FUNCTION.03Thickeners (Rheology Control Agents)
For coating materials that are best represented by paint, it is crucial to execute rheological adjustment according to the paint application or coating method. Thickeners - also commonly known as rheology modifiers or rheology control additives - control the rheological properties of the coating material to prevent sagging during paint application, adjust application thickness, facilitate painting, improve levelling, and prevent sedimentation of the filler, among other functions.
The most commonly used thickeners at present are synthetic or natural types. Our company offers its SN-Thickener series of synthetic polymer and associative thickeners for use in various applications, such as papermaking, coating and ink, civil engineering and construction, and emulsion and latex for chemical industries.

Associative Thickeners

As seen in the figure below, associative thickeners are polymers with a molecular weight in the thousands to several tens of thousands and consist of hydrophobic and hydrophilic parts. They act to thicken aqueous liquids in which hydrophobic substances such as resin emulsion or latex have been dispersed. The thickening mechanism is illustrated in the figure below where through hydrophobic interaction, the hydrophobic parts of the thickener assemble with itself or other hydrophobic substances, such as resin, to form a net-like structure and thicken the liquid. The nature of associative thickeners changes significantly with the associative group, and the stronger the association, the higher the viscosity it demonstrates. However, since its net-like structure is weaker than the one formed with polymeric thickeners (which will be explained further), the thickening effect is considered mild. Our company has associative thickeners possessing various associative groups so that we can develop the rheology properties you need.

As seen in (a), associative-type rheology control agents are surfactants with a hydrophobic group at each end. When a hydrophobic group encounters another hydrophobic group or particle, a new association occurs. When a sufficient amount of associative-type rheology control agents exists, a micelle is formed at each point as seen in (b) creating an overall net-like structure.

Synthetic Polymer Thickeners

Synthetic polymer thickeners are polymers with a molecular weight in the hundreds of thousands to several million and consist of (metha)acrylic acid as their chief component. Water-soluble polymers with a large molecular weight perform their thickening effect when dissolved in water. The thickening mechanism depends mainly on the entanglement of a macromolecular chain.
Two types of products are available: an aqueous type, where the polymers dissolve in water; and an emulsion type, where the polymers are emulsified in water. The emulsion-type products are extremely easy to handle as the insoluble polymers are emulsified in water to create a low product viscosity while achieving high-thickening power. Emulsion-type thickeners are also called ‘alkali-thickening type’, as they thicken polymers through a process of alkali solubilization and are further divided broadly into two types: ASE (Alkali-Soluble Emulsion), which do not carry association groups base, and HASE (Hydrophobically-modified Alkali-Soluble Emulsion), which increase thickening power through the introduction of association groups.
Our company offers a line-up of products with differing thickening powers and applied rheology properties and can deliver the thickener that best matches the rheological properties you request.

In (c), high-molecular weight polymer-type rheology control agents associate and adsorb to the particle's surface at multiple points. When these high-molecular agents encounter another particle, they will associate and adsorb to its surface forming a bridge between the particles. As this process continues, an overall net-like structure is formed as seen in (d), raising the viscosity.

Water Retention Agent

Thickeners are used on paper coating colors to prevent binder migration, inhibit coating unevenness, blade wear, and, streaking during application, stabilize blade coating pressure and coating volume, and improve the finishing of coating paper by smoothing it. In addition to offering the most suitable rheology properties for paper coating colors, thickeners also regulate water retention and, in the pulp and paper industry, are known as water retention/flow (rheology) modifiers. The thickener type most commonly used as water retention/flow (rheology) modifiers are synthetic polymer thickeners.