Wednesday, March 13, 2024 Our attempt at Paper B 2024 - Biodegradable face mask

Difficult. This would be one word to describe this year's Paper B. Judging from the comments on our ‘first impressions’ blog post, many would still consider it an understatement. 

The difficulty stems at least from the length of the paper.  There were 30 pages and 5400+ words (English version) compared to 21 pages and 4200+ words of the 2023 paper.  The theme was also very chemistry-related. We as non-chemists felt that candidates with specialist knowledge in this domain may have had an advantage in sorting out the patentability situation. Further adding to the difficulty was the fact that there were 11 claims in total including two independent claims (which in itself is not unusual, but adds to the complexity) and some legal issues relating to post filed evidence.

Unusually, the paper does not caution against adding additional dependent claims, which was the norm in recent papers. Is this to be understood as an invitation to add further dependent claims? Probably not, but explicit guidance in the paper would have been helpful. 

Below is our attempt in broad outlines (with in particular the letter not being fully worked out).

Comments are welcome in any official EPO language, not just English. So, comments in German and French are also very welcome!

Please do not post your comments anonymously - it is allowed, but it makes responding more difficult and rather clumsy ("Dear Mr/Mrs/Ms Anonymous of 02-03-2021 22:23"), whereas using your real name or a nickname is more personal, more interesting and makes a more attractive conversation. You do not need to log in or make an account - it is OK to just put your (nick) name at the end of your post.

Edit: changed title from "our solution" to "our attempt" since we found that this year's paper offers limited guidance on identifying the optimal solution among various alternatives (including those which are mentioned in the comments to this and the 'impressions' blog post).

Nico, Sander

Claims

1. Biodegradable disposable respiratory face mask comprising at least one filter layer
comprising cellulose fibres, wherein the cellulose fibres are  made of individually loosened native cellulose nanofibres.

Support: Combination of claims 1 and 3 as filed, which is further limited by:

• "individually loosened”: supported by [042] 1^st sentence, [048]
• “native”: supported by [022], [023], [024], [041], [042], …

Novelty/inventive step:

• Distinguishing feature over  D1: “individually loosened”, technical effect/advantage high filtration capacity, [036], with enhanced mechanical properties, in particular air permeability [037], client’s letter 2^nd paragraph.
• Distinguishing feature over D2: “native”, technical effect/advantage: green/biodegradable [043], [055], client’s letter 3^rd paragraph.

Remarks:

• Why the limitation to “individually loosened”? According to [041], ordinary cellulose already consists of cellulose nanofibres, but in bonded form. Thus, it appears that D1’s face mask is also made of native cellulose nanofibres (but not made of individually loosened ones).
• Why not "a pore size in the range of ..." as limitation? The application as filed defines it as a "challenge" to provide such fibres, cf. [036], while it appears from [042] and [048]-[050] that the 'solution' to this challenge is the nanofibres being "individually loosened". In other words, we considered the pore size as a potential 'result to be achieved' with the 'individual loosened' being the underlying technical feature that achieves this result.
• Note that “biodegradable” alone does not distinguish over D2, since D2 is also biodegradable (cf. D3, Examiner’s communication point 3), but to a lesser degree.
• Perhaps “single” instead of “individually loosened” could be an alternative formulation for “individually loosened”, supported by [041] and [048].
• Does "made of" exclude the nanofibres being coated with gelatin? We're unsure, but choose to maintain this wording (instead of "comprising" as mentioned in [022]) for the mere reason that this wording is already used in originally claim 3 and, most importantly, the proposed claim 1 of the client.
• Why not specify that the nanofibres have a “cellulose-I crystal structure”? According to [042] and [048], this is the “native” crystal structure and thus inherent to “native cellulose nanofibres”. As such, the crystal structure limitation is already implicitly present in “native cellulose nanofibres”. Adding the feature would not further change the scope. 
• Why not limited to “FFP2”. See client’s letter page 2, “We therefore need to have our invention solidly protected by the patent to stop competitors from selling similar products, such as FFP2 face masks comprising nanofilter layers made using other plant fibres”. The client thus wishes broader protection than only FFP2 masks.

2. The biodegradable disposable respiratory face mask according to claim 1 wherein the
cellulose fibres are derived from cotton or hemp.

[[3. The biodegradable disposable respiratory face mask according to any one of claims 1
or 2 wherein the at least one filter layer is made of cellulose nanofibres.]]

3[[4]]. The biodegradable disposable respiratory face mask according to claim 1[[3]] wherein the
cellulose nanofibres are derived from papermaking waste residues which comprises at least 1% (in weight) of cellulose fibres.

Support:

• [045]: “As a by-product of that method of papermaking, waste residues comprising at least 1% (in weight) of cellulose fibres are generated”

 

4[[5]]. The biodegradable disposable respiratory face mask according to any one of claims 1
to 3[[4]] which is a surgical face mask or a dust face mask.

5[[6]]. The biodegradable disposable respiratory face mask according to claim 4[[5]] which is an
FFP2-type face mask.

6[[7]]. The biodegradable disposable respiratory face mask according to claim 5[[6]] wherein the
FFP2 face mask comprises a multilayer structure with at least three layers comprising at
least one outer layer (A) with a thickness of about 40 μm acting as a water barrier; at
least one inner (middle) layer (B) with a thickness of about 8 μm acting as a filter layer;
and at least another outer layer (A’) with a thickness of about 40 μm for contact with the
skin.

Remarks:

• Claim 6 refers anew to “a” filter layer instead of referring to “the” filter layer of claims 1-5. However, the Examiner did not raise a clarity objection and we therefore refrained from further clarifying the claim.

7[[8]]. The biodegradable disposable respiratory face mask according to claim 6[[7]] wherein the
FFP2 face mask comprises five layers comprising the outer layers (A and A’) and further
comprising two inner (middle) layers (B and B’), acting as filter layers, separated by a
hydrophilic separation layer (C).

8[[9]]. The biodegradable disposable respiratory face mask according to any one of claims 6[[7]]
or 7[[8]] wherein at least one layer is manufactured by conventional techniques for making
nonwoven fabrics such as melt-blowing or spunbonding.

9[[10]]. The biodegradable disposable respiratory face mask according to any one of claims
6[[7]] to 8[[9]] wherein the outer layers (A and A’) are made of nonwoven cotton or hemp fabric.

10[[11]]. Process for manufacturing a biodegradable filter layer for a multilayer FFP2-type
face mask, the process comprising: providing papermaking waste residues which comprise at least 1% (in weight) of cellulose fibres, milling using grinding balls, and casting into a thin nonwoven layer by melt-blowing or spunbonding.

Support:

• [045]: “As a by-product of that method of papermaking, waste residues comprising at least 1% (in weight) of cellulose fibres are generated”

Remarks:

• Why not add “gelatin”? According to [046], “in our method of paper making, gelatin is admixed…” which suggests that that other papermaking waste residues may not need to comprise gelatin. In addition, the technical effect of being able to generate native cellulose nanofibres in a simple manner and without any need of chemical treatment seems to be independent of the gelatin, cf. [048].

 

Patentability of claim 1

Note: the following is a broad outline of the argumentation, but not fully worked out.

Novelty

Claim 1 is novel over D1 since the cellulose nanofibres in D1 are bonded and not “individually loosened”.

Claim 1 is novel over D2 since the cellulose nanofibres in D2 are synthetic polymer fibres and not “native” cellulose nanofibres.

Claim 1 is novel over D3 for at least the reason that it does not disclose a face mask.

Inventive step

D2 may be considered as the closest prior art since it relates to a face mask made of cellulose nanofibres providing protection against aerosols (nanoparticles smaller than 1μm, cf. [035]). D1 does not address aerosols, while D3 does not even concern face masks.

The distinguishing feature of claim 1 over D2 is that the face mask is made of native cellulose nanofibres.

The technical effect of the distinguishing feature is that the face mask is highly biodegradable, cf. [055] which states that the nanofilter layer disintegrates completely within 30 days, whereas according to D3 [004], D2’s cellulose acetate nanofibre layer can take years to completely biodegrade.

The objective technical problem may be formulated as how to obtain a more biodegradable face mask.

D2 does not contain any hint or suggestion towards biodegradability.

D1 does disclose a completely compostable face mask. However, in view of the disclosure of D1, the skilled person would replace D2’s cellulose acetate nanofibre layer by D1’s layer of 100% organic filtering felt made of compacted cellulose fibres. This combination, however, would not lead to a solution falling within the scope of claim 1 since D1’s layer does not comprise “individually loosened” cellulose nanofibres.

D3 merely confirms that D2 is insufficiently biodegradable and does not contain any teaching towards improving the biodegradability.

Remarks on the patentability of claim 10

D2 also makes sense as CPA since it discloses a process of making cellulose nanofibres (albeit a chemical process which makes synthetic and not native polymer nanofibres).

D1 and D3 do not seem to lead to a solution falling within the scope of claim 1 as they are entirely silent on manufacturing processes.

Significance of the additional laboratory experiments and D4:

The  additional laboratory experiments and D4 represent 'post-filed evidence' which together demonstrate that the use of individually loosened native cellulose nanofibres not only achieves a much better biodegradability, but also better breathing comfort.

This technical effect is already implied by ('encompassed by') the application as originally filed (cf. [042] which states that the cellulose nanofibres of D2 have poorer mechanical properties, which according to [037] relate to the breathing comfort, or cf. [056] which also compares to commercially available FFP2 masks made from synthetic polymers).

As such, it is likely that the additional laboratory experiments and D4 as reference for the used test methods would be allowable under the 'free evaluation of evidence' principle, GL G-VII, 11. This is recently confirmed by G 2/21.

However, the laboratory experiments relate to FFP2 masks, while claim 1 is broader than that. One can normally not rely on experiments pertaining to a specific embodiment to demonstrate inventive step over a much broader claimed range. On the other hand, if the advantage of better breathability is obtained in a FFP2 mask, it stands to reason that similar improvements are obtained in other types of face masks compared to synthetic polymer nanofibres. It therefore would make sense to also include the laboratory experiments and reference to D4 in the response letter to the EPO as further demonstration of the improvements obtained over D2 (for example, as part of the problem solution approach using the “improved breathing comfort” as an additional technical effect, or perhaps as a separate section in the letter).

On balance, although not directly relevant for claim 1, we would file the new experimental results together with document D4 together with our letter.