T 1469/05 17-07-2008

Reasons for the Decision

1. The appeal is admissible.

Main request

2. Wording of the claims

The Board is satisfied that Claims 1 to 7 of the main request meet the requirements of Article 123(2) and 84 EPC.

3. Novelty

3.1 In its decision the Examining Division has considered that the subject-matter of the main request then on file was novel over the cited prior art. In its communication dated 22 April 2008, the Board indicated that it saw no reason to depart from that view.

3.2 Since the subject-matter of Claim 1 of the present main request has been further restricted, the Board is satisfied that the requirements of Article 54 EPC are met by Claims 1 to 7 of the main request.

4. Problem and solution, closest state of the art

4.1 According to the Appellant the aim of the claimed method according to Claim 1 is to reduce the color of freshly polymerized PPE resins.

4.2 In that context, document D7 which is concerned with the problem of reduction of coloration in freshly polymerized PPE resins would, in the Board's view, represent the closest state of the art.

4.3 According to D7, a substantial decolorization of PPE resins obtained by oxidative polycondensation of alkylphenols in the presence of copper-amine catalysts can be achieved by treating a solution of the polymer, that may be the same mixture coming directly from the polymerization of the alkylphenols, with one or more compounds containing at least a sulphydrylic SH function (thiols) in an acid medium.

4.4 As disclosed in Examples 1 to 6, 11, 12, 14, 24, 29, 30 and 31 of D7 the treatment can be carried out in toluene at a temperature of 35ºC.

4.5 According to these examples the color number of the treated PPE resins is between 2.2 (Example 29) and 4.6 (Example 5) while the untreated PPE (cf. control example, page 10, lines 25 to 26 ) exhibits a color number of 10, i.e. the treatment according to D7 effectively reduces the color of the fresh polymerized PPE resin.

4.6 In this connection the Board firstly notes that there is no comparison between the method disclosed in D7 and the method according to Claim 1 in the application in suit. Furthermore, no such comparison has been submitted by the Appellant in the course of the examination and appeal proceedings.

4.7 Thus, starting from D7, the technical problem would hence be seen in the provision of an alternative process for reducing the color of fresh polymerized PPE resins.

4.8 According to the Appellant, this problem is solved by using the specific alcohol components as defined in Claim 1 instead of thiols as taught in D7.

4.9 In that context, the Board, however, firstly notes that none of the Examples 1, 2, and 3 of the application in suit fall under the scope of Claim 1, because in these examples the PPE resin is only submitted to heat treatment in the melt (i.e. not in an organic solvent) with a specific hydroxy compound as defined in Claim 1.

4.10 While in Example 4 of the application in suit, the freshly polymerized PPE resins are treated with benzoin in toluene before extruding at 280ºC the thus obtained mixtures of PPE resin and benzoin, the Board observes that the temperature at which the treatment in toluene has been carried out has not been indicated in that example.

4.11 Nevertheless, even if one would consider that, in Example 4, the treatment in toluene has been indeed carried out at a temperature between 20 and 50ºC, the Board further observes that absolutely no indication is given in Example 4 concerning the color number either of the fresh polymerized PPE resin or of the PPE resin after treatment in toluene and before extrusion.

4.12 While it is true that in Table IV the yellowness index values of the PPE resins after extrusion are indicated, the Board can only state that there is no indication either of the yellowness index value of the fresh polymerized PPE resin or of the PPE resin after treatment with benzoin in the toluene solution and before extrusion.

4.13 Under these circumstances, the only evidence provided by Example 4 is that extruded PPE resins containing benzoin exhibit better yellowness index values than the same extruded PPE resins not containing benzoin (cf. comparison between Runs 1 to 2 (no benzoin) and Runs 3 to 5, and comparison between Run 7 (no benzoin) and Runs 8 to 10).

4.14 In other words, in view of the known problem of color formation in PPE resins during melt processing (cf. page 2, lines 26 to 27 of the application in suit), Example 4 shows only that color formation is less during melt processing of PPE resins containing benzoin than during melt processing of PPE resins not containing benzoin, but in no way it provides evidence that the color of the fresh polymerized PPE resins has been effectively decreased by contacting them with benzoin in toluene.

4.15 This conclusion cannot be altered by the statement at line 56 on page 6 concerning Example 4 that "it is apparent from yellowness index values that color is effectively decreased" for the following reasons:

4.15.1 As submitted by the Appellant the color number of fresh polymerized PPE resins obtained using copper/DBEDA catalyst system is generally of the order of 10 but their color number might increase to about 30 after melt processing (cf. application in suit page 2, lines 26 to 27).

4.15.2 On that basis, it can be considered that Table I shows that the color number of a PPE resin melt processed in the presence of a decolorizing agent increases from 10 to 11.6 in the case of benzoin to up to 23,5 in the case of 2,3 diphenylbutane-2,3-diol while the color number of a PPE resin melt processed without decolorizing agent increases to 25.

4.15.3 Nevertheless, despite the increase in color number of PPE resin containing the decolorizing agent, it is concluded at the bottom of Table I that "it is apparent from the results in Table I that the method of this invention is effective to reduce the color of polyphenylene ether resins".

4.15.4 Thus, under these circumstances, this statement can only make sense when interpreted as expressing that the color of PPE resins melt processed in the presence of the decolorizing agent is lower than the color of the polyphenylene resin melt processed in the absence of that decolorizing agent, i.e. that the color formation during melt processing is less in the presence of the specific hydroxy compounds (e.g. benzoin).

4.15.5 As indicated above in paragraphs 4.13 and 4.14, the results in Table IV only show that the yellowness index and hence the color of PPE resins extruded in the presence of a decolorizing agent (benzoin) are lower than the yellowness index and hence the color of the polyphenylene ether extruded in the absence of such decolorizing agent.

4.16 Consequently, there is no reason for the Board not to interpret the reduction of color referred to at the bottom of Table IV in the same manner as the reference at the bottom of Table I, i.e. as expressing only the fact that the color of PPE resins extruded in the presence of benzoin is lower than the color of the PPE resins extruded in the absence of such decolorizing agent, or, in other words, that the color formation during melt processing of PPE resins is less in the presence of the specific hydroxy compounds (e.g. benzoin).

4.17 The further argument of the Appellant in view of the low increase in color of PPE resins containing benzoin in Example 1 (cf. Section VI above, points (ii.4) to (ii.5)) that the reduction of yellowness index from 4.32 (Run 2 in Example 4) to 2.90 (Run 5 in Example 4), had to be attributed to the solvent treatment also cannot be accepted for the following reasons:

4.17.1 Independently of the fact that the heat treatment in Example 1 (compression molding at 270ºC) is not the same as in Example 4 (extrusion molding at 280ºC), and that the color changes are expressed in totally different manners in these examples (color number in Example 1 versus yellowness index in Example 4), so that a valid comparison between color changes in Example 1 and in Example 4 is more than questionable, this is because the respective contributions of the solvent treatment step and of the melt processing step in the color change of the PPE resin cannot be estimated in the absence of indication of the yellowness index of the fresh polymerized PPE, i.e. of any evidence that this index was very close to or greater than 2.90.

4.18 Nor could the further argument of the Appellant be accepted that the rapid decolorization of freshly polymerized PPE resins occurring in solution at ambient temperatures with thiols as shown in D7 would support that alcohols according to the application in suit were capable of reducing color in solution at ambient temperature (cf. Section VI above, point (ii.5)), because this argument is contradicted by the Appellant's own submissions that, alcohols and thiols being totally different chemical entities, it could not be expected that alcohols would behave as thiols (cf. Section VII above, point (ii.4)).

4.19 Consequently, there is no convincing evidence that the claimed measures provide an effective solution of the technical problem defined in paragraph 4.7 above. It thus follows that this technical problem cannot be used for the assessment of inventive step, and that the technical problem must be hence reformulated.

4.20 Nevertheless, it still remains that Example 4 shows that the claimed method leads to a reduced color formation during melt processing of PPE resins.

4.21 In that connection, the Board observes that document D1 is the only document which deals with the reduction of color formation in PPE resins during melt processing.

4.22 In Examples 1 and 3 of D1, a discoloration preventing additive (benzoin) is melt compounded with a PPE resin and the obtained mixture is injection molded. The obtained injection molded articles show a reduced color (higher lightness) than injection molded articles of PPE resin without benzoin (57 versus 41 in Example 1, 73 versus 59 in Example 3).

4.23 D1 teaches that the PPE and the discoloration additive could be mixed by any of a variety of techniques (cf. D1, column 6, lines 5 to 9) but it does not disclose the mode of incorporation of the discoloration preventing additive by mixing it with a solution of PPE in an organic solvent.

4.24 Thus, taking document D1 as the closest state of the art, the technical problem underlying the application in suit can be formulated as the provision of a further method of reducing color formation in PPE resins during melt processing, since this problem can be clearly inferred by the person skilled in the art from the experimental evidence in the application as originally filed (cf. also T 13/84, OJ EPO 1986, 253).

4.25 The solution proposed according to Claim 1 of the main request is to mix an hydroxy compound as defined in Claim 1 (e.g. benzoin) with the PPE resin in an organic solvent before melt processing.

5. Inventive step

5.1 It remains to be decided whether the proposed solution was obvious in view of the cited prior art.

5.2 As indicated above D1 clearly discloses that the discoloration preventing agent (e.g. benzoin) can be incorporated into the PPE resin by any methods.

5.3 In this connection, the Board however notes that there is no evidence on file of any specific effect of the method of incorporation according to Claim 1 of an hydroxy compound such as benzoin in the PPE resin.

5.4 Consequently, the subject-matter of that claim can only be considered as an obvious alternative to the method disclosed in D1.

5.5 It thus follows that the subject-matter of Claim 1 of the main request does not meet the requirements of Article 56 EPC, and hence, that the main request must be refused.

Second auxiliary request

6. Wording of the claims

6.1 Claim 1 of the second auxiliary request differs from Claim 1 of the main request only in that the hydroxy compounds have been restricted to benzopinacol, benzoin, acetoin, allyl alcohol, acetol, 2-butene-1,4-diol, benzyl alcohol or hydrobenzoin, benzhydrol, methylphenylcarbinol, pinacol or 2,3-diphenylbutane-2,3-diol.

6.2 It is thus evident that Claim 1 of the second auxiliary request still encompasses the use of benzoin as decolorizing agent.

7. Inventive step

7.1 Since Claim 1 of that request still encompasses the use of benzoin, the same considerations as for the main request inevitably apply.

7.2 Consequently, the subject-matter of Claim 1 of the second auxiliary request must be considered as not meeting the requirements of Article 56 EPC.

7.3 It thus follows that the second auxiliary request must be refused.

8. Since none of the requests of the Appellant can be granted, the appeal must be dismissed.