IE914553A1

IE914553A1 - Fibrous component for paper production, paper made therewith¹and use thereof and method for producing fibrous component¹and paper

Info

Publication number: IE914553A1
Application number: IE455391A
Authority: IE
Original assignee: Pwa Industriepapier Gmbh
Priority date: 1990-12-29
Filing date: 1991-12-23
Publication date: 1992-07-01
Also published as: FI916139A0; NO914956L; CA2058541A1; EP0493726A1; JPH04316688A; NO914956D0; DE4042221A1; FI916139A

Abstract

The processing of a fibrous composition, preferably of waste paper, is described, wherein particles of a thermoplastic are attached to the fibres, without causing interference with the paper production on the paper machine. The fibrous material is preferably used for producing raw paper for corrugated board. At the elevated temperatures in the machine for producing the corrugation for the corrugated board, the thermoplastic agglomerates in the paper and leads to an improvement in the properties of the corrugation and of the corrugated board produced therewith.

Description

Fibrous component for paper production, paper made therewith and use thereof and method for producing fibrous component and paper Descript ion The invention relates to a method for preparing a fibrous component for the production of paper, a method for paper production using such a fibrous component, a fibrous component prepared by said method, a paper produced by the paper producing method and a special use for such a paper.

In the context of this description, paper is to be understood to mean a material as is usually produced on known paper-making machines, this including apart from paper directly also cardboard and paperboard which differ from the actual paper essentially only in their higher weight per unit area, for which reason they can be included under the same term for the purpose of this description. Fibrous substances refers to substances which are substantially on a vegetable basis and have been produced preferably by chemical, or also semichemical or mechanical pulping from wood or other plant raw materials. These fibrous substances may also have the additives usual in paper making.

A paper is essentially fixed in its properties when it last leaves the paper-making machine after a drying operation, unless it is subsequently changed in the composition of the resulting overall product by adding other materials, for IE 9K4653 example certain coating agents or impregnating agents, this possibly resulting of course also in altered properties.

The physical fundamental behaviour of paper is governed decisively by the vegetable fibrous raw material of which it essentially consists, and the usual production method in which the fibres in aqueous suspension settle to form the sheet and during the subsequent drying are joined together by the formation of hydrogen bridges for the cohesion of the paper sheet. This production method has firstly the disadvantage that unless it has been previously treated with special wet-strength agents a paper usually disintegrates again into its fibrous constituents in the presence of water and possible additional action of mechanical energy. On the other hand, this is a great advantage for the reprocessing of waste paper and the biological decomposability of vegetable fibrous material from the point of view of environmental protection. Wet strength of papers is generally obtained by chemical additives which for example on drying of the paper harden irreversibly, or alternatively by subsequent waterresistant coatings. The choice of such additives which can be added to the pulp mixture before the paper-making machine is limited because these materials firstly must not prevent or appreciably disturb the hydrogen bridge formation in the sheet formation and secondly must not impair the production cycle in the paper-making machine, this impairment including primarily the tendency to stick, which makes the operation of any paper-making machine practically impossible.

These restrictions lead to the properties of a final product made from a paper not being influencable in any desired manner either. Although in many cases paper can be replaced by other materials, it is generally an economic IE 9W653 raw material and for environmental reasons is to be preferred because of its natural character.

The limits of the material paper are for example apparent in packaging boxes and crates made from corrugated board.

If fresh vegetables or the like are packed in corrugated cartons then even without leaving these structures standing in the rain it can still be determined that they lose their original stability on absorption off moisture. Even climatic differences lead to certain packed materials, for example fruit and vegetables, giving of moisture which is absorbed partly by the corrugated board and substantially reduces the dimensional stability and resistance to deformation thereof.

The invention is based on the problem of improving methods for the production of certain papers in such a manner that from the start additives are added to the pulp which do not disturb the paper-making operation but which enable end products to be made in which the paper itself has properties which it did not have on leaving the papermaking machine. This conversion however should nevertheless not prevent this paper being reprocessed as waste paper and in addition to the fibrous material the special additives are also to be subjectable to a regeneration .

This problem is solved according to the invention in that from the start additives are added to the paper which change their state or their influence on the paper properties only under the conditions under which a finished paper in the form it leaves the paper-making machine is further processed to higher quality intermediate or end products. These conditions for the further processing may for example be temperatures which lie above those achieved in the production of the paper up to the end of the paperIE 9145^ making machine. The decisive factor governing the economy of introducing such additives is that in the paper-making process said additives remain as far as possible substantially in the paper sheet and do not leave the fibrous structure again with the process water when the web is dewatered or drained, then concentrating themselves in the process water and generating further undesired waste water problems.

In the preferred embodiment the invention therefore starts with the very preparation of the pulp for the paper production and for this reason hereinafter the essential features of the total production method will be described without thereby impairing the protectabi1ίty of individual method steps and individual material features.

Intensive investigations have led to the result that certain thermoplasts, essentially polyethylene (PE) and polypropylene (PP), can be entrained directly from the material preparation under certain conditions through the paper-making machine into the finished dried paper in a state which does not disadvantageously affect the operation of the paper-making machine and also does not appreciably change the strength properties of the paper as it leaves the paper-making machine. If however such a paper is subjected to a deformation under increased temperature conditions as cannot occur in the paper-making process, these thermoplasts can be brought to agglomerate and this results not only in an increase in certain strength values in the dried state of the paper but also leads to a substantially smaller loss of stiffness and other properties being observed in the moist state. It has not yet been finally explained whether this possibly protects the hydrogen bridges in the fibrous structure or results in formation of an overlying stiffening structure.

It has further surprisingly been found that the thermoplasts mentioned under certain conditions in finely dispersed forms can apparently be attached to the fibres in a pulp suspension without thereby decisively impairing the ability of the fibres to form hydrogen bridges. It has been found that the thermoplast may even be introduced into the fibrous material in amounts of up to more than 50 % by weight with respect to the sum of fibrous material and thermoplast. Proportions up to 60 % by weight are admittedly possible; however, the operations are preferably carried out in the range between 30 and 50 % by weight if only a specific fibrous component, that is a specific fibrous component of the final mixture provided for the paper making, is coated with the thermoplast. The proportion of the thus modified fibrous material in the total pulp mixture is expediently between 2 and 10 %. For special requirements, the amount of thermoplast can of course be modified in accordance with the possibilities available .

The further description will proceed from a subcomponent of the total fibrous material provided for the paper production, said subcomponent being provided with the additive. The mixing together of this fibrous component with other components can take place in known manner in the material mixing station of a paper-making machine.

Investigations have shown that the thermoplast can accumulate well on the cellulose fibres if it is made available in finely ground form with grain sizes of 0.6 mm and less. Too fine a dispersion could lead to the fibre surfaces being covered too densely with the particles so that their ability to form hydrogen bridges would therefore be impaired. A preferred range for the grain size distribution is therefore between 0.05 and 0.5 mm.

The attachment of the thermoplast powder to the fibres requires a special temperature profile and is preferably carried out in a pulp beating unit usual in the paper industry, this preferably however being a beating unit with stone fittings, for example a stone twin-disc refiner. The thermoplast powder can be mixed into the fibrous material before the beating unit, but is preferably injected into the beating unit via its own entrance in metered amount.

The pulp consistency during beating may be between 6 and 15 % by weight abs. dry with respect to the suspension water, but is preferably in the region of 10 % and above.

The process of the attachment of the thermoplast particles to the fibres has not yet been investigated in detail . It would appear to take place at temperatures in the region of 100°C. Certainly, temperatures at which an agglomeration of the thermoplasts already occurs are to be avoided.

Since the fixation apparently does not take place on its own but under the mechanical influences of the beating unit, it is not necessary to keep the entire suspension at a corresponding temperature; on the contrary, temperature peaks which arise under the action of mechanical energy in the beating zones are apparently sufficient. The necessary temperature can therefore be controlled by the energy consumption of the beating unit. As an auxiliary step, of course, the pulp suspension can be brought to a possibly necessarv previous temperature. The correct energy introduction can be checked by investigating the substance component leaving the beating unit. If the temperature is too low the pulp suspension will contain too many free thermoplast particles. If the temperature is too high agglomeration of the thermoplasts already occurs and the effect thereof is likewise detectable on the fibrous material.

IE 914555s The beating unit is expediently followed by a fine sorting apparatus for the pulp suspension, the rejects of which also contain too coarse unbonded thermoplast constituents. Thermoplast rejects can result if the thermoplast powder contains fractions of too large a particle diameter. If a mill for grinding the thermoplast granulate is provided before the pulp beating unit in order to produce the thermoplast powder, said mill can be accordingly adjusted. The rejects from the fibrous material subsequent sorting can be reintroduced in front of the beating unit. The grinding of the granulate can take place in a dry state but also in a moist state.

As fibrous material for application of the thermoplast powder a long-fibre component is preferably provided because the latter can be still further increased in strength in the processing in the stone beating unit by fibrillation .

Advantageously, the fibrous material charged with thermoplast particles can be used in the production of corrugated board raw paper. Within the scope of this description corrugated board raw paper means the paper which serves to form the corrugation in the corrugated board. This corrugation, which is glued on both sides with a covering layer, must of course have adequate resistance to compression. The socalled C.MT value determined in a measuring method especially developed for that purpose is a measure of the crush resistance of the corrugation. In the production of corrugated board the corrugation is generated between heated fluted rolls. The temperatures of these rolls are about 170°C. Under these conditions, the thermoplasts provided in a corrugated board raw paper according to the invention agglomerate and impart to the corrugation an improved resistance to crushing and also a reduced drop of strength on absorbing moisture.

For making corrugated board raw paper, in the German Federal Republic at least waste paper is used to a great extent and for this reason paper factories for manufacturing corrugated board raw paper are generally equipped with waste paper processing plants. One objective in processing waste paper is to use in addition to sorted waste paper as obtained generally in bale form from the waste paper trade a certain amount of domestic or other waste as well. This of course leads to an increased proportion of separated waste materials which are not readily processable and which are divided into socalled heavy trash, which cannot be further processed, and light trash, which fundamentally contains raw materials which can be used again. For preparing this light trash in a parallel patent application a novel method has been proposed which can effectively reduce the total waste of a waste paper processing plant and at the end of which a fibrous component is collected which consists substantially of long fibrous material and a thermoplast granulate which to a slight extent still contains fibrous materials. It is an obvious step within the scope of the present invention to combine this fibrous component and at least a part of the accruing thermoplast granulate in the manner described to give the fibrous component according to the invention.

In this manner, in the waste paper processing itself by environment-compatible waste material regeneration a directly further processable half stuff is generated which, added in fractions to the remaining pulp, not only leads to the advantage according to the invention but also contributes to solving a serious environmental problem.

The further advantage resides in that in particular a corrugated paper made using the corrugated board raw paper according to the invention can be subjected to a regeneration again in the aforementioned processing plant.

When producing corrugated board raw paper using the fibrous or pulp component according to the invention it should be ensured that the temperatures in the dry section in the paper-making machine are not increased to such an extent that agglomeration of the thermoplast particles already occurs .

The thermoplasts contained in the corrugated board raw paper do not have any disadvantageous influences in the course of the paper-making process; nevertheless, under certain circumstances at the higher temperatures obtaining in the corrugated board manufacturing machine a sticking of the raw paper might occur. Consequently, a corrugated board raw paper according to the invention is preferably also surface-treated in a sizing press with starch in the paper-making machine, as is generally usual. By this starch application, the thermoplast particles disposed at the surface of the paper can be enveloped if necessary and thus deactivated, avoiding any sticking of the paper surface in the corrugated board manufacturing machine.

Hereinafter the configuration of the invention in accordance with the method thereof will be additionally explained with the aid of a flow chart attached as single Figure.

A paper fibrous material or pulp 4 is prepared in an intermediate vat 2. This fibrous material may be fresh paper pulp but preferably for the method described a regenerated fibrous material is used which has been obtained from the processing of waste paper. This fibrous material is continuously led to a beating unit 6. The beating unit 6 may for example be a twin-disc refiner of known design which is provided with stone fittings so that the fibrous material is subjected to a more fibrillating and less cutting treatment. The beating of the fibrous material or pulp in the refiner takes place at material densities of 6 % to 15 % abs. dry, preferably at material densities of 10 % abs. dry and above. In this state, the pulp slurry is no longer readily pumpable and for this reason it is indicated in pulpy form in the intermediate vat 2. Accordingly, the conveying of the fibrous material 4 into the beating unit is not by means of a pump but by means of a conveying screw 8.

Above the pulp beating unit 6 a supply container 10 for the thermoplast material is shown. This thermoplast material may be present in the form of fresh granulate but within the scope of the method described thermoplast material is preferred which is obtained from the regeneration of partially foil-coated waste paper. This thermoplast material consisting essentially of polyethylene and polypropylene is present preferably in dry form either as small flake particles as have resulted from the waste paper preparation or alternatively, if the thermoplast regenerating line is provided with a granulating apparatus at the end, the thermoplast material may also be available in the form of said granulate.

The thermoplast material 12 disposed in the supply container 10 is supplied in continuous metering to a mill 16 by means of a conveying screw 14 and in said mill is ground to a fine powder having a grain size of 0.6 mm and less. For tests, a fine mill of the company Condux of the type CGM 280 was successfully employed. The grinding may be carried out dry or also moist. In the case of dry grinding it may be expedient for the mill 16 to be followed by a dedusting cyclone.

The thermoplast powder emerging from the mill 16 is also introduced into the pulp beating unit 6 via a conduit 18.

At the elevated temperature in the beating region of the pulp beating unit 6 the thermoplast powder attaches itself to the cellulose fibres. The beaten fibrous material leaving the pulp beating unit 6 passes into a dilution vat 20 in which the fibrous material is diluted by adding diluting water 22 from the beaten pulp density to a sorting pulp density of about 1 % abs. dry. From samples of the fibrous material leaving the beating unit 6 it may be investigated whether adequate fixing of the thermoplast powder to the fibres has taken place. Should this not be the case, by increasing the energy consumption of the beating unit 6 the stuff temperature in the beating region can be increased in order to promote the fixing of the thermoplastic material to the fibres.

From the dilution vat 20 the fibrous material is conveyed by a pump 24 into a vertical screener 26 of known design. Suitable for example is a Voith vertical screener with a screen basket perforation of 0.25 inch. In this vertical screener components having a fineness or disintegration which still does not meet the requirements of paper making are separated out of the pulp suspension. This reject material is conducted back via a return conduit 28 into the intermediate vat 2 from whence it is again subjected to the beating treatment in the pulp beating unit 6. The material from the vertical screener 26 passes via a conduit 30 into a collecting vat 32 from whence said finished fibrous component charged with thermoplast is supplied to the manufacturing plant for corrugated board raw paper.

Tests have been carried out in which a long-fibre pulp was coated in the manner described above with thermoplast powder, in an amount of about 50 % thermoplast with respect to the total fibrous component, consisting of fibrous material and thermoplast material. Of this fibrous component, an amount of 2 % was added to a pulp obtained from waste paper for the production of corrugated board raw papers. On sample sheets subsequently subjected to a heat treatment of 170°C, compared with a blank sample increased values were determined for the crush resistance (CMT value) and the bursting pressure.

Claims

1. Paper, characterized in that it contains additives which are adapted to be transformed into a productimproving state only under the conditions of the further processing to higher-quality intermediate or final products.

2. Paper according to claim 1, characterized in that the additive is a substance improving the paper stiffness.

3. Paper according to claim 1 or 2, characterized in that the additive is a substance improving the wet strength or stiffness in the moist state.

4. Paper according to at least one of claims 1 to 3, characterized in that the product-improving properties are activatable by the action of a temperature which lies above the temperatures which were reached in the paper-making process.

5. Paper, in particular corrugated board raw paper according to at least one of claims 1 to 4, characterized in that the additive is a thermoplast.

6. Paper according to at least one of claims 1 to 5, characterized in that the additive is attached or fixed to paper fibres.

7. Paper according to claim 5 or claim 6, appended to claim 5, characterized in that the thermoplast is essentially polyethylene and/or polypropylene.

8. Paper according to at least one of claims 5 to 7, characterized in that the additive is contained in the paper in an amount of 0.4 to 6 % by weight.

9. Fibrous component for the production of a paper according to claim 1, characterized in that it contains additives which are adapted to be transformed to a product-improving state only under the conditions of the further processing of the paper to be made employing said additives to higher-quality intermediate or final products.

10. Fibrous component according to claim 9, characterized in that the additive is a substance improving the paper stiffness.

11. Fibrous component according to claim 9 or 10, characterized in that the additive is a substance improving the wet strength or stiffness in the moist state of the paper.

12. Fibrous component according to at least one of claims 9 to 11, characterized in that the product-improving properties are obtainable by the action of temperatures which lie above the temperatures reached in the paper making.

13. Fibrous component according to at least one of claims 9 to 12, characterized in that the additive is a thermoplast.

14. Fibrous component according to at least one of claims 9 to 13, characterized in that the additive is attached or fixed to at least part of the individual fibres of the fibrous material.

15. Fibrous component according to claim 13 or claim 14, appended to claim 13, characterized in that the thermoplast is essentially polyethylene and/or polypropylene .

16. Fibrous component according to at least one of claims 13 to 15, characterized in that the additive is added in amounts of 20 to 60 % by weight with respect to the sum of fibrous material and additive in the fibrous component.

17. Fibrous component according to claim 16, characterized in that the additive is added in amounts of 30 to 50 % by weight with respect to the sum of fibrous material and additive in the fibrous component.

18. Fibrous component according to at least one of claims 13 to 17, characterized in that the additive is a regenerate from waste paper processing.

19. Fibrous component according to at least one of claims 1 to 18, characterized in that the fibres are a fibre regenerate from waste paper processing.

20. Fibrous component according to claim 11, characterized in that the fibres are a long-fibre pulp partial regenerate from waste paper processing.

21. Method for preparing a fibrous component for the manufacture of paper, characterized in that there is added to the fibrous component disposed in a aqueous suspension before or during the beating of the fibres in a beating unit a finely dispersed additive which under the conditions of the beating is attached or fixed to the fibres without disadvantageously influencing the sheet-forming properties of the fibrous material.

22. Method according to claim 21, characterized in that the additive is a finely ground thermoplast in dry or moist state.

23. Method according to claim 22, characterized in that as thermoplast a regenerate from reprocessing of thermoplast-containing waste paper is used which consists essentially of polyethylene and/or polypropylene.

24. Method according to claim 22 or 23, characterized in that a thermoplast powder is used having a grain size of 0.6 mm and less.

25. Method according to at least one of claims 22 to 24, characterized in that the thermoplast powder is obtained by grinding a thermoplast granulate.

26. Method according to at least one of claims 22 to 25, characterized in that the thermoplast powder is added in amounts of 20 to 60 % by weight with respect to the sum of fibrous material and thermoplast powder.

27. Method according to claim 26, characterized in that the thermoplast powder is added in amounts of 30 to 50 % by weight with respect to the sum of fibrous material and thermoplast powder.

28. Method according to at least one of claims 21 to 27, characterized in that a beating apparatus with stone fittings is used.

29. Method according to at least one of claims 21 to 28, characterized in that the beating is to substance densities between 6 and 15 % by weight fibres in the suspension water.

30. Method according to at least one of claims 21 to 29, characterized in that as fibrous material a long-fibre generate from waste paper processing is used.

31. Method according to at least one of claims 21 to 30, characterized in that the fibrous material is subjected after the beating to a fine sorting and the reject component is returned in front of the beating unit.

32. Method according to at least one of claims 24 to 31, characterized in that the fixing of the thermoplast powder to the fibres is controlled by the process temperature in the beating region in such a manner that an attachment but no agglomeration takes place.

33. Method according to claim 32, characterized in that the control of the process temperature is regulated by the loading of the beating unit and if necessary additionally by the suspension temperature.

34. Method for producing corrugated board raw paper on a paper-making machine, characterized in that a proportion of a fibrous component according to one of claims 12 to 20 is admixed to the pulp mixture in front of the paper-making machine-.

35. Method according to claim 34, characterized in that a proportion of said fibrous component of 2 to 10 % by weight with respect to the dry theoretical total fibrous material is added.

36. Method according to claim 34 or 35, characterized in that the temperature in the dry section in the papermaking machine is regulated so that the thermoplast contained in said fibrous component does not agglomerate.

37. Method according to at least one of claims 34 to 36, characterized in that in the paper-making machine a surface sizing of the paper with starch is carried out.

38. Use of a paper according to any one of claims 5 to 8 for making corrugated board.

39. Paper according to any preceding claim substantially as hereinbefore described.

40. A fibrous component for the production of paper according to any preceding claim substantially as hereinbefore described.

41. A method for preparing a fibrous component for the manufacture of paper according to any preceding claim substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.