How to use water-based unstable foam wetting agent

When using water-based unstable foam wetting agents, it is necessary to combine specific application scenarios (such as coatings, inks, adhesives, etc.), system characteristics and target effects, and scientifically control the key links such as the timing of addition, dosage, and mixing method to give full play to its wetting performance while avoiding negative effects caused by improper use. The following are detailed usage methods and precautions:

I. Determine the applicable system and model

Different types of water-based unstable foam wetting agents have different adaptability to substrates (such as metals, plastics, fibers), pigments/fillers, and need to first select matching products according to system characteristics:

Substrate type: For low surface energy substrates (such as PE, PP plastics), fluorine-containing or silicone-modified unstable foam wetting agents (such as fluorocarbons, polyether-modified siloxanes) are preferred, which have stronger ability to reduce surface tension; for porous substrates (such as concrete, wood), non-ionic alkylphenol polyoxyethylene ethers or fatty alcohol polyoxyethylene ethers can be used to enhance penetration.

System compatibility: Check the compatibility of the wetting agent with other components in the system (such as resin, defoamer, thickener) to avoid stratification, precipitation or demulsification. It is recommended to do a small test first (such as mixing at a 5% concentration to observe stability).

II. Control the amount of addition

The more water-based unstable foam wetting agent is added, the better the effect. Excessive addition may cause negative effects (such as stabilizing foam and reducing film adhesion). It needs to be adjusted according to the solid content of the system, the type of pigment and the characteristics of the substrate:

Conventional addition ratio: generally 0.1%~1.0% of the total mass of the system.

Low pigment content system (such as varnish, transparent ink): 0.1%~0.3%;

High pigment content system (such as paint, thick color paste): 0.5%~1.0%;

Difficult to wet substrates (such as plastics, metals): can be appropriately increased to 0.8%~1.2%, but it needs to be verified by experiments.

Test method: Use gradient addition method (such as 0.2%, 0.5%, 0.8%) to test the wettability (such as contact angle, spreading speed) and foaming conditions (such as foam height, defoaming time) under different addition amounts, and select the optimal value.

III. Grasp the timing of addition

The timing of addition directly affects the dispersion effect and efficiency of the wetting agent, and needs to be determined in combination with the production process:

Pigment dispersion stage: If you need to improve the wettability and dispersibility of pigments (such as titanium dioxide, carbon black), it is recommended to add it before or at the beginning of pigment grinding to help the wetting agent quickly wrap the pigment particles, reduce grinding time, and avoid pigment agglomeration.

Paint/ink mixing stage: If the main goal is to improve the wettability of the substrate (such as substrate wetting during construction), it can be added after the system is evenly dispersed and before adjusting the viscosity to ensure that the wetting agent is evenly distributed in the system to avoid uneven dispersion due to high viscosity in the later stage.

Avoid premature conflict with defoamer: If defoamer needs to be added to the system, it is recommended to add the wetting agent first, and then add the defoamer after it is evenly dispersed to reduce the performance reduction caused by the direct reaction between the two (some wetting agents and defoamers may have antagonistic effects).

IV. Mixing and dispersion method

To ensure that the wetting agent is evenly dispersed in the aqueous system, a suitable mixing method is required:

Slow-speed stirring: Keep the system at a low-speed stirring (300~500rpm) when adding, and slowly add the wetting agent to avoid excessive air and foam due to high-speed stirring.

Segmented dispersion: For high-viscosity systems, the wetting agent can be diluted with a small amount of deionized water (1:1~1:3 ratio) first, and then slowly added to the system to reduce compatibility problems caused by excessive local concentration.

Avoid severe shearing: There is no need to use grinding or high-shear dispersion (such as a sand mill) to avoid destroying the molecular structure of the wetting agent and reducing its surface activity.

V. Construction and application precautions

In the construction process, the use effect needs to be optimized in combination with the process characteristics:

Coating/printing process:

During spraying construction, if the substrate is found to be insufficiently wetted (such as shrinkage holes and exposed bottom), the amount of wetting agent added can be appropriately increased (not exceeding 1.2%), or the construction viscosity can be reduced (adjusted by adding water) to enhance the spreadability;

When rolling/brushing, ensure that the system viscosity is moderate to avoid the wetting agent from being unable to effectively migrate to the substrate surface due to excessive viscosity.

Drying conditions: Some wetting agents may affect the drying speed of the system. If it is found that the drying is too slow, the drying temperature can be appropriately increased (such as water-based paint can increase the baking temperature by 5~10℃), but high temperature should be avoided to cause cracking of the coating film.

Storage stability: The water-based system after adding the wetting agent needs to be stored in a sealed manner to avoid long-term exposure to the air to cause water volatilization and concentration changes. The storage temperature should be controlled at 5~35℃ to prevent freezing at low temperatures or degradation at high temperatures.

VI. Common Problems and Solutions

Poor wettability: It may be due to insufficient addition or mismatch of models. You need to change to a suitable model or increase the addition amount (not exceeding the upper limit).

Foaming: Although it is an "unstable foam" type, excessive or reaction with other ingredients may cause slight foaming. You can reduce the addition amount or add a small amount of defoamer (such as silicone defoamer).

Decreased film adhesion: Excessive wetting agent may form a weak boundary layer on the surface of the substrate. You need to reduce the addition amount and test the adhesion (such as the cross-cut test).

Summary

The core principle of using water-based unstable foam wetting agents is: "Select as needed, add the right amount, disperse evenly, and adapt the process". By determining the optimal parameters through small tests and flexibly adjusting them in combination with system characteristics and construction requirements, you can avoid foam problems while improving wettability and ensure product performance.