T 1072/98 (Refrigerator oil/IDEMITSU KOSAN) 03-06-2003

Reasons for the Decision

1. The appeal is admissible.

2. Article 114 EPC - Late-filed evidence

2.1. Documents (7) and (8) are new evidence submitted for the first time by the Appellant with the statement of grounds of appeal. The admissibility of both documents was contested by the Respondent on the ground of being belated submissions.

2.2. The Appellant submitted document (7) in support of his objection under Article 100(b) EPC. This document is part of a textbook and, therefore, belongs to the general technical knowledge of the person skilled in the art. The citation of this document was put forward in response to the finding of the Opposition Division that the degree of esterification of the compound defined by the feature (a) was not crucial to the invention (cf. point IV above).

2.3. In the Board's judgment, the submission of a new document furnishing proof of common general knowledge and aiming at reinforcing a line of attack already made before the first instance and discussed in the decision under appeal, is to be considered as the normal behaviour of a losing party. It follows that document (7) is admitted into the appeal proceedings.

2.4. At the oral proceedings, document (8) was put forward by the Appellant as the closest state of the art (cf. point VI above).

2.5. Document (8) relates to the technical field of compression refrigeration equipment using tetrafluoroethane as a working fluid and discloses to this end a lubricating composition comprising polyoxyalkyleneglycol as lubricating oil and additives to enhance performance such as antiwear additives (cf. column 3, lines 33 to 55, column 9, lines 56 to 68). This document aims at the same objective as the patent in suit and has the most relevant technical feature in common with it.

2.6. The Board does acknowledge that this document was late filed and that the Appellant provided no reason why it could not have been filed earlier in the opposition proceedings. However, the disclosure of this document is highly relevant in that it aims at the same objective as the patent in suit and the sole distinguishing feature between the claimed invention and this document is the feature (a) (cf. point II above). Furthermore, this document was well-known to the Respondent since it was the sole document acknowledged in the patent in suit and the problem to be solved as set out in the patent in suit was clearly defined in view of the state of the art represented by this document (cf. page 2, lines 16 to 28 and lines 32 to 45). A document of this kind forms part of the opposition or opposition appeal proceedings even if it was not expressly cited within the opposition period (cf. T 536/88, OJ EPO 1992, 638, point 2.1 of the reasons). It follows that document (8) is admitted into the appeal proceedings.

3. Article 100(b) EPC - Article 83 EPC

3.1. The question to be decided is whether the claimed subject- matter as defined in Claim 1 of the patent-in-suit complies with the requirements of Article 83 EPC or gives rise to objections pursuant to Article 100(b) EPC.

3.2. That requires determination of whether there is evidence that not all oil compositions defined in Claim 1 can be actually used in compression-type refrigerators without detrimental effect.

3.3. Since both parties have a different understanding of the meaning of the feature (a), i.e. "an aliphatic acid partially esterified with a polyhydric alcohol", it is appropriate, in the present case, to construe what is actually claimed within the wording of Claim 1.

3.4. The patent-in-suit mentions on page 5, lines 38 to 42 the following definition:

"By the term "an aliphatic acid partially esterified with a polyhydric alcohol" as used herein is meant a partially esterified product formed from a polyhydric alcohol such as glycol, glycerol, trimethylol propane, pentaerythritol, sorbitan, sorbitol or the like and a saturated or unsaturated straight-chain or branched chain aliphatic acid having 1 to 24 carbon atoms, preferably from glycerol, sorbitan or sorbitol and an aliphatic acid having 8 to 22 carbon atoms. In particular, an monobasic aliphatic acid ester is most suitable".

3.5. Contrary to the interpretation of the Respondent, the Board considers in agreement with the Appellant that the above definition (cf. point 3.4 above) does not exclude that acids be present in the partially esterified product. Indeed, an aliphatic acid partially esterified by a polyhydric alcohol matches this definition.

3.6. Document (7) teaches that suitable lubricating oils should be acid-free and produce no acids in the long run (cf. right- hand column, page 3106). However, this very general teaching does not give any indication as to the type of acid which is detrimental to the satisfactory working of a machine using lubricating oils. Document (7) is silent as to whether inorganic or organic acid or both are envisaged and the Appellant did not file any argument in that respect.

3.7. Furthermore, document (8) casts doubts on the argumentation of the Appellant. Indeed, this document relates to the specific technical field of lubricating oils for use in compression-type refrigerators and describes among other additives enhancing performance, organic acids as corrosion inhibitors (cf. column 10, line 32).

The Board is, therefore, not convinced as alleged by the Appellant, that the presence of aliphatic acids renders the lubricating compositions unusable for compression-type refrigerators.

3.8. The second argument of the Appellant relates to the lack of instructions in the patent-in-suit as to the amount of free aliphatic acids in the composition, this silence imposing on the person skilled in the art an undue burden for carrying out the invention. However, since the Appellant has not demonstrated the detrimental effect of organic acids in the use of oil compositions as defined in Claim 1, this argument is irrelevant.

3.9. Furthermore, the possible overlapping between the definition of features (a) and (b) addresses a clarity objection only and cannot be argued as an objection under Article 100(b) EPC.

3.10. In conclusion, in the absence of convincing evidence showing the contrary, the Board holds that the patent-in-suit discloses the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art. The ground of opposition under Article 100(b) EPC is rejected.

4. Article 100(a) EPC

4.1. The patent-in-suit as reflected by Claim 1 as granted (cf. point II above) relates to the use of a refrigerator oil composition for hydrogen-containing hydrofluorocarbon refrigerant. As set out in the description, this lubricating oil is to be employed for effecting lubrication in a compression-type refrigerator using a hydrofluorocarbon as a refrigerant (cf. page 2, lines 46 to 47), namely a type of refrigerator where the metal surfaces of different elements of the device are in moving contact with each other causing a wear effect.

4.2. In accordance with the "problem-solution approach", it is necessary to establish the closest state of the art to determine in the light thereof the technical problem which the invention addresses and solves. The "closest prior art" is normally a prior art document disclosing subject-matter aiming at the same objective as the claimed invention and having the most relevant technical features in common.

4.3. The Opposition Division and the Respondent elected document (5) as the closest state of the art. Document (5) relates to absorption-type refrigerators, the working of which is quite different from a compression-type refrigerator which the patent-in-suit relates to. Absorption-type refrigerators differ from compression-type refrigerators in that they work without rotative elements and only through difference of temperature. Therefore, as submitted by the Appellant, the problem of minimizing the wear resistance between aluminium material and steel material, one of the problems encountered with compression-type refrigerator, was not one which arose for the subject-matter of document (5). For these reasons, document (5) cannot qualify as the closest state of the art.

4.4. As stated above (cf. point 2.5 above), document (8) relates to the technical field of compression refrigeration equipment using tetrafluoroethane as a working fluid and discloses to this end a lubricating composition comprising polyoxyalkyleneglycol as lubricating oil and additives to enhance performance such as antiwear additives (cf. column 3, lines 33 to 55, column 9, lines 56 to 68). This document aims at the same objective as the patent in suit and has the most relevant technical feature in common with it. This document is, thus, considered as the closest state of the art for defining the technical problem to be solved.

4.5. In view of this state of the art the problem underlying the patent in suit as formulated in the specification of this patent is to provide the use of a refrigerator oil which is excellent in lubrication performance as well as miscibility with hydrofluorocarbon and, at the same time, effective for improving wear resistance of the friction surfaces of a compression-type refrigerator, especially wear resistance between aluminium material and steel material (cf. page 2, lines 20 to 25 and 32 to 34).

4.6. As the solution to this problem the patent in suit proposes the use of an oil composition which comprises at least one compound selected from (A) a polyoxyalkylene glycol derivative, and (B) polyester compounds having a kinematic viscosity at 40°C of 5 to 1000 cSt and at least two esters linkages, which are compounded with (a) an aliphatic acid partially esterified with a polyhydric alcohol, and (b) at least one compound selected from among phosphate compounds and phosphite compounds.

4.7. Examples Nos. 1 to 18 relate to lubricating compositions comprising polyoxypropylene glycol polymers or polyoxypropylene glycol/polyoxyethylene glycol copolymers as oils showing excellent performances in terms of wear resistance, stability and miscibility in mixture with tetrafluoroethane. Examples Nos. 19 to 33 relating to lubricating compositions comprising various polyester compounds show similar good performances. Furthermore, it can be derived from comparative examples Nos. 2 and 6 that the absence of sorbitan monooleate as compound (a) of Claim 1 leads to lubricating compositions having an insufficient wear- resistance effect. For these reasons the Board is satisfied that the problem underlying the patent in suit has been successfully solved. Nothing relevant was submitted by the Appellant in that respect.

4.8. It remains to be decided whether or not the claimed solution is obvious in view of the cited prior art.

The relevant question is whether the person skilled in the art guided by the technical problem to be solved would have been directed in order to improve the wear- resistance effect of a lubricating composition for effecting lubrication in a compression-type refrigerator using a hydrofluorocarbon as a refrigerant to propose the claimed solution (cf. point 4.6 above).

4.9. When starting from the lubricating compositions disclosed in document (8), the person skilled in the art is aware of the fact that, in addition polyoxyalkylene glycols such as polyoxypropylene glycols (cf. Table A), additives may be used to enhance performance such as extreme pressure and anti-wear agents (cf. column 9, lines 61 to 63). Among those additives phosphates or phosphites corresponding to compounds (b) according to the claimed invention are mentioned (cf. column 10, lines 19 to 20). However, document (8) is completely silent about the use of a component (a) as defined in Claim 1 (cf. point II above).

4.10. Document (1a) discloses lubricating compositions comprising as base oils mineral oils or synthetic oils and, as anti-friction agents, mixtures of phosphate esters and polyolesters corresponding to component (a) according to present Claim 1, such as sorbitan monooleate. It is, in particular, stated that these mixtures offer excellent anti- friction properties in the long run along with good oxidation stability and anti-corrosion properties (cf. page 2, point 3, first paragraph and sixth paragraph; page 3, last paragraph; page 4, first paragraph).

These oils are designed to be used for automatic transmissions, hydraulic brakes in tractors and front- wheel driven cars (cf. page 2, point 3 and page 6, third and fourth paragraph).

However, the person skilled in the art seeking to solve the above defined technical problem would have turned his attention to documents belonging to the same technical field. In absence of any documents teaching the possibility to transfer the teaching of documents related to the domain of automatic transmissions and brakes in cars to that of compression-type refrigerators, it is to be concluded that document (1a) would not have been considered by the skilled person, because it belonged to a different technical field, and the skilled person had no reason to believe that beneficial lubricating properties in that field would also mean beneficial properties when used in compression-type refrigerators.

4.11. At the oral proceedings, the Appellant did in fact abandon all other lines of argument involving the disclosures of documents (2), (3), (4), (5) and (6). The Board sees on its own no reason to raise objections in that respect. Indeed:

Document (2) relates to lubricating oils for lubrication of aviation turbines or in the preparation of greases and other lubricating compositions intended for high temperature use (cf. page 1, lines 12 to 18).This document relates to a different technical field not relevant for solving the above defined technical problem (cf. point 4.5 above).

As acknowledged by the Appellant, document (5) addresses a different technical problem (cf. point 4.3 above), namely the provision of a liquid absorbent for absorption-type refrigerator. Document (4) also relates to absorption cooling agents. These documents would not have been considered by the skilled person for solving the above defined technical problem, either.

Document (3) discloses a lubricating Freon-resistant ester oil mixed with phosphates. Document (6) discloses an oil for use in refrigeration apparatus including a compressor consisting of an organic ester of pentaerythritol (cf. column 1, lines 15 to 50). Those documents give no hint to the claimed solution.

4.12. Since starting from document (8) and in the light of the other documents cited, the person skilled in the art would not have been directed in an obvious manner to the claimed solution in order to solve the technical problem defined above (cf. point 4.5 above), the subject-matter of Claim 1 meets the inventive step requirement. The same applies to dependent Claims 2 to 9.

4.13. Independent Claims 11 and 12 relating, respectively to a method for effecting lubrication in a compression-type refrigerator and to a compression-type refrigerator system involving the refrigerator oil composition as defined in Claim 1, are based on the same inventive concept and derive their patentability on the same basis as does Claim 1.