GOHSENOL GM-14

GOHSENOL GM-14 is a partially hydrolyzed polyvinyl alcohol (PVOH) powder with a degree of hydrolysis of 86.5–89.0 mol% and a 4% aqueous solution viscosity at 20°C of 20.5–24.5 mPa·s when tested according to JIS K6726. The material is supplied as a white to pale-yellow granule or powder, with volatile content not exceeding 5.0% and ash content expressed as Na₂O not exceeding 0.5%. The pH of a 4% aqueous solution is typically 5.0–7.0, and the CAS registry number is 9002-89-5. The grade is defined by simultaneous partial saponification and medium-low molecular weight, which reduces cold-water dispersion energy compared with fully hydrolyzed PVOH of the same solution viscosity and allows more uniform penetration into porous substrates.

The combination of hydrolysis and viscosity places GOHSENOL GM-14 between low-viscosity partially hydrolyzed grades such as GL-05 and higher-viscosity partially hydrolyzed grades such as GH-17. In adhesive compounding, the 20.5–24.5 mPa·s solution viscosity permits wetting of cellulose surfaces without excessive thickening, while the residual acetyl content of 11.0–13.5 mol% retards crystalline domain development during film drying. This property set shifts the grade toward applications requiring cold-water re-dispersibility, controlled penetration, and moderate film strength.

What process constraints govern cold-water compounding of this partially hydrolyzed PVOH?

Process constraints in cold-water compounding are determined by dissolution temperature profile and shear history. GOHSENOL GM-14 disperses in cold water at 10–20°C; however, a top-entering propeller agitator at 0.5–1.5 kW/m³ power input is normally required to prevent particle agglomeration before the batch is heated. If the powder is added directly to water above 40°C, gel skins form on the particle surface and partially hydrolyzed PVOH particles become resistant to further hydration without high-shear homogenization. The recommended dissolution procedure is to sift the powder into a vortex under moderate agitation, hold the slurry at 10–20°C for 15–30 min, then raise the batch to 80–85°C and hold for 30 min until the solution clears. Exceeding 95°C promotes chain scission and yellowing; below 75°C, residual microgel persists and filtration through 100 µm screen packs becomes difficult.

In production mixers, the dissolution endpoint can be checked by refractive index or by torque stabilization rather than visual clarity alone. For a 10% solids solution, the Brookfield viscosity at 25°C is higher than the 4% datasheet value; when a process is transferred from a laboratory propeller to a gear-driven side-entry mixer, the apparent viscosity can be underestimated if measured only at low shear. Published data for this specific configuration is limited, but batch logs from jacketed mixing vessels show that the torque curve reaches equilibrium only after the temperature has remained above 80°C for at least 20 min.

For emulsion polymerization of vinyl acetate and vinyl acetate–ethylene systems, GOHSENOL GM-14 functions as a protective colloid and viscosity control agent. The 86.5–89.0 mol% hydrolysis range is a partial-saponification window that balances surface activity at the monomer–water interface with water solubility; in a 65°C batch reactor with an anchor or pitched-blade agitator, a 4–6 wt% aqueous solution of the grade is charged before monomer addition to maintain particle size stability. The 20.5–24.5 mPa·s viscosity of a 4% solution at 20°C corresponds to relatively low shear viscosity during initial dispersion; once the reactor reaches polymerization temperature, the solution viscosity decreases with temperature, which can reduce the protective colloid layer thickness under high shear. Reactor optimization therefore relies on monitored torque curves and particle-size distributions measured by dynamic light scattering in accordance with ISO 22412:2017.

The material is also used as a secondary protective colloid in acrylic and styrene-acrylic emulsion synthesis where it contributes to shear stability rather than primary stabilization. In such systems, addition rates of 0.5–2.0 wt% based on monomer are typical, but higher loadings can increase latex viscosity beyond the target range for spray application. Coagulum formation in the reactor or on the agitator shaft is a known failure mode when the grade is substituted for a higher-viscosity PVOH without reducing stirrer speed; the lower molecular weight of GM-14 reduces the thickness of the grafted PVOH layer, and under 1,500 rpm high-shear dispersion the polymer can undergo chain scission and lose protective-colloid capacity. Post-polymerization filtration through 250 µm mesh is used to detect destabilized polymer.

When low-shear viscosity and redispersibility govern film-former selection

In low-shear applications such as warp sizing and paper surface sizing, the grade is selected for its ability to form a dry film that re-disperses in hot water. For warp sizing of spun polyester and textured yarns, a 6–10% solids solution at 55–65°C is applied through a size box with rubber-covered squeeze rolls; the low viscosity of GM-14 allows add-on to be controlled primarily by nip pressure rather than by viscosity drift. The partial hydrolysis keeps the size film re-dispersible at 80–90°C, which reduces the need for enzymatic desizing agents on synthetic yarns. Fully hydrolyzed PVOH of equivalent solution viscosity requires higher wash-off temperatures and may leave insoluble crystalline residues on hydrophobic yarn surfaces.

For paper and board, GOHSENOL GM-14 is added to starch-based size-press formulations at 0.5–2.0 dry wt% based on starch. In film-press units with 45–60 Shore A rubber rolls, the grade reduces blade pressure fluctuation because its solution viscosity remains lower than that of GH-17 at the same solids. Cobb water absorption after surface sizing, measured according to ISO 535, is typically controlled by the starch component rather than by the PVOH addition; the contribution of GM-14 is mainly to film continuity and surface strength. During size-press run, the solution temperature is maintained at 50–60°C to avoid viscosity buildup; below 40°C, partially hydrolyzed PVOH can form weak gel networks with starch and reduce penetration into the sheet.

Storage of GOHSENOL GM-14 at relative humidity above 60% increases moisture content; when volatile content exceeds 5.0%, batch-to-batch viscosity can shift toward the lower limit of 20.5 mPa·s due to weight errors in solids calculation. For critical adhesives or emulsion polymerization, the material should be kept sealed and, when necessary, dried in a dehumidified hopper dryer at ≤ 50°C before use. Aqueous solutions are vulnerable to borate-induced gelation because 1,2-diol sites in the PVOH chain form reversible complexes with borate ions; if tackification or gelling is desired, borax addition should be evaluated at 0.1–0.5 dry wt% to avoid precipitation. The grade is also incompatible with strong oxidizing agents and with some aluminum salts that cause rapid coagulation.

The powder should not be subjected to prolonged mechanical shear in a high-speed disperser above 1,500 rpm for more than 30 min, because shear-induced chain scission lowers solution viscosity and protective-colloid performance. In an industrial setting, the use of a positive-displacement gear pump to transfer 10% solutions at 50°C can create a pressure drop that is lower than that of GH-17 but higher than that of GL-05 at the same flow rate; pump sizing must account for the shear-thinning behavior of PVOH solutions under pipe flow conditions. Published data for this specific configuration is limited.

Direct comparison with higher- and lower-viscosity GOHSENOL grades at equivalent solids

Compared with GOHSENOL GH-17, GM-14 delivers lower solution viscosity at the same degree of hydrolysis. In a 10% solids solution at 25°C, the Brookfield viscosity of GM-14 is lower than that of GH-17; this reduces mixer motor load and improves penetration into porous substrates but also lowers the cohesive strength of the dried adhesive film. When GM-14 replaces GH-17 in a paper converting adhesive, wet tack can decrease unless solids are raised by 1–2 wt% or a secondary thickener is added. Conversely, compared with GL-05, the 20.5–24.5 mPa·s viscosity of GM-14 provides higher film tensile strength and better binding capacity in paper coating.

Against a fully hydrolyzed PVOH of similar solution viscosity, the 86.5–89.0 mol% hydrolysis of GM-14 improves cold-water dispersion and lowers the dissolution temperature, but the dried film exhibits lower resistance to cold water. Tensile properties of films cast at 23°C and 50% relative humidity, when measured according to ISO 527-3, show lower stiffness and higher elongation for partially hydrolyzed grades than for fully hydrolyzed grades of the same viscosity class. These differences must be evaluated through coated-paper or adhesive application testing rather than inferred from viscosity alone.

End-use compliance for GOHSENOL GM-14 is application-specific. The grade is not a direct food additive; use in food-contact adhesives or paper coatings must be verified against 21 CFR 175.105 and 21 CFR 176.170, or regional legislation such as Commission Regulation (EU) No 10/2011 where applicable. Industrial hygiene controls should limit dust generation during bag unloading; a dust extraction system with 0.5 m/s capture velocity at the transfer point is used in compounding plants. The material should not be mixed with strong oxidizers in dry form because combustible dust hazards apply to finely divided PVOH powders.