What is hot air non-woven fabric

Hot air non-woven fabric belongs to a type of hot air bonded (hot-rolled, hot air) non-woven fabric. Hot air non-woven fabric is produced by using hot air from a drying equipment to penetrate the fiber web after the fibers are combed, allowing it to be heated and bonded together.

Principle

Hot air bonding refers to the production method of using hot air to penetrate the fiber mesh on drying equipment and melt it under heat to produce bonding. Hot air bonding penetrates the fiber network through hot air, causing the hot melt components (such as low melting point fibers or coatings) in the fibers to melt under heat, and then cool and solidify to form adhesive points, cross-linking the fibers into a stable structure. Its core is: heat transfer, hot air evenly penetrates the fiber mesh, avoiding local overheating or uneven bonding. Selective bonding, only the low melting point portion melts, while the high melting point fibers maintain their original shape, balancing strength and flexibility. Three dimensional bonding, forming multi-point bonding between fibers, high fluffiness, and good breathability.

In the selection of fibers, it is necessary to consider the matching of thermal properties between the main fiber and the bonding fiber, and try to make the difference between the melting point of the bonding fiber and the melting point of the main fiber as large as possible, in order to minimize the thermal shrinkage rate of the main fiber and maintain its original properties. The strength of bonding fibers is lower than that of normal fibers, so the amount added should not be too large, generally controlled between 15% and 50%. Due to its low thermal shrinkage rate, two-component fibers are highly suitable for use alone or as bonding fibers in the production of hot air bonded nonwoven fabrics, forming effective point bonding structures. The products produced by this method have high strength and soft hand feel.

Adaptability

Fiber type

Suitable for ES fibers (PE/PP skin core structure), two-component fibers (such as PET/PE), and fibers containing low melting point powders. Not suitable for single high melting point fibers (such as pure PET, pure PP requiring adhesive, cotton, wool, linen, viscose and other fibers that do not have thermoplasticity).

Fiber webs composed of thermoplastic synthetic fibers can be reinforced by thermal bonding, such as polyester, nylon, polypropylene, etc. commonly used in non-woven fabric production. Due to the lack of thermoplasticity of fibers such as cotton, wool, hemp, and viscose, the fiber network composed solely of these fibers cannot be reinforced by thermal bonding.

Product characteristics

Suitable for producing high fluffy, soft, and breathable non-woven fabrics (such as sanitary napkins and insulation materials). Not suitable for high-density, high-strength demand scenarios (requiring combination of hot rolling or needle punching processes).

The hot rolling bonding method is generally suitable for thin products with a net weight ranging from 20 to 200g/m ², and is most suitable for thin products with a net weight ranging from 20 to 80g/m ². If the net is too thick, the bonding effect of the intermediate layer is poor, and delamination is prone to occur. Hot air bonding is suitable for products with a quantitative range of 16~2500g/m ². In recent years, the development of thin hot air bonded nonwoven fabrics has been rapid, with a quantitative range generally between 16-100g/m ².

In addition, thermal bonding is also commonly used in the production of composite nonwoven fabrics (such as melt laminated nonwoven fabrics), or as a supplementary means to other reinforcement methods. For example, mixing a small amount of low melting point fibers into the fiber web, reinforcing with needle punching, and then bonding with hot air can significantly improve the strength and dimensional stability of needle punched products.

Main raw materials

ES fiber is the most ideal thermal bonding fiber, mainly used for non-woven fabric thermal bonding processing. When the combed fiber network is subjected to hot rolling or hot air penetration for thermal bonding, low melting point components form melt adhesion at the intersections of the fibers, while after cooling, non intersection fibers remain in their original state. This is a form of “point bonding” rather than “zone bonding”, thus the product has characteristics such as fluffiness, softness, high strength, oil absorption, and blood sucking. In recent years, the rapid development of thermal bonding applications relies entirely on these new synthetic fiber materials.

After mixing ES fibers with PP fibers, heat bonding or needle punching treatment is carried out to crosslink and bond ES fibers, which has the advantage of not requiring adhesives and substrate fabrics.

Production equipment

Key equipment composition

Open loosening mixing system: pre opening machine+multi bin cotton mixer to ensure uniform dispersion of fibers.

Web forming machine

Sorting machine+cross laying machine (used for thin and uniform fiber mesh). Airflow web forming machine (used for high fluffiness products).

Hot air oven

Flat mesh: Static heating, suitable for small batches and multiple varieties. Round mesh type: continuous type, high efficiency of hot air penetration, large production capacity.

Cooling and shaping device

Cold air circulation system+calendering roller.

post-processing unit

Immersion tank, spraying equipment, laminating machine, etc.

Basic Requirements

In hot air bonding, air is the heat carrier, and as the air penetrates the fiber mesh, it transfers heat to the fibers. Therefore, first of all, it is necessary to ensure that the structure of the fiber web is not damaged during the circulation of hot air. At the initial stage of entering the drying room, the fibers are only bonded by the gripping force. If the introduction method and speed of the hot air flow are not appropriate, the structure of the fiber web will be damaged. Secondly, it is necessary to ensure that the fiber web is uniformly heated to ensure that the various properties of the reinforced fiber web are uniform and stable. The temperature deviation at all locations should be controlled within a range of ± 1.5 ℃. Thirdly, the temperature in the drying room should meet the process requirements. Ordinary drying equipment is mainly used for drying moisture, and its heating temperature is generally low, which is not suitable for hot air bonding production.

The temperature in the drying room should be able to reach the melting point temperature of the bonding fibers used, usually between 140~220 ℃. In addition, it is necessary to ensure that the fiber web has sufficient heating time to achieve good bonding effect, that is, the drying room needs to have sufficient length.

Production process

One step method: Open the package, mix and loosen → Vibration quantitative cotton feeding → Double Xilin Double Dove → Wide width high-speed combing into a net → Hot air oven → Automatic coiling → Slitting.

Two step method: opening and mixing cotton → cotton feeding machine → pre combing machine → web laying machine → main combing machine → hot air oven → coiling machine → slitting machine.

Craftsmanship and Products

Craftsmanship

Hot bonded nonwoven fabrics can be achieved through different heating methods. The bonding method and process, fiber type and combing process, and web structure will ultimately affect the performance and appearance of non-woven fabrics.

For fiber webs containing low melting point fibers or two-component fibers, hot rolling bonding or hot air bonding can be used. For ordinary thermoplastic fibers and fiber webs mixed with non thermoplastic fibers, hot rolling bonding can be used. Under the same web forming process, the thermal bonding process has a significant impact on the performance of non-woven fabrics and determines the purpose of the product.

typical products

Low weight (15-30g/m ²): Surface of hygiene products, wet wipes.

Medium to high weight (50-150g/m ²): Warm floc, filter material.

Functional products: antibacterial medical dressings, flame-retardant automotive interiors.

Product application

Medical field: surgical gowns, inner layer of masks (soft and breathable), medical dressings.

Sanitary products: surface layer of diapers, flow guiding layer of sanitary napkins (high fluffiness absorption).

Home textile: Warm bedding filling, sofa lining (fluffy and resilient).

Industrial materials: air filter cotton, car soundproofing felt (customizable weight and thickness).

Environmental protection field: biodegradable agricultural covering cloth, environmentally friendly shopping bags.

Summarize

Hot air bonded non-woven fabric has the core advantage of non-destructive bonding, and the product combines softness and breathability, making it suitable for scenarios with high tactile requirements. Future development directions include the replacement of biobased materials, intelligent temperature control systems, and the integration of nanotechnology to enhance functionality.

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.