T 0361/95 19-10-1998

Reasons for the Decision

1. The appeal is admissible.

2. Text

The text of the application in suit on which the present decision is based, in accordance with the request of the Appellant, is as follows:

Claims: Claims 1 to 7 (DE, GB, FR, IT, NL, SE, CH/LI, BE, AT, LU, DK), filed on 19 August 1998, with letter of same date;

Claims 1 to 7 (ES), filed on 19 August 1998, with letter of same date;

Description: Pages 1 to 4, filed on 19 August 1998, with letter of same date.

3. Amendments

3.1. The claims of both sets correspond to the claims as originally filed, subject to minor clarifying amendments to meet objections raised by the Examining Division under Article 84 EPC, in the communications issued on 16 April 1993 (point 5A) and on 19 November 1993 (point 4). No objection was raised by the Examining Division to these amendments under Article 123(2) EPC, and the Board sees no reason to raise any objection of its own. Consequently, both sets of claims are held to meet the requirements of Article 123(2) EPC.

3.2. The description corresponds to the description as originally filed, subject to amendments to adapt the latter to the revised claims, and to acknowledge the background art pursuant to Rule 27(1)(b) EPC. These amendments are not such as to contravene the requirements of Article 123(2) EPC.

3.3. Consequently, the requirements of Article 123(2) EPC are met.

4. The application in suit; the technical problem

The application in suit is concerned with a composition which contains a polymer derived from an unsaturated hydrocarbon monomer and an additive for improving biodegradability. Such a composition is, however, known from D1, which by common consent represents the closest state of the art.

4.1. According to D1, there is provided a biodegradable synthetic polymer composition consisting essentially of a polymer having carbon to carbon linkages, for instance a polyvinyl chloride, polyethylene or polypropylene resin, and, dispersed therein, from 5 to 50% by weight particles of a biodegradable substance, and up to 5.5% by weight of an auto-oxidisable substance containing at least one double bond which, when in contact with a transition metal salt, auto-oxidises to generate a peroxide or a hydroperoxide. The auto-oxidisable substance is selected from a fatty acid, a fatty acid ester, and mixtures thereof, such as ethyl oleate/oleic acid (Claim 1 in conjunction with column 2, lines 33 to 40; Example I). The particles of biodegradable substance may be lactose sugar granules (Claim 6), but are preferably natural starch granules, and in particular, a multi-occupation starch such as rice or maize starch, which has a granule of polyhedral form. To optimise the starch concentration, a mixture of two starches each having a different grain size is preferred. The greater the starch concentration, the greater the biodegradability (column 2, lines 41 to 62).

The starch granules are normally added to prepare the raw polymer for processing at elevated temperatures, which are survived by the starch granules. If, however, the polymerisation takes place under conditions such that the starch is not altered chemically or physically, then the starch granules can be added to the monomer (column 3, lines 3 to 11).

The compositions have, at least to some extent, the physical characteristics of paper, i.e. the ability to hold a crease and to receive a printed impression. Treatment with hot water to gelatinize or dissolve surface starch granules renders the composition more paper-like (column 3, lines 19 to 39).

According to Example I, a blown film was prepared by extruding a blend, with unfilled low density polyethylene (density 0.916; melt flow index 1), of a masterbatch made by compounding, in a two-roll mill at 140 C, 200g pre-dried maize starch (moisture content 0.5%), 39g ethyl oleate, 1g oleic acid and 160 g low density polyethylene film (density 0.920; melt flow index 1), so as to give 8% starch in the final composition. The blown film had a tensile strength in the machine direction of 7.59 units, and in the transverse direction of 6.9 units, compared with a corresponding film made without the starch etc., of 8.28. units in the machine direction, and 5.52 units in the transverse direction.

4.2. The products according to D1, although combining the desirable properties of plastics with significant biodegradability, show less than desired strength and elongation properties.

4.3. Thus, the technical problem arising from this disclosure is to provide such a composition having improved strength and elongation properties.

4.4. The solution proposed according to Claim 1 of the application in suit is to replace the granular starch filler by a C1-4 alkyl or hydroxyalkyl starch ether having a degree of substitution of at least 0.25.

4.5. A direct comparison of the properties of the claimed compositions with those of D1 is neither possible (i) in relation to tensile strength, because the dimensions of the blown films exemplified in D1 are not identical with those of the extruded films exemplified in the application in suit, nor (ii) as regards elongation at break, since D1 makes no reference to this property. Furthermore, the amount of starch incorporated into the composition according to Example I of D1, at 8%, is lower than that exemplified in the application in suit, at 30 or 40%.

A relevant comparison is, however available, in the experimental report filed with Statement of Grounds of Appeal, which shows pressure moulded Compositions X and Y, X being according to the application in suit, and Y falling within the disclosure of D1, respectively, comprising:

............................Composition.X......Composition Y

..................................wt%...........wt%

extrusion cooked starch.........................50

hydroxypropyl starch..............50

linear low density polyethylene...45............45

ethyl oleate.......................5.............5

Whereas the moulded product of Composition X has a tensile strength of 5 MPa, that of Composition Y is 4 MPa. Thus Composition X is capable of giving a product having a higher tensile strength than that of Composition Y.

Furthermore, as regards extensibility, the product of Composition X has an elongation at break of 420%, compared with 5% for that of Composition Y. Hence, Composition X is capable of giving a product of far higher elongation at break than that of Composition Y.

4.6. Composition X, however, differs from Composition Y only by the replacement of the starch component by hydroxypropyl starch, none of the other parameters being changed. It therefore represents a closer comparison than the specific disclosure of D1.

4.7. In this connection, an Applicant or Patentee may discharge his onus of proof by voluntarily submitting comparative tests with newly prepared variants of the closest state of the art making identical the features common with the invention in order to have a variant lying closer to the invention so that the advantageous effect attributable to the distinguishing feature is thereby more clearly demonstrated (T 35/85 of 16. December 1986, not published in OJ EPO, Reasons for the decision, point 4, supplementing T 181/82 "Spiro-compounds", OJ EPO 1984, 401).

4.8. In view of the above, it is credible that the claimed measures provide an effective solution of the stated problem.

5. Novelty

The decision under appeal explicitly recognised a distinction in the claimed subject-matter over the closest state of the art, namely the use of an etherified starch instead of starch, a view with which the Board fully concurs (decision under appeal; Reasons for the decision, point 2, second paragraph). The remaining documents are more remote. Consequently, the subject-matter claimed in the application in suit is novel.

6. Inventive step

In order to assess the question of inventive step, it has to be considered whether the skilled person, starting from D1, would have expected to be able to improve the tensile strength and stretchability of the products, by replacing the starch by a C1-4 alkyl or hydroxyalkyl starch ether having a degree of substitution of at least 0.25.

6.1. Whilst the preferred embodiment of the biodegradable additive in D1 is starch, the only alternative proposed being lactose, the additive must in any case be present as particles (Claim 1). With regard to the preferred particles, which are starch granules, furthermore, it is made clear that these will survive even severe polymer processing at elevated temperatures. Thus, the addition of the granules to the monomer prior to polymerisation is only permitted under conditions in which the starch is not altered chemically or physically (column 3, lines 3 to 14). This is in contrast to the application in suit in which, according to the submission of the Appellant, which the Board has no reason to doubt, the starch derivative leads to a "mutual solution" of hydrocarbon polymer and starch derivative (section III.(a), above). Consequently, there is no hint in D1 to the solution of the technical problem.

6.2. According to D2, an expanded, biodegradable, low-density packaging material having a closed cell structure with good resilience and compressibility properties, is prepared by extruding starch containing at least 45% by weight amylose content in the presence of a total moisture content of 21% or less by weight and at a temperature of from about 150 to 250 C (Claim 1; column 2, lines 32 to 60). The starch may be unmodified or modified, in the latter case by forming a derivative, e.g. by esterification, etherification, oxidation, acid hydrolysis, cross-linking or enzyme conversion (column 3, lines 55 to 61). One advantageous modification is the etherification with alkylene oxides, propylene oxide being especially preferred, generally in an amount of up to 15% by weight based on the weight of the starch, extruded starches modified in this manner showing improved expansion, uniformity and resiliency (column 4, lines 9 to 21). Additive compounds may be combined or blended with the starch starting material to improve properties such as strength, flexibility, water resistance, etc., compounds such as polyvinyl alcohol, monoglyceride and polyethylene vinyl acetate being suitable. Typically, up to about 50% by weight of such additives, and preferably up to 10% by weight, may be used (column 4, lines 22 to 33). When etherified starch is used, the extrusion temperature is preferably 160 to 210 C (column 5, lines 17 to 59).

According to a typical example, a high amylose starch (70% amylose) modified with propylene oxide (5%) with the addition of polyvinyl alcohol (2.40% by weight) gave good expanded products (Example III).

6.2.1. Whilst other materials may be present together with the hydroxypropyl starch, contrary to the argument of the Appellant in the Statement of Grounds of Appeal (section III.(b), above), it is evident that D2 is concerned exclusively with an expanded product, i.e. packaging material having the character of a foam, of which the relevant physical properties are bulk density, resiliency and compressibility (D2; column 6, line 58 to column 7, line 55). These qualities are, however, irrelevant to the aims set out in the technical problem, the latter two even being diametrically opposed to the relevant qualities aimed at, namely increased tensile strength and elongation. Consequently, the disclosure of D2 cannot be regarded as giving any information useful to the skilled person for solving the stated problem.

6.2.2. In any case, it has not been alleged, let alone demonstrated in the decision under appeal, that the level of reactant disclosed in D2 (up to 15%) would result in a degree of conversion of the starch of 0.25 (25% conversion) or more, required by the solution of the technical problem.

6.2.3. In summary, the skilled person starting from D1 and faced with the technical problem would not regard the disclosure of D2 as relevant to his purpose, and even if, in spite of this, he endeavoured to make use of its teaching, the result has not been shown to correspond to the solution of the problem as stated.

6.3. According to D3, film prepared from hydroxypropyl-high- amylose corn starch (71% apparent amylose; 1.11% hydroxypropyl) is water-soluble, transparent, and impermeable to oxygen at 25 over a wide range of humidities. Hydroxypropylation reduces tensile strength of the film but increases elongation and burst strength and maintains folding endurance. Plasticisation with 5% glycerol is not beneficial (page 347, third complete paragraph).

6.3.1. The information contained in D3 is, in the Board's view, even less relevant to the technical problem than that in D2, since it is neither concerned with packaging, nor the behaviour of the starch derivative when blended with other materials.

6.3.2. To the extent that the skilled person could derive any relevant information from such a general text, it would evidently be concluded that elongation is improved at the expense of tensile strength. It is a requirement of the solution of the technical problem, however, that both elongation and tensile strength are improved simultaneously (sections 4.3, 4.4., above). Consequently, D3 would not offer the skilled person a solution of the technical problem. The situation is no different, even if D3 is viewed in the light of D2, since there is no discernable relationship between the parameters dealt with in D2 and those referred to in D3.

6.4. In other words, the solution of the technical problem does not arise in an obvious way from the state of the art.

6.5. On the contrary, the simultaneous increase in tensile strength and elongation at break, brought about by the different and unsuggested role of the third component (the fatty acid ester), which functions as a compatibiliser to assist the formation of a "mutual solution" of the polymer and the starch ether (section 6.1, above) and furthermore results in the stretchable character of the composition according to the application in suit, rather than the paper-like quality referred to in D1, must be regarded as a surprising result.

6.6. Consequently, the subject-matter of Claim 1, and, by the same token, of dependent Claims 2 to 5 of both sets of claims involves an inventive step. Furthermore, the subject-matter of Claims 6 and 7 of both sets of claims, which are equally limited to applications of compositions according to the relevant Claim 1, also involves an inventive step.