Compounding of the most popular pppe spunbonded no

2022-10-16
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Composite of pp/pe spunbonded nonwovens

in recent years, China's spunbonded nonwovens industry has developed by leaps and bounds. Especially since 2003, more than 100 production lines have been added across the country, and they have been integrated into a new automobile platform with a production capacity of more than 200000 tons. It has become a real spunbonded production country in the world. However, China has few varieties of spunbonded products and lacks independent intellectual property rights, It is an indisputable fact that it cannot become a world power in the spunbonded industry

in 2002, Shanghai Institute of synthetic fiber established a research group of "pp/pe two-component composite spunbonded nonwovens", which thoroughly transformed the first Italian NWT spunbonded production line introduced in 1988. The annual output increased from 1000 tons to 2500 tons, and the variety was changed from PP single component to pp/pe two-component composite. The door width was still 3 meters, and the gram weight range was unchanged. The research group made use of the technology and experience accumulated in the two national key research projects "pp/pe low melting point composite fiber" and "spinning direct fabric formation" (i.e. spunbonded nonwovens) undertaken and completed by the Institute during the "Seventh Five Year Plan" to tackle key problems in raw materials, processes and equipment. At the end of 2003, the project achieved preliminary results and passed the appraisal of an expert group headed by academicians of the Chinese Academy of engineering and chaired by the Shanghai Science and Technology Commission and the Economic Commission. The project achievements have been applied for and accepted invention patents

process: the two-component spunbonded method adopts the method of composite spinning. Two screws melt two different raw materials, and form composite fibers with different cross-section shapes at the outlet of the spinneret assembly according to the product design requirements. At present, what has been produced is skin core composite fiber, skin is ethylene fiber, and core is polypropylene fiber

spinning temperature: the spinning process of composite fiber is much more complex than that of single component fiber. The spinning temperature should be determined according to the properties of PE and PP raw materials, especially the size of MFR, and meet the fiber forming requirements of the two raw materials at the same time. When the temperature is low, the melt fine flow viscoelasticity is large, and the spinnability and tensile properties are poor, which is easy to break; If the temperature is high, thermal decomposition will occur, which will not only produce aldehydes low molecular harmful gases, but also reduce the physical and mechanical properties of the fiber, and ultimately affect the quality of the product. In addition, according to the research results of ES (i.e. pp/pe skin core composite staple fiber) fiber of the synthetic fiber Institute, the cross-section of the composite fiber is shaped into a partial skin shape rather than a joint core shape, which is conducive to the thermal bonding effect. This form also needs to be controlled by the regulation of spinning temperature. To sum up, the spinning temperature should be as low as possible on the premise of ensuring spinnability and cross-section shape

cooling conditions: the melting point, thermal conductivity, crystal structure and crystallization rate of the two components of the skin and core are different. It is very difficult for the cooling forming conditions to make the two components cool evenly and have good tensile properties

Figure 1: relationship between mechanical stretching speed and fineness

equipment: spinning, understretching and finishing equipment are all designed and developed by ourselves. The original 120mm diameter screw is retained and a straight screw is added; Abandoned the original single box, more than half of which were processed in the Asia Pacific region, and added two self-designed composite boxes; The product is changed from single layer to double layer, which improves the uniformity of the product; The specially designed spinning components ensure that the fiber has a good skin core composite shape, and the elongation is also changed from the original low-pressure large flow device to high-pressure small flow device, which improves the elongation efficiency. Hot rolling mill, winding machine and Slitter are imported equipment from Italy

spinning temperature: the spinning process of composite fiber is much more complex than that of single component fiber. The spinning temperature should be determined according to the properties of PE and PP raw materials, especially the size of MFR, and meet the fiber forming requirements of the two raw materials at the same time. When the temperature is low, the melt fine flow viscoelasticity is large, and the spinnability and tensile properties are poor, which is easy to break; If the temperature is high, thermal decomposition will occur, which will not only produce aldehydes low molecular harmful gases, but also reduce the physical and mechanical properties of the fiber, and ultimately affect the quality of the product. In addition, according to the research results of ES (i.e. pp/pe skin core composite staple fiber) fiber of the synthetic fiber Institute, the cross section of the composite fiber is shaped into an inner circle of partial skin core type, which is conducive to the thermal bonding effect. This form also needs to be controlled by the regulation of spinning temperature. To sum up, the spinning temperature should be as low as possible on the premise of ensuring spinnability and cross-section shape

Figure 2: relationship between air flow tensile pressure and fineness

cooling conditions: the melting point, thermal conductivity, crystal structure and crystallization rate of the two components of the skin and core are different. It is very difficult for the cooling forming conditions to make the two components cool evenly and have good tensile properties. In the composite spinning of PP and PE, because the PE molecular chain is regular and flexible, it can cut into the lattice with the smallest and most stable zigzag energy, so it is very easy to crystallize, and the maximum crystallinity is 95%. The molecular weight of PP is helical structure. Although the arrangement is regular, it is less crystalline than PE, and the maximum crystallinity is only 80%. The spinning speed of spunbonded method is relatively high. For example, the cooling conditions are intense, and the crystallization of the core layer is much lower than that of the skin layer, which is easy to produce the phenomenon of skin core separation, and it is easy to rapidly increase the viscoelasticity of the melt flowing out of the spinneret, resulting in the failure of the deformation rate of the melt trickle to keep up with the development of tensile stress, resulting in end breakage and affecting normal production. In order to overcome the above shortcomings, relatively mild cooling conditions should be adopted. For example, reduce the wind speed, increase the wind temperature and increase the cooling distance

tensile properties of fibers: it can be seen from Figure 2 that the higher the tensile air pressure, the finer the fiber fineness; The lower the pressure is, the coarser the fiber fineness is, but the relationship between the tensile pressure and the fiber fineness is not linear even in the stretchable range. This is because in air stretching, with the continuous increase of the initial strength of the fiber, the slip coefficient of the air flow and the fiber increases, and the effective stretching gradually decreases

Figure 1 shows that the higher the speed is in mechanical stretching, the finer the fineness is, and the relationship between speed and fineness is basically linear. This is because in the process of mechanical stretching, the holding force of the fiber is large, and the slip coefficient can be ignored. Therefore, when the motor power is sufficient, the mechanical speed is in line with the fiber fineness

cross section of fiber: the flow test of two kinds of chips at 270 ℃ on the melt index instrument shows that the flow speed of PE is only a little more than half that of PP, which is basically consistent with the previous judgment. The cross-section morphology of the composite fiber can be adjusted by appropriately changing the spinning temperature of PP and PE. Observe the melting point test of the fiber under the microscope. When the temperature rises to 130 ℃, the skin begins to melt, and the core also melts when it continues to rise to 165 ℃, indicating that the spun fiber is consistent with the previous design. The skin is PE and the core is PP

hot rolling process: the hot rolling process of two-component composite fiber is different from the general PP spunbonded hot rolling process. PP spunbonded fabric is a bonding point that melts the fibers at the rolling point to form fibers. The fibers at the bonding point are completely destroyed, and the rolling point is safe and transparent (see Figure 3)

Figure 3: except for the rolling point of polypropylene spunbonded fabric

, the tensile property of composite fiber is different from that of single component fiber, which mainly depends on the component with poor tensile property. In the two components of pp/pe composite fiber, the spinning and tensile properties of PE are much worse than pp. when the PE component in composite fiber breaks, the PP component is not fully stretched. Therefore, the influence of drawing air flow on the fineness of composite fiber is far less obvious than that of PP fiber

cross section of fiber: the flow test of two kinds of chips at 270 ℃ on the melt index instrument shows that the flow speed of PE is only a little more than half that of PP, which is basically consistent with the previous judgment. The cross-section morphology of the composite fiber can be adjusted by appropriately changing the spinning temperature of PP and PE. Observe the melting point test of the fiber under the microscope. When the temperature rises to 130 ℃, the skin begins to melt, and the core also melts when it continues to rise to 165 ℃, indicating that the spun fiber is consistent with the previous design. The skin is PE and the core is PP

product performance and characteristics: according to the data analysis in Table 1, the strength of two-component spunbonded fabric is similar to that of PP single component spunbonded fabric, but the tear strength is higher and the elongation is larger. This is because the skin component PE becomes a binder after melting under the action of temperature and pressure during hot rolling, which increases the strength of the fiber, while the core component PP is not damaged after hot rolling, which retains the original properties of the fiber

in addition, compared with polypropylene spunbonded cloth, the composite spunbonded cloth has obviously soft hand feeling, silky smoothness, good water repellency and good printing effect, and can be applied to cobalt 60 radiation disinfection because of its polyethylene skin

rolling process: the hot rolling process of two-component composite fiber is different from the general PP spunbonded hot rolling process. PP spunbonded fabric is a bonding point that melts the fibers at the rolling point to form fibers. The fibers at the bonding point are completely destroyed, and the rolling point is safe and transparent (see Figure 3). The outer layer of the two-component composite fiber is polyethylene with low melting point, and the core layer is polypropylene with high melting point. Low temperature is adopted for thermal bonding, so that the outer layer of the fiber, namely polyethylene, is fused and bonded to each other, while the core layer polypropylene fiber keeps the fiber as it is, and many unmelted fibers can be seen in the middle of the rolling point (see Figure 4)

Figure 4: rolling point of composite spunbonded fabric

product performance and characteristics: according to the data analysis in Table 1 in the application process of changing the experimental machine, the two-component spunbonded fabric has the same strength as PP single component spunbonded fabric, but the tear strength is higher and the elongation is larger. This is because the skin component PE becomes a binder after melting under the action of temperature and pressure during hot rolling, which increases the strength of the fiber, while the core component PP is not damaged after hot rolling, which retains the original properties of the fiber

in addition, compared with polypropylene spunbonded cloth, the composite spunbonded cloth has obviously soft hand feeling, silky smoothness, good water repellency and good printing effect, and can be applied to cobalt 60 radiation disinfection because of its polyethylene skin

application:

composite spunbonded fabric can be used in the following fields:

◆ disposable sanitary products: polyethylene is as non-toxic and side effects as polypropylene. Composite spunbonded fabric can be used as an upgrading product of polypropylene spunbonded products and composite short fiber hot-rolled fabrics. As mentioned above, this product has basically the same strength as polypropylene spunbonded fabric, and has good hand feel and comfortable wearing. It is suitable for surgical clothes, surgical caps, visiting clothes Work clothes, masks and other products

until the late 1980s, the vast majority of sanitary napkins and baby diapers in China were hot-rolled short silk polypropylene and polyester cloth. However, since the successful research of pp/pe composite staple fiber in our institute in the early 1990s, it has quickly replaced the conventional C and polyester staple fiber. At present, the national output has exceeded 100000 tons, completely covering the sanitary napkin and diaper market. Compared with composite staple fiber hot rolled cloth, composite spunbonded cloth has the same fiber shape and higher strength. Especially, no spinning oil is added in the production process, which has good water repellency and will not have any side effects on the skin. It should be able to replace composite staple fiber hot rolled cloth

◆ film composite products now most used in medical insurance are polyethylene, and the outer layer of composite spunbonded fabric is also polyethylene, so the composite of composite spunbonded fabric and film can be cast, ultrasonic and thermal composite. The peel strength of the final composite is much higher than that of the polypropylene spunbonded composite

a waterproof material currently used is a polyethylene casting film sandwiched between two layers of polypropylene spunbonded cloth. In use, non-woven fabrics are combined with building materials,

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