T 0409/11 16-05-2013

Reasons for the Decision

1. The appeal is admissible.

2. Admissibility of the new requests filed with letter dated 12 March 2013

The new main request and auxiliary requests 1 to 5 were filed in an attempt to overcome the objection raised by the respondent under Article 123(3) EPC against amended claim 1 of the requests filed with the statement setting out the grounds of appeal. Due to the limitation of the crosslinkable monomers to a specific group in claim 1 of these requests, there was no longer any limitation on the amount of other crosslinkable monomers outside this definition but still covered by the claim.

The new requests prima facie overcome the respondent's objection by arranging the two requirements relating to the crosslinkable monomer (i.e. amount and nature) in a "cascade-like" manner. Furthermore, such a restriction had been the appellant's intention from the beginning of the appeal procedure, so that these new requests cannot have come as a surprise to the respondent. The respondent did not file any objection to them.

During the oral proceedings the board observed that the main request (as well as the auxiliary requests) filed with the letter dated 12 March 2013 appeared to be objectionable by virtue of the separation of the feature (ii) ("a crosslinkable monomer") from the features (i)(a) and (b). The discussion continued on the basis that if, apart from this objection, one of the requests of this set was found to be allowable, an amended request would be filed by the appellant to deal with this objection.

On this basis, the board admitted the requests filed with the letter dated 12 March 2013 into the proceedings.

3. Admissibility of documents filed in appeal

The appellant filed documents D13 to D15 with a letter dated 12 March 2013. Document D13 was filed in order to demonstrate that D10 was not novelty destroying and D14 and D15 in support of the argument that the claimed subject-matter involved an inventive step. The respondent did not object to the admissibility of these documents and the board considered them prima facie relevant for the respective issues and admitted them into the proceedings.

The main request

4. Novelty

4.1 The appellant raised novelty objections in view of D1 to D4. Although the reasoning was given only for D2, it was argued that it was applicable also to D1, D3 and D4. In fact D1 to D4 originate from the same corporate applicant and each of the documents discloses nearly the same heat-expandable microcapsules (a synonymous term for microspheres as used in the patent in suit).

4.2 D2 discloses thermally expandable microcapsules excellent in heat resistance after expansion (page 2, lines 1-2). The microcapsules comprise a shell and an expanding agent, wherein the shell is made from a copolymer consisting essentially of a polymerizable monomer (A) having two or more polymerizable double bonds and a monomer (B) which can produce a homopolymer having a high glass transition temperature (claim 1). An especially preferred monomer (B) is, amongst others, methacrylonitrile (page 2, lines 44-49).

The polymerizable monomer (A) is a polyfunctional vinyl monomer and/or an inner olefin-containing monomer. The most preferred polyfunctional vinyl monomers are the bifunctional ethylene glycol di(meth)acrylate and the trifunctional trimethylolpropane tri(meth)acrylate and triacrylformal (page 2, lines 29-34).

For optimal cross-linking the polymerizable monomer (A) may be used preferably in the amount of 0.01 - 3% by weight, more preferably 0.05-2% by weight (page 2, lines 38-43).

However, there is no direct and unambiguous disclosure in D2 as regards the combination of the overlapping range of 1.1 to 3 wt.-% with the bifunctional crosslinkable monomer ethylene glycol di(meth)acrylate. Such a combination would be necessary to arrive at an embodiment falling within the scope of claim 1 of the main request. Therefore novelty of the subject-matter of claim 1 over the general disclosure of D2 is acknowledged.

Regarding the examples in D2, it is noted that the exemplified combinations always use a trifunctional crosslinkable monomer, namely the trimethylol propane trimethacrylate (TMPRMA), in a proportion based on the polymerizable monomers, namely acrylonitrile, methacrylonitrile and methyl methacrylate or isobornyl methacrylate, which is about 0.5 wt.-%. Thus novelty is also acknowledged over the specific examples of D2.

4.3 Also the similar documents D1, D3 and D4 do not disclose the use of a bifunctional crosslinking monomer having the structure required in claim 1 in combination with the required amount of 1.1 to 5 wt-% thereof.

4.4 D10, a statement including technical evidence filed by the applicant of D2 during prosecution thereof before the EPO, was also cited in the decision under appeal. In example 7 of this document thermally expandable microcapsules were obtained by polymerizing acrylonitrile and methacrylonitrile together with a trifunctional crosslinkable monomer, namely trimethylolpropane trimethacrylate (TMPTMA), and dicyclopentenyl acrylate (DCPA). Although DCPA could be considered as a bifunctional crosslinkable monomer (which was disputed by the appellant), it does not have the structure required by claim 1, namely two polymerizable carbon-carbon double bonds linked together via a flexible chain derived from a diol compound. Therefore D10 is irrelevant for the novelty of claim 1.

5. Inventive step

5.1 Closest state of the art

As already mentioned above, D1 to D4 disclose nearly the same thermally foamable microspheres and could equally be selected as closest state of the art. Since both parties agreed with the view of the opposition division to start from D2 as the closest state of the art, the board follows this line.

5.2 The technical problem

The appellant saw the technical problem underlying the patent in suit in the light of D2 as being the provision of thermally foamable microspheres having a shell polymer with limited dependency of its modulus of elasticity on temperature so that a wide range of appropriate processing temperatures could be ensured, an improved resistance to polar solvents and plasticizers, and high capability of retaining foaming properties (paragraphs [0020], [0021] of the patent in suit).

5.3 The appellant argued that this problem had been successfully solved by thermally foamable microspheres characterized by the features which distinguish the claimed subject-matter from D2, namely the use of a crosslinkable monomer in the shell polymer that must satisfy the following two requirements:

(1) the proportion of crosslinkable monomer, based on the polymerizable monomer, is 1.1-5 wt.-%; and

(2) the crosslinkable monomer is a bifunctional compound having a structure in which two polymerizable carbon-carbon double bonds are linked together via a flexible chain derived from a diol compound selected from polyethylene glycol, polypropylene glycol, an alkyldiol, an alkyl ether diol and an alkyl ester diol.

In this context the appellant referred to the experimental part of the patent in suit (examples 1 and 2; figure 2) and the additional experimental evidence D15.

5.4 However, as the respondent correctly observed only one single bifunctional crosslinkable monomer is used in the patent in suit, namely diethylene glycol dimethacrylate (DEGDMA). With regard to D15, two additional bifunctional crosslinkable alkyl diol acrylate monomers were used, namely 1,10 decanediol dimethacrylate (1,10-DDDA) and 1,6-hexanediol dimethacrylate (1,6-HDMA).

Although in principle some extent of generalisation from specific examples might be allowed, the board agrees with the respondent that there is no sufficient evidence supporting the solution of the problem over the entire scope of claim 1 of the main request. In fact the bifunctional crosslinkable monomers of claim 1 concern a very broad spectrum of chemical compounds. The appellant has also not provided any convincing argument or evidence that the alleged improvement would be achieved by other chemical compounds than those exemplified.

The board also does not agree with the appellant that technical evidence for the successful solution of the technical problem can be found in figure 1, "a graph showing relations between the modulus of elasticity of the shell polymer of a thermally foamable microsphere and temperature" (paragraph [0027]). Even if figure 1 shows an improvement, the board observes that the curves of figure 1 do not relate to any concrete experimental data mentioned in the patent. Thus, an advantage derived from figure 1 cannot be attributed to bifunctional crosslinkable monomers. In fact claim 1 as granted relates merely to "a crosslinkable monomer" and even the patent specification refers in this context to polyfunctional compounds having two or more carbon-carbon double bonds (see paragraphs [0047] to [0049]). In other words, it is completely unclear on the basis of which experimental data the curves of figure 1 have been drawn.

5.5 In view of the above considerations the problem to be solved in the light of D2 can only be seen in the provision of an alternative thermally expandable microsphere.

5.6 Obviousness

The board in agreement with the opposition division and the respondent considers that the skilled person starting from D2 (page 2, lines 24-44 and examples 1-4) and looking for alternative thermally expandable microspheres would find in this document the disclosure of:

- the use of any vinyl monomer having two or more polymerizable double bonds as the crosslinkable monomer (page 2, lines 29-30), which disclosure encompasses the monomers now required in claim 1 of the main request, and even specifically mentions DEGDMA;

- the use of such monomer in an amount of 0.01-3% by weight, a range which overlaps with the amount of 1.1-5% by weight of claim 1 of the main request.

Thus the selection on the one hand of the specifically claimed crosslinkable monomers and on the other hand of the specifically claimed amount is nothing more than an arbitrary selection from the disclosure of D2, such selection not being associated with any unexpected technical effect.

5.7 Consequently claim 1 of the main request lacks an inventive step with the result that the main request is not allowable.

Auxiliary requests 1 and 2

6. In claim 1 of auxiliary requests 1 and 2 the nature of the crosslinkable monomer has been further restricted.

6.1 Claim 1 of auxiliary request 1 defines the carbon-carbon double bonds as follows:

"the crosslinkable polymer is a bifunctional compound having a structure in which two polymerizable carbon-carbon double bonds, selected from vinyl, methacryl, acryl and allyl, are linked together via a flexible chain derived from a diol compound selected from polyethylene glycol, polypropylene glycol, an alkyldiol, an alkyl ether diol and an alkyl ester diol". (amendment over claim 1 of the main request in bold)

6.2 Claim 1 of auxiliary request 2 provides a list of crosslinkable monomers:

"the crosslinkable polymer is at least one bifunctional compound selected from polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate an alkyldiol di(meth)acrylate, an alkyl ether diol di(meth)acrylate and an alkyl ester diol di(meth)acrylate". (amendment over claim 1 of the main request in bold)

6.3 However, for the reasons set out above regarding the main request, the subject-matter of claim 1 of auxiliary requests 1 and 2 also lacks an inventive step. The board considers that the definition of the crosslinkable monomer in the respective requests is still very broad in comparison to the available technical evidence. Therefore these requests are not allowable.

Auxiliary request 3

7. Auxiliary request 3 was filed during the oral proceedings in view of the board's objection against the separation of the crosslinkable monomer, i.e. feature (ii), from the polymers defined in (i)(a) and (b). The amended wording merely re-establishes that the crosslinkable monomer is used in the polymerisation of the shell polymers (a) and (b). The respondent had chosen not to attend oral proceedings and the board saw no reason not to admit this request into the proceedings (see also point 2 above).

8. Amendments under Article 123(2) EPC

8.1 Claim 1 of the third auxiliary request differs from claim 1 as granted (point I above) in that:

- the shell polymer is defined as either (a) a vinylidene chloride (co)polymer or (b) a (meth)acrylonitrile (co)polymer (based on claim 5 as filed);

- the crosslinkable monomer has to meet the following two requirements:

(1) the proportion of crosslinkable monomer, based on the polymerizable monomer is 1.1-5 wt.-%; and

(2) the crosslinkable monomer is at least one bifunctional compound selected from polyethylene glycol di(meth)acrylate and an alkyldiol di(meth)acrylate (based on the last paragraph on page 19 of the application as filed).

8.2 The respondent argued that the amendment of the lower limit for the crosslinkable monomer from "greater than 1% by weight" to "1.1 wt.-%" was not supported by the application as filed.

However, the amendment is based on the first full paragraph on page 19 of the application as filed, which states:

"The lower limit to the proportion of the crosslinkable monomer used is greater than 1% by weight, preferably 1.1% by weight, more preferably 1.2% by weight, and even more preferably 1.3% by weight based on the polymerizable monomer … ."

The board does not accept the respondent's argument that that the term "greater than" in this passage is also associated with the preferred values. "Greater than 1%" merely defines the most general lower limit, whereas the preferred values disclose specific lower limits, each of which is greater than 1.

8.3 Moreover, the board does not agree with the respondent that the restriction of the shell polymers to vinylidene chloride (co)polymers and (meth)acrylonitrile (co)polymers in combination with the restriction of the crosslinkable monomer to specific types and amounts thereof results in an unsupported combination.

As regards the types of the polymers, page 10, line 26 to page 11, line 1, of the application states:

"In consideration of these, vinylidene chloride (co)polymers and (meth)acrylonitrile (co)polymers are preferred for the shell-forming polymer".

This is an explicit disclosure of a general preference of the shell-forming polymers now defined in claim 1 of auxiliary request 3. This applies to all embodiments, and clearly also to embodiments in which preferred crosslinkable monomers are used.

Similarly, the preference for bifunctional crosslinkable monomers is disclosed in the passage bridging pages page 15 and 16 (some of the compounds have been merely deleted without singling out a specific compound), and the preferred amounts thereof are described on page 19, lines 7-14, directly following the detailed definition of the preferred bifunctional crosslinkable monomers. The skilled person reading the entire application would understand that the preferred types of shell polymers can be combined with the preferred crosslinkable monomers and preferred amounts thereof.

8.4 Similar amendments have been made to independent claim 14, which relates to a process for producing a thermally foamable microsphere. For the same reasons as given for claim 1, these amendments are also allowable.

8.5 In view of the above, the amendments to auxiliary request 3 fulfil the requirements of Article 123(2) EPC.

9. Amendments under Article 123(3) EPC

In independent claims 1 and 14 of this request the crosslinkable monomer used in the preparation of the shell polymer has to meet two requirements, each of which has to be fulfilled individually. These two requirements are (1) the content of crosslinkable monomer in general, and (2) the chemical nature of the crosslinkable monomer that is actually present. This "cascade-like" formulation ensures that the amount of crosslinkable monomer is within the claimed range (even if further crosslinkable monomer not specified in (2) were to be present) and that the specified crosslinkable monomer is present (in this context see T 999/10). Consequently the scope of the independent claims of auxiliary request 3 does not extend beyond the scope of the claims as granted and thus these claims are in conformity with the requirements of Article 123(3) EPC.

10. Clarity

The respondent did not raise any objection concerning the clarity of this request and the board is satisfied that the claimed subject-matter is clear and concise and is supported by the description. Therefore it fulfils the requirements of Article 84 EPC.

11. Sufficiency of disclosure

The respondent contested sufficiency of disclosure on the ground that not all claimed bifunctional crosslinkable monomers could be used in the preparation of microspheres with the desired properties. It was argued that the technical evidence of the patent in suit related only to DEGDMA and that crosslinkable monomers which were even structurally similar to DEGDMA did not provide useful expandable microspheres. In this context reference was made to D11.

The board cannot accept the argument of the respondent:

Firstly, the definition of the crosslinkable monomer has been drastically limited in the third auxiliary request and concerns only two groups of compounds: polyethylene glycol di(meth)acrylate and alkyldiol di(meth)acrylate.

Secondly the respondent did not provide any concrete explanation as to why the technical evidence of D11 was relevant for the sufficiency of auxiliary request 3. The respondent argued in its letter dated 18 August 2011 (see page 3; under the title "Article 100(b)") that D11 should show that none of 1,4-butanediol divinylether (BDDVE), ethylene glycol dimethacrylate (EGDMA) or polyethylene glycol dimethacrylate (PGDMA) could be used in amounts greater than 1.1% by weight and still give useful expandable microspheres. In view of the limitation of the crosslinkable monomer this objection becomes irrelevant for all compounds referred to except for polyethylene glycol dimethacrylate. However for this compound there is no detailed analysis of the data; the respondent has simply stated in very general terms that no useful expandable microspheres could be obtained by using those bifunctional crosslinkable monomers.

Thirdly, as pointed out by the appellant, the person skilled in the art using his common knowledge and the general information presented in the application as filed would consider different polymerization conditions, depending on the nature of the crosslinking monomer to be used, and would adapt the polymerization conditions for a given reaction system so that the desired expansion ratio would be achieved.

Under these circumstances the board considers that the claimed invention is disclosed in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art.

12. Novelty

The subject-matter of claim 1 of auxiliary request 3 is narrower in scope than the corresponding claim 1 of the main request which has been considered to be novel over the opposed state of the art (see point 5 above). Therefore the subject-matter of claim 1 of auxiliary request 3 and, by the same token, the subject-matter of claim 14 are also novel over that state of the art.

13. Inventive step

13.1 The closest prior art

As for the main request, D2 is still considered to represent the closest state of the art, a document which discloses thermally expandable microcapsules excellent in heat resistance after expansion (page 2, lines 1-2).

13.2 The technical problem

The appellant still saw the technical problem in the provision of thermally foamable microspheres wherein (a) the shell polymer has a limited dependency of its modulus of elasticity on temperature, so that a wide range of proper processing temperatures can be ensured, (b) the microspheres have resistance to polar solvents and plasticizers (chemical resistance and solvent resistance) and (c) the microspheres have a high capacity of retaining foaming properties.

13.3 This problem is solved by thermally foamable microspheres characterized by the use of a crosslinkable monomer in the shell polymer that must satisfy the following two requirements:

(1) the proportion of crosslinkable monomer, based on the polymerizable monomer is 1.1-5 wt.-%; and

(2) the crosslinkable monomer is a bifunctional compound selected from polyethylene glycol di(meth)acrylate and an alkyldiol di(meth)acrylate.

13.4 The solution of the technical problem is indeed illustrated in the technical evidence of the patent in suit (concerning the bifunctional crosslinkable monomer DEGDMA), the additional technical evidence provided by the appellant as D12 (concerning the bifunctional crosslinkable monomer DEGDMA) and D15 (concerning the bifunctional crosslinkable monomers 1,10-DDDA and 1,6-HDMA). On the basis of this technical evidence and in view of the narrower scope of claim 1 of auxiliary request 3 and in the absence of any clear and unambiguous counter-evidence presented by the respondent the board accepts that the technical problem has successfully been solved over the entire scope of claim 1.

13.4.1 The respondent argued that the experimental data of D11 showed that some crosslinkable monomers encompassed by claim 1 gave significantly inferior expansion capability when used in amounts exceeding 1.1% by weight. However, this objection of the respondent had essentially been raised for the main request. No specific argument regarding auxiliary request 3 in view of the technical problem was raised in writing and the respondent did not attend the oral proceedings in order to provide the necessary clarifications on this point. Considering the experimental evidence of D11 the board has come to the conclusion that it is not prima facie relevant since it does not clearly demonstrate that compounds falling within the claimed bifunctional crosslinkable monomers in a proportion between 1.1-5 wt.-% do not solve the technical problem set out above.

The respondent also relied on D8, a document produced by the appellant in other proceedings, in order to undermine the credibility of the experimental data in the patent in suit. D8 reports that microspheres with a shell comprising 1.5% by weight of the trifunctional crosslinkable monomer TMPDMA are thermally foamable, whereas for microspheres with 1.6% by weight of TMPDMA in comparative example 2 of the patent in suit no foaming is observed. D8 can only show that comparative example 2 of the patent is not conclusive. However no conclusion can be drawn with respect to the specific bifunctional crosslinkable monomers now required in claim 1.

Finally, the respondent argued that the technical problem, although not explicitly mentioned in D2, was implicitly disclosed therein since the modulus of elasticity of the microspheres, their resistance to polar solvents and plasticizers and their capacity of retaining foaming properties were properties clearly encompassed by the more general term of heat resistance disclosed in D2. The board does not agree with these assertions of the respondent, which do not find any support in the disclosure of D2.

13.4.2 In summary, there is nothing on file which casts doubt on the above identified technical problem as also being the objective technical problem and on the conclusion that this problem has been credibly solved.

13.5 The question of obviousness

13.5.1 The question which remains to be answered is whether the skilled person starting from D2 and intending to provide microspheres with a shell polymer having a limited dependency of its modulus of elasticity on temperature, improved chemical and solvent resistance, and high capability of retaining foaming properties, would find in this document or the other cited documents of the state of the art any motivation to select from the crosslinkable monomers encompassed by the disclosure of D2 at least one bifunctional compound selected from polyethylene glycol di(meth)acrylate and an alkyldiol di(meth)acrylate in a proportion of 1.1 to 5-wt.% based on the polymerizable monomer.

13.5.2 The board in agreement with the appellant considers that the skilled person would not find such a motivation in D2 itself since this document is essentially interested in high heat resistance after expansion (page 2, lines 21-23; page 3, line 30; table 1). Moreover the skilled person following the teaching of D2 would rather be motivated to use trifunctional rather than bifunctional crosslinkable monomers since in all examples a trifunctional crosslinkable monomer was used, namely TMPTMA. Furthermore, all the examples use the crosslinkable monomer in an amount of around 0.5% by weight. The board thus concludes that the claimed subject-matter is not obvious in view of D2.

13.5.3 The respondent also alleged that a skilled person would expect from his common general knowledge that an increased amount of crosslinkable monomer would give polymers with higher modulus of elasticity and higher resistance to solvents. In this context, reference was made to D9, a textbook representing common knowledge in respect of polymers, which discloses on pages 138, 151 and 348 that the effect of crosslinking is dependent on the quantities of the difunctional monomer in a copolymerization, that crosslinked polymers do not dissolve easily and that the addition of crosslinks in a polymer leads to stiffer and stronger products.

However, the board does not concur with the respondent's view. Firstly, D9 is very general in nature with no direct relation to thermally foamable microspheres. Secondly, although D9 states on page 138 that "It is usual to reduce the effect of the crosslinking reaction by utilising only small quantities of the difunctional monomer in a copolymerization", the board has difficulties to read into this sentence a direct or indirect link to the dependency of the modulus of elasticity on temperature of a thermally foamable microsphere. Thus, it appears that the respondent's attack is based on hindsight.

13.6 Claim 14 is directed to a process for producing the thermally foamable microsphere as defined in claim 1. Due to the patentability of claim 1 the patentability of the process claim is also established. The same applies to dependent claims 1 to 13 and 15 to 18.

Auxiliary requests 4 and 5

14. Since the claims of auxiliary request 3 are considered to fulfil the requirements of the EPC, there is no need to consider these hierarchically lower auxiliary requests.