GB2112830A

GB2112830A - Upgrading used paper

Info

Publication number: GB2112830A
Application number: GB08234165A
Authority: GB
Inventors: Bernhard Steinbeis; Karl Eisenschmid
Original assignee: STEINBEIS PAPIER GmbH
Current assignee: STEINBEIS PAPIER GmbH
Priority date: 1981-12-09
Filing date: 1982-12-01
Publication date: 1983-07-27
Also published as: IT8268445A0; IT1157132B; FR2517713A1

Abstract

A process for the upgrading of used paper, obtaining a half-stuff which is suitable for the manufacture of paper, especially of high quality graphic paper comprises: a) speck-free and careful dissolution preferably in a high pulp density pulper; b) separation out of the heavy particles preferably in a sorting drum 3 and in a thick pulp centrifuge; c) fine sorting I at a pulp density of from 2.5 to 7%; optionally fine sorting II at a pulp density of from 1 to 2.5%; d) de-inking process; optional pressure sorting for the separation of laminar impurities; e) dewatering preferably on the screen press (22); f) emulsification and optionally a bleaching process.

Description

SPECIFICATION Process for the upgrading of used paper, installation for the completion of this process, as well as use of the half-stuff thus obtained The present invention relates to a process for the upgrading of used paper while employing stages for dissolution, de-inking, sorting, emulsifying and optionally a bleaching stage, as well as to an installation for the completion of this process and use of the half-stuff thus obtained. In particular the invention concerns a process for the upgrading of used paper while obtaining a halfstuff, which is suitable for the manufacture of recycled paper e.g. graphic paper, in particular for format papers.

The increasing need for fiber raw materials growing with the consumption of paper makes it necessary on a larger scale to have recourse to secondary fiber sources, i.e. to used paper.

Therefore the regeneration of used paper, especially in the light of the predictable increasing shortage of natural raw materials, will gain in importance in the future.

The high consumption of used paper, which in the Federal Republic of Germany is at present almost 50% based on the consumption of fiber materials, compels the used paper processing industry to employ ever less pure qualities. Apart from this growing degree of pollution of the used paper an adaptation of the upgrading installations is necessary which takes into consideration the constantly increasing demands on quality made on the half-stuff or regenerated pulp obtained.

The pulp upgrading process must in addition in view of the ancillary pulps which are used, the expenditure of energy and the waste removal problems, be optimized.

Whereas previously the half-stuff obtained in the upgrading of used paper was employed mainly for packing papers, especially for corrugated paper, there is an increasing need now to employ the half-stuff obtained for graphic paper, i.e. printing paper, writing paper and tabulating paper and especially format papers.

Here it must be taken into account that the quality of the old paper to be upgraded, e.g. of the goods collected from households, is deteriorating to an increasing degree. When proceeding on the basis of used papers, which are of low quality, it is however especially difficult to obtain a half-stuff which is suitable for the manufacture of high quality graphic papers which are machine smooth or satinized, in format or rolls. In the light of the shortage of raw materials there is in addition a desire to use the upgraded half-stuff in the largest possible shares for the new papers to be manufactured. Previously the half-stuff obtained from used paper was normally used in proportions of about 50% for recycling papers. When using higher proportions of half-stuff, papers were obtained which were grey in color and therefore were only usable to a limited extent as graphic papers.For this reason it is desirable to develop a process in which the used paper is carefully regenerated but whereby at the same time a degree of whiteness is obtained which permits the manufacture of graphic papers over a broad range.

Until now it has not been possible to manufacture graphic paper from upgraded used paper. Especially format papers and satinized papers were difficult to produce because the adhesive substances still contained in the paper pulp gave the sheets a tendency to stick together easily, which led to stoppages of the printing machine.

Thus there is a need for the development of a process in which used paper of low quality is upgraded, whereby proportions of from 30 to 100% of upgraded used paper can be used in the manufacture of high quality graphic papers.

In the literature, several processes for the upgrading and purification of used paper are described.

For example, German Auslegeschrift No.

2,701,731 describes a process for used paper upgrading, according to which the fiber suspension is divided by sorting into a quality pulp stream as well as a waste pulp stream, the waste pulp having to undergo a despecking process.

This despecking is necessary because otherwise all the undissolved agglomerates which also contain valuable fiber pulp would be removed with the impurities. But when using despeckers the adhesive impurities are pulverized into many small parts, so that they also cannot be separated out by the fine slit-type cages. But when producing e.g. format papers this means, that on the printing machine there may be a double sheet intake due to two sheets sticking together, which leads to great wastage and to stoppages of the printing machines.

From German Auslegeschrift No. 2,311,674 a process for the regeneration of used paper is known, in which bleaching and chelating chemicals are employed. This process too functions by using despeckers. The use of bleaching chemicals is especially necessary in order to remove the print color. Here peroxides are used as the bleaching chemicals. However the employment of peroxides has a harmful effect on the fibers, leads to problems in the purification of the effluent and produces papers which are unsuitable for e.g. offset printing.

German Auslegeschrift No. 2,813,448 also describes a process in which peroxide bleaching is carried out. According to this process, dissolution of used paper takes place in a pulp solvent with the addition of de-inking chemicals, followed by rough sorting, treatment in a despecker and the completion of a de-inking process which is then followed by the fine sorting. In this process the fine sorting of the paper pulp forms one of the last process steps, as is usual in this branch. But high proportions of impurities are carried forward over long periods in the upgrading process. The result is that the paper pulp has to be more strongly thinned in various process steps, which results in a higher consumption of energy and in addition due to the greater volume higher investments are needed with respect to the necessary installations.Moreover the removal of print color from a paper pulp which still contains high proportions of impurities is difficult which in turn leads to the use of higher concentrations of chemicals or to a worse result of the de-inking process.

It is an object of the present invention to make available a process as well as an installation for upgrading used paper in which used paper of low quality can be employed.

According to one aspect of the invention, there is provided a process for the upgrading of used paper to obtain a half-stuff which is suitable for the manufacture of recycled paper e.g. graphic paper, in which the following steps are performed: (a) dissolution of the used paper to form a pulp; (b) coarse sorting; (c) fine sorting; (d) subsequent de-inking; (e) dewatering; and (f) emulsifying.

According to another aspect of the invention, there is provided apparatus for the execution of the above process, which comprises means for forming a pulp from used paper; means for coarse sorting; means for fine sorting; means arranged for de-inking pulp which has been fine-sorted; means for dewatering; and means for emulsifying.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a diagram of the basic process steps in one example of a process according to the invention; and Figures 2a and 2b illustrate in more detail a block diagram of a preferred process, in which the following signs are used: thick lines signify the primary pulp circuit, thin lines signify the secondary pulp circuit, dashed lines signify a water circuit, and chain dotted lines signify chemicals, steam or waste.

Figure 1 shows the basic process steps carried out in the upgrading and recycling of used paper.

First of all, the old paper is carefully dissolved in a high pulp density pulper.

Following this, the pulp is taken to a sorting drum for the separation of coarse impurities and is then subjected to a fine sorting process preferably using a slit-type cage.

Following these sorting operations, a de-inking process is carried out and then a further sorting process to remove laminar impurities.

Following this, emulsification is carried out, optionally with a bleaching process, then a thickening and a thinning process before the resulting half-stuff is taken to a paper making machine.

When carrying out the process it is the combination of the individual devices within the installation for used paper upgrading that produces a half-stuff of high quality suitable for the manufacture of graphic papers, especially those with a proportion of upgraded used paper ranging from 30 to 100%.

For the upgrading process primarily used paper is employed which is obtained mainly from households. Newspapers, periodicals and paper and cardboard wastes in general and unsorted goods are included therein. These so-called household collection goods generally also comprise rear pasted periodicals with proportions of plastic, e.g. advertising stickers, and further impurities such as paper clips, screws, string, crushed aluminium, sand and gravel.

Wastes from printing shops, illustrated magazines which have been cut up, heavy weight papers, brochures, catalogs, etc. as well as used paper in sorted form, are also suitable for reprocessing.

In one preferred mode of execution of the process according to the invention shown in Figures 2a and 2b, the used paper bails arrive in a high pulp density pulper 1. With the addition of water and chemicals, especially sodium hydroxide solution, chelating agent, foamer and collector, the used paper is carefully dissolved. The pulp density in the pulper is preferably from 12 to 18%.

Then the paper pulp is moved to a vat 2, where it swells for one hour. Then the paper pulp with a pulp density of about 4.5% arrives at the coarse sorter drum 3, where the separation out of the heavy pulp impurities takes place. Passing through a vat 4 the paper pulp having a solid substance content of about 2.9%, then arrives in a thick pulp centrifuge 5, in which again heavy pulp impurities are separated out. Then in the sorters 6, a first fine sorting stage I is carried out. The paper pulp now has a density of about 2.3%. As the fine sorters, it is expedient to use horizontal sorters which are equipped with slit-type cages.

In the fine sorting stage I, the slit width amounts preferably to 0.3 mm. A secondary flow of waste pulp from this fine sorting stage passes through vat 9 to a resorter 7, whilst the sorted pulp passes to a level box 10 to a second fine sorting stage II using the sorters 11. It is preferable to use horizontal sorters equipped with slit-type cages as the sorters 1 The slit width in the fine sorting stage II is 0.2 mm. The paper pulp in this sorting stage has a solids content of about 1.3%. The waste pulp from fine sorting stage II is also taken through vat 9 to the resorter 7.

The fine sorting stages I and II are followed by the de-inking process which is carried out in vertical floatation towers 12 and 13. The substances removed are stored in a vat 14 and separated in a decanter 1 5. During the de-inking process no further chemicals, in particular no bleaching chemicals, are added. The de-inking process is followed by a vat 1 6 and a further sorting stage which is primarily intended to sort out laminar impurities by means of a perforated screen. This sorting process takes place in a sorter 1 7 to which a further sorter 1 8 is connected for waste re-sorting purposes, and sorter 1 8 is expediently also equipped with a perforated screen. It is however possible to equip this sorter 18 with a slit-type screen.

Following sorter 1 7, by means of a disk filter 19, thickening of the paper pulp to about 12% is undertaken followed by thinning to about 4%.

Passing through a vat 21, the pulp reaches a screen press 22 where the paper pulp is thickened to a condition having about 25 to 30% of solids content. With a concentration of up to 30%, the paper pulp then arrives in an emulsifier 23. Here it is treated with hot steam. After the emulsifier treatment the pulp stream is divided by means of a distributor coil. For the manufacture of graphic papers the pulp stream is thinned in pulper stage 24, passes a vat 25, has chemicals added in stage 26 and finally arrives at a bleaching tower 27, in which hydrosulphite bleaching is carried out. After thickening by the screen press 28 to about 25% and subsequent thinning in a pulper stage 30, the upgraded halfstuff arrives via vats 31 and 32 at a paper machine.

For the manufacture of recycling papers however, the bleaching treatment can be dispensed with, and the pulp stream then arrives after the emulsifier 23 via a pulper 30 directly at a paper machine.

Separated material from resorters 7 and 1 8 is mixed in an agitator 8.

The initial dissolution of the used paper in the form of bails takes place in a pulp solvent. It is preferable to use a pulp solvent which possesses an extraordinarily strong solvent capabiiity and operates in a consistency range of more than 10%, preferably 12 to 13% related to used paper employed in an absolutely dry state.

Preferably, the pulp dissolver used is a high pulp density pulper 1 which is capable of dissolving the used paper so that it is speck-free and is carefully processed. The core of a preferred pulp dissolver can be a dissolver member which rotates at low rpm and is helical in form. This dissolver member is so designed that the pulp is very carefully dissolved in slow motion and that a pulverisation of foreign bodies is avoided. Due to the large contact surface of the dissolver member with the raw material an operation with high working consistency is made possible. Because of the high pulp density of the pulper preferably there arises a fiber-to-fiber friction, which ensures a careful dissolution of the paper pulp. Such a fiber-to-fiber friction is to be preferred to a primarily stirrer/fiber friction.

Particularly suitable is the use of a discontinuously working high pulp density pulper such as is made by the firm Lamort.

The use of fiber-fiber-friction energy such as primarily occurs with the pulper is also of significance in the dissolution of print colours, which are well dissolved in this manner.

Use of a pulp dissolver with a rotating helicaltype dissolver member and the fiber friction ensured thereby provide effective protection of the paper fiber and avoid pulverization of foreign bodies.

An important feature is the avoidance of the pulverization of impurities, because pulverized impurities are far more difficult to remove in the subsequent sorting process and can no longer be wholly removed from the half-stuff. Therefore the process in particular aims to ensure that the impurities are separated out at a relatively high concentration of thick pulp and at an early point in time.

Because of the above-named high pulp density pulper there is also a substantial reduction of the dissolving time as well as a reduction of the quantity of chemical additives which in turn avoids to a large extent harmful influences on the paper fiber itself.

In the high pulp density pulper 1 the fiber bundles are activated to the extent that they decompose into individual fibers. In order to accelerate the dissolution of the used paper, lyes are added to the pulper, preferably sodium lye, and chelating agents such as for example diethylene triamine pentacetic acid (DTPA), as well as the usual firming agents and collectors are added. Preferably 50% sodium hydroxide solution is added until the concentration in the pulper amounts to 2% by weight based on the weight of the fiber. Chelating agents are used in a concentration of from 0.2 to 0.5% by weight, preferably 0.3% by weight, firming agents in proportions of from 0.2 to 0.6% by weight preferably 0.4% by weight, and collectors in a concentration of from 0.1 % by weight (based on the paper).

In general the work is based on dissolution times of 10 to 60 minutes, preferably 1 5 to 20 minutes which are non-continuous in the pulp dissolver. The temperature in the high pulp density pulper amounts preferably to from 40 to 550C.

After dissolution in the pulp dissolver a speckfree paper pulp is obtained. Longer dissolution times in the high pulp density pulper are less suitable, because in that case the harmful substances, such as adhesives etc. are pulverized and then later they can only be removed from the paper pulp with difficulty.

After dissolution in the pulper the paper pulp is placed in the collector vat 2 to swell for about one hour.

An important feature of the process is the fact that the operation is carried out without the use of despeckers. Due to the complete dissolution in the high pulp density pulper 1 there is no need for the despecking of the paper pulp. Thus the disadvantages of the despecking process are also avoided, which consist in particular of the fact that particles of adhesives etc. are pulverized and subsequently cannot be separated out to an adequate degree. From the swelling vats 2, a stoppage-free pump conveys the paper pulp at a concentration of from 4 to 6% of pulp density to the sorting drum 3, in which impurities such as string, plastic bags, screws, wires, adhesive residues etc., are separated out.

As the sorting drum 3, advantageously a conventional drum can be used with a perforation magnitude of from 6 to 12 mm preferably 6 mm, which makes it possible to separate out the above-named heavy materials.

A further separation of the heavy materials then preferably takes place by means of the thick pulp centrifuge 5.

In accordance with the recognition that during the pulp dissolution the non-pulverized harmful substances must be removed as early as possible from the paper pulp, so that the subsequent process can be carried out with a higher degree of efficiency and the possibility of pulverization of the harmful substances in this process stage can be largely avoided, the process then provides for fine sorting to take place directly after the separation out of the heavy materials. For fine sorting of the paper pulp it is preferable to use a horizontal sorter, which is opertaed with a pulp consistency of from 2 to 6%, preferably at 2.8 to 3.5%. The horizontal sorters 6, 11 used with advantage in the process have a centripetal modus operandi and are operated without additional thinning at very small slit widths. Such sorters are sold as horizontal sorters with an enclosed rotor by the firm Lamort.

The horizontal sorter used in the process is preferably equipped in this sortering stage with a slit cage. Here the work is conducted with slit widths of from 0.3 to 0.6 mm, preferably 0.3 mm.

The horizontal sorter which is preferably equipped with an enclosed rotor avoids "spinnings". The device operates with a low take off of waste pulp, which amounts with the centripetal method of working to a maximum of 5 to 10%. Thus no thickening of the waste pulp takes place.

An important feature of the horizontal sorter used consists expediently of the fact that the rotor, which keeps the screen free, is on the good pulp side of the screen, and therefore it does not strike the adhesive particles which have not yet been separated out and consequently it does not pulverize them.

The pulp density amounts in the abovementioned fine sorting stage preferably to from 2.5 to 3.5%. After the above-mentioned fine sorting stage 6, which is designated as fine sorting I, optionally a further fine sorting (fine sorting II) may follow. The fine sorting II is also carried out with a horizontal sorter 11 of the same design and with centripetal modus operandi.

Before the paper pulp arrives at fine sorting II, it is thinned to from 1 to 2.5%, preferably 1.5% pulp density. The fine sorting stage II is carried out with slit cages 7 having a slit width of 0.2 to 0.3 mm, preferably of 0.2 mm. By means of fine sorting stage II, a further separation out of the non-pulverized harmful substances is attained.

The waste pulp of both fine sorting stages, which can be kept in each case at maximum of 1 0% of the inflow, is then supplied to the resorter 7. Here again the sorting takes place using slits of preferably 0.3 mm or 0.2 mm slit width. After the good pulp has passed through the resorter 11, it is again led back to fine sorting stage I. Preferably the sorters 6 and 11 of fine sorting stages I and II, as well as the re-sorting horizontal sorter 7 are of the same type, in which the rotor to keep the screen free is located on the good pulp side thereof.

Due to the fine sorting of the paper pulp which follows directly on the dissolution process, as well as the treatment of the waste pulp obtained thereby in resorters 7 and the return of the good pulp obtained therefrom to sorting stage I, an especially effective separation out of harmful substances is achieved in an early stage of the upgrading of the used paper. Since in addition the work is carried out with a relatively high pulp consistency, the devices for carrying out this part of the process require lower investment costs and less energy expenditure in comparison with the resorting stages accomplished according to the prior art, which to some extent are performed in costly cascade circuits, whereby the impurities to be separated out are either concentrated or are separated out in vibration sorters.

After the sorting stages I and II, there follows the de-inking of the paper pulp. In the de-inking installation 12, 13 the print colors are floated out preferably in de-inking towers from the pulp suspension. The use of a de-inking installation having vertical de-inking cells, such as are sold by the firm FELDM HLE-LAMORT, is advantageous.

During the de-inking process no further chemicals are added. This means that the paper pulp only contains the chemical added in the high pulp density pulper as well as the firming agents added in a later process stage (a further 0.4% by weight).

It is particularly advantageous that the use of bleaching chemicals can be avoided in the deinking process. The use of bleaching chemicals in this process stage is not excluded, but it also provides the opportunity to operate the process in the de-inking stage without the use of bleaching chemicals. However, at a later time after the emulsion process a bleaching treatment can follow, to the extent that this is desirable. In this case the bleaching is carried out using hydrosulphite.

The avoidance of the addition of peroxides for bleaching the paper pulp according to the process is an advantage in several ways: 1. The peroxide damages the paper fiber which can be largely avoided by the use of e.g. hydrosulphite. In this way the process provides a more protective treatment of the paper fiber.

2. The use of hydrogen peroxide or of peroxide salts causes problems in the purification of the effluent.

Since, according to the invention, the de-inking process is carried out after the fine sorting of the paper pulp, i.e. with a substantial degree of absence of impurities, the elimination of print colors can be carried out with substantially greater efficiency.

Since moreover under the conditions named the work can be effected in the range of a pulp density of from 1 to 2.5%, the de-inking installation saves space and also requires a relatively low energy consumption. Because of the removal by suction of the print color foam, the pulp loss is so small that according to the invention no secondary stage is necessary.

Because of the smaller design of the de-inking installation there are also savings in investment costs.

Optionally the first de-inking installation 12 can be followed by the second de-inking installation 13.

In the de-inking process, a degree of whiteness is by comparison with the half-stuff obtained conventionally from used paper under comparable conditions, of a high order.

After the de-inking process the paper pulp is thinned to from 0.8 to 1.5% and then again it is led to a pressure sorter 1 7 equipped with a perforated screen. The pressure sorter is used for the separation of the laminar thin impurities which could pass through the fine slits of the fine sorting stages I and II. It is preferable to work with perforated screens having a perforation diameter of 1.6 mm.

The concentration of the reject obtained during resorting can be carried out by means of the sorter 1 8 with the same perforation pattern of 1.6 mm.

By means of the disk filter 1 9 the thickening of the pulp is then undertaken to about 12% solid pulp content, and thereafter it is thinned to 4- 6%; then by means of the screen press 22 it is concentrated to from 20 to 32% of solid pulp content, preferably 28 to 30%.

Thereafter the paper pulp is treated in the emulsifier 23 at about 90 to 1000C. In the emulsifier 23 the pulp is processed using hot steam, preferably without the addition of chemicals. The use of an emulsion installation, such as is sold by the firm ESCHER WISS, is particularly suitable. Then the heating is undertaken without pressure in the heating coil.

In the emulsifier, the impurities and soft unformed adhesives, to the extent that such are present, are finely ground and the bonding capacity of the pulp is then reactivated in a manner protective of the fibers. Due to the far reaching pulverization of the adhesive particles, they are evenly distributed throughout the paper pulp; later they do not come to the surface of the paper, so that they cannot develop any adhesive power there.

The physical strength values of the final product, i.e. for example the breaking length, bursting pressure etc., are not disadvantageously influenced by the emulsion treatment.

Then the pulp stream can be divided by means of a distributor coil: a) for the manufacture of recycling papers, the half-stuff is used in an unbleached state.

b) for the manufacture of white or colored graphic papers, i.e. writing and printing papers, a bleaching treatment preferably carried out with hydrosulphite is then employed.

To carry out the bleaching process the pulp stream is thinned to about 5%, and passes through the bleaching tower 27 with the addition of a fiber protective bleaching agent, especially hydrosulphite. After the rethickening process the unused chemicals are recycled into the circuit.

Regardless of whether a bleaching process is carried out or not, the paper pulp is then thinned to a lower concentration, advantageously from 0.6 to 1.2%, before it is used on the paper machine.

Moreover, the process also comprises the economic recycling of process water via vats 20 and 29. the preferred circuits for the recycling of the water can be seen in dashed lines in Figures 2a and 2b.

The percentages shown in Figures 2a and 2b refer to the consistency of the paper pulp, i.e. the percentage proportion by weight of dry paper fiber.

The half-stuff obtained by the process according to the invention, which can have a whiteness degree of 62% and more when a bleaching process is carried out, is suitable for the manufacture of graphic papers, such as writing paper, printing paper and tabulating papers, and especially it is also possible to use the half-stuff obtained for the manufacture of format papers, which may be satined format papers.

The half-stuff obtained by the process according to the invention can be used in proportions of up to 100% for the manufacture of recycled paper, e.g. high quality graphic paper. It is preferable to use the half-stuff in proportions of from 30 two 100%.

Claims

1. A process for the upgrading of used paper to obtain a half-stuff which is suitable for the manufacture of recycled paper e.g. graphic paper, in which the following steps are performed: (a) dissolution of the used paper to form a pulp; (b) coarse sorting; (c) fine sorting; (d) subsequent deinking; (e) dewatering; and (f) emulsifying.

2. A process according to claim 1 wherein the step (a) results in a substantially speck-free pulp.

3. A process according to any one of claims 1 or 2 in which step (a) provides a high fiber-to-fiber friction, which favors dissolution in a manner protective of the fibers and largely avoids the pulverization of impurities.

4. A process according to any one of claims 1 to 3 wherein step (a) is carried out by a high pulp density pulper.

5. A process according to claim 4 wherein said pulper has a helical stirrer arranged to rotate at low rpm.

6. A process according to claim 4 or 5 in which said pulper operates non-continuously.

7. A process according to any one of claims 1 to 6 in which step (a) is carried out at a pulp density of from 12% to 18%.

8. A process according to any one of claims 1 to 7 in which step (a) is carried out for a period of from 15 to 20 minutes.

9. A process according to any one of claims 1 to 8 in which step (a) is carried out at a temperature in the range of from 400C to 550C.

10. A process according to any one of claims 1 to 9 in which to the paper pulp in step (a) the following are added: sodium hydroxide solution in a concentration of 2%, chelating agent in a concentration of 0.3%, firming agent in a concentration of 0.4% and collector in a concentration of 0.1%, respectively based on the weight of dry used paper employed.

11. A process according to any one of claims 1 to 10 wherein step (b) is carried out by a sorting drum and a centrifuge.

12. A process according to claim 11 wherein the sorting drum has a perforation size of 6 mm.

13. A process according to any one of claims 1 to 12 in which step (c) is carried out at a pulp density in the range from 2.5% to 7%.

14. A process according to any one of claims 1 to 1 2 in which step (c) comprises at least two sorting stages.

1 5. A process according to claim 14 in which the first stage is carried out at a pulp density in the range from 2.5% to 7% and the second stage is carried out at a pulp density in the range from 1% to 2.5%.

1 6. A process according to claim 1 5 in which the pulp density in the first stage is in the range from 2.5% to 3.5%.

1 7. A process according to claim 15 or 16 wherein the pulp density in the second fine sorting stage amounts to from 1.5% to 2.5%.

18. A process according to claim 14 or 15 wherein sorters with slit-type cages are used for said fine sorting stages.

1 9. A process according to claim 18 wherein the fine sorters are horizontal sorters.

20. A process according to claim 18 or 19 in which for the first fine sorting stage a slit-type cage is used which has a slit width of 0.3 mm.

21. A process according to claim 1 8, 19 or 20 in which for the second fine sorting stage aslit- type cage is used which has a slit width of 0.2 mm.

22. A process according to any one of claims 14 to 21 in which the fine sorting stages utilise a rotor which, in order to keep the screen free, operates on its good pulp side.

23. A process according to any one of claims 14 to 22 in which the waste pulp separated out in said fine sorting stages is led in each case to a resorter, which is preferably equipped with a slittype cage having the same slit width as in the previous fine sorting stage, and then the good pulp is returned to the first fine sorting stage.

24. A process according to any one of claims 1 to 23 in which step (d) is carred out as a flotation process without the addition of bleaching agents.

25. A process according to any one of claims 1 to 24 in which the upgrading of the used paper takes place without the employment of despeckers.

26. A process according to any one of claims 1 to 25 in which a further sorting step is performed after said de-inking step.

27. A process according to any one of claims 1 to 26 in which step (e) includes a thickening step and a pressing step.

28. A process according to any one of claims 1 to 27 in which the pressing step of step (e) is carried out by means of a perforated screen.

29. A process according to claim 28 in which the perforated screen has a perforation size of 1.6 mm diameter.

30. A process according to any one of claims 1 to 29 in which step (f) is carried out by means of steam and without the addition of chemicals at a temperature from 90 to 1000C.

31. A process according to any one of claims 1 to 30 in which a bleaching step follows step (f).

32. A process according to claim 31 wherein said bleaching of the good pulpis carried out using hydrosulphite.

33. A process according to any one of claims 1 to 32 in which thickening and thinning steps follow step (f).

34. A process according to claim 33 wherein said thickening takes place using a disk filter to about 12%, followed by thinning to from 4 to 6%, and then a further thickening on the screen press to from 25 to 30% pulp density.

35. A process according to claim 33 or 34 in which the wash water obtained during the thickening process is recycled.

36. A process according to any one of claims 1 to 35 in which household waste, cut up illustrated magazines, printed waste, print rejects and/or mixed and sorted used paper are employed as said used paper.

37. Apparatus for carrying out the process according to claim 1 comprising: means for forming a pulp from used paper; means for coarse sorting; means for fine sorting; means for deinking pulp which has been fine-sorted; means for dewatering; and means for emulsifying.

38. Half-stuff produced by the process of any one of claims 1 to 36 or by the apparatus of claim 37.

39. Use of the half-stuff obtained according to claim 38 for the manufacture of format papers.

40. Use of the half-stuff obtained according to claim 38 for the manufacture of graphic papers.

41. Use according to claim 39 or 40 in which a proportion of from 30 to 100% of the upgraded used paper is added.

42. A method of manufacturing paper in which half-stuff is produced by the method of any one of claims 1 to 36 and is supplied to a paper manufacturing machine.

43. Paper manufactured by the method of claim 42.

44. A process for the upgrading of paper, and/or the use thereof, substantially as hereinbefore described.