KURARAY POVAL 26-88 LV

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.

Vinyl Acetate Emulsion Polymerisation: Colloid Loading and Graft Partitioning

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.

Does 26-88 LV Disrupt the Starch Cook at the Metering Size Press?

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.

Polyester/Cotton Warp Sizing with High-Pressure Squeeze Roll Configurations

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.

When Remoistenable Adhesives Need Low Viscosity Without Blocking

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.