All kinds of raw materials used in spinning melt nonwovens production are "thermoplastic" plastics. Thermoplasticity refers to the property that plastics can be repeatedly softened by heat within a specific temperature range and then hardened after cooling. Various raw materials used in spunbond and melt-blow nonwovens production processes are solid at room temperature, sometimes called "slice" or "resin". Because in the use of different raw materials, the characteristics of the product will be different, the production process will be different, the performance and configuration of equipment are also different, which will have a significant impact on the use of the product, the market, economic benefits and the price of the production line. Therefore, the raw material is the first prerequisite to determine the performance index of the production line.

The main raw materials used in the production process of spunmelt nonwovens are polypropylene (PP), polyethylene (PE), polyester (PET), polyamide (PA), polyurethane (PU), polylactic acid (PLA), etc. Among them, polypropylene (PP) is the most commonly used, the largest amount, the most widely used one of the raw materials, the following characteristics of polypropylene (PP) and the spinning melting production line of PP slicing raw material requirements to do some introduction.

Polypropylene (PP)

Polypropylene is the most commonly used raw material and also the most important polymer fiber raw material. Nearly 94% of spunbonded cloth and melt-blown cloth are made of polypropylene. In the fields of medical treatment, hygiene and health care, the application of polypropylene nonwoven fabric accounts for 50% of the total amount of nonwoven fabric.

Characteristics of polypropylene (PP)

Polypropylene fiber has a very low density (0.91g/cm3); Low water content (< 0.1%,); Good chemical resistance (acid, alkali, solvent); Anti-mildew, anti-corrosion, anti-moth, antibacterial; Good heat insulation, heat preservation and insulation performance; High stiffness, good tensile strength (4.5 ~ 7.5cN/dtex); Good fatigue resistance and wear resistance; Temperature resistance 120℃, melting point 165℃; Easy to reuse and other properties. These characteristics, make polypropylene fiber and other synthetic fibers have two big differences: first, its moisture absorption is very low, which makes polypropylene fiber has excellent pollution resistance and almost the same dry and wet characteristics; Second, it has the lowest density of all fibers, which makes it good coverage under the same weight conditions.

Due to the thermal conductivity of polypropylene is the lowest of all fibers, its thermal insulation effect is better than wool, and its fiber density is not only low, but also has a larger coverage area, can be used for home and car interior packing, warm floc material and sound absorption, heat insulation materials.

On the other hand, polypropylene does not react with general chemical reagents, has strong chemical resistance, polypropylene nonwoven cloth can be used to manufacture geotextile, lead battery diaphragm, filter materials, etc. Because there is no active group in the main chain of polypropylene fine denier fiber, the material itself is not easy to be eroded by bacteria, mold, and human skin contact without irritation, non-toxicity, has good health performance, therefore, can be widely used in the field of medical and health. In addition, the lipophilic chain structure of polypropylene and the internal capillary structure formed by the transformation of the crystal during the post-fiber stretching result in the strong oil absorption of the product and the production of linoleum absorbing material.

Requirements for PP slicing materials in spinning melting production line

In the process of polypropylene spinning, different brands of PP slices are often used, and their spinnability will be greatly different, such as the length of the service cycle of the spinneret component, the rate of filament breaking, the uniformity of the fiber and so on. However, to be used as the raw material for spinning grade polypropylene (PP) slicing for spinning melt production, the following conditions must be met:

(1) Melting index (MFI) :

25 ~ 40g/10min for spunbond method,

Use 400 ~ 1500g/10min for meltblowout.

(2) Molecular weight distribution width (Mw/Mn) : < 4 ~ 5.

(3) Melting point: 164 ~ 170℃ (pure isotactic polypropylene melting point is 176℃).

(4) Density: 0.91 g/cm3;

(5) isometric: ≥ 96%.

(6) Ash content: ≤ 0.025% (weight).

(7) Moisture content: ≤ 0.05% (weight).

(8) Smooth appearance, uniform particle size, no connected grain phenomenon.

The raw materials used in the production line are related to the market positioning of the product and the use of the product. In the production of low-end products, due to the low requirements of raw materials, in order to reduce the production cost, we can choose the inferior raw materials; And high-end products have higher requirements on the performance of raw materials, so they need to choose high-quality raw materials with higher prices. The price of PP slices is directly related to the size of its MFI. Generally, the larger the MFI is, the higher the price will be. Therefore, it is necessary to comprehensively consider the production process, equipment characteristics, product use, product selling price, production cost and other factors to choose the raw materials used.