Dairen DA-180L Emulsão VAE

Dairen DA-180L is a vinyl acetate–ethylene (VAE) copolymer emulsion stabilised with polyvinyl alcohol. The product is supplied at a non-volatile content of 54–56 % by weight, with a Brookfield RVT viscosity (spindle #4, 20 rpm, 25 °C) of 2000–4000 mPa·s and a pH of 4.0–5.0. The glass transition temperature of the dried copolymer is approximately 0 °C, which translates to a minimum film-forming temperature below 5 °C. Unlike higher-T_g VAE grades produced by the same manufacturer—such as DA-102 (T_g ~10 °C) and DA-101 (T_g ~30 °C)—DA-180L incorporates a higher ethylene segment content. This internal plasticisation eliminates the need for coalescents or external plasticisers in ambient-cure film formation, while still delivering cohesive strength comparable to a medium-molecular-weight polyvinyl acetate homopolymer. The emulsion exhibits pseudoplastic flow behaviour and is designed for water-based adhesives that require bond integrity on low-surface-energy substrates, including polyethylene-laminated kraft paper and clay-coated board. Table 1 summarises typical physical properties across the Dairen VAE adhesive-grade range, drawn from manufacturer’s published technical datasheets; all values are typical ranges and must be verified against the lot-specific certificate of analysis.

When DA-180L Replaces PVAc Homopolymer in High-Speed Packaging Lines

Conversion from polyvinyl acetate homopolymer adhesive to DA-180L on a gravure roll-coater running at line speeds of 150–250 m/min alters the entire rheological and drying dynamic. PVAc grades typically require 5–10 phr dibutyl phthalate or benzoate plasticiser to achieve film formation at ambient temperature, whereas DA-180L creates a continuous film without any external coalescent—this alone reduces volatile organic compound (VOC) inventory, a point verified against U.S. EPA Method 24 for waterborne adhesives. The key processing difference, however, lies in the high-shear viscosity profile. At the nip of the application roller, shear rates on the order of 10⁴ s⁻¹ are common. Under these conditions, the pseudoplastic DA-180L exhibits a measured apparent viscosity of 200 ± 30 mPa·s (controlled-stress rheometer, cone-plate geometry, 25 °C), which is substantially lower than the low-shear Brookfield value. This shear-thinning behaviour permits a wet coat weight of 2–5 g/m² with minimal misting, provided the transfer roller gap is set to 50–70 µm. On production lines equipped with closed-loop viscosity control, the emulsion must be diluted to 40–45 % solids to maintain a drain time of 18–22 s (DIN 53211 flow cup, 4 mm orifice). An often-overlooked prerequisite is inline filtration through a 150 µm mesh screen immediately before the coating head; agglomerates formed during extended storage above 35 °C can generate micro-streaks on the substrate and increase scraper-blade fouling frequencies by a factor of two when compared to equivalent solids PVAc. Drying energy demand also shifts: the higher ethylene content reduces the heat of vaporisation requirement marginally, but hot-air tunnels must stay below 90 °C skin temperature to prevent surface skinning, which traps residual moisture and leads to bubble defects when the laminate is subsequently heat-sealed. Preheating the paper substrate to 40–45 °C using infrared banks before the application station has been shown to improve wetting uniformity, particularly on recycled board with high-ash content, without triggering premature film formation.

How Does DA-180L Maintain Wet Tack on Clay-Coated Board at 50 % RH?

Wet tack development on dense, low-porosity substrates is a function of the initial adhesive-water phase separation rate and the cohesive strength of the resulting concentrated polymer layer. DA-180L exhibits a wet-tack maximum of 400–600 g/cm² when evaluated by a probe-tack method (modified FINAT FTM-9, stainless steel probe, 100 µm wet film, dwell 1 s, separation speed 300 mm/min) at 23 °C and 50 % relative humidity. This value declines to below 200 g/cm² if the relative humidity drops below 30 %, because accelerated evaporation creates a surface skin before the emulsion has fully coalesced against the substrate pores. In side-by-side trials on a rotary die-cut folding carton line, DA-180L delivered an open time of 15–20 minutes—measured as the interval during which the bonded coupon achieves 90 % of the ultimate fibre tear after compressive nip at 0.4 MPa—whereas a PVAc homopolymer of identical solids content failed to achieve fibre tear beyond 8 minutes under the same conditions. The difference is attributed to the ethylene segments, which retard water loss by reducing the polymer’s free volume, while the PVAc film vitrifies rapidly at the evaporative front. Nevertheless, when board surface energy drops below 36 mN/m (as seen on multiple recycled grades with wax and silicone contaminants), wet tack falls below 150 g/cm² regardless of open time. In such cases, incorporating 0.5–1.0 wt% of a non-ionic acetylenic diol surfactant (e.g., 2,4,7,9-tetramethyl-5-decyne-4,7-diol, HLB 2–4) into the adhesive compound restores wet tack to acceptable levels, although pot-life stability must be re-validated because excessive surfactant loadings above 2 wt% can strip protective colloid from the particle surface and cause viscosity drift over 48 h.

In wet-bond lamination of metallised polyester (MPET) films to paperboard, DA-180L replaces casein-based laminating adhesives on specific jobs where oil and grease resistance under FDA 21 CFR 175.105 is not required. A coating weight of 4–6 g/m² dry using a reverse-gravure coater at 80 m/min yields a bond strength exceeding 2.5 N/15 mm when measured by ASTM D1876 T-peel at 23 °C with a crosshead speed of 254 mm/min. Film delamination occurs cohesively within the paper layer rather than adhesively at the interface, provided the corona-treated polyester surface maintains a dyne level above 42 mN/m immediately prior to lamination. Published quantitative data for this exact product–substrate pair under ASTM D1876 is limited; the values cited represent typical laboratory trials on a 200 mm-wide pilot coater and must be confirmed for each specific board-polyester combination.

Freeze-Thaw Resistance and Colloidal Stability at Low pH

DA-180L is not freeze-thaw stable. Storage or transport below 0 °C causes ice crystal growth that disrupts the polyvinyl alcohol steric barrier, and after 2–3 cycles between -5 °C and +20 °C the emulsion coagulates irreversibly into a non-redispersible gel. Consequently, temperature-controlled warehousing above +5 °C is mandatory for bulk tank farms and intermediate bulk containers. The emulsion tolerates pH adjustment within a narrow window; adding dilute sodium hydroxide to raise the pH above 5.5 increases the ionic strength sufficiently to compress the electrical double layer, leading to a viscosity rise of 30–50 % within 24 h. Cationic additives—quaternary ammonium salt biocides, cationic starch, or amine-functional crosslinkers—must be excluded because they cause instantaneous shock coagulation at addition levels as low as 0.1 wt%. The manufacturer recommends blending only with non-ionic or anionic auxiliary components, and any formulation adjustment should be preceded by a vial-scale compatibility test at the intended addition ratio, observed for 72 h at 40 °C to accelerate any latent instability. Storage viscosity drift is typically less than 10 % per year when the original drum is kept sealed at 15–25 °C.

For cold-press assembly of hardwood veneers, DA-180L is applied at 120–150 g/m² wet to one bonding surface and the open assembly time is kept below 10 minutes at 20 °C and 65 % relative humidity. Pressing at 0.5–0.8 MPa for 20–30 minutes produces an immediate handling strength sufficient for edge-trimming. Bond durability testing per EN 204 (non-structural, durability class D3) requires minimum tensile shear strengths of 5 N/mm² dry and 2 N/mm² after 4 days soaking in cold water followed by 7 days reconditioning. Formulations based solely on neat DA-180L typically achieve dry values in the range of 6–8 N/mm² and wet values of 2–3 N/mm² on birch, as reported for similarly formulated VAE adhesives of 55 % solids and 0 °C T_g; direct grade-specific data under the full EN 204 protocol has not been published by the manufacturer. The addition of 5–10 wt% of an emulsifiable polymeric isocyanate crosslinker extends water resistance into the EN 204 D4 range, with boiled-water tensile strengths above 3 N/mm², but the working pot life of such two-component systems drops to less than 60 minutes at room temperature and must be accounted for in line scheduling. Table 2 collates the adhesive performance test methods most frequently cited for DA-180L applications together with the relevant standard designations.

Dispersion of DA-180L with fully hydrolysed polyvinyl alcohol (degree of hydrolysis 98–99 mol%) can improve wet-bond strength on porous substrates, as the added PVOH fills inter-particle voids. Trials on a 300 mm-wide knife-over-roll coating station indicate that blending 10 parts of a 10 % PVOH solution (viscosity 25–30 mPa·s, 4 % aqueous, 20 °C) with 100 parts DA-180L increases the dried film’s water contact angle from 55° to 68° after 24 h acclimation, while reducing dry shear adhesion by approximately 15 % on birch blocks due to dilution of the VAE binder content. The addition must be made under low-shear agitation, and the pH of the final blend must be checked—values above 5.8 risk destabilisation. Published data for this specific configuration is limited, and the cited contact angle values originate from single-batch laboratory goniometry measurements; lot-to-lot variation in PVOH acetate residuals can shift these figures. Production experience with the emulsion on continuous label laminators running at 60–100 m/min confirms that edge-lifting failures can occur when the die-cut label stock has an internal bond strength below 100–150 J/m² (Scott bond test), irrespective of the adhesive’s intrinsic peel values. Therefore, substrate integrity must be qualified alongside the adhesive film when converting lightweight release liners.