Preface:

     In the formulation research and development of pastes in industries such as coatings and inks, using the same pigment and grinding process, and changing to a different dispersant, the grinding efficiency, storage stability, and solid content of the paste are significantly improved. The fundamental difference behind this lies in the molecular structure design of dispersants. Traditional dispersants have inherent deficiencies such as uncontrollable molecular structure, wide molecular weight distribution, and imbalanced anchoring and solvation chain segments. Controlled polymerization technology is designed to solve these problems from a molecular structure perspective.

01 Technical Highlights

     Tech-6310, a polymer dispersant developed based on Tiger controlled polymerization technology, features advanced synthesis technology for more flexible polymerization control. Its performance has the following three significant highlights:

① Control production - high production consistency

     In industrial coatings, comb shaped polyurethane hyperdispersants or block polyurethane hyperdispersants commonly used in the market require high control over the production of additives due to their water sensitivity to NCO, narrow R-value window, and the dilemma of dissolution reaction of hydrophilic chain extenders in reaction synthesis. In terms of production stability and structural accuracy, products developed based on controlled polymerization technology will be more advantageous, such as the new polymer dispersant Tech-6310, which is superior to polyurethane products in terms of production efficiency and consistency.

Table 1   Production Differences between Conventional Polyurethane and Controlled Polymers

     Tech-6310 has a narrower molecular weight distribution. In GPC gel permeation chromatography test, the molecular weight response of controlled polymerization is more concentrated than that of random polymerization (PDI<1.3), and the effective range of dispersion and stabilization actually occurs is more.

Figure 1 Effect of different polymerization technologies on molecular weight distribution in GPC gel chromatography

② Space steric hindrance formed by the formation of a regular structure in the control position

     Long term experimental results have shown that hyperdispersants are more conducive to the spatial stability of pigment particles in terms of tail and ring shapes, while block dispersants are more likely to form tail or ring shapes for adsorption. Traditional dispersants often use random copolymerization or homopolymerization, with anchoring groups dispersed in the main chain, resulting in inefficient adsorption morphology and insufficient effective adsorption layer thickness to support the stability of nanoparticles.

Figure 2: The attachment morphology of different polymers to carbon black

     Tech-6310 is a block+comb copolymer based on controlled polymerization technology, with a molecular structure containing multiple pro pigment groups. Compared to traditional single chain segments, the group composition is more diverse and free. Its amine/polar groups can form hydrogen bonds and acid-base interactions with the - COOH and - OH on the surface of carbon black, forming a well ordered structure with excellent spatial hindrance.

Figure 3: Pigment anchoring of block comb hyperdispersant structure

     Compared to polyurethane hyperdispersants, Tech-6310's various pro pigment groups can also exhibit excellent dispersion effects in dealing with complex structured Red HPP high pigment organic pigments such as anthraquinone and perylene diimide (such as RP177, RP179).

Figure 4: Carbon black functional groups and acidity/alkalinity in different production processes

     When dispersing acidic gas black FW-200 (pH ≈ 2.5), the alkaline characteristics of Tech-6310 are more conducive to anchoring and adsorbing on FW-200 carbon black, combined with the steric hindrance formed by the regular structure of the dispersant, significantly improving the particle stability at nanoparticle size (D50 ≤ 100nm).

③ Control excessive behavior - prevent gel

     In addition to the gel state caused by the insufficient solvent resistance of the pigment, the gelation will also be caused when the anchoring group in the dispersant has poor compatibility with the medium, and part of the slurry will return to its original state after stirring

Figure 5 Aggregation and dispersion of pigment particles

     This phenomenon is common in the medium with a wide polar span or in the nanometer size slurry system, and the main reason may be that after the dispersant content exceeds the critical micelle concentration CMC, a large number of micelles are formed at the anchoring end of the free dispersant, which makes the slurry change from a high flow state to a gelled state. Thermal storage can intensify the Brownian motion of pigments, increase compatibility differences and contradictions, and accelerate the formation of gelatinization, which is particularly evident in end anchored branched dispersants.

Table 2 Changes of dispersants with different structures in critical micelle concentration

     However, R&D engineers usually retain a portion of free dispersants as supplements to ensure the long-term stability of pigments. For random dispersants and controlled flocculants, there may be a contradiction between adding less easily causing coarse flocculation and adding more easily causing thickening. The use of multiple anchoring groups of block hyperdispersants can improve the compatibility with the medium. Even if the concentration of CMC is exceeded, the anchoring groups cannot form stable micelles due to their discontinuity, which avoids the occurrence of gel

Application of 02 controlled polymerization dispersant

1、 High pigment carbon black

     High pigment carbon black (such as FW200, FW255, Raven 5000, etc.) has fine particle size, huge specific surface area (500-600 m ²/g), high structural degree, and is prone to agglomeration and coarsening. The requirements for dispersants are much more stringent than those for ordinary pigments:

     Blue phase carbon black is rich in acidic groups, and its excellent dispersion effect can present better viscosity reduction and blackness. Taking the automotive repair coating system as an example, four commonly used high pigment blacks in the dispersion test market have been tested, and the actual test results are as follows:

     1K Hydroxyacrylic Acid System [Light Oil: Color Paste=10:3], 8% High Color Carbon Black+8% Dispersant (Commercial Form)

① FW200 carbon black:


② FW255 carbon black:


③ 1300 carbon black:


④ 5000 carbon black:

2K Hydroxyacrylic Acid System - [Light Oil: Color Paste: Curing Agent=10:3:3]

Color ratio: 8% high pigment carbon black+8% dispersant (product form)

① FW200 carbon black:


② FW255 carbon black:


③ 1300 carbon black:

2、 HPP Red Color Material

     PR177 (anthraquinone red) and PR179 (perylene based red) are both high-performance organic pigments, but their specific surface area is lower than that of high pigment carbon black. However, they have more demanding requirements for the molecular structure of dispersants. For example, PR177 molecules have a flat anthraquinone configuration and are prone to stacking and aggregation. Dispersants need to release their transparent blue light red properties; PR179 is a rod-shaped crystal of perylene series, which is prone to flocculation and flowering by aligning along specific crystal planes. It requires higher requirements for the ability of dispersants to flocculate and resist floating color. PR177/PR179 with sufficient dispersion should exhibit high transparency, bright red phase, low viscosity, and no floating color or blooming.

1K Hydroxyacrylic Acid System [Light Oil: Color Paste=10:3]

Appearance ratio: 8% HPP red pigment+12% dispersant (product form)

① PR177 Red Material:


① PR179 Red Material:

Coloring Strength Test [Gloss: Silver Paste: Color Paste=10:10:3]

【left】Red color material       【right】Red color material

     Compared to traditional polyurethane hyperdispersants, controlled polymerization hyperdispersants provide more efficient dispersion solutions for high pigment black and HPP red pigments, with better steric hindrance effects, and help with the dispersion stability of organic nanoparticles.