A method for improving the flatness of paper sheets

Abstract

The present application discloses a method for improving the flatness of paper sheets. The method for improving the flatness of paper sheets comprises: guiding the wet paper formed by the wire part to the pressing part; adjusting the opening of the lower felt cloth water absorption box and / or adjusting the opening of the upper felt cloth water absorption box; drying and calendering the wet paper after pressing. The present application reduces the rewetting of paper sheets, slows down the phenomenon of paper sheet pressure feeding, and improves the flatness of paper sheets by adjusting the opening of the lower felt cloth water absorption box and / or adjusting the opening of the upper felt cloth water absorption box.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking, and in particular to a method for improving the flatness of paper sheets. Background Art

[0002] Pressing is an important part of the papermaking process. It not only improves the dryness, wet strength and flatness of the paper sheets after pressing, but also ensures that the wet paper sheets have good runnability after being pressed to the drying section. In the actual production process, inappropriate felt design and selection of the press section often cause a series of problems such as paper sheet damage and poor processing performance, causing considerable trouble to production. Summary of the invention

[0003] In view of the above problems, the present application provides a method for improving the flatness of paper sheets, thereby reducing the rewetting of paper sheets, alleviating the phenomenon of paper sheet pressure feeding, and improving the flatness of paper sheets.

[0004] In order to solve the above problems, the present application provides a method for improving the flatness of paper sheets, including: guiding the wet paper formed by the wire part to the pressing part; adjusting the opening of the lower felt cloth water absorption box, and / or adjusting the opening of the upper felt cloth water absorption box; drying and calendering the pressed wet paper.

[0005] In some embodiments, adjusting the opening of the lower felt cloth water suction box is adjusting the opening of the lower felt cloth water suction box to 80%-100%.

[0006] In some embodiments, adjusting the opening of the upper felt cloth water suction box is adjusting the opening of the upper felt cloth water suction box to 40%-60%.

[0007] In some embodiments, the method for improving the flatness of a paper sheet further includes adjusting the high-pressure spray pressure of a lower felt cloth and / or adjusting the high-pressure spray pressure of an upper felt cloth.

[0008] In some embodiments, adjusting the high-pressure spray pressure of the lower felt cloth and / or adjusting the high-pressure spray pressure of the upper felt cloth includes: increasing the high-pressure spray pressure of the lower felt cloth and / or reducing the high-pressure spray pressure of the upper felt cloth.

[0009] In some embodiments, increasing the high-pressure spraying pressure of the lower felt cloth is increasing the high-pressure spraying pressure of the lower felt cloth to 18 bar-25 bar.

[0010] In some embodiments, reducing the high-pressure spraying pressure of the upper felt cloth is reducing the high-pressure spraying pressure of the upper felt cloth to 5 bar-10 bar.

[0011] In some embodiments, the method for improving the flatness of a paper sheet further comprises: reducing the amount of a retention agent on the first side of the paper sheet, and / or increasing the amount of a retention agent on the second side of the paper sheet.

[0012] In some embodiments, reducing the amount of the retention agent on the first side of the paper sheet is reducing the amount of the retention agent on the first side of the paper sheet to 50 ppm-100 ppm.

[0013] In some embodiments, increasing the amount of the retention agent on the second side of the paper sheet is increasing the amount of the retention agent on the second side of the paper sheet to 250 ppm-350 ppm.

[0014] The beneficial effect of the present application is that by adjusting the opening of the lower felt cloth water absorption box and / or adjusting the opening of the upper felt cloth water absorption box, the rewetting of the paper sheet is reduced, the paper sheet pressure feeding phenomenon is alleviated, and the flatness of the paper sheet is improved.

[0015] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0017] Figure 1 A schematic flow chart of a method for improving the flatness of a paper sheet according to some embodiments of the present application;

[0018] Figure 2 A schematic flow chart of a method for improving the flatness of a paper sheet according to some other embodiments of the present application;

[0019] Figure 3 A schematic flow chart of a method for improving the flatness of a paper sheet according to some other embodiments of the present application;

[0020] Figure 4 A schematic flow chart of a method for improving the flatness of a paper sheet according to some other embodiments of the present application;

[0021] Figure 5 The paper sheet generated for Application Example 1;

[0022] Figure 6 This is the paper sheet generated for Comparative Example 1. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] It should be noted that the terms "first", "second", etc., hereinafter are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0025] The words in this specification are used to illustrate the embodiments of the present invention, but are not intended to limit the present invention. It should also be noted that, unless otherwise clearly specified and limited, the terms "set", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, an indirect connection through an intermediate medium, or the internal connection of two components. For those skilled in the art, the above-mentioned specific meanings in the present invention can be specifically understood.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] It is understandable that there are many methods for making paper, and any suitable papermaking method can be used in the embodiments of the present application.

[0028] In some embodiments, papermaking is carried out by a papermaking method, and the papermaking process of the paper sheet is as follows: the papermaking machine consists of two parts: the wet part and the dry part. The wet part includes a headbox, a wire part and a press part; the dry part includes a dryer, a calender and a paper reel. The paper stock sent by the purification system is a floating liquid, which is sprayed to the middle of two wires at a uniform and stable pulping speed through the headbox (generally sprayed at a 45-degree or 90-degree angle). After being formed by removing most of the water from both sides of the two wires, it is sent to an advanced shoe press for pressing and dehydration, and the performance of the paper sheet is improved, and the tightness and surface smoothness of the paper sheet are increased. After the paper sheet is dehydrated by the pressing machine, it is sent to the drying part to use heat energy for further dehydration to meet the moisture content requirements of the finished paper. The offset paper is also subjected to surface sizing treatment in the drying part to improve the surface strength and other properties of the paper to meet the requirements of high-speed printing. The surface of the paper sheet coming out of the drying part is still very rough and cannot meet the requirements of printing and writing. In order to improve the smoothness of the paper and adjust the thickness of the paper, the paper must also be calendered by one or more metal rollers (usually two calenderings, one positive and one negative). After calendering, the paper can be cut into flat sheets or rolled into rolls by a rewinder.

[0029] It is understandable that the structural composition of the press section of different paper machines is different, but their basic composition is roughly similar. The various devices and components contained in the press section can be divided into the following parts: 1. Various types of presses formed by various types of press rolls in different matching combinations; 2. Various accessories for presses such as pressure lever system, scraper, jet scraper, water spray pipe, water receiving tray, etc.; 3. Various felt cloth laying parts such as corrector, tensioner, spreader roller, guide roller and its scraper, washing and state adjustment device (felt cloth suction box, felt cloth squeezing water press, water spray pipe), etc.; 4. Various suction and transfer devices for paper web such as suction roller, suction box, paper guide rope, paper guide jet, etc.; 5. Rollers on the paper web line such as paper guide roller and damaged paper conveying device; 6. Pneumatic pressure system and hydraulic pressure system; 7. Frame and walkway, etc.

[0030] It is understood that the wet paper sheet formed in the wire section needs to be mechanically pressed in the pressing section before being sent to the drying section for drying. Pressing is a basic unit in the papermaking process, which removes moisture from the wet paper web through the mechanical squeezing action of two rollers or rollers and boots. The moisture removed in the press area is transferred to the pressing felt or fabric, or to the pores on the surface of the roller. Heating is also often used in production to increase the temperature of the wet paper web fiber network and the water contained in it to improve the dehydration efficiency. Pressing is an important part of the papermaking process, affecting the economic efficiency of production and product quality. The final quality of the paper sheet is affected by the following factors: 1. The mechanical compressibility of the wet paper web during pressing; 2. The tightness distribution of the paper sheet in the thickness direction; 3. The surface contact between the press roller and the felt and the wet paper web.

[0031] It can be understood that the embodiments of the present application improve the surface contact between the pressure roller and the felt cloth and the wet paper sheet, thereby reducing the rewetting of the paper sheet, alleviating the paper sheet pressure feeding phenomenon, and improving the flatness of the paper sheet.

[0032] Please refer to Figure 1 , Figure 1 This is a schematic flow chart of a method for improving the flatness of a paper sheet according to some embodiments of the present application.

[0033] In some embodiments, the method for improving the flatness of a paper sheet comprises the following steps:

[0034] S10: Lead the wet paper formed in the wire section to the press section.

[0035] It is understood that in the wire section of the papermaking process, the paper material flows out from the head box onto the circulating copper wire mesh or plastic mesh and is evenly distributed and interwoven to form wet paper. The wire surface is removed and the wet paper is led between two rollers with a felt cloth attached. Through the squeezing of the rollers and the water absorption of the felt cloth, the wet paper is further dehydrated and the paper is made denser to improve the paper surface and increase the strength.

[0036] S20: adjusting the opening of the lower felt cloth water suction box and / or adjusting the opening of the upper felt cloth water suction box.

[0037] In some embodiments, only the opening of the lower felt suction box is adjusted.

[0038] In some embodiments, only the opening of the upper felt suction box is adjusted.

[0039] In some embodiments, the opening of the lower felt cloth water suction box and the opening of the upper felt cloth water suction box are adjusted simultaneously.

[0040] In some embodiments, the opening of the lower felt water absorption box is adjusted to 80%-100%.

[0041] In some embodiments, the opening of the upper felt water absorption box is adjusted to 40%-60%.

[0042] In some embodiments, the opening degree of the lower felt water suction box is adjusted to 80%-100%, and the opening degree of the upper felt water suction box is adjusted to 40%-60%.

[0043] In some embodiments, the opening of the lower felt water absorption box can be adjusted to 80%, 82%, 85%, 87.5%, 90%, 95%, 97.5%, 100%, etc.

[0044] In some embodiments, the opening of the upper felt cloth water absorption box can be adjusted to 40%, 42%, 45%, 47.5%, 50%, 55%, 57.5%, 60%, etc.

[0045] S30: Drying and calendering the pressed wet paper.

[0046] It is understandable that the wet paper sheets after dehydration by the press section need to be further dehydrated by heating and drying. The drying section of the paper machine consists of many drying cylinders, which can be heated from the inside by steam. The drying cylinders are covered with dry cloth to press the paper sheets tightly against the cylinder surface to improve the heat transfer efficiency. After thorough drying, a calender consisting of 6-8 rollers will be used to calender the paper sheets to improve the overall surface quality of the paper sheets, such as the flatness of the paper sheets.

[0047] See also Figure 2 , Figure 2 Schematic diagram of the flow of methods for improving the flatness of paper sheets according to other embodiments of the present application.

[0048] In some embodiments, the method for improving the flatness of a paper sheet comprises the following steps:

[0049] S10: Lead the wet paper formed in the wire section to the press section.

[0050] S20: adjusting the opening of the lower felt cloth water suction box and / or adjusting the opening of the upper felt cloth water suction box.

[0051] In some embodiments, only the opening of the lower felt suction box is adjusted.

[0052] In some embodiments, only the opening of the upper felt suction box is adjusted.

[0053] In some embodiments, the opening of the lower felt cloth water suction box and the opening of the upper felt cloth water suction box are adjusted simultaneously.

[0054] In some embodiments, the opening of the lower felt water absorption box is adjusted to 80%-100%.

[0055] In some embodiments, the opening of the upper felt water absorption box is adjusted to 40%-60%.

[0056] In some embodiments, the opening degree of the lower felt water suction box is adjusted to 80%-100%, and the opening degree of the upper felt water suction box is adjusted to 40%-60%.

[0057] In some embodiments, the opening of the lower felt water absorption box can be adjusted to 80%, 82%, 85%, 87.5%, 90%, 95%, 97.5%, 100%, etc.

[0058] In some embodiments, the opening of the upper felt cloth water absorption box can be adjusted to 40%, 42%, 45%, 47.5%, 50%, 55%, 57.5%, 60%, etc.

[0059] S22: adjusting the high-pressure spraying pressure of the lower felt cloth, and / or adjusting the high-pressure spraying pressure of the upper felt cloth.

[0060] In some embodiments, adjusting the high-pressure spray pressure of the lower felt cloth and / or adjusting the high-pressure spray pressure of the upper felt cloth includes: increasing the high-pressure spray pressure of the lower felt cloth and / or reducing the high-pressure spray pressure of the upper felt cloth.

[0061] In some embodiments, only the high pressure spray pressure of the lower felt is increased.

[0062] In some embodiments, only the high pressure spray pressure of the upper felt is reduced.

[0063] In some embodiments, the high-pressure spray pressure of the upper felt is reduced while the high-pressure spray pressure of the lower felt is increased.

[0064] In some embodiments, the high pressure spray pressure of the lower felt is increased to 18 bar-25 bar.

[0065] In some embodiments, the high pressure spray pressure of the upper felt is reduced to 5 bar-10 bar.

[0066] In some embodiments, while the high pressure spray pressure of the lower felt is increased to 18 bar-25 bar, the high pressure spray pressure of the upper felt is reduced to 5 bar-10 bar.

[0067] In some embodiments, the high pressure spray pressure of the lower felt cloth can be increased to 18 bar, 18.5 bar, 19 bar, 20 bar, 21 bar, 21.3 bar, 22 bar, 23 bar, 24 bar, 24.5 bar, 25 bar, etc.

[0068] In some embodiments, the high pressure spray pressure of the upper felt cloth can be reduced to 5 bar, 5.5 bar, 6 bar, 6.5 bar, 7 bar, 7.3 bar, 8 bar, 8.5 bar, 9 bar, 9.5 bar, 10 bar, etc.

[0069] S30: Drying and calendering the pressed wet paper.

[0070] See also Figure 3 , Figure 3 Schematic diagram of the flow of methods for improving the flatness of paper sheets according to other embodiments of the present application.

[0071] In some embodiments, the method for improving the flatness of a paper sheet comprises the following steps:

[0072] S10: Lead the wet paper formed in the wire section to the press section.

[0073] S20: adjusting the opening of the lower felt cloth water suction box and / or adjusting the opening of the upper felt cloth water suction box.

[0074] In some embodiments, only the opening of the lower felt suction box is adjusted.

[0075] In some embodiments, only the opening of the upper felt suction box is adjusted.

[0076] In some embodiments, the opening of the lower felt cloth water suction box and the opening of the upper felt cloth water suction box are adjusted simultaneously.

[0077] In some embodiments, the opening of the lower felt water absorption box is adjusted to 80%-100%.

[0078] In some embodiments, the opening of the upper felt water absorption box is adjusted to 40%-60%.

[0079] In some embodiments, the opening degree of the lower felt water suction box is adjusted to 80%-100%, and the opening degree of the upper felt water suction box is adjusted to 40%-60%.

[0080] In some embodiments, the opening of the lower felt water absorption box can be adjusted to 80%, 82%, 85%, 87.5%, 90%, 95%, 97.5%, 100%, etc.

[0081] In some embodiments, the opening of the upper felt cloth water absorption box can be adjusted to 40%, 42%, 45%, 47.5%, 50%, 55%, 57.5%, 60%, etc.

[0082] S22: adjusting the high-pressure spraying pressure of the lower felt cloth, and / or adjusting the high-pressure spraying pressure of the upper felt cloth.

[0083] In some embodiments, adjusting the high-pressure spray pressure of the lower felt cloth and / or adjusting the high-pressure spray pressure of the upper felt cloth includes: increasing the high-pressure spray pressure of the lower felt cloth and / or reducing the high-pressure spray pressure of the upper felt cloth.

[0084] In some embodiments, only the high pressure spray pressure of the lower felt is increased.

[0085] In some embodiments, only the high pressure spray pressure of the upper felt is reduced.

[0086] In some embodiments, the high-pressure spray pressure of the upper felt is reduced while the high-pressure spray pressure of the lower felt is increased.

[0087] In some embodiments, the high pressure spray pressure of the lower felt is increased to 18 bar-25 bar.

[0088] In some embodiments, the high pressure spray pressure of the upper felt is reduced to 5 bar-10 bar.

[0089] In some embodiments, while the high pressure spray pressure of the lower felt is increased to 18 bar-25 bar, the high pressure spray pressure of the upper felt is reduced to 5 bar-10 bar.

[0090] In some embodiments, the high pressure spray pressure of the lower felt cloth can be increased to 18 bar, 18.5 bar, 19 bar, 20 bar, 21 bar, 21.3 bar, 22 bar, 23 bar, 24 bar, 24.5 bar, 25 bar, etc.

[0091] In some embodiments, the high pressure spray pressure of the upper felt cloth can be reduced to 5 bar, 5.5 bar, 6 bar, 6.5 bar, 7 bar, 7.3 bar, 8 bar, 8.5 bar, 9 bar, 9.5 bar, 10 bar, etc.

[0092] S24: reducing the amount of the retention agent on the first side of the paper sheet, and / or increasing the amount of the retention agent on the second side of the paper sheet.

[0093] In some embodiments, the amount of retention aid is reduced only on the first side of the sheet.

[0094] In some embodiments, the retention aid dosage is increased only on the second side of the sheet.

[0095] In some embodiments, the amount of retention agent on the first side of the sheet is decreased while the amount of retention agent on the second side of the sheet is increased.

[0096] In some embodiments, the retention aid dosage on the first side of the paper sheet is reduced to 50 ppm to 100 ppm.

[0097] In some embodiments, the retention aid dosage on the second side of the paper sheet is increased to 250 ppm to 350 ppm.

[0098] In some embodiments, the retention agent dosage on the first side of the paper sheet is reduced to 50 ppm-100 ppm, and the retention agent dosage on the second side of the paper sheet is increased to 250 ppm-350 ppm.

[0099] In some embodiments, the amount of retention aid on the first side of the paper sheet can be reduced to 50 ppm, 55.5 ppm, 60 ppm, 70 ppm, 75.5 ppm, 80 ppm, 90 ppm, 95 ppm, 97.5 ppm, 100 ppm, etc.

[0100] In some embodiments, the retention aid dosage on the second side of the paper sheet can be increased to 250 ppm, 255.5 ppm, 260 ppm, 270 ppm, 280 ppm, 290 ppm, 295.5 ppm, 300 ppm, 310 ppm, 320 ppm, 330 ppm, 340 ppm, 345.5 ppm, 350 ppm, etc.

[0101] S30: Drying and calendering the pressed wet paper.

[0102] See also Figure 4 , Figure 4 Schematic diagram of a process for improving the flatness of a paper sheet according to some other embodiments of the present application.

[0103] In some embodiments, the method for improving the flatness of a paper sheet comprises the following steps:

[0104] S10: Lead the wet paper formed in the wire section to the press section.

[0105] S21: adjusting the opening of the lower felt cloth water absorption box to 80%-100%, and / or adjusting the opening of the upper felt cloth water absorption box to 40%-60%.

[0106] In some embodiments, the opening of the lower felt water absorption box is adjusted to 80%-100%.

[0107] In some embodiments, the opening of the upper felt water absorption box is adjusted to 40%-60%.

[0108] In some embodiments, the opening degree of the lower felt water suction box is adjusted to 80%-100%, and the opening degree of the upper felt water suction box is adjusted to 40%-60%.

[0109] S23: Increase the high pressure spray pressure of the lower felt to 18 bar-25 bar, and / or reduce the high pressure spray pressure of the upper felt to 5 bar-10 bar.

[0110] In some embodiments, the high pressure spray pressure of the lower felt is increased to 18 bar-25 bar.

[0111] In some embodiments, the high pressure spray pressure of the upper felt is reduced to 5 bar-10 bar.

[0112] In some embodiments, while the high pressure spray pressure of the lower felt is increased to 18 bar-25 bar, the high pressure spray pressure of the upper felt is reduced to 5 bar-10 bar.

[0113] S25: reducing the amount of the retention agent on the first side of the paper sheet to 50 ppm-100 ppm, and / or increasing the amount of the retention agent on the second side of the paper sheet to 250 ppm-350 ppm.

[0114] In some embodiments, the retention aid dosage on the first side of the paper sheet is reduced to 50 ppm to 100 ppm.

[0115] In some embodiments, the retention aid dosage on the second side of the paper sheet is increased to 250 ppm to 350 ppm.

[0116] In some embodiments, the retention agent dosage on the first side of the paper sheet is reduced to 50 ppm-100 ppm, and the retention agent dosage on the second side of the paper sheet is increased to 250 ppm-350 ppm.

[0117] Embodiment 1:

[0118] The parameter settings in the production process of the paper sheet of FK1230 are shown in Table 1, the control speed is 1350m / min, the main steam pressure is 2.09bar, the first press line pressure (shoe pressure) is 985, the retention agent of the first side layer of the paper sheet is 100ppm, the retention agent of the second side of the paper sheet is 350ppm, the high pressure spray pressure of the first press felt cloth is 8bar, the high pressure spray pressure of the first press felt cloth is 22bar, the opening of the first press felt cloth water absorption box is 40%, and the opening of the first press felt cloth water absorption box is 100%. The relevant indicators of the final generated paper sheet are shown in Table 1. The parameter settings and paper sheet related indicators of Example 2 and Comparative Examples 1-3 are shown in Table 1. Figure 5 The paper sheet of Example 1, Figure 6 This is the paper sheet of Comparative Example 1.

[0119] Table 1: Comparison of relevant indicators of paper sheets of various embodiments and comparative examples

[0120]

[0121]

[0122] In summary, the following three adjustment measures can be taken to make the paper sheet out of the pressing nip stick to the felt cloth to improve the flatness of the paperboard surface. 1. Adjust the opening of the felt cloth water absorption box. 2. Adjust the high-pressure spray pressure of the upper and lower felt cloths. 3. Adjust the amount of retention agent on both sides of the paper sheet.

[0123] It is understandable that by adjusting the opening of the felt cloth suction box, i.e. increasing the suction of the lower felt cloth suction box, i.e. the opening of the lower felt cloth suction box to 80%-100%, the suction of the upper felt cloth suction box can be reduced, i.e. the opening of the upper felt cloth suction box to 40%-60%, so that the paper sheet out of the pressing nip is attached to the felt cloth. The openings of the upper and lower felt cloth suction boxes can also be adjusted at the same time, i.e. while adjusting the opening of the lower felt cloth suction box to 80%-100%, the opening of the upper felt cloth suction box can be adjusted to 40%-60%. Because the moisture in the paper sheet is removed under the vacuum suction of the felt cloth suction box after the moisture in the paper sheet is transferred to the felt cloth, the moisture in the felt cloth is removed under the vacuum suction of the felt cloth suction box, so increasing the suction of the lower felt cloth suction box reduces the moisture content of the felt cloth and reduces the rewetting of the paper sheet, so the wet paper sheet is easy to be peeled off; conversely, reducing the suction of the upper felt cloth suction box increases the moisture content of the felt cloth and increases the rewetting of the paper sheet, so the wet paper sheet is not easy to be peeled off.

[0124] It is understandable that the high-pressure spraying pressure of the upper and lower felt cloths can be adjusted, that is, the high-pressure spraying pressure of the upper felt cloth can be reduced to 5bar-10bar; or the high-pressure spraying pressure of the lower felt cloth can be increased to 18bar-25bar; or the high-pressure spraying pressure of the upper felt cloth can be reduced to 5bar-10bar while the high-pressure spraying pressure of the lower felt cloth can be increased to 18bar-25bar. Under normal circumstances, the high-pressure spraying pressure of the upper and lower felt cloths is 15bar-18bar. Because the high-pressure spraying of felt cloths is used for cleaning and maintaining felt cloths, the surface of the felt cloths is a flocking layer of polyester material, and the high-pressure spraying of a 1mm water column can penetrate the flocking layer and even the base net under pressure to achieve the purpose of cleaning, so that the flocking layer of the felt cloth remains fluffy, the air permeability of the felt cloth remains at a high level, and the wet paper sheets are easy to be peeled off; on the contrary, the flocking layer of the felt cloth will be compacted and dense after the pressure of the pressure zone, and the air permeability is low, so the wet paper sheets are not easy to be peeled off.

[0125] It is understood that the amount of retention aid on both sides of the paper sheet is adjusted, that is, the retention aid on the first side of the paper sheet is reduced to 50ppm-100ppm; or the retention aid on the second side of the paper sheet is increased to 250ppm-350ppm; or the retention aid on the first side of the paper sheet is reduced to 50ppm-100ppm, while the retention aid on the second side of the paper sheet is increased to 250ppm-350ppm. The first side of the paper sheet faces the lower felt cloth, and the second side of the paper sheet faces the upper felt cloth, which is conducive to the wet paper sheet being attached to the upper felt cloth. Because the main function of retention is to retain fine fibers and ash and slow down the dehydration effect, reducing the retention aid can make the paper sheet filter water faster, the fine fiber retention worse, the paper surface rougher and the dryness increased, so the wet paper sheet is easy to be peeled off; conversely, increasing the retention aid can make the paper sheet filter water slower, the fine fiber retention better, the paper surface finer and the humidity increased, and the wet paper sheet is not easy to be peeled off.

[0126] In the above embodiment, by adjusting the opening of the water absorption box of the lower felt cloth and the upper felt cloth; adjusting the lower felt cloth and reducing the high-pressure spray pressure of the upper felt cloth; and adjusting the amount of retention agent on the first side of the paper sheet and the amount of retention agent on the second side of the paper sheet, the paper sheet coming out of the pressing zone is attached to the felt cloth, thereby reducing the rewetting of the paper sheet, slowing down the paper sheet pressure feed phenomenon, and improving the flatness of the paper sheet.

[0127] In the description of this specification, the description of the terms "one embodiment", "another embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0128] The above are only implementation methods of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for improving the flatness of a paper sheet, characterized in that: include: Lead the wet paper formed in the wire section to the press section; Adjust the opening of the lower felt cloth water absorption box to 80%-100%, and / or adjust the opening of the upper felt cloth water absorption box to 40%-60%; Increase the high pressure spray pressure of the lower felt and / or reduce the high pressure spray pressure of the upper felt; reducing the amount of retention agent on the first side of the paper sheet, and / or increasing the amount of retention agent on the second side of the paper sheet; The wet paper after pressing is dried and calendered.

2. The method for improving the flatness of a paper sheet according to claim 1, characterized in that: The increasing of the high-pressure spraying pressure of the lower felt cloth is to increase the high-pressure spraying pressure of the lower felt cloth to 18 bar-25 bar.

3. The method for improving the flatness of a paper sheet according to claim 1, characterized in that: The reducing the high-pressure spraying pressure of the upper felt cloth is to reduce the high-pressure spraying pressure of the upper felt cloth to 5 bar-10 bar.

4. The method for improving the flatness of a paper sheet according to claim 1, characterized in that: The reducing the amount of the retention agent on the first side of the paper sheet is reducing the amount of the retention agent on the first side of the paper sheet to 50 ppm-100 ppm.

5. The method for improving the flatness of a paper sheet according to claim 1, characterized in that: The increasing the amount of the retention agent on the second side of the paper sheet is to increase the amount of the retention agent on the second side of the paper sheet to 250 ppm-350 ppm.

Images