T 1819/07 – Average Danger

The applicant filed an appeal against the decision of the Examining Division (ED) to refuse its European patent application for lacking unity of invention.

Claim 1 of the main request before the Board read:

1. A method for Direct Synthesis of organohalosilanes

comprising the steps of :

providing a silicon metal;

providing an organohalide of formula RX wherein R is a saturated or unsaturated aliphatic or aromatic hydrocarbon radical having from 1 to 10 carbon atoms, and X is a halogen;

providing a copper catalyst precursor selected from the group consisting of copper metal, copper (I) oxide, copper (II) oxide, copper (I) chloride, copper (II) chloride, copper (I) carboxylates, copper (II) carboxylates, other copper salts, and mixtures thereof, said copper catalyst precursor having an average particle size from 0.1 to 600 nanometers;

providing one or more promoters; and

reacting said silicon metal, said organohalide and said copper catalyst precursor for a time and temperature to effectuate D/T selectivity (gravimetric ratio of R2SiX2/RSiX3) of greater than 10.

The Board found this claim to lack clarity:

[3.1] Claim 1 of the Main Request and of both Auxiliary Requests characterises the copper catalyst precursor by indicating a range for the “average particle size” of from 0.1 to 600 nanometers or of less than 600 nanometers.

[3.2] Document D5 states that average particle sizes (more precisely: mean particle diameters) such as the arithmetic mean diameter (or count mean diameter) đ, the volume or mass mean diameter đv and the mean surface area diameter đs are among the most commonly used quantities for describing the average diameter of a particle population […]. The values of the average particle sizes đ, đv, and đs differ for any particle size distribution […].

“It is not unusual for a polydispersed particle population to exhibit a diameter of average mass as being one or two orders of magnitude larger than the arithmetic mean of the diameters.” […]

Hence, there are different methods for determining the average particle size yielding values for the same particle distribution which generally differ, under particular conditions by one or two orders of magnitude. 

[3.3] The Appellant considered the method described in document D6 to be the most common one by which the person skilled in the art would determine the average particle size […].

[3.3.1] This document mentions that the “Determination of particle size may be done by transmission electron microscopy (TEM) or high resolution scanning electron microscopy (HRSEM).”.

[3.3.2] The present application deals with the Direct Synthesis of organohalosilanes, i.e. the copper catalysed reaction of silicon with organohalides […]. Of the prior art documents cited by the ED, documents D1, D2 and D4 also deal with said Direct Synthesis […].

Document D1 states that the “mean particle size … indicates a median diameter known as dP50 corresponding to 50% on a volume basis cumulative distribution curve …” ([…]; emphasis added by the Board).

According to document D2 “… an average particle size means the mass median particle size as measured with …” ([…]; emphasis added by the Board).

Document D4 considers it “desirable that the area mean diameter of the particles” be within a certain range ([…]; emphasis added by the Board)).

Hence, there is no reason to assume that there is a most common method of determining the average particle size in the field of the Direct Synthesis of organohalosilanes. Moreover, the values determined by calculating the volume or mass average will differ from those taking the area average […].

[3.4] Finally, the appellant argued that the claims were clear as the method for determining the average particle size was disclosed in U.S. patent D6 as the respective patent application was referred to in the application as filed […].

[3.4.1] On the one hand, A 84 requires that the claims shall be clear. “This implies that the claims must be clear in themselves when being read with the normal skills, but not including any knowledge derived from the description of the patent application …” (T 908/04 [3.5]). Therefore, a reference in the description can generally not render an otherwise unclear claim clear.

[3.4.2] On the other hand, the appellant relies on references to the US patent application on which the patent D6 was granted. Said references are found in the application as published […].

These references are the following (emphasis added):

“It is preferred that the nanosized copper and copper oxides used in the present invention are prepared by the methods taught ..., and, most preferably, by the method taught in co-pending patent application entitled PREPARATION OF NANOSIZED COPPER AND COPPER COMPOUNDS, Attorney Docket No. 0066-OS, filed on even date herewith.”

“Nanosized copper (I) oxide was prepared by thermal decomposition of KOCIDE® Cu(OH)2 in NALKYLENE® 500 as taught in co-pending patent application entitled PREPARATION OF NANOSIZED COPPER AND COPPER COMPOUNDS, Attorney Docket No. 0066-OS.”

This means that the nanosized particles could be made according to the method disclosed in this document, not that the average particle size is to be determined according the method described in said U. S. patent application.

For this reason, the methods for determining the average particle size as disclosed in document D6 […] do not form part of the disclosure of the present application as filed. Hence, these methods can neither establish clarity of the claims nor form the basis for an amendment which might render the claims clear.

[3.5] Therefore, the parameter “average particle size” in claim 1 of the main request and of the first and second auxiliary requests renders these claims unclear. As claim 1 is the only independent claim in each of these requests, the parameter “average particle size” forms part of a mandatory feature in each claim of these requests, thus rendering all these claims unclear.

[3.6] Hence, the claims of the main request and of the first and second auxiliary requests do not meet the requirement of A 84 that the claims shall be clear. As no other set of claims was filed as a basis for a further auxiliary request, the Board had to dismiss the appeal.

To download the whole decision, click here. The file wrapper can be found here.

NB: This decision has already been presented on Le blog du droit européen des brevets.