| HS Code | 680790 |
| Product Name | KURARAY POVAL 55-95 |
| Chemical Type | Polyvinyl alcohol (partially hydrolyzed) |
| Cas Number | 9002-89-5 |
| Appearance | White to slightly yellowish granular powder |
| Degree Of Hydrolysis | 94.0-96.0 mol% |
| Viscosity | 50.0-60.0 mPa·s (4% aqueous solution at 20°C) |
| Ph | 5.0-7.0 (4% aqueous solution) |
| Solubility | Soluble in hot water; practically insoluble in organic solvents |
| Specific Gravity | 1.26-1.31 |
| Bulk Density | Approximately 0.4-0.6 g/cm³ |
| Volatile Content | ≤5% |
| Ash Content | ≤0.5% |
| Thermal Decomposition Temperature | Approximately 230°C |
As an accredited KURARAY POVAL 55-95 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Kuraray POVAL 55-95 is supplied as a white granular powder in 25 kg multiwall paper bags, palletised and shrink-wrapped. |
| Container Loading (20′ FCL) | KURARAY POVAL 55-95 is shipped in 20′ FCL, packed on pallets, secured, and protected from moisture in a dry container. |
| Shipping | KURARAY POVAL 55-95 is a polyvinyl alcohol resin shipped as solid granules in multi-layer paper or polyethylene bags, palletized and stretch-wrapped. It is non-hazardous for transport, but should be kept dry, protected from moisture, and stored in ventilated areas. Avoid direct sunlight and extreme heat during shipping and handling. |
| Storage | Store KURARAY POVAL 55-95 in a cool, dry, well-ventilated area, away from heat, sparks, and direct sunlight. Keep containers tightly sealed to prevent moisture absorption and contamination. Avoid dust generation and contact with strong oxidizers. Maintain stable temperatures, separate from incompatible materials, and follow safe handling practices to preserve product quality. |
| Shelf Life | Shelf life is typically 2 years when stored in original, unopened container under cool, dry conditions. |
On flooded-nip size presses running 600–1,200 m/min, KURARAY POVAL 55-95 is introduced as a high-viscosity surface sizing binder where the nominal 55 mPa·s 4% aqueous solution viscosity at 20°C per JIS K6726 controls penetration and maintains surface film continuity. The grade is dissolved in a steam-sparged stainless steel jet cooker at 90–95°C for 25–40 min; complete hydration below 85°C is not achievable. A working solution of 4–8% solids is maintained at 55–65°C in the press pan. Dry addition is set at 0.5–2.0 wt% of base sheet mass. The residual acetyl content of approximately 5 mol% limits hydrogen-bond-driven crystallisation, reducing dusting on slitter knives. Ammonium zirconium carbonate is dosed at 5–10 wt% on PVOH solids to react with hydroxyl groups and lower water sensitivity; the pH is buffered to 6.0–7.5 after cooking because low-pH rosin sizes cause flocculation. Filtration through a 150 μm bag is standard before the metering pump. For folding carton and inkjet grades, Cobb60 water absorption is specified below 25 g/m² under ISO 535:2023, and surface pick resistance is monitored with IGT equipment under ISO 3783; the 95 mol% hydrolysis grade produces higher wet pick resistance than 88 mol% grades at equal pickup. End products include high-scuff folding carton stock, release liner base paper, and coated inkjet paper. Food-contact use follows FDA 21 CFR 176.170 and BfR Recommendation XXXVI when the coating is applied in compliance with good manufacturing practice.
The 55-95 grade functions as a temporary thermoplastic binder in dry-pressed and tape-cast ceramic bodies. For alumina tape casting, a starting slurry contains 100 parts by mass alumina powder, 3.0–6.0 parts PVOH solids, 0.5–1.5 parts glycerol, and 0.1–0.3 parts defoamer in deionized water. The PVOH is first dissolved to 8–10% solids and then added to the ceramic slurry; deagglomeration is carried out in a horizontal bead mill for 24 h at 25–35% total solids. Tape casting uses a doctor blade gap of 200–500 μm on a carrier speed of 0.3–0.8 m/min. Drying is run in a multi-zone air flotation oven with the first zone at 25°C and the final zone at 40°C to prevent skinning. Lamination of green sheets for multilayer ceramic capacitors and LTCC substrates is performed at 60–80°C under 5–10 MPa. Binder burnout is the critical process window: the heating rate between 200°C and 600°C is held at 0.2–0.5°C/min, and a 2 h dwell at 350°C is required when body thickness exceeds 6 mm. The residual sodium acetate concentration in the dissolved PVOH should be below 0.5 wt% to avoid flux residue in low-temperature co-fired dielectric formulations. End products include alumina substrates, LTCC green tapes, and piezoelectric PZT blanks. Thermogravimetric analysis per ASTM E1131 is used for batch-to-batch burnout profiling; published data for this specific grade in LTCC tape is limited and pilot runs are required before production.
Because the 55-95 grade retains a residual acetyl content of approximately 5 mol%, it functions as a steric stabiliser and graft-protective colloid in vinyl acetate and vinyl acetate-ethylene emulsion polymerisation. The material is pre-dissolved at 8–12% solids and charged to the reactor at 2.0–6.0 wt% based on total monomer. A semi-continuous process at 45–65°C using potassium persulfate or a redox initiator maintains particle size in the 0.8–2.0 μm range for polyvinyl acetate homopolymers. The final dispersion viscosity is controlled less by particle size than by free PVOH and grafted PVOH content; unreacted PVOH above 1.5 wt% thickens the dispersion and lowers shear stability. The reactor is equipped with a cooled jacket, an anchor stirrer at 40–80 rpm, and nitrogen purge. Additions of 0.02–0.05 wt% defoamer and 0.1–0.3 wt% sodium bicarbonate buffer are made before monomer feed. Terminal products are D3/D4 wood adhesives tested under EN 204, paper-to-paper laminates, and nonwoven filter-paper binders. Food-contact adhesive use is governed by FDA 21 CFR 175.105. Operational boundaries include pH control between 5.0–6.5; below 4.5 acid-catalysed hydrolysis generates acetaldehyde. Incompatibility is observed with cationic surfactants, which coagulate the latex; only anionic or nonionic emulsifiers are used at 0.1–0.5 wt%. Published data for high-pressure ethylene copolymerisation with 55-95 is limited, so pilot trials are required before 300 L scale.
Size box stability on polyester-cotton warp yarns is governed by solution viscosity, surface film formation, and blocking tendency on dry cans. KURARAY POVAL 55-95 is cooked to 10–12% solids and supplied to the size box at 65–75°C. Add-on is set at 6–10% dry mass for staple polyester yarns and 8–15% for polyester-cotton blends. A wax lubricant is added at 0.5–2.0 wt% on PVOH solids to reduce friction at heald eyes and reed dents. Nip pressure is held at 2.0–3.5 bar in a two-roll squeeze station. Drying cylinder temperature is set from 105°C in the first can to 125°C in the final can; operation above 130°C embrittles the film and creates weaving dust. The key failure mode is size box skinning: the surface gel forms after 15 min of idle time at bath temperature. A closed size box with a circulation rate of 0.2–0.5 L/min and lid temperature above 70°C prevents filming. Desizing is carried out at 85–95°C using 0.5–1.0 g/L sodium hydroxide and 1–3 g/L hydrogen peroxide; the 95 mol% hydrolysis level requires more energy than 88 mol% grades. End products include plain-weave shirting, bed linen, and workwear. Tensile strength retention on sized yarn is measured under ASTM D2256. Formulations for ZDHC MRSL Version 3.1 are achieved by excluding alkylphenol ethoxylates.
Dispersion of KURARAY POVAL 55-95 into an existing starch-adhesive line is carried out as a separate cooked stock at 10–15% solids and blended into the final adhesive at 5–15 wt% dry solids. The 55 mPa·s viscosity contributes wet tack and dry film strength in spiral paper tube winding and multiwall sack lamination. A starting formula contains 10–15 parts PVOH, 65–75 parts water, 20–30 parts kaolin clay, and 0.1–0.3 parts preservative. Mixing is performed in a 150–500 L stainless steel vessel with a slow anchor stirrer at 30–50 rpm; high-shear mixing above 500 rpm introduces chain scission and irreversible viscosity loss. The adhesive is applied at 40–55°C with a notched doctor roll. Open time is specified at 12–25 s depending on roll gap and board absorbency. Water resistance of the dried bond is assessed by 24 h water immersion at 23°C; user specifications typically require no delamination after 24 h. The grade cannot fully replace borated starch in high-humidity storage; additional crosslinker such as 5–10 wt% ammonium zirconium carbonate or 1–3 wt% glyoxal is required. End products include spiral paper tubes, multiwall sack laminations, and edge protectors. Food-contact laminates are formulated under FDA 21 CFR 175.105. Compliance with REACH (EC) No 1907/2006 applies to the polymer CAS 9002-89-5; no intentional RoHS-regulated substances are present in the as-supplied grade.
Barrier coating formulators switch from 88 mol% grades to 55-95 when a higher modulus and lower residual tack are required in paper-based packaging. The grade is applied by rod or roll coater at 4–10 g/m² dry coat weight. Drying at 90–110°C produces a continuous film. Because PVOH oxygen barrier is humidity-dependent, converters specify oxygen transmission rate only at defined relative humidity using ASTM D3985-17; published data for 55-95 at 80% RH is limited and must be measured before lamination design. The coating is not recommended as a sole oxygen barrier in retort pouches above 70% RH without lamination. A co-binder or crosslinker such as 0.5–2.0 wt% citric acid with a suitable acid catalyst improves wet strength. Water vapour transmission rate is measured under ISO 2528:2017. End products include dry food packaging, bakery box liners, and release liner base stock. The operational boundary is 60% RH; above that level the coating functions as a primer or seal layer rather than a primary oxygen barrier.
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KURARAY POVAL 55-95 belongs to the medium-viscosity, partially hydrolyzed polyvinyl alcohol segment of the Kuraray Poval portfolio. The four-digit designation carries two nominal specifications: the first two digits, 55, correspond to a 4 wt% aqueous solution viscosity of 55 mPa·s at 20 °C; the final two digits, 95, correspond to 95 mol% hydrolysis. The residual 5 mol% acetate groups modify hydrogen-bonding density, crystallinity, water solubility, and interfacial activity relative to fully hydrolyzed grades. The product is a solid granular resin intended for aqueous formulation, not for melt processing. It is used as a protective colloid, surface-sizing additive, textile size, ceramic binder, and water-soluble adhesive intermediate. Indirect food-contact suitability must be assessed under 21 CFR 175.105 and 21 CFR 176.170; the grade is not a direct food additive.
The medium-viscosity class distinguishes 55-95 from low-viscosity PVOH grades that are pumpable at high solids. In solution, the grade develops a pronounced thickening response above 8–10 wt%, which limits its use in high-solids coating and spray-drying processes but provides film toughness and shear stability in adhesive and binder applications. Because the resin is partially hydrolyzed, its aqueous solutions are less prone to irreversible gelation than fully hydrolyzed Poval grades stored at low temperature, though warm-water make-down and preservative use remain practical requirements in production plants.
In lot-release testing, the 55 mPa·s nominal viscosity is measured on a 4 wt% aqueous solution at 20 °C using JIS K6726 methodology. This is a solution viscosity, not a melt-flow rate. The value should not be compared directly with ISO 1133-1 melt-mass flow rate data used for thermoplastic polyolefins because PVOH does not melt cleanly without plasticizer and thermal degradation begins before a stable melt viscosity can be obtained. The degree of hydrolysis is determined by saponification residue and reported as mole percent hydroxyl relative to total side groups; the nominal 95 mol% value translates to an average residual acetate content around 5 mol%. This residual acetate content is sufficient to reduce crystallite size and lower the incipient dissolution temperature, but it is not high enough to allow instantly clear solutions in cold water as with an 88 mol% grade. Plant make-down tanks use heated water, and the solution should be cooled below 40 °C before long-term storage to reduce skinning and microbial growth.
| Parameter | Representative specification | Test method |
|---|---|---|
| 4% solution viscosity at 20 °C | 55 mPa·s nominal | JIS K6726 |
| Degree of hydrolysis | 95 mol% nominal | JIS K6726 |
| Volatile matter | ≤5 wt% | JIS K6726 |
| Ash as Na₂O | ≤0.5 wt% | JIS K6726 |
| pH of 4% solution | 5.0–7.0 | JIS K6726 |
Volatile matter and ash are controlled because water vapor content affects feeding accuracy in gravimetric dosing systems, and sodium ash influences ionic strength in emulsion polymerization and ceramic sintered bodies. A lot with volatile matter above 5 wt% can exhibit caking in humid storage, making screw feeding less consistent. Ash values above 0.5 wt% as Na₂O are generally unacceptable in high-purity electronic ceramic binder applications, where sodium contamination influences dielectric loss. The pH 5.0–7.0 specification minimizes corrosion of mild steel make-down vessels and avoids alkaline hydrolysis of ester-containing co-binders during storage.
In vinyl acetate and vinyl acetate-ethylene emulsion polymerisation, 55-95 is charged as a protective colloid at 0.5–5 wt% on total monomer. The residual acetate groups of the 95 mol% hydrolysis grade adsorb onto the monomer-swollen poly(vinyl acetate) particle surface and participate in radical chain transfer to the polymer backbone, forming grafted PVOH segments. These grafted segments provide greater steric stabilization than non-grafted PVOH at the same molecular weight. In a 30-m³ stirred reactor with a flat-blade turbine, the addition sequence controls coagulum formation. If the entire colloid charge is dumped into the initial aqueous phase, local high-viscosity regions reduce monomer diffusion and produce oversized coagulum observed on a 150 µm screen filter. A staged addition over 10–20 min after the first monomer feed eliminates this defect. In pilot-scale baffled reactors with high-shear agitation, the gradient is lower, but stagewise feeding is retained because pre-emulsion gelation can still occur at high colloid concentration.
The latex particle size and freeze-thaw stability improve as the medium-viscosity grade thickens the aqueous phase. However, the relationship is non-linear. Above 5 wt% protective colloid, conversion can decrease because the continuous-phase viscosity impedes monomer diffusion and initiator redistribution. Below 0.5 wt%, insufficient steric protection leads to shear-induced coagulation during transfer through diaphragm pumps or within the finishing filter. Batch-to-batch variation in residual acetate content of ±0.5 mol% is sufficient to shift grafting frequency and final latex particle size; plants that require tight particle size control verify the acetate content on the certificate of analysis before setting initiator feed rate. The final film has lower cold-water resistance than a 55-98-stabilized latex because the residual acetate groups remain weakly hydrophilic. This is an intentional trade-off when improved emulsification, lower gel content, or better adhesion to polyolefin surfaces is more important than maximum water resistance.
Paper surface sizing and coating binder systems employ 55-95 in combination with oxidized starch or styrene-butadiene latex to increase pick strength without the full water-resistance penalty of a superhydrolyzed PVOH grade. In blade coating formulations containing 2–5 parts 55-95 per 100 parts total pigment, the medium viscosity elevates low-shear Brookfield viscosity in the 20–30 s⁻¹ range and reduces blade chatter on high-speed coaters. The 95 mol% hydrolysis grade retains enough hydroxyl groups for hydrogen bonding to cellulose, while the residual acetate groups reduce film brittleness. However, when packaging grades require low Cobb water absorption under ISO 535, 55-95 alone may not meet the lowest moisture-barrier targets; 55-98 or an insolubilizing crosslinker is specified instead. In publication-grade coated paper, IGT pick tests demonstrate improved surface strength at PVOH addition levels around 1 wt% of total binder, but published data for this specific grade are limited and mill trials are required to confirm formulation interactions with optical brighteners and calcium carbonate dispersion.
The primary decision path is whether viscosity or hydrolysis dominates the application requirement. 55-95 and 55-98 share nominal 55 mPa·s solution viscosity, so they are interchangeable from a thickening standpoint; the hydrolysis difference changes dissolution energy and dried-film water resistance. 55-98 at 98.5 mol% hydrolysis produces more crystalline, water-resistant films but requires higher make-down temperature and may gel on standing at room temperature. 48-88 has a lower nominal viscosity of 48 mPa·s and 88 mol% hydrolysis, giving true cold-water solubility and easier tank make-down, but lower film strength and higher moisture sensitivity. A formulator selecting 55-95 accepts warm-water make-down in exchange for moderate water resistance and better hydrophobic-substrate adhesion than fully hydrolyzed Poval grades.
| Grade | Nominal 4% viscosity | Nominal hydrolysis | Solubility behaviour | Water resistance of dried film |
|---|---|---|---|---|
| Poval 55-95 | 55 mPa·s | 95 mol% | Warm-water; limited cold-water dissolution | Moderate |
| Poval 55-98 | 55 mPa·s | 98.5 mol% | Requires elevated temperature | Higher |
| Poval 48-88 | 48 mPa·s | 88 mol% | Cold-water soluble | Lower |
This intermediate placement makes 55-95 particularly useful where both colloidal protection and film flexibility are needed, such as vinyl acetate-ethylene copolymer emulsions and coated paper sizing, but less suitable for barrier coatings requiring minimal water uptake. In those applications, 55-98 or crosslinked systems are preferred. Conversely, when low-temperature dissolution is the primary constraint, 48-88 or an 88 mol% grade is selected despite lower film strength.
Textile warp sizing uses 55-95 as a film-forming size for cotton, polyester, and cotton-polyester blends. Size boxes operating at 55–65 °C apply the size solution at 8–12 wt% to warp yarns; the higher viscosity relative to low-viscosity PVOH at equivalent solids increases size-film cohesion. The 95 mol% hydrolysis grade provides sufficient water solubility for desizing in warm water without the high desizing energy sometimes required for fully hydrolyzed PVOH films. Compared with 55-98, it leaves less insoluble size residue on polyester under low-temperature washing conditions, but its lower water resistance should not be selected where size films must survive prolonged high-humidity weaving environments.
In ceramic powder granulation, 55-95 is added at 1–3 wt% of dry batch to increase granule hardness and pressed green strength. The 55 mPa·s viscosity contributes to granule formation under rotary atomization, but feed solids above 25–30 wt% can generate hollow granules and poor die fill. Ash as Na₂O is controlled at ≤0.5 wt% under JIS K6726, a level that is sufficiently low for many oxide ceramic formulations but must be verified for high-purity alumina or zirconia requiring 0.1 wt% total alkali limits. Thermal debinding removes the PVOH binder between 250–400 °C in air; for thick parts, published data for this specific grade is limited, so kiln burnout must be confirmed by thermogravimetric analysis to avoid carbon residue.
