1. Foam Formation and its Detrimental Impact in Paper Manufacturing The paper production process involves transforming pulp into paper, serving as the foundational material for our specialty paper coating procedures. Throughout this process, numerous additives are employed, encompassing sizing agents, retention aids, dry and wet strength agents, softeners, deinking agents, fillers, among others. The pulping process retains natural components like lignin, fatty acids, and resin acids.

Within the backwater circulation system of papermaking, air becomes entrained into the backwater through agitation and other mechanisms, resulting in foam formation. Fiber and fine solid components act as impediments to defoaming. The slurry, containing exceptionally fine fibers and pigment fillers, acts as a substrate for bubble adsorption. Different fiber types may lead to adsorption on fiber surfaces or penetration within fibers. 

Additionally, pigments and fillers tend to adhere to bubble surfaces, bolstering foam stability. Excessive foam content can lead to bubble coalescence, forming larger bubbles that float on the liquid surface, presenting as surface foam. Surface foam can impede pulp cleaning, fiber swelling, result in air leaks from pulp pumps, cause concentration fluctuations in pulp chests, hinder paper flow stability, complicate mesh dewatering, and lead to pulp degradation, ultimately impacting paper quality and cardboard interlayer bonding. Additionally, waterborne bubbles can cause variations in paper properties, leading to hydrophobic substance accumulation on gas-liquid interfaces, such as flow boxes, resulting in paper breakage and reduced production efficiency.

2. Categories and Mechanisms of Defoamers Defoamers for papermaking primarily fall into two categories: high carbon alcohol defoamers and polyether defoamers.

2.1 High Carbon Alcohol Defoamers: Also termed degassing agents, these defoamers remove small foam adhering to fiber surfaces. Structurally akin to surfactant molecules, fatty alcohols feature an amphiphilic structure with a long-chain hydrocarbon segment and a hydrophilic hydroxyl group. The hydroxyl groups infiltrate fiber surface hydroxyl groups, exerting pressure on adsorbed bubbles, facilitating their detachment. Freed bubbles amalgamate and rise due to buoyancy. Fatty alcohol molecules also adsorb onto gas-liquid interfaces of bubbles, disrupting molecular film tension equilibrium, leading to bubble film thinning and rapid rupture.

2.2 Polyether Defoamers: These defoamers self-emulsify in water, adsorb onto foam surfaces, lower foam surface tension, and induce foam rupture. Being non-ionic surfactants, their efficacy is temperature-dependent, requiring specific temperature ranges for optimal performance.

3. Defoamer Selection for Papermaking Appropriate defoamer utilization swiftly eliminates foam, curtails foam regeneration, diminishes gas content in pulp and white water, augments pulp dewatering, reduces residuals, improves product quality, and slashes comprehensive production and management costs.

Long-term application insights: ① For sized paper production or medium to low-speed paper machine systems, incorporating high carbon alcohol defoamers ensures manageable foam control without compromising adhesive effects, all while maintaining cost-effectiveness. ② In sized or coated paper manufacturing or high-speed paper machine setups, employing polyether defoamers yields superior and faster defoaming outcomes.

Qingdao JIERUIXIN Machinery & Technology CO., Ltd, offers a diverse range of defoamers and associated chemicals tailored for papermaking and coating processes, boasting ample inventory and offering free samples.