| HS Code | 793522 |
| Product Name | KURARAY POVAL 25-100 |
| Chemical Name | Polyvinyl alcohol |
| Cas Number | 9002-89-5 |
| Appearance | White granular powder |
| Viscosity 4 Percent Aqueous Solution 20c | 24.5-26.5 mPa·s |
| Degree Of Hydrolysis | 99.4-100 mol% |
| Ph 4 Percent Solution | 5.0-7.0 |
| Ash Content | ≤0.5% |
| Volatile Content | ≤5.0% |
| Solubility | Soluble in hot water; only slightly soluble in cold water |
| Melting Point | Approximately 230°C |
| Density | 1.27 g/cm³ (typical) |
As an accredited KURARAY POVAL 25-100 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | KURARAY POVAL 25-100 is supplied as a white free-flowing powder in 25 kg multi-wall paper bags with a polyethylene liner. |
| Container Loading (20′ FCL) | KURARAY POVAL 25-100 is loaded as a 20′ FCL, using palletized bags, secured properly for safe, dry transport. |
| Shipping | KURARAY POVAL 25-100 is a polyvinyl alcohol powder supplied in sealed multi-wall bags. Ship dry, protected from moisture and direct sunlight. Keep upright, avoid tearing, and handle gently to prevent dust generation. Non-hazardous under normal transport conditions, but maintain clean, ventilated handling and secure pallets during transit. |
| Storage | Store KURARAY POVAL 25-100 in a cool, dry, well-ventilated area away from direct sunlight, heat, and moisture. Keep the original container tightly closed when not in use to prevent absorption of humidity, which can affect product quality. Avoid contact with strong oxidizing agents. Maintain stable temperatures and follow first-in, first-out rotation to preserve shelf life. |
| Shelf Life | Shelf life is typically two years from manufacture when stored in original, unopened containers under dry conditions. |
KURARAY POVAL 25-100 is introduced into the aqueous phase at 0.05–0.10 parts per hundred monomer in suspension polymerisation of vinyl chloride. The fully hydrolysed grade, with a Brookfield viscosity of 25.0–31.0 mPa·s at 4% aqueous solution, 20 °C and hydrolysis above 99.0 mol%, forms a low-foaming water phase with sufficient interfacial film strength to stabilise monomer droplets under turbulent agitation. In a 70 m³ stirred autoclave operating with turbine impeller tip speeds of 6–8 m/s, the adsorbed polyvinyl alcohol film limits droplet coalescence during the pressure-drop stage. Residual acetyl content below 1.0 mol% reduces the formation of graft-mediated water-soluble by-products that would otherwise broaden the particle size distribution. The stock solution is prepared by cold-water slurrying at 10–15 °C, followed by jet cooking at 90–95 °C for 45–60 minutes and filtration through a 100–200 μm mesh before metering into the polymerisation vessel.
Continuous particle size measurement by laser diffraction under ISO 22412:2017 shows a narrower span when the hydrolysis level remains above 99.0 mol%, while apparent bulk density measured under ISO 60-1:2019 stays within 0.52–0.58 g/cm³ for suspension-grade PVC. The critical process window is the dosing rate of the PVA solution during the initial agitation period; deviations greater than ±10% can shift the d50 by more than 20 μm in plant-scale batch records. K-value repeatability is evaluated under ISO 1628-2:2020, and the use of POVAL 25-100 at fixed dosage improves batch-to-batch consistency when compared with lower molecular weight partially hydrolysed grades. Published data for this specific grade in every autoclave configuration is limited, but the interfacial stabilisation mechanism is consistent across industrial suspension polymerisation systems.
On high-speed film press lines for recycled linerboard and folding boxboard, KURARAY POVAL 25-100 is applied at 5–8 wt% solids and 45–55 °C surface temperature, with the film transfer nip running at 1,200–1,800 m/min. The 25.0–31.0 mPa·s viscosity of the 4% stock solution produces a metered film that suppresses fibre picking without excessive misting. Surface strength is evaluated by IGT pick test under ISO 3783-2:2016, and water absorption is measured by Cobb test under ISO 535:2014. Because the grade is fully hydrolysed, the dried film develops crystallinity above 160–180 °C on calender rolls, requiring surface temperature control to avoid sheet blocking when calender pressure exceeds 40 kN/m.
Oil and grease resistance in specialty bag papers is obtained by combining POVAL 25-100 with a fluorochemical-free barrier dispersion at a dry solids mass ratio of 1:0.3 to 1:0.7. The coated sheet is tested under TAPPI T559 cm-12 for kit value and ISO 8791-2:2013 for Bendtsen roughness to verify coverage of recycled fibre shives. Repulping is assessed by low-consistency laboratory pulping with macro-stickies screening adapted from PTS-RH:021/97; the fully hydrolysed film releases at pH 7 and 40 °C without persistent macro-stickies when the broke is processed for 15–25 minutes in a standard disintegrator.
In aqueous alumina tape-casting slip, KURARAY POVAL 25-100 is dosed at 1.5–3.5 wt% relative to ceramic powder. The polymer solution is pre-dissolved at 8–10 wt% solids and added after the dispersant and before any latex binder. Tape-cast green sheets of 150–250 μm dry thickness show measurable handling strength after drying at 35–40 °C and 5–10% RH. The critical failure mode is edge curl during doctor-blade casting when the shear rate under the blade exceeds 1,000 s⁻¹; the 25.0–31.0 mPa·s solution viscosity, used at 0.6–1.2 wt% dry polymer on ceramic solids, provides sufficient low-shear structure to maintain tape width without introducing high-shear viscosity peaks that cause streaking.
Debinding behaviour is measured by thermogravimetric analysis under ASTM E2550-21 in air at 5 K/min; onset of mass loss occurs near 220 °C, and the maximum decomposition rate appears between 280 °C and 350 °C. The heating profile through this interval is held at 0.5–1.0 K/min to prevent gas-pressure defects in dense alumina compacts. Green flexural strength is evaluated as a relative handling indicator under ASTM C1161-18 on unfired bars. After sintering at 1,600 °C, residual carbon below 0.05 wt% requires a controlled air purge of at least 3–5 m³/h per kg compact in the burnout zone; whether the target is met depends on atmosphere control and part thickness because published data for this exact binder grade is limited.
Because fully hydrolyzed polyvinyl alcohol forms crystalline domains upon drying, KURARAY POVAL 25-100 is used in high-density cotton and polyester blend warp sizing at 7–12% solution solids in the size box, with the box temperature held at 80–85 °C to prevent skinning. Sized yarn tensile strength is measured under ASTM D2256-21; the increase in breaking force relative to unsized yarn is a function of film strength, elongation, and adhesion rather than size add-on alone. In air-jet looms running at 700–900 rpm, size shed dust generation is reduced when the PVA content in the blended size formulation is 30–60% of dry solids, with the balance consisting of oxidised starch and a wax lubricant at 0.3–0.8%.
Desizing is performed with hot water at 85–95 °C for 20–40 seconds in a continuous open-width washer. Because POVAL 25-100 is fully hydrolysed and therefore less cold-water-soluble than partially hydrolysed grades, peroxide dosing in the desizing bath at 1–3 g/L H₂O₂ is used to maintain removal efficiency above 95% as measured by Tegewa violet scale rating 6–8. Wastewater from desizing carries high COD, and biological treatment is designed for a COD load of 0.9–1.1 kg O₂/kg PVA, with the exact value dependent on sludge retention time and pretreatment pH.
For tube winding and carton side-seam adhesives, KURARAY POVAL 25-100 is dissolved at 18–22% solids. The solution is plasticized with glycerol or sorbitol at 5–15 parts per hundred PVA solids to reduce dry film brittleness. Viscosity response under ISO 3219-1:2021 shear sweeps shows pronounced shear thinning above 50 s⁻¹, which is necessary for roller application but must not drop below 1,500 mPa·s at the application shear rate to prevent starved transfer. Borax or boric acid is added at 0.2–1.5 parts per hundred PVA solids to build body through borate-diol complexation; excess boron above this range causes gel particles that clog 80–120 μm doctor-bar gaps.
Bond strength on recycled board is evaluated by ISO 11339:2022 T-peel after 24 h at 23 °C and 50% RH. The adhesive film remains repulpable under laboratory pulper conditions, but final fibre rejection screens at 150 μm must be monitored because fully hydrolysed PVA can form films that adhere to screen wires if the pulper temperature falls below 40 °C. In remoistenable packaging applications, the dry film is reactivated by water at 60–70 °C; open time is prolonged by increasing glycerol content, but the crystallinity of POVAL 25-100 limits stable glycerol loading to 20 parts per hundred before blocking develops on stacked blanks.
The conversion of fully hydrolyzed polyvinyl alcohol into polyvinyl butyral for laminated safety glass interlayer uses POVAL 25-100 as the aqueous precursor at 7–9 wt% solids. Butyraldehyde is added at a molar ratio of 0.55–0.65 relative to vinyl alcohol units, with hydrochloric acid catalyst at 0.4–0.8 N and reactor temperature held at 10–15 °C to minimise chain cleavage. The condensation is terminated when the desired degree of acetalization is reached; for automotive interlayer precursor, the product is washed to remove free acid and neutralised until the ash target drops below 0.05 wt%. Precipitation temperature and agitation speed in a 2,000 L jacketed reactor determine final powder particle size and plasticizer uptake.
Molecular weight retention is assessed by viscosity measurement in ethanol/toluene mixed solvent under ISO 1628-1:2021; the resulting PVB resin for sheet extrusion is plasticized with 28–32 parts per hundred resin triethylene glycol bis(2-ethylhexanoate) and calendered at 130–150 °C. The influence of residual acetate on optical haze is quantified by ISO 14782:2021 after lamination. The uniform hydrolysis level above 99.0 mol% in POVAL 25-100 minimises side reactions during butyraldehyde condensation, although published data for this precursor grade in specific interlayer formulations is limited and must be confirmed against targeted haze and adhesion specifications.
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KURARAY POVAL 25-100 is a fully hydrolysed polyvinyl alcohol resin manufactured by Kuraray. The grade designation combines a nominal solution viscosity of 25 mPa·s with a hydrolysis range of 99.0–100.0 mol%. Viscosity is determined at 20 °C on a 4 wt% aqueous solution according to JIS K6726. The polymer is supplied as a granular or fine powder with volatile matter typically not exceeding 5.0 wt% and ash typically not exceeding 0.5 wt%. Because the residual acetyl content is below 1 mol%, the dried polymer develops higher crystallinity than partially hydrolysed grades such as KURARAY POVAL 22-88, and the aqueous solubility behaviour differs sharply from grades in the 86.5–89.0 mol% hydrolysis range. Compared with lower-viscosity fully hydrolysed grades such as KURARAY POVAL 3-98, the 25-100 grade provides a higher solution viscosity and greater film cohesion at equivalent solids.
The product is not a cold-water-soluble grade in practical process conditions. Dissolution requires a cold-water pre-slurry step followed by heating to 90–95 °C and holding under agitation for 30–60 min. Direct powder addition to heated water produces gel skins and lump formation in stirred vessels. The temperature and shear requirements therefore make the grade suitable for processing lines equipped with jacketed mixing tanks, steam-injection cookers, or jet cookers, but less suitable for low-energy make-down systems designed for partially hydrolysed Poval grades.
The viscosity designation in the Poval series is not a direct molecular weight value. It is a standardized solution viscosity that correlates with hydrodynamic volume and chain entanglement in water. For KURARAY POVAL 25-100, the 4 wt% aqueous solution viscosity falls within 24.0–30.0 mPa·s at 20 °C under JIS K6726. This is approximately eight times higher than the 3.2–3.8 mPa·s range specified for KURARAY POVAL 3-98. The rheological consequence is significant in pigment dispersions, emulsion polymers, and size-press solutions. Solutions of 25-100 at concentrations above 8 wt% exhibit pseudoplastic behaviour: apparent viscosity decreases as shear rate increases, but low-shear viscosity remains high enough to reduce sedimentation of dispersed phases.
In a production-scale vessel using a pitched-blade turbine or anchor impeller, the torque demand for 10 wt% solutions at 60 °C is higher than for equivalent solutions of 3-98. Pump selection should account for this yield-stress-like behaviour at low flow velocities. When the same solution is processed through a Cowles-type high-shear disperser at a tip speed of 3–5 m/s, viscosity decreases under shear and the dispersion remains processable, but air entrainment and surface skinning increase if the mixing vortex is uncontrolled. The grade’s higher molecular weight compared with 3-98 also increases the extensional viscosity, which can improve thread formation in adhesive coating but complicates doctor-blade metering at low line speeds.
In vinyl acetate emulsion polymerization, KURARAY POVAL 25-100 is charged as a protective colloid at 2–5 wt% based on total monomer. Persulfate initiators abstract hydrogen from the PVOH backbone and generate radical sites for vinyl acetate grafting. The grafted PVOH then acts as a steric stabilizer at the latex particle surface. With 25-100, the aqueous phase develops a higher low-shear viscosity than with 3-98 at the same charge, and the finished latex shows a more pronounced yield stress. This reduces particle settling in storage tanks but increases transfer-pump load. In agitated glass-lined reactors with an anchor impeller and baffle cage, the grade is frequently used where higher finished latex viscosity and mechanical shear stability are required. The operating limit is typically set by the reactor cooling jacket capacity, because the higher aqueous viscosity reduces convective heat transfer and can extend the monomer feed period.
Batch-to-batch variation in PVOH viscosity is a known contributor to finished latex viscosity drift. For 25-100, incoming viscosity and hydrolysis should be verified against the supplier certificate because particle size distribution and coagulum formation shift when the hydrolysis degree approaches the lower or upper boundary of the specification.
In paper coating binder systems, KURARAY POVAL 25-100 is used at addition levels between 3 and 8 parts per hundred pigment in clay or calcium carbonate coating colours. The fully hydrolysed structure reduces equilibrium moisture uptake compared with KURARAY POVAL 22-88 at 50% RH. This property translates into less blocking of coated paper under humid storage and improved water resistance of the dried binder film. The trade-off is thermal energy in solution preparation. Partially hydrolysed 22-88 can be dispersed at 20–30 °C in make-down tanks, while 25-100 requires a starch cooker or jet cooker capable of maintaining 90–95 °C. A coating plant relying on simple ambient-water dispersion equipment cannot substitute 25-100 for 22-88 without adding a cook system.
| Grade | 4 wt% solution viscosity at 20 °C | Degree of hydrolysis | Typical solution preparation |
|---|---|---|---|
| KURARAY POVAL 25-100 | 24.0–30.0 mPa·s | 99.0–100.0 mol% | pre-slurry in cold water, heat to 90–95 °C |
| KURARAY POVAL 3-98 | 3.2–3.8 mPa·s | 98.0–99.0 mol% | heat to 80–90 °C |
| KURARAY POVAL 22-88 | 20.5–24.5 mPa·s | 86.5–89.0 mol% | disperse at 20–30 °C |
In textile warp sizing, 25-100 can be applied at 6–12 wt% dry solids through a double-squeeze size box. The fully hydrolysed grade forms a tougher film than partially hydrolysed types and is preferred for fine-count cotton or synthetic blends where warp hairiness and abrasion resistance are limiting in the slasher. Laboratory abrasion testing can be performed according to ASTM D2256 or equivalent yarn tensile and abrasion protocols, although end-use weaving performance must be confirmed on the specific loom type because size-film behaviour changes with shed humidity. Compared with 22-88, 25-100 reduces rewetting and size-film tack under high-humidity weave rooms, but desizing requires a hot enzyme or oxidative desize step rather than simple cold-water removal.
For solution-cast monolayer film, KURARAY POVAL 25-100 requires plasticizer addition at 10–30 wt% on dry PVOH because unplasticized films from fully hydrolysed grades are brittle below 30 °C. Glycerol and sorbitol are common plasticizers. Tensile testing should follow ASTM D882 or ISO 527-3 after conditioning at 23 °C and 50% RH for at least 48 h. Under these conditions, films based on 99.0–100.0 mol% hydrolysis PVOH generally exhibit higher tensile stress and lower elongation than films made from partially hydrolysed grades. Oxygen barrier is high at low relative humidity but deteriorates sharply above 70% RH. Published data for this specific configuration is limited when nonstandard plasticizer combinations are used, and barrier claims must therefore be generated on the final formulated film rather than extrapolated from resin data alone.
In remoistenable adhesive systems and water-activated tape formulations, the grade can serve as a water-soluble film former in which bond regeneration is triggered by water application. The higher molecular weight of 25-100 relative to 3-98 increases film tear resistance and contributes to slower water penetration, which can extend open time. The same property may reduce re-moistening speed when compared with lower-viscosity or partially hydrolysed grades. Formulators using alkaline borate-treated systems should anticipate gelation. Borate ions crosslink PVOH through diol complexes, and the fully hydrolysed 25-100 is sensitive to this interaction; borax addition at levels used with partially hydrolysed grades can produce a hard gel that is incompatible with transfer pumps and coating dies.
Storage and moisture control are non-trivial for this grade. The powder remains free-flowing when stored in sealed containers at 20–30 °C and relative humidity below 60%. Pre-drying is required at relative humidity above 60% when the material is used for moisture-sensitive compounding or when additive premixes demand low water content. As with most organic powders, airborne dust can form a combustible cloud; dust extraction and electrical bonding should follow NFPA 652 or local equivalent. The product is not incompatible with most nonionic and anionic surfactants, but cationic additives can reduce solution clarity at high pH. Compliance for food-contact use must be established on the final article, not on the resin alone. Polyvinyl alcohol is referenced in EU Regulation (EC) No 1935/2004 and in U.S. FDA 21 CFR 177.1670 for certain film and coating applications, but migration testing remains article-specific.
