FI124591B - METHOD AND EQUIPMENT FOR THE MANUFACTURE OF PAPER OR PAPERBOARD - Google Patents

Description

METHOD AND APPARATUS FOR PAPER OR PAPERBOARD FIELD OF THE INVENTION

The invention relates to a method and apparatus for making paper or board. In particular, but not exclusively, the invention relates to surface sizing of fine paper and outer carton.

BACKGROUND OF THE INVENTION

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At certain points in the manufacturing process, paper or board, for example fine paper or outer board such as corrugated board (liner) or fluting board, is desired to be treated with a web strength enhancing agent such as liquid glue. The adhesive treatment of the web essentially determines the strength properties of the 15 final products. In most cases, various types of starch are used as adhesives, to which various additives can be combined. The present invention is not limited to any particular adhesive composition, and the adhesive is to be understood to mean all at least partially absorbable web strength enhancing compositions.

20 The purpose of bonding outer carton and corrugated board is to achieve good penetration of the adhesive to achieve CMT and splitting strengths (Huygen, Scott-Bond). In film gluing or spray application, soft press nipples have not achieved good penetration-dependent strengths at high basis weights.

Applying devices are known to use soft-surface rollers in the press nip associated with the application. Soft-surface rollers are used e.g.

x to form a smooth adhesive film. The soft press surfaces also increase the length of the press n'P to increase the action of the press pressure and the adhesive penetration 30 into the web. High dry solids? however, there is a lot involved in appliqué and the use of soft press surfaces

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difficulties as the dry matter content of the adhesive mixture increases. When the amount of water in the adhesive mixture is reduced to form a high solids content, the 2 adhesive mixture becomes sticky and adheres to the soft surface of the pressing member. Keeping the soft press surface clean is difficult. A soft press nip massages the web and removes material from the web. It is difficult to clean the material adhered to the web 5 from a soft press surface, for example the soft surface of a nip roll. The material adhering to the soft press surface ends up in the web to be bonded in the press nip, reducing the quality of the end product.

Removing water from the web during gluing limits the efficiency of paper machines and board machines. Since only a limited amount of water can be removed from the moving web 10 with one dryer device, the number of successive dryer devices must be increased as the web speed increases. The increasing number of drier equipment increases the machine's length and cost.

In spray application and film bonding, the dry solids content of the adhesive is limited by the viscosity of the 15 adhesives. It is known that by simply spray application, the high viscosity adhesive mixture has not been smoothed to the surface of the web, but the adhesive mixture has remained as droplets. The viscosity is to be kept low so that too high a viscosity does not cause spray irregularity or streaking of the applied adhesive film. The highly modified and expensive starches achieve 20% 20 solids content before the viscosity exceeds 40 mPas. Such pre-converted starch typically costs about 70% more than unmodified native starch. From native starch, the viscosity of the enzymatically converted and cooked surface adhesive can be modified up to a certain limit by adding more enzyme or extending the duration of action. Adding enzyme 25 is expensive and the life of the modified starch is short. After a certain point, starch ώ begins to degrade into sugar, and in addition, it is difficult to change the action time to 0 when the adhesive is manufactured to a certain amount.

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The use of a low dry solids content causes a high drying need, increases the post-drying section and reduces the potential line speed. For pond gluing with pond glue press for high dry

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the use of a material concentration and thus a viscosity can result in a strong line braking force and collapse of runnability.

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FI 20011455 discloses a process for making adhesive-treated paper or paperboard. The adhesive-water mixture to be applied has a dry solids content of at least 15%, and the adhesive mixture is applied to the web up to 5 g / m 2 per side 5, expressed as the amount of wet adhesive mixture.

Fl 121084 B discloses a method and apparatus for treating a paper or board web. The treatment mixture is injected onto the surface of the web, the web is led to pass through the press nip and the wet treatment mixture is pressed into the web 10 in the press nip.

SUMMARY

According to a first aspect of the invention, there is provided a method of making paper 15 or paperboard comprising spraying an adhesive composition having a dry solids content of more than 15% directly into at least one surface of the web and injecting the adhesive mixture into a loaded rotating press member, and the method comprises providing an adhesive mixture 20 in injection nozzles to an injection pressure of 20-100 bar and, after injection, compressing the web in a hard press nip formed between the hard surface press members.

Preferably, an adhesive mixture having a dry substance content of more than 20%, more preferably greater than 40%, is sprayed.

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Preferably, an adhesive mixture having a viscosity of more than 10,000 Pa is injected. Preferably, the viscosity of the adhesive may be greater than 100 mPas when the adhesive is dry

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content greater than 40%.

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T- Preferably, a turbulent flow of adhesive mixture is formed in the injection nozzles by means of a high injection pressure. According to some embodiments, the adhesive mixture is provided in the injection nozzles at a injection pressure of 20-50 bar. According to some embodiments 4, the adhesive mixture is provided in the injection nozzles to an injection pressure of 20-35 bar.

Preferably, the web is pressed with a roller or belt comprising at least a surface 5 of metal, steel, polymer, epoxy, rubber or a combination thereof. Preferably, the web is compressed by a deflection compensated roll.

Preferably, recycled fiber is used to make the web and the adhesive composition is sprayed onto at least the recycled fiber side of the web.

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Preferably, the web is pressed in a press nip with a line load of 30 to 80 kN / m.

Preferably, the web is pressed in a press nip with a line load of 80 to 200 kN / m.

Preferably, the application rate of the adhesive mixture is controlled by the injection nozzle spacing, nozzle size, and / or dry solids content of the adhesive mixture. Preferably, the application rate of the adhesive mixture is fine-tuned by varying the injection pressure level.

Preferably, the adhesive mixture is applied in the form of starch, PVA, silicone, coating paste, latex or pigment-surface adhesive.

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In another aspect of the invention, there is provided an apparatus for making paper or board comprising injection nozzles for spraying an adhesive composition having a dry solids content of more than 15% directly onto at least one surface of the web and pressing the web after pressing ra loadable rotatable compression member. The apparatus is provided with a high pressure pump configured to provide an injection pressure of 20-100 bar x and the apparatus is adapted to be compressed in a hard press nip which

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is formed by hard surface press members.

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Preferably, the apparatus is configured to spray an adhesive mixture having a dry solids content of more than 20%, more preferably greater than 40%. Preferably, the apparatus is configured to inject an adhesive mixture having a viscosity of greater than 100 mPas.

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Preferably, the injection nozzles are configured to spray a flow of turbulent adhesive mixture by means of high injection pressure. According to some embodiments, the high pressure pump is configured to provide an injection pressure of 20-50 bar. According to some embodiments, the high pressure pump is configured to provide an injection pressure of 20-35 bar.

Preferably, the hard surface press member is provided with a roll or belt comprising at least a surface of metal, steel, polymer, epoxy, rubber or a combination thereof. Preferably, the compression member is provided with a deflection compensated roll.

Preferably, the apparatus comprises loading means for loading the press nip with a line load of up to 200 kN / m.

The adhesive mixture may be applied to the web at higher dry solids contents than previously believed possible. The use of high viscosity also allows the use of cheap starches without an exact viscosity limit.

The high solids adhesive mixture can be brought to a turbulent state at high injection pressures. A turbulent state can be created by increasing the flow rate of the adhesive mixture by means of high injection pressure. The high injection pressure helps to weaken and break the bonds in the high solids adhesive mixture, which makes the adhesive mixture more applicable. A smaller nozzle size can also influence the increase in flow rate δ 25.

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o ^ The hard press nip achieves a higher contact pressure than the soft x press nip. Strength of the web with a hard nipple and high dry-

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the material can be grown relative to the strength of the adhesive treated web with a soft 30 nip in half the dry solids. In the hard nip? the clamping members may be kept clean without grasping while driving.

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A good adhesion penetration of the adhesive can be achieved by injection application and a particularly hard nip. Good penetration of the surface adhesive can be achieved especially with heavy grades, for example grades above 90 g / m2 Single-sided application can improve the penetration of the adhesive without unnecessary increase in the total amount of adhesive. 5 Double-sided bonding is also possible.

The gluing can be accomplished with an adhesive press, a calendar, a wire section, a belt press, a drying section or other papermaking apparatus. The species to be glued can be e.g. cartons, corrugated board surface, corrugated board, 10 fine paper, newspaper. The liquid mixture to be applied may be starch, PVA, silicone, coating paste, latex, pigment-surface adhesive or the like, which is typically applied to the surface of the fibrous web. Preferably, the applied liquid mixture increases the web strength.

Various embodiments of the present invention will be described or described only in connection with some or some aspects of the invention. One skilled in the art will appreciate that any embodiment of an aspect of the invention may be applied to the same and other aspects of the invention, alone or in combination with other embodiments.

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BRIEF PRESENTATION OF THE PATTERNS

The invention will now be described, by way of example, with reference to the accompanying drawing, in which: Fig. 1 shows a syringe application apparatus in which the press nip is formed by ώ two hard surface press members;

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Figure 2 schematically shows the difference between a hard and a soft press nip and the Huygen strength of x glued paperboard with different amounts of glue when 110g / m2 of base board is sprayed with a high solids content adhesive; and

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Figure 3 schematically illustrates the difference between hard and soft press nip and CMT30 strength of surface-glued paperboard at 110 g / m2

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a high dry solids adhesive mixture has been sprayed onto the base board.

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DETAILED EXPLANATION

It should be noted that the figure shown is not to scale, and that it mainly serves the purpose of illustrating embodiments of the invention.

Figure 1 shows a syringe application apparatus 10 comprising two hard-pressed press members to be loaded against one another, a first hard-faced roll 1 and a second hard-faced roll 2. The hard-pressed press members 1, 2 form a press nip 3. of the adhesive is sprayed onto the web. The injection application apparatus 10 comprises, before the press nip, the first injection nozzles 4 and / or the second injection nozzles 5. The web may be treated with an adhesive mixture on one side or double by the first injection nozzles 4 and / or the second injection nozzles 5.

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The adhesive is preferably applied to the web with a spray applicator comprising injection nozzles prior to the nip. The web is introduced into a press nip, which is preferably of high contact pressure. At high contact pressure, the adhesive is forced into the web. When the adhesive film is also particularly large, the adhesive 20 is allowed to penetrate the web. The high pressure in the nip also flattens the web and brings the web surfaces closer to each other, thereby reducing the distance traveled by the adhesive. The other side of the web can also be surface glued. Bonding can take place on the dirtier underside of the web, particularly on a recycled fiber machine and in connection with a web containing recycled fiber. The adhesive can also be applied essentially to one side of the web, thereby forming a large liquid film on the surface of the web.

To increase the contact pressure level of the press nipple 1, the hard press nip 3 is provided with x hard surface press members for generating a sufficiently high contact pressure

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and a high solids content to achieve sufficient penetration 30 into the web 6. Preferably, the press nip 3 is of two steel rolls or? combination of steel roll and hard polymer roll. There may be a pressure member surface

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the hard material also includes rubber, polyurethane, epoxy, steel, steel strap, a combination thereof or other typical material used in the hard nip 8 of a papermaking machine. The press roll may be coated to prevent adhesion of the adhesive, since film forming capability is not necessarily required. The rollers may also be scraped or equipped with a cleaning device. Scrubbing of the hard surface is much better than the soft surface 5 and the adhesive mixture does not stick so easily to the hard surface.

The adhesive penetration into the web can be enhanced by driving the web from the hard roll nip after application. This has not been possible in film gluing due to the scratches of the rolls when using the groove rod or the lack of film forming ability. 10 At the press nip 3, a line load higher than that of a typical film sizing can also be used, e.g.

It is also possible to use a belt or belts as a pressing member. The clamping member may be a hard belt. Preferably, the belt is guided through a roll nip. Press roll 2; The 3 may also be a deflection compensated roll to allow high line loading in the nip. The deflection-compensated roll can be used to provide a high and uniform contact pressure on the nip and improve the penetration of the adhesive mixture into the web. The use of a deflection compensated roll can also substantially reduce the roll diameters as compared to tubular rolls.

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The adhesive is applied to the web 6 preferably by conventional injection nozzles 4, 5, using a conventional higher injection pressure. The pressure causes the rigid liquid to flow faster from the nozzles, thereby making the fluid flow turbulent. The formation of a steady jet requires a turbulent flow through the 'ίο 25 nozzle hole. Preferably, the pressure is in the range of 20-35 bar, although lower and g higher pressures may be used. After application, the web is driven to a nip where the droplets of adhesive are evened out and the adhesive penetrates the web.

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The adhesive mixture can be first pumped through a pressure screen at low pressure and then the pressure is raised by a separate high pressure pump to the desired level. Since the pressure 5 can no longer be used to control the application rate, it is no longer possible to adjust it

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application rate for selected spray nozzle distribution 4, 5 in spray nozzle, 9 nozzle size, and dry solids content. The pressure can be used to fine-tune the spray application.

Figures 2 and 3 illustrate significant differences in the increase in strength of the adhesive-treated web 5. Significant differences occur between adhesive treatments with hard and soft press nip, when adhesive mixtures with different solids contents have been sprayed onto the web and then pressed in the press nip under different loads. The Huygen strength of the surface-glued 110 g / m2 bottom board is shown in Fig. 2, where the vertical axis shows the 10% increase in Huygen strength and the horizontal axis shows the amount of starch in grams per square meter. The CMT30 strength of the surface-glued 110 g / m 2 bottom board is shown in Fig. 3, where the vertical axis shows the percentage increase in CMT30 strength and the horizontal axis shows the amount of starch in grams per square meter.

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The results shown in Figures 2 and 3 have been reached in an experimental design comparing the difference between hard and soft nips with liner / fluting strengths. In the experimental set-up, a 40% increase in strength with dry adhesive was tested. Two modified maize starches were used as adhesive mixtures as follows: 20-40% dry matter content - viscosity 118mPas - 20% dry matter content - viscosity 24mPas.

In addition, low viscosity oxidized potato starch at a dry matter content of 25% was used for the strength comparison. The high solids adhesive mixtures were applied to both sides of the web by 25 high pressure pumps of the spray coating apparatus using conventional spray nozzles of the spray application bar. In the results shown in Figures 2 and 3, the amount of starch remaining on both sides of the web is measured, so the amount of starch dispensed on one x side is half that of the graphs

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numerical values. In high-viscosity driving, the amount of adhesive was limited by the yield of the high pressure pump.

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In the test arrangement, hard surface press rolls 1, 2 of hard calender nip were used as hard-pressed press members. In the test setup, the first press roll 1 was a 10 hard surface polymer roll (375 mm diameter, 95 ShD hardness) and the second press roll 2 was a steel roll (500 mm diameter). Line loads of 30 and 60 kN / m for a high 40% dry solids adhesive and 5 series of 10, 30, 60 and 80 kN / m for 20% dry solids adhesive were used as the line loads for the hard press nip 3.

The test set-up used soft-pressed press rolls with a 1425 mm diameter and 20 P&J hardness as the soft-pressed press members. The line pressure of the soft nip was 50 kN / m.

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From the diagrams shown in Figures 2 and 3, it can be seen that the same strength improvement can be achieved for the adhesive-treated web with smaller amounts of adhesive when the web is pressed in a hard nip. A high solids blend of 40% high viscosity and a high viscosity adhesive blend can provide a good strength improvement in a cost effective manner because less water needs to be dried from the web. In this way, drying energy can be saved, investment in drying equipment reduced and, if necessary, production capacity increased.

The foregoing description provides non-limiting examples of some embodiments of the invention. However, it will be apparent to one skilled in the art that the invention is not limited to the details set forth, but that the invention may also be practiced in other equivalent ways. Some features of the embodiments shown may be utilized without the use of other features.

The above description is to be considered as a description only of the principles of the invention, and not a limitation of the invention. Thus, the scope of the invention is limited only by the appended claims.

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Claims (19)

A method of making paper or paperboard, in which a spray mixture having a dry matter content of more than 15% is sprayed from spray nozzles (4,5) to a liquid film directly on at least one surface of a web (6) and pressed. the web together after the spraying of the adhesive mixture by passing the web through a press nip (3) consisting of two mutually loaded rotating pressing means (1, 2), characterized in that the adhesive mixture is arranged at a spray pressure of 20 to 100 bar in the spray nozzles, and after the spraying is pressed the web together in a hard press nip (3) between the pressing means (1,2) having a hard surface. Process according to claim 1, characterized in that an adhesive mixture having a dry matter content of more than 20%, preferably more than 40%, is sprayed. 15 Method according to claim 1 or 2, characterized in that an adhesive mixture having a viscosity above 100 mPas is sprayed. Method according to any one of claims 1 to 3, characterized in that in the spray nozzles (4, 5) a turbulent glue mixing flow is created by means of a high spray pressure. Method according to any one of claims 1 to 4, characterized in that the web is pressed together with a roller (1, 2) or a band which at least has on its surface metal, frame, polymer, epoxy, rubber or a combination thereof. δ 25 c \ j ra Method according to any one of claims 1 to 5, characterized in that the web 0 is compressed with a bending-compensated roller. CC CL Process according to any one of claims 1 to 6, characterized in that for the preparation of the web (6), recovered fiber is used, and the glue mixture? is sprayed on at least the side of the web on which the recovered fiber is located. CVJ Method according to any one of claims 1 to 7, characterized in that the web (6) is compressed in the press nip (3) with a line load of 30 - 80 kN / m. Method according to any one of claims 1 to 8, characterized in that the web (6) is compressed in the press nip (3) with a line load of 80 - 200 kN / m. 5 Method according to any of claims 1 to 9, characterized in that the amount of glue mixture applied is controlled by the distribution of the spray nozzles (4, 5), the size of the nozzles and / or the dry matter content of the glue mixture. 10 Method according to any of claims 1-10, characterized in that the applied amount of glue mixture is fine-tuned by changing the size of the spray pressure. 15 Process according to any one of claims 1 to 11, characterized in that starch, PVA, silicone, coating paste, latex or pigment-surface adhesive mixture are applied as an adhesive mixture. An apparatus (10) for making paper or cardboard, said plant comprising spray nozzles (4, 5) for spraying an adhesive mixture having a solids content above 15% into a liquid film directly on at least one surface of a web ( 6), and a press nip (3) for compressing the web after spraying the adhesive mixture, said press nip consisting of two mutually loaded rotating press members (1, 2), characterized in that the plant is provided with a high pressure pump configured to provide a spray pressure of 20-100 co bar, and that the adhesive mixture is arranged to be pressed into the plant after spraying 0 in a hard press nip (3) between the pressing means (1, 2) having a hard surface. CC CL Plant according to claim 13, characterized in that the plant is configured to spray a glue mixture having a dry matter content above 20%, preferably more than 40%. o CVJ Plant according to claim 13 or 14, characterized in that the plant is configured to spray an adhesive mixture having a viscosity above 100mPas. Installation according to any of claims 13 to 15, characterized in that the spray nozzles (4, 5) are configured to spray a turbulent glue mixing stream by means of a high spray pressure. Installation according to any one of claims 13 to 16, characterized in that as a hard surface press means a roller (1, 2) or a belt having at least 10 on its surface has metal, frame, polymer, epoxy, rubber or a combination of these. Installation according to any one of claims 13 - 17, characterized in that a bending-compensated roller is arranged as a pressing means. Plant according to any one of claims 13 - 18, characterized in that the plant comprises load means for fully compressing the nip with a line load up to 200 kN / m. 't δ c \ j 00 o X CC CL 00 CD C \ l CD O O CM