T 0108/14 - Basis for "consisting essentially of"

Key point

• During prosecution, " containing"  was restricted to "consisting essentially of". The application does not provide literal basis. Is the amendment allowable under Article 123(2) EPC?
• The patentee argued that, according to decision T 1170/07, the substitution of the expression "consisting essentially of" for the term "comprising" was allowable.
• The board notes that, according to T 1170/07, the expression "consisting essentially of" excluded the presence in the claim of further active agents useful in the treatment of a specific disease but allowed the presence of additional compounds which were not active agents according to this definition, for instance the carrier for said active agent.
• "For the board, this decision does not apply to the case at issue because it is not directly and unambiguously derivable from the application as filed, which "active agents" are useful or not for the primary phase and for the secondary bond phase, respectively." 

T 0108/14 - link 

Consisting essentially of

Summary of Facts and Submissions

I. The present appeal lies from the decision of the opposition division to revoke European patent No. 1 666 433, with claim 1 as granted reading as follows:

"1. A silicon nitride-bonded SiC refractory which contains SiC as a main phase and a secondary bond phase essentially consisting of Si3N4 and Si2N2O along with at least one element selected from Al, Ca, Fe, Ti, Zr and Mg in terms of oxide, and which has a bending strength of 150 to 300 MPa and a bulk density of 2.6 to 2.9, and which contains the at least one element selected from the group consisting of Al, Ca, Fe, Ti, Zr and Mg in an amount of 0.1 to 3% by mass in terms of oxide."

Reasons for the Decision

1. Main request - Article 123(2) EPC

1.1 It is undisputed that claim 1 as granted has no literal basis in the application as filed. The question thus arises whether the subject-matter of this claim is, as required by the jurisprudence, directly and unambiguously derivable from the application documents as originally filed.

1.2 In the application as filed, the invention was defined as follows in claim 1:

"1. A silicon nitride-bonded SiC refractory which contains SiC as a main phase and Si3N4 and/or Si2N2O as a secondary phase and which has a bending strength of 150 to 300 MPa and a bulk density of 2.6 to 2.9."

In the particular embodiment according to claim 5, the invention was further specified as follows:

"5. The silicon nitride-bonded SiC refractory according to any of claims 1 to 4, which contains at least one member selected from the group consisting of Al, Ca, Fe, Ti, Zr and Mg, in an amount of 0.1 to 3% by mass in terms of oxide."

1.3 In the patent as granted, the invention was defined differently (see point I above), in particular as regards the secondary phase, which is now defined as being a "secondary bond phase essentially consisting of Si3N4 and Si2N2O along with at least one element selected from Al, Ca, Fe, Ti, Zr and Mg in terms of oxide", and the question thus arises as to whether there is a direct and unambiguous disclosure in the application as filed for this amended definition of the secondary phase, in particular as regards the features emphasised in bold.

1.4 The board did not find any basis in the original application documents for a secondary phase essentially consisting of Si3N4, Si2N2O and one or more oxides of Al, Ca, Fe, Ti, Zr and Mg. Moreover, the sole compositional analysis of a refractory according the invention (example 2) reveals the presence of at least a further component, namely SiO2 in an amount of 1.75 mass % (see table 3, page 16 as filed).

1.5 The appellant argued that the SiO2 in the refractory of example 2 was exclusively located, as explained at page 12, lines 15 to 25, on its surface in the form of a strong oxide film, as a result of a heat treatment in air at 1300 to 1500°C of the final refractory.

The passage at page 8, lines 4 to 10 furthermore made clear that, apart from those compounds defined in claim 1 at issue, no further compounds, in particular those in form of a glassy phase or cristobalite, were present in the refractory according to the invention.

1.6 These arguments do not convince the board because, as explained by the respondent, a substantial part of the SiO2 identified in the refractory of example 2 is necessarily located between the SiC grains of the main phase, i.e. in the secondary phase as a result of:
- the mandatory presence of 0.01 to 2.00% of oxygen in the nitrogen atmosphere used for firing the raw materials (see page 12, lines 3 to 5);
- the presence of oxygen in a bound form in Al2O3 and Fe2O3 (see Table 1);
- the post-treatment in air mentioned at page 12, lines 15 to 25.As all these oxygen atoms inevitably react at high temperature with the Si powder present in the starting raw materials (page 13, lines 15 to 18 and Table 1), the presence of SiO2 in the secondary bond phase, in addition to the Si2N2O already defined in claim 1, is evident to the skilled person.

1.7 The board also cannot accept the argument that a glass phase and cristobalite were explicitly excluded from the secondary phase, since the passage at page 8, lines 4 to 10, merely discloses that the "refractory of the present invention is preferred to contain at least one member selected from the group consisting of Al, Ca, Fe, Ti, Zr and Mg, in an amount of 0.1 to 3% by mass in terms of oxide, from the standpoint of [...], control of the amount of cristobalite to be formed, and control of the amount of glass phase to be formed", and so this passage merely means that the cristobalite and the glass phase are "controlled", not that these phases are excluded.

The appellant further argued that, according to decision T 1170/07, the substitution of the expression "consisting essentially of" for the term "comprising" was allowable.

The board notes that, according to T 1170/07, the expression "consisting essentially of" excluded the presence in the claim of further active agents useful in the treatment of a specific disease but allowed the presence of additional compounds which were not active agents according to this definition, for instance the carrier for said active agent.

For the board, this decision does not apply to the case at issue because it is not directly and unambiguously derivable from the application as filed, which "active agents" are useful or not for the primary phase and for the secondary bond phase, respectively.

1.9 The board is further aware of certain jurisprudence (e.g. T 1095/09, reasons 6; T 0759/91, reasons 2.2; T 0522/91, reasons 2.2; T 0472/88, reasons 3) according to which the expression "consisting essentially of" was found to be clear and to allow the presence of other components in addition to the components mandatory in the claimed composition, provided that the essential characteristics of the claimed composition were not materially affected by their presence.

In the present case, however, the application as filed is silent as regards the components which, in addition to those defined in claim 1 at issue, could be allowed in the claimed refractory without affecting its essential characteristics. The board furthermore notes that the application as filed also does not disclose whether SiO2, which is explicitly disclosed as being present in the refractory according to example 2 of the patent, affects the essential characteristics of the claimed refractory composition or not.

It follows that in the present case, the expression "essentially consisting of" is not unambiguous, since the meaning of essential is not evident from the application.

1.10 As a consequence of the above considerations, the limitation of the secondary bond phase to "essentially consisting of Si3N4 and Si2N2O along with at least one element selected from Al, Ca, Fe, Ti, Zr and Mg in terms of oxide" is not directly and unambiguously derivable from the application as filed, so this amendment does not meet the requirements of Article 123(2) EPC.

1.11 Since the main request does not meet the requirements of the EPC, it cannot be allowed.