Emulsão de VAE de viscosidade média para adesivos de cigarros JZ-II

In continuous high-speed cigarette assembly, the adhesive applied to the longitudinal side seam and the filter-tipping interface must transition from a flowable coating to a load-bearing bond within milliseconds. The product Cigarette Adhesive JZ-II is a medium-viscosity vinyl acetate-ethylene (VAE) copolymer emulsion engineered to meet this requirement across equipment platforms including the Molins Mark 9, Hauni Protos-M8, and GD121 lines. Its polymer backbone, polymerised from vinyl acetate monomer with an ethylene co-monomer content of 10–15 wt%, lowers the glass transition temperature (T_g) to approximately 0 °C, enabling rapid film coalescence at ambient factory conditions without the need for external plasticisers. The dispersion’s Brookfield viscosity, measured at 20 rpm with spindle #4 per ASTM D2196, falls within 2 500–3 500 mPa·s at 25 °C, a range that balances sufficient wet tack to prevent end-opening of the cigarette rod against the capillary absorption rates of common plug wrap papers and tipping base papers with Cobb values between 20 and 40 g/m².

What Distinguishes the Coalescence Profile of JZ-II from Alternative VAE Grades?

The emulsion’s minimum film-forming temperature (MFFT), determined by ISO 2115, is ≤2 °C, which permits coherent film formation at application temperatures as low as 8 °C—a critical attribute for unconditioned production halls in winter months. Low-viscosity VAE alternatives typically require higher dilution or lower solids to maintain sprayability, reducing the deposited wet-film thickness below the threshold required for uniform fibre contact. JZ-II, at 55–57 % non-volatile content (ASTM D2369, 1 h at 105 °C), delivers a wet-film coverage of 8–12 g/m² without excessive penetration. The ethylene sequences disrupt the crystallinity of the polyvinyl acetate domains, imparting intrinsic flexibility and lowering the heat-seal temperature. Consequently, on a plug-wrapping drum where the garniture rail temperature cycles between 140 and 180 °C, the film transforms to a viscoelastic solid with a fibre-tear onset time of 0.8–1.2 s, established by a modified tongue-tear test on 70 g/m² plug wrap. By contrast, medium-viscosity PVA homopolymer emulsions often demand a longer thermal input or remain tacky, causing drag marks and offset on downstream turning guides. The controlled open time of JZ-II—8–12 s at 23 °C /50 % RH, measured by the finger-transfer method—provides an adequate window for machine splices without sacrificing immediate green strength.

Adhesive formulations for tobacco products fall under indirect food-contact regulations because components can migrate to the tobacco filler and subsequently to mainstream smoke. JZ-II is produced with raw materials listed in the U.S. FDA inventory, and the finished emulsion conforms to 21 CFR §175.105 (“Adhesives”) and the component migration limits of 21 CFR §176.170 when applied to paper and paperboard components. Overall migration into the tobacco rod under simulated use conditions, tested per EN 1186-1 using 95 % ethanol as fatty food simulant, remains below 10 mg/dm². Formaldehyde release—a critical parameter for cigarette adhesives—is below the detection limit of 0.5 mg/kg when analysed by the acetylacetone method (CORESTA Recommended Method No. 74), attributable to the absence of N-methylol acrylamide crosslinkers in the VAE chemistry. Heavy-metals content complies with the RoHS Directive 2011/65/EU; specific migration of lead and cadmium is below 0.01 mg/kg. The emulsion carries no phthalate-based plasticisers and exhibits negligible odour after film coalescence, a requirement validated by an odour panel in accordance with ISO 13301:2018.

Nozzle Wetting and Fibre Tear Onset at 16,000 min⁻¹

On high-speed makers, the side-seam adhesive is dispensed through a precision nozzle onto the wrapper travelling at over 400 m/min. JZ-II exhibits shear-thinning behaviour: its apparent viscosity at a shear rate of 1 000 s⁻¹ (capillary rheometry) drops to 800–1 200 mPa·s, ensuring flow through 0.3–0.5 mm orifices without excessive pressure drop. The plateau in low-shear viscosity prevents misting and stringing when the bead exits the nozzle. On a Protos-M8 running at 16 000 cigarettes/min, the target wet-deposit weight is 10–14 mg per cigarette, equivalent to 8–12 g/m². Rapid water uptake by the cigarette paper (Cobb 30 g/m²) together with contact-heating from the garniture at 150–200 °C raises the polymer concentration above the critical coalescence point within 0.3 s. T-peel adhesion on specimens pulled 5 minutes after the gariture exit, measured per ASTM D1876 adapted to a 15 mm strip width, yields 3.2–4.0 N/15 mm with 100 % fibre tear on standard 27 g/m² cigarette paper. This rapid cohesive-strength build-up minimises reopen defects during cut-off and transfer to the filter assembler. Any emulsion that dries too slowly leaves a thermoplastic skin on the garniture surface, increasing the risk of burn-on deposits that impede heat transfer; JZ-II’s fast water-release profile and low film tack at 120 °C reduce such fouling to an acceptable cleaning interval of 8 hours.

Storage stability of JZ-II is maintained for 6 months from the production date when kept in sealed, opaque HDPE containers at temperatures between 5 °C and 35 °C. Freeze-thaw cycle testing per ISO 1147 demonstrates irreversible coagulation after 1 cycle; heated warehousing is therefore required where winter temperatures fall below 0 °C. Prior to use, gentle agitation with a low-shear anchor stirrer at 30–60 rpm restores any slight settling without air entrainment. Microbial spoilage is controlled by the acidic pH and low residual monomer content; no additional biocide is needed under normal turnover rates.

If the tipping paper adsorption rate exceeds 50 g/m² Cobb,…

High-porosity tipping papers with Cobb values above 50 g/m² challenge low-viscosity adhesives by draining the aqueous phase into the substrate before film formation can occur. This leads to adhesive starvation at the bond-line, poor fibre tear, and potential staining visible on the printed surface. JZ-II’s medium-viscosity profile, with a yield stress of approximately 5–10 Pa measured by controlled-stress rheometry, restricts penetration depth to the top 20–30 µm of the paper, leaving a sufficient polymer film at the interface. On a 60 g/m² tipping base with Cobb 55 g/m², the bond strength after 24 h conditioning at 23 °C /50 % RH reaches 3.5–4.5 N/15 mm with fibre tear exceeding 95 % of the bonded area, whereas a low-viscosity (800 mPa·s) VAE alternative of identical solids yields only 2.0 N/15 mm and partial substrate failure. The same grade also outperforms plasticised PVA homopolymer adhesives in wet-strength retention: after immersion in 60 °C water for 30 min, JZ-II bonds retain 65–75 % of their original dry peel strength, a critical attribute during the tipping-paper rewinding step in humid environments. Differences in heat-seal activation between JZ-II and PVA systems are summarised in the comparative dataset below.

Peel tests conducted per ASTM D1876 (conditioning at 23 °C, 50 % RH, crosshead speed 300 mm/min) on commercial 32 g/m² tipping paper bonded to cellulose acetate filter rod segments. Formaldehyde determined by CORESTA Recommended Method No. 74.