T 0388/00 12-11-2002

Summary of Facts and Submissions

I. The appellant (patent proprietor) lodged an appeal against the decision of the Opposition Division revoking European patent No. 0 645 226.

An appeal against this decision was also lodged by respondents II (opponents 02, Earl Doyle and Scott Carson).

Oppositions had been filed against the patent as a whole based on Article 100(a) EPC (lack of novelty and lack of inventive step), Article 100(b) EPC and Article 100(c) EPC by opponent 01, Hennecke GmbH, and by respondents II. The Opposition Division held that claims 1 and 12 as granted as well as claims 1 and 12 of the auxiliary request lacked an inventive step.

II. Oral proceedings were held before the Board of Appeal on 12 November 2002. As announced on 5 November 2002, respondents II were not represented. Opponent 01, having withdrawn the opposition on 19 April 2002, was not represented either.

III. The appellant requested that the decision under appeal be set aside and that the patent be maintained on the basis of the following documents:

(a) main request: claims 1 and 12, submitted as main request during oral proceedings, and claims 2 to 11. and 13 to 23 filed as main request on 19 June 2000; or

(b) first auxiliary request: claims 1 and 11, submitted as first auxiliary request during oral proceedings, and claims 2 to 9 filed as main request on 19 June 2000, and claims 10 and 12 to 22. filed as first auxiliary request on 11 October 2002; or

(c) second auxiliary request: claims 1 and 12, submitted as second auxiliary request during oral proceedings, and claims 2 to 11 and 13 to 23 filed as main request on 19 June 2000; or

(d) third auxiliary request: claims 1 and 12, submitted as third auxiliary request during oral proceedings, and claims 2 to 11 and 13 to 23 filed as main request on 19 June 2000.

Before withdrawal of the opposition, opponent 01 had requested that the appeal of the appellant be dismissed.

Respondents II requested that the decision under appeal be set aside and that the patent be revoked on each of the grounds pursuant to Article 100(a) EPC (lack of novelty; cf. Article 54 EPC), Article 100(b) EPC and Article 100(c) EPC. As regards revocation of the patent by the Opposition Division for lack of inventive step, respondents II requested that the decision under appeal be left to stand in this respect.

IV. Claim 1 of the main request reads:

"1. A process for continuous production of polyurethane slab-stock foam (16) including the steps of:

forming a mixture of reactive chemical components;

mixing the reactive chemical components with CO2 under sufficient pressure conditions to maintain the CO2 in a liquid state,

characterized by,

distributing the mixture by passing the resulting mixture along a frothing device (13) comprising an elongated pressure equalizing chamber (21), an elongated pressure drop zone (17) and a frothing cavity (19) wherein said elongated pressure drop zone (17), in the direction of flow, consists of one slot (17; 64, 66, 68) axially extending in the direction of the flow and is dimensioned to maintain back pressure on the upstream mixture to keep the CO2 in a liquid state and to initiate frothing under pressure controlled conditions, wherein said frothing device (13) avoids turbulent evaporation of the CO2 upon discharge of the mixture from the pressure drop zone;

and forming the discharged mixture into a progressively expanding frothing material by progressively releasing the CO2 in the frothing material as the frothing material flows along the frothing cavity (19) and through an outlet aperture (20), thereby discharging the frothing mixture onto a substrate (2)."

Claim 1 of the first auxiliary request reads:

"1. A process for continuous production of polyurethane slab-stock foam (16) including the steps of:

forming a mixture of reactive chemical components;

mixing the reactive chemical components with CO2 under sufficient pressure conditions to maintain the CO2 in a liquid state,

characterized by,

keeping a pressure during mixing which ranges from about 5 to about 18 bar,

distributing the mixture by passing the resulting mixture along a frothing device (13) comprising an elongated pressure equalizing chamber (21) and through an elongated pressure drop zone (17) and a frothing cavity (19) wherein said elongated pressure drop zone (17), in the direction of flow, consists of one slot (17; 64, 66, 68) axially extending in the direction of the flow and is dimensioned to maintain back pressure on the upstream mixture to keep the CO2 in a liquid state and to initiate frothing under pressure controlled conditions, wherein said frothing device (13) avoids turbulent evaporation of the CO2 upon discharge of the mixture from the pressure drop zone;

and forming the discharged mixture into a progressively expanding frothing material by progressively releasing the CO2 in the frothing material as the frothing material flows along the frothing cavity (19) and through an outlet aperture (20), thereby discharging the frothing mixture onto a substrate (2)."

Claim 1 of the second auxiliary request reads:

"1. A process for continuous production of polyurethane slab-stock foam (16) including the steps of:

forming a mixture of reactive chemical components;

mixing the reactive chemical components with CO2 under sufficient pressure conditions to maintain the CO2 in a liquid state,

characterized by,

distributing the mixture by passing the resulting mixture along a frothing device (13) comprising an elongated pressure equalizing chamber (21) and through an elongated pressure drop zone (17) and a frothing cavity (19) wherein said elongated pressure drop zone (17), in the direction of flow, consists of one slot (17; 64, 66, 68) axially extending in the direction of the flow and having a height of less than or equal 0.5. mm and is dimensioned to maintain back pressure on the upstream mixture to keep the CO2 in a liquid state and to initiate frothing under pressure controlled conditions wherein said frothing device (13) avoids turbulent evaporation of the CO2 upon discharge of the mixture from the pressure drop zone;

and forming the discharged mixture into a progressively expanding frothing material by progressively releasing the CO2 in the frothing material as the frothing material flows along the frothing cavity (19) and through an outlet aperture (20), thereby discharging the frothing mixture onto a substrate (2)."

Claim 1 of the third auxiliary request reads:

"1. A process for continuous production of polyurethane slab-stock foam (16) including the steps of:

forming a mixture of reactive chemical components;

mixing the reactive chemical components with CO2 under sufficient pressure conditions to maintain the CO2 in a liquid state,

characterized by,

distributing the mixture by passing the resulting mixture along a frothing device (13) comprising an elongated pressure equalizing chamber (21) and through an elongated pressure drop zone (17) and a frothing cavity (19) wherein said elongated pressure drop zone (17), in the direction of flow, consists of one slot (17; 64, 66, 68) axially extending in the direction of the flow and having a height in the range of 0.3 to 0.5. mm and is dimensioned to maintain back pressure on the upstream mixture to keep the CO2 in a liquid state and to initiate frothing under pressure controlled conditions, wherein said frothing device (13) avoids turbulent evaporation of the CO2 upon discharge of the mixture from the pressure drop zone;

and forming the discharged mixture into a progressively expanding frothing material by progressively releasing the CO2 in the frothing material as the frothing material flows along the frothing cavity (19) and through an outlet aperture (20), thereby discharging the frothing mixture onto a substrate (2)."

V. The following documents are referred to in the present decision:

D1: US-A-3 181 199

D2: US-A-5 120 770

D10: "Flexible Polyurethane Foams", Ron Herrington and Kathy Hock, Dow Plastics 1991, pages 9.2 and 9.3

D21: "Bayer/Hennecke add CO2", Urethanes Technology, August/September 1995, pages 9 and 10

VI. In the written and oral proceedings the appellant argued essentially as follows:

The expression "progressively releasing the CO2 in the frothing material" in claim 1 of the main request does not cause an extension beyond the original disclosure. The description as originally filed supports both a gradual release and a progressive release of the blowing agent in the frothing mixture. Thus, even if the terms "gradually" and "progressively" had to be construed as having different meanings, the use of the term "progressively" in the claim was in accordance with Article 123(2) EPC.

With the amendments made, the claims of the main request are clear and in line with the description and drawings. The disclosure of the patent specification is sufficient as concerns the design of the slot and the pressure conditions. With respect to the latter, however, the common general knowledge of the person skilled in the art has to be included. It is then clear that the pressure to keep CO2 in liquid form within the mixture is less than the pressure to keep free CO2 in liquid form. The requirements of Articles 84 and 83 EPC are therefore fulfilled.

Independent claims 1 and 12 of the main request relate to the production of polyurethane slab-stock foam. The mixture which is released onto the substrate has a density of about 1100 to 1200 kg/m³ whereas the finished slab-stock foam typically has a density in the range of 16. to 48 kg/m³. Consequently, a high amount of gas is needed to expand the mixture by such a degree. This expansion also needs a certain time and thus takes place along a considerable transport distance of the substrate conveyor. The fully expanded foam reaches a height of about 1,2 m. Document D1 relates to a coating machine which produces a foam coating on a substrate, the foam thus formed having typically a density of about 350 kg/m³ and a height of a few millimetres. Thus, significantly less gas is needed and the foaming process takes a short time and a short distance and is already finished when the mixture is released onto the substrate. Since the necessary amount of gas is small, the problem of an explosion-like evaporation of the gas and the consequent turbulences in the mixture do not occur. Moreover, document D1 is silent about the gas used as blowing agent. Finally, document D1 does not disclose a pressure drop zone which consists of one slot axially extending in the direction of the flow and which is able to maintain a back pressure sufficient to keep CO2 in liquid form. It discloses only a simple slit. Table 9.1 of document D10 shows some typical characteristics of slab-stock foam which differ significantly from the foam produced with the process of document D1. Document D1, therefore, will not be considered by a skilled person when designing a slab-stock foam production process and system using CO2 as blowing agent.

In document D2 CO2 is used as a blowing agent and, therefore, an explosion-like evaporation occurs. This instantaneous evaporation is a necessary element of the process of document D2 as can be seen from step (b) of claim 1 of this document. It is not designated as a disadvantage. For this reason a skilled person would not omit this step. Starting from document D2, a skilled person would not consider document D1 which does neither show CO2 as blowing agent nor slab-stock foam. The combination of these two documents would not make sense; however, even if combined, this combination would not result in the process of claim 1 of the patent in suit according to the main request.

The pressure range of 5 to 18 bar as an additional feature in claim 1 according to the first auxiliary request emphasizes that the patent in suit relates to the production of slab-stock foam and implies specific features of the system according to claim 11 of the first auxiliary request. The system of document D1 lacks these specific features.

Although the description of the patent mentions only three distinct values of the slot height, a skilled reader will recognize that these are only preferable examples and that all slot heights smaller than 0.5 mm, but at least all slot heights within the range of from 0.3. to 0.5 mm, are possible. The additional features in claim 1 according to the second auxiliary request and in claim 1 according to the third auxiliary request are therefore in accordance with Article 123(2) EPC.

The slot height is an essential feature of the invention because it is the slot which creates the necessary back pressure to keep the CO2 in liquid form and which is instrumental in avoiding turbulent evaporation of the blowing agent. The slot height specified in claim 1 according to the second or third auxiliary request implies a certain depth of the slot which is necessary for the smooth release of the gas. With the slot as shown in document D1 it would not be possible to avoid this turbulent evaporation.

VII. As regards the subject-matter of the claims filed by the appellant on 19 June 2000 respondents II argued essentially as follows:

The claims (all requests) are not in accordance with Article 123(2) EPC. Firstly, the application as filed does not provide a basis for the feature that the slot axially extending in the direction of the flow is dimensioned to maintain back pressure on the upstream mixture to keep the CO2 in a liquid state. Secondly, the original disclosure does not show that the discharged mixture is formed into a progressively expanding frothing material by progressively releasing the CO2. It shows that the blowing agent is gradually released. However, progressively and gradually have different meanings.

The patent specification lacks sufficient disclosure so that a person skilled in the art is not able to carry out the claimed subject-matter. The definition of the shape and configuration of the pressure drop zone is so broad that a person skilled in the art would be required to engage an unreasonable amount of research and development to arrive at a suitable design. Furthermore, it is questionable whether the CO2 can be kept in a liquid state. The pressure at the lower end of the range of 5 to 18 bar is not sufficient, not even at very low temperatures, to keep CO2 liquid. For these reasons the patent specification is not in accordance with Article 83 EPC.

The use of conventional blowing agents such as CFCs was outlawed for environmental reasons, and CO2 has been established as a suitable substitute. Document D2 shows that CO2 is the most suitable blowing agent. However, it was also known that this gas leads to a very turbulent evaporation and thus to a poor foam quality. Having this problem in mind, a person skilled in the art would inevitably consider document D1 when seeking for a solution to produce slab-stock foam without such a turbulent evaporation of the blowing agent. This document makes it clear that the apparatus which is described therein is intended for operation at high pressure and is thus suitable for use with liquid CO2. Especially a pressure in the range from 5 to 18 bar can easily be achieved with the apparatus of document D1. In addition, this prior art apparatus has a high degree of adjustability so that the necessary adaptation can also easily be achieved. Especially the slit through which the mixture is released is fully adjustable and thus able to permit a flow at a controlled rate and to produce the necessary back pressure. Thus, when seeking a solution to the problem of turbulent evaporation a person skilled in the art would start from document D1 and perform the necessary modifications and thus arrive at the process and system according to the patent in suit.