Claudio Villa
EUROSYN
Have you ever spilled a drink on a wooden table? What you would expect is to see the wood being impregnated by a large, sticky, colored stain. Sometimes, though, one is surprised by the formation of many little droplets, which don’t come to contact with the wood, and it almost seems like they are repelled by it; why’s that? This phenomenon is given by an ingredient in the formulation, inserted to coat and protect the wood; but what is it exactly?
Waxes are a large family of additives characterized by different chemical natures, but similar physical properties. By the term ‘wax’ a general line of products is identified: it presents long aliphatic chains, or fatty acid esters with a molecular weight between 700 and 10.000u1). Another aspect to take in consideration when talking about waxes is temperature; they are solid at 20° C, their melting point is at least 40° C and once liquid they are characterized by a low viscosity2).
The utilization of these products is wide. Thanks to their diversity and versatility they find use in varnishes, inks, and resins. In these fields, they are classified as surface conditioners thanks to their mechanism of action. In order to obtain significant properties in the formulation, waxes have to migrate to the surface at a sufficient quantity to impart the desired final properties3).
Thanks to the differences in chemical natures, products with different chemical-physical parameters can be obtained, which take on various nuances depending on the format in which they are used. The choice should be taken considering the compatibility with the system and the benefits expected. A water-based wax dispersion, for example, would result easier to incorporate into a water-based system than a solid wax, which would have great difficulty dispersing, being hydrophobic. Another aspect to keep in mind is that waxes also have different particle sizes: this has a particular influence on the final textures and its ease of incorporation into a system. When the active surface of the wax is not sufficient to give certain characteristics, the micronizing process could be of help. This physical process leads to formation of even smaller particles increasing the total active surface area4).
As a consequence, greater homogeneity and improved mechanical properties will be achieved in the formulation, in all fields of application.
Today there is a large variety of waxes, classified according to their origin and chemical nature; the most common ones are the synthetic waxes (polyethylene, polypropylene, Fischer & Tropsch, PTFE, silica coated waxes, amine waxes, etc)5) natural waxes (Carnauba, Candelilla, Beeswax, etc) and lately, a new category is emerging: the biodegradable waxes.
Waxes and microplastics
According to attachment XVII of the regulation (CE) n. 1907/2006, recently modified with the reform (UE) 2023/2055, microplastics are defined as synthetic polymer microparticles that meet the following requirements: they must contain at least 1% by weight of synthetic polymer or create a continuous surface coating on the particles themselves. Additionally, at least 1% by weight of the particles must meet one of the following conditions: all particle sizes must be 5 mm or less, or the length of the particles must be 15 mm or less, and the ratio of particle length to particle diameter must be greater than 36. There are different types of microplastics depending on their origin: primary ones are released into the environment as small particles. Secondary ones, instead, are produced by the degradation of larger plastic products.
Since synthetic waxes of fossil origin fall into the category of microplastics, the most promising alternative is waxes of biological origin. Some companies have already come to market with these technologies, particularly sugarcane-based wax. The production of this wax dates back to 1840, when the American pharmacist Avequin first succeeded in extracting it from “bagasse”, the residue of suga-
rcane processing, resulting in a relatively pure product; thus, with a process of ‘upcycling’7). Today, the sugar market is remarkable, with a raw sugarcane production reaching 1.9 billion tons in 2018, promising a great production potential for this wax, given the high amounts of material that can be destined for recovery8).
Biomere waxes
The waxes under the commercial name of Biomere, produced by Deurex AG, are biodegradable waxes, of synthetic origin and naturally derived origin. Often there is some misconception between this concept and biodegradability: although correlated, they are different. With bio-based we mean the origin from renewable sources of the molecule; while for biodegradability we intend the aptitude of a molecule9) to take part on a series of chemical processes, which lead to an irreversible transformation of the one, becoming innocuous for the environment, by means of bacteria present in nature. Deurex AG has decided to combine these two aspects into a single series of waxes that increasingly aim for biodegradable10) and biobased waxes.
The figure 2 shows the test conducted according to the OECD 3011) standard11 on various Biomere products. The test provides the guidelines and the mandatory conditions in order to evaluate the biodegradability. The graphic obtained shows on the x-axis the time in days, while on the y-axis there’s shown the percentage of material that has biodegraded. Notice that various products have different biodegradability times, and this can be related to the average molecular weight; in fact, the higher the weight, the longer it takes for the chains to break down.
Biodegradability depends on many factors; sometimes, it is possible to ‘program’ molecules to have this property, however, this turns them into a synthetically derived product. Among the Biomers, not all of them are bio-based, as shown in Figure 3.
Each one of these waxes has different chemical and physical properties, among the most important to consider in application we have: chemical resistance, melting point, and color. Let’s consider Biomer 60 and 140, which are at the extremes of Figure 2.
The technical data show that Biomer 60 is a soft, low molecular weight, amber-colored wax. It is an unrefined wax, so his applications range from fertilizers to leather for the textile industry and elastomer coating. Just like all waxes, it will be characterized by strong water repellency, and with low mechanical strength and high elasticity.
Biomer 140, on the other hand, is a high molecular weight and oxidized wax (thus with strong mechanical strength characteristics) its main characteristics are the antiblocking, antistick and antistatic effect. Because of its high temperature resistance, it can be used as a release agent (particularly in dispersion format). Of interest is its ability to act as a matting agent in water-based acrylic systems, providing a commonality with Biomer 60.
From a technical point of view, the two products that are different from each other, both in performance and application. The common attribute of these waxes is their biodegradability, each of them with their own time.
Conclusions
The worlds of coatings, inks, and varnishes are constantly looking for alternative solutions, with a view to future regulations and environmental friendliness. Considering this, a rapid transition is taking place, requiring high-performance products in a short time. Biodegradable waxes are an excellent alternative, as they are comparable in performance to non-biodegradable synthetic waxes but also avoiding the range of problems inherent, contributing to a more sustainable future.
Deurex’ products in Italy are distributed by Eurosyn
References
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10) “What Makes Something Biodegradable?” Chemistry Stack Exchange Accessed May 20, 2024 https:// chemistry.stackexchange.com/questions/19896/ what-makes-something-biodegradable.
11) “Test No. 301: Ready Biodegradability.” OECD iLibrary. Accessed May 20, 2024. https://www.oecd-ilibrary.org/environment/test-no-301-ready-biodegradability_9789264070349-en.
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May 22, 2024
