T 0460/13 25-03-2015

1. The opponent's appeal is admissible.

Main request

2. The main request is identical to auxiliary request 1 found allowable by the opposition division (see point IV above). Claim 1 of this request refers to a low noise adhesive product comprising an adhesive layer formed by the drying of an emulsion polymer on a polyolefin film; wherein the emulsion polymer comprises:

(a) a fine mode comprising 5-95% by weight, based on a total weight of polymer, of first particles having a weight average diameter of less than or equal to 250 nanometers; and

(b) a large mode comprising at least 5% by weight, based on a total weight of polymer, second particles having a weight average diameter of greater than 250 nanometers; and

further wherein the overall Tg of the emulsion polymer is less than -20°C and the emulsion polymer does not comprise one or more aziridines; and

further wherein the emulsion polymer is (i) an acrylic dispersion containing from 1 to 2.5% by weight of (meth)acrylic acid units and 99 to 97.5% by weight of n-butyl acrylate or 2-ethylhexyl acrylate units or any combination thereof, or (ii) is an acrylic dispersion containing 80-90% by weight of 2-ethylhexyl acrylate units and from 8 to 20% by weight of n-butyl acrylate units.

3. Amendments - Articles 84 and 123(2) EPC

3.1 The opponent argued that the further limitation in claim 1 by means of the two alternatives (i) and (ii) introduced a lack of clarity. The wording "the emulsion polymer is" in this limitation implied that the emulsion polymer consisted of the monomer units cited in this claim, which was in contradiction to the fact that the amounts of monomers for alternative (ii) of claim 1 (80-90% by weight of 2-ethylhexyl acrylate units and from 8 to 20% by weight of n-butyl acrylate units) did not add up to 100% such that further monomer units had to be present.

However, the wording quoted by the opponent is incomplete. The relevant wording in claim 1 in total reads "the emulsion polymer is (i) an acrylic dispersion containing ..., or (ii) is an acrylic dispersion containing 80-90% by weight of 2-ethylhexyl acrylate units and from 8 to 20% by weight of n-butyl acrylate units". It is thus not true that according to claim 1 the emulsion polymer consists of the monomer units cited in this claim. In fact, what the claim requires is that the emulsion polymer is, i.e. consists of, an acrylic dispersion and that the dispersion contains, i.e. comprises, 2-ethylhexyl acrylate units and n-butyl acrylate units. There is thus no contraction between the closed language "the emulsion polymer is" and the fact that the percentages of monomer units do not add up to 100%.

3.2 The opponent argued that the requirement in claim 1 that the emulsion polymer was a dispersion did not make sense since the term "emulsion polymer" implied the polymer as such while a dispersion contained a liquid phase apart from the polymer. Also for this reason claim 1 was unclear.

The board acknowledges that from an academic point of view an emulsion polymer is the polymer as such (obtained by emulsion polymerisation) while a dispersion contains a solid phase (i.e. the polymer) together with a liquid phase. However, in the first two lines of claim 1, the claim refers to "the drying of an emulsion polymer". Furthermore, claim 7 requires the solids-content of the emulsion polymer to be greater than 56 weight percent. Both the fact that the emulsion polymer is dried according to claim 1 and the fact that claim 7 refers to a solids-content well below 100% can only mean that, in terms of the opposed patent, the "emulsion polymer" refers to the polymer when in emulsion or dispersion, i.e. together with a liquid phase. In terms of the opposed patent, the requirement in claim 1 that the emulsion polymer is a dispersion therefore does make sense such that claim 1 is not unclear in this respect.

3.3 The opponent also argued that the monomer composition defined in claim 1 differed from that disclosed on page 11, lines 9 to 14 of the application as filed in that the monomer amounts were given as "% by weight" in claim 1 rather than "%" as was the case on page 11 of the application as filed. Claim 1 did therefore not meet the requirements of Article 123(2) EPC.

The board does not agree. The first sentence of the first full paragraph on page 11 (lines 7 to 8) states that

"The acid monomer content in the present invention ranges from upper limit of 5, 3, and 2.5% by weight to 0.25, 0.5, and 1% by weight" (emphasis added by the board).

Then the text goes on (page 11, lines 8 to 14):

"An example of acid monomer is (meth)acrylic acid. In one example, acrylic dispersions containing from 1 to 2.5% of (meth)acrylic acid units and 99.5 to 90%, with particular preference 99 to 97.5%, of n-butyl acrylate or 2-ethylhexyl acrylate units are used and any combination thereof. Another example of acrylic dispersions of the invention are acrylic dispersions containing 80-90% of 2-ethylhexyl acrylate units and from 8 to 20% of n-butyl acrylate units."

The skilled person would immediately understand that the amounts indicated in lines 9 to 14 in "%" have to be read in the context of the first sentence, where the amount is given in % by weight, and which sets the framework for the whole paragraph. Therefore, lines 9 to 14 in combination with lines 7 and 8 provide a basis for the monomer composition defined in claim 1 including the requirement that the percentages are weight percentages. The monomer composition as defined in claim 1 therefore meets the requirements of Article 123(2) EPC.

4. Sufficiency

4.1 The opponent raised an insufficiency objection as regards the requirement that the adhesive product of claim 1 had to be a "low noise" adhesive product.

The patent specifies in paragraph [0035] the feature "low noise" to mean a decibel level under 100 dB when unwinding the adhesive product at 60 m/min. According to the patent (paragraph [0035]), this decibel level is to be determined as follows:

"Rolls of tape are prepared and then aged for 1 week at 50°C. The tapes are removed from the oven and then equilibrated in an environmental room which is set at 23°C and 50% relative humidity. After at least 24 hours equilibration, noise was then measured under these conditions by placing standard commercial sound level meter from Bruel & Kjear (type 2226) 8 cm from the tape as it was being unwound."

4.1.1 The opponent argued that the distance between the sound-level meter and the tape of 8 cm as specified in the patent was unclear. The opponent in this respect referred to D19 in which six different positions of the sound level meter are shown, all meeting the requirement of being positioned 8 cm from the tape (positions 2 to 7 in the figure on page 4 of D19). According to the opponent, depending on the position chosen, different sound levels were measured so that it was not clear what "low noise" in claim 1 meant. Therefore, the claimed subject-matter was insufficiently disclosed.

The board acknowledges that the definition "8 cm from the tape" in paragraph [0035] of the patent leaves the skilled reader with some freedom as to the specific position of the sound level meter. The board furthermore agrees with the opponent that D19 shows that for different positions, but all meeting the requirement of being spaced 8 cm from the adhesive tape, different noise levels are obtained. However, the variation in the noise level ranges only from 95 to 103 dB (table on page 3 of D19). Such a variation, if not within the experimental error range, at most implies an ambiguity at the edge of claim 1. For an insufficiency arising out of ambiguity it is, however, not enough to show that an ambiguity exists at the edges of the claims (T 608/07, point 2.5.2). In the absence of any evidence that the ambiguity is such that it leads to insufficiency of disclosure, the opponent's argument must therefore fail.

The opponent argued in this respect that according to decision T 1404/05 a vaguely formulated claim led to insufficiency of disclosure and that in the light of this decision, sufficiency had to be denied in the present case as well.

The board acknowledges that the case underlying T 1404/05 is comparable to the present one in so far as also in that case an ambiguity was present in claim 1. However, in that case it was undisputed that due to this ambiguity, the claim covered embodiments that could not be put into practice (see in particular point 3.4 of the decision). It was for this reason that the board decided in that case to deny sufficiency of disclosure. This is different from the present case where it has not been argued, let alone been proved, that due to the alleged ambiguity of the feature "low noise", the claim covers embodiments that cannot be carried out.

4.1.2 The opponent argued that the specification of the measurement method in paragraph [0035] of the patent left it open which frequency scales had to be used during the measurement so that also for this reason the feature "low noise" was unclear, leading to insufficiency.

This is however not correct since for the sound-meter "Bruel&Kjear 2226" specified in paragraph [0035] of the patent, frequency scale A has to be used (entry "2226" in the table on the bottom of page 2 of D18). There is thus no uncertainty as regards the frequency scale and, linked thereto, the feature "low noise".

4.1.3 The opponent argued that the conditioning of the adhesive product prior to the measurement of the noise level as specified in paragraph [0035] of the patent was different from that described in paragraph [0038], that the measured noise levels depended on the type of conditioning, and that also for this reason, the feature "low noise" in claim 1 was unclear.

The opponent's argument is however of no relevance since the definition of the feature "low noise" is given only in paragraph [0035]. Hence, the skilled person, having to decide on whether an adhesive tape satisfies the requirement "low noise" of claim 1, would apply the conditioning as specified in this paragraph rather than that of paragraph [0038].

4.1.4 The opponent finally argued that the noise level depended on the pH during the preparation of the emulsion polymer and the type of corona treatment of the film onto which the emulsion polymer was applied.

The board does not see how this argument can lead to insufficiency of disclosure as regards the feature "low noise". The preparation of the emulsion polymer and the corona treatment are not part of the measurement of the noise level but are steps during the preparation of the adhesive product. Therefore, even though it is true that the way the emulsion polymer is prepared and treated has an impact on the noise level, this does not imply that the noise level is unclear. There is thus no ambiguity, let alone insufficiency in this respect.

4.1.5 For the above reasons, the feature "low noise adhesive product" in claim 1 does not lead to any insufficiency of disclosure.

4.2 The opponent's second insufficiency attack related to the weight percentages of the fine and large modes of the emulsion polymer used to prepare the adhesive product of claim 1. The opponent in particular argued that for a fine and large mode with similar particle sizes, the weight percentages of these modes could not be determined.

However, in the same way as for the feature "low noise adhesive product" (point 3.1.1 above), this at most implies that there is an ambiguity at the edge of claim 1, namely for embodiments where the fine and large modes have similar particle sizes around 250 nm. The opponent has however not shown that this ambiguity is such that it leads to insufficiency of disclosure.

4.3 The opponent's third insufficiency attack related to the particle size distribution in the claimed adhesive product.

According to the patent (claim 6), the claimed adhesive product is prepared by coating the surface of a polyolefin film with the emulsion polymer comprising the fine and large modes. The opponent argued that after drying at high temperature and/or after a longer time period, i.e. for older adhesive products, the particle size distributions of the fine and large modes of the emulsion polymer initially used changed or even disappeared. Hence, the particle size distribution in the adhesive product, if present at all, would be different from the particle size distributions present in the fine and large modes of the emulsion polymer used to prepare the adhesive product.

However, claim 1 merely requires that the low noise adhesive product is formed by drying of an emulsion comprising two different modes of particles. In other words the mode requirement concerns the starting material and not the final product. The board accepts that such a product-by-process feature leads to a broad claim. The broadness of a claim does not however mean that the invention defined by this claim is insufficiently disclosed.

Apart from that, the proprietor even contested that the particle size distributions of the emulsion polymer used to prepare the adhesive product would no longer be visible in the final product and provided evidence in this respect.

4.4 Therefore, the ground under Article 100(b) EPC does not prejudice the maintenance of the patent in the form of the main request.

5. Admissibility of the public prior use attack Mac

5.1 According to the statement of grounds of appeal, the public prior use Mac Autoadesivi s.r.l. ("Mac") destroys the novelty of the claimed subject-matter.

5.2 The proprietor requested that this public prior use attack not be admitted into the proceedings because no documentation or proof of any kind had been submitted during the opposition proceedings as regards the alleged Mac public prior use. In fact, this objection had been made for the first time during the appeal proceedings.

It is established case law (see, e.g., decision T 328/87) that in order to substantiate a public prior use, information must be provided as to what was made available, when it was made available, where it was made available, by whom it was made available and,

finally, how it was made available.

The public prior use Mac was mentioned in the notice of opposition under the heading "8.3. Weitere offenkundige Vorbenutzungen" on the penultimate page, together with the following information:

Delivery date: 24 March 2005

Client name: MAC AUTOADESIVI srl

Article: PLEXTOL X 4500 CA.57.

This information does not address at all the questions "what, when, where and how", needed for the substantiation of a public prior use. At no point during the opposition proceedings did the opponent provide any such substantiation and, accordingly, this public prior use was not dealt with in the decision of the opposition division at all.

Therefore, the attack on the basis of the public prior use Mac in the statement of grounds of appeal constituted a new attack, made for the first time in the appeal proceedings.

5.3 The essential nature of appeal proceedings is to determine whether the decision reached by the department of first instance was correct (G 9/91, point 18; G 4/93, point 5; G 1/99, point 6.1). Appeal proceedings are not a means of continuing the first instance proceedings whereby a party is free to improve or repair holes in its case by filing additional material. In this respect, it lies within the discretion of the board to hold inadmissible evidence which could have been presented in the first instance proceedings.

As set out above, the alleged public prior use Mac was mentioned in the opposition proceedings but not pursued by the opponent: it is not even mentioned in the decision of the opposition division. It is not acceptable to substantiate the alleged public prior use Mac for the first time with new evidence in the appeal proceedings, i.e. the numerous documents submitted under the heading "Supplementary evidence relating to prior use Mac" (point VII above). The board therefore saw no reason to admit new evidence relating to the alleged public prior use Mac and the novelty attack associated therewith into the proceedings.

5.4 The present board is aware that in exceptional cases, a new novelty objection based on a new document in appeal proceedings has been admitted on the ground that it was prima facie relevant (see, e.g., T 2542/10, point 2.2.2). However, in the present case, all that is contained in the statement of grounds of appeal with regard to the alleged public prior use Mac is a reference to tables A02a and A02b, without further explanation. Table A02b, which deals with four public prior uses relating to Mac, namely Mac-1, Mac-2, Mac-3 and Mac-4, does not contain any information as regards, e.g., the questions of when, where, by whom and how the adhesive tape mentioned in this table ("avana" (M17) and "transparent" (M18)) had been rendered accessible to the public before the priority date of the patent. Consequently, the alleged public prior use attack Mac is not prima facie relevant.

5.5 In the exercise of its discretion under Article 12(4) RPBA, the board therefore decided not to admit the alleged public prior use attack Mac into the proceedings.

6. Admissibility of the further public prior use attacks

6.1 The statement of grounds of appeal relied on three further public prior use attacks, namely:

- the alleged public prior use of the product Acronal**(TM) DS 3547X from BASF, which was handed over to PolymerLatex (see S05), hereinafter referred to as the public prior use "BASF";

- the alleged public prior use based on the delivery of the product Plextol**(TM) X4365 to Straptech, hereinafter referred to as the public prior use "Straptech"; and

- the alleged public prior use based on the delivery of the product Plextol**(TM) D260 to Fabo, hereinafter referred to as the public prior use "Fabo".

6.2 The opponent no longer relied on the alleged public prior use BASF in relation to its novelty and inventive step attacks as regards the main request. Consequently, the admissibility of this public prior use needs not to be dealt with in the present decision.

6.3 The public prior use: Straptech

6.3.1 Unlike the public prior use Mac, this public prior use was to at least some extent discussed in the notice of opposition and was dealt with in the decision of the opposition division. Hence, the above considerations made with regard to the public prior use Mac do not necessarily lead to the conclusion that the public prior uses Straptech is inadmissible.

6.3.2 As set out above when discussing the public prior use Mac, appeal proceedings aim at contesting a decision. This implies that reasons must be given in the statement of grounds of appeal why the decision under appeal should be reversed, amended or upheld (Rule 99(2) EPC and Article 12(2) RPBA). The submissions in the statement of grounds of appeal must be such as to enable the board (and any other party) to understand immediately why the decision is alleged to be incorrect, without first having to make investigations on their own (T 2532/11, points 2.2.1 and 2.2.5 and decisions cited therein: T 220/83, OJ EPO 1986, 249, headnote; T 213/85, OJ EPO 1987, 482, points 2 and 3; T 145/88, OJ EPO 1991, 251, headnote; T 169/89, points 2 and 3 and T 1581/08, point 3). Even assuming that laborious sequences of exercises would tell the reader what the appellant's case against the decision might be, such conjecture is exactly what the statement of appeal is designed to prevent (T 2532/11, point 2.5.1). It cannot be expected that a board fills in the missing links of the chain of reasoning of an appellant and thereby establishes a coherent and complete chain of argument for the appellant, no matter how straightforward it may seem in light of the particulars of the specific case (T 922/05, point 16).

6.3.3 Turning back to the present case, the opposition division decided that the subject-matter of claims 1 and 6 was novel over the public prior use Straptech.

This decision was based on two grounds, the first being that it was doubtful whether the allegedly prior used product, namely the batch sold to Straptech, had been prepared with the recipe given in S12c, which the opponent had relied upon as regards the composition of the allegedly prior used batch. The opposition division's second ground was that the monomer composition of the product disclosed in S12c was unknown due to the fact that several data in S12c were blackened, while others were coded with acronyms (such as NAPS) without definition of their meanings, and at least one line had been deleted at the bottom of the table in S12c, thereby creating doubt as to the presence or not of other constituent(s). S12c did thus not constitute evidence that the allegedly public prior used product did not contain aziridines.

As observed in the board's preliminary opinion, it is not clear how the opponent's submissions in the statement of grounds of appeal relate to the objections raised by the opposition division in its decision, in particular as regards S12c and the absence of aziridines. In fact, the only submission present in this respect in the statement of grounds of appeal is that F20 shows that no nitrogen compounds are detectable and thus aziridines are not present. However, F20 does not contain any reference to the recipe of S12c and thus does not address at all the opposition division's objections as regards this recipe. The opponent's submissions in the statement of grounds of appeal therefore do not put the board in a position to understand why the opposition division's decision on the public prior use Straptech were wrong in the opponent's view.

In response to the board's preliminary opinion, the opponent argued that the proprietor had brought forward its arguments concerning the public prior uses only during the oral proceedings before the opposition division and had submitted new auxiliary requests at the last moment during opposition proceedings. Therefore the opponent should be allowed to file further evidence with the statement of grounds of appeal in reaction to the proprietor's arguments and auxiliary requests.

The board acknowledges that indeed the statement of grounds of appeal would have been the appropriate point in time to react to the proprietor's claim requests. However, as set out above, in fact the opponent did not properly react and did not submit a substantiated attack on the basis of the alleged public prior use Straptech when filing the statement of grounds of appeal.

In the absence of any further submission of the opponent during the oral proceedings, the board did not see any reason to diverge from its preliminary opinion and decided not to admit the public prior use Straptech into the proceedings.

6.4 The public prior use: Fabo

6.4.1 In the same way as for the Straptech public prior use, it needs to be examined whether the statement of grounds of appeal puts the board and the proprietor in a position to understand why the opposition division's decision was said to be wrong. In this respect, the opponent argued during the oral proceedings that document F23 referred to in the statement of grounds of appeal disclosed the composition of the allegedly prior used batch of the product Plextol**(TM) D260 and provided evidence that this product did not contain aziridines. F23 indeed refers to an analysis of the product Plextol**(TM) D260 isolated from an allegedly prior used adhesive tape. It shows the monomer composition of this product and states that the nitrogen amount and the analytical results gave no indication that aziridines were present. The board therefore accepted the opponent's argument and admitted the allegation of a public prior use in relation to Fabo into the proceedings.

6.4.2 Incidentally, it is noted that F23 refers only to an adhesive tape containing Plextol**(TM) D260 and does not give any information about a tape with the product Plextol**(TM )X4365 having been the object of the alleged public prior use Straptech. This is why the board admitted the alleged public prior use Fabo but not Straptech.

7. Novelty

7.1 The opponent declared during the oral proceedings that it no longer made any novelty attack on the basis of the only public prior use admitted into the proceedings, i.e. the Fabo public prior use. Furthermore, the opponent accepted during the oral proceedings that the claimed subject-matter was novel over the cited written prior art.

7.2 In the absence of any novelty attack or any reason for not acknowledging novelty, the board accepts that the claimed subject-matter is novel.

8. Inventive step

8.1 Inventive step on the basis of the alleged public prior use Fabo

8.1.1 During the oral proceedings, the opponent argued that the subject-matter of claim 1 was not inventive in view of the public prior use Fabo as the closest prior art. The proprietor requested that this attack be not admitted into the proceedings.

As stated above, the allegation of a public prior use in relation to Fabo was admitted into the proceedings. The next issue would have ordinarily been whether the alleged Fabo prior use was in fact established. However, in view of the proprietor's request not to admit the new inventive step attack based on this public prior use into the proceedings, it appeared to be more economical to the board to decide first on whether such an attack should be admitted.

8.1.2 The only indication in the statement of grounds of appeal as regards the relevance of the public prior use Fabo for inventive step is the following:

"Aufgrund der geringen Abweichungen in der Monomerkonzentration, ist gegenüber den neugefassten Ansprüchen 1 und 6 zumindest keine erfinderische Tätigkeit gegeben."

The newly drafted claims 1 and 6 ("neugefasste Ansprüche 1 und 6") referred to in this statement can only be those of auxiliary request 1 found allowable by the opposition division, which request is identical to the present main request. The reference to small variations in the monomer concentration ("geringe Abweichungen in der Monomerkonzentration") can, in the opponent's favour, be interpreted to mean that the monomer concentration in claims 1 and 6 of this request is a distinguishing feature over the public prior use Fabo. However, the opponent's statement in the grounds of appeal does not permit any conclusion to be drawn as regards why the alleged public prior use Fabo constitutes the closest prior art, whether and if so what effect is obtained by the distinguishing feature and whether the claimed solution is obvious. The statement of grounds of appeal therefore does not put the board or the proprietor in a position to understand why in the opponent's view the claimed subject-matter lacks inventive step in view of the alleged public prior use Fabo.

Also during the further written proceedings, the opponent did not raise any inventive step attack on the basis of the alleged public prior use Fabo, not even after the board had observed in its preliminary opinion that D4 was considered to be the closest prior art.

The inventive step attack on the basis of the public prior use has thus effectively been made for the first time during the oral proceedings before the board.

This inventive step attack raises complex new issues, being precisely those issues which the statement of grounds of appeal was silent about, in particular why the alleged public prior use Fabo constitutes the closest prior art, whether and if so what effect is obtained by the distinguishing feature and whether the claimed solution is obvious. There would have been no possibility for the proprietor to react to this attack during the oral proceedings. It would have been, e.g., not possible to carry out experimental tests to study whether the difference identified by the opponent resulted in any effect. Consequently, neither the board nor the proprietor could be expected to deal with this attack at the oral proceedings without an adjournment.

The opponent argued that the proprietor had submitted its auxiliary request very late during the opposition proceedings such that the inventive step objection in the statement of grounds of appeal was a timely reaction to this claim request. The board acknowledges that indeed the statement of grounds of appeal would have been the appropriate point in time to react to the proprietor's claim request. However, as set out above, in fact the opponent did not properly react and did not submit a substantiated attack against this claim request on the basis of the alleged public prior use Fabo when filing the statement of grounds of appeal.

Therefore, the opponent's inventive step attack on the basis of the alleged public prior use Fabo was not admitted by the board under Article 13(1) and (3) RPBA.

8.2 Inventive step on the basis of D4

8.2.1 The invention underlying the opposed patent relates to a low noise adhesive product, more specifically, a low noise tape containing an adhesive coating of a bimodal emulsion polymer and a process for making such a product (page 2, lines 3 to 5 and claims 1 and 6). The invention in particular addresses the problem of noisy unwind (page 2, lines 13 to 15).

8.2.2 In the same way, D4 refers to adhesive tapes and addresses the problem of noisy unwind (page 2, lines 3 to 4 and 41). Therefore, the board considers D4 to represent the closest prior art.

D4 discloses an adhesive product comprising an adhesive layer formed from an acrylic dispersion on a polyolefin film (page 2, lines 3 to 4). The acrylic dispersion consists of first and second acrylic dispersions (b1) and (b2) being present in a ratio of 99:1 and 90:10 (page 3, lines 23 to 28). In the only example of D4 (trial B on page 7), the acrylic dispersion used to prepare the adhesive product consists of a mixture of Primal**(TM) PS83D (first acrylic dispersion) and Neocryl**(TM) A45 (second acrylic dispersion) in a weight ratio of 95 to 5.

Primal**(TM) PS83D has an average particle size of 681 nm (see D9) and thus corresponds to the large mode of claim 1. Neocryl**(TM) A45 has an average particle size of 109 nm (see D8) and thus corresponds to the fine mode in claim 1. As acknowledged by all parties, the overall glass transition temperature of the acrylic dispersion of D4 lies within the range of claim 1.

As stated in paragraph [0049] of D4, Neocryl**(TM) A45 is an example of the "specific acrylic dispersion" disclosed in paragraph [0048], which comprises propylene imine, which is an aziridine. Consequently, Neocryl**(TM) A45 and thus the acrylic dispersion used in trial B of D4 contains an aziridine. Furthermore, as not disputed by the opponent, the amounts of monomer units in the acrylic dispersion in trial B of D4 are different from the amounts as required by claim 1. Therefore, the subject-matter of claim 1 differs from D4 firstly in that the emulsion polymer comprised in the claimed adhesive product does not contain aziridines and, secondly, in terms of the amounts of monomer units present in the emulsion polymer.

8.2.3 Both parties agreed during the oral proceedings that the objective technical problem was the provision of an alternative adhesive product that exhibited low noise upon unwinding while not containing toxic aziridines.

8.2.4 The board agrees with the opponent that aziridines are disclosed in D4 as optional components only and that the skilled person reading D4 and looking for less toxic adhesive products would therefore have omitted aziridines. However, even if the skilled person would omit aziridines in the composition of trial B of D4, he would not arrive at the claimed amounts of monomer units. Therefore, the claimed alternative is inventive in view of D4.

None of the further documents cited by the opponent discloses an emulsion polymer with monomer amounts as required by claim 1, let alone that any of these documents suggests that such an emulsion polymer would result in an adhesive product with low noise. Therefore the claimed alternative is also inventive in view of D4 in combination with any of the further documents cited by the opponent.

8.3 Inventive step on the basis of D5

8.3.1 Apart from D4, the opponent considered D5 to represent the closest prior art.

8.3.2 D5 discloses a process for preparing polymer dispersions with a bimodal particle size distribution (page 2, lines 3 to 5). The problem addressed in D5 is the provision of a process by which aqueous polymer dispersions can be prepared that have a high polymer volume concentration, low viscosity and a reduced amount of micro-coagulates and that are essentially independent from the type of monomers or surfactant used in the process (page 2, lines 45 to 48). The aqueous polymer dispersions can be used as binding agent for coatings, adhesives or for finishing paper, leather, and woven or non-woven fabrics (claim 16).

8.3.3 D5 is not concerned with adhesive tapes, let alone with the problem of noisy unwind. It is to be noted in this respect that the reference to adhesive tapes ("Klebefilme", page 2, line 8 of D5) referred to by the opponent is made when discussing the prior art in D5, but not the invention. D5 thus is neither in the same technical field nor does it address the technical problem referred to in the opposed patent. D5 therefore does not qualify as the closest prior art.

8.4 Inventive step on the basis of D6

8.4.1 The opponent mentioned during the oral proceedings that also D6 could be considered to represent the closest prior art. However, all arguments presented during the oral proceedings as regards D6 in fact started from D5 as the closest prior art and combined this document with D6.

8.4.2 In the same way as the opposed patent, D6 is directed to adhesive tapes with low noise upon unwinding (second paragraph on page 797 and first paragraph on page 792). Therefore, D6 can also be considered as the closest prior art.

This documents describes polypropylene tapes that contain an acrylic dispersion based on 2-ethylhexylacrylate, n-butylacrylate and acrylic acid (paragraph above the figure on page 796). D6 is silent as regards the particle size distribution and the glass transition temperature of the acrylic dispersion and whether aziridines are present.

The subject-matter of claim 1 differs from D6 by (i) the absence of aziridines, (ii) the amounts of monomer units, (iii) the fact that the acrylic dispersion has a bimodal particle size distribution, (iv) the average particle sizes, (v) the amounts of fine and large modes, and (vi) the overall glass transition temperature. In the same way as for the closest prior art D4, the objective technical problem is the provision of an alternative adhesive product that developes low noise upon unwinding while not containing toxic aziridines. In the same way as for the closest prior art D4, the claimed alternative is neither disclosed nor suggested by D6 or any of the further cited prior art documents. Therefore, the subject-matter of claim 1 and by the same token of all remaining claims is inventive in view of D6 as the closest prior art.

8.5 Inventive step on the basis of D28

8.5.1 The opponent argued that the claimed subject-matter was not inventive in view of D28 as the closest prior art in combination with D3 or D27. The proprietor requested that D27 and D28 be not admitted into the proceedings.

8.5.2 The attack on the basis of D28 in combination with D3 or D27 was filed by the opponent with the statement of grounds of appeal. D28 discloses the specific monomer concentrations as required by claim 1 (see point 8.5.3 below). The inventive step attack on the basis of D28 present in the statement of grounds of appeal can thus be considered to constitute a direct reaction to the filing of auxiliary request 1 during the opposition proceedings, where the monomer concentrations had been included into claim 1 (this auxiliary request was found allowable by the opposition division and is the main request in the present appeal proceedings). Therefore, the board decided to admit D27 and D28 into the proceedings.

8.5.3 Unlike D4, D28 does not address the problem of low noise adhesive products. Therefore it is D4 rather than D28 which constitutes the closest prior art. For this reason alone, the opponent's inventive step attack on the basis of D28 must fail. Furthermore, even if one assumes, in the opponent's favour, that D28 represents the closest prior art, the claimed subject-matter is inventive:

D28 discloses a polypropylene film onto which an acrylic dispersion composed of 98.5 wt% butylacrrylate ("BA") and 1.5 wt% of methacrylic acid ("MAS") has been coated (Item "Herstellung des Klebebandes" in conjunction with dispersion 1 disclosed on page 7 of D28). As not disputed by the proprietor, the overall glass transition temperature of this acrylic dispersion is -52°C. The monomer concentrations and the overall glass transition temperature of dispersion 1 of D28 are thus as required by claim 1.

The subject-matter of claim 1 differs from this dispersion in that the emulsion polymer according to the claim has a bimodal particle size distribution containing a fine and a large mode, and in that the fine mode has 5 to 95 wt% of particles with an average particle size of less than or equal to 250 nm and the large mode at least 5 wt% of particles with an average particle size of greater than 250 nm.

The objective technical problem in view of D28 is the provision of an alternative adhesive product with low noise.

The opponent argued that the claimed alternative was obvious since the claimed particle size distribution was known from D3, which was specifically referred to in D28. D28 discloses on page 5, lines 55 to 58, that in order to avoid a too large viscosity increase, the polymer dispersion should have a bimodal or polymodal particle size distribution, which can be prepared by, e.g., adding a seed as described in EP-A-81083 (which is D3 in the present proceedings). D3 discloses a bimodal particle size distribution with the small mode having an average particle size in the range of 50 to 500 nm and the large mode having an average particle size of 200 to 4000 nm and a ratio of fine to large mode of 1:1 to 100:1 (page 7, lines 22 to 29 and first six lines of page 8). However, first of all, there is no suggestion in D3 that if this particle size distribution is used, a low noise adhesive product will be obtained. Secondly, even if the skilled person were to incorporate the teaching of this particle size distribution into D28, he would not necessarily arrive at the claimed alternative since the ranges for the particle sizes and ratios of the fine and large mode in D3 only overlap with those in claim 1.

The opponent furthermore argued that the claimed alternative was obvious since the claimed particle size distribution was known from D27. This document discloses in figure 3 a model PSA latex with a bimodal particle size distribution with average particle sizes of the fine and large mode within the ranges as required by claim 1 (about 100 nm for the fine mode and about 700 nm for the large mode). However, this model PSA latex of figure 3 is composed of 88.2 wt% of 2-ethylhexyl acrylate (2-EHA) and 11.8 wt% of methylmethyrylic acid and acrylic acid (MMA and AA) (point "3.2 Synthesis of model PSA latexes" on page 327 of D27), and these monomer amounts are not as required by claim 1 (97.5 to 99 wt% of 2-ethylhexylacrylate and 1 to 2.5 wt% of (meth)acrylic acid. Consequently, even if the skilled person were to incorporate the teaching of the particle size distribution of D27 into D28, he would not arrive at the claimed alternative since the monomer composition would then not be as required in claim 1. Furthermore, in the same way as for D3, there is no suggestion in D27 that if the particle size distribution disclosed in this document was used, a low noise adhesive product would be obtained.

The subject-matter of claim 1 and by the same token of all remaining claims is therefore inventive in view of D28 as the closest prior art.

9. Request to hear a witness

9.1 In its statement of grounds of appeal the opponent requested that Ms Menegato be heard as a witness as regards the processing of the product Plextol**(TM) X4500 and the sale of adhesive tapes by Fabo.

9.2 In its preliminary opinion, the board informed the opponent that the issues with regard to which Ms Menegato had been offered as a witness appeared not to be relevant to the reasons why the opposition division considered the public prior uses not to be pertinent. Therefore the offered testimony of Ms Menegato as witness would be irrelevant, such that the request to hear her as a witness was likely to be refused. Consequently, the board saw at that stage no reason to summon Ms Menegato as a witness.

No arguments were presented by the opponent in reaction to this preliminary opinion, either in writing or during the oral proceedings. The opponent simply affirmed at the oral proceedings its request that an invitation be issued to Ms Menegato to be heard as a witness.

In the absence of any arguments being presented after the issuance of its preliminary opinion, the board did not see any reason during the oral proceedings to diverge from this opinion that the offered testimony of Ms Menegato as a witness would be irrelevant.

9.3 In fact the irrelevance of the witness statement offered by the opponent became even more pronounced in the course of the oral proceedings. More specifically, during the oral proceedings the alleged public prior use attack BASF was withdrawn, the alleged public prior uses Mac and Straptech were not admitted into the proceedings and the inventive step attack on the basis of the alleged public prior use Fabo was equally not admitted into the proceedings. The issues for which Ms Menegato was offered as a witness, namely the processing of the product Plextol**(TM) X4500 and the sale of adhesive tapes by Fabo, would not have been related to the board's decisions on admissibility. The hearing of Ms Menegato as a witness could thus not have changed these decisions of the board.

9.4 Therefore the board decided to refuse the opponent's request that Ms Menegato be heard as a witness.

9.5 It is to be noted that the opponent was free to bring Ms Menegato to the oral proceedings. Should it have turned out that the offered witness statement had any relevance (which it did not), the board could have heard Ms Menegato. Furthermore, even after the oral proceedings had started in the absence of Ms Menegato, the opponent was free to request an adjournment of the oral proceedings such that Ms Menegato could have been heard as a witness later. Such a request could have been allowed by the board if the offered witness testimony had had any relevance (which it did not). Hence that no summons to hear Ms Menegato as a witness was issued during the written proceedings and the fact that oral proceedings were carried out in her absence did not violate the opponent's right to be heard.