The application of dyeing, printing and coating additives for nonwoven fabrics is a key process to enhance their functionality and added value, and needs to be designed in combination with material characteristics, application scenarios and environmental protection requirements. The following is a systematic analysis from three aspects: process technology, auxiliary agent selection and special material processing:
Dyeing process and technology
Nonwoven fabrics have a loose structure and low strength. Traditional woven fabric dyeing processes are prone to deformation, so most of them use coating dyeing as the main method and dye dyeing as the auxiliary method.
1. Coating dyeing (mainstream process)
Online dyeing: completed directly in the production line, such as loose fiber → combing → spunlace → foam dyeing → drying → winding. The advantage is energy saving, but the uniformity of dyeing needs to be controlled.
Offline dyeing: impregnate the formed nonwoven fabric with dyeing liquid (adhesive + coating + auxiliary agent) → pre-drying → drying → winding. The process is stable and has strong applicability.
Key technical parameters:
Adhesive dosage: 20%-40% (adjusted according to moisture content); Drying temperature: 120-170℃ (avoid high temperature damage to fibers); Color fastness improvement: high temperature and high pressure dyeing method (such as 6-8 treatments at 140℃), combined with soaping and washing.
2. Dyeing (special needs)
Applicable scenarios: high color depth (such as extra black) or functional requirements (such as medical antibacterial cloth) is required.
Process selection:
Loose fiber dyeing: dyeing first and then cloth, uniform color but high cost;
Dyeing of cloth: similar to woven fabric process, tension needs to be controlled to prevent deformation.
Example: The high color fastness dyeing of spunlace cloth adopts multi-pass treatment of the jigger dyeing machine (50-140℃ gradient heating), and the tentering setting enhances stability.
Printing process and technology
Non-woven fabric printing is dominated by paint printing, which needs to match its porous structure and low strength characteristics.
1. Mainstream printing technology
| Process type | Applicable scenarios | Advantages and limitations | Technical points |
| Gravure printing | Highly hygroscopic materials such as spunlace | High-speed production, fine patterns | Engraving rollers need to be carefully designed to avoid clogging |
| Screen printing | Decorative fabrics (tablecloths, curtains) | Suitable for local reinforcement | easy to control slurry viscosity Round screens are prone to clogging and are mostly used for flat screens |
| Double-sided synchronous printing | High value-added products (medical, clothing lining) | Precise alignment of double-sided patterns to improve strength | Rubber roller + printing roller extrusion to avoid misalignment |
| Transfer printing | Decorative fabric with a smooth surface | Bright colors, no wastewater | High cost, restrictions on fiber raw materials |
2. Key process control
Slurry preparation: coating + adhesive + thickener, viscosity needs to be precisely controlled to prevent seepage;
Pre-drying: 80-100℃ pre-drying to reduce moisture content and avoid blurring of printing;
Fixation process: baking (140-160℃) to cross-link the adhesive and improve wash fastness.
Coating and auxiliary system
Auxiliary selection directly affects the dyeing/printing effect and environmental protection, and both functional and ecological standards must be taken into account.
1. Core auxiliary type and function
| Additive category | Representative product | Mechanism of action | Application case |
| Adhesive | Acrylate core-shell type | Soft core provides softness, hard shell improves wear resistance | Improves hand feel and reduces chipping |
| Environmentally friendly surfactants | Alkyl polyglycoside (APG), α-olefin sulfonate (AOS) | Low toxicity, easy to degrade, improves wetting/dispersibility | Replaces traditional detergents and meets OEKO-TEX standards |
| Color fixative | Acid color fixative (aromatic sulfonate condensate) | Improves nylon/spandex wet fastness and prevents discoloration in sunlight | 70℃ for 20 minutes, dosage 1-4% o.w.f |
| Bioenzyme preparations | Thermoresistant amylase, cellulose polishing enzyme | Catalyze desizing/polishing, reduce chemical pollution | Usage in desizing is 1-3g/L, saving energy by 30% |
2. Special functional auxiliary
Anti-yellowing agent (such as Solpon SPX): protects nylon/spandex blended fabrics from yellowing during heat setting9;
Super absorbent (such as Synthesin 7290): used for sanitary materials to improve liquid absorption capacity;
PFAS-free barrier coating: replaces fluorinated compounds and provides environmentally friendly water repellent properties (such as Michelman products).
Dyeing and printing of special materials
1. Water-soluble polyvinyl alcohol (PVA) non-woven fabric
Technical difficulties: Dyeing needs to maintain water solubility to avoid swelling and damage to the structure.
Innovative process:
→ Pre-dyeing liquid (containing 1-100g/L coating color paste + 2-100g/L adhesive)
→ Liquid rolling to control the liquid rate
→ Low-temperature pre-drying (<80℃)
→ Baking and cross-linking
Effect: Color fastness ≥ level 4, solubility is not affected, and the gram weight is adapted to 45-130g/㎡.
2. Spunlace non-woven fabric
Online printing: Directly dip glue after spunlace → printing → drying, simplifying the process but preventing the fiber mesh from deforming;
High color fastness solution: Multi-stage stentering and shaping after dyeing (such as patent CN201210119254.6) to solve the problem of uneven coloring of the adhesive.
Technical Challenges and Development Trends
Existing Problems
Adhesive Defects: Easy to stick to the roller during baking, and the generated rubber particles are difficult to remove;Uniformity Control: Foam dyeing is prone to unevenness, and a precise liquid feeding system needs to be developed;Cost Pressure: Environmentally friendly additives are expensive (such as APG is 30% more expensive than traditional additives).
Innovation Directions
Low-temperature curing adhesives: Reduce energy consumption and avoid damage to heat-sensitive materials;Gemini surfactants: Double hydrophobic structure improves wetting/dispersion efficiency;Digital printing technology: Adapt to small batch customization and reduce slurry waste.
Summary
Non-woven fabric dyeing and finishing needs to be “applied according to the material”: conventional products are mainly dyed/printed with paint, relying on adhesives and environmentally friendly additives to improve performance; water-soluble PVA cloth requires low-temperature process to balance color fastness and water solubility; high-end fields need to combine double-sided printing, bio-enzyme treatment and other refined technologies. Future development will focus on the multifunctionalization of additives (such as anti-yellowing + color fixation in one), low-carbonization of processes (low temperature/water-free) and intelligent control (uniformity optimization)1
Precise alignment of double-sided patterns to improve strength
Post time: Jul-22-2025