T 0144/16 (METH(ACRYLIC) ADHESIVE COMPOSITIONS/Sika Schweiz) 09-03-2021

Reasons for the Decision

1. The appeal is admissible.

Main request: patent as granted

2. Document (1)

Document (1) relates to compositions suitable for use as an adhesive which overcome the problems of formulation and application of the adhesive compositions of document (2) comprising a methacrylate ester monomer, a core/shell polymer which swells in the monomer but does not dissolve therein and an elastomeric polymer having a Tg below about -25°C (see claim 4). Document (1) identifies the cause of these problems as being the presence of high molecular weight elastomeric polymer. Hence, the adhesive composition proposed by document (1) comprises: (a) a polymerizable monomer; (b) a core/shell polymer; and (c) a liquid polymerizable oligomer capable of imparting toughness on the polymerisation thereof (see claim 3).

The polymerizable monomer component (a) includes inter alia ethylenically unsaturated carboxylic acid esters, such as alkyl (meth)acrylates methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, cyclohexyl (meth)acrylate, dodecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, eicosyl (meth)acrylate, isodecyl (meth)acrylate); alkoxy (polyethyleneoxide) (meth)acrylates; alkylphenoxy (polyethyleneoxide) (meth)acrylates; vinyl esters of alkyl carboxylic acids; hydroxy alkyl (meth)acrylates; other hydroxy (meth)acrylates; (meth)acrylic acid esters with C1 to C18 alcohols; vinyl esters; vinyl stearate; vinyl acetate; poly(meth)acrylate esters (e. g ethylene glycol di (meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, neopentyl di (meth)acrylate and 1,1,1-trimethylol propane tri (meth)acrylate); basic substituted (meth)acrylates (e.g. amine substituted acrylates - such as dimethylaminoethyl (meth) acrylate, tertiarybutyl-aminoethyl (meth) acrylate); isobornyl (meth)acrylate; dicyclopentadienyl (meth)acrylate; dicyclopentadienyl oxyethyl (meth)acrylate (see page 8, line 29 to page 9, line 25).

Preferred methacrylate monomers includes hydroxypropyl methacrylate, ethylhexylmethacrylate, polypropylene glycolmonomethacrylate, tetraethylene glycol dimethacrylate, methacrylic acid and methacrylate functional silane (page 10, line 11 to 14)

The monomer mixture of the composition of example 1 of document (1) comprises hydroxy propyl methacrylate, ethylhexyl methacrylate, polypropylene glycol monomethacrylate and triethylene glycol dimethacrylate.

The monomer mixture of the composition of example 2 of document (1) comprises methyl methacrylate, hydroxy propyl methacrylate, triethylene glycol dimethacrylate and propylene glycol monomethacrylate.

The monomer mixture of the composition of example 4 of document (1) comprises hydroxy propyl methacrylate, propoxylated neopentyl glycol diacrylate and triethylene glycol dimethacrylate

The liquid polymerizable oligomer has preferably a number average molecular weight of less than 10,000, preferably less than 8000 (see page 11, lines 26 to 30). It includes polymerizable compounds having methacrylate functionality and a butadiene group and an acrylonitrile group, such as the commercial product HYCAR**(TM) VTBNX (see page 17, lines 5 to 12; examples 1,2 and 4). The oligomer HYCAR**(TM) VTBNX is specified at the preceding pages as being the product HYCAR VTBNX 1300 x 33 (see page 15, lines 24 to 26). Other suitable oligomers (c) include acrylate and methacrylate functional urethane oligomers, such as those supplied by Cray Valley (page 16, lines 10 and 11). In the composition of example 4, an aliphatic urethane acrylate oligomer named Craynor 965 is used. According to the Respondent's submissions this product is now available under the commercial name CN965 (see document 13).

The core/shell polymer component (b) of the compositions of document (1) does not dissolve in the composition formulation. Typically, the core is a polymer of butadiene or ethyl acrylate and the shell is a polymer of methylmethacrylate or styrene. A preferred core is a methacrylate - butadiene - styrene core. A preferred shell is a polymethacrylate shell. A preferred core/shell polymer is PARALOID**(TM) EXL 2655, supplied by Rohm and Haas Company. The compositions of the examples comprise this core shell polymer.

Preferably from 15% to 65% of the polymerizable monomer and from 10% to 30% liquid polymerizable oligomer are present in the adhesive composition. The ratio of the liquid polymerizable oligomer based on the total reactive monomer + polymerizable oligomer is comprised in the ranges of 15 to 60% for the compositions of examples 1, 2 and 4 of document (1).

The compositions of examples 1,2 and 4 of document (1) comprised also t-butyl perbenzoate or t-butyl hydroperoxide (free radical initiators) and N-phenyl-2-propyl-3,5-diethyl-1,2-dihydropyridine (PDHP) as a catalyst.

The adhesive composition of example 1 has better impact resistance than the compositions lacking either the polymerizable oligomer Hycar VTBNX or else the core shell polymer Paraloid EXL 2655 (see TEST 1; page 23, line 27 to page 25, line 9).

3. According to the Appellant, there was no proof that the products Hycar VTBNX and CN 965 used in the compositions of examples 1, 2 and 4 of document (1) had a molecular weight comprised between 1000 and 9000 and that Paraloid EXL 2655 core shell polymer swelled in the monomers present in compositions 1, 2 and 4 of document (1). Hence, according to the Appellant, the subject matter of claim 1 of the patent as granted differed from the compositions of Examples 1, 2 and 4 of document (1) by the choice of a molecular weight of 1000 to 9000 for the oligomer functionalized with ethylenically unsaturated groups and by the selection of a suitable pair core shell polymer /monomer(s), wherein the polymer swells in the monomer(s).

4. Even if it were accepted, in favour of the Appellant, that the subject matter of claim 1 of the patent as granted was novel with respect to examples 1, 2 and 4 of document (1) because of uncertainties about the molecular weight of the Hycar VTBNX or Craynor 965 oligomers and/or the ability of the core shell polymer Paraloid EXL 2655 not to swell in presence of certain monomers, it would in any event lack an inventive step, since document (1) also represents the closest state of the art to the invention. Therefore, the Board, as a measure of efficiency, deals with the issue of inventive step first.

5. Technical problem underlying the invention

The Appellant defined the problem to be solved as the provision of an adhesive composition having improved impact resistance at low temperature and improved flexibility.

6. Proposed solution

The solution is the composition of claim 1 of the granted patent characterized by the choice of a molecular weight of 1000 to 9000 for the oligomer functionalized with ethylenically unsaturated groups and by the selection of a suitable pair core shell polymer /monomer(s) wherein the polymer swells in the monomer(s).

7. Success

The Appellant relied on the results of table 1 of the contested patent comparing the properties of compositions 1 to 4 according to the invention with comparative compositions 6 and 7 to show that the problem of improving the properties has been solved by the claimed compositions.

In the case where comparative tests are chosen to demonstrate an inventive step with an improved effect over a claimed area, the nature of the comparison with the closest state of the art must be such that the effect is convincingly shown to have its origin in the distinguishing feature of the invention, i.e. the choice of a molecular weight of 1000 to 9000 for the oligomer functionalized with ethylenically unsaturated groups and the selection of a suitable pair core shell polymer / monomer(s) wherein the polymer swells in the monomer(s).

Neither composition 6 lacking a liquid oligomer nor composition 7 lacking a core/shell polymer reflects a composition of document (1), which requires both a core/shell polymer and a polymerizable liquid oligomer (see claims 1 and 3; also see TEST 1; page 23, line 27 to page 25, line 9).

The Appellant's comparison thus cannot reflect the impact of the technical feature distinguishing the claimed composition from the closest prior art, and consequently, does not demonstrate the purported improvement of the claimed compositions over those disclosed in document (1).

The Appellant argued that it was the migration of the polymerizable monomers in the shell core polymer causing its swelling which was the origin of the improved adhesive properties, however, without providing any evidence in support of its argumentation. Hence, in the absence of any substantiating facts and corroborating evidence, the Board considers the Appellant's allegation as a mere speculation, all the more because the Appellant has even not proved that Paraloid EXL 2655 did not swell in the monomers present in the compositions 1, 2 and 4 of document (1).

Since the required evidence is missing to support an improvement of the flexibility and impact resistance at low temperatures of the claimed compositions compared to the compositions of document (1), the technical problem as defined above needs to be reformulated in a less ambitious way, and in view of the teaching of document (1), as the provision of alternative adhesive compositions.

8. Obviousness

Finally, it remains to be decided whether or not the proposed solution to this objective technical problem is obvious in view of the cited state of the art, namely whether the composition according to claim 1 of the patent in suit, is an obvious alternative composition in view of the state of the art.

8.1 The composition of document (1) requires a polymerizable monomer, a core/shell polymer and a liquid polymerizable oligomer (see claim 3).

Suitable polymerizable monomers include alkyl(meth)acrylates such as methyl methacrylate (MMA) (see page 8, lines 29 to 31), suitable oligomers include VTBNX 1300 X 33 (page 15, line 24-25), suitable core shell polymers includes those having a polymethacrylate shell (see page 10, lines 28 to 31).

Suitable oligomers include methacrylate functional butadiene-acrylonitrile oligomers, such as Hycar VTBNX 1300 X 33 which is also used in the exemplified composition of the contested patent. The Appellant did not contest that a core shell polymer having a polymethacrylate shell will swell in the presence of methyl methacrylic esters.

The choice of a particular pair monomer/core shell polymer within the ambit envisaged by the general teaching of document (1), i.e. one as required in claim 1, is neither critical nor purposive for solving the objective problem underlying the patent in suit, but is an arbitrary restriction. Thus, this choice is seen as lying within the routine activity of the skilled person faced with the objective problem of providing alternative adhesive compositions and thus does not involve an inventive step.

For these reasons, the subject-matter of claim 1 the granted patent is obvious in the light of document (1).

8.2 The Appellant argued in support of inventive step that document (1) did not prompt the skilled person to select a non-polar monomer necessary for the swelling, since the preferred monomers of document (1) had polar groups.

However, when looking for alternative compositions, the skilled person does not restrict the teaching of document (1) to its preferred embodiments, but takes into consideration all features taught in that document, among them, that the polymerizable monomer may be methyl methacrylic esters (see page.....).

8.3 According to the Appellant, document (1) does not describe the properties of the compositions at low temperatures. Hence, there is nothing to suggest that the claimed compositions have favourable properties in terms of flexibility and impact resistance at low temperature. The combination of good flexibility and high impact resistance of the claimed composition was therefore unexpected from the teaching of document (1).

However, the adhesive compositions of document (1) are deemed to have good adhesive properties, especially as the Appellant has not demonstrated that a core shell polymer having a polymethyl methacrylate shell does not swell in polar monomers, such as hydroxypropyl methacrylate, and/or that polar monomers prevent the core shell polymer from swelling in non-polar monomer esters such as methyl methacrylate ester, which is present in the composition of example 2 of document (1).

The Appellant's argument related to the unexpected good adhesive properties of the claimed compositions must therefore be rejected.

8.4 Therefore, the subject-matter of claim 1 represents an obvious solution to the problem underlying the present invention. Hence, the subject-matter claim 1 of the patent as granted does not involve an inventive step (Article 56 EPC).

First auxiliary request

9. In claim 1 of auxiliary request 1, the liquid elastomer is a PU(meth)acrylate obtainable by the reaction of a polyethylene polyol or polypropylene polyol, a diisocyanate and a hydroxy functionalized ethylenically unsaturated monomer. This liquid elastomer is, for example, the CN 965 aliphatic polyurethane-acrylate with a Mw 5600 from Cray Valley (see page 5, line 4 of the contested patent)

However, document (1) also contemplates that the oligomer may be acrylate or methacrylate functional urethane oligomers, such as those supplied by Cray Valley, for instance Craynor 965, which is an aliphatic urethane acrylate oligomer (see page 16, lines 10-11; example 4).

According to the Appellant, there is no proof that the product Craynor 965 was the same as the CN 965 product, especially as regards to the molecular weight of the compound. However, an obvious option for the skilled person looking for an alternative adhesive composition is to consider other aliphatic urethane diacrylates from the Cray Valley catalogue (see document (13)), i.e. for instance by CN 965, having a molecular weight average of 5600, all the more if product Craynor 965 ex Cray Valley is no longer available. The skilled person would therefore arrive at the subject-matter of claim of the first auxiliary request without the exercise of inventive step.

Hence, the subject-matter of claim 1 of auxiliary request 1 also lacks an inventive step.

Second auxiliary request

10. In claim 1 of the second auxiliary request the ratio of the component B to A+B present in claim 1 of the patent as granted has been reintroduced in order to avoid non-compliance with Article 123(3) EPC. However, as respects inventive step, the same reasoning and conclusion as for the first auxiliary request apply. Accordingly this request must also be rejected for lack of inventive step.

Third to seventh auxiliary requests

11. The composition of claim 1 of third to sixth auxiliary requests differs from that of the first and second auxiliary request in that the reactive monomer is a (meth)acrylic ester in the form of a linear or branched or cyclic C1-C6-alkyl ester or heterocyclic or aromatic ester (third and fourth auxiliary requests), or is selected from methylmethacrylate (MMA), tetrahydrofurfurylmethacrylate (THFMA), cyclohexylmethacrylate (CHMA), cyclic trimethylolpropane formal acrylate (CTFA), isobornylmethacrylate (IBMA), benzylmethacrylate (BMA), diclopentadienyloxyethylmethacrylate (DCPOEMA), t-butylmethacrylate (tBMA), isobornylacrylate (IBH) anddihydrodicyclopentadienylacrylat (DH-DCPA) (fifth and sixth auxiliary request).

The composition of claim 1 of the seventh auxiliary request differ form that of claim 1 of the main request in that the reactive monomer comprises at least 50% of tetrahydrofurfuryl methacrylate or methyl methacrylate or mixtures thereof.

Document (1) specifically mentions methyl methacrylate as a suitable polymerizable monomer. Methyl methacrylate is also present in the composition of example 2 of document (1).

The Appellant argued that the choice of only non-polar monomers provided better properties and therefore was a purposive choice.

The Appellant, however, did not provide any evidence showing that the use of only non-polar monomers, such as methyl methacrylate provided better properties compared to the use of the monomers present in the examples of document (1). Accordingly, in the absence of any substantiating facts and corroborating evidence, the Board considers the Appellant's allegation as a mere speculation.

The choice of for instance methyl methacrylate as the polymerizable monomer is therefore neither critical nor purposive for solving the problem of providing alternative adhesive compositions. The act of arbitrarily picking out polymerizable monomers listed in document (1) without providing a particular technical effect lies within the routine activity of the skilled person.

Accordingly, the third to seventh auxiliary requests should also be rejected for lack of inventive step.