A defoamer knocks foam. A stickies programme disperses or detackifies adhesive particles so they do not plate out on wires, felts, and dryers.
Stickies are not ink and not foam
Recycled mills lose clothing life when pressure-sensitive adhesives and coating binders agglomerate. The particle is hydrophobic and tacky. A flotation deinking chemical can leave it behind. A defoamer can even make small particles easier to deposit if the only change is less air.
Treat pitch from virgin mechanical pulp the same way: name the wood source and the temperature where pitch goes soft. A summer pitch outbreak is not a winter defoamer problem.
Where surfactants help
Nonionic dispersants and selected anionic packages keep particles small and less tacky through screens and the former. They do not replace mechanical cleaning or a felt-conditioning programme. If the felt is already filled, clean it and then hold the incoming load down.
Specify the passivation or detackifier dose point separately from the defoamer dose point so the trial can show which chemical moved the deposit count.
| Symptom | First chemistry question | Wrong first move |
|---|---|---|
| Spots that melt on the dryer | Stickies or pitch identity | More defoamer |
| Ink in the sheet | Deinking and washing | A release aid |
| Felt filling | Felt cleaning plus incoming stickies | A Yankee adhesive change |
| Washer foam | Liquor antifoam | A detackifier |
Where stickies and pitch come from
Recycled furnish carries pressure-sensitive adhesives, hot-melt adhesives, coating binders, and waxes. Virgin softwood and hardwood carry resin and fatty acids that become pitch soaps in alkaline pulping and then become tacky again if the pH or the calcium level shifts. Both populations are hydrophobic particles suspended in a water system that also contains fines and starch.
Temperature is the trigger people miss. A particle that is hard in a cold chest softens on a warm dryer or in a hot white-water loop and smears. A control program that only looks at the pulper will miss the deposit that forms two stages later.
Detackify, disperse, or float
A detackifier adsorbs on the tacky surface and lowers its adhesion to metal, fabric, and fibre. A dispersant raises the charge or the steric barrier so particles do not collide and grow. Flotation in deinking wants the opposite surface story: the particle should attach to an air bubble and leave with the froth. A strong dispersant can stabilise the ink or sticky in the water and hurt flotation yield.
That is why one “stickies chemical” cannot be the answer for deinking, for the machine loop, and for felt conditioning. Name the particle, the stage, and whether you need it in the froth, in a dispersed state, or passivated so it does not smear.
Calcium, pH, and why deposits return
Calcium soaps of resin acids are classic pitch deposits. If the white water hardens, or if an acid shock protonates a soap, the particle changes from a soluble or dispersed soap into a tacky acid or salt. Fixing pH and hardness is part of the chemistry, not a separate utility problem.
Judge the trial by deposit weight on a panel or by holes and spots in the sheet, not only by a visual of the pulper. A clean pulper and a dirty dryer means the control was in the wrong chest.
How to Specify with Esteem
- Identify the contaminant: hot-melt stickies, latex binders, wood pitch, or wax.
- Say where it plates out: pulper, screen, wire, felt, or dryer.
- Separate the deinking flotation result from residual stickies in the sheet.
- State temperature and pH at the deposit point.
- Ask for a dispersant or detackifier trial, not a higher defoamer dose, unless foam is the measured defect.
Pair this with de-inking chemicals and felt cleaning. Deinking removes ink; felt cleaning removes what already deposited.