One of the applications with the greatest impact on the growing demand for bioplastics is for containers and packaging, particularly biodegradable materials in food packaging. Before the COVID-19 pandemic, many multinationals, such as Danone, Coca-Cola, and Nestle, had committed to adopting bioplastics in their packaging [ 273 ]. In this sense, there are numerous investigations and developments of biodegradable and biobased materials due to their potential lower environmental impact. Numerous works have been reported and an extensive literature revision has been conducted by various researchers in the field of material sciences and the packaging industry [ 4 275 ]. A comparison of different biomass sources for bioplastics and biopolymers along with various processing technologies discussion can be found among available literature [ 55 279 ]. The latest works focus on new biomass sources to reduce bioplastics cost and climate impact due to extensive land use [ 14 290 ]. In view of more sustainable packaging systems, fully biobased packages are sought, considering all parts. Therefore, herein, a thorough overview of biobased adhesives, inks, and dyes for food packaging is presented.
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The term adhesive describes a formulation that can hold two or more specimens together. In other words, an adhesive can join materials by surface bonding (adhesion), with a bond possessing adequate internal strength (cohesion) [ 291 292 ] ( Figure 4 a). The materials which are to be joined are called adherents or substrates and the process of attaching one adherent to another is called bonding. The adhesives include a wide range of materials with very different specifications that produce adhesion through different mechanisms depending on the characteristics of the substrate. The effectiveness of the adhesive bonding capacity depends on several factors, which are intermolecular forces in the adhesive, wettability of the adhesive in the adherent, types of chemical bonds, functional groups involved, type of interface between the adhesive and the adherent, type of substrate, and surface tension generated [ 293 ]. Likewise, Dohr and Hirn reported that the strength of the adhesive bond depends on various physical properties of both the substrate and the adhesive [ 294 ].
Both the way the adhesive is applied and its chemical composition determine the possible applications. Other factors, such as the dispersion of the adhesive over the substrate and the contact area, which in turn have a great impact on the adhesive forces that can develop, are also relevant [ 294 ].
Although in former times adhesives were prepared from natural sources, synthetic formulations of adhesive are nowadays based on thermoset resins: phenol-formaldehyde, an alkaline catalytic salt (PF), urea-formaldehyde, an acid catalytic salt (UF), melamine-formaldehyde (MF), and polymeric diphenylmethane diisocyanate resin (pMDI) [ 295 296 ]. These synthetic adhesives cause health problems during the manufacture process. For instance, formaldehyde was declared a carcinogen by the World Health Organization (WHO) in . Similarly, the International Agency for Research on Cancer (IARC) reclassified formaldehyde as carcinogen category 1 in [ 297 ]. In addition, a comparative increase in price and the foreseen lack of availability for petroleum-based synthetic adhesives have prompted the development of green derivatives from economic and renewable resources.
Biobased adhesives are formulations based on natural raw materials, which are not derived from mineral or fossil sources. This term includes adhesives formulated with biopolymers obtained from plants, animals, and natural gums [ 298 ]. In the search to develop bio-based adhesives with properties similar to traditional formulations, proteins, tannins, lignin, and polysaccharides are eco-compatible biopolymers that could fit these requirements [ 299 300 ]. Their use is mainly limited to paper, cardboard, aluminum foil, and wood for construction applications. These adhesives develop stickiness quickly but exhibit low-strength properties. Most are soluble in water and use water as a solvent agent. They are supplied as liquids or dry powders to mix with water, though some are dispersions [ 300 ].
Figure 4 b shows a classification of adhesives according to the source of the polymers from which they are prepared, as it was reported by Ebnesajjad and Landrock [ 301 ].$
85.8 billion by , with packaging being one of the most relevant applications [The global market for adhesives and sealants is growing rapidly and is expected to be worth85.8 billion by , with packaging being one of the most relevant applications [ 302 ]. Adhesives in packaging industries are critical to the structure of most paper and paperboard packaging. In this regard, paper-based materials have been broadly applied as packaging material for food products.
From a production point of view, adhesive selection can significantly affect process line efficiency and production performance [ 303 ]. Adhesives are commercialized in many shapes and types, and the choice will be determined by the substrates on which the adhesive for bonding will be applied, the machinery used in the process, and other factors, such as potential requirements for food-safe materials [ 303 ].
The types of adhesives used in the paper industry are water-based adhesives, both synthetic and biopolymer-based (starch, cellulose derivatives, proteins), solvent-based adhesives (polyurethane and acrylic base), and 100% solid adhesives, such as heat-sealing adhesive and hot melts. Gadhave and Gadhave reported the development of a water-based heat-expandable adhesive that has thermally insulating properties and has been used in protective food packaging [ 303 ].
Protein-based adhesives (animal or vegetable) were the first polymers to be used in ancient times as adhesives in contact with the skin due to their biocompatibility and biodegradability properties. Likewise, protein-based adhesive formulations have been developed as substitutes for formaldehyde resins, particularly urea-formaldehyde resins in applications for construction material adhesives and paper and coating manufacturing [ 298 ].
307,There is numerous research on adhesives to bond wood made from tannins [ 304 ], lignin [ 305 ], cellulose derivatives [ 306 ] and modified starches [ 302 308 ], and vegetable proteins, such as casein [ 309 ], gluten [ 310 ], and soy proteins [ 311 ]. Adhesives based on animal protein can be formulated from collagen, gelatin, or casein. Collagen is prepared from different parts of animal bodies, such as skins or bones, and gelatin is derived from the denaturation of collagen. The reversible gel-sol conversion by water absorption is an important property for the application of these adhesives. Casein is obtained from cow&#;s milk by acid precipitation using different acid media, which can result in diverse properties depending on the resulting molecular structures. The primary structure of this protein can be chemically modified to achieve different rheological behaviors [ 292 309 ].
300,313,314,Research related to the development of biobased composite adhesives for applications in food packaging is still incipient. Fatty acids derived from vegetable oils were used as the base for monomers that once polymerized form pressure-sensitive adhesives [ 312 ]. Heinrich, Wang et al., Wu et al., Mahieu et al., and Ding et al. have reported the use of blends based on starches and proteins from different sources for green bioadhesives preparation [ 58 315 ]. Due to the high number of polar groups in both proteins and polysaccharides, the hydrophilicity of composite systems is often the biggest obstacle to overcome in adhesive formulations [ 300 ]. For proteins, this includes making functional groups available for crosslinking, for instance, by tertiary and quaternary structure modification. Chemical modifications can be made in the structure of the polysaccharides and proteins (starch, cellulose, gelatin, soy proteins, among others) to improve the crosslinking of the matrix using crosslinking agents. Kumar et al. have reported that the use of crosslinked starch with citric acid results in materials with good mechanical performance [ 316 ]. These properties are explained and revealed from a structural point of view by the interactions established between the carboxyl groups of citric acid and the hydroxyl groups in starch. On the other hand, Olomo informed that adhesives chemically treated using HCl as a cassava starch gelatinization modifier were of higher quality than those modified in presence of NaOH [ 317 ].
Manihot esculenta
) is produced mainly in the tropical and subtropical regions of Africa, South America, and Asia. The high starch content of cassava and its higher proportion of amylopectin, compared to other starch sources, make it an important source of biopolymers to be used in the development of biobased adhesives. It can be employed as native starch, but it can be modified by different means to improve its properties of consistency (viscosity) [While native starch contains only hydroxyl groups and is limited in scope, chemically modified starch shows superior water resistance properties for adhesive applications [ 302 ]. Other modifications to prepare biobased adhesives with improved water resistance may involve esterification, transesterification, alkylation, acetylation, succinylation, or enzymatic reactions. The use of starch as a raw material in the manufacture of adhesives has the advantages of its renewability, biodegradability, and availability, in addition to its low cost and non-toxicity [ 317 ]. Cassava () is produced mainly in the tropical and subtropical regions of Africa, South America, and Asia. The high starch content of cassava and its higher proportion of amylopectin, compared to other starch sources, make it an important source of biopolymers to be used in the development of biobased adhesives. It can be employed as native starch, but it can be modified by different means to improve its properties of consistency (viscosity) [ 315 ]. Cassava starch as a base to produce adhesives has many notable characteristics, including high paste viscosity, high paste clarity, and high freeze-thaw stability [ 318 ]. Besides, Li et al. worked on improving the adhesion-to-fibers and film properties of corn starch by starch sulfo-itaconation for a better application in warp sizing [ 299 ].
Biobased adhesives based on colloidal solutions in general dry slowly and therefore require a very long setting time. Bioadhesives containing starch, dextrin, and/or casein are primarily used in labeling applications, while starch-based formulations are also widely used in the obtention of corrugated boards [ 319 ]. Starch-based adhesives are mainly composed of water, starch, sodium hydroxide, borax or boric acid, and other additives, such as preservatives, adhesion enhancers and defoamers, among others [ 320 ]. Most starch-derived adhesives are used in the paper and textile industries as bonding agents and gluing materials. Corrugated cardboard is produced by the adhesion of a grooved layer of paper to another flat layer. To join them, a two-phase adhesive is usually employed: a liquid and a solid phase containing a mixture of starch and sodium hydroxide or native starch and borax, respectively. Developing biobased adhesive formulations for bonding different substrates, such as corrugated cardboard paper, glass, among others, to propose applications in the formation of film packaging and in the labeling process, constitute a great challenge.
Currently, most containers that are in contact with food have adhesive in their structure. Adhesive formulations can be found in three different forms ( Figure 4 a). It can form the structure of food packaging by combination with different materials (usually polymers, paper, cardboard, or glass), commonly known as laminate or multi-layer packaging. Moreover, the adhesive can help to provide the geometry of the container (box sealing) or can be used for labeling. The most common way to find adhesives on food packaging is of the first type; where the adhesive is applied on the total surface of the materials or substrates, joining different materials and forming multi-layer materials. Examples of practical applications are flexible film lamination, paper-film combinations, cardboard-film, aluminum-film, cardboard-aluminum, cardboard-aluminum-plastic, rigid multi-layer systems based on plastic, sacks, bags, among others. For such applications, the adhesive industry uses a wide variety of raw materials and formulations, combining different compounds to form special types of biobased adhesives.
There is currently a growing push in the packaging and adhesive industry to improve the sustainability of processes and products. Therefore, the general trend in the adhesive industry for use in food packaging is a reduction in the use of solvents as well as molecular weight components of the adhesive that could more easily migrate from the package to the food.
The use of biobased adhesives in the labeling of glass containers is an interesting alternative, since for this purpose there are few studies that contemplate the use of bioadhesives. The removal of the label-adhesive using only water is a desirable characteristic not only from an operational point of view, but also from an economic and environmental level. Easily removable labels would facilitate the sorting of recyclable waste packaging and therefore increase the recyclability of the whole package and reduce water and energy use. In addition, compared to the common industry practice for label removal using diluted NaOH solutions, water is a low-cost natural resource that, most importantly, could be reused, ultimately requiring simple effluent treatments before discharge.
Regarding the legal background surrounding adhesives intended to be used for food contact applications, normally, the adhesives are used to stick together packaging materials and not intended for direct food contact. However, the adhesives as components of the packaging material might contribute to the migration of constituents into the food matrix. Adhesives, as well as food contact materials, are regulated according to EU Framework Regulation (EC) No /. Plastic materials and articles are additionally regulated by a specific measure, Regulation (EU) No 10/ on plastics and therefore harmonized at EU level. This regulation establishes, among other requirements, a list of authorized compounds. It is pertinent to emphasize that adhesives do not yet have such specific harmonized legislation. Alternatively, reference is made to the opinions of the European Authority focusing on aspects of Food Safety, Council of Europe resolutions, national legislation, and even non-European legislation for risk assessments [ 319 ]. The Commission Regulation (EC) No. /, recommends procedures to assure the safety of adhesives for food contact applications, particularly on Good Manufacturing Practices for adhesives. Yet, there is currently no legal obligation for adhesive manufacturers to provide a declaration of conformity with Regulation (EC) No /. However, if the adhesive falls under the Plastics Regulation, the adhesive manufacturer shall provide the specific information to enable the adhesive user to ensure compliance of substances with migration potential [ 319 ].
According to the specifications reported by Romero Zaliz et al., adhesives for returnable glass containers must be formulated with raw materials that are included in the positive lists of the FDA and the Argentine Food Code (Mercosur) for use in Food Containers and Equipment in Contact with Food (Argentine Food Code Chapter IV, FDA 21 CFR 175.105) [ 321 ]. For this reason, there is a high interest in the development of new strategies to produce new renewable materials that totally or partially replace petroleum-derived reagents, resulting in innovative products with special functionality, less toxicity, high biocompatibility, and/or biodegradability [ 322 ].
Using natural resources or bio-based materials as adhesive raw materials could help future societies become less dependent on hazardous chemicals, volatile organic compounds, and petroleum-derived chemicals; in addition to promoting safer working conditions. Consumer trends toward green products are prompting plastics industries to investigate more benign alternatives to petroleum-based polymers. Moreover, the recent classification of formaldehyde as a harmful substance has accelerated the investigation of more ecological and renewable alternatives, such as protein-based adhesives, to avoid harmful emissions both during production and during the lifetime. Furthermore, the use of bio-renewable or waste raw materials helps to reduce the carbon footprint, aligned with the current circular economy framework. As an added benefit, the inherent biodegradability of renewable materials, e.g., starch, polyhydroxyalkanoates, or cellulose, is often higher than that of synthetic materials, e.g., polypropylene and polyethylene.
The shift towards more ecofriendly alternatives has manifested itself in the adhesives industry first through the gradual change from solvent adhesives to water-based or high-solid content adhesives, and now by the renewed interest in the design of biobased adhesives. Nonetheless, it is convenient to modify the formulations based on natural polymers, such as polysaccharides and proteins, to improve their rheological properties, their adhesion capacity, and their mechanical resistance when applied for the bonding of different substrates to be used in food packaging. Consequently, composite adhesive formulations obtained from chemically modified biopolymers constitute an innovative proposal to overcome such difficulties.
Further research on the selection and compatibility of biobased adhesive formulations is essential since the adhesive characteristics presented will depend as well on the type of substrates applied to. Additionally, progress is still required in relation to the legislation that frames the adhesives that can be used in the manufacture of containers in contact with food.
1. Order confirmation:
After having your purchase order, we will contact you and confirm each detail via and . You are welcome to reach us 7*24 by or call whenever you like.
You will have our sales confirmation within 24 hours, including the size, color, add-ons and lastly the purpose. We will specify the requirement or properties you need to be included in your Coffee Bags.
2. Down payment:
We will send you the proforma invoice after you sign and send back the sales confirmation. You are supposed to arrange the down payment according to the PI. Normally, it will be 30% to 50% of the order amount.
We will launch the process upon the receipt of the down payment bank slip.
3. Raw materials preparation:
Our production department will prepare all the plastic films, and add-ons like valves, ziplock, spouts, etc.
If there is printing on the pouches, the printing cylinders will be arranged at the same time. It takes 7-10 days for the preparation of all raw materials and coffee pouch accessaries.
Contact us to discuss your requirements of Whoelsale Biodegradable Starch Resin Exporter. Our experienced sales team can help you identify the options that best suit your needs.
4. Printing:
All printing processes reproduce lines and / or dots that form an image. Printing is the process of manufacturing multiple copies of graphic images. Although most people think of printing as putting ink on paper, printing is not limited to any particular materials or inks. The embossing process uses no ink at all, and all shapes and sizes of metals, wood and plastics are common receives of printed messages.
The following major printing processes are used to reproduce graphic images. Each of these processes is suited for specific applications, such as newspaper, book, packaging bags, or textile printing.
&#;Relief printing:
The relief printing process includes letterpress printing, flexographic printing, and all other methods of transferring an image from a raised surface.
&#;Intaglio printing:
Intaglio printing is the reverse of relief printing. An intaglio image is transferred from sunken surface. It&#;s also known as gravure printing, photogravure printing.
&#;Screen printing:
Screen printing transfers an image by allowing ink to pass through openings in a stencil that has been applied to a screen mesh.
&#;Lithography printing:
It&#;s a relatively new process, dating from around . Offset lithographic printing is the most widely used printing process in the commercial printing industry.
5. Composition:
The advent of composites was a revolutionary shift in packaging.Each single material has its own advantages, disadvantages and characteristics.
For example, metallic materials are brittle and not resistant to corrosion, but have excellent barrier properties; LDPE is chemically resistant, easy to heat seal, and easy to process, but its strength and oxygen barrier properties are poor.
Composite can make up for the shortcomings so that a variety of single-performance materials are combined into a new material with comprehensive performance.
The soul of composite flexible packaging lies in the composite, is the superposition of performance. This is also the technical core of the production of composite flexible packaging.
6. Curing:
After the packaging bag roll films are composited, it could not go for slicing right away. Because it takes 72 hours of curing before it&#;s available for next process. It&#;s important to make sure it&#;s a fully curing, otherwise the composite layers may peel off.
7. Slicing:
The roll-form raw material will be cut by slicing machines to exactly the width needed for a pouch. There will be always big quantity of film rolls, the slicing machine will cut with an accuracy of 0.1mm, and keep the roll in perfect conditions.
A perfect slicing will help to speed up the converting process. Otherwise, it will slow the production speed, and waste the coffee bag raw materials, bringing lots of lots and time and costs.
8. Converting:
Most of the converting job is done by machines. After loading the coffee bag film roll onto the converting machine, it will go through the first part of the machine, folding according to the pouch type, sealing the bottom and both edges, punching holes, adding ziplock, etc.
9. QC (Quality Control):
Product quality is the basis for the long-term development of enterprises. In order to ensure that all goods meet quality standards, we have established a perfect quality control system:
A. IQC: In-Line QC, there will be 3 production engineers keep checking each section on the production line during the whole production. In fact, the machines have auto monitoring functions, but we still arrange QC checking for 100% assurance.
B. FQC: Final QC: at the end of the production line, there is 1 QC checking each bag, and pick out the disqualified one.
C. OQC: Outgoing QC: before packing to export cartons, we arrange outgoing QC to do another 100% quality checking and pick out disqualified items in the case.
10. Packaging:
After the packaging pouches & bags are through the full QC process, they will be packed by bundles, putting into transparent poly bags. Pouches in bundles will be packed into corrugated cardboard cartons.
The packing quantity of each carton could be indicated by clients, according to different sales methods and purposes. In this way, the pouches will be packed by customized cartons specially for this order, instead of standard size. There will be extra cost for custom cartons.
There could be custom printing on cartons and labels as well. This will also cost a small amount from the client, but it will bring great help to the promotion and storage.
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