All About Stickies and How to Control Them

In the paper and pulp industry, contaminants can significantly impact productivity, the quality of the papermaking final product, and the converting processes of the mill’s customers.

One category of contaminants is known as stickies. Stickies are tacky substances that can be present in the paper, pulp, and process water systems of paper machines. They are prevalent in recycled fiber and encompass various materials.

When virgin fiber is used, residual wood resins and colloidal wood pitch infiltrates the papermaking process along with the pulp. In pulp manufacturing, wood pitch presents challenges including buildup on equipment and increased dirt counts. Silicone-based defoamers can exacerbate pitch deposition issues. Inadequate control over pitch can also create problems for pulp end users.

It is important to control the amount of stickies in your paper processes to prevent equipment malfunctions and reduce downtime. This article will detail the problem stickies can cause, what materials are used for stickie control, how to handle them, and a helpful solution.

Caused by Stickies

Stickies can quickly become a headache in the paper and pulp industry due to the problems they can cause including:

• Holes in Sheet: Stickie build-up on wires, press felts, or rolls can result in sheet holes or tears, causing breaks.
• Buildup on Roll: If stickies build up on a roll around one area, you could get a band of stickies around the roll. When the sheet passes over that area, it could put an embossed mark in the sheet or tear out bits.
• Blinding of Wires : If stickies are causing the wires or forming fabric to be blinded, water will not go down to that area because there is nowhere for it to drain through. This can cause reduced drainage which can then lead to decreased machine speeds and uneven moisture profiles. It usually must be corrected with downtime solvent cleaning.
• Blinding Felts: If stickies blind the press section, water can’t leave the sheet and go into the felt. This forces the stickies to stay in the sheet. Because that area will be wetter than the section around it, it can cause further issues including cockling.

KEY INSIGHT: Cockling is when paper bulges out in certain places to present a wrinkled or creased surface.

So, how can you deal with stickies? One way is to mechanically remove them from the system completely. Getting the right equipment to remove and consolidate the stickies also has costs associated with it, and the rejects often need to be sent to landfill.

There are two main ways that stickies are controlled in the paper and pulp industry. The first is to pacify them to make the surface of the stickie non-sticking.

Another method that is often more popular is making the stickies so small that they go out with the product. Because of their small size, they do not cause as much of a problem.

Stickies Control Agents

When managing the amount of stickies in your production, there are several control agents that can be used. Here is an incomplete list of materials for dealing with stickies:

• Talc: Has both hydrophobic and hydrophilic edges to the particles and coats the stickies to make them non-tacky.
• Bentonite: Has a high surface area and negative charge. This attracts, neutralizes, and collects hydrophobic sticky particles to avoid deposits on the machinery.
• Aluminum Sulfate (Alum): Uses detackification, microfixation, and charge neutralization to control stickies.

Key Insight: A detackifier is a process chemical that is used to reduce the tackiness of other substances.

Pacifying Stickies

If you put a control agent such as talc into your system, the talc will stick to the surface of the stickie and make it non-stickie. However, as it goes through pumps, screens, and refiners, new untreated surfaces will be exposed. Solutions like talc also comes with adverse health and safety risks that could include coughing, breathing troubles, and a higher risk of some cancers. Because of these reasons, pacifying stickies isn’t always the right answer.

Make Them Smaller

One common solution is to make the stickies too small to be a problem. You can keep them small and dispersed so they do not amass to become larger stickies. You can also break down large ones to become smaller, causing little to no damage.

NexShield

NexShield is a concentrated pulp and paper industry contaminant control agent that creates a hydrophilic shell around hydrophobic pitch and stickies particles. This keeps them small and dispersed while preventing them from becoming tacky even at high temperatures.

DuBois’ latest pitch and stickies control solution prevent deposit issues and keeps your machine running efficiently. Because the melting temperature of most wood pitch and stickies particles is below the temperature reached in the dryer system, pitch and stickies agglomerate and become tacky. This causes machine runnability and product quality issues.

Next Shield prevents this. Unlike other treatment solutions, NexShield forms a hydrophilic barrier around pitch and stickies contaminants. This allows the contaminants to remain small and dispersed in solution. They then stay solid through the dryer section and prevent contamination of your machine’s fabric.

Tested against a nontreated stickie, the NexShield treated sample remained solid at 180ºF (82 ºC) while the former completely melted. The NexShield treated sample did not begin to soften until 260ºF (126ºC).

Conclusion

Pitch and stickies can lead to complicated problems in your operations. That is why employing control strategies like removal or pacification is vital to maintaining smooth production. Products like NexShield can keep pitch and stickies small, making them no longer attractive to paper machine fabrics and roll.

DuBois offers comprehensive solutions tailored to each stage of the pulp and papermaking process, addressing concerns related to pitch, stickies, and other stubborn contaminants.