news

In combination with the high-frequency failure of water-based lotion (styrene acrylic, pure acrylic, acetic acrylic, acrylic lotion, polyurethane dispersion) coating field and formula debugging, classify and sort out:

1、 Related to poor film formation (powdering, cracking, whitening, lack of continuous paint film)

1. Poor low-temperature film formation, powdering of paint film, and powder loss

Phenomenon: After low-temperature painting, the powder is wiped off by hand, and the paint film is loose and lacks strength

reason

1) Insufficient addition of film-forming aids;

2) The film-forming efficiency of additives is low (such as EB, benzyl alcohol efficiency is lower than alcohol ester 12);

3) High Tg hard lotion can not meet the requirements of MFFT only by low efficiency additives;

4) The construction temperature is lower than the minimum film-forming temperature of the coating.

solve

Increase the dosage of film-forming aids; Replace high-efficiency varieties such as alcohol ester-12 and alcohol ester-16;

Compound a small amount of slow drying ether to assist in film formation;

Ensure that the construction environment temperature is higher than the system MFFT;

Measure the MFFT of the coating, do not rely solely on theoretical estimation.

2. Whitening, loss of gloss, and fogging on the surface of the paint film

Phenomenon: After drying, it turns white and its luster decreases, especially in high humidity environments

reason

1) The water solubility of film-forming aids is relatively high (such as ethylene glycol butyl ether EB), and during drying, water and aids migrate to the surface. After the water evaporates, the aids precipitate;

2) The addition method of film forming agent is wrong. Directly and quickly add lotion, and the swelling of local lotion is uneven;

3) The solvent evaporates slowly under high humidity, and the water vapor envelops the auxiliary agent to form a mist shadow;

4) Poor compatibility between additives and resins.

solve

Reduce highly water-soluble ethers such as EB, with priority given to alcohol ester 12;

The film-forming agent is diluted with propylene glycol/wetting water in advance and slowly added;

Avoid construction in rainy and high humidity environments;

Replace the film forming agent with better compatibility with lotion.

3. Cracks and fissures in the paint film (more likely to occur with thick coating)

The reason is that there are too few additives, insufficient fusion of latex particles, and high internal stress; Or the additives evaporate too quickly, and the particles do not have enough time to fully fuse. Moderately increasing the dosage of film-forming agents; Avoid using only fast acting hair styling aids; Combined with slow drying additives to extend fusion time.

2、 Storage stability issue (coating failure during static stage)

1. Flocculation, caking and demulsification of lotion/coating after adding film forming additives

Phenomenon: lumps and clumps appear after adding materials, and cannot be dispersed by stirring

reason

1) Undiluted film-forming agents come into direct contact with latex particles at high concentrations, leading to strong swelling and emulsion breaking;

2) The pH of additives is not matched, and some additives are weakly acidic, impacting the stable system of lotion;

3) Acetate acrylic lotion has poor tolerance to strong solvent based film forming additives (benzyl alcohol is easy to cause flocculation of acetate acrylic).

4) Resolve

Standardize the feeding process: the film-forming agent is first diluted with antifreeze (propylene glycol) or a small amount of water;

Slowly add dropwise while stirring at low speed, and do not pour it all at once;

Try to minimize the use of benzyl alcohol in the acetic acid propylene system and prioritize alcohol esters;

Control the pH of the system within the formula design range (generally 8.0-9.0).

2. Storage layering and floating oil droplets

Phenomenon: A layer of oily liquid floats on the surface of the bucket due to the low solubility of film-forming agents in water, resulting in insufficient wetting and dispersion of the system; Excess additives exceed the capacity of lotion.

solve

Do not add excessively;

Add with wetting agent and ethylene glycol/propylene glycol;

Select a compound system with moderate solubility in water;

Mix thoroughly and evenly before discharging the finished product.

3、 Dry and apparent defects of paint film

1. Slow drying, sticky paint film, sticky ash, and re sticking

Phenomenon: Despite being applied for several days, it still feels soft and sticky when touched, with poor stain resistance

reason

1) Excessive addition of film-forming aids;

2) Choose film-forming agents with extremely slow evaporation, which can remain in the paint film for a long time and continue to plasticize;

3) Poor ventilation and low temperature environment make it difficult for additives to evaporate.

solve

Reduce the amount of addition to meet the minimum amount required for film formation;

Reduce the use of super long slow drying additives; Priority should be given to alcohol ester 12 for latex paint on both interior and exterior walls, and caution should be exercised when using high boiling point ethers in large quantities;

Improve ventilation conditions to ensure sufficient escape of additives in the later stage.

2. Pinholes, bubbles, and shrinkage cavities

reason

1) Adding film-forming agents to introduce bubbles;

2) The migration of additives changes surface tension, and improper combination disrupts wetting equilibrium;

3) The concentration of local additives is too high, and the drying rate is inconsistent. Solve the problem of low-speed mixing of materials to avoid excessive gas entrapment; Paired with suitable wetting and leveling agents; Do not use benzyl alcohol in large quantities alone PPH。

3. Unstable gloss, fluctuating gloss within the same batch

The reason is that the film-forming agent is unevenly dispersed; The additives affect the melting degree of lotion particles; There is a significant difference in drying rate between thickness and thickness. Resolve standardized feeding processes; If necessary, use a combination of alcohol ester and a small amount of ether to balance melting and volatilization.

4、 Odor, environmental protection, and water and weather resistance issues

1. The finished paint has a strong odor and a construction irritant odor

Reason for choosing benzyl alcohol PPH、 Ethylene glycol ethers; Poor quality film-forming agents contain impurities; The volatilization cycle of additives is long, and they slowly release flavor over a long period of time. Replace with alcohol ester 16 and low odor alcohol ester 12; Reduce the usage of benzyl alcohol and PPH; Design formulas to minimize the total solvent content as much as possible.

2. Decreased water resistance, foaming, and water permeability of the paint film

Phenomenon: Whitening and foaming after soaking in water, and decreased scrub resistance

reason

1) A large amount of film-forming agents remain in the paint film, forming hydrophilic channels;

2) Select ether based additives with high water solubility;

3) The amount added exceeds the standard. Prioritize the selection of alcohol ester-12 with low water solubility; Strictly control the maximum addition amount; Avoid large amounts of EB and benzyl alcohol.

3. Outdoor paint film weather resistance deterioration, easy powdering, and loss of gloss (exterior wall paint)

reason

Benzyl alcohol and some ethers are UV resistant and prone to aging and degradation under long-term sun exposure; Residual solvents accelerate resin aging.

solve

The exterior wall system should mainly use alcohol ester 12 and minimize the use of benzyl alcohol; Control the total amount of additives.

5、 Common problems with complex systems

1. Single use of fast drying agent (EB): poor film-forming efficiency, requiring increased dosage, prone to whitening, poor water resistance;

2. Using extremely slow drying additives alone: slow drying, rebound, and ash sticking;

3. Compound of benzyl alcohol and alcohol ester: the cost is reduced, but the odor is increased, the acetate acrylic lotion is easy to flocculate, and it is resistant to water decline.

6、 General practical suggestions (key points for avoiding pitfalls)

1. The feeding sequence is key water → dispersant/wetting agent → filler → lotion → (diluted film forming agent) → antifreeze → defoamer → thickener

2. It is forbidden to rush the stock solution into lotion quickly and directly

3. First, do gradient test: 5%, 8%, 10%, 12% (based on the solid content of lotion), find the critical amount of film forming addition, and do not blindly add more

4. Conditional testing of MFFT minimum film-forming temperature to visually assess the effectiveness of additives

5. High Tg lotion needs more film forming additives; The solvent tolerance of vinegar propylene system is weaker than that of pure propylene and styrene propylene