Patent Analysis and Trends Related to 2D Nanomaterials for Active Food Packaging

1. Introduction

According to the World Health Organization (WHO), approximately 600 million people are estimated to contract a foodborne illness annually, resulting in approximately 420,000 deaths per year. The consumption of food that is contaminated with harmful bacteria, viruses, parasites, or chemical substances can result in the onset of various diseases [1]. It has been acknowledged that packaging, storage conditions, and transportation factors have a significant impact on food quality, safety, and shelf life. One promising solution that has been identified as a means of preventing food contamination is the use of active and intelligent packaging systems [2]. Active food packaging technology encompasses systems that incorporate active substances into the polymeric matrix. The embedded components exhibit antimicrobial, antifungal, antioxidant properties and are able to absorb or reduce oxygen, carbon dioxide or ethylene, thereby enhancing the quality and safety of food products [3].

The classification of nanomaterials is based on their structural features and functional properties. Specifically, nanomaterials can be categorized into the following groups: zero-dimensional (0D) nanoparticles (such as metal and metal oxide nanoparticles, quantum dots, SiO₂ nanoparticles), one-dimensional (1D) nanotubes (CNTs), metal nanowires or nanofibers, two-dimensional (2D) nanosheets (graphene and derivatives, carbon nitride nanosheets and layered double hydroxide), and three-dimensional (3D) structures (metal organic framework, covalent organic framework or nanocomposites) [4].

In the broad spectrum of nanomaterials, two-dimensional (2D) materials have emerged as a particularly promising class, exhibiting considerable potential in the domain of active and intelligent food packaging. The embedded components exhibit antimicrobial, antifungal, antioxidant properties and are able to absorb or reduce oxygen, carbon dioxide or ethylene, thereby enhancing the quality and safety of food products [3].

The utilization of two-dimensional materials, such as graphene, has facilitated the advent of novel avenues for the advancement of active packaging (AP). The integration of these materials with polymers has the potential to enhance the barrier, thermal, mechanical and bioactive properties of packaging [5,6].

The objective of this paper is to provide a comprehensive overview of patented two-dimensional materials in the field of active packaging.

Patents function not only as legal documents but also as a valuable repository of technical information, which is often not readily available elsewhere.

The retrieval of this information necessitates the interrogation of patent databases, which serve as repositories for a substantial volume of invention data that is subject to continuous updating.

A plethora of patent databases are currently available for use, as evidenced by the list provided on the WIPO website [7]. The decision to utilize Espacenet [8] as a primary database was motivated by its cost-free nature and its substantial document collection, which encompasses over 150 million records. The aforementioned database boasts a comprehensive global scope, enabling users to seek information concerning published patent applications from over 90 patent-granting authorities.

2. Materials and Methods

A series of searches were conducted using Espacenet, a database provided by the European Patent Office (EPO), to analyze patents reflecting the main trends in the use of 2D nanomaterials in active food packaging. A combination of keywords in the title/abstract/claims search fields with Boolean and proximity operators and classification codes was used in the searches.

The exhaustive list of search queries employed to retrieve patent data can be found in Appendix 1. Given that Espacenet is a freely accessible database, any researcher is capable of reproducing and retrieving updated data by simply copying and pasting the query into the "Smart Search Editor" on Espacenet.

Classification symbols were retrieved by means of the Espacenet classification search tool [9], the WIPO IPCCAT-neural system [10] and the new CPC text categorizer [11], powered by AI and provided by the EPO.

A summary of the IPC (International Patent Classification) and CPC (Cooperative Patent Classification) codes used in the search is shown in Table 1.

3. Results and Discussion

The search was initiated with a basic query in the title/abstract/claims field to ascertain the classification of patents. The query was formulated as follows: ctxt all "food packaging" and yielded 110,432 results.

The IPC symbols that were retrieved and identified as primary were A23L, B32B27, C08J5/18, and B65D+. The corresponding definitions can be found in Table 1.

A similar procedure was employed for the CPC symbols, which are listed below: A23V2002/00, Y02W90/10, Y02A40/90 and B32B2439/70 (the definitions are also contained in Table 1).

All these classification symbols were used to construct the primary search query, which is as follows:

(ctxt=("food " prox/distance<2 "packag*") AND (cl all "B65D" OR cl all "B32B27" OR cl all "C08J5/18" OR cl all "A23L")) OR cpc all "B32B2439/70" OR ((cpc all "Y02W90/10" OR cpc all "Y02A40/90" OR cpc all "A23V2002/00") AND ctxt=("food " prox/distance<2 "packag*")) [QUERY 1]

This query yielded 30,857 results (database accessed on 31 December 2024).

The results were analyzed according to the earliest priority date of filing and within the time frame between 2003 and 2022, which contains 21,222 patent documents. As illustrated in Figure 1, there is a discernible upward trend, with a slope change between 2014 and 2016, followed by a period in which the trend remains constant.

A series of queries were developed in order to identify patent documents that claim 2D nanomaterials. These queries are reported in Table A1 (see Appendix A).

A review of the literature reveals that the most widely utilized 2D materials in active food packaging systems are graphene and its derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), as well as MXenes and silicate clay [4].

The patent analysis aligns closely with scientific literature, indicating that the top five two-dimensional nanomaterials include montmorillonite, graphene, GO, LDHs, and vermiculite (as illustrated in Figure 2).

An exhaustive examination of priority filings from 2018 to 2022 reveals that carbon-based nanomaterials and MXenes have been increasingly claimed in patent applications (see Figure 3).

As illustrated in Table 2, the primary methods of graphene preparation are exfoliation and chemical vapor deposition (CVD).

The patent data set did not include other recently developed carbon-based nanomaterials, including hydrogenated graphene (graphane), fluorinated graphene (fluorographene), and graphene introduced by acetylenic chains (graphyne and graphdiyne).

In addition to graphene derivatives, another family of 2D compounds, specifically transition metal carbides and/or nitrides, known as "MXenes," has garnered attention in the field of food packaging due to their unique properties. While the number of patents related to MXenes is currently limited, the potential implications of this emerging material are significant.

Ti₃C₂T_x, a 2D MXene that has been extensively studied and claimed, is produced by etching the Al layers in Ti₃AlC₂, followed by exfoliation.

A compendium of additional compositions, as delineated within the scope of patent documents, is enumerated in Table 3.

A compelling family of compounds that merits further consideration is that of LDHs, also named as anionic clays or hydrotalcite-like compounds, which are distinguished by their mechanical, barrier, and antimicrobial properties.

These substances are utilized as fillers in biopolymers, such as cellulose, and polylactic acid (PLA) and polyvinyl alcohol (PVA). Additionally, they are frequently employed in blends with metal nanoparticles, including zinc oxide and titanium dioxide, which serve to augment the antimicrobial properties of the nanocomposite.

A survey of the patent literature reveals that the most frequently utilized biopolymers in conjunction with two-dimensional nanomaterials are cellulose, polyvinyl alcohol, starch, polylactic acid, and chitosan [12] (see Figure 4).

From a legal perspective, as well as from a geographic point of view, China has been identified as the country with the highest number of patent applications filed for 2D-materials in AP technology. The United States and Japan have been identified as the countries with the second- and third-highest numbers of patent applications, respectively.

A significant number of applicants have opted to utilize the PCT procedure, which permits the postponement of entry into the national phases (see Figure 5).

4. Conclusions

China, the USA and Japan are the countries with the highest number of filings. In terms of the materials most frequently claimed in patent applications, carbon allotropes are the most prevalent, together with silicate-clay-based 2D materials.

Montmorillonite, graphene and graphene oxide are the most frequently claimed compounds in patents, followed by vermiculite, kaolinite, layered double hydroxides and hexagonal boron nitride.

Other two-dimensional materials, such as transition metal dichalcogenides, reduced graphene oxide, MXenes and graphitic carbon nitrides (g-C₃N₄), have been the subject of fewer patent applications.