Key points
- Board 3.3.06 in the headnote: "If a claim is unduly broadened with respect to the scope of the examples used to illustrate a technical effect, particularly when this broadening concerns the feature/s allegedly providing that effect, the burden of proof might shift back to the proprietor to prove that the effect observed in the examples would also be obtained throughout the entire scope of the claims. If no evidence is provided in this respect, a conclusion may have to be drawn on the basis of plausibility arguments"
- The Board in r.2.2.5: "In the absence of specific evidence to address this issue, conclusions might have to be drawn on the basis of plausibility arguments, in particular by assessing whether the effects in the examples can be plausibly extrapolated to other technically reasonable embodiments covered by the claims. In the board's view, this approach is in line with other decisions (e.g. T 2579/11, reason 2.5.1) in which the technical effect of the invention was also determined by a plausibility check of the evidence on file."
- It may be useful to refer to T939/92 AgrEvo which is the landmark case on the issue at hand. See in particular r.2.6.3 of T939/92.
- "Since the relative retention improvement provided by nanocellulose is already very low (1,7%) for dosage 1 of PAM and dosage 1 of nanocellulose/bentonite, the board considers that it is not technically plausible that an improvement in retention would also be observed at significantly lower concentrations of both nanocellulose and PAM. In view of the fact that such embodiments are covered by claim 1 at issue and are not technically unreasonable, it follows that the effect of improving retention would not be plausibly obtained throughout the entire scope of the claims."
- "The board thus concludes that the only effect which would be observed throughout the entire scope of the claims is that of providing a good retention performance (no better than that obtained with other alternatives such as bentonite), so the problem solved by the invention is to propose an alternative process that has a good retention performance."
2. Main request - Inventive Step
The requirements of Article 56 EPC are not complied with for the following reasons:
2.1 Closest prior art
2.1.1 The opposition division concluded that document D10 should be regarded as the closest prior art. The opponents however considered that any one of D1, D2, D4, D7, and D10 represented a valid starting point for the inventive step argumentation. While at the oral proceedings the opponents only relied on documents D1, D2 and D10, for the sake of completeness the board will take all the cited documents into consideration.
2.1.2 Document D1 discloses the use of nanocellulose as additive in paper manufacturing processes. In particular, this document indicates (pages 41 and 42, left and middle columns) that the carboxylic groups in nanocellulose provide anionic sites which counteract excess positive charges from wet cationic polymers used as wet strength agents. The introduction of anionic nanocellulose promotes reactions with the cationic wet strength agent, leading to larger particles, better retention and higher wet strength.
Document D2 discloses (pages 306 and 310-311, figure 8) the sequential addition of PAE (Poly(amideamine) epichlorohydrin) as wet strength agent and nanocellulose to form a bilayer on the fibers, thereby promoting wet and dry strength of the paper web. This improvement is said to be at least partially due to a better retention.
Document D4 discloses (page 22, lines 5-15; claims 134-153) a process for improving at least one of sizing, strength, scale control, drainage, dewatering, retention, clarification, formation, adsorbancy, film formation, membrane formation, and polyelectrolyte complexation of a paper manufacturing process by using nanocellulose. In an embodiment (example 16), the nanocellulose is combined with a cationic polymer.
Document D7 is an article by the same author as D1 concerning the use of nanocellulose as additive in paper manufacturing processes.
Document D10 discloses a papermaking process including a retention system comprising the steps of adding a cationic polymer such as polyacrylamides having a molecular weight above 500000 to the stock (col. 8, lines 40-65) to form flocs, exposing these flocs to shear forces to break them and finally adding bentonite microparticles to form new flocs (col. 7, lines 5-19).
2.1.3 For the board D10 represents the closest prior art, not only because it is the document which would require the least modifications/additions to arrive at the subject-matter of the invention, but also because it is the only cited document which discloses a paper making process with a retention system having the same sequential steps as defined in claim 1 at issue.
By contrast, D1 and D2 make no reference to the formation and breaking-up of the flocs using shearing forces, and while these documents disclose the addition of cationic polymers, these are wet strength additives (e.g. PAE) and not retention aids in the form of polyacrylamides having a molecular weight above 500000 as defined in claim 1. Furthermore, document D1 does not even disclose the sequence of addition of the polymer and the nanocellulose. All these differences appear to relate to the fact that D1 and D2 concern processes to improve wet strength rather than processes including a retention system as defined in claim 1 at issue. In view of the correlated improvement of wet strength and retention in D1 and D2, there seems to be a certain overlap between processes for improving wet strength and retention systems. In particular, both wet strength additives and retention aids promote cross-linking of fibers, which in turn improves the retention of the fibers and additives on the wire as well as the strength of the manufactured paper web. However, while wet strength additives mainly intend to create strong bonds in the final paper web, retention systems are conceived to promote the formation of stable flocs to retain both fibers and additives on the wire while facilitating dewatering. Thus, even though there might be substances which can be used both as wet strength additives and as retention aids, processes for promoting wet strength (e.g. D1 and D2) are not the same as retention systems.
In view of the above, the board considers that a skilled person intending to develop a retention system would not choose a document dealing with processes for improving wet strength, such as D1 or D2, as starting point. Such choice would inevitably be contaminated by hindsight, and would fail from the outset because the modifications required to arrive at the subject-matter of claim 1 would essentially imply transforming a process conceived to promote the wet strength of a paper web into another process intended to maximise retention of additives and fibers on the wire.
Consequently the board concludes that neither D1 nor D2 can be regarded as the closest prior art.
Documents D4 and D7 are also not considered to represent suitable starting points, because D4 is further away from the invention than D2 (there is no disclosure of a sequential addition of the cationic polymer and the nanocellulose), and document D7 is considered to be equivalent to D1.
2.1.4 Document D10 is therefore regarded as the best starting point for assessing the inventive step of the subject-matter of claim 1 at issue, which differs therefrom in that nanocellulose is added in an amount of less than 1% as active substance based on dry solids weight of the stock.
2.2 Technical effect and problem solved
2.2.1 According to the patent in suit (see par. [0014]) the purpose of the invention is to provide an alternative substance acting like a microparticle, which results in an improved retention as compared to mineral microparticles and which is made of renewable material.
To support the alleged technical effect of improving retention the patent discloses three examples comparing processes using different dosages of bentonite (i.e. a mineral microparticle) and nanocellulose.
In particular, Example 1 shows that for equivalent dosages the use of nanocellulose gives rise to a clear improvement with respect to processes using bentonite in first pass retention (table 1) and in first pass ash retention (table 2).
Example 2 demonstrates that the use of nanocellulose also provides an improved (i.e. faster) dewatering (table 3) for all dosages when compared with the use of bentonite.
Finally, the results in Example 3 indicate that the floc stability when using nanocellulose is better than when using bentonite with dosages 1 and 2, yet worse with dosage 3.
2.2.2 The opponents argued that the results shown in said examples were insufficient to conclude that the nanocellulose improved retention with respect to bentonite. Some of the differences were insignificant (e.g. results in table 3, dosage 2) and according to Example 3, at dosage 3 the retention obtained with nanocellulose was worse than that obtained with bentonite (table 4). Furthermore, the additional tests performed during the examination proceedings (see table 1 on page 3 of the letter dated 16 September 2013) gave rise to significantly worse retention values despite being a repetition of the tests in the patent, which demonstrated that the invention did not consistently provide an improvement in terms of retention.
The subject-matter of claim 1 was also defined in very broad terms. In particular, the definition of a process which comprised an amount of less than 1% of nanocellulose effectively encompassed processes with very low amounts of nanocellulose alone or in combination with other microparticles, including bentonite. It was therefore not plausible that such embodiments would provide the technical effect of improving the retention.
The opponents concluded that the alleged technical effect of improving retention with respect to mineral microparticles would not be obtained throughout the entire scope of claim 1, so the only problem solved was to find an alternative process or, at most, an alternative process with good retention performance.
2.2.3 The proprietor argued that the improved retention in the examples was clear and significant. In particular, the retention values obtained with nanocellulose in tables 1 and 2 were not only better than those with bentonite at an equivalent dosage, but comparable or even better than those obtained with bentonite at much higher dosages (e.g. results with dosage 2 of nanocellulose versus those with dosage 3 of bentonite in tables 1 and 2).
The results in Example 3 and table 4 corresponded to turbidity measurements related to flocs and floc stability. These measurements were indirectly related to retention, but had to be read in combination with the more direct estimation of retention in tables 1 and 2, which involved the sampling of the filtrate to measure all the additives and fibers dragged through the wire (i.e. the non-retained portion of the pulp). The combined results indicated that while the flocs and floc stability obtained with bentonite and nanocellulose were comparable (generally better with nanocellulose but slightly worse with dosage 3), the retention as such was clearly better when using nanocellulose microparticles. Thus, the process according to claim 1 provided the effect of improving retention with respect to mineral microparticles, so the problem solved by the invention was to provide a process with an improved retention.
2.2.4 In view of the above arguments, the board agrees with the proprietor that the examples of the patent show a clear improvement in terms of retention when nanocellulose is used instead of bentonite. While in its preliminary opinion the board considered that example 3 (in particular dosage 3 in table 4) appeared to imply that the effect was not reliably obtained, the subsequent explanations of the proprietor are convincing. In particular, the board agrees with its view that example 3 and table 4 do not represent an alternative way to measure retention, but rather an estimation of flocs and floc stability, an aspect which is indirectly related to retention but which does not necessarily provide a direct measurement of the amount of additives retained on the wire. The board also agrees with the proprietor in that the first pass retention results in table 1 represent the most direct way of estimating the retention in the paper making process, because this parameter measures the proportion of additives and fibers retained on the wire. Additionally, the results in table 2 measure the retention of the filler and those in table 3 provide an indication of the dewatering speed.
Since all the above examples appear to be carried out using an identical or very similar stock (i.e. all 3 examples include stock from a fine paper machine with 45% of precipitated calcium carbonate, wherein the stock is diluted to a consistency of 8 g/L and wherein starch is added) as well as the same bentonite and nanocellulose dosages, the board agrees with the proprietor in that they should be read in combination. When the results in table 4 are read in combination with those in tables 1 and 2, it is apparent that while the formation and the stability of the flocs are similar for both bentonite and nanocellulose (i.e. one or the other being slightly better depending on the dosage), the retention as such (overall retention and filler retention) is significantly better when using nanocellulose. The board also notes that the tests submitted during examination (table 1 on page 3 of the letter dated 16 September 2013) were carried out with a different stock, which is apparent from the fact that the retention value when no microparticle is added is significantly lower than that shown in table 1 of the patent. These tests do therefore not question the validity of the examples of the patent. The board also notes that the opponents have not filed any test report to contest the results in the examples of the patent.
In view of the above, the board concludes that the examples of the patent demonstrate that, within certain operating ranges, nanocellulose gives rise to significantly better retention values than bentonite.
However, as explained hereunder, the board agrees with the opponents in that this technical effect would not be obtained throughout the entire scope of claim 1 at issue.
2.2.5 The board considers that if a claim is unduly broadened with respect to the scope of the examples used to illustrate a technical effect, particularly when the feature/s allegedly providing that effect are broadly defined, it might be justified to shift the burden of proof back to the proprietor to demonstrate that the technical effect observed within the narrow scope of the examples would also be obtained throughout the entire scope of the claims. In the absence of specific evidence to address this issue, conclusions might have to be drawn on the basis of plausibility arguments, in particular by assessing whether the effects in the examples can be plausibly extrapolated to other technically reasonable embodiments covered by the claims. In the board's view, this approach is in line with other decisions (e.g. T 2579/11, reason 2.5.1) in which the technical effect of the invention was also determined by a plausibility check of the evidence on file.
2.2.6 According to the opposed patent (par. [0015] and [0016]), the effect of improving retention (with respect to mineral microparticles) results from the addition of nanocellulose and of a cationic polymer to the paper pulp. While the examples of the patent illustrating this technical effect are conducted within narrow concentration ranges for these substances (300-600 g/tonne of PAM and 500-3000 g/tonne of nanocellulose/bentonite), claim 1 at issue defines the addition of nanocellulose in an amount of less than 1% or 10000 g/tonne (i.e. with an open end bottom value) and does not restrict the concentration of cationic polymer. The claimed invention therefore encompasses processes with very low amounts of nanocellulose and a broad range of cationic polymer concentrations. The question therefore arises as to whether the improved retention observed in the examples would also be obtained in some of the embodiments covered by the claims. As no further evidence has been submitted in this respect, the board considers that this question can only be answered by means of a plausibility assessment of the evidence on file.
2.2.7 The board notes that the relative improvement in retention obtained when using nanocellulose instead of bentonite is significantly affected by the concentrations of cationic polymer and nanocellulose. Looking in particular at table 1 of the patent, it can be observed that the relative improvement in retention of nanocellulose versus bentonite with dosage 1 of PAM (300 g/tonne) goes from 7,8% for dosage 2 of nanocellulose/bentonite (1500 g/tonne) to 1,7% for dosage 1 (500 g/tonne), which represents an almost 5-fold reduction of the effect with the lower nanocellulose/bentonite dosage. With dosage 2 of PAM (600 g/tonne) the relative improvement of nanocellulose versus bentonite goes from 9,2% for dosage 2 to 3,6% for dosage 1 (almost 3-fold reduction). While it would be expectable for the retention results to be dosage-dependent in absolute terms (i.e. smaller retention for smaller dosages of nanocellulose or bentonite), the above results indicate that the relative improvement of nanocellulose with respect to bentonite decreases drastically with lower dosages of the microparticle, particularly when lower concentrations of the cationic polymer (PAM) are used. Since the relative retention improvement provided by nanocellulose is already very low (1,7%) for dosage 1 of PAM and dosage 1 of nanocellulose/bentonite, the board considers that it is not technically plausible that an improvement in retention would also be observed at significantly lower concentrations of both nanocellulose and PAM. In view of the fact that such embodiments are covered by claim 1 at issue and are not technically unreasonable, it follows that the effect of improving retention would not be plausibly obtained throughout the entire scope of the claims.
2.2.8 The board thus concludes that the only effect which would be observed throughout the entire scope of the claims is that of providing a good retention performance (no better than that obtained with other alternatives such as bentonite), so the problem solved by the invention is to propose an alternative process that has a good retention performance.
2.3 Obviousness of the solution
2.3.1 The proprietor argued that none of the documents on file suggested the use of nanocellulose as microparticles in a retention system as defined in claim 1. In particular, document D1 proposed using nanocellulose either as a positively charged microparticle or as a negatively charged microparticle only for promoting formation of large particles to improve the filtration effect. Both mechanisms differed from the retention system in D10, in which the microparticles were added after breaking the flocs in order to promote reflocculation of more stable flocs, thereby improving retention without negatively affecting the quality of the resulting paper.
Document D19, on the other hand, did not disclose nanocellulose, but simply referred to microparticles of cellulose-based materials. Such materials were however not necessarily nanocellulose, as they could include other particulate cellulose-based material such as CMC (carboxymethyl cellulose).
2.3.2 The board does not agree with the proprietor's argumentation, because the problem solved by the invention is simply to find an alternative process with good retention performance, which implies that the only relevant question is whether the skilled person would consider using nanocellulose microparticles as a reasonable alternative or complement to the bentonite in document D10. In other words, all which is required to render claim 1 obvious is an indication in the prior art that nanocellulose can be used as an alternative or supplementary microparticle in a retention system as that described in D10.
In this respect, document D1 essentially presents nanocellulose as a recommended additive for the purpose of improving wet strength and retention when an excess of positive charges are present in the stock. While it is true that document D1 does not explicitly refer to a retention system as disclosed in D10 or as defined in claim 1 at issue, it is clear in view of the explanations on page 42, left and middle columns of D1 that the function of the negatively charged nanocellulose in this document is analogous to that of the bentonite in D10. In particular, in both cases a cationic polymer is added to promote the cross-linking of fibers and the anionic nanocellulose is added to promote binding between different portions of this cationic polymer, thereby forming interlinked structures which improve both wet strength and retention.
The fact that nanocellulose is a known alternative to the bentonite in D10 is further supported by document D19, which represents common general knowledge and indicates that certain organic substances such as cellulose based micro- and nanoparticles can be used as an alternative to bentonite microparticles in retention systems as those described in D10. Even if, as the proprietor argued, this cellulose based micro- and nanoparticles were considered to encompass substances different from nanocellulose, a person skilled in the art would readily recognise that this reference also encompasses nanocellulose.
In view of the above argumentation, the board concludes that nanocellulose microparticles represent a known alternative to bentonite in the retention system of document D10. It would thus be obvious for a skilled person to substitute (part of) the bentonite with nanocellulose with a reasonable expectation to obtain good retention performance.
Additionally, in the absence of further guidance, the skilled person would manifestly consider nanocellulose concentrations ranges similar to those proposed in D10 (0,03 to 0,5% of bentonite according to column 10, lines 44-45) or D1 (0,1 to 0,4% of nanocellulose according to the middle column on page 42), all falling within the range of "less than 1%" defined in claim 1 at issue.
The board therefore concludes that the subject-matter of claim 1 at issue is not inventive in view of D10 combined with D1 in the light of the common general knowledge illustrated in D19.
3. Auxiliary request 1 - Sufficiency of disclo
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