What is the paper pulp preservative? A comprehensive explanation of its principles, selection, and application.
The paper pulp contains cellulose, hemicellulose and water. In the production environment with a pH of 4-8 and a temperature of 25-45℃, it is highly prone to the growth of bacteria, molds, yeasts and algae and other microorganisms. The metabolic activities of these microorganisms will decompose the fibers and produce mucus, leading to problems such as rotten pulp, paper holes/black spots/ruptures, equipment sludge blockage, and foul smelling white water. This seriously reduces production efficiency and product quality. Paper pulp preservatives inhibit or kill microorganisms to ensure the stability of the pulp system, extend the cleaning cycle of equipment, and improve the qualification rate of paper. They are indispensable functional additives in modern papermaking industry.
II. Microbial Hazards and the Necessity of Preservation
2.1 Main Harmful Microorganisms
Bacteria: Bacillus, Pseudomonas, etc., break down cellulose to produce mucus, resulting in a decrease in the viscosity of the pulp and a reduction in the strength of the paper.
Molds: Aspergillus niger, Penicillium, etc., cause the pulp to mold and the paper to turn yellow and discolored, especially in high-humidity environments, the risk is particularly prominent.
Algae: Attach to the filter section and pipes, forming a biofilm, which affects dehydration and clogs the equipment.
2.2 Core Hazards
Product defects: Rotting pulp causes holes, black spots, light transmission points, and broken ends, resulting in a decrease in product qualification rate.
Efficiency reduction: Bio-mud clogs pipelines and screen sections, increasing the frequency of shutdowns for cleaning, and the production capacity loss can reach 10% - 20%.
Cost increase: Fiber degradation and pulp loss, and additional investment in cleaning and maintenance costs is required.
Environmental risk: Microbial metabolites lead to an increase in COD, unpleasant white water odor, and increase the pressure of wastewater treatment.
2.3 Core Value of Preservation
Kill / inhibit harmful microorganisms, prevent moldy pulp and paper diseases;
Decompose biological sludge, ensure efficient operation of equipment;
Protect the integrity of fibers, stabilize paper strength and whiteness;
Extend cleaning cycle, reduce overall production costs.
III. Classification and Mechanism of Main Anticorrosive Agents
3.1 Thiiazolinones (Non-oxidative, Mainstream Choice)
Representative products: BIT (Benzothiazolinone), MIT (Methylthiazolinone), CMIT/MIT combination.
Mechanism of action: Penetrates the cell walls of microorganisms, binds to protein sulfhydryl groups, disrupts enzyme systems and nucleic acid structures, rapidly kills bacteria and inhibits reproduction.
Core advantages: Broad-spectrum and highly effective (kills bacteria/molds/algae), wide pH applicability (2–11), low toxicity and environmental friendliness, good compatibility.
Application scenarios: Pulp, white water, starch glue, coating paints, with an addition amount of 0.01%–0.03%.
3.2 DBNPA (2,2 - Dibromo - 3 - Dialkylaminoacrylamide, Rapid Disinfectant Type)
Mechanism of action: Destroys cell membranes, interferes with metabolic enzyme activity, kills microorganisms within minutes, and decomposes completely without residue after killing.
Core advantages: Extremely fast sterilization speed, high efficiency at low concentrations (0.01% - 0.05%), does not affect fibers and whiteness, environmentally friendly and easily degradable.
Application scenarios: High-risk pulp decomposition systems, waste paper pulp, white water, pH 4-9 environment, suitable for intermittent impact dosing.
3.3 Oxidizing Disinfectants (Auxiliary / Severe Contamination Scenarios)
Representative products: Chlorine dioxide (ClO₂), sodium hypochlorite.
Mechanism of action: Strong oxidizing property damages the structure of microorganisms, quickly kills bacteria and removes sludge.
Core advantages: Strong bactericidal power, low price, no residue.
Limitations: Corrodes equipment, affects fiber strength and whiteness, narrow pH range (best in acidic conditions), prone to generating by-products.
Application scenarios: Disinfection of white water systems, removal of pipe sludge, not recommended for direct addition to slurry.
3.4 Organic Composite Preservatives (Long-lasting Antibacterial Type)
Representative product: Organic bromine and quaternary ammonium salt combination.
Mechanism of action: Adsorbs onto the bacterial cell surface, damages the cell membrane, inhibits metabolism, and has both bactericidal and long-lasting antibacterial functions.
Core advantages: Long-lasting stability (3–6 months), low irritation, compatible with neutral / alkaline systems.
Application scenarios: Long-term antibacterial, high-humidity storage of slurry, dosage 0.02%–0.05%
