What is hydroxyethyl methylcellulose coating?

Hydroxyethyl methyl cellulose (HEMC) coating is a water-based coating with hydroxyethyl methyl cellulose as a key additive, which is widely used in the fields of construction, decoration and industry. HEMC, as a non-ionic cellulose ether, can significantly improve the rheological properties, water retention and construction performance of the coating.

1. Characteristics of Hydroxyethyl Methyl Cellulose (HEMC)
HEMC is a polymer compound obtained by chemically modifying natural cellulose (hydroxyethyl and methyl substitution) and has the following characteristics:
Excellent water retention: delays water evaporation, prevents the coating from drying too quickly, and reduces cracking.
Good thickening effect: increases the viscosity of the coating and prevents sagging (more stable construction on vertical surfaces).
Improves leveling: makes the coating more uniform and reduces brush marks and roller marks.
Antimicrobial properties: inhibits mold growth and extends the storage life of the coating.
Environmentally friendly and safe: non-toxic, odorless, and meets the standards of green building materials.

2. The role of HEMC in coatings
(1) As a thickener
Adjusts the viscosity of the coating to adapt to different construction methods (brush coating, spray coating, roller coating). Prevent pigments from settling and maintain the stability of the coating.

(2) As a water-retaining agent Slows down the evaporation of water, especially suitable for cement-based coatings (such as putty and mortar) to avoid cracking.

(3) As a dispersant Helps pigments and fillers to be evenly dispersed to avoid agglomeration.

(4) Improves workability Improves the thixotropy of the coating (viscous when still, thinner during construction), making it easier to operate.

3. Applications of HEMC Coatings
Architectural Coatings:
Interior and exterior wall latex paints, putty powders, and gypsum-based paints.
Decorative Coatings:
Artistic paints, textured mortars, and relief paints.
Industrial Coatings:
Water-based anti-corrosion coatings and floor coatings.
Specialty Coatings:
Fire retardant coatings and thermal insulation coatings (HEMC enhances coating adhesion).

4. Key points for the construction of hydroxyethyl methylcellulose coating
(1) Preparation before construction
Base treatment
Cleaning: Thoroughly remove dust, oil stains, and loose objects from the base to ensure that there are no hollows or cracks.
Smoothness: Use sandpaper or a grinder to level the surface, and use putty to repair uneven areas (HEMC modified putty is recommended).
Moisture content: The base moisture content is ≤10% (concrete/cement-based) or ≤12% (gypsum-based).
Sealing primer: Porous bases (such as gypsum, cement) must be painted with sealing primer first to prevent excessive water absorption.

Environmental conditions
Temperature: 5°C~35°C (low temperature will delay drying, and high temperature will easily cause cracking).
Humidity: Relative humidity ≤85%, avoid construction on rainy days.
Ventilation: Maintain moderate ventilation, but avoid strong winds (to prevent the surface from drying out). 

(2) Coating preparation 
HEMC addition ratio Conventional dosage: HEMC accounts for 0.1%~0.5% of the total weight of the coating (refer to the product manual for details). 
Adjustment principle: High temperature environment: Appropriately increase HEMC (to improve water retention). 

Mixing process
Low-speed mixing: Use an electric stirrer (300~600 rpm) to avoid introducing bubbles at high speed.
Add in batches: Slowly add HEMC powder to water and stir until completely dissolved before adding other components.
Standing and defoaming: After stirring, stand for 5~10 minutes and wait for bubbles to escape before construction.

(3) Construction method Brushing Applicable scenarios: small area construction or edge processing. Tool selection: high-quality nylon brush or wool brush (to avoid hair loss). Tips: Brush in the same direction and avoid dragging back and forth. The thickness of each coat is ≤0.2mm. Multi-layer construction requires an interval of 2~4 hours (after surface drying).

Roller Coating
Suitable for: Large surface applications (such as walls and ceilings).
Tools: Medium or short-hair roller (for even grout absorption).
Techniques:
Apply the roller in a "W" or "M" pattern, finishing with a vertical finish.
Avoid excessive roller pressure, which may damage the HEMC gel structure.

Spray Coating
Suitable for: Efficient application of large areas (such as industrial floors).
Equipment Parameters:
Airless sprayer, nozzle diameter 1.5-2.5mm.
Spray pressure 15-20MPa, spray from a distance of 30-50cm from the wall.
Techniques:
Move the spray gun evenly, overlapping the area by 1/3.
Allow 4-6 hours between spraying multiple layers (to ensure complete drying).

5. Common problems and solutions

6. Storage precautions for hydroxyethyl methylcellulose coatings
Hydroxyethyl methylcellulose (HEMC) coatings are widely used in construction and industrial fields due to their excellent water retention and stability. To ensure that their performance is not affected, special attention should be paid to the following matters during storage:

(1) Environmental conditions
Dry and moisture-proof: relative humidity ≤ 60%, avoid moisture absorption and agglomeration (it is recommended to use a moisture-proof agent or dehumidifier).
Temperature control: 5°C~30°C, avoid high temperature (＞40°C will degrade) or freezing (＜0°C may damage the structure).
Light-proof and ventilated: away from direct sunlight, store in a cool and ventilated place.

(2) Packaging management
Sealed storage: unused HEMC powder should be immediately tied up in the original packaging bag or transferred to a sealed container.
Clear labeling: mark the opening date, and give priority to using earlier batches (shelf life is usually 2 years).

(3) Stacking specifications
≥20cm from the ground, ≥30cm from the wall, avoid direct contact with the ground or wall. When stacking in multiple layers, the height should not exceed 5 layers to prevent the bottom layer from being compressed and agglomerated.