SELVOL Álcool Polivinílico 15-103 Solução

In vinyl acetate homopolymerization and vinyl acetate-ethylene copolymerization, SELVOL Polyvinyl Alcohol 15-103 Solution acts as the primary protective colloid rather than as a simple thickening additive. The grade is a partially hydrolyzed PVOH with a nominal hydroxyl content of 87–89 mol%; residual acetate sequences lower interfacial tension at the monomer-water boundary, while the 1,3-diol backbone retains cold-water solubility and steric stabilisation of the latex. The solution is normally diluted with deionized water to 6.0–8.0 wt% PVOH solids before reactor charging. Industrial latex recipes allocate 3.0–5.5 wt% PVOH on total vinyl acetate monomer, with 15–20% of the colloid placed in the initial aqueous heel and the remaining 80–85% metered as a delayed feed over 3.0–4.5 h. Monomer feed is synchronized to the delayed colloid stream to hold the nucleation droplet population within 200–500 nm. Reactor jacket temperature is controlled at 68–75 °C, and the aqueous phase pH is buffered between 4.5 and 5.5 with sodium bicarbonate or dilute acetate buffer. Baffled glass-lined reactors with dual hydrofoil impellers are operated at a tip speed of 1.5–2.5 m/s. At tip speeds above 3.0 m/s, production-scale batches can develop shear-induced microflocculation that raises final filter pressure drop and increases coagulum on the reactor wall.

The delayed feed ratio is not adjusted arbitrarily. When the PVOH protective colloid level is pushed below 2.5 wt% on monomer, the latex particle size shifts upward and shear stability collapses; when the level exceeds 6.0 wt%, final emulsion viscosity typically rises above 20,000 mPa·s and water resistance of the dried adhesive film decreases. Post-polymerization pH adjustment with sodium bicarbonate solution brings the product to pH 4.0–5.0. Defoamer dosage is limited to 0.1–0.3 wt% because excessive silicone defoamer creates fisheyes in downstream cast adhesive films. The finished polyvinyl acetate homopolymer emulsion is discharged at 50–55% solids, with Brookfield viscosity from 5,000 mPa·s to 15,000 mPa·s at 25 °C using spindle 3 at 20 rpm according to ASTM D2196. Residual vinyl acetate monomer is reduced below 0.1 wt% by a post-polymerization initiator polish. The emulsion is used in woodworking adhesives classified under EN 204 D3 for interior non-structural assembly, in paper-to-paper laminating adhesives, and in envelope back-seam adhesives. Compliance for indirect food-contact adhesive applications follows FDA 21 CFR 175.105, and paper or paperboard coated with the emulsion may be evaluated under FDA 21 CFR 176.170.

Surface sizing response in clay-coated board at low size-press solids

At the size press of a clay-coated recycled board machine, 15-103 solution is metered into a starch-based or styrene-acrylate size-press formulation to improve IGT pick strength and wet rub resistance. The use concentration on a dry basis is typically 2.0–4.5 wt% PVOH on total size-press solids. The as-supplied solution is diluted to 5.0–6.0 wt% solids and combined with a thin-boiling starch or an anionic dispersant; the final size-press bath is run at 50–65 °C and pH 7.0–8.5. On machine, a puddle-type size press or metering film press applies a dry pick-up of 0.4–1.2 g/m² per side. The wet film is dried with conventional steam-heated cans and air caps at sheet surface temperatures not exceeding 105 °C. For water resistance, glyoxal conditioning is incorporated at 2.0–5.0 wt% on PVOH solids, catalyzed by ammonium chloride at 0.2–0.4 wt%; this reaction is pH-sensitive, and bath pH must be held below 5.5 after glyoxal addition to avoid premature acetal formation before the size press. The major process conflict on production machines is viscosity drift caused by starch retrogradation when the size-press bath is held for longer than 4 h. The resulting board is used for folding carton stock, beverage carrier board, and preprint liner. Test methods applied to finished board include TAPPI T 441 for Cobb water absorptiveness, TAPPI T 476 for wet rub resistance, and ISO 8791-2 for Parker PrintSurf roughness.

In addition to size-press work, 15-103 solution is used as a PVOH barrier precoat on paperboard before extrusion coating with low-density polyethylene. The precoat is applied at 0.5–1.5 g/m² dry by rod coater; its function is to close surface pores and reduce pinholing at 15–25 g/m² LDPE. The precoat is evaluated by pinhole testing under TAPPI T 538 and by hot-tack peel after extrusion. This application requires the precoat surface to resist rewetting from residual moisture in the paperboard; a wetting-agent level above 0.3 wt% in the precoat formula is therefore avoided.

What limits warp-sizing add-on control when 15-103 replaces starch?

Spun polyester/cotton warp sizing uses 15-103 solution as a film former at a concentration of 6.0–9.0 wt% solids in the size box. A typical size liquor blends 55 wt% of 15-103 PVOH solids, 38 wt% modified starch, 5 wt% high-density polyethylene wax dispersion, and 2 wt% antistatic agent on a dry solids basis. The combined liquor is held at 85–90 °C and applied by a two-squeeze-roll size box using squeeze pressures between 8 kN/m and 15 kN/m. Filament or spun yarns are processed at 70–120 m/min, with dry-can section temperatures staged from 90 °C to 120 °C. Squeeze rolls are operated at 70–85 Shore A hardness, with the top roll offset 3–5 mm toward the warp sheet to prevent size splash and edge bead defects. The primary process limitation is not solubility but high-humidity elongation: 15-103 films plasticized by residual moisture above 8% will generate size coat shedding at lease rods and drop wires. Control therefore requires constant moisture measurement after the final can, with target regain below 6% before the yarn enters the split rod section. Desizing of woven fabric made from sized warp is performed in a continuous open-width washer at 80–90 °C with 1.0–2.0 g/L nonionic wetting agent. Sized-yarn tensile and abrasion are tested according to ASTM D2256 for breaking force and ISO 2062 for single-end yarn tenacity. The formulation avoids alkylphenol ethoxylates and is suitable for mills operating under ZDHC MRSL conformance. End uses include bed sheeting, workwear shirting, and coated abrasives backings.

Reactivation speed, open time, and block resistance in remoistenable tape gums

For water-activatable kraft tape and envelope seam gum, 15-103 solution is compounded in a high-shear dissolver at 1,500–2,000 rpm with a dextrin co-binder, a humectant plasticizer, and a biocide. A production formula consists of 60 wt% PVOH solids, 22 wt% thin-boiling dextrin, 12 wt% glycerol, 4 wt% urea, and 2 wt% preservative/defoamer blend on dry solids. The coating compound is held at 55–65 °C and applied to bleached or unbleached kraft by reverse gravure or air-knife coating at a dry coat weight of 15–20 g/m². Drying is conducted in a floating dryer with the first zone at 80 °C and the final zone at 100 °C; web surface temperature is not allowed to exceed 105 °C because tack would develop in the cumulative dryer hood before re-moistening. Rewetting activation speed is characterized by applying a 10 µm water film to the dry adhesive and measuring the interval to develop measurable fibre tear on recycled corrugated board under 180° peel. This partially hydrolyzed grade rewets faster than fully hydrolyzed high-viscosity PVOH because the residual acetate groups reduce crystallinity, but the same structural feature lowers high-humidity block resistance at 35 °C and 80% RH. The formulated gum is therefore tested for blocking under a 5 kg weight on 25 cm² stacked specimens according to TAPPI T 477, and for adhesion of gummed tape according to TAPPI T 455. End products include water-activated tape for case sealing, envelope closures, and paperboard label gums.

In oxide ceramic powder granulation, the 15-103 solution is injected into the spray-dryer feed slurry as a binder for alumina, zirconia, silicon nitride, or mixed-oxide press powders. The solution is added at 0.5–2.0 wt% PVOH on dry ceramic solids, normalized to the solids content of the as-supplied solution. The slurry is milled to a median particle size of 0.6–1.2 µm before spray drying. A rotary atomizer running at 10,000–15,000 rpm or a single-fluid nozzle at 20–30 bar generates droplets that are dried in a chamber with inlet air temperature 180–220 °C and outlet temperature 85–105 °C. The formed granules are screened to 75–250 µm for dry pressing. In subsequent uniaxial pressing at 100–200 MPa, the binder imparts green strength sufficient for edge retention and green machining. The binder burnout is performed in air at 400–550 °C, with a slow ramp of 1–3 °C/min through the 200–350 °C decomposition window to avoid carbon residue and interlayer delamination. Green strength of pressed compacts is measured according to ASTM B312 for metal and carbide powders or by a three-point bend method adapted from ASTM C1161 for advanced ceramic test bars. The binder system is free of chlorinated solvents and is compatible with air-emission permit limits for volatile organic carbon during spray drying. End products include ceramic substrates, honeycomb catalyst supports, and multilayer capacitor dielectric bodies.

Slurry pH is adjusted to 9–10 with ammonium hydroxide before binder addition when processing alumina, because the anionic PVOH interacts with aluminum hydroxide surfaces to produce a controlled flocculation that stabilizes spray-dried granules. The zeta potential of the final slurry is maintained between -30 mV and -45 mV to prevent binder segregation and settling. Binder addition must be delayed until after the final pH adjustment; adding PVOH to an acidic alum-containing slip above 60 °C can form visible gel strings that survive the atomizer and appear as hard agglomerates in dry-pressed tile bodies.

When a 15-103 cast film is dried below its glass transition

Water-soluble film can be cast from 15-103 solution onto a polyethylene terephthalate carrier using a comma bar or slot die. The solution is adjusted to 8–12 wt% solids and deaerated under vacuum at 50–80 mbar before casting. Wet film thickness is set between 400 µm and 700 µm to yield a dry film of 35–50 µm after passing through a three-zone convection dryer with air temperatures of 80 °C, 100 °C, and 110 °C. Drying below the glass transition of the solution-cast PVOH film leads to curl and physical aging after stripping from the carrier. To prevent this failure mode, the third drying zone is held at 100–110 °C, and the carrier surface temperature is allowed to drop below 35 °C before peeling. Glycerol or sorbitol is required at 10–20 phr to maintain flexibility; above 25 phr plasticizer surface migration becomes visible within 72 h at 23 °C and 50% RH. The cast film is evaluated according to ASTM D882 for tensile strength and elongation at break, and ASTM D570 for water absorption. Dissolution time in water at 25 °C for a 40 µm unplasticized film is typically below 60 s; plasticized films dissolve more slowly. End uses include embroidery stabilizer, detergent pod backing film, and water-transfer printing film. For water-transfer printing film, corona treatment at 2.0–3.0 kW is applied before ink deposition, and printed transfer time should be kept below 90 s to limit premature solubilisation of the carrier film. For detergent unit-dose packaging, the film must also pass EN 13432 biodegradation testing or the specific brand owner solubility protocol.