T 0205/83 (Vinyl ester/crotonic acid copolymers) 25-06-1985
Téléchargement et informations complémentaires:
1. The polymer product of a known chemical process is not new automatically as a result of the said process being modified.
2. If such a chemical product cannot be defined by structural characteristics (substance parameters) but only by its method of manufacture (process parameters), novelty can be established only if evidence is provided that modification of the process parameters results in other products. It is sufficient for this purpose if it is shown that distinct differences exist in the properties of the products.
3. This evidence may not include properties which cannot be due to the product's substance parameters (in this case, absence of monomer impurities with an unwanted odour).
Novelty of a polymer product defined only by process parameters
Removal of unexpected impurities/measures not featured in state of art
Inventive step - process parameters
Inventive step - substance parameters
Summary of Facts and Submissions
I. European patent No. 1810 incorporating four claims was granted on 4 November 1981 on the basis of European patent application No. 78 101 239.8 filed on 27 October 1978 and claiming a German priority of 2 November 1977. Claim 1 reads as follows: "Process for the manufacture of a vinyl ester copolymer by polymerizing at least one vinyl ester and crotonic acid, optionally in the presence of a polyalkylene glycol, in the presence of a radical-forming initiator and a regulating substance, characterized by copolymerizing 70 to 98 percent by weight of the total amount of the vinyl ester with the total amount of the crotonic acid and optionally the total amount of the polyalkylene glycol, completing the polymerization by adding the residual amount of the vinyl ester, the ratio by weight of the total amounts of momomers vinyl ester/crotonic acid being from 100:1 to 100:20, and subsequently removing unreacted monomers and possible volatile impurities from the reaction mixture by distillation by means of an alkanol having from 1 to 3 carbon atoms as entrainer in an amount of from 5 to 50 percent by weight, referred to the copolymer". (English translation as filed under Rule 51(4) EPC).
II. The opponents filed opposition to the grant on 11 May 1982 on the basis of the document already considered in the examination proceedings, namely (1) DE-A-1 177 825 and of (2) DE-A-1 077 430, and requested that the patent be revoked in its entirety on grounds of lack of inventive step.
III. The Opposition Division rejected the opposition in its decision of 4 October 1983, commenting as follows: The subject-matter of the patent was new in relation to each of the two citations. Moreover it was beyond dispute that neither of the two citations in any way suggested the purposive addition of a single monomer to reduce the impurities present after the first stage of the process; in particular there had been no reason to expect, in view of the reaction kinetics in question, that troublesome quantities of free monomeric crotonic acid would still be present at this stage. If the skilled person had not known this he would not have been able to recognise the need for its removal by adding extra vinyl ester. Under these circumstances there was no need to examine to what extend the entrainer distillation, which was also provided for, would make an inventive contribution.
IV. The appellants (opponents) lodged an appeal against the decision of the Opposition Division on 29 November 1983, paying the prescribed fee. The grounds for appeal given on 3 February 1984, with subsequent additions, were approximately as follows: The presence of residual monomers was something which could have been expected in view of the very different polymerisation parameters of crotonic acid on the one hand and of vinyl esters on the other and could have been found in the newly introduced passage from the literature: (3) Encyclopedia of Polymer Science and Technology, Vol. 15 (1971), pages 584 to 587, which mentioned a retarding effect of crotonic acid on the copolymerisation of vinyl esters. The addition of extra vinyl ester had therefore been obvious, since the unpleasant odour of crotonic acid had also been known. The subsequent removal of volatile impurities by distillation was a matter of course, particularly as distillation with isopropanol had already been described in (1). Furthermore, Comparative Example 1 was not significant in this context as it did not include this distillation process, which was described in the state of the art. The odour referred to in the comparative example was a consequence not of the fact that vinyl ester had not been added but of the absence of distillation.
V. The respondent (patent proprietor) contested this, commenting essentially as follows: Although it had been known that crotonic acid delayed the polymerisation of vinyl esters, there had been no reason to expect any substantial residues of crotonic acid if the quantity of the latter had been less than stoichiometric; thus, it had not been obvious to add extra vinyl ester. Surprisingly, moreover, this extra addition also served to modify, or incorporate by polymerisation, other scarcely volatile and strongly-smelling impurities which had hardly been identified, which was also why it had not been possible to expect that they could be rendered harmless by post-polymerisation. Nor could it have been expected that the subsequent distillation with a lower alcohol would result in a further reduction in odour, since it could be shown that there was practically no further reduction in the crotonic acid content. Finally, the respondent submitted a further test report which indicates more clearly than do the comparative examples in the contested patent that both the post-polymerisation with extra vinyl ester and also the following distillation with isopropanol help substantially to reduce the odour.
VI. In its summons to the oral proceedings the Board also drew attention to doubts about the patentability of Claim 4, which reads as follows: "Vinyl ester/crotonic acid copolymer obtained by the process according to Claim 1".
VII. The parties reaffirmed their points of view in the oral proceedings on 25 June 1985. With regard to the results of comparative tests received from the respondent on 10 January 1985, the appellant, while recognising the effect produced (reduction in odour), says that it is "as expected". He requests that the decision of the Opposition Division be set aside and the patent revoked. The respondent, on the other hand, requests that the appeal be dismissed and that the patent be maintained in the alternative in amended form, Claim 4 being deleted. He defended Claim 4 on the grounds that the extra quantity according to the invention would necessarily lead to a variation in the resulting macromolecules, largely eliminating the odour. It was also surprising that the polymers modified in this way could still be used as a base for hairsprays.
VIII. After deliberation the Board informed the parties that it intented to maintain the patent as requested in the alternative. A one-month period for submitting observations was granted in accordance with Rule 58(4) EPC, but the parties dispensed with this facility.
Reasons for the Decision
1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is therefore admissible.
2. According to the main request the subject-matter of the patent relates to a process for the manufacture of a vinyl ester/crotonic acid copolymer and the copolymer obtained by this process. The process according to Claims 1 to 3 is in essence concerned with initially copolymerising the total amount of crotonic acid with 70 to 98% by weight of the vinyl ester to be used, then adding the rest of the vinyl ester, completing the polymerisation process and then carrying out entrainer distillation using a lower alcohol. Claim 4 relates to the end product obtained.
3. The main request has to be rejected if only because Claim 4 cannot be granted.
3.1 The Board has already decided that claims for chemical products defined in terms of processes for their preparation ("product-by-process" claims) are admissible only if - apart from any other conditions - the products themselves fulfil the requirements for patentability, i.e. in particular if they are new and involve an inventive step (Decision T 250/82, "Claim Categories/IFF", OJ (EPO) 7/1984, pp. 309 to 317; see in particular Headnote II on page 310).
3.2 In the present case, too, Claim 4 relates to products of a chemical process which are defined not by structural characteristics (substance parameters) but only by the method of their preparation (process parameters).
3.2.1 Products of the same type, namely vinyl ester/crotonic acid copolymers and corresponding graft copolymers based on polyalkylene glycol, are already known from (1) and (2) respectively; the method of preparing the claimed products also follows the same principle as that set forth in (1) and (2), namely copolymerisation in the presence of a radical-forming initiator and a regulating substance, using a large excess of vinyl ester referred to crotonic acid, with initial polymerisation being carried out to begin with and the polymerisation process then being completed with the further addition of monomers. The method of preparing the claimed products therefore involves only the modification of a fundamentally known process. According to an empirical principle in chemistry, approximately identical process conditions generally result in identical or approximately identical products. Consequently, the polymeric product of a process modified in this way cannot automatically be new as a result of modification of the process. To establish novelty, it will be necessary to provide evidence that modification of the process parameters results in other products. In principle such evidence could conceivably be provided in a variety of ways, for example on the basis of conclusive considerations which accord with the general state of the art. It is also sufficient, however, if distinct differences in the products' properties are demonstrated; this is because, according to an empirical principle in chemistry, a products properties are determined by its structure, so that differences in the properties of products indicate a structural modification.
3.2.2 With a view to providing such evidence, the respondent asserts that he modified method of preparation according to the contested patent necessarily results in structurally different products. He contends that copolymerisation of vinyl ester with crotonic acid takes place in the initial polymerisation stage, while (in contrast to the known method of preparation, where a monomer mixture of the same composition as for the initial polymerisation stage is added) the addition of extra vinyl ester alone is followed by a chain prolongation involving only vinyl ester units. This submission by the respondent is in no way conclusive in the above sense. In particular the respondent overlooks the fact that the has himself demonstrated experimentally that crotonic acid still capable of copolymerisation is present at the end of the initial polymerisation stage and is then more or less fully incorporated in the macromolecules in the second polymerisation stage. This means that with the modified method of preparation according to the invention, too, chain prolongation is caused in the second polymerisation stage both by vinyl ester units and by crotonic acid units. This is all the more important since the modified method of preparation also allows only small quantities of extra vinyl ester - down to 2% by weight of the total quantity - to be added. Finally, it must also be remembered that a polymer, however defined (e.g. in terms of a manufacturing process or physical parameters), is not a chemical species like a low-molecular organic compound, but a complex mixture of species with molecular weights (K values) statistically spread over a more or less broad range, and also, in the case of copolymers, with statistically spread units of the two (or more) basic monomers. It is therefore to be expected that the statistical ranges of distribution of the species present after post-polymerisation according to the contested patent on the one hand and in the state of the art on the other overlap so considerably that there can no longer be any question of a significantly different, i.e. new, product. All in all, the above-mentioned submission by the respondent fails to demonstrate the novelty of the products according to Claim 4.
3.2.3 Nor is there any evidence that the properties of these products differ markedly from those of the known products. Credence cannot be given to the respondent's objection that the novelty of his products derives alone from their being practically odourless compared with the known products, which have an odour similar to that of an artificial food seasoning ("Maggi"); he did, after all, himself concede when questioned that this unwanted odour or the lack of it is due not to the substance parameters of the known products or of those according to the patent but to the presence or absence of insignificant quantities of monomer impurities with an odour of that type. Evidence of novelty, however, cannot involve properties which are not attributable to the substance parameters of the product itself, i.e. which are not inherent in it. In other words, a known product does not necessarily acquire novelty merely by virtue of the fact that it is prepared in a purer form. Nor, therefore, does their lack of odour make the claimed products new.
3.3 There is no need in these circumstances to examine whether Claim 4 is based on an inventive step. Since a decision can only be taken on a request as a whole, there is no need, in the context of the main request, to look into the patentability of Claims 1 to 3 as well. Instead, the main request is to be refused as a whole.
4. The same does not apply to the alternative request, which pursues only the granted process Claims 1 to 3.
5. The closest state of the art is represented by (1) in respect of ordinary copolymers and by (2) in respect of graft copolymers. Both documents are concerned with processes for manufacturing vinyl ester/crotonic acid copolymers - see (1), column 4, lines 46 to 49, and Example 4, column 6; and (2), Example 13, column 12 - in the presence of a radical-forming initiator and a regulating substance, and also mention odour problems which occur, when polymer products are used for certain purposes, as a result of the impurities they contain; cf. (1), column 1, lines 10 to 15, and column 3, lines 50 to 54; and (2), column 3, line 65, to column 4, line 56. According to the patent proprietor the unpleasant odour of the known copolymer presents an obstacle to their being used as hair-setting lotions.
6. By contrast, the problem of the invention is to indicate a process which produces vinyl ester/crotonic acid copolymers with only a faint odour and particularly without an odour similar to that of artificial food seasoning ("Maggi").
7. Claim 1 proposes to solve this problem by means of a process in which (a) with a vinyl ester/crotonic acid weight ratio of 100:1 to 100:20 (b) 70 to 98% by weight of the total amount of vinyl ester is copolymerised with the total amount of crotonic acid optionally in the presence of the total amount of polyalkylene glycol - and then post-polymerised while the remainder of the vinyl ester is added, after which (c) entrainer distillation is carried out with 5 to 50% by weight, referred to the copolymer, of an alcohol having from 1 to 3 carbon atoms. Carrying out the actual polymerisation process in this way is intended to remove scarcely volatile odour-producing residual monomers, while the purpose of entrainer distillation is to eliminate highly volatile odour-producing residual monomers and other impurities and thus to obtain end products which are practically odourless.
8. As demonstrated in particular by the test report received on 10 January 1985, the problem in question is indeed solved by the characteristics indicated. This is not disputed by the appellant.
9. The subject-matter according to the alternative request is indisputably new and does not therefore require comment.
10. An assessment of inventive step must be based on (1) or (2), which describes processes of the type given in the pre-characterising portion of Claim 1.
10.1 Both these documents, moreover, incorporate characteristic (a). For an ordinary copolymerisation process (albeit involving a third monomer component, which, however, is not indispensable within the total disclosure of (1); cf. column 4, lines 46 to 49), Example 4 of (1) discloses a vinyl acetate/crotonic acid weight ratio of 100:7.8, while Example 13 of (2) discloses a corresponding ratio of 100:8 for a graft copolymerisation process in the presence of polyethylene glycol.
10.2 It is beyond dispute that characteristic (b) is not disclosed in (1) and (2). In both documents, initial polymerisation is first of all carried out, after which - in the case of copolymerisation, which is the only aspect of interest in this context - the residual monomer mixture is added (see (1), column 2, lines 50 to 52, in conjunction with column 3 lines 6 to 9; and Example 4, column 6, lines 5 to 15; and (2), column 2, lines 31 to 33). This process differs markedly from the process according to the contested patent, where copolymerisation involves introducing the total quantity of one monomercomponent and only part of the other, and then adding the remainder of the second one. Furthermore, (3) contains no reference to any retarding effect of crotonic acid on the copolymerisation of vinyl esters, but only to a deceleration (retarding) of the vinyl ester polymerisation process, i.e. of a homopolymerisation process. But if we consider this statement together with the word "copolymerization", which follows the word "retardation" in the table on page 587, and with (1) and (2), according to which vinyl esters are capable of copolymerisation with crotonic acid, the obvious conclusion is that a deceleration takes place in addition to the participation of the crotonic acid in the polymerisation process (copolymerisation). This does not mean, however, that the copolymer obtained initially still necessarily contains troublesome residues of monomeric crotonic acid. The presence of such residues cannot be inferred directly or indirectly from any part of the cited state of the art, nor could it be regarded as probable in view of the substantial excess of vinyl ester. Even if it is conceded that it was obvious to the skilled person concerned with the present odour problem to use analytical means to determine the causes of the troublesome odour and that he was able in the process to establish - with a greater or lesser degree of surprise - the presence of monomeric crotonic acid, this was not enough to suggest post-polymerisation with extra vinyl ester added as the means of removing it. When the appellant maintains that this was "the only way" of eliminating the troublesome odour, he overlooks the fact that no precedent for this expedient exists anywhere in the cited state of the art; on the contrary, the state of the art refers only to reprecipitation (see, for example, (2), column 5, lines 51 to 53, and column 6, lines 28 to 30), to extraction (see, for example (2), column 10, lines 57 and 58) and to the application of a pulsating vacuum for the removal of volatile monomers (see, for example, (2), column 8, lines 1 and 2, and column 5, lines 46 and 47). Thus, the cited state of the art contains no reference to characteristic (b). The surprising finding that this characteristic helps considerably in solving the problem in question is therefore of an inventive nature.
10.3 With regard to characteristic (c), document (2) deals primarily with polymerisation without the use of solvents or subsequent distillation with a solvent. Example 11 describes solvent polymerisation in methanol without subsequent distillation. Document (2) consequently does not disclose characteristic (c). Document (1) mentions the copolymerisation of vinyl esters in organic solvents followed by their removal (column (1), lines 26 to 31). Lower aliphatic alcohols are stated to be the solvents commonly used up to that time (column 1, lines 38 to 40), although the teaching in (1) recommends secondary ones (column 2, lines 39 to 44, and the claim). The quantities indicated are from 1 to 50% referred to the total weight of solvent and monomers, corresponding to roughly 1 to approximately 100% referred to the resulting polymer product (column 3, lines 1 to 5). The secondary alcohol can be removed in vacuo after polymerisation (column 3, lines 47 to 50). However, since the use (and subsequent distilling off) of secondary alcohols according to (1) is intended not to remove volatile impurities but to serve another purpose (reduction of the K value), document (1) does not on its own suggest characteristic (c) either. Although entrainer distillation does not seem unusual for removing volatile impurities in the present state of the art, characteristic (c) cannot be regarded as "self-evident", at least within the context of the solution to the problem according to the invention.
10.4 To summarise, the combination of characteristics according to Claim 1 involves an inventive step.
11. Claims 2 and 3 are concerned with preferred embodiments of the process according to Claim 1. Their patentability derives from that of Claim 1.
ORDER
For these reasons, it is decided that:
1. The decision appealed against is set aside.
2. The case is remitted to the authority of first instance with the instruction that the European patent be maintained in amended form without Claim 4.