Patent Application
20250098882
The invention relates to compositions, methods, and applications for improving paper straws and related tubular articles to enhance their wet strength in water while providing biodegradable proprieties.
There is a significant need to replace the widely used disposable plastic drinking straws with sustainable yet environmentally friendly alternatives. While plastic straws are easy to produce and convenient to use, their disposal after use poses harmful and toxic effects on the environment and ecosystem due to their difficulty in decomposing naturally.
Recently, there has been a growing emphasis on replacing plastic drinking straws with environmentally friendly paper straws, driven by environmental awareness and the need for eco-friendly solutions. However, most paper straws have difficulties in the chemicals used to make them having any residues remaining in the straw, and having a robust structure that is not subject to deterioration on use.
In the United States alone, it is estimated that between 170 million to 490 million plastic straws are discarded daily, equating to 63 billion to 142 billion straws per year. (N. Chokshi, www.nytimes.com/2018/07/19/business/plastic-straws-ban-fact-check). It is likely that these numbers increased sharply during the Covid 19 pandemic. These plastic straws can pose issues for landfills as they do are not easily biodegrade and are often an issue in water ways for the marine life.
In response to the urgent need to replace plastic straws, paper straws have been developed with a cylindrical shape, ensuring durability and stability as a sustainable alternative. This shape allows for easy consumption of beverages containing large gelatinous balls like Tapioca and aligns with the push for environmental sustainability. The manufacturing process of cylindrical paper straws requires carefully selecting high-quality paper and adhesive, as these factors greatly influence not only the performance and production speed but also the overall eco-friendly nature of the product. (See also, https://www.hbfuller.com/en/north-America/products-and-technologies/markets-and-applications/paper-converting/paper-straws).
The manufacturing process of currently available paper straws begins with three narrow longitudinal strips of paper, known as plies, obtained from paper rolls. Typically, a spirally core-winding machine applies water-based, food-grade adhesives like starch or gelatin glue, which may be approximately 10 wt. % of the total paper straw weight, to plies to bond the three plies. The small but not negligible amount of the water-based glue has been the main culprit for the unpleasant tastes during use of paper straws. Subsequent drying at elevated temperatures is required to remove the water from the glue treatment. All paper straws made with starch-based glue are manufactured in this manner. A slot nozzle machine is sometimes used in high-speed production lines to apply predominantly non-biodegradable hot melt adhesives. This choice might prevent unpleasant taste from starch-based glue and enhance production efficiency but could affect the straws' compostability. It's worth noting that starch may contain gluten if wheat starch is used as an adhesive, which may pose issues for some consumers and labeling of the product.
To ensure efficient production the use of food-grade raw materials is employed, including inks or hot melt adhesives. The quality of the paper and adhesive used is crucial as it directly affects the paper straws' performance and the manufacturing process's overall efficiency. This objective has also had its challenges.
While current paper straws have shown promise as an eco-friendly alternative to plastic, they come with several limitations that hinder their practicality. These include an unpleasant taste due to the use of water-based adhesives, causing a poor taste imparted to the beverage. Additionally, they may deform and weaken when immersed in beverages, leading to reduced durability, that is, loss of structural integrity when exposed to liquids (referred to as ‘wet strength’), and compromised compostability when non-biodegradable adhesives are employed. Indeed, recent studies have reported significantly deteriorating properties of paper straws. These studies have shown a 70% to 90% loss in compressive strength and liquid absorption at about 30% of the straw-weight gain after being exposed to liquid for 30 minutes. (Gutierrez, J. N., et al., Evaluation of paper straws vs. plastic straws, BioRes. 14(4), 8345-63, (2019)). These shortcomings have prompted consumers to seek alternatives rather than continue using existing paper straws for their beverages.
Some commercial paper straw products use non-toxic soybean oil to coat a straw's inside and outside. However, the paper straw still experiences the problems noted above, even with this coating.
The desire to enhance paper straws' durability and water resistance led to the application of coatings with polyethylene (PE) or polypropylene (PP). However, these seemingly advantageous coatings introduce unintended consequences. While PE and PP coatings improve water resistance and durability, they also pose environmental challenges due to potential release of microplastics and harmful substances into beverages. (Ranjan, V. P. et al., J. Hazard. Mater. 404, 124118 (2020)). This deviation from sustainable practices underscores the need for a novel approach that balances performance and eco-friendliness.
Several patents and patent applications have been filed to address the issues related to paper deformation and sogginess due to the deteriorated wet strength while maintaining the positive environmental aspect and the strength of the paper straws over a long period. For example, various techniques involve coating thermoplastic resins like PE and PP with light-induced degradable additives, as described in patents and patent applications such as EP3581071B1, US20190380520A1, HK1255119A2, and CN201356396Y. Similarly, there are techniques that utilize environmentally friendly and bio-based coating materials like polybutylene succinic acid (PBS), polylactic acid (PLA), polyhydroxyalkanoate (PHA), and analogous compounds, as demonstrated in patent applications KR20190141608A and CN202981353U. As taught in this prior art, a frequently used method is coating paper straws with biodegradable polylactic acid (PLA), which is readily available. PLA is readily decomposed and biodegradable. However, PLA's brittleness, moisture sensitivity, and higher cost collectively still limit its broader use in drink paper straws.
In search for eco-friendly alternatives, environmentally friendly choices such as rice and pasta straws have gained popularity in the market, including brands like Yeonjigonji Rice Straws (from Yeonjigonji Company in Korea) and Wheat Pasta Straws (from Bucatini Company in Italy). Additionally, there are brands from the USA, such as The Amazing Pasta Straws and Stroodles. While rice straws replicate the appearance of petroleum-based plastic straws and offer biodegradability, they present challenges related to their shelf life and performance under hot beverage conditions. Similarly, pasta straws, primarily composed of wheat flour, show excellent biodegradability and minimal alteration of drink taste. While testing pasta straws, it was observed that they initially functioned moderately well in water, but had limited durability, losing their shape after 45 minutes. In iced latte coffee, these straws acquired a pasta taste and disintegrated, leaving residue. Despite being cost-effective and eco-friendly for water use, their performance limitations are still a challenge (source: https://www.insider.com/i-drank-out-of-a-pasta-straw-for-a-week-2019-10). Nevertheless, gluten in wheat-based pasta straws poses limitations for individuals with gluten sensitivity. While it is possible to create a gluten-free pasta straw from gluten-free wheat flour, this process is costly and may still contain trace amounts of gluten. This gluten content would require labeling of the product.
US 2006/0286214A1 introduces an edible drink straw coated with zein via an alcohol solution, utilizing fruit fibers and sugars as materials. It diverges from conventional paper straws by excluding paper fiber sources and lacking mechanical property data in water. While US 2006/0286214A1 demonstrates potential edible compositions with specific hydrophobic coating properties, its focus is not on enhancing current paper straws. Moreover, it has limited versatility in desired applications.
CN114635307B outlines a biodegradable paper straw designed with a specific five (5)-layer structure, including a central composite straw paper layer crafted from combinations of wheat straws with bagasse, corn straws, or rice straws, two prolamin layers, and two beeswax layers. The mandated sequenced layer structure is, from outside to inside, beeswax, alcohol-soluble protein, prolamin, wherein the prolamin used is zein, gliadin wheat or gliadin glutinous rice, composite straw paper, prolamin, and beeswax. CN114635307B employs the sequenced combination of wax and prolamin by coating and focuses on utilizing natural fiber sources and, therefore, is not related to the improvement of current commercial paper straws. Notably, CN114635307B relies on food-grade adhesives such as modified starch. The latter contrasts with the invention wherein starch-free or starch-migration-free straws are obtained using zein, even when utilizing starch-based glues. Conventional paper straws made of starch-based glues experience significant mechanical degradation over time in water and give off-taste. CN114635307B lacks information on water-related mechanical properties and coating effects.
US20220205184A1 reveals its utilization of a crosslinker applied through printing on a substrate. An innovative aspect of the present invention is that when a crosslinker is utilized for surface coating of the zein polymer, it can be homogenously mixed without requiring printing, thus eliminating the need for such printing processes.
U.S. Pat. No. 7,172,814B2 pertains to processing biodegradable thermoplastic and meltable polymers, including Polylactic Acid (PLA) and polyhydroxybutyrate (PHB), among others. While zein is mentioned as a possible polymer in the specification, it's essential to note that zein does not fall under the thermoplastic or meltable polymers category. The application of zein in the present invention is via a coating solution, which deviates from the meltable thermoplastic pressing method.
United States Patent Application Publication No. US2020/0352373A1 introduces an inventive biodegradable straw method employing edible soy protein isolate and natural coatings. However, its reliance on soy protein isolates causes limited shelf life and the traditional use of shellac in coatings highlight challenges related to availability and sustainability.
Clearly, the need for viable solutions for eco-friendly beverage straws is apparent. This arises due to the complex challenges associated with current paper straw limitations and the imperative for sustainability. Tubular devices and articles are also possible using this coating to protect the container from liquids.
The present invention provides such a tubular article that comprises a biodegradable and compostable substrate, which is coated with, impregnated with, or both coated and impregnated with, a biodegradable and compostable zein or mixtures of zein. These zein coated tubular products, including straws, have one or more the following characteristics: enhanced mechanical properties; enhanced wet strength properties; restricted starch migration; and increased salinity resistance. They minimize or reduce any adhesive, starch, gluten and PFAS compounds from migrating out of the paper. They have improved performance, durability, and superior mechanical resilience, while maintaining firmness over time and exhibiting enhanced resistance to saltwater exposure.
Moreover, the present invention provides an improved user experience and benefit by overcoming the current mono-functionality of paper straw products and also provides the zein coated tubular products have other possible uses such as controlled release properties from actives contained in the zein coating or within the tube space, optionally encapsulated. Some of these uses include, but are not limited to:
To achieve additional approaches for this present product, it is provided to include these active agents, that can augment the product with additional functionalities while still maintaining its biodegradability and compostability. Such active agents include, but are not limited to: bioactive agents; medicinally active agents; hygienically active agents; cosmetically active agents; stimulating agents selected from the group consisting of nicotine and its salts, caffeine, and cannabinoids; essential oils; flavoring agents; sweetening agents; and pest control agents; or a combination thereof. The actives may be encapsulated and incorporated into the zein coating on the straw or tube and/or be incorporated and inserted inside the tube.
This present invention provides a paper straw article comprising a zein polymer coating a straw as the substrate. The coating can be applied to existing paper straws or to the paper that is made into a straw.
The paper straw article comprises a substrate, a paper strip or sheet form of about 0.1-2000 gsm (wherein gsm denotes gram per square meter), and a zein treatment. The treatment comprises zein ranging approximately 0.01-99 wt. % based on the total weight of the article. The article is manufactured by a process that applies the zein treatment to a pre-manufactured paper straw or a substrate in layer form. After treatment, the substrate in layer form is subsequently wound into a cylindrical tubular shape. The process to make the zein coating is provided by the flow diagram in
The process to coat the straw involves applying one or more coating layers of zein polymer to commercial paper straw surfaces. This process enables coating the cylindrical-tube paper straw's outer and/or inner surfaces. The thickness of the dry films can be controlled through repeated coatings.
The paper straw undergoes a coating process involving a renewable water-insoluble surface treating composition comprising zein polymer. The resultant surface coating film shows a smooth, uninterrupted appearance upon drying. Notably, unlike untreated paper straws, the article does not show an intense deep blue/indigo color reaction from the starch-iodine complex when applied to commercial paper straws prepared using starch-based glue. (
In another process, the zein coating is applied to either one or both sides of the paper strips as substrates. After coating, the paper strip is further subjected to a longitudinal winding process to form a cylindrical-tube paper straw. The zein material's weight ratio ranges from approximately 0.01 to 100, relative to the weight of the substrate. This treatment has a broad range from low to very high weight ratios.
When desired, an optional crosslinking agent is introduced to the zein solution or directly to zein coating surfaces to form crosslinked structures, enhancing the mechanical integrity of the coatings or films. The process may include a heating step for more efficient crosslinking, but some curing also occurs at room temperature.
The paper substrate that is used when the straw is zein coated—other than existing straws—has this coating applied to Hanji, as a traditional Korean paper, substrate while also recognizing the potential value of alternative materials, specifically other East Asian papers. Notable among these papers are Washi, a traditional Japanese paper, and Xuan paper, a traditional Chinese paper and Kozo paper. Despite Hanji being the principal material of interest, Washi and Xuan's paper are believed that they would demonstrate similar efficacies in analogous inventions or applications. These papers have a weight range of approximately 0.1-2000 gsm (gram per square meter).
In its simplest form, the paper straws comprise paper strips and zein polymer. Notably, there is no need for adhesives or glue to bond paper strips during spiral winding. Instead, the zein polymer is an inherent adhesive during the coating, winding, and drying. This design results in a lightweight paper straw. Despite being lightweight, the structural enhancing effects from thin papers make the paper straws from this treatment robust.
This characteristic for not requiring adhesive is highly advantageous for producing consumer product articles requiring complex final product forms. The treatment also facilitates easier recycling due to its low-weight paper fraction.
The paper straws of the present invention are disposable, biodegradable, and compostable and have improved wet strength over commercial paper straws, preventing them from getting softer and soggy when contacted with water, keeping them dry for longer times and enhancing touch and feel when in use. These results are shown in the later examples.
Additionally, the paper straw is designed to deliver active agents for improved user experiences, pleasure, health benefits, and enhanced leisure time activities. The paper straw incorporates an active agent which may be controlled and released as desired during use. As an example, the active agent is incorporated into the surface coating composition by joining to the surface coating and being coated on and/or adsorbed in the zein polymer film via solution treatment.
As a further example, the active agent is applied or adsorbed onto a particulate carrier, assuming an approximate spherical particle geometry via solution treatment. The carrier functionalizes the surfaces, enabling the controlled release and delivery of various active agents for diverse applications. The active agent becomes an integral part of the composition by being incorporated into the carrier particle, forming a substantially homogenous admixture within the dry-coated composition. (
The preferred carrier material is a spherical particle or beads, such as glass beads, porous glass beads, hollow glass beads, ion-exchange resins, crosslinked hydrogels, granular activated carbons, spherical activated carbons, with a particular preference for spherical cellulose particles.
The composition of the present invention provides a plurality of active agents, wherein, for example, the active agents include a flavor, a flavonoid, nicotine, cannabinoids, caffeine, oral hygiene agents, and mouth malodor controls.
Additionally, this invention involves an encapsulation of spherical carrier particles laden with active agents. These encapsulated particles may be further treated using the zein solution or alternative methods such as biodegradable waxes, known as phase-changing material (PCM). Also, the invention incorporates the use of diverse biodegradable and naturally occurring materials, selected for their eco-friendliness, to enhance the functional versatility of the encapsulated carrier particles.
To contain the actives within the straw, the paper straw has an inlet fibrous bed as a porous spacer or filter at one end and an outlet fibrous bed at the other end. These fibrous beds, made of natural materials, separate and divide the straw's sections, with carrier materials between them. Additional fibrous beds or filters can be added as needed. The porous layer thickness is achieved through mechanical insertion of the inlet and outlet spacers. (
The fibrous bed in this invention is a biodegradable porous layer comprised of lightweight natural fibers or foams. These materials form stable fibrous layers or pads with mechanical stability, allowing for the free flow of liquids without significant deformation and effectively guiding the flow of fluids when drawn into them. Some common raw materials that possess these characteristics include, but are not limited to, the following: natural fibers, comprising cotton, hemp, bamboo, jute, kenaf, flax, wool, silk, coconut fiber, banana, kapok, pineapple, nettle; natural foams, comprising natural latex foam, soy-based lightweight materials.
The pore size of the inlet and outlet fibrous beds is smaller than that of the spherical carrier particles. The presence of the sandwiched fibrous beds facilitates the retention of the spherical carrier particles within the structure. A preferred pore size for the fibrous bed layers ranges from about 1-5000 microns, while the thickness of the fibrous bed layer ranges from about 0.1 mm to 15 cm.
When a zein coated straw is used, the user experience is heightened by the suction of liquids, such as water or beverages, through the packaged bed of the present invention containing active agents and spherical carrier particles. As the user draws in fluid, it traverses the tubules from the inlet fibrous bed to the packaged bed of active agent-loaded spherical carrier particles and finally reaches the outlet fibrous bed. As the liquid passes through the bed of packaged spherical particles, it absorbs the migrating active agents, delivering the desired flavor or other intended properties from the active agents to the water or beverage.
In a different aspect of the present invention, tubular devices made having this zein coating on its tubular surface offers a unique approach to pest control, utilizing zein articles to target common pests like termites, ants, and roaches. This method addresses challenges often faced in conventional methods, including resistance, environmental impact, and safety for non-target organisms. The zein articles, comprising spherical particles designed for attraction and targeted eradication, present a multifunctional solution that ensures child and pet safety, aligns with environmentally responsible practices, and avoids potential allergens.
The present invention offers an approach to effectively reduce or eliminate PFAS contamination, including sources from paper straws themselves and/or the water, using advanced materials to target these persistent chemicals. It addresses challenges such as their long-lasting nature, environmental impact, and potential health risks. Specialized materials, including engineered spherical carrier particles, effectively capture and remove PFAS, while zein coatings reduce PFAS movement from the paper phase to the water phase, enhancing overall remediation effectiveness and reliability. This provides a feature that has proven difficult for other systems to address.
One example of the article paper straw of the present invention has (a) about 0.01- to 99 wt. % of a biodegradable and compostable substrate, (b) about 0.1-99 wt. % of zein polymer, forming a dry film thickness ranging from about 0.01-5000 m, characterized by the lack of iodine-starch-complex color reaction; optionally, (c) about 0.01-10 wt. % of water, (d) about 0.01-15 wt. % of a plasticizer, (e) 0.01-5 wt. % of inorganic colloidal particles, (f) about 0.1-80 wt. % of at least one active agent, (g) about 0.1-95 wt. % of spherical carrier particles, and (h) about 0.01-5 wt. % of natural fibers, based on the paper straw total weight.
The tubular article is prepared using treated zein solutions via an adsorptive filtration treatment process to effectively remove impurities and unwanted odor compounds. As a result, the article exhibits a less yellowish color and reduced potential off odors.
This invention introduces a paper straw with an innovative zein treatment, surpassing traditional methods bonded with starch-type glues. The inventive method overcomes the starch-related off taste and reduced durability associated with these glues, offering enhanced performance, user-friendliness, and versatility for an improved consumer experience. Importantly, this treatment opens the possibility of many new applications, expanding the potential uses of the product.
The invention finds several diverse uses, including biodegradable coatings for paper straws, disposable plastic ware (e.g., cups, plates, cutlery), smoke-free nicotine straws, controlled delivery tubes for fertilizers in gardening and agriculture, pest control devices, oral care products, and various packaging materials for consumers and industrial purposes.
The above and other features and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings.
To better understand the principles of this disclosure, descriptions, and figures illustrating the embodiments of this invention found in the specifications and drawings will be discussed.
It is understood that the terminology used herein is to describe particular embodiments only and is not intended to be limiting. As used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. The following terms in the Glossary, as used in this application, are to be defined as stated below, and for these terms, the singular includes the plural.
Various headings are present to aid the reader but are not the exclusive location of all aspects of that referenced subject matter and are not to be construed as limiting the location of such discussion.
Also, certain US patents and PCT-published applications have been incorporated by reference. However, the text of such patents is only incorporated by reference to the extent that no conflict exists between such text and other statements set forth herein. In the event of such conflict, then any such conflicting text in such incorporated by reference US patent or PCT application is specifically not so incorporated in this patent.
Article means a product made using zein, including paper straws and larger-diameter tubular articles made by coating substrates with zein, either through surface application or impregnation, followed by processes like winding or forming tubular structures using zein-treated substrates. This term can be used interchangeably with terms like device, zein-coated articles, zein-coated or paper straws, zein-straws, zein-Hanji papers, and zein-coated or impregnated tubular articles, all of which are intended to describe various zein-based items.
Coating refers to the process of applying the defined zein composition of the present invention to the surfaces of pre-manufactured paper straws or paper strips or sheets for coating and includes any coating methods, including but not limited to coating treatment, surface coating, surface treating, surface films or film layers, surface treatment, or impregnation by various convention means.
Coating composition means:
Such aqueous dispersion compositions can be made in a manner similar to the discussion found in the article ‘Aqueous Dispersions from Biodegradable/Renewable Polymers’ by Mika Vähä-Nissi et al. (TAPPI PLACE Conference 2010; www.researchgate.net/publication/47904226), U.S. Pat. No. 9,273,227B2, and International Patent Applications. WO2013010119A3 and WO2021211995A1.
Crosslinking of Zein Coatings or Films means creating a network structure within the film and/or on coating surface regions, thereby enhancing the mechanical integrity of the resulting coating or film. Crosslinking agents are added to the zein solution and/or to the surfaces of the zein coated surfaces prior to drying. Natural, biodegradable hydrogel materials are selected for food-grade suitability in Crosslinked Hydrogels of this invention. Achieving water-insolubility and swellability involves cross-linking with agents like divalent cations, genipin, or food-grade agents. Alginate, chitosan, gelatin, carrageenan, tapioca starch, among others, can be crosslinked for greater stability and functionality. Biodegradable superabsorbent polymer (SAP) might be suitable in specific instances. These eco-friendly hydrogels decompose similarly to composting.
Fibrous Bed/Porous Spacer or Filter: means biodegradable materials, including natural fibers, comprising cotton, hemp, bamboo, jute, kenaf, flax, wool, silk, coconut fiber, banana, kapok, pineapple, nettle; and natural foams, comprising natural latex foam, soy-based foam, cork, and cellulose foam.
GRAS is an acronym for Generally Recognized as Safe under §§ 201(s) and 409 of the Federal Food, Drug, and Cosmetic Act (US FDA).
gsm means grams per square meter.
Hanji is a traditional Korean paper. Recent preservation studies have highlighted the enduring qualities of Hanji paper, emphasizing its exceptional strength and durability. (Lee, H. J. et al., Preservation of Hanji, Traditional Korean Paper: Review and Prospects, International Journal of Conservation Science, 9(1), 233-242, (2018)). Hanji, made from the bark of mulberry trees, is produced through a rigorous process that involves carefully harvesting, boiling, and beating the fibers. What sets it apart from other kozo papers is the addition of Hibiscus manihot. The manihot aids in holding the pulp fibers together adding a level of strength and durability not found in other mulberry-based papers. The resulting paper exhibits remarkable resistance to tearing and aging, making it highly suitable for a wide range of applications. In addition to using Hanji paper as primary substrate, this invention is also compatible with other East Asian papers like Washi and Kozo from Japan, and Xuan paper from China. (Song J. E. et al., A Study on the Characteristics of Traditional Hanji, Xuan Paper, and Washi for UNESCO Registration, Journal of Korea TAPPI, Vol. 55. No. 1, 92-102 (2023)). The unexpected effects of zein coating is seen in these papers. However, Hanji paper was found to be remarkably superior than the standard paper when zein coating was applied.
Paper or Sheet means thin papers or sheet materials weighing less than approximately 2000 grams per square meter (gsm), produced via Kraft pulping, sulfite pulping, or mechanical pulping, suitable for making straws or other tubular structures, or derived from plant fibers such as Hanji ((Korean), Washi (Japanese), or Xuan (Chinese) paper, or other biodegradable papers and sheets made of chitosan, alginate, gelatin, mycelium, bamboo, banana, polylactic acid (PLA), polyhydroxyalkanoate (PHA) such as polyhydroxybutyrate (PHB), polybutylene adipate terephthalate (PBAT), and seaweed sheets. The paper or sheet of the present invention may or may not contain starch-based glues. When viable the starch is removed from the zein solution as shown in
Pest controlling zein article of this invention facilitates targeted pest eradication by coating spherical particles with attractants specific to pests. Utilizing cellulose-based or biodegradable or inert spherical particles of the present invention, it attracts and eliminates roaches, ants, termites, prioritizing user-friendliness, aesthetics, and eco-agents for safety and biodegradability. Diverse agents for pest control span inorganic, organic, and chemical categories. Inorganics include minerals, metals, salts, boric acids, borax (sodium borate, sodium tetraborate, disodium tetraborate and their hydrates), diatomaceous earth, sulfur, and copper sulfate. Organics range from pyrethrins to neem oil. Chemicals include chlorpyrifos and carbaryl. Of these active agents boric acids and borax are preferred, especially when combined with controlled-size spherical particles integrated with attractant-coated particles in this invention.
PFAS is an acronym for Per- and Polyfluoroalkyl Substances, representing a vast family of synthetic, persistent chemicals known for their exceptional resistance to degradation (U.S. Environmental Protection Agency (US EPA, 2023; Comptox chemicals dashboard: master list of PFAS substances, version 2.2.1). Within this category, PFOA (Perfluorooctanoic Acid) and PFOS (Perfluorooctanesulfonic Acid) stand out as prominent members.
PFAS controlling zein article of this invention addresses recent findings from Boisacq P. and colleagues which highlight the concerning presence of PFAS in eco-friendly paper and bamboo straws. (Pauline Boisacq P., et al., Food Additives & Contaminants: Part A Volume 40, 2023—Issue 9; Assessment of poly- and perfluoroalkyl substances (PFAS) in commercially available drinking straws using targeted and suspect screening approaches). An alarming 90% of the examined paper straws contained PFAS, notably dominated by the PFOA type, which was globally banned in 2020. Similar findings were reported by Timshina A. et al. (Timshina A. et al., Chemosphere, March 2021; The last straw: Characterization of per- and polyfluoroalkyl substances in commercially-available plant-based drinking straws). Despite their low concentrations, the cumulative nature of PFAS poses significant health threats.
Room Temperature means ambient temperature or about 20° C. to about 25° C.
Solvent means any liquid medium capable of dissolving the zein components described in zein composition of the present invention. The solvent dissolves the zein components and is capable of dissolving or dispersing the active components.
Spherical Carrier Particles or Beads means:
Water-Soluble Polymers refer to biodegradable, semi-synthetic, water-soluble polymers and copolymers used in this invention, such as Methocel™ (commercially available from The Dow Chemical Company), polyvinyl alcohol (PVA), polylactic acid (PLA), polyglycolic acid (PGA), polyethylene glycol (PEG), Chitosan, Hyaluronic acid, Alginate, poly(ethylene oxide) (PEO), poly(ethylene glycol) (PEG), polyaspartic acid, or polyacrylamide.
Zein means:
Zein articles represent one of the desired outcomes of the present invention, attainable through coating, pre-impregnation, in-situ production method, or combination thereof. If other zein composition objects are desired, then a variety of articles (more than a paper straw or Hanji straw although straws are preferred), may similarly be obtained by these methods.
Zein Coating in this invention denotes the process of coating the outer and/or inner surfaces of the pre-manufactured tubular cylindrical articles such as paper straws with the zein coating composition of this invention using methods like spraying, immersion, roller-coating, blade-coating, gravure-coating, or a combination thereof. A continuous coating process is preferred. A flow diagram of the process to make the zein coating is shown in
Zein-Coated Paper Straws refer to surface-coated, pre-manufactured paper straws that involve partial or entire body parts of the straw being coated using the zein coating compositions of the present invention.
Zein Straws means the unique paper-based straw constructs obtained using the innovative zein treatment methods on non-premanufactured straws. They consist of a zein polymer and a substrate made of paper, including thin paper, Hanji, and other East Asian papers, as well as natural papers (mentioned above). The production process involves a specialized zein coating composition solution treatment either by pre-impregnating the paper and winding the paper strips or by directly coating the paper and spiral winding these strips. Both methods result in the creation of the designated zein straw. Zein straws offer several advantages over traditional alternatives, such as durability, biodegradability, and compostability.
Zein Solutions means a composition wherein zein is dissolved in a solvent and may contain other additives for added functionalities. The zein solution, typically, contains a zein polymer and a solvent, and at least one of a plasticizer, an inorganic colloidal particle, and an active agent.
Zein Treatment in this invention involves treating an object, like a premanufactured or non-premanufactured substrate, using a zein coating composition in solution. The treatment includes specialized methods, such as coating, pre-impregnating, and winding the paper strips, along with direct in-situ coating during the winding process.
The present invention relates to an advanced method for fabricating a zein tubular article using a substrate, such as a paper straw or a zein straw, and coating it with zein polymer.
The method comprises several steps that may be carried out in any sequential order unless otherwise specified.
Fabrication of Zein-Coated Paper Straws and Related Tubular Articles using a process for preparing a zein coated article, comprising:
This process further comprising one or more of the following steps:
The use of these biodegradable and compostable articles coated with zein in present invention provides diverse applications for use of the zein treated article. Various consumer product articles where a more complex final product form is needed are now possible, including but not limited to paper straws but also other disposable plastic party-tableware products such as coffee stirrers, cups, plates, forks, knives, chopsticks, food picks, and food containers for fries, nuggets, and burgers are now envisioned. Where delivery tubes can be used then also as nicotine delivery straws; delivery straws for caffeine and cannabinoids; pest control. These delivery tubes are depicted by
The zein treatment of the substrate of the present invention uses a zein powder, which may comprise a zein polymer ranging from about 10-99.9 wt. %, water from about 0.1-10 wt. %, and starch about 0.01-50 wt. % based on the total powder weight.
The zein coating composition primarily consists of alpha (a) and beta (p) zein polymer classes, which are commonly the main components in commercial zein products. The mixture may also contain gamma (γ) and delta (6) zein classes. With a weighted average molecular weight (Mw) ranging from approximately 1,000 to 200,000 g/mol, the commercially available zein powder used is a blend of these polymer classes.
The zein coating composition may also have a solvent, which is any liquid medium capable of dissolving or dispersing the components. Suitable solvents may include, but are not limited to, (i) aqueous alcohol of not less than 65% by vol. to 99.9% by vol. of alcohol, such as 95% by vol. of bioethanol, isopropyl alcohol, propylene glycols, ethyl ether, furfuryl alcohol, or tetrafurfuryl alcohol, or (ii) an aqueous alkaline solution of pH 11.5 or greater, or (iii) a mixture thereof. The remaining % in these values is water, unless otherwise stated. The solvent in the zein coating composition must demonstrate the ability to dissolve zein effectively. Additionally, it should be able to dissolve or disperse active agents when present as required.
The zein coating composition comprises a zein polymer mixture concentration ranging from approximately 0.1-80% by wt., preferably 5-40% by wt., based on the zein solution weight.
The solvent is used in a concentration ranging from approximately 40-99% by wt., preferably 60-90% by wt., based on the zein solution weight.
Additionally, these zein coatings or films made as the zein coating composition may be further improved through specific crosslinking processes. Zein is crosslinked at room temperature or higher by diverse agents that react with its functional groups, resulting in enhanced mechanical strength and barrier properties compared to prior versions. The mechanical integrity of zein polymer can be improved through chemical covalent bonding and/or oxidation-induced or physical crosslinking. Physical crosslinking involves non-covalent interactions like hydrogen bonding and van der Waals forces, while crosslinking agents create a network structure within the film or can be used as post-treatment.
The crosslinking agents are selected from the group consisting of formaldehyde, glutaraldehyde, ethylenediamine, genipin, transglutaminase, epichlorohydrin, dextran, aldehyde, carbodiimides, hydrogen peroxide, and UV radiation with photo-initiators. Hydrogen peroxide is preferred crosslinking agent.
Furthermore, the zein coating composition may have a plasticizer, selected from the group consisting of glycerin, vegetable glycerin, propylene glycol, triethylene glycol, dibutyl tartrate, levulinic acid, polyethylene glycol 300, and oleic acid, or a mixture thereof. The plasticizer in the zein coating solution is used in a concentration of about 1-90% by wt. and preferably about 10-50% by wt., based on the zein polymer weight.
Using ground raw zein powder in the zein coating composition has advantages. The ground powder passes through a 500 m sieve to ensure the size of the granules. However, this grinding process is complicated by the electrostatic phenomenon exhibited by zein powder, which can be solved by incorporating a small amount of inorganic colloidal particles into the zein powder prior to grinding that effectively reduces the electrostatic issue.
This present invention includes a water-insoluble zein polymer composition to be used by enabling its encapsulation, storage, and controlled release of active agents. The zein powder or zein solution coating composition may incorporate one or more active agents, applied to the surface of carrier particles, or infused into a zein polymer solution, forming an active agents-loaded zein film matrix.
The present invention also includes the addition of another entity (compound, molecule, polymer) as an active additive (“active”) to the porous or non-porous spherical carrier particles (“carrier”), resulting in the active-loaded carrier. This is a separate spherical particle that can be coated with actives. (See
For this invention, active agents comprise a variety of compounds that can be released from the substrate and/or zein film and independently, including water, essential oil, flavoring agents, sweetening agents or a combination thereof. The concentration of actives in the active carrier composition ranges from 0.001-15% by wt., based on the active-loaded carrier weight.
An active agent has a broad definition so long as it is compatible, meaning it should either be soluble or capable of homogeneous dispersion within the zein polymer matrix or coating. Examples are a broad-spectrum active release agent, encompassing a wide array of active agents with biological, surface, medicinal, hygienic, cosmetic, and stimulating properties, including but not limited to medicinally and/or bioactive agents, surface active agents, hygienically active agents, cosmetically active agents, stimulating agents like nicotine and its salts, caffeine, cannabinoids oil; or a combination thereof. Based on the active-loaded carrier weight, the broad-spectrum active agents can be used in a concentration ranging about 0.01-80% by wt., preferably about 20-50% by wt.
In one embodiment, the carrier comprises porous or non-porous spherical particles or beads, which can be used per se or provide surfaces for carrying active agents. The carrier particles may comprise one or more of the following: glass beads, porous glass beads, hollow glass beads, polymer-based resin particles such as ion-exchange resins, spherical granular activated carbons, spherical activated carbons, crosslinked hydrogels, spherical micro calcium carbonate particles, and spherical cellulose particles. The crosslinked hydrogel and spherical cellulose particles are preferred due to their compostability, biodegradability, and controlled packing within the tubular article.
The carrier particles comprise a mean particle size d(0.5) of about 10-5000 m, preferably about 100-2000 m and a BET-specific surface area of about 0.1-2500 m2/g, preferably about 100-1300 m2g or 200-1000 m2/g, and used in an amount of approximately 0.01-99.99% by wt. based on the total article weight (the substrate treated with the zein coating composition).
Additionally, these spherical carrier particles may be encapsulated with natural phase change materials (PCMs), such as natural waxes such as Beeswax, Candelilla wax, Carnauba wax, soy wax, or a combination thereof. The particles may include a melting point depressed PCM and a lower alkyl chain hydrocarbon-like hydrophobic MCT oil. The encapsulation is conducted by applying a melt coating or aqueous dispersion of virgin PCM or melting point depressed PCM, with PCM concentration ranging from about 0.01-99% by wt. based on the total weight of the active-loaded carrier.
Included in this invention are several other processes, such as the zein treatment of pre-manufactured paper straw, impregnating of paper strips and in-situ coating of paper strips via zein coating solution, the addition of the active agents, and inclusion of active agent-loaded carrier particles.
The invention will be further clarified by considering the following examples, which are intended to be purely exemplary of the invention.
The following materials are used in the examples below. All percentages are by weight unless otherwise stated.
Zein: Two different zein powder samples were used. Zein powder sample A (hereafter “ZEIN A”) was obtained from Richwood Trading Company LTD (Seoul, South Korea), which sourced it from Flozein Products Company (MA, USA), and zein powder sample B (“ZEIN B”) was obtained from YTBio Co., LTD (Xi'an, China). It has been communicated by the zein sample provider to the inventor that ZEIN B's origin is China.
The zein powder was used as received or after grinding and subsequent sieving using a 500 m sieve. The ZEIN A appeared flakier and had a yellowish color, while ZEIN B had a slightly finer and denser flour-like consistency. Sometimes, a small quantity of TiO2 was incorporated into ZEIN A before grinding. In the context of this invention, TiO2 represents the principal colloidal inorganic particles present.
Paper straws: Four commercially available paper straws were used as control paper straws, including Kraft pulp-type brown and white bleached paper straws. The paper straws were measured for their weight, length, and internal and external diameter at room temperature and about 50-60% relative humidity. An electronic balance was used for the weight measurements. These control straws are as follows.
Two Paper straws designated Control A and B were obtained from different Starbucks® Coffeehouses (Daejeon, South Korea) and used as control samples. Both straws had identical sizes, dimensions, and outer appearance of shiny surfaces with a thin oil coating. Both straws were lightly brown colored. Control A had a white interior color, while Control B had a light brown color. They had an outer diameter of 7 mm, an inner diameter of 6 mm, and a length of 20.9 cm. Control A weighed about 1.60 grams, and Control B about 1.50 grams.
Two retail brands of paper straws were also tested and purchased through Coupan.com, Inc., South Korea. These straws had the same dimensions as the Starbucks® paper straw. Control C was brown inside and outside, with a dry weight ranging from approximately 1.50 to 1.60 grams. Control D was white inside and outside, with a dry weight ranging from about 1.30 to 1.40 grams.
Colloidal inorganic particles and colorant: Cosmetic grade titanium dioxide, TiO2, (CAS No.: 13463-67-7) obtained from SoapGoods.com (GA, USA) was used as a colloidal inorganic particle, and McCormick's Food coloring blue and green was used as a colorant
Fibrous bed: is hand-made wool (Wool felt set, item #1033386) purchased from Daiso, South Korea.
Natural coloring agent and natural Anthocyanin color: The Curcumin/Turmeric powder was obtained from Absolute Nutrition Inc. (Haryana, India). A red cabbage dye was obtained from fresh red cabbage.
Medium-chain triglycerides (MCTs): The MCT oil was obtained from Chemres Technologies Inc (Quezon City, Philippines).
Spherical Particles: Spherical micro calcium carbonate spheres (Grade CCS-710: 710-810 μm): obtained from Umang Pharmatech PVT. LTD (Mumbai, India). Spherical cellulose particles (marketed under Cellets) of various sizes ranging from approximately 100 μm to 1400 μm were obtained from Transpharma Sanaq AG (Basel, Switzerland). Spherical activated carbon particles (BAC, Grade G-BAC GR-70R: 0.70 mm≤, 0.6 mm or less ≤5 wt. %) from Kureha Corporation (Tokyo, Japan).
Test Liquid: Water: Tap water was used as the test liquid for the dipping tests at room temperature. Saline solution: 0.9 or 4.0% by wt. was prepared using table salt (sodium chloride) and tap water and was used to study the effects of salinity.
Wax: Candelilla wax in flake form was obtained from the Korea Similac company (Coupang, South Korea).
Examples of treatment or preparation methods have designations by alphanumeric numbers.
A. Blending: Zein powder (ZEIN A) is placed in a small glass jar (50 mL or 200 mL volume). When colloidal inorganic particles are used, the mixture is manually stirred for 2-3 minutes to achieve a homogenous blend. The resulting mixture can be used for preparing zein solution.
B. Grinding, sieving, and Sizing: The blended zein mixture is sometimes ground using a household coffee grinder (150 mL mixing volume). The zein powder is ground to reduce particle size, and the size fraction passing through a 500 m sieve is selected for further use.
C. Preparation of zein treatment solution: Zein A powder was used in this step, ranging from a few grams to 50 grams, was placed into a 150 mL glass bottle at room temperature, followed by the addition of a predetermined amount of solvent. When using a plasticizer, the predetermined amount was added to the solvent before use. The mixture was periodically swirled by hand to facilitate dissolution and ensure homogeneity.
When working with zein B powder containing insoluble residues, the zein solution was obtained by decanting and suctioning the supernatant from the residue. Similarly, if significant insoluble residues were present, the zein solution was obtained by separating the supernatant from the residues using a pipette. In either case, gravimetry was again employed to determine the actual concentration. This approach ensured accurate results while maintaining efficiency.
The prepared zein solutions also showed an intense yellowish-to-amber color, becoming clearer and more transparent over time. Careful decantation and suctioning were essential to avoid including the resulting zein film's small white-yellowish fine particles (“fines”). The solution's quality was checked using the film formation test method described herein.
D. Zein Film Formation Testing: Various zein solutions were tested for quality and film-forming ability. A transparent PP plastic sheet (15.2×11.4 cm, thickness: 100 μm) was used as the substrate for the film preparation. Liquid strips were created by drawing approximately 0.5-1 mL of the respective zein solution onto the PP film using a disposable PE pipette (3 mL, opening diameter: 1 mm). The film strips were left to dry at room temperature for several hours, producing well-formed films as the solvent evaporated.
E. Preparation of Zein Article Paper Straws via Dipping: Virgin paper straws were immersed in the zein solution in a glass cup (50 mL or 300 mL). The lower portion of the straw was submerged for about 5 cm or 10 cm, while the straw was rolled with fingers for approximately 60 seconds to ensure even coverage. Excess zein solution flowed out of the tube, and the wet-state zein-coated paper straw was gently tapped to remove any remaining excess. The zein-coated paper straw was placed in a preheated oven at 50° C. and dried for 30 minutes.
In some instances, virgin straws underwent a comprehensive coating process where the zein solution was applied to the inside and outside of the entire straw body. For the inside coating, the zein solution was gently poured from the top while simultaneously rolling the straw with fingers to remove any excess. This iterative process was repeated multiple times to ensure a uniform coating throughout.
F. Drying: The wet-state surface-coated paper straw samples were dried in an air-circulated oven preheated to approximately 50° C. for approximately 30 minutes. The drying process was sometimes conducted at an elevated temperature of around 80° C.
G. Preparation of Zein Straw via Pre-Impregnation Method: The paper substrates used for zein polymer pre-impregnation had different weights: 2 gsm (paper), 14 gsm (paper), and 80 gsm (Hanji). The strips were cut into the following sizes: 15 mm×540 mm (average weight: ca. 0.013 g) for 2 gsm paper, 20 mm×240 mm (average weight: 0.07 g) for 14 gsm paper, and 20 mm×297 mm (average weight: 0.5 g) for 80 gsm paper.
To ensure uniform coverage, the strip was treated with the zein solution (Example 16, Table 3) using a brush, allowing uniform zein coating on both sides through solvent penetration. The zein-impregnated wet strips (2 and 14 gsm) were air-dried at room temperature for several hours. As a result of this process, a mechanically robust and flexible zein pre-impregnated paper strips weighing approximately 0.3 g for strips (for 2 gsm paper) and 0.15 g (for 14 gsm paper) were obtained, making it suitable for roll (spirally-winding) processes. The impregnated strips of the 80 gsm Hanji dried readily due to the rapid and uniform distribution of the zein solution at room temperature. The robust and flexible zein pre-impregnated Hanji weighed approximately 0.73 g for strips and was highly suitable for roll (spirally-winding) processes. This efficient drying for thin paper and Hanji, even at room temperature, demonstrates potential process advantages. The thin papers and Hanji utilized throughout this invention did not exhibit any signs of starch-iodine color reaction, affirming the absence of starch-based glues.
The primary zein straw was created by spirally winding the zein pre-impregnated strip around a mandrel (stainless-steel or PP straw) at approximately 35-45 degrees angle. The zein solution (Example 16) acted as an adhesive to secure the overlapped edges, with a width of approximately 2-3 mm. The primary zein straw was then lightly coated with zein solution, enabling the adhesion of the second layer of the pre-impregnated strip wound in the opposite direction. If desired, this process is repeated for additional layers, with the zein solution applied after each layer application. Following layering, the wet tube was heated at 50° C. for 30 minutes, as described above, then cooled to room temperature. The mandrel was carefully removed, and the zein straw samples were trimmed to approximately 7 mm in diameter and 200 mm in length.
The resultant zein straw is made from 2 gsm paper and weighs about 1.34 g. This zein straw consists of 3 strips of thin paper (2 gsm paper), comprising less than 5% of the paper. Using six strips of 14 gsm thin paper, the process yields zein straws weighing approximately 1.0 g, while 1 and 3 strips of 80 gsm Hanji result in about 1.1 and 2.7 g, respectively. All zein straws exhibited mechanical strength comparable to the control paper straws. The zein impregnation treatment on Hanji proved especially effective, making it an excellent substrate, yielding glossy and robust zein straws with a subtle yellow hue.
H. Zein Straw Preparation via in-situ Coating Method: A dry virgin paper strip was spiral-wound around a stainless-steel or PP straw as the base substrate for zein coating. The initial winding was saturated with zein solution using a brush. Additional layers were applied using the zein solution, repeatable as needed. After the final layer, the tube was heated, cooled, and the mandrel removed. The straws' ends were trimmed to the desired length, resulting in spirally wound, multi-layered zein straws. PP straw proved more effective than stainless steel for removing the dried zein straw.
I. Finger Squeeze Test: Fingers offer higher sensitivity than mechanical stress testing, enabling a comprehensive assessment of the product's physical properties and subjective perception. This user-centric approach detects changes in characteristics, like wetness, hardness, texture, and slipperiness, when in contact with liquids, providing valuable insights into usability and durability in real-world scenarios.
J. Color Treatment: Blue color-loaded spherical particles were prepared by adding about 1.4 g of blue coloring to approximately 5 g of spherical micro calcium carbonate particles or other carrier particles in a 50 mL glass cup. The color was evenly distributed onto the particle surfaces. The mixture was then placed in an air-circulated oven set at about 50° C. for 120 minutes.
K. Assembly of Zein Straw with Carrier Particles and Fibrous Beds: This process involved assembling a Zein straw filled with active-loaded carrier particles. An inlet fibrous bed of about 0.05-0.1 grams acted as a porous spacer or filter, positioned approximately 9-10 cm above the tube's bottom using a rod and tweezers for precise placement. Next, about 0.5 grams of active (blue color)-loaded spherical calcium carbonate particles were carefully poured into the straw via a funnel, forming a bed of approximately 2-3 cm thickness. An outlet fibrous bed of 0.1-0.15 grams was placed above the active-loaded carrier to seal the opposite end of the tube.
The following test methods outline the evaluation of specific properties associated with various components or articles of this invention.
The test methods are designated by alphanumeric numbers following the caption “Test” indicated, providing examples of procedures used for testing.
Test-A. Dipping Test: The dipping test method evaluated paper straws' water absorption and mechanical strength during various immersion times. Two test volumes were used: 50 mL and 500 mL glass cups, with approximately 40 mL and 400 mL of water, respectively. The paper straw was placed in the water-filled glass cup, leaning against the rim, and left for 10 minutes to several hours. The paper straws were coated with zein up to the 5 cm mark for the 50 mL glass cup and the 10 cm mark for the 500 mL glass cup.
The test straw was gently subjected to controlled removal of excess water at each time interval by allowing it to fall from a height of approximately 5 cm onto a pre-folded Kleenex® facial tissue, forming a 5×5 cm square, five times. The straws were then re-immersed in the water in a glass cup, with the liquid level slightly below the bottom height of the paper straw (5 cm and 10 cm). The dipping test was conducted at intervals ranging from 10 minutes to over 6 hours, weighing the sample at each interval.
Test-B. Pumping Test via Ear Syringe Bulb: The straws of the present invention underwent a pumping test using an ear syringe bulb (ESB) with a volume of 30 mL at room temperature. The pumping action simulates drinking, and the pumping process consists of five cycles of suctioning and releasing the water into the cup at regular intervals.
Test-C. Wet-State Firmness Test (FT) via Finger Squeeze: The wet-state firmness test simulates radial compression of wet samples with the bottom part of the straw immersed in the water. After the dipping test and weighing, the water contact area was gently squeezed with a finger to determine the firmness. A skilled individual repeated the finger squeeze test, and scores were rounded to the nearest 0.5 unit for comparison. Reproducibility was confirmed by conducting tests using the same materials simultaneously at room temperature and at different times. The consistent trends observed in the data support the reliability and robustness of the findings. The firmness scores of the wet-state paper straw area are as follows:
To facilitate the comparison of results, the obtained finger squeeze test scores are converted into letter grades according to the following scale in Table 1 below. The finger squeeze test assesses the firmness of the wet-state paper straw, and the corresponding letter grades allow for easy comparison of the test results by this scoring method.
Test-D. Turbidity/Color: After testing each sample, the turbidity or color of the water in which the paper straw was immersed was examined. The inspection of water turbidity was conducted using an LED magnifying lamp. Turbidity is attributed to extractables and particles originating from the paper straw during immersion.
Test-E. Starch-Iodine Test: The starch-iodine test was performed on a 7.5% by wt. Povidone solution to detect starch in paper straws, including starch as a contaminant in zein powder and any potential starch in solid water-insoluble residues within the zein solution. Starch reacts with iodine, forming a dark blue to almost black starch-iodine complex, with intensity corresponding to the starch concentration (
Test-F. Water-Absorption Percent (%) Test: The weight percent of the water absorbed represents the relative percentage of water absorbed based on the weight of dry paper straw at a specific time and was calculated using the following equation:
Test-G. Biodegradation Test: A 12-week biodegradation test assessed the degradation of the test straw. A round plastic flowerpot (1 L volume) was placed outdoors as a compost bin, exposed to rain and sunshine. Commercial potting soil filled the flowerpot. The test straw was inserted into the pot soil, elevated halfway (ca. 10 cm). No additional watering other than rain was provided throughout the testing period. Temperature history: July (25° C., 14 rainy days), August (25.2° C., 13 rainy days), September (20° C., 9 rainy days), October (13.8° C., 4 rainy days). After 12 weeks, the test straw was carefully removed from the soil, gently cleaned, and evaluated for degradation.
Test-H. Suctioning Test for Active-Loaded-Carrier-Filled-Straw: This test simulated the controlled release of loaded actives on carrier particles from the straw. A 30 mL ear syringe bulb drew water through the straw filled with blue-colored active-loaded carrier particles (micro calcium carbonate). Water was drawn from a 500 mL glass cup (containing 400 mL of water) and transferred to a 50 mL glass cup. The volume of water drawn through the straw was measured at different times, and the blue color was graded on a scale of 0 to 5, with 5 being dark blue and 0 colorless.
In the following Examples, letters denote Comparative Examples while numbers represent the embodiments of this invention.
Control samples (A-D) are current commercial paper straws, including Kraft pulp-type brown and white bleached paper straws. All samples were identical in size, dimension, and appearance. These straws may or may not contain starch-based glues.
Control samples A and B are two Starbucks® paper straws.
Control C represents a brown paper straw.
Control D is a white paper straw. (
Examples 1-7 show different solutions prepared using the zein polymer A (ZEIN A), an 83% aqueous alcohol solution (S-I), and an inorganic colloidal particle additive such as TiO2.
Examples 8-11 demonstrate solutions prepared using the zein polymer A (ZEIN A), an 83% aqueous alcohol solution (S-I), and the plasticizer propylene glycol (PG).
Examples 12-14 showcase solutions made from using the zein polymer A (ZEIN A), an 83% aqueous alcohol solution (S-I), and the active agents such as Curcumin/Turmeric and Anthocyanin color, both acting as a colorant and soluble active agent. Methylcellulose served as a swellable and insoluble agent.
Examples 15-21 detail solutions prepared using zein polymer B (ZEIN B), an 83% aqueous alcohol solution (S-I), anhydrous ethanol (99.9% by vol.) (S-II), and a bioethanol (95% by vol.) (S-III), and an inorganic colloidal particle additive such as TiO2.
Examples 22 to 25 illustrate the effects of zein treatment (ZEIN A) on Control A, evaluated through dipping tests.
Examples 26-28 illustrate the effects of zein treatment (ZEIN B) on Control B, evaluated through dipping tests. The treatments involve solutions prepared using three different solvents: an 83% aqueous alcohol solution (S-I), anhydrous ethanol (99.9% by vol.) (S-II), and bioethanol (95% by vol.) (S-III).
Examples 29-33 illustrate the effects of the combined effects of zein (ZEIN A) and TiO2 treatment on the properties of Control C, evaluated through dipping tests.
Comparative Examples A-C illustrates the effects of hydrophobic treatment on Control D, prepared using MCT oil, Olive oil, and Candelilla wax, respectively, assessed via dipping tests.
Examples 34-36 illustrate the common effects of zein (ZEIN B) and hydrophobic treatment on Control D, prepared using MCT oil, Olive oil, and Candelilla wax, evaluated via dipping test.
Control D-HT, a preheated Control D sample, studies the effects of pre-drying, evaluated through a dipping test.
Examples 37-38 illustrate the effects of common effects of pre-drying and zein treatment (ZEIN B) on Control D, assessed via dipping test.
Control D-0.9% and Control D-4.0% study the salinity effects of Control D in a high salinity solution of 0.9% and 4.0%, respectively, evaluated via dipping test.
Examples 39 and 40 illustrate the effects of zein treatment (ZEIN B) on Control D in a high salinity solution of 0.9% and 4.0%, respectively, evaluated via dipping test.
Example 41 (
Examples 42-49 demonstrate the properties of the zein straws (ZEIN A), prepared using different substrates: thin paper (EX. 43/2 gsm and EX. 46 and 47/14 gsm) and Hanji (Examples 44 (
Examples 50-53 showcase the effects of drinking simulation using Ear Syringe Bulb (ESB) on various straws: Control D-ESB, zein straws made from Hanji (pre-impregnation method—EX. 44/
Example 54 represents the blue color active-loaded carrier (micro calcium carbonate) particles, prepared according to Method J.
Examples 55-56 showcase the controlled release effects of the active agent through water suction using zein straws made from Hanji and filled with blue color active-loaded carrier particles (micro calcium carbonate). Examples 55 and 56 represent the data obtained from utilizing the samples of Example 44 (
The following Examples, an Example and Comparative Example are abbreviated as EX. and COMP. EX., following the number, respectively.
Table 2 following this discussion outlines a series of experiments conducted with zein polymer solutions (Examples 1-8) using ZEIN A and diverse S-I compositions from an 83% aqueous alcohol solution. This included ethanol, propylene glycol (PG), and an inorganic additive, TiO2. The PG serves as a plasticizer for zein polymer. Each Example utilized ground ZEIN A, presenting a challenge due to the electrostatic charges inherent in grinding the fluffy and flaky zein powders. However, introducing a small amount of TiO2 significantly facilitated the grinding process by effectively reducing electrostatic and dust problems.
The zein polymer concentration in the solution varied between approximately 6-24 wt. %. The weight ratio of ZEIN A to PG was about 0.48 to 0.55, while PG to S-I varied from about 0.08 to about 0.6. Adding TiO2, comprising about 3% by wt. of the ZEIN A weight, prior to grinding, led to less fluffy and more flowable powder, reducing potential processing issues. The resulting TiO2-infused zein solution was a stable, milky dispersion free from agglomerates and remained usable for coating over extended durations. Interestingly, these initially opaque solutions produced translucent films upon drying.
In all examples from Table 2, ZEIN A dissolved effectively in both solvents. The initial solutions, colored pale to dark yellow based on the concentration, were gently swirled for 5 to 12 hours post-preparation without agitation. Over time, small amounts of white-yellowish fines-contaminants like corn starch particles from the zein separation process-settled, clarifying the solutions. Due to their minimal presence, a starch-iodine test was deemed inapplicable.
It was observed that finely ground zein powder dissolved faster in the solvent than its non-ground version, suggesting potential benefits for large-scale production. The findings indicate a wider possible use of TiO2 and other inorganic colloids and nanoparticles such as SiO2, alumina, zirconia, Aerogels, and others.
aThe weight percentage of zein polymer based on the solution,
bAn 83% by vol. aqueous ethanol solution (S-I),
cReproducibility,
dPropylene glycol (PG),
eThe weight percentage of TiO2 based on the weight of the zein polymer A (ZEIN A),
fThe weight (g)/weight (g) ratio of zein to PG,
gThe weight (g)/weight (g) of PG to ethanol (83% by vol.; S-I).
Table 3 following this discussion shows zein polymer solutions (ZEIN A) prepared using an 83% ethanol solution (S-I) and active agents like Anthocyanin, green coloring, Curcumin/Turmeric powder, and Methylcellulose (Methocel®). Soluble agents dissolved in the ethanol, while Methylcellulose dispersed for coating. The prepared 50 mL solutions, as in Table 3, were suitable for coating. Dyes were under 0.1% by wt. of the solution. Methylcellulose addition to the ethanol solution and zein mixture caused minor swelling (Example 12), not impeding the coating process.
Adding Curcumin/Turmeric powder to the zein solution (Example 12) resulted in an orange solution, effectively masking the initial yellow tint. When tested the turbidity, the water in which the paper straws were immersed revealed a yellow to orange color for Curcumin/Turmeric sample (Example 12) and a green color for Example 13. Methylcellulose remained on the surface despite slight swelling, indicating potential for controlled active release with zein polymer coating.
aZein solutions were prepared using an 83 vol. % aqueous ethanol solution,
bThe weight percentage of zein polymer based on the solution,
cThe weight percentage is based on the weight of the zein solution,
dThe exact concentration of red cabbage color concentration is not determined. The actual concentration is assumed to be much smaller than 1 wt. %.,
eThe weight of the dye and food coloring solution.
Table 4 following this discussion presents the zein solutions (Examples 15 to 21) prepared with ZEIN B and using diverse solvents, including 83% ethanol, anhydrous ethanol (99.9% by vol), and bioethanol (95% by vol.). ZEIN B, which is less fluffy, flaky, and chick yellow than ZEIN A, dissolved readily in the solvent. However, ZEIN B left significant insoluble residues in ethanol (S-I), removed via decantation and suction. Final concentrations were confirmed by gravimetry.
The solutions displayed a deep yellow to amber color. Improper decantation or suctioning left visible fines in these yellow-to-amber, translucent solutions (Table 4). After treating the isolated white solid residue with 99.9% alcohol, rinsing, and drying at 80° C. for 2 hours, it exhibited a dark blue-to-almost black reaction with a Povidone solution of corn starch particles. Table 4 features zein solutions from ZEIN B, with concentrations from 13 to over 30% by wt., each producing a white solid residue mass. Table 4 indicates that zein solutions can be prepared seamlessly using varied alcohols and concentrations (20 to over 30% by wt.).
aThe weight percentage of zein polymer B based on the solution,
bThe weight percentage of TiO2 based on the weight of the zein polymer B,
cS-I = An 83% by vol. aqueous ethanol solution (83% by vol.),
dS-II = EtOH (99.9% by vol.), and
eS-II = Bio EtOH (95% by vol.).
This summarizes the behavior and quality of film formation from zein solutions detailed in Examples 1-21 (Tables 2 and 4).
Example 1 (Table 2) produced a thin, pale-yellow film that was removable but prone to electrostatic coiling. Example 10 resulted in a firmly adhering yellow film without electrostatic tendencies, likely due to PG's plasticizing effect. Unexpectedly, increasing PG enhanced tackiness and extended drying time.
Solutions with TiO2 formed milky but dried into translucent films, regardless of PG (Examples 4, 6, 9). The Curcumin/Turmeric zein solution (Example 13, Table 3) yielded a dark yellow-orange film, while the dye zein solution (Example 14, Table 3) created a translucent dark green film. Example 15 was a medium-concentrated solution that formed a yellowish film that adhered to the PP surface, while the highly concentrated Example 17 yielded a shiny, translucent film. Zein solutions (Examples 15-21) from ZEIN B produced comparable surface films when properly decanted and suctioned, despite high starch content and unidentified residues.
Table 5 following this discussion summarizes the impact of zein coating on commercially available paper straws (Control A). Water absorption and mechanical properties at various time intervals were evaluated through dipping tests, comparing Control A and its zein-coated versions. Control A weighed approximately 1.65 grams.
Coating treatment notably improved mechanical strength against radial compression (Table 5). Similar zein treatments with PG (Example 2 vs. 10) raised water absorption (Example 22 vs. 23). Water absorption of the Control A sample showed consistent incremental progress over time, suggesting high-quality paper straws and stable adhesive bonding even after 400 minutes of immersion.
Control A showed a correlation between increased water absorption and significantly decreased mechanical strength, aligning with previous literature. (Gutierrez, J. N., et al., BioRes. 14(4), 8345-63, (2019). The zein coating slightly increased water absorption compared to Control. At 60 minutes, Control A showed a 15% weight increase, while zein-coated samples (Example 22 and 23) showed 17% wt. and 22% wt. increases, respectively, attributed to PG. (2019)). The Interestingly, in zein-coated samples, increased water absorption didn't proportionately decrease mechanical strength, contradicting the usual relationship.
1.73/A
1.78/A
1.82/A
aAll testing was conducted in a 50 mL glass cup,
bReproducibility,
cZein solutions used for the treatment,
dWeight (g) of the dry paper straw before dipping test,
eFinger squeeze test (FT),
f% weight gain from water absorption.
Table 6 following this discussion outlines the impact of zein treatment (ZEIN B) using various ethanol solvents (S-I, S-II, and S-III representing an 83% by vol., 99.9% by vol. anhydrous ethanol, and 95% by vol. bioethanol, respectively) on Control B samples shows water absorption and mechanical properties using a 500 mL dipping test. Control B demonstrated slightly elevated water absorption than Control A but with a slower degradation rate.
Zein treatment produced positive outcomes regardless of the alcohol solvent used. Performance improvement and resilience in all zein-coated samples (Table 6) are evident, maintaining wet strength consistently and outperforming commercial untreated paper straws.
No starch-iodine reaction was seen in Control B or zein-coated paper straws, Examples 26-28, implying non-starch-based binders used in straw production. Paper straws prepared using adhesives-based synthetic polymers such as hot melt may result in only partially biodegradable materials and unsuitable for compost.
1.50g/Ah
aAll testing was conducted in a 500 mL glass cup,
bZein solutions were used for the treatment,
cEthanol type used as a solvent,
dS-I = An 83% by vol. aqueous ethanol solution (83% by vol.),
eS-II = anhydrous alcohol (99.9% by vol.), and
fS-II = Bioethanol (95% by vol.),
gWeight (g) of the dry paper straw before absorption testing,
hFinger squeeze test (FT),
i% weight gain from water absorption.
Table 7 following this discussion outlines the influence of ZEIN A on Control C's water absorption and mechanical attributes. Tests were conducted in a 50 mL glass cup.
Table 7 indicates consistent water absorption over time for all samples, confirming previous results. Zein treatment resulted in similar or greater water absorption than Control C but with lesser deterioration of mechanical strength. The maximum water absorption for all samples remained under or around 30% even after 1065 minutes (17¾ hours). Control C's quality aligns with Control A's high standards.
The zein treatment at a concentration of about 9% by wt. yielded comparable results and showcased improved firmness (Examples 30 and 31), indicating good reproducibility. Control C showed a strong starch-iodine complex reaction, unlike Control A or B. Table 7 reaffirms the invention's unexpected positive outcomes: the zein-coated paper straws exhibit significantly improved mechanical properties despite comparable or increased water absorption relative to Control C.
In a series of experiments conducted in 500 mL test volumes, the impacts of zein treatment, derived from ZEIN B, in combination with different hydrophobic substances on Control D's properties, were studied. Hydrophobic treatments with MCT oil (COMP. Ex. A), Olive oil (COMP. Ex. B), and Candelilla wax (COMP. Ex. C) were applied to Control D paper straws. In a specific instance, the paper straw coated with zein received an additional layer of coating, either with MCT oil or wax.
Results from Table 8 following this discussing show hydrophobic oil treatment, irrespective of whether it was MCT oil or Olive oil, provided no significant improvement in the wet strength of the paper straws over time. Hydrophobic oils such as olive oil and MCT oil proved ineffective at augmenting paper straw's water resistance. However, zein treatment (Example 34) showcased improved firmness and reduced water absorption. MCT oil diminished, however, this advantageous effect of zein treatment when it was applied to the surface of the zein film (Example 35).
Comparative Examples A and B exhibited a strong positive starch-iodine complex, indicating that a thin oil surface layer failed to prevent starch molecule migration from the straw substrate. In contrast, the zein-coated straw (Example 34) and zein and oil-treated straw (Example 35) proved better barrier properties, evidenced by the negative starch-iodine tests.
Further, the application of hydrophobic Candelilla wax showed promising results initially, delaying deterioration and reducing water absorption compared to Control D, but this effect was short-lived. The combined treatment of zein and Candelilla wax significantly extended the straw's wet strength duration, indicating a synergistic effect. This combination also successfully prevented starch molecule migration, even after prolonged water exposure.
Control D exhibited a strong starch-iodine reaction in all conditions, whereas Comparative Example C showed a weaker response, indicating structural decay and the wax surface layer's inefficiency. However, the straw treated with zein and wax (Example 39) successfully prevented starch migration even after prolonged water exposure.
1.33d/Ae
1.39/A
17%/C
20%/C
29%/D
23%/D
26%/D
25%/D
28%/D
aAll testing was conducted in a 500 mL glass cup,
bZein solutions were used to treat the Control D straw sample. Example samples were prepared using zein solution 17 (Example 17) with a zein concentration of 33% by wt.,
cHydrophobic treatment using MCT oil, Olive oil, Candelilla wax,
dWeight (g) of the dry paper straw before absorption testing,
eFinger squeeze test (FT),
f% weight gain from water absorption.
Table 9 following this discussion displays the impacts of zein coating (ZEIN B) on water absorption and mechanical properties of paper straws in 500 mL tests. Pre-heating untreated Control straws barely affected water absorption, with all showing quick strength deterioration. However, increasing concentrations of zein treatment appeared to improve straw firmness and durability, with lesser deterioration than Controls. Control D showed a potent starch-iodine complex regardless of pre-heating, whereas zein-coated straws (Examples 37 and 38) largely showed no such reaction.
1.40/A
28%/C
23%/C
32%/C
32%/C
33%/D
33%/D
40%/D
37%/D
aTesting conducted in a 500 mL glass cup;
bZein solutions used for the treatment,
cWeight (g) of the dry paper straw before absorption testing;
dFinger squeeze test (FT),
e% weight gain from water absorption.
Table 10 following this discussion demonstrates the effects of high salinity solutions on zein-treated paper straws in 500 mL tests. Control samples deteriorate rapidly, showing minimal salinity dependence due to cellulose pulp's non-charged nature. However, zein-treated samples (Examples 39 and 40) showed remarkable resistance to salinity, with stronger saline solutions yielding higher efficacy. This suggests an anti-salt effect of zein treatment, hinting at potential high salinity applications. While Control D showed a potent starch-iodine complex, zein-coated straws exhibited largely negative results, displaying the effectiveness of zein as a barrier even in prolonged saline exposure.
1.37f/Ag
1.51/A
30%/C
24%/C
28%/D
31%/D
25%/D
aAll testing was conducted in a 500 mL glass cup,
bZein solutions used for the treatment,
cTap water (arbitrarily assumed to be 0),
dan aqueous saline 0.9% by wt. solution,
ean aqueous saline 4.0% by wt. solution,
fWeight (g) of the dry paper straw before absorption testing,
gFinger squeeze test (FT),
h% weight gain from water absorption.
Summary of Overall Results from Examples 22 to 40
This invention shows the influence of zein treatment on paper straw characteristics such as water absorption, structural integrity, starch migration, salt tolerance, and water resistance. Results indicate that zein-treated straws have enhanced durability and firmness, despite similar or greater water absorption levels, thus offering a potential improvement for eco-conscious products. Standard straws can lose their flexibility over time, detrimentally affecting user experience.
Tests using the starch-iodine complex confirm the absence of starch migration from zein-treated samples, regardless of salinity levels. This lack of starch migration could address prevalent gluten concerns in paper and natural straws, leading to the production of non-starch, adhesive-free, and gluten-free renewable straws.
Although the effectiveness of hydrophobic treatments such as vegetable and olive oils is limited, their combination with zein treatment shows potential for better results. Additionally, paper straws demonstrate increased resilience in high salinity conditions, indicating improved saltwater resistance.
In the biodegradability test of a zein straw, a sample from Example 41 (
After 12 weeks, the straw was entirely decomposed. As shown in
Therefore, Example 41 showcases significant biodegradability and compostability, mainly composed of minimal paper or degradable and/or compostable thin sheets and a substantial weight portion of the zein polymer. While the tests were qualitative, the evident biodegradability under natural weather conditions is a significant finding.
Table 11 following this discussion shows zein straws prepared from thin paper (Examples 43, 46, and 47) and Hanji (Examples 44, 45, 48, and 49). These straws, all with a thin-wall structure and a yellowish-amber hue, offered comparable mechanical strength to Control D. Notably, Examples 43, 44, 46, and 48 showcased lightweight zein straws, weighing roughly 1 g or less, significantly lighter than Control D (1.33 g) and other Controls. This result also implies potential economic benefits due to their significantly reduced weight compared to commercial paper straws.
Irrespective of using thin paper or Hanji and different production methods of the pre-impregnation or in-situ coating, the zein straws consistently outperformed Control D regarding wet strength. Moreover, the zein straws made with pre-impregnated Hanji exhibited remarkable and sustained wet strength improvement throughout the testing period. Notably, Example 45 showed exceptional properties surpassing those of any other control samples.
1.65/A
0.99/A
40%/D
aAll Testing was conducted in a 50 mL glass cup; all samples were prepared using zein solution (ZEIN A) (Example 7),
bTreatment methods,
cFull body coating. Zein-coated paper straw obtained by completely coating the inside and outside of Control D,
dPre-impregnation,
eIn-situ coating,
fx = the number of virgin paper or pre-impregnated strips used,
ggram per square meter of the substrate strip used;
hThe samples (EX. 44 and EX. 48) are robust and firm in the dry state despite the lightweight,
hThe sample (EX. 46) is thin and soft due to lightweight,
iWeight (g) of the dry paper straw before absorption testing,
jFinger squeeze test (FT),
k% weight gain from water absorption.
Table 12 displays the zein straws' effects on water absorption and mechanical properties, determined using a 500 mL pumping test simulating drinking conditions. Example 50, a fully zein-coated straw, was prepared by coating the entire straw body inside and out with a zein solution (Example 7), as per Method E. The drying process involved several days at room temperature, followed by 30 minutes at 50° C. for straws (Examples 44, 45, and 46), with no weight change observed.
The Control D-ESB rapidly lost strength within 10 minutes, culminating in bursting and disintegration under extreme stress, proving the harshness of the pumping test. However, Examples 50-53 showcased the zein treatment's benefits, displaying superior mechanical strength compared to Control D-ESB. Example 52 demonstrated persistent high wet strength throughout the 80-minute test, highlighting substantial quality improvement over conventional paper straws.
The outcomes presented in Table 12 illustrate that the zein straws produced through this invention's pre-impregnation or coating techniques hold significant potential to replace conventional paper straw structures while maintaining exceptional biodegradability and compostability.
0.97/Bi
aAll pumping testing was conducted in a 500 mL glass cup using an ear bulb syringe,
bPumping testing of Control D,
cFull body coating. Zein coated paper straw obtained by complete coating the inside and outside of Control D,
dZein Hanji straws prepared by pre-impregnation method (EX. 44/FIG. 5 and EX. 45),
eZein Straw prepared by in-situ method (EX. 46),
fWeight (g) of the dry paper straw before absorption testing;
gFinger squeeze test (FT),
h% weight gain from water absorption,
iThe sample (EX. 46) is thin and soft due to lightweight,
jThe samples (EX. 44) are robust and firm in the dry state despite the lightweight,
kNon-applicable: bursting of its end part within water and complete disintegration.
Example 54 represents the micro calcium carbonate carrier particles loaded with blue color as an active, prepared according to Method J. The microparticles exhibited an even distribution of the blue color, implying its potential for accommodating water-soluble actives, as mentioned earlier. The zein Hanji straws, Examples 55 and 56, were prepared under the same conditions as Examples 44 and 45.
Examples 55 and 56 affirmed their robustness and exhibited characteristics consistent with the previous results. The volume of water suctioned into the ear syringe bulb, later transferred into a 50 mL glass cup, was consistently 6-7 mL, even up to 60 minutes. The color varied over time: 0 (0 min), 3 (10 min), 5 (20 mi), 4 (30 min), 3 (40 min), 2 (min), and 1 (60 min) for both Examples 55 and 56.
The observed color distribution indicates a gradual and controlled release over time, with increasing intensity signifying progressive liberation. The controlled suction method employed in this invention proves valuable for this purpose. Additionally, surface modifications, especially encapsulation, hold promise for enhancing control, leading to a more substantial release effect.
Summary of Overall Results from Examples 41 to 56
The overall results on zein straws have yielded significant, unexpected findings. The biodegradability test confirmed the complete degradation and compostability of the zein straws under natural weather conditions. Applying zein treatment to Hanji has resulted in remarkable improvements in the paper straw's properties, including a pleasant hue, a thin-wall structure, and superior wet strength compared to commercial paper straws. Pre-impregnated Hanji further showcased sustained enhancements in wet strength throughout the testing period. The pumping tests, simulating real-world scenarios, highlighted the advantages of using zein Hanji straw.
The zein straws of the present invention exhibited substantial improvements in mechanical strength compared to the commercial control sample, which experienced considerable deterioration and disintegration under stress. A modestly controlled and gradual release profile was observed in the water suction experiments conducted with zein straws filled with blue color-loaded micro calcium carbonate carrier particles. This release pattern suggests the potential for enhancing control through surface modifications such as encapsulation.
The findings indicate that zein straws possess desirable characteristics, including robustness, water resistance, biodegradability, and compostability. These attributes make it an innovative invention with various potential applications where such qualities are highly valued.
