Water based transparent iron oxide slurry is recognized by the market for its environmental friendliness, functionality (UV protection, weather resistance), and aesthetic value. With the tightening of global green regulations (such as EU REACH) and the increasing demand for high-end manufacturing, the emergence of the new product Tech-6752 provides a new option for the preparation of transparent iron oxide slurry

1. About Transparent Iron Oxide
    ① Why is 01 transparent? ​
     Transparent Iron Oxide is a type of nanoscale inorganic powder commonly used for pigment coloring, including α - Fe ₂ O3 (iron red) and α - Fe ₂ O3 · H ₂ O (iron yellow), with particle sizes typically ranging from 10-100 nm, much smaller than visible light wavelengths of 380-760 nm. Therefore, it has no scattering effect on light and exhibits high transparency. Common examples include: Transparent Iron Yellow P.Y.42, Transparent Iron Red P.R.101, etc.

    ② Synthesis process and morphology
     Taking transparent iron oxide red (α - Fe ₂ O3) as an example, in order to achieve high transparency, the particle size needs to be controlled at the nanometer level, which enhances the diffraction effect of light. In the current production process :

*Electron microscopy: P.R. 101 Sicotrans Red L 2817 needle shaped morphology

●  Wet synthesis (such as neutralization precipitation, hydrothermal method)
Tends to generate needle shaped or spindle shaped particles. The advantage of needle like structure lies in its high aspect ratio, which can enhance the ordered arrangement in the coating, improve transparency, and is suitable for high-end scenarios such as metallic glitter paint

●  Dry process technology (such as calcination method)
Producing spherical particles is commonly used in ordinary transparent iron oxide red. To achieve transparency, a smaller particle size (<50nm) is required for compensation, which is technically difficult. In actual production, the proportion of spherical transparent iron oxide red is low

2、 Why is it difficult to prepare pulp ?
     Transparent iron oxide (including iron red, iron yellow, etc.) has become an ideal coloring material for high-end water-based wood coatings, automotive metal coatings, and industrial coatings due to its nanoscale particle size (about 100nm), high transparency, and excellent weather resistance. However, its high specific surface area and surface energy also bring significant technical pain points :

① Poor dispersion stability
     Nanoparticles spontaneously aggregate and form flocs due to their high surface energy. Transparent iron oxide pigments have a high specific surface area (80-100 m ²/g), making it difficult to completely and stably encapsulate the pigments. Thermodynamically, agglomeration is an inevitable trend in reducing surface energy, while kinetic stability depends on the forced maintenance of hyperdispersants.

Transparent iron oxide red pigment

② Difficulty in viscosity control
     When the pigment content is greater than 20%, the viscosity of the dispersion system increases exponentially. This is because the spacing of nanoparticles shrinks, forming a "gel like network structure", the free dispersant molecules are wound and thickened, and the grinding shear heat intensifies the Brownian motion of particles to promote agglomeration

Dispersion of transparent red iron oxide paste (normal on the left and gelatinization on the right)

③ Balance of Coloring Power and Transparency
     Taking transparent iron oxide red pigment slurry as an example, its transparency depends on the visible light wavelength (i.e. about<200 nm) of the transparent iron oxide pigment particle size D50<189. Once the pigment aggregate size exceeds 200 nm, light scattering will be enhanced and the coating haze will increase.
     The lower the particle size, the better. Pigment particles with a particle size of less than 50nm not only bring high transparency, but also result in low coloring power. This is because the increase in specific surface area leads to a high proportion of surface atoms, which in turn weakens the absorption efficiency of visible light. Research has found that the particle size of transparent iron oxide red paste is recommended to be between 90-220nm, while meeting both high transparency and high coloring power, but this has high requirements for the molecular weight distribution (PDI) of hyperdispersants

Particle size above visible light wavelength, transparency, and coloring power are positively correlated

④ Difficulties in compounding silver paste
     In the preparation of champagne gold paste, the flake silver powder has a visible light reflectance of over 95% across the entire wavelength range, forming strong specular reflection and masking the absorption reflection spectrum of iron-based pigments. It is also possible for silver particles to float up and iron oxide pigments to sink after standing, or for dispersants to compete for adsorption, which poses a challenge to the dynamic balance of dispersants during the drying process and is highly complex

3. Tech-6752 New Choice
     Tech-6752 belongs to a high molecular weight hyperdispersant containing multiple pigment groups, which has a very good viscosity reducing effect and bright effect on inorganic pigments. This product has high glossiness and low foaming, strong coloring power, and is suitable for dispersing various inorganic pigments in aqueous systems. Especially suitable for water-based resin free transparent iron oxide pigment colorants

① Basic Formula
     We use water-based transparent iron oxide pigments (needle shaped) with a specific surface area of 80-85 m ²/g, and a dispersant addition of 15% of the pigment amount (effective fraction). The high pigment concentrate slurry with a specific surface area of 20-30% is tested under the same process. The basic formula is as follows :

② Performance Comparison
     We compared the performance of dispersants of the same type under the following testing conditions: zirconium bead grinding medium was used, the shaking machine was used for grinding for 6 hours, the color paste was filtered, and a paint water-based hydroxypropyl gloss oil: color paste=10:1 scraper (RDS18 # wire rod about 41.1um wet film) was used to compare the performance differences of dispersing iron oxide red/iron yellow

■ Transparency : The degree of contrast reduction in light transmission under strong light


Transparency: Tech-6752 ≈ international competitors>similar products

■ Foggy : scattering degree under strong light and natural light, Tech-6752 is excellent





■ Clarity: transparency and text clarity

     Use the DATACOLOR ColorReaderPRO to measure the L * value of the black card section. Generally, the lower the L * value, the better the transparency and clarity of the coating

■ Color rendering: display effect of uniform light plate/strong light reflection

Similar products show obvious color deviation. Due to different degrees of flocculation under the same grinding process, Tech-6752 has better grinding efficiency



     
     The particle size of transparent iron oxide red (α - Fe ₂ O ∝) is correlated with its color expression. Generally speaking, the smaller the particle size, the more inclined the color is towards blue-green phase, and the same applies to transparent iron oxide yellow. This phenomenon originates from the interaction between optical principles and material properties, balancing light scattering and absorption

●  The particle size is larger than the wavelength of visible light, mainly scattering, reflecting red/yellow light, and presenting a purple red or deep red color.

●  The particle size is smaller than the wavelength of visible light, and absorption is dominant. The absorption of short wavelength light (blue-green light) is enhanced by small particle size, and the green component in the reflected light is relatively increased

■ Compound silver paste
After mixing evenly with water-based silver paste, Tech-6752 is not prone to foaming, does not separate layers after long-term storage, has a strong metallic feel, and has high glossines


Facing side view state





Positive Light: Tech-6752 has excellent metallic feel

Glossiness :


4.  Summary
     The extraordinary experience of Tech-6752 ultra transparent iron oxide slurry brings better transparency, clarity, glossiness, and extraordinary metallic feel. In the future, Taige additives will focus on breaking through the dispersion and stability of more nano oxides, empowering high-end environmentally friendly slurries