The raw material of polypropylene chips used in the melt spinning web production line is spinning grade polypropylene (PP) chips, and its specific properties are as follows.
- (1) Melt index (MFI): 25~40g/10min for spunbond method, 400~1500g/10min for meltblown method.
- (2) Relative molecular weight distribution width (Mw/Mn): <4~5.
- (3) Melting point: 164~170℃ (the melting point of pure isotactic polypropylene is 176℃).
- (4) Density: 0.91g/cm3.
- (5) Isotacticity: not less than 96%.
- (6) Ash content: not more than 0.025% (weight).
- (7) Moisture content: not more than 0.05% (weight).
- (8) Smooth appearance, uniform particle size, no continuous particle phenomenon.
Selection of raw materials
The raw materials used in the production line are related to the market positioning and purpose of the product. When producing products in the low-end market, since the product has low requirements for raw materials, in order to reduce production costs, inferior raw materials can be selected.
Vice versa. Most spunbond nonwoven production lines use granular polypropylene (PP) chips as raw materials, but a considerable number of small production lines use powdered PP raw materials, and some production lines use recycled polypropylene raw materials. In addition to granular raw materials, meltblown nonwoven production lines may also use pelletized raw materials.
The price of chips is directly related to the size of their MFI value. Generally, the larger the MFI value, the higher the price. Therefore, it is necessary to comprehensively consider the production process used, equipment characteristics, product use, product sales price, production cost and other factors to select the raw materials used.