Heat-sealed paper packaging

Abstract

The present invention relates to a process for producing packaging, said process comprising a step of heat-sealing wherein the heat-sealing is performed using polysaccharide coated on a paper substrate, wherein the coated polysaccharide comprises uronic acid. The present invention also relates to heat-sealed packaging obtainable by the process.

Description

Technical Field

[0001] The invention relates to a heat-sealed paper packaging in which the packaging is heat-sealed using polysaccharide comprising uronic acid.Background Art

[0002] The wrapping industry plays a crucial role in packaging goods for safety, transportation, storage, and retail. Today, plastic-based materials dominate the industry due to their versatility, durability, and cost-effectiveness. Plastics such as polyethylene and polypropylene are widely used for wrapping, offering lightweight and waterproof solutions that meet the demands of modern logistics and consumer preferences. However, the convenience of plastic wraps comes with significant environmental costs.

[0003] For environmental reasons, it is imperative to move away from plastic wrapping paper. Plastic waste contributes significantly to pollution, with large amounts ending up in oceans and landfills. Plastics are non-biodegradable, taking centuries to break down and releasing harmful microplastics into ecosystems. Additionally, the production and incineration of plastic materials generate greenhouse gases, exacerbating climate change. Transitioning to eco-friendly alternatives can help reduce the ecological footprint of the wrapping industry.

[0004] Paper wrapping stands out as a practical and eco-friendly alternative to plastic. It is biodegradable, recyclable, and made from renewable resources, making it an excellent choice for reducing environmental impact. Additionally, paper wrapping can be easily customized, printed, and shaped to meet diverse packaging needs. However, one limitation of paper wrapping is that it cannot be heat-sealed, which is a common method for ensuring airtight and secure closure in plastic packaging. This drawback may pose challenges for industries requiring tamper-proof or moisture-resistant packaging solutions. Some solutions exist on the market today in which the paper is coated with fossil sourced layer which assure heat-seal closure. Yet, these solutions can generate microplastic pollution.Technical problem

[0005] There is therefore a need to develop paper wrapping packaging that incorporates the ability to be heat-sealable, addressing a critical limitation in its functionality while retaining its properties that are beneficial to environmental standards.

[0006] It is thus to the credit of the inventors to have found that it was possible to meet this need by means of natural biosourced materials coated on paper substrate.Summary

[0007] It is proposed a process for producing packaging, said process comprising a step of heat-sealing wherein the heat-sealing is performed using polysaccharide coated on a paper substrate, wherein the coated polysaccharide comprises uronic acid, in particular the coated polysaccharide is a gum, more particularly the coated polysaccharide is arabic gum.

[0008] Unexpectedly, the inventors have noticed that heat-sealing can be performed using biosourced materials such as polysaccharide comprising uronic acid coated on a paper substrate, in order to produce heat-sealed packaging.

[0009] The process for producing packaging of the invention enables the production of packaging with all the properties of conventional heat-sealing plastic packaging, such as ensuring airtight and secure closure but using bio-sourced materials.

[0010] Advantageously, the process for producing packaging of the invention is compatible with existing heat-sealable machinery, reducing the need for costly new equipment.

[0011] In another aspect, it is thus proposed heat-sealed packaging obtainable by the process for producing packaging of the invention.

[0012] In contrast to heat-sealed plastic packaging, the heat-sealed packaging of the invention may, by virtue of its composition, degrade very rapidly in the environment. This is particularly advantageous since the environmental impact of the packaging of the invention is smaller than the environmental impact of typical heat-sealed plastic or paper packaging used in industry.

[0013] In another aspect, it is proposed a process for producing heat-sealable wrapping paper comprising a step of coating a paper substrate with polysaccharide comprising uronic acid.

[0014] In another aspect, it is proposed heat-sealable wrapping paper obtainable by the process for producing heat-sealable wrapping paper of the invention.

[0015] The inventors have noticed that biosourced materials such as polysaccharide comprising uronic acid can be used to make substrate paper heat-sealable and maintaining its environmental interest since no plastic are needed.

[0016] According to an embodiment, the polysaccharide comprising uronic acid is arabic gum.Description of Embodiments

[0017] It is proposed a process for producing packaging, said process comprising a step of heat-sealing wherein the heat-sealing is performed using polysaccharide coated on a paper substrate, wherein the coated polysaccharide comprises uronic acid.

[0018] In the context of the present invention, the term "polysaccharides" refers to a natural, plant-derived materials that is used as a biosourced coating material on the paper substrate to enable heat-sealing. The polysaccharide used in this invention comprises uronic acid.

[0019] Uronic acid refers to a class of sugar acids with both carbonyl and carboxylic acid functional groups. They are sugars in which the hydroxyl group furthest from the carbonyl group has been oxidized to a carboxylic acid. Typically, uronic acid may be glucuronic acid, iduronic acid, or galacturonic acid.

[0020] Without wishing to be bound by any theory, the inventors are of the opinion that uronic acid content in polysaccharide enhances the polysaccharide's ability to form strong, durable bonds when heat-sealed.

[0021] According to an embodiment, the polysaccharide comprising uronic acid may be a gum.

[0022] According to an embodiment, the polysaccharide comprising uronic acid may be a gum comprising at least 30 wt% of arabinogalactan (AG).

[0023] Arabinogalactan (AG) is a naturally occurring polysaccharide composed of arabinose and galactose monosaccharides. It is a complex carbohydrate that is commonly found in the cell walls of plants, particularly in the larch tree (Larix species) and gum arabic derived from the acacia tree. Arabinogalactan consists of a backbone of galactose units with side chains of arabinose units. The structure can vary in terms of the length and branching of these chains, contributing to its diverse functional properties.

[0024] According to an embodiment, the gum comprising at least 30 wt% of arabinogalactan (AG) is arabic gum.

[0025] Typically, the polysaccharide comprising uronic acid may be arabic gum, ghatti gum, karaya gum, pectin, methylated pectin, alginate, dextran, dextrin orxanthane, in particular arabic gum, pectin or alginate, more particularly arabic gum.

[0026] The term "heat-sealing" as used herein refers to a process used to join two materials by applying heat and pressure to the areas to be sealed.

[0027] Depending on the type of desired heat-sealed packaging, the heat-sealing step can be performed in several embodiments.

[0028] According to an embodiment, the step of heat-sealing is performed by contacting two areas of the paper substrate coated with the polysaccharide. This embodiment ensures that the bond formed during heat-sealing is strong and durable, providing a secure seal, which is particularly advantageous for wrapping applications.

[0029] According to another embodiment, the step of heat-sealing is performed by contacting an area of paper substrate coated with the polysaccharide with an area of paper substrate that is not coated with the polysaccharide. This approach provides adequate seal strength for many packaging applications, such as food packaging, personal care product packaging, and lightweight consumer goods packaging.

[0030] The heat required for sealing can be provided by various mechanisms, including heated bars or bands, ultrasonic waves, or radiofrequency energy, in particular heated bars or bands, more particularly heating bars.

[0031] Typically, when the step of heat-sealing is performed using heated bars, the heat-sealing is performed at a temperature of from 80°C to 300°C, in particular of from 100°C to 250°C, more particularly of from 110°C to 200°C.

[0032] Typically, when the step of heat-sealing is performed using heated bars, the heat-sealing is performed at a pressure of from 100 kPa to 650 kPa, in particular of from 200 kPa to 500 kPa, more particularly of from 300 kPa to 400 kPa.

[0033] Typically, when the step of heat-sealing is performed using heated bars, the heat-sealing is performed for a period of from 0.1 seconds to 2 seconds, in particular of from 0.2 seconds to 1.5 seconds, more particularly of from 0.5 seconds to 1 second.

[0034] According to an embodiment, the step of heat-sealing is performed using heated bars at a temperature of from 110°C to 200°C, a pressure of from 300 kPa to 400 kPa, during a period of from 0.5 seconds to 1 second.

[0035] In the present invention, the step of heat-sealing is performed : using biosourced materials coated on paper substrate; to produce heat-sealed packaging comprising strong, durable, airtight seals that can withstand handling and transportation.

[0036] In another aspect, it is proposed heat-sealed packaging obtainable by the process of the invention.

[0037] The term "packaging" as used herein can be defined as a material or assembly designed to enclose, protect, and facilitate the handling, storage, transport, or presentation of a product. In the context of the present invention, packaging may serve functional purposes such as containment, preservation, or barrier protection, as well as aesthetic or informational purposes, including branding and product labeling.

[0038] Adapted ISO 1924-2:2008 standard can be used to determine the peel strength of the heat-sealed packaging of the invention. Heat seal specimen of 15 mm of width is secured in opposing jaws and the seal remains unsupported while test is being conducted. The rate of separation of the jaws is 10 mm / min.

[0039] Typically, the heat-sealed packaging of the invention has a peel strength of from 80 cN / 15mm to 400 cN / 15mm, in particular of from 100 cN / 15mm to 300 cN / 15mm, more particularly of from 120 cN / 15mm to 280 cN / 15mm. Advantageously, a peel-strength in these value ranges enables heat-sealed packaging to be used in various applications, such as food packaging, pharmaceutical and medical packaging, personal care and cosmetic packaging, household and cleaning product packaging, industrial and chemical packaging, electronics and component packaging, textile and apparel packaging, automotive and mechanical part packaging, stationery and office supply packaging, tobacco and related product packaging, pet food and supply packaging and agricultural and horticultural packaging.

[0040] In another aspect, it is proposed a process for producing heat-sealable wrapping paper comprising a step of coating a paper substrate with polysaccharide, said polysaccharide comprising uronic acid, in particular said polysaccharide is arabic gum.

[0041] In the context of the invention, the paper substrate refers to the base web onto which the polysaccharide is coated to perform the heat-stealing step of the process for producing packaging.

[0042] The base web is obtainable by a wetlaid process. Accordingly, the paper substrate of the process for producing packaging according to the invention is obtainable by a wetlaid process.

[0043] Typically, the paper substrate comprises at least 90 wt%, in particular 95 wt%, more particularly 100 wt% of natural fibers.

[0044] The paper substrate may comprise 90 wt% cellulose fibers, in particular 95 wt% cellulose fibers, more particularly 100 wt% cellulose fibers.

[0045] Typically, natural fibers may be wood fibers, bast fibers, botanical fibers or mixtures thereof, in particular wood fibers, bast fibers or mixtures thereof, more particularly wood fibers.

[0046] For the purposes of the present application, "bast fiber" denotes a plant fiber contained in the bast of the plants.

[0047] The bast fibers may be abaca fibers, hemp fiber, Indian hemp fiber, jute fiber, kenaf fiber, kudzu fiber, coin vine fiber, flax fiber, okra fiber, nettle fiber, papyrus fiber, ramie fiber, sisal fiber, esparto fiber or mixtures thereof, in particular flax, hemp, abaca or mixtures thereof, more particularly flax, hemp, or mixtures thereof.

[0048] Wood fibers may be softwood fibers, hardwood fibers or mixture thereof.

[0049] Fibers that are not wood fibers may be used. Typically, botanical fibers from any type of plant may be used, such as tobacco, cocoa tree, coffee tree, tea tree, vine, ginger, ginkgo, camomile, tomato, ivy, maté, rooibos, cucumber, mint, a cereal such as wheat, barley or rye.

[0050] Typically, the density of the paper substrate can be chosen according to the type of packaging desired, allowing for customization to meet specific application requirements. The basis weight and thickness of the paper substrate, typically measured in grams per square meter (g / m 2< ) and micrometers (µm) respectively, can be adjusted to achieve the desired density. For example, for lightweight packaging needs such as food or personal care products, a lower density paper with a basis weight ranging from 18 g / m 2< to 40 g / m 2< and a thickness of 18 µm to 70 µm may be suitable. For medium-duty packaging applications, such as household and cleaning product packaging, a basis weight of 40 g / m 2< to 80 g / m 2< and a thickness of 40 µm to 130 µm may be appropriate. For packaging applications that require enhanced strength and durability, such as industrial or heavy-duty packaging, a higher density paper with a basis weight ranging from 80 g / m 2< to 150 g / m 2< and a thickness of 80 µm to 250 µm may be selected. By choosing the appropriate density, the heat-sealed packaging can be optimized for various uses, ensuring that it provides the necessary protection, functionality, and performance for different products. This flexibility in paper density selection enhances the versatility and applicability of the heat-sealed packaging of the invention across a wide range of industries.

[0051] The standard ISO 536:2012 can be used to determine the basis weight of the paper substrate. The paper substrate can be conditioned for at least 30 min at 23°C and 50% humidity before the measurement.

[0052] The standard ISO 534:2011 can be used to determine the thickness of paper substrate. The measurements were performed on one layer. The fibrous substrate can be conditioned for at least 30 min at 23°C and 50% humidity before the measurement.

[0053] According to an embodiment, the paper substrate has a basis weight of from 18 g.m -2< to 40 g.m -2< and a thickness of from 18 µm to 70 µm.

[0054] Before the coating process, the polysaccharide is solubilized from a spray-dried powder. This involves dissolving the spray-dried polysaccharide powder in water to create a uniform and consistent solution. The solubilization process ensures that the polysaccharide is evenly dispersed and free of clumps, which is essential for achieving a smooth and effective coating on the paper substrate. By converting the polysaccharide into a solubilized form, it can be easily applied using various coating techniques such as spray, slot die, size-press, film-press, bar coating, printing, in particular flexographic printing or gravure printing, knife coating, or air knife coating. This preparation step is crucial for ensuring that the polysaccharide adheres properly to the paper substrate, enabling the formation of homogeneous coating layer and low humidity uptake.

[0055] Typically, the coating step may be performed by spray, slot die, size-press, film-press, bar coating, flexographic printing, gravure printing, knife coating, or air knife coating. In particular, the coating step may be performed by bar coating or flexographic printing. More particularly, the coating step may be performed by flexographic printing.

[0056] Typically, the coating weight of the polysaccharide, i.e. the mass of the polysaccharide applied per unit area of the paper substrate is of from 1 g / m 2< to 10 g / m 2< , in particular of from 2 g / m 2< to 8 g / m 2< , more particularly of from 3 g / m 2< to 7 g / m 2< .

[0057] According to the desired packaging application, the coating patterns of the polysaccharide on the paper substrate can be tailored to meet specific requirements. The polysaccharide can be applied in various patterns, such as continuous coatings, stripes, or spot coatings, depending on the intended use and performance criteria of the packaging. For instance, a continuous coating may be preferred for applications requiring a uniform barrier and strong, consistent seals, such as in food packaging to ensure airtightness and grease resistance. Alternatively, striped or spot coatings can be used to optimize material usage and reduce costs while still providing adequate sealing properties for less demanding applications.

[0058] According to an embodiment, the coating step is performed on one side of the paper substrate. Typically, the polysaccharide comprising uronic acid is coated on a surface of at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96% at least 97%, at least 98%, at least 99%, or 100% of the surface of said side of the paper substrate. Advantageously, in this embodiment, the heat-sealing step can be carried out by contacting any surface of the paper substrate with any other surface of the paper substrate. Furthermore, the heat-sealable wrapping paper obtained enables grease-resistant packaging to be produced.

[0059] According to an embodiment, the polysaccharide comprising uronic acid is coated on a specific area of one side of the paper substrate where the heat-sealed step is to be performed. Typically, this specific area is not more than 10%, not more than 9%, not more than 8%, not more than 7%, not more than 6%, not more than 5%, not more than 4%, not more than 3%, not more than 3%, not more than 2% or not more than 1% of the surface of the paper substrate.

[0060] In another aspect, it is proposed heat-sealable wrapping paper obtainable by the process for producing heat-sealable wrapping paper of the invention.

[0061] According to an embodiment, the heat-sealed packaging of the invention may be edible.

Claims

1. Process for producing packaging, said process comprising a step of heat-sealing wherein the heat-sealing is performed using polysaccharide coated on a paper substrate, wherein the coated polysaccharide comprises uronic acid.

2. Process according to claim 1, wherein the coated polysaccharide is a gum.

3. Process according to claim 2, wherein the gum comprises at least 30 wt% of arabinogalactan.

4. Process according to claim 1, wherein the coated polysaccharide is arabic gum, ghatti gum, karaya gum, pectin, methylated pectin, alginate, dextran, dextrin or xanthane.

5. Process according to claim 1, wherein the coated polysaccharide is arabic gum.

6. Heat-sealed packaging obtainable by the process of any of claims 1 to 5.

7. Heat-sealed packaging according to claim 6 having a peel strength of from 80 cN / 15mm to 400 cN / 15mm.

8. Process for producing heat-sealable wrapping paper comprising a step of coating a paper substrate with polysaccharide, said polysaccharide comprising uronic acid.

9. eat-sealable wrapping paper obtainable by the process of claim 8.

10. Process according to claim 8, or heat-sealable wrapping paper according to claim 9, wherein the polysaccharide is arabic gum.

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