FI126292B

FI126292B - DEVICE FOR PROCESSING FIBERS

Info

Publication number: FI126292B
Application number: FI20155594A
Authority: FI
Inventors: Ilkka Naatti; Petri Ristola
Original assignee: Valmet Technologies Oy
Priority date: 2015-08-20
Filing date: 2015-08-20
Publication date: 2016-09-15
Also published as: DE102016114968A1; CN106468037A; FI20155594A

Description

Device for treating fiber webs

The invention relates to a device for treating fiber webs. Especially the invention relates to a device for treating fiber webs by applying treatment substance on both surfaces of the fiber web, which device applies the treatment substance directly or via a roll onto the surface of the web. In particular the invention relates to a device according to the preamble of claim 1.

As known from the prior art in fiber web producing processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in the process line. A typical production and treatment line comprises a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other devices and sections for finishing the fiber web, for example, a sizer, a calender, a coating section. In this description and the following claims by fiber webs are meant for example paper and board webs.

In production of fiber webs, for example of paper or board webs, sizing is used to alter the properties of a fiber web by adding sizing substances, for example glue chemicals. In surface sizing the sizing substance is added onto the surface of the fiber web directly or via a roll at the dry end of the fiber web machine. The sizing of paper and board web typically utilize a separate sizer. In connection with the sizer different kinds of sizing technology are employed in prior art arrangements, for example pond sizing technology or film-transfer technology or spray sizing technology.

Coated fiber web grades and coating are becoming more and more popular and thus the coating process and equipment have increasing demands imposed thereon. In coating, especially in pigment coating, the surface of a fiber web is formed with a layer of coating color (coating substance) at a coating station followed by drying. The process of coating can be divided in supplying the coating color onto the web surface, which is called the application of the coating color, as well as in the adjustment of final amount of coating color. The coating of paper and board web typically utilize a coating device - a coater. In connection with the coater different kinds of coating technology are employed in prior art arrangements, for example for example pond technology or film-transfer technology or spray technology.

By fiber web producing processes different types and grades of fiber webs are produced. Sometimes one production and treatment line is used for producing different grades of fiber webs, which require different treatments for finishing the fiber web and in some cases the different treatments cannot be made by one device type for a certain technology, especially in sizing or coating, and thus the production and treatment line is to be provided with devices for each technology. Typically good runnability properties for the fiber web to be treated and good penetrability of the treatment substance for different grades of fiber webs is not achievable simultaneously in most cases. For example in sizing by using pond technology good penetrability and good coverage and appearance is achieved but runnability properties achieved are not very good and also the control of amount of size needed is difficult. For example in sizing by using film-transfer technology good runnability properties are achieved and also even coverage and good appearance even when small amounts of size are used but the penetrability is lower. For example in sizing by using spray technology good adjustability of size amount is achieved and the spray technology is also suitable to be used in connection with sizing of unclean fiber web grades as the size does not recirculate back from the spray application.

In sizers and coaters sizing/coating rolls are used to press the treatment substance into the web in nip formed between these rolls and through which nip the fiber web is guided. In treatment devices, i. e. sizers and coaters, based on pond technology one of the rolls is so called hard roll, provided with hard surface, typically with ceramic or metallic surface, and the other is so called soft roll provided with soft surface, typically formed by a polymer cover, and in treatment devices based on film-transfer technology the rolls are soft rolls. In spray technology based treatment devices the rolls can be soft or hard rolls. Thus in production and treatment lines where different types of technologies are needed for production of desired fiber web grades at least one of the rolls of the treatment device must be changed for grade change. The time consumed is long, typically at least 1,5-2 hours for a roll during which time the production and treatment line must be stopped and therefore also the production is stopped.

For example when sizing liner or fluting fiber web grades a sizer type with means for applying the treatment substance based on pond technology for heavy grades and with means for applying treatment substance based on film transfer technology for light grades have been used but optimal sizing result, when one set of rolls have been used, has not been achieved, since with pond technology a hard roll and a soft roll set would be advantageous and with film transfer technology a soft roll and a soft roll set must be used. Typically also a different crowning for each set of rolls has been needed. This has resulted need for numerous rolls and spare rolls for each device and for numerous roll changes, in case the device has been used for treatment of both heavy and light grades in short intervals.

In DE utility model publication 202009016157U1 is disclosed a device for treating a paper or cardboard web with a roll press nip formed by two rolls and through which nip the paper or board web runs through, which device comprises at least a first spray device for applying treatment substance to one side of the paper or cardboard web and at least one first supply means for supplying treatment substance between one of the two rollers and the paper or board web, wherein the treatment substance forms a pond. The device may also comprise a second spray device on the other side of the paper or board web for applying treatment substance to the other side of the paper or board web and a second feeding means for supplying treatment substance to a pond between the other of the two rollers and the paper or board web is provided. In this known device no film transfer treating is disclosed.

In CN utility model publication 204224917U is disclosed a device for treating fiber webs by applying treatment substance on at least one surface of the fiber web, which device may apply the treatment substance directly onto the at least one surface of the fiber web or the treatment substance may be applied onto the at least one surface of the fiber web via a roll onto surface of which the treatment substance is first applied, which device comprises two rolls, in between of which a treatment nip is formed. The device comprises at least two different types of means for applying treatment substance selected from a group consisting of: means based on pond technology, means based on spray technology and means based on film transfer technology.

An object of the present invention is to create a device for treating fiber webs in which the problems and disadvantages of the devices known from the prior art are eliminated or at least minimized.

An object of the present invention is to create a new type of device for treating fiber webs in connection with a production and treatment line of a fiber web.

In order to achieve the above objects and those which will come apparent later the device is characterized by the features of claim 1. Advantageous embodiments and features are disclosed in the dependent claims.

According to the invention the device for treating fiber webs by applying treatment substance on both surfaces of the fiber web, which device comprises two rolls, in between of which rolls a treatment nip is formed, and means for applying treatment substance, which device applies the treatment substance directly or via surfaces of the rolls onto surfaces of the fiber web, wherein means for applying treatment substance comprise means based on pond technology and means based on film transfer technology for coating or sizing the top surface of the fiber web and means based on spray technology for coating or sizing the back surface of the fiber web.

According to the invention the means for applying treatment substance further comprise means based on pond technology for coating or sizing the back surface of the fiber web.

According to the invention the rolls of the device the roll located on the side of the top surface of the fiber web is a soft roll and the roll located on the side of the back surface of the fiber web is a hard roll.

According to an advantageous feature the rolls are used irrespective of choice of different means for applying treatment substance.

According to an advantageous feature the device the means for applying treatment substance for each surface of the fiber web are selectively used for producing and treating different grades of fiber webs such that at least one of means for applying treatment substance at time are used for each surface.

According to an advantageous feature the device is a sizer and the treatment substance is sizing agent, advantageously starch.

According to an advantageous feature the device is a coater and the treatment substance is coating color.

By the invention several advantages are achieved: for example the same rolls can be used irrespective of the fiber web grade to be used and thus the roll need no to be changed even though the grade to be produced is changed and for example the top surface of the web will have an excellent visual properties and the back surface of the web can be applied by means that are more tolerant to dirty pulp. Also by the device according to the invention both liner and fluting fiber web grades can be treated on the same device without need for changing rolls.

In the following the invention is described in more detail with reference to the accompanying drawing in which

Figure 1 discloses schematically one example of a device according to the prior art,

Figure 2 discloses schematically one advantageous example of a device according to the invention and

Figure 3 discloses schematically another advantageous example a device according to the invention.

In the following description and in the accompanying drawing by same reference signs similar or corresponding parts and part-components are denoted unless otherwise mentioned.

In the example of figure 1 is shown a device 10 for treating a fiber web W such as a paper or cardboard according to prior art. The device 10 comprises two rolls 11, 12, such as sizing rolls or coating rolls, in between of which rolls 11, 12 a treatment nip such as a sizing nip or a coating nip is formed. The treatment nip is advantageously a press nip. The fiber web W runs through the treatment nip N. The rolls 11, 12 are supported rotatably at each end in bearing housings 13, 14 supported by a frame 20. The device 10 also comprises means for applying treatment substance 31, 32, 34, 35. In the example of figure 1 the means for applying the treatment substance the fiber web W comprise means based on pond technology 31, 32 for coating or sizing the fiber web W and means based on film transfer technology 34, 35 on both surfaces WT, WB of the fiber web. The fiber web W has a top surface WT, which in the final product will be on the front side i.e. on the visible side of the product, and a back surface WB, which in the final product will be on the back side i.e. on the non-visible side of the product.

In the examples of figures 2 - 3 is shown a device 10 for treating a fiber web W such as a paper or cardboard according to advantageous examples of the invention. The device 10 comprises two rolls 11, 12, such as sizing rolls or coating rolls, in between of which rolls 11, 12 a treatment nip such as a sizing nip or a coating nip is formed. The treatment nip is advantageously a press nip. The fiber web W runs through the treatment nip. The rolls 11, 12 are supported rotatably at each end in bearing housings 13, 14 supported by a frame 20. The roll 11 located on the side of the top surface WT of the fiber web W is a soft roll, advantageously a roll with a polymeric roll cover (rubber or polyurethane) having surface softness 10-70 P&J. The roll 12 located on the side of the back surface WB of the fiber web W is a hard roll, advantageously a roll with a ceramic or carbide coating having surface hardness 800 - 1600 HV0.3, or advantageously a roll with a polymeric roll cover (rubber, polyurethane or composite) having surface hardness 80-100 shoreD, advantageously 85 - 95 shoreD. The rolls 11, 12 are used irrespective of use of different means for applying treatment substance i.e. the rolls 11, 12 are not changed due to grade change of the fiber web W to be produced.

The device 10 also comprises means for applying treatments substance 31, 32, 33, 34.

In the example of figure 2 the means for applying treatment substance comprise means based on pond technology 31 and means based on film transfer technology 34 for coating or sizing the top surface WT of the fiber web W and means based on spray technology 34 for coating or sizing the back surface WB of the fiber web W.

In the example of figure 3 the means for applying treatment substance the fiber web W comprise means based on pond technology 31 and means based on film transfer technology 34 for coating or sizing the top surface WT of the fiber web W and means based on spray technology 34 and means based on pond technology 32 for coating or sizing the back surface WB of the fiber web W.

The device 10 in the examples of figures 2 and 3 comprises for treating the top surface WT of the fiber web W at least two different types of means for applying treatment substance 31, 32 that can selectively be used: means based on pond technology 31 and means based on film transfer technology 34 and for treating the back surface WB of the fiber web W at least two different types of means for applying treatment substance 32, 33 that can selectively be used: means based on pond technology 32 and means based on spray technology 33.

The means for applying treatment substance 31, 32, 33, 34 for each surface WT, WB of the fiber web W are selectively used for producing and treating different grades of fiber webs such that at least one of the means at time are used for each surface. In connection with fiber web grade change that need different type of means for applying treatment substance than already in use, the means already in use for the grade in production are switched off and the means needed for the production of the new grade are switched on.

Above only some advantageous examples of the inventions has been described to which examples the invention is not to be narrowly limited and many modifications and alterations are possible within the invention.

Reference signs used in the drawings: 10 device for treating fiber webs 11, 12 roll 13, 14 bearing housing 20 frame 31, 32 means for applying treatment substance based on pond technology 33 means for applying treatment substance based on spray technology 34, 35 means for applying treatment substance based on film transfer technology W fiber web WT top surface of the fiber web WB back surface of the fiber web

Claims

Apparatus for treating fibrous webs (W) by applying a treating agent to each surface (WT, WB) of the fibrous web (W), the device (10) comprising two rolls (11, 12) with a concept nip formed between the rolls (11, 12), and means (31, 32, 33, 34) for applying a treatment agent, the device (10) applying the treatment agent directly or through the surfaces of the rolls (11, 12) to the fiber web surfaces, the means for applying the fiber web comprising pond technology (31) and film transfer technology means (34) for covering or surface gluing the top surface (WT) of the fibrous web (W) and means (33) for spray technology (32) and rear surface (WB) for the fibrous web (W), characterized in that 12) the roll (11) located on the top surface (WT) of the fibrous web (W) is a soft roll and the roll (12) located on the back (WB) of the fibrous web (W) is a hard roll.

Device according to Claim 1, characterized in that the rollers (11, 12) are used independently of the choice of application of a treatment agent for different means.

Apparatus according to claim 1 or 2, characterized in that the means (31, 34; 32, 33) for applying a treating agent to each surface (WT, WB) of the fibrous web (W) are selectively used to produce and process different types of fibrous webs (W) at least one means for treating the fibrous web at a time is used for each surface (WT, WB).

Device according to one of Claims 1 to 3, characterized in that the device (10) is a surface sizing device and the treatment agent is a surface sizing agent, preferably starch.

Device according to one of Claims 1 to 3, characterized in that the device (10) is a coating device and the processing agent is a coating agent.