GOHSENOL NL-300

GOHSENOL NL-300 is a fully hydrolysed low-viscosity poly(vinyl alcohol) supplied as a white to off-white powder and identified by CAS 9002-89-5. The grade belongs to the GOHSENOL NL series, where the designation indicates a fully saponified backbone and a reduced solution-viscosity target relative to GOHSENOL NL-05 and GOHSENOL NH grades. Representative published physicochemical values include a 4 % aqueous solution viscosity at 20 °C of 2.5–3.5 mPa·s when determined according to JIS K 6726, degree of hydrolysis of 98.0–99.0 mol%, pH of a 4 % aqueous solution between 5.0 and 7.0, volatile matter not exceeding 5.0 %, and ash content not exceeding 0.5 %. These values are typical of a low molecular weight fully hydrolysed PVA and place the product between very low-viscosity specialty grades and higher-viscosity film and adhesive grades. The low degree of polymerisation implied by the viscosity range reduces chain entanglement in aqueous solution, which directly affects dissolution time, adhesive penetration into porous substrates, and film tensile strength. At 4 % solids the solution is Newtonian; at 10 % solids and 25 °C, the viscosity typically remains below 100 mPa·s for low-DP fully hydrolysed PVA, although the value is shear-rate dependent and should be confirmed with a Brookfield viscometer per ISO 2555 or a cone-plate rheometer per ISO 3219. The fully hydrolysed backbone retains a glass transition temperature near 75–80 °C, and the powder is not melt-processable without plasticiser because thermal degradation begins above 200 °C. Batch-specific release limits are defined in the certificate of analysis; the technical data sheet values are representative and should not be used as release limits.

How does GOHSENOL NL-300 differ from GOHSENOL NL-05 and partially hydrolysed grades?

The primary differentiation is viscosity at equal solids. Because GOHSENOL NL-300 exhibits a 4 % solution viscosity of 2.5–3.5 mPa·s, a 10 % aqueous solution remains pumpable at temperatures above 60 °C, whereas GOHSENOL NL-05 and GOHSENOL NH-18 develop higher viscosity at the same concentration. The fully hydrolysed character of 98.0–99.0 mol% distinguishes the grade from partially hydrolysed products such as GOHSENOL GH-17, which dissolve more readily in cold water but yield films with lower water resistance and higher elongation. Fully hydrolysed PVA films typically exhibit tensile strength of 40–60 MPa and elongation at break of 100–200 % when conditioned at 23 °C and 50 % RH per ISO 527-3; the low-DP NL-300 grade is expected to fall at or below the lower end of this range, while NH-18 is closer to the upper end. Published grade-specific tensile data for NL-300 is limited, but the trend is consistent with the viscosity-molecular weight relationship described in JIS K 6726. Table 1 summarises representative manufacturer values.

In aqueous solution preparation, the powder is first dispersed in cold water under agitation to prevent lump formation, then heated to 80–95 °C for 30–60 min to complete dissolution. A jacketed stainless-steel vessel with high-shear dispersion is recommended because fully hydrolysed PVA particles that contact hot water too early can form a gelled skin that shields undissolved powder and increases filtration load. In production-scale mixing, the low solution viscosity of GOHSENOL NL-300 permits a higher powder charge at a given mixer torque limit than NL-05 or NH-18. However, uncontrolled addition rates above the vortex capacity produce fisheyes and downstream filter blockage. In a typical 500 L jacketed vessel with a rotor-stator mixer, powder addition is controlled at 0.5–1.0 kg/min per 100 L of water to maintain a vortex without excessive air entrainment. The heating cycle is held at 85 °C for 30 min after the last powder addition; solution clarity is confirmed by a 100 µm filter test. Failure modes observed when this sequence is shortened include filter pressure rise above 0.5 bar and visible fisheyes in cast films. For high-solids stock solutions above 15 %, staged powder addition is required, and a defoamer at 0.05–0.1 % of total batch is commonly used, provided compatibility with the end-use adhesive is confirmed. Solution pH is typically between 5.0 and 7.0, and viscosity is stable for 24 h under closed storage at 20–25 °C; preservative addition is required for longer hold times. Pre-drying at 60–80 °C for 1 h is recommended only when bags have been exposed to high humidity, because moisture uptake changes gravimetric solids calculations.

Surface sizing and paper-coating binder performance at low addition levels

Paper surface-size formulations use GOHSENOL NL-300 at 0.5–2.0 parts per 100 parts of cooked starch solids in the size press. The low molecular weight reduces solution viscosity at size-press solids of 8–12 %, allowing better transfer uniformity and fewer blade or rubber-roll film-splitting defects. Size-press evaluation is conducted with a laboratory or pilot coater and measured by IGT pick resistance per ISO 3783 or by the Hercules size test per TAPPI T 530. Published data specific to this grade in paper formulation is limited; therefore, mill trials typically run a starch/PVA blend at 80:20 to 95:5 solids ratio and record Cobb values per ISO 535 to quantify water penetration. Because the grade is fully hydrolysed, the sized sheet develops water-resistant film after drying at 90–120 °C, but the low chain length contributes less film toughness than NH-18, so heavy-weight packaging grades requiring high fold-crack resistance may require a higher-viscosity grade. The critical addition level for surface strength improvement is typically 0.5 phr on starch; below this level, the effect on IGT pick is negligible. Above 2.0 phr, drying demand increases and the risk of size-press roll deposit rises. The operational window is therefore narrow.

Emulsion polymerisation stabilisation is a second established use. The product functions as a protective colloid in vinyl acetate and vinyl acetate-acrylic polymerisations conducted at 60–80 °C in jacketed reactors with pitched-blade or anchor impellers. Compared with higher-viscosity GOHSENOL grades, NL-300 produces lower reactor viscosity during the nucleation phase, which improves heat transfer and reduces the risk of coagulum formation on reactor walls; however, the lower chain length may require a higher colloid concentration to achieve the same latex viscosity and particle-size stability. Typical reactor charge ranges are 4–10 wt% based on monomer when used as the sole protective colloid, and the powder is pre-dissolved at 10–15 % solids before charging. The pre-dissolved PVA solution is charged at 10–15 % solids; monomer is fed over 2–4 h. Reactor agitator power draw is lower with NL-300 than with NH-18 at the same monomer feed rate; however, latex particle size may increase unless the colloid concentration is raised by 1–3 wt% relative to a higher-DP grade. The final latex is monitored for coagulum on a 100 mesh screen; acceptable levels are typically below 0.1 % of monomer charged. Published data for this specific grade in emulsion polymerisation is limited, but the stabilisation mechanism follows the grafted PVA layer dynamics described in the manufacturer’s polymerisation-grade documentation.

When a low-viscosity fully hydrolysed PVA is used as a textile warp size

Textile warp-size formulations benefit from the low viscosity when high loom speeds require size penetration into the yarn core. A size mix containing 6–10 % GOHSENOL NL-300, 0.5–1.0 % lubricant wax, and optional starch is cooked at 85 °C and applied in a slasher. The fully hydrolysed structure gives a hard size film that resists abrasion, while the low molecular weight permits desizing in hot water at 80–90 °C without the extended wash cycles required for high-DP grades. Film hardness is measured by König pendulum damping per ISO 1522 or by tensile strength of cast film per ISO 527-3. A low-DP fully hydrolysed film typically shows lower elongation at break than a high-DP grade but sufficient abrasion resistance for medium-density cotton warps. The size mix is held at 85 °C and applied at 8–12 % add-on; low viscosity ensures penetration into the yarn core and reduces surface deposit on split rods. Desizing efficiency is tested by iodine staining; residual PVA after hot-water desizing at 85 °C for 5 min should be below the visible staining threshold. The limitation is that film abrasion resistance is lower than that obtained with NH-18; thus high-twist synthetic yarns or dense staple-fibre warps may require blending with a higher-viscosity grade at 20–30 % of the PVA component.

Adhesive formulations for paper lamination and carton sealing use GOHSENOL NL-300 as a secondary rheology modifier and water-resistant film former. A typical formulation combines 5–10 parts NL-300 with 90–95 parts poly(vinyl acetate) emulsion or starch-dextrin adhesive to reduce stringing and improve bond strength under humid conditions. Viscosity is adjusted to 1000–2000 mPa·s at 25 °C; the low molecular weight avoids excessive viscosity build, but wet tack may be lower than with NH-18. FDA status under 21 CFR 175.105 is relevant for food packaging carton sealing, and the supplier’s letter of assurance should be consulted for the specific formulation.

Regulatory and storage boundaries are defined by the supplier’s SDS and food-contact statement. Typical references for PVA in packaging adhesives and paper coatings include FDA 21 CFR 175.105, 21 CFR 176.170, and 21 CFR 176.180; current compliance for GOHSENOL NL-300 must be confirmed against the supplier’s letter of assurance because clearance conditions are grade- and end-use-specific. Under EU food-contact legislation, compliance is evaluated under Commission Regulation (EU) 10/2011 when the polymer is used as a coating or adhesive layer; specific migration of vinyl acetate monomer and methanol is covered by the overall migration limit of 10 mg/dm² unless a specific lower limit applies. The powder should be stored in sealed bags at 10–30 °C and below 60 % RH. Open packages must be resealed because moisture uptake alters the apparent solids and can cause caking in screw feeders. Storage above 60 % RH leads to moisture absorption and changes in flow properties; if the moisture content exceeds 5 %, caking in screw feeders becomes likely. Before use in gravimetric blending, moisture content should be checked by oven drying at 105 °C for 3 h or by Karl Fischer titration. The powder should not be handled around open flame due to dust explosion risk; minimum ignition energy and Kst values are available in the supplier SDS. Avoid combination with strong oxidisers, borate ions, and glyoxal unless staged addition and pH control are implemented, because gelation can occur at low shear and block transfer lines. For aqueous solution storage, a biocide is required beyond 24 h to prevent microbial growth, and the solution should be maintained above 60 °C or below 10 °C to reduce viscosity loss and gel formation. Table 2 summarises the standard test and compliance matrix.