Water based paints

Wall Putty Formulations

December 30, 2024
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by Dr E. Ramanathan PhD, Surface Coatings Consultant

Wall putty is typically formulated to provide a smooth, durable base for painting. It consists of various components that contribute to its adhesive, filler, and leveling properties. Below is a general outline of wall putty formulations:

1. Cement-Based Wall Putty

Ingredients:

  • White Cement (40-60%): Main binding material.
  • Calcium Carbonate (Limestone Powder) (30-50%): Filler material for smoothness.
  • Polymer Additives (2-5%): For improved adhesion and workability (e.g., redispersible polymer powder or water-retentive polymers like hydroxypropyl methylcellulose).
  • Preservatives (0.2-0.5%): Prevent microbial growth.
  • Pigments (if required): To achieve desired shade.

Mixing Process:

  1. Mix white cement and calcium carbonate thoroughly.
  2. Add polymer additives for adhesion and flexibility.
  3. Include pigments and preservatives as required.

2. Acrylic-Based Wall Putty

Ingredients:

  • Acrylic Binder/Emulsion (15-25%): Provides adhesion and flexibility.
  • Calcium Carbonate (50-70%): Acts as a filler.
  • Talc or Kaolin Clay (5-10%): Improves smoothness and workability.
  • Titanium Dioxide (TiO₂) (2-5%): Enhances whiteness and opacity.
  • Water (as needed): For consistency.
  • Additives (2-5%): Includes anti-fungal agents, dispersing agents, and thickening agents like hydroxyethyl cellulose.

Mixing Process:

  1. Disperse calcium carbonate and talc in water with dispersing agents.
  2. Add acrylic emulsion and mix until homogeneous.
  3. Incorporate TiO₂ and other additives.

3. Gypsum-Based Wall Putty

Ingredients:

  • Gypsum (Calcium Sulfate Hemihydrate) (60-70%): Base material.
  • Calcium Carbonate (20-30%): Filler material.
  • Polymer Additives (3-5%): For workability and strength.
  • Retarders (0.5-1%): To control setting time.
  • Preservatives (0.2-0.5%): To prevent microbial growth.

Mixing Process:

  1. Combine gypsum with fillers.
  2. Add retarders and polymer additives.
  3. Blend thoroughly to achieve a consistent formulation.

Key Considerations:

  1. Binder Selection: White cement for exterior durability, acrylic for interior flexibility, and gypsum for quick-drying applications.
  2. Filler Properties: Should ensure smoothness without compromising adhesion.
  3. Additives: Must enhance properties like water resistance, crack resistance, and workability.

Packaging: Store in moisture-proof containers to maintain quality.

Problem of Air Bubbles in Wall Putty

Air bubbles in wall putty formulations can occur during mixing, application, or curing. To solve this issue, the following measures can be taken:

1. Proper Mixing Techniques

  • Slow Mixing Speed: High-speed mixing can trap air. Use a low-speed mixer to minimize air entrapment.
  • Use a Defoamer: Add defoaming agents such as silicone-based or non-silicone defoamers to the formulation to release trapped air.
  • Gradual Addition of Water: Add water slowly during mixing to prevent the formation of air pockets.
  • Adequate Mixing Time: Ensure thorough but not excessive mixing to disperse air.

2. Adjusting Formulation Components

  • Thickeners and Rheology Modifiers:
    • Optimize the amount of hydroxypropyl methylcellulose (HPMC) or other thickeners. Excessive use can trap air.
    • Use thickeners with better air-release properties.
  • Particle Size Distribution:
    • Ensure a proper balance of fine and coarse fillers to reduce air voids.
  • Polymers:
    • Choose polymers with low foaming tendencies. Some redispersible powders and acrylic emulsions can help reduce air bubbles.

3. Application Techniques

  • Proper Troweling: Apply putty with consistent pressure using a smooth-edged trowel to avoid trapping air.
  • Thin Layers: Apply multiple thin coats rather than a single thick coat to allow air to escape easily.
  • Timing Between Coats: Let the first coat partially dry before applying the second to prevent air from being trapped underneath.

4. Environmental and Curing Conditions

  • Avoid High Temperatures: Excessive heat can cause rapid drying, leading to air bubbles.
  • Humidity Control: Maintain moderate humidity levels to allow proper curing.
  • Surface Preparation: Ensure the substrate is clean, even, and free from dust or oil to improve adhesion and reduce air entrapment.

5. Use of Anti-Bubbling Agents

Incorporate commercially available anti-bubbling agents specifically designed for putty and paint formulations.

6. Post-Application Measures

  • Rolling Over Surface: Use a spike roller or bubble popper tool after application to release trapped air.
  • Light Sanding: Once dried, lightly sand the surface to remove any bubble marks.

By combining these preventive and corrective steps, you can significantly reduce air bubbles in wall putty formulations.

Anti-bubbling Agents (Defoamers)

Anti-bubbling agents for putty formulations are additives designed to minimize or eliminate air bubbles formed during mixing, application, or curing. These agents work by reducing surface tension, breaking trapped air pockets, and improving air-release properties. Below are some commonly used anti-bubbling agents:

1. Defoamers

Defoamers help prevent and eliminate bubbles in both water-based and solvent-based formulations.

  • Types:
    • Silicone-Based Defoamers: Effective for both aqueous and solvent-based systems. Examples: Polydimethylsiloxane, modified siloxanes.
    • Non-Silicone Defoamers: Used when silicone residues are undesirable. Examples: Mineral oil-based or organic polymer-based defoamers.
    • Polyether Siloxane Copolymers: Effective for hybrid systems with better compatibility.
  • Example Products:
    • BYK-028 (BYK Additives)
    • TEGO Airex (Evonik)
    • Foamaster (BASF)

2. Air Release Agents

These agents help release entrapped air during mixing or application.

  • Examples:
    • Fluorinated surfactants.
    • Polyglycol ethers.
    • Acetylenic diols.
  • Example Products:
    • Airase 4650 (Ashland)
    • Additol XW 395 (Allnex)

3. Wetting and Dispersing Agents

These agents improve wetting of fillers and pigments, reducing the possibility of air entrapment.

  • Examples:
    • Polyacrylate-based dispersants.
    • Ionic and non-ionic surfactants.
  • Example Products:
    • Dispex AA 4140 (BASF)
    • Efka FA 4645 (Evonik)

4. Foam Stabilizers

For applications where controlled air inclusion is needed (e.g., lightweight formulations), foam stabilizers can be used to regulate bubble formation.

Usage Tips:

  • Concentration: Typically 0.1-1.0% of the total formulation weight.
  • Compatibility Testing: Test the agent’s compatibility with the putty’s other ingredients to avoid issues like surface defects or curing delays.
  • Mixing: Add the agent during the final mixing stage to ensure uniform distribution.

Choosing the right anti-bubbling agent depends on the type of putty (cement-based, acrylic-based, or gypsum-based) and specific application requirements.

Machinery and Equipments

Pony Mixer

Pony Mixer for paste like material mixing

Ribbon Blender Mixing Mechanism

5 T Ribbon Blender Machine

1 T Powder Mixer / Blender

Ribbon Mixer & Blender Animations

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