| HS Code | 537974 |
| Chemical Name | Poly(vinyl alcohol) |
| Cas Number | 9002-89-5 |
| Appearance | White granular powder |
| Degree Of Hydrolysis | 96.0 - 98.0 mol% |
| Viscosity 4 Aqueous Solution At 20 C | 27.0 mPa·s |
| Ph 4 Aqueous Solution | 5.0 - 7.0 |
| Specific Gravity | 1.25 - 1.27 |
| Bulk Density | 0.6 - 0.7 g/cm³ |
| Solubility | Soluble in hot water |
| Ash Content | ≤ 0.5% |
| Volatile Matter | ≤ 5.0% |
As an accredited KURARAY POVAL 27-96 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | KURARAY POVAL 27-96 is a free-flowing granular powder supplied in 25 kg multi-layer paper bags with an inner polyethylene liner. |
| Container Loading (20′ FCL) | 20′ FCL: KURARAY POVAL 27-96 loaded as full container load, palletized and secured, no co-loading. |
| Shipping | KURARAY POVAL 27-96 is shipped as solid granules in sealed multi-layer paper or PE-lined bags, palletized and stretch-wrapped. Keep dry, away from moisture and direct sunlight. Avoid dust generation and static discharge. Handle with care to prevent bag damage. No special hazardous transport classification required under normal conditions. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers tightly sealed to prevent moisture absorption and contamination. Avoid creating dust clouds; keep away from oxidizers and incompatible materials. Ensure proper labeling and handling to maintain product stability and safety. |
| Shelf Life | KURARAY POVAL 27-96 has a shelf life of about 2 years when stored unopened in a cool, dry place. |
In vinyl acetate homopolymer and vinyl acetate-ethylene reactor feeds, KURARAY POVAL 27-96 functions as the primary protective colloid at addition levels of 3.0–6.0 wt% based on total monomer charge. The grade’s nominal 96.0 mol% degree of hydrolysis and 27.0 mPa·s viscosity at 4% solids and 20 °C place it in a processing window where the colloid stabilizes growing polymer particles without generating the excessive high-shear viscosity associated with fully hydrolysed grades. For production on a 12 m³ glass-lined reactor with a two-stage 45° axial-flow impeller, a 6.0 wt% aqueous stock solution is prepared at 85–90 °C for 45–60 min, cooled to 28–32 °C, and filtered through a 250 µm screen before charging. Metering the solution at 15–20% monomer conversion keeps coagulum on a 100 µm filter bag below 250 mg/kg; addition before 10% conversion broadens the particle size distribution and raises the span above 1.4 on a Malvern Mastersizer 3000 measured per ISO 22412:2017.
Brookfield viscosity of the finished dispersion measured per ASTM D2196-20 at 25 °C shifts from approximately 1,800 mPa·s at 3.0 wt% colloid to 4,200 mPa·s at 6.0 wt%. In vinyl acetate-ethylene systems with 15–25% ethylene pressure, the use of 27-96 raises the minimum film formation temperature by 2–4 °C relative to a low-viscosity 88 mol% grade when measured per ISO 2115:1996. The moderate hydrolysis level is less sensitive to calcium ions in hard water than fully saponified grades, but the hold tank should be maintained below 70 °C in high-electrolyte recipes to avoid cloud-point destabilization and grit formation inside the colloid feed line.
The wet-end and size-press conditions on high-speed fine paper and linerboard machines require holdout control that low-viscosity polyvinyl alcohol grades cannot provide at low addition rates. KURARAY POVAL 27-96 is blended with oxidized corn starch or enzyme-converted starch at 2.0–6.0 dry parts per 100 dry parts starch, yielding a size solution viscosity of 50–150 mPa·s at 60 °C before application through a film-transfer or metering size press. At a production speed of 1,200 m/min, the high-shear viscosity measured with a Hercules viscometer per TAPPI T 512 remains above 18 mPa·s at 2,000 rpm, which reduces nip misting and limits excess penetration into recycled linerboard with a Gurley porosity of 40–70 s per ISO 5636-5:2013.
Film formation and surface closure are controlled by drying-web surface temperature in the range 110–130 °C; below this envelope the size film remains thermoplastic and can block in the sheet stack. Water absorption measured by ISO 535:2014 is typically held at 25–30 g/m² Cobb 60, while surface strength measured by ISO 3783:2006 exceeds 1.5 m/s IGT pick on coated board. For packaging grades, the use of 27-96 as a size-press binder falls under the component provisions of 21 CFR 176.170 when the treated paper or paperboard contacts aqueous and fatty foods. The formula should not be acidified below pH 6.0 if optical brightening agents are present, because cationic OBA retention can drop by more than 5% under quench conditions.
| Control parameter | Standard or test method | Typical control window |
|---|---|---|
| Size solution viscosity at 60 °C | ASTM D2196-20 | 50–150 mPa·s |
| Cobb water absorption | ISO 535:2014 | 25–30 g/m² at 60 s |
| IGT surface strength | ISO 3783:2006 | minimum 1.5 m/s |
| Food-contact paperboard component | 21 CFR 176.170 | Compliant for aqueous and fatty foods |
When high-speed air-jet looms process polyester–cotton blended yarns between Ne 20 and Ne 40, the warp size film must remain hard at weaving-room temperature yet release cleanly during open-width washing. KURARAY POVAL 27-96 is combined with thin-boiling starch and polyacrylate size in a size box at 60–90 mPa·s and 80 °C, with PVA representing 20–35% of total size solids and total solids held at 10–14%. The 96.0 mol% hydrolysis level reduces ambient hydration, which prevents blocking during extended loom stops and maintains a controlled size add-on of 8–12% on warp yarn by mass.
Residual yarn elongation after sizing is retained above 95% of the unsized value when tested per ASTM D2256-22, and loom shed breaks at 650 rpm remain below 0.2 breaks per 100,000 picks on a standard air-jet loom. Desizing is performed in a continuous open-width washer with chamber temperatures of 60 °C, 75 °C, and 85 °C and residence times of 15–20 s per chamber; residual PVA on the fabric drops below 0.1% when measured by spectrophotometric iodine complexation at 690 nm after hot-water extraction. Wash temperatures below 60 °C cause redeposition and uneven reactive dye penetration after desizing, while hard water above 200 mg/kg CaCO3 can precipitate residual starch–PVA complexes on the fabric surface.
Water-activatable tapes and envelope adhesives formulated with 27-96 provide a cleaner rewetting response than animal glue when the converting line requires stable viscosity at 50 °C and reduced biological fouling in open tanks. A high-solids solution is prepared at 18–22% solids by dissolving the polymer at 85–90 °C, followed by the addition of glycerol or sorbitol at 5–10 phr dry polymer and defoamer at 0.1–0.3% of wet formulation. The compound is applied by reverse gravure or slot die at 20–30 g/m² dry coat weight onto Kraft paper having surface energy above 38 mN/m; viscosity is maintained at 2,500–6,000 mPa·s at 50 °C per ASTM D2196-20.
Water activation at 20–25 °C requires 2–4 s wetting before the adhesive develops fibre-tearing bond to recycled corrugated board; T-peel adhesion measured per ASTM D1876-08 falls in the range 2–4 N/15 mm when pressed at 0.5 MPa for 10 s. Blocking resistance tested by ASTM D4946-89 at 50 °C and 70% RH remains pass if plasticizer content does not exceed 10 phr. Above 12 phr glycerol, blocking force exceeds 5 N/cm² and causes feed failures on high-speed envelope lines. Cold-water tack is lower than with 88 mol% hydrolysis grades, so winter converting should use activation water above 25–30 °C to avoid slow tack development.
Tape casting of alumina and barium titanate substrates uses KURARAY POVAL 27-96 as a temporary organic binder at 0.5–2.0 wt% of dry ceramic powder. The powder is first dispersed in water at 75–80 wt% solids with an anionic polyelectrolyte; the binder is then added as a 6.0 wt% solution to avoid competing with the dispersant during the initial adsorption stage. Slurry viscosity at 25 °C is maintained between 1,500 and 4,000 mPa·s at 1.0 s⁻¹ for blade gaps of 0.5–1.0 mm on a polyethylene terephthalate carrier film.
Green tape tensile strength measured per ASTM D638-14 increases from 0.8 MPa at 0.5 wt% binder to 2.1 MPa at 2.0 wt%, while strain at break remains below 5% to prevent via punching distortion. Thermogravimetric analysis at a ramp rate of 5 °C/min to 600 °C shows decomposition onset near 280 °C and residual ash below 0.1 wt%; a box furnace burnout profile of 0.5 °C/min from 200 °C to 500 °C with a 1 h hold avoids bloating and delamination in tapes thicker than 0.5 mm. Borate-bearing dispersants or rheology modifiers are incompatible with this grade because borate–PVOH complexation produces unpredictable viscosity increases and gel particles that cannot be filtered from the tape-casting slurry.
Cast transfer carriers and embroidery backing films based on 27-96 are processed from 8–12% solutions containing 5 phr glycerol or a non-ionic polyol release additive at 0.5–1.0 wt% of dry polymer. The solution is cast at 30–50 g/m² dry film weight and dried at 90–110 °C on a polyester or paper release liner. At 23 °C and 50% RH, the resulting film exhibits tensile strength of 35–45 MPa, elongation at break of 150–200%, and modulus of 1,000–1,500 MPa when tested per ASTM D882-18.
Dissolution in warm water at 40–60 °C reaches 95% mass loss within 30 s under 200 rpm stirring, whereas water at 20 °C requires longer than 5 min because of the 96.0 mol% hydrolysis level. Storage humidity must remain below 60% RH; at 70% RH the film becomes tacky within 24 h and cannot be unwound cleanly from roll stock. Crosslinking with borate additives raises the dissolution temperature above 60 °C and produces insoluble residue, so borate-based wet-strength modification is limited to constructions where warm-water release is intentionally delayed.
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KURARAY POVAL 27-96 is a medium-viscosity, fully hydrolysed polyvinyl alcohol powder obtained by controlled alcoholysis of poly(vinyl acetate). The grade designation is not arbitrary: the prefix 27 indicates a nominal viscosity of 27 mPa·s for a 4 wt% aqueous solution at 20°C, while the suffix 96 indicates a degree of hydrolysis of approximately 96 mol%. In the Kuraray Poval range, this positions the product between cold-water-soluble, partially hydrolysed grades such as 22-88 and hot-water-soluble, higher-hydrolysis grades such as 28-98. The residual acetyl content of 3.5–4.5 mol% reduces the degree of molecular order relative to 98 mol% grades; this is the structural basis for differences in dissolution temperature, viscosity development, film water sensitivity, and oxygen transport behaviour.
The product is supplied as a white-to-cream granular powder with a bulk density of approximately 0.45–0.65 g/cm³. Because the material is hygroscopic, storage at ambient relative humidity above 60% can increase moisture content by more than 1 wt% within 24 h. Pre-drying at 50–60°C for 2–4 h in a desiccant dryer is recommended when the powder is to be gravimetrically compounded. Aqueous dissolution does not occur at ambient temperature; the powder swells and may form a suspension, but a clear solution is obtained only after heating above 70°C. The practical dissolution window for ungelled solutions is 85–90°C under shear. The typical lot release profile is shown in Table 1.
| Parameter | Typical value / range | Test method |
|---|---|---|
| Viscosity of 4% aqueous solution at 20°C | 25.0–29.0 mPa·s | ISO 2555:2018, Brookfield LV, 60 rpm |
| Degree of hydrolysis | 95.5–96.5 mol% | JIS K6726, saponification back-titration |
| Volatile matter | ≤5.0% | ISO 3251:2019 |
| Ash as Na₂O | ≤0.5% | ISO 3451-1:2019 |
| pH of 4% solution | 5.0–7.0 | JIS K6726 |
The degree of hydrolysis is the main specification differentiating 27-96 from both lower and higher hydrolysed PVOH. In a 96 mol% grade, the residual acetate groups disrupt the regularity of the polymer chain, lowering the crystalline melting point and reducing the energy required for aqueous dissolution. At 25°C the apparent cold-water soluble fraction is below 0.1 wt%, whereas an 88 mol% grade can dissolve to 10 wt% or higher at the same temperature. This difference cannot be overcome by simple pH adjustment within the normal range of 4.0–9.0; acid or alkali sufficient to force dissolution at 25°C would degrade the polymer. The solution-viscosity response to solids concentration is approximately linear up to 6 wt% at 60°C, above which the slope increases because of chain entanglement. At 10 wt%, the Brookfield viscosity at 60°C is typically 1,200–1,800 mPa·s; this is still pumpable with positive-displacement gear pumps but unsuitable for diaphragm metering pumps with narrow clearances.
Replacement of a partially hydrolysed grade with 27-96 in a paper-laminating adhesive changes the process from cold compounding to heated compounding. A production-scale mixing cycle in a jacketed stainless-steel vessel at 6 wt% polymer solids is typically run by dispersing the powder in water at 25°C, then heating at 1°C/min to 88°C under a helical-ribbon agitator at 40–50 rpm. Batch dissolution is complete in 45–60 min; the final Brookfield viscosity at 25°C after cooling is in the range of 250–400 mPa·s before plasticisation. Direct addition to hot water at 80°C or higher causes the particle surface to hydrate and swell before the interior is wetted; this is the main source of insoluble fisheyes observed on production lines.
In adhesive performance, 27-96 provides water resistance in the dried film when applied to porous paper and board. A wet laydown of 15–25 g/m² on 175 g/m² kraft linerboard, dried at 80°C for 3 min, can maintain fibre-tear failure after 24 h immersion in deionised water at 23°C, whereas 22-88 under the same conditions tends to re-wet and fail at the bond line. Peel strength is measured according to ASTM D903-98; published comparative data for this exact adhesive formulation is limited, so end users should validate the bond using the specific substrate and moisture exposure cycle. Plasticiser selection matters more for low-temperature flexibility: sorbitol or glycerol at 5–15 wt% on dry polymer reduces embrittlement, but excessive glycerol lowers water resistance.
Batch-to-batch viscosity variance on a production scale is controlled by powder moisture. A 1 wt% moisture increase in the powder shifts the as-is polymer content by 1% and can change final adhesive viscosity by 8–12% at constant formulation weight. Therefore, powder weight should be corrected for volatile content if viscosity must be held within ±5%. As a protective colloid in vinyl acetate emulsion polymerisation, 27-96 is used at 0.5–2.0 wt% based on monomer. Its high degree of hydrolysis yields a more water-resistant emulsion film than low-hydrolysis PVOH stabilisers and reduces the amount of hardener required in the finished adhesive. The main process conflict is grafting of vinyl acetate onto the PVOH at acidic pH 4.0–5.0; buffering with sodium acetate at 0.1–0.2 mol/L suppresses excessive viscosity drift in the reactor. Defoamer consumption is lower than with partially hydrolysed grades because the higher hydrolysis reduces surface activity; the static surface tension of a 4% solution at 20°C is approximately 50 mN/m, compared with 43–46 mN/m for typical 88 mol% grades.
| Property | POVAL 22-88 | POVAL 27-96 | POVAL 28-98 |
|---|---|---|---|
| Nominal 4% solution viscosity at 20°C | 22 mPa·s | 27 mPa·s | 28 mPa·s |
| Degree of hydrolysis | 87–89 mol% | 95.5–96.5 mol% | 98–99 mol% |
| Dissolution temperature | 25–35°C | 80–90°C | 85–95°C |
| Film water resistance at 23°C | Low; re-moistenable | High; resists 24 h soak | Very high; suitable for water-resistant barrier tie layers |
| Typical application focus | Cold-water remoistening, emulsion polymerisation, mould release | Water-resistant adhesives, paper surface sizing, textile sizing | High-water-resistant film, barrier film, heat-seal primer |
These comparative values should be treated as grade-selection guides rather than absolute process settings, because superimposed shear, pH, and salt content in a specific formulation can shift dissolution temperature by 5–10°C.
Paper surface sizing with 27-96 is conducted at size-press solids of 3–6 wt%. A 5 wt% solution at 60°C has a Brookfield viscosity below 100 mPa·s, which is compatible with conventional metering size-press circulation systems. The grade is typically blended with oxidised maize starch at 10–20% replacement of dry starch to improve water-fastness. Cobb60 values measured according to ISO 535:2023 can be reduced when the dry pickup of PVOH is 0.5–1.5 g/m² per side; however, the absolute change depends strongly on internal sizing agents, filler content, and calendering conditions, and published data for this specific grade in a full-scale size press is limited.
An operational boundary is salt tolerance. Concentrations of sodium chloride or calcium chloride above 2 wt% in the size-press solution can induce salting-out of 27-96, producing gel particles that mark the sheet. The higher degree of hydrolysis makes the grade less tolerant of divalent cations than 88 mol% grades. For sheet moistening and drying, the low oxygen transmission rate of 27-96 at low relative humidity is a secondary benefit; a 20 µm film conditioned at 0% RH shows an oxygen transmission rate below 1 cm³/(m²·day·atm), but at 75% RH the value rises to 50–100 cm³/(m²·day·atm) as water plasticises the amorphous phase and increases free volume. This behaviour is measured by ASTM D3985-17 and must be accounted for in barrier packaging applications.
Textile warp sizing with 27-96 uses a cooking kettle at 85–90°C and a size-box temperature above 65°C to prevent gel formation. The dry size film is harder and more water-resistant than 88 mol% grade films; film tensile strength measured by ISO 527-3:2018 is in the range of 60–80 MPa without plasticiser, compared with 30–40 MPa for typical oxidised starch films. The limitation is desizing: the film does not wash out in cold water. Desizing is performed in an oxidative bath containing sodium persulphate at 2–5 g/L and 1–2 g/L wetting agent at 90°C for 1–3 min, or with hot-water washing above 80°C. Sizing formulations typically include a paraffin wax lubricant at 0.5–1.0 wt% on dry size solids to reduce reed marking.
Dissolution rate is limited more by particle wetting and shear history than by water temperature alone. In a recirculating rotor-stator system with a tip speed of 12–18 m/s, a 10 wt% slurry of 27-96 reaches 95% solubility in 20–25 min at 80°C when the powder is dispersed at 25°C before heating. If the same powder is charged directly into water at 80°C, the particle surfaces gel and encapsulate dry core, increasing the time to gel-free solution to 90 min or longer under identical tip speed. This is a practical failure mode observed in batch tanks that lack a cold-water premix chamber.
High-shear mixing introduces air, and air entrainment affects downstream film quality. Vacuum deaeration at −0.8 bar for 15–20 min before use removes visible micro-bubbles and reduces pinholes in cast films. The solution should not be held above 90°C for more than 2 h; extended heating can cause local oxidation and slight yellowing of the solution, although the polymer is not thermally degraded at these temperatures in the absence of oxygen. When the solution is cooled below 40°C, a reversible gel network forms; reheating to 70–80°C restores flow.
Borate ions are a hard incompatibility. Borax decahydrate at 0.02 wt% causes a Brookfield viscosity increase of more than 300% in a 4% solution at 25°C; at 0.05 wt%, gel formation occurs. This is due to didiol-borate crosslinking at the 1,3-diol sites of polyvinyl alcohol. Consequently, 27-96 should not be combined with borate-modified starch, borate-containing dextrin adhesives, or borax-preserved process water without chelation or dilution below the critical borate threshold. Strong oxidising agents such as sodium hypochlorite and persulphate at high concentrations can also cause chain scission; mild oxidative desizing in textile applications is intentional and is controlled at 2–5 g/L persulphate at 90°C.
For food-contact applications, the polymer type is listed in U.S. FDA 21 CFR 177.1670 for polyvinyl alcohol film, subject to extraction limits and end-use conditions. A finished packaging adhesive or size-press coating must also meet overall migration limits under 21 CFR 177.1200 or the relevant food-contact notification; listing of the polymer does not automatically approve a compounded formulation. Under EU Regulation (EC) No 1907/2006, polyvinyl alcohol is a polymer exempt from registration under Article 2(9), provided the constituent monomers meet their registration obligations. The grade contains no intentionally added RoHS-restricted substances; ash as Na₂O is controlled at ≤0.5% to minimise ionic contamination in coating applications.
Industrial handling requires dust explosion assessment under ATEX Directive 2014/34/EU and national DSEAR implementations because organic polymer powders can form explosive atmospheres. The powder should be grounded during pneumatic transfer, and conveying velocity should be kept below 10 m/s to limit static charging. For aqueous handling, concentrated solutions above 10 wt% should be stored above 40°C or preserved with a non-borate biocide if ambient storage is required. No exposure limit specific to polyvinyl alcohol is established in many jurisdictions; standard particulate nuisance dust limits and local ventilation should be applied.
