PVC contamination in PET recycling is difficult to correct after the bottles have been ground. PVC and PET both sink in water, so a standard float-sink tank cannot reliably separate the two polymers. A stable process removes PVC as early as possible, then uses flake-level sorting and quality checks to control what remains.
This guide explains where PVC enters a PET bottle stream, which detection method fits each process stage, and how to set up practical control points without treating one machine as a complete solution.
PVC Contamination Control at a Glance
| 공정 단계 | Typical PVC source | Preferred control | Main limitation |
|---|---|---|---|
| Before debaling | Out-of-specification bales | Supplier specification and bale inspection | Inspection cannot find every hidden label or liner |
| Whole-bottle sorting | PVC bottles, sleeves, and safety seals | Manual quality control plus sensor-based polymer sorting | Dirty, overlapping, or black items can reduce detection accuracy |
| After granulation | PVC fragments and label pieces | Flake sorting or dry electrostatic separation | Moisture, particle size, and presentation affect separation |
| Finished PET flakes | Residual PVC missed upstream | Representative sampling and buyer-specific laboratory testing | A small sample may not represent an uneven batch |
Why PVC Is a Serious PET Contaminant
PET는 PVC의 탈염화수소 반응을 일으킬 수 있는 온도에서 가공됩니다. 이때 발생한 염화수소는 PET 열화를 촉진하며 황변, 검은 반점, 분자량 저하 및 취성을 유발할 수 있습니다. 동료 평가를 거친 가공 연구에서는 PVC가 100 ppm 포함된 PET에서 측정 가능한 열화와 변색이 관찰됐습니다. 따라서 겉보기에 깨끗한 플레이크도 고객 규격을 통과하지 못할 수 있습니다.
허용 한계는 모든 용도에 동일하지 않습니다. 섬유, 시트, 스트래핑 및 보틀투보틀 구매자는 서로 다른 기준을 정할 수 있고, 식품 접촉 용도에는 PVC 외에도 추가 관리가 필요합니다. 따라서 운전 목표는 하나의 일반적인 ppm 수치가 아니라 완제품 플레이크 구매자의 서면 규격과 정해진 시험법을 기준으로 설정해야 합니다.
Where PVC Enters a PET Bottle Stream
- PVC bottles can resemble PET bottles when shape and color are the only sorting criteria.
- Shrink sleeves, tamper-evident seals, and pressure-sensitive label components can remain attached until granulation.
- Closure liners and small PVC components can pass through coarse manual inspection.
- Cross-contamination can occur when conveyors, bunkers, or flake handling equipment process more than one polymer without adequate cleaning.
How to Separate PVC from PET
Whole-Bottle Sorting Before Granulation
Remove PVC while the item is still large enough to identify and eject. Manual quality control can catch obvious PVC bottles and sleeves, while near-infrared or other sensor-based systems classify polymers and trigger air-jet rejection. The sorter must receive a stable, single-layer material presentation; unopened bales, overlapping bottles, dirt, and excessive conveyor loading reduce the value of even a capable sensor.
Why Plain-Water Float-Sink Separation Is Not Enough
Float-sink separation is effective for removing floating PP and PE caps from sinking PET. It does not provide a dependable PET/PVC split because PVC also has a density above water and sinks with PET. The Association of Plastic Recyclers specifically identifies PVC as difficult to remove from PET, particularly after it has become small fragments.
Flake-Level Optical and Electrostatic Sorting
분쇄와 세척 후에도 PVC가 남아 있으면 플레이크 전개에 맞게 설계된 시스템을 사용해야 합니다. 광학 플레이크 선별기는 고분자나 색상 차이를 식별해 개별 입자를 배출합니다. 건식 정전 또는 마찰대전 시스템도 조정된 PET와 PVC 플레이크를 분리할 수 있지만 수분, 입도 분포, 표면 청정도 및 공급 속도를 관리해야 합니다. 일반적인 장비 목록만으로 고르는 것보다 실제 공장 원료로 파일럿 시험을 하는 편이 신뢰도가 높습니다.
Why Thermal Treatment Should Not Be the Primary Control
Heating a mixed PET/PVC stream can expose PVC to the same degradation pathway the recycler is trying to prevent. Any thermal method needs engineered temperature control, corrosion-resistant components, gas capture, and an emissions review. For a PET washing plant, upstream polymer sorting and flake-level rejection are normally safer control points than intentionally heating contamination.
Recommended Control Points in a PET Recycling Line
- Define the incoming bale specification and record contamination by supplier and load.
- Open bales and spread bottles into a consistent single layer before automated sorting.
- Place manual quality control after the primary sorter to monitor misses and changing feedstock.
- Remove labels before granulation whenever the container and label format allow it.
- Use washing and float-sink separation for dirt, adhesive, caps, and polyolefins, but not as the sole PVC control.
- Verify finished flakes with a documented sampling plan and retain samples when investigating a rejected batch.
Quality-Control Questions Before Selecting Equipment
- Is the PVC present as whole containers, labels, or small flakes?
- What PVC limit and test method does the finished-flake buyer require?
- Does the sorter receive dry, clean, separated material within its specified particle-size range?
- Where will rejected material go, and how will the plant measure false rejects and recovery loss?
이 질문에 대한 답으로 통용기 선별기, 플레이크 선별기, 정전 분리기 또는 단계별 조합 중 무엇이 필요한지 결정할 수 있습니다. 또한 오염물의 형태와 고객의 합격 시험을 정하기 전에 분리 장비부터 구매하는 흔한 설계 오류를 피할 수 있습니다.
자주 묻는 질문
PET 재활용에서 PVC가 문제가 되는 이유는 무엇입니까?
PVC can degrade under PET processing conditions and release hydrogen chloride. This accelerates PET degradation and can cause yellowing, black specks, reduced molecular weight, corrosion risk, and brittle recycled products.
PVC와 PET는 어떻게 분리합니까?
Sort PVC from whole bottles before granulation with manual quality control and sensor-based polymer sorting. For washed flakes, use a validated optical flake sorter or a properly conditioned electrostatic process. Plain-water float-sink separation alone cannot reliably separate PET from PVC because both polymers sink.
PET에서 PVC를 제거하지 않으면 어떻게 됩니까?
잔류 PVC는 재생 PET를 변색시키고 검은 반점을 만들며 물성을 저하시키고 가공 장비를 부식시킬 수 있습니다. 또한 완제품 로트가 구매자의 오염 규격을 충족하지 못하게 할 수 있습니다.
Related PET Recycling Equipment and Guides
- PET 병 세척 라인 및 재활용 시스템
- PET 재활용 장비 구매 가이드
- PET bottle recycling process guide
- PET flake grades and quality requirements
- Sink-float separation tank for PET, PP, and PE
Technical Sources
- Association of Plastic Recyclers: PET Rigid Design Guide
- Peer-reviewed study on small amounts of PVC in recycled PET
- Sensor-based flake sorting equipment reference
Build PVC Control Around the Feedstock
하나의 분리기로 모든 PVC 유입원을 해결할 수는 없습니다. 입고 원료부터 확인하고, 분쇄 전에 통째 오염물을 제거하며, 측정된 위험이 정당화할 때만 플레이크 선별을 추가하고, 구매자 규격에 맞춰 완제품을 시험하십시오. 병 혼합비, 처리량 및 목표 플레이크 등급에 맞는 라인 구성이 필요하다면 contact Energycle about a PET recycling project.
