T 0428/05 02-10-2007

I. Mention of the grant of European Patent No. 1 036 103 in the name of Henkel Kommanditgesellschaft auf Aktien in respect of European patent application No. 98964426.5, filed on 21 November 1998 as international application No. PCT/EP98/07496, published as WO 99/28363 on 10 June 1999, and claiming priority of US patent application no. 60/067,197 dated 1 December 1997, was announced on 11 September 2002 (Bulletin 2002/37) on the basis of 26 claims, claim 1 of which read as follows:

"1. A solvent-free moisture-curing polyurethane hot melt adhesive composition, wherein said hot melt adhesive composition is solid at room temperature, comprising the product of combining:

a) 95 to 3 % by weight of the reaction product of a first polyisocyanate and a polymer of ethylenically unsaturated monomers having an average molecular weight below 60 000, wherein said polymer has active hydrogen groups; and is not a copolymer of ethylene, vinylacetate and of an ethylenically unsaturated monomer containing at least one primary hydroxyl group,

b) 5 to 90 % by weight of at least one polyurethane prepolymer with free isocyanate groups prepared from at least one polyol selected from the group consisting of polyether diols, polyether triols, polyester polyols, aromatic polyols and mixtures thereof and at least one second polyisocyanate which may be the same as or different from the first polyisocyanate; and

c) 0 to 40 % by weight of at least one additive selected from the group consisting of catalysts, tackifiers, plasticizers, fillers, pigments, stabilizers, adhesion promoters, rheology improvers and mixtures thereof, wherein the sum of a), b) and c) is 100 % by weight."

Claims 2-17 and 20-26 were directed to preferred embodiments of the solvent-free, moisture-curing polyurethane hot melt adhesive of claim 1.

Claims 18 and 19 were directed to a process for joining substrates with the hot melt adhesive of claim 1 and the resulting joined substrates, respectively.

II. Notices of opposition against the grant of the patent were filed by:

Sika Technology AG (OI) on 11 June 2003 and

Klebchemie M.G. Becker GmbH + Co. KG (OII) also on 11 June 2003.

Both opponents invoked the grounds of opposition pursuant to Art. 100(a) EPC, specifically that the subject matter of the patent was not novel (Art. 54 EPC) and was not founded on an inventive step (Art. 56 EPC) and the ground of opposition pursuant to Art. 100(c) EPC.

The following documents, inter alia were cited together with the notices of opposition:

D2: EP-A-369 607

D3: US-A-5 155 180

D4: EP-B1-777 695 (and D4a WO-A-96/06124)

D7: EP-A-246 473

D8: US-A-4 214 061

D9: US-A-3 532 652

D10: WO-A-91/15530

D13: DE-A-195 18 656.

In their written submissions with respect to Art. 56 EPC, the opponents relied inter alia on D7 as the closest state of the art. However at the oral proceedings held before the opposition division a new approach, based on D3 as the closest state of the art was introduced.

III. By a decision announced orally on 25 January 2005 and issued in writing on 10 February 2005 the opposition division held that the patent could be maintained in amended form on the basis of the second auxiliary request (claims 1 to 25), filed during the oral proceedings.

Claim 1 of this request read as follows, the additions compared to claim 1 of the patent as granted being indicated in bold and the deletions compared to claim 1 as granted being indicated in [deleted: strikethrough ].

"1. A solvent-free moisture-curing polyurethane hot melt adhesive composition, wherein said hot melt adhesive composition is solid at room temperature, comprising the product of combining:

a) 95 to 3 % by weight of the reaction product of a first polyisocyanate and a copolymer of ethylenically unsaturated comonomers having an average molecular weight below 60 000, wherein said polymer has active hydrogen groups; and [deleted: is not a copolymer of ethylene, vinylacetate and of an ethylenically unsaturated monomer containing at least one primary hydroxyl group, ]said monomers are selected from the group consisting of C1 to C18-alkylesters of acrylic acid, C1 to C18-alkylesters of methacrylic acid, acrylic acid, methacrylic acid, hydroxyethylacrylate, hydroxyethylmethacrylate (HEMA), hydroxypropylacrylate, hydroxypropylmethacrylate, hydroxybutylacrylate, hydroxybutylmethacrylate, and/or the corresponding aminofunctional (meth)acrylates, esters of (meth)acrylic acid and glycol oligomers and polymers, esters of (meth)acrylic acid and glycol ethers, vinylesters, vinylethers, fumarates, maleates, styrene, alkylstyrenes, butadiene, acrylonitrile and mixtures thereof

b) 5 to 90 % by weight of at least one polyurethane prepolymer with free isocyanate groups prepared from at least one polyol selected from the group consisting of polyether diols, polyether triols, polyester polyols, aromatic polyols and mixtures thereof and at least one second polyisocyanate which may be the same as or different from the first polyisocyanate; and

c) 0 to 40 % by weight of at least one additive selected from the group consisting of catalysts, tackifiers, plasticizers, fillers, pigments, stabilizers, adhesion promoters, rheology improvers and mixtures thereof, wherein the sum of a), b) and c) is 100 % by weight."

Claim 2, which had no counterpart in the claims of the patent as granted read as follows:

"2. A solvent-free moisture-curing polyurethane hot melt adhesive composition of claim 1, wherein the glycol oligomers and polymers are selected from di-, tri-, tetra and/or polyethylene glycol, and/or the glycol ethers are selected from methoxyethanol and/or ethoxyethanol, and/or the vinylesters are selected from vinylacetate, vinylproprionate, vinylesters of highly branched monocarboxylic acids, vinyl ester of the versatic acid."

Claims 3-7 corresponded to claims 2-6 of the patent as granted. Claims 8-25 corresponded to claims 9-26 of the patent as granted, whereby claims 8-14, 19, 20 and 23-25 were further amended to take account of the restriction of the subject matter of part a) of claim 1 to co-polymers.

According to the decision:

(a) The claims of the second auxiliary request satisfied the requirements of Articles 84 and 123(2) EPC.

(b) With regard to novelty, inter alia the decision held with respect to the disclosure of D3:

(i) that at least three selections of the soft segment had to be made:

- firstly two soft segments of different nature had to be selected;

- secondly one had to be an acrylic polyol in component (b) of D3 which corresponded to component a) of the second auxiliary request and

- thirdly it had to be a polyester or polyether polyol in component (a) of D3 which corresponded to component b) of the second auxiliary request.

(ii) Furthermore the origin of the alcohol moieties in the acrylic polyols of D3 was not disclosed.

(iii) Therefore it was concluded that the subject matter claimed was novel.

(c) With regard to inventive step the decision held:

(i) Considering D7 as the closest state of the art:

The subject matter of claims 1 and 2 of D7 corresponded to the comparative example of the patent in suit. The subject matter claimed differed from the disclosure of D7 in that the copolymer of ethylenically unsaturated monomers contained active hydrogen and was reacted with a polyisocyanate.

With reference to the experimental results reported in the patent in suit, in particular example 4 (according to the invention) compared with the comparative example, the problem underlying the invention could be regarded as the provision of hot-melt adhesives with improved solvent resistance and adhesion to problematic substrates such as fluorinated polyethylene. With respect to an objection by the opponents that only the more "modest" problem formulated in paragraph [0019] of the patent had been solved, i.e. to retain the favourable properties of reactive polyurethane hot melt adhesives containing low molecular weight polymers and to improve their resistance to solvents and/or plasticizers, the opposition division considered that there was little doubt that the firstly formulated more demanding problem had been solved.

D7 was only concerned with the provision of hot-melt adhesives having superior initial adhesion to a broad range of substrates and having heat resistance, and did not contain any suggestion to replace the copolymer of ethylenically unsaturated monomers having no active hydrogen atoms with one such having active hydrogen atoms. Thus it was extremely doubtful that the skilled person following the teachings of D7 would have arrived at the claimed subject matter, let alone have foreseen the improved adhesion to substrates such as fluorinated polyethylene.

(ii) The arguments advanced - for the first time at the oral proceedings before the opposition division - with respect to D3 as the closest state of the art were likewise not held to be convincing. The substance of these arguments is however not relevant for the present decision (see section 8 below) and will not be further discussed.

(iii) Thus it was concluded that the subject matter of claims 1 to 25 of the second auxiliary request met the requirements of Art. 56 EPC.

(d) Accordingly the opposition division held that the patent could be maintained in amended form on the basis of the set of claims (1-25) according to the second auxiliary request.

IV. Notices of appeal against this decision were filed on:

11 April 2005 by OI and on

19 April 2005 by OII, the appeal fees being paid on the respective same dates.

Both opponents - now appellants - requested that the decision under of the opposition division be set aside and patent revoked. As an auxiliary measure, OII requested oral proceedings.

V. Statements of grounds of appeal were filed on 9 June 2005 and 16 June 2005 by OI and OII respectively.

(a) OI, in its statement of grounds of appeal submitted four further documents:

D27: "Epoxy Resins, Chemistry and Technology", Clayton A. May (ed), 2nd edition, 1988, pp. 506-509, 536-550;

D28: S.J. Shaw in "Chemistry and Technology of Epoxy Resins" B. Ellis (ed), 1993, pp. 117-121

D29: US-A-4 115 472

D30: US-A-6 001 931.

An auxiliary request for oral proceedings was made.

OI also stated:

"Es werden alle im Einspruchsverfahren aufgebrachten Einspruchsgründe nach Art 100 a) EPÜ bezüglich Neuheit und erfinderische Tätigkeit und Art 100 c) aufrecht erhalten und damit alle im Einspruchsverfahren angeführten Dokumente und Argumente ins Beschwerdeverfahren mit übernommen"

("All the grounds for opposition pursuant to Art. 100(a) EPC concerning novelty and inventive step and Art. 100(c) EPC put forward in the opposition procedure are maintained and therewith all the documents and arguments advanced in the opposition procedure are likewise taken over into the appeal procedure"- translation by the board).

(b) With regard to Art. 54 EPC, OI maintained its objections with respect to D3.

The finding of the decision under appeal that the subject matter of claim 1 was novel with respect to D3 on the one hand since three selections were necessary (see section III.(b).(i) above) and on the other hand since the nature of the origin of the alcohol group in the acrylic polyol was not disclosed (see section III.(b).(ii) above) were disputed.

Firstly, only a single selection from a small list was necessary.

With regard to the first selection identified (see section III.(b).i first bullet above) according to operative claim 1, the polyol components of prepolymer b) could be mixtures. The named polyols could result in both hard and soft segments in the sense of D3. Thus reaction of a soft-segment polyol and a hard-segment polyol (polyesterpolyol) with excess polyisocyanate, as disclosed at column 5, lines 35-38 of D3 would automatically result in a polyurethane prepolymer b) according to the patent in suit, with no need for a selection.

With regard to the third selection identified by the opposition division (see section III.(b).(i) third bullet) it was submitted that no such selection was necessary since all the polyurethane polymers (b) of D3 containing hard and soft segments were based on polyesters.

Therefore the only necessary selection was that identified as the second selection - namely to select "acrylic polyol" from the short list of soft segment polymers disclosed in D3. Such a single selection from a short list could however not confer novelty. Nor could it constitute a selection invention.

It was also disputed that the nature of the alcohol group in the acrylic polyols of D3 was not disclosed (see section III.(b).(ii) above). The skilled person would understand by the term "acrylic polyols" copolymers of hydroxyalkyl esters of ethylenically unsaturated carboxylic acids with one or more ethylenically unsaturated monomers. In particular, copolymers of hydroxyethyl acrylate or -methacrylate and one or more lower alkylacrylates would be understood by this term. As evidence that this was the prevailing view of the skilled person at or before the application date of the patent in suit, reference was made to D29 (col. 3 lines 30-62).

Thus the subject matter of claim 1 and also that of claims 17 and 18 lacked novelty with respect to the disclosure of D3.

OII did not advance any arguments with respect to novelty.

(c) Objections with respect to Art. 56 EPC were maintained with respect to D7 as the closest prior art by both opponents. OI also advanced objections based on each of D1 and D4a as the closest prior art.

According to both appellants the technical problem to be solved was, consistently with the statement at paragraph [0019] of the patent in suit, to improve the resistance of the hot melt adhesives to solvents and plasticizers, while retaining the other properties thereof.

(i) With respect to D7 OI invoked, with reference to D2, D8, D13 and to the newly introduced D27, D28 and D30 for the first time in the statement of grounds of appeal, the principle of reactive diluents, which diluents became chemically bound to the polymer to which they were added. The skilled person would be aware of the benefits of reactive diluents which provided enhanced chemical resistance and based on this knowledge would consider replacing the acrylic copolymers of D7, which were submitted to be non-reactive diluents, by reactive analogues. These were well known to the skilled person as "acrylic polymers".

(ii) It was also submitted that the subject matter claimed was rendered obvious by the combination of D7 with D9. D9 disclosed an acrylic/ethylenic interpolymer whereby two types of olefinic monomers were employed, one of which contained active hydrogen groups. The interpolymer thus corresponded to component a) of the patent in suit. D9 taught further that the use of a polyisocyanate reaction product of such an interpolymer resulted in improved adhesion to a range of substrates as well as improved solvent resistance. The combination of the teaching of D9 with that of D7 in order to solve the problem set out in D7, was obvious, even though D9 related to pressure sensitive adhesives.

(iii) Regarding a combination of D7 with D10 it was submitted that D10 taught that in order to provide hot melts with solvent resistance it was necessary to ensure that chemical curing and not merely physical bonding took place, thus rendering it obvious to provide hot melts which underwent such a chemical reaction on curing.

(iv) With respect to D1 as the closest prior art, it was submitted that this related to a reactive hot melt adhesive, which, after curing, in particular with atmospheric moisture, exhibited good mechanical properties. Solvents were not disclosed as one of the constituents thereof. The adhesive of D1 differed from the subject matter of the patent in suit in that component a) was not mentioned. Thus the objective problem to be solved with respect to D1 was to provide hot melt adhesives with improved resistance to solvents and/or plasticizers, whilst maintaining the other properties. The solution to this problem, i.e. to incorporate copolymers according to component a) of operative claim 1 was known from a number of documents (D2, D13, D8, D9).

(v) With respect to D4a it was submitted that this disclosed a hot melt adhesive. According to the examples solvents were not employed. The adhesive contained components a) and b) according to operative claim 1. The relative amounts of the two components was however not disclosed. This however was a matter of routine for the skilled person who would find indications in D2 and D7. Thus the proportions of components could not support an inventive step.

VI. In its response, dated 19 October 2005 the patent proprietor, now the respondent requested that the appeals be dismissed. A further document was submitted

D31: Römpp Chemie Lexikon, "Reaktivverdünner".

(d) With respect to Art. 54 EPC and the objection on the basis of D3, it was submitted that D3 failed to give a definition of "acrylic polyols". It was disputed that this was a term that would be unambiguously understood by the skilled person. The newly cited D29 also did not provide evidence that the average skilled person would understand the term "acrylic polyols" as employed in D3 to be exclusively those compounds as set out at column 3, lines 30 to 35 of D29. Reference was made in this respect to the reference in D29 to "so-called" acrylic polyols. Had "acrylic polyols" been a standard term then it would not have been necessary to describe these as "so-called" acrylic polyols. It was also submitted that D29 related to a different technical field (coating compositions) to that of the patent in suit (hot melt adhesives), and that it was not correct to consider that the terminology employed in each of these two distinct technical fields would necessarily be identical.

Thus the subject matter claimed was novel with respect to the disclosure of D3.

(e) With regard to Art. 56 EPC:

(i) With respect to the objections based on D7 it was disputed that the skilled person would derive from D7 the teaching to replace the nonfunctionalised low molecular weight component derived from ethylenically unsaturated monomers by one containing active hydrogen. On the contrary, D7 explicitly emphasised that the low molecular weight component should be non-functional.

The submissions of OI (see section V.(c).(i) above) that the low molecular polymer from ethylenically unsaturated monomers fulfilled the function of a reactive diluent was dismissed with reference to D31 which showed that such diluents were monomeric or oligomeric.

(ii) With respect to the objections based on D7 in combination with D9 it was submitted that D9 related to a pressure sensitive adhesive - PSA - (Haftklebstoff) that was employed on flexible carriers or as an adhesive film. These adhesives were applied to the substrate in solution form or were applied to a transfer substrate and then fully cured. It was submitted that a PSA was not a reactive adhesive, the latter being supplied to the end user in a reactive form and which only developed its final properties by chemical reaction after being applied to the substrate. On the other hand, a PSA had to be permanently tacky in order to fulfil its function. Thus the skilled person starting from D7 would have derived no information from D9 that would lead to the subject matter of the present invention.

Similarly, D10 taught only to include further non-reactive components, as long as these did not affect the essential character of the composition. Thus this teaching, when combined with the disclosure of D7 would not provide any guidance to the claimed subject matter.

(iii) With regard to the arguments based on D1, the respondent disputed that this teaching represented the closest state of the art. The compositions thereof contained a non-reactive thermoplastic, and the document contained no hint or suggestion to provide an adhesive composition containing as a reactive component a product of a polyisocyanate with a copolymer of ethylenically unsaturated monomers containing active hydrogens. This deficit was not overcome by combination of D1 with any of the other documents invoked (D2, D13, D8, or D9).

(iv) With regard to the arguments based on D4a as the closest state of the art it was submitted that D4a related to the preparation of polyurethane compositions with a low content of monomeric diisocyanates, which compositions preferably were prepared on the basis of specifically defined trifunctional isocyanates, optionally with a monofunctional terminator. It was taught that these compositions could also be employed as hot melt adhesives. Although it was stated in D4a that lightly branched acrylic ester copolymers could be used in preparing the polyurethane compositions, there was no disclosure of a solvent free hot melt adhesive according to the operative claims and there was no teaching in D4a that the addition of such lightly branched acrylic copolymers compound would be appropriate in particular for the preparation of hot melt adhesives.

VII. In a second letter dated 31 January 2006 OII submitted three further documents:

D32: EP-A-0 544 672

D33: Datasheet HL-9637

D34: Datasheet of Forbo Helmitin.

D33 and D34 which were cited as "expert opinions" ("gutachtlich").

On the basis of these documents, it was submitted that the skilled person would not consider there to be a clear and precise distinction between the two classes adhesives hot melt adhesives and pressure sensitive adhesives.

VIII. The board issued on 11 July 2007 a summons to attend oral proceedings.

IX. The respondent in a letter dated 14 August 2007 submitted three sets of claims forming a first, second and third auxiliary request, the details of which are however not of relevance for the present decision.

A further document:

D35: Römpp Chemie Lexikon, (CD-ROM version 1.0, 1995), relating to the term "Haftklebstoff" (pressure sensitive adhesive) was submitted.

X. Appellant OII in a letter dated 22 August 2007 submitted a further argument against inventive step. This was based on D9 as the closest prior art.

It was submitted that the problem addressed by D9 was to provide polyurethane based adhesives which, while maintaining the other properties, exhibited improved resistance to solvents and resistance to plasticizers. The problem was solved according to D9 by providing a combination of an organic polyisocyanate with an acrylic interpolymer containing a functional monomer with active hydrogen atoms, and which therefore was coreactive with the polyisocyanate. It was implicit and unambiguous from D9 that curing occurred by reaction of the free isocyanate groups with free hydrogen after application of the adhesive. It was submitted that it was this reaction which was responsible for the reported improved resistance to solvents and plasticisers in D9.

Although the adhesives of D9 were pressure sensitive adhesives and not reactive hot melt adhesives which were solid at room temperature, these two classes of adhesive were closely related, and partially overlapped.

As D9 disclosed that the polymers derived from ethylenically unsaturated monomers were "normally tacky" this implied that they were of low molecular weight. The proportions of the two polymers was not disclosed in D9. The range specified in the operative claims was however very broad and further was conventional, as indicated inter alia by D7.

All technical features of the claimed subject matter - with the exception of the active hydrogen component - were known from D7. Thus the combination of D9 in particular with D7 rendered the claimed subject matter obvious.

XI. Oral proceedings were held on 2 October 2007.

(f) The appellants stated that they had no objections on formal grounds (Article 84 or Article 123 EPC) to the claims of the main request.

(g) With regard to novelty the appellants maintained their objections with respect to the disclosure of D3.

In particular it was submitted that component (a) of the composition of D3, had hard and soft segments, the soft segments being derived from polyester polyols or polyether polyols. Accordingly, component (a) of D3 was equivalent to component b) of the operative claims.

Regarding component (b) of D3 it was submitted that this was a polymer with soft segments, the soft segments having a molecular weight less than or equal to 8 000, the polymer being derived from a polyol and a diisocyanate. The polyol could be selected inter alia from acrylic polyols. By reference to D29 it would be understood that this term corresponded to the hydroxy (meth)acrylate monomers specified in operative claim 1 for component a). Thus component (b) of D3 corresponded to component a) of the operative claims.

The two components of D3 were present in amounts of 10-90 wt% and 90-10 wt% and thus anticipated the ranges of 95-3 wt% a) and 5-90 wt% b) specified in operative claim 1.

The compositions of D3 were solvent free and were used as a hot melt adhesive, from which information it was inherent that these were solid at room temperature.

The respondent submitted that the definition of feature a) of claim 1 with respect to the acrylic polymers was much narrower than D3. D3 did not give any emphasis to acrylic polyols, which were presented as monomers which could be used interchangeably with the others listed. D3 further provided no information about the constitution of this class of monomer. The cited passages of D29 did not demonstrate that the term "acrylic polyols" as employed in D3 inevitably meant the monomers defined in claim 1.

(h) With regard to inventive step, objections based on D7 and D9 as closest prior art were discussed.

(i) With regard to D7 as the closest prior art the appellants submitted that the only difference of the claimed subject matter was that the acrylate polymer of D7 had no functional groups and hence could not become incorporated into the polymer. The objective problem to be solved was, with reference to paragraph [0019] of the patent, to improve the stability of the adhesive to solvents maintaining the favourable properties reactive polyurethane hot melt adhesives. This problem was solved by bonding the acrylic polymer to the network.

The skilled person was however aware of the concept of reactive diluents from polyurethane and epoxy chemistry. By analogy with this concept, the skilled person would realise that in order to solve the objective technical problem, it would be necessary chemically to link the acrylic polymer to the network. D7 itself contained a hint to this by the reference to interpenetrating networks on page 4 lines 37-44 where it was taught that such networks arose by crosslinking reactions.

The respondent accepted that D7 represented the closest state of the art. It was submitted that the teaching of D7 explicitly excluded the presence of hydrogen functional acrylic polymers. The crosslinking groups which were disclosed in D7 as resulting in - undesired - interpenetrating networks were not necessarily hydrogen groups but could be multiply unsaturated groups, which were common in acrylate chemistry. The argument based on the analogy to reactive diluents was dismissed as irrelevant to the teaching of D7.

(ii) With regard to D9 as the closest prior art the appellants submitted that D9 concerned pressure sensitive adhesives and hence concerned a technical area related to that of the patent in suit. The aim of D9 was to improve the stability of the pressure sensitive adhesives to solvent and plasticizers. This was achieved by a reaction between a polyisocyanate prepolymer and a compound with active hydrogen. The composition of D9 was applied as a hot melt and formed a pressure sensitive adhesive. There was no clear distinction between these two types of adhesives - the transition was continuous.

The respondent disputed that D9 could represent the closest state of the art since it was not concerned with hot melt adhesives, but with pressure sensitive adhesives, e.g. for adhesive tapes. Further although the compositions of D9 could, in principle, be solvent free all the examples employed solvents. All the NCO groups had been reacted thus in the adhesive there was no residual reactivity. Further the respondent submitted that D9 addressed a different problem from that of the patent in suit, namely to prevent the plasticizer migrating into the bond line. The patent in suit however was concerned with preventing components of the adhesive migrating out.

(i) The appellants sought to introduce a further line of argument concerning inventive step based on D3 as the closest prior art.

The respondent objected to this, submitting that this argument had not been advanced in the statement of grounds of appeal and hence was late filed.

The appellants submitted that since a novelty objection had been based on the disclosure of D3 it would have been illogical also to base an objection of lack of inventive step on the same document. In any case an attack of lack of novelty by implication included an attack of lack of inventive step.

The appellant further referred to the statement in the statement of grounds of appeal referring to all the arguments from the opposition procedure (see section V.(a) above). In support of this approach reference was made to T 131/01 (OJ EPO 2003, 115 and 282).

Following deliberation, the board informed the parties, that, with reference to the Rules of Procedure of the Boards of Appeal, Article 10b(1) it had decided not to exercise its discretion to admit the line of argument concerning inventive step based on D3 as the closest prior art.

XII. The appellants (opponents I and II) requested that the decision under appeal be set aside and that the European patent No. 1 036 103 be revoked.

The respondent (patent proprietor) requested that the appeals be dismissed (main request) or in the alternative that the patent be maintained on the basis of the sets of claims according to the first, second or third auxiliary requests, all filed with the letter dated 14 August 2007.