Science Popularization | 5 Preparation Methods of Waterborne Resin

Waterborne resin is a type of polymer compound that can dissolve or disperse in water, forming a liquid substance. Compared to traditional oil-based resins, waterborne resins are more environmentally friendly, as they do not contain harmful volatile organic compounds (VOCs) and do not release harmful gases. Additionally, waterborne resins offer many other advantages, such as ease of processing, ease of application, and non-flammability. As a result, waterborne resins are widely used in fields such as coatings, adhesives, and inks.

The preparation process of waterborne resin is not overly complex, but it requires strict control of preparation conditions, such as temperature, stirring speed, and resin concentration, to ensure the quality and stability of the final product. Below, Jinzong Enterprise, with over 20 years of experience in manufacturing and developing resin production equipment, provides a brief introduction to the preparation methods of waterborne resins.

Neutralization into Salts Method

The neutralization into salts method is an effective way to prepare water-soluble resins. The key to this method lies in controlling the content of hydrophilic groups to ensure both the water solubility and application performance of the resin. The specific steps are as follows:

① Monomers undergo polymerization in a solvent to form polymer macromolecular chains.
② Through specific chemical reactions, a certain amount of strongly hydrophilic groups, such as -COOH or -NH₂, are introduced onto these polymer chains. These hydrophilic groups impart good water solubility to the polymer.
③ An appropriate amount of alkali or acid is used to neutralize the polymer into salts, allowing it to be diluted with water to form a water-soluble resin.

Ionomer Method

Ionomers refer to polymers containing a small number of carboxylic acid functional groups. By neutralizing these carboxylic acid groups to different degrees, the polymer is obtained. The curing temperature for such resins is typically high, usually around 250°C. When heated above 200°C, anhydride bridges form between molecules, promoting the curing of the resin.

However, due to the high curing temperature required, the application scope of the ionomer method is limited. Despite this, it still holds practical value, especially in specialized fields requiring high-temperature curing.

Bunte Salt Method

The Bunte salt method is a specific approach for preparing water-soluble resins. Its advantage lies in the ability to adjust the resin's water solubility by controlling the content of Bunte salts, thereby meeting different application requirements.

The specific steps are as follows:

① Sodium thiosulfate and haloethane are reacted under heating conditions to synthesize organic thiosulfates, known as Bunte salts.
② The Bunte salts are copolymerized with other monomers (such as halogenated alkene monomers or glycidyl methacrylate) to form water-soluble resins. The water solubility of this resin depends on the content of Bunte salts in the polymer chain. To enhance the resin's curing performance, melamine is typically used as a curing agent, with a curing temperature range of 123–135°C (without catalyst).

Zwitterion Intermediate Method

The zwitterion intermediate method involves introducing zwitterion intermediates into the polymer molecular chain to produce waterborne resins. A zwitterion intermediate is a special type of ionic group that carries both positive and negative charges, hence the name "zwitterion." This unique structure imparts excellent water solubility and stability to zwitterion intermediates. Waterborne resins prepared using the zwitterion intermediate method exhibit favorable application properties, particularly in fields such as coatings, adhesives, and inks.

Introduction of Non-Ionic Groups Method

In addition to ionic groups, introducing certain non-ionic groups into the polymer molecular chain can also enhance the water solubility of the resin. For example, polyhydroxy groups, polyether bonds, and similar structures can effectively improve the resin’s water solubility. Commonly used monomers or segments include polyethylene glycol, polypropylene glycol, poly(1,4-butanediol), polyether-esters, polyether-urethanes, and polyether-polyols.

It should be noted that the water resistance of the coating film from resins produced by this method is relatively poor, and their adhesion to steel substrates is also less than ideal. Therefore, before applying this method, practical requirements should be carefully considered.

As an important material, waterborne resins are widely used in multiple fields. In the coatings industry, they can be used to produce waterborne paints and inks, which are extensively applied in sectors such as construction, furniture, automotive, and electronics.

Additionally, waterborne resins play a significant role in the adhesives industry, where they are used to manufacture waterborne adhesives to meet various bonding needs.

Due to their environmental friendliness, safety, and ease of processing, the market demand for waterborne resins continues to grow. In today’s society, increasing attention to environmental protection and safety provides broader development opportunities for the application of waterborne resins. It is foreseeable that the future application prospects of waterborne resins will be even more expansive, contributing to a better living and working environment for humanity.