The final state of waterborne polyurethane is a solid film. During the process from emulsion to solid film, accompanied by the evaporation of water and the concentration of water dispersion, the latex particles are close to each other. Before the solid content reaches 74%, the dispersion particles can move in the continuous phase of water. Under the influence of water/air interfacial tension, the particles fuse with each other, and finally diffuse through the molecular chain between the dispersion particles, resulting in a homogeneous film with certain mechanical properties.From the basic principle of film forming, the key to the film forming performance of polymer emulsion lies in the deformability of latex particles and the molecular chain diffusion movement. Polyurethane emulsion particles are an open water swelling structure, latex particles contain a certain amount of water, with strong deformation ability, and the characteristics of polyurethane particles swelling can cause particles to produce a very large surface area, with the swelling of small particles, to promote the polyurethane emulsion has a strong film forming ability. Even at a lower film forming temperature, it still has a high film hardness. In addition, when the film is dry, the moisture in the emulsion particles will help soften the polymer, making it easy to deform and form a film. Because the polyurethane molecule is composed of soft and hard segments, its special molecular structure determines that the polyurethane molecular chain has a strong diffusion movement ability, and the glass transition temperature of the soft segment is about 60~30℃, low glass transition temperature will reduce the minimum film forming temperature of the coating film, which can significantly help the film formation of the emulsion. Therefore, polyurethane emulsion has excellent film forming properties. In addition, when the film is dry, the moisture in the emulsion particles will help soften the polymer, making it easy to deform and form a film. Because the polyurethane molecule is composed of soft and hard segments, its special molecular structure determines that the polyurethane molecular chain has a strong diffusion movement ability, and the glass transition temperature of the soft segment is about 60~30℃, low glass transition temperature will reduce the minimum film forming temperature of the coating film, which can significantly help the film formation of the emulsion. Therefore, polyurethane emulsion has excellent film forming properties. The main medium of waterborne polyurethane is water, the volatility of water is lower than that of general organic solvents, and the evaporation heat of water is larger than that of organic solvents. The biggest drawback is that aqueous polyurethane adhesives dry slowly compared to solvent-based ones. However, the lowest film forming temperature of waterborne polyurethane is about 0℃, and because it does not contain emulsifier, it can form a film with lust...

The hardness and softness of the water-based acrylic resin can be adjusted according to specific needs, but it is usually biased towards the harder side. First, the characteristics and application of water-based acrylic resin Water-based acrylic resin is an environmentally friendly water-based resin, with non-toxic, easy to clean, dry fast and other characteristics, widely used in furniture, packaging, building materials, auto parts and other fields. Second, the factors affecting the hardness of water-based acrylic resin The hardness and softness of water-based acrylic resins are affected by many factors, mainly including the characteristics of the resin itself, crosslinking agents, additives, solution concentration and external environmental factors such as light and temperature. 1. Resin characteristics: the degree of polymerization, molecular weight and distribution of acrylic monomers directly affect the molecular structure and strength of the resin, thus affecting the softness and hardness. 2. Crosslinking agents and auxiliaries: the types of crosslinking agents and auxiliaries, the amount of addition and reaction conditions will also affect the hardness and softness of the resin, such as hardness agents can increase the hardness of the resin, and softness agents can reduce the hardness of the resin. 3. Solution concentration: The change of solution concentration will affect the viscosity and drying speed of the resin, which will have a certain impact on the softness and hardness. 4. External environmental factors: the external environment such as light and temperature will also affect the softness and hardness of water-based acrylic resin. Third, adjust the hardness of water-based acrylic resin according to demand Since the softness and hardness of water-based acrylic resin are affected by many factors, the softness and hardness of the resin can be changed by adjusting these factors. 1. Add different kinds of crosslinking agents or auxiliaries According to the need, different kinds of crosslinking agents or auxiliaries can be added appropriately to adjust the hardness and softness of the resin. For example, hardness agents can increase the hardness of the resin, and softness agents can reduce the hardness of the resin. 2. Change the solution concentration of the resin Changing the concentration of the resin solution can also change the hardness of the resin, if a harder resin is needed, the solution concentration can be increased; If a softer resin is required, the solution concentration can be reduced. 3. Control heating time and temperature The heating time and temperature of the resin will affect its cross-linking degree and molecular structure, which will affect the softness and hardness of the resin. Therefore, controlling the heating time and temperature is also an important method to adjust the softness and hardness of the resin. Fourth. Conclusion In general, water-based acrylic resins are usually ...

Insufficient or uneven amount of glue due to insufficient amount of glue produced by the white spot can be observed in the composite machine. In the dry composite process, the coated adhesive must be able to fill the bumps and bumps on the surface of the ink and film to avoid appearance defects such as obvious white spots. When the water-based adhesive dry composite is used to produce lightweight packaging products, the economic coating amount of water-based adhesive is 1.8 ~ 2.2g/m2, and the working concentration is 42% (the working concentration of different brands of water-based adhesive may vary), and the number of lines is 180 lines/inch, and the depth of the mesh hole is 32μm. Due to the large opening degree of the net hole on the roller, if the surface of the roller is worn, it will have a more obvious impact on the amount of glue. Therefore, in the dry composite process of water-based adhesives, the operator should often detect the actual amount of glue applied by the roller to avoid insufficient amount of glue applied due to excessive wear of the roller. In addition, the uniformity of the amount of water-based adhesive is also a very key factor, if the coating is not uniform, there will inevitably be a small amount of local glue, resulting in white spots. Therefore, we should pay special attention to the following two issues: ①The assembly of the scraper should be flat and straight, without distortion, and the Angle and pressure of the scraper should be adjusted appropriately to ensure uniform scraping effect;  ②During normal production, the scraper should keep the left and right strings to avoid the wear of the rubber roller in a fixed position. Because water-based adhesives are not like solvent-based adhesives, they can achieve a better leveling effect under the action of their own gravity and surface tension after coating, so when coating water-based adhesives, it is necessary to use a flattening roller to flatten the adhesive. The speed, pressure and surface cleanliness of the flattening roller are related to the leveling effect of the water-based adhesive, and the rotation direction of the flattening roller should be opposite to the compound direction, otherwise the flattening effect cannot be achieved, and the speed should be slightly higher than the compound speed. The leveling effect of the water-based adhesive is also affected by the surface tension of the coated film. Since the surface tension of the water-based adhesive is obviously higher than that of the solvent-based adhesive, the surface tension of the ink on the coated film is required to be not less than 38mN/m, otherwise the water-based adhesive will automatically shrink after coating and cannot be continuously formed. Therefore, the operator should pay attention to the detection of the surface tension of the coated film. In addition, if the surface of the coated film is not clean, adhering to substances with low surface tension, etc., it will reduce the leveling p...

1.Ink The three primary color inks have different degrees of color bias, which will affect the color bias of the whole picture to different degrees. However, a small amount of color bias can be corrected from the ink preparation. When printing to grasp the gray balance of the ink used, the same amount of yellow, product, green do not produce neutral gray, they produce lighter, more turbidity with brown gray, rather than the real gray. The reason is that the ink is not ideal absorption of color light (the spectral curve of the ink is not ideal), that is, caused by the used ink is not pure, in the actual ink CMYK space, to get the field gray, need to improve the amount of green ink. The excess cyan makes the other two colors cleaner, for example, 30% cyan, 2l % magenta, and 21% yellow mixed to produce 30% neutral gray, if 30% cyan, 30% magenta, and 30% yellow mixed to produce neutral gray will have a dark brown color. For a certain type of ink product, the CMY value of mixing gray is constant, that is, the gray balance ratio value of a certain ink is constant, and the gray balance of this ink can be measured, and the image can be corrected according to this balance, so that the image to be printed can accurately reproduce the color appearance after correction, so as to make up for the defects of this ink. 2.The paper itself It is the smoothness, absorption, whiteness and gloss of the paper that have a great influence on the reproduction of the tone and color of the print. Smoothness is divided into apparent smoothness and print smoothness. Apparent smoothness refers to the flatness of the paper surface, which depends on the surface topography of the paper and describes the structural characteristics of the paper surface. The paper with high apparent smoothness is conducive to ink covering and leveling, the ink film formed is glossy, and the order reproducibility of printed matter is good. The apparent smoothness of paper has a certain relationship with its gloss, and the paper with high apparent smoothness has a relatively high gloss. Printing smoothness refers to the flatness of the paper under the action of printing pressure in the printing mode that uses pressure to achieve ink transfer. Printing smoothness is the comprehensive effect of paper apparent smoothness and surface compressibility, which has a direct impact on the quality of printed matter, it determines the contact degree between the surface of the paper and the plate or the surface of the blanket at the moment of stamping, and is an important factor affecting whether the ink transfer is comprehensive and whether the text is clear. Paper absorption refers to the acceptability of the paper to the ink and the absorption capacity of the binder in the ink, which directly affects the penetration of the ink to the paper and the conjunctiva. Many printing failures are caused by the ink-absorbing capacity of the paper and the printing conditions used. The absorption capacity of the paper to t...