Rovene 7007 VAE Emulsão

Rovene 7007 VAE Emulsion: Composition, Rheological Signature, and Film Profile

Aqueous vinyl acetate-ethylene copolymer dispersions providing a measured offset between minimum film formation temperature and glass transition temperature constitute the product category from which Rovene 7007 is drawn. The polymer solids content is maintained at 54–56% by weight with a residual vinyl acetate monomer ceiling of <500 ppm. The dispersion is sterically stabilised, not surfactant-thickened, yielding a Brookfield viscosity (spindle 3, 20 rpm, 25 °C) centred on 1 500 mPa·s, although lot-to-lot variation between 1 200 and 1 800 mPa·s is recorded on manufacturing logs from 4 000 L reactor trains. The pH is adjusted with a volatile base to 4.5–5.5, deliberately below the pKₐ of surface carboxylic acid groups contributed by a minor co-monomer (<3 wt%), ensuring viscosity remains Newtonian during high-speed transfer through ring-piston pumps. Particle size distribution, measured via photon correlation spectroscopy, exhibits a D₅₀ of 0.35 µm and a D₉₀ of 0.78 µm; the narrow span reduces shear-induced coagulation when circulated through 100-mesh inline screens upstream of slot-die coaters.

Commercially, the product is positioned as a high-ethylene-content VAE that depresses the glass transition temperature to -12 °C (mid-point of DSC scan at 10 K/min, second heat, sealed pan) without the addition of external plasticiser. Film formed at 23 °C and 50% RH dries translucent and remains tack-free under a 1 kPa static load up to 60 °C. The high-ethylene backbone imparts hydrophobic character relative to homopolymer PVAc emulsions, a difference quantified by a water contact angle on air-dried films of 78° versus 58° for a comparative PVAc homopolymer of identical solids. The coalesced film is insoluble in toluene and methyl ethyl ketone at 23 °C after 24 h immersion, yet it swells measurably (18% mass uptake) in ethyl acetate, which informs solvent-bonding procedures with polyester substrates.

What limits T-peel on untreated LDPE to 3.2 N/25 mm despite a Tg of -12 °C?

When Rovene 7007 is knife-over-roll coated at 25 g/m² dry coat weight onto polyethylene terephthalate film and laminated to untreated low-density polyethylene, the 24 h T-peel strength measured per ASTM D1876 reaches a plateau of 3.2 N/25 mm. The value is limited not by cohesive fracture within the bulk adhesive but by the work of adhesion at the LDPE interface. Surface energy of the polyethylene adherend, measured by Owens-Wendt method using diiodomethane and water, sits at 28 mN/m with a dispersive fraction exceeding 90%. Rovene 7007’s polar contribution, originating from hydrolysed acetate units and carboxylic acid groups, raises the interfacial energy when paired against a purely dispersive substrate. Corona pre-treatment raising the LDPE surface energy above 42 mN/m elevates peel to 8.5 N/25 mm, shifting failure mode to cohesive; optical microscopy of the fracture surface reveals fibrillation domains exceeding 200 µm in length. This sharp transition between 40 and 42 mN/m underscores a processing window narrower than the ±5 mN/m typically tolerated by styrene-butadiene latexes with lower hydroxyl content. In contrast, Rovene 7006, a VAE with lower ethylene incorporation and a Tg of +3 °C, reaches only 1.9 N/25 mm on corona-treated LDPE under identical lamination conditions due to insufficient compliance to follow substrate deformation at 300 mm/min crosshead speed. Rovene 7005, with a Tg of +15 °C, fails adhesively with no measurable fibrillation. The ethylene content of Rovene 7007, estimated at 20–25 wt% relative to total polymer mass, is the primary microstructural driver of these divergent behaviours.

Nonwoven Binder Wet Strength and Line-Side Defect Statistics

Carded rayon-polyester blends (60:40 ratio, basis weight 45 g/m²) sprayed with a 10% solids dilution of Rovene 7007 through air-atomising nozzles operating at 0.3 MPa atomising air pressure produce an add-on of 18% dry polymer by weight after passage through a through-air dryer with web temperature tracked at 115 °C for 45 s. Wet tensile strength in the machine direction, determined on 25 mm wide strips saturated with deionised water per EDANA 20.2-89, averages 12.4 N with a coefficient of variation of 6.2% across 12 consecutive full-width reels. The primary contributor to reel-to-reel drift is foam accumulation in the run tank, traced back to the dynamic surface tension of the diluted emulsion which equilibrates to 38 mN/m (bubble pressure tensiometer, 1 Hz). Defoamer class is constrained: silicone-based antifoams at concentrations above 0.05% on emulsion weight cause fish-eye cratering in subsequent coating operations; mineral oil defoamers suppress foam but increase linting at the oven exit due to a film softening effect detectable by a −3 °C depression of Tg in thermomechanical analysis. Wet web line speeds up to 180 m/min are sustained without deposit formation on the dryer mesh, provided the machine is cleaned every 8 h with a 2% sodium hydroxide flush at 60 °C. In comparative trials with PVAc homopolymer binders under identical throughput, four-hourly cleaning intervals were necessary to remove congealed polymer from perforation holes, a difference attributed to the larger hydrodynamic volume per chain of ethylene-rich copolymer reducing shear-induced adsorption onto metallic surfaces.

In nonwoven carded web bonding, the need for a balance between dry tensile and hand renders standard machine-direction tensile-energy-to-break data insufficient for choosing a binder. Rovene 7007 delivers a bending length (cantilever method, ISO 9073-7) of 2.8 cm at 18% add-on on the same rayon-polyester matrix, whereas Rovene 7006 at equal add-on records 3.6 cm, a stiffness difference directly perceivable in tactile panel ratings by 5 out of 6 panellists in a blinded sensory evaluation using a forced-choice paired comparison protocol. The decrease in modulus arises from the longer ethylene sequences that disrupt crystallinity of the acetate blocks; FTIR crystallinity index (A₁₇₃₆/A₁₂₄₀ ratio) decreases from 1.24 in Rovene 7006 to 0.87 in Rovene 7007.

Table 1 — Benchmark Properties of Rovene VAE Emulsion Series Under Identical Test Regime

Property /Standard	Rovene 7007	Rovene 7006	Rovene 7005
Solids (%) — ASTM D4758	54–56	54–56	54–56
pH — ASTM E70	4.5–5.5	4.5–5.5	4.5–5.5
Brookfield viscosity (mPa·s, 20 rpm, 25 °C) — ASTM D2196	1 200–1 800	800–1 400	600–1 200
Tg (°C, DSC, midpoint) — ISO 11357-2	-12	+3	+15
Minimum film formation temp. (°C) — ISO 2115	<1	+5	+14
Ethylene content (approx. wt%) — in-house FTIR	20–25	10–14	<5
Tensile strength (MPa, dried film) — ASTM D882	5.8	8.2	14.6
Elongation at break (%) — ASTM D882	820	560	210
Water contact angle (°, sessile drop, 60 s) — ASTM D7334	78	65	54

When the coalescing solvent selection fails at ≤5 °C

Rovene 7007 coalesces at temperatures approaching freezing point without the addition of volatile coalescents, a trait not shared by VAE grades with lower ethylene content. Film formation tests conducted in a controlled-climate tensile stage fitted to an atomic force microscope show that close-packed particle ordering completes at 1 °C under 65% RH for Rovene 7007, whereas Rovene 7005 requires 14 °C. This difference is exploited in cold-weather paper coating operations where the use of ester-alcohol coalescents such as 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate is restricted by slow evaporation rates at substrate temperatures below 10 °C; residual solvent retained in the coating lowers block resistance, measurable as an increase in the ISO 4624 pull-off adhesion test value drift by 0.2 MPa over 14-day ageing. The lower film formation temperature arises from a hydroplasticisation effect of water swelling the more hydrophilic acetate-rich surface of the latex particle, a mechanism confirmed by modulated differential scanning calorimetry showing a surface Tg approximately 18 K below the bulk Tg. In practical terms, Rovene 7007 can be applied at web temperatures of 3–5 °C in unheated coating heads without the film developing the reticular cracking pattern visible under 40× stereomicroscopy that signals incomplete coalescence.

Offset press repulpability trials with coated paperboard further distinguish this emulsion from competitors. After pulping at 3% consistency in a 10 L TAPPI disintegrator for 5 000 revolutions, hand sheets formed from stock containing 20% Rovene 7007-coated broke exhibit repulped fibre recovery exceeding 92%, with stickies counts (TAPPI T 277) of 425 ppm, which is within the acceptable threshold for OCC recycling streams. Emulsions relying on external plasticiser generate stickies counts above 2 000 ppm in the same protocol, leading to chronic downtime for screen basket cleaning on the paper machine approach flow.

Table 2 — Regulatory Status and Compliance Reference Numbers

Regulation/Standard	Clause/Reference	Status
FDA 21 CFR 175.105 — Adhesives	Components listed; migration limits apply	Compliant
FDA 21 CFR 176.170 — Paper & paperboard in contact with aqueous & fatty food	Condition of use E–G	Compliant
EU REACH — Regulation (EC) No 1907/2006	Polymer registration exempt, monomers registered	Substances pre-registered
EU 10/2011 — Plastics materials and articles intended to come into contact with food	Overall migration limit 10 mg/dm²	Passes simulant D2
CONEG Heavy Metals (sum of Pb, Hg, Cd, Cr(VI))	<100 ppm total	Passes
ECOLABEL — EU 2017/1945 indoor paints and varnishes	VOC <0.5 g/L, no APEO	Compliant
ASTM D6868-21 — Biodegradable plastics used as coatings on paper	Biodegradation & heavy metal limits	VAE polymer matrix is not inherently biodegradable; compostable certification requires specific additive packages; without them, this standard is not met.

Film Morphology and Ethylene Content Gradients Across the Drying Front

Scanning electron microscopy of freeze-fractured cross-sections of Rovene 7007 films dried at 60 °C and 30% RH reveals a homogenous matrix absent of discernible particle boundaries, indicative of full coalescence. Residual emulsifier exudates to the air interface, forming an ultrathin (<50 nm) surfactant layer that can be detected by X-ray photoelectron spectroscopy as an elevated sodium signal (0.8 at% versus bulk 0.1 at%). This layer is water-removable by a short (5 s) deionised water rinse, restoring interfacial adhesion for a subsequent lamination step. In comparison, Rovene 7005 exhibits incomplete coalescence under these drying conditions, with particle memory persisting as surface roughness of Ra 0.8 µm versus Ra 0.2 µm for the high-ethylene variant. Dynamic mechanical analysis from -50 °C to +100 °C at 1 Hz shows a tan delta peak at -5 °C with a peak half-width of 22 K for Rovene 7007, broader than the 16 K width of Rovene 7006, reflecting the broader distribution of chain segmental dynamics imparted by random incorporation of ethylene into the vinyl acetate backbone. This broad damping profile correlates with acoustical loss factor measurements in constrained-layer damping configurations, where a beam coated with 2 mm of Rovene 7007 film exhibits a composite loss factor of 0.12 at 500 Hz over the 10–25 °C range. Published data for this specific configuration in damping applications is limited; field trials on HVAC ductwork indicate a reduction in structure-borne noise transmission of 4 dB in the 250–800 Hz octave bands relative to uncoated galvanised steel. The product is shipped in 1 000 L IBCs fitted with dip-tube extraction. After prolonged storage exceeding 6 months at ambient warehouse temperatures cycling between 5–35 °C, a thin supernatant skin may form; passing the contents through a 200 µm mesh bag filter before feed tank charging is recommended. Blending with high-gloss acrylic latexes for hybrid coating formulations requires attention to the difference in surface tension: Rovene 7007 exhibits an equilibrium surface tension of 42 mN/m, which can induce cratering in films driven by acrylics with surface tensions near 35 mN/m. Substrate wetting on low-energy polymer films is adequate without surfactant addition, but downtime wetting of stainless steel doctor blades during pauses in roll coating necessitates a continuous misting of cleaning solution to prevent edge solidification.