How We Solved the Problem of Sticky Deposits in a Paper Machine: Practical Procedure and Prevention

Photo: Charlotte Harrison / Unsplash

In the paper industry, sticky deposits (so-called stickies) are among the most common operational problems. They form from impurities in recycled paper, adhesives, or coating residues and gradually accumulate on rolls, screens, and other parts of the machine. The result is defects in the paper, frequent shutdowns for cleaning, and increased energy consumption. In this article, we describe a specific case where, using a combination of dispersing and cleaning additives, we not only removed existing deposits but also prevented their recurrence—without the need for costly mechanical interventions.

Problem: Sticky Deposits and Their Impact on Production

Sticky deposits, also known as stickies, represent one of the most common and problematic operational issues in the paper industry. They form as a by-product of paper recycling, when adhesives, waxes, printing inks, or plastic particles from packaging materials enter the pulp. These impurities transform into viscous, sticky masses under operational temperatures (40–70 °C) and pressures in the paper machine, adhering to rolls, wires, drying cylinders, and other parts of the equipment.

The consequences are immediate and costly: reduced paper quality (spots, holes, uneven thickness), more frequent machine downtime for cleaning, increased energy consumption, and equipment wear. In our case, the problem was particularly evident on wires and press rolls, where deposits caused paper web breaks and increased the consumption of surface treatment chemicals. Without a systematic solution, the situation would have rapidly worsened, making it necessary to act quickly and purposefully.

Diagnosis: How we identified the cause and extent of the problem

The first step toward a solution was the precise determination of the source and nature of the deposits. We conducted a comprehensive analysis of pulp samples and the deposits themselves using standard laboratory methods. Microscopic examination revealed the presence of synthetic polymers (e.g., acrylates and polyvinyl acetates) and waxes, which entered the raw material from recycled paper. We also mapped critical points in the paper machine where the most intense accumulation occurred—particularly in the wire section, press rolls, and drying section.

A key tool was thermogravimetric analysis (TGA), which helped us determine the thermal stability of deposits and their behavior under various operating conditions. We found that at temperatures above 60 °C, significant softening and stickiness of some components occur. Simultaneously, we monitored process parameters such as pulp pH (typically 6.5–8.0), water hardness, and chemical dosing to rule out the influence of incorrect operating conditions.

Photo: Jorge Fernández Salas / Unsplash

Solution: Combination of chemical and mechanical measures

Based on diagnostics, we proposed a multi-step approach that combined chemical treatment with adjustments to operational conditions. The most effective solution proved to be the use of special dispersing agents based on surfactants and polymeric additives, which prevent the agglomeration of sticky particles and keep them in suspension. These substances were dosed directly into the pulp at a concentration of 0.05–0.2% (by weight), specifically in the phase before screening and cleaning, to allow sufficient time for effective interaction with impurities.

In parallel, we optimized the mechanical cleaning of the machine: we introduced regular hot water flushes (70–80 °C) with the addition of alkaline cleaning agents, which dissolve organic deposits. For critical machine parts (e.g., screens), we increased the cleaning frequency from weekly to daily. We also adjusted the operating temperatures in the drying section to minimize the softening of sticky components. The result was a reduction in deposit occurrence by more than 70% within the first two weeks after implementing the measures.

Prevention: How to Keep a Paper Machine Free of Sticky Deposits Long-Term

Long-term prevention requires a systematic approach and regular monitoring. The foundation is controlling the quality of the input raw material—recycled paper—and its pretreatment using flotation and screening processes that remove coarse impurities. We recommend implementing regular pulp analyses for sticky substance content, at least once a week, to enable timely responses to changes in raw material composition.

No less important is machine maintenance: regular cleaning of critical parts, using suitable lubricants and low-adhesion coatings (e.g., silicone- or fluoropolymer-based), and training operators to promptly recognize the first signs of problems. Last but not least, it is crucial to maintain stable operating conditions—especially temperature, pH, and chemical dosing—and to regularly calibrate sensors and measuring equipment. This approach minimizes the risk of sticky deposits and ensures smooth and efficient operation of the paper machine.

Photo: Nadiia Ganzhyi / Unsplash

Optimizing additive dosing to reduce stickiness

In the paper industry, additives play a key role in controlling sticky deposits, known as stickies. These impurities, originating from recycled fibres, adhesives, or printing inks, can accumulate on screens, rollers, and other machine parts. The solution lies in the targeted use of dispersing and retention agents, which prevent particle agglomeration and facilitate their removal by water. Dispersing agents, often based on polyacrylates or phosphonates, disperse sticky particles into a fine suspension, thereby reducing their ability to adhere to surfaces. Retention agents, such as cationic polymers, then help capture these particles in the paper pulp and remove them from the process.

The dosage of additives must be carefully balanced – too low a concentration does not solve the problem, while excessive amounts can lead to foaming, impaired drainage, or even new deposits. It is recommended to start with a dosage of 0.05–0.2% based on the dry fibre mass and gradually adjust it according to the results of laboratory tests and operational observations. Monitoring effectiveness can be carried out by measuring the size and quantity of sticky particles in pulp samples using standard test methods, such as microscopic analysis or filtration through screens with a defined mesh size.

Adjusting Process Parameters to Minimise Deposits

In addition to chemical measures, it is essential to optimise the operational conditions of the paper machine. The temperature and pH of the process water have a significant impact on the behaviour of sticky particles. High temperatures (above 50 °C) can increase the stickiness of some polymers, while excessively low temperatures slow down dispersion. The ideal range is usually between 40–45 °C, but the specific value depends on the composition of the input raw materials. The pH should be maintained in a slightly alkaline range (7.5–8.5), as an acidic environment can promote the coagulation of sticky substances and their deposition on machine parts.

Another key factor is the flow rate of pulp and water in the machine. A flow rate that is too low increases the risk of sedimentation, while one that is too high can cause mechanical stress and foam formation. It is recommended to regularly inspect and clean nozzles, screens, and other critical points where flow slowdown occurs. In some cases, adjusting the pipeline geometry or adding turbulators, which improve mixing and reduce the risk of deposition, may help. Such modifications should be carried out in cooperation with the machine equipment supplier to avoid compromising the overall efficiency of the machine.

Long-term monitoring and maintenance for stable operation

Preventing sticky deposits requires a systematic approach and regular monitoring. It is recommended to introduce an operational logbook to record key parameters such as additive dosage, temperature, pH, pressures, and the visual condition of the machine. This data allows trends to be identified and deviations to be addressed promptly. For example, a gradual increase in pressure on screens may indicate the accumulation of deposits, while changes in pH may suggest the need to adjust the chemical regime.

Regular maintenance should include not only chemical cleaning of critical machine parts but also mechanical removal of deposits. Special cleaning agents based on surfactants or alkaline solutions, which effectively dissolve organic impurities, can be used for cleaning. It is important to adhere to the recommended concentrations and exposure times to avoid damaging the machine materials. After chemical cleaning, all parts must be thoroughly rinsed with water to prevent residual effects of cleaning agents on the quality of the paper produced.

Need a Custom Solution?

Every paper mill has its specific conditions. GCG Group supplies a broad portfolio of additives for controlling sticky deposits, including dispersing and cleaning agents with detailed technical data sheets and safety data sheets (SDS). Contact us for a consultation and optimization of your process. Get in touch – or browse our catalog of over 1,300 products right away.