T 1266/16 26-02-2018

Reasons for the Decision

1. The appeal is admissible.

Amendments, main request, second and fourth auxiliary requests

2. Claim 1 of these requests contains the feature

"hydrolyzing the obtained isothiuronium salt in the presence of aqueous ammonia to produce a (poly)thiol compound".

3. The appellant argued that paragraph [0025] of the application as originally filed provided the required basis for the wording "in the presence of aqueous ammonia". This passages discloses

"Hydrolysis which subsequently carried out after producing an isothiuronium salt is conducted by using usual base water, similar to a conventional method. Examples of the kind of base water in use include [...] ammonia water[...]".

4. However, paragraph [0025] of the application as originally filed only discloses aqueous ammonia in a specific role, namely for hydrolising the corresponding thiouronium salt. This role implicitly introduces limitations to the process, for example with respect to the amount of ammonia required, which are not inherent to the feature "in the the presence of aqueous ammonia".

For this reason alone, claim 1 contains subject-matter going beyond that disclosed in the application as originally filed, with the consequence that the ground of opposition defined in Article 100(c) EPC precludes the maintenance of the patent as granted.

5. The appellant argued that the skilled person would have read claim 1 of the patent as granted with a mind willing to understand. The standard preparation of thiols using thiourea requires an aqueous base hydrolysis. Considering that aqueous ammonia would not have taken part in the process of claim 1 was not a reasonable reading of claim 1.

However, the skilled reader would consider that claim 1 as granted, by mentioning "in the presence of aqueous ammonia", also relates to a process in which the amount of ammonia is too low for hydrolysing a thiouronium salt. This embodiment is, however, not envisaged by the wording of paragraph [0025] of the application as originally filed. This argument of the appellant is thus not convincing.

6. In a different line of argument, the appellant concluded that, since ammonia is a product of the basic hydrolysis of thiouronium salts, its presence was an inherent feature of the claimed process and could not represent added subject-matter.

However, the description of the application as originally filed, including the examples, discloses aqueous ammonia as a reagent. The interpretation of the appellant that aqueous ammonia in claim 1 could refer to ammonia formed in the reaction is not in agreement with the disclosure of the patent application as a whole. For this reason, this argument of the appellant fails to convince the board.

7. As claim 1 of the second and fourth auxiliary requests also contains the feature "in the presence of aqueous ammonia", in the same context as claim 1 of the patent as granted, these requests contain added subject-matter for the same reasons as the latter, with the consequence that they are not allowable.

Novelty: first, third and fifth auxiliary requests

8. Claim 1 is directed to a process for producing a (poly)thiol compound for an optical material using thiourea with a calcium content of not more than 1.0 wt%.

It is not disputed that example 1 of document D1 explicitly discloses all the features of claim 1 with the exception of the amount of calcium in thiourea. The parties were, however, divided on whether or not this example implicitly disclosed a process carried out with thiourea having a calcium content below the threshold required by claim 1.

9. According to respondent 1, citing decision T 242/88 (not published in OJ EPO), the appellant arguing that the calcium content in the thiourea used in D1 is above the threshold indicated in claim 1 bears the burden of proof of showing the fact it alleges.

10. The appellant has not disputed that the burden of proof was on its side in this respect, and argued that the evidence submitted credibly showed that the authors of D1 could have used thiourea having more than 1.0 wt% calcium.

In this respect, the appellant relied on three lines of argumentation, namely that

- it was at least plausible, if not likely, that thiourea available from commercial sources had a calcium content greater than 1.0 wt% at the filing date of D1,

- having regard to APHA values in the art, the authors of documents such as D3 relating to polythiol synthesis must have used thiourea having more than 1.0 wt% calcium and, lastly, that

- the authors of D1 could have synthesised thiourea instead of purchasing it from a commercial source; D36 proved that it was highly possible that such urea would have contained more than 1.0 wt% of calcium.

The appellant concluded for these reasons that it was not proven beyond reasonable doubt that the process of D1 had been carried out with thiourea containing less than 1.0 wt% calcium, as required by claim 1, whose subject-matter was for this reason novel.

On the three lines of argumentation, the board concludes as follows:

10.1 Commercially available thiourea

There is no evidence on file which could show that thiourea with a higher content of calcium than required by claim 1 was commercially available at the filing date of D1.

The appellant submitted two declarations (D29, D30) by the inventors of the patent in suit stating that "during the development of the invention, thiourea was obtained from a number of different commercial suppliers. The Ca content in the commercially available industrial thiourea from some of these suppliers was found to be more than 1.0 wt%".

Notwithstanding that both declarations are word-for-word identical regarding thiourea purity, they do not contain any specific detail with respect to the suppliers they refer to, let alone any data regarding purchase or analysis performed. As such, these statements, devoid of any corroborating evidence, cannot be considered as proof of the appellant's argument.

In contrast, the respondents have submitted ample evidence that thiourea having a very low calcium content was not only available but standard before the filing date of D1. D4 refers to 98.0% pure thiourea having an ignition residue (sulfate) of 0.01% of lower, which includes not only calcium, but also sulfate conterions and other cationic impurities; D5 and D6 also refer to 99% pure thiourea (see partial translations); D10 relates to 99.7% pure thiourea having less than 0.1% sulfate-ash; D14 discloses 99.0% pure thiourea having less than 0.10% ash.

This argument of the appellant is thus not convincing.

10.2 Relationship between APHA value and Yellow Index and calcium content

The appellant acknowledged that none of the examples of document D3 were relevant for the novelty of claim 1, as the hydrolysis step was carried out with NaOH instead of with aqueous ammonia.

Document D3 disclosed the APHA of the polythiol obtained, and these values reflected its colour: the smaller the value, the less coloured the product.

The appellant relied on the experimental evidence D34 and D35 for showing that some processes for producing polythiols of the prior art, such as that of D3, used thiourea having a calcium content above the threshold defined in claim 1, in particular having regard to the APHA values obtained.

D34 and D35 disclose the results of carrying out various examples of D3 with thiourea having different relative amounts of calcium. The appellant concluded from them that D3 must have been carried out with thiourea having more than 1.0 wt% of calcium.

10.2.1 Experimental evidence D34

The polythiol obtained according to example 1 of D3 has an APHA value of 15. D34 relates to experiments carried out according to examples 1 (synthesis of polythiol) and 9 (preparation of lenses from the polythiol of example 1) of document D3, using thiourea containing different amounts of calcium.

The data in D34 shows a higher APHA value of those polythiols obtained with thiourea having a higher calcium content (1.2 wt% vs. 0.05 wt%). Thiourea having 1.2 wt% calcium lead to polythiols having the same APHA value as in example 1 of D3.

D34 merely proves that the APHA value disclosed in D3 could have been due to the presence of calcium in the thiourea, i.e. that its presence is sufficient for the colouring, notwithstanding that this conclusion is rebutted by the results of D35 (see following point). It fails to prove, however, that such presence is necessary for achieving it.For this reason alone, the appellant's argument is not convincing.

10.2.2 Experimental evidence D35

D35 relates to experiments carried out in accordance with example 3 of document D3, according to which an APHA value of 10 was obtained.

As in the previous case, D35 shows a link between the colouring of polythiols and the amount of calcium present in thiourea, but fails to show that the authors of D3 had used thiourea with an unusually high calcium content.

In addition, D35 proves that the conclusion drawn from D34 by the appellant (see previous point), i.e. that the presence of a high relative amount of calcium is a sufficient condition for the colouring is not correct, as it is possible to obtain a polyol with an APHA value of 10 by using thiourea containing more than 1.0 wt% of calcium.

10.2.3 Experimental evidence D42

The appellant further argued that the yellow index (YI) of a sample was a more accurate colour indication than the APHA value. D42 showed a direct relationship between the yellow index and the calcium content of the thiourea used.

As in the previous cases, even acknowledging that the alleged relationship existed, i.e. that the presence of a high relative amount of calcium were sufficient for the colouring, this experimental evidence fail to prove its presence above the threshold defined in claim 1.

10.3 Alleged synthesis of thiourea by the authors of D1

The appellant argued that the inventors of D1 could have prepared thiourea, instead of purchasing it from a provider. Document D36 proved that such a thiourea could contain more than 1.0 wt% calcium.

Contrary to the arguments of the appellant, experimental evidence D36 does not disclose the preparation of urea using the standard process described for example in D14, section 2.3, as it does not include a CO2 treatment step to form (water insoluble) calcium carbonate.

In addition, thiourea having 98.70% purity cannot contain 1.2 wt% calcium, even if it were the sole impurity present, as it requires a counterion. Due to the synthesis process, calcium in the product of D36 should be in the form of calcium hydroxyde, which implies that, at most, 54% of the impurities can be calcium Mr(Ca(OH)2)=74; Ar(Ca)=40. Thus, the amount of calcium in a 98.70% pure urea cannot be higher than 0.65 wt%.

The appellant argued in this respect that purity could have been determined using a technique which would not take into account the amount of calcium, such as **(1)H NMR, and the purity obtained by this technique would be compatible with the relative amount of calcium in D36.

However, section 2.6 of D14 discloses that thiourea's purity is analysed by titration. The board sees no reason why a product which is produced in large amounts (D10 refers to 5 tons; D14, section 2.7 discloses that it can be packed in folding containers holding up to 1500 kg) and whose synthesis has been known for more than 50 years (statement of grounds of appeal, page 18, lines 28-33) should be analysed using a non-accurate method such as **(1)H NMR, which would not detect inorganic impurities, as long as an accurate protocol is available. This argument of the appellant is thus dismissed.

In conclusion, the board is of the view that it is not plausible that the skilled person would have either carried out the preparation of thiourea as in D36, or analysed its purity, as argued by the appellant, let alone have used such a starting material in the process of D1.

10.4 The appellant has thus also not proven that thiourea having calcium above the required threshold was available to the skilled person from usual sources, such as providers, nor that such thiourea must have been used by the authors of documents in the field of the patent in suit, nor that if the authors of document D1 had synthesised thiourea following generally acceptable preparation processes such as that of D14, a product having more than 1.0 wt% of calcium would have been obtained.

For these reasons, it is concluded that the appellant has not proved that the process disclosed in document D1 could have been carried out using thiourea having a calcium content over the threshold defined in claim 1.

11. Considering the above, with respect to the novelty of the claimed process over that of document D1, the skilled reader's understanding of the disclosure of the latter remains to be examined.

It is not disputed that document D1 neither discloses the purity of thiourea used, let alone its calcium content, nor refers to any commercial source or discloses any preparation method.

It is further not disputed that thiourea having a very low calcium content was not only available but standard before the filing of D1.

The appellant acknowledged that the preparation of thiourea had not substantially changed for more than 50 years (see for example its statement of grounds of appeal, page 18, lines 28-33). Document D14 (section 2.6) discloses that commercial thiourea is of relatively high quality; every data on file refers to calcium contents well below 0.1 wt % (see for example D4, point 2.5, calcium is quantified as "ash"; D5, D6, D10).

12. Taking into consideration that

- document D1 is directed to a process for producing polythiols suitable for the preparation of plastic lenses [0055], i.e. that colouring of the final product is important

- thiourea containing very few impurities (calcium included) was standard in the market before the filing date of D1, and

- it is generally known that impurities present in starting materials may have an influence on the colouring of the final product,

the board concludes that the skilled reader, despite D1 being silent on the amount of impurities of thiourea, would consider the use of thiourea at least of standard purity (D4-D6, D10, D14), i.e. with a relative amount of calcium well below the threshold defined in claim 1, to be inherently disclosed.

For these reasons, the process of claim 1 of the first auxiliary request is not novel (Article 54(2) EPC), with the consequence that this request is not allowable.

13. The appellant argued that there was no indication that thiourea with a low content of calcium could be used for obtaining thiols in a process such as that of D1 and that, in any case, the arguments in the previous point related to inventive step and not to novelty.

However, the issue is not whether the skilled reader would have considered urea of standard purity (such as that of D14) as a suitable starting material in the process of D1, which would indeed be an issue related to inventive step.

This argument of the appellant is thus not convincing.

14. The appellant has not disputed that the conclusion on the issue of novelty would not differ with respect to claim 1 of the third and fifth auxiliary requests, as the amount of calcium defined by these requests also lies well above the limit of calcium in thiourea of standard purity. These requests are thus not allowable for the same reasons as the first auxiliary request.