CORRUGATED BOARD COATING METHOD AND APPARATUS

Abstract: Method and apparatus for coating corrugated board (4). According to the invention, a single-face laminating coating film web with sufficiently high heat resistance is laminated to the surface of the corrugated board (4) by routing the coating film web directly to heating (2) and pressure (3) rolls of a corrugated board machine in order to laminate the coating film web to the surface of the corrugated board (4). The method in accordance with the invention achieves a homogeneous coating of corrugated board (4).

Description: Corrugated board coating method and apparatus The present invention relates to a corrugated board coa ±-R^ method in accordance with the preamble of claim 1. 5 Further, the invention concerns an apparatus for the implementation o£ the coating method. Corrugated board coating methods of the prior art are 10 implemented primarily in two ways: either by using a separate coating process for coating the linerboard used in ' production or by coating the factory-ready corrugated board box blanks through spraying of coating mix onto the surface of the linerboard. - χ 5 Precoating of linerboard used in corrugated board manufacture is implemented as a separate process, and the coating materials common in use are such as to cause considerable diffaculties and slowing in the manufacture of corrugated 20 board. Furthermore, a waxing method is also implemented as a supplemental process, which impedes the production phase of corrugated board box itself. The aim of this invention is to overcome the disadvantages 25 associated with the technology described above and to achieve a totally new kind of a coating method for corrugated board. The invention is based on guiding a single-side-laminating film web onto a preheating roll together with the linerboard 30 web so that the laminating side of the film web faces the linerboard web. ^ More specifically, the method in accordance with the invention is characterized by what is stated in the characterizing 35 part of claim 1. Furthermore, the apparatus in accordance with the invention is characterized by what is stated in the characterizing part of claim 4. The invention provides outstanding benefits. The method in accordance with the invention provides the advantage of not slowing the manufacturing process of the final product, i.e., the corrugated board box and it does not require the supplemential procedures now mandatory in the production process, thus being able to offer a much improved final product as regards to the costs and quality. The invention is next examined in detail with help of the exemplifying embodiments illustrated in the attached drawings. Figure 1 illustrates schematically an apparatus for the implementation of the coating method in accordance with the invention. Figure 2 shows a coating apparatus in accordance with the invention in a cross-sectioned side view. Figure 3 shows another coating apparatus in accordance with the invention in a cross-sectioned side view. Figure 4 shows a third coating apparatus in accordance with the invention in a cross-sectioned side view. In accordance with Figure 1, a plastic film web 1 having a hea -laminating surface on one side and possessing a heat durability sufficient for the manufacturing process of corrugated board is routed over a first small preheating roll 2 and a second small preheating roll 2 ' of the corrugated board manufacturing machine. The material of the plastic film web is polyester film whose one side has a high heat durability (about 240 °C) . This kind of material is available under such trade names as, e.g., Melinex 850. The surface temperature of the heating rolls 2 and 2 is typically 130 °C. The plastic film web 1 passes over the first small-diameter preheating roll 2 initially alone until a linerboard web 4 of corrugated board is guided over the plastic film web 1. Thanks to the heating, the plastic film web 1 is laminated to the linerboard web 4. After the first preheating roll 2, the web combination 1 and 4 is guided to the second preheating roll 2' so that the plastic film web 1 is now outermost. A pressure roll 6 with a heat-resistant rubber coating of 5...8 mm thickness is advantageously used in conjunction with the second small-diameter preheating roll 2'. The diameter of the pressure roll is typicaliy 200...250 mm and the bulging at the middle of the roll is about 1...1.5 mm. The lineal pressure is about 10...20 kg/cm and the total pressing force of the nip is typically 2500...5000 kg. The pressing force can be adjusted by hydraulic means. A cor¬ rugating medium web 7 is corrugated by corrugating rolls 31 and glue is applied to the corrugating medium " web 7 by a glueing unit 8. The corrugating medium web 7 is glued to the nonlaminated surface of the laminated linerboard web 4 in a nip 28 formed between a pressure roll 3 and one of the corrugating rolls 31. The plastic film web 1 can be applied over the entire width of the corrugated board web or only over a part of its width or over several places across the width, thus allowing the same corrugated board web to be used for the manufacture of both a noncoated box and a coated box. The auxiliary equipment required to complement the corrugated board machine comprises simply a laminating film roll stand 5 and possibly also the extra pressure roll 6 of the second preheating roll 2'. The laminating film roll stand 5 must be provided with a brake system for the tension control of the film web 1. To ensure the straightness of the plastic film web 1, the apparatus must be provided with web spreading equipment (not shown). Because the method uses a film with only one side laminating, the film web 1 does not adhere to the preheating rolls 2, 2' and the pressure rolls 3, 6 of corrugated board. The manufacturing process of corrugated board is not slowed because the temperatures and heat conducting surfaces of the heating rolls of a normal manufacturing process of corrugated board are sufficiently effective to achieve lamination even at the maximum web speed of corrugated board. I -Figures 2 and 3, the auxiliary equipment required for lamination are presented in dashed lines. In accordance with Figure 2, the corrugating medium web 7 is routed over a guide roll 22 to a steam jet 21 and then to an upper corrugating roll 9 that incorporates a steam box 10. The corrugating medium web 7 is corrugated in a nip formed between the upper corrugating roll 9 and a lower corrugating roll 11. The lower corrugating roll 11 also incorporates a steam box 12. The corrugating medium web 7 is sucked to the surface of the lower corrugating roll 11 by means of a suction arm 36 and a suction tube 19. The glueing unit 8 is used to apply glue to the corrugated board web. The film web 1 to be used in lamination is unwound from a unwinder unit 15 onto a sp_iral-type spreading roll 16 and further routed to a banana- type spreading roll 18 and guided over a ' guide roll 34 to another guide roll 33, on which the film web 1 meets the linerboard web 4. The laminating side of the film web 1 faces the linerboard web 4. Next after the second guide roll 33, the linerboard web 4 together with laminating film web 4 is guided to a preheating roll 14, and a first preheating roll 13 is used for pressing the webs against each other in a nip formed between the first pressure roll 13 and the preheating roll 14. The corrugated corrugating medium web 7 is glued to the unlaminated side of the laminated linerboard web 4 in a nip 28, which is formed between a second pressure roll 20 • • with a steam box 32 and a lower corrugating roll 11. The ready corrugated board is guided over a guide roll 18 to subsequent processing stages. According to Figure 3, the corrugated board web 7 is corrugated by corrugating rolls 31, and glue is applied on the corrugated web by a glueing unit 8. The laminating side of a linerboard web 4 is preheated by a preheating roll 37 and guided to a first preheating roll 30 and a second preheating roll 38, and next after these, over a pressure roll 27 to a lamination nip 28, in which the corrugated and glue-coated corrugated board web 7 is adhered to the linerboard web 4. A film web 1 is laminated to the linerboard web 4 in * 5 conjunction with the preheating rolls 30 and 38. The film web 1 is unwound from a unwinder unit 25 with a brake control over a spiral-type spreading roll 23 and a banana-type spreading roll 24 to guide rolls 26 and 35, from where the film web is routed to a first preheating.roll 30 and then to 10 a second preheating roll 38. To achieve lamination, the second preheating roll 38 and a pressure roll 27 are configured to form a pressure nip, in which the film web 1 is finally laminated to the linerboard web 4. 15 According to Figure 4, also a double-faced corrugated board can be provided with laminated coating. A single-faced corrugated board web 39 is guided over a preheating roll 40 - to a glueing unit 8. A second linerboard web 41 is guided over a preheating roll 42 to ^ a pressure nip 45, into which 20 also a laminating film web 1 is routed over a spreading roll 44 and a preheating roll 43. The laminating side of the laminating film web 1 faces the linerboard web 41 in the pressure nip 45. Next after the pressure nip 45, the laminated linerboard web 41 is adhered to the single-faced corrugated 25 board web 39. *rt

Claims: WHAT IS CLAIMED IS: 1. A method for manufacturing corrugated board, in which method - a corrugating medium web (7) is corrugated in a. nip formed between corrugating rolls (31), - glue is applied to the corrugating board (7), and - a linerboard web (4) is adhered to the corrugating board web (7) in a joining nip (28), c h a r a c t e r i z e d in that - the linerboard web (4) is preheated " at least by one preheating roll (30, 31), - a single-face laminating film web is fed from a roll unwinder unit (15, 25), -which is provided with a braking means, and - the film web (1) is routed at least over one spreading roll (23) to the periphery of a preheating roll (30, 31, 43) and to a contact with the linerboard web (4, 41) so that the laminating side of the film web (1) faces the linerboard web (4, 41). 2. K method in accordance with claim 1 / c h a r a c t r- i z e d in that the film web (1) is pressed by a pressure roll (13, 27) against the preheating roll (30, 31). 3. A method in accordance with claim 1 or 2, c h a r a c¬ t e r i z e d in that the surface of the linerboard web (4) to be laminated is preheated. 4. An apparatus for manufacturing corrugated board comprising - corrugating rolls (31, 9, 11) for corrugating a corrugating medium web (7), - a glueing unit (8) for applying glue onto the corrugated medium web (7), and- - guide rolls (10, 3) for guiding a linerboard 10 web (4) to make contact with the corrugating medium web (7) having glue applied on it, c h a r a c t e r i z e d by 15 - at least one preheating roll (30, 38, 14, 20), with which the linerboard web (4) can be preheated, - a roll unwinder unit with brake control, with . which the single-face laminating film web can be 20. " unwound, - at least one spreading roll (23) , with which the film web unwound from the roll unwinder unit can be unwound, and 5 - guide rolls (35), with which the film web (1) can be guided toward the periphery of the preheating roll so that its laminating side faces the linerboard web (4). 0 5. An apparatus in accordance with claim 4, c h a r a c¬ t e r i z e d in that the spreading rolls (23, 24) are of spiral or banana type.

Inventors: SILVESALO JUHA, SILVESALO, JUHA
Applicants: KASTEKNO OY
Application year: 1987
Main classification: B31F1
IPC codes: B31F1, B32B3