7 Advantages of wetting agents 755W for aqueous coatings

2021-09-30   Pageview:211

1,  Particularly suitable for pigment concentrates with and without resins
2, For organic and inorganic pigments
3, Excellent coloring power, very significant viscosity reduction effect
4, Good storage stability of color pastes
5, Excellent water resistance
6, Solvent free
7, Free of ethoxyalkyl phenols

 

 

 

 

 

 

 

 

 

 

 

 

 

Oxidation-reduction initiation system
The redox initiation system uses the free radicals generated by the electron transfer between the reducing agent and the oxidizing agent to initiate the polymerization reaction. Since the decomposition activation energy of the redox initiation system is very low, about 40~60kJ/mol, it is often used to initiate low-temperature (0~50℃) polymerization reactions.

The commonly used redox initiation systems mainly include water-soluble redox initiation systems and oil-soluble redox initiation systems.

1. Water-soluble redox system
Water-soluble redox systems mainly include ferrous hydrogen peroxide initiation system, persulfate-ferrous initiation system and persulfate-sulfite initiation system.

(1) Ferrous peroxide initiation system The hydrogen peroxide-ferrous initiation system is the earliest redox initiation system discovered, which forms oxygen free radicals through electron transfer, as shown in formula (4-26).
H, O: +Fe2+→HO.+0H+Fel+(4-26)
The hydrogen peroxide-ferrous initiation system reduces the decomposition activation energy of Hz O 2 from 220 kJ/mol to 39.29 kJ/mol, and the decomposition rate is greatly increased, and the generated oxyoxy radicals initiate monomer polymerization. However, the attractive trivalent iron ions are not easy to remove, microcrystalline polyethylene wax contaminate the resin, and practical applications are limited.
(2) Persulfate-ferrous initiation system This system is composed of peroxide or persulfate, water-soluble metal salt and auxiliary reducing agent. Take the combination of persulfate, ferrous sulfate and sulfite as an example. The reaction is shown in formula (4-27),

Sg Of+Fel+–SO, ·+Fel
2Fel++H SO, +H gO+2Fel++H SO+2H(4-27)
Iron ions remain in the polymer and affect the color and aging resistance of the resin. In fact, since the ferrous ions in the system can be regenerated, the amount of ferrous ions added is very small, which has little effect on the performance of the resin. The initiation system can reduce the pH value of the system due to the generation of sulfuric acid. This system is mainly used for styrene butadiene emulsion polymerization.

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