| HS Code | 803254 |
| Product Name | KURARAY POVAL 26-88 LV |
| Manufacturer | Kuraray Co., Ltd. |
| Chemical Family | Polyvinyl Alcohol (PVOH) |
| Cas Number | 9002-89-5 |
| Physical Form | White to pale yellow granular powder |
| Degree Of Hydrolysis | Approximately 88 mol% (typical range 86.5-89.5 mol%) |
| Viscosity | 24.0-28.0 mPa·s (4% aqueous solution at 20°C, nominal 26 mPa·s) |
| Ph | 5.0-7.0 (4% aqueous solution) |
| Ash Content | ≤ 0.5 wt% |
| Volatile Content | ≤ 5.0 wt% |
| Bulk Density | 0.4-0.6 g/cm³ |
| Solubility | Soluble in hot water; slightly soluble in cold water; insoluble in organic solvents |
| Melting Point | Approximately 180-190°C |
As an accredited KURARAY POVAL 26-88 LV factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Kuraray Poval 26-88 LV is supplied as free-flowing powder in 25 kg multilayer paper bags for safe handling and storage. |
| Container Loading (20′ FCL) | 20′ FCL: Palletized bags of KURARAY POVAL 26-88 LV, securely stowed and braced for safe transit. |
| Shipping | KURARAY POVAL 26-88 LV is a polyvinyl alcohol resin shipped as a dry, free-flowing powder. It is non-hazardous for transport, but keep bags sealed to avoid moisture absorption and dust generation. Store in a cool, dry area away from ignition sources; no special transport classification required. |
| Storage | Store KURARAY POVAL 26-88 LV in a cool, dry, well-ventilated area, away from heat, open flames, and direct sunlight. Keep the original container tightly sealed when not in use to prevent moisture absorption and contamination. Avoid creating dust; use appropriate ventilation. Follow manufacturer’s recommendations for shelf life and handling. |
| Shelf Life | Store in a cool, dry place away from moisture. Shelf life is typically 2 years from production date when unopened. |
KURARAY POVAL 26-88 LV is a partially hydrolysed polyvinyl alcohol with a nominal degree of hydrolysis of 86.5–89.0 mol% and a 4% aqueous solution viscosity of 25.0–31.0 mPa·s at 20°C measured by JIS K6726 and DIN 53015 methods. The ash content is controlled to not more than 0.5 wt% as Na₂O. This low-viscosity designation allows solution make-down at 10–25 wt% solids in standard dissolving vessels without exceeding low-shear mixing torque limits, provided the powder is sifted into water at 25–30°C and heated to 90–95°C for 60–90 min. The residual acetate content of 11–13 mol% gives cold-water solubility while retaining surface activity at vinyl acetate and air-water interfaces. The product is not soluble in toluene, methyl ethyl ketone, or butyl acetate, and this solvent boundary must be respected during cleaning and changeover.
| Application | Standard or method | Parameter | Target range |
|---|---|---|---|
| PVOH solution viscosity | JIS K6726 | 4% aqueous viscosity at 20°C | 25.0–31.0 mPa·s |
| Vinyl acetate wood adhesive | EN 204:2016 D2/D3 | Durability class after conditioning | Pass |
| Paper surface strength | ISO 3783:2006 | IGT pick speed | 2.0–2.5 m/s |
| Water-soluble film tensile | ISO 527-3:2018 | Elongation at break | >200% |
| Remoistenable adhesive food contact | FDA 21 CFR 175.105 | Indirect food additive status | Compliant |
| Technical ceramic green body | ISO 14704:2016 | Three-point flexural strength after 40–60°C drying | >5 MPa |
In a 10,000 L jacketed reactor with a pitched-blade turbine at 120 rpm, KURARAY POVAL 26-88 LV is pre-dissolved at 15 wt% in deionised water at 90–95°C, cooled to 25°C, and charged before monomer addition. The dry-basis protective colloid dosage is 3.0–5.0 wt% on vinyl acetate monomer; this range is lower than the 5.0–7.0 wt% often required for fully hydrolysed grades because partial hydrolysis produces more frequent graft sites for polyvinyl acetate radicals. Potassium persulfate initiation is set at 0.25 wt% on monomer and fed over 4 h while the batch temperature is held at 72–78°C. The reaction window is critical: the 30–60% conversion interval requires ±3°C control around 75°C, as excursions above 80°C raise graft frequency to the PVOH backbone and increase latex viscosity by 25–40% before the stabiliser is fully consumed. Final solids are controlled at 48–55 wt%, and Brookfield viscosity is measured by ISO 2555:2018 using spindle 4 at 20 rpm and 25°C; the allowable upper limit is 3,000 mPa·s for subsequent pumping and filtration through 100 µm bag filters. The coalesced film from the latex exhibits D2 and D3 durability under EN 204:2016 after addition of 5–10 wt% dibutyl phthalate or benzoate plasticiser. The terminal products are D2/D3 wood adhesives and laminated paperboard packaging adhesives qualified under FDA 21 CFR 175.105. Pilot-scale data in 60 L reactors with axial turbine at 180 rpm show coagulation below 0.1 wt% on total monomer when the PVOH solution is pre-charged and initiator is delayed; full-scale validation at the target solids is required because particle size data for this exact colloid grade at production scale is limited.
Oxidised corn starch at 8–12 wt% solids is jet-cooked at 130–140°C and held at 65–70°C before the PVOH stream is blended into the size press feed. KURARAY POVAL 26-88 LV is prepared as a separate 10–15 wt% solution and dosed at 0.5–2.0 dry parts per 100 dry parts starch; the low-viscosity grade limits the blend viscosity to 200–250 mPa·s at 60°C, which is low enough for rod-metering or film-transfer size presses without exceeding pump shear limits. The size press film temperature is held at 50–60°C, and dry pick-up is controlled at 1.0–2.5 g/m² per side on woodfree fine paper. Surface strength is qualified on IGT AIC2-5 equipment by ISO 3783:2006; the supplier target for offset papers is 2.0–2.5 m/s at 23°C and 50% RH. Internal sizing response is measured by Hercules Size Test with 1% formic acid ink using TAPPI T530; targets from 5 s to 30 s are set by base sheet porosity. The terminal products are offset printing papers, inkjet base papers, and recycled linerboard that must withstand corrugator hot-plate speeds of 200–250 m/min without surface dusting. Processing boundary: above 5 dry parts PVOH per 100 dry parts starch, film split tack increases and centre-roll release becomes unstable; feed tank temperatures above 75°C cause foaming unless a defoamer is added. This grade is a co-binder that supplements starch film strength; it does not replace external sizing agents.
In slasher warp sizing, POVAL 26-88 LV is dissolved at 8–10 wt% and combined with modified starch or acrylic size in size boxes maintained at 85–90°C. Squeeze rolls apply 20–25 kN/m linear pressure; wet pick-up on polyester/cotton spun yarn is 80–110% on yarn weight, producing a dry size add-on of 8–14%. The low-viscosity grade penetrates compact yarns before drying; surface-only size films cause high loom fibre shedding and warp breakage. Drying cylinder surface temperatures are staged 130°C to 150°C; over-drying above 160°C reduces film elongation and raises warp stops during loom acceleration. Weaving benchmark is conducted on air-jet looms at 800–1,000 rpm; a target of 0.5 warp stops per 100,000 picks is used to determine size cohesion. Desizing is accomplished with hot water at 80–90°C and 0.5–1.0 g/L nonionic wetting agent; no α-amylase is required for the PVOH fraction. Desize effluent COD is monitored below 5,000 mg/L before biological treatment under local permits implementing Directive 2010/75/EU. The terminal products are shirting, workwear, and upholstery fabrics. Boundary: size solids above 12 wt% cause dry-can deposition and hard size particles; this grade is not suited for low-pick-up pre-wet filament warp lines where a 20–25 wt% high-viscosity PVOH is needed.
Detergent unit-dose film casting through a slot die requires KURARAY POVAL 26-88 LV to be dissolved at 20–25 wt% in deionised water at 85–95°C, deaerated under 200–300 mbar absolute vacuum, and cast onto a chrome-plated steel belt at 60–90°C. Plasticizer addition is 15–25 phr glycerol or sorbitol, and the low-viscosity grade permits higher casting solids while keeping die pressure below 40 bar. Film thickness is maintained at 35–75 µm by in-line beta gauge calibrated to ISO 4593:1993. After conditioning at 23°C and 50% RH for 24 h per ISO 291:2008, elongation at break is evaluated by ISO 527-3:2018; converter specifications generally require above 200%. Tear strength is measured by ISO 6383-2:1983 with targets above 20 N/mm. Cold-water disintegration is sensitive to residual moisture; films stored above 70% RH block and develop slow dissolution. Terminal products include detergent pouches, dye transfer inhibitor sachets, and water-soluble agrochemical bags. For heavy detergent loads, probe puncture force above 50 N by ISO 14477:2004 may require blending with a higher-viscosity or fully hydrolysed PVOH; published data for this specific blend configuration is limited, so pilot casting on a 600 mm pilot line is required before full-width production. Boundary: formulations without plasticizer below 10 phr show brittleness below 30% elongation at 23°C and 50% RH.
For remoistenable envelope and paper tube adhesives, POVAL 26-88 LV is made down at 12–20 wt% in a high-shear Cowles dissolver at 1,200–1,500 rpm for 30–45 min. The solution is applied by engraved roller at 2–4 g/m² dry coat weight and dried in a forced-air tunnel at 80–100°C for 10–20 s. Remoistening speed and adhesion are tested on a rotary tube winder at 80–120 m/min; the spiral tube must withstand T-peel force above 250 N/m at 23°C when measured by ISO 11339:2022. The partially hydrolysed film remains water-remoistenable but does not redissolve instantly at 20°C; remoistening water at 25–35°C gives the most consistent tack. Humectant addition is 5–10 wt% ethylene glycol or glycerin to prevent edge cracking. Compliance is assessed under FDA 21 CFR 175.105 and FDA 21 CFR 176.170 for paperboard food contact; EU compliance for surface adhesives is managed under Regulation (EC) No 1935/2004, while Plastics Regulation (EU) 10/2011 applies only if the adhesive is incorporated into a plastic layer. Terminal products are spiral-wound paper cores, envelopes, and case-ready board sleeves. Boundary: without preservative, aqueous solutions above 10 wt% are susceptible to microbial growth within 48–72 h at 25–30°C. Borax addition raises wet tack but increases viscosity by 20–40% and can gel above pH 8.5.
Technical ceramic extrusion uses KURARAY POVAL 26-88 LV as a temporary binder in alumina, cordierite, and zeolite pastes. A binder solution at 8–15 wt% is added to the ceramic powder premix at 2–5 wt% dry basis on total solids; mixing in a sigma-blade kneader continues for 45–60 min until torque stabilises. The paste is extruded through a single-screw extruder at 10–20 MPa die pressure into honeycomb or thin-wall tube geometries with wall thickness down to 2 mm. Green strength after drying at 40–60°C and 20–30% RH is measured by three-point bending per ISO 14704:2016 on an Instron universal tester; handling of 600 mm long cordierite substrates requires above 5 MPa. Debinding in air uses a ramp of 0.5°C/min from 200°C to 500°C to avoid cracking; the 0.5 wt% Na₂O ash specification is critical because residual sodium can change dielectric loss in aluminium nitride substrates. Finished electronic ceramic components are assessed for hazardous substances under RoHS Directive 2011/65/EU, with compliance determined by the inorganic material formulation rather than the organic binder. Terminal products are catalytic converter honeycombs, diesel particulate filter segments, and ceramic heater substrates. Boundary: this low-viscosity grade is less suited to tape casting where PVOH solution viscosity above 40 mPa·s is needed for green tape strength; published data for this specific configuration is limited.
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KURARAY POVAL 26-88 LV is a partially hydrolysed polyvinyl alcohol grade produced by alcoholysis of polyvinyl acetate. The grade designation follows the Kuraray Poval convention: the first numerical block corresponds to the nominal 4% aqueous solution viscosity at 20 °C, and the second block corresponds to the degree of hydrolysis expressed as a mole percentage. The standard 26-88 reference grade is published with a viscosity of 25.0–31.0 mPa·s when measured by ISO 2555:2018 rotational viscometry and a degree of hydrolysis of 86.0–89.0 mol% when determined by JIS K6726:1994; the LV suffix identifies a lower-viscosity variant within the same hydrolysis band. The product is supplied as a white to off-white granular powder. Typical lot data include pH 5.0–7.0, volatiles not exceeding 5.0%, and ash not exceeding 0.4% under JIS K6726:1994. Bulk density is commonly reported in the range of 0.4–0.6 g/cm³. Regulatory documentation typically references 21 CFR 175.105 and 21 CFR 176.170 for indirect food-contact applications; direct use under 21 CFR 177.1670 requires verification of the finished article.
| Reference | Scope | Application boundary |
|---|---|---|
| ISO 2555:2018 | Rotational viscometry of 4% aqueous solution | Quality control; viscosity class confirmation |
| JIS K6726:1994 | PVOH test methods for hydrolysis, volatiles, ash, pH | Certificate of analysis |
| 21 CFR 175.105 | Adhesives for indirect food contact | Adhesive formulations |
| 21 CFR 176.170 | Paper and paperboard in contact with aqueous and fatty foods | Paper surface sizing |
| 21 CFR 177.1670 | Polyvinyl alcohol for food-contact articles | Direct use requires final-article verification |
| REACH EC 1907/2006 | Registration, evaluation, authorisation and restriction of chemicals | EU supply chain |
For production-scale stock preparation, the powder is dispersed in cold water at 20–25 °C and then heated to 80–95 °C under low-shear agitation in a jacketed mixing vessel. A 10–15 wt% stock solution is commonly prepared and held at 40–50 °C; filtration through a 100–200 µm in-line strainer removes undissolved fines. The solution is shear-stable, but prolonged recirculation through a centrifugal pump can generate foam, and a defoamer is often added when the solution is used in paper sizing or adhesive coating. The grade dissolves more readily in cold water than fully hydrolysed PVOH, so low-temperature post-dilution does not require pre-heating the dilution water to 90 °C.
The LV suffix does not move the degree of hydrolysis out of the 86.0–89.0 mol% window; residual acetyl content therefore remains approximately 11–14 mol%. That residual acetate distribution preserves cold-water solubility and reduces crystallinity relative to fully hydrolysed grades. The primary difference is rheological: the LV modification reduces the 4% solution viscosity target, permitting higher solids at equivalent Brookfield viscosity. In production-scale adhesive compounding on a high-shear disperser, this is observed as lower pump discharge pressure at a given solids level and reduced shear heating during recirculation. Published data for this specific configuration is limited; the exact solids increase must be established on the actual mixing line because pH, dissolved salts, and shear history affect final rheology. The change is not accompanied by a reduction in the degree of polymerisation sufficient to move the grade into the 22-88 or 17-88 viscosity classes; therefore, film toughness remains closer to the high-DP 26 series when measured under ISO 527-3 tensile testing.
Compared with lower-DP partially hydrolysed grades such as 22-88 and 17-88, the 26 series retains a higher degree of polymerisation, which increases dilute-solution viscosity and dried-film tensile strength. In emulsion polymerisation, the higher-DP protective colloid provides greater mechanical shear stability but also raises final emulsion viscosity; the LV suffix partially offsets this by reducing the viscosity contributed by the protective colloid. Selection between 22-88 and 26-88 LV is made after measuring final emulsion viscosity under ISO 2555:2018 and coagulum content by filtration through a 100 µm screen. The 26-88 LV grade is preferred when high shear stability is required in high-speed mixing or pumping; lower-DP grades are preferred when low viscosity is the dominant constraint and some shear stability can be sacrificed.
In vinyl acetate homopolymer and vinyl acetate-ethylene copolymer emulsion polymerisation, the grade is pre-dissolved at 10–15 wt% solids in demineralised water and metered into a jacketed stirred reactor over the feed cycle. The partially hydrolysed 88 mol% PVOH provides interfacial activity and graft stabilization; the high degree of polymerisation contributes to shear stability, while the reduced viscosity of the LV variant allows the same protective colloid content to be delivered with less dilution. Reactor operators select the LV grade when final emulsion viscosity must remain within the discharge pump curve of a 10 m³ reactor or when a 100–200 µm bag filter must remain unblocked during transfer. The grade is also used in combination with non-ionic surfactants of the alcohol ethoxylate type; the ratio is adjusted to control particle size and coagulum. Because the hydrolysis band is 88 mol%, the polymer retains sufficient cold-water solubility for low-temperature post-reaction dilution without pre-heating the dilution water to 90 °C.
For suspension polymerisation of vinyl chloride, partially hydrolysed PVOH functions as a primary suspending agent when combined with a low-hydrolysis secondary agent. The high degree of polymerisation provides droplet stability under high-shear agitation, while the LV viscosity reduces pressure drop in the dosing line. Reactor fouling and particle size distribution are typically evaluated in a pilot stirred reactor before scale-up; published data for this specific configuration is limited.
Fully hydrolysed PVOH grades with hydrolysis above 98 mol% require dissolution temperatures above 90 °C and produce films with higher tensile strength, higher melting point, and lower equilibrium water absorption. Replacing such a grade with 26-88 LV lowers solution preparation temperature and improves adhesion to hydrophobic substrates because the residual acetate groups reduce interfacial tension. The trade-off is measurable water sensitivity: a dried film from an 88 mol% grade absorbs more water than a fully hydrolysed film, which limits use in moisture-exposed wood joints. Adhesive formulators therefore restrict the grade to interior applications or combine it with crosslinking agents that consume the 1,3-diol groups. Under DIN EN 204 classification, a PVOH-only adhesive containing this grade would not be expected to satisfy D3 or D4 water-resistance classes without a secondary crosslinking resin. The lower viscosity is beneficial in roll-coating lines where a viscosity of 5,000–15,000 mPa·s is targeted; the LV variant reaches this window at higher solids than unmodified 26-88, but the exact solids-to-viscosity curve is batch-dependent and should be generated with a Brookfield viscometer under ISO 2555:2018.
On a metering size press, the grade is applied as a 2–5 wt% aqueous solution at machine speeds up to 1,200 m/min; the LV viscosity improves transfer uniformity and reduces rod or blade streaking. Surface strength is evaluated by IGT pick velocity under ISO 3783:2006, and water absorption by Cobb value under ISO 535:2014. Because an 88 mol% hydrolysed PVOH contributes dry pick strength but limited water resistance, the size formulation commonly includes a hydrophobic co-binder at 1–3 wt% on dry fibre. The grade is also used as a carrier for optical brightening agents and as a binder in pigmented coatings; however, its water sensitivity must be corrected with insolubilising agents when the final paper is intended for contact with water.
Aqueous solutions of 26-88 LV undergo reversible crosslinking with borate ions; addition of borax at 0.1–1.0 wt% on PVOH solids produces a rapid viscosity increase that can be exploited for rheology control but can gel the batch if added as a dry powder to a concentrated solution. Aldehyde donors such as glyoxal or glutaraldehyde acetalise the 1,3-diol units and reduce water sensitivity of the dried film, but they shorten pot life and require pH adjustment to the acid range. Polyvalent metal salts, including aluminium sulfate and ferric chloride, can precipitate the polymer at low pH; these additives should be introduced as dilute solutions and never into a high-solids PVOH hold tank. Aqueous solutions at pH 5–7 are susceptible to microbial growth; storage beyond 24–48 h without a validated biocide is not recommended. The powder is hygroscopic and should be kept in closed containers below 30 °C and below 60 % relative humidity to avoid caking.
Under REACH EC 1907/2006, the polymer is supplied with a safety data sheet that identifies the substance as a polymer and provides workplace exposure limits for nuisance dust. Dust generated during handling should be controlled because organic polymer dust can form explosive mixtures; transfer equipment should be grounded under process safety practice. The product is not classified as dangerous under CLP EC 1272/2008; nevertheless, dust exposure limits apply.
Air-jet weaving lines running polyester/cotton warp yarns use the grade as a cooked size at 70–85 °C and apply it at a size-box solids level of 6–10 wt%. The high degree of polymerisation provides abrasion resistance against reed and heald wear; the 88 mol% hydrolysis band gives sufficient adhesion to polyester to reduce size shedding, while hot-water desizing at 60–80 °C removes the film without enzyme treatment. Compared with a fully hydrolysed grade, the 26-88 LV film shows lower desizing temperature and lower energy demand, but the dried film is more sensitive to high-humidity storage and should not be left in a weaving shed at relative humidity above 70 % for extended periods.
