Questions in the modification production of PP melt-blown granule

Questions in the modification production of PP melt-blown granule

The mechanism of melt blown PP throughout the production process is that polypropylene undergoes free radical degradation under the action of initiator, high temperature melting and screw shear, its molecular chain is broken, the molecular weight is from large to small, and the melt finger is from low It becomes higher, the fluidity has been greatly improved, and finally we get the raw material of our melt-blown non-woven fabric. What problems should be paid attention to in the production process of PP melt-blown material modification process.

1: Accurate metering and feeding is the key to the stability of raw material batches

1..1 Precision requirements for a pair of measuring equipment

1.2 The selection of replenishing material level is appropriate to avoid the impact of feeding fluctuation during replenishing.

1.3 A liquid feed needs to achieve continuous and stable output in a short time.

Without high-precision feeding equipment, the melting finger fluctuates greatly, and the peroxide has a small deviation. For the melting finger, the difference is ± 200, which is a headache for the cloth production enterprise. It is recommended that meltblown fabric companies should prepare a melt finger tester for incoming inspection.

2: Barrel configuration, length-diameter ratio above 56 is better

2.1 One reaction extrusion requires long residence time. The length-diameter ratio of the cylinder is selected from 56 to 60

2.2 The choice of a liquid addition position, in order to participate in the reaction as early as possible, should be left in Section 2 or 3

2.3 First, due to the low viscosity of the material, the length of the extrusion section should be appropriately lengthened.

The production process of PP melt-blown material is a controllable rheological production process. For the extruder, it is a reactive extrusion. It focuses on some characteristics of reactive extrusion, such as residence time, residence time and screw configuration , Equipment and supporting upstream and downstream. Batch stability depends on equipment accuracy, stability, and reliability.

Many manufacturers can not reach the aspect ratio, do not open too fast! The reaction time is not enough, and there are many peroxide residues.

3: Vacuum devolatilization helps reduce residue

3.1. In order to reduce the residue, the vacuum should increase the amount of degassing

3.2 The control of a vacuum degree is not as high as possible, and the vacuum degree should be ensured while avoiding the return of the vacuum port.

3.3 The most effective way to control residue is to control the amount of peroxide added

4: filter

4.1 First, to avoid wasteful shutdown, plunger-type dual-station non-stop filter should be selected

4.2 Another reason for choosing the plunger filter is that the plunger type has high processing accuracy, is not easy to leak material, and is well adapted to the characteristics of low viscosity and good fluidity of melt-blown material

4.3 The heating efficiency of a filter should not be lower than the heating efficiency of the extruder, saving heat preservation time.

This thing can't be less, there are fewer modification plants, so you have to be careful when making the die of meltblown cloth, plug it!

5: The discharge part of the extruder

5.1 The hole spacing should not be too small to avoid the material sticking together at the exit

5.2 The aperture is generally Φ2.8mm-Φ3.2mm

5.3 The discharge is connected with the cooling water tank, and it should be ensured that the material strip enters the water for cooling immediately when it flows out from the die opening

6: Auxiliary cutting machine part

6.1 The cooling water tank should be controlled at 10 meters to 12 meters to ensure that the strip can be fully cooled when passing through the water tank at high speed

6.2 Due to the rapid flow rate of the material strip, the pelletizer should be equipped with a pelletizer with a traction speed of more than 100 meters / minute

6.3 Equipped with a homogenization tank for finished products to ensure that the batch of products is stable, similar to the treatment of low VOC materials.

7: About the smell of melt-blown material

7.1 In the selection of raw materials, for example, the choice of peroxide must be of better quality. First, choose the odorless one at the source.

7.2 The position of the evacuation device and the amount of evacuation should be properly controlled. Because the fluidity of the material is particularly good, the vacuum degree cannot be particularly high.

7.3 No matter how good the vacuum is, this large amount of peroxide residue cannot be evacuated, and the amount must be controlled.