Sappi Fine Papers (Pty) Ltd v ICI Canada Inc (Formerly CIL Inc)

• Jurisdiction: South Africa
• Judge: Corbett CJ, E M Grosskopf JA, Nestadt JA, Vivier JA, Nicholas AJA
• Judgment Date: 30 March 1992
• Citation: 1992 (3) SA 306 (A)
• Court: Appellate Division

Corbett CJ:

The respondent in this appeal, ICI Canada Incorporated (formerly CIL Incorporated and hereafter referred to as 'CIL'), a Canadian corporation, is and at all material times has been the patentee of South African patent No 76/5250 for an invention entitled 'Delignification G Process'. The patent was granted on a convention application which was lodged at the patent office on 1 September 1976. The application for the protection of the invention in the convention country (Great Britain) was made on 5 September 1975.

Towards the end of 1984 CIL instituted action against the appellant, H Sappi Fine Papers (Pty) Ltd ('Sappi'), in the Court of the Commissioner of Patents, alleging that Sappi was and had been infringing certain of the claims in patent No 76/5250 ('the patent in suit') and claiming an interdict and certain other relief, including an inquiry as to damages. Sappi defended the action, denying infringement and damages, and it also counterclaimed for the revocation of the patent in suit, alleging that it I was invalid upon a number of grounds.

The case was heard by Van Zyl J as Commissioner. After a lengthy trial he non-suited CIL on the infringement issue and dismissed its claim. In regard to the counterclaim the learned Commissioner upheld two of Sappi's grounds of invalidity, viz material misrepresentation and anticipation, J and made an order revoking the patent in suit. The finding

Corbett CJ

A of anticipation related to only six of the 12 claims of the patent in suit (Sappi claimed that two other claims, Nos 9 and 11, were also anticipated) and was made in respect of only one of four alleged anticipatory documents, viz a printed publication known as 'the Swedish Honshu' patent application. Because Sappi failed in establishing several of the grounds B of invalidity claimed by it, including inutility, ambiguity and insufficiency, and was partially unsuccessful on the issue of anticipation, the Commissioner made an order granting Sappi only two-thirds of its costs in respect of the claim and the counter-claim.

CIL appealed successfully to the Transvaal Provincial Division ('TPD'), which set aside the order of the Commissioner and substituted one C interdicting Sappi from infringing claims 1, 3, 4, 5, 6, 9 and 11 of the patent in suit, ordering an inquiry as to damages and dismissing Sappi's counterclaim. The TPD granted Sappi leave to appeal against the order interdicting the infringement of the aforementioned claims, against the order dismissing the counterclaim for revocation (but only in respect of D the ground of material misrepresentation) and against the consequential order for costs. On a petition to this Court leave to appeal was given in respect of a further ground of revocation, viz anticipation by the Swedish Honshu patent application.

There are thus three main issues on appeal: infringement, material misrepresentation and anticipation by the Swedish Honshu patent. Before E considering these issues it is necessary, however, to sketch the general industrial background to the invention which forms the subject-matter of the patent in suit and to examine the patent specification.

Background

F The invention of the patent in suit relates to a process for the delignification of lignocellulosic material, such as wood, straw and bagasse (the residue after extracting the juice from sugar cane) undertaken in order to produce cellulose suitable for the manufacture of paper products. As this case relates to the process as applied to wood I shall omit further reference to straw and bagasse.

G Wood is composed mainly of hairlike fibres, consisting primarily of cellulose, which are bound together by a substance known as lignin. Cellulose is a sugar polymer with a very long molecular chain. Lignin is also a polymer and similarly has a long molecular chain. In wood the cellulose and the lignin are intermixed to form a solid matrix with a H rigid structure. There is a third minor component of most woods, comprising gums and oils, but these may be disregarded. Woods are classified into soft woods and hard woods. Soft woods are derived from trees of the conifer class, whereas hard wood come from certain types of deciduous trees. Soft woods contain much longer fibres than hard woods, but both are valuable in the making of paper products.

I In order ultimately to produce paper it is necessary that the wood be pulped. There are basically two methods of pulping: mechanical pulping and chemical pulping. Mechanical pulping is achieved by grinding, using stone mills. It does not involve delignification and it produces a pulp suitable for making newsprint. In the case of chemical pulping, on the other hand, J delignification is the object of the process and it produces pulp

Corbett CJ

A suitable for a wide range of paper-making. There is also a hybrid process called semi-chemical pulping. In this matter, however, we are concerned only with chemical pulping.

Delignification in terms of chemical pulping involves the removal from the wood of the lignin and the other non-cellulosic components, such as B gums. It is achieved by means of a process known as 'digesting' or 'cooking', in which the wood (usually in the form of chips) is placed in a vessel, called a 'digester', together with a chemical agent in an aqueous solution, known as the 'pulping liquor', and the contents of the digester are heated under pressure for a chosen period of time. During this process the liquor penetrates the wood and reacts with the lignin and takes it into solution, leaving the wood fibres relatively lignin-free (depending C on the degree of effectiveness of the cooking process). When the cook is complete the liquor (with the lignin in solution) is separated from the cellulose, which then constitutes the wood pulp available for paper-making. Different types and concentrations of chemical agents in the liquor and different conditions and methods pertaining to the cook will D produce varying degrees of delignification; and in general the greater the degree of delignification the higher will be the quality of the paper produced by the wood pulp.

One of the problems inherent in the chemical pulping process is that E while the delignification is taking place the cellulose fibres themselves are to some extent degraded and in particular tend to undergo a process known as 'peeling', which has the effect of shortening the molecular chains, thereby decreasing the yield of cellulose and reducing the strength of the pulp produced. For many years it has been the object of research chemists in the pulping field to devise ways and means of F controlling or eliminating the peeling reaction and of removing the lignin while minimising the degradation of the cellulose in the fibres.

Chemical pulping processes fall into two main categories, based on the ingredients of the pulping liquor. These are (i) the acid, which uses an acid pulping liquor and of which the sulphite process is an important example; and (ii) the alkaline, which uses an alkaline pulping liquor and G of which the soda and kraft (or sulphate) processes are the best known. This case is concerned only with the alkaline processes.

The soda process involves the use of a liquor containing sodium hydroxide (popularly known as caustic soda); while the kraft process H employs a mixture in solution of sodium hydroxide and sodium sulphide. There is also a modification of the kraft process, which involves the inclusion in the pulping liquor of polysulphide, but this does not call for separate consideration.

The soda process is the oldest of the alkaline processes, but the kraft process, which was subsequently invented, was found to have the advantage I of producing 'stronger' pulp (hence the name 'kraft', meaning, in German, strong). On the other hand, the kraft process has the side-effect of producing a very obnoxious odour, which tends to pollute the atmosphere. The soda process does not have this side-effect, but the process is inclined to degrade the cellulose faster than the kraft process does and J consequently produces an inferior pulp.

Corbett CJ

A There are fundamentally two types of cooking or digestion used in pulping: batch digestion and continuous digestion. In the case of the batch digestion the process consists of a single complete operation, which may be repeated as often as required. Typical apparatus for batch digestion consists of a large cylindrical metal vessel, which stands upright and which is connected by pipes to a circulation pump and a heat B exchanger. At the bottom of the cylinder is a 'blow' valve, connected to a blow line. The batch digester is operated by filling the vessel with wood chips to the desired level and then pumping in cooking liquor, which enters the vessel at the top. When the appropriate amount of liquor is in the digester, it is closed up. (Usually the proportion of liquor to wood C chips would be between 3:1 and 5:1.) Thereafter the circulation pump is brought into operation and this causes the liquor to be drawn off at a point called 'the circulation screen' near the bottom of the vessel, to pass through the heat exchanger, where it is heated, and to re-enter the vessel at the top. The liquor continues to circulate in this way and the D temperature thereof to be raised until the desired maximum is reached. This temperature is then maintained for a desired period of time. The period during which the contents of the digester are being heated up to the maximum temperature, which could be from 35 to 120 minutes, is known as the 'time to temperature'; and the period during which the maximum temperature is maintained, which varies considerably but on average could E be about 90 minutes, is known as the 'time at temperature'. A typical maximum temperature would be 170 øC. Attainment of this temperature causes a high pressure -...