The production efficiency and quality of PVC shrink film directly determine an enterprise’s production capacity, costs, and market competitiveness. Low efficiency leads to wasted capacity and delayed deliveries, while quality defects (such as uneven shrinkage and poor transparency) result in customer complaints and returns. To achieve the dual improvement of “high efficiency + high quality,” systematic efforts are required across four key dimensions: raw material control, equipment optimization, process refinement, quality inspection. Below are specific, actionable solutions:
Source Control: Select the Right Raw Materials to Reduce Post-Production “Rework Risks”
Raw materials are the foundation of quality and a prerequisite for efficiency. Inferior or mismatched raw materials cause frequent production halts for adjustments (e.g., clearing blockages, handling waste), directly reducing efficiency. Focus on three core types of raw materials:
1. PVC Resin: Prioritize “High Purity + Application-Specific Types”
• Model Matching: Choose resin with an appropriate K-value based on the thickness of the shrink film. For thin films (0.01–0.03 mm, e.g., food packaging), select resin with a K-value of 55–60 (good fluidity for easy extrusion). For thick films (0.05 mm+, e.g., pallet packaging), opt for resin with a K-value of 60–65 (high strength and tear resistance). This avoids uneven film thickness caused by poor resin fluidity.
• Purity Control: Require suppliers to provide resin purity reports, ensuring residual vinyl chloride monomer (VCM) content is <1 ppm and impurity (e.g., dust, low-molecular polymers) content is <0.1%. Impurities can clog extrusion dies and create pinholes, requiring additional downtime for cleaning and affecting efficiency.
2. Additives: Focus on “High Efficiency, Compatibility, and Compliance”
• Stabilizers: Replace outdated lead salt stabilizers (toxic and prone to yellowing) with calcium-zinc (Ca-Zn) composite stabilizers. These not only comply with regulations such as EU REACH and China’s 14th Five-Year Plan but also enhance thermal stability. At extrusion temperatures of 170–200°C, they reduce PVC degradation (preventing yellowing and brittleness) and lower waste rates by over 30%. For Ca-Zn models with “built-in lubricants,” they also reduce die friction and increase extrusion speed by 10–15%.
• Plasticizers: Prioritize DOTP (dioctyl terephthalate) over traditional DOP (dioctyl phthalate). DOTP has better compatibility with PVC resin, reducing “exudates” on the film surface (avoiding roll sticking and improving transparency) while enhancing shrink uniformity (shrinkage rate fluctuation can be controlled within ±3%).
• cosmetic packaging)• Functional Additives: For films requiring transparency (e.g., cosmetic packaging), add 0.5–1 phr of a clarifier (e.g., sodium benzoate). For outdoor-use films (e.g., cosmetic packaging), garden tool packaging), add 0.3–0.5 phr of a UV absorber to prevent premature yellowing and reduce finished product scrap.
3. Auxiliary Materials: Avoid “Hidden Losses”
• Use high-purity thinners (e.g., xylene) with a moisture content <0.1%. Moisture causes air bubbles during extrusion, requiring downtime for degassing (wasting 10–15 minutes per occurrence).
• When recycling edge trim, ensure impurity content in recycled material is <0.5% (filterable via a 100-mesh screen) and the proportion of recycled material does not exceed 20%. Excessive recycled material reduces film strength and transparency.
Equipment Optimization: Reduce “Downtime” and Improve “Operational Precision”
The core of production efficiency is “equipment effective operation rate”. Preventive maintenance and automation upgrades are needed to reduce downtime, while improving equipment precision ensures quality.
1. Extruder: Precise Temperature Control + Regular Die Cleaning to Avoid “Blockages and Yellowing”
• Segmented Temperature Control: Based on the melting characteristics of PVC resin, divide the extruder barrel into 3–4 temperature zones: feed zone (140–160°C, preheating resin), compression zone (170–180°C, melting resin), metering zone (180–200°C, stabilizing the melt), and die head (175–195°C, preventing local overheating and degradation). Use an intelligent temperature control system (e.g., PLC + thermocouple) to keep temperature fluctuation within ±2°C. Excessive temperature causes PVC yellowing, while insufficient temperature leads to incomplete resin melting and “fish-eye” defects (requiring downtime for adjustments).
• Regular Die Cleaning: Clean residual carbonized material (PVC degradation products) from the die head every 8–12 hours (or during material changes) using a dedicated copper brush (to avoid scratching the die lip). For die dead zones, use an ultrasonic cleaner (30 minutes per cycle). Carbonized material causes black spots on the film, requiring manual sorting of waste and reducing efficiency.
2. Cooling System: Uniform Cooling to Ensure “Film Flatness + Shrink Uniformity”
• Cooling Roll Calibration: Calibrate the parallelism of the three cooling rolls monthly using a laser level (tolerance <0.1 mm). Simultaneously, use an infrared thermometer to monitor roll surface temperature (controlled at 20–25°C, temperature difference <1°C). Uneven roll temperature causes inconsistent film cooling rates, leading to shrinkage differences (e.g., 50% shrinkage on one side and 60% on the other) and requiring rework of finished products.
• Air Ring Optimization: For the blown film process (used for some thin shrink films), adjust the air uniformity of the air ring. Use an anemometer to ensure the wind speed difference in the circumferential direction of the air ring outlet is <0.5 m/s. Uneven wind speed destabilizes the film bubble, causing “thickness deviations” and increasing waste.
3. Winding and Edge Trim Recycling: Automation Reduces “Manual Intervention”
• Automatic Winder: Switch to a winder with “closed-loop tension control”. Adjust winding tension in real time (set based on film thickness: 5–8 N for thin films, 10–15 N for thick films) to avoid “loose winding” (requiring manual rewinding) or “tight winding” (causing film stretching and deformation). Winding efficiency is increased by 20%.
• On-Site Immediate Scrap Recycling: Install an “edge trim crushing-feeding integrated system” next to the slitting machine. Immediately crush edge trim (5–10 mm wide) generated during slitting and feed it back to the extruder hopper via a pipeline (mixed with new material at a 1:4 ratio). Edge trim recycling rate increases from 60% to 90%, reducing raw material waste and eliminating time loss from manual scrap handling.
Process Refinement: Refine “Parameter Control” to Avoid “Batched Defects”
Minor differences in process parameters can lead to significant quality variations, even with the same equipment and raw materials. Develop a “parameter benchmark table” for the three core processes—extrusion, cooling, and slitting—and monitor adjustments in real time.
1. Extrusion Process: Control “Melt Pressure + Extrusion Speed”
• Melt Pressure: Use a pressure sensor to monitor the melt pressure at the die inlet (controlled at 15–25 MPa). Excessive pressure (30 MPa) causes die leakage and requires downtime for maintenance; insufficient pressure (10 MPa) results in poor melt fluidity and uneven film thickness.
• Extrusion Speed: Set based on film thickness—20–25 m/min for thin films (0.02 mm) and 12–15 m/min for thick films (0.05 mm). Avoid “excessive traction stretching” (reducing film strength) caused by high speed or “capacity waste” from low speed.
2. Cooling Process: Adjust “Cooling Time + Air Temperature”
• Cooling Time: Control the film’s residence time on the cooling rolls at 0.5–1 second (achieved by adjusting traction speed) after extrusion from the die. Insufficient residence time (<0.3 seconds) leads to incomplete film cooling and sticking during winding; excessive residence time (>1.5 seconds) causes “water spots” on the film surface (reducing transparency).
• Air Ring Temperature: For the blown film process, set the air ring temperature 5–10°C higher than the ambient temperature (e.g., 30–35°C for 25°C ambient). Avoid “sudden cooling” (causing high internal stress and easy tearing during shrinkage) from cold air directly blowing onto the film bubble.
3. Slitting Process: Precise “Width Setting + Tension Control”
• Slitting Width: Use an optical edge guide system to control slitting precision, ensuring width tolerance <±0.5 mm (e.g., 499.5–500.5 mm for a customer-required width of 500 mm). Avoid customer returns caused by width deviations.
• Slitting Tension: Adjust based on film thickness—3–5 N for thin films and 8–10 N for thick films. Excessive tension causes film stretching and deformation (reducing shrinkage rate); insufficient tension leads to loose film rolls (prone to damage during transportation).
Quality Inspection: “Real-Time Online Monitoring + Offline Sampling Verification” to Eliminate “Batched Non-Conformities”
Discovering quality defects only at the finished product stage leads to full-batch scrap (losing both efficiency and costs). Establish a “full-process inspection system”:
1. Online Inspection: Intercept “Immediate Defects” in Real Time
• Thickness Inspection: Install a laser thickness gauge after the cooling rolls to measure film thickness every 0.5 seconds. Set a “deviation alarm threshold” (e.g., ±0.002 mm). If the threshold is exceeded, the system automatically adjusts extrusion speed or die gap to avoid continuous production of non-conforming products.
• Appearance Inspection: Use a machine vision system to scan the film surface, identifying defects such as “black spots, pinholes, and creases” (precision 0.1 mm). The system automatically marks defect locations and alarms, allowing operators to stop production promptly (e.g., cleaning the die, adjusting the air ring) and reduce waste.
2. Offline Inspection: Verify “Key Performance”
Sample one finished roll every 2 hours and test three core indicators:
• Shrinkage Rate: Cut 10 cm × 10 cm samples, heat them in a 150°C oven for 30 seconds, and measure shrinkage in the machine direction (MD) and transverse direction (TD). Require 50–70% shrinkage in MD and 40–60% in TD. Adjust plasticizer ratio or extrusion temperature if deviation exceeds ±5%.
• Transparency: Test with a haze meter, requiring haze <5% (for transparent films). If haze exceeds the standard, check resin purity or stabilizer dispersion.
• Tensile Strength: Test with a tensile testing machine, requiring longitudinal tensile strength ≥20 MPa and transverse tensile strength ≥18 MPa. If strength is insufficient, adjust resin K-value or add antioxidants.
The “Synergistic Logic” of Efficiency and Quality
Improving the efficiency of PVC shrink film production focuses on “reducing downtime and waste,” which is achieved through raw material adaptation, equipment optimization, and automation upgrades. Enhancing quality centers on “controlling fluctuations and intercepting defects,” supported by process refinement and full-process inspection. The two are not contradictory: for example, selecting high-efficiency Ca-Zn stabilizers reduces PVC degradation (improving quality) and increases extrusion speed (enhancing efficiency); online inspection systems intercept defects (ensuring quality) and avoid batch scrap (reducing efficiency losses).
Enterprises need to shift from “single-point optimization” to “systematic upgrading,” integrating raw materials, equipment, processes, and personnel into a closed loop. This enables the achievement of goals such as “20% higher production capacity, 30% lower waste rate, and <1% customer return rate,” establishing a competitive edge in the PVC shrink film market.
Post time: Nov-05-2025