Method for making crepe paper

Abstract

Method for producing creped paper characterised by feeding a creping machine (2) with a paper web (4) which has a dryness level between 70% and 95%, preferably between 80% and 90% and is extensible by at least 5% in the transverse direction CD.

Description

[0001] 1

[0002] METHOD FOR MAKING CREPE PAPER.

[0003] The present invention relates to a method for producing creped paper and more particularly to a method for producing creped paper which is also extensible in the transverse direction (Cross Direction or CD).

[0004] Methods for producing creped paper are known, described for example in GB 1016486, in CA 809925, in US 3507745 and in US 4090385. In particular, these known methods provide that a web of paper in formation, having a dry content of between 40% and 55%, is made to adhere to a rotating drying cylinder and, after having been brought to a dry content of between 70% and 95%, is subjected to the action of a blade or doctor blade, which presses with one of its edges against the surface of the cylinder and with the rotation of this detaches the paper web from this surface and at the same time forms in it a series of small transverse folds with characteristics linked to the degree of adhesion of the paper to the shell of the cylinder, to the characteristics of the blade, to its arrangement with respect to the cylinder, to the material from which both are made, to the force with which the blade presses on the cylinder, to the temperature of the cylinder, to the shape and dimensions of the final tooth of the blade, to the dry content of the paper web. to the peripheral speed of the cylinder surface, to which the paper web adheres, and essentially to a series of construction and operating parameters of the creping machine and its operating method.

[0005] These well-known methods of producing creped paper are still in use and are widely used, although they have revealed some drawbacks, which the present invention aims to eliminate.

[0006] A drawback of this well-known method is that it allows to obtain creped papers having a certain extensibility in MD, but since this extensibility is due exclusively to the unfolding of the small folds that determine the crepe of the paper and develop in a transversal direction, they evidently lead to a significant extensibility of the paper only in MD and therefore an almost zero extensibility in CD, since it is practically equal to that of the normal paper introduced at the input, i.e. generally less than 4%.

[0007] Another drawback consists is that the adhesion of the paper web being formed to the drying cylinder requires a certain pressure of the blade against the surface of the cylinder itself to detach the web from it and to crepe it; and this pressure in turn causes a high and progressive wear of the blade and at the same time a deterioration of the surface of the drying cylinder. This results in the need for periodic replacement of the worn crepe blade and periodic grinding of the drying cylinder, with significant costs, linked to the direct cost of the blade, the direct cost of labor for its replacement and for the grinding of the cylinder by specialized personnel, and the indirect cost linked to the 701 .2345

[0008] 2 loss of production due to the need to stop the plant for the entire time required for these maintenance interventions and for the restoration of normal operating conditions.

[0009] In order to try to overcome this problem and in particular to try to make the adhesion of the paper web being formed to the drying cylinder more regular and to facilitate its subsequent detachment by the creping blade, it has already been proposed to use chemical products (well known to those skilled in the art), which however increase the final cost of the creped paper thus obtained.

[0010] Another drawback related to the characteristics of crepe paper obtained with the known methods consists in the fact that if it is subjected to traction, it stretches with a certain ease thanks to the unfolding of the transverse folds formed in the creping machine, but if the traction continues after the folds have been completely relaxed, it tears.

[0011] Aim of the invention is to propose a method capable of eliminating all the drawbacks mentioned above.

[0012] In particular, an aim of the invention is to propose a method for producing creped paper that, in addition to being extensible in MD, is also extensible in CD.

[0013] Another aim of the invention is to propose a method for producing creped paper that requires a lower frequency of maintenance interventions on the creping machine than the current frequency.

[0014] Another aim of the invention is to propose a method that allows to obtain paper capable of withstanding without tearing a stretching in the MD direction that extends beyond the unfolding of the folds of the creped paper.

[0015] Another aim of the invention is to propose a method that, with the same product obtained, involves lower production costs.

[0016] Another aim of the invention is to propose a method that can also be implemented with traditional creping machines.

[0017] All these aims and others which will result from the following description can be achieved according to the invention with a method for producing creped paper as defined in claim 1 and with a creped paper web as defined in claim 7.

[0018] The present invention is further clarified below in some of its preferred forms of practical and non-limiting embodiment with reference to the attached table of drawings in which:

[0019] Figure 1 shows a block diagram illustrating the successive phases of the method according to the invention in a first embodiment,

[0020] Figure 2 shows it in a second embodiment, and

[0021] Figure 3 shows it in a third embodiment. 701 .2345

[0022] 3

[0023] As can be seen from the figures, the method according to the invention consists in feeding a traditional creping machine 2 with a paper tape 4 that is extensible by at least 5% in CD.

[0024] The creping machine 2 is traditional and is of the type described for example in US 3507745; it comprises a large diameter metal drying cylinder 6, which is fed with a paper web 4, and a blade 8, which is held with an edge adhering to the rotating cylindrical surface of the cylinder 6 so as to continuously detach the paper web 10, which meets the blade itself, and at the same time to form in it a plurality of small transverse folds with characteristics linked to a series of factors, which in turn are linked both to characteristics of the creping machine 2 and to process parameters, including the degree of dryness of the extensible paper web 4, the peripheral speed of the cylinder 6 with respect to the fixed blade 8, the pressure with which the blade 8 is pressed against the surface of the cylinder 6, etc.

[0025] From an operational point of view, it has been found that when the paper web 4 impacts against the edge of the blade 8, it essentially undergoes three effects: the first is a sort of compaction in MD, the second is its detachment from the cylinder 6; the third is the formation in it of a sequence of small transverse folds, which are due to the effect of the detachment of the paper tape from the cylinder 6.

[0026] However, the fact of feeding the creping machine 2 with a paper web 4, which unlike the paper that traditionally feeds a creping machine 2 does not consist of a normal paper web but of a normal paper web 12 previously subjected to a treatment 14 to be made extensible in CD, in particular as disclosed in EP 2326501 , means that at the exit of the creping machine there is a paper web 10 that is extensible both in CD (due to the properties of the paper fed to the creping machine 2) and in M D (due to the crepe-making caused by the blade 8 of the creping machine 2) and this allows to obtain, with a traditional creping machine, which is generally configured to produce only paper extensible in MD, paper that is extensible in both MD and CD and, in essence, paper that is extensible in all directions.

[0027] The fact that the creping machine 2 is fed with a paper web 4, which is extensible in CD, and that generally the surface of all extensible papers is rougher than that of the non-extensible papers normally used to produce creped papers, implies that the contact with the surface of the cylinder is not continuous, but discontinuous and makes it easier to detach the paper web 4 from the surface of the cylinder. Consequently, less pressure is required from the blade 8 against the surface of the cylinder 6 than would be required if the feed had been carried out with non-extensible paper and 701 .2345

[0028] 4 consequently less energy is consumed to carry out the creping, as well as less wear of both the blade 8 and the surface of the cylinder 6.

[0029] In turn, the reduced stress on the creping blade 8 reduces the maintenance that must be carried out on both the blade 8 and the cylinder 6 for the same paper production capacity with a predefined final degree of extensibility.

[0030] Since traditional chemical products that regulate the adhesion / detachment of the paper to / from the cylinder 6 are usually used to facilitate the detachment of the paper from the cylinder 6 by the blade 8 on the surface of the cylinder, the smaller extension of the effective contact surface existing between the surface of the cylinder 6 and the paper web 4 allows the use of chemical products to be significantly reduced and in certain cases eliminated.

[0031] In a different embodiment of the method according to the invention (fig. 2) the paper web 4, which is fed to the creping machine 2, is also extensible in MD. In this case the creped paper obtained 10, in addition to presenting an extensibility in the transverse direction CD, also presents a greater extensibility in MD than that which would have been obtained if the creping machine had been fed with paper extensible only in CD, since the extensibility of the paper 10 in MD is due not only to the unfolding of the folds, but also to the extensibility in MD of the paper web 4 fed and is expressed beyond the unfolding of the folds and to a greater extent the greater the extensibility in MD of the paper itself.

[0032] More particularly, a paper web 12 coming from a traditional paper machine and has been brought to have a dry content of for example around 50%, is submitted to a treatment, as disclosed for example in EP 2326501 , to be made extensible in CD and then, after being brought to have a dry content of for example around 70%, is submitted to a treatment, as disclosed for example in EP 3024977, to be extensible also in MD and subsequently is submitted to the treatment in the creping machine 2.

[0033] In both embodiments described above, the paper web 4, which is fed to the creping machine 2 and which can be, as seen, either CD-only extensible or CD- and MD-extensible, comes from a paper machine, followed by a specific transverse compaction station 14 and possibly a longitudinal compaction station 16 of the still plasmable web 12 being formed.

[0034] In some cases it is also envisaged that the paper web 4, which is fed to the creping machine 2, is only extensible in MD, and in this case the method according to the invention allows to obtain a creped paper web 10 which has a greater extensibility in MD than that due only to the unfolding of the folds, and this greater extensibility is 701 .2345

[0035] 5 obtained with a lower consumption of energy and chemical products than that required to obtain a similar extensibility starting from a normal paper web.

[0036] In a third embodiment of the method according to the invention (fig. 3) the extensible paper web 4 that is fed to the creping machine 2 comes from a pre-formed reel 20, from which the web itself is unwound to be fed to the creping machine 2. Since, however, the dry content of the web unwound from the reel 20 may not be suitable for its treatment in the creping machine 2, it may advantageously be foreseen that it passes through a wetting station 22 to be subjected to traditional wetting techniques (spraying, contact with a wetting roller, etc. ) and be brought to an optimal dry content for creping, in particular to a dry content of between 70% and 90%. The paper web unwound from the reel 20 may be extensible in CD and / or MD, depending on the final product that is desired to be obtained.

[0037] Regardless of the particular form of implementation described above, the method according to the invention has proven to be particularly advantageous because: It allows to produce extensible creped paper in MD and CD and essentially creped paper that had never been made before,

[0038] It allows to produce creped paper which, with the same total extensibility compared to traditional creped paper, can be obtained with lower energy consumption and lower consumption of chemical products,

[0039] It allows to produce creped paper which, with the same total extensibility compared to the creped papers currently obtainable, can be obtained with a significant reduction in maintenance interventions, and in particular in blade replacement and cylinder grinding, against which the blade is pressed during the creping work, It allows to produce creped paper which, compared to traditional creped papers, has revealed in experimental tests to be softer, less noisy when crumpled, more voluminous and has a higher capacity for absorbing liquids,

[0040] It allows to produce creped paper which, after being extended by unfolding the folds, can be further extended without tearing, thanks to its initial extensibility, allows it to be implemented with traditional paper creping plants.

[0041] The paper obtained with the method according to the invention, in particular when obtained from CD and MD extensible paper, offers considerable possibilities for use both in sectors in which traditional creped papers cannot be used, and in sectors in which traditional creped papers can be used but with inferior results compared to those obtainable with creped papers according to the invention.

[0042] In particular, the creped paper according to the invention finds an advantageous use for wrapping irregularly shaped objects placed on pallets, since, thanks to its 701 .2345

[0043] 6 extensibility in MD and CD, it allows it to be made to adhere to objects even of irregular shape and to keep them compacted together and stabilized during pallet movements. This use is advantageous, for example, for keeping objects / products in general grouped together, in particular for forming multipacks of bottles, yoghurt packages, etc.

[0044] Furthermore, the creped paper according to the invention can be advantageously used to wrap individual objects, even irregularly shaped ones, for example to wrap gifts.

[0045] As regards the uses that are already possible with traditional creped papers, in particular health uses (toilet paper, diapers, etc.), these are more valid if carried out with the creped paper according to the invention due to the improved characteristics that it presents in terms of softness, absorbency and extensibility. Indeed, thanks to the extensibility even in CD, not present in traditional creped papers, the creped paper according to the invention finds an advantageous use in sectors in which traditional creped papers cannot be used, for example to make disposable garments, in particular underwear for incontinent subjects.

[0046] The following examples will further clarify the invention.

[0047] EXAMPLE 1

[0048] A paper web 12 with a dryness of 69% was fed to a so-called Clupak unit , from which a paper web 4 came out, extensible at 8% in both CD and MD; this was then subjected to further drying and when its dryness reached 80%, it was fed to a creping machine 2, configured to confer itself an MD extensibility of 40% with the application of a pressure of 70 Nm to the blade 8. Thanks to the feeding with the paper web 4, having a certain surface roughness, a paper web 10 was obtained at the exit of the creping machine 2, extensible by 8% in CD and 60% in MD, even with a pressure applied to the blade of 50 Nm.

[0049] EXAMPLE 2

[0050] A paper web 12 with a dryness lof 55% was fed to a CD compacting unit 14, which resulted in a paper web 18 that was extensible by 12% in CD. This was then dried and when it reached a dryness level of 70% it was fed to a MD compacting unit 16, which resulted in a paper web 4 that was extensible by 12% in CD and 20% in MD. After this had been brought to a dryness level of 85% it was fed to a creping machine 2 configured to confer an extensibility of 40% in M D. At the exit of this a paper web 10 was obtained that was extensible by 12% in CD and 75% in MD.

[0051] EXAMPLE 3

[0052] A finished paper web having a degree of extensibility of 15% in MD was unwound from a reel and fed to a creping machine. Creping added a further MD extensibility of 701 .2345

[0053] 7

[0054] 30%. Given the presence of a certain surface roughness of the starting paper, it was possible to reduce by approximately 30% the pressure that the blade 8 exerted on the surface of the cylinder 6; the consequent reduction in wear, to which the blade 8 was subjected, allowed to increase by approximately 30% the time of use of the blade itself before its replacement was necessary.

Claims

701 .23458C L A I M S1 . Method for producing creped paper characterised by feeding a creping machine (2) with a paper web (4) which has a dryness level between 70% and 95%, preferably between 80% and 90% and is extensible by at least 5% in the transverse direction CD.

2. Method according to claim 1 characterised in that said creping machine (2) is fed with a paper web (4) having a dryness level between 70% and 95%, preferably between 80% and 90% and extensibility of at least 8% in the longitudinal direction MD and at least 5% in the transverse direction CD.

3. Method according to claim 1 and / or 2 characterised in that said creping machine (2) is fed with a paper tape (4) which comes out of a production line of CD and possibly also MD extensible paper.

4. Method according to one or more of the preceding claims characterised in that said creping machine (2) is fed with a web (4) of CD and / or MD extensible paper coming from a compacting station (14, 16) in turn fed by a paper machine.

5. Method according to one or more of claims 1 to 3 characterised in that said creping machine (2) is fed with a web (4) of extensible paper unwound from a reel (20) and previously passed through a wetting station (22) to be brought to an optimal dry content for creping.

6. Method according to claim 5 characterised in that said creping machine (2) is fed with a belt (4) exiting from said wetting station (22) and having a dry content between 70% and 90%.

7. Creped paper characterised by having a dry content of between 70% and 95%, preferably between 80% and 90% and being extensible by at least 5% in CD.

8. Creped paper according to claim 7 characterised in that it is also MD extensible by at least 5% more than its MD extensibility due to the unfolding of the transverse folds caused by the folding.

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