What Does a 120 °C Softening Point Hydrogenated C9 Resin Change in Tenter-Line Core Extrusion?

Addition of NOVARES PURE 1120 to the core layer of a tenter-stretched BOPP film is performed as an in-line gravimetric blend with PP homopolymer pellets, normally after a 15 min low-speed tumble mixing step to reduce hopper stratification. The resin has a nominal softening point of 120 °C as measured by ASTM E28, and its hydrogenated structure provides a Gardner colour below 1 under ASTM D1544; these two parameters define the dosing window rather than the final film properties. The modified PP enters a single-screw extruder with L/D 30–40, a barrier screw, and a melt pump, where the low-molecular-weight resin reduces pressure drop across the melt filter and permits either a 5–12 °C reduction in melt temperature or a higher screw speed at constant torque, depending on the control strategy of the line. In tenter operations producing 20–40 µm film, the resin is typically evaluated in the range of 3–10 wt% of the core layer; published data for this specific grade under full ISO testing are limited, and converter trials must isolate the resin effect from the β-nucleant or additivation package used in the same layer. Tensile modulus is measured according to ISO 527-3, haze according to ISO 14782, and water vapour transmission rate according to ISO 15106-3; because draw ratio and orientation temperature alter the amorphous phase distribution, the same addition level can shift modulus differently on a sequential longitudinal-then-transverse orientation line compared with a simultaneous stretching line. The resin should be pre-dried at 80 °C for 2 h when silo or day-bin relative humidity exceeds 60 %, because absorbed moisture generates micro-voids and die-lip deposits. Extrusion melt temperature should not exceed 280 °C for a residence time above 8 min; although hydrogenation removes reactive unsaturation, thermal-oxidative yellowing can still occur in the presence of oxygen at the feed throat if the blend is starve-fed unevenly. Above 10 wt%, processing trials on comparable hydrogenated C9 grades have shown an increased tendency to form die-lip build-up and reduced transverse-direction stretch uniformity, which appears as gauge bands on the finished roll.

Skin-Layer Seal Initiation, Blocking Thresholds, and Coefficient of Friction

Coextruded BOPP skin layers are usually based on propylene-ethylene or propylene-butene copolymers with a low seal initiation temperature. If NOVARES PURE 1120 is added to a heat-sealable skin layer, the addition level is kept below 5 wt%, and the development target is usually a lower seal initiation plateau rather than a higher ultimate seal strength. Seal strength after 0.5 s dwell and 2 bar jaw pressure is measured by ASTM F2029; hot tack is measured by ASTM F1921. The hydrogenated C9 resin broadens the onset of interfacial melting but also raises the blocking tendency of the wound roll, especially at storage temperatures above 35 °C. Blocking is evaluated through ASTM D3354 or an internal peel-blocking fixture; coefficient of friction is measured by ASTM D1894. Because the skin layer is only 0.8–2.0 µm thick, the resin concentration at the surface is not equivalent to the bulk formulation; film ageing can concentrate low-molecular-weight species at the outer 10–20 nm through surface segregation, even when the skin layer is not directly modified. Above 5 wt%, blocking becomes difficult to control without increasing anti-block masterbatch silica to 0.5–1.5 wt%, which then raises haze beyond acceptable limits for transparent packaging. If surface energy falls below 38 mN/m after corona treatment, as measured by ASTM D2578 wetting tension fluids, print adhesion on solvent-based flexo inks may fail. Consequently, most converters restrict the resin to the core or tie layer and leave the seal skin unmodified unless a specific hot-tack deficit must be corrected.

In white opaque BOPP label film production, the cavitated core layer contains CaCO3 at 8–15 wt%, often with a β-nucleating package that promotes void formation during sequential stretching. NOVARES PURE 1120 is not used as the cavitation agent itself but as a dispersion modifier at 3–6 wt% in the same layer. The low-viscosity resin wets the mineral surface and reduces the agglomerate size that survives the masterbatch dilution stage; this effect is monitored by filter pressure value, film optical defects under a 500 lux light table, and opacity measured according to ISO 2471. Biaxial stretching of the filled layer at temperatures between 145 °C and 160 °C creates elongated voids whose geometry controls the opacity-to-density trade-off; the resin modifies the elongational viscosity of the PP matrix, allowing the voids to extend without excessive film rupture. The final label film is typically 50–70 µm thick, with a density of 0.65–0.85 g/cm³ depending on draw ratio, and is subsequently corona-treated to 38–42 mN/m under ASTM D2578 for UV flexo or offset printing. Die-lip build-up is the primary failure mode when the resin is overdosed or when the CaCO3 grade contains excessive moisture; pre-drying of the mineral masterbatch at 80 °C for 2 h is standard when ambient relative humidity exceeds 60 %. The grade is not a substitute for the cavitation agent, and reducing CaCO3 below the minimum specified by the masterbatch producer while increasing resin concentration leads to incomplete void formation and an opacity loss that cannot be recovered by additional TiO2.

When 40 nm Aluminium Metallization Meets a Resin-Modified Core: Surface Defect Density and Barrier Data

Metallization trials on BOPP films are conducted in a vacuum chamber at 10^-4 mbar to 10^-5 mbar with aluminium wire feed, producing an optical density of 2.0–3.0 and a deposited layer thickness near 40 nm. The resin-modified core film is evaluated for oxygen transmission rate according to ASTM D3985 at 23 °C and 0 % RH, and water vapour transmission rate according to ASTM F1249 at 38 °C and 90 % RH. A clear metallized barrier improvement is not guaranteed by resin addition alone; the barrier depends on the density of pinholes, surface defects, and oligomer-induced weak boundary layers at the metal-polymer interface. In a three-layer coextrusion, NOVARES PURE 1120 is therefore restricted to the core layer, while the metallizable skin remains an unmodified PP homopolymer or a low-additive metallic skin. If the resin is present in the skin above 2 wt%, corona treatment at 38–42 mN/m cannot compensate for the surface segregation of low-molecular-weight resin, and aluminium anchorage failure appears as metal pick-off during tape pull tests. This is tested internally after metallization with a pressure-sensitive tape method adapted from ASTM D3359, although the method is not specific to metallized film. Process control includes residual gas analysis of the vacuum chamber, because moisture and volatiles released from the film during pump-down suppress adhesion; films containing NOVARES PURE 1120 are therefore held in a low-humidity storage room at 35–40 % RH for 24 h prior to metallization. Published quantitative barrier improvement figures for this specific grade in metallized BOPP are limited; converter trials generally report that the benefit is an improvement in film flatness and drawability rather than a direct drop in oxygen transmission.

The qualification matrix applied to the modified film follows the standards listed below.

High-speed tobacco overwrap lines running at 300–450 packs/min require a 16–20 µm BOPP film with high stiffness, low elongation, and a neutral odour profile. In this application, NOVARES PURE 1120 is evaluated in the core layer at 3–5 wt% to raise the secant modulus measured by ISO 527-3 and to improve cut-and-fold deadfold on the wrapping stations. The skin layers remain an unmodified sealable PP copolymer to avoid changes in organoleptic performance and to maintain seal integrity at high speed. Odour and sensory carry-over are qualified by DIN 10955:2008; because the overwrap is not in direct contact with tobacco in the sealed pack, the primary concern is volatile transfer into the pack headspace. Process limitations appear when the resin loading exceeds 5 wt% in the core: elongation at break can fall below the level required for the initial fold, and the film may split at the crimp edges on older overwrappers that use reciprocating sealing jaws. Moisture barrier is confirmed by ISO 15106-3, and optical clarity is checked by ISO 14782. For this specific tobacco configuration, published data with NOVARES PURE 1120 are limited; the industrial practice is to run a controlled plant trial using the same batch of resin, PP, and masterbatch that will be used in production, because the sensory threshold is not predicted by physical constants alone.

Evaluating Silicone Anchorage on Corona-Treated BOPP Tape Backing Containing NOVARES PURE 1120

BOPP pressure-sensitive tape backing in thickness from 30 µm to 50 µm is often a three-layer film with a stiff core and a release- or adhesion-modified skin. NOVARES PURE 1120 at 5–10 wt% in the core raises tensile modulus and reduces elongation under unwind tension, which improves slitting and tape conversion at speeds above 500 m/min. The side to be silicone-coated is corona-treated to 38–44 mN/m as measured by ASTM D2578 before silicone application. Low-molecular-weight hydrocarbon resin that migrates into the skin can create a weak boundary layer that reduces silicone anchorage; this is detected by a rub-off test after solvent extraction and by stable peel adhesion according to AFERA 5001 or FINAT FTM 1. If the resin is inadvertently compounded into the release skin instead of the core, the low-molecular-weight fraction can bloom under warm storage and the silicone layer can delaminate during unwinding. The operational boundary is therefore structural: resin belongs in the core, and release-layer migration must be checked after 30 days at 40 °C. Surface energy decay below 36 mN/m during post-corona ageing is a rejection criterion; inline plasma treatment immediately before silicone coating is sometimes used but does not remove surface-segregated resin already present after film winding. For direct food-contact tape applications, the entire film construction must still meet overall migration below 10 mg/dm² under EN 1186-1, and the specific monomers or additives in the food-contact layer must comply with EU 10/2011; NOVARES PURE 1120 itself is not a direct food-contact layer component unless the film’s migration testing demonstrates compliance.