Controlling PVC contamination is one of the toughest challenges in PET bottle recycling, especially when you target high-end applications and food-grade rPET. Even at concentrations around 50 ppm, PVC can damage PET quality, causing brittleness, yellowing and unwanted by-products during extrusion. For PET recyclers, keeping PVC as low as possible is not just a technical requirement – it directly impacts selling price, customer acceptance and long-term profitability.
In this article, we look at where PVC comes from in a typical PET bottle line, what “good” looks like in terms of ppm levels, and how a combination of front-end sorting, washing and dry electrostatic separation can help you reliably stay below 50 ppm.
TL;DR (for plant managers & buyers)
- PVC can cause serious PET degradation even around 50 ppm.
- The most effective strategy is prevent PVC before grinding, then use washing + float-sink for bulk cleaning, and a dry polishing step (often electrostatic) to remove trace PVC.
- Prove performance with routine testing + trend monitoring, not one-off samples.
Why 50 ppm PVC matters so much
Multiple industry sources point out that PVC contamination at or even below 50 ppm can already trigger quality issues in PET flakes when they are remelted. PVC degrades and releases chlorine-containing compounds at PET processing temperatures, which can:
- Promote chain scission and embrittlement in the PET resin.
- Cause yellowing or off-color in pellets and final products.
- Corrode processing equipment and complicate exhaust gas treatment.
For high-end applications such as food-contact rPET, bottle-to-bottle recycling and premium polyester fibers, buyers often require PVC levels below 50 ppm – and in some cases below 30 ppm – as part of their specifications. This means PET recyclers need a process that consistently delivers this quality, not just in lab samples but in full-scale, 24/7 operation.
Typical sources of PVC in PET bottle streams
In a PET bottle recycling line, PVC can enter the system from several sources:
- Whole PVC bottles and containers that slip through front-end sorting.
- Shrink sleeves, labels and safety seals made from PVC or PETG.
- Cap liners, multilayer components and residual films in the bale mix.
Even when PVC is only a small fraction of the incoming bales, its impact on the final flake quality is disproportionate. A contamination level of 50 ppm corresponds to only about 0.05 kg PVC per 1,000 kg of PET flakes – a tiny amount in mass, but enough to compromise high-spec applications.
What “below 50 ppm” looks like in practice
Technical datasheets and buyer specifications for high-quality rPET flakes often list maximum PVC limits in the range of 10–50 ppm, combined with tight limits on other polymers. For example, some clear rPET flake specs call for:
- PVC below 10–50 ppm.
- Total foreign polymers below 80–100 ppm.
- Overall flake purity >99.8% on a mass basis.
Reaching these numbers reliably requires more than one single “magic” machine. Instead, successful plants design their lines as a sequence of complementary steps:
- Bale inspection and pre-sorting.
- Manual and/or automated bottle sorting.
- Label removal and size reduction.
- Cold and hot washing.
- Flotation and density separation.
- Drying and final dry-cleaning / polishing stages.
Electrostatic separation sits at the very end of this chain as a dry polishing technology, removing the last traces of PVC and other polymers from already-washed, dried PET flakes.
Front-end: keeping as much PVC out as possible
The first line of defense against PVC is simply not to let it enter the flake stream. Common strategies include:
- Manual sorting with UV or visual aids: Experienced operators can identify PVC bottles and labels, and UV illumination can enhance contrast between PET and PVC.
- NIR-based bottle sorters: Near-infrared optical sorters classify bottles by polymer type and eject PVC, PETG and other undesired materials before shredding.
- Mechanical and label removal steps: De-labelling systems and pre-wash stages strip sleeves and labels, reducing downstream PVC load.
These technologies are highly effective on whole bottles and large pieces, and they can dramatically reduce the amount of PVC arriving at the grinding and washing sections. However, they are not perfect and do not fully address small fragments and mixed flakes.
Washing, float-sink and what they can (and can’t) do
Most PET bottle lines rely on a combination of hot washing, friction washing and float-sink separation to remove glues, paper, organics and low-density contaminants. In a typical process:
- Wet grinders reduce the bottles into flakes.
- 摩擦洗浄用のワッシャーと熱洗浄タンクは、ラベル、汚れ、接着剤を取り除きます。.
- Float-sink tanks 密度に基づいてポリオレフィン（PP/HDPE）をPETから分離します。.
これらの手順は、汚染全体を減らし、PETをキャップやラベルから分離するのに非常に有効です。しかし、PETとPVCの密度の差は比較的小さく、多くの密度に基づくシステムはPVCの除去に特化して最適化されていません。そのため、追加の抛光ステップが使用されていない場合、デザインが非常に良い洗浄ラインでもPETフラックにPVCレベルが100～200ppm以上になることがあります。.
各ステップが実際に取り除けるもの（簡単な参照）
| ステップ | Best at removing | Limits for PVC control |
|---|---|---|
| Front-end sorting (manual / optical) | 全体のPVC容器、明らかに規格外のアイテム | 小さな破片や混在したフラックが通過する |
| De-labelling / sleeve removal | スリーブ、ラベル、シールが破片になる前に | 材料が小さなピースに砕かれた後は効果が低くなる |
| Hot wash + friction wash | 接着剤、汚れ、有機物；全体的な清掃を向上させます | 清掃はポリマーの分離ではありません；PVCは残ります |
| Float-sink | PP/HDPE vs PET separation (caps/labels) | PETとPVCの密度分離は一貫して鮮明ではありません |
| Dry polishing (often electrostatic) | 乾燥フラックに含まれるトレースPVCと他のポリマー | 水分と粒子径の厳密な制御が必要です |
乾燥電気静電分離が抛光ステップとして必要な理由
PVCレベルを50ppm以下に押し下げるために、多くのリサイクラーが乾燥後の dry electrostatic separation ステージを追加します。電気静電分離機はPETとPVCの電気的性質の違いを利用します：
For a practical equipment overview, see: Plastic Electrostatic Separator
- フラックは充電機構（冠充電または摩擦充電）にさらされ、異なるポリマーに異なる極性を引き起こします。.
- 充電されたフラックは電極間の電場または充電されたドラムを通過します。.
- 充電と導電性に基づいて、PETとPVCは異なる軌跡を辿り、分離された分画として収集されます。.
ケーススタディと機器サプライヤーは、適切に統合された場合、電気静電分離はPETフラックのPVC汚染を約1,000ppmから50ppm以下に減少させると報告しており、他のポリマー汚染も除去します。これにより、品質管理とパッケージングの前の最終精製ステップとして、この技術は特に魅力的です。.
Process conditions that influence electrostatic performance
To achieve reliable separation and stay below 50 ppm, several process parameters need to be controlled:
- Moisture content: Electrostatic separators generally require dry feed, often with residual moisture below about 0.5–0.8%, to prevent charges from dissipating.
- Particle size and shape: Flake size should be within a defined range (for example below 10–12 mm), with limited fines, to maintain stable trajectories in the electric field.
- Blend composition: Feed composition should be relatively stable, or the machine should be adjusted for different PVC/PET ratios to keep middling and reject fractions under control.
- Voltage, electrode configuration and splitter settings: Optimizing these parameters is critical to balance PVC removal efficiency with PET yield and minimize losses.
In practice, many plants implement a two-stage strategy: a first electrostatic pass to separate a high-PET product and a high-PVC reject, followed by a second pass on middling material to further reduce PVC and recover PET.
Role of integrated PET bottle washing lines
End-to-end system suppliers show that combining a well-designed PET bottle washing line with a final electrostatic polishing stage can deliver flake purities above 99.8%, with very low PVC levels. Typical design elements include:
- Bale opening, metal removal and pre-sorting.
- Automated bottle sorting (NIR) plus manual quality control.
- High-efficiency label removal, hot wash and friction cleaning.
- Multi-stage float-sink and density separation for polyolefins.
- Low-residue drying to reach the required moisture level for electrostatic separation.
- One or more electrostatic separators for PET/PVC and other mixed plastics.
When these stages are properly engineered and tuned, the result is a stable output of clean PET flakes ready for food-grade or high-performance applications, with PVC well below the 50 ppm threshold.
Monitoring, testing and continuous improvement
Reaching a PVC target once is not enough – recyclers need to demonstrate consistent performance over time. This usually involves:
- Regular laboratory testing of PVC content, often using oven tests or specialized analytical methods, against defined ppm limits.
- Process monitoring on key variables such as bale quality, sorting reject rates, wash performance and electrostatic separator settings.
- Periodic audits of the line to identify new contamination sources or drift in performance.
Plants that formalize this into a quality management system are better positioned to meet brand-owner requirements and secure long-term contracts for high-value rPET.
Acceptance & QA: how to prove you can hold < 50 ppm
To make “PVC < 50 ppm” defensible for buyers, define your acceptance plan and stick to it:
- Sampling plan: specify where and how often samples are taken (e.g., after drying / after polishing / before packaging).
- Trend, not snapshots: track results over time and tie excursions to inbound bales, sleeve types, moisture drift, or separator settings.
- Process KPIs to log: inbound bale quality, optical-sorting reject rates, dryer moisture, flake size distribution (fines), electrostatic voltage/splitter settings, and PET yield losses.
- Escalation rules: what happens when you see a spike (hold lot, reprocess middlings, adjust settings, audit bale source).
Putting it all together
Controlling PVC in PET bottle recycling lines below 50 ppm is achievable, but it requires a system-level view:
- PVCをできるだけラインから排除するために、バレーコントロールとフロントエンドの分別を使用してください。.
- 粗い汚染物を取り除くために堅牢な洗浄と密度分別を使用してください。.
- 最終的なポリマーの最終分別ステップとして乾燥電気分別を追加し、最後のPVCと異なるポリマーを捕獲してください。.
- テストとプロセス管理をバックアップして、指定を一貫して満たしていることを証明してください。.
これらの戦略を組み合わせることで、PETリサイクル業者はより高い品質のフラックを生産し、より厳しい終端市場にアクセスし、運営全体の経済性を向上させることができます。.
よくある質問
ボトルからボトルや食品接触用のrPETにどの程度のPVCレベルが必要ですか？
Many high-spec buyers treat ≤ 50 ppm 重要な制限として、アプリケーションやリスク許容度に応じてより厳しいものが推進されます。.
強力な洗浄ラインだけでPVC < 50 ppmを保証できますか？
通常はありません。洗浄は土壌/接着剤/有機物を効果的に取り除きますが、PVCのコントロールにはそれが必要です polymer-selective separation, especially for small fragments.
電気分別がどのようになぜパフォーマンスが劣りますか？
Feed conditions: moisture too high, 過剰な微粒子や不安定な原料組成/設定が原因です。.
Where should PVC testing be done?
少なくとも、最終製品ポイント（包装前に）に近く、中間チェック（乾燥後/ポリッシュ後など）を使用して、逸脱がどの部分から始まったかを診断してください。.
