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In addition to the differences in performance and scene, the three acrylic lotion have exclusive taboos in production paint mixing, additive compatibility, pH control, feeding process, storage stability, and are also the core incentives for workshop batch fluctuations, flocculation, viscosity drift, instability and coarsening. This section provides targeted supplements on pH adaptation range, additive compatibility rules, feeding process, storage taboos, and common compatibility failures, fully adapting to mass production implementation.

1. Three lotion standard pH adaptation ranges

Styrene acrylic lotion system: optimal pH 8.0 – 8.5

The stability of styrene acrylic lotion colloid is moderately sensitive to pH, and the weak alkaline environment can stabilize and maintain the negative charge of particles to ensure thickening activation and antibacterial activity. PH below 7.5 is prone to thickening fatigue, low viscosity, and water separation during storage; A pH higher than 9.0 will accelerate the aging and hydrolysis of the benzene ring side group, and the paint film will be resistant to scrubbing and decay, with slight yellowing in the later stage.

Pure acrylic lotion system: optimal pH 7.8 – 8.4

Pure acrylic lotion has purer molecular structure, narrower colloid tolerance range, and too high pH is likely to cause slow hydrolysis of acrylate bond, resulting in viscosity decline and poor water resistance of finished products during long-term storage; Low pH is easy to cause micro instability of lotion and fine particle precipitation, which is the high-frequency inducement of fine slag defects of exterior wall paint.

Silicone acrylic lotion system: optimal pH 7.5 – 8.2 (most severe)

Silicon propylene contains active siloxane groups and is extremely sensitive to acidity and alkalinity. PH>8.5 will accelerate the early crosslinking of silicon groups, thickening and caking of the system, and the appearance of gel particles; PH<7.2 can easily lead to the hydrolysis failure of silicon oxygen bonds, directly losing the core properties of hydrophobicity, weather resistance, and pollution resistance, and is also the main reason for the hydrophobic failure of silicon acrylic coating.

2. pH regulator exclusive selection taboos

Styrene acrylic lotion: AMP ‑ 95, ammonia can be used; Low end interior wall systems can be moderately reduced in cost by using ammonia water. Inorganic strong alkali (NaOH/KOH) is strictly prohibited, which may cause the stability of calcium ion in lotion to decline and return to coarseness during storage. Triethanolamine is not recommended as it can reduce the scrub resistance of interior walls and promote the growth of microorganisms.

Pure acrylic lotion: AMP ‑ 95 is preferred for industrial exterior wall, and single ammonia water alkali adjustment is prohibited. Ammonia water evaporates quickly and causes pH collapse during storage, which can lead to viscosity drift, anti-corrosion failure, mold and alkali return in the later stage of exterior wall paint. Triethanolamine is completely prohibited to avoid outdoor yellowing and water resistance degradation.

Silicone acrylic lotion: only low volume AMP ‑ 95 dilution and fine adjustment are allowed. Prohibit ammonia water, triethanolamine, and strong inorganic bases. The volatilization of ammonia water leads to an imbalance in the hydrolysis of silicon groups, and strong alkali can damage the cross-linking structure of siloxane, directly discarding its hydrophobic and weather resistant properties.

3. General and specific contraindications for the compatibility of additives

(1) Compatibility with antibacterial and antifungal agents

The three lotion are suitable for BIT, CMIT/MIT tank bacteriostatic agent, OIT/IPBC dry film antifungal agent, but the pH range must be strictly matched: silicon acrylic strictly control pH ≤ 8.2, to avoid strong alkaline hydrolysis of the antifungal agent; Phenylpropanoid and pure propanoid have a pH not exceeding 8.5, ensuring long-lasting and stable antibacterial activity. The three lotion systems are incompatible with high content of free amine additives, which will consume antibacterial activity and cause later odor.

(2) Compatibility with dispersants and wetting agents

Phenylpropanoid and pure propanoid are compatible with conventional anionic dispersion systems and have excellent compatibility; Silicone acrylic lotion is a high-risk compatibility system. High content of anionic surfactant will wrap active silicon groups, inhibit cross-linking and bonding, resulting in hydrophobic failure, film shrinkage, wetting and blooming. The silicone acrylic system requires the use of low surface activity and low foam specialized dispersing wetting agents, and the additives should be diluted in advance and added at low speed.

(3) Compatibility with thickening rheological system

Phenylpropanoid is suitable for ASE and HASE alkali swelling thickening, with fast viscosity response and stable system; Pure propylene compatible polyurethane and alkali swelling complex system, with balanced leveling; Silicon propylene should be used with caution when swelling and thickening with high water absorbing alkali. Excessive hydrophilic thickeners can counteract the hydrophobic advantage of silicon propylene and reduce its water and stain resistance. Hydrophobic polyurethane rheological agents should be preferred.

4. Taboos on feeding process and addition process

General core rules: all lotion systems, regulators and additives are prohibited from direct feeding of stock solution at high speed, and must be diluted, dropped at low speed, and added several times at a small amount.

Phenylpropanoid process: It can be ground to adjust pH and fine tuned in the later stage, with the highest fault tolerance, suitable for extensive production control.

Pure acrylic process: give priority to pre adjust the pH of the aqueous phase in the grinding stage. After the addition of lotion, it is forbidden to add alkali substantially to avoid the instability of ester bond hydrolysis.

Silicon propylene process (strictest): high alkalinity in the early stage and high alkalinity in the later stage are strictly prohibited. The aqueous phase is suitable for weak alkali. After the lotion is added, it is only slightly adjusted, and the whole process is stirred at a low speed, so as to prevent the local alkali from causing the silicon group to cross link the gel at a high speed.

5. Key points for storage stability control

Styrene acrylic lotion: the storage pH fluctuates slightly and has little impact. The focus is on preventing high temperature stuffy storage, which is easy to soften the paint film and accelerate aging.

Pure acrylic lotion: high temperature thermal storage is prone to pH decline and viscosity thinning, so it is necessary to ensure the basic buffer reserve, and give priority to AMP ‑ 95 to build a stable system.

Silicone acrylic lotion: extremely sensitive to storage temperature, 5 – 35 ℃ constant temperature storage is the best; High temperature can cause premature cross-linking, thickening, and agglomeration of the system, while low temperature can easily cause delamination and deactivation. Exposure to sunlight and freeze-thaw storage are strictly prohibited.

6. Taboos for mixing and compounding

1. The combination of phenylpropanoid and pure propanoid is compatible and commonly used in high abrasion resistant formulations for interior walls and economical formulations for exterior walls;

2. It is prohibited to mix phenylpropanol and silicone propanol at will: phenylpropanol contains a benzene ring structure, which does not match the crosslinking rate of silicone groups, and can easily lead to uneven hardness, local hydrophobic failure, and loss of gloss in the paint film;

3. Pure acrylic and silicone acrylic can be scientifically compounded, making it the most cost-effective solution for high-end exterior walls with high weather resistance and pollution resistance, but the overall pH needs to be strictly controlled not to exceed 8.2.

7. Quick traceability and summary of defects

• Yellowing and poor weather resistance of styrene acrylic system → Incorrect selection, prohibited for outdoor use

• Pure propylene system viscosity drift, later thinning → high pH, ester bond hydrolysis or insufficient ammonia buffering

• Hydrophobic failure and particle shrinkage in the silicone acrylic system → pH exceeding the standard, inadequate additives, rapid feeding, and high storage temperature