NOVARES CA80 is a phenol-modified coumarone-indene resin supplied in pastille and flake form, with a softening point typically reported at 75–85 °C under DIN ISO 4625-1. The product is used in solventborne printing inks and overprint varnishes where a hard aromatic binder with low acid value, moderate hydroxyl character, and controlled solvent-release behaviour is required. The grade designation CA80 denotes the phenol modification and the nominal softening point near 80 °C. Unlike petroleum C9 hydrocarbon resins, the indene-coumarone backbone contains fused aromatic rings that increase refractive index and film hardness at relatively low addition levels. The phenolic modification shifts the surface interaction with organic pigments and reduces the acid-base reactivity that can appear with rosin-modified phenolics. Routine specification control covers softening point, Gardner colour, acid value, ash content, and solvent clarity in a 50 wt% toluene solution. Because CA80 is thermoplastic and non-reactive, it functions as a modifying binder rather than a crosslinkable film former.

On production-scale bead mills, direct addition of solid pastilles can create transient elastic masses at the screen gap if mill-base temperature exceeds 50 °C before dissolution is complete. The failure mode is minimized by pre-dissolving CA80 at 40–45 °C in a high-shear dissolver with a tip speed of 18–22 m/s before the milling stage. In a 1000 kg batch, pre-dissolved resin typically reduces cycle time by 15–25 min compared with direct addition of flakes, based on production runs with horizontal bead mills using zirconia media of 0.6–0.8 mm. Filtration through a 10–20 µm cartridge after cooling removes trace gel particles and prevents screen plugging at the printing press.

For a resin of this softening range, the melt viscosity at 150 °C is generally in the range 0.5–2 Pa·s by rotational rheometry. The solution viscosity at 50 wt% in toluene is typically 50–150 mPa·s at 23 °C under ISO 2555. These values are class-typical rather than grade guarantees, and batch release should be verified against the supplier’s certificate of analysis.

What shifts in resin architecture occur when phenolic moieties are copolymerized into indene-coumarone chains?

A conventional coumarone-indene resin consists primarily of polymerized indene, coumarone, styrene, and related aromatic monomers, producing an oligomer with low hydroxyl content and a softening point controlled by chain length and aromatic substitution. When phenol or a substituted phenol is introduced during polymerization, the resulting oligomer retains the aromatic solubility parameter but acquires hydrogen-donor sites. The resin class generally shows number-average molar mass values in the range 600–1000 g/mol with a polydispersity of 2–3 measured by size-exclusion chromatography using polystyrene standards. The hydrogen-bonding sites change pigment-wetting behaviour and raise low-shear viscosity at equal solids. Under cone-and-plate rheometry on an Anton Paar MCR 102 at 23 °C, the effect appears as a faster recovery of the low-shear viscosity plateau at 0.1 s⁻¹ after preshear at 1000 s⁻¹ and a lower Casson yield stress in carbon-black offset ink mill bases than unmodified coumarone-indene resin at the same softening point. Quantitative adsorption isotherms for CA80 on pigment-grade surfaces are limited in the public literature; comparative supplier data show the practical difference mainly in mill-base viscosity and tack stability rather than in printed colour strength alone.

In offset ink mill bases ground on a three-roll mill at 40 °C, pigment wetting can be assessed by changes in Hegman fineness under ISO 1524 and by blade-out drawdown gloss. When CA80 is used at 12 wt% of a carbon-black formulation, the fineness after two passes is typically 7–8 units, with a mill-base viscosity of 80–120 Pa·s at 25 °C and 0.1 s⁻¹. Published data for this specific grade are limited; the values reflect the product class and should be confirmed by laboratory trial.

A standard sheetfed offset letdown vehicle is prepared by dissolving 35–45 parts of CA80 with 15–25 parts of high-viscosity linseed alkyd and 30–40 parts of aromatic distillate. The vessel is heated to 60–70 °C under an anchor stirrer; after dissolution, the varnish is cooled to 25 °C and filtered through a 10–20 µm cartridge. A clear solution with no haze after 24 h at 20 °C is the basic compatibility check. Haze in this test generally indicates that the aromatic content of the solvent blend has fallen below the resin’s solubility window, or that a high-alkane diluent was introduced too rapidly.

Formulation limits in high-solids gravure and heatset offset vehicles

In toluene-based publication gravure ink, CA80 is typically added at 8–15 wt% of the liquid ink and combined with nitrocellulose, dibutyl phthalate, and ketone solvents. The resin increases the glass transition temperature of the dried ink film and improves block resistance at press speeds up to 300 m/min. The low acid value of ≤1 mg KOH/g reduces the risk of acid-catalyzed degradation of nitrocellulose during storage at 40 °C for 28 days as evaluated by solution viscosity retention under ISO 2555. In heatset web offset, CA80 is introduced into the letdown varnish at 15–25 wt% of vehicle solids, where it contributes to ink setting and reduces retained mineral oil after forced-air drying at 130–160 °C. Residual solvent after laboratory drying at 160 °C for 2 s is typically below 0.5 wt% when measured by thermogravimetric analysis with infrared detection.

In high-solids overprint varnishes, CA80 is used at 10–30 wt% of resin solids. At the upper limit, varnish viscosity may rise above 1500 mPa·s at 23 °C under ISO 2555; this requires letdown with aromatic solvents or dibasic esters to maintain application viscosity below 60 s in a DIN 4 mm flow cup at 23 °C per DIN 53211. Hardness development in overprint varnishes applied to paperboard is commonly tracked by König pendulum damping under ISO 1522 after 24 h at 23 °C and 50% relative humidity. The observed hardness difference depends on co-resin and plasticizer level, and published data for this specific substitution is limited.

On a commercial heatset web offset line with a dryer temperature of 150–180 °C and web speed of 10–15 m/s, CA80-containing inks demonstrate faster ink setting than straight hydrocarbon-modified systems. The setting rate is measured by the interval between impression and dry rub resistance. The resin’s high softening point produces a sharp viscosity rise during cooling, which is beneficial for dot sharpness but can increase misting at high press speeds if the tack is not reduced with mineral oil.

Differences from other resin classes are most evident in acid value, solvent tolerance, and interaction with reactive additives. Rosin-modified phenolics used in offset vehicles often show acid values between 15 and 25 mg KOH/g; this acid functionality improves adhesion to metal pigments but can create viscosity drift with amine-neutralized acrylic dispersions. CA80, with an acid value of ≤1 mg KOH/g, avoids the competing acid-base equilibrium. Relative to C9 aromatic hydrocarbon resins, CA80 is less tolerant of pure aliphatic hydrocarbons but shows better compatibility with ketone-soluble polyamide binders and nitrocellulose, as judged by cloud point titration under ISO 3015. Relative to polyterpene resins, CA80 generally has a higher aromatic content and a more pronounced Gardner colour. The resin is therefore selected where hardness, gloss, and solvent-release behaviour in aromatic and ester solvent blends are more important than aliphatic dilution capacity.

When aliphatic diluents exceed 20% of the letdown solvent blend

Because CA80 is a high-aromaticity resin, formulators should maintain the aliphatic fraction below the phase boundary when designing low-odour or low-tack vehicles. If more than 20–25 wt% of the letdown solvent is aliphatic hydrocarbon, the resin may separate as haze or a soft precipitate when the temperature falls to 15 °C. The actual cloud point depends on the aromatic content of the aliphatic stream and on co-resin concentration. For low-odour mineral spirits with aniline point above 70 °C, tolerance can fall below 15 wt%. The incompatibility is observable as filter cake on 10 µm bag filters after storage at 5 °C, and also as a loss of gloss and transfer stability in long press runs. In systems requiring high aliphatic tolerance, part of the CA80 content should be replaced with a hydrogenated hydrocarbon resin or a rosin ester, but the substitution reduces film hardness and may increase tack.

CA80 is supplied in multi-layer paper bags of 25 kg or bulk bags of 500–1000 kg. The pastille form reduces dust formation and improves flow through loss-in-weight feeders. Blocking can occur above 35 °C; warehouse temperature should remain below 30 °C with relative humidity below 60%. In unopened bags, shelf life is typically 24 months.

In metal decorating, CA80 is used as a hard thermoplastic modifier in epoxy ester or polyester-melamine coatings at 5–15 wt% of total solids. The resin contributes to overprint varnish flow and adhesion to printed tinplate after stoving at 180–200 °C for 10–12 min; adhesion is evaluated by cross-cut tape test under ISO 2409. Because the resin is non-reactive, crosslink density remains controlled by the aminoplast or phenolic resole component. For food-contact applications, the finished coating must be tested under FDA 21 CFR 175.300; the final regulatory status depends on extraction testing of the formulated and cured film rather than on the resin alone.