Label Removal Before Washing: Why It Decides Flake Quality
Every bale of post-consumer bottles carries labels held on by glue, and every kilogram of that glue you let into the crusher ends up somewhere you do not want it: on the flake, in the wash water, and in the specification dispute with your buyer. Label removal is not a side stage of a washing line — it is the stage that decides whether the rest of the line can do its job. This guide explains where de-labeling sits in the sequence, what each type of label demands, and how friction washing and hot washing deal with the glue that gets through.
Why Labels Are the Most Expensive Contamination in the Bale
A typical PET bale carries paper and film labels, glue residue, caps and rings, sand, organic residue and traces of metal. Of these, labels are the only contamination class that is bonded to the value material itself. Sand sinks, caps float, metal is picked up by magnets — but label adhesive clings to the polymer surface and behaves like a dye: a small amount discolours a large amount of flake.
This is why the PET bottle washing line product page states the principle directly: bottle-to-flake production lives or dies on label, cap and glue removal, and label removal, friction washing and dewatering are the three stages that decide flake quality. The label problem is not cosmetic. Residual glue shows up later as colour defects and intrinsic-viscosity problems in the finished flake, and it is one of the first parameters a serious flake buyer tests.
The economics follow from the chemistry. Adhesive that is removed early — while it is still attached to an intact label — leaves the line in a single, concentrated waste stream. Adhesive that reaches the wash bath dissolves and disperses, and from that moment the water system, the flake surface and the density separator all carry a share of it. Early removal is cheaper than late removal by a wide margin.
Where De-Labeling Sits in the Sequence — and Why Before Crushing
The published PET line process has six stages, and their order is not arbitrary:
Published PET Line Sequence
- De-baling — bales are opened and metered at a steady rate.
- De-labeling — labels and sleeves are separated before the bottles are crushed.
- Crushing — a PS-series crusher reduces bottles to flake size.
- Hot washing — heated wash liquor with dosing removes glue and organic residue.
- Density separation — caps, rings and other PP/PE fractions float off; heavies sink.
- Dewatering and drying — flakes are dewatered and dried to the target moisture.
The position of stage two is the whole point. Whole bottles present a large, smooth, intact surface that a de-labeling unit can grip and strip. Crushed flake presents a thousand small fragments per bottle, each carrying a smear of adhesive on some edge. Once the crusher has run, no machine can find and remove the glue economically — the only option left is to wash harder and hope the bath stays clean. That is why the sequence rule on the product page is stated bluntly: de-labeling before crushing is what keeps glue out of the wash bath.
The same logic holds for rigid PP and PE. On the PP/PE rigid plastic washing line, paper labels are listed among the contamination classes the line handles, and each stage is tuned to remove one class before it can spread to the next.
Three Label Types, Three Removal Problems
Not all labels behave the same way, and the de-labeling stage has to be configured for the dominant type in your feed:
- Sleeve and stretch labels (PET bottles) — loose plastic film around the bottle body. These separate mechanically once bottles are intact, which is exactly why they are stripped at stage two, before crushing destroys the geometry the separator relies on.
- Glue-on paper labels — the adhesive is the problem, not the paper. The label is removed with the bottle surface intact; whatever adhesive residue remains is handed to the friction-washing and hot-washing stages downstream.
- Printed film (film and bags) — on the film and flexible plastic washing line, paper labels and printing ink are surface contamination handled by wet size reduction and intensive washing, not by a bottle-style de-labeler.
Mixing streams changes the answer again. A bale blend of bottles, thermoforms and household rigids carries all three label types at once, and the removal scope is designed from a material study of your actual feed rather than assumed from the material name.
Friction Washing: the Second Line of Defence Against Glue
No de-labeling stage removes every gram of adhesive, so the line needs a stage that scrubs residue off flake surfaces after crushing. That is the friction washer. Rinsing removes loose dirt; adhered oil, label adhesive and compacted soil need mechanical friction against the polymer surface, combined with spray rinsing. The published FW-series data:
| Model | Power | Rotation speed | Capacity | Drum diameter | Water use |
|---|---|---|---|---|---|
| FW-500 | 15 kW | 500 rpm | 300-500 kg/h | Ø500 | 2-4 m³/h |
| FW-800 | 22 kW | 600 rpm | 500-1,000 kg/h | Ø800 | 4-6 m³/h |
| FW-1000 | 37 kW | 700 rpm | 1,000-1,500 kg/h | Ø1000 | 6-8 m³/h |
| FW-1200 | 55 kW | 800 rpm | 1,500-2,000 kg/h | Ø1200 | 8-12 m³/h |
Three published selection notes matter for glue control. First, the material should be pre-crushed, typically to 10-30 mm — too coarse reduces cleaning, too fine complicates separation, which is another reason the crushing stage is sized carefully. Second, the washer capacity must match the upstream PS-series crusher so it does not become the bottleneck. Third, larger or heavily contaminated lines use two or three friction washers in series, because the number of passes — not the rotor speed alone — is what brings residual adhesive down to the cleanliness target.
Hot Washing and the Water System
After friction washing, the hot-wash stage removes what mechanical rubbing cannot: the published PET sequence describes it as heated wash liquor with dosing that lifts glue and organic residue. For oily material, heated wash liquor improves results — but whether heat is needed for your feed, and at what setting, is confirmed in a material test on your actual labels and glues. Glue chemistry varies by label supplier and region, so this is a trial question, not a catalogue question.
Everything the stages release ends up in the water, which is why the published lines run a closed-loop water system including treatment. Wash water circulates, treatment removes the fines, glue and organics it picks up, and only the treatment side consumes fresh make-up water — the published series ranges from 3-5 t/h on the WL-500 to 12-20 t/h on the WL-5000. When a de-labeling stage works as designed, the glue load reaching the water system drops sharply, and the water system is what keeps the bath clean across shifts.
What Skipping De-Labeling Actually Costs
Run the sequence without stage two and the cost appears in four places:
- Flake specification — residual label and glue content is a graded parameter for flake buyers, and glue that survives the line is visible as colour defects and haze.
- Wash chemistry — more detergent, more heat and more dwell time are spent fighting adhesive that a de-labeler would have removed intact.
- Water system load — dissolved adhesive accumulates in the bath and the treatment stage works harder for the same output quality.
- Downstream stages — the dewatering machine in the VD series reaches a dewatering rate of 95% or more, but no dewatering stage can remove contamination that was never washed off; dirty water carries glue back onto clean flake.
The published WL series — 500-800 kg/h on the WL-500 up to 3,000-5,000 kg/h on the WL-5000, with outlet moisture of 2% or less — assumes the line runs in its designed order. Flake quality targets such as residual moisture and label content are confirmed after a wash trial on your bales, because input contamination varies by region and collection scheme.
Frequently Asked Questions
Why should labels be removed before bottles are crushed?
Because removing labels and sleeves before crushing keeps glue out of the wash water and off the flake surface. Once labels are crushed together with the bottles, adhesive smears across the flake and contaminates the wash bath, and every downstream stage has to fight it.
Does friction washing remove label glue that is already on the flake?
Yes. Adhesive residue left after de-labeling is one of the main things friction washing removes, together with oil and soil. High-speed rubbing between the rotor and the plastic, combined with spray rinsing, lifts the glue off the flake surface and carries it away with the rinse water.
Is hot water needed to remove label glue?
For oily material, heated wash liquor improves results. Whether heat is needed for your feed depends on the glue type and contamination level, and is confirmed in a material test before the line is finalised.
What about labels printed directly on film?
On film and flexible packaging, paper labels and printing ink sit on the film surface and are handled by the film route: wet size reduction, intensive friction washing and squeezing, rather than the rigid-plastic sequence. Cleaning performance for your specific print and soil load is confirmed in a material trial.
Not Sure Which Label Removal Scope Your Feed Needs?
Send bale photos and your target flake specification. LVKESORT's engineering team will size the de-labeling and washing stages and confirm quality targets with a wash trial on your material.