FI116080B - Cardboard product and process for its manufacture - Google Patents

Description

116080

Cardboard product and process for its manufacture

The invention relates to a coated paperboard product and its manufacture.

The object of the invention is to improve the quality of paperboard products, in particular cartonboard, and to make it economical.

The carton board is required to have a certain surface quality to ensure the desired gloss and print quality, stiffness and tear resistance to ensure that the package functions properly. In addition, as the board mill produces large quantities of board, efficient use of the raw material is important. These requirements are partly contradictory. Calendering the cardboard by squeezing it in a nipple, often soaked in some way and heated, provides sufficient gloss to the board. This pressing advantageously presses the fibers and coating of the paperboard surface smooth without, however, compressing the inner 15 layers of the paperboard. Compaction of the inner layer reduces the stiffness of the board and reduces the tear strength. This inner layer condensation is often referred to as the loss of a sweater. Bulk in this case refers to the inverse of the density, and thus its loss means compression of the paper or cardboard.

20 Because paper and board manufacturing is very resource-intensive, even small raw material savings offer a significant advantage over competitors. Percent savings can • ,; | in this sense already considers a considerable competitive advantage and the return on investment:. ,,:: payback time is short. Furthermore, saving the raw material is desirable from an environmental point of view.

•,: | The advantageous multiplier effects of the carton of this invention extend to boils. Thanks to its 25-vented design, the product's entire life cycle, due to its lower raw material consumption * * *, ·, results in lighter packaging, which ultimately also saves on transportation and reduced waste.

• ·: ,,, · Packaging cartons are often coated or multilayer. Typically:. . 30 Base paperboard consists of three layers of fiber with a top and back layer; * '': Bleached cellulose. The backing layer is often mechanical pulp, typically ground. '. (GW), but in many cases also pressure grit (PGW) and chemothermomechanical pulp [V (CTMP) or in addition to the hull layer. The cardboard surface is generally * · ♦ coated twice and the reverse side is coated once. The coating and adhesive 2 116080 are used to customize the properties as desired. Typically, the cartonboard has a basis weight range of 180 to 350 g / m2. The required basis weight depends on the rigidity required in the package, lighter cardboard is sufficient for small cases. By saving the cardboard sweats in the surface treatment and thereby making the stiffer carton 5, raw materials and energy are saved, since lower basis weight cardboard can be used. Typical applications for cardboard are cigarette packs, medicine packs, postcards, cardboard book covers, various food packaging.

Often, cartons are often ironed prior to coating with a Yankee drum that achieves good bulk and stiffness, good surface properties, as well as low dry shrinkage at the edges, however speed limits, hardware space requirements and the enormous size of a Yankee cylinder on a machine. Wet-stack calendering is another typical processing method, with problems of runnability and water application control, and because cardboard has to be dried before and after calendering, this causes extra cost.

The machine calender is often used in combination with other calendars, the machine calender being a hard calender with no rolls. The machine calender is not preferred to be used as the sole surface treatment method. A soft calender is a soft nip: '' ': a calender with a calendar roll surface that can be of hard wood:;': surface hardness but flexible.

I ·: It is an object of the present invention to provide a uniform printing surface, good gloss stiffness to the cartonboard with reduced material consumption, and to avoid production gaps and improve runnability by the method of the invention.

This object is achieved by the packaging board as claimed in claim 1.

; The coated packaging board according to the invention consists of one or more:: fibrous layers in which the surface layers are bleached cellulose and the inner layers:. 30 mechanical pulp or chemothermomechanical pulp or scrap.

. According to the invention, the carton board is treated with a long-nip canister before the cover *; ; 116080 3, as in the case of a Yankee cylinder, the process is not speed-limited. A long-nip calender suitable for making the carton of the invention is described, for example, in US Patent No. 6,164,198.

5, the structure of the long-nip calender suitable for surface treatment of the carton according to the invention will be described in greater detail with reference to the figures.

The solution achieves a significantly higher running speed than a board machine with a Yankee cylinder. In addition to improved runnability, this also contributes to improved quality and reduced wastage.

The following describes the carton suitable for surface treatment of a carton according to the invention.

Figure 1 is a sectional view of a long nip calender with a long nip between the closed shoe calender and the counter roll.

Fig. 1A is a partial enlargement of Fig. 1 Fig. 2A is a partial sectional view of the device of Fig. 1 in the axial direction of the roll, ': shows the drive mechanism; Figure 2B shows the operation of the press shoes in a longitudinal section.

A calender suitable for surface treatment of a carton according to the invention has a fixed support member 14, shown in Figures f 25 1-2, surrounded by a tubular jacket 12. The heated counter member 22 is disposed on one side of the tubular jacket 12 with respect to the support member between the jacket.

; The fixed support member is provided with loading members 18, 20 which press against the jacket 12 against the heated counter member 22 and thereby enable the diaper and diaper to be calendered. 30 countermeasures. The opposite ends of the diaper are fixed to the ends 24, 26 pivotally attached to the support member, and the rotation of the ends is driven by a separate drive motor independent of the movement of the fibrous web to prevent the diaper from overheating. The traction motor is marked with dotted lines.

116080 4

The web speed in the calender can exceed 600m / min, preferably above 800m / min and more preferably 1000m / min, up to about 4000m / min. Thus, the calender does not limit the speed of the board machine. The temperature of the aforementioned heated roller is 150-350 ° C, preferably above 170 ° C, most preferably about 200-250 ° C. The line pressure in the nip is between 100 and 500 kN / m, preferably less than 400, most preferably about 50 to 300 kN / m.

The maximum pressure in the nip is 3 to 15 MPa, preferably less than 13 MPa, most preferably about 0.5 to 8 MPa.

In Figure 1, the carton web 80 passes through an elongated and heated nip 1. The nip 1 10 is formed by a closed shoe roll 10 underneath the web 80. Above the web 80 there is a heated back roll 22. The closed shoe roll comprises a liquid impervious elastic jacket 12. The jacket is, for example, fiber-reinforced polyurethane. The stationary fixed support member 14 supports at least one clamping shoe 18. Between the pu clamping shoe 18 and the supporting member is an actuator 20, such as a hydraulic cylinder 15, presses the concave clamping shoe 18 and thus the elastic sleeve 12 against the unloaded 22. from the center of the closed shoe roll. The sheath 12 is secured at both ends to the end walls 24, 26 to form a closed space 13 (see Figure 2). As also shown in Fig. 1, at least one detection device 99 is disposed along the web 80 to detect web breaks. The detector device 99 is coupled to a control device 98 which controls the calendering process depending on whether the web is broken:.

• »:. As shown in Fig. 1, the heated counter roll 22 has a separation mechanism consisting of a lever 95 which is pivotable by a hydraulic cylinder arrangement 94 and has a support point 96 with respect to which the lever pivots. The separation mechanism presses the retaining wire 22 onto the nip 1 and releases it from the nip 1.

I «· I * ♦ ·;, (: A pressurized oil is supplied between the press shoe 18 and the diaper 12, which causes: 30 hydrostatic pressure on the nip area and presses the diaper onto the roller 22 over the entire length of the nip 1. At the same time, the oil protects the diaper due to the damage caused by the rise in temperature.

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Figure 2A shows that the end walls 24, 26 are mounted for rotation! to the pivot shafts of the support limb 14 16.17. (The end walls are preferably not intact, but divided into a static part and a rotatable part, as shown in Fig. 2B) At one end of the pivot shaft, you are able to rotate! cylindrical arm 32 by means of bearings 34 5. The support profile 36 is provided on a cylindrical arm with self-centering bearings 38 which allow spherical movement to permit deformation / deflection of the support member 14 under heavy load. One of the end walls 24 is fixedly connected to a cylindrical arm. The transmission means 40, in the embodiment shown, a gear wheel, is fixedly fixed to the cylindrical arm end wall.

The gear wheel is connected to the transmission 42 and further to the drive means 44. The gear wheel 46 is fixedly connected to the cylindrical arm inside the end wall. The drive shaft 48 is disposed inside the housing and parallel to the support member 14. The drive shaft 48 is supported by bearings 50 which are mated to bearing housings 52 which are secured to the support member. At each end of the drive shaft 15 gears 54 are provided. These gears preferably have an elongated toothed portion to allow axial movement of the synchronizing gear mounted on the end wall. The additional gear wheel 56 is fixedly connected to the second end wall 26 on the inside of the housing. Each gear on the inside of the housing is toothed with the corresponding gear on the drive shaft. The second end wall 26 is rotatably mounted on the second pin shaft 17. The second pin shaft is in turn fixedly connected to the second support profile 58.

• *> 't: The function is as follows. The heated roll 22 used during normal operation is:: interacting with the fibrous web and the flexible sheath 12 by applying the desired pressure 25 to the loading shoe 18, thereby providing friction-based movement of both the fibrous web and the flexible sheath 12. Thus, in normal operation, the forces exerted on the nip cause the closed shoe roll to rotate.

:. ,,: Only in certain situations it is necessary to use the independent operation of the closed roll 10: for example, when starting the calender. If the calender were started by accelerating. "Without first elastic diaper 12, this would inevitably result in the elastic diaper being damaged due to overheating. In addition, it would be detrimental to the fibrous web, 'I', because at start-up it would cause exceptional tensile forces on the fibrous web.

Thus, the self-standing arrangement of a closed shoe roll must be used, for example, to start the 6116080 calendering surface. At start-up, the nipple slot is not closed and the roll 22 is moved out of contact with the nip 1. Before moving the heated counter roll into the nip, the operating arrangement 44 of the closed shoe roll 10 is activated to accelerate the first end wall 24 through transmissions. Rotation of the end wall 5 causes rotation of the inner first gear 46, and hence the drive shaft 48. The drive shaft transfers rotation to the second end wall 26 via the second inner gear 56. Each end wall is thus accelerated to rotate at the same speed until the desired peripheral speed is reached, usually the same as the speed of the fibrous web. The nip is closed by activating the hydraulic piston 94 to pivot the lever 95 and thereby move the counter roll 22 to the nip and subsequently the loading shoe 18 is forced against the heated roll 22 by its actuators 20. When the calender operates as desired, the operating arrangement of the closed shoe roll can be deactivated and the press roll can be operated in a conventional manner by friction in the nip 1.

Figure 2B shows an alternative embodiment of a closed shoe roll drive arrangement. This embodiment uses friction to transfer the rotational forces.

Figure 2B also shows a more advantageous embodiment of the support member and the end walls. The end walls are divided into an inner part 24A; 26A, a non-rotatably ribbed portion 24B; 26B and a bearing 24C; 26C between the support member 14. The support member 14 is provided with self-centering bearings 23, 25 at each end to allow the support member 14 or-: Λ Puma.

The figure shows an actuator 44 having an axis 19B. The shaft 19B is provided with: '.! 25 a disc 19 having a rubber layer at its peripheral end 19A. The outer: ends of the flexible sheath 12 are fixedly connected between a circular ring 15 which acts as a replaceable transmission member and the periphery of each end wall. Ring 15 is fixedly connected to the end; : On the wall. Inside the rotating part 24B, 26B of each end wall is fixedly connected: a gear 46, 56. The actuators 44, 19 can be moved into contact with the force:. 30 with and away from contact with the transfer device 15. Accelerate when closed. · ·. the shoe roll 10 drive means is moved so that the rubber layer 19A becomes frictional, », known with the transmission device 15. Toothed wheel 46 and drive shaft 48 to move; control the rotation of the end wall 24 to the second end wall 26 via the gears 54.55 and 56, which at the same time act as a synchronizing device. Thus, each of the 116080 7 end walls 24, 26 is operated in the same manner as described with reference to Figure 2A. Figure 2B further shows a schematic view of a preferred embodiment of the function of the load shoe 18. Usually, the loading shoe 18 is not positioned diametrically relative to the drive shaft but perpendicularly as shown in Figure 5 2A.

During the tests, it was found that the batches of the carton produced with the above-mentioned long-nip shoe calender provided a better sweat-to-smooth ratio than the present board grades. Thus, according to the measurements, the object of the invention is well achieved.

Significantly high speeds can be used in the shoe calender, and additionally using an elevated temperature, e.g., about 250 ° C and taking into account the long residence time in the calendering area, provides the same polishing effect as a slower Yankee cylinder solution. In addition, the carton provides a better bulk. In addition to factors that directly affect the quality of the board, the mill's production space is saved, the Yankee cylinder with production limitations is eliminated, and a more manageable, more easily adjustable system is achieved.

In order to obtain the carton according to the invention, it is preferable to provide surface wetting prior to calendering. Even without surface wetting, it is possible to produce a carton according to the invention.

i:: Performed with the same sweat gave better surface properties: ': for cardboard. Test runs were performed on cardboard which was calendered with the pit-i: nip calender described above without smoothing it with a Yankee cylinder.

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Measured methods for the same board grade

Pre-Calibration Conditioner Board Properties Ratios Heat Line Water Bulk Bendsen PPS Hunter 5 Mode Pressure Increase cm3 / g roughness hardening ° C kN / m g / m2 ml / min heus pm

Yankee Reference - - - - 1.83 22 1.4 35 10 Shoe Calender 200 100 4 1.84 41 1.5 33

Shoe Calender 200 200 ~ 4 1.82 ~ 25 12

Shoe Calender 25Ö lÖÖ 4 Ϊβ2 Ϊ6 ΰ 33

Shoe Calender 250 2ÖÖ 4 Ϊβ2 17 1 ^ 2 32 15

In the test run, the reference board and the pilot-calendered board were twice coated at a blade coating station with a total coating amount of about 24 g / m 2. No products were finally calendered 1

Thus, without bulk deterioration, a lower roughness and greater luster than: Yankee reference were obtained. Based on experience, the interpretation of test results means edis-::; for example, the quality of cartonboard and the economics of manufacturing.

: Usually, pilot tests give worse results than the final environment, so it can already be deduced from these initial tests that the method provides a better and at the same time easier and more economical paperboard. In addition, the method is suitable for significantly higher speeds than a Yankee cylinder.

Claims (15)

1. Coated cardboard product having one or more fibrous layers, the surface layer of which consists of bleached cellulose and the base layers of mechanical pulp and / or reject, and whose cardboard surface weight is 150-400 g / m2, said cardboard having a front and a back , and for the manufacture of the product, a calendering surface forming device has been used which consists of: a fixed support member (14), a flexible jacket (12) arranged around the fixed support member (12), so that the cardboard web (80) ) runs between the manifold (12) and a support roller (22), a load member (18, 22) arranged in conjunction with the support member (14) such that the load member (18, 22) presses the flexible manifold (12) against the support roller ( 22), which can be heated, whereby the cardboard web (80) between the mannequin (12) and the support roller (22) is calendered, and Itmin at least a gable wall at the end of the fiexible menein is arranged so that the fiexible meneine (12) is attached to the the end wall (24, 26) and the male end (12) are rotated with the end wall The gutter (24, 26) with a drive machinery, wherein, for the preparation of the product, one or more pre-calender surface forming devices used, characterized in that the surface characteristics of the coated product on the front of the carton are as follows: PPS-slO surface roughness (ISO 8791-4) 0.5 - 2.0 µm: Hunter gloss (ISO / DIS8254) ~ 35-80%, and that product *; Tens density (SCAN-P7: 75) is between 500 - 1000 kg / m3. *; A product according to claim 1, wherein the intermediate layer material consists of one or more materials: 25 selected from the group: abrasive pulp (GW), pressurized abrasive pulp (PGW), chemical thermomechanical (CTMP) and reject. Product according to claims 1-2, characterized in that the front side is coated with a t; “*: Gang or multiple gangs. :: ·. 30 Product according to claims 1-3, characterized in that the back side is uncoated. 5. Product according to any one of claims 1-3, characterized in that the back side is designated; the stroke at least one bunch. 116080 6. Product according to any of the preceding claims, characterized in that the surface weight is within the range 180 - 350 g / m2. Product according to any of claims 1-5, characterized in that the surface weight is in the range 180 - 300 g / m2. Product according to any one of claims 1-7, characterized in that the Bendt seneness of the front face (SCAN-P21: 67) is 0 - 50 ml / min. 10 Product according to any one of claims 1-7, characterized in that the Bendt seneness of the front face (SCAN-P21: 67) is 0 - 20 ml / min. Product according to any one of claims 1-9, characterized in that the front PPS-15 sloO purity (ISO 87911-4) is 0.8 - 1.5 μίτι. 11. Product according to any one of claims 1-9, characterized in that the Hunter face gloss (ISO / DIS 8254) is 45-65%. 12. Product according to any preceding claim, characterized in that its density; ; (SCAN-P7: 75) is 750-1000 kg / m3. ♦ »»: '': 13. Product according to any one of claims 1-12, characterized in that at the product •; : calendering has also used a single or multiple type machine or soft calender. 25 Product according to any one of claims 1-13, characterized in that surface wetting of the carton has been used in conjunction with its pre-calendering. :: 15. Product according to any of claims 1-13, characterized in that in connection with: / 1 its pre-calendering, surface wetting of the carton has not been used. • I> • * * · »I * l>