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Difficulties and solutions in the development of water-based UV plastic paint

difficulties and solutions in the development of water-based UV plastic paint

April 29, 2020

emerging technologies of plastic paint - difficulties in the development of water-based UV

the water-based UV system combines the comprehensive efficiency of UV curing and water-based technologies, has more advantages in environmental protection and safety than the traditional solvent based UV system, and is becoming an emerging technology in the formulation of plastic paint. However, there are some difficulties in the application of water-based UV system in plastic paint. For example, due to the large surface tension of water (72 dynes/cm), it is difficult for the water-based paint to fully wet and spread on the plastic substrate (dynes/cm) with low surface tension, and it is easy to produce shrinkage, orange peel and other defects. At this time, it is urgent to add appropriate substrate wetting agent to reduce the surface tension of the system to achieve the purpose of wetting the substrate

according to our years of application experience, the wetting agent Tego ® Twin 4200 and Tego ® Wet KL 245 is a good coating for this application. The following is the performance evaluation and results of the above substrate wetting agent and two common competitors in a system with aqueous UV curable aliphatic polyurethane dispersion as the main resin. Considering the formulation and application requirements of plastic paint, we studied the foam stability of wetting agent, the wettability on plastic substrate and the influence of film forming on the gloss and fog shadow value of paint film as key properties

wetting agent products involved in the evaluation:

1 have strong competitiveness. Experimental evaluation: foam stability

because wetting agent is a common foam stabilizing agent in the formula, the support of the policy is a beneficial guarantee source for the development of recycled plastic granulator, which is not conducive to later defoaming and is easy to bring a variety of paint film defects. We usually suggest that the foam stability of wetting agents should be evaluated as a key item when selecting wetting agents. When other properties are similar, it is usually the best choice to choose the wetting agent with unstable foam or even foam inhibition

we can evaluate the foam stability of additives by foam height method. Specific test method: it is reported that the liquid coating is contained in a transparent glass bottle and divided into blank group and four different wetting agent groups. The addition amount of wetting agent is 0.5%. Use a high-speed oscillation machine to produce foam. After oscillation, stand for different times. Observe and measure the height of the paint solution. The higher the height, the more stable the wetting agent is

place for 5 minutes, foam height:

place for 30 minutes, foam height:

tego ® Compared with other base wetting agents, twin 4200 has the least initial foam and almost no foam after 30 minutes, which will be of great help to the defoaming of the overall formula

2. Experimental evaluation: the wetting ability and dry film surface effect have not been contacted in this industry in detail in addition to procurement.

for wetting agents, their biggest role is to help the coating wet on the substrate, so the wetting performance is the key performance that must be evaluated. The following is our assessment methodology. Specifically: dilute the liquid paint to a certain viscosity and spray it on the ABS substrate. After baking at 60 degrees for 5 minutes, it passes through the UV exposure machine. After drying, the visual appearance and dry film thickness are micron

experimental results, dry film surface state:

effect drawing (lamp reflected on the paint film surface):

relative reference competitors 1 and 2, Tego ® Twin 4200, TEGO ® Wet KL 245 has excellent wetting ability and leveling effect

3. Experimental evaluation: film gloss and fog shadow value after film formation

the application of water-based plastic paint, especially the high gloss system, requires high gloss and transparency of the film. At this time, the influence of additives in the formula on the gloss and transparency after film forming is also a key evaluation item. Test method: use a gloss haze tester to test the dry film thickness in microns

the experimental results are as follows, Tego ® Twin 4200, TEGO ® Wet KL 245 has little effect on the gloss and fog of the paint film, and does not affect the transparency of the paint film

to sum up

1. Tego ® Twin 4200 can be used as the first choice product of Waterborne UV plastic paint system. It not only has strong substrate wetting ability and surface leveling effect, but also has unstable foam, which greatly reduces the difficulty of defoaming paint in the later stage, and can reduce or even completely do not use defoaming agent. Accordingly, the paint film problems caused by defoaming will be greatly improved. Therefore, the selection of the wetting agent is a more preferred solution regardless of the formulation performance or cost. TEGO ® The main reason for twin 4200's relative foam inhibition is its special Gemini structure, which we call gemini type. Gemini type surfactants are formed by connecting two hydrophobic chains and two polar chains through spacer groups. Compared with traditional surfactants, this structure has particularly high surface activity and different aggregation characteristics

2、TEGO ® Wet KL 245 has excellent substrate wetting ability and surface effect, and can be used as the second alternative of Waterborne UV plastic paint system, but Tego ® Wet kl245 is a traditional substrate wetting agent, which is relatively foam stable compared with 4200. Therefore, it is necessary to consider matching appropriate Defoamers in the formulation

3. The above is the recommended wetting agent for plastic paint based on aqueous UV system. For aqueous 2k-pu and other systems, Evonik also has appropriate additives recommended. For example: Tego with ultra-fine atomization effect ® Wet 240; Tego meeting higher recoating requirements ® Wet 280。

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