Air-Through Bonding (ATB) Nonwoven: Technology, Properties, And Applications

Air-Through Bonding (ATB) Nonwoven: Technology, Properties, and Applications

1. Introduction to Nonwoven Fabrics

Nonwoven fabrics are a distinct and versatile category of textile materials, differing fundamentally from traditional woven or knitted textiles. Their unique manufacturing processes and resulting properties have led to widespread adoption across numerous industries.

1.1. Definition and Fundamental Characteristics of Nonwoven Fabrics

Nonwoven fabric is a fabric-like material made from staple fibers or continuous long filaments, bonded together using chemical, mechanical, heat, or solvent treatments. Unlike woven or knitted fabrics, nonwovens are formed by randomly piling webs of filaments into a sheet. This distinct formation method gives nonwoven materials several key characteristics. They typically have dimensional stability, resisting stretching or shrinking, and cut portions do not fray, which simplifies manufacturing and application. Production flexibility allows precise adjustment of texture, strength, thickness, and density by varying raw materials or manufacturing methods. Furthermore, the absence of complex weaving or knitting steps allows for lower production costs and high-volume mass production, making them economically attractive for a vast array of applications.

1.2. Overview of General Nonwoven Manufacturing Methods

Nonwoven fabric production involves diverse manufacturing methods, categorized by bonding mechanisms: mechanical, thermal, and chemical bonding. Prior to bonding, fibers are formed into a web, usually through dry-laid, wet-laid, or polymer-laid techniques.

• Mechanical Bonding: Involves physically interlocking fibers.

• Spunlace (Hydroentangling): Uses high-pressure water jets to entangle deposited fibers into a sheet. This process avoids binders, resulting in a soft, cloth-like fabric suitable for sensitive applications like sanitary and cosmetic products.

• Needle Punch: Fibers are mechanically interlocked using barbed needles that repeatedly pierce the web. This can create dense, felt-like or open, voluminous structures.

• Thermal Bonding: Utilizes heat and pressure to fuse fibers together.

• Spunbond: Molten polymer is extruded into continuous filaments, then deposited and thermally bonded. Spunbond nonwovens are known for high strength and dimensional stability.

• Meltblown: Polymers are melted and blown into extremely fine fibers, creating a web ideal for filtration due to its fine fiber composition and good barrier properties.

• Air-Through Bonding (ATB): A specialized thermal bonding process applying heated air to the nonwoven surface.

• Chemical Bonding: Employs adhesives or binders to join fibers, applied via spraying, foaming, printing, or impregnation.

Understanding these diverse methods provides a comparative framework for appreciating the unique position and advantages of Air-Through Bonding within the nonwoven landscape. The flexibility in adjusting properties by selecting different raw materials and manufacturing methods is a hallmark of nonwoven production.

Table 1: Comparison of Nonwoven Bonding Methods

2. Understanding Air-Through Bonding (ATB) Nonwovens

Air-Through Bonding (ATB) is a highly specialized thermal bonding process known for its precise control over heat application, yielding nonwoven fabrics with distinct performance characteristics.

2.1. Definition and Core Concept of ATB

ATB is a specific type of thermal bonding that applies heated air to the surface of a nonwoven fabric to achieve web integrity. What sets ATB apart is its unique air circulation mechanism. Unlike conventional hot ovens that push heated air through the material, the ATB process uses a system of negative pressure or suction. This suction actively pulls heated air through an open conveyor apron supporting the nonwoven web as it traverses the oven. This "pulling" action is a critical engineering design choice that enables superior thermal management. This mechanism ensures rapid and remarkably even heat transmission throughout the entire cross-section of the nonwoven material. Uniform temperature exposure is a distinguishing feature of ATB, preventing localized overheating or underheating that could compromise material integrity. This precise thermal control minimizes nonwoven material distortion, allowing the delicate web structure to be smoothly bonded into a stable product without sacrificing its high-lofted character and superior softness. Preserving these delicate attributes, which might be degraded by less controlled heat application or mechanical compression, underscores a core competitive advantage of ATB.

2.2. The Role of Binding Agents

Bonding in ATB nonwovens is primarily achieved through the strategic use of crystalline binder fibers and powders. As the nonwoven web, containing these binders, passes through the heated air, the binding agents melt. They form molten droplets distributed throughout the nonwoven material's cross-section, gathering at fiber contact points. As the material exits the heated zone and cools, these molten droplets solidify, effectively fusing the fibers together at these contact points, creating a stable and cohesive fabric. A crucial and differentiating aspect of the ATB process is that it typically does not rely on chemical binders. This deliberate avoidance of chemical adhesives provides substantial benefits, contributing to a much safer production process and working environment by eliminating the need for handling and preparing chemical solutions. Furthermore, the resulting material is considered safer for the environment, aligning the technology with "green technologies" and environmentally friendly solutions consistent with circular economy principles. This strategic decision to forgo chemical binders extends beyond mere process efficiency; it positions ATB technology as inherently more sustainable and health-conscious. In sectors such as hygiene and medical, where consumer contact and ecological footprint are paramount, this "clean" manufacturing approach becomes a compelling market differentiator. It not only mitigates operational hazards and waste but also caters to a growing consumer demand for products that are both safe and environmentally responsible, potentially influencing purchasing decisions and regulatory frameworks.

3. The ATB Manufacturing Process: A Detailed Overview

The production of ATB nonwovens involves a meticulously engineered multi-stage process, designed to optimize fiber handling, web formation, and thermal bonding for superior product quality.

3.1. Fiber Preparation and Web Formation

The journey of an ATB nonwoven begins with precise fiber preparation.

• Opening & Blending: Raw fibers, which can include bi-component fibers, cotton, polyester, rayon, or plant-derived polylactic acid (such as TERRAMAC), are received in bales. These fibers undergo an opening process to separate them, followed by blending to ensure a homogeneous mix. This careful preparation ensures an even distribution of fibers as they proceed towards the web former. Manufacturers like ANDRITZ highlight their expertise in this initial stage, emphasizing its role in achieving optimum fiber opening, facilitating quick fiber batch changes, ensuring accurate blending ratios, and ultimately contributing to substantial cost savings.

• Carding: Following blending, the prepared fibers are pneumatically conveyed to carding machines. Carding is a critical step where fibers are untangled and aligned, forming a uniform web. The quality of this web directly impacts the final product's consistency and performance. ANDRITZ's carding machines, for instance, are recognized as fundamental to achieving "perfect web uniformity and comfort". These machines offer various configurations, including single or double card set-ups, different web structure solutions, and varying numbers of doffers, allowing for customization of web qualities to meet specific product requirements.

3.2. The Air-Through Bonding Oven System

The heart of the ATB process lies within the specialized oven system, where the actual bonding occurs.

• Mechanism of Bonding: Once the fragile, unbonded nonwoven web is formed, it enters the ATB oven. Inside, hot air is precisely directed to activate the low-melt polymers present within the fiber matrix. As these polymers soften and flow, they gather at the numerous contact points between individual fibers. Upon subsequent cooling, these molten points solidify, creating strong, permanent bonds that integrate the entire web into a stable nonwoven fabric.

• Oven Types and Airflow: To accommodate different production needs and web structures, manufacturers offer various oven systems. Two prominent types are:Both flat and Omega oven designs are engineered to feature one-sided, air-through ventilation, which is a defining characteristic of ATB processes in the hygiene market. These ovens can be powered by either indirect heating methods (such as electrical power or thermal oil) or direct heating methods (using natural or liquid gas).

• Flat Oven System: This system uses an air-permeable conveyor belt to transport the nonwoven web through the heating zone. Advanced features, such as ANDRITZ's SoftJet air guidance system, are integrated into flat ovens to ensure that even the most sensitive fiber blends maintain their high loft and superior softness after the bonding process.

• Omega Oven System: This alternative system employs a perforated and/or sieve-fabric covered drum surface for web transport.

• Temperature and Air-flow Uniformity: A critical benefit of both oven designs is their capacity to ensure the "highest uniformity of temperature and air-flow". This consistency is paramount for producing nonwovens with uniform quality, preventing variations in softness, bulk, and strength across the material.

3.3. Post-Bonding Treatments and Converting

After the primary bonding in the oven, the nonwoven material undergoes further processing to finalize its properties and prepare it for end-use.

• Cooling and Finishing: Following the heating phase, a gentle cooling-down phase is essential. This is succeeded by various finishing steps designed to ensure the nonwoven web permanently retains its desired resiliency and final characteristics, such as loft and softness.

• Calendering: A common post-bonding treatment is calendering, a smoothing process that involves passing the bonded material through rollers. Hot roll calendering typically results in a thinner fabric. Cold calendering is used to create a thicker material. Regardless of the calendering method, the ATB material is designed to remain flexible and extensible, maintaining its desired drape and stretch properties.

• Converting: The finished nonwoven fabric is then wound into large rolls. These rolls are subsequently prepared for slitting into narrower widths, packaging, and shipping. For applications in the hygiene sector, this often involves integration with specialized converting lines that transform the nonwoven into final products like feminine hygiene items, baby diapers, and adult care products.

The high performance and consistent quality of ATB nonwovens are not solely attributable to the bonding oven itself, but rather emerge from a meticulously optimized, integrated manufacturing line. The precise interplay between fiber preparation, uniform web formation, controlled thermal bonding, and tailored finishing processes is indispensable. Any compromise in an earlier stage, such as inadequate fiber blending or uneven carding, would inevitably diminish the quality of the final product, irrespective of the oven's efficiency. This highlights that achieving top-tier ATB material necessitates a holistic approach to process engineering and equipment synergy, underscoring the importance of system suppliers capable of delivering comprehensive, integrated solutions rather than just individual machines.

Table 2: Key Stages of the ATB Manufacturing Process (Example: ANDRITZ Line)

4. Unique Properties and Performance Characteristics of ATB Nonwovens

The Air-Through Bonding process imparts a distinctive set of physical, mechanical, and functional attributes to nonwoven fabrics, making them highly desirable for specific, demanding applications.

4.1. Physical and Mechanical Attributes

ATB nonwovens are renowned for their exceptional physical and mechanical characteristics, which are a direct result of precise thermal management and binder activation without the need for mechanical compression or chemical stiffening.

• Softness: A hallmark property, often described as "superior softness". This attribute is frequently enhanced by advanced technologies like ANDRITZ's SoftJet air guidance system, ensuring a luxurious feel.

• Bulkiness/Loftiness: ATB nonwovens are characterized by being "bulky" and "lofty". The process is designed to maintain a high-lofted character even after bonding, which is crucial for comfort and absorbency.

• Open Structure: These materials possess an "open" structure, a feature that significantly contributes to their breathability and absorbent capabilities.

• High Strength/Durability: Despite their inherent softness and bulk, ATB nonwovens exhibit "high strength" and "tensile strength". This combination ensures durability for various demanding applications.

• Extensibility/Flexibility: The material retains its "flexibility and extensibility" even after production and post-bonding treatments like calendering.

• Resiliency: ATB nonwovens are engineered to be "resilient," meaning they can spring back to their original form. The bonding process ensures this desired resiliency is permanently conserved after the heating and cooling phases.

• High Uniformity: The manufacturing process consistently delivers "perfect web uniformity" and a "consistent and even structure" throughout the fabric.

• Lower Basis Weights: ATB technology allows for the production of high-performance fabrics with reduced material density, maintaining desired performance while potentially decreasing material usage.

4.2. Functional Attributes

Beyond their structural properties, ATB nonwovens offer critical functional advantages.

• Breathability: The open structure of ATB nonwovens ensures excellent air permeability, making them highly breathable. This is a vital attribute for user comfort in hygiene products and for effective performance in filtration systems.

• Absorbency: Depending on the fiber type used, ATB nonwovens can effectively absorb and retain moisture. Their bulky and open structure naturally enhances this absorbent capacity.

• High Filtration Capacity: ATB technology is capable of producing materials with high filtration capabilities. For instance, Texol's "Hot Air Cotton," derived from ATB technology, is specifically designed for high-loft wearing comfort masks, such as FFP2, while effectively preserving their filtering efficiency.

4.3. Environmental Advantages

The environmental profile of ATB nonwovens is a significant factor in their growing market preference and aligns with increasing regulatory demands.

• No Chemical Binders: A standout environmental benefit of ATB is the absence of chemical binders in the bonding process. This not only results in a "safer production process" by eliminating the need for hazardous chemical preparation but also contributes to a product that is "safer for the environment".

• Lightweight: ATB nonwovens are inherently lightweight, which can lead to reduced material consumption and lower transportation costs, further contributing to their environmental appeal.

• Alignment with Green Technologies: Leading manufacturers explicitly position ATB solutions as "green technologies" and "environmentally friendly solutions," emphasizing their consistency with circular economy principles.

• Biodegradable Options: While not exclusive to ATB, the broader nonwoven industry is moving towards environmentally conscious raw materials. For example, Unitika produces nonwovens from plant-derived polylactic acid (TERRAMAC), which is biodegradable, indicating the potential for ATB to incorporate such sustainable fibers.

The convergence of softness, bulkiness, and breathability in ATB nonwovens is not a coincidental grouping of attributes; it forms a synergistic combination that holds strategic importance, particularly for the hygiene market. Softness ensures comfort against delicate skin, bulkiness facilitates superior absorbency and cushioning, and breathability is essential for preventing discomfort and skin irritation. This unique blend of properties, achieved through the precise ATB process without the use of chemical binders, positions ATB as a superior material choice for sensitive applications where user comfort and skin health are paramount. This illustrates a direct relationship between the specific process technology, the resulting synergy of properties, and the dominance of ATB in high-value, sensitive consumer product segments.

Table 3: Key Properties and Benefits of ATB Nonwovens

5. Key Applications and Market Impact

The unique combination of properties offered by ATB nonwovens makes them indispensable across several critical industries, particularly where comfort, performance, and safety are paramount.

5.1. Hygiene Products

The hygiene market is the predominant application area and a primary driver for ATB technology. This sector demands materials with high uniformity, exceptional softness, significant bulkiness, and robust tensile strength. ATB nonwovens perfectly meet these stringent quality requirements.

• Baby Diapers: ATB materials are extensively used for various layers within baby diapers, including soft top-sheets, acquisition distribution layers (ADL), and breathable back sheets. Polypropylene-based spunbond, often produced with ATB technology, is a prevalent material choice for these applications.

• Feminine Hygiene Products: Similar to baby diapers, ATB nonwovens are integral components in feminine hygiene products, contributing to comfort, absorbency, and breathability.

• Adult Incontinence Products: With an aging global population, demand for high-quality adult incontinence products is rising. ATB nonwovens address this need by providing materials that offer comfort, absorbency, and discretion.

The inherent softness, superior absorbency, high breathability, and desirable bulkiness of ATB nonwovens are perfectly suited for these sensitive, skin-contact applications, making them the material of choice for leading hygiene brands.

5.2. Filtration Materials

Beyond hygiene, ATB nonwovens play an increasingly critical role in various filtration applications, particularly those requiring high performance and user comfort.

• Medical Masks: A notable and rapidly growing application is in the production of high-performance masks, such as FFP2 and FFP3 respirators. "Hot Air Cotton," an ATB-derived material by companies like Texol, is specifically designed for these masks, offering high loft for wearing comfort while effectively preserving filtering capacity essential for particle capture. This particular application has seen significant market demand.

The open, bulky, and breathable structure of ATB nonwovens, combined with their inherent high filtration capacity, makes them ideal for efficiently capturing fine particles while maintaining air permeability.

5.3. Other Durable and Disposable End Uses

The versatility of ATB nonwovens extends to a range of other durable and disposable products where their unique properties are beneficial.

• Bedding & Furniture: ATB materials are utilized in products such as infant sleeping bags, sofa cushions, and various bedding components, where their bulkiness, softness, and durability are valued.

• Carpet Backing: They provide structural integrity and durability when used as carpet backing.

• Personal and Cleaning Wipes: The absorbency and soft texture of ATB nonwovens make them suitable for both personal care wipes and general cleaning wipes.

• Dryer Sheets: Another common disposable consumer product utilizing ATB nonwovens is dryer sheets.

The strong market penetration of ATB nonwovens, particularly in hygiene and filtration, demonstrates its ability to precisely meet evolving consumer and public health demands. For hygiene products, the technology delivers comfort and performance driven by demographic shifts and rising living standards. In filtration, especially for masks, it addresses critical safety standards while also providing user comfort, a demand significantly amplified by recent global health events. This indicates that ATB technology is not static but dynamically adaptable, leveraging its inherent properties to address specific, high-stakes market needs, showcasing a robust and versatile manufacturing capability.

Table 4: Primary Applications of ATB Nonwovens

6. Industry Landscape and Leading Manufacturers

The ATB nonwoven market is characterized by several key players who are driving innovation and production, offering specialized equipment and materials to meet global demand.

6.1. Key Players and Technological Contributions

• ANDRITZ: A prominent global system supplier for ATB technology, ANDRITZ offers comprehensive, customized solutions primarily for the hygiene product sector. Their product lines include the neXline air-through bonding eXcelle for high-capacity production and the neXline air-through bonding aXcess for small to medium capacities. ANDRITZ provides a complete range of equipment, from initial fiber opening and blending to advanced carding machines and sophisticated oven systems (both flat and Omega designs). Their SoftJet technology is specifically designed to ensure superior softness in the final product. Furthermore, ANDRITZ maintains technical centers, such as CETI (European Center for Innovative Textiles), which serve as vital R&D platforms for prototyping new hygiene applications and conducting extensive testing.

• Texol - Orma Group: This group is actively involved in developing "air through bonded" nonwovens, with a strong focus on producing resilient, soft, breathable, and uniform materials, often at lower basis weights. Texol is particularly recognized for its "Hot Air Cotton," an ATB-derived material specifically engineered for high-loft wearing comfort masks, such as FFP2 respirators, while maintaining filtering efficiency. The company demonstrates a clear commitment to "green technologies" and environmentally friendly solutions that align with circular economy principles.

• WPT Nonwovens: As a domestic source for through-air bonded nonwoven material, WPT Nonwovens emphasizes the versatility and environmental safety of its products. The company highlights its capability for rapid sample production and efficient order fulfillment, typically within four to six weeks.

• YINGYANG: A manufacturer of through-air bonded nonwoven production lines and nonwoven fabrics, YINGYANG serves a broad international market across more than 70 countries. Their product range includes thick materials suitable for infant sleeping bags, bedding, and sofa cushions, as well as filter media for medical protective masks. The company has a continuous development program, including new products like through-air bonded nonwoven production lines.

• Unitika: While Unitika is a major nonwoven producer primarily utilizing spunbond and spunlace methods, its focus on environmentally conscious materials, such as TERRAMAC (a biodegradable plastic made from plant-derived polylactic acid), is indicative of broader industry trends relevant to ATB nonwovens.

6.2. Production Capabilities and Metrics

The industrial scale and efficiency of ATB manufacturing are reflected in the impressive production capabilities reported by leading manufacturers.

• GSM Range: ATB lines are capable of producing high-performance fabrics with basis weights typically ranging from 16 to 80 grams per square meter (gsm). Specifically, Texol's perforated and embossed nonwovens for hygiene applications range from 18 to 40 gsm, while YINGYANG's production lines produce materials between 16 and 60 gsm.

• Production Speed: High production speeds are a hallmark of modern ATB lines. ANDRITZ's lines, for instance, can achieve speeds of up to 250 meters per minute (m/min). YINGYANG's lines operate at speeds of up to 100 m/min.

• Capacity: The annual production capacities of ATB lines are substantial, reflecting their suitability for mass production. ANDRITZ's aXcess range offers capacities up to 5,500 tons per annum (t/a), while their high-capacity eXcelle range can reach up to 12,000 t/a.

The market leadership in ATB nonwovens is demonstrably driven by a combination of technological specialization and the ability to scale production efficiently. Companies that can provide tailored solutions for varying capacity requirements, from high-volume hygiene products to more niche filtration applications, and deliver integrated, high-speed production lines, are strategically well-positioned. This suggests that success in the ATB sector extends beyond merely possessing the core bonding technology; it encompasses the advanced engineering capability to optimize the entire production chain, from initial fiber handling to final converting, to meet diverse and demanding market requirements at a competitive scale.

Table 5: ATB Production Capabilities and Manufacturer Focus

7. Quality and Sustainability Standards in Nonwovens

The nonwoven industry, particularly for high-performance and consumer-facing products like ATB nonwovens, places significant emphasis on quality assurance and adherence to sustainability standards. These standards are crucial for ensuring product safety, environmental responsibility, and market acceptance.

7.1. Relevant Industry Certifications

Several industry certifications provide benchmarks for quality and sustainability in textiles, including nonwovens.

• NSF/ANSI 336 Facts Certification: This is a multi-attribute standard specifically designed for commercial textiles, encompassing nonwovens, that evaluates environmental, economic, and social aspects across the entire product life cycle. It covers critical areas such as fiber sourcing, material safety, water conservation and quality, energy consumption, recycling practices, air quality in manufacturing, and social accountability. Certification to NSF/ANSI 336 is based on a point system, offering ascending thresholds of sustainability: Compliant, Silver, Gold, or Platinum.

• Oeko-Tex Standards: The Oeko-Tex Association offers a suite of globally recognized certifications focused on human-ecological safety and sustainable production processes in textiles.

• Standard 100: This widely adopted standard tests textile products for harmful substances. Recent updates include stricter limits for chemicals like Bisphenol A (BPA), reflecting a commitment to enhanced safety.

• Made in Green: This label identifies textile products tested for harmful substances and manufactured in environmentally friendly and socially responsible workplaces. It now includes an option for organic cotton certification, providing greater transparency and traceability.

• STeP (Sustainable Textile Production): This certification focuses on optimizing environmental impact throughout the production chain and aligns with initiatives like the ZDHC (Zero Discharge of Hazardous Chemicals) Programme, encouraging sustainable practices across the textile and leather industries.

The inherent characteristics of ATB nonwovens, particularly the absence of chemical binders in their production, naturally align with many sustainability goals and can significantly contribute to achieving these rigorous certifications. This characteristic positions ATB as an environmentally advantageous technology within the broader nonwoven market. For ATB nonwovens, especially in sensitive applications such as hygiene and medical products, obtaining relevant sustainability and safety certifications is no longer merely a beneficial attribute but a critical requirement for market entry and a substantial competitive advantage. The intrinsic environmental benefits of ATB, such as its binder-free nature, provide a head start in meeting these stringent standards. This implies that manufacturers must proactively integrate certification compliance into their research, development, and production strategies, as consumer awareness and regulatory pressures for sustainable and safe products continue to intensify, making these certifications a key differentiator in a competitive market.

7.2. Research and Development in Nonwovens

The nonwoven industry is highly dynamic, with continuous research and development efforts aimed at enhancing material performance, improving manufacturing processes, and exploring new applications. Ongoing research critically examines material constituents, processing steps, and the optimal integration of various fabric layers to create advanced nonwoven products. This includes a focus on refining existing bonding techniques—mechanical, thermal, and chemical—and exploring emergent processes such as electrospinning and centrifugal spinning to produce unique ultrafine nanofibers with novel properties. Studies are also conducted on nonwoven composites, such as spunbond/meltblown (SM) and spunbond/meltblown/spunbond (SMS) laminates, to optimize their production parameters and evaluate their barrier performance and tensile properties for diverse uses. Leading manufacturers actively invest in R&D. For example, ANDRITZ operates technical centers, including one at CETI (European Center for Innovative Textiles), which serves as a dedicated R&D platform for prototyping new hygiene applications using both flat and Omega ATB ovens. These efforts underscore the industry's commitment to innovation, ensuring that ATB technology continues to evolve and meet future market demands.