Mocom ALCOLOR Function SAN UV A OR3070-09 is a functional UV-absorbing masterbatch built on a styrene-acrylonitrile carrier and supplied as free-flowing cylindrical granulate. The grade is intended for metering into SAN and SAN-rich formulations at 3.0–5.0 % by mass during injection moulding, sheet extrusion, and compounding. The active radiation-protection component is a benzotriazole-type ultraviolet absorber whose primary absorption covers the UV-A band from 320 nm to 400 nm. This distinguishes the product from colour-only SAN concentrates that distribute pigments or dyes but do not provide active photochemical stabilisation. The OR3070-09 designation refers to a controlled orange colour point, and lot-specific colourimetric values are reported in the certificate of analysis. The SAN carrier is selected for its close refractive-index and solution-parameter match to bulk SAN, which reduces visible haze and flow lines in transparent and translucent mouldings.

Published product-class data for SAN-carrier UV functional masterbatches place carrier density between 1.06 g/cm³ and 1.10 g/cm³ when measured according to ISO 1183-1. The melt-volume-flow rate is designed to allow distributive mixing in short plastication units without excessive dilution of host-polymer modulus. Moisture content at packaging is typically controlled below 0.10 % by Karl Fischer titration. The active absorber is dispersed at the molecular level in the carrier during compounding and remains dissolved under normal storage conditions. If cooling after compounding is too fast, recrystallisation of the absorber can occur at high loadings, producing surface haze or pitting. For the recommended dosage range, the active UV-absorber concentration in the final component is generally expected to fall between 0.15 % and 0.25 % by mass, although exact active content is not published for this configuration and should be confirmed with the manufacturer.

For continuous processing, the masterbatch is preferably introduced through a gravimetric feeder into the main feed port of a co-rotating twin-screw extruder. Extruder specifications for production-scale dispersion include an L/D ratio between 32:1 and 44:1, vacuum venting at −0.08 MPa, and a barrel profile from 180 °C in the feed zone to 230 °C at the die. Specific energy input in the range 0.20–0.30 kWh/kg is typical for SAN-carrier masterbatch dilution. If specific energy rises above 0.35 kWh/kg, melt temperature can exceed 250 °C, leading to visible yellowing and loss of absorber activity. For direct injection moulding, a 150-tonne machine with a 35 mm diameter, 20:1 L/D barrier screw can produce adequate dispersion when peripheral screw speed exceeds 0.08 m/s and back pressure is held near 8 MPa. Lower back pressure can leave isolated masterbatch islands in the melt channel, visible as orange streaks or bimodal colour patterns under transmitted light.

What Distinguishes OR3070-09 from Non-functional SAN Colour Concentrates?

The principal difference is the addition of a UV-absorber chemistry to the colourant package. A pigment-only SAN concentrate modifies colour but leaves the styrenic host polymer exposed to near-UV radiation. In the functional grade, the benzotriazole absorber converts absorbed radiation into low-intensity thermal energy by excited-state intramolecular proton transfer, reducing the formation of free radicals in the SAN phase. Failure of this protective mechanism in unstabilised SAN is measurable by an increase in the FTIR-ATR carbonyl index near 1720 cm⁻¹ after accelerated weathering. Accelerated weathering for validation is performed under ISO 4892-2 cycle 1 with xenon-arc irradiation, an irradiance of 0.51 W/m² at 340 nm, black-standard temperature 65 ± 3 °C, and chamber relative humidity 50 ± 5 %. Under these conditions, SAN plaques containing 4.0 % OR3070-09 are compared with unstabilised controls for yellowness index and colour shift. A ΔE below 3.0 after 1000 h is generally considered acceptable for interior automotive trim and non-load-bearing technical components, although product-specific data for OR3070-09 must be confirmed by the current technical data sheet.

At the molecular level, stabiliser permanence is influenced by migration kinetics in the polymer matrix. Benzotriazole absorbers with moderately high molecular weight exhibit lower diffusion coefficients in SAN than benzophenone alternatives, reducing bloom during prolonged outdoor exposure. The carrier pre-disperses the absorber so that the diffusion distance into the surrounding matrix is shortened. In production-scale twin-screw dilution, this manifests as a reduction in the mixing time needed to reach a coefficient of variation below 5 % in active concentration. Batch-to-batch variability in masterbatch carrier MFR is controlled because a shift greater than 15 % alters the effective letdown shear stress in the moulding machine and can change the final colour appearance.

The SAN carrier also differentiates this product from polyolefin-carrier UV masterbatches. Polyethylene or ethylene-vinyl acetate carriers have lower polar solubility and a larger refractive-index mismatch with SAN, producing visible light scattering and micro-domain haze in polished transparent parts. Because the SAN carrier has a similar glass-transition temperature and viscoelastic response to bulk SAN, the masterbatch disperses without creating a second phase. In glossy injection-moulded surfaces, carrier incompatibility would appear as flow lines, silver streaks, or hazy patches. The absence of a butadiene phase in the SAN carrier prevents light scattering from rubber particles, but it also means OR3070-09 is not an impact-modification route; the host formulation already must contain the required impact modifier. Compared with a PMMA-carrier UV masterbatch, the SAN carrier sits closer to styrenic processing temperatures and avoids the high melt temperatures required for complete PMMA melting.

Thermo-Oxidative Stability and Melt Processing Boundaries

During melt processing, SAN undergoes chain scission and discolouration if temperature and residence time exceed critical limits. For OR3070-09 blends, melt temperatures between 200 °C and 250 °C are typical, with the highest temperature permitted only for short injection cycles. Residence time above 250 °C should not exceed 5 min to avoid visible yellowing of the orange shade and degradation of the UV absorber. Barrel profiles for injection moulding normally run from a feed zone at 180 °C to a nozzle at 230 °C, with the compression zone held at 210 °C. In sheet extrusion, a flat-to-reverse barrel profile is used to maintain melt-viscosity stability. If the addition level rises above 5.0 %, the melt-volume-flow rate shifts in proportion to carrier dilution, and hot-runner pressure may rise or fall depending on the exact carrier viscosity. Published data for this specific configuration is limited, so processing trials are recommended when the dosage approaches 6.0 %.

Pre-drying is mandatory after storage in ambient relative humidity above 60 %. Residual moisture above 0.10 % creates splay marks and can accelerate hydrolytic degradation of the functional additive during melt processing. Desiccant dryers with a dew point of −30 °C or lower and a set point of 80 ± 5 °C for 2–4 h are suitable. For vented-barrel compounding and sheet extrusion, vacuum at 0.08 MPa removes residual moisture and low-boiling volatiles. These moisture requirements are more stringent than for pigment-only colour concentrates because the polar UV absorber can bind atmospheric moisture at the granule surface. Drying should not exceed 6 h at 80 °C because prolonged exposure of the carrier to warm air can cause surface oxidation and colour drift.

An additional failure mode observed on manufacturing lines is plate-out at the die lip. Low-molecular-weight portions of the UV absorber can volatilise at 250 °C and condense on cooler tool surfaces. Die lip plate-out appears as an oily film that disturbs surface gloss and can carry colourant particles, producing specks on the surface. Reducing die temperature below 230 °C and ensuring melt seal at the vent port decreases the plate-out tendency. The condition is most evident when running thin sheet below 1 mm at high throughput because the die residence time is short but the surface area is large.

Injection moulding of SAN/OR3070-09 blends is commonly performed at mould surface temperatures between 40 °C and 80 °C. Higher mould temperatures improve surface gloss and reproduce polished tool surfaces but extend cooling time. Packing pressure is generally 60–80 % of injection pressure, and switch-over is controlled by screw position or cavity pressure rather than timer alone. For thick-wall parts, gate diameters below 0.8 mm may cause jetting or high shear at the gate, disrupting dispersion and producing localised colour variation. In such cases, a tab or fan gate with a land length of 1.0–1.5 mm improves flow-front stability. On hot-runner systems, dead spots and unheated valve-gate areas can produce stationary melt volumes that degrade over time; colour streaks can be eliminated by opening the hot-runner tip heater set point by 5–10 °C only if the residence time remains below the thermal degradation limit.

Clamp force requirements follow the host SAN compound rather than the masterbatch because the addition rate is small. On production machines, cavity pressure is usually kept below 80 MPa to avoid flash and internal stress. A 150-tonne machine in a dedicated production cell with a 32-cavity tool and hot runner at 230 °C can maintain stable mass balance if the masterbatch granule size distribution is within ± 1 mm of the virgin pellet length. This is critical for gravimetric feeding; inconsistent pellet dimensions cause short-term feeder oscillations that appear as colour drift over a 15–30 s period.

When a UV-Absorbing SAN Carrier Replaces Separate Liquid Stabiliser Dosing

In compounding operations that previously injected liquid benzotriazole stabilisers directly into the melt, substitution with OR3070-09 eliminates heated additive feed lines and reduces volatile processing emissions. Liquid dosing systems can exhibit pump fluctuation, especially when the target addition rate is below 0.5 %, causing batch-to-batch variation in stabiliser concentration. A solid masterbatch metered at 3.0–5.0 % through a gravimetric feeder reduces this variability. However, the dispersion mechanism changes: the active component must migrate from the carrier phase into the bulk SAN during melt mixing. In a co-rotating twin-screw extruder with L/D 40:1, screw speed 300–600 min⁻¹, and residence time 30–60 s, homogeneous distribution is achieved for the specified dosage range. In short reciprocating-screw moulding machines without pre-compounding, dispersion may be incomplete if the screw lacks a shear element; polished plaques should be inspected under transmitted light to verify mix quality.

Against an ABS-based UV carrier, OR3070-09 has a narrower compatibility envelope because ABS contains butadiene rubber that contributes impact strength but also introduces a second phase. For transparent SAN glazing, diffuser panels and moisture-vapour packaging, the absence of a rubber phase in the carrier is an advantage. For impact-modified applications, the host polymer must already contain the required impact modifier. Against a PMMA-carrier UV masterbatch, OR3070-09 offers closer thermal and rheological behaviour to styrenic matrices, reducing the risk of viscosity stratification during fast injection velocities. PMMA has a higher glass-transition temperature and can provide better heat resistance in the final part, but it requires higher melt temperatures outside the normal SAN window. Polyethylene and ethylene-vinyl acetate carriers are generally unsuitable for transparent SAN because they create visible domains.

The orange colour reference OR3070-09 introduces a defined CIELAB colour point. Colourimetric control is carried out with a spectrophotometer using D65 illumination and the 10° observer. Lot-to-lot deviations are typically held at ΔE ≤ 0.7 against the master standard. In translucent packaging, transmission spectrophotometry from 400 nm to 700 nm is applied to verify that the UV absorber package does not produce unacceptable absorption in the visible blue region. Benzotriazole absorbers have a tail absorption near 400 nm, so very thick sections can appear slightly yellow; the effect is dose-dependent and should be evaluated at the maximum wall thickness of the final part. For applications requiring yellowness index below 1.0 or light transmission above 92 %, validation is required because the orange colour point inherently shifts the transmission spectrum.

For thick-wall components with wall thickness above 4 mm, the dosage should be held at the low end of the range to limit total absorber loading and avoid a yellow edge effect from the benzotriazole absorption tail. The UV absorber concentration in the core may be lower than at the surface after injection moulding because shear-induced migration can stratify additives; this is measured by UV microspectrophotometry in cross-section. If the core concentration falls below 50 % of the surface concentration, the letdown is not achieving uniform protection and a pre-compounded material may be required.

In coextruded sheet, OR3070-09 is used in the cap layer rather than the substrate. The cap layer thickness is typically 80–200 μm, which requires the masterbatch dosage to be raised to the top of the recommended range to achieve sufficient UV protection. The carrier viscosity must match the cap-layer compound to prevent interfacial wave defects. A viscosity ratio between masterbatch and cap-layer SAN greater than 3:1 can create layer distribution instability at high draw ratios. When the cap layer is thin, the masterbatch is predried with the main resin and fed through a separate gravimetric feeder into the cap-layer extruder.

Accelerated Xenon-Arc Weathering and Standards Verification

For outdoor and high-UV indoor applications, the material is evaluated according to ISO 4892-2 method A. The method specifies xenon-arc apparatus with daylight filters, irradiance 0.51 W/m² at 340 nm, black-standard temperature 65 ± 3 °C, and chamber relative humidity 50 ± 5 %. Plaques containing 4.0 % masterbatch in injection-moulded SAN are aged alongside unstabilised controls. Yellowing is measured by yellowness index and CIELAB colour change. A ΔE below 3.0 after 1000 h is generally considered acceptable for many technical components, but specific OR3070-09 data must be confirmed. For critical lighting or optical applications, UV stabiliser distribution across the part wall may be checked by microtomed cross-sections and UV microspectrophotometry.

Shear rheology of the host compound with 4.0 % masterbatch addition shows a slight decrease in complex viscosity at low angular frequencies, typically less than 8 % compared with unfilled SAN. This shift is within natural lot-to-lot variation for many SAN grades and does not usually require a change in moulding machine settings. At high shear rates above 1000 s⁻¹, the viscosity difference is smaller because the carrier and host polymer share similar polystyrene-type chain segments. In oscillatory shear measurements from 0.1 rad/s to 100 rad/s, the defined cross-over frequency is not strongly changed; therefore moulding pressure predictions from standard simulation software remain valid if the carrier MFR is within the specified range.

The table presents a product-class envelope, not a substitute for the OR3070-09 certificate of analysis. For specific applications, mechanical and optical testing must be performed on moulded or extruded specimens. Tensile properties are evaluated according to ISO 527-2, flexural properties according to ISO 178, and impact properties according to ISO 179-1 as applicable to the final compound. Because the masterbatch carrier has a different molecular architecture than the host polymer, final mechanical values may shift by a measurable amount at higher addition rates. The orange colour point also contributes to lower blue-light transmission; hence optical performance must be defined in terms of the customer’s spectral requirements rather than a generic haze value.

Regulatory compliance is validated against REACH Article 33 for substances of very high concern, RoHS 2011/65/EU for heavy metals and restricted phthalates, and relevant food-contact requirements for styrene-acrylonitrile copolymers where the final component is intended for such use. These statements apply to the product class and should be verified for the specific production batch. In colour-critical applications, the final part should be evaluated under the same light source and viewing geometry used in the customer’s master standard, not solely under a single illuminant. Storage life is governed by moisture ingress and granule surface oxidation. In sealed original packaging stored below 40 °C, the product class remains processable for at least 12 months from the production date. After opening, the masterbatch should be returned to a moisture-tight container and dried before use if ambient conditions exceed 60 % relative humidity. Mixing with other carrier types is not recommended unless compatibility has been confirmed by melt-rheology and optical testing, because carrier phase separation can occur in low-shear regions.