Discussion on the production process of silver powder coated fabric
Discussion on the production technology of silver powder coated fabric
Introduction Silver powder coating is a type of metal coating. Specifically, the silver powder slurry for coating is a coating glue made of aluminum that has been ground and anti-oxidation treated, and is mixed with PU slurry in an appropriate proportion. Because the particles of aluminum powder are in the shape of smooth scales, its covering power is very strong and can prevent the penetration of infrared and ultraviolet rays. In addition, there are extremely fine powder particles in the silver powder, which can make the coating surface look like a mirror and have a certain reflection and anti-radiation effect. Therefore, as a branch of the coating, the silver powder coating is used in tents, clothing, curtains, bags, etc. Has a wide range of uses. However, silver powder coatings cause more problems than ordinary PU coatings, such as silver infiltration on the fabric surface, shedding of silver powder on the surface, and silver paste particles and bubbles falling during the coating process, which all affect the inner surface of the silver powder-coated fabrics. , appearance quality, and other problems must be analyzed and studied from the aspects of process formula, process control, etc. 2. Production Overview 211 The main coating equipment used is the floating knife coating equipment imported from South Korea. The characteristics of this equipment are that the tension is adjustable and has a constant tension device. There are bending rollers to adjust the cloth surface to be smooth, and hot air is used for drying. circulation (use thermal oil as heat carrier), and have good upper and lower exhaust devices. The oven adopts segmented temperature control, there are two oven sections, and there is a cooling device at the outlet. The mixing device adopts a toothed disc type high-speed disperser with a rotation speed of 1400 rpm, and a needle plate type shaping machine. The base fabrics used for 212 silver powder coating include polyester poplin, nita poplin, pure cotton or polyester-cotton plain weave, and Oxford cloth.
213 The coating slurry uses imported solvent-based PU resin and imported silver powder slurry. The solvents use MEK and TOL U E E, as well as other additives. 214 Process Flow Gray Fabric Preparation Dyeing Styling Silver Powder Coating Styling Waterproof Finished Product 3 Production Process Optimization and Selection Here we take the production of N/190 T silver powder coated fabric as an example to introduce the production process optimization and selection. 311 Metallic feel on the coating surface 31111 Selection of silver powder mesh number The silver powder coating must first highlight the metallic feel on the surface of the fabric, avoid exposing the bottom and making it look dull, and make the surface smooth and smooth. In production, we have selected silver powder slurries ranging from 250 mesh to 800 mesh. The specific results are shown in Table 1. Table 1 Silver powder mesh number Note: N/ 190 T Dry weight of silver powder coating: 102 ~ 104g/ y From Table 1, it can be seen that the effect of 500 mesh silver powder slurry coating is close to the luster of silver, but the uniformity is not as good as that of 800 mesh silver powder slurry coating ;The 250-mesh and 800-mesh silver slurry coatings have poor surface uniformity, have a dark and old feel, and have poor mirror effects. Since the aluminum powder is fixed through PU bridges, the larger the mesh number of the silver powder, the larger its specific surface area, and the better the bonding fastness between the aluminum powder and PU glue. Taking into account the above factors, we finally chose 500 The silver powder paste can fully reflect the metallic feel of the coating surface. 31112 Selection of the amount of silver powder slurry The proportion of silver powder slurry in PU affects the metallic feel of the surface of the coated fabric. Generally speaking, the greater the proportion of silver powder slurry in PU, the stronger the metallic feel on the surface of the coated fabric. However, after exceeding a certain amount, it cannot significantly improve the metallic feel of the coating surface. On the contrary, the bonding fastness will decrease. Decreasing, appropriate silver powder slurry can only reflect a good metallic feel if it is evenly dispersed in the coating slurry. Excessive aluminum powder often overlaps in the coating and cannot be evenly dispersed.
In production, we selected the proportions of silver powder paste in PU to be 8%, 12%, and 16% respectively for comparative tests. The results are shown in Table 2. Table 2: Silver powder slurry dosage and result proportion Item 8 % 12 % 16 % Brightness difference Good rubbing fastness (grade) 3 2～3 1 Mirror effect bad Good Note: N/ 190 T Silver powder coating dry weight 103～105g/ y from It can be seen from Table 2 that we choose 12% of the silver powder slurry in the PU slurry as appropriate. The friction fastness is acceptable, the metallic feel of the coating surface can be better reflected, and the cost has been reduced. 31113 Effect of vehicle speed The faster the coating vehicle speed, the more it can overcome the influence of unstable tension control, making the coating surface uniform and consistent, with good continuous film formation, smooth and flat surface, and strong metallic feeling; the slower the coating vehicle speed, the better the coating surface will be. It takes a long time for the layer slurry to penetrate into the base fabric, and the amount of penetration is large, which will inevitably affect the smoothness of the coating surface formed by the silver powder slurry on the base fabric, thereby affecting the metallic feel of the coating surface. Therefore, when selecting the vehicle speed, it should not affect production. Under the premise, try to increase the coating speed as much as possible. 31114 The influence of drying speed. We choose MEK and TOL UEN E as the dissolving agents of PU, and add DMF to PU. Therefore, there are three substances with different volatilization points in the entire coating slurry. If the drying temperature is too high, MEK, a solvent with a lower volatilization point, will escape in a very short time, causing pores and affecting the flatness of the coating surface, thus affecting the metallic feel of the coating surface. This situation has a great impact during primer coating, because there cannot be no gaps on the base fabric surface, and the positions left by the escaped solvent will undoubtedly form holes, affecting the smoothness of the top coating, so the drying room temperature is generally between 85 and 85 95 ℃; when applying the second knife, since the primer is well controlled, relatively speaking, the flatness of the surface is already very good, so the temperature of our second drying room can be controlled at 110~120 ℃ to allow for complete drying and prevent The fabric sticks, which affects the production of the next process. 312 Elimination of Bubbles When applying silver powder coating, bubbles are formed due to the rolling of the knife edge in the slurry. When the bubble film wall ruptures on the cloth surface,Leaving stains will inevitably affect the effect of the coating surface. To address this problem, we mainly start from the following aspects: 31211 Coating Mixture Silver Powder Coating Mixture. The time should not be too short or too long. If the time is too short, the silver powder slurry cannot be fully dispersed in the PU slurry, resulting in uneven coating; if the time is too long, the aluminum powder will absorb heat and expand, and the solvent in the slurry will evaporate faster, thus forming bubbles .
Generally speaking, the mixing time of silver powder coating slurry is controlled at 4 to 5 minutes and left to stand for about half an hour to allow the bubbles in the slurry to fully escape. In addition, when preparing the silver powder coating glue, the solvent must be added while stirring. When stirring the material, the gear cannot be exposed on the upper part of the slurry to avoid bringing in air, thereby causing the generation of bubbles in the slurry. 31212 Vehicle speed control: The vehicle speed is too fast when coating. The coating cloth has a short cooling time in the cylinder. After drying after primer coating, the temperature has not completely cooled down, causing the temperature of the cloth surface to be brought into the top coating knife edge material. , aggravating the volatilization of the solvent in the material, so when producing N/190 T silver-coated fabrics, it is better to control the vehicle speed at 55-60m/min; at the same time, we should also frequently check the water temperature and flow conditions in the cooling cylinder to ensure Keep the cooling water temperature in the cooling cylinder constant. 31213 Viscosity control The viscosity of silver powder coating slurry is also a reason why bubbles are easy to burst. The solvent content in the slurry is high, and the bubble film wall formed is relatively thin, which makes it easier for the bubbles to burst. The viscosity of the slurry is too high and the fluidity of the slurry is poor. The rolling slurry will form pits and stains on the cloth surface. After experiments, we found out the amount of bubbles occurring under different viscosities, as shown in Table 3. Table 3 Silver powder slurry viscosity and result viscosity items 120 150 180 210 240 270 Number of bubbles (within 5 minutes) 22 20 10 7 7 – Pits – – – – Appearance Note N/ 190 T Silver powder coating speed: 55m/ minIt can be seen from Table 3 that in order to control the amount of bubbles, the viscosity of the silver powder coating slurry is generally controlled at 180~210dps. 313 Overcoming the Threshing Phenomenon During the silver powder coating process, the silver powder slurry is squeezed by the knife edge. If the silver powder particles fall from the direction of the knife edge, bright spots will appear on the cloth surface, seriously affecting the quality of the cloth surface. For this kind of defect, To overcome, we solve it through the following methods. 31311 Add adjusting materials to the silver powder coating material. Add some PU slurry or other polypropylene ester slurries with superior tensile elasticity to the silver powder coating material, which can increase the resilience of the silver powder slurry in the direction of the knife edge, making it rebound and adhere to the knife edge. to prevent silver powder slurry particles from falling on the cloth.
31312 The choice of solvent increases the proportion of solvents with high volatile points in the slurry to slow down the drying speed of the knife edge slurry and maintain a certain viscosity. This can also prevent the silver powder slurry particles from falling off at the knife edge. 314 Silver-infiltrated silver-coated products sometimes have silver threads and silver-white highlights showing through the fabric yarns on the non-coated surface. This is not acceptable for clothing fabrics and industrial fabrics with high quality requirements. The phenomenon of silver infiltration has a great relationship with the amount of coating on the knife, the speed of the machine, the tension, and the specifications of the base fabric. 31411 Control of the amount of primer The amount of coating directly affects the degree of silver coating, especially the amount of primer is the key. The more coating amount of primer, the thicker the thickness of the film, the more fully the gaps between the yarns are filled, and the stronger the resistance to the penetration of silver powder slurry on the surface is. As far as the N/190 T silver powder coating is concerned, we control the coating amount of the primer to be above 30g/y (wet weight), which can basically eliminate the phenomenon of silver bleed. 31412 The selection of the knife is to reduce the coating shear force and reduce the penetration of the substrate. Choosing a knife with a large arc is effective in reducing silver infiltration. Because the penetration into the base material is reduced, the thickness of the primer on the surface of the base fabric is relatively increased, and the ability to resist the penetration of the top coat is enhanced. 31413 Effects of gray fabrics Some gray fabrics are too thin in density during the weaving process, which will make the silver infiltration phenomenon more prominent. We can more effectively control the occurrence of silver bleed by adding fillers and some specialized resins to the primer to fill the gaps in the yarn, or using methods such as waterproofing first and then coating.
315 The main production process summarizes some problems in the silver powder coating process. On this basis, we develop the following production process 31511 Silver powder coating formula primer (knife): PU glue 100; filler 5; bridging agent 2; Accelerator 1; Solvent 10; Top coating (second cut): PU glue 100; Bridging agent 2; Accelerator 1; Silver powder slurry (mesh number 500) 15; Solvent 1531512 Main process parameters Primer viscosity: 210 ~ 240dps ( Normal temperature) Top coating viscosity: 180～240dps (normal temperature) Vehicle speed: 55～60 m/min First cut temperature (primer coating): 85～95 ℃ Second cut temperature (top coating): 110～120 ℃ 4 Conclusion In summary, We conducted a lot of analysis and experiments on problems that often occur in the silver powder coating process, such as metallic feeling, bubbles, silver infiltration, degranulation and other phenomena, and finally found a way to solve the problem. At the same time, we summarized the production process of such products, and provided Smooth production and improved product quality provide favorable conditions, which are summarized as follows: 411 To improve the metallic feel of the coating surface, reasonable choices must be made from the mesh number of silver powder and the amount of silver powder slurry, and the effects of vehicle speed and drying temperature must also be considered. 412 The elimination of bubbles must start with coating mixing, and control the mixing time and standard operations as well as vehicle speed and coating viscosity. 413 The elimination of threshing phenomenon can be solved by adding conditioning materials, improving coating performance and rationally selecting solvents. 414 To solve the problem of silver infiltration, we can consider the control of the amount of primer, the selection of coating knives and the reasonable pretreatment of gray fabrics. In short, these are some of our experiences and practices in the production process of silver powder-coated fabrics. We definitely need further research. If there are any inappropriate points, we hope that colleagues can enlighten us and correct them.
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AAAconsider. In short, these are some of our experiences and practices in the production process of silver powder-coated fabrics. We definitely need further research. If there are any inappropriate points, we hope that colleagues can enlighten us and correct them.
Disclaimer:
Disclaimer: Some of the texts, pictures, audios, and videos of some articles published on this site are from the Internet and do not represent the views of this site. The copyrights belong to the original authors. If you find that the information reproduced on this website infringes upon your rights, please contact us and we will change or delete it as soon as possible.
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