EXCEVAL RS-2117

EXCEVAL RS-2117 is a partially hydrolyzed polyvinyl alcohol resin supplied as a granular powder, positioned in the mid-viscosity segment of the EXCEVAL RS series. The grade is defined by a 4% aqueous solution viscosity of 21.0–25.0 mPa·s at 20°C and a degree of hydrolysis of 87.0–89.0 mol% when tested under JIS K6726 or equivalent certificate-of-analysis methods. Industrial consumption is concentrated in water-activated adhesives, paper and board lamination, textile warp sizing, ceramic binder systems, and emulsion polymerization where the polymer functions as a protective colloid. The partially hydrolyzed structure lowers dissolution energy relative to fully hydrolyzed polyvinyl alcohol grades above 98 mol%, but the powder is hygroscopic above 60% relative humidity, which can increase agglomeration and shift volatile-matter results on a certificate of analysis.

What Limits Hydration Uniformity in High-Solids Adhesive Batch Processing?

High-solids batch preparation using EXCEVAL RS-2117 is governed less by final viscosity than by the hydration sequence. The powder is dispersed in water below 30°C before jacket or steam heating is applied. Direct addition to water at 70°C or higher often forms a gelatinous shell around undissolved granules, extending hydration time and increasing the risk of transfer-line filter blockage. A production-scale 2,000 L conical-bottom vessel equipped with a top-entering disperser at 900–1,200 rpm and a 100 µm basket filter in the recirculation loop can prepare a 20 wt% solution at 80–85°C within 60–90 min, provided the pH is held between 5.0 and 7.0. If pH drifts below 5.0 during extended heating, aldehyde impurities can promote acetal formation, altering apparent viscosity and reducing wet tack in the finished adhesive. Cooling to 20–25°C before viscosity verification is required because solution viscosity is strongly temperature-dependent.

The solution should be held under low-shear agitation and consumed within 48 h at 20–25°C unless a preservative is present. The grade is incompatible with borate ions, which cause gelation through diol complexation, and with strong acids or oxidizing agents that promote chain scission. Prolonged storage at 50°C in unsealed tanks can increase viscosity drift from evaporation rather than polymer degradation. For critical adhesive batches, filtered solution is monitored by rotational viscometry at 20°C and compared with the certificate-of-analysis viscosity band before transfer to the coating line.

For paper tube lamination and carton side-seam adhesives, EXCEVAL RS-2117 is typically formulated at 8–18% solids with plasticizers such as glycerol or sorbitol. The 4% viscosity band places the material between lower-viscosity RS-1717 and higher-viscosity RS-2817/RS-4107 grades. Replacing a lower-viscosity polyvinyl alcohol with RS-2117 raises green tack and non-contact open time but reduces the maximum pumpable solids content at a fixed rotary lobe pump flow rate of 0.8 L/min. Dried film performance should be verified using TAPPI T 441 for Cobb water absorption and ISO 527-3 for tensile modulus of cast films. Published data for this specific converting configuration is limited.

Compared with fully hydrolyzed polyvinyl alcohol grades above 98 mol%, RS-2117 exhibits better cold-water solubility and lower tendency to skin over in open tanks, but dried film water resistance is lower unless a crosslinker is added. Compared with low-viscosity polyvinyl alcohol, the longer chain fraction increases high-shear apparent viscosity and stringiness in spray-applied adhesives. Spray nozzles with orifices above 0.8 mm are preferred to avoid filament breakage at pressures exceeding 2.5 bar.

Residual Acetate, Ash, and Granule–Fines Distribution

Certificate-of-analysis data for EXCEVAL RS-2117 normally include degree of hydrolysis, solution viscosity, volatile matter, ash, and pH. These release properties do not independently define adhesive performance; they control storage stability, dusting, and batch-to-batch dosing compatibility in automated systems. Fines accumulation in pneumatic transfer lines can alter bulk density at the feed screw and produce localized viscosity differences when dry granules are metered into a continuous dissolver.

The specification boundaries are not arbitrary. Residual acetate in the 87.0–89.0 mol% hydrolysis window determines cold-water solubility, surfactant compatibility, and the onset point of heat-induced turbidity. A lower degree of hydrolysis would improve solubility but reduce film strength; a higher degree of hydrolysis would increase thermal demand and increase gelation tendency during tank cleaning. Ash below 0.5% is relevant for electronic-grade ceramic binder applications where sodium residues can shift sintering behavior and green-body conductivity after burnout.

When RS-2117 Replaces Lower-Viscosity PVOH in Water-Soluble Film Casting

Water-soluble film casting imposes stricter demands than adhesive compounding because the solution must remain homogeneous at 20–30 wt% solids while drying to thicknesses below 60 µm. When RS-2117 substitutes for a lower-viscosity polyvinyl alcohol, the drying-rate profile changes because the higher molecular weight fraction increases solution viscosity and reduces capillary migration of dissolved resin toward the drying surface. A reverse-roll coater operating at 15 m/min with a 20 µm wet gap typically requires a reduction in coating speed or an increase in web temperature to maintain moisture content below 12% at the winding station. The recommended drying profile uses three zones at 60°C, 80°C, and 105°C, with dew-point control at 15°C to prevent surface skinning.

Plasticizer compatibility is similar to other partially hydrolyzed polyvinyl alcohol grades. Glycerol at 10–20 phr lowers film modulus, while sorbitol gives higher tensile strength but increases equilibrium moisture uptake. Film properties should be evaluated using ISO 527-3 and ASTM D882. Lot-specific viscosity variation of ±1.5 mPa·s can shift coating thickness by approximately 2–5% if the coating gap is not adjusted. Published data for this specific coating configuration is limited; pilot-line correlation is necessary before commercial speed increases are approved.

Granules that are not fully dissolved before casting can produce visible gel defects or pinholes in dried film. In practice, a 50 µm screen upstream of the slot die or reverse-roll applicator removes agglomerates without significantly reducing line pressure. The cleaned solution should be deaerated under vacuum at −0.08 MPa for 20–30 min to reduce microbubbles that otherwise nucleate defects at the web surface.

Storage of unopened bags in a dry warehouse below 30°C and below 60% relative humidity is recommended because the powder is hygroscopic. Opened bags should be re-sealed under nitrogen or consumed within 30 days. Pneumatic conveying into hoppers should be designed for soft granules; high-speed rotary feeders above 1,200 rpm can generate fines that accumulate in dust-collection filters and shift apparent bulk density. In emulsion polymerization, predissolution at 10–15% solids and filtration through a 50 µm mesh before reactor dosing reduce coagulum formation and improve protective-colloid performance. The material is not classified as hazardous under REACH 1907/2006 or CLP 1272/2008, but dust should be controlled to avoid explosive atmospheres. Minimum ignition energy data should be obtained from the lot-specific safety data sheet.

In continuous paper-converting lines, viscosity stability under shear and pH is tested before each shift. A 4% solution maintained at 20°C and subjected to recirculation through a centrifugal pump at 1,500 rpm shows negligible shear-induced chain scission over 8 h when pH remains above 5.0. Below that value, gradual viscosity loss can be mistaken for poor hydration when the cause is acid-catalyzed degradation. Ash-neutralizing additives should not be used unless their compatibility with the adhesive formulation is confirmed by ISO 1133-1 melt-flow indices or equivalent solution viscosity data.