Technical Characteristics and Application Value of SBR Latex for Papermaking

Introduction
Carboxylated SBR (styrene-butadiene rubber) latex is an innovative functional additive for papermaking. It is produced by incorporating carboxylated styrene-butadiene rubber into a waterborne emulsion through high-speed dispersion, uniform mixing, and stabilization treatment. As a nonionic aqueous adhesive, it freely disperses in cold water and exhibits high adhesion, excellent transparency, superior film-forming ability, and water resistance. Consequently, it has been widely applied in the papermaking industry, achieving outstanding results.

1. Molecular Design and Colloidal Properties

• Structural Characteristics:
  The material is based on a styrene-butadiene rubber backbone that has been chemically grafted with carboxyl groups (-COOH), forming an amphiphilic structure with both hydrophobic and hydrophilic segments.
• Colloidal Attributes:
  The latex particles are controlled within a range of 80–150 nm (as measured by dynamic light scattering) and exhibit a surface zeta potential between -30 to -40 mV, which ensures excellent colloidal stability.
• Chemical Compatibility:
  Its nonionic nature allows the latex to remain stable over a wide pH range (4–10), offering significantly better chemical compatibility with the wet-end papermaking system compared to traditional anionic additives.

2. Fiber Bonding Enhancement Mechanism

• Penetration and Film Formation:
  During the drying process, the latex particles penetrate into the fiber pores and form a three-dimensional polymer network.
• Hydrogen Bonding and Physical Entanglement:
  The carboxyl groups form hydrogen bonds with the hydroxyl groups of cellulose, while the styrene-butadiene segments physically entangle with fibers, reinforcing the bonding between fibers.
• Performance Improvement:
  This synergistic effect results in a 20%-35% increase in tensile strength and a 15%-25% improvement in ring crush strength (as determined by ISO standard tests), making it particularly suitable for producing high-strength packaging papers.

3. Surface Finishing Function Realization

• Film Formation on Paper Surface:
  During the sizing process, the latex forms a continuous transparent film on the paper surface with a thickness ranging from 0.5 to 2 μm.
• Optical Properties:
  With a refractive index of 1.48–1.52, which is close to that of cellulose (1.53), the film effectively reduces surface light scattering.
• Enhanced Gloss and Printability:
  When combined with calendering, the surface gloss at a 75° angle can be increased by 10-15 points (as per TAPPI T480 standards), and the ink absorption is optimized by 15%-20%, significantly improving printing suitability.

4. Process Adaptation and Environmental Advantages

• Ease of Incorporation:
  This additive can be directly introduced into the pulp system at room temperature at an addition rate of 0.5%-2.5%. Compared to traditional rosin sizing agents, it can reduce the required amount of cationic starch by 15%-20%.
• Environmental Benefits:
  Made from a waterborne system, carboxylated SBR latex releases no formaldehyde (as verified by GB/T 35601-2017) and reduces wastewater COD load by 30%-40%, aligning with clean production and green environmental requirements.

5. Specialty Paper Product Development Applications

• Digital Inkjet Printing Paper:
  Its porous film structure can precisely control ink droplet diffusion, achieving print resolutions up to 1200 dpi.
• Food-Grade Packaging Paper:
  The latex film demonstrates an oil resistance barrier efficiency of over 98% (as per GB 31604.1 tests), significantly enhancing the paper’s oil-proof properties.
• Antimicrobial Paper:
  Recent studies indicate that silane-coupled carboxylated SBR latex can elevate the antibacterial rate of paper to 99.9% (in accordance with ISO 20743 standards), broadening its application in high-hygiene fields.

Conclusion
Carboxylated SBR latex for papermaking leverages its unique molecular design and excellent colloidal stability to significantly enhance paper’s mechanical strength and surface quality. It not only improves the tensile and ring crush strength of paper but also optimizes its surface gloss and printability, thereby increasing the overall market competitiveness of paper products. Moreover, its simplified production process and environmental advantages support sustainable manufacturing practices in the papermaking industry. With ongoing advancements such as microencapsulation and photo-responsive modifications, the future applications of carboxylated SBR latex are poised to expand into emerging fields like smart packaging and information recording, further increasing its industrial value.

Lior Lee 

Email: lilin@hzruico.com