The opinion
ALMOND, Judge
(concurring).
The question before us is whether, at the time the invention was made, it was or was not obvious to use TBPAA having less than 5 ppm ferric iron in a polyesterification reaction. It seems clear that if TBPAA having the required degree of purity was in fact readily commercially available at the time the invention was made, it would have been quite obvious to use it in such reactions, particularly in view of the suggestion of Hoffman that ferric iron is desirably removed from the very similar compound tetrachlorophthalic acid anhydride before its use in plastics production.
*667 On the other hand, if all TBPAA' which was commercially available at the time the invention was made had a high iron content and hence was unusable in polyesterification reactions, it would appear that appellants have made an advance in the art by recognizing a solution to an existing problem. Such a solution can be given effect in determining the obviousness or nonobviousness under section 108.
Our problem, therefore, seems to revolve about the availability or nonavailability of TBPAA of low ferric iron content at the time the invention was made. The evidence on both sides of the question is meager.
First of all, appellants concede that TBPAA had previously been used to form polyesters. This is in agreement with the teachings of the references. Now, since appellants tell us that no reaction at all will occur at high ferric iron contents, it stands to reason that the prior art had available TBPAA having relatively low ferric iron content. Whether the ferric iron content was within the 5 ppm level where consistently good results are obtained, or slightly above that level where results are inconsistent, is something we do not know. We are told by appellants’ Example III that they prepared “technical” grade TBPAA by the “conventional” method and achieved an 8 ppm ferric iron content material, presumably without any post-reaction purification ‘steps whatever. We receive no guidance whatever on whether this 8 ppm content is a normal, low, or high level of ferric iron for commercially available “technical” grade material. However, we can infer from this example that “technical” grade TBPAA having ferric iron content on the order of 8 ppm was available to the art.
The only other evidence before us is that the commercially available TBPAA used in appellants’ experimental work contained 34 ppm. But this does not tell us how many other commercial suppliers there may have been, or how many different grades of material were available.
It is argued that the mere fact that appellants went to the expense of filing a patent application is some evidence that they had found a solution to an existing problem. This argument is entitled to little, if any, weight. At best, the filing of a patent application shows that appellants thought they had solved a problem. This could mean merely that appellants had not investigated sources of TBPAA, and that the only problem which existed was in their own laboratory.
It seems to us that an applicant who urges patentability based upon solution of a recognized but previously unsolved problem must carry the burden of showing that a problem in truth existed and was recognized in the art. In re Allen, 324 F.2d 993 , 51 CCPA 809. The burden is even heavier where, as here, the art mentions the very reaction involved in the application, but makes no mention whatever of the existence of a problem.
A review of the evidence before us shows that the appellants have not met that burden. The evidence before us tells us only that one commercial source of TBPAA had a high iron content, and it raises an inference that TBPAA having an iron content very close to the claimed level was available to the art. This is a far cry from showing the existence or recognition of a problem in the art. In view of the failure of appellants to show either that TBPAA within their claimed purity range was unavailable, or that if available its use in this application was unobvious, the Board of Appeals was correct in holding that the use of a pure material in a reaction would be expected of one skilled in the art. I therefore concur in affirming the board’s decision.