T 0921/96 09-01-2001

1. The appeal is admissible

2. Admissibility of claim 1 of the main request

According to Article 123(2) EPC a European Patent may not be amended in such a way that it contains subject matter which extends beyond the content of the application as filed. The question to be decided is whether the amendment in step (a) of claim 1 can be directly und unambiguously derived from the application as filed even when account is taken what is implicit to the person skilled in the art.

According to this amendment a first monomer charge "of the alkyl acrylate or alkyl methacrylate and at least one vinylic monomer", the latter being selected from a specific group, listed in sub-paragraph (a) of the claim, is polymerized. Thus, the amendment defines in relation to the first monomer charge, a combination of the alkyl acrylate or alkyl methacrylate monomers with the "at least one vinylic monomer" as listed under (a). No such combination is, however, referred to in the specification of the patent as granted or in the documents of the application as originally filed.

2.1. The passages in the text of the application as filed, relied upon by the appellant to show that the amended definition could be at least implicitly derived from the documents as originally filed, including claim 2, the general description and the examples, do not alter the position for the following reasons.

2.1.1. According to pages 9 and 10, bridging paragraph, of the application as filed, "The acrylic polymer emulsion of the present invention is a polymer comprising one or more vinylic monomers wherein at least about 40% by weight of the polymer is an alkyl acrylate or alkyl methacrylate or mixtures ...". This phraseology is similar to the version of claim 1 as originally filed and as granted, defining "a polymer comprising at least 1 vinyl monomer wherein at least 40. % by weight of said vinyl monomer is an alkyl acrylate or alkyl methacrylate" and emphasizes that the alkyl acrylate or alkyl methacrylate refers to the composition of the polymer emulsion. There is, however, no reference to a "first monomer charge".

2.1.2. A similar lack of contextual connection between the alkyl acrylate or alkyl methacrylate monomers on the one hand and the first monomer charge on the other is evident from granted dependent claim 2, which is identical to claim 2 as filed and relates to preferred "alkyl acrylate or alkyl methacrylate" monomers but without mention of the first monomer charge. Thus, from the above disclosure no specific context can be derived between the "alkyl acrylate or alkyl methacrylate monomers" and the "first monomer charge".

2.1.3. Although the sentence: "The vinylic monomers employed in the acrylic emulsion polymer in addition to alkylacrylate can be any vinylic monomer" (page 10, lines 7 to 9) and the following sentence "These vinylic monomers are copolymerized with the alkylacrylate..." admittedly refer to a combination of the alkylacrylate monomers and the specific vinylic monomers listed in step (a) of granted claim 1 (page 10, lines 17 to 24 as filed) these sentences are also not related to any "first monomer charge" and in particular do not amount to a statement that the "alkylacrylate and alkylmethacrylate" and the listed "vinylic monomers" are to be present in combination in the "first monomer charge" during polymerization.

2.1.4. Nor does the general concept for carrying out emulsion polymerization (pages 10 and 11, bridging paragraph), which only refers to a non-defined "monomer mixture", make available any disclosure with respect to the type of monomers used in the "first monomer charge".

2.1.5. Finally, the sentence that the "precharge should contain all of the monomers, which will be solubilized by the alkali" (page 12, lines 27 to 34) makes reference to monomers which are neither covered by the term "alkyl acrylate or alkyl methacrylate" nor included in the list of the specified vinylic monomers, so that this passage does not provide any support for the amendment effected.

2.1.6. As far as the appellant referred to the examples of the application as originally filed, these are fragmented in several "parts A to H" including those containing monomers (parts A, D and H (or G)). Although in each of the examples 1 to 3 parts B and D contain the same type of monomers in the same weight ratio, part B is first initiated by means of part C (containing an initiator) before part D is introduced into the polymerization mixture. Thus, there is no reference in the examples whether part B alone or parts B and D together may form the "first monomer charge". But even if parts B and D together were to be regarded as a "first monomer charge", these specific monomers do not support the generality of the combinations presented in the amended claim 1.

Hence, from this exemplified disclosure, it can neither explicitly nor implicitly be derived, that in general the "alkyl acrylate or alkyl methacrylate monomers" should be present in combination with the specified list of vinylic monomers in the "first monomer charge".

2.1.7. In summary, there is no general context, in the documents as originally filed, between the vinyl monomers (alkyl acrylate or alkyl methacrylate) present in the final emulsion polymer on the one hand and the vinylic monomers which should form a "first monomer charge" on the other (even if the terms "vinyl" and "vinylic" are regarded as being used interchangeably), from which the amendment effected in claim 1 of the main request could be directly and unambiguously derived.

2.1.8. Consequently, the amendment in step (a) of claim 1 of the main request violates Article 123(2) EPC.

2.2. The further argument of the appellant, that the polymer part of claim 1 must have a correspondence in the process part thereof to make clear where the alkyl acrylates or methacrylates are introduced into the process, is regarded by the board as somewhat subjective in nature, and in any case not such as to justify amendments, which are otherwise unallowable, for the reasons given (section 2.1. above).

2.3. Hence, the main request is not allowable.

3. Admissibility of the first auxiliary request

3.1. In claim 1, feature (a) has been restored to the form as granted. Such an amendment clearly does not involve the addition of subject-matter or any broadening of scope, and indeed no formal objections have been raised by the respondent.

3.2. The amendment in feature (b) is supported by page 4, lines 27 to 29 of the application as filed corresponding to page 3, lines 15 and 16 of the patent as granted and limits the time point at which the support resin is added.

3.3. Consequently, the subject matter of the first auxiliary request meets the requirements of Article 123(2) and (3) EPC.

4. Patent in suit; the technical problem (first auxiliary request)

The patent in suit is concerned with an adhesive composition having a viscosity of less than 3,500 centipoise comprising an aqueous polymer emulsion of water and 30-60% by weight of a polymer comprising at least 1 vinyl monomer wherein at least 40% of said vinyl monomer is an alkyl acrylate or alkyl methacrylate, and wherein the polymer is prepared by: (a) polymerizing a first monomer charge comprising at least one specified vinylic monomer such as vinyl acetate in the presence of a surfactant, and an initiator to initiate emulsion polymerization of said first monomer charge and (b) adding a polymer having a molecular weight ranging from 500 to 20,000 to the emulsion.

4.1. Such a composition is, however, known from D1, which according to the decision under appeal and the submissions of the parties was to be regarded as the closest prior art.

4.2. D1 describes a pressure-sensitive adhesive composition obtained by emulsion polymerization of alkyl acrylates such as ethyl acrylate as main component and further vinylic monomers such as vinylacetate to form an acrylic polymer mixture. After polymerization a low molecular weight, water soluble or water dispersible (meth)acrylic acid ester-based polymer resin having an average molecular weight of 1 000 to 50 000, for example 4 500, is added to the emulsion polymer (claim 1, comparative example 1 in connection with example 1).

By the use of the low molecular weight support resin the peel strength is improved on rough surfaces whilst the cohesive strength is not unduly reduced (page 4, first full paragraph, example 1, page 14, second paragraph).

4.3. Compared to this state of the art, the technical problem may be seen in providing a pressure sensitive adhesive composition having substantially Newtonian-like flow characteristics i.e. emulsion viscosities, which are stable under high shear conditions such as those encountered in roll coating operations (page 2, lines 31 to 32 and 54 to 56).

4.4. The solution proposed according to claim 1 of the first auxiliary request is to add a support resin to the polymerization mixture after initiation of the emulsion polymerization reaction but before the emulsion polymerization reaction is substantially complete.

4.4.1. As shown by the experimental report submitted on 10 November 1997, the addition of the support resin during the emulsion polymerization reaction results in pressure-sensitive adhesives, the viscosities of which vary little in response to the shear applied, i.e. show substantially Newtonian-like rheological properties and thus improved stability (pages 3 and 4, tables, samples 1 to 3). Further, the experimental report filed on 12 December 1996 shows a low percentage of coagulum and thus good stability when using the claimed stage of addition of the support polymer (page 6, table, samples 2 and 4). Due to these properties, the claimed adhesive compositions have excellent flow, coating and levelling characteristics especially on low energy surfaces and on high speed equipment (page 3, lines 2 to 4 of the patent in suit).

4.4.2. The argument of the respondent, that the problem cannot be solved over the whole scope of the claims because of the unspecified time point within the stage of addition and unspecified nature of the support resin, since the appellant has not shown this by its additional experimental data, is not convincing.

4.4.2.1. Although the respondent refers in this connection to the broad definition of the support resin in step (b) of claim 1, the crucial point of the claimed invention is not the chemical nature of the support resin, but rather the stage at which the support resin is added to the emulsion polymerization reaction. This has been shown, convincingly in the board's view, by the experimental report, received on 10 November 1997, according to which the addition of the support resin as claimed results in substantially Newtonian-like rheological properties whether the support resin is added shortly after initiation of the polymerization or near the end of the reaction (page 1, first paragraph, page 3, table, "% coagulum" and page 4, table, samples 2 and 3). Conversely, the addition of a support resin after polymerization, i.e. in accordance with the teaching of D1, has been shown to result in an unstable blend which coagulated completely (experimental report filed on 10 November 1997, page 4, sample 5). Thus, the precise point in time of addition is of minor importance provided that such addition is made at the relevant stage, i.e. during emulsion polymerization. Furthermore, the experimental report of 12 December 1996 illustrates the preparation of stable emulsions with two chemically completely different support resins (styrene acrylic resin and polyurethane; page 2 first paragraph, page 6, samples 2 and 4).

4.4.2.2. From the above, it follows that the appellant has shown that the addition of different support resins at different time points within the relevant stage still provides stable polymer emulsions having Newtonian- like flow properties.

4.4.2.3. Quite apart from the above reasons, the respondent has filed no counter-evidence of its own to show that a relevant effect is not achieved over the whole ambit of the claim. The onus of proof in this respect lies, however, with the opponent (T 219/83, OJ EPO 1986, 211). This the respondent has failed to discharge.

4.4.2.4. In view of the above reasons, it is credible to the board that the claimed measure provides an effective solution of the technical problem and this over the whole scope of the claims.

5. Novelty (first auxiliary request)

Novelty of the subject matter of the claims of this request has not been contested, and the board sees no reason to take a different view. Consequently, the subject matter is held to be novel.

6. Inventive step (first auxiliary request)

It is necessary to consider, whether the skilled person, starting from a pressure-sensitive adhesive according to D1 and faced with the problem of providing Newtonian-like properties to them, would have expected this result to be achieved, by adding the support resin to the polymerization mixture after initiation of the emulsion polymerization reaction but before the emulsion polymerization reaction is substantially complete.

6.1. There is no disclosure in D1 of adding the low molecular weight polymer of an ester of (meth)acrylic acid at any other stage than after the emulsion polymerization process is complete, whereby the latter dissolves in the acrylic emulsion polymer of the adhesive and has a plastifying effect on it (page 4, second complete paragraph). This is not surprising, since the aim of D1 is not to modify the viscosity of the adhesive compositions so as to provide Newtonian-like flow properties, but rather to obtain an improved peel strength on rough surfaces whilst the cohesive strength is not unduly reduced (page 4, second paragraph). Thus, there is no hint in D1 to the essential step characterizing the solution of the technical problem, of adding the support resin at a quite different time point, namely during the emulsion polymerization reaction.

In summary, D1 is not related to the problem posed and consequently teaches a completely different approach. It does not provide any hint to modify the teaching of D1 in the direction of the solution of the technical problem.

6.2. Whilst the obviousness argument of the decision under appeal was based on the concept of the support resin being an "inert" material, which would not take part in the reaction (page 10, paragraph in the middle), this was unsupported by any reference to a prior art document and is to this extent speculative. It has in any case turned out to be irrelevant, since it has been demonstrated, to the satisfaction of the board, that the relevant effect does in fact occur, even when using a support resin species such as a polyurethane, which had been identified in the decision under appeal as being "inert" (sections 4.4.1 and 4.4.2).

Consequently, the argument that the claimed different addition is a "conventional measure" (pages 10 and 11 bridging paragraph) cannot be supported by the board.

For these reasons, the decision under appeal must be set aside.

6.3. The argument of the respondent put forward at the oral proceedings, that the relevant improved flow characteristics, as shown for instance in the experimental report of 10 November 1997, could have been expected, as the support resin would function as a protective colloid, was based on the amounts of coagulum reported for samples 1 to 4 (table on page 3, Annex II). It is not convincing for the following reasons.

6.3.1. Although samples 1 to 4 according to that report show that the percentage of coagulum increases the later the support resin is added to the emulsion, such results do not belong to the state of the art but were obtained by using the disclosure in the patent in suit. Consequently, the phenomenon in question has not been shown to belong to the state of the art.

6.3.2. Nor has the respondent provided convincing evidence that a support resin will indeed function as "protective colloid" when added during an emulsion polymerization reaction. On the contrary, a closer examination of the results of the coagulum formed, in the experiments of the further test report filed on 12. December 1996, which use the same polyurethane support resin as those relied upon by the respondent (Spensol L-54), reveals an opposite trend, since the amount of coagulum formed in sample 2 (addition after commencement of the emulsion polymerization) is ten times less than that of sample 1 (addition prior to emulsion polymerization).

6.3.3. Consequently, the respondent's argument is not supported by the totality of the experimental data available in the proceedings, and even if it had been, there is no reason for supposing that the skilled person would have expected such a technical effect from the addition as claimed in the absence of any relevant prior art teaching.

6.4. Finally, the respondent's arguments having regard to the experimental report of 12 December 1996, that the adhesive properties of sample 1 were better than those of sample 2 are irrelevant for the following reasons:

6.4.1. Sample 1 illustrating the addition of the support resin in front (before emulsion polymerization) is not a prior art sample in comparison with which a technical effect has to be shown. Furthermore, the main aim of the claimed invention is not to improve any specific adhesive properties, but to provide Newtonian-like flow properties which have been shown to occur (sections 4.4.1 and 4.4.2, above).

6.4.2. Consequently, it is immaterial whether there exists another variant which belongs neither to the claimed subject matter nor to the prior art, but which has interesting properties. On the contrary, the provision of such information is in effect a gift from the appellant to the public.

6.4.3. In summary, the comments of the respondent in this connection have no bearing on the issue of inventive step in relation to the claimed subject-matter.

6.5. Hence, the solution of the technical problem does not arise in an obvious way from the state of the art. Consequently, the subject-matter of claim 1, and, by the same token, that of dependent claims 2 to 6, involves an inventive step in the sense of Article 56 EPC.

6.6. It follows that the first auxiliary request is allowable.