Tensioning roller for flexographic printing press and flexographic printing method using same in the production of laminated plywood

Abstract

The invention relates to a flexographic printing device and a flexographic printing method. The aim of the present invention is to improve the quality of flexographic printing by providing for the steady and uniform impregnation of paper, and to reduce expenditure on paper through the use of cheaper materials, while preserving print quality and the aesthetic appearance of the end product, namely laminated plywood. The invention also makes it possible to speed up the paper impregnation process, thus increasing the productivity of an impregnation line. To solve the problem of interest, a tensioning roller for a flexographic printing press is proposed which comprises sharp-edged channels across the entire surface of the roller or in the central part of the surface of the roller, wherein the sharp edges of said channels penetrate into the underside of the paper and lift the flocking thereof, allowing resins to penetrate unimpeded throughout the paper during impregnation. This makes it possible to use cheaper, less homogeneous paper that is not designed for impregnation and has poor absorbency for the process of impregnation with phenol resins and subsequently for printing in the production of laminated plywood, which in turn makes it possible to carry out uniform impregnation of the paper and to speed up the paper impregnation process, thus increasing the productivity of an impregnation line, reducing expenditure on paper, and preserving print quality and the aesthetic appearance of the end product, namely laminated plywood.

Description

[0001] B41F 5 / 00

[0002] B41F 5 / 04 B41F 5 / 06 B41F 5 / 08 B41F 5 / 16 B41F 5 / 24 B41M 1 / 04

[0003] Tension roller of a flexographic printing machine and a method of flexographic printing using it in the production of laminated plywood

[0004] The invention relates to a device for flexographic printing and a method for flexographic printing.

[0005] Flexographic printing is a printing method that involves direct, high-press rotary printing with quick-drying liquid inks that adhere to various materials, including flexible ones.

[0006] Flexographic printing uses flexible printing plates, typically made of photopolymer materials. These plates are created using a photographic process where the image is transferred to the plate, leaving raised areas that will receive the ink. A flexographic printing press operates on the following principle. Ink is fed to an anelox roller, which has special cells to hold the ink. The anelox roller rotates and transfers the ink to the printing plate. The amount of ink transferred depends on the cell structure and depth. The inked printing plate contacts the substrate (such as film, cardboard, or paper) to which the image is applied. The printing process can involve multiple passes if multi-layer printing is required. After the ink is applied to the substrate, it passes through drying units, which can use hot air or ultraviolet light to quickly dry the ink.After drying, the finished product can be cut into the required sizes.

[0007] A device for flexographic printing and a method for simultaneously printing on at least two webs of materials having different thicknesses are known [1], comprising a printing unit comprising a printing roller bearing on its surface an image to be printed, a pressure roller and an anilox roller configured to supply printing ink from a printing ink chamber to the printing roller. The printing unit is configured to simultaneously print on at least two webs of materials having different thicknesses, wherein printing on the webs of materials occurs when they pass through a printing contact zone formed between the printing roller and the pressure roller. The objective of the present invention is to propose a single-step printing process in which printing on substrates to be printed having different thicknesses can be performed simultaneously.In addition, the challenge is to ensure better control of the production process so that the supply of printed material matches the demand for printed material.

[0008] A device is known for printing a web of packaging material with printing ink [2] which comprises a reservoir or chamber for ink and an anilox roller, partially rotating inside the ink chamber for picking up and transferring printing ink from the ink chamber to a printing cylinder rotating in transfer contact with the anilox roller, as well as an additional counter-pressure cylinder, which rotates adjacent to the printing cylinder and which, together with the printing cylinder, forms a gap through which the web of packaging material must pass in order to transfer the printing ink from the printing cylinder to the web, wherein the reservoir or chamber for ink extends axially along the anilox roller and has an upper axial doctor blade in contact with the peripheral surface of the anilox roller for scraping off excess ink and a lower similar axial doctor blade in contact with the peripheral surface of the anilox roller for preventing leakage of printing ink from the ink chamber,wherein the paint chamber has a first end wall at one axial end thereof and a second end wall at its other axial end.

[0009] The disadvantage of these analogs is that there is no provision for improving print quality through higher-quality impregnation when using cheap materials.

[0010] A known method of flexographic printing [3] includes the possibility of printing on a wet layer and is based on the controlled deposition of a polymer or polymer segments, which leads to the gelation of printing ink compounds due to the control of the solubility parameter of the printing ink system. The mechanism for achieving the required ink pickup during wet-layer printing consists of the formation and / or presence of a gel in the applied printing ink film due to a controlled physicochemical mechanism of resin precipitation. This is achieved either as a result of a controlled change in the Hansen solubility parameter of the liquid in the printing ink due to the evaporation of some or all of the non-reactive and volatile solvent, or, alternatively, as a result of the use of a polymer containing two different and separate segments, one of which is soluble in the monomer / oligomer mixture, and the other of which is not.The insoluble segments form a reversible gel that liquefies to form a liquid under shear during application, enabling the application of liquid printing ink. The gel then reforms within the applied ink film in a manner and with sufficient strength to permit overprinting using wet-on-wet flexographic printing. The purpose of this invention is to create a system and method for flexographic printing combined with overprinting using solvent-free or reduced-solvent color printing, and to create printing inks characterized by increased color saturation and good adhesion.

[0011] The closest analogue is a method for improving the quality of printing on flexographic printing plates [4] by adapting the shape of the printing dots created during the manufacture of printing plates for letterpress printing, and can be used for printing on a variety of substrates, such as paper, cardboard, corrugated cardboard, films, foil and laminated materials. The present invention is based on the problem of creating a method for adapting or changing the relief shape of the printing dots of an element for printing relief images to ensure optimal printing on various substrates and / or under various conditions.

[0012] The objective of this invention is to improve the quality of flexographic printing by stabilizing and uniformly impregnating paper, reducing paper costs by using cheaper materials, while maintaining print quality and the aesthetic appearance of the final product—laminated plywood. This invention also accelerates the paper impregnation process, thereby increasing the productivity of the impregnation line.

[0013] The technical result of the present invention is the creation of a tension roller for a flexographic printing press containing channels with sharp edges over the entire surface of the roller or in the central portion thereof. These channels are preferably shaped like 1 x 1 mm diamonds. The technical result also consists of the sharp edges of the channels penetrating the underside of the paper and raising its nap, allowing resins to freely penetrate the entire surface of the paper during impregnation.This makes it possible to use cheaper, non-uniform paper, not intended for impregnation, with poor penetration, for the process of impregnation with phenolic resins and subsequently for printing in the production of laminated plywood, which in turn allows for uniform impregnation of the paper and speeds up the paper impregnation process, and therefore increases the productivity of the impregnation line, reduces paper costs, while maintaining the quality of printing and the aesthetic appearance of the final product - laminated plywood.

[0014] The technical result is achieved due to the fact that the tension roller of the printing machine for flexographic printing contains a shaft with cut channels, which are made with sharp edges with the ability to penetrate the surface of the paper and raise the pile.

[0015] Figure 1 shows a tension roller of a flexographic printing machine with channels cut over the entire surface.

[0016] Figure 2 shows a tension roller of a flexographic printing machine with channels cut on the central surface.

[0017] Figure 3 shows a fragment of the tension roller of a printing machine for flexographic printing with cutting of channels 1.5 mm * 1.5 mm. List of positions on the drawing:

[0018] 1. Shaft;

[0019] 2. Channels;

[0020] 3. The central part of the tension shaft surface;

[0021] 4. Lateral parts of the tension shaft surface.

[0022] Flexography uses web-fed machines operating on a reel-to-reel principle for printing on most substrates. A take-up roll is used to evenly wind the material onto the reel with the required tension after printing. The take-up roll of a flexographic printing press plays a key role in the flexographic printing process, ensuring the correct material tension. Here are the main aspects of its operation:

[0023] • Tension function. The tension roller maintains the required tension on the printed material, preventing it from shifting or wrinkling during printing. This is especially important for ensuring uniform and high-quality prints.

[0024] • Tension adjustment. Most flexographic presses have tension adjustment mechanisms on the tension roller. This can be achieved using springs, pneumatic systems, or electric drives, allowing the operator to adjust the tension depending on the type of material and printing conditions.

[0025] • Synchronization with other shafts. The tension shaft operates in synchronization with other machine shafts, such as the print shafts and feed shafts. This ensures coordinated movement of all components and prevents problems associated with speed mismatches.

[0026] Figure 1 shows tension roller 1 of a flexographic printing press with channels 2 cut across the entire surface of the tension roller. Channels 2 are 1 mm deep and slope at a 45-degree angle on the surface of tension roller 1, forming diamond-shaped corrugations measuring 1.5 x 1.5 mm. The sharp edges of the channels penetrate the underside of the paper and raise its nap. During impregnation, the resin penetrates evenly and quickly across the entire surface of the paper thanks to the raised nap.

[0027] Figure 2 shows the tension roller 1 of a flexographic printing press with channels 2 cut into the central surface 3 of the tension roller 1. The cutting of channels 2 into a specific central surface 3 of the tension roller 1 has direct technological significance for the use of paper of varying widths and densities: for thin, light paper with a width less than the roller length, it is necessary to use a cut in the central part of the roller surface, positioned so that the edges (approximately 5 mm) remain uncut. This avoids additional paper web breaks during impregnation and lamination on presses with roll unwinding, as it leaves the edges undamaged.

[0028] Figure 3 shows a section of tension roller 1 of a flexographic printing press with 1.5 mm x 1.5 mm channels. The channels on the roller surface can be shaped as 1 mm x 1 mm diamonds, or in sizes ranging from 0.5 mm to 1.5 mm.

[0029] Before starting work, the paper roll must be unwrapped and installed in the unwinder, which is part of the machine. The paper passes through rollers that guide it along the central axis of the machine and maintain tension. After passing through the printing pair (the plate and impression cylinders), where the printing is applied, the paper passes through a drying unit. The paper is wound onto a roll on the winder, which is also an integral part of the machine, using alignment rollers and a tension roller. Tension rollers can be made of various materials, such as steel or aluminum, and can have various coatings to reduce friction and wear. The roller design may also include special elements, such as rubber bands or pads, to improve adhesion to the material.

[0030] Impregnation is the saturation of materials with various chemical substances for the purpose of preservation, imparting water-repellent properties, as well as protection from fire, bacteria, etc. In particular, such a material is paper with a density of 40 g / m2 to 155 g / m2.

[0031] Laminated plywood is a plywood sheet covered on both sides with a protective film based on paper and phenol-formaldehyde resin, which provides moisture resistance.

[0032] A film is applied to both sides of a plywood sheet. The plywood is then loaded into a multi-span press, which can hold several sheets simultaneously. Pressing, during which the film adheres to the surface of the board, is carried out at high temperature for a specified time and pressure. The temperature is determined by the adhesive used and the number of layers. The pressure for the work is determined by the design of the elements involved in the transfer and marking of the future products. When using hot pressing, the pressure should be set depending on the type of plywood being manufactured: for general-purpose sheets - 1.8-2.2 MPa, decorative plywood - 3 MPa, bakelized plywood - 3.5-4.5 MPa, chipboard - 15 MPa. Pressing time depends on the film density, plywood thickness, and the type of coating (smooth or mesh).The film provides plywood with additional protection against water, mechanical damage, and aggressive environments. Thus, regular "white" plywood can be converted into coated, or laminated, plywood.

[0033] The proposed method of flexographic printing using a tension roller of a flexographic printing machine, which includes at least: winding a roll of material with the required tension and raising the pile on the underside of the paper; ink application; drying; impregnation with phenolic resins; lamination, allows for uniform impregnation, increased productivity of the impregnation line, reduced paper costs, improved print quality and the aesthetic appearance of the final product - laminated plywood.

[0034] Sources of information:

[0035] 1. Patent for invention RU 2750096, publication date 06 / 22 / 2021 2. Patent for invention RU 2608706, publication date 10 / 25 / 2012.

[0036] 3. Patent for invention RU 2517015, publication date 01 / 27 / 2013.

[0037] 4. Patent for invention RU 2531201, publication date 10 / 20 / 2014.

Claims

Invention formula 1. A tension roller for a flexographic printing machine, comprising a roller with cut channels, characterized in that the channels are made with sharp edges with the ability to penetrate the surface of the paper and raise the lint.

2. A tension roller for a printing machine for flexographic printing according to item 1, characterized in that the channels on the surface of the roller are made in the form of diamonds with a size from 0.5 mm to 1.5 mm.

3. A tension roller for a printing machine for flexographic printing, according to item 1, characterized in that the channels are made on the central part of the surface of the roller.

4. A tension roller for a printing machine for flexographic printing, according to paragraph 1, characterized in that the channels are formed over the entire surface of the roller.

5. A method of flexographic printing using a tension roller of a flexographic printing machine in the production of laminated plywood, made according to paragraphs 1-4, including at least: winding a roll of material with the necessary tension and raising the pile on the underside of the paper; paint application; drying; impregnation with phenolic resins; lamination.

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