Powder cleaning method

Abstract

To solve such a problem that in DTF printing, since small particles once adhering to a film do not fall off only by a vibration effect of film tapping, powders with a relatively larger size classified in a range of around 100 μ to 200 μ are used, thereby a thick resin layer adheres to transferred textile products, which degrades the texture, and the film is largely curved into a U-shape, which enlarges a housing in a vertical direction, and film tapping causes a larger noise.SOLUTION: A film with powder adhering to the entire surface of a white ink layer is heated at a constant temperature to enhance the adhesion of the white ink film and the powder. Then, excess powder is removed by rotating a rotary brush obtained by radially planting a hair material to a rotary shaft across both ends of the rotary shaft, and scraping a surface of the film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for cleaning powder adhered to a film. Specifically, in DTF (Direct To Film) printing, after printing a solid image on a film using white ink and then spraying powder over the entire film surface, the method relates to cleaning only the powder adhered to the image and removing the extra powder adhered to the film as contamination.

Background Art

[0002] Recently, transfer printing has been performed on textile products using an apparatus called DTF. This generally consists of the following four steps. In the first step, a thin polyester receiving film (hereinafter referred to as the film) is color-printed by inkjet. In the second step, white ink is used to overprint a solid white thickly by inkjet on the color-printed part. In the third step, urethane powder with a size of about 100 to 200 μm is sprayed and adhered to the sticky solid white printed part, and then the extra powder is brushed off. In the fourth step, heating is performed to melt the powder layer and weld it to the film together with the color image. Thereafter, this film is cut into a predetermined size, heat-pressed onto a textile product to transfer the printed image, and then the film base is peeled off. This has the advantage of being able to perform color printing on textile products made of any material including dark colors without pre-treatment. Also, continuous printing on roll film is possible, and there is an advantage of being able to perform mass production at low cost.

[0003] Hereinafter, the third step by an apparatus called SHAKER in the case of using a roll film as the center will be specifically described. The film that has entered with the printed part becoming sticky after the second step is passed through the bottom of a powder tank filled with powder, and the powder is brought into contact with the entire printed surface of the film under pressure. Thereafter, the film is advanced in a shape bent in a U shape about 50 to 60 cm downward, and during this time, the back surface of the film is struck to vibrate greatly. As a result, the extra powder adhered to parts other than the sticky part falls to the bottom of the film. Then, the film is returned to its original height and advanced horizontally to the fourth step.

[0004] After the third step, the film with powder adhering only to the adhesive part passes through a high-temperature tank while being heated by an infrared lamp installed on the heat-reflective ceiling surface. As a result, the powder that was sparsely attached to the film completely melts and connects to each other to form an adhesive layer with a flat and uniform thickness (this is called BAKING). Then the film is wound up by a roller.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The first problem is that the fine powder once attached to the film does not completely fall off only by the vibration caused by tapping, so powder with a large size classified in the range of about 100 - 200 μm that is easy to fall off is used. For this reason, a thick resin layer in which the powder has melted adheres to the transferred textile product, and the texture is impaired. The second problem is that since the film is greatly curved into a U shape, the housing becomes large in the vertical direction. The third problem is that a large noise is generated by tapping the film.

Means for Solving the Problems

[0006] As a result of intensive studies, the inventor came up with a method to fundamentally solve the problem of the adhesion of unnecessary powder to the film, which is the root cause of the problem. That is, in the third step, after heating the film that has passed through the powder tank to a certain temperature, the surface of the film is scraped with a rotating brush. At this time, among the components of the white ink printed on the film, low-boiling liquids such as water have evaporated due to the previous heating, so the white ink layer increases its adhesive strength and adheres to the film, and at the same time, the adhering powder is firmly grasped. As a result, even when the tip of the bristles of the rotating brush contacts and scrapes the film surface, the powder adhering to the white ink layer is retained as it is. And the unnecessary powder existing on the rest of the film is pushed back in the reverse direction of the film progress by being blown away.

[0007] The heat treatment of the film is carried out by arranging a heat roller at the corner where the film returns horizontally from the U-shaped curve through the SHAKER, and setting the mechanism to be from vertical to horizontal while the back of the film contacts the circumference. And by installing a rotating brush in the vicinity where the film advances, the pushed-back powder falls to the bottom of the U-shaped film. As a result, even if powder much finer than the current size is used, the problem of powder adhesion to the film does not occur. Since the temperature at which urethane softens and exhibits adhesiveness is generally about 100 to 120 °C, it is important that the powder heating temperature is below that range. If the heating temperature is too high, the extra powder to be removed will adhere to the film. The fallen powder is appropriately recovered and reused.

[0008] Hereinafter, according to the perspective view of FIG. 1, the specifications of the rotating brush will be described. The bristles are planted as a continuous line in a plurality of rows of about 1 to 8 rows radially on the rotating shaft across both ends of the rotating shaft. Since the bristles spread at the tips, if they are connected without gaps at the tips, the planting at the roots may be in a scattered dot pattern instead of a continuous line. The bristles are animal hair or resin hair, with a thickness of about 0.05 to 0.2 mm in diameter, preferably 0.05 to 0.1 mm. If it is thinner than this, the powder cannot be dredged, and if it is thicker than this, it becomes rigid and peels off the powder adhering to the adhesive part. The length of the bristles is about 2 to 6 cm, preferably 3 to 5 cm. If it is shorter than this, the powder once removed stays between the bristles and is not smoothly removed, and if it is longer than this, the bristles bend and lie down, making it difficult to efficiently dredge the powder. The rotation speed of the rotating brush is related to the number of its radial rows, but generally it is about 1 to 10 rotations per second, preferably 2 to 6 rotations.

[0009] According to the present invention, it becomes possible to use fine powder, and a compact, low-height, and noise-free Smart post-processor (which refers to a device responsible for the processes after inkjet printing in DTF printing) becomes possible. Practically, it is also necessary to consider the adhesion strength with fibers, and powders classified in the range of about 30 to 100 μm in powder size are appropriate. When powders of this size are melted and welded to fibers with a color image, a product with excellent texture can be obtained, different from conventional DTF printing. This is comparable to products produced by a method called DTG (Direct To Garment), which directly prints color ink onto fiber products by inkjet.

[0010] The fundamental difference between this Smart post-processor and conventional DTF is that it does not require hitting the film, so it does not require a deep U-shaped curve. Simply a shallow U-shaped curve (so-called depression) of about 5 cm is sufficient to receive the powder that naturally falls off the film and the powder pushed back by the action of the rotating brush when the film exits the powder tank. As a result, the overall height of the device is approximately within 20 cm. Also, since the powder size becomes a fraction of that of conventional products, its weight becomes less than one-tenth, and the amount of heat required to melt the powder also becomes less than one-tenth. As a result, a high-temperature tank for BAKING is not required, and contact heating of the back of the film by a heat roller arranged at the end of the film progression is sufficient.

[0011] The mechanism of the rotating brush and heating roller of this invention can be easily added as an attachment at the corresponding position of the current DTF. As a result, products equivalent to high-quality DTG printing can be printed, so the modification effect is very large. Although the use of white ink is assumed in this description, it is also similarly applicable to DTF printing that combines transparent ink and white powder, disclosed by the inventor in Japanese Patent Application No. 2022-65919.

Effects of the Invention

[0012] The present invention realizes a compact and smart DTF that can also be placed on an office table. Moreover, fine powders that could not be used with conventional DTFs can now be used, enabling high-quality printing comparable to expensive DTG printing. Additionally, it is possible to incorporate this invention mechanism as an attachment to a conventional DTF to enhance its functionality.

Brief Description of the Drawings

[0013]

Figure 1

Modes for Carrying Out the Invention

Examples

[0014] It is as described in the text.

Industrial Applicability

[0015] As described in detail in the text, except for the inkjet printer part, the height of this printing device is about 20 cm, so the introduction effect of the Smart post-processor is significant. Moreover, it is quiet. And since the printed textile products have excellent texture, they can be developed for high-end applications.

Claims

1. In the step of cleaning excess powder adhering to a film in DTF printing, there is a step of rotating a rotary brush formed by radially planting bristles on a rotary shaft across both ends of the rotary shaft to scrape off the excess powder on the film surface. A method for cleaning powder, characterized by this.

2. Having a step of heating the film at a stage prior to the step of scraping off the powder. A method for cleaning powder according to Claim 1, characterized by this.

3. Having a step of heating by bringing the back surface of the film into contact with a heat roller. A method for cleaning powder according to Claim 2, characterized by this.

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