Concept
Hot air nonwoven fabric belongs to a type of hot air bonding (hot rolling, hot air) nonwoven fabric. Hot air nonwoven fabric is a nonwoven fabric that is formed by using hot air on a drying device to penetrate the fiber web after the fibers are combed, so that they are heated and bonded.
Hot air bonding refers to a production method in which hot air is used to penetrate the fiber web on a drying device to melt it and bond it. The heating method used is different, and the performance and style of the products made are also different. Generally, the products made by hot air bonding have the characteristics of being fluffy, soft, elastic, and warm, but the strength is low and easy to deform.
Principle
Hot rolling refers to rolling the fibrous material through a roller at high temperature to change its physical structure and morphology, so that its fibers are arranged more closely, thereby forming a layer of woven material with stronger integrity. The main function of hot rolling is to make the woven material uniform in the thickness direction and more integrated.
Thermal bonding refers to adding hot melt adhesive to fibrous materials at high temperature, melting the hot melt adhesive, and then, under a certain pressure, bonding the fibers together through heat and mass transfer in the melt to form a woven material. Thermal bonding mainly uses adhesives to interlace the fibers together, thereby forming a loosely arranged woven material.
In hot air bonding production, a certain proportion of low-melting point bonding fibers or bicomponent fibers are mostly mixed into the fiber web, or a powdering device is used to apply a certain amount of bonding powder before the fiber web enters the drying room. The melting point of the powder is lower than that of the fiber, and it melts quickly after being heated, so that the fibers are bonded.
The heating temperature of hot air bonding is generally lower than the melting point of the main fiber. Therefore, in the selection of fibers, the matching of the thermal properties of the main fiber and the bonding fiber should be considered, and the difference between the melting point of the bonding fiber and the melting point of the main fiber should be as large as possible to reduce the thermal shrinkage of the main fiber as much as possible and maintain the original performance of the fiber.
The strength of bonding fiber is lower than that of normal fiber. Therefore, the amount added should not be too large, and it is generally controlled at 15%~50%. Due to its small thermal shrinkage, bicomponent fiber is very suitable for use alone or as bonding fiber in the production of hot air bonded nonwoven fabrics, forming a point bonding structure with good effect. The products produced by this method are strong and soft.
Fiber webs composed of thermoplastic synthetic fibers can be reinforced by thermal bonding, such as polyester, nylon, polypropylene, etc., which are commonly used in the production of nonwoven fabrics. Since fibers such as cotton, wool, linen, and viscose are not thermoplastic, fiber webs composed of such fibers alone cannot be reinforced by thermal bonding. However, a small amount of cotton, wool, and other fibers can be added to thermoplastic fiber webs to improve certain properties of nonwoven fabrics, but it should generally not exceed 50%. For example, hot-rolled bonded nonwoven fabrics made of cotton/polyester with a mixing ratio of 30/70 can significantly improve hygroscopicity, feel, and softness, and are very suitable for medical and sanitary products. As the cotton fiber content increases, the strength of the nonwoven fabric will decrease. Of course, for webs composed entirely of non-thermoplastic fibers, powdering thermal bonding can also be considered for reinforcement.
Different heating methods
Thermal bonding of nonwoven fabrics can be achieved through different heating methods. The bonding method and process, fiber type, combing process and web structure will ultimately affect the performance and appearance of nonwoven fabrics.
For webs containing low-melting point fibers or bicomponent fibers, hot rolling bonding or hot air bonding can be used. For webs of ordinary thermoplastic fibers and webs mixed with non-thermoplastic fibers, hot rolling bonding can be used.
Hot rolling bonding is generally suitable for webs with a quantitative range of 20~200g/m, and is most suitable for thin products with a quantitative range of 20~80g/m. If the web is too thick, the bonding effect of the middle layer is poor, and stratification is easy to occur.
Hot air bonding is suitable for products with a quantitative range of 16~2500g/m. In recent years, thin hot air bonded nonwovens have developed rapidly, and the quantitative is generally 16~100g/m.
In addition, thermal bonding is also commonly used in the production of composite nonwovens (such as melt-laminated nonwovens), or as a supplement to other reinforcement methods. For example, a small amount of low-melting point fiber is mixed into the fiber web, and then hot air bonding after needle punching reinforcement can significantly improve the strength and dimensional stability of the needle punched product.
Application scenario
Hot air bonded products have the characteristics of high fluffiness, good elasticity, soft hand feel, strong warmth retention, good air permeability and water permeability, but their strength is low and easy to deform. With the development of the market, hot air bonded products are widely used in the manufacture of disposable products with their unique style, such as baby diapers, adult incontinence pads, fabrics for women’s hygiene products, as well as napkins, bath towels, disposable tablecloths, etc.; thick products are used to make cold-proof clothing, bedding, baby sleeping bags, mattresses, sofa cushions, etc. High-density hot melt bonding products can be used to make filter materials, sound insulation materials, shock-absorbing materials, etc.
Hot calendering is often used to make thicker nonwoven materials, such as filter materials, sound insulation materials, and linoleum. Since hot calendering forms a more integrated woven material from the fibrous material, it is often used for woven materials that require higher strength and thickness.
Dongguan Liansheng Non woven Technology Co., Ltd. was established in May 2020. It is a large-scale non-woven fabric production enterprise integrating research and development, production, and sales. It can produce various colors of PP spunbond non-woven fabrics with a width of less than 3.2 meters from 9 grams to 300 grams.
Post time: Apr-06-2025