Products | Small dosage, big purpose

"Green", "environmental protection" and "sustainable development" are the new labels for China's coatings industry.

China has taken the lead in the water-based coatings industry and has made domestic water-based coatings technology at the forefront of the world. The water-based process is in full swing in various coatings fields, and the proportion of water-based coatings continues to rise. Compared with solvent-based systems, water-based coatings have incomparable advantages in environmental protection. Product innovation and technological upgrades have also made the performance of water-based coatings comparable. "Water-based" has benefited the present and future generations!

Due to the limitations of its own formula design, the initial performance of water-based coating systems in many aspects was not satisfactory, and performance additives are indispensable in improving its performance.

Among them, silane coupling agents, as an important type of performance additives, have performed outstandingly and are crucial in improving the performance of water-based coatings.

 

Momentive offers a full range of silane coupling agent products that can be matched with various coatings, adhesives and sealant systems, and are effective in improving mechanical properties, enhancing substrate adhesion and enhancing coating resistance.

It is particularly worth mentioning that in order to assist the water-based process, Momentive has innovatively developed a "water-based" silane performance additive, which is specially developed for water-based paint formulations. It has "small dosage, wide application" and has contributed to the water-based process of China's coatings.

Silicone coupling agent?

Silicone coupling agent is a small molecule compound centered on silicon atoms. Its application history can be traced back to the 1940s, when Ralph K. Witt of Johns Hopkins University in the United States first applied silane coupling agent in glass fiber processing. Subsequently, Union Carbide, the predecessor of Momentive Silicones, first realized the industrial production of silicone chemicals. Soon after, silane coupling agent, as "industrial MSG", developed more abundant applications in a wider range of fields.

Organic silicon coupling agents, as their name suggests, can "couple" the interface between two phases like a "bridge", forming a "molecular bridge" connecting two surfaces: organic surface and inorganic surface. The organic group of the silane coupling agent can react with the corresponding organic group to connect the organic surface; its hydrolyzed group can react with the active hydroxyl group on the inorganic surface to connect the inorganic surface. In this way, the silane coupling agent forms a strong chemical bond between the inorganic and organic interfaces.

Figure 1. Basic structure of silicone coupling agent and its working principle

Silane coupling agents can be used to improve the adhesion of resin coatings to substrates, improve the binding force of fillers in resins, and improve the film resistance of coatings. Although they are small-molecule organosilicon compounds, silane coupling agents also exhibit properties common to organosilicon polymers such as silicone resins, silicone rubbers, and silicone oils, such as excellent heat resistance, water resistance, and low surface energy.

The reaction between the silane coupling agent and the inorganic interface requires the participation of water. In the presence of trace amounts of water, the hydrolysis group of the silane coupling agent can undergo a hydrolysis reaction to generate silanol groups, which then undergo a condensation reaction with the hydroxyl groups on the surface of the inorganic material to complete the chemical bonding.

Figure 2. Hydrolysis condensation reaction of silane coupling agent

Due to the instability of silane in water, traditional silane coupling agents are more suitable for solvent-based or water-free formulations. In water-based formulations, the application of silane coupling agents is limited by their stability in water media: silane coupling agents will undergo hydrolysis and condensation in water prematurely, and then fail.

The application of silane coupling agents in water-based formulations requires breakthrough innovations in their structures.

Water-based silane coupling agent? !

The concept of waterborne silane coupling agent seems to contradict the principle at first glance, but Momentive engineers have found a perfect balance. It is generally believed that the reactivity of silane with water and its stability in water medium cannot be achieved at the same time. For waterborne silane coupling agent, the reactivity/stability balance of its hydrolyzed group in water is the key to control. The waterborne silane products developed by Momentive can greatly improve the stability in waterborne formulas without sacrificing reactivity.

Figure 3. The structural design of waterborne silanes should take into account the balance between their reactivity and stability in water.

Momentive innovatively uses traditional silane coupling agents as a blueprint, hydrolyzing and condensing them to a certain extent to form linear oligomers with a certain degree of polymerization. The preparation process will inevitably consume some hydrolyzed groups, but the number of hydrolyzed groups in the newly generated molecules is greater than that in the monomeric silane coupling agent; at the same time, the number of organic groups in the oligomers also increases exponentially with the degree of polymerization. The final generated oligomer molecules have more functional groups at both the inorganic and organic reaction ends.

So how is the "reactivity/stability balance of hydrolyzed groups" adjusted in this process?

It turns out that the reactivity of the hydrolyzable group is related to the number of hydrolyzable groups on the same silicon atom: that is, when there are three hydrolyzable groups at the same time, the third group has the highest activity; when one hydrolyzable group is reacted, the activity of the remaining hydrolyzable groups decreases accordingly when they participate in the hydrolysis condensation reaction.

Although the number of hydrolyzed groups in the oligomer molecules has increased, the reactivity of the individual groups has decreased, and the overall reactivity has decreased instead of increased, thus achieving the "reaction stability in aqueous media" we need. At the same time, the lipophilic characteristics of the oligomer molecules can also enable it to actively seek benefits and avoid harm in aqueous formulations, and it is more inclined to hide in the oil and only play a real role during the construction process.

CoatOSil® MP 200！！

CoatOSil MP 200 is a water-based silane product launched by Momentive. Its excellent effect has been repeatedly verified in various applications and is widely praised by customers.

CoatOSil MP 200 is an oligomer with epoxy functional groups. The organic group in its structure, the epoxy group, is versatile and can react with many different organic functional groups. The oligomer also has hydrolysis groups that can be firmly bonded to inorganic substrates. CoatOSil MP 200 can be used as a solvent-based system or a water-based system. Its biggest advantage is that it greatly improves hydrolysis stability compared to traditional monomer silanes.

Balanced hydrolysis/stability in aqueous media makes CoatOSil MP 200 silane compatible with a wide range of water-based systems:

Used in various epoxy systems such as epoxy dispersions to improve substrate adhesion and corrosion resistance;

Used in acrylic emulsion and styrene acrylic emulsion to improve wet adhesion and water resistance;

Used in waterborne polyurethane and other formulations to significantly improve salt spray resistance;

……

Figure 4. Typical application examples of CoatOSil MP 200

CoatOSil MP 200 has been widely used in coating, adhesive and sealant formulations, including decorative paints and protective coatings, wood coatings, heavy anticorrosive coatings, metal protection and anticorrosive primers, printing inks, screen printing inks, tile adhesives and sealants. As a performance additive, CoatOSil MP 200 can significantly improve the properties of the paint film. At an addition amount as low as 0.1%wt (weight percentage), it can help improve dry and wet adhesion, improve the corrosion resistance of coatings, adhesives and sealant formulations, and improve mechanical properties.

Compared with traditional silanes, CoatOSil MP 200 has a lower VOC emission equivalent, and spares no effort to promote the environmentally friendly and green Chinese coatings industry!

CoatOSil MP 200 not only shows excellent formula stability in many water-based coating systems, but also can improve various properties of coating formulas in a long-term manner. It has been widely used in industrial anti-corrosion, container paint, steel structure anti-corrosion, engineering machinery, construction and wood coatings, concrete coatings and roof coatings. Its good adhesion, corrosion resistance, durability, UV resistance, hydrophobicity, etc. can make us more stable and at ease in the process of water-based coating.