| HS Code | 671631 |
| Product Name | KURARAY POVAL 8-88 LA |
| Chemical Type | Partially saponified polyvinyl alcohol |
| Appearance | White granular powder |
| Degree Of Hydrolysis | 88 mol% |
| Viscosity 4 Aqueous Solution 20 C | 8.0 mPa·s |
| Ph 4 Aqueous Solution | 5.0 - 7.0 |
| Ash Content | ≤0.1% |
| Volatile Content | ≤5.0% |
| Average Degree Of Polymerization | 300 |
| Bulk Density | 0.50 g/cm³ |
| Solubility | Soluble in hot water; practically insoluble in organic solvents |
| Specific Gravity | 1.27 - 1.31 |
As an accredited KURARAY POVAL 8-88 LA factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Kuraray POVAL 8-88 LA is supplied in 20 kg multi-ply paper bags with polyethylene liner, ensuring safe handling and storage. |
| Container Loading (20′ FCL) | 20′ FCL: KURARAY POVAL 8-88 LA loaded on pallets, secured and containerized for safe, efficient transport. |
| Shipping | KURARAY POVAL 8-88 LA is a water-soluble polyvinyl alcohol powder. Ship as non-hazardous material in sealed, moisture-proof packaging. Protect from humidity, direct sunlight, and extreme temperatures. Store in dry, ventilated area. No special transport classification required, but avoid contact with water during transit. |
| Storage | Store KURARAY POVAL 8-88 LA in its original, tightly sealed container in a cool, dry, well-ventilated area. Protect from moisture, excessive heat, and direct sunlight. Keep away from open flames and oxidizing agents. Avoid dust formation; after each use, reseal immediately. Under proper conditions, shelf life is typically two years. |
| Shelf Life | Shelf life is typically 2 years from manufacture date when stored in original, tightly sealed containers under dry, cool conditions. |
In a 10 m³ jacketed stainless-steel polymerisation reactor producing vinyl acetate–ethylene copolymer dispersions, KURARAY POVAL 8-88 LA is pre-dissolved in demineralised water at 8.0–10.0 wt% and metered into the pre-emulsion feed as the primary protective colloid. The grade is controlled to 87.0–89.0 mol% hydrolysis and 7.0–9.0 mPa·s viscosity measured on a 4 wt% aqueous solution at 20°C according to JIS K6726:1994; the low-ash specification reduces electrolyte carryover that otherwise shifts particle nucleation rates and increases coagulum accumulation on the reactor wall during extended campaigns. For vinyl acetate-rich VAE systems, the addition ratio is commonly 2.0–5.0 wt% based on total monomer mass. At 2.0 wt% the dispersion remains shear-stable but may settle during prolonged storage; at 5.0 wt%, Brookfield viscosity at 20 rpm typically approaches 8,000–12,000 mPa·s, which exceeds the transfer capacity of diaphragm pumps on some single-coat adhesive lines. Production campaigns therefore hold the protective colloid charge within ±0.2 wt% to avoid batch-to-batch variation in wet tack and open time. Dissolution is conducted at 85–90°C for 120 min under low-shear anchor agitation at 30–60 rpm; the solution is then cooled to 35–45°C and filtered through a 100 µm bag filter before injection into the reactor. During polymerisation at 2.0–4.5 MPa ethylene pressure and 65–85°C, the partially hydrolysed polyvinyl alcohol undergoes grafting and phase separation at the particle surface, producing a steric layer that controls low-shear viscosity and freeze-thaw stability. Qualification against ISO 3251:2019 for non-volatile matter, ISO 2555:2018 for Brookfield viscosity, ISO 976:2013 for pH, and ISO 22412:2017 for particle-size distribution is performed before the dispersion is transferred to downstream compounding. For woodworking adhesives, EN 204:2016 and EN 205:2016 shear-strength classifications apply; for food-contact packaging adhesives, FDA 21 CFR 175.105 and EU Regulation 10/2011 overall migration limits are referenced. Terminal finished products include D3 and D4 woodworking adhesives, carpet-backing compounds, nonwoven binders, paper-to-paper laminating adhesives, and redispersible polymer powders for cementitious dry-mix products. Published data for this exact grade in reactor campaigns below 60°C is limited; validation batches are therefore run before reducing polymerisation temperature, because the partially hydrolysed stabiliser shell changes its phase behaviour at lower temperature and can alter coagulum formation in ways not captured by standard formulation models.
| Standard or regulation | Scope | Application point in downstream control |
|---|---|---|
| ISO 3251:2019 | Determination of non-volatile matter in polymer dispersions | Reactor discharge and final blend solids |
| ISO 2555:2018 | Brookfield apparent viscosity of liquid dispersions | Base dispersion viscosity before adhesive compounding |
| ISO 976:2013 | pH of polymer dispersions and latices | Neutralisation and storage stability check |
| ISO 22412:2017 | Particle size analysis by dynamic light scattering | Nucleation control and shelf-sedimentation assessment |
| EN 204:2016 | Classification of thermoplastic wood adhesives for non-structural applications | D3 wet-use adhesive qualification |
| EN 205:2016 | Determination of tensile shear strength of wood adhesives | D4 load-bearing adhesive qualification |
| FDA 21 CFR 175.105 | Adhesives for food-contact packaging | Indirect food-contact adhesive formulation |
| EU Regulation 10/2011 | Plastic materials and articles intended for food contact | Overall migration and specific migration limits |
Vinyl acrylic semi-gloss architectural coatings that employ 1.0–3.0 wt% KURARAY POVAL 8-88 LA on total monomer during polymerisation exhibit shear-thinning behaviour that reduces roller spatter and improves film build at 25°C. The limiting technical constraint is post-polymerisation viscosity drift when residual persulphate initiator remains above 0.05 wt%; the residual oxidant oxidises the secondary hydroxyl groups on the polyvinyl alcohol backbone, increasing apparent molecular weight and causing high-shear viscosity to rise after ageing. On a 500 L pilot line equipped with a double-motion agitator and a Cowles disperser operating at 18–20 m/s tip speed, pigment is dispersed in the absence of PVA to prevent competition with dispersing agents on titanium dioxide. The PVA is then added as a 4.0 wt% aqueous solution during letdown at 0.2–0.8 wt% based on total wet paint mass; addition prior to pigment wetting raises high-shear pigment dispersion viscosity and can reduce tint strength by 1.0–2.0% due to incomplete deagglomeration. The finished coating is qualified to ISO 11998:2006 for wet-scrub resistance, ISO 6504-3:2019 for hiding power, ASTM D562-10(2023) for Krebs viscosity, and Directive 2004/42/EC for volatile organic compound limits. For toy coatings, EN 71-3:2019+A1:2021 migration limits apply. The operational boundary is a pH below 4.0 in anionically stabilised emulsions, because coacervation between partially hydrolysed PVA and protonated dispersant can produce gel specks in tint bases. Terminal products are interior low-VOC wall and ceiling paints, tint bases, and primer systems.
Because size press formulations based solely on oxidised starch often show insufficient surface strength on high-filler woodfree paper at machine speeds above 900 m/min, a partial replacement with KURARAY POVAL 8-88 LA is used at 0.5–2.0 wt% solution concentration in the size press bath. The amount corresponds to 0.3–1.0 dry wt% polyvinyl alcohol on dry paper and is balanced against starch solids to maintain a total bath solids of 6.0–10.0 wt%. In this formulation, the 8-88 LA grade increases film modulus and dry pick resistance without the full water-insolubility penalty of fully hydrolysed grades. The starch is jet-cooked at 95–100°C, blended with a separately prepared 10 wt% PVA solution at 60–65°C, and applied by film press or pond size press. Size uptake is maintained at 1.5–2.5 g/m² per side; above 2.5 g/m² the film may interfere with sheet breathing during drying and increase curl on lightweight grades. Evaluation uses ISO 3783:2006 for IGT pick resistance, ISO 8791-4:2007 for Parker PrintSurf roughness, ISO 536:2019 for grammage, and TAPPI T 558 for surface wettability; food-contact paper is assessed under FDA 21 CFR 176.170 and EU Regulation 1935/2004. Published data for size press speeds above 1,200 m/min with this exact grade is limited; mill trials are required to confirm rod clamping and misting behaviour. Terminal finished types include uncoated woodfree printing paper, envelope stock, inkjet paper, and recycled board liner.
The pre-coating layer on recycled board stock presents a high-shear blade-coating environment in which co-binder migration controls immobilisation time and coatweight uniformity. KURARAY POVAL 8-88 LA is incorporated at 1.0–3.0 wt% based on dry pigment, or 0.5–1.5 parts per 100 parts of coating pigment, in combination with a carboxylated styrene-butadiene latex and a rheology modifier such as bentonite or carboxymethyl cellulose. The addition ratio is set by high-shear viscosity at the blade metering zone; above 3.0 wt%, extensional viscosity can generate blade streaks and whiskering at coating speeds above 1,000 m/min. A high-shear jet cooker and a turbine disperser are used for pigment slurry preparation; PVA solution is added after latex to prevent competitive adsorption on calcium carbonate. Coating is applied by a stiff-blade coater with blade load controlled to 5–15 kN/m to maintain coatweight at 8–12 g/m² with ±0.5 g/m² cross-direction variation. Compliance with ISO 534:2011 for thickness, ISO 5626:1993 for folding endurance, and ISO 8791-4:2007 for smoothness is applied; for food-contact board, FDA 21 CFR 176.170 and EU Regulation 1935/2004 are used, and heavy metal release is checked under EN 71-3:2019+A1:2021 where the board is used for toys. Avoid combination with zirconium ammonium carbonate insolubilisers at pH above 8.0, because insoluble polyvinyl alcohol complexes increase viscosity and can gel the coating in the recirculation line. Finished types include folding carton board, cupstock, linerboard, and barrier base paper.
When high-density polyester/cotton warp yarns are slashed at 350–500 m/min in a multi-cylinder sizing machine, the size formulation containing 8.0–14.0 wt% KURARAY POVAL 8-88 LA on warp yarn mass produces a film with sufficient elongation to withstand shedding and beat-up without excessive size break-out. The partially hydrolysed grade is selected over fully hydrolysed PVA when warp yarns contain 50–80% polyester, because the residual acetyl groups reduce intra-film crystalline domains and lower the glass transition of the dried size film, reducing shedding on high-speed air-jet looms. Formulation composition is typically 20–40 wt% PVA, 50–65 wt% starch, 0.5–2.0 wt% wax, and 2.0–5.0 wt% acrylic binder on dry solids; dissolved solids in the size box are kept at 8.0–12.0 wt% and temperature at 75–85°C. Squeeze pressure is adjusted to 2.0–4.0 kN/m to control wet pick-up around 70–90% before drying. Warp strength is tested according to ISO 13934-1:2013 and ASTM D2256/D2256M-21; size film tensile properties are measured according to ISO 527-3:2018, and desizing effluent chemical oxygen demand is monitored under the facility discharge permit. For textiles sold into children’s apparel, EN 71-3:2019+A1:2021 heavy metal migration and REACH Annex XVII restrictions apply. Full desizing requires oxidative or amylase treatment; residual PVA not removed before dyeing can cause uneven dye uptake and harsh fabric handle. Published data for this exact grade in polyester/cotton slashing is limited; the operating window above is derived from production reports rather than formal interlaboratory studies. Finished woven articles include workwear, trousers, military uniforms, and technical woven interiors.
Modifying a cementitious dry-mix formulation with 0.5–1.2 wt% KURARAY POVAL 8-88 LA by total dry mass alters both rheology and sag resistance before final set, while contributing polymer film bridges that improve adhesion after 28-day water immersion. The grade is dry-blended into a twin-ribbon mixer at 60–80 rpm for 15–20 min before addition of cellulose ether and calcium formate accelerators, because PVA particles smaller than 100 µm can segregate during long silo residence times. In low-shear planetary mixing at 140 rpm for 60 s, the polyvinyl alcohol dissolves sufficiently to delay surface skin formation and extend open time by 10–20 min at 23°C depending on base mix. Qualification is performed under EN 12004:2017 for cementitious tile adhesives, with EN 1348:2007 tensile adhesion strength, EN 1346:2007 open time, and EN 1308:2007 slip resistance; for gypsum-based skim coats, EN 13279-1:2008 applies. Indoor air emissions are controlled under ISO 16000-9:2006 chamber testing and GB 18582-2020 where specified. Terminal products include C1 and C2 cementitious tile adhesives, gypsum skim coats, EIFS base coats, and repair mortars. Do not exceed 1.5 wt% in calcium aluminate cement-based systems, because premature PVA film formation can reduce adhesion after 28-day water immersion.
| Standard or regulation | Scope | Application point in dry-mix qualification |
|---|---|---|
| EN 12004:2017 | Adhesives for ceramic tiles | Classification of C1 and C2 cementitious adhesives |
| EN 1348:2007 | Tensile adhesion strength of cementitious tile adhesives | Dry cure, water immersion, heat ageing, freeze-thaw cycles |
| EN 1346:2007 | Open time of cementitious tile adhesives | Extended workability verification |
| EN 1308:2007 | Slip resistance of tile adhesives | Heavy-tile vertical installation performance |
| EN 13279-1:2008 | Gypsum binders and gypsum plasters | Gypsum-based skim coat compliance |
| ISO 16000-9:2006 | Indoor air emission test chamber method | VOC emission control for interior products |
| GB 18582-2020 | Limit of harmful substances in interior wall coatings | Indoor decoration hazardous-substance compliance |
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KURARAY POVAL 8-88 LA is a partially hydrolyzed polyvinyl alcohol (PVOH) grade in which the commercial designation encodes a nominal solution viscosity of 8 mPa·s measured as a 4 mass% aqueous solution at 20°C and a nominal degree of hydrolysis of 88 mol%. The suffix LA identifies a low-ash variant; residual sodium acetate is reduced relative to standard 8-88. Specification testing follows JIS K6726 for viscosity, degree of hydrolysis, ash as Na2O, pH, and volatile matter. Commercial viscosity limits are generally 7.0–9.0 mPa·s, and hydrolysis limits are generally 86.0–89.0 mol%. Volatile matter is controlled at ≤5.0 mass%. The low-ash grade is controlled below the standard-grade ash ceiling; several industrial data sheets list ≤0.2 mass% as Na2O, but lot-specific certificates remain authoritative. Under ISO 15023-1, the material is designated by viscosity and hydrolysis data rather than by a single molecular-weight value. This is significant because PVOH commercial grades are specified by solution viscosity as a process-relevant proxy for molecular weight. In plant practice, batch-to-batch differences in viscosity and ash are monitored because both properties shift downstream performance in emulsion polymerization, adhesive compounding, ceramic binder burnout, and textile sizing. The powder is supplied as white to pale-yellow granules or powder and is hygroscopic; storage in sealed containers below 30°C and 60% relative humidity is required to prevent caking and microbial growth in warm, humid conditions.
| Property | Value or range | Method or condition |
|---|---|---|
| Viscosity | 7.0–9.0 mPa·s | JIS K6726, 4 mass% aqueous solution, 20°C |
| Degree of hydrolysis | 86.0–89.0 mol% | JIS K6726 |
| Volatile matter | ≤5.0 mass% | JIS K6726 |
| Ash as Na2O | ≤0.2 mass% typical low-ash ceiling; lot certificate authoritative | JIS K6726 |
| pH | 5.0–7.0 | JIS K6726, 4 mass% solution |
Dissolution of 8-88 LA in a 5,000 L jacketed vessel is controlled less by the thermodynamic solubility limit than by particle wetting, dispersion, and gel-layer formation. The 88 mol% hydrolysis level leaves residual acetate groups that disrupt PVOH crystallinity; cold-water swelling occurs below 30°C, but complete molecular dispersion normally requires heating to 85–95°C after the powder is wetted. In a vessel equipped with a bottom-entry rotor-stator disperser and a low-speed anchor stirrer, the powder is charged slowly into demineralized water at 20–25°C. Charging too fast creates agglomerates in which dry powder is encapsulated by a swollen gel layer; these fisheye defects persist for hours even at 90°C. A disperser tip speed of 15–20 m/s during powder addition is used on production lines to separate grains before dissolution. Once the batch reaches 90°C, the anchor stirrer at 30–60 rpm is maintained for 30–60 min. The final solution is cooled to 25–40°C before transfer to storage. Foam formation is a common processing bottleneck and is controlled by slow cooling and, where permitted, defoamer addition. Viscosity is checked before use with a Brookfield rotational viscometer according to JIS K6726; deviations above ±5% from the target typically require adjustment of solids or further dilution. Because the grade is partially hydrolyzed, dissolution is faster than for fully hydrolyzed grades of the same viscosity, but the resulting solutions show greater sensitivity to alkaline pH drift and borate crosslinking.
In vinyl acetate-ethylene (VAE) emulsion polymerization, 8-88 LA is dissolved to 4–8 mass% and used as the protective colloid in a 10 m³ stainless steel reactor, typically with a pitched-blade turbine running at 120–180 rpm. The low-ash variant reduces the concentration of sodium acetate entering the polymerization; this is significant when persulfate initiators are dosed at 0.2–0.5 wt% of total monomer because ionic residues alter initiator decomposition and latex viscosity. The residual acetate groups on the partially hydrolyzed polymer increase interfacial activity relative to fully hydrolyzed PVOH, giving finer monomer droplets and better stability during the high-exotherm stage. Coagulum filters on the reactor discharge line are monitored per batch; an increase in filter pressure beyond the established alarm threshold typically indicates coalescence or excessive grafting. PVOH-stabilized VAE latices produced with 88 mol% hydrolysis grades tend to show shear-thinning flow and larger mean particle size than surfactant-only formulations; typical mean particle sizes reported for PVOH-protected VAE dispersions fall between 0.5 µm and 3.0 µm, but published data for this specific configuration is limited. The choice of 8-88 LA rather than an 8-98 fully hydrolyzed grade shifts the balance toward cold-water removability of the dried film while retaining sufficient aqueous solubility for handling. Residual vinyl acetate monomer in the latex is measured by gas chromatography; plant-specific specifications commonly require residual monomer below 0.5 mass%, although the PVOH grade itself is not the direct control variable.
In cotton and cotton-blend warp sizing on a slasher line, 8-88 LA is typically cooked to 10–14 mass% solids and applied through a size box maintained at 60–80°C. The low-ash property reduces roller scale and deposit formation on dry cans. Because the hydrolysis level is 88 mol%, the size film is soluble enough for enzymatic or hot-water desizing, but the film strength is lower than fully hydrolyzed size grades. Slasher operators monitor size box viscosity with a Brookfield viscometer or flow cup; a drop below the mill-specific target at 70°C may indicate dilution or polymer degradation. Batch-to-batch viscosity variation in the supplied powder is controlled by JIS K6726, but plant cooks often compensate by adjusting solids rather than temperature. Published data for this specific configuration is limited, and mill trials determine the exact size pickup on the warp sheet.
Low ash content becomes a critical parameter in ceramic green tape casting and dry press binder systems. In alumina tape casting, 2–5 mass% PVOH based on dry ceramic powder is added as an aqueous solution to provide green strength before burnout. The sodium acetate present in standard PVA acts as an alkali-containing residue during burnout; even small residues can alter shrinkage and lower final fired density. The LA suffix is therefore selected where ash as Na2O must be minimized. Thermogravimetric analysis of PVOH binders shows the main polymer decomposition occurring between 250°C and 350°C under air, but the inorganic residue is determined after heating to 700°C according to JIS K6726. Binder removal in continuous kilns is limited by the heating ramp through 200–400°C; residual carbon and sodium are a known cause of tape warpage. In spray-dried ceramic granules, the 8 mPa·s solution viscosity at 4 mass% is low enough for atomization through a rotary atomizer but high enough to provide green compression strength after pressing. Process limitations include incomplete solubility when added to cold ceramic slurries below 20°C and pH shifts caused by alkaline ceramic powders that can accelerate gelation if borate ions are present. Published data for this specific configuration is limited, but the low-ash specification is routinely referenced in ceramic binder qualification documents.
In water-based paper and packaging adhesive compounding, 8-88 LA is dissolved at 10–25 mass% solids and combined with plasticizers such as glycerol or sorbitol at 5–20 phr of PVOH dry weight to lower film brittleness. The 88 mol% hydrolysis level provides a measurable advantage in cold-water re-wetting compared with fully hydrolyzed grades; remoistening adhesives based on 88 mol% PVOH soften more readily when wetted, but the resulting film has higher moisture sensitivity and lower wet strength than 98–99 mol% analogues. Borax or boric acid may be added at 0.5–2.0 wt% of PVOH solids to increase tack and viscosity through diol complexation; this reaction is pH-dependent and accelerates above pH 8.5. Because amine-based additives raise pH and can promote premature crosslinking or gelation, they are avoided in borate-containing formulations. Adhesive viscosity is measured by Brookfield viscometer at 20 rpm and 25°C; production batches are adjusted to a target of 2,000–5,000 mPa·s, though the exact range depends on application method. Failure modes observed on industrial laminating lines include viscosity drift after 48 h storage, skin formation on open tanks, and microbial growth if the adhesive is stored at ambient temperature without preservative. Therefore, storage below 30°C and use within 24–48 h after thickening adjustment are common operational boundaries; published data for this specific configuration is limited. The low-ash variant reduces salt-induced changes in tack and pH stability compared with standard 8-88.
Regulatory status depends on the finished article use. Polyvinyl alcohol is evaluated in some food-contact constructions by generic polymer identity; in the United States, compliance may be assessed under 21 CFR 177.1670 for polyvinyl alcohol film or 21 CFR 175.300 for resinous and polymeric coatings, depending on the final construction. The low-ash grade does not create a separate regulatory category but may support lower extractables in the finished article. Under REACH, the polymer is exempt from registration under Article 2(9), while the monomers and manufacturing impurities remain within the scope of the relevant registration obligations. RoHS applies to the finished electrical or electronic article, not to the raw polymer as supplied.
Grade identity is not based on a single molecular weight but on the combination of viscosity and hydrolysis. Compared with 8-98, 8-88 LA has higher residual acetate content, giving lower-temperature water solubility and lower film water resistance. Compared with 20-88, 8-88 LA has the same nominal hydrolysis but lower solution viscosity, allowing higher solids in coating or adhesive formulations at similar application viscosity. Compared with standard 8-88, the LA variant differs primarily in ash specification rather than in viscosity or hydrolysis. Table 2 summarizes the substitution-relevant differences.
| Grade | Nominal viscosity (mPa·s, 4%, 20°C) | Nominal hydrolysis (mol%) | Ash classification | Cold-water solubility | Film water resistance |
|---|---|---|---|---|---|
| 8-88 LA | 8 | 88 | Low ash | Partial at 20–30°C; complete at 85–95°C | Moderate |
| 8-88 | 8 | 88 | Standard | Similar | Similar |
| 8-98 | 8 | 98–99 | Standard | Requires heat | Higher |
| 20-88 | 20 | 88 | Standard | Partial | Moderate, higher viscosity |
Substitution of standard 8-88 with 8-88 LA in a continuous paper-laminating line requires verification of adhesive pH, Brookfield viscosity, and peel adhesion after 48 h storage because ash reduction changes buffering capacity. Films cast from 88 mol% hydrolysis grade exhibit greater water uptake than 98–99 mol% analogues when tested according to ASTM D570; this is the operational boundary that limits use in damp packaging environments. Published data for niche end-use configurations remains limited, and substitution trials under plant-specific mixing, drying, and sintering conditions remain necessary before grade transfer.
