Properties and Applications of Matting Agent for Waterborne Coatings and Varnishes

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New Matting Agent for Waterborne Coatings and Varnishes

A good matte finish is often preferred or required in paint and coating formulations for wood coatings. In order to fully optimize this important parameter, Michelman has recently developed two wax dispersions: Michem® Guard 349 and Michem® Guard 350. Both dispersions aid in imparting a matting effect to most aqueous coatings and varnishes, while enhancing other properties such as abrasion resistance and water repellency.

Michelman's Range of Matting Agents for Surface Modification in Coating Applications

Characterized by a large particle size, Michem® Guard 349 and Michem® Guard 350, extend the range of existing Michelman additives for surface modification in coating applications. Building on an existing range of water-based dispersions, Michem® Guard 349 and Michem® Guard 350 are designed to highlight the positive properties of large particle sized wax and minimize unnecessary interaction from dispersing agents.

How Does a Wax Dispersion Control Matting?

As a coating film dries, wax particles are transported to the film surface, as a consequence of the turbulence flow induced by the water evaporation. Because of the large particle size, protruding wax particles create a certain degree of micro-roughness, induced as the film shrinks. As a result, the incident light is scattered instead of being reflected, conveying the impression of low gloss or matte appearance.

Degree of Micro-Roughness Dependant on the Properties of the Wax

The degree of the so-created micro-roughness is determined by the number of particles present at the surface, which directly depends on wax properties such as:

• Particle size and particle size distribution
• Particle density
• Amount of matting agent incorporated

Modifying Optical Properties of Coating with Larger Wax Dispersions Particle Size

Unlike wax emulsions - where the particle size is much lower than 1 µm - large particle size wax dispersions modify the optical properties of a coating. Not only do wax dispersions reduce gloss, as explained previously, but also significantly impact other surface properties. Formulations based on Michem® Guard 349 and Michem® Guard 350 will benefit from:

• Enhanced scratch, mar & abrasion resistance
• Improved barrier properties such as water repellency
• Enhanced slip & anti-blocking
• Enhanced soft-feel

Features of Michem® Wax Dispersions

In addition, the new Michem® wax dispersions present the following features:

• Totally solvent-free
• Do not contain APE
• Reduced amount of surfactant
• High solids content
• No tendency for sedimentation
• Easy incorporation by single mixing
• No dust generation

Charateristics of Michem® Wax Dispersions

Table 1 outlines the characteristics of Michem® Wax Dispersions.

Table 1. Characteristics of Michem® Guard 349 and Michem® Guard 350

Application of Michem® Wax Dispersions

Typical application of Michem® Guard 349 and Michem® Guard 350 include:

• Wood coatings, particularly furniture and parquet lacquers
• Decorative and industrial coatings

Procedures for Obtaining Optimum Matting Performance

Michem® Guard 349 and Michem® Guard 350 can be post-added with gentle mixing to ensure a homogeneous distribution. Selection of the appropriate matting agent depends on the dry film thickness. Optimum matting performances are obtained with dispersion particle size closely matched to the required dry film thickness. A level addition of 3% Solids on Solids is recommended to start with.

Case Studies - Incorporation of Matting Agent in High Glossy Paints and Varnishes

Both Michem® Guard 349 and Michem® Guard 350 have been successfully incorporated in various high glossy paints and varnishes. Their performance in reducing the level of gloss is illustrated in the following graphs. High quality, haze free films were obtained in the case studies described hereunder. In all cases, the gloss was measured at 60° angle on a Leneta chart.

Case Study No. 1 - Matting Performance in an Acrylic Resin (5% Solids on Solids)

Case Study No. 2 - Matting Performance in an Acrylic/PU Lacquer for Wood Coating (3% Solids on Solids)

Case Study No. 3 - Matting Performance in a Black High Glossy Paint (3% Solids on Solids)

In all the above case studies, performances of Michem® Guard 349 and Michem® Guard 350 were compared to a well-established matting agent considered as being a market reference.

This information has been sourced, reviewed and adapted from materials provided by Michelman.

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