SELVOL Álcool Polivinílico 513S

SELVOL Polyvinyl Alcohol 513S (CAS 9002-89-5) is a partially hydrolyzed polyvinyl alcohol supplied by Sekisui Specialty Chemicals. The polymer is produced by the controlled alcoholysis of polyvinyl acetate, leaving both hydroxyl and residual acetate functionality on the chain. The grade designation 513S identifies the standard product form in the medium-viscosity partially hydrolyzed series. Manufacturer-published specification ranges include a 4% aqueous solution viscosity of 13.0–15.0 mPa·s at 20 °C using a Brookfield rotational viscometer, degree of hydrolysis of 86.0–89.0 mol%, pH of 4.5–6.5 in 4% solution, ash as sodium oxide at ≤0.7%, and volatiles at ≤5.0%. The residual acetate content, typically 11–14 mol%, interrupts polyvinyl alcohol crystallite formation and lowers the minimum dissolution temperature compared with fully hydrolyzed grades. The S suffix distinguishes the standard grade from specialized low-dust or surface-modified forms; published morphological data for 513S is limited.

How Does 513S Differ from Fully Hydrolyzed and Lower-Viscosity Grades?

Fully hydrolyzed polyvinyl alcohol grades such as Selvol 103, Selvol 325, and Selvol 350 retain residual acetate levels below 2 mol% and require solution temperatures above 80 °C to achieve complete hydration. In contrast, the 11–14 mol% residual acetate in 513S allows cold-water dispersion and full dissolution after heating to 80–85 °C with moderate shear; the solution remains stable after cooling to ambient temperature. Films from 513S are more water-sensitive than films from fully hydrolyzed grades. This property is useful in repulpable paper applications and reworkable adhesives but becomes a limitation in barrier layers unless insolubilizing agents or crosslinkers are used.

The water-sensitivity difference arises from crystallite disruption by residual acetate groups. Fully hydrolyzed polyvinyl alcohol has a high degree of crystalline order and requires thermal energy to disrupt hydrogen bonding for dissolution. The partial hydrolysis of 513S reduces crystallite size and perfection, lowers the temperature required for solvation, and produces less ordered films with greater moisture uptake at a given relative humidity. These differences directly affect adhesive open time, coating flexibility, and water resistance.

Lower-viscosity partially hydrolyzed grades such as 502S dissolve more rapidly and generate less solution viscosity, but they require higher solids to achieve equivalent film strength and size-press pickup. Higher-viscosity grades such as 523S and 540S produce tougher films and higher solution rheology, but they raise transfer pump pressure and can reduce coating uniformity at high line speeds. The 13.0–15.0 mPa·s solution viscosity of 513S places it near the center of this formulation space, balancing handleability, film tensile strength, and penetration into porous substrates. When tensile comparisons are made, the test method—commonly ISO 527-3 or ASTM D882-18—must be fixed because polyvinyl alcohol film properties are strongly dependent on moisture content and strain rate.

In production-scale vinyl acetate emulsion reactors, SELVOL PVOH 513S is pre-dissolved in demineralized water and charged as the protective colloid before monomer addition. The 4% solution viscosity of 13.0–15.0 mPa·s gives predictable pumping and heat-transfer behavior in stirred tank reactors operating at 60–85 °C, while the partially hydrolyzed acetate groups adsorb at monomer droplet surfaces and provide steric stabilization to growing polymer particles. Lower hydrolysis values within the 86.0–89.0 mol% window tend to increase hydrophobic adsorption on monomer droplets; higher hydrolysis values can increase aqueous-phase thickness and raise latex viscosity. Batch-to-batch emulsion variance therefore depends on hydrolysis distribution rather than average viscosity alone.

In semi-batch vinyl acetate homopolymer and vinyl acetate-ethylene copolymer reactions, the pre-charge of 513S solution is typically heated to reactor temperature before initiator injection. The colloid concentration, expressed as parts per hundred monomer, influences nucleation and the balance between soluble polymer in the aqueous phase and adsorbed polymer on particles. At low colloid levels, particle size increases and coagulum can accumulate on baffles and thermocouples. At high colloid levels, final latex viscosity increases, water resistance of the dried film often decreases, and reactor heat transfer may be limited. The medium molecular weight of 513S allows colloid levels to be tuned within a practical range without exceeding agitator load; quantitative optimum levels are formulation-specific and are established through reactor trials. Measurement of particle size distribution by laser diffraction or dynamic light scattering, followed by coagulum screening through a 100-mesh or finer screen, is common in production. Published comparative particle-size data for this specific grade in industrial vinyl acetate or vinyl acetate-ethylene emulsion formulations is limited; reactor trials are required to establish nucleation rates, coagulum formation, and final latex rheology for a specific comonomer ratio and initiator system.

Paper surface sizing, coating binder, and remoistenable adhesive applications use 513S from aqueous solution on size presses, film presses, or roll coaters. The partial hydrolysis level permits rewetting and repulping of broke without insoluble film fragments. On high-speed paper machines, the rheology of the size-press solution controls pickup and film split. The 13.0–15.0 mPa·s value at 4% solids is a reference point; at size-press solids, which may range from 5% to 15%, the solution viscosity increases and becomes shear-rate dependent. Drying after application must remove enough water before the film enters subsequent dryers; otherwise the partially hydrolyzed film may block on calender rolls. The rewettability of 513S films allows rework of off-spec coated board and reduces broke processing cost compared with fully hydrolyzed or crosslinked coating binders.

In paperboard and paper intended for food contact, polyvinyl alcohol can be used as a component under 21 CFR 176.170; in adhesives it can be used under 21 CFR 175.105, subject to the extraction limits and intended end-use conditions specified in those regulations. Remoistenable adhesive formulations benefit from the adhesion of hydroxyl groups to cellulosic substrates and controlled open time; a fully hydrolyzed grade would require higher application temperatures and would produce a more water-resistant but less redispersible film. Bond strength is not an intrinsic material constant; it must be measured with a specific substrate and conditioning protocol, often using ASTM D903-18 for peel strength or ASTM D905-08 for shear strength of adhesive bonds.

Textile warp sizing on slasher equipment uses 513S as a film former and binder, often blended with starch or acrylic size. The 86.0–89.0 mol% hydrolysis level contributes adhesion to both hydrophobic polyester and hydrophilic cotton fibers; the intermediate molecular weight maintains weaving efficiency without excessive shedding. Desizing is easier than with fully hydrolyzed grades because the film disperses at lower temperature and redissolves more completely. Quantitative desizing efficiency data for 513S on specific fabric constructions is limited.

Polyvinyl alcohol solutions containing 513S are sensitive to borate ions. Addition of borax or boric acid can form reversible crosslinks that increase solution viscosity and can produce gel at alkaline pH. This behavior is exploited in some adhesive formulations but must be controlled in paper coating and emulsion polymerization because uncontrolled borate contact can destabilize the prepared solution. The product is also incompatible with strong oxidizing agents and strong acids, which can depolymerize the chain and reduce viscosity. Mixing and storage equipment should be stainless steel or lined; long residence time in unlined carbon steel may introduce iron contamination that darkens the solution and affects color-sensitive coatings.

Solution Preparation and Storage Limits

Preparation of a 4% solution for specification verification uses cold-water dispersion of the solid followed by heating to 80–85 °C under moderate shear. Failure to disperse the powder uniformly before heating can form gel particles that require extended agitation to hydrate. The solution is stable after cooling, but preservatives may be required during storage because polyvinyl alcohol solutions are susceptible to microbial growth. Processing at solids above 10% can produce shear-thinning behavior that affects pump sizing and heat transfer. The product is hygroscopic; storage in humid environments can increase moisture uptake and powder caking. Pre-drying is necessary before melt-processing if moisture content exceeds the manufacturer’s volatile limit of ≤5.0%.

Melt extrusion of water-soluble film from 513S generally requires plasticizers such as glycerol or polyols. The thermal processing window is narrow compared with polyolefins because polyvinyl alcohol begins to degrade near its melting point. Published data for 513S-specific melt rheology and degradation kinetics is limited; extrusion trials should establish the stable melt temperature, screw torque, and die pressure for a specific plasticizer system. Excess moisture in the melt promotes bubble formation and can shift degradation onset to lower temperatures.

Under European REACH, polyvinyl alcohol is registered as a polymer substance; current safety data sheets provide exposure limits, disposal instructions, and any applicable product-specific hazard classifications. Dust generation during solids handling requires local exhaust ventilation and bonded grounding because polyvinyl alcohol dust can form combustible dust clouds. Facility assessments should follow NFPA 652 or equivalent local standards for combustible dust. Published data for 513S-specific dust explosion parameters is limited; site-specific testing of the as-received powder is recommended before large-scale pneumatic conveying.

Receipt testing at production sites typically verifies solution viscosity, moisture, ash, and degree of hydrolysis against the certificate of analysis. Viscosity measurement must use a standardized dissolution procedure because incomplete hydration or solution aging can shift readings. For incoming inspection, a lot-to-lot viscosity check at 4% solids is recommended before large-scale adhesive or coating batch preparation; variations near the upper or lower end of the 13.0–15.0 mPa·s range can alter final formulation viscosity and coating holdout.

For comparative formulation work, the following nominal ranges position 513S within the partially hydrolyzed Selvol series.

The selection between 502S, 513S, 523S, and 540S is primarily a rheological decision because the degree of hydrolysis ranges are closely matched. In adhesive and coating formulations, 513S provides a midpoint between substrate penetration and film strength. In emulsion polymerization, higher-viscosity grades can reduce monomer droplet coalescence but raise reactor viscosity and require larger agitator motors; lower-viscosity grades reduce solution handling costs but may require higher colloid levels to achieve equivalent latex stability. Compared with fully hydrolyzed grades, 513S yields films that redisperse more readily but exhibit lower resistance to water vapor and liquid water. Compared with lower-viscosity partially hydrolyzed grades, it provides higher thickening efficiency at equal solids. Compared with higher-viscosity partially hydrolyzed grades, it permits lower line pressure and better leveling on high-speed coaters. These differences are not absolute; they depend on solids, substrate porosity, drying rate, and final film thickness. Published formulation data for 513S in specific downstream formulations is limited; the grade should be evaluated in laboratory and pilot equipment before line-scale implementation.