Carbonless paper, also known as NCR paper, is categorized into three types: upper page (CB paper, Coated Back), middle page (CFB paper, Coated Front & Back), and lower page (CF paper, Coated Front).

• CB Paper (Upper Page): Coated on the back with CB coating.
• CFB Paper (Middle Page): Coated on the front with CF coating and on the back with CB coating.
• CF Paper (Lower Page): Coated on the front with CF coating.

Carbonless paper coatings include CB and CF coatings. The CB coating on CFB paper differs slightly from that on CB paper, primarily in the amount of microcapsules used. The CF coating on both CFB paper and CF paper is generally the same to simplify production and management.

CB Coating Components and Performance Requirements

1. Microcapsules:

• The most crucial component, impacting color rendering, light resistance, and pollution.
• Typically composed of colorless dye oil, wall material, and emulsifier, with a solid content of 40-50%.
• Optimal particle size is below 10μm, with 5-6μm being ideal to balance color effect and paper contamination.
• Accounts for about 50-60% of the total paint (absolute dry ratio).

2. Spacers:

• Prevent premature breaking of microcapsules during dosing and coating.
• Commonly used spacer: Wheat starch.
• Particle size should range from 15-25μm, accounting for 60-80% of the total.
• Amount required: 30-50% of microcapsules (absolute dry ratio).

3. Adhesives:

• Carboxylated styrene-butadiene latex (3-4% of paint, dry ratio).
• Modified starch (10-12% of paint, dry ratio).

4. Additives:

• Dispersant (sodium polyacrylate): 0.2-0.3% (for paint, dry ratio).
• Sodium carboxymethyl cellulose (CMC): 0.5-1.5% (for paint, dry ratio).

• Preservatives: 0.5% (for starch, dry ratio).

CF Coating Components and Performance Requirements

1. Pigments:

• Fill and cover the base paper, improve whiteness, opacity, smoothness, and gloss.
• Kaolin: 50-70% of total pigments, hexagonal flake, with 70% of particle size less than 2μm.
• Calcium Carbonate: 30-50% of total pigments, light calcium carbonate with particle size of 0.1-1μm.

2. Color Developing Agent:

• Primarily phenolic resin, with zinc salicylate to enhance low-temperature color development.
• Amount: 11-13% of total paint (absolute dry ratio).
• Phenolic resin to zinc salicylate ratio: 10:1 (absolute dry ratio).

3. Adhesives:

• Carboxylated styrene-butadiene latex (4-5% of paint, dry ratio).
• Modified starch (12-14% of paint, dry ratio).

4. Additives:

• Dispersant: Sodium polyacrylate, 0.2-0.3% (for pigment, absolute dry ratio).
• Sodium Carboxymethyl Cellulose (CMC): 1.0-1.5% (for pigments, dry ratio).
• Foam Suppressant: 0.02-0.05% (for pigment, dry ratio).
• Lubricant: Calcium stearate, 1.0-1.5% (for pigment, dry ratio).
• Preservatives: 0.5% (starch, dry ratio).
• Caustic Soda: Used to adjust pH value of paint.

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