KURARAY POVAL 22-88 LV

In vinyl acetate-ethylene (VAE) dispersion polymerisation, KURARAY POVAL 22-88 LV serves as the primary protective colloid in a stirred stainless-steel pressure reactor fitted with a 45° pitched-blade turbine impeller and jacket cooling capable of maintaining polymerisation temperature within ±2°C during the ethylene/vinyl acetate copolymerisation stage. The colloid is prepared by dispersing the powder in demineralised water at 8–12 wt% and heating to 90–95°C for 45–60 min until a clear solution with a Brookfield viscosity of 220–260 mPa·s at 20°C is obtained. It is then charged to the reactor at 4–8 phm based on vinyl acetate monomer mass. This addition range permits 54–60% solids VAE dispersions with final viscosity controlled to 3,500–6,500 mPa·s measured according to ISO 2555:2018 using a Brookfield RVT viscometer, spindle 6, 20 rpm, at 20°C. The same dispersion lot is checked for pH within 4.2–5.0 and residual vinyl acetate monomer below 1,000 mg/kg before release. The low-viscosity colloid leaves sufficient formulation headroom for high-solids end-use compounds without exceeding the pumping and filtration thresholds of downstream adhesive lines.

During production-scale polymerisation, the pre-dissolved KURARAY POVAL 22-88 LV is split between initial charge and delayed feed. The delayed feed is introduced over 4–6 h as monomer conversion passes 35% to maintain narrow particle-size distribution and to limit reactor wall fouling. If the initial charge exceeds 70% of total colloid, batch-to-batch viscosity variability increases because later-stage grafting is insufficient. Feeding the colloid too late, after 55% conversion, raises gel content and produces filter-coating defects in the finished dispersion. The polymerisation pH must remain below 6.5; amine-based buffers should be avoided because hydrolysis of residual acetate groups can cause a storage viscosity drift greater than 500 mPa·s. Non-volatile matter is checked using ISO 3251:2019, and adhesives made from the dispersion fall under FDA 21 CFR 175.105 or REACH Regulation 1907/2006 as appropriate for the final market. Terminal products include D3/D4 wood adhesives classified under EN 204:2016, carpet-backing compounds, and paper-to-paper lamination adhesives.

How does 22-88 LV behave when casting water-soluble unit-dose film?

In water-soluble film produced by aqueous solution casting, the low-viscosity partial-hydrolysis grade permits a higher solids content in the casting solution than medium-viscosity PVOH grades, typically 22–28 wt% solids at 80–95°C, while maintaining slot-die pressure below 1,500 kPa on a polished steel belt or drum drier. The dry-film formulation is built around 60–75 wt% KURARAY POVAL 22-88 LV on dry solids, with 8–15 wt% plasticiser such as glycerol or sorbitol, 0.5–2.0 wt% anti-foam and antiblock additives, and process water adjusted to laydown weight. Compliance for detergent unit-dose packaging is screened through OECD 301B ready biodegradability, EU Regulation 648/2004 detergent safety requirements, and ISO 527-3:2018 for cast-film tensile properties after conditioning at 23 ± 2°C and 50 ± 5% RH according to ISO 291:2008. Published data for this specific 22-88 LV cast-film configuration is limited; therefore, solubility and seal-strength specifications should be verified on the intended pouch converting line before formula finalisation.

The aqueous solution is filtered through a 2–5 µm depth filter before the slot die to remove undissolved microgels, then cast as a wet film and dried in a multi-zone tunnel with zone temperatures rising from 70°C to 110°C until residual moisture falls to 6–10 wt%. Production-scale lines show that initial-zone air velocity must remain below 8 m·s⁻¹ to prevent surface skinning and entrapped bubbles, which later appear as pinhole defects in converted pouches. Water temperature below 20°C slows film disintegration; cold-water unit-dose formats require additional disintegrants or higher-plasticiser film designs. Terminal products are detergent unit-dose pouches, dishwasher tablet wrap, and agrochemical water-soluble sachets.

Paper size press response with 22-88 LV in co-batched starch systems

At the size press or film press, KURARAY POVAL 22-88 LV is co-batched with thin-boiling starch at 10–30% of dry starch mass, corresponding to 1.0–4.0 wt% total solids in the size solution. The low-viscosity grade is selected when the target wet pickup is 40–70 g/m² and the sheet surface must retain openness for downstream ink absorption; final dry pickup of polyvinyl alcohol typically falls between 0.15–0.60 g/m² per side at machine speeds of 600–1,000 m·min⁻¹. Compliance for food-contact paper and board is evaluated under FDA 21 CFR 176.170 and 176.180, while sizing response is measured by ISO 535:2014 Cobb60 and TAPPI T 530 om-17 Hercules size test.

The size solution is cooked at 95–100°C for 20–30 min and held at 60–70°C in the run tank. A metering size press or rod coater applies the film to uncoated fine paper or recycled board, followed by a drying section with cylinder temperatures decreasing from 120°C to 90°C. Because 22-88 LV has lower molecular weight than 30-88 grades, it penetrates more aggressively into the sheet; at addition above 4.0 wt% of total size solution, single-pass film strength gain is limited. Production-scale trials have also shown increased starch/PVOH gel filming on doctor blades when run-tank solids exceed 12%. The treated paper and board are converted into offset printing, inkjet-compatible stationery, and folding-carton packaging.

Dry-pressed technical ceramic bodies require a temporary binder that is fully water-soluble, does not introduce polyvalent cations, and burns out below the onset of densification. KURARAY POVAL 22-88 LV is added at 0.5–1.5 wt% on dry body solids, typically as a 5–10 wt% aqueous solution dosed into a ball-milled slip containing 55–65 wt% solids prior to spray drying. The slip is spray-dried through a rotary atomiser at inlet 180–220°C and outlet 70–90°C to produce free-flowing spherical granules with a moisture content of 1–3 wt%, which are then uniaxially pressed at 30–50 MPa and sintered. Compliance for the fired tile or technical ceramic is evaluated under ISO 13006:2018 and EU Construction Products Regulation 305/2011. Binder lot release commonly includes ash content below 0.5 wt% and residue on a 45 µm sieve below 0.1%. Burnout must be completed between 400°C and 700°C in oxidising atmosphere for at least 30 min; residual carbon above 0.1 wt% after burnout has been associated with edge cracking and glaze pinholes in production-kiln trials. Terminal products include dry-pressed technical alumina substrates, steatite electrical ceramics, and porcelain stoneware tiles.

When 22-88 LV replaces higher-viscosity grades in warp sizing

In shuttleless air-jet and rapier weaving, replacement of higher-viscosity PVOH grades with KURARAY POVAL 22-88 LV calls for a size formulation at 8–12 wt% solids containing 0.5–1.5 wt% wax or softener on total liquor, applied in a multi-cylinder wet-on-dry sizing box at 75–85°C with a wet pickup of 120–180% to produce sized warp yarn for polyester-cotton apparel and furnishings, with compliance verified against OEKO-TEX Standard 100 for extractable residues on the finished fabric.

Remoistenable adhesive film formation, rewetting, and block resistance

Aqueous rewettable adhesive formulations containing 5–12 wt% KURARAY POVAL 22-88 LV on dry solids are applied by differential-speed roll coater at 20–40 g/m² dry coat weight onto paper or board substrates, then dried in an air-float oven at 50–70°C to residual moisture of 6–10%. The grade provides film cohesion at low coat weight while re-activation with a water mist under 1–3 kPa rewetting pressure re-opens the film for envelope flaps, label backs, and stamp gum. Compliance for food-contact packaging adhesives falls under FDA 21 CFR 175.105, with adhesive film blocking resistance evaluated by subjecting stacked coated sheets to 50°C and 70% RH for 48 h in a conditioned pressure jig. At relative humidity above 65%, unplasticised film absorbs atmospheric moisture and tack increases; therefore, dry coat weight should not exceed 40 g/m² in high-humidity conversion environments without the addition of 0.5–1.0 wt% glyceryl monostearate anti-block. Terminal product types are remoistenable envelope flaps, label backing adhesives, and postage-stamp gum.