Solid Sheet Extrusion: Resin Processing Parameters
Processing Bayer resins on extrusion lines requires an understanding of equipment settings as well as the properties of the specific resin. The following sections give an overview of the processing parameters for commonly used Bayer products in each of the four lines available for solid sheet extrusion. Keep in mind that processing parameters can vary considerably, depending on the product to be manufactured and the plant technology available.
You can find more information about most grades and standard values in Bayer product information bulletins. See http://bayermaterialsciencenafta.com/products/index.cfm.
Moisture Content
Moisture in polycarbonate based resins can adversely affect processing and the quality of sheet. Manage moisture levels for all types of Bayer resins so the recommended moisture content of a specific resin is not exceeded. Drying is required prior to processing using dehumidifying or vacuum dryers. Hot air dryers will prolong drying times. Maintain specific drying temperatures and times during pre-drying. If the resin is not pre-dried, it may be degassed using vacuum during extrusion.
Bayer recommends a moisture level of 0.02% or less for all extrusion products. A slightly higher moisture level is acceptable if a vacuum vented extruder is used. Undried polymer can be processed with a well maitained, double vented extruder,though this must be closely monitored, and may not be effective with unusually wet polymer.
Please refer to the individual product information bulletins available for each grade for specific drying conditions.
Makrolon® Polycarbonates
For coextrusion of Makrolon® 3103 polycarbonate (a standard resin grade) and the UV concentrate DP1-1852 polycarbonate, use the following processing parameters. Depending on the product to be manufactured or the plant technology, processing parameters may vary considerably.
Extruder Temperatures
For the main extruder (with a degassing screw), use a decreasing temperature profile of 570°F to 535°F (300° to 280°C) from the barrel to the screw tip. The temperature in the degassing area should be 500°F to 535°F (260° to 280°C). The melt temperature upstream from the screw tip should be in the range of 535°F to 570°F (280° to 300°C).For the coextruder (with a single stage, non-vented screw), the extruder barrel temperature profile should be between 500°F to 535°F (260° to 280°C). The melt temperature of the coextruded material should be approximately 70°F (20°C) lower compared to the base material. Reach this objective by using a constant temperature window of 520°F to 535°F (260° to 270°C) all along the barrel length.
Downstream Unit Temperatures
Temperatures of units downstream from the extruder, such as the screen exchanger, melt pump coextrusion adapter, and sheet extrusion die, should be adjusted to that of the last barrel zone.Roll Stack Temperatures
Roll stack temperatures depend on roll type, sheet thickness, and take-off speed. In general, they should be below the glass transition temperature of the polycarbonate.
Table 1. Standard roll stack temperatures for Makrolon® 3103 polycarbonate Roll Stack Temperature Values Roll stack 1 230°F to 250°F (110° to 120°C) Roll stack 2 (center) 255°F to 275°F (125° to 135°C) Roll stack 3 265°F to 285°F (130° to 140°C) Roll stacks 1 and 2 form nip number 1, into which the melt emerging from the die is fed. In order to achieve a uniform sheet thickness, roll 3 usually has a considerably higher temperature of up to 340°F (170°C), thus exceeding the glass transition temperature.
Take-off Speeds
Some extrusion lines allow variable take-off speeds. As a result, the line can produce a broad range of thicknesses of the same sheet width even though the throughput from the main extruder remains constant.
Table 2. Typical take-off speeds for different sheet thicknesses Sheet thickness in inches (mm) Take-off speeds in ft/min (m/min) 0.040 (1) 8.3 to 13.3 (2.5 to 4.0) 0.080 (2) 6.0 to 7.3 (1.8 to 2.2) 0.125 (3.2) 3.3 to 5.0 (1.0 to 1.5) 0.250 (6.4) 1.7 to 2.3 (0.5 to 0.7) 0.400 (10) 0.7 to 1.0 (0.2 to 0.3)
Production Stop/End of Production
Do not change over to other thermoplastics without first cleaning.
In the case of a production stop, the extruder should be run until empty of the polycarbonate resin. Temperatures of all parts that come into contact with the polycarbonate melt (extruder barrel, screen exchanger, melt pump, adapter, and die) should be maintained at 320°F to 340°F (160°C to 170°C). If the extruder will be cleaned at the end of production, run the extruder until empty with high-viscosity polyethylene. This makes any subsequent mechanical cleaning much easier.Process Optimization
Some general recommendations can help you optimize your extrusion line processes:
Optimizing extrusion line processes typically involves increasing production speed while, at the same time, meeting quality criteria such as optical quality (cleanliness, reduced distortion, minimum surface defects), evenness, reduced shrinkage, and thickness tolerance.
- Keep the die lip as close to the nip as possible.
- Keep boss thickness over total width as even as possible by setting the die gap and/or die restrictor bar precisely.
- Keep the sheet temperature as it leaves the roll as high as possible. The roll temperatures should be as high as possible and the roll contact angle as small as possible without causing cobbling.
- Keep tension between rolls 3 and 2 or between take-off unit and roll 3 as small as possible. If you experience increased shrinkage of thick sheets, you may need to use negative tension.
- Adjust the second roll nip to the desired sheet thickness as precisely as possible.
Apec® Copolycarbonates
The processing conditions of Apec® copolycarbonates vary depending on the grade used, the product to be manufactured, and the plant technology available. The following processing parameters for grade 1803 (a standard grade for solid sheet extrusion) can be used as a starting point for other grades.
Extruder Temperatures
Use a decreasing temperature profile of 610°F to 570°F (320° to 300°C) from the feed hopper to the screw tip. The melt temperature upstream from the screw tip should be between 610°F to 645°F (320° to 340°C).Downstream Unit Temperatures
Temperatures of units downstream from the extruder, such as the screen exchanger, melt pump coextrusion adapter, and sheet extrusion die, should match the last barrel zone.Roll Stack Temperatures
Roll stack temperatures depend on roll type, sheet thickness and take-off speed. In general, they should be below the glass transition temperature of the copolycarbonate.
Table 3. Standard roll stack temperatures for Apec® 1803 copolycarbonate Roll Stack Temperature Values Roll stack 1 285°F to 330°F (140° to 165°C) Roll stack 2 (center) 300°F to 345°F (150° to 175°C) Roll stack 3 320°F to 355°F (160° to 180°C) Roll stacks 1 and 2 form nip number 1, into which the melt emerging from the extruder die is fed.
Bayblend® Polycarbonate/Styrenic Alloys
The following processing parameters for Bayblend® ET1000 alloy (a standard grade for solid sheet extrusion) can be used as a starting point for other Bayblend® grades. Specific processing conditions will depend on the sheet being produced and the production technology available.
Extruder Temperatures
Use the following barrel and die extruder temperatures as a guide for processing other grades.
Table 4. Extruder temperatures for processing Bayblend® ET1000 Extruder Component Recommended Temperatures Section 1 420° to 440°F (215° to 225°C) Section 2 440° to 460°F (225° to 240°C) Section 3 440° to 470°F (225° to 245°C) Section 4 440° to 480°F (225° to 250°C) Die 440° to 480°F (225° to 250°C) The extruder should be set to yield a maximum melt temperature of 520°F (270°C). Overheating and excessively long residence times should be avoided, as these conditions can lead to discoloration and material degradation.
Downstream Unit Temperatures
Temperatures of units downstream from the extruder, such as the screen exchanger, melt pump, coextruder adapter, and sheet extrusion die, should match the temperature of the last barrel zone.Roll Stack Temperatures
Roll stack temperatures depend on roll type, sheet thickness, and take-off speed. In general, they should be below the glass transition temperature of the polycarbonate.For equipment with a vertical roll arrangement and melt introduction between rolls 1 and 2, the following conditions can be taken as a guide.
Table 5. Standard roll stack temperatures for Bayblend® ET1000 alloy Roll Stack Temperature Values Roll stack 1 (bottom) 180° to 230°F (80° to 110°C) Roll stack 2 (center) 190° to 250°F (90° to 120°C) Roll stack 3 (top) 180° to 230°F (80° to 110°C)
Makroblend® Polycarbonate/Polyester Alloys
The following processing parameters for Makroblend® EC150 alloy (a flame-retardant grade for solid sheet extrusion) can be used as a starting point for other grades. Specific processing conditions will depend on the sheet being produced and the production technology available.
Extruder Temperatures
Use the following barrel and die temperatures as a guide for processing other grades.
Table 6. Extruder temperatures for processing Makroblend® EC 150 alloy Extruder Component Recommended Temperatures Section 1 480° to 500°F (250° to 260°C) Section 2 480° to 500°F (250° to 260°C) Section 3 500° to 520°F (260° to 270°C) Section 4 500° to 520°F (260° to 270°C) Die 520° to 530°F (270° to 275°C) The extruder should be set to yield a maximum melt temperature of 545°F (285°C). Overheating and excessively long residence times should be avoided, as these conditions can lead to discoloration and material degradation.
Downstream Unit Temperatures
Temperatures of units downstream from the extruder, such as the screen exchanger, melt pump, coextruder adapter, and sheet extrusion die should match the temperature of the last barrel zone.Roll Stack Temperatures
Roll stack temperatures depend on roll type, sheet thickness, and take-off speed. In general, they should be below the glass transition temperature of the polycarbonate.For equipment with a vertical roll arrangement and melt introduction between rolls 1 and 2, the following conditions can be taken as a guide.
Table 7.Standard roll stack temperatures for Makroblend® EC150 alloy Roll Stack Temperature Values Roll stack 1 (bottom) 230° to 250°F (110° to 120°C) Roll stack 2 (center) 250° to 260°F (120° to 125°C) Roll stack 3 (top) 265° to 275°F (130° to 135°C)
If you have any questions about using Bayer products on your extrusion equipment, you can reach the technical team at BMS using the Contact form.
