BACKGROUND OF THE INVENTION The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.

Hydroxymatairesinol is a lignan with anti-oxidative properties. It has been found to have valuable therapeutical effects, e. g. as an agent for preventing cancer, hormone dependent diseases and cardiovascular diseases. Moreover, it has been found that intake of hydroxymatairesinol increases the enterolactone level in the individual's serum. The increased level of enterolactone leads in turn to certain favourable therapeutical effects, such as improved protection against cancer, see WO 00/59946, Hormos Nutraceutical Oy Ltd. Therefore it has been suggested to use hydroxymatairesinol as a pharmaceutical or as a food additive, either in the form of a functional food or as a unit dosage form (capsule or the like) for intake in addition to the daily food. The published patent application WO 03/045376, Hormos Nutraceutical Oy Ltd. , describes the effect of hydroxymatairesinol for decreasing overactivity of certain cells, i. e. certain phagocytes and T-lymphocytes, and subsequently preventing many diseases. Furthermore, hydroxymatairesinol is also a useful starting material in the synthesis of other therapeutically valuable lignans such as matairesinol (WO 03/057209, Hormos Nutraceutical Oy Ltd.), secoisolariciresinol, lariciresinol and cyclolariciresionol (WO 03/059340, Hormos Nutraceutical Oy Ltd. ). A common feature for all these lignans is, that their supply

has been very restricted, because they cannot be recovered from any plant source in greater amounts. Previously, no feasible methods for their synthesis have been presented.

Considerable amounts of hydroxymatairesinol have been found in coniferous trees, especially in spruce. The concentration of hydroxymatairesinol is particularly high in knotwood (wood rich in knots). In the knots of Norway spruce (Picea abies L), the hydroxymatairesinol concentration is 5 to 7 %, calculated on knots.

Therefore spruce wood, and particularly knots of spruce wood, is an especially useful source for recovery of hydroxymatairesinol. The published patent application <BR> <BR> WO 03/044004, Hormos Nutraceutical Oy Ltd. , describes a method for recovery of hydroxymatairesinol wherein finely divided wood is extracted with a polar solvent, such as alcohol, and where a complexing agent is added to the extract, resulting in precipitation of hydroxymatairesinol as a complex. According to a preferable embodiment, the wood material is enriched with respect to knots. Such an enriched material, which is produced along with the manufacture of pulp, is the fraction of oversized chips, derived from the chipping and subsequent screening step. This fraction of oversized chips has unfavorable effects on the pulp quality, and therefore its entry into the pulping process should be avoided. This fraction of oversized chips, which can be about 5 % of the total amount of chips, is in practice often led to combustion for energy production.

The fraction of oversized chips contains 10 to 30 % of knots, which in turn contain high concentrations of hydroxymatairesinol. The remaining part of the oversized chips is normal wood. Leading the fraction of oversized chips directly to combustion means that considerable amounts of raw material in the form of normal wood are withdrawn from the pulping process. The use of the fraction of oversized chips as such for recovery of hydroxymatairesinol by extraction is, although technically possible, an unfavorable load on the extraction process because only about 30 % of the wood material to be extracted contains considerable amounts of hydroxymatairesinol. The fraction of normal wood is just a load on the extraction

process while this fraction would be a valuable additional raw material for the pulp manufacture.

Therefore there is a need to further process the fraction of oversized chips in order to achieve a more enriched material of knots for recovery of extractive substances, such as hydroxymatairesinol, and in order to return as much as possible of the normal wood to the pulping process. The Finnish patent application FI 20001739, Separation Research Ltd. , describes such a method. The fraction of oversized chips or an air-screened, heavy fraction thereof is ground to splinters after which the splinters are dried and subsequently mixed with water, resulting in a separation of the splinters in a light fraction and a heavy fraction (sediment). The sedimented splinters, which are rich in extractive substances, are led to extraction while the light fraction, which mainly constitutes of normal wood, can be led to the pulping process.

The aforementioned separation method suffers, however, from certain disadvantages: - drying of the wood material before the separation is an energy consuming step - wet sedimented material, aimed for extraction (which process in practice is not feasible for integration with the pulping process) cannot be stored as such without foregoing drying - also the extraction step needs preceding drying of the sedimented knot-rich material - the moisture content of the wood material returned to the pulping process varies and deviates from the moisture content of the main flow of chips - water-based sedimentation technique is a unit operation difficult to integrate into the chip-handling process.

SUMMARY OF THE INVENTION The aim of the present invention is to achieve an improved extraction method for recovery of hydroxymatairesinol from knotwood derived from oversized chips,

obtained in the chip-handling process in a pulp mill. The improvement concerns the fractioning of the oversized chips. The fractioning step according to this invention aims at an improved, non-water based method which does not suffer from the drawbacks related to the known water-based sedimentation process described above.

The method according to the present invention is characterized in that a) oversized chips, or an air-separated heavy fraction thereof, is finely divided, b) the finely divided material from step a) is without preceding drying and/or mixing with water separated into a light fraction and a heavy fraction, c) the heavy fraction from step b) is extracted with a polar solvent, and d) hydroxymatairesinol is recovered from the extract.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows schematically a known method for enriching of knots from a chip flow, Figure 2 shows schematically a method for recovery of hydroxymatairesinol from knotwood in a flow of oversized chips, wherein the material passed to extraction has been enriched with respect to knots by the method according to the present invention, Figure 3 shows the method of this invention according to one alternative, Figure 4 shows the method of this invention according to another alternative, Figure 5 shows the method of this invention according to a third alternative.

DETAILED DESCRIPTION OF THE INVENTION The term"knotwood"shall be understood to include the"knots", i. e. the part of the branches that is embedded in the stem, and the branches extending outwards from the stem.

Figure 1 shows the water-based method for enriching knots from a chip flow according to the Finnish patent application FI 20001739. According to the figure, an air-separated fraction of the oversized chips is led to comminution, but alternatively, the total fraction of oversized chips can be charged to comminution, subsequent drying, mixing with water and water-based sedimentation. In case air-screening is used, a useful method is Air Density Separation, ADS, which is described in US 5,568, 896, for example.

Figure 2 shows a method according to the present invention. The oversized chips are led to comminution. The comminution can, with respect to the preceding extraction step, basically be any method of dividing material finely. However, if it also is desirable to ensure that the fraction of the finely divided material to be returned to the pulping process is of good quality for manufacture of pulp, then it is feasible to use a comminution method giving thin splinters, avoiding essentially cutting of the length of the fibres. As an example of such comminution processes can be mentioned the"pin chips"-process, which normally is used for comminution of oversized chips for the manufacture of mechanical pulp. As examples of suitable comminution apparatuses can be mentioned the devices disclosed in US 5,937, 923, US 4,235, 382 and US 4,953, 795. Another example of a possible comminution apparatus is an impact grinder, for example an Atrex impact grinder described in the Finnish patent FI 105699.

After the comminution, the material is led to separation without any preceding drying and/or mixing with water. The object of the separation step is to separate the finely divided material into a knot-rich fraction and another fraction with no or low content of knots. It is known that the knot-rich chips have a higher specific weight than chips with no or low concentrations of knots. Therefore it can be said that the object is to achieve a separation of the finely divided material into a heavy (i. e. knot-rich) fraction for use in the subsequent extraction and recovery of hydroxymatairesinol, and into a light fraction which, in case the fibre quality requirements are fulfilled, is returned to the pulping process, or, if the quality requirements are not fulfilled, is led to another use, such as combustion.

The separation can be performed in many alternative ways. As example can be mentioned air separation (Air Density Separation, ADS) which is described for example in US 5,568, 896 and US 5,829, 597 Beloit Technologies Inc. and in US 6,283, 300. The principle is that the finely divided material is led into a tower in which an upwardly moving air flow is arranged. Heavy material descends while light material is moved ahead with the air flow. Alternatively, the finely divided material can be separated in a cyclone or in several cyclones arranged in series or in parallel, where heavy material present in a charged air flow is forced to the periphery of the cyclone (s) due to the centrifugal force.

The separation into a heavy fraction and a light fraction does not necessarily need to be a unit operation using differences in the specific weight of the material to be fractioned. It is known from practice that the knotwood is much more difficult to comminute than normal wood. By using conventional screening based on particle size (grid or disk sieve, for example according to FI 92476, or a rod sieve, for example according to FI 101203). The usefulness of a screening method based on particle size depends highly on the comminution method used.

Figure 3 shows an alternative method in which the oversized chips have been screened in an air screening step. Only the knot-rich fraction is led to comminution and subsequent treatment.

Figure 4 shows a third alternative where at least part of the heavy fraction from the screening step is returned to the preceding comminution step.

Figure 5 shows a fourth alternative employing two subsequent comminution steps and screening steps.

The method according to the present invention is not limited to the above embodiments illustrated in the figures. It is obvious for the skilled person that also modifications and combinations can be used. Thus the processes according to

figures 4 and 5 can be combined. The number of comminution and screening steps can be increased and the steps can be coupled together in different ways.

Furthermore, it should be noted that a comminution or screening step illustrated in the figures can as such compose of two or more different subsequent or parallel unit operations.

The comminution and screening process can naturally be stationarily integrated with the wood treating process in the pulp mill. Alternatively it would be possible to build a transportable, ambulatory machinery for these processes. Such machinery can easily be transported to different pulp mills. The comminution and screening apparatuses, which can be made up of one or more units, can be mounted on the same or different easily transportable, for example wheel-equipped supports which can be transported by car to the destination desired.

Summary of the benefits of the present invention: - the treated wood material which is led to extraction and recovery of hydroxymatairesinol, has a high content of knots, and therefore saving of chemicals and investment costs for extraction apparatuses are achieved due to a smaller amount of wood material used, - energy and time consuming drying of the wood material before fractioning is avoided, - the knot-rich wood material achieved has not been subjected to water and is thus dry and storable and can be used for extraction on a desired place at a suitable time, - the apparatuses are of common type and easy to integrate with the chip handling process in a pulp mill, - the knot-rich material can be extracted as such without preceding drying, - the apparatuses for comminution and screening can easily be built as a transportable unit.

It will be appreciated that the methods of the present invention can be incorporated in the form of a variety of embodiments, only a few of which are disclosed herein. It will be apparent for the expert skilled in the field that other embodiments exist and do not depart from the spirit of the invention. Thus, the described embodiments are illustrative and should not be construed as restrictive.