A METHOD FOR TREATING A FIBROUS MATERIAL AND A PLANT FOR CARRYING OUT THE METHOD

Abstract: A fibrous material, in particular a cellulose material, is subjected to heating and subsequent treatment at high pressure, in particular with application of an impregnation agent after the heating and before the high pressure treatment. High pressure treatment may be performed by means of rollers (12'). Heating and high pressure treatment render fibrous material more reactive with reactive impregnating agents. Material may be dry defibrated after impregnation. Impregnation agent is, in particular, metal oxide acylate or isocyanate. Resulting fibers are useful as reinforcing fibers in matrices and as absorbing fibers.

Description: A Method for Treating a Fibrous Material and a Plant for Carrying out the Method . The present invention relates to a method of treating a material including fibers each having inner and/or outer su rface parts defin¬ ing interstices or voids, so as to impart desi red characteristics to such fibers . The fibers may be natural fibers having inner cavities or cell cavities, for example cellulose fibers or wool fibers , or they may be man-made fibers having such inner cavities or outer su rface parts defining interstices or voids . Such artificial fibers may, for example, have a cross-sectional shape with projections defining spaces therebe¬ tween, and/or the fibers may have a "curled" configuration resulting in many inter-fiber voids in the material . As an example, the material may be a fibrous cellulose material, such as straw, wood waste, or other wooden material, or it may be a fibrous sheet or web . material, such as composite paper or woven or non-woven textile material . The method according to the invention comprises exposing the material to a heating and/or drying treatment and thereafter compressing the material sufficiently to at least pa rtly compress the interstices or voids . I n principle, the compression may be carried out in any suit¬ able manner, for example by means of hydraulic or mechanical pres¬ ses . However, in order to obtain the compression of the interstices or cavities defined by the single fibers and/or present between the fibers, it is necessary to expose the fibers to extremely high pres¬ su res which may best be obtained by subjecting the material to a rolling treatment, for example by passing the fibrous material th rough a nip defined between a roller and a suitable countersurface while the roller and the countersurface are being pressed together at an ex- tremely high pressure. The countersu rface may be stationary and have a plane or cu rved shape. The rolling treatment is, however, preferably performed by passing the fibrous material th rough the nip defined between a cooperating pair of rollers . When the material OMPI includes natural fibers, the material is preferably compressed suf¬ ficiently to permanently deform the cell walls of at least some of these fibers . If the fibrous material, such as straw, veneer, wood waste, or other wooden material , or pulp, cardboard, or pasteboard, is compressed or rolled in a substantially dry condition at sufficiently high pressu res, the fibers are subjected to a certain crushing, whereby the fineness of the fibers as expressed by the SR of the fibers, is substantially increased so that the treated material may be pulped without further treatment and be used for the production of for example grease proof paper, parchment paper, and the like. I n various known processes, for example, in calendering, a cellulose fiber web is subjected to a rolling pressure. However, in these known processes, the pressure to which the fibers are exposed is not suffi- ciently high to permanently deform the cell walls of the fibers . I n the method according to the invention, the pressure to which the fibers are exposed, is typically sufficient to substantially permanently de¬ form the cell walls of the fibers and is thus substantially higher than in the known methods . Hence, in the method according to the invention the pressure in the nip area defined between a cooperating pair of rollers may typically 2 substantially exceed 100 kp/cm and may be as high as 10,000 2 2 kp/cm ; often the pressu re will be between 1000 and 10,000 kp/cm , such as between 2000 and 10,000 kp/cm~ or even between 5000 and 10,000 kp/cm 2 . I n an important embodiment of the invention , a liquid substance is supplied to the material prior to or during the compression or rolling treatment. The liquid substance may, for example, be a substance which may impart desired characteristics to the fibers, such as an impregnating or modification agent or a combination of impregnating or modification agents to impart desired properties to the fibers, or it may be a liquid substance which is later on substantially evaporated, but which functions solely as a lubricant; vide below. When the fibrous material is exposed to a compression or rolling treatment as described above with an effective amount of a liquid substance present, this substance will function as a lubricant, where- by crushing of the fibers may be avoided . However, during the rolling treatment the fibers are compressed and flattened, whereby gas, such as air, is expelled from interstices or voids defined by the fibers , while the fibers are surrounded by a film or matrix of the liquid substance. This compression or rolling treatment causes a very even distribution of the liquid substance in the fibrous mass and an intimate contact between the liquid substance and the single fibers . The fibers have a certain resiliency which causes that after the compression or rolling treatment the flattened fibers tend to return at least partly to their original shape, whereby the original cavities and voids within the fibers and/or between the fibers will partly be re¬ established . However, as the fibers are surrounded by the liquid substance, this substance will then be sucked into the cavities wh ereby the contact su rface between the liquid and the fibers is further increased . Thus, one aspect of the method according to the invention may be considered as a continuous treatment of a fibrous mass, in which method the mass is subjected to compression under a high pressu re and subsequent relief in the presence of a liquid substance so as to provide a pressu re/vacuum effect causing at least partial filling of the interstices or voids defined by and/or between the fibers with the liquid substance. The energy supplied to the rollers is partly converted into heat in the nip area, and the resulting increased temperatu re in that area promotes possible chemical reactions between the liquid substance and the fibers during the rolling treatment. Experiments have indicated that the rolling treatment per se also causes a chemical-physical change of the amorphous structu re of cellulose fibers , possibly inclu¬ ding the formation of hydrogen cross-links between the cellulose chains . When the fibrous material is to be treated according to the aspect of the invention in which a liquid is supplied prior to or in connection with the compression or rolling , any moistu re present in the material prior to the supply of the liquid will counteract the obtainment of satisfactory good contact or affinity between the fibers and the liquid substance. Therefore, it is extremely important that such moisture be removed to the highest possible extent prior to the supply of liquid substance (which liquid substance may contain water) to the fibrous material before and/or after compression thereof. I n order to remove such moisture (which may be free moisture as well as moisture bound to the fibrous material) and possibly also increase the temperature in the compression area, the fibrous material is exposed to a heating and/or drying treatment prior to the application of liquid substance and/or compression treatment, preferably an intensive heating treat- ment. It is desirable to obtain a drying to a dry matter content of the fibrous material of more than 98%, preferably as much as 99%, and especially in a range of about 99.1-99.999%, expressed, e. g . , as reactive cellulose hydroxy groups relative to the theoretical amount thereof. The heating temperature is preferably chosen as high as it is possible without damaging or deteriorating the fibrous material (and without removing any crystal water present in components of the fibrous material) . When the fibers are cellulose fibers, the temperature to which the fibrous material is heated is preferably 100-275°C, in particular 120-250°C, preferably about 160-220°C, more preferably 180-200°C. Hereby, a drying to more than 98%, preferably as much as 99%, and especially in a range of 99. 1 - 99.999%, is aimed at. Such drying must be presumed also to break even the monomoiecular layer of water bound to the fiber surface and will render the cellulose more reactive with any substance capable of reacting with cellulose hydroxy groups . Both in the cases where it is desired to obtain a reaction between cellulose fibers and an added liquid substance and in the cases where no such reaction is aimed at, the heating of cellulose fibers is an essential feature which is believed to result in a soften- ing of the lignin content of the cellulose fibers, which softening is believed to enhance the penetration of liquid substance (when used) into the fibers and to contribute to reduction of the "brittleness" of the cellulose fibers and hence to reduce the danger that the cellulose fibers will be damaged du ring the compression treatment. It is known that by heating to temperatu res somewhat above 250°C under exposure to oxygen , cellulose will decompose. Therefore, if it is desired to dry the cellulose fibers at higher temperatu res, this will normally necessitate that the heating be performed under a substanti¬ ally oxygen-free atmosphere. In the absence of oxygen , charring of cellulose fibers is avoided, and the cellulose fibers can be dried at temperatu res higher than 250°C without losing any crystal water bound in their components . The heating of the fibrous material may be performed by means of infrared irradiation, e. g. by means of infrared heating means irra¬ diating the fibrous material supplied to the treatment, by high fre- quency treatment of the fibrous material, or by passing the fibrous material th rough heated, dry atmospheric air or heated, dry oxy¬ gen-free gas or gas mixture, or by a combination of these measures . The compression of the fibers may be obtained by passing the fibrous mass through the nip of a single pair of compression rollers at suit- ably low speed . Normally, the rollers are rotated so that their cylin¬ drical surface parts defining the nip area are moved in the same di rection and at the same velocity. Alternatively, the rollers may be rotated so that the velocities of the roller parts defining the nip area are different from each other, and these roller parts may even be moved in opposite di rections . The compression treatment imparted to the fibrous material is dependent on the rotational speed of the rol¬ lers, the roller diameters , and the thickness of the web or layer of material supplied to the nip area of the rollers . I n order to obtain a uniform and effective compression of all of the fibers in the fibrous material and/or to allow feeding of a thicker web or layer of material to the nip area of the rollers , the material may be passed th rough the nips of two or more consecutive pairs of rollers . According to a par¬ ticular embodiment, two consecutive pairs of rollers may be consti¬ tuted by th ree rollers , of which one (the intermediate roller) coope- rates with the two other rollers to define a nip with each of the two other rollers. The consecutive pairs of rollers may define decreasing nip area spaces and/or be pressed together by forces increasing in the moving direction of the material being treated. The use of several pairs of rollers improves the distribution of the liquid substance in the fibrous mass . When the fibrous material is passed through two or more pairs of rollers, the the liquid substance and/or further liquid or partϊculate additives, such as described in greater detail below, may be applied to the material between two adjacent pairs of rollers . The liquid substance may be applied to the fibrous material in any suitable manner, for example by passing the material through a bath of the liquid substance. However, in one preferred embodiment, the liquid substance is sprayed on to the fibrous material, preferably by an airless spray technique, for example by means of one or more nozzles. When the liquid substance corftains dissolved or suspended solid material , the nozzle or nozzles may tend to become clogged. This may, however, be counteracted by feeding the liquid substance to the nozzle or nozzles as a pulsating flow and/or by heating the nozzle or nozzles to a temperature at which the the liquid substance has a suitable viscosity (and heating of the liquid supply nozzle or any other liquid supply means is normally necessary when the liquid is a molten solid such as is explained below) . Another interesting embo¬ diment comprises adding the liquid substance from the surface of one of the rollers, e. g . by having the roller partially immersed in a bath of the liquid substance. The liquid substance is preferably applied to the fibrous material in a metered amount slightly exceeding the neces¬ sary amount, and excessive liquid will then be removed from the fibrous material when this material is passed through the first pair of rollers . One way of supplying a metered amount of the liquid sub- stance to the fibrous material comprises applying the liquid substance at a controlled rate to one or both of the rollers, e. g . , by means of an applicator roller or by spraying . As mentioned above, it may be advantageous to obtain a substantially increased temperature at the nip area between the pair or pairs of rollers . This temperature may be further increased by heating at least one of the rollers used in the rolling treatment. If the liquid substance is of a type solidifying at room temperatu re, heating of the roller or rollers also counteracts or prevents the building up of solidified substance on the roller surface or surfaces . After ■ the compression or rolling treatment, the fibrous material may be fu rther treated and defibrated in a defibration or fluffing device. The defibration device may be a wet defibration device such as a pulper or a dry defibration or fluffing device such as a hammer mill . It has been found that by subjecting a fibrous material to a high pressure compression or rolling treatment as described above and to a succeeding treatment in a hammer mill, an exceptionally homogeneous defibrated product without lumps or fiber agglomerates may be ob¬ tained . If desired, further liquid, particulate, and/or pulverulent additives may be added to the fibers during treatment in the hammer mill, such as described in greater detail below. When the fibrous mass is compressed in a dry condition , i. e. without addition of a lubricating liquid substance, and is subsequently treated in a fluffing device, such as a hammer mill, the fibers may be dete¬ riorated because of the high temperatures caused by the mechanical treatment of the fibers . It has been found that this deterioration may be controlled or even avoided when a suitable lubricant, for example kerosene or ethanol (or any other liquid substance, e. g. an impreg¬ nating agent) , is added to the fibrous material before it is introduced into and/or while it is being treated in the fluffing device. The addition of such a lubricant seems to reduce the proportion of kinetic energy converted into heat energy, and the lubricant will also to some extent serve as a coolant. The invention also relates to an apparatus for use in carrying out the method described above, the apparatus comprising rolling means including at least one pair of rollers , supply means for supplying a sheet or web of fibrous material to the nip defined between the pair of rollers , and heating and/or drying means for heating and/or dry¬ ing the fibrous material supplied . Preferably, the apparatus also comprises means for applying a liquid substance to the fibrous mate- vfø rial at a position upstream of the rolling means or for applying a liquid substance to the rolling means, and means for defibrating, in particular dry defibrating, the fibrous material downstream of the rolling means, especially a hammer mill . The invention also relates to a fibrous material comprising fibers having cell walls permanently deformed by compression . The invention will now be fu rther described with reference to the drawings, wherein Fig. 1 diagrammatically illustrates an apparatus or a plant for treating a fibrous material in accordance with the present invention. Fig. 2 is an enlarged view illustrating rolling of a fiber at an ex¬ tremely high rolling pressure, Ffg. 3 is a perspective view illustrating in greater detail an apparatus or a plant as that shown in Fig . 1 , Fig . 4 diagrammatically illustrates a more compact embodiment of the plant or apparatus. Fig . ,4a diagrammatically illustrates a modification of the apparatus shown in Fig . 4, Fig . 5 is a side view diagrammatically illustrating a third embodiment of an apparatus for treating straw, wooden chips, and similar starting materials, and Fig . 6 is a perspective view in an enlarged scale illustrating rolling of a plate material made from a number of plate members which have been joined together. Fig. 7 is a scanning electron microscopy photo showing a treated fibrous web with an impregnating agent distributed therein, Fig . 8 is a scanning electron microscopy photo showing the character of the treated fibers, Figs . 9 and 10 show single fibers treated in accordance with the present invention and thereafter extracted with dichloromethane, and Figs . 11 and 12 show fibers treated in accordance with the invention and thereafter extracted with dichloromethane (Fig . 11 ) and not extracted (Fig . 12) , respectively. Fig . 1 diagrammatically illustrates a plant or an apparatus for treating a fibrous cellulose material in the form of a web 10, which is fed continuously from a supply roll 11 to a rolling device 12 comprising at least one pair of high pressu re rollers 12' . The fibrous web material passes a heating and drying device 13 which is interposed between the supply roll 11 and a liquid applicating device 14 comprising a liquid reservoi r 15 and a spraying nozzle 16 which is positioned so that a liquid substance contained in the reservoir 15 may be sprayed on to the web material 10 at a position downstream of the heating and drying device 13 and upstream of the rolling device 12. I n the rolling device 12, the fibrous web is compressed under an extremely high pressure which is sufficient to deform the cell walls of the single fibers and to compress the cell cavities 17 therein as illustrated in Fig . 2. When the fibrous web which has been completely dried by the drying device 13 and thereafter wetted by the liquid substance sprayed thereon by the nozzle 16 is passed th rough the nip area defined between the rollers 12' , the liquid substance will be brought into intimate contact with all su rface pa rts of each single fiber, and possible excessive liquid substance 18 is continuously removed as illustrated in Fig. 2. When the cell cavities 17 of the fibers are compressed within the nip area, gas or air is forcibly expelled there¬ from. After the material has passed the nip area, the resiliency of the cell walls of the fibers tend to reform the cavities, whereby some of the liquid substance present is sucked into the cavities . However, the fibers having passed the rolling device 12 do not completely attain their original shape, because the rolling pressu re is so high that the cell walls are to some extent deformed, and the single .fibers are flattened . The compression/expansion effect or pressu re/vacuum effect to which the fibers and the liquid substance applied thereto are exposed during the rolling treatment causes that a very intimate contact and uniform distribution of the liquid substance over all inner and outer su rface parts of the fibers is obtained . Because the energy used for driving the rollers 12' is partly converted into heat energy, the fibrous material is exposed to an elevated temperature during rolling which in connection with the uniform distribution of the liquid substance creates optimum ^ conditions for physical and chemical reac¬ tions in the fibrous material and between the fibrous material and the liquid substance. As explained below, the liquid substance may, e. g. , be any desired impregnating liquid substance which is able to impart desired characteristics to the fibrous material . When the fibrous web 10 so treated leaves the rolling device 12, it may be supplied to a hammer mill 19 or another fluffing device, in which the material is defibrated and may, at the same time, be further treated . Fig . 3 illustrates the plant or apparatus of Fig . 1 in greater detail . I n this embodiment, the heating and drying device 13 comprises a tunnel 20 through which the fibrous web 10 supplied from the supply roll 11 is passed. While the web 10 is passed through the tunnel 20 it is heated by means of a number of infrared radiation devices 21 arranged in the upper part of the tunnel . The radiation devices 21 may be cooled partly by means of a blower 22 which may blow cooling air th rough a separate passage 23 at the upper part of the tunnel, and partly by means of pressurized air circulated through cooling passages formed in the radiation devices 21 and supplied from a suitable source, such as a compressor 24 combined with the driving motor. If necessary, the web may also be heated from below, or water vapour may be removed from below the web . The web 10 leaving the heating and drying device 13 in a completely dry and heated condition is passed beneath the spraying nozzle 16 having a number of nozzle orifices so that a uniform spray of a liquid substance may be applied to the web 10 in the full width thereof, and the nozzle is preferably arranged so that the spray provided thereby obtains a velocity component in the moving direction of the web 10. From the liquid reservoir 15 the liquid substance is pumped to the nozzle 16 by means of a feeding pump 25 through a supply conduit 26. When the liquid substance is of a type which is solid or which has a too low viscosity at room temperature, the reservoir 15 may be surrounded by a heating jacket containing electrical heating elements, and the liquid being pumped from the reservoir 15 into the supply conduit 26 (which is suitably also surrounded by an electrical heating jacket) may pass a heating device 27, e.g. , of the "hot melt" type. in which the liquid substance is further heated . I n the reservoi r 15, the heating device 27, and the supply conduit 26, the liquid sub¬ stance is heated so as to obtain a viscosity of the liquid at which the liquid may be pumped by the feeding pump 25 and satisfactorily distributed by the nozzle 16, and so as to secure a satisfactory penetration of the liquid substance into the fibrous material . How¬ ever, the heating of the liquid substance is controlled so as to avoid at any stage of the heating process excessive heating which might cause decomposition, deterioration , or undesired polymerisation , of the liquid substance. I n order to prevent that the liquid substance stored within the reservoi r 15 and the heating device 27 is oxidized by exposu re to atmospheric air, nitrogen or another inert gas may be supplied to the reservoir 15 and the heating device 27 from a pres¬ surized gas container 28. The liquid application device 14 may contain a valve (not shown) controlling the supply of liquid substance to the nozzle 16, so that this supply will be intermittent. This valve as well as the feeding pump 25 may be driven by pressurize ' d air generated by the compressor 24, and the intermittent supply of pressurized air to the valve may be obtained " by means of an electrically controlled magnet valve. The resulting pulsating flow of liquid substance through the spraying nozzle effectively counteracts clogging of the nozzle orifices . The web 10 sprayed with liquid substance- is passed between a pair of guiding rollers 29 and along a guiding channel 30 to the rolling device 12 which in the embodiment shown in Fig . 3 comprises two separate rolling units 12a and 12b . Each of these units comprises a pai r of rollers 12', which are rotatably mounted in a frame 31 and driven by a driving motor 32. Each of the rolling units is designed to exert an extremely high pressu re at the nip and may, e. g . , be of the type used for making foils of gold or other metal , and the rolling pressu re may be adjusted by means of a manually operatable handle 33. Excessive liquid substance separated from the web 10 by the rolling unit 12a is collected in a tray 34 and retu rned to the heating device 27 through a return conduit 35. I n order to prevent adherence of the liquid substance with which the web 10 is impregnated to the rollers 12' , and also in order to further improve penetration and distribution of the liquid substance in the fibrous web 10, these rollers are preferably heated, for example by means of heating de¬ vices 36 directing a flow of heated air towards the rollers and the web 10 passing therebetween . While two consecutive rolling units 12a and 12b are shown in Fig. 3, it is possible to use a single rolling unit or any plurality of consecu¬ tively arranged rolling units, whereby the thickness of the web 10 and/or the rate of motion of the web through the rolling units may be increased. At any rate, the web should preferably be moved through the rolling unit or units at a rate which is controlled so as to obtain an optimum treatment of the fibers in the web . This rate may, for example, depend on the thickness of the fibrous web, the number of rolling units, and of the diameter of the rollers . Thus, for example, the compression of the fibers will be less abrupt when the diameters of the rollers are relatively large and, therefore, the rate of motion of the web may be increased when the roller diameters are increased. Furthermore, the use of a plurality of rolling units may improve distribution of the liquid substance in the fibrous web 10. When two or more rolling units are used, it is necessary to accurately control the mutual rotational speeds of rollers in the units so as to prevent stretching of the part of the web 10 located between adjacent rolling units, but also in order to prevent formation of an excessive loop 37 on the web 10 between adjacent units . Because the length of the web 10 is increased while passing the first rolling unit 12a, the second rolling unit 12b must be driven at a slightly higher rotational speed, even if the two units are identical. This may be obtained by control¬ ling the driving motors 32 by means of a frequency transformer (not shown) . If desired, further additives in liquid or solid form * may be supplied to the web 10 between the rolling units 12a and 12b and/or between the rolling unit 12b and the hammer mill 19, for example by means of a further spraying nozzle 38. The rolled and impregnated web 10 is now drawn into the hammer mill 19 by means of a pair of drawing rollers 39 driven in synchronism with the rolling unit 12b . In the hammer mill 19, which is driven by O FI an electric motor 40, the treated fibrous web is subjected to extreme¬ ly heavy mechanical forces, whereby the fibrous material is completely defibrated ' . The defibration process is to a high extent facilitated by the preceding rolling treatment to which the fibers have been ex- posed . The heat generation within the hammer mill is rather heavy, and the temperature may be controlled by a supply of cooling air. The high temperatu re and the heavy mechanical action to which the fibrous material is exposed within the hammer mill 19 complete the physical and chemical reactions between the fibers and the additive or additives which started du ring the rolling treatment. Fu rthermore, it is possible to supply further additive directly to the hammer mill, for example a powdered material which may be supplied continuously to a funnel 41 indicated in dotted lines in Fig . 3. Such further additives may comprise any liquid substance imparting desired properties to the fibers, for example, a lubricant, such as kerosene or ethanol . The defibrated mass discharged from the hammer mill 19 is supplied to a filtering device 42 th rough a conduit 43. The filtering device com¬ prises a rotating filtering cylinder 44 which has a cylinder surface defined by a wi re mesh and which is driven by an electric motor 45. This filtering device 42 separates the defibrated fibrous mass 46 from dust and additive residues which may pass through the wire mesh of the filtering cylinder 44 and into the inlet conduit 48 of a blower 49 having an outlet conduit 50 which is connected to a filter (not shown) for collecting the dust material . Fig . 4 shows a modified embodiment of the apparatus or plant illustra¬ ted in Fig . 3, and corresponding elements of the two embodiments have been provided with the same reference numerals . I n the embodi¬ ment shown in Fig . 4, the tunnel 20 of the heating and drying device 13 has been divided into a number of vertically arranged sections 20a, 20b, and 20c, and at the ends of these sections the web 10 is guided by guiding bars 51 - 53. Similarly, the liquid applicating device 14, the rolling device 12, the hammer mill 19, and the filtering device 42 are arranged along a vertical path . Fig . 4a shows a modification of the apparatus or plant illustrated in Fig. 4. I n Fig. 4a the liquid applicatϊng device 14 is replaced by a liquid bath 66 contained in a receptacle which is confined by the oppositely arranged parts of the cylindrical surfaces of the rollers 12' and by suitable stationary end walls 67. The liquid level of the bath 66 is sensed by a liquid sensor 68, and liquid may be supplied to the bath 66 from a liquid reservoir 69 through an outlet tube 70 contain¬ ing a valve 71 . A control device 72 controls the valve 71 on the basis of signals received from the level sensor 68 so as to maintain a sub- stantially constant liquid level in the bath 66. As illustrated dia¬ grammatically by springs 73, the rollers 12' are pressed together at extremely high forces so as to compress the web 10 therebetween as described above. While the embodiment shown in Figs . 3 and 4 are adapted to process a fibrous web, the embodiment shown in Fig . 5 is adapted to process straw, wooden chips, and other ' pa rticu late materials . The starting material, such as straw, is supplied into a receving funnel 54, from which ma-ferial is supplied into a heating and drying device 55, in which the material may for example be dried by means of heated air. From the device 55 the heated and dried material is discharged into a second funnel 56, and while the material is falling from the drying device 55 into the funnel 56 a liquid substance may be applied to the material by means of • spraying nozzles 57 to which liquid may be supplied from a reservoir 58 by means of a pump 59. From the funnel 56 the wetted material may be supplied to a rolling device 60 which may be of the type previously described, and excessive liquid sepa¬ rated from the cellulose mass when passing the rolling device 57, is returned to the reservoir 58 through a return conduit 51 . The mate¬ rial having passed the rolling device 60 is dropped into a hammer mill 62 or another fluffing device from which the defibrated fibers are discharged to a filtering device 63 of the same type as that described in connection with Fig . 3. The fibrous web 10 being treated in the apparatuses or plants illu¬ strated in Figs . 3 and 4 may be a flexible, highly porous material . However, it is also possible to use the method according to the inven- tion in connection with a panel or sheet material , for example a wooden sheet material which is relatively stiff . I n that case the sheet material or panel being treated may be made up from sheet elements which may be mutually joined along V-shaped joints 64 in order to avoid any separation in the nip between the rollers 65 along a joint parallel to the roller axis (such type of, e. g . , V-shaped joint is also suitable for joining sheets of flexible material) . When such a panel is passed th rough a pair of rollers 65 without addition of a liquid addi¬ tive or substance and exposed to so extremely high compressive forces that the cell walls of the single fibers are permanently de¬ formed, the fibers are to some extent crushed, and the material so treated may without further processing be pulped and used for the producting of grease-proof paper and the like. While the embodiments shown in the drawings have been described in connection with processing of cellulose fibers , it should be understood that the method and apparatus according to the invention could also be used for treating other natu ral fibers, such as wool fibers, and even for treating man made or artificial fibers having inner or outer su rface pa rts defining interstices or spaces in the single fibers . From the above explanation , it will be understood that the method of the present invention is useful for a wide va riety of treatments of fibrous materials , ranging from the case where the high pressure treatment is utilized for crushing a fibrous ' material to obtain a finer fiber size (a higher SR , e. g . , a SR of 70 - 80) by omitting any "lubricant" liquid substance du ring the high pressu re treatment, to the case where liquid substances for impregnation of the fibers and simultaneously "lubricating" du ring the high pressu re treatment are added and are optionally combined with addition of further substances of liquid of solid character subsequent to the high pressu re treat- ment, e. g . , supplied immediately prior to or in the fluffing or des- integration unit, typically the hammer mill , and/or - for solids of abrasive character or solids which might tend to clog the filter 44, such as cement or silica - optionally added after the hammer mill or even after the fibers have been removed from the filter 44. When the high pressure treatment in the absence of any substantial amount of "lubricant" is utilized to treat a fibrous material to increase the fineness of SR of the fibers, the high pressure treated material may be passed th rough the remaining stages of the treatment as illustrated in Fig . 3, in which case a "lubricant" or "coolant" is suitably added prior to or in the hammer mill, such as mentioned above, or the high pressure treated material may be withdrawn as it is from the high pressu re treatment for later dry defibration or for later conventional wet pulping . When the high pressure treatment is performed in the presence of a liquid substance penetrating the material, the liquid substance will normally serve as a "lubricant" and will counteract fiber crushing. According to a special embodiment of the present invention, the fibrous material subjected to defibration, e.g. in the hammer mill, is in itself a composite fibrous material comprising different types of fibers which, when defibrated, will result in a "fiber mixture" tailored for incorporation into fiber- reinforced composite materials bonded by means of an organic matrix ..(e. g . , a polymer) or an inor¬ ganic matrix (e.g. , cement) . As an example, a "composite paper" comprising 60% of sulphate pulp, 30% of eucalyptus fibers, 6% of 6 mm rayon fibers, and 4% of 8 mm rayon fibers could be defibrated in the hammer mill . Evidently, also other fibers or materials could be incor¬ porated during the preparation of such a "composite paper", including other fibers such as sisal , coir, mineral fibers, and optionally also particles or fibers of polymer which will form the matrix or part of the matrix of the later composite material in which the fibers in question serve as reinforcing fibers . According to a special embo¬ diment of this aspect of the invention where the fiber reinforcing design in a later composite material is tailored by incorporating the desired fibers in the desired ratios during the papermaking, the resulting " composite paper" is subjected to the high pressure treat¬ ment discussed above, with or without impregnation with desired impregnation agents and/or combinations thereof. It will be under¬ stood that in this manner, almost unlimited possibilities are provided for establishing a treated fiber material of exactly defined properties for a given purpose. O ?I According to a very important aspect of the present invention , the liquid substance supplied to the dried fiber material prior to the high pressure treatment, in particular the high pressure rolling, is an impregnation agent, that is , an agent, which will completely or parti- ally be incorporated in the fiber material to impart desired properties to the fibers . I n the present context, the term "impregnation agent" designates a substance which will combine chemically and/or physically with the fibers to result in a substantially permanent chemical and/or physical bond between the fibers and the substance. In this connection, it will be understood that the heating and com¬ pression treatment of the fibers, in particular cellulose fibers, which is performed in accordance with the present invention , will bring the fibers into a desired chemically activated and thereby enhance their capability of reacting with added reactive substances . The importance of the heating of the fibrous material has been ex¬ plained above, and one aspect of the invention is constituted by a method in which a cellulose-containing material is heated to the tem¬ peratures mentioned above and is thereafter reacted with a reactant capable of reacting with cellulose hydroxy groups . The impregnation of a cellulose-containing material with, e. g . a reactive material such as a metal oxide acylate or an isocyanate after heating of the material to the temperatures stated above is believed to be novel per se and is important per se for several purposes, e. g . for preparing waterproof liner (wrapping paper) and the like. One important class of impregnation agents which is most advanta¬ geously incorporated into the fiber material by means of the high pressu re treatment according to the invention comprises the so-called metal oxide acylates . Metal oxide acylates constitute a class of metal organic compounds described, e. g . , in US Patents Nos . 3,087,949, 3, 243,447, 3, 177,238, 3,518,287, 3, 625,934, 3,546,262, 3, 634,476 and 3, 673,229, BE Patent ' No. 735,548, and GB Patents Nos . 1 ,230,412, 1 ,274, 718, 1 , 552, 601 , and 1 , 552, 602. The general composition of the metal oxide acylates is supposed to be divalent metal : ( R-Me-O-Me-R) linear compounds trivalent metal : (O -Me -R,,-) planar compounds tetravalent metal : (O fi -Me .-R 4 ) tetrahedron -shaped compounds wherein Me is a metal atom, R is an acylate group which is an organic acid residue with at least 12 carbon atoms, and x, y, and z = 3 - 7 is a presumed molecular size in solution . It should be noted that metal oxide acylates wherein each molecule contains two or more different metals, possibly of different valence, can also be made, and such types of compounds, as well as other variants of metal oxide acylates and mixtu res thereof are also described in the above-mentioned patent specifications. Further details concerning metal oxide acylates and their use in impregnation of cellulose fibers are found in I nternational Patent Application No. PCT/DK79/00055, published under publication No. WO 80 101176 on June 12, 1980. As appears from the experiments reported below, the incorporation of metal oxide acylates in cellulose fibers by the high pressu re impreg¬ nation method of the present invention results in fibers which are extremely uniformly impregnated throughout their cross section, and which show excellent desired properties for a variety of uses . When cellulose fibers are impregnated with metal oxide acylates by the method of the invention, the metal oxide acylate seems to be perma¬ nently and un removably bonded to the fibers, such as will appear from the experimental results reported below. This "impregnation bond" may be due to chemical reaction between the metal oxide acylate and reactive sites, such as hydroxy groups, of the chemical structure of the cellulose fibers, or due to intimate bond of a predominantly physical character between the cellulose fiber and a coating of poly¬ merized metal oxide acylate, or due to a combination of these effects . Cellulose fibers impregnated with metal oxide acylates by the method of the invention show drastically reduced tendency to absorb water, and hence, retain dimension stability when incorporated in water or an aqueous slurry. I n this regard, e.g . , cellulose fibers impregnated with aluminum oxide acylate have been found to have substantially the C ?I same freedom from water absorption as, e. g . , polypropylene fibers . Hence, the invention provides very interesting metal oxide acylate- impregnated cellulose fibers for a number of purposes where a dimen¬ sion stable, non water-absorbing fiber is desired. According to a particular aspect of the present invention, the fibers are treated with a combination of a coupling agent, such as a silane, and a metal oxide acylate. The coupling agent and the metal oxide acylate may be added to the cellulose fiber material separately, or they may, according to a particularly preferred embodiment of the invention, be added together in that the coupling agent is incorpo¬ rated in the metal oxide acylate supplied to the fibers . Su rprisingly, it has been found that this combination, which is illustrated in the examples below, does not seem to result in any disadvantages with respect to the function of the metal oxide acylate or the coupling agent. The treatment of cellulose fibers with a combination of a metal oxide acylate and a coupling agent such as a silane constitutes a particular aspect of the present invention, and this aspect is not limited to the incorporation in connection with the high pressure treatment described above (although this is the presently preferred incorporation method) , but may, within the scope of this aspect of the present invention, be performed by any suitable incorporation method that will result in efficient impregnation, including incorpo¬ ration under high shear conditions such as in a hammer mill or the like. According to another very interesting aspect of the present inven¬ tion , treatment of cellulose fibers with a metal oxide acylate and preferebly also a coupling agent is combined with the application of inorganic particulate substances on the fibers . As is explained above, inorganic substances may be applied on the fibers , e. g . , prior to the treatment in the fluffing or defibration unit such as a hammer mill, or in the hammer mill , or pa rticulate substances may be applied to the fibers after thei r removal from the filter 44. As important examples of inorganic substances incorporated may be mentioned cement, silica, in particular ultrafine silica precipitated from a gas phase, e. g . , of the type obtained as a by-product in the production of silicon metal or ferrosilicium in electrical fu rnaces, which is the type of ultrafine silica used in the examples . Cement or silica applied on metal oxide acylate- impregnated, dimension stable fibers for use, e.g. as reinfor¬ cing fibers for incorporation in cement-bonded composite materials such as for the preparation of the type of shaped articles normally made from asbestos-reinforced cement, will tend to further improve the dispersion of the fibers in an aqueous cement-containing slu rry. Cellulose fibers according to the invention with cement particles applied thereon may even be designed, with respect to the amount of cement and possible other additives, in such a manner that the fibers will require only addition of a correct amount of water to establish the slurry for formation of the fiber- reinforced cement-bonded mate¬ rial . Another type of particulate material which may suitably be incorporated on the impregnated cellulose fibers, in particular the metal oxide acylate- impregnated cellulose fibers, is absorbant particles such as charcoal. The metal oxide acylate-impregnated cellulose fibers carrying charcoal particles have been found to constitute a most useful type of absorbant high quality fiber for a number of purposes . Also in this case, the metal oxide acylate may suitably be combined with a coupling agent such as a silane. Again, the aspect of the invention constituted by metal oxide acylate-impregnated cellulose fibers carrying charcoal is not limited to the particular high pressure method of preparing such fibers as is described above (although this is the presently preferred method) , but also encompasses the cases where other suitable methods are used for impregnating the cellulose fibers with the metal oxide acylate and applying the charcoal . When metal oxide acylate-hydrophobized cellulose fibers are to be incorporated in aqueous slurries, e. g . , cement-containing slurries, it is desirable that they should be as easily dispersible therein as possible. To a certain extent, the hydrophobization may counteract the dispersibilϊty of the fibers in aqueous media . However, according to a particular aspect of the present invention , the dispersibility of such hydrophobized cellulose fibers is improved by incorporation of one or more surface- active agents of a character imparting hydrophilic properties . Surprisingly, it has been found that although cellulose fibers are rendered non-water absorbing and hence inherently hydro- v7IPO phobic by impregnation with a metal oxide acylate, they may, never¬ theless, obtain improved hydrophilicity or dispersibility in aqueous media by incorporation of suitable tensides or combinations of tensides of types which increase hydrophilicity or water dispersibility. As appears from the experimental section below, nonionic or cationic tensides are suitable for this purpose. Even more surprisingly, it has been found that such tensides need not be added separately from the metal oxide acylate (although they may, of cou rse be added separately from, in particular after, the addition of the metal oxide acylate) , but may be added together with the metal oxide acylate and even incorpo¬ rated in the metal oxide acylate. Hence, a further aspect of the present invention comprises cellulose fibers which are impregnated with a metal oxide acylate and additionally comprise one or several surface active agents modifying the character of the fibers towards greater hydrophilicity. In accordance with what has been stated above, this aspect of the invention is not limited to the case where the metal oxide acylate and/or the su rface active agents are incorpo¬ rated by means of the high pressure impregnation technique disclosed herein , but generally comprises such fibers irrespective of how the metal oxide acylate (or other useful hydrophobizing agent) and the surface active agents have been incorporated, but the high pressure vacuum impregnation method disclosed herein constitutes the presently preferred method for preparing these hydrophobic cellulose fibers with increased dispersibility in aqueous media . As will appear from the examples, it is within the scope of the inven¬ tion to combine the metal oxide acylate impregnation with the incorpo¬ ration of one or more of the su rface active agents modifying the fibers towards greater hydrophilicity or dispersibility in aqueous media, the incorporation of coupling agent, and the application of inorganic particulate matter in any desired manner, and also combi¬ nations of the above-mentioned principles, but without metal oxide acylate, may be used, depending on the particular end use of the cellulose fibers so treated . As will be understood from the above explanation, the cellulose fibers according to the aspects of the present invention or prepared accor- O PI ding to the aspects of the present method may be designed for and useful for a wide variety of purposes . The use of the cellulose fibers of the invention as reinforcing fibers for composite materials having inorganic or organic matrices has already been mentioned above. Other interesting aspects of the utility of the treated fibers according to the invention are: According to one aspect of the invention, active carbon -treated metal oxide acylate-impregnated fibers are used as absorbant fibers, e.g . , for absorptive filters liquid or gases, e.g . , for wine, beer, household uses, gas masks, etc. According to a particular aspect of this utility, these absorbant fibers carrying charcoal or other absorbant are used for hygiene articles or napkins (diapers) . If desired, antibacterial properties could be impar¬ ted to such fibers, such as by using, as the metal oxide acylate or part of the metal oxide acylate component, a metal oxide acylate having antimicrobial properties, such as a zinc oxide acylate. The application of activated carbon on cellulose fibers to obtain cellu¬ lose fiber-borne or -bonded activated carbon constitutes a particular aspect of the present invention . According to the invention, the activated carbon may be applied not only to metal oxide acylate-trea- ted cellulose, but quite generally to any suitable cellulose fiber, impregnated or not impregnated, and the application may be per¬ formed by a method according to the present invention or by any suitable method for applying activated carbon to cellulose fibers, including application in a pulper or hollander. Another suitable method of applying activated carbon on cellulose fibers is to apply the activated carbon in a hammer mill or in another high shear treatment apparatus . Another interesting use of the metal oxide a cy late-treated or -im- pregnated cellulose fibers, e. g. , aluminum oxide acylate-impregnated cellulose fibers, is as oil absorbant fibers, for example for use in oil absorbant tissues for use in workshops and factories or for removing oil waste or oil pollution . For removal of larger amounts of polluting oil , the oil-absorbing cellulose fibers of the present invention may be packed, in non-bonded form, into permeable bags of a design adapted for being placed or moved at the location of the oil pollution . A further interesting use of the fibers prepared according to the present invention is as binder or bonding fibers for consolidation of e. g . dry laid , paper, non-woven fabrics, etc. For this purpose, the fibers are suitably impregnated with a bonding agent, e. g . , a poly¬ mer, which elicits its bonding properties at an elevated temperatu re, suitably a temperatu re of up to about 150 C, e. g . from about 80 degrees Celsius to about 150 degrees Celsius . A further use of the impregnated fibers according to the invention is as hydrophobic fibers in hygiene a rticles and diapers or napkins as an intermediate layer between hydrophilic fibers therein and the exterior of these articles. For this purpose, the fibers are suitably impregnated with a metal oxide acylate or a metal oxide acylate combination which is hydro¬ phobizing , e. g . aluminum oxide stearate or tallate. A further field of utility of the impregnated fibers of the invention is as flameproof fibers . For this purpose, the fibers may be impregnated with conventional flame-retardant or fireproofing agents such as phosphorus and/or chlorine-containing flame-retarding agents, and/or with a metal oxide acylate which in itself is flame- retardant or fire¬ proofing such as an antimony oxide acylate. A further interesting utility of the metal oxide acylate-impregnated cellulose fibers of the invention is as antistatic tissues, e. g . , for glasses or lenses . EXAMPLES . I n an apparatus of the type illustrated in Fig . 3, cellulose materials 11 were passed th rough the treatment stages shown and were treated with a number of liquid substances and , in some cases , solid addi- tives during passage through the treatment stages, to yield a great variety of useful treated cellulose fibers 46. OMPI * ? AT Details on products used in the examples are as follows: MOA C 1460 Aluminum oxide stearate, solution of 60% solid contents in white spirit. Available from MOACO S.A., Lausanne, Switzerland. MOA C 1400 Aluminum oxide stearate, solid. Available from MOACO S.A., Lausanne, Switzerland. MOA DF-00 Silicon-titanium alkoxide condensed oligomer, 100%. (An oligomer of titanium and silicium in which each silicon atom is linked to a titanium atom through an oxygen bridge. To each silicon atom are furthermore attached ethoxide groups. To each titanium atom are attached ϊsopropoxide groups on the free valencies. Flash point 30°C, metal content 12.9% Ti, 3.8% Si. Available from MOACO S.A., Lausanne, Switzerland. MOA DF-1400 Silicon-titanium alkoxide stearate. (An oligomer of titanium and silicon in which each silicon atom is linked to titanium atom through an oxygen bridge. To each silicon atom three ethoxide groups are attached. To each titanium atom two stearyl groups are attached.) Tan waxy solid having a flash point of 210°C, metal content 4.8% Ti, 5.6% Si. Available from MOACO S.A., Lausanne, Switzerland. MOA DF-1000 Silicon-titanium alkoxide tallate. Available from MOACO S.A., Lausanne, Switzerland. MOA CDF-1400 Silicon -titanium-aluminium alkoxide- stearate. Available from MOACO S.A., Lausanne, Switzer¬ land. f OMPI MOACO C-10-50-AM A β-amino-ethoxy-aiuminum-hydroxy-tallate. 50% solution in white spirit. Available from MOACO S . A. , Lausanne, Switzerland . Manalox 403 Solid A solid polyoxy aluminum stearate represented by the formula (O=AI-X) where X is a stearate radical . Aluminium content 8.8%. Viscosity ranging from 40 OP at 60°C to 3 P at 185°C. Available from Manchem Limited, Manchester, England. Manalox 205 A polymeric organic aluminum compound with a composition which may be represented by the formula (O=AI-X) (AI (OR)X ) . The product m 2 n also contains about 25% of the solvent ester RX, which is the isopropyl ester of a satu rated fatty acid . Available from Manchem Limited, Manche¬ ster, England . Manalox DP11/C/22ζ A solid polyoxy aluminum stearate represented by the formula (O=AI-X) where X is a stearate radical . Aluminum content 8.6%. Viscosity rang¬ ing from 3.6 P at 60°C to 0.25 P at 185°C . Freezing point below 90°C. Available from Man¬ chem Limited, Manchester, England. BEROL 370 A nonionic tenside consisting of an ethylene oxide/propylene oxide block polymer. Has a hydrophilic (water-soluble) character. Its surface-active properties are as follows : Surface tension according to Du Noϋy, 25 C, 0. 1% active substance: 41 dyn/cm. Wetting capacity according to Draves, 25 C, 25 s sinking time: 7 g/liter. Foam height according to Ross-Miles, 50 C, 0.05% active substance, immediately 5 mm, after 5 minutes 0 mm. Available from BEROL KEMl AB, Stenungsund, Sweden . BEROL 563 A cationic tenside consisting of alkyl-poly- glycoletherammonϊummethy! sulphate. Its sur¬ face-active qualities are as follows : Surface tension according to Du Noϋy, 25 C, 0, 1% active substance: 43 dyn/cm. Wetting capacity according to Draves, 25 C, sinking time 25 s : more than lOg/liter. Foam height according to Ross-Miles, 50 C, 0.05% solution in hard water, 300 pp CaCO~ : immediately 100 - mm, after 10 minu¬ tes 0 mm. Available from BEROL KEMl AB, Stenungsund, Sweden . BEROL 572 A cationic tenside of the type quaternary ammonium compound having antibacterial proper¬ ties . Its surface- active properties are as fol¬ lows: Surface tension according to Du Noϋy, 25 C, 0. 1% active substance: 32 mN/m. Wetting capacity according to Draves, 25 C, concentration for 25 s sinking time: at least lOg/liter. O PI Foam height according to Ross-Miles, 50 C, 0.05% active substance: immediately 1 mm, after 5 minutes 0 mm. BEROL FI NTEX 573 A cationic surfactant consisting of al kyl poly- glycolether ammoniumethyl sulphate and a non- ionic wetting agent. Its su rface-active proper¬ ties are as follows : Surface tension according to Du Noϋy, 25 C, 0. 1% active substance: 35 mN/m. Wetting capacity according to Draves, 25 C, concentration for 25 s sin king time: 1 g/liter. Foam height according to Ross-Miles, 50 C, 0.05% active substance: immediately 140 mm, after 5 minutes 125 mm. Available from BEROL KEMl AB, " Stenungsund, Sweden . Silane A-175 A silane coupling agent, consisting of Y-metha- cryloxypropyl-tris (2-methoxyethoxy) silane from Union Carbide Silane A-1100 A silane coupling agent, consisting of Y-amino- propyltriethoxysilane, from Union Carbide. Silane A-1 102 A silane coupling agent, consisting of Y-amino- propyltriethoxysilane, from Union Ca rbide. Silane A-1120 Silane coupling agent, n-β- (aminoethyI) -ϊ-ami- nopropyltrimethoxysilane, from Union Ca rbide. "& JREΛ OMPI Silane Y-9566, 40% From Union Carbide TES 40 Mixture of ethyl silicic acid esters having 1 -9 silicon atoms per molecule. From Wacker Chemie Isocyanate MDI DiphenyImethane-4,4'-dϊϊsocyanate Desmodur T80 and Desmodur T65 Mixtures of the two isomeric forms 2,4-diiso- cyanato-toluene and 2, 6-dϊisocyanato- toluene in the ratio 80:20 (Desmodur T80) and 65:35 (Desmodur T65) , respectively. From Bayer. MOBI LWAX 2360 Microwax having a melting point (ASTM D 127) of 75 C, a needle penetration (1/10mm) of 26 at 25°C and 150 at 42°C, a flame point COC of 276°C, and a viscosity at 98,9°C (DIN 51562) of 11 .4 cSt. ANTI BLAZE 78 A flame retardant, chlorinated phoshonate ester, phosphorus content 12.0%, chlorine content 34.0%, clear liquid that may crystallize at, or below, 75 F. V1 RCOL 82 A flame retardant phosphorus-containing polyol from Mobil Chemical designed for use as a chemically bound, co-reactant flame retardant for urethane foams . Hydroxyl No. , mg KOH/g: 205 Acid No. , mg KOH/g: 0.3 Water content: nil Functionality: 2 Phosphorus Content, %: 11 .3 Viscosity (cps at 23°C) : 250 O FI WIFO Ultrafine silica Fine spherical SiO«- rich dust. Specific su rface (determined by BET technique) about 250,000 2 cm /g, corresponding to an average particle 3 diameter of 0. 1 μm. Density 2.22 g/cm . Super Rapid 4500 Super Rapid Portland cement, specific surface ( Blaine) 4500 cm 2 /g . Talc Sedimentation analysis: Smaller than 10 ym, 93%, Smaller than 5 ym, 81%, Smaller than 2 ym, 35%, Oil number (DI N 53 199) : 56. MOB I LCER Q An acid stable microwax emulsion , solid content average 51%, congealing point of wax 65 C, particle size 1 - 3 ym, from Mobil . LUDOX HS 40% An aqueous colloidal dispersion of silica par¬ ticles from Du Pont. Stabilizing counter ion : sodium . Particle charge: negative. Average particle diameter: 12 nm. Specific surface area 230 m 2 /g . AQUAPEL 3100 XL A synthetic gluing agent which reacts with cellulose under neutral or alkaline conditions, a 15% emulsion of al kylketene dimer having a cationic starch derivative as protective colloid . From Hercules Kemiska Aktiebolag, Hisings Backa, Box 2019, Sweden . KYMENE 557 H A highly effective cation active wet strength resin , polyacrylamide epichlorohydrin . From Hercules Kemiska Aktiebolag, Hisings Backa, Box 2019, Sweden . - URE OMFI cA IPO MELMENT L 10-. 20% A concrete superplasticizer: 20% solution of an anionic melamine resin . CEM-MIX A concrete superplasticizer: Sodium salt of a highly condensed naphthalene sulphonic acid/ formaldehyde condensate, of which typically more than 70% consist of molecules containing 7 or more naphthalene nuclei . Available from Aalborg Portland, Denmark. TRITON CF 10 Benzyl ether of octylphenylpoiyethoxylate. AI RFLEX 120 self-crosslinkϊng vinyl-ethylene emulsion, 52%, from Air Products δ- Chemicals, Waϊne, PA. , U . S . A. GORI Colourless Fungicidal wood preservation oil, from GORI , Denmark. Silicone, curing Wacker Si-Dehasiv 920 from Wacker Silicone, a 100%, absolutely solvent-free addϊtion-cross- Iinkϊng silicone. Cab-O-Sil Colloidal silica particles, particle size about 10 - 20 ym . Norit W 20 Activated carbon from Norit, iodine number 700 mg/g, apparent density 600 g/l . PVC solution Composition : 50 g of pure PVC (without plasti- cizer) , 300 g of tetrahydrofuran, 500 g of methylene chloride, and 0.5 g of Silane A-1100. Potassium water glass Be° 28 - 30. Bleached sulphate pulp Sheet weight about 750 g/m . From Stora Kop- parberg, Sweden . CTMP pulp Chemo-thermo-mechanical pulp. Consists of about 15% of bleached sulphate cellulose having an SR° of about 16 and about 85% of thermo- mechanical pulp having an SR° of about 16. The pulp is free from anti-bonding agents and other 2 chemicals . Sheet weight about 750 g/m . Straw cellulose Sulphite pulp made from rye and wheat straw. SR° about 32. From Fredericia Cellulosefabrik, Denmark I n the examples which follow, the treating agents or combinations of treating agents listed were supplied to the cellulose web 10 th rough the supply conduit 26 (except when otherwise indicated) , heated by means of the heating unit 27 and the heating jacket of the supply conduit 26 to 200 C (when no other temperature is stated) and were added, in the amounts stated in the examples, to 10 kg of dried, bleached sulphate cellulose which was heated to about 110 C during passage through the tunnel 20. I n some of the examples, additional material was added in the hammer mill 19, or immediately prior to the hammer mill 19. OMPI cA Treating Agent Amount Added, G rams per 10 kg Example No. MOA C 1460 1000 1000 1000 MOA C 1400 600 MOACO C-10-50-AM 600 MOA D 1200 600 Manalox 403 Solid 600 MOA D-00 60 MOA DF-00 60 Example No. 10 11 12 13 14 15 MOA C 1460 1000 1000 1000 1000 1000 100O 1000 Manalox 403 Solid 600 MOA DF-1400 60 MOA DF-1000 60 MOA CDF- 1400 60 BEROL 370 30 30 15 15 15 BEROL 563 15 15 15 Silane A-1 100 30 30 30 Silane A-1102 30 Example No. 16 17 18 19 20 21 22 MOA C 1460 500 500 500 1000 1000 1000 1000 MOB I LWAX 2360 300 ANT I BLAZE 78 300 V1 RCOL 82 300 BEROL 370 15 15 15 15 BEROL 563 15 15 15 15 Silane A-1100 30 .30 30 30 Added in Hammer Mill : Ultrafine silica 5000 1000 Super Rapid 4500 4000 Calcinated diato- maceous earth 5000 Gypsum 5000 Example No. 23 24 25 26 27 28 29 30 MOA C 1460 1000 1000 1000 1000 1000 1000 1000 1000 BEROL 370 15 15 30 60 BEROL 563 15 15 Silane A-1 100 30 30 30 30 30 Added in Hammer Mill : Calcined diato- maceous earth 5000 Talc 5000 Woilastonite 5000 Charcoal (Norit activated carbon W20) 1000 1000 1000 I ron Powder 5000 Epoxy polyester powder 1000 Example No. 31 32 33 34 35 36 37 MOB1 LCER Q 500 500 1000 1000 500 500 LUDOX HS 40% 500 Potassium water glass 500 Diammonium phosphate 35% 250 Boric Acid 30% 250 ALMID 7 50% 500 Ammonium sulphate 30% 100 AQUAPEL 3100 XL 1000 Silane A-1100 50 Silane Y-9566 40% 50 Example No. 38 39 40 41 42 43 44 45 MOBI LCER Q 500 500 500 450 250 LUDOX HS 40% 400 Potassium water glass 400 500 Diammonium phosphate 35% 250 Boric Acid 30% 250 ALMI D 7 50% 500 Ammonium sulphate 30% 100 AQUAPEL 3100 XL 500 500 450 450 250 KYMENE 557 H 50 MELMENT L 10 20% 100 CEM-MIX 50 Silane Y-9566 40% 50 TRITON CF 10 50 AI FLEX 120 50% 950 OMPI Example No. 46 47 48 49 50 51 52 53 Bitumen Solution * 1000 GORI Colourless * 1000 Silicone, curing * 1000 PVC solution * 1000 MOA C 1460 1000 1000 1000 1000 Sprayed on in Hammer Mill : Silane A-1 100 100 300 200 MOA D-00 500 200 Potassium water glass 1000 Cab-O-Sil 500 Ethanol 1500 2-Propanol 1000 250 Methylene chloride 250 * Added at room temperatu re Example No. 54 55 56 57 58 59 60 61 Silicone, cu ring * 1000 MOA C 1460 1000 1000 1000 1000 Sprayed on in Hammer Mill : Silane A-1100 300 60 60 60 100 MOA D-00 60 60 120 Cab-O-Sil 100 Ultrafine silica 300 Ethanol** 1500 1500 1500 1500 1500 1500 1500 2-Propanol 1000 BEROL 370 15 BEROL 563 15 BEROL 572 30 * Added at rooπi temperatu re ** Also sprayed on before high pressu re roller Example No. 62 63 64 65 66 67 68 69 MOA C 1400 500 500 500 MOA DF-1400 500 500 500 400 400 MOA DF-00 200 200 400 TES 40 200 200 TES 40 ÷ Silane A1102 in the ratio 96:4 • 200 200 400 Example No. 70 71 72 73 74 75 76 77 MOA DF -1400 400 MOA DF -00 200 • TES 40 400 300 Manalox DP11/C/22P 600 300 MOA C ■ 1400 500 500 Manalox 403 Solid 500 500 Manalox 205 500 TES 40 150 150 150 Silane A -175 30 30 BEROL 370 15 15 Mixture 50:50 of "* BEROL 563 and 573 15 15 OI.ΪP Example No. 78 79 80 81 82 82 83 84 Manalox 205 500 600 Silane A-175 30 BEROL 370 15 50:50 Mixture of BEROL 563 and BEROL 573 15 I socyanate MDI 450 400 500 400 Desmodur T80 500 Added in Hammer Mill : LUDOX HS 40% 200 Potassium waterglass 300 TES 40 100 100 I n examples 85-95, the fibrous material treated was 'straw cellulose. Example No. 85 86 87 88 89 90 91 92 MOA C 1400 500 500 500 MOA DF-1400 500 500 500 400 400 MOA DF-00 200 200 400 TES 40 200 200 TES 40 + Silane A1102 in the ratio 96:4 200 200 400 Example No. 93 94 95 MOA DF-1400 400 MOA DF-00 200 TES 40 400 300 Manalox DP11/C/22P 600 300 Example 96 A sulphate cellulose pulp was dried and passed through the rollers at maximum pressure (about 10,000 kp) without addition of any liquid prior to the rolling treatment. The resulting rolled product had a "tobacco flake-like" appearance and consisted of fibers which had a considerably higher fineness than the starting fibers . When dispersed in water, these fibers sedimented, indicating a high density. Paper made from the fibers on a laboratory sheet former was parchment¬ like, indicating that the fibers had obtained a considerably higher SR°. The paper had a high tensile strength, but a poor tear strength, like parchment paper. Example 97 Subject liner (wrapping paper) made from sulphate cellulose to drying at 200°C. To this, apply metal oxide acylate (aluminum oxide tallate or stearate or zinc oxide tallate or stearate) preferably in the undi¬ luted form and heated to about 200°C. The resulting impregnated paper may either be used per se, or it may, preferably, be subjected to the rolling treatment described in the previous examples . The resulting impregnated liner is water-proof (water-repellant) . When the metal oxide acylate is a zinc oxide acylate, the liner is also resistant against fungal attacks. I n the same manner, e. g. , sulphate pulp may be treated and either high pressu re rolled or used per se with¬ out rolling, in either case for example as a carpet backing, a roof paper, or a sheet-shaped reinforcement for cement materials and plastics materials such as phenolic resins and polyesters . Example 98 I n a plant as illustrated in Fig . 3, 500 kg of bleached sulphate fluff 2 pulp having a sheet weight of about 700 g/m and without any con¬ tent of chemicals was impregnated with a solution of 70% of aluminum oxide stearate in white spirit in an amount of 100 kg . The impregnant was admixed with 3.5 kg og Silane A-1100 and 3.5 kg of BEROL 370. The mixture was preheated about 90-100°c. The fiber web was heated to such an extent that its temperatu re immediately prior to the im¬ pregnation was about 140°C. The resulting fibers were used for preparation of Eternite-type cement sheets in a Bell flow-on Eternite machine. The fibers were made into a slu rry by pulping 140 kg of treated fibers with 5000 liters of water for 20 minutes . To the resul¬ ting slurry, a slurry of 3 tons of cement and about 50 kg of ultrafine silica, calculated on the cement incorporated, was added . Both the dispersion of the fibers and their incorporation in the cement slu rry were easy. In the loader of the machine, the resulting fiber slurry was admixed about 0. 1%, calculated on the dry matter content of the slurry, of a strongly cationic polyelectrolyte (Hercuflox 816 from Hercules Kemiska Aktiebolag, Hisings Backa, Box 2019, Sweden) immediately prior to the dewatering. The retention was excellent. The resulting panels were cu red in the normal way and are dimension stable. Example 99 10 g of sheet straw cellulose having an SR° of about 32, 2.5 g of 2 activated carbon having a specific su rface of 700 m /g and 2.5 g of 2 activated carbon having a specific su rface of 1400 m /g were slurried in 1000 ml of water, whereafter the slurry was dewatered and dried to a sheet on a laboratory sheet former. The retention of the activa¬ ted carbon was excellent; there was substantially no coal in the backwater, and the coal is fixed on the fibers . Comments on the fibers produced in the Examples : Examples 1 - 5: The fibers had pronounced hydrophobic character. Examples 6 - 10: The fibers are suitable for incorporation as reinfor¬ cing fibers in cement-based materials . Examples 11 - 15: The fibers show excellent properties in that they do not absorb water, but yet are easily dispersed, e.g. , in cement- containing slurries . Example 16: The fibers are somewhat stϊffer than the fibers impreg¬ nated with metal oxide acylate alone. They are envisaged to be use- ful, e.g. , as reinforcing fibers in polymers such as polyurethane or polyester. Examples 17 and 18: I n these examples, the fibers were impregnated with ire- retarding agents . A similar experiment was performed with chloroparaffin . Examples 19 - 24: In these examples, the fibers were impregnated with a combination of metal oxide acylate and surface active agents to yield stabilized fibers which are not water-absorbing and, hence, do not swell, but which, nevertheless, are sufficiently hydrophilic, due to the incorporation of the surface-active agents, to be easily disper- sible in aqueous slurries . Furthermore, the fibers were treated with particulate materials, added prior to the hammer mill . Examples 25 - 27: The fibers produced in these examples show ex¬ cellent absorbent properties due to their content of charcoal and are useful, e.g . , as filter materials for liquids or gases, e. g . , as filter materials for filtering wine, beer, as household or kitchen filters , as filters for gas masks, and as filter materials for drin king water. Examples 28 and 29: The fibers produced according to these examples are particularly well suited as reinforcing fibers for cement, gypsum, etc. OMPI Example 30: The fibers are useful as hydrophilic substrate fibers for soil-less plant cultures, but are also useful, e. g . as filter material . Examples 31 - 36: These experiments were performed to show that the method of the invention may also be used for aqueous dispersions, solutions, etc. Even when impregnating with such aqueous materials, it is very advantageous first to perform a thorough drying treatment in the tunnel 20, as this secures a fast penetration . Example 38: I n this experiment, the latex applied was "filtered" by the cellulose web and remained on top of the web which is undesired . It would be desirable to use dispersions having a higher film forming temperature, e. g . , a temperature above 110 C. Example 39: The fibers obtained showed an excellent combination of hydrophobicity and fire resistance. Example 40: the fibers were relatively stiff and hydrophobic, but were not fi re resistant. Examples 43 and 45: The fibers had an excellent dispersing capacity. Examples 46 and 47 : The fibers showed good hydrophobicity. Example 48: The fibers are envisaged to be useful as fillings for pillows, as heat insulation materials, for clothes , etc. The fibers are very smooth and slide easily relative to each other. Example 49 : The fibers are suitable as bonding fibers in non-woven structures, e. g . dry-formed paper. Examples 50 - 56: I n these experiments, the metal oxide acylate was combined with other agents by adding the other agents in or imme- diately prior to the hammer mill . Although excellent fibers were obtained, the addition of the other agents to the metal oxide acylate, such as illustrated in Examples 11 - 15, is preferred . f OMP Example 57: The fibers had very special properties . They were stiff and elastic, and did not bond well to each other when used in paper- making experiments, but rather resulted in large fluffy structures . Example 58: I n contrast to Example 57, the fibers prepared in this example have retained their capability of bonding together when being suspended in water and thereafter filtered and dried . Examples 62-72: The fibers are excellently suited for incorporation (in amounts of about 4-10% by weight in cement panels . Examples 85-95: Because the straw cellulose fibers are very small, the impregnated fibers prepared according to these examples are very well suited as thixotropic agents in water-based and solvent-based paints. Fibers prepared according to the above Examples 1 , 11 , 12, 13, 19, and 20, respectively, were subjected to testing as follows : Fibers prepared according to Example 1 were subjected to extraction in Soxhlet apparatus with dichloromethane and petroleum ether, re¬ spectively. It was found that 5.2% of the substance applied could be extracted with dichloromethane, and that 4.5% of the substance ap¬ plied could be extracted with petroleum ether, that is, about half of the weight of the aluminum oxide stearate applied . While the elementary analysis of aluminum oxide stearate should be C: 66.3; H : 10.7; O: 14.7; Al : 8.3, the two extracts, on elementary analysis, showed the following compo¬ sition : Petroleum ether extract: C: 77.5; H : 13.1 ; O: 9.1 = 99.7 Dichloromethane extract: C: 77.7; H : 13.5; O : 9.2 = 100.4 This shows that the extracted material does not consist of un reacted aluminum oxide stearate, considering that aluminum is not present; presumably, the extracted material is stearic acid which may have been present in excess in the aluminium oxide stearate. Fig . 7 is a scanning electron microscopy (SEM) photo (magnification 54x) showing the distribution of aluminum through the treated web. It will be noted that the distribution is very even. Fig . 8 is a SEM photo (magnification 110x) of the fibers and shows that some of the fibers are quite collapsed while others are quite round . This also appears from Figs . 9 and 10 (magnification 930x and 1570x, respectively) which show single dichloromethane extracted fibers . Figs. 11 and 12 (magnification 2050x and 3000x, respectively, and dichloromethane extracted fiber (Fig . 11 ) and fiber as is (Fig . 12) , respectively) show that the fiber end (Fig . -11 ) and the fiber surface (Fig. 12) have an appearance quite different from a - normal pulp fiber. I nvestigations comprising contact angle measurements and absorption measu rements on the fibers (extracted and non-extracted) show that the surface of the fibers is clearly hydrophobic and lipophilic. Also, it was clearly found that the fibers do not swell in solvents . Fur¬ thermore, it is evident that the fibers retain their hydrophobicity even after extraction . The water retention value (WRV) of the fibers was determined . The results appear from the following table, which also states the dry matter content, the contact angle, and the wettabϊlity of the fibers . OMPI Sample Dry matter WRV, % Contact Wettability* Angle Example 1 93.9 44.4 no -25 Example 19 93.2 39.5 88 2.5 Example 11 92.5 55. 1 86 • 5.1 Example 13 93.7 63.2 89 1 .3 Example 12 93.2 50.0 83 8.9 Example 20 93.0 43.2 92 0.0 Polypropy¬ lene fibers 49.0 Polyethylene fibers 98.3 16.4 Bleached su Iphate pulp -94 172 * Wettability = Z x cos φ The fibers prepared according to Example 1 were subjected to a thermal analysis which showed that an endothermic reaction starts at 50°C and is complete at 120°C, maximum at 85°C. The reaction cor¬ responds to the removal of about 5% of water. An exothermic reaction occurs between 2 5 and 335°C, which is a thermal degradation . The weight loss is 66%. Thereafter, an exother¬ mic reaction occurs again at 400-450°C, corresponding to an ignition and combustion of remaining material . This means that the fibers are thermally stable up to 275°C, and that the first degradation takes place wthout ignition . The fibers have a low degree os swelling in water, and the zeta potential corresponds to the zeta potential of a normal pulp. O P cAK. WIP

Claims: CLAIMS 1 . A method of treating a material including fibers each having inner and/or outer surface parts defining interstices or voids, said method comprising exposing said material to a heating and/or drying treat- ment and thereafter compressing said material sufficiently to at least partly compress said interstices or voids . 2. A method according to claim 1 , wherein said said fibers are natural fibers such as cellulose fibers, including natural cellulose fibers such as sulphate or sulphite pulp, TMP and CTMP pulp, hardwood and softwood pulp, cereal cellulose pulp, including straw cellulose pulp, wood chips, saw dust, wood wool or synthetic or regenerated cellulose fibers , or wool fibers, kapok, sisal , acacie, or coconut fibers, or cotton . 3. A method according to claim 1 or 2, wherein material is compressed sufficiently to permanently deform the cell walls of at least some of the fibers . * 4. A method according to any of the claims 1 - 3, wherein said mate¬ rial is a fibrous sheet or web material . 5. A method according to any of the claims 1 - 4, wherein said com- pression is performed by subjecting said material to a rolling treat¬ ment. 6. A method according to any of the claims 1 - 5, wherein a liquid substance is applied to said material prior to or during said compres¬ sion . 7. A method according to any of the claims 1 - 6, wherein the liquid substance is applied to the material subsequent to the heating and/or drying treatment. 8. A method according to any of the claims 1 - 7, wherein said rol¬ ling treatment is performed by passing said material th rough the nips defined by consecutive pairs of rollers . O ?I WI 9. A method according to claim 8, wherein said liquid substance and/or further liquid or particulate additives is/are applied to said material between two adjacent pairs of rollers. 10. A method according to any of the claims 6 - 9, wherein said liquid substance is sprayed onto said material, preferably by an airless spraying technique. 11 . A method according to claim 10, wherein said liquid substance is sprayed onto said material by means of a nozzle, a pulsating flow of said liquid flow being supplied to the nozzle. 12. A method according to claim 9 wherein said liquid substance is supplied to said material from at least one of the rollers. 13. A method according to claim 12 wherein the liquid substance is applied to the material from a roller immersed in a bath of said liquid substance. 14. A method according to claim 12 wherein the liquid 'substance is applied to the material from a roller to which the liquid substance is supplied at controlled rate. 15. A method according to any of the claims 1 - 11 , wherein at least one of the rollers used in said rolling treatment is heated . 16. A method according to any of the claims 1 -15, wherein said mate¬ rial is defibrated in a hammer mill or another fluffing device after compression . 17. A method according to claim 16, wherein a lubricant is added to said material after said compression , and prior to or during said defibration in a fluffing device. 18. A method according to any of the claims 1 -17, wherein activated carbon is applied to said material prior to and/or after said compres¬ sion . 19. A method according to claim 18 wherein the activated carbon ia added du ring defibration of said material in a fluffing device such as a hammer mill . 20. A method as claimed in any of claims 6-19 wherein the liquid substance ia an impregnation agent. 21 . A method as claimed in claim 20 wherein the impregnation agent is one or several metal oxide acylates , for example alumin um oxide stearate or tallate or a combination of about 50% of aluminium oxide stearate or tallate and about 50% of a silicon-titanium alkoxide con- densed oligomer. 22. An apparatus for use in carrying out the method according to any of the claims 1 -21 , said apparatus comprising rolling means including at least one pair of rollers , supply means for supplying a fibrous material to the nip defined between said pair of rollers, and heating and/or drying means for heating and/or drying the fibrous material supplied . 23. An apparatus according to claim 22, further comprising means for applying a liquid substance to said fibrous material at a position upstream of said rolling means . 24. An apparatus according to claim 23, wherein said liquid applica¬ tion means comprises a nozzle and means for feeding a pulsating flow of said liquid substance to said nozzle. 25. An apparatus according to any of the claims 22-24, fu rther com¬ prising means for heating and/or drying said fibrous material at a position upstream of said liquid application means . 26. An apparatus according to any of the claims 22-25, further com¬ prising means for defibrating said fibrous material at a position down¬ stream of said rolling means . 27. An apparatus according to claim 26, wherein said defibrating means comprises a hammer mill . 28. A fibrous material comprising natural fibers having cell walls which have been permanently deformed by compression . 29. A fibrous material as claimed in claim 28 which comprises cellulose fibers . 30. A fibrous material as claimed in claim 29 which is impregnated with a metal oxide acylate and/or carries active carbon particles . 31 . Cellulose fibers impregnated with a metal oxide acylate and com- prising a coupling agent such as a silane. 32. Cellulose fibers impregnated with a metal oxide acylate and com¬ prising one or several tensides increasing the dispersibility of the fibers in aqueous media. 33. Cellulose fibers as claimed in any of claims 29 - 32 when prepared by the method according to any of claims 1 - 21 . 34. A method for impregnating cellulose fibers, comprising treating the fibers a metal oxide acylate in containing a coupling agent incor¬ porated therein . 35. A method as claimed in claim 34 wherein the coupling agent is a silane. 36. A method as claimed in claim 34 or 35 wherein the treatment is performed under high shear conditions . 37. A method as claimed in claim 34 or 35 wherein the treatment is performed by the method claimed in any of claims 6-21 , the combina- tion of the metal oxide acylate and the coupling agent constituting the liquid . 38. A method * ~τ r treating cellulose fibers, comprising applying a metal oxide acylate and a particulate substance on the fibers . 39. A method as claimed in claim 38 wherein the particulate substance is ultrafine silica precipitated from a gas phase, and/or cement. 40. A method as claimed in claim 39 wherein cement is added in such an amount that the fibers, when admixed with water, form a slu rry for formation of fiber-reinforced cement-bonded material . 41 . A method as claimed in claim 38 wherein the particulate material is an absorbant particulate material . 42. A method as claimed in claim 41 wherein the absorbant particulate material is charcoal . 43. A method as claimed in any of claims 38 to 42 whichs is per¬ formed by the method as claimed in any of claims 6-21 . 44. Cellulose fibers which are impregnated with a metal oxide acylate and additionally comprise one or several su rface active agents modi¬ fying the character of the fibers towards greater hydrophilicity. 45. A method for preparing metal-oxide acylate-impregnated cellulose fibers, in particular for incorporation in aqueous slurries, comprising combining the impregnation with the metal oxide acylate with an impregnation with a surface-active agent imparting hydrophilic pro¬ perties . 46. A method as claimed in claim 45 wherein the su rface-active agent is a nonionic or cationic tenside. 47. A method as claimed in claim 46 wherein the tenside is added together with the metal oxide acylate, optionally incorporated in the metal oxide acylate. OI.ΪPI 48. A method as claimed in any of claims 45-47 wherein the metal oxide acylate and/or the surface active agent is incorporated by the method according to any of claims 6-21 . 49. A method as claimed in any of claims 45-48 wherein a coupling agent/and or a particulate material is also added to the fibers . 50. Absorbant fibers comprising active carbon -treated metal oxide acylate-impregnated fibers . 51 . Hygiene articles or napkins (diapers) comprising fibers as claimed in claim 50 " . 52. Hygiene articles or napkins (diapers) as claimed in claim 51 wherein the metal oxide acylate or a part thereof has antimicrobial properties . 53. Hygiene articles or napking (diapers) as claimed in claim 50 wherein the " metal oxide acylate or part thereof is a zinc oxide acy- late. 54. Oil absorbant fibers comprising metal oxide acylate-impregnated cellulose fibers . 55. Oil absorbant fibers as claimed in claim 54 wherein the metal oxide acylate is aluminum oxide acylate. 56. Oil absorbant fibers as claimed in claim 54 or 55 which are packed, in non-bonded form, into permeable bags . 57. Hygiene articles and diapers or napkins comprising metal oxide acylate-impregnated hydrophobic cellulose fibers as an intermediate layer between hydrophilic fibers therein and the exterior of the articles . 58. Hygiene articles as claimed in claim 57 wherein the metal oxide acylate is aluminum oxide stearate or tallate. 59. Antistatic tissues comprising metal oxide acylate-impregnated cellulose fibers . 60. Cellulose fibers impregnated with an isocyanate. 61 . Cellulose fibers as claimed in claim 61 when prepared by the method according to any of claims 1 -21 . 62. Impregnated cell ulose fibers as claimed in any of claims 30-33, 44 or 60, wherein the impregnation agent is present in an amount of 4-10% by weight, in particular 6-8% by weight, calculated on dry basis . 63. A composite material comprising fibers as claimed in any of claims 30-33, 44 or 60. 64. A composite material comprising fibers which have been compres¬ sed sufficiently to permanently deform the cell walls of at least some of the fibers . 65. A method of impregnating natural or synthetic cellulose fibers, comprising heating a material comprising natu ral or synthetic cellulose fibers to a temperatu re of 100-275°C, in particular 120-250°C, prefer¬ ably about 160-220°C, more preferably 180-200°C, and thereafter applying an impregnating agent on the material . 66. A method as claimed in claim 65 wherein the impregnating agent comprises a metal oxide acylate or an isocyanate . 67. A method according to claim 65 or 66 wherein the material is subjected to a compression subsequent to the heating . 68. A method according to any of claims 65-67 wherein the material is a pulp or wet-formed or dry-formed sheet or web . 69. A method according to any of claims 65-68 wherein the impreg¬ nating agent is an agent which is reactive with cellulose hydroxy groups .

Inventors: HOLBEK KJELD
Applicants: HOLBEK KJELD, HOLBEK KJELD APS
Application year: 1982
Main classification: D21B1
IPC codes: A61F13, A61L15, B27K3, B27K5, C04B18, C04B20, C09K3, D21B1, D21C1, D21C9, D21H17, D21H25, D21H27