BJ-705 VAE Emulsion is a carboxylated vinyl acetate‑ethylene copolymer dispersion stabilized with a poly(vinyl alcohol) protective colloid system. The product is supplied at
55 ± 1 % non‑volatile content (ISO 3251, 105 °C /2 h), with a pH of
4.0–5.5 (ISO 976) and a Brookfield RVT viscosity of
1500–3000 mPa·s (spindle 3, 20 rpm, 23 °C, ISO 2555). The dispersed phase exhibits a mean particle size of
0.8–1.2 µm (laser diffraction, ISO 13320), and the minimum film‑formation temperature (MFFT) lies below
0 °C (ISO 2115), reflecting a glass transition temperature (Tg, DSC midpoint, ISO 11357‑2) of approximately
−5 °C. The ethylene comonomer content, on a dry polymer basis, is
18–22 wt%, imparting permanent flexibility without external plasticizers and a surface energy low enough to wet low‑polarity substrates such as corona‑treated LDPE and polypropylene nonwovens. The residual vinyl acetate monomer is controlled to
< 500 ppm (GC headspace, EPA 8260D), and the emulsion is free of alkylphenol ethoxylates (APEO).
How does the ethylene comonomer ratio alter film mechanics and cohesive strength?
Raising the ethylene fraction from the range typical of a homopolymer‑modified VAE (8–12 %) to the
18–22 % incorporated in BJ-705 shifts the film from a semi‑rigid thermoplastic to an elastomeric network. Tensile properties measured on films cast and conditioned according to ISO 527‑3 (type 5 specimens, 200 mm/min) show an elongation at break of
600–750 % accompanied by a tensile strength of
4.5–6.5 MPa. By contrast, a conventional vinyl acetate homopolymer emulsion of similar solids content often fractures below
50 % elongation unless externally plasticized. The trade‑off appears in the shear‑resistance domain: the higher ethylene content reduces the storage modulus (G′) above the glass transition, and lap‑shear specimens prepared with BJ-705 on beech (Fagus sylvatica) under EN 204 D2 conditions yield failure adhesion values of
3.2–4.0 N/mm² when formulated as‑is, compared with>5.5 N/mm² obtainable from a homopolymer with a Tg of 30 °C. The internal plasticization mechanism eliminates plasticizer migration, a critical factor in long‑term adhesive bond stability on porous substrates.
Physical and rheological profile – BJ-705 VAE Emulsion
| Property | Method | Typical Value |
|---|
| Solids content | ISO 3251 (105 °C, 2 h) | 55 ± 1 % |
| pH | ISO 976 | 4.0–5.5 |
| Viscosity (Brookfield RVT, 20 rpm) | ISO 2555 | 1500–3000 mPa·s |
| MFFT | ISO 2115 | <0 °C |
| Glass transition temperature (Tg) | ISO 11357‑2 (DSC, midpoint) | −5 °C |
| Average particle size | ISO 13320 | 0.8–1.2 µm |
| Residual VAc monomer | GC‑HS, EPA 8260D | <500 ppm |
| APEO content | DIN EN ISO 18254‑1 | none detected |
In laminated paper‑board packaging, the absence of external plasticizers allows direct contact with fatty and dry foodstuffs without plasticizer extraction (migration testing per EU 10/2011, overall migration <10 mg/dm²). Converters running air‑knife or rod‑coat lines at line speeds exceeding
150 m/min observe good mechanical stability under recirculation: after
30 min in a high‑shear gear pump loop (Waukesha Cherry‑Burrell, 600 s⁻¹), viscosity loss is typically below
8 %, and micro‑foam generation remains below
2 % of the total volume when defoamer is omitted. The low‑shear viscosity profile makes BJ-705 suitable for roller‑coat applications where a coat weight of
40–60 g/m² (wet) is targeted, because the emulsion does not “crawl” or dewet from clay‑coated board surfaces at application speeds. When formulated with
1.0–1.5 % (on wet weight) of a glyoxal‑based crosslinker, wet rub resistance (ISO 105‑X12, water) improves by a factor of 3 over the uncrosslinked control, while preserving a film elongation above
400 %.
Where BJ-705 Diverges from PVAc Homopolymer Emulsions – a Comparative Snapshot
Product differentiation becomes most apparent under conditions of fluctuating ambient humidity. PVAc homopolymer films plasticized with 10–15 % dibutyl phthalate (DBP) lose dimensional stability at relative humidity (RH) above 80 % because water ingress accelerates plasticizer hydrolysis and surface‑blooming. BJ-705 films, containing no external plasticizer, do not exhibit exudation. In high‑frequency wood bonding, assembly‑line trials on a Hess OMS multi‑spindle glue spreader with spruce (Picea abies) lamellas demonstrated that BJ-705, when catalyzed with
3 % aluminum chloride solution (
30 % conc.), met the EN 204 D3 durability classification (4 h cold water soak, recovery> 60 % of dry strength), whereas a DBP‑plasticized homopolymer failed due to plasticizer leaching, yielding residual strengths below
2 N/mm². BJ-705 also circumvents the volatile organic compound (VOC) burden associated with coalescing‑solvent‑laden acrylic dispersions, maintaining a VOC content of
<1 g/L (ISO 11890‑2) without the need for Texanol or butyl glycol.
Open‑time extension without sacrificing heat creep resistance
On fully automatic edge banding machines (e.g., Homag KAL 310) where hot‑melt polyurethane reactive adhesives dominate, BJ-705 is employed in specialty cold‑press manual operations for curved profiles. The key formulation challenge is balancing open time against heat resistance. Neat BJ-705 exhibits a wet tack time of approximately
4–7 minutes on high‑pressure laminate (HPL) with moisture content <8 %. Addition of
0.3–0.8 % (w/w dry polymer) carboxymethyl cellulose (low‑viscosity type, DS <0.9) extends the open phase to
10–12 minutes, allowing repositioning. However, the inclusion of water‑soluble thickeners depresses heat‑resistance temperature (EN 14257, step test) from
65–70 °C to
52–58 °C. To recover performance, a blocked isocyanate dispersed in BJ-705 at
2.5 % on resin solids is preferred; post‑cure (
3 days at 40 °C) elevates the heat resistance beyond
80 °C while the thickener‑extended open time is preserved.
The emulsion demonstrates high compatibility with a range of water‑dispersible isocyanates and aziridine crosslinkers, but pot‑life constraints demand attention. When mixed with a hydrophilically modified HDI‑trimer (NCO content 19–21 %), the formulation gels within
45–55 minutes at 23 °C, requiring static mixer application and frequent purging on discontinuous layouts. Anhydrous aluminum chloride catalysis avoids the pot‑life cliff but necessitates a forced‑drying station; without thermal activation (
> 45 °C for 2 min), crosslinking efficiency drops below 40 %.
Textile lamination of nonwoven webs (carded polyester, 30 gsm) using spray‑foam application benefits from the pseudoplastic flow character. Viscosity measured at a shear rate of 1000 s⁻¹ (controlled‑stress rheometer, ISO 3219) remains below
200 mPa·s, enabling fine atomization through nozzle systems operating at 2–3 bar air pressure. Peel strengths on PET nonwoven‑to‑PET film (T‑peel, ASTM D1876, 300 mm/min) reach
2.3–3.1 N/25 mm after
24 h ambient cure, without the “zippy” peel typical of stiff acrylic binders that crack the fiber loops. Published data on low‑denier (<1 dpf) bicomponent fiber interlaminar bonding confirms that high‑ethylene VAEs like BJ-705 prevent fiber‑tear migration failures seen with vinyl acetate‑VeoVa copolymers, because the adhesive film’s elongation better matches the substrate’s deformation.
Operational Boundaries and Material Incompatibilities
Two explicit processing restrictions govern the use of BJ-705 in non‑woven and construction adhesives. First, direct blending with polyamine‑based curing agents (e.g., diethylenetriamine adducts) rapidly causes pH shock and micro‑coagulation because the isoelectric point of the PVOH stabilizer is near
pH 3.5, and an alkaline environment above
pH 8.5 de‑stabilizes the colloid. Pre‑buffering with citric acid to a pH of
5.8–6.2 is necessary before amine addition. Second, cement‑based tile adhesive formulations should be avoided entirely: the alkaline hydrolysis of the vinyl acetate backbone releases acetate ions that retard alite hydration and can depress 28‑day compressive strength (EN 196‑1) by more than
30 %. Published saponification half‑lives at
pH 12.5 and 23 °C indicate significant degradation within
6–8 hours, making BJ-705 unsuitable for hydraulic‑binder modification. The product is fit for cement‑free mastics and waterproofing pastes where it acts as the sole binder, providing crack‑bridging ability (DIN EN 1062‑7, class A4) at dry film thicknesses from
0.5–1.5 mm. When stored in unopened containers at 5–30 °C, the emulsion shows less than
0.5 % sediment after
6 months (ISO 15715), and scraping of bottom‑settle is unnecessary if gentle recirculation is applied for
10 minutes prior to transfer to day tanks.
BJ-705 versus a lower‑ethylene VAE grade (BJ-704) in a model bookbinding adhesive
| Performance criterion | Method | BJ-705 (18–22 % ethylene) | BJ-704 (9–11 % ethylene) |
|---|
| Film elongation at break | ISO 527‑3 | 680 % | 350 % |
| Adhesion to biaxially oriented PP (corona 42 dynes/cm) | FINAT FTM 1 (180° peel) | 2.8 N/25 mm | 0.8 N/25 mm |
| Low‑temperature flexibility (mandrel bend, −20 °C) | DIN EN 13523‑7 | no cracking | hairline cracks |
| Page‑pull strength (coated art paper, 80 gsm, PUR‑bound) | Internal method (ISO 1924‑2 adapted) | 5.2 N/cm | 4.2 N/cm |
| Dry shear on oak (EN 204 D2) | EN 205 | 4.1 N/mm² | 5.8 N/mm² |
Where the process demands high cohesive strength and shear resistance on wood, the lower‑ethylene grade may be preferred; however, BJ-705 is selected when substrate wetting, elongation, and low‑modulus flexibility dominate. Published adhesion tests using flame‑treated polypropylene (contact angle with water <55°) confirm that BJ-705 provides a critical surface tension overlap without primer, while the lower‑ethylene analog requires an additional chlorinated polyolefin prime coat to reach comparable peel levels. In carpet secondary backing lamination, BJ-705, compounded with
20 wt% calcium carbonate filler (d50 = 8 µm), delivers tuft‑bind strength averaging
6.4 N (ISO 4919), approaching the performance of styrene‑butadiene latexes but without the 4‑phenylcyclohexene odor and with lower total VOC. The emulsion withstands the mechanical work input of a twin‑screw compounder (Werner & Pfleiderer ZSK‑25, L/D 40) at 80 °C barrel temperature without pre‑coagulating, provided the free water content remains> 40 % throughout the processing zone. When higher filler loadings are attempted (> 30 phr), dynamic surface tension constraints cause foaming that requires vacuum de‑aeration of the makedown tank; published recommendations suggest adding 0.15 % by weight of a non‑silicone acetylenic diol‑based defoamer to maintain entrained air below
2 vol%.
