In the water-based coating curing agent system, CAPS buffer(3-cyclohexylaminepropanesulfonic acid) is a key modified raw material, and its process control accuracy directly determines the curing agent performance and coating quality. For coating companies, mastering the core process points of CAPS is the key to stabilizing quality and avoiding risks. This article will break down the control logic from three dimensions: addition amount, reaction temperature and time, and pre mixing.

CAPS powder

Suggested control of CAPS addition amount

The amount of CAPS added is the primary influencing factor on the performance of the curing agent. After industry verification, it is recommended to control it within 3.0-3.5 parts by weight. Insufficient addition can lead to insufficient hydrophilic modification of polyisocyanates, poor water dispersibility and easy delamination of curing agents, decreased compatibility with water-based resins, and then problems such as floating color and poor adhesion of coatings, affecting coating quality.

If the amount added exceeds 3.5 parts by weight, it will cause the viscosity of the curing agent to soar, increase the difficulty of mixing and construction, and lead to problems such as uneven leveling and obvious brush marks, thereby increasing costs and waste rates. Therefore, precise measuring equipment is needed to strictly control the amount of additives and ensure stable batch quality.

The dual key to controlling reaction efficiency and quality

1. Temperature control: a "safe reaction window" of 85-90 ℃

The modification reaction between CAPS and polyisocyanates is highly sensitive to temperature, with a safe range of 85-90 ℃. When the temperature is below 85 ℃, the molecular activity is insufficient, the reaction is incomplete, and residual raw materials can lead to unstable curing agent performance, and the coating is prone to yellowing and cracking. If the temperature exceeds 90 ℃, it may cause side reactions, generate impurities that damage the cross-linking structure of the curing agent, resulting in a decrease in curing efficiency, coating water resistance, and hardness. Enterprises need precise temperature control reaction vessels for real-time monitoring to avoid temperature fluctuations.

2. Time control: 4-hour 'complete response threshold'

At 85-90 ℃, 4 hours is the "threshold time" for complete reaction. Insufficient time can lead to incomplete modification, which cannot meet the requirements of water dispersion and resin compatibility; Blind extension increases energy consumption and may lead to performance degradation. Strictly follow the standard of "85-90 ℃+4 hours" to balance efficiency and quality.

3. Pre mixing first: the "key prerequisite step" for improving reaction stability

Pre mixing is a key prerequisite for improving reaction stability. The standard procedure is to pre mix pre measured polyisocyanates with CAPS powder at 50 ℃ for 20 minutes. This can evenly disperse CAPS, avoid uneven local concentration, and ensure sufficient reaction. If the premix is omitted or the parameters are not up to standard, CAPS is prone to agglomeration, resulting in deviations in curing agent performance and poor batch consistency, which affects large-scale production. Standardized pre mixing is the core guarantee for uniform quality.

Collaboration of three key points to build a solid foundation of quality

In summary, CAPS process control needs to achieve synergy of "precise addition amount, temperature time coordination, and thorough pre mixing". The addition amount of 3.0-3.5 parts by weight is the basis, the combination of 85-90 ℃+4-hour temperature is the core, and 50 ℃/20 minute pre mixing is the guarantee. Strictly controlling the parameters of each link is necessary to produce high-quality curing agents and support the performance upgrade of water-based coatings.

Product packaging

It should be emphasized that high-quality CAPS raw materials are a prerequisite for the implementation of the process, and insufficient purity of the raw materials will directly affect the final quality. Hubei Xindesheng has been deeply involved in the chemical industry for more than 20 years. Its CAPS purity exceeds 99%, with low impurities and stable batches, and has been recognized by many coating companies. If you are facing difficulties with CAPS quality or adaptation, you can contact Hubei Xindesheng for free samples!