I. Overview of additives
The amount of additives is generally between 0.1% and 2.0%, and pigments are added to improve various properties of the pigments, such as adjusting the viscosity, preventing precipitation of crusts, accelerating drying, preventing water loss, inhibiting foaming and defoaming, improving thixotropy, Anti-floating color hair, eliminating agglomeration, anti-mildew antibacterial, improve flow and leveling, adjust gloss, improve stability, improve brushing, improve hiding power.
Second, the role of additive performance
Thixotropic
Thixotropy is the nature of the gel-liquid-gel process that the coating undergoes during agitation and subsequent quiescence. The coating is usually in solid or gelatinous form at rest, but becomes a very fluid material after agitation, which can be manifested by non-dripping coatings. The paint forms a gel on the brush and does not flow or drip over the brush. When it is brushed, it becomes a liquid and can be brushed well. After the brush is applied, it forms a gel on the construction surface to prevent sagging or falling.
The increase of substrate and swelling agent can change the solubility of the pigment in the base material, thereby imparting viscous flow properties, such as bentonite, special organic compounds, amine soaps, and the like.
2. Gelation and Hepatification
The ability to indicate that a paint, paint, or enamel will solidify after aging is actually a representation of the dispersion of the solid in the liquid. Despite its solid nature, it retains a significant amount of liquid. The reason for the gelation or liverification is the reaction of the pigment and the base material, such as the basic pigment (zinc oxide, white lead or red lead) ground in the acidic base material.
Oxidized rubber paints sometimes form gels in tanks. This can be prevented by adding a small amount of chlorine-epoxy-epoxy-propane additive.
3. Cake or block
Most of the agglomerating (flocculation) agent is an over-polymerized liquid, tending to reduce the wetting properties of the base, and to a certain extent causes the pigment to precipitate from the dispersed phase. In the manufacture of paints, if the viscosity is too low, it may be possible to add over-polymerized oils, such as TroykyBodying and Puffing Agent 2lBA, Nuodex's NuvisB, etc., to bring the viscosity to the desired level. On the other hand, if the coating viscosity is too high, it will swell in the coating and will produce a rough film that appears to contain sand during construction applications. In this case, the addition of a deblocking agent, such as a wetting agent, can effectively eliminate the knot. Piece.
4. Wetting
Wetting agents can be used to control the viscosity of the system. The wetting agent helps the substrate to wet the pigment while reducing the viscosity of the coating. Wetting agents can also improve gloss and maintain brightness, allowing more pigment to be added to the coating system while also improving the leveling of the coating and preventing the formation of granules. Commonly used wetting agents include zinc naphthenate, zinc rosinate, and lutein.
All the pigments are wetted by water at different stages of the production process, and the pigment absorbs moisture more or less in the air, so the relative ease with which the pigment particles are wetted by the paint base material is The first problem encountered. To give a typical example, white lead is a pigment that is more easily wetted by dry oil than water. It is mixed with linseed oil in viscous white lead paste, to a certain extent, in white lead paste. Most of the water is replaced by oil and can be poured from the oil slurry.
The evaluation of the degree of wetting of high opacifying pigments and extender pigments can have the following three conditions:
(1) Pigments are quickly scattered into linseed oil, and the high content of water in the pigment paste is replaced;
(2) The pigment is drawn by oil in the pigment paste, but does not drive away any moisture;
(3) Pigments do not absorb any amount of oil in the pigment paste.