SELVOL Álcool Polivinílico 165

SELVOL Polyvinyl Alcohol 165 is a fully hydrolyzed, medium-viscosity polyvinyl alcohol resin supplied by Sekisui Specialty Chemicals. The material is identified by CAS 9002-89-5 and is normally supplied as a white to cream granular solid. Viscosity is specified as 5.2–6.2 mPa·s for a 4% aqueous solution at 20°C; degree of hydrolysis is controlled between 98.0–99.0 mol%. The residual acetate content therefore falls in the range of 1–2 mol%. Volatiles are limited to ≤5.0%, ash to ≤0.5%, and aqueous solution pH to 5.0–7.0. Viscosity and hydrolysis are assessed by the methods of JIS K6726, with ash determined by muffle-furnace ignition at 800°C and volatiles by oven drying to constant mass. The grade is not cold-water soluble; complete dissolution requires mechanical dispersion in water and heating to 85–90°C with low-shear agitation until no gel particles remain visible on a Hegman gauge. The product is selected for textile warp sizing, paper surface sizing, emulsion polymerization, remoistenable adhesives, and water-soluble film where a balance of film strength and handling viscosity is required.

How Does SELVOL 165 Differ from Partially Hydrolyzed PVOH in Aqueous Adhesive Films?

In comparison with partially hydrolyzed polyvinyl alcohols of equivalent solution viscosity, SELVOL Polyvinyl Alcohol 165 produces adhesive films with lower equilibrium moisture uptake and higher tensile strength. The hydrolysis window of 98.0–99.0 mol% permits dense interchain hydrogen bonding after water evaporation; film tensile properties are assessed by ASTM D882-18 on cast films conditioned at 23 ± 2°C and 50 ± 5% relative humidity, and water absorption is measured by ASTM D570. Blocking resistance under storage loads is measured by ASTM D3354, with fully hydrolyzed grades typically showing lower blocking force than partially hydrolyzed grades at equivalent plasticizer content. The tradeoff occurs during application: substrate wetting on low-energy polymer films must be verified by wetting-tension solutions per ASTM D2578 because the 98.0–99.0 mol% hydrolyzed resin has higher aqueous surface tension than 87–89 mol% hydrolyzed resins. In addition, full dissolution requires water temperatures above 80°C, while partially hydrolyzed resins may hydrate at 40°C or below. These properties make the grade more suitable for films requiring water resistance and block resistance than for formulations requiring low-temperature cleanup.

During vinyl acetate/ethylene emulsion polymerization in a jacketed stainless-steel reactor equipped with a retreat-curve impeller, SELVOL Polyvinyl Alcohol 165 is typically charged as a predissolved 5–8% aqueous solution. Polymerization temperature is commonly maintained at 70–80°C while the PVOH acts as a protective colloid, controlling particle nucleation and preventing coalescence. The 5.2–6.2 mPa·s viscosity at 4% solids permits transfer with a diaphragm or progressing-cavity pump without excessive line pressure, while the hydrolysis range provides graft-site density for steric stabilization. Process control becomes critical after the initiator feed begins: excessive grafting onto the PVOH raises latex viscosity and forms macro-gel particles that are retained on a 150 μm screen; insufficient grafting leaves free PVOH in the serum and can allow particle aggregation during residual monomer stripping. The medium viscosity of the grade reduces agitator torque compared with high-viscosity fully hydrolyzed PVOH at equal charge, which is relevant in large reactors where agitator load defines the upper solids limit. Ash control at ≤0.5% narrows the influence of buffering salts on persulfate initiator decomposition; batch-to-batch shifts in ash can otherwise appear as variation in latex particle-size distribution. Published data specific to SELVOL Polyvinyl Alcohol 165 in ethylene-rich or crosslinking-comonomer formulations are limited; plant verification is required when the comonomer system departs from standard vinyl acetate/ethylene parameters or when multifunctional monomers are present.

When High-Humidity Storage or Low-Temperature Water Demand Process Adjustments

When storage relative humidity exceeds 60%, SELVOL Polyvinyl Alcohol 165 takes up atmospheric moisture. The granular solid may then become inconsistent in loss-in-weight feeding, and the equilibrium moisture content can rise above the volatiles limit of 5.0%. Pre-drying at 60–80°C for 2–4 h in a circulating-air or desiccant dryer is recommended when the moisture content is found to be above 0.5% by gravimetric analysis. Drying above 100°C should be avoided because localized thermal history can yellow the resin. In cold-weather plants, makeup water below 20°C lengthens the swelling phase; a jacketed mixing vessel is preferred over direct steam sparging, which can generate foam and gel particles at the sparge point. The dissolution temperature is held at 85–90°C for 30–60 min, and the solution is then screened through a 150–250 μm basket strainer. Addition of the dry polymer to high-shear mixers at temperatures below 60°C is a known source of fish-eye agglomerates that resist later dispersion. Once dissolved, the solution must be used or preserved: microbiological degradation in unpreserved PVOH solutions occurs readily at 20–35°C, so holding times beyond 48 h require a compatible biocide. Borate ions, boric acid, and borax are incompatible with stable Newtonian handling because the 1,3-diol units form reversible but strong borate ester crosslinks, producing thixotropic gels or insoluble networks.

Aqueous paper surface-sizing formulations use SELVOL Polyvinyl Alcohol 165 to increase surface strength without the same degree of sheet closing observed with high-level starch-only formulas. The 4% solution viscosity permits metering-rod or puddle press application at solids of 2–6%, depending on sheet absorbency and size-press configuration. Oil and grease resistance of conditioned sheets is evaluated with TAPPI T 559; the fully hydrolyzed resin contributes barrier integrity when the sheet exits the after-dryer above 90°C. The grade can be blended with oxidized or modified starch to increase film flexibility and reduce formulation cost, but phase separation must be verified when the total solids exceed 15% because high-molecular-weight starch fractions may reduce homogeneity under shear. In textile warp sizing, the resin provides abrasion resistance after drying, low ash after singeing, and removal in hot water at 70–90°C during desizing. Size add-on is determined gravimetrically on the warp sheet, and the desired add-on range is set by loom speed, yarn hairiness, and humidity rather than by universal fixed values.

Comparative Viscosity and Hydrolysis Effects in Aqueous Film Formation

Viscosity differences among fully hydrolyzed polyvinyl alcohol grades alter solution handling, wet film thickness, and drying rate. SELVOL Polyvinyl Alcohol 165 occupies an intermediate position: it gives higher aqueous viscosity and film strength than lower-molecular-weight fully hydrolyzed grades, but it dissolves more rapidly and imposes lower mixer torque than high-viscosity grades. For absorbent substrates, a lower-viscosity grade penetrates more deeply but lowers film tensile strength as measured by ASTM D882-18. A higher-viscosity grade increases final film toughness but limits the maximum pumpable solids in diaphragm and progressing-cavity transfer lines. The specification envelope and process-relevant limits for SELVOL Polyvinyl Alcohol 165 are summarized in the table below.

In cast water-soluble film production, the 98.0–99.0 mol% hydrolysis level of SELVOL Polyvinyl Alcohol 165 yields high oxygen barrier at low relative humidity. Oxygen transmission rate is measured by ASTM D3985 on conditioned film; barrier performance degrades as relative humidity increases because water acts as a plasticizer in the amorphous phase. Film formulations intended for high-humidity service therefore require multilayer structures, barrier coatings, or crystallinity enhancement through orientation and heat setting. The medium viscosity of the grade allows casting from aqueous solution at practical solids while maintaining enough film tenacity after drying for orientation on a tentering line. Plasticizer is usually required at 5–15 phr to prevent brittleness; the exact level is determined by tensile testing per ASTM D882-18 and by tear strength per ASTM D1922. Cold-water solubility of the resulting film is limited below 40°C, so the grade is less suitable for rapid dissolution in cold water than lower-hydrolysis grades, but it is selected when the film must remain intact in humid handling environments and still dissolve in hot water.

For food-contact applications, compliance is determined by end-use conditions and must be confirmed against the manufacturer’s regulatory statement. Polyvinyl alcohol is recognized in FDA 21 CFR 175.105 for adhesives and 21 CFR 176.170 for components of paper and paperboard in contact with aqueous and fatty foods, subject to the limitations in those sections. The resin is not a direct food additive and must not be used as such. In electronic-grade or high-purity ceramic processes, residual ash and volatiles must be rechecked against the ≤0.5% ash and ≤5.0% volatiles lot data because thermal decomposition residues can affect downstream electrical or sintering performance.