| HS Code | 857036 |
| Product Name | KURARAY POVAL 56-98 LA |
| Chemical Name | Polyvinyl Alcohol |
| Cas Number | 9002-89-5 |
| Appearance | White to pale yellow granular powder |
| Saponification Degree | 98.0 - 98.8 mol% |
| Viscosity 4 Percent Solution 20c | 54 - 60 mPa·s |
| Ph 4 Percent Solution | 5.0 - 7.0 |
| Ash Content | ≤ 0.3% |
| Volatile Content | ≤ 5.0% |
| Bulk Density | 0.45 - 0.65 g/cm³ |
| Specific Gravity | 1.27 - 1.31 |
| Solubility | Soluble in hot water; insoluble in most organic solvents |
| Melting Point | Approx. 230 °C (with decomposition) |
As an accredited KURARAY POVAL 56-98 LA factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | KURARAY POVAL 56-98 LA is supplied as a free-flowing granular powder in 25 kg multi-ply paper bags with inner liner. |
| Container Loading (20′ FCL) | KURARAY POVAL 56-98 LA is loaded into a 20′ FCL on pallets, shrink-wrapped, moisture-protected, and secured safely for transport. |
| Shipping | Kuraray Poval 56-98 LA is a polyvinyl alcohol resin shipped as a free-flowing powder. It is non-hazardous but hygroscopic, so use dry containers, protect from moisture, and avoid dust accumulation. Avoid extreme temperatures and handle using standard industrial hygiene procedures. |
| Storage | Store KURARAY POVAL 56-98 LA in its original, tightly closed container in a cool, dry, well-ventilated area. Protect from moisture, humidity, and direct sunlight. Keep away from heat sources, open flames, and incompatible materials. Avoid dust generation and accumulation. Ensure proper labeling and segregation from food products. Follow local regulations and manufacturer guidelines. |
| Shelf Life | Shelf life is typically two years from manufacture date when stored unopened in a cool, dry place. |
On high-speed paper machines, the grade is introduced at the size press as a co-binder with oxidised or enzyme-converted starch. A typical size press make-down uses 5–10 mass% Poval 56-98 LA solids in the cooked starch solution, with the PVOH fraction representing 10–30% of total binder solids. Pre-dissolution in a high-shear jet cooker is set at 90–95 °C for 30 min; residual undissolved gel particles are removed through 150 μm pressure filters. On rod-metering film presses operating at 800–1500 m/min, the 4% aqueous viscosity of 56–66 mPa·s under JIS K6726 raises size press pick-up and controls penetration into the base sheet. The fully hydrolysed chain, with 98.0–99.0 mol% vinyl alcohol units, produces a continuous high-strength film that reduces dusting and raises IGT surface strength when tested under ISO 3783:2014. Oil and grease resistance is measured by the 3M KIT test under TAPPI T559 cm-12; a 2–4% PVOH/starch blend on an 80 g/m² bleached kraft base typically yields KIT values in the 7–12 range depending on starch type and base sizing. Cobb water absorption under ISO 535:2023 shifts from 45–60 g/m² for unsized sheet to 20–25 g/m² after addition of 2.0 wt% Poval 56-98 LA on dry fibre. The low-ash LA designation is critical for closed water loops because residual sodium oxide below 0.10 mass% minimises conductivity drift in acid or neutral sizing systems. Process limits include solution hold tanks maintained below 80 °C after cook; extended holding above 85 °C produces viscosity loss through chain scission, and at pH below 5.0 precipitation with cationic wet-end additives must be avoided. Use in food-contact paper requires compliance with 21 CFR 176.170 and BfR Recommendation XXXVI when the dried size press film does not transfer to food as a direct additive.
| Parameter | Nominal range | Test method |
|---|---|---|
| 4% aqueous solution viscosity | 56.0–66.0 mPa·s at 20 °C | JIS K6726 |
| Degree of hydrolysis | 98.0–99.0 mol% | JIS K6726 |
| Ash content as Na₂O | <0.10 mass% LA designation | JIS K6726 |
| Volatile matter | <5.0 mass% | JIS K6726 |
KURARAY POVAL 56-98 LA is prepared as a 4–6 mass% aqueous stock solution and dosed at 400–1200 ppm on VCM mass in suspension polymerisation. The grade is fully hydrolysed at 98.0–99.0 mol% under JIS K6726, while the high molecular weight creates a protective adsorbed layer that reduces coalescence during the 30–45% conversion stage when PVC particles are most tacky. Reactor temperature is held at 50–70 °C, corresponding to K-value 57–68 resin, and the vinyl chloride droplet-to-particle transition is followed by monitoring reactor pressure drop at 0.1–0.3 MPa from saturation. Published production data for this exact low-ash grade in large reactors of 80–150 m³ is limited; however, suspension PVC lines using fully hydrolysed grades at 500–800 ppm report median grain size 100–180 µm by laser diffraction under ISO 13320:2020 and bulk density 0.48–0.58 g/cm³ when combined with a secondary partially hydrolysed PVOH at 30–50% of the primary charge. The low ash content of LA material reduces formation of PVC specks and improves whiteness, with residual sodium oxide controlled below 0.10 mass% via washing. Incompatibility arises with strong oxidising initiators dosed as aqueous emulsions; pre-mixing PVOH with organic peroxides at temperatures above 40 °C must be avoided because radical attack on the polymer backbone reduces interfacial tension control. Post-bed filtration through 50–100 µm screens is required before injection to avoid destabilised polymer droplets from filtration pressure. Residual monomer stripping at 0.08–0.12 MPa vacuum and 70–85 °C does not require additional antifoam when LA-grade ash content is below 0.10 mass%, though foaming becomes measurable above 0.3 mass% ash.
When warp yarns move through size boxes on high-speed air-jet looms running at 700–1100 picks/min, fully hydrolysed Poval 56-98 LA is formulated in warp size mixes as a film former with acrylic copolymer and starch derivatives. A production-size preparation typically contains 6–10 mass% Poval solids, 3–5 mass% acrylic ester copolymer size, and 0.5–1.5 mass% wax lubricant based on total size liquor. The size box temperature is maintained at 85–90 °C; viscosity of the sizing liquor at 85 °C is 50–150 mPa·s when measured with a Brookfield LV viscometer at 60 rpm. Cotton warp yarns sized with 8–14% dry add-on show breaking strength retention of 85–95% under ASTM D2256/D2256M-21 and improved abrasion resistance in the Reutlingen Webtester to 150–300 cycles depending on yarn count and size recipe. The low ash content is relevant where desizing effluent is treated anaerobically; sodium oxide below 0.10 mass% does not increase sludge conductivity. Poval 56-98 LA must be dissolved separately at 90–95 °C because undissolved gel specks cause warp breaks at reed beat-up. Desizing is performed with α-amylase at 60–70 °C followed by a hot wash at 90 °C; residual PVOH is determined by iodine colour reaction and should be below 0.5% on fabric weight before bleaching. Textile sizing is not directly regulated as food contact, but wastewater discharge is evaluated under EU BAT reference documents for textile wet processing.
For remoistenable envelope adhesives and paper tube winding, Poval 56-98 LA is combined with dextrin or pregelatinised starch at PVOH:starch ratios from 10:90 to 30:70 on dry mass. A standard aqueous adhesive batch is mixed at 75–85 °C for 20–40 min; total solids are 35–50 mass%, with plasticiser glycerol at 2–5 mass% of total solids. The 56–66 mPa·s 4% solution viscosity under JIS K6726 produces high wet tack after rewetting; T-peel adhesion on recycled board under ASTM D1876-08 typically reaches 0.5–1.5 N/mm when the adhesive is applied at 20–30 g/m² dry coat weight. Low-ash PVOH is used because sodium salts reduce remoistening speed and cause visible bloom on dark-coloured paper stocks. Viscosity stability in the glue pot is maintained by cooling to 50–60 °C and controlling pH between 5.5–7.5; borax is excluded above 0.2 mass% because fully hydrolysed PVOH forms a thermoreversible gel within 2–10 min, blocking doctor blade manifolds. Compliance for indirect food contact is assessed under 21 CFR 175.105 for adhesive components when the dry adhesive is separated from food by a functional barrier; migration of the low-molecular-weight fraction is controlled by PVOH chain length and washing process.
KURARAY POVAL 56-98 LA is charged into semi-batch vinyl acetate homopolymerisation as a 4–6 mass% aqueous pre-dissolved solution at 2–5 mass% protective colloid on total monomer. The fully hydrolysed backbone with 98.0–99.0 mol% vinyl alcohol units under JIS K6726 produces coarse emulsion particles in the 0.5–2.0 µm range by laser diffraction under ISO 13320:2020, and the final dispersion at 50–55% solids develops Brookfield viscosity 5000–15000 mPa·s at 20 rpm and 25 °C. The LA grade, with ash below 0.10 mass% as Na₂O, prevents polyvalent ion bridging that would otherwise increase grit formation during ammonium persulfate/sodium metabisulfite redox initiation. Reactor pH is controlled at 4.5–5.5 with sodium bicarbonate; below 4.0, residual vinyl acetate hydrolysis releases free acetic acid and emulsion viscosity rises rapidly through protonation of acetate groups on the particle surface. Polymerisation temperature is held at 65–75 °C for standard PVAc homopolymers; monomer feed is adjusted so that free VAM remains below 0.5 mass% at final stripping. When formulated into one-part wood adhesives, the dispersion is compounded with 2–5 mass% plasticiser and 0.1–0.5 mass% defoamer; D3 durability is assessed according to EN 204:2016 and wet shear after 4 h water soak at 20 °C is controlled by crosslinker addition. Storage stability requires keeping the emulsion above 5 °C and below 40 °C, with mild agitation to prevent skinning. The high-viscosity grade may not be suitable for high-solids low-viscosity coatings, but for wood adhesive bases its water resistance contribution is measurable in D3 wet shear after 4 h water soak at 20 °C.
Aqueous alumina or barium titanate tape casting slurries incorporating Poval 56-98 LA are prepared by dissolving the binder at 10–15 mass% in deionised water and adding the solution to give 3–7 g PVOH per 100 g ceramic powder. Milling is conducted in a ball mill with 10–20 mm zirconia media for 12–24 h. The resulting slip viscosity is adjusted to 1000–4000 mPa·s at 20 rpm for doctor blade casting at 0.2–2.0 mm wet film thickness. Green tape tensile strength after drying at 60–80 °C is tested under ASTM C1499-15; values above 2–6 MPa are typical for tape thickness 100–300 µm depending on powder surface area and binder content. The fully hydrolysed grade gives higher green strength than partially hydrolysed PVOH at equal addition because of crystallite formation during solvent evaporation. Thermal debinding is carried out in air at 450–600 °C for 1–4 h; residual carbon after burnout is below 0.05 mass% when the heating rate is kept below 1 °C/min to 500 °C. Low ash is essential because sodium in standard PVOH can form eutectic phases with silica and reduce the firing temperature of ceramic substrates, causing warpage during sintering at 1300–1600 °C. Published data for this specific LA grade in direct lamination of multilayer ceramic capacitors is limited; production-scale casting on continuous casters requires defoaming and vacuum dearation at 50 mbar to avoid pinholes. Compliance under REACH does not require specific migration testing for ceramics, but outgassing during binder burnout must meet workplace exposure limits for acetaldehyde and acetic acid.
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KURARAY POVAL 56-98 LA is a fully hydrolysed polyvinyl alcohol supplied as a white to off-white granular powder with CAS Registry Number 9002-89-5. The grade designation encodes two key rheological and compositional properties: the first segment places the nominal dynamic viscosity of a 4 wt% aqueous solution at 20 °C near 56 mPa·s, and the second segment corresponds to a degree of hydrolysis of 98.0–99.0 mol%. The suffix LA identifies a low-ash variant in which residual sodium acetate and inorganic ash are controlled below the tolerances commonly assigned to the standard 56-98 grade. Viscosity and degree of hydrolysis are measured according to JIS K6726 or ISO 15023-2, with exact lot-release values reported on the certificate of analysis. The polymer is produced by controlled alcoholysis of polyvinyl acetate and therefore carries a linear carbon backbone substituted with hydroxyl groups; the fully hydrolysed structure exhibits strong interchain hydrogen bonding, limited cold-water solubility, high film tensile strength, and reduced moisture swell relative to partially hydrolysed grades. Bulk density, volatile content, pH, and residual acetyl content are lot-dependent and should be taken from the manufacturer’s lot-specific documentation rather than generic datasheet values. The powder is not classified as dangerous goods under GHS criteria in the as-supplied form, but plant-scale handling must control combustible dust formation through local exhaust ventilation, antistatic bonding, and housekeeping limits. The low-ash attribute is the principal specification difference that directs this grade into ceramics, high-purity binders, and electronics-adjacent process streams where sodium residues from polymerisation catalysts are considered process-relevant variables.
The selection boundary between KURARAY POVAL 56-98 LA and other Poval grades is established by three factors: molecular weight reflected in 4% solution viscosity, degree of hydrolysis, and ash residue. Fully hydrolysed grades such as 56-98 LA require elevated-temperature dissolution but yield dried films and binders with high water resistance and cohesive strength. Partially hydrolysed grades with hydrolysis near 88 mol% dissolve in cold water and are suited to low-viscosity protective colloid duties, but their films show increased water uptake and lower shear strength after drying. Compared with 28-99, 56-98 LA raises solution viscosity at equal solids, thus increasing wet adhesion and green-body mechanical properties while increasing mixing torque and limiting the solids level that can be pumped through standard coating equipment. The LA suffix does not alter the primary polymer architecture but signals a reduced ash ceiling; this is operationally significant when the dried binder must disappear without leaving sodium-bearing defects. Film tensile properties may be compared through ASTM D882-18, and water resistance can be ranked through equilibrium water absorption tests referenced in supplier technical bulletins; the exact numerical values depend on plasticiser content, film thickness, and drying history.
| Grade | Nominal 4% aq viscosity at 20 °C (mPa·s) | Degree of hydrolysis (mol%) | Ash profile | Primary formulation consequence |
|---|---|---|---|---|
| 56-98 LA | 56 | 98.0–99.0 | Low ash | High cohesion; reduced ionic residue after burnout |
| 28-99 | 28 | 99.0 | Standard | Lower solution viscosity; easier make-down |
| 22-88 | 22 | 88.0 | Standard | Cold-water soluble; lower water resistance |
The values in the table are supplier-nominal midpoints or published grade designations. They are not substitutes for certificate-of-analysis data when qualifying a production lot.
During vinyl acetate and vinyl acetate–ethylene emulsion polymerisation, KURARAY POVAL 56-98 LA is pre-dissolved in a dedicated make-down vessel before it is metered into the reactor as a protective colloid. The powder is slurried in cold demineralised water, then heated to 85–95 °C under low-shear agitation until optical clarity is achieved; direct powder addition to a cold latex charge produces fisheyes and can obstruct reactor transfer lines. Once dissolved, the fully hydrolysed polymer participates in grafting reactions with vinyl acetate radicals and sterically stabilises latex particles. The resulting latex exhibits pseudoplastic flow, so transfer pumps and coating stations are selected for shear-sensitive viscosity rather than simple centrifugal delivery. In adhesive compounding, the grade contributes water redispersibility after drying and improves heat-seal strength in coated paper structures. Viscosity measurements on compounded adhesives are usually made with a Brookfield rotational viscometer at controlled spindle speeds because Newtonian assumptions fail for these systems. The main operational boundary is viscosity drift: solutions of fully hydrolysed grades can build viscosity on standing, particularly below 40 °C. Therefore, hold time, temperature, and agitation history must be fixed in batch records to keep adhesive coat weights reproducible. Production lots should be qualified by comparing final latex particle size distribution and cake filtration behaviour, because lot-to-lot ash variation may influence emulsion electrical stability.
The make-down procedure for 56-98 LA is governed by the polymer’s tendency to form unhydrated gel aggregates if the powder is added too rapidly to hot water. A production-scale vessel equipped with a side-entering propeller or an eductor is charged with ambient demineralised water, and the powder is fed gradually into a well-formed vortex at moderate impeller speed. After wetting, the batch is heated with saturated steam or jacketed hot water to 90 °C and held for 30–60 min with continued low-shear agitation. High-shear rotor–stator devices may be used for dispersion during powder addition but should be stopped during the hydration phase to prevent polymer chain scission. The finished solution is filtered through a 100–200 µm bag or cartridge filter and deaerated by vacuum or centrifugal degassing before use. At 4% solids and 20 °C, Brookfield viscometry returns a nominal viscosity in the region of 56 mPa·s; at 10% solids, the solution is a sluggish gel at room temperature and should be maintained above 60 °C for metering into coating baths. Preservatives are added only after cooling below 40 °C to avoid thermal degradation of the biocide. Borate ions, glyoxal, and certain multivalent metal cations create strong physical crosslinks that can raise viscosity sharply or form irreversible gels; these additives must be segregated or buffered before incorporation. When the solution is stored, the tank should be blanketed or sealed to prevent skinning, and recirculation should be gentle to avoid shear-induced viscosity loss. The solution temperature should not be allowed to fall below 30 °C during transfer; otherwise gelation in unheated pipework can occur, especially at solids above 6%.
In oxide and non-oxide ceramic processing, the low-ash profile of KURARAY POVAL 56-98 LA becomes the controlling variable for binder selection. Tape-casting formulations combine ceramic powder, solvent, dispersant, plasticiser, and binder; the fully hydrolysed grade contributes green tape tensile strength through high molecular weight chain entanglement and interfacial hydrogen bonding. Binder demand is formulation-dependent, but laboratory evaluations often begin near 2–5 wt% of dry ceramic mass and are adjusted until the dried green tape reaches the required handling strength. The LA variant is specified when sodium acetate residues from standard PVOH grades would otherwise survive burnout and contaminate dielectric layers or create pinholes in fired ceramic sheets. In continuous doctor-blade casting, the slurry is applied to a carrier film, and the wet-film thickness is controlled by the blade gap and casting speed; high solution viscosity reduces slurry settling but may require vacuum deairing to prevent bubbles in the green film. Burnout of the binder in air is typically completed before 500 °C, and the low-ash composition leaves less inorganic residue. Published data for exact green-strength values with this specific LA lot are limited; manufacturers must run fixture-based three-point bend or tensile measurements on their own green tape because strength is sensitive to particle size distribution, solvent system, and plasticiser type. The dried green sheet should be tested with a universal testing machine using a three-point bend fixture adapted from ASTM C1161 or internal protocols; no universal green-strength specification exists.
In ceramic injection moulding feedstocks, KURARAY POVAL 56-98 LA is compounded as a temporary organic backbone in low-pressure injection moulding machines equipped with heated tanks and planetary mixers. The feedstock consists of ceramic powder, binder, and minor plasticiser; mixing is carried out at temperatures that keep the PVOH fluid without inducing thermal decomposition. The high viscosity of the grade produces green parts with sufficient handling strength for demoulding, while the low-ash profile reduces residue after solvent debinding and thermal burnout. Thermal debinding profiles are developed to avoid skin formation; hold steps are typically introduced below the decomposition onset of fully hydrolysed PVOH. Published data for this specific configuration is limited; processors should establish debinding profiles by thermogravimetric analysis rather than relying on generic supplier curves.
In textile warp sizing, the film-forming properties of fully hydrolysed PVOH can be exploited when water resistance is required in finishing steps. The 56-98 LA grade is generally too high in viscosity for high-speed single-end sizing unless diluted, but it can serve in formulations requiring high abrasion resistance. Size boxes must be maintained at controlled temperature and concentration; viscosity control by automatic refractometer or viscometer is common. The low-ash profile is beneficial in dyeing operations where sodium residues can shift dye uptake. Production-scale trials should include weaving efficiency and desizing residue checks.
If KURARAY POVAL 56-98 LA is applied at a size press or film press, the full molecular weight of the polymer raises surface strength and oil holdout but also limits the solids level that can be pumped and metered. Size-press trials with fully hydrolysed PVOH are typically run at solution temperatures between 50 °C and 70 °C to maintain sufficient flow without excessive drying load. The polymer forms a continuous film on the fibre surface and reduces porosity; when a crosslinker such as glyoxal is used, the wet strength of the dried coating increases but the open time of the size-press formulation decreases because of progressive crosslinking. Air-knife and roll misting may occur at high machine speeds if the solution viscosity is too high, so the grade is often diluted below the viscosity ceiling of the coater. Surface sizing response can be measured by the IGT pick strength test and TAPPI T 459 wax pick method, while grease resistance is commonly screened with TAPPI T 559 and oxygen transmission with ASTM D3985. In barrier papers, the dried PVOH layer contributes oxygen and grease resistance but remains sensitive to liquid-water penetration unless insolubilised. Published data for the exact speed limits of specific paper machines with this LA variant is not available; a pilot-scale trial is required before full-width commercial runs. The low-ash designation is less important in standard paper sizing than in ceramic or electronics applications, but it still reduces the ionic load introduced into the mill water circuit.
For indirect food-contact applications, polyvinyl alcohol may be used as a component of paper and paperboard under 21 CFR 176.170 and as an adhesive component under 21 CFR 175.105, provided the finished article meets the applicable extractives limitations and use restrictions in those sections. Compliance is not conferred by the polymer alone; it depends on coating weight, substrate, food type, and end-use temperature. Direct addition to food is outside the scope of this grade. In the European Union, the material is subject to REACH registration duties and should be checked against the supplier safety data sheet for the current registration status. The powder absorbs moisture from ambient air; storage areas must be kept below 35 °C and below 60% RH, with bags re-sealed immediately after use because caking can occur under humid conditions. Dust from the powder is combustible when suspended in air; housekeeping must prevent accumulation on hot surfaces and electrical equipment. The LA low-ash specification does not remove all inorganic matter from the polymer, but it lowers the sodium residue available for migration into process water or sintered ceramic bodies. For applications requiring a specific ash limit, the certificate of analysis must be verified against the internal specification before the lot is released to production.
