Non-woven fabric color masterbatch: Coloration scheme, process compatibility and quality control 

In the production process of non-woven fabric, color masterbatch is the core coloring material for achieving dyeing of the base liquid. It uniformly disperses high-concentration pigments into the carrier resin, directly giving the fibers their color through melt spinning or spunbonding processes, eliminating the subsequent dyeing procedure. Compared with post-treatment dyeing, the direct dyeing route in the original liquid has clear advantages in terms of color fastness, processing cost and environmental emissions. However, for the production of non-woven fabric, the selection of color masterbatch needs to particularly consider process constraints such as fineness, filtration performance and spinning stability. 

Material composition and technical features 

The Non-woven fabric color masterbatch is composed of three parts: pigments, carriers and dispersing aids. 

The pigment system is the core component of non-woven fabric color masterbatches. The pigments used in spinning-grade color masterbatches must meet the following conditions: the heat resistance temperature is higher than the spinning process temperature (polypropylene spinning is approximately 220℃ - 280℃, polyester is approximately 280℃ - 300℃) by more than 20℃; they do not decompose or change color during the melt extrusion process; the particle size is controlled below 1μm to ensure that the spinneret holes (with diameters typically ranging from 0.2 to 0.8mm) are not clogged; the heavy metal content complies with food contact material standards such as GB 4806 or FDA. 

The carrier resin is usually selected as the same type of polyolefin (polypropylene or polyethylene) as the target non-woven fabric substrate. The melt index (MFI) is controlled within the range of 25-50g/10min, slightly higher than that of the base resin, to ensure good fluidity and compatibility in the spinning melt. The compatibility between the carrier and the base resin directly affects the retention rate of the mechanical properties of the fibers. 

The dispersing agents include low-molecular-weight waxes and coupling agents. Their function is to reduce the cohesive force between pigment aggregates, promoting the uniform disintegration and dispersion of the particles in the carrier under the action of shear force. The selection of the agents should take into account both lubricity and heat resistance, avoiding volatilization at high temperatures that may cause gas (foaming) or precipitates (scale) to form. 

Key performance indicators of spinning-grade color masterbatches 

The quality requirements for color masterbatches used in non-woven fabric spinning are different from those for color masterbatches used in injection molding or extrusion. The following indicators directly affect the production stability and product quality: 

Filterability (Filter Pressure Value, FPV): This is one of the most crucial indicators for spinning-grade color masterbatches. After mixing the color masterbatch with the base material in a certain proportion and in the molten state, the pressure difference before and after passing through a filter with a specified mesh size is measured. The higher the FPV value, the more large particle impurities or pigment agglomerates are present in the color masterbatch. The FPV value of high-quality spinning-grade color masterbatches is typically ≤ 1.0 MPa·cm²/g, and the pressure rise rate during the spinning process is gentle, with the pressure increase not exceeding 30% of the initial value within a single usage cycle. 

Filtering value (DF value): An indicator used to characterize the content of particles larger than 5μm in color masterbatches. The lower the DF value, the better the pigment dispersion. Generally, the DF value of color masterbatches should be ≤ 2.0. For ultra-fine filament spinning (single filament fineness < 1.0 dtex), the DF value is recommended to be controlled at ≤ 1.0. 

Thermal stability: The thermal decomposition temperature of the color masterbatch is determined through thermogravimetric analysis (TGA). It is required that the weight loss rate should be ≤ 0.5% within 30 minutes at the spinning process temperature to prevent the accumulation of decomposition-generated gases in the spinning box, which could cause broken fibers or bubble fibers. 

Coloring power and color difference control: The color difference between different batches of the same color code should be controlled within ΔE ≤ 0.8 (D65 light source, 10° viewing angle), and the coloring intensity deviation should be ≤ ±3%. 

Application scenarios and product correspondence relationship 

The requirements for color masterbatches vary significantly depending on the type of non-woven fabric used: 

Medical and healthcare use non-woven fabrics: such as surgical gowns, masks, sanitary napkin linings, etc., have the strictest requirements for the safety of color masterbatches. They need to use a pigment system that meets food contact grade standards, without the presence of heavy metals (lead, cadmium, mercury, hexavalent chromium, etc.) and specific aromatic amines. At the same time, it is necessary to ensure that the anti-static or hydrophilic additives added to the color masterbatch do not interfere with the breathability and liquid penetration performance of the non-woven fabric itself. 

Cotton lining fabric and shoe materials: These non-woven fabrics have certain requirements for color saturation and sunfastness. The light resistance of the color masterbatch needs to reach ISO 105-B02 standard 4-5 or above to meet the need that the clothing does not fade easily during wearing and storage. 

Filtering material: Non-woven fabric used for air or liquid filtration. The color masterbatch must ensure that the pigment particles do not precipitate or migrate during the spinning process, to prevent fine particles from falling out and contaminating the filtering medium. At the same time, the ash content of the color masterbatch itself should be controlled at a relatively low level (≤0.5%) to avoid affecting the filtration accuracy. 

Geotextile and agricultural fabric: For such outdoor application scenarios, the weather resistance of color masterbatches is highly required. Anti-ultraviolet stabilizers need to be added to ensure that the color of the non-woven fabric does not change significantly within 1-2 years of outdoor use (ΔE ≤ 5). 

Selection and practical suggestions for use 

Addition ratio: The recommended addition amount of conventional Non-woven fabric color masterbatchis 1% to 5%. An excessively high addition amount not only increases the cost but also leads to a decrease in fiber strength due to excessive pigment (typically, for every 1% increase in addition amount, the fiber breaking strength decreases by approximately 2% to 5%). It is recommended to determine the minimum effective addition amount through small sample production. 

Homogeneity of premixing: The degree of uniformity in the mixing of color masterbatch with the base resin directly affects the color difference of the finished product. It is recommended to use a high-speed mixer for premixing, with a mixing time of no less than 5 minutes. Regularly check the degree of uniformity (by inspecting the color differences of the mixed materials at different positions for assessment). 

Drying requirements: The color masterbatch may absorb moisture during storage. It is recommended to dry it at 80°C - 90°C for 2 - 4 hours before spinning, with the moisture content controlled below 0.1% to reduce the risks of hydrolysis and bubble fibers. 

Color change cleaning: When changing the color masterbatch type or color, it is recommended to use a high-MFI polypropylene washing machine material to thoroughly clean the screw and spinning box body to prevent residual materials from mixing in and causing color differences and clogging of the screen. 

Overall, non-woven fabric color masterbatches are a type of auxiliary material with a relatively high technical threshold in the liquid dyeing process. Their quality directly affects the operational efficiency of the non-woven fabric production line and the consistency of the product quality. When selecting, the focus should be placed on three core indicators: filtration, thermal stability, and batch stability, rather than simply focusing on pigment concentration or price factors. By coordinating with standardized drying, mixing, and color-changing management, stable and predictable coloring effects can be achieved.