What inventors should consider when drafting patent applications for alternatives to single-use plastics – part two

Part one of this article (see here) discussed alternatives to single-use plastics and offered advice for inventors of such materials. Part two elaborates on specific types of plastic and the IP rights surrounding the sustainable materials sector.

A notable and recent advance in sustainable polymer technology is – poly(diketonenamine) (PDK). While not a biopolymer per se, PDK is a new material capable of reversible polymerisation, giving it the potential to provide a plastic with minimal environmental impact. Researchers at Berkeley Lab discovered that PDK can be depolymerised to its monomers with the simple addition of an acid and then easily separated from the other chemical additives to improve material properties (eg, flexibility), among others.

The discovery allows for the recovery of the monomers from PDK, which can then be remanufactured into the same, or other, polymer compositions without loss of performance. This represents a significant advance from traditional plastics recycling, where the materials are normally ‘downcycled’ (ie, made into products of inferior quality). The material, termed a ‘circular plastic’, has the potential to improve the efficiency of plastic recycling and ultimately provide ‘closed loop’ plastic recycling, where the same material can theoretically be remade an infinite number of times. More research into how to tweak the properties of PDKs to make them suitable in consumables such as textiles and foams is now on the cards.

However, there are still some significant challenges for PDK. The material req­­uires processing to be depolymerised diverted from landfills and oceans, and this requires energy. Further, it will be challenging to scale up the depolymerisation process to the size required should PDK become a commodity material. It is desirable that the PDK monomers are bio-derived to ensure that PDK is not another petrochemically derived plastic material.

What about intellectual property?

From an IP perspective, while new bioplastic materials may be readily patentable, it may prove more challenging to obtain protection for improvements to existing materials and processes. While such improvements are essential for obtaining materials with the improved properties and reduced cost required to facilitate effective market penetration, the fact that many of the most promising replacement bioplastics have been known for decades means that the prior art landscape could be quite congested.

Innovators will need to consider the new features of their material or process and the improvements that they provide. For example, if two known bioplastics are blended together, does this blend have properties that are unexpectedly improved relative to the properties of the individual materials? For bioplastics, this will often involve its material properties, in which case the invention may need to be defined using a parameter such as molecular weight, viscosity, modulus or particle size.

When claiming a material using a parameter, it is important that this is clearly defined in the patent application, especially when its particular value distinguishes the invention. Typically, this is achieved through the inclusion of the specific method of measurement in the description. Defining this method is particularly important when there is more than one method of measuring the parameter, as different methods could lead to different values and therefore result in ambiguity in what is actually being claimed.

For example, a bioplastic may be defined in terms of its molecular weight. However, the molecular weight parameter has multiple variants (eg, number or weight average) and can be determined using different methods, for example, gel permeation chromatography, dynamic light scattering and viscosity.

In order for such a parameter to be clearly defined, all of this relevant information needs to be included in the application at the time of filing. In the absence of such a definition, a patent examiner may raise a clarity objection to a claim including an ill-defined parameter during examination. Depending on whether the invention can be defined in alternative ways, such an objection may prevent the application from proceeding to grant. Further, opponents can attack parameters in opposition proceedings at the EPO by arguing that, in the absence of a defined measurement method, the application does not sufficiently disclose the invention and cannot be worked. While there may be options for responding to such clarity and sufficiency objections, the best option is to avoid any potential objections by defining any parameters with a specific measurement method.

In summary, there is no one single solution to the plastics problem. While replacement materials may be more environmentally benign both to produce and at their end of life, the success of such replacements may rely on significant investment in both infrastructure and education. Innovators looking to patent bioplastics will need to carefully consider the new features of their inventions and the improvements that these features provide, in addition to being sure that any parameters included in their claims are clearly defined.