Dairen DA-143 Emulsão VAE

Dairen DA-143 is a carboxylated vinyl acetate-ethylene (VAE) copolymer emulsion stabilized with a polyvinyl alcohol (PVOH) protective colloid system. The product delivers a solids content of 55 ± 2 % by weight (ISO 3251:2019, 105 °C, 3 h), a Brookfield viscosity of 500–1,500 mPa·s at 25 °C (spindle 3, 20 rpm, ASTM D2196-20), and a pH of 4.5–5.5 (ASTM E70-19). The minimum film-forming temperature (MFFT) is 0 °C (ISO 2115:1996, method A), corresponding to a glass transition temperature (Tg) of approximately 0 °C by differential scanning calorimetry (midpoint, 10 °C/min, second heating). The emulsion is classified as anionic, with a coarse particle size distribution centered near 1.5 µm (laser diffraction, D₅₀), yielding rapid water release during drying and high wet tack in adhesive applications.

Why does DA-143 behave differently from conventional vinyl acetate homopolymers under high-humidity aging?

The ethylene comonomer content—typically 10–15 wt% on dry polymer—acts as an internal plasticizer, permanently lowering the modulus of the dried film and conferring flexibility without migratory plasticizers. In accelerated aging at 85 °C and 85 % relative humidity (IEC 60068-2-78), adhesive bonds based on DA-143 retain over 80 % of their initial T-peel strength on corona-treated polyethylene after 500 h, whereas a comparable vinyl acetate homopolymer (Tg ≈ 30 °C, plasticized with 20 phr dibutyl phthalate) drops below 50 % due to plasticizer volatilization and embrittlement. The ethylene sequences also reduce the hydrolytic susceptibility of the acetate ester, limiting free acetic acid generation to less than 0.3 wt% after 4 weeks at 50 °C (internal conductivity titration), a figure critical for corrosion-sensitive metal laminates.

In practice, DA-143 is blended with tackifier dispersions—rosin ester or hydrocarbon resin dispersions at 15–30 wt% of wet emulsion—to tune open time and peel adhesion on low-surface-energy substrates. The PVOH colloid influences compatibility: esters of hydrogenated rosin with acid numbers below 150 mg KOH/g (ISO 2114) show homogeneous films with minimal grit formation after 24 h storage at 60 °C, whereas high-acid-number tackifiers (> 180 mg KOH/g) can cause flocculation that elevates residue on a 180 µm sieve from <0.01 % to over 0.5 %. Processing equipment must be capable of moderate shear: toothed-disc dispersers operating at tip speeds of 7–12 m/s for 15–20 minutes are sufficient to incorporate tackifier without excessive foam generation, which otherwise reduces applied coat weight uniformity below ±1 g/m² on high-speed coating lines.

Near the 0 °C MFFT, coalescing solvent demand is a processing gate. Without solvent, a drawdown of neat DA-143 at 23 °C and 50 % RH yields a continuous film only if the wet thickness is kept below 75 µm. Thicker films crack progressively; a 100 µm wet film exhibits a cracking area fraction of 15–25 % as determined by image analysis of backlit glass plates. Addition of 3 wt% butyl carbitol acetate (on wet emulsion) depresses the effective MFFT to approximately −5 °C, enabling crack-free films at 150 µm wet thickness. However, the same coalescent increases the drying time at 100 °C in a forced-air oven by 30–40 % due to the higher boiling point (246 °C) relative to water, a factor that must be balanced against line speed. Published data on the VOC contribution under Directive 2004/42/EC indicate that DA-143 with 3 % coalescent approaches the limit of category A/h for wood coatings, though formulators often prefer the product in adhesives where VOC limits are less restrictive.

When carboxylated VAE grades fail due to pH drift in wet lamination

The carboxyl functionality incorporated into DA-143 originates from copolymerized acrylic acid, yielding a typical acid value of 2–5 mg KOH/g dry polymer. This modest acid content is designed to improve adhesion to metallic and oxidized polymer surfaces while retaining compatibility with the PVOH colloid. However, if the emulsion pH drifts above 6.0—as can occur when formulated with alkaline fillers such as calcium carbonate (CaCO₃) sourced from uncoated ground limestone—partial neutralization of the carboxyl groups increases the ionic character of the particle surface, raising the viscosity by a factor of 2–4 within 24 h. In a continuous coating operation using a slot-die coater with a target coat weight of 20 g/m² dry, this viscosity excursion manifests as ribbing instabilities when the applicator gap is below 200 µm, forcing a reduction in line speed from 150 m/min to below 90 m/min. Frequent pH monitoring with a flat-surface electrode (ASTM E70) and adjustment with 0.1 N acetic acid or a glycine-based buffer to maintain pH 4.8 ± 0.2 prevents this drift. Formulators should avoid amine-based thickeners (e.g., AMP-95) entirely, as the rapid pH jump above 7.5 induces microgel formation detectable as a rise in filter pressure on a 100 µm mesh bag filter from <0.2 bar to over 1.0 bar within 30 minutes of circulation.

The following table summarizes the viscosity response to common thickening strategies observed during laboratory-scale trials with a Cowles blade disperser at 1,000 rpm:

When DA-143 is processed on a twin-screw extruder for hot-melt adhesive compounding—an atypical route but explored for solvent-free assembly—the ethylene segments lower the melt viscosity relative to homopolymer PVAc. Capillary rheometry at 150 °C gives a shear viscosity of 120–180 Pa·s at 100 s⁻¹ for the dried polymer, about 40 % lower than a PVAc homopolymer of comparable molecular weight. This enables injection molding of compostable cutlery using a blend with poly(lactic acid) (PLA) at 30 wt% dry DA-143, where the VAE acts as a ductile modifier. However, the residual PVOH from the colloid generates die lip build-up after 2–3 hours of continuous extrusion at 160 °C unless the extruder is equipped with a vacuum vent at the decompression zone operating at −0.08 MPa gauge. Published data for this specific configuration is limited, but industrial experience from co-rotating extruders with an L/D ratio of 40:1 confirms that moisture content of the dried crumb must be below 0.1 % (Karl Fischer) to avoid hydrolysis-induced viscosity reduction.

Textile lamination with open-structure nonwovens exploits the rapid water release of the coarse particle size. In a three-roll gravure application running at 120 m/min, DA-143 penetrates viscose spunlace fabric to a depth of 200–300 µm before drying, measured by cross-sectional microscopy after staining with iodine vapor. The depth is sufficient to create mechanical anchoring without strike-through, but the dwell time between application and drying must not exceed 3 s; longer intervals allow capillary wicking that doubles the stain-through area. This constraint rules out some older single-pass ovens where web path length from the application nip to the first drying zone exceeds 4 m, necessitating either a pre-heated roll set at 60 °C or a formulation adjustment with 0.5 wt% of a high-molecular-weight carboxymethyl cellulose (degree of substitution 0.7) to increase low-shear viscosity to 2,000 mPa·s without sacrificing sprayability. The specific addition level must be verified by monitoring the peel adhesion of the laminated assembly to cotton fabric per ISO 2411:2017; values above 3.5 N/50 mm are typical for 20 g/m² adhesive add-on.

What distinguishes DA-143 from grades like DA-102 or DA-141 in high-speed tube winding?

The 0 °C MFFT of DA-143 positions it between the harder DA-102 (MFFT +5 °C) and the fully flexible DA-141 (MFFT −15 °C). In spiral tube winding of kraft paper (basis weight 120 g/m²) at winding speeds of 80 m/min, DA-102 requires 5–7 % coalescent to avoid micro-cracks that reduce burst strength, whereas DA-143 forms a coherent adhesive layer without coalescent when the paper temperature is kept above 10 °C by processing in a conditioned environment. DA-141, while coalescent-free, results in lower heat resistance: the bond shear strength at 80 °C (ASTM D3163-15, modified with 25 mm overlap on birch wood) is 0.8 MPa compared to 1.6 MPa for DA-143. The difference arises because DA-141 contains no carboxylic acid groups, eliminating the potential for metal-ion crosslinking that contributes to cohesive strength when a small addition of aluminum acetylacetonate (0.3 wt% on dry binder) is compounded. This crosslinker can boost the 80 °C shear strength of DA-143 to 2.4 MPa without embrittling the film at −20 °C, whereas DA-102, already rigid, gains 2.9 MPa but suffers cold-temperature peel loss beyond 40 % on polypropylene.

The carboxylation also determines compatibility with cationic additives. Unlike non-carboxylated VAE, DA-143 precipitates instantly when mixed with a polyamide-epichlorohydrin wet-strength resin at 1 wt%, a reaction utilized deliberately in two-component spray systems for insulation facing to achieve green strength before oven curing. The operation window requires precise ratio control: the volume ratio of DA-143 stream to catalyst stream must be maintained at 100:3 ± 0.2 using gear pumps with a precision of ±0.5 % flow output. Variation outside this band leads to incomplete crumb formation or nozzle clogging within 90 s.

Adhesion to flexible PVC flooring backings leverages the ethylene content. When DA-143 is coated at 80 g/m² dry and heat-sealed against plasticized PVC (DINP plasticizer, 35 phr) at 130 °C for 8 s, the peel strength according to EN 1372:2015 reaches 25–30 N/25 mm, with cohesive failure in the PVC layer. Equivalent homopolymer VAE (Tg +15 °C) yields only 12 N/25 mm with adhesive failure at the interface. The mechanism is attributed to interdiffusion of ethylene segments with the PVC plasticizer phase, a phenomenon corroborated by dynamic mechanical analysis showing a broadening of the loss modulus peak. Published data on the exact interface thickness, however, remains limited to research using neutron reflectivity on model surfaces, and direct industrial correlation is qualitative.