa 8015D PCL. On the other hand, the higher viscosity of 8025D PCL was observed to create a greater challenge in the release of coated bacon board sheet from the counter- rotating rollers during the size-press operation.Experimental Analysis of Sustainable Barrier Board

[0048] Further testing was conducted on the sustainable barrier board using two lamination processes: F2S and F1SX2. These processes involved applying a heat-sealable film to either one or both sides of a barrier-coated bacon board and then processing it through heated and cold rollers. The HS Bio Film, mainly BioPBS-coated cellulose acetate, was used in these tests.Corn Oil Immersion Test Results

[0049] The results, as shown in FIG. 6, from the Com Oil Immersion Test were particularly noteworthy. The film-laminated and barrier-coated bacon board sheets, when subjected to a O.IMPa vacuum for 25 seconds in a corn oil bath, demonstrated significantly lower edge-wick values. Specifically, "8015D PCL / HS Bio Film" recorded a value of 3.9 cg / 100", and "8025D PCL / HS Bio Film" achieved an even lower value of 1.9 cg / 100", outperforming the incumbent "Wax / LDPE P2S" which had a value of 7.5 cg / 100".Conclusion

[0050] These experimental results demonstrate the potential of liquid polycaprolactone, such as Capa 8015D or Capa 8025D, as a sustainable and effective alternative to paraffin wax in bacon board barriers. With its lower oil absorption rates and significant environmental advantages, it represents a step forward in sustainable packaging solutions.

[0051] Although various embodiments of the disclosed cellulosic structure and method for manufacturing have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.

Claims

What is claimed is:

1. A cellulosic structure, comprising: a cellulosic substrate having a first major side and a second major side; and polycaprolactone impregnated within the cellulosic substrate.

2. The cellulosic structure of Claim 1, wherein the polycaprolactone has a mean molecular weight of 200 g / mol to 10,000 g / mol.

3. The cellulosic structure of Claim 1, wherein the polycaprolactone has a mean molecular weight of 300 g / mol to 5,000 g / mol.

4. The cellulosic structure of Claim 1, wherein the polycaprolactone has a mean molecular weight of 400 g / mol to 3,500 g / mol.

5. The cellulosic structure of Claim 1, wherein the polycaprolactone has a mean molecular weight of 500 g / mol to 2,500 g / mol.

6. The cellulosic structure of Claim 1, wherein the polycaprolactone comprises polycaprolactone diol.

7. The cellulosic structure of Claim 1, wherein the polycaprolactone has a hydroxyl value of at least 25 mg KOH / g.

8. The cellulosic structure of Claim 1, wherein the polycaprolactone has a hydroxyl value of at least 50 mg KOH / g.

9. The cellulosic structure of Claim 1, wherein the polycaprolactone has a hydroxyl value of at least 100 mg KOH / g.

10. The cellulosic structure of Claim 1 , further comprising a first biopolymer layer applied onto the first major side of the cellulosic substrate.

11. The cellulosic structure of Claim 1 , further comprising a second biopolymer layer applied onto the second major side of the cellulosic substrate.

12. The cellulosic structure of Claim 1, further comprising a first biopolymer layer applied onto the first major side of the cellulosic substrate, and a second biopolymer layer applied onto the second major side of the cellulosic substrate.

13. The cellulosic structure of Claim 1, further comprising a multilayer biopolymer structure on at least one side of the cellulosic substrate.

14. The cellulosic structure of Claim 1, further wherein the cellulosic substrate is a cellulosic board substrate.

15. A food package for high grease and / or moisture content food product, the food package comprising the cellulosic structure of Claim 1.

16. A method for manufacturing a cellulosic substrate, the method comprising: providing a cellulosic substrate; and impregnating liquid polycaprolactone within the cellulosic substrate.

17. The method of Claim 16, wherein the step of impregnating the liquid polycaprolactone is performed by way of a size press.

18. The method of Claim 16, wherein the step of impregnating the liquid polycaprolactone is performed at room temperature.

19. The method of Claim 16, wherein the polycaprolactone has a mean molecular weight of 200 g / mol to 10,000 g / mol.

20. The method of Claim 16, wherein the polycaprolactonc comprises polycaprolactonc diol.

21. The method of Claim 16, wherein the polycaprolactone has a hydroxyl value of at least 25 mg KOH / g.

22. The method of Claim 16, further comprising applying a first biopolymer layer onto a first major side of the cellulosic substrate.

23. The method of Claim 16, further comprising applying a second biopolymer layer onto a second major side of the cellulosic substrate.

24. The method of Claim 16, further comprising applying a first biopolymer layer applied onto a first major side of the cellulosic substrate, and a second biopolymer layer applied onto the second major side of the cellulosic substrate.

25. The method of Claim 16, further comprising applying a multilayer biopolymer structure on at least one side of the cellulosic substrate.

Images