GOHSENOL EG-48P

GOHSENOL EG-48P is a partially hydrolysed polyvinyl alcohol powder characterised in the manufacturer’s certificate of analysis by a 4 wt% aqueous solution viscosity of 43–53 mPa·s at 20 °C under JIS K6726 rotational viscometry. The degree of hydrolysis lies between 86.5 mol% and 89.0 mol%, equivalent to a residual acetyl content of 11.0–13.5 mol%. Volatile matter is controlled at ≤ 5.0 wt% and ignition residue at ≤ 0.5 wt% after calcination. The hydrolysis window places EG-48P in the partially saponified class, where cold-water wetting is retained while the high degree of polymerisation raises extensional viscosity, film strength, and water-phase stabilisation at low addition rates. In downstream processing, the powder is slurried in cold water before heated dissolution to avoid gel skins on vessel walls; the hydration rate is non-linear above 8 wt% solids and depends on impeller tip speed and vessel geometry.

Does a High-DP Partially Hydrolysed PVOH Reduce Fish-Eye Defects in Vinyl Chloride Suspension Polymerisation?

In vinyl chloride suspension polymerisation, EG-48P is charged as the primary suspending agent at 0.06–0.12 wt% on VCM mass, with total PVOH charge split between EG-48P and a lower-hydrolysis secondary PVOH of 72–74 mol% at a mass ratio of 3:1 to 4:1. The water phase is prepared by dispersing the powder in deionised water at 15–25 °C, then heating to 85–90 °C for 60–90 min under 300–600 rpm low-shear agitation. The solution is cooled to 20–30 °C before reactor charging. The high degree of polymerisation raises water-phase viscosity and interfacial film strength at the VCM/water boundary; this influences PVC grain porosity and plasticiser uptake measured as dioctyl phthalate absorption per ISO 4608, which is typically controlled in the 0.25–0.35 cm³/g range for suspension resin. In production autoclaves of 10–30 m³ with Rushton turbines at 250–350 rpm, undissolved PVOH microgels appear as clear fish-eye particles in calendered sheet. To avoid this, the make-up vessel is fitted with a PTFE scraper and the solution is filtered through a 100 µm stainless steel screen before charging. Residual ash above 0.5 wt% can stabilise reactor emulsion carryover and increase PVC dry resin fines below 63 µm; periodic reactor inspection for polymer scale is required. Compliance for final PVC food-contact uses is assessed under Commission Regulation (EU) No 10/2011 for overall migration, while the PVOH component is documented in the resin producer’s food-contact declaration. The terminal product is suspension PVC resin for rigid and plasticised applications, including pipe, profiles, and packaging film, where fish-eye density is a critical downstream quality parameter.

In vinyl acetate–ethylene and vinyl acetate–acrylic emulsion polymerisation, EG-48P is handled as a 10 wt% stock solution and post-added into the initial reactor charge at 1.5–4.0 wt% on total monomer. The solution is prepared with demineralised water and held at 85–90 °C for 60 min; the pH of the stock is adjusted to 5.0–7.0 with dilute acetic acid or sodium bicarbonate, not with strong alkali, to prevent base-catalysed deacetylation during storage. The protective colloid adsorbs at the growing polymer particle surface; partially hydrolysed PVOH with a residual acetyl content above 11 mol% reduces particle coagulation while maintaining final emulsion viscosity in the 3,000–15,000 mPa·s range at 25 °C by ISO 2555. The terminal products are woodworking and packaging adhesives meeting EN 204 durability classes D2 or D3, depending on crosslinker addition. Process incompatibility arises with borate ions: boron above 0.1 wt% on latex solids causes reversible PVOH-borate network formation, increasing low-shear viscosity and producing stringing in roller coating. Stability trials include freeze-thaw cycling per ASTM D2243 and overnight viscosity drift at 50 °C. Because the high-DP grade produces high extensional viscosity, delayed addition during the monomer feed can cause transient viscosity spikes; the stock solution is metered into the aqueous phase rather than into the pre-emulsion.

When a 48 mPa·s PVOH Grade Replaces Cooked Starch in High-Speed Paper Sack Bottom Pasting

In high-speed paper sack bottom pasting, EG-48P is compounded with borated dextrin at a dry-weight ratio of 1:1 to 1:2, diluted to a final viscosity of 200–500 mPa·s at 25 °C by Brookfield LVF, spindle 3, 60 rpm. The PVOH solution is first prepared at 8–10 wt%; the cooked starch component is added at 80–85 °C, and the mixture is cooled under slow agitation. The high-DP PVOH contributes wet tack on recycled kraft liner, and the target open time is set by the packaging line, typically 10–30 s, tuned with the starch ratio. On rotary bottom-paste lines running at 120–180 bags/min, the adhesive is applied through a 0.3 mm doctor-roll gap; excessive high-shear viscosity causes fibre picking and doctor-roll streaking. Defoamer addition is limited to 0.1–0.2 wt% because mineral-oil defoamers above this level reduce wet tack. Biocide preservation is required at pH 5.0–7.0 to prevent Pseudomonas growth in overnight hold tanks. Regulatory status for dry food packaging is documented under FDA 21 CFR 175.105 and 21 CFR 176.170. Failure mode in summer production is viscosity loss due to microbial degradation, identified by a drop of more than 15% in Brookfield viscosity within 24 h. The terminal product is multi-wall paper sacks for dry food and industrial powder packaging, where adhesive stringing and seam pop-open are the primary rejection criteria.

At 800 rpm air-jet loom speed for 60/40 polyester-cotton warps, a size bath containing 10–12 wt% EG-48P and 4–6 wt% oxidized corn starch produces a size add-on of 8–12% dry weight on warp. The PVOH is dissolved in the size kitchen at 85–90 °C and delivered to the slasher box at 80–85 °C; viscosity in the size box is held between 15–25 s by a Zahn cup No. 3 at 80 °C. High-DP PVOH reduces size penetration into the yarn core and increases surface film formation; for spun yarns this lowers hairiness and improves weaving stops per 100,000 picks, although exact loom efficiency data for EG-48P are line-dependent. After weaving, the size is removed at 90–95 °C with 0.3–0.5 g/L non-ionic wetting agent and, where required, oxidative desizing with 1–2 g/L hydrogen peroxide at pH 10–11. Effluent compliance follows ZDHC MRSL V3.1; drains are assessed for COD load because EG-48P contributes soluble organic carbon, and PVOH recovery by ultrafiltration is feasible only if starch is excluded from the formulation. The terminal product is woven polyester-cotton fabric for workwear and home textiles, where residual size after desizing is controlled to avoid dyeing defects.

Water-Soluble Film Casting and Detergent Unit-Dose Compatibility Limits for 86.5–89.0 mol% PVOH

For water-soluble film casting, EG-48P is dissolved at 15–20 wt% and cast through a slot die onto a chill roll at 80–100 °C; glycerol plasticiser is added at 10–20 parts per hundred resin. A similar partially saponified high-DP PVOH yields film tensile strength in the 40–60 MPa range and elongation at break of 150–250% when conditioned at 23 °C and 50% RH and tested per ISO 527-3:2018, though published data specifically for EG-48P are limited and should be confirmed on a laboratory caster. In detergent unit-dose applications, the 86.5–89.0 mol% hydrolysis window provides a cold-water dissolution time below 60 s in 10 °C water at a film thickness of 76 µm, but the high degree of polymerisation increases solution viscosity within the dissolving film boundary layer and may slow disintegration in low-water washing machines. Alkalinity above pH 11 causes saponification of residual acetate groups and can shift solubility upward over time; films stored at 40 °C and 75% RH show blocking and increased insoluble residue. Compatibility with liquid detergents containing anionic surfactants, glycols, and propylene carbonate is tested by accelerated storage at 40 °C and 75% RH. The terminal product is water-soluble film for detergent pouches and agrochemical packaging, where dissolution residue after cold wash and blocking during tropical storage are the primary failure modes.

Dry-pressed alumina bodies are compounded with 2.0–3.0 wt% EG-48P based on ceramic solids, added as a 10 wt% solution during spray drying of a 50 wt% solids slip. The binder increases green strength measured by three-point bending per ASTM C1161 on 4 mm × 8 mm × 40 mm bars; green density is not adversely affected if residual moisture is kept below 1.5 wt%. During burnout, EG-48P decomposes below 500 °C; the 0.5 wt% ash specification is acceptable for alumina but must be verified for silicon nitride or other non-oxide ceramics where metallic residues affect high-temperature properties. The terminal products are wear-resistant alumina plates and spark plug insulators, where binder burnout must not leave carbon clusters above 0.1 wt% before sintering.

Pigment Coating Binder Viscosity Can Be Predicted from EG-48P Spray-Dried Granule Hydration Kinetics

In paper and paperboard pigmented coating, EG-48P is employed as a co-binder at 2–5 parts per hundred dry pigment, with the pigment blend typically 70 parts fine ground calcium carbonate and 30 parts No. 2 kaolin. The coating colour is prepared at 60–65% solids and applied by blade coater; high-shear viscosity at 10⁵ s^-1 must remain below 120 mPa·s, measured with an ACAV capillary viscometer, to prevent bleeding and streaking. EG-48P addition raises low-shear viscosity and water retention, but the high-DP chain also increases surface strength measured by ISO 3783 IGT pick. A process conflict occurs when the PVOH is added as dry powder directly into the high-solids coating slip: undissolved granules persist and appear as clear spots after calendering. The granule is therefore pre-dissolved at 10 wt% and post-diluted into the letdown at 50–60 °C. The terminal product is double-coated fine paper for offset printing; compliance for food-contact paperboard is documented under 21 CFR 176.170 and 21 CFR 176.180.