Masterbatches for Fiber Extrusion | Rifra

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Fiber Extrusion

Extrusion and Spinning

Rifra addresses the critical issues of fiber extrusion by understanding the physical and chemical mechanisms behind defects. Whether it involves hopper bridging, shark skin at the spinneret, water carry-over, or fouling of hot drawing rollers, the technical team identifies the root cause and proposes targeted masterbatch solutions. The Filter Test is a fundamental diagnostic tool: it certifies the cleanliness of the formulation and prevents filter clogging, the main cause of downtime and defects. With a complete range of anti-blocking agents, rheological modifiers (melt strength), PPA, thermal stabilizers, antistatic agents, and hydrophobic agents, Rifra intervenes at every stage of the process—from material preparation to yarn collection.

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Phase one

1. Dosing and Preparation of Raw Materials

In the production process of polymeric yarns, the first fundamental step is the dosing of raw materials. Dosing systems are predominantly gravimetric or mixed (with both volumetric and gravimetric systems in series). At this stage, it is essential that products have good dosability, achieved through uniformity of granule size, ensuring they are not caked and have not absorbed water. The phenomenon of caking—the tendency of granules to aggregate—can occur in bags or during plant feeding, especially when the hopper is not insulated and reaches temperatures above 40-50°C. Essential plant measures and controls on raw materials fed into the line include:

Where applicable, gravimetric dosing: ensures precision and repeatability in masterbatch feeding.

Inhibit granule caking: a critical issue managed with balanced formulation and adherence to maximum use-by dates.

Granule caking in storage: managed with anti-blocking agents in the formula and recommendations on maximum use-by dates.

Phase two

2. Extrusion and Spinning

Extruders in fiber extrusion are predominantly single-screw, equipped with filtration systems both in the extruder and on the extrusion head. Filter packs are designed to allow filter replacement without stopping the machine, with pressure sensors signaling the limit. Downstream of the extruder filter, there is almost always a volumetric metering pump that ensures constant back pressure. The spinneret can be circular or rectangular, equipped with numerous holes whose shape depends on the desired cross-section of the filament (circular, trilobal, oval, etc.). An extremely critical parameter at the outlet is melt strength: a rheological property of the melt that depends on raw materials and processing conditions. Specific points of this technology include:

Volumetric pump downstream of the filter: ensures constant back pressure at the spinneret and consistent denier.

Controlled melt strength: a critical parameter that determines the stability of the yarn exiting the spinneret.

Materials with excellent filterability: selection of raw materials and careful dispersion in the carrier matrix of the masterbatches.

Common defects related to this phase include:

1

Molten Yarn Instability

When melt strength is insufficient, the yarn does not maintain a straight trajectory: instead of falling vertically, it ‘rotates,’ oscillates, or forms loops (looping), making proper start-up and stable drawing impossible.

2

Shark Skin

A phenomenon that appears above a certain flow rate, describable as a permanent modification of the yarn surface (micro-fractures). It makes the yarn less resistant to drawing, with a dull appearance and rough texture.

3

Die Build-Up

Accumulation of degraded material or low-volatility components around the spinneret holes. Causes irregularities in yarn cross-section, frequent breaks, and the need for periodic spinneret cleaning with machine downtime.

Phase three

3. Cooling and Drawing

Upon exiting the spinneret, filaments can be cooled in water, air, or by contact with cold rollers. In water cooling, a critical issue is water carry-over: the drawing speed can cause some formulations to retain water on the yarn, creating problems in subsequent processing stages. Downstream of cooling, drawing and annealing are performed. Drawing imparts the necessary mechanical properties to the yarn, particularly tenacity. Annealing fixes the drawing conditions over time. These stages use ovens and/or both hot and cold cylinders. Hot cylinders can become fouled by migration of low-melting components present in the yarn. Specific elements of this technology include:

Water carry-over: hydrophobic formulations reduce water retention on the yarn after the cooling bath.

Drawing: orients molecules in MD, imparts tenacity and mechanical strength to the yarn.

Hot roller fouling: anti-blocking agents and thermal stabilizers minimize surface migration.

The main critical issues are:

1

Water Carry-Over

Some formulations tend to retain water on the yarn after the cooling bath. This creates problems in subsequent stages and can cause surface defects and denier variations.

2

Hot Roller Fouling

Migration of low-melting components from the formulation to the hot drawing and annealing cylinders causes deposits that alter the coefficient of friction, generate surface defects on the yarn, and require machine downtime for cleaning.

3

Yarn Breakage During Drawing

During the orientation phase (hot and cold drawing), the yarn cannot withstand tensile stresses and breaks. Insufficient melt strength prevents the yarn from being drawn without breaking, leading to frequent machine downtime and high scrap rates.

Phase four

4. Yarn Collection and Finishing

The final stage of the process is yarn collection, which occurs with winding systems. At this stage, surface treatments with spin finishes are often performed: liquid products with specific characteristics that impart lubrication, cohesion between filaments, and antistatic effect to the yarn. Spin finishes are essential for yarn processability in subsequent transformation stages (weaving, knitting, nonwovens), reducing friction between yarns and guides/rollers and preventing breaks and oscillations. Package quality—uniformity of tension, absence of surface defects, denier consistency—is the final parameter that certifies the quality of the entire production process.

Critical issues include:

1

Denier Irregularity

Variations in yarn diameter along its length (denier irregularity) are the consequence of upstream instability: melt strength fluctuations, pressure variations at the spinneret, or irregularities in masterbatch dosing.

2

Package Blocking

Adhesion between yarn layers in the package (blocking) is caused by low surface energy components or insufficient anti-blocking effect of the formulation. It makes yarn unwinding difficult in subsequent stages.

Markets

Markets for Fiber Extrusion

In fiber extrusion, every instability or defect is a signal. Not simply an inconvenience, but a starting point for understanding the process, identifying causes, and improving its balance. The critical issues you encounter daily—from granule caking to melt strength management, from shark skin to water carry-over, to hot roller fouling—are not problems to tackle alone. They are the common ground on which we build solutions together. Our role is not limited to supplying color masterbatches and additives, but to support you as a technical and problem-solving partner. Every variable is read as part of a complex system, to contribute to process stability and finished yarn quality.

Products

Product Line for Fiber Extrusion

Rifra has operated for decades alongside polymeric yarn producers, with deep knowledge of the critical issues of this process: from granule caking in hoppers to melt strength management at the spinneret, from shark skin to water carry-over in the cooling bath, to hot roller fouling during drawing. This technical expertise translates into color masterbatches and additives that meet aesthetic and functional requirements and actively contribute to process stability and finished yarn quality. Each product is developed to optimize the production process and ensure the best aesthetic and functional result, with a focus on sustainability and the circular economy.

Color Masterbatches

Our design rules for color formulations

Rifra has always chosen not to focus on producing standard formulas, but on custom developments to maximize color performance and enhance the product for the customer’s specific end use. In fiber extrusion, pigment selection is particularly critical: Low deniers require maximum attention to dispersion to avoid filter clogging. Rifra guarantees maximum pigment dispersion and compatibility with the polymer matrix, ensuring consistent yarn quality. The following table is a tool for this ongoing dialogue. It relates the most common critical issues with the mechanisms that generate them and, above all, with the synergistic strategies we can activate together. From our complete range of additives, such as anti-blocking agents, rheological modifiers (melt strength), PPA, thermal stabilizers, antistatic agents, and hydrophobic agents, to process guidelines that maximize their effectiveness, each entry is a starting point for targeted technical conversation. We work on the same side of the bench. Your process challenge is our development priority.

Regulated and High-Performance Sectors	Values for Products	How to Obtain Value from Rifra Formulas
Early Childhood and Toys	Yarns for sewing and assembly of plush toys and soft toys. Bright colors stable to washing. Tensile and break resistance for child safety.	Selection of non-toxic pigments. Maximum dispersion to avoid color variations on low-denier yarns. Fastness to washing and artificial saliva.
Medical	Yarns for nonwoven fabric production. Standard colors and fully traceable formulations.	Maximum dispersion and filterability during the spinning process. Formulations are developed by selecting pigments and additives that are non-toxic and resistant to sterilization processes.
Electrical / Electronic	Conductive or insulating yarns for wiring and coatings. Colors for functional coding (e.g., red for phase, black for ground). Heat and flame resistance.	Pigments selected not to interfere with the electrical properties of the yarn. Thermal stability in high-temperature processes. Possibility of formulations with flame-retardant additives that do not interact with color.
Automotive	Yarns for interior fabrics (seats, headliner coverings) and technical components (belts, brake hoses). Resistance to UV rays, heat, and abrasion. Colors stable over time.	Pigments with extremely high light and heat fastness. Selection of chemistries that do not interact with UV and thermal stabilizers. Maximum dispersion for low-denier yarns.
Food Packaging	Yarns for bags and nets for packaging fruits, vegetables, and food. Coloring as a distinctive brand of the producer. High tenacity and wear resistance during transport and storage.	*Compliance with food contact regulations (EU 10/2011). Selection of pigments with very low migration. Dispersion optimization to maintain yarn mechanical properties. Support in final product certification.

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Sectors with high aesthetic impact and durability	Value for manufactured goods	How to obtain value from Rifra formulas
Furnishing Elements	Yarns for upholstery fabrics (sofas, armchairs, curtains). Colors stable to sunlight and artificial lighting. Resistance to abrasion and rubbing.	Pigments with high light fastness (at least scale 6-7 blue scale). Selection of chemistries that do not yellow over time. Maximum dispersion for chromatic uniformity on large textile surfaces.
Household Goods	Yarns for household fabrics. Colors resistant to washing and approved for food contact.	Pigments with high color fastness, possibility of custom color development.
Outdoor furniture	Yarns for outdoor fabrics (awnings, garden cushions, umbrellas). Colors resistant to UV rays, mold, rain, and salt spray. Maximum aesthetic durability.	Pigments selected for very high weather fastness. Formulas with anti-mold and anti-UV additives that do not negatively interact with color. Stability to wet-dry cycles.

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Specialized high-stress sectors	Value for manufactured goods	How to obtain value from Rifra formulas
Non-Food Packaging	Yarns for big bags, industrial sacks, and cargo nets. Colors for product coding and hazard identification (e.g., orange for hazardous substances). Maximum tenacity and tear resistance.	Selection of pigments with minimal impact on mechanical properties. Dispersion optimization to avoid discontinuity points under load. Resistance to solvents and aggressive chemical agents.
Construction	Yarns are designed to have significant mechanical strength and resistance over the service life.	Rifra’s choice is to select pigments and dyes that have minimal interaction with the polymer matrix, so as not to modify the yarn mechanics. High color fastness and selection of chemistries that do not interfere with other additives present (e.g., flame retardant, anti-UV, etc.).
Apparel / Accessories	Yarns for technical garments and fashion accessories. Bright and saturated colors. Resistance to washing, perspiration, sunlight, and rubbing. Softness and comfort on the skin.	*Selection of pigments with high wash and light fastness. Maximum dispersion for very low-denier yarns (e.g., 20-50 denier). Formulas that do not release additives that alter the fabric’s hand feel.
Sports Equipment	Yarns for ropes, sports nets, climbing straps, technical shoes. High-visibility colors for safety. Maximum resistance to tension, abrasion, repeated flexing, and atmospheric agents.	Pigments with minimal interaction on tenacity and elongation at break. Selection of chemistries compatible with EN certification requirements (e.g., standards for harnesses and ropes). Stability to ozone, UV, and humidity.
Artificial Turf	Whether FIFA-approved fields, LND, or sports facilities in general, yarn quality must be maximum. Minimal thermal shrinkage, minimal color variations over time, maximum yarn resistance to abrasion wear and atmospheric agents.	The formulation choice for the pigment part is very careful, drawing from a list of raw materials already tested according to F.I.G.C. – LND and FIFA regulations. Selection rules are completed by in-depth knowledge of additives related to sector performance and a consequent ability to select raw materials that do not negatively interact with the total raw materials in the recipe.
Agriculture	Yarns are predominantly designed for outdoor use. Mechanically resistant to tension and abrasion.	Rifra’s choice is to select pigments and dyes that have high weather fastness to ensure that the yarn retains its initial coloring as well as possible even when subjected to the aggressive action of atmospheric agents and chemical compounds used in the sector.

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Additive Masterbatches

Our long-standing additive solutions

As with all well-done things, the best result is obtained through teamwork. Rifra translates this motto by favoring solutions that combine color formulation with the most performant chemistries, providing ‘all-in-one’ additive structures directly in the plant. Rifra COMPLEX for fiber extrusion are multifunctional masterbatches that integrate the functionalities of multiple additives, optimized for the specific process conditions: high drawing speeds, melt strength criticalities, the need for clean and defect-free surfaces, yarn durability in outdoor applications. The synergy between components guarantees performance superior to the sum of the parts, with a single addition to the process.

Value for Products	Process Benefits	Properties
Matte yarn more resistant to breakage in the machine direction.	The yarn production process becomes more stable because the additive modifies the melt strength of the material exiting the spinneret, limiting the movement of the filament itself. More stable filaments at the spinneret reduce breakage events both at the spinneret and during the drawing phase.	ANTIBLOCKING + MECHANICAL MODIFIER
Filament with smooth, glossy surface free of roughness.	PPA lubricates the metal surfaces of spinneret holes, lowering pressure and temperature and extending cleaning cycles.	PROCESSING AID (PPA)
Fiber with tenacity preserved after drawing and winding.	Antioxidant protection prevents thermal degradation during residence in the melter and head, maintaining molecular weight.	ANTI-UV
Yarn for outdoor applications with mechanical stability and color over time.	The combination of UV absorbers and HALS minimizes accumulation on the spinneret and protects the polymer from photodegradation in use.	UV STABILIZER + HALS
Fiber or monofilament with low surface friction for textile processes (knitting, weaving).	The addition of internal slip agents reduces the coefficient of friction between fiber-metal and fiber-fiber, improving slipperiness and reducing pilling formation.	INTERNAL SLIP AGENT
Self-extinguishing yarn for carpets, rugs, or technical fabrics.	The compatibility of the flame-retardant system with stabilizers prevents spinneret corrosion and maintains a stable process window.	FLAME RETARDANT
Antistatic yarn for clean rooms or electronic applications.	The dissipative system eliminates electrostatic charges during winding and weaving, reducing dust attraction and formation defects.	ANTISTATIC

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Complex Masterbatches

Our Best Formulations: COMPLEX

As with all well-done things, the best result is obtained through teamwork. Rifra translates this motto by favoring solutions that combine color formulation with the most performant chemistries, providing ‘all-in-one’ additive structures directly in the plant. Rifra COMPLEX for fiber extrusion are multifunctional masterbatches that integrate the functionalities of multiple additives, optimized for the specific process conditions: high drawing speeds, melt strength criticalities, the need for clean and defect-free surfaces, yarn durability in outdoor applications. The synergy between components guarantees performance superior to the sum of the parts, with a single addition to the process.

Rifra solutions	Synergistic advantage	Guaranteed efficiency
RIFRACHEM CX PPA	The synergy between color and PPA produces yarn with a particularly smooth surface, free of aesthetic defects and with constant cross-section. PPA stabilizes flow at the spinneret, reducing melt fracture and die build-up, preserving chromatic homogeneity.	Drastic reduction of downtime for spinneret cleaning and breaks due to cross-section non-uniformity. Stable process, higher line speed, uniform color throughout production.
RIFRACHEM CX PPA + ANTIOX	The synergy between color, PPA, and antioxidant guarantees glossy yarn with mechanics preserved from thermo-degradative attacks of the process. The antioxidant protects the polymer and pigment from thermal degradation in the barrel; PPA enhances plant performance.	Maintenance of mechanical properties (tenacity, elongation) and chromatic brilliance even after prolonged extrusion. No gel formation or color alteration.
RIFRACHEM CX PPA + ANTIOX + ANTIBLOCK	The synergy between color, PPA, antioxidant, and antiblocking imparts a surface finish that adds an anti-blocking effect essential in subsequent yarn processing (weaving, braiding, winding). PPA ensures cross-section stability; the antioxidant preserves mechanics and color.	Very high control throughout the plant. No blocking between coils in the package, fewer tears during conversion, consistent chromatic and mechanical quality batch after batch.
RIFRACHEM CX PPA + ANTISTATIC	The synergy between color, PPA, and antistatic guarantees glossy yarn with short/medium-term antistatic performance. The antistatic supports yarn flow along all operating units (guides, rollers, winding heads), exerting a lubricating effect that does not alter the surface or color.	Drastic reduction of dust formation from yarn-metal friction. Less machine wear, cleaner yarn, superior surface and chromatic quality.
RIFRACHEM CX PPA + UV	The synergy between color, PPA, and UV stabilizer produces yarn for outdoor applications (awnings, agricultural nets, ropes, geotextiles) with smooth surface and integrated solar protection. PPA ensures process stability even with UV loads; UV protection preserves color from bleaching and polymer from embrittlement.	Chromatic and mechanical stability after prolonged exposure. No embrittlement, loss of breaking load, or color bleaching. Ideal for high-durability yarns in outdoor environments.
RIFRACHEM CX PPA + FR	The synergy between color, PPA, and flame retardant produces self-extinguishing yarn for curtains, technical coatings, upholstery. PPA prevents the pressure increase at the spinneret typical of FR loads, maintaining smooth surface, constant cross-section, and chromatic uniformity.	Stable fire reaction class, maintained aesthetic and chromatic quality, less machine downtime for cleaning even with high-load FR formulations.

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