GB2625249A

GB2625249A - Method

Info

Publication number: GB2625249A
Application number: GB2218052.5A
Authority: GB
Inventors: Mckenna Martin
Original assignee: Encorra Ltd
Current assignee: Encorra Ltd
Priority date: 2022-12-01
Filing date: 2022-12-01
Publication date: 2024-06-19
Also published as: GB202218052D0

Abstract

A method of corrugate production and a machine 10 for making packaging. The method requires at least one top 30 or bottom 34 liner, and a fluting paper 32. Lateral and/or longitudinal tension is created in the or each liner 30, 34 and/or fluting paper 32 by application of infrared energy. The application infrared energy may reduce the moisture content of the fluting paper. A machine for production of double face corrugate from fluting paper, top liner, and bottom liner, comprising first infrared energy source 17, second infrared energy source 18 and third infrared energy source 19, means for corrugating the fluting paper, and bonding means.

Description

Method

Field of Invention

This invention relates to the field of packaging and more particularly, though not exclusively, to a machine and method for producing corrugated board

Background

Corrugated board or cardboard ("corrugate") is popular for making packaging as it is easily recycled and much more environmentally friendly than plastic. Corrugated packaging is a $250bn/year global market and is steadily growing. However, companies making boxes and cartons -sheet converters -have to buy and store corrugated board in bulk as it is made elsewhere in huge manufacturing plants which are usually located far from where it is required by end users.

Since the corrugating process was invented (USA, the 1890s) the steam-based method of producing corrugate has hardly changed, apart from the scale of production: fluting paper is pressed between two fluted rolls like a mangle, and because the paper has a resistance to being formed, it wants to spring back to its original shape. This is where the use of steam is most relevant: first, steam is used to soften the fluting paper, and the mangle is heated using high-pressure steam. As the fluting paper passes through the mangle, a starch-based adhesive is smeared over the tips of the flutes, and a paper liner (which is also steam treated to soften it) is applied, under pressure, to the flutes. The result is a single face board. Applying a second (bottom) liner is a more gradual procedure, as the board would crush under pressure, and steam-heated hot plates provide the curing and drying. The hot plates, which use temperatures of up to 300 degrees C, contact with the board. Such conventional methods of corrugate production allow 3-4-metre-wide webs to be processed at high speed. Conventional corrugation processes and machines, which rely on temperature, pressure, and friction have several further disadvantages. First, the use of steam and hot plates in conventional corrugate manufacturing processes means that sensitive coatings such as waterproofing or metallising have to be applied in a separate process as the sensitive coatings do not tolerate the use of steam and high temperatures as they will often be burnt off. Second, the conventional hot process for the production of corrugate is wasteful of energy and generates effluents and high levels of 002. Third, as conventional corrugating processes use hot starch glue, they require a long shut down cycle meaning that they are best used for long production runs and are typically run for a minimum of 24 hours a day. Fourth, the heat and pressure used by conventional corrugate producing machines means that they can only process relatively thick paper.

One aspect of corrugate production is creating and controlling tension in the liner papers used in the process. GB2513226 discloses an apparatus and method for corrugate production based on One aspect of corrugate production is creating and controlling tension in the liner papers used in the process. GB2513226 discloses an apparatus and method for corrugate production based on applying tension to the liners by additional mechanical means, i.e., braked nip rolls, before gluing the liners to the fluting. The method disclosed avoids the need for steam. EP0602104A disclose a method of corrugate production in which a liner is adhesively bonded to a corrugated medium (i.e fluting paper) using low wavelength infrared energy to cure the adhesive. US4589944 also uses infrared energy for the heating and pre-gelling of the starch glue on the upper internal single face, but still uses steam heated plates to cure the board. US2019/0084287 discloses a method of corrugate production in which the corrugate is printed, and infrared energy is used to dry inkjet printing on the corrugate. A re-humidification device is disposed downstream of the infra-red drying device in the method disclosed in US2019/0084287 to add moisture to the lamination web. The scale of the machinery used in conventional corrugate manufacturing processes may be appreciated from the drawings of US2019/0084287.

Corrugate comes in various grades (A, B, C, E etc) where the letter designates the height of the corrugations. Conventional corrugators create a certain number of flutes per inch (2.54cm) (viz. B flute is typically 4 flutes per inch (2.54cm) and are challenged to create much higher flute densities.

It is an object of the invention to provide a method of corrugate production involving less energy.

It is a further object of the invention to provide a compact machine for operating the method of corrugate production.

It is a further object of the invention to provide a method of corrugate production which can be conveniently operated on site by end users of corrugate such as sheet converters and packers.

It is a further object to provide novel or improved corrugate products and in particular corrugate having higher flute densities.

Summary of the Invention

According to one aspect of the invention there is provided a method of corrugate production according to claim 1.

The method of the invention is advantageous in that it may use far less energy and reduce carbon emissions by over 72% compared to conventional manufacturing methods.

As the conventional corrugating process uses pressure between rollers to form the corrugated board, any printing or coating must be applied to the board after it has been corrugated, as the heat, pressure, and associated friction would otherwise damage these treatments. Because the method of the invention applies no pressure to the liner papers it can make corrugated board directly from all sorts of coated papers -waterproof, metallised, etc. This means that a user can make short runs of the specialised corrugated board they require directly from rolls of paper, without any need for post-processing.

A further advantage of the method of the invention is the ability to stop and start the process with little waste.

Production of a packing item includes directly forming packaging or a packaging blank from corrugate produced by a method or machine according to the invention. Thus, sheet converters, contract packers, and manufacturers of consumer products may be able to produce packaging on site without having to buy in corrugate.

According to another aspect of the invention, there is provided a corrugate product directly obtained by the method of the invention according to claim20. The corrugate product may have a higher flute density for a particular corrugation/flute height than conventional corrugate products. This means that the corrugated board created by the method of the invention can be stronger than the equivalent corrugated board produced by conventional corrugate production processes because the higher density of flutes enables the liners to be glued at more points.

According to a further aspect of the invention, there is provided a machine for the production of corrugate according to claim 22.

A further advantage of machines incorporating the method of the invention is that they are simple to operate and may be small enough to be incorporated into packaging lines making cartons and boxes. Additionally, the corrugate can be made directly from pre-printed or special coated liner/fluting papers, removing the need for separate processing to apply printing or coating.

Brief Description of the Drawings

A machine for the production of corrugate, and a method of producing corrugate, as well as novel corrugate products in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings, Figures 1 to 4, in which: Figure 1 is an elevation of a machine for the production of corrugate by a method in accordance with the invention in use; Figure 2 is a detail transverse elevation of the machine of Figure 1 with parts of the machine shown in cross-section; Figure 3 is a perspective view of the machine of Figure 1; and Figure 4 is a comparison of the flute density of comparable corrugate products of the same flute height made in accordance with the invention and by conventional processes.

Description

In this specification, the terms "longitudinal" and "lateral" are used in the sense of along the length, or across the width respectively, of the corrugate, web liner or fluting paper, as the case may be.

Machine and Method for Corrugate Production A machine 10 for producing corrugate from fluting paper and top and bottom liner papers using a method of the invention, is shown in Figure 1 and 2 by way of example. The machine 10 primarily comprises a highly perforated corrugator drum 12, forming roll 14, vacuum box 16, and first, second, and third arrays 17, 18, and 19 of non-contact infra-red lamps. The corrugator drum 12 is shaped like a large gear wheel with approximately 10,000 holes of 3mm diameter formed through the "gear teeth". The size and quality of the vacuum holes can be altered for the web being processed. Larger flutes may require larger diameter holes and less of them per square metre. The forming roll 14 is shaped like a much smaller gear wheel. A suitable lamp is an IS twin tube fast medium wave, with a power output of 2500W/ metre, operating at 415V with gold or ceramic reflectors supplied by Heraeus Noblelight Ltd. In this embodiment of the invention, the infra-red lamps in the first, second and third arrays 17,18, and 19 operate at a wavelength of peak range 1.4 to 1.6pm and power density of up to 50W /cm. It is important to use lamps with an instant on and off, otherwise if the machine stopped the slow shut off of the heaters could scorch or turn the web to ash. The lamps in the arrays 17, 18, 19 are arranged and operated so that they are spaced apart in relation to the corrugate materials and can extract moisture from the materials without shrinking or warping the webs. Other lamps operating in the wavelength range of 1.41Am to 1.6j.Lm may be used. The machine 10 further comprises first and second gluers 20 and 22 and an opposed pair of braked nip rollers 24 and a sandwich roller conveyor arrangement 26 with pairs of gripper chains 28. The gripper chains and the third array of infra-red lamps are shown in more detail in relation to the web in Figures 2 and 3.

Operation of the machine 10 is governed by a control system (not shown).

Production of single face corrugate In use, in a method in accordance with the invention, the machine is fed with top liner 30, fluting paper 32, and bottom liner 34 stock. Lighter weight stock can be used for the top liner, fluting paper and/or bottom liner. In this context, the industry is trying to reduce the amount of fluting paper it uses to make corrugations for a given length.This is called the "take-up"). The primary use of heavy gauge papers in the smaller fluted boards (B, E, and F flutes) is more for printability than for strength so the board is overweight for the application. The method of the invention produces good flat printable board with much lighter papers, while still having the strength required for the packaging application. Also, it is common practice when using heavy top liner (e.g., 200gsm) to have a bottom liner of similar weight because of the complications with warp control of dissimilar liners. The method of the invention can produce board with dissimilar weighted liners by tension control. Tension is applied to the bottom liner 34 by nip rollers 24. The corrugator drum 12 is rotated in the direction of arrow A, with the forming roll 14 rotating in the opposite direction. Flutes are formed in the fluting paper 32 by the interaction of the forming roll 14 and corrugator drum 12. As the flutes are pressed out, a vacuum system behind the teeth of the corrugator drum 12 draws the air out of the gap between the fluting paper 32 and the drum surface, thereby forcing the fluting paper 32 which is firmly held against the drum's surface to retain the corrugated shape of the surface of the drum 12. Immediately the flutes are formed in the fluting paper 32, adhesive is applied to the tips of the flutes, in dot form by gluer 20. These adhesive dots are applied at regular intervals across the web which can be varied at between 5mm and 8mm, preferably 5-6 mm, spacings. Due to the range of contemplated flute sizes and board applications, these adhesive dots are applied in line or staggered, at regular intervals across the web which can be varied between 2mm and 10 mm. The top liner 30 is applied to the tips of the flutes as the corrugator drum 12 revolves: if the drum 12 is seen as a clock face this introduction of the top liner 30 takes place at about 20 minutes past, (the forming roll 14 is arranged at 15 minutes past) and as the drum revolves (clockwise) the adhesive bonds to the top liner (the adhesive is applied by gluer 20 at about 17 minutes past).

Infrared light is applied from the second IR lamp array 18 to the drum face as the top liner 30 comes into contact with the corrugated fluting paper 32 at 20 minutes past on the 'clock face', to extract moisture from the single-face web 36 as it is formed. The heating is applied over a 30 "minute" section of the drum face to a "10 minutes to" position. The heating is controlled to extract not too much moisture from the single face corrugate 36, as this will result in both curling and shrinkage, resulting in the single face corrugate becoming too narrow to enter the gripper chains 28.

In the method of the invention, the moisture in the papers used in is maintained throughout the process. Thus, when the finished corrugate is produced its weight in terms of grammes per square meter should be similar say plus/minus 5% to the weight of papers prior to the process, plus the dry weight of the adhesive. In a typical method in accordance with the invention where adhesive is applied at 30 grammes per square metre, and the adhesive is 50% solids, therefore 15 grammes of moisture per metre of corrugate have to extracted during operation.

Production of double faced corrugate Subsequently the single face web/corrugate 36 at approximately 10 minutes past, is moved over the second gluer 22 which applies dots of adhesive to the exposed underside of the fluted single face corrugate, i.e, to the underside of the fluting paper 32. Immediately the adhesive is applied, the bottom liner 34 is brought into contact with the fluted single face, to create double wall/face wall corrugate web 36. All three paper layers, 30, 32, and 34 then enter the gripper chain 28, which transports the resulting three-layer double face corrugate 40 through the roller conveyor sandwich 26, applying constant pressure to allow undisturbed bonding.

Control of tension in the production of corrugate In the method of the invention, tension in the elements of the corrugate may be carefully controlled to improve the quality of the corrugate which is produced. This is achieved by the careful control of moisture content in those elements as further described below.

Before applying the wet adhesive to the fluting paper 30, infrared energy is applied to extract a percentage of the moisture in the paper. This achieves two things: first, it slightly shrinks the fluting paper laterally, and second it allows the moisture in the adhesive to be absorbed more quickly, which in turn reduces the moisture content absorbed by the top liner 30. It is important not to extract too much moisture from the fluting paper 32, as this will affect the bond with the top liner 30. In effect, a percentage of the moisture that would laterally expand the top liner is being transferred into the fluting paper, resulting in a lateral bow in the single face corrugate 36 (the top of the flute with the wet adhesive has expanded, whilst the dry bottom remains shrunk).

In the embodiment of the method of the invention described above, the resistance created by the vacuum in the corrugated drum 12, and the drag of the revolving drum and the pressure of the forming roll 14 while the drum is revolving is sufficient to tension the top liner 30 in a longitudinal direction i.e. the direction of arrow B of Figure 1 (longitudinal tension), avoiding the need for pre-tensioning of the top liner as is required in the process described in GB2513226. The skilled addressee will appreciate that other means for holding the top liner 30 may be used. Longitudinal pre-tension is applied to the bottom liner 34 by nip rollers 24.

Tension in a lateral direction across the corrugate layers of the web i.e., in the direction of arrow C in Figure 2 (lateral tension) is also carefully controllable in the method of the invention. In particular, as the moisture from the adhesive is absorbed into the top liner 30, the liner can only expand laterally. As noted above, in a preferred embodiment the adhesive is applied in dots, at regular intervals of 5 -6 mm across the web. Each dot of adhesive is drawn into the fluting paper fibres by the wetting. The adhesive at this stage begins to key (bond) and owing to the wraparound pressure created by the drag of the drum 12, the top liner 30, and fluting paper 32 are pressed hard against the circumference of the drum, preventing any movement of those elements. The fluting paper 32 is tight against the drum face, and the now-setting adhesive is preventing the top liner 30 from expanding laterally. The result is a slight bellowing of the top liner 30 between each dot of glue. However, once the infrared energy is applied by the second IR lamp array 17 which extends about a portion of the corrugator drum's circumference at the correct wavelength, and for the required time, the excess moisture is removed from the top liner 30 and the top liner 30 reverts to its normal, original state. For a one metre wide web,15Kw of infrared heat will allow a paper speed of 3 seconds per metre for the production of single face corrugate. A further 10Kw of infrared heat will produce double wall corrugate board at a similar speed.

When the bottom liner 32 is applied as described above, the tension causing the bow in the single face 36 is trapped, and if left would create warping of the finished corrugate. Infrared energy which is being applied to the bottom liner by the third infra-red lamp array 20 extracts its existing moisture, which in turn draws the wet adhesive (on the tips of the flutes formed by the fluting paper on the underside of the single face) into the bottom liner 34 and speeds up the curing process. As the bottom liner 34 is under tension, assisted by the braked nip rolls, the tendency is for the web to shrink across its width as it is heated, but the gripper chains 28 on either side will not allow the web to shrink, thus creating the lateral tension in the web, and as the moisture in the adhesive is absorbed into the bottom liner 34, it wants to expand laterally again, thus creating the rippled bellows effect. If the infrared heat is only applied when all three layers are held in the gripper chains, then the counter effect to the flute bow (in the single face) is initiated. With the bottom liner 34 under tension along its length, the application of infrared energy tries to shrink the double face web 40, creating lateral tension in the web as well. The result is that, rather than stress relieving the single face tension/bow, increases the tension working against each liner 30,34, to produce a more taut and rigid double-faced corrugate product.

While the three layers, gripped by the gripper chains 28, travel through the conveyor sandwich, they are exposed to extra heating stations, with the objective of using every opportunity to extract excess moisture and return the web to its original moisture content. If too much moisture is removed the board will curl or warp, so it is a finely controlled procedure, but with the correct application of infrared energy it can be ensured that the corrugate 40 emerges totally flat and taut. In order to increase the output speed of the machine or when using heavy weight papers, further heating stations can be added to help the curing process.

At the end of the process there is a minimal downtime before the process can be repeated with the same or different liners/fluting paper and little waste. Therefore, the machine and process of the invention do not require the extended downtimes of conventional processes as described above. The method of the invention provides an easy stop start operation and does not require the long run cycles of the conventional method which typically run 24/7. It is ideal for continuous running or for short runs. There is no risk of "cooked starch" glue going off and setting. At the end of the method of the invention the machine is stopped, the gluers are withdrawn and, covered until needed again.

Finally, in an optional further processing step, the corrugate is pushed through a conventional cutoff knife (not shown) and is chopped to the required length before subsequent processing if the corrugate.

Corrugate product Production of thinner, lighter corrugated cardboard The method and machine of the invention can corrugate much lighter grades of paper than conventional corrugators. This is because the heat and pressure used by conventional machines means that they can only process relatively thick paper. Aspects of the method of holding the papers in place -for example, the vacuum retention of the web on the corrugate drum -enable lighter papers to be corrugated, thus allowing lighter corrugated board to be made.

One example of a useful lightweight corrugate board produced by a method in accordance with the invention is set out below. The top liner was 100gsm, the bottom liner was 85gsm, and the fluting paper was 70 gsm, formed in S flutes (i.e, 2.3 mm high). The corrugate therefore has a total weight of 275gsm. In contrast, a conventional comparable corrugate uses 120gsm top and bottom liners with a fluting paper of 85/100 gsm i,e, a total of 350/ 370 gsm with adhesive. Top and bottom liners are the same weight to avoid issues with curling and warping.

Control of flute size and strength.

The method of the invention can readily create corrugate with finer and more closely spaced flutes than conventional methods of corrugated production. As noted above, this means that corrugate board created by the method can be stronger than the equivalent conventional board because the higher density of flutes enables the liners to be glued at more points.

For example, B flute is amongst the most commonly used categories of corrugate used for packaging applications. The flute height of B flute corrugated is 3 mm. In one example method in accordance with the invention, B corrugate was produced having 5 flutes per inch (2.54 cm.). Figure 4 is a comparison of the flute density of comparable corrugate products of the same flute height made in accordance with the invention and by conventional processes. Figure 4A and Figure 4B show a conventional B flute corrugate, and a B flute corrugate produced by the method of the invention respectively. The increased or finer spacing of flutes for the same flute height in the corrugate of the invention can be seen. The corrugate of the invention is stronger because of the finer flutes.

By changing the flute shape from a soft wave to a sharp triangular form, 20% extra flutes per 30cm can be achieved. B flute typically has 48 flutes per ft (30cm) when produced by conventional processes but can have 61 flutes per 30cm when produced by a method in accordance with the invention. The resulting board has a more rigid fluting structure which also enables the weight of the fluting paper in grams per square metre gsm to be reduced from the standard 90/100 gsm, to 70 without reducing the printable quality or the strength of the board. Similarly, the gsm of the outer liners can be reduced without affecting the surface printability. In this connection, with conventional processes, printability is more important than the strength aspect of most of the smaller (E, F, and B) boards and heavier gauge papers have to be used to assist in this.

Production of corrugate from pre-coated and pre-printed papers The conventional corrugating process uses pressure between rollers to form the corrugated board. This means that any printing or coating has to be applied to the board after it has been corrugated, as the heat, pressure, and associated friction would otherwise damage these treatments. Because the machine of the invention applies no pressure to the liner papers it can make corrugated board directly from all sorts of coated papers -waterproof, metallised, etc. This means that sheet plants operating the method of the invention can make shod runs of the specialised board they require directly from rolls of paper, without any need for post-processing. This is especially convenient for sheet converters and contract packers. By using a pre-coated paper to manufacture the board, the customer saves on the transportation, time and at least one extra process cost. Depending on the nature of the specialist board and the minimum quantity orders, the cost savings are very significant compared to current processes. Also because extra sheets of paper do not have to be laminated onto the board this greatly reduces the fibre and glue content.

Claims

Claims 1. A method of corrugate production from at least one top or bottom liner, and a fluting paper in which lateral and/or longitudinal tension is created in the or each liner and/or fluting paper by the application of infrared energy.
2. A method of corrugate production according to the preceding claim in which the moisture content of the fluting paper is reduced by the application of infra-red energy from a first infrared energy source.
3. A method of corrugate production according to any preceding claim in which the moisture content of the fluting paper and the paper (s) is maintained throughout the process.
4. A method of corrugate production according to any preceding claim in which infra-red energy is applied to the fluting paper prior to corrugating the fluting paper.
5. A method of corrugate production according to any preceding claim in which infra-red energy is applied to the fluting paper prior to bonding the fluting paper to the top liner.
6. A method of corrugate production according to any preceding claim in which a top liner is contacted with infrared energy after application of an adhesive to the upper surface of the fluting paper for bonding the top liner to the fluting paper.
7. A method of corrugate production according to the preceding claim in which the infrared energy applied prior to and after the application of adhesive to the top liner.
8. A method of corrugate production according to any preceding claim in which infrared energy is applied to the single faced web formed by the top liner, corrugated fluting paper and adhesive.
9. A method of corrugate production according to any preceding claim in which the fluting paper is held by vacuum against a corrugator drum for forming corrugations in the fluting paper prior to application of an adhesive to the fluting paper.
10. A method of corrugate production according to the preceding claim in which the single faced web formed by the top liner, corrugated fluting paper and adhesive is held by vacuum against the corrugator drum to maintain tension in the single faced web whilst infrared energy is applied to the web.
11. A method of corrugate production according to the preceding claim in which the infrared energy is applied over about 50% of the circumference of the corrugator drum.
12. A method of corrugate production according to any preceding claim in which adhesive is applied to the lower surface of the fluting paper prior to application of a bottom liner to the fluting paper.
13. A method of corrugate production according to the preceding claim in which the bottom liner is held against the fluting paper after application of a bottom liner to the fluting paper to form a double-faced corrugate web.
14. A method according to the preceding claim in which infrared energy is applied to the double-faced corrugate web.
15. A method according to the preceding claim in which the infrared energy is applied to the lower surface of the double-faced corrugate web.
16. A method of corrugate production according to the preceding claim in which the bottom liner is held against the fluting paper by holding means which contact the lateral edges of the double face corrugate web.
17. A method of corrugate production according to the preceding claim in which the holding means is in the form of gripper chains arranged to grip the lateral edges of the double face corrugate web.
18. A method according to any preceding claim in which at least one of the bottom liner and top liner is introduced as pre-printed or pre-coated stock.
19. A method according to any preceding claim comprising at least one postproduction step selected from cutting the corrugate to size or folding the corrugate to form a product such as packaging.
20. A corrugate product obtainable by a method according to any preceding claim.
21. A corrugate product according to the preceding claim formed by a bottom liner paper of 85gsm, fluting paper of 70gsm, and top liner paper of 100gsm.
22. A machine for the production of double face corrugate from fluting paper, a top liner, and a bottom liner, the machine comprising: a. A first infra-red energy source for applying infra-red energy to the fluting paper to reduce the moisture content of the fluting paper; b. Means for corrugating the fluting paper; c. Means for bonding the corrugated fluting paper to a top liner; d. Means for holding the bonded top liner and corrugated fluting paper; e. A second infra-red energy source for applying infra-red energy to the bonded top liner and fluting paper; f. Means for bonding the bonded top liner and corrugated fluting paper to a bottom liner; g. Means for holding the bonded top liner, fluting paper, and bottom liner together; and h. A third infra-red energy source for applying infra-red energy to the bonded top liner, fluting paper and bottom liner.
23. A machine according to the preceding claim in which at least one infra-red energy source operates at a wavelength of peak range 1.4 to 1.6 pm.
24. A machine according to the preceding claim in which the at least one energy source operates at a power density of up to 50 W1cm.
25. A machine according to any one of claims 22 to 24 in which the means for holding the bonded top liner and fluting paper comprises a corrugated vacuum drum.