DE1411892A1 - Process for the production of fine powdered cellulose - Google Patents

Description

Process for the production of fine-powdered cellulose.

The invention relates aioh to a process for the production of finely powdered Cellulose (powder cellulose) based on processed cellulose or pulp, in particular cellulose in sheet form or roll form, and devices for implementation of the procedure.

Zvar have become aware of proposals, such native, processed To convert cellulose in powder form, which to a part also practically carried out are, however, the professional world is also known that these procedures are extraordinary are expensive and entail considerable disadvantages, and that the costs of these Processes are so high that so far these proposals have not been used in technology and powdered cellulose remained a special product is his relatively high prices because of only in special Use cases is used. t.

So, for example, the suggestion has become known, fresh or dry and moistened wooden strips, corn stalks etc. through a mill a hydraulic pressure of about 2000 pounds per square inch 1 (140 kg cm2) and to roll more in the cylinders, whereby a product is obtained that is as loose, fragile mass is described, the. Single fibers are separated from each other in such a way that wd they can be used directly in the manufacture of paper (US Pat 2 229 141), and the suggestion ag, vegetable material, has also become known such as grasses, plant stem parts, etc. su a powdery material This means that you can process the dry starting material in a calender The effect of a high squeezing pressure turned into a brittle and fragile mass and then in comminution devices such as impact pin mills or ball mills is treated further.

It is stated that air-dry straw in uncomminuted or chopped form between steel rollers that are carried out at a distance of 0.09 mm are applied next to each other and, if necessary, are slightly heated, where the bolts have a width of 500 mm and a diameter of Have 300 mm and with a pressure of about 300 kg per centimeter of surface line and work at a speed of about 8 to 12 revolutions per minute.

Even with this relatively low overall pressure only 15 to but the material can fall below the gap limit of 0.09 dodge mm so that also dilua ac oll vJit would try on this Wise native, processed cellulose e.g. in the usual form of cellulose sheets, - to crush bows or rolls less than 2 mm thick into cellulose dust, so the mother is completely negative. Neither would grinding occur during the rolling Powder, another one for a later grinding process, which will lead to considerable varsproung, yet the cellulose could be chopped through such a rolling mill after repeated through @@ that they become brittle, for example using a cross beater mill Cellulose powder. Trials with rolling mills failed so that the result of walking this path led away.

As a result, one did not go these ways, but one has either satisfied with imperfect powdering or long-lasting treatment in oversized Ball mills made what to be sure Powder cellulose leads to the invention, but at a practically unacceptable expense is now creating a way to produce powdered cellulose that is economical and avoids the previous disadvantages.

A very large number of examinations carried out over years and tests have shown that a number of requirements must be met with it performed a satisfactory process and obtained a good powdery product become can; n.

The exit must be from cellulose sheets, like all starches less than 2 mm, preferably 1 mm, as pulp webs are on the market. With these Cellulose leaves are native, processed and purified form Cellulose present, e.g. wood pulp cellulose.

These flowers, sheets or strips must be proportioned in strips can be divided into a small width and fed into a die press in this sand mold, see e.g. next to each other and at a distance with separate feeding of each single band. These exit strips should keep a water content in a certain range. The effect of pressure must in order to have a brittle cellulose received, extraordinary intense - as linear as possible - and must be from the beginning of the pressing pressure Follow up in the shortest possible time until the maximum pressure is reached.

According to the experience of the inventor, it is possible to use a rolling mill with rollers The aim of embrittlement of the cellulose is achieved through diameter and with the roll gap cannot be achieved. In contrast, the embrittlement succeeds with a 3-roller mill without Own roll gap with hydraulically driven rolls and a pair of rolls with rollers of the usual size with a roller floating between the two rollers very small diameter with rigid driving of all three rollers with the same Circumferential speed that exerts an extremely high, almost linear pressure on the Cellulose strips passed between a large and the intermediate small roller exercises.

In such a roller frame according to the invention, the center roller is of a very small diameter necessary to: once an effective in the maximum pressure zone, to achieve shear stress on the cellulose that is perpendicular to the direction of pressure (lines equal pressure on the opposing rollers due to the differences Diameter of the rollers up to the line of absolute maximum pressure different tiers) and further around as linear a pressure zone as possible and thus very much to achieve high pressures per unit area.

3Dabef should be the circumferential speed, which is the case with the three rollers of the Rolling mill is the same, at least 5 m and at most 40, preferably about. 14 m per Minute and wear.

The strip or strips must continue up to the roll mouth be guided as a rolling mill with such high pressure of the rollers on that between them does not accept guided goods, sheets or strips or shifts them, one on top of the other and thus leads to results .. which are completely unsatisfactory.

<In addition, it must be ensured that the temperature of the Rolling is in a certain range and that this range is neither fallen below is still exceeded. While the rollers in the procedure according to the Ex invention are initially heated, they usually have to be cooled in the course of the process - if the cooling by the water evaporation of the supplied with the cellulose Water is insufficient; this temperature range is between 100 and 160 ° C, in particular between 120 and 160 °, with a roller temperature of 120 ° being expedient one is held. The two big rollers can Temperatures of about 160 °.

Wfl, according to the invention, a rolling mill with two tubes. alzen and a small roller floating between them, whereby the small @alze has a diameter of e.g. 162.5 mm, while the large rollers have a diameter of, for example, 500 mm, which are expediently arranged one above the other, and are on the bearings of the large roller with fixed storage of the other large roller and floating storage of the small intermediate roller separately prints of 30 each up to 40 tons, which rise up to 80 tons, so that the total pressures 60 to 60 or up to 160 can be on n9 (the campers refer to a salt length of 500m), and will There are three rigid rollers at a circumferential speed of, for example, 15 m per minute Transmission ratios drive the output cellulose in the form of strips of about 6cm wide with a water body mix 5 and 15%, expediently below 10%, preferably about 7% continuously added, woebi each of these strips is led to the inner roller mouth and the strips be held at a distance from each other up to the roller mouth, demalting mouth between e.g. upper large salts and the middle small roller and, after passing through, reversing the direction the roll mouth between e.g. lower '.' Salts and medium-sized alcohols while complying with a Temperature of the roll surfaces in the roll mouth of e.g. about 130 ° supplied, see above an embrittled cellulose is obtained in the form of a brittle film, which easily can be crushed by simple devices, for example a Häckaelvorrichtung can.

The extraordinarily high mechanical pressure and also the roller temperature leads to evaporation of a significant part of the moisture of the starting celluloae and it an embrittled cellulose with about 2.5% water is produced.

According to the invention, this embrittled cellulose is then preferred in an intensive grinder-after-one Embodiment in one with flowing suspensions of the embrittled cellulose grinding devices operating in air, in particular so-called flow mills as they are known as cycomats - converted to a powdery cellulose @, which is particularly suitable for all purposes, for the powdery Cellulose is used.

High-speed counter-rotating ones are also suitable as intensive grinding devices Pin mills, gear mills, toothed disk mills, etc. are preferred, however Flow mills, e.g. an Ultrafine Cyclomat.

The læenmUhl is supplied with cellulose sheet strips according to the invention can also be designed so that when the rollers are arranged one above the other the upper large roller is firmly mounted and the bearings of the lower large roller are hydraulically loaded; you can also use bearings for both large rollers hydraulic pressure can be supplied. The rollers can also be arranged next to one another The feeding could be done from below and / or from above.

An attempt would be made to feed cellulose in the form of fibers to a rolling mill according to the invention the mill will not accept these fibers; one would try through special facilities to design the fiber feed in such a way that the roller mouth accepts it, that would be the case As a result, these fibers go through the rollers irregularly one above the other and a cellulose is produced, which is unevenly brittle, so that the grinding process either does not lead to powdered cellulose at all or to an imperfectly powdered xelluloseIm The same is essentially the case when using brown sheets or webs.

According to a preferred embodiment, the intermediate roller is not heated and not cooled, so that the rolling temperature of preferably 120 to 160 ° Maintained solely by heating or cooling of the large rollers while the process is running will.

You can work with one pass, in which case zanzi is wake-up The double-acting work is carried out in such a way that from one side the roll mouth between lower and smaller intermediate roll material and on the other hand material from the other @eite fed to the roller mouth between the small m alose and the upper large roller will.

It is essential that the two salt areas between Großerur and medium and between medium and the other large salts not metal-on-metal run, but lead to embrittling cellulose between them, whereby the evaporation of the water of this cellulose is incidentally helps to regulate the temperature and prevents the temperature from becoming too high, so that in many cases it is possible to work without roller cooling. z After the failures leading attempts in pulp to work with a rolling mill like the one for that Powders and embrittlement of plant parts has been proposed, it is surprising that when using the Rolling mill according to the invention, taking into account the other inventive conditions the production of embrittled cellulose and from it pulverulent cellulose succeeds, which is due, among other things, to the high pressures with simultaneous shear stress is.

The sheets of embrittled celluloses have a leaf thickness of between 50 and 90 / on. This shows that e.g. the use of rolling mills with a set Roll gap of 90 @ can not lead to success, especially since the embrittled and after The cellulose sheet measured during the salting process is considerably stronger due to its elasticity must be than at the moment of its passage through the maximum pressure zone.

Good results have been achieved with ribbons cut into strips of great length, e.g. 40 m, these strips being cut from wide Lanes and spooled onto individual reels, so that the feed is made of strips by means of guide rails and driving rails from Z. B. 6 - 8 cm wide is safe. The width <of the stripes can vary, but the width of the strips should be 12 or 10 cm and preferably 8 do not exceed cm. the stripe width can be chosen to be considerably smaller and e.g. be 2 cm and less.

As the imported cellulose under the high pressure and temperature Water loses in an explosion-like manner, is the danger of wide webs The displacement of the cellulose introduced is very great.

Each of the strips is wound onto a separate spool, from which the rolling mill the strips - by the way nit different Speeds-subtracts; the take-off speed are in the middle of the malts generally lower than at the roller edges.

To the roller length, which for example el 650, preferably 500 mm can be, it is advisable to use the space between the individual, @ z. B. the width of the fed strips separating, laterally leading ledges, not too large to choose, but about 10 mm not to be undercut.

These gaps disappear through rolling and pressing in such a way that a film, albeit a brittle one, which is relatively irregular, out of the salting process.

.

The distance between the strips should not be so small that through the displacement of the introduced material in the roller and through the spreading Overlays go on. t The guide of the strip or strips up to to the inner roll mouth happens according to a preferred embodiment by a at the inner roll mouth protruding guide table, which according to a preferred Embodiment has a recess adapted to the outer surface of the large roller, according to a further preferred embodiment, a lower free-running, through the Introduced tape in rotation offset guide roller upstream is pressed against the lower guide roller by means of a spring, for example pressing small roll.

With a return of the only partially embrittled water to a large extent liberated - band is usually superfluous such leadership.

On the other hand, it is useful to redirect the band around the small To secure the roller by means of a guide, its displacement on a clamping device acts at the feed point in the sense of clamping the fed tape, so that the feed is shut off by tearing off the tape. This clamping device according to a preferred embodiment, works electrically in such a way that the Displacement of the guide piece away from the small @alze - by accumulating Material in the event of a diversion failure - a circuit is actuated which, e.g., by ' Activation of an electromagnet or the release of a spring, which acts on the track - on the underneath but a guide pushes the running tape, causing the tape to tear off as a result the pull of the rollers is effected. After clearing or processing the behind the small roller of accumulated material, return of the Leadership in the normal age, @, breaking the circuit and nd regiabe the way for that band by returning the clamping piece to the normal position, e.g. under the action of a Return spring, the cellulose strip can be fed back to the rolling mill and processed will. According to a preferred embodiment, a guide stick is used for each band and a clamping device assigned, so the processing of the remaining tapes continue to run without interference.

When using a rolling mill and a guide of the invention to the innermost @alzenmund, with the inner edge of the guide piece, just before the line of contact between the two malts will not be applied to the banjo only a high pressure is exerted, but also at right angles to the direction of the pressure horizontal shear stress.

Figure 1 shows a schematic of the process of the invention under transit of cellulose strips through a rolling mill according to the invention and introduction of the crushed cellulose after crushing in a fluid mill (cyclomat) and separating the powder fractions Cellulose oS the suspension with air ..

Cut from a spool in a strip 5 cm wide from a web of cellulose, t is wound up, the strip becomes 2 fed via a deflection roller 3 through a 'guide 4 to the rolling mill, which consists of a upper lze 5 consists. on whose bearings hydraulic pressure is exerted, a fixed one Roller 6 and one floating between the two rollers 5 and 6 ga-. camped smaller lze 7, which are driven at the same peripheral speed, between roller 5 and inserted and guided by the guide piece 8 between roller 7 and 6 returned.

The embrittled cellulose is by a coarse grinder 9 in individual Leaflets divided and in a line 10 by means of a pump 11 to a cyclone 12, aas dom the flakes of emitted cellulose .., through a cyclone 12 through an allocation bunker 13 a line 14, fed to a cyclomat 15.

In this xyclomia the agreed cellulose is ground to powder, which is derived from the suspension flow with air in the syklon separator 16, from which Exhaust line 17, the remaining cellulose powder in air filter box 16, the air is loaded through a line 19 is fed to the cyclone 12 again, is separated.

From the lines 20 of the cyclone separator 16 and the air filter bags 18 the finished grist is drawn off.

Figure 2 shows sections of the a '"alzwerkes according to the invention.

The rollers 5, 7 and 6 are arranged one above the other, the roller 6 is fixed while the bearings 21, 22 of the roller 5 are separately hydraulically pressurized are set by the pressing devices 23, 24.

The <? Alze smaller diameter 7 is stored in t 25, 26, namely floatingly mounted in such a way that the pressure exerted on the bearings 21, 22 of the roller 5 is transferred via the roller 7 to the roller 6 and its bearings.

All three rollers are driven, with the speed of rotation n1 and n3 of reels 5 and 6 are the same. By corresponding to the smaller radius of the small intermediate roller 7, the higher speed of rotation nS, the circumferential speed UderWaise7 increases they are the same as the Umlaof speeds U1 and U3 of the rollers 5 and 6.

The section on the right-hand side of FIG. 2 shows details the guidance of the tape 2, in particular the roller guide device 28, 29 for the tape 2, as well as the clamping device 4, which consists of a clamping piece 30 on the Belt 2 running over counterpart 31 pressing or releasing it Electromagnet 32, which is actuated by the position of the circulating guide piece 8 via a splitting device 33.

In these representations, the guide 34 is the cellulose belt indicated up to the roll mouth.

In 2 pale 1 for a cellulose volume 2 drawn; become practical several such coils with oneeine en tapes 2 next to each other, which are independent . can rotate from each other, arranged, and a plurality of tapes 2 next to each other of the roller 5, 7, 6 zage - loitet * This guide is shown in Figure 3 (vertical section The roller guide device for the xellulose belt is shown in detail 2 consists of a sub-roller 28 and, which is set in rotation by the belt 2 an upper small roller 29 pressed by spring pressure, between which the Cellulose tape 2 is guided. This guiding device also serves to make things easier feeding the tape. The tape 2 passes from the rollers 28, 29 onto a guide piece 34, 8as the tape 2 leads to just before the roll mouth.

The e surface of this guide piece 34 is in the roll mouth of the Adapted to the roller 5, as shown at 35. The guide rollers 28 are shown in FIG Arranged at a distance from each other. The spacer bars 36 are arranged between them, which the bands 2 - as well as the end strips 37-guide laterally.

Claims (10)

8 1. Process for the production of powdered cellulose, thereby marked that native leaf cellulose with. a water content of 5 to 15, expediently below 10, preferably about 7%, in the form of relatively narrow Strips under the guidance of each strip at a distance from one another up to the roller mouth a rolling mill, consisting of two large rolls of normal diameter, "f on their Bearing - with a roller length of 500 mm - @ in n pressure of about 30 up to 80 tons per bearing, with an interposed, floating roller small diameter, with the same peripheral speed of all three rollers, under Adherence to a roller temperature between about 120 and 160 °, after which Passage or, after repeated passage, mechanically on single-acting devices crushed into flakes and in this form-with moisture contents of about 2.5 % - is added to an intensive grinder. 2 Method according to claim 1, characterized in that tracks any L in strip form, e.g. in strips of. about 60 mm Wide, cut, wound on separate spools next to each other and guided of each individual stripe at a distance from each other, e.g. at a distance of 20 =, in the inner roller mouth are guided. . 3 3. The method according to claim 2, characterized in that the Strips held individually by guide plates at a pre-wetted, mmth distance from each other and fed to @alzenmund. 4. The method according to claim 1, 2 or 3, characterized in that that the pressure and temperature as well as the number of treatments are set in such a way that the resulting yersprodete cellulose has a moisture content between 2 and 5% <preferably about 2.5. 5. The method according to claim 1, 2, 3 or 4, characterized in that that the brittle cellulose after the embrittlement process becomes leaflets is crushed, e.g. in a coarse chopper, and then an intensive grinding device is fed. 6. The method according to claim 5, characterized in that as an intensive grinding device a flow mill is used @ 7. Method according to claim 1, characterized in that by installing different roller diameters with the same Circumferential speeds of the rolls the material to be rolled in addition to the Druckeimvirkung-one transverse to the direction of pressure is subjected to shear stress. 8. device for performing the method of claims 1 - 7, consisting of a three-roller mechanism consisting of two relatively large rollers Roller diameter of, for example, 500 mm and a floating roller relatively small diameter, for example 140 to 220 mm in diameter, preferably about 160 mm in diameter, preferably hydraulic loading The bearing of a large roller or both large rollers with the drive of the three rollers with the same peripheral speed, 9 device for carrying out the method according to claim 8, characterized in that the rollers are angecrdnat one above the other and the lower large roller is fixed, while the bearing of the upper large roller is separate are hydraulically pressurized. 10. Device according to claim 8 or 9, characterized in that that the large rollers can be heated and cooled and, if necessary, the small intermediate roller are designed to be coolable. l device for carrying out the procedure gera-4 claims 1 - 7 and according to claims 8 - 10, characterized by flat, guide pieces loaded with individual strips that end just before the Valzenmund, whose surface in the roll mouth of the outer surface of the large roll corresponding recesses wearing.