SELVOL Álcool Polivinílico 310

SELVOL Polyvinyl Alcohol 310 is a partially hydrolyzed, medium-viscosity grade of polyvinyl alcohol supplied by Sekisui Specialty Chemicals America, LLC. The grade designation identifies a controlled solution-viscosity band rather than a single molecular weight. The resin is composed of a vinyl alcohol homopolymer backbone with residual acetate groups, and it is registered under CAS 9002-89-5. Release specifications include degree of hydrolysis 87.0–89.0 mol%, apparent viscosity 10.0–13.0 mPa·s in a 4 wt% aqueous solution at 20 °C, solution pH 4.5–6.5 for the same solution, volatile matter maximum 5.0 wt%, and ash maximum 0.5 wt% calculated as sodium oxide. Viscosity is measured by rotational viscometry under ISO 15023-2 or JIS K6726. Because the product is not a single molecular entity, the distribution of chain length and residual acetate groups determines its dissolution rate, interfacial activity, and film crystallinity after drying.

Solution preparation follows a swelling-then-dissolution mechanism. On an atmospheric make-down tank fitted with an axial-flow turbine, the powder is dispersed into a well-formed vortex at 25–35 °C, then heated under low-shear agitation to 85–95 °C and held until the solution clears. Cold-water addition without a vortex or with high-shear rotor-stator mixing may create fish-eye agglomerates because the particle surface hydrates faster than water diffuses into the core. The apparent viscosity of the 4 wt% solution is not linear with concentration; a 10 wt% solution develops substantially higher viscosity and is typically handled at 50–60 °C in size-press operations to maintain flow through metering equipment.

What release specifications distinguish Selvol 310 from adjacent viscosities in the partial hydrolysis series?

The differentiation between Selvol 205, Selvol 310, and Selvol 325 is primarily solution viscosity rather than hydrolysis band. All three grades share the partially hydrolyzed range of 87.0–89.0 mol%, but the viscosity specification separates molecular weight grades. Selvol 205 is controlled at 5.0–6.6 mPa·s in the same 4 wt% aqueous solution at 20 °C. Selvol 310 is controlled at 10.0–13.0 mPa·s. Selvol 325 is controlled at 25.0–31.0 mPa·s. Higher solution viscosity corresponds to higher average molecular weight and greater chain entanglement after film formation. The property difference appears in formulated systems as higher wet-tack and cohesive strength for the higher-viscosity grades, but also as higher mixing torque and slower deaeration.

In vinyl acetate and vinyl acetate-acrylate emulsion polymerization, Selvol 310 functions as a protective colloid rather than as an inert thickener. It is metered as a pre-dissolved 4–8 wt% solution into the aqueous phase of the reactor charge or into the pre-emulsion feed on continuous reactor lines fitted with pitched-blade turbine agitators. The residual acetate groups stabilize growing polymer particles by interfacial adsorption, while the solution viscosity of the grade influences the particle-size distribution and the shear stability of the finished latex. Latices stabilized with Selvol 310 generally exhibit higher low-shear viscosity at equal solids than latices made with Selvol 205 because the molecular weight of the protective colloid contributes to the continuous-phase viscosity. This effect is measured by ISO 2555 Brookfield viscosity on the finished compound; the magnitude depends on total solids, plasticizer level, and reactor shear history.

Adhesive and paper-sizing operations use the grade where a balance of penetration control and film strength is required. On a rod-metering size press, a 6–10 wt% solution can be held at 50–60 °C to reduce viscosity while maintaining film-transfer uniformity. In water-based adhesives, the resin contributes wet tack, open time, and bonding to porous substrates. Bonding tests include ASTM D903 for peel strength and ASTM D6195 for loop tack; numerical results depend on substrate and coat weight. Published data for this specific formulation space is limited. In textile warp sizing, the grade provides film flexibility and abrasion resistance on slasher equipment, with add-on and desizeability controlled by size-box solids and squeeze-roll pressure.

When Selvol 310 replaces Selvol 205 in water-based adhesive formulations

The substitution changes the solution rheology and final film mechanical response because the higher molecular weight of Selvol 310 increases chain entanglement. Formulators can compensate by reducing the polymer addition by an amount determined by the target ISO 2555 Brookfield viscosity of the compounded adhesive. At equal addition level, Selvol 310 will require higher torque on a dual-motion scraped-surface mixer at room temperature. The larger molecular weight also slows deaeration after mixing; vacuum deaeration at 0.08–0.09 MPa negative gauge pressure may be necessary for transparent films. In paper-to-paper laminations, peel strength per ASTM D1876 is generally governed by substrate failure if the adhesive wetting is maintained. If the greater continuous-phase viscosity reduces wet-out, the peel strength may plateau or decrease despite higher cohesive strength. No published data for this specific configuration is available; plant trials on the target stock are required to establish the reduction in application roller speed.

Compared with fully hydrolyzed grades of similar solution viscosity, Selvol 310 dissolves at lower temperature and yields films with lower crystallinity and greater water sensitivity. The difference arises from the residual acetate content in the polymer backbone. Fully hydrolyzed analogues typically require dissolution temperatures above 90 °C and form more rigid films after drying. Differential scanning calorimetry under ISO 11357-3 can be used to compare crystallinity through the measured melting enthalpy, although the absolute value is formulation-dependent. In applications requiring water resistance after drying, a fully hydrolyzed grade may be preferred; in applications requiring remoistenability or alkali-strippability, the partially hydrolyzed grade is selected.

Regulatory compliance and food-contact status

Compliance documentation should be verified against the specific supply lot because food-contact clearance depends on extraction testing, residual monomer content, and end-use conditions. The typical designations that apply to polyvinyl alcohol grades of this type include FDA 21 CFR 175.105 for components of adhesives used in packaging, FDA 21 CFR 176.170 and FDA 21 CFR 176.180 for paper and paperboard components. The product is not intended for direct addition to food; extraction limits are set by the applicable regulation and the food type.

Aqueous solutions of Selvol 310 are susceptible to microbial hydrolysis and must not be stored without preservation for extended periods. Practical storage limits for unpreserved 4 wt% solutions are typically 24–48 h at 20 °C unless a biocide is added; solutions preserved with an appropriate biocide may still require viscosity and pH monitoring because acetate hydrolysis can occur slowly under alkaline conditions. The polymer is incompatible with borate ions, which cause reversible gelation through diol-borate complexation; this can be used deliberately for controlled rheology, but unintentional borate carry-over from recycled paper stock may produce lumpy gel particles. Strong acids and strong bases accelerate hydrolysis of residual acetate groups and chain scission at elevated temperature. Drying of the film or coating should be conducted below the crystalline melting range of approximately 160–220 °C depending on hydrolysis level; processing above this range in melt form requires plasticization and moisture control because thermal degradation of the vinyl alcohol backbone becomes measurable. For melt extrusion, pre-drying to less than 0.3 wt% moisture is a practical boundary at ambient relative humidity above 60%. Published data for this specific grade in injection-molding-grade formulations is limited.