The off-line compound machining technology is one of the most commonly used technologies to improve the added value of products. It has the characteristics of flexibility, convenience and wide adaptability. The composite processing of different materials and processes can produce many new materials with excellent properties. This paper introduces several off-line compounding methods often used in spunbond non woven fabric, including hot rolling compounding, ultrasonic compounding, film compounding, etc., to provide some reference and guidance for the production enterprises of spunbond non woven to improve their product differentiation level and enhance their competitive advantage.
Hot rolling composite is a common composite process, which consolidates multi-layer materials together by hot rolling mill. Hot rolling compound has high production speed, mature and reliable process, and relatively simple operation and management. The product has high strength and good barrier performance. In order to ensure the bonding strength, the melting point of each layer of material shall not differ too much, and the total weight of the product shall be less than 150g/m2. The disadvantage of this process is that the handle of spunbond non woven fabric products after hot rolling becomes poor and the air permeability decreases.
Ultrasonic compounding is a kind of technology that uses ultrasonic wave to consolidate multilayer materials. When the ultrasonic composite process is adopted, the melting point requirements for each layer of materials are not strict. It is suitable for materials with large melting point differences. The operation and management of the production process are relatively simple.
Ultrasonic composites have high production speed, high strength and good barrier properties. By changing the shape of the mold, beautiful patterns can be formed on the spunbond non woven fabric products, which is also convenient for product recycling; However, the strength of the product is not as good as hot rolling bonding, and there are higher requirements for the surface cleaning state of each layer of material.
Film compounding is a multi-layer material of consolidated composite spunbond non woven fabric, which is an important method to manufacture products with high barrier performance. In actual production, there can be "one cloth and one film", "two cloth and one film", "three cloth and two film" and other composite methods. The film composite technology is also relatively mature, with strong controllability of film thickness, high production speed (about 100m/min), simple operation and management, high product strength and good barrier performance.
When the film composite process is adopted, the film material is generally PE with low melting point, while the commonly used PP and pet nonwovens have high melting point, and the temperature of PE melt will not damage other materials. Therefore, the melting point of each layer of material is not strictly required, but the uniformity of the substrate is strictly required. Holes or serious thin mesh defects are not allowed to avoid "slurry leakage" during processing. Under normal conditions, the weight of the base material coated shall be ≥ 18g/m2.
Hot melt adhesive compounding is to use the fluidity of hot melt adhesive to penetrate the surface of the bonded object, and then solidify after cooling or reactive curing to achieve bonding. The hot melt adhesive composite is a non-contact composite, which has low requirements for the minimum gram weight, uniformity and unwinding tension of the substrate; Due to the small amount of spraying, it has little effect on the permeability of the substrate and low requirements for temperature resistance.
The main characteristics of hot melt adhesive composite process are fast bonding speed, solvent-free, simple production process and so on.
The hot melt adhesive compound production line is mainly composed of unwinding device (2 sets), glue spraying equipment (2 sets), compound device, slitting and winding device, with small installed capacity. At the same time, compared with film method, hot melt adhesive spraying has the advantages of fast production speed, high efficiency, small sizing amount, convenient adjustment, low cost, small equipment area, short investment payback period and so on.
This kind of spunbond non woven fabric product has the advantages of soft hand feel, strong shielding, high barrier ability, good air permeability, and is breathable and liquid tight. The fracture strength is also greater than that of the traditional composite process.
Spunbond non woven fabric's off-line composite processing technology has become an important means for international well-known multinational companies to improve their product market competitiveness, but China's application, promotion and innovation have just begun. Enterprises can flexibly select different technologies and equipment according to their own spunbond non woven production lines and market characteristics, so as to improve their competitive advantages and obtain the best economic benefits.