Window mulching is a special kind of mulching technology, which not only has the advantages of mulching products, but also makes the packaged goods visible. Window coating is mainly used in carton packaging, and is widely used in food, medicine, and light industrial products, especially in the packaging of export goods, and has broad prospects. However, in actual production, due to a variety of uncertainties, the product quality also fluctuates greatly, and defects such as blistering, stripping, wrinkles, snow spots, aprons, and roll paper are prone to occur, seriously affecting its application and development of. In this paper, through the analysis and study of the window coating technology, the factors that affect the product quality in the coating process are discussed, and the process is optimized and improved.
After the window is opened, the printed matter is coated with glue by a coating roller along the paper path, and the laminating process is completed by pressing the upper and lower pressure rollers together with the plastic film. The difference between its working principle and general coating is as follows.
(1) The adhesive is first applied to the printed surface of the printed product, and then the plastic film is covered on the surface of the printed product. Finally, the adhesive is pressed into a finished product.
(2) Window coating is performed on a printed matter with a window.
During the entire work process of windowing and laminating, all aspects may affect the quality of the final product. Below we will analyze the various factors that affect the quality of finished products.
printed matter
Since the window-opening and laminating process directly applies the adhesive on the surface of the printed matter, the surface quality of the printed matter will definitely affect the quality of the coated film. Among them are the following reasons.
(1) If the ink on the printed surface is too thick or not dried, the coated adhesive cannot penetrate through the pores between the ink layer and the paper and cause false adhesion, resulting in the finished film. Blisters in a short time.
(2) In the printing process it is unavoidable to use chemical liquids, and it is easy to change the surface structure of the paper so that the adhesive does not make good contact with the paper, causing the product to foam after being left for a long time.
(3) The surface of the film print is dried to the initial dryness, and the thickness is about 0.002 to 0.003mm. Therefore, if the spray material on the print material is too thick, thin snowflake-like spots may appear on the product due to inaccurate film pressure.
(4) After the product is printed, it should be stored for a period of time in order to facilitate the volatilization of the paper moisture. Otherwise, after the film is coated, as the moisture evaporates, the paper fiber shrinks and the film wrinkles.
(5) Excessively high surface roughness of the print will affect the flowability (leveling and spreading) of the adhesive, resulting in uneven spread of the adhesive and a bright spot or “fog†on the surface of the product after the film is coated.
(6) Prints with poor flatness tend to wrinkle when they are covered with films, and due to unevenness of the paper, the adhesive cannot be evenly applied to the paper, resulting in phenomena such as release and blistering.
Adhesive
The contact between the printed matter and the plastic film depends entirely on the adhesive, so care should be taken to the physical and chemical properties of the adhesive.
The viscosity of the adhesive
If the viscosity of the adhesive is too high, the fluidity and wettability of the adhesive will be reduced, and the adhesive coating will not be uniformly applied, resulting in the coating layer becoming flowered, and the coating layer will produce snow spots. At the same time, during the coating process, excessively high viscosity makes it easy for prints to stick on the coating roller (coil roller) and is rolled up with the rotation of the coating roller. If the viscosity of the adhesive is too low, the solvent in the adhesive cannot be fully volatilized in the drying process, so that the solid content of the adhesive is reduced, and the phenomenon that the film is not strong, film peeling, blistering, etc. easily occurs.
2. The thickness of the adhesive coating layer
If the amount of adhesive applied is too small and the thickness is too thin, the adhesive force will be insufficient and the film will easily fall off. However, if the coating layer is too thick, the effects are even worse. For Example, the solvent evaporation in the adhesive slows down, and the product tends to foam after being placed; due to the moisture content of the paper, the paper fiber shrinks at the window opening and even folds. Open the apron at the window. All of these can cause fatal damage to the quality of the coating.
3. Admixing agent and thinning water
The proportion of adhesive and thinning water must be strictly in accordance with the requirements of the film and adhesive, otherwise it will result in poor adhesion.
Film properties
Because the essence of the film is to bond the printed matter and the plastic film together with the adhesive, the quality of the film is not only related to the nature of the adhesive, but also has a very close relationship with the surface properties of the plastic film. Enhancing the surface roughness of the plastic film, improving its surface crystallinity, increasing the cohesive strength of the surface layer, or removing the weak surface layer can effectively improve the film quality. In addition, since the film is subjected to a mechanical force during the film coating process, it must have a certain mechanical strength and flexibility. If the film is too soft, wrinkles are easily generated during the pressing process.
Drying temperature
If the temperature of the drying tunnel is too low, the solvent in the adhesive cannot be fully volatilized, which will affect the fastness of the coating film, and it is easy to produce blisters and release film. The temperature of the drying tunnel is too high, and the surface after coating may produce many folds.
Pressing process
Pressure pressure
The large pressure helps to improve the adhesion of the film and the print, but the pressure is too large to cause the plastic film to deform and wrinkle, and it is easy to squeeze out the apron at the window opening. And because the bottom of the floor has a window, so the floor will inevitably be uneven force, the window will have a stress change, the plastic film is easy to wrinkle. If the pressure is too low, the adhesion is not strong and it is easy to produce release film. The uneven pressure on the left and right sides of the lamination roller can easily cause deformation and wrinkling of the film.
2. Film speed
The filming speed is affected by the pressing force. If the pressure is high, the filming speed can be appropriately faster, but if the filming speed is too high, the time for laminating the paper and the plastic film becomes shorter and the adhesion is liable to be caused.
other reasons
(1) In the event of inaccurate transfer of the paper, the adhesive will transfer from the part of the film that has not been covered with the film to the rubber roller. As time passes, the amount of glue applied will gradually increase and the viscosity will increase. To a certain extent, the binder accumulating on the rubber roller will produce a certain strength of the adhesive force on the printed matter, resulting in localized tensile deformation of the laminated film print, resulting in wrinkles.
(2) The installation and manufacturing errors of the applicator roll will cause uneven application of the adhesive, resulting in problems such as snow spots and blisters.
(3) The installation and manufacturing errors of the pressure roller cause the surface of the printed product to be unevenly distributed, which can easily lead to uneven surface effects of the film product, and the film is prone to wrinkles. Other mechanical reasons will also lead to similar problems.
Through the analysis of the entire work flow of the window coating, we basically found out the relationship between the parameters and the quality of the window coating. There are many factors that affect the quality of the product in the window coating process. Figure 1 shows the main factors affecting the quality of the window coating.
From Figure 1, it can be seen that every detail in the production process will affect the quality of the final product. However, after the experiment and analysis, the main influencing factors are: the viscosity of the adhesive, the thickness and uniformity of the coating layer, the characteristics of the paper, and the variation of the compression force. The effects are shown in Table 1.
In summary, there are many factors affecting product quality in the process of window coating, including the factors of process parameters, the factors of binder, the influence of paper moisture, the influence of ink and its additives, and the manufacture and installation of the machine itself. The impact of precision, etc., and these factors affect each other. It is very difficult to quantitatively optimize the calculation of so many interacting factors. So we monitored the entire process and optimized the process, as shown in Figure 2. Through process optimization, product quality has been improved and social needs have been met.
After the window is opened, the printed matter is coated with glue by a coating roller along the paper path, and the laminating process is completed by pressing the upper and lower pressure rollers together with the plastic film. The difference between its working principle and general coating is as follows.
(1) The adhesive is first applied to the printed surface of the printed product, and then the plastic film is covered on the surface of the printed product. Finally, the adhesive is pressed into a finished product.
(2) Window coating is performed on a printed matter with a window.
During the entire work process of windowing and laminating, all aspects may affect the quality of the final product. Below we will analyze the various factors that affect the quality of finished products.
printed matter
Since the window-opening and laminating process directly applies the adhesive on the surface of the printed matter, the surface quality of the printed matter will definitely affect the quality of the coated film. Among them are the following reasons.
(1) If the ink on the printed surface is too thick or not dried, the coated adhesive cannot penetrate through the pores between the ink layer and the paper and cause false adhesion, resulting in the finished film. Blisters in a short time.
(2) In the printing process it is unavoidable to use chemical liquids, and it is easy to change the surface structure of the paper so that the adhesive does not make good contact with the paper, causing the product to foam after being left for a long time.
(3) The surface of the film print is dried to the initial dryness, and the thickness is about 0.002 to 0.003mm. Therefore, if the spray material on the print material is too thick, thin snowflake-like spots may appear on the product due to inaccurate film pressure.
(4) After the product is printed, it should be stored for a period of time in order to facilitate the volatilization of the paper moisture. Otherwise, after the film is coated, as the moisture evaporates, the paper fiber shrinks and the film wrinkles.
(5) Excessively high surface roughness of the print will affect the flowability (leveling and spreading) of the adhesive, resulting in uneven spread of the adhesive and a bright spot or “fog†on the surface of the product after the film is coated.
(6) Prints with poor flatness tend to wrinkle when they are covered with films, and due to unevenness of the paper, the adhesive cannot be evenly applied to the paper, resulting in phenomena such as release and blistering.
Adhesive
The contact between the printed matter and the plastic film depends entirely on the adhesive, so care should be taken to the physical and chemical properties of the adhesive.
The viscosity of the adhesive
If the viscosity of the adhesive is too high, the fluidity and wettability of the adhesive will be reduced, and the adhesive coating will not be uniformly applied, resulting in the coating layer becoming flowered, and the coating layer will produce snow spots. At the same time, during the coating process, excessively high viscosity makes it easy for prints to stick on the coating roller (coil roller) and is rolled up with the rotation of the coating roller. If the viscosity of the adhesive is too low, the solvent in the adhesive cannot be fully volatilized in the drying process, so that the solid content of the adhesive is reduced, and the phenomenon that the film is not strong, film peeling, blistering, etc. easily occurs.
2. The thickness of the adhesive coating layer
If the amount of adhesive applied is too small and the thickness is too thin, the adhesive force will be insufficient and the film will easily fall off. However, if the coating layer is too thick, the effects are even worse. For Example, the solvent evaporation in the adhesive slows down, and the product tends to foam after being placed; due to the moisture content of the paper, the paper fiber shrinks at the window opening and even folds. Open the apron at the window. All of these can cause fatal damage to the quality of the coating.
3. Admixing agent and thinning water
The proportion of adhesive and thinning water must be strictly in accordance with the requirements of the film and adhesive, otherwise it will result in poor adhesion.
Film properties
Because the essence of the film is to bond the printed matter and the plastic film together with the adhesive, the quality of the film is not only related to the nature of the adhesive, but also has a very close relationship with the surface properties of the plastic film. Enhancing the surface roughness of the plastic film, improving its surface crystallinity, increasing the cohesive strength of the surface layer, or removing the weak surface layer can effectively improve the film quality. In addition, since the film is subjected to a mechanical force during the film coating process, it must have a certain mechanical strength and flexibility. If the film is too soft, wrinkles are easily generated during the pressing process.
Drying temperature
If the temperature of the drying tunnel is too low, the solvent in the adhesive cannot be fully volatilized, which will affect the fastness of the coating film, and it is easy to produce blisters and release film. The temperature of the drying tunnel is too high, and the surface after coating may produce many folds.
Pressing process
Pressure pressure
The large pressure helps to improve the adhesion of the film and the print, but the pressure is too large to cause the plastic film to deform and wrinkle, and it is easy to squeeze out the apron at the window opening. And because the bottom of the floor has a window, so the floor will inevitably be uneven force, the window will have a stress change, the plastic film is easy to wrinkle. If the pressure is too low, the adhesion is not strong and it is easy to produce release film. The uneven pressure on the left and right sides of the lamination roller can easily cause deformation and wrinkling of the film.
2. Film speed
The filming speed is affected by the pressing force. If the pressure is high, the filming speed can be appropriately faster, but if the filming speed is too high, the time for laminating the paper and the plastic film becomes shorter and the adhesion is liable to be caused.
other reasons
(1) In the event of inaccurate transfer of the paper, the adhesive will transfer from the part of the film that has not been covered with the film to the rubber roller. As time passes, the amount of glue applied will gradually increase and the viscosity will increase. To a certain extent, the binder accumulating on the rubber roller will produce a certain strength of the adhesive force on the printed matter, resulting in localized tensile deformation of the laminated film print, resulting in wrinkles.
(2) The installation and manufacturing errors of the applicator roll will cause uneven application of the adhesive, resulting in problems such as snow spots and blisters.
(3) The installation and manufacturing errors of the pressure roller cause the surface of the printed product to be unevenly distributed, which can easily lead to uneven surface effects of the film product, and the film is prone to wrinkles. Other mechanical reasons will also lead to similar problems.
Through the analysis of the entire work flow of the window coating, we basically found out the relationship between the parameters and the quality of the window coating. There are many factors that affect the quality of the product in the window coating process. Figure 1 shows the main factors affecting the quality of the window coating.
From Figure 1, it can be seen that every detail in the production process will affect the quality of the final product. However, after the experiment and analysis, the main influencing factors are: the viscosity of the adhesive, the thickness and uniformity of the coating layer, the characteristics of the paper, and the variation of the compression force. The effects are shown in Table 1.
In summary, there are many factors affecting product quality in the process of window coating, including the factors of process parameters, the factors of binder, the influence of paper moisture, the influence of ink and its additives, and the manufacture and installation of the machine itself. The impact of precision, etc., and these factors affect each other. It is very difficult to quantitatively optimize the calculation of so many interacting factors. So we monitored the entire process and optimized the process, as shown in Figure 2. Through process optimization, product quality has been improved and social needs have been met.
Pet Jar,Thick Pet Jar,Pet Spice Jar
Itop Cosmetic Packaging Co., Limited , http://www.jiulingplastic.com