Re: Patent Application 2,237,960 CD 1342
Background
The application relates to the manufacture of precipitated calcium carbonate from impure calcium oxide.
On 17th of January 2007 the Examiner issued a Final Action rejecting all of the claims on the basis that they constituted double patenting based upon Canadian patent 2,208,150.
The ‘960 application contains an independent claim 1 with dependent claims 2-17. Claim 1 reads in part as:
A method for the manufacture of precipitated calcium carbonate from impure calcium oxide, comprising: (a) admixing said impure calcium oxide with an aqueous solution consisting essentially of a salt of at least one compound selected from the group consisting of organic amines of the formula RNH2…
The ‘150 Patent claim 1 reads:
A method for the manufacture of precipitated calcium carbonate with a high brightness of impure calcium oxide, comprising: (a) admixing said impure calcium oxide with an aqueous solution consisting essentially of a salt of at least one compound selected from the group consisting of organic amines of the formula RNH2…
Analysis
There are two types of double patenting. The first is ‘same invention’ double patenting which is where the claims are identical or coterminous. The second branch is obviousness double patenting where the claims are not distinct. To avoid obviousness double patenting the claim must exhibit ingenuity over the claim under comparison.
Double patenting is based upon a comparison of the claims.[23] It is not to be done on a literal construction but rather a purposive one from the perspective of a person of ordinary skill in the art.[23] During this process elements are identified as essential or non-essential. To be “non-essential” it must be shown that it was clearly not intended to be essential or that at the date of publication it would not have been deemed essential by a person of ordinary skill.[23]
Claim 1 in the present application adds the reducing agent subsequent to filtration while the ‘150 requires the addition prior to filtration. The Applicant argued that this difference in steps results in a different method. The description however indicates that the process is interchangeable.[30] This implies that the order is a non-essential element and is therefore incapable of differentiating the two applications.[31]
Several other differences between the patents were argued by the Applicant. These include that the minimum temperature threshold is 50 Celsius for the application while it is 70 Celsius for the ‘150 patent. The Applicant argued that the 50 Celsius threshold is needed to avoid gel formation. No evidence was lead that this formed a part of the common general knowledge and so it was held to be patentably distinct.[38]
To be distinct from the other claims in the ‘150 patent the range must be distinguished by restricting the range to 50 Celsius minimum and less that 70 Celsius maximum.
Numerous other process features were identified as being different from the ‘150 patent including different reducing agents, different amounts of reducing agents, different admixing steps and additional treatments of the solutions.
The Board concluded that the difference with respect to filtration does not distinguish the claims from the ‘150 patent. The other additional features do not distinguish the claims from the ‘150 patent. The temperature range does distinguish the claims from those found in the ‘150 patent. In order to remain patentably distinct the range in claim 1 must be specified to be between 50 Celsius and 70 Celsius.
The patent application must therefore be amended to include this limiting temperature range. Once such an amendment is made the application will be in compliance with the Patent Act and Patent Rules.