Brief introduction of nylon sleeve production process

1, drying process

Since the nylon material is a polar medium, it is easy to absorb moisture. According to the material manufacturer, when the water content of the nylon material exceeds 0.3%, it cannot be extruded. After the nylon material is wetted by the actual production process, the extruded sheath will be foamed. Such as foam, granules or breakage. The nylon 6 material itself is packed in a  vacuum bag and can be directly used without a broken bag. However, if the transportation process is broken, the sealing is poor, or the unpacking is not used up in time, it must be dried before use.

Therefore, the wet nylon material should be pre-dried before use. It is best to use a vacuum and a rotating drum to remove moisture, and the amount of drying should not exceed 3/5 of the dryer volume. If the capacity is too large, the material in the dryer is difficult to rotate, resulting in uneven heating. The short time is difficult to remove the moisture. The longtime will cause some materials to oxidize and turn yellow, which cannot meet the requirements of the extruded surface. The vacuum degree of vacuuming should reach 0.05MPa or more, otherwise, the water is difficult to remove. If it is heated by steam, the heating temperature should be controlled by the amount of water vapor. The temperature should be 80±50°C. The heating temperature is too high. The nylon material will oxidize and turn yellow. 

2, the requirements of the extruder

The extruder is available in both vertical and horizontal versions. The screw length to diameter ratio is generally 20:1; 25:1, the screw and barrel clearance is 0.14-0.18mm, and the compression ratio is 4:1 or 3.5:1.

The conventional progressive type screw can ensure plasticization at a low speed, but the amount of extrusion is not large, and the separation type screw is more plasticized and the amount of extrusion is larger.

Nylon 6 has a narrow extrusion temperature and high-temperature control requirements. If the temperature is too high, nylon will cause the coke bake temperature to be too low. The nylon will condense and solidify to cause clogging of the mould. Nylon 6 has a distinct melting point of 215 ° C, and the condensation is particularly fast, so the temperature of each section of the extruder must be slightly higher than 215 ° C, the extruder control temperature from the feed inlet to the extrusion die  tolerance ± 7 ° C) as follows：

1 section 2 section 3 section 4 section 5 section

230°C 235°C 235°C 235°C 235°C

The extrusion temperature should be adjusted according to the temperature, outlet speed and the amount of nylon glue. Pay special attention to the temperature of the neck of the extruder, because this is the joint, plus the filter plate and filter in this area. Flange jacket, etc., the heat dissipation area is large, so it is difficult to heat it in place. If the heating does not meet the requirements, and the nylon 6 has a fast condensation speed, it is easy to form part of the nylon solidification in the area immediately after starting the machine, so that the extruder cannot be discharged. Glue, at which point the screw is at risk of breaking. Therefore, the temperature of the neck or the temperature at the two ends of the neck should be 5 °C higher at the beginning of the machine to facilitate heat transfer. After the temperature of each section reaches the specified value, it should be kept for 5-10 minutes to ensure that the temperature at the neck reaches the predetermined requirement. So that there will be no condensation and blockage. In addition, the screw should be immediately observed at the same time as the screw current meter to observe whether the current is abnormally large. If the current is too large, stop it at this time and increase the heating temperature or continue heating.