| HS Code | 912480 |
| Product Name | KURARAY POVAL 4-98 LA |
| Chemical Name | Polyvinyl alcohol |
| Cas Number | 9002-89-5 |
| Appearance | White granular powder |
| Degree Of Hydrolysis | 98.0 - 99.0 mol% |
| Viscosity 4 Percent Aqueous Solution At 20c | 4.0 ± 0.5 mPa·s |
| Ph 4 Percent Aqueous Solution | 5.0 - 7.0 |
| Ash Content | ≤ 0.3 wt% |
| Volatile Content | ≤ 5.0 wt% |
| Density | 1.27 g/cm³ |
| Bulk Density | 0.4 - 0.6 g/cm³ |
| Solubility | Soluble in hot water; insoluble in organic solvents |
As an accredited KURARAY POVAL 4-98 LA factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Kuraray POVAL 4-98 LA is a fine white powder supplied in 25 kg multi-ply paper bags for safe handling. |
| Container Loading (20′ FCL) | 20′ FCL of KURARAY POVAL 4-98 LA, packed in sealed bags on pallets, secured and ventilated for safe transport. |
| Shipping | KURARAY POVAL 4-98 LA is a water-soluble polyvinyl alcohol resin supplied as free-flowing powder. Ship in sealed multiwall bags on pallets, protected from moisture, humidity, and direct sunlight. Not classified as dangerous goods for transport; handle with clean, dry equipment and store below 30°C. |
| Storage | Store KURARAY POVAL 4-98 LA in a cool, dry, well-ventilated area away from direct sunlight, moisture, and heat sources. Keep the container tightly sealed when not in use to prevent humidity absorption. Avoid dust accumulation and keep away from open flames and strong oxidizers. Use suitable protective equipment when handling. |
| Shelf Life | KURARAY POVAL 4-98 LA has a shelf life of at least two years when stored unopened in a cool, dry place. |
At a film press or metering size press running 800–1,500 m/min on woodfree fine paper, a 3–7 wt% aqueous solution of KURARAY POVAL 4-98 LA is blended with oxidised tapioca or corn starch that has been jet-cooked at 130–135°C and cooled to 60–70°C. The PVOH is prepared as a separate 10 wt% solution in a stainless steel atmospheric dissolver at 90–95°C for 30 min and filtered through 150 µm mesh before injection into the starch circulation loop. When PVOH replaces 10–30 wt% of the starch solids, size press pick-up of 0.4–1.2 g/m² per side produces a continuous surface film that reduces Cobb60 water absorption to 18–28 g/m² on 80 g/m² base paper according to ISO 535. Film split performance at the metering rod is maintained within 20–60 mPa·s Brookfield RVT spindle 3 at 100 rpm and 60°C; below this range, misting and skip coating occur, and above it, rod streaks and fibre picking increase. The dry film contributes surface strength measured by IGT pick resistance of ≥2.0 m/s under ISO 3783. For food-contact grades, formulations comply with FDA 21 CFR 176.170 and FDA 21 CFR 176.180, and the final article is assessed under EU Regulation 1935/2004. Terminal product types include offset printing papers, inkjet base papers, folding boxboard, and release liner base papers where the PVOH film controls fibre lint and improves toner adhesion without increasing surface porosity.
In suspension polymerisation of vinyl chloride in a 20–60 m³ stirred, baffled reactor, KURARAY POVAL 4-98 LA functions as a secondary suspending agent when dosed as a 4–6 wt% aqueous solution at 20–25°C through a mass flow meter into the pre-homogenised monomer–water dispersion. The total PVOH charge is 0.05–0.15 wt% of the vinyl chloride monomer mass, typically split 60/40 between a primary suspending agent and this higher-hydrolysis secondary grade. Agitation at 7–10 m/s tip speed during the first 30 min establishes a target droplet distribution with a Sauter mean diameter of 120–180 µm; the 98.0–99.0 mol% hydrolysis and 4.0–5.0 mPa·s 4% solution viscosity of the secondary PVOH preserve droplet identity at 53–70°C and 0.7–1.3 MPa autogenous pressure. Over-concentration above 0.15 wt% raises continuous-phase viscosity and causes wall fouling on baffle shear zones, while under-concentration below 0.05 wt% produces coarse agglomerates and poor plasticizer absorption after drying. At 80–90% conversion the slurry is stripped and dried; residual vinyl chloride monomer is controlled under 1 ppm per REACH Annex XVII Entry 2, and the suspension PVC resin is classified by ISO 1628-2 K value and ASTM D1755 sieve retention. Terminal products include rigid pipe, profile, and injection-moulded fittings where resin particle porosity, bulk density, and dry-blend flow are governed by the suspending-agent package.
Aqueous tape-casting slips for alumina substrates are compounded with KURARAY POVAL 4-98 LA at 0.5–3.0 wt% of the dry ceramic powder, added from a 10–15 wt% stock solution containing the PVOH. The slip is milled in a high-alumina jar mill for 24 h at 60–70 rpm, then de-aired under 0.1–0.2 bar vacuum for 15–30 min before doctor-blade deposition. Tape gap settings of 150–400 µm yield dried green tapes with thickness 60–180 µm at a drying temperature of 50–80°C. The addition ratio is set by green density and lamination pressure: below 0.5 wt% the dried tape lacks the tensile strength to survive punch handling; above 3.0 wt% the organic content creates bubble entrapment at lamination pressures of 10–40 MPa and 70–85°C. Thermal debinding in a five-zone air furnace ramps from 200°C to 500°C at 0.5–2.0°C/min, with a dwell of 60–120 min at the exothermic oxidation peak of the PVOH; published data for this specific configuration is limited, so DTA/TGA screening of the green sheet is required before full production. The low-ash attribute, with residue on ignition as Na₂O tested by JIS K6726 controlled under 0.5%, is relevant where alkali contamination creates dielectric reliability defects. Sintered substrates are evaluated by ASTM C373-18 for water absorption and ISO 4287 for surface roughness Ra ≤0.8 µm. Terminal products include thick-film alumina substrates, multilayer ceramic capacitor cofired tapes, and ferrite filter elements.
Remoistenable paper adhesives are prepared in a jacketed planetary or anchor-agitated mixer by dispersing KURARAY POVAL 4-98 LA into cold water at 20–30°C, then heating to 85–95°C under 20–40 rpm agitation for 30 min until a clear solution forms. The final adhesive contains 4–8 wt% PVOH, 10–20 wt% kaolin or calcium carbonate, 2–5 wt% glycerin or sorbitol as humectant, and 0.1–0.3 wt% silicone-free defoamer. This formulation is applied by roller or slot die at 40–60°C onto gummed paper and dried in a tunnel dryer at 70–90°C to a dry coating weight of 6–12 g/m². The dry film is non-blocking below 65% RH, while remoistening at 20–25°C with 5–10 µL of water per 25 mm bond line re-activates fibre-tear adhesion on kraft and clay-coated stocks. Borate or titanium crosslinkers are incompatible because they produce viscosity instability and gel lumps in the holding tank. Formulations intended for indirect food-contact service comply with FDA 21 CFR 175.105. Terminal products include envelope flaps, paper tube and core winding, strip-gummed packaging tapes, and label laminating operations where intermittent water application and short open time are production constraints.
At the slasher/cooker interface, high-count cotton and cotton–elastane warps require a size film that withstands abrasion from drop wires and reed dent arrays during weaving at 400–700 picks/min. KURARAY POVAL 4-98 LA is cooked as a 12–15 wt% stock solution at 95–98°C for 30–45 min and then metered into a starch size bath to yield 6–12 wt% total solids, with PVOH representing 20–40 wt% of dry size solids. The size bath is maintained at 75–85°C; below 70°C, the fully hydrolysed PVOH begins to gel on the slasher roll surface and causes lint accumulation. A high-pressure squeeze mangle operating at 2.0–4.0 bar controls size pick-up at 8–14% on warp yarn, measured gravimetrically. Wax at 0.5–1.5 wt% and urea at 0.5–2.0 wt% are added as lubricant and viscosity modifier, respectively. Sized yarn tensile strength after drying at 110–130°C over 4–6 cylinders is tested by ASTM D2256; desized woven fabric tensile properties are evaluated according to ISO 13934-1. Desizing of the woven fabric uses hot water at 80–95°C, and residual PVOH must be removed before bleaching because recrystallised film interferes with peroxide penetration. Compliance for textile chemical inputs is documented under OEKO-TEX ECO PASSPORT and permitted discharge limits under ZDHC MRSL. Terminal products include shirting fabrics, denim, and home-textile woven goods.
Roll-to-roll barrier coating of corona-treated PET with an 8–12 wt% PVOH solution in demineralised water is performed at 85–95°C using reverse gravure or forward roll coating. The PET film is corona-treated to 42–50 dyn/cm surface energy immediately before coating. The wet coat weight is 1.5–4.0 g/m², yielding a dry KURARAY POVAL 4-98 LA layer of 0.12–0.35 g/m² after drying at 80–110°C in a flotation dryer with 10–20 s residence time. Oxygen transmission rate is measured according to ASTM D3985-17 at 23°C and 50% RH; PVOH provides a sharp reduction in OTR compared with uncoated PET, but the barrier effect is conditional because above 65% RH water plasticization of the fully hydrolysed PVOH increases free volume and OTR by one to two orders of magnitude. The coated film is therefore positioned for dry product packaging or used in lamination as an internal barrier layer between moisture-resistant outer layers. Coating formulations for food packaging must comply with FDA 21 CFR 175.300 and EU Regulation 10/2011, including overall migration limits of 10 mg/dm². Terminal products include snack bar wrappers, dry cereal liners, and lamination webs for oxygen-sensitive dry foods where the PVOH layer permits downgauging of sealant films without sacrificing oxygen barrier.
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KURARAY POVAL 4-98 LA is a fully hydrolysed polyvinyl alcohol resin produced by controlled alcoholysis of polyvinyl acetate. The grade code separates three independent ordering parameters: the numeric prefix 4 identifies the nominal viscosity band in a 4% aqueous solution at 20 °C; the suffix 98 corresponds to a nominal saponification degree of 98.0–99.0 mol%; and the LA designation identifies the low-ash variant, subject to tightened alkali residue control relative to standard 4-98. The product is normally supplied as white to off-white granules or powder. It carries CAS 9002-89-5 and is manufactured under ISO 9001:2015 quality systems. The dry polymer exhibits a glass transition temperature in the region of 75–85 °C and a crystalline melting range of approximately 180–230 °C, although formulated plasticizers and residual moisture shift both values downward.
The polymer backbone is linear with a low residual acetyl content below 2 mol%. The resulting strong intermolecular hydrogen bonding limits cold-water solubility but improves film tensile strength, oil resistance, and humidity resistance relative to partially hydrolysed grades. The 4.0–5.0 mPa·s viscosity band places the product at the low end of the fully hydrolysed POVAL portfolio, which is advantageous when high solids, low wet viscosity, and rapid penetration are required in aqueous coating or adhesive formulations.
The analytical profile is normally reported against JIS K6726. Equivalent determinations may be cross-referenced to ISO 15023-2 where national standards are not invoked. Viscosity is measured on a dry-weight basis in a 4% aqueous solution at 20 °C; hydrolysis degree is determined by saponification or instrumental methods. The table below summarises the typical control profile. Lot-specific values should always be obtained from the supplier certificate of analysis because normal process variation can shift hydrolysis degree and ash content within the declared grade band.
| Property | Test reference | Range or limit | Unit |
|---|---|---|---|
| Degree of hydrolysis | JIS K6726 | 98.0–99.0 | mol% |
| Viscosity, 4% aqueous at 20 °C | JIS K6726 | 4.0–5.0 | mPa·s |
| pH, 4% aqueous solution | JIS K6726 | 5.0–7.0 | — |
| Volatile matter | JIS K6726 | ≤ 5.0 | wt% |
| Ash content as Na₂O | JIS K6726 | Standard grade ≤ 0.5; LA lot limit lower | wt% |
The low ash ceiling for the LA designation is typically controlled below the general-purpose ash limit, but the exact numerical lot limit should be confirmed with the supplier because regional grade nomenclatures and production campaigns differ. The viscosity value is not a direct molecular weight specification; it is a solution parameter influenced by residual moisture, degree of hydrolysis, and molecular weight distribution.
Unlike partially hydrolysed polyvinyl alcohol, a fully hydrolysed 98.0–99.0 mol% grade requires thermal energy to disrupt crystallites before complete solubilisation. The standard make-up procedure begins with powder dispersion in water at ambient temperature under high-shear mixing. A Cowles blade or rotor-stator device is used to create a vortex and separate individual particles before hydration. The dispersion is then heated to 90–95 °C and held for 30–60 min. Direct steam injection is used on large process vessels, but the sparge must remain below the liquid surface and the tank agitator must be sized for the viscosity peak; otherwise localized overcook can form insoluble gel particles.
After the hold period, the solution is cooled to below 40 °C before storage. Fully hydrolysed PVOH solutions are metastable at intermediate temperatures. Gelation can occur in static tanks held at 40–60 °C, especially at concentrations above 10 wt%. A 10% solution of 4-98 LA normally remains flowable at room temperature but may form a surface skin or soft gel after quiescent storage for more than 24–48 h. Slow agitation and a sealed or vented tank are recommended. Solutions intended for storage beyond 48 h generally require an approved preservative because PVOH is susceptible to microbial degradation.
Boric acid, borax, and certain transition-metal salts produce reversible didiol crosslinking with fully hydrolysed PVOH. This interaction is deliberately used in some adhesive and paper-sizing formulations to build tack or wet adhesion, but it narrows the processing window. Borax addition above approximately 0.5 wt% of solution weight can cause rapid viscosity rise or gelation, particularly in fully hydrolysed grades. Metering must therefore be constant-rate and the injection point should feed into a high-shear zone or static mixer to avoid localized gel masses that clog filters and coating heads.
In surface sizing of fine paper and paperboard, KURARAY POVAL 4-98 LA is supplied as the primary film-forming component or in combination with oxidised or cationic starch. The fully hydrolysed backbone reduces water sensitivity compared with starch alone and increases surface strength as measured by IGT pick velocity under ISO 3783 and Scott bond under TAPPI T 569. The low viscosity of the 4 band permits a higher polymer fraction at fixed size-press solids without exceeding the rheological limits of rod metering or film-transfer equipment. Typical addition ratios on dry fibre range from 0.3 to 2.0 wt%; above this range, drying demand and film brittleness become process constraints. The LA low-ash attribute is relevant in fine paper converting because residual sodium salts can interact with optical brightening agents and shift shade stability after ultraviolet exposure.
Film tensile properties for formulated PVOH films are evaluated according to ASTM D882 or ISO 527-3. Unplasticized film data are suitable only for raw polymer screening because production films normally contain glycerol, sorbitol, or polymeric plasticizers that lower tensile strength and increase elongation. The grade’s molecular weight range gives adequate film integrity for paper sizing and temporary binders, but it should not be substituted into high-strength structural film applications without reformulation and tensile verification.
When ash-derived sodium oxide is held below the general-purpose ceiling, downstream ionic contamination is reduced in applications where the PVOH functions only as a temporary binder and is later removed or decomposed. In ceramic green-sheet processing, the polymer is compounded with alumina or barium titanate powders at binder loads of 3–6 wt% based on solids. The 4.0–5.0 mPa·s viscosity allows tape-casting slurries to be formulated with lower solvent demand than high-viscosity PVOH, while the fully hydrolysed character provides sufficient green strength for handling and punching.
In vinyl acetate and vinyl acetate–ethylene emulsion polymerisation, PVOH serves as protective colloid. Fully hydrolysed 4-98 LA produces coarser latex particles and higher final latex viscosity than partially hydrolysed grades at the same polymerisation temperature because of greater grafting tendency and lower surface activity. Reactors using this grade are typically operated at 60–85 °C with initiator feed adjusted to maintain particle size distribution. The PVOH is charged as a pre-dissolved 3–6% aqueous solution relative to total monomer. Low ash is also beneficial in emulsion binders for nonwoven wipes and glass fibre sizes where extractable ionic content affects wetting and electrolyte stability. Published data for this specific LA configuration in every emulsion system is limited; preliminary plant trials are required to confirm the ash contribution relative to other raw materials.
Operational boundaries include powder moisture sensitivity. At relative humidity above 60%, granules absorb atmospheric water and should be dried before weighing when formulation tolerance is less than 1 wt%. Dry blending with strong acids, aldehydes, or free-radical generators should be avoided because acetalisation or oxidative gel formation can occur in storage or heated lines. The organic powder is combustible as a dust; grounding, inerting, and dust collection are governed by local dust hazard analysis and ATEX or NFPA requirements.
Grade selection between 4-98 LA, 4-88, and 20-98 is typically governed by water sensitivity, film toughness, and solution viscosity envelope. 4-88 has a hydrolysis degree of 86.5–89.0 mol%. It dissolves in cold water and remains solution-stable at higher solids, but its film exhibits higher moisture uptake and lower resistance to humidity ageing. 20-98 shares the same hydrolysis chemistry as 4-98 LA but its viscosity band of 20.0–24.0 mPa·s at 4% produces more chain entanglement, higher film tensile strength, and slower penetration into porous substrates.
| Parameter | 4-98 LA | 4-88 | 20-98 |
|---|---|---|---|
| Hydrolysis degree | 98.0–99.0 mol% | 86.5–89.0 mol% | 98.0–99.0 mol% |
| Viscosity, 4% solution at 20 °C | 4.0–5.0 mPa·s | 4.0–5.0 mPa·s | 20.0–24.0 mPa·s |
| Cold-water solubility | Limited; hot-water make-up | Readily soluble | Limited; hot-water make-up |
| Film moisture sensitivity | Low | High | Low |
| Ash control | Low-ash variant available | Standard | Standard |
| Typical use emphasis | Paper sizing, adhesives, ceramic binder | Cold-water packaging films, release coatings | High-strength textile sizing, structural adhesive films |
The fully hydrolysed grades 4-98 LA and 20-98 develop water-resistant films after drying and generally do not require additional crosslinking in many barrier-sizing applications. Partially hydrolysed 4-88 is preferable when cold-water removability or rapid cold dispersion is the primary requirement. In emulsion polymerisation, 4-98 LA tends to generate larger latex particles and higher final latex viscosity than 4-88 at the same colloid loading. Because 20-98 contributes higher solution viscosity, formulation solids must be reduced or dilution water added to remain within metering pump and coating die pressure limits.
Compliance status for food-contact or pharmaceutical use must be confirmed with the supplier statement for the specific grade and production campaign. Polyvinyl alcohol of this type is listed in 21 CFR 175.105 for adhesives and in 21 CFR 176.170 and 21 CFR 176.180 for paper and paperboard components under specified extraction limits. The listing does not automatically extend to the LA variant because ash control and residual monomer levels may differ by campaign. Under REACH, polyvinyl alcohol is registered and subject to standard industrial hygiene controls. Atmospheric dust exposure should be maintained below the applicable occupational exposure limit; local guidance rather than grade-level statements should determine control measures.
