| HS Code | 739213 |
| Product Name | KURARAY POVAL 4-88 LV |
| Chemical Family | Polyvinyl alcohol (PVOH) |
| Cas Number | 9002-89-5 |
| Degree Of Hydrolysis | 87.0 - 89.0 mol% |
| Viscosity 4 Solution 20 C | 4.0 ± 0.5 mPa·s |
| Ph 4 Solution | 5.0 - 7.0 |
| Appearance | White granular powder |
| Bulk Density | 0.40 - 0.60 g/cm³ |
| Specific Gravity | 1.27 |
| Solubility | Soluble in hot water, insoluble in organic solvents |
| Melting Point | 230°C (approximate) |
| Glass Transition Temperature | 85°C (approximate) |
As an accredited KURARAY POVAL 4-88 LV factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | KURARAY POVAL 4-88 LV is packaged in 25 kg multi-layer paper bags with an inner polyethylene liner. |
| Container Loading (20′ FCL) | KURARAY POVAL 4-88 LV is loaded as palletized, sealed bags into a 20′ FCL, ensuring dry, clean, secure stowage. |
| Shipping | Kuraray Poval 4-88 LV is a polyvinyl alcohol grade shipped as a free-flowing powder in moisture-proof bags, drums, or bulk containers. It is non-hazardous under normal conditions, but should be kept dry, stored away from ignition sources, and protected from physical damage during transit. |
| Storage | Store KURARAY POVAL 4-88 LV in a cool, dry, well-ventilated area, away from heat, sparks, and open flames. Keep containers tightly sealed to prevent moisture absorption and contamination. Avoid dust accumulation and exposure to strong oxidizers. Maintain stable temperatures and follow manufacturer’s recommended shelf life for optimal performance. |
| Shelf Life | Shelf life is typically 2 years from manufacture date when stored unopened in a dry, sealed container. |
KURARAY POVAL 4-88 LV, a partially hydrolysed polyvinyl alcohol with a nominal degree of hydrolysis of 86.7–88.7 mol%, a 4% aqueous solution viscosity at 20 °C of 3.5–4.5 mPa·s measured by DIN 53015, and a solution pH of 5.0–7.0 per JIS K6726, functions as a primary protective colloid in the semibatch emulsion polymerisation of vinyl acetate-ethylene copolymer dispersions. In a baffled jacketed stainless-steel reactor of 10–25 m³ working capacity, the colloid is first dissolved in demineralised water at 85–95 °C, cooled to 40–50 °C, and charged before the monomer feed is initiated. The reactor impeller is usually a dual-flight pitched-blade turbine operated at 45–75 rpm; vinyl acetate is metered over 3–5 h while ethylene partial pressure is maintained at 0.5–1.5 MPa. The protective colloid addition is split between the initial reactor charge and the vinyl acetate pre-emulsion at a total of 2.0–6.0 wt% on total monomer. The partially acetylated PVOH chains adsorb at the monomer/water interface and reduce coalescence during the seeding stage, while the low molecular weight of the grade prevents the continuous-phase viscosity from exceeding the range in which radical starve-feeding remains stable. Chain-transfer grafting during radical propagation yields PVOH-g-poly(vinyl acetate), and the graft fraction is controlled by the oxidant shot programme with ammonium persulfate/sodium metabisulfite redox initiation kept at 0.08–0.25 wt% total oxidant on monomer. If the oxidant shot exceeds 0.05 wt% per addition, the graft fraction rises and the water resistance of the dried film deteriorates. Coagulum formed in the reactor is screened on 100 µm filters and is typically held below 0.05 wt% of dispersion mass.
Finished dispersion quality is controlled by solids content per ISO 3251 at 52–55%, Brookfield viscosity per ISO 2555 at 20 °C with spindle 3 at 20 rpm between 1 500 and 4 500 mPa·s, and mean particle size by laser diffraction per ISO 13320 between 0.4 and 0.9 µm after the vinyl acetate-ethylene feed is exhausted. The minimum film formation temperature determined by ISO 2115 is 0–3 °C when butyldiglycol acetate or dibutyl phthalate is post-added at 2–5 wt% on polymer solids. Water hardness above 15 °dH interferes with interfacial packing of the acetate groups; therefore process water conductivity is held below 50 µS/cm to limit batch-to-batch variance. The dilute PVOH solution is susceptible to microbial degradation when held for more than 24 h at 20–30 °C; preservation is required in make-down tanks. High-shear mixing above 1 000 rpm during solution preparation can shear-degrade the low molecular weight grade and reduce the solution viscosity by more than 5% in a single pass.
In vinyl chloride suspension polymerisation, the final PVC particle size distribution and grain porosity are controlled by the dynamic balance of droplet breakage and coalescence under autoclave shear. KURARAY POVAL 4-88 LV is introduced as a secondary suspending agent together with a high-hydrolysis primary polyvinyl alcohol or a hydroxypropyl methylcellulose ether at total levels of 0.05–0.50 kg per 100 kg vinyl chloride monomer. The low aqueous viscosity of 4-88 LV reduces continuous-phase viscosity during the early droplet coalescence window, which permits finer droplet breakage under a retreat-blade impeller in a 60–80 m³ jacketed autoclave at 80–110 rpm and 55–65 °C. Typical reactor pressure is 0.8–1.1 MPa. The partially hydrolysed acetate units form a compressible interfacial film that is sufficiently robust to arrest coalescence but not so rigid that it blocks the fusion required for desired grain porosity. The resulting PVC resin has a volume-weighted median grain size of 120–180 µm, with sieve retention on 63 µm per ISO 4610 below 5% and oversize on 250 µm below 2%. Plasticiser absorption is measured by ISO 4608 and remains at 22–30 g DOP/100 g resin when the secondary colloid addition is not overdosed.
The K-value of the suspension resin, measured by ISO 1628-2, is controlled by polymerisation temperature rather than by suspending agent composition; rigid pipe and profile grades are typically fixed at 57–68. If 4-88 LV is used as the sole suspending agent above 0.5 kg per 100 kg VCM, the interfacial layer becomes too soluble in the monomer phase, producing oversized grains and elevated extractable residues. Published data for this grade in autoclaves above 100 m³ is limited, and plant-scale trials are required before replacing an incumbent secondary suspending agent on very large production lines.
Blade-coated microporous inkjet receptor layers impose contradictory demands on the water-soluble binder: the coating colour must suspend high-surface-area silica pigments without yield stress build-up, yet after drying it must insolubilise sufficiently to prevent print mottling. KURARAY POVAL 4-88 LV is used at 8–15 parts by weight per 100 parts fumed or precipitated silica, with the coating adjusted to pH 8.5–9.5 using ammonia or a volatile amine. The 3.5–4.5 mPa·s solution viscosity of the grade at 4% solids permits coating colour solids of 25–35% while retaining a Brookfield viscosity below 300 mPa·s per ISO 2555 at 20 °C. Boric acid at 0.4–1.2 parts per 100 parts pigment is introduced by dynamic in-line mixing immediately ahead of the die head because the borate-diol network is shear-sensitive; static hold time longer than 60 min without recirculation produces gel particles that block 40 µm line filters. The coated layer after drying has a coat weight of 8–15 g/m² by TAPPI T 410 and gloss retention by TAPPI T 480. Water fastness is checked after 24 h immersion at 23 °C by optical density bleed onto a laminated receiver, with quantitative limits set by the printer OEM.
On high-speed coating lines of 800–1 200 m/min, the low molecular weight of the binder reduces extension thickening and ribbing because the solution relaxation time remains below the roll-splitting time. The same low molecular weight that improves coatability reduces cohesive film strength; therefore boric acid addition must be matched to the live coating pH. A pH drift of more than 0.5 units shifts the borate gel point outside the drying window and produces cracked or water-sensitive coated surfaces. The coated substrate is conditioned at 23 °C and 50% RH before ink receptivity testing. Storage of the coating colour above 30 °C or pH above 9.5 accelerates acetal formation and produces insoluble specks that plug the filtration stage.
On high-speed envelope backgumming equipment, the remoistenable adhesive is applied at 45–60 °C by slot die or roller to 80–110 g/m² kraft paper and dried within 2–6 s before flap folding. A production starting-point formulation contains 55–70 parts thin-boiling white dextrin, 8–15 parts KURARAY POVAL 4-88 LV, 5–10 parts urea or sodium nitrate as plasticiser, 0.5–1.5 parts preservative, and water to 55–65% solids. The PVOH is pre-dissolved separately at 15–20% solids and added to the dextrin cook, after which the blend is held at 60 °C for 30 min to complete hydration. Adhesive viscosity is measured by ISO 2555 at 50 °C with spindle 4 at 50 rpm and maintained between 500 and 1 500 mPa·s; below 500 mPa·s misting increases on roller applicators, and above 1 500 mPa·s the film thickness causes flap curl after drying. The remoistening open time is governed by the PVOH/dextrin ratio and plasticiser content; laboratory values on 80 g/m² wove paper at 23 °C and 50% RH range from 30 to 90 s. Dry blocking is assessed after conditioning for 24 h, and preservative performance is challenged by ASTM D4783.
For food-contact envelope and paper-label converting, the formulation must operate within the conditions of 21 CFR 175.105 for remoistenable adhesives and, when indirect contact with aqueous or dry food is possible, 21 CFR 176.170. The low ash of the LV grade and its solvent-free composition support these uses, but the dried adhesive is hygroscopic and remoistenability declines below 25% RH. In arid converting rooms, humectant levels above 10 parts are used, which can accelerate plasticiser migration into the paper and must be validated through blocking tests before commercial release.
On shuttleless weaving machines operating above 700 picks/min, spun polyester and polyester/cotton warp yarns require a size film that resists heald-frame abrasion and shedding while maintaining flexibility through high-frequency cyclic loading. Low-viscosity KURARAY POVAL 4-88 LV is compounded with oxidised starch and an acrylate ester size at 20–40% of dry size solids, giving a size-box bath solids of 8–12%. The size is applied in a two-box slasher at 80–85 °C, with squeeze roll pressure between 120 and 250 kN/m and dry add-on targeted at 6–10%. The PVOH film after conditioning at 23 °C and 50% RH shows tensile strength per ISO 527-3 of 38–52 MPa and elongation at break of 120–180%, which is more than twice the elongation of oxidised starch film. Desizing after weaving is performed in water at 60–80 °C; where starch is present, alpha-amylase at 0.1–0.5 g/L and 65–70 °C is used to remove the combined size. Dust generation on air-jet looms, assessed by Reutlingen Webtester data, typically falls by 30–50% relative when the PVOH fraction is increased from 20% to 35% of size solids, depending on yarn twist and loom speed.
The low viscosity of the grade reduces size-box viscosity drift under drying-cylinder heat, which is a known cause of uneven pick-up on multi-cylinder slashers. The size-bath viscosity is measured by ISO 2555 at 80 °C and held at 30–70 mPa·s; a viscosity increase above 20% within 8 h indicates starch retrogradation and requires fresh size feed or pH adjustment. The size film is hygroscopic, and weaving rooms are held at 55–65% RH to prevent embrittlement and end breaks. Long-term storage of sized warp beams above 30 °C or below 35% RH can cause film cracking and must be avoided.
In aqueous tape casting of low-temperature co-fired ceramic substrates, KURARAY POVAL 4-88 LV is used as the primary binder for borosilicate glass-alumina composites. The binder is added at 6–12 wt% of ceramic powder after a preliminary dispersion stage with polycarboxylate deflocculant at 0.2–0.8 wt%. Slurry viscosity at 10 s⁻¹ is controlled between 1 500 and 4 000 mPa·s, and the slurry is deaired under vacuum at 50–100 mbar before doctor-blade casting onto silicone-coated carrier film. The cast gap is 200–300 µm for a dried green tape thickness of 80–150 µm after two-zone drying at 40 °C and 60 °C. Dried tape is punched at 25 °C and 40–50% RH; green tensile strength and elongation are measured by ASTM D882 with lower control limits above 2.0 MPa and 5% elongation. Below 40% RH the tape loses bound-water plasticisation and microcracks appear around via edges, so punching-area climate control is mandatory.
Binder burnout is evaluated by thermogravimetric analysis in flowing air at 2 °C/min from 25 °C to 500 °C. The partially hydrolysed PVOH decomposes with acetate-group cleavage at 250–350 °C and oxidative backbone decomposition completing below 480 °C. Residual ash after burnout is specified below 0.1% of original binder mass for the low-ash LV grade; this is necessary for co-fired silver conductors where alkaline residues promote silver migration. Lamination of punched tape is performed at 60–80 °C and 5–15 MPa; softening above 60 °C permits layer adhesion without geometric distortion. Published data for the viscoelastic relaxation of 4-88 LV green tape after solvent steaming is limited, and storage trials at 50% RH beyond 30 days should be conducted before qualification.
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KURARAY POVAL 4-88 LV is a partially hydrolysed polyvinyl alcohol resin manufactured by Kuraray Co., Ltd. The product designation encodes a nominal 4 mPa·s viscosity class for a 4 mass% aqueous solution at 20 °C and a hydrolysis band centred at 88 mol%. The material is supplied as a white granular solid under CAS 9002-89-5 and is used in aqueous preparation routes, emulsion polymerization protective-colloid systems, remoistenable adhesives, paper sizing, textile sizing, and specialty coatings. The LV suffix distinguishes the product from standard 4-88 by a reduced residual volatile fraction; exact lot values are stated on the certificate of analysis.
Representative specification ranges from Kuraray technical literature place the degree of hydrolysis at 86.5–89.0 mol% and the viscosity of a 4 mass% aqueous solution at 20 °C at 3.5–4.5 mPa·s when measured according to JIS K 6726. Volatile matter is controlled to ≤5.0 %, ash to ≤0.5 %, and pH of a 4 mass% solution to 4.5–7.0. International property determination may also follow ISO 15023-2:2019. Unlike fully hydrolysed polyvinyl alcohol such as KURARAY POVAL 4-98, the residual acetate groups in 4-88 LV lower crystallinity and permit complete dissolution in water below 30 °C. The same structural feature makes the dried film more water-sensitive than a 98 mol% grade.
| Parameter | Test method / condition | Typical range |
|---|---|---|
| Degree of hydrolysis | JIS K 6726 saponification titration | 86.5–89.0 mol% |
| Viscosity of 4 mass% aqueous solution at 20 °C | JIS K 6726 / Brookfield rotational viscometer | 3.5–4.5 mPa·s |
| Volatile matter | JIS K 6726 drying method | ≤5.0 % |
| Ash content | JIS K 6726 ignition method | ≤0.5 % |
| pH of 4 mass% aqueous solution | JIS K 6726 glass electrode | 4.5–7.0 |
| Residual volatile matter | Headspace gas chromatography | Reduced ceiling versus standard 4-88; exact value per certificate of analysis |
At a degree of hydrolysis of 88 mol%, approximately 12 mol% of the original acetate groups remain distributed along the polymer chain. These acetate groups act as internal separators that reduce interchain hydrogen bonding and crystallite size. Their presence lowers the minimum dissolution temperature to 20–30 °C under low-shear agitation, whereas a 98 mol% grade such as KURARAY POVAL 4-98 requires dissolution temperatures above 80 °C. The acetate groups also impart interfacial activity; equilibrium surface tension measured by Wilhelmy plate method is lower than that of fully hydrolysed polyvinyl alcohol at equivalent concentration, which assists wetting of hydrophobic substrates in coating and sizing.
Solution stability is governed by dissolved oxygen, trace metals, and microbial activity rather than thermal hydrolysis under normal storage below 35 °C. In non-sterile unpreserved solutions, bacterial growth can produce organic acids and reduce pH from the initial 4.5–7.0 range. Production-scale atmospheric make-down tanks with heating jackets have shown that poor pre-wetting of the granular resin in cold water leads to swollen gelatinous lumps. These lumps can be removed only by 100–150 µm bag filtration or high-shear recirculation, and the recirculation step itself can introduce foam if not deaerated.
Cast films from 4-88 LV dry to transparent, moderate-strength layers under controlled relative humidity. Tensile testing per ASTM D882-18 at 23 °C and 50 % RH shows that the 88 mol% hydrolysis grade is softer and more extensible than fully hydrolysed polyvinyl alcohol; measured values are highly dependent on plasticizer content and film thickness, and published data for this specific configuration is limited. Water-vapour transmission rate under ASTM E96/E96M-22 is higher for partially hydrolysed grades than for 98 mol% films. Consequently, 4-88 LV is not selected for barrier packaging layers unless a secondary moisture-proof layer is present.
Oxygen transmission rate under ASTM D3985-17 at 0 % RH is low because the dry polyvinyl alcohol matrix is dense. At 80 % RH, the permeation rate increases by 1–2 orders of magnitude as water plasticizes the amorphous phase. This property cliff-edge means that applications requiring gas barrier under high-humidity storage should combine 4-88 LV with ethylene-vinyl alcohol copolymer or polyolefin layers rather than relying on the polyvinyl alcohol alone.
In vinyl acetate and vinyl acetate/ethylene emulsion polymerization, 4-88 LV is charged as a protective colloid in the aqueous phase before monomer addition. Typical colloid loadings range from 2.0–4.0 wt% on total monomer. The low molecular weight fraction of the grade keeps the aqueous phase viscosity low at 50–55 % solids. Final emulsion viscosity measured by Brookfield rotational viscometer at 25 °C, 20 rpm remains below that of equivalent formulations using 26-88 or 13-88 at the same colloid loading. High-shear dispersion of vinyl acetate monomer at 1000–3000 s⁻¹ in a rotor-stator mixer yields stable pre-emulsions. The partially acetylated polyvinyl alcohol participates in grafting reactions with the propagating poly(vinyl acetate) chain and contributes to particle-size control in the 0.5–2.0 µm range.
The reduced volatile residual of the LV designation is relevant when the resulting emulsion is formulated into low-odour interior paints and adhesives. Residual methanol and methyl acetate from the polyvinyl alcohol can otherwise contribute to indoor air emissions and labelling. Residual volatile content should be verified by headspace gas chromatography against the lot certificate of analysis.
In surface sizing of alkaline fine paper, fully hydrolysed 4-98 is often selected for film strength and water resistance after drying. However, 4-98 requires heated dissolution above 80 °C and can form high-viscosity solutions that limit runnability at size press solids above 6–8 mass%. Substitution with 4-88 LV permits cold-water pre-slurry and lower solution viscosity at equal solids, allowing pump recirculation and metering-rod application without excessive shear. The trade-off is a softer dried film and higher Cobb absorption. Papermakers compensate by increasing internal AKD or ASA sizing agent dose and verifying water uptake per ISO 535:2023.
On high-speed fine paper machines operating above 1200 m/min, the low molecular weight of 4-88 LV reduces misting and size-press film-split viscosity. Published production data for this specific configuration is limited. Pilot trials at 600–1000 m/min show acceptable runnability when polyvinyl alcohol solids are held between 4.0 and 7.0 mass% and the solution temperature is maintained at 45–55 °C.
| Grade | Hydrolysis range | 4 mass% viscosity at 20 °C | Principal difference |
|---|---|---|---|
| KURARAY POVAL 4-88 LV | 86.5–89.0 mol% | 3.5–4.5 mPa·s | Low residual volatile profile; cold-water soluble |
| KURARAY POVAL 4-98 | 98.0–98.8 mol% | 4.0–4.5 mPa·s | Fully hydrolysed; hot-water processing; higher water resistance |
| KURARAY POVAL 5-88 | 86.5–89.0 mol% | 5.0–5.8 mPa·s | Higher viscosity for stronger film build |
| KURARAY POVAL 13-88 | 86.5–89.0 mol% | 12.5–14.5 mPa·s | Medium viscosity for release coatings and thickeners |
| KURARAY POVAL 26-88 | 86.5–89.0 mol% | 25.0–28.0 mPa·s | High-viscosity binder for adhesives and sizing |
Remoistenable adhesive coating for envelopes and paper labels is prepared at 15–25 mass% solids with 4-88 LV. The low solution viscosity allows slot-die or reverse-roll application at wet-film thicknesses of 40–80 g/m² without exceeding 500–1500 mPa·s in the coating pan. Drying is carried out at web temperatures of 80–105 °C; complete water release is required before reeling to prevent blocking. The dried polyvinyl alcohol layer remains tack-free until remoistened, at which point the partial acetate content permits rapid re-wetting and activation of the adhesive bond. Compared with 26-88, the 4-88 LV grade gives a thinner film at the same dry coat weight and penetrates coated paper less, which can be modified by adding plasticizers or lower-viscosity starch.
Aqueous solutions of 4-88 LV are near-Newtonian at low concentrations. Below 5 mass%, viscosity is stable over a shear rate range of 1–100 s⁻¹. Above 12 mass%, shear-thinning behaviour becomes measurable, and solution viscosity is sensitive to both temperature and the presence of co-solvents. Solutions prepared in deionized water should be stored below 35 °C. At temperatures above 90 °C during make-down, the polymer can adsorb onto heating surfaces and form gel skins. These skins detach as gel specks if tank wall cleaning is not performed between batches.
pH drift in stored solutions is commonly caused by microbial activity. Preservative choice must be compatible with polyvinyl alcohol; cationic antimicrobial agents can reduce solution clarity. Sodium benzoate at 0.1 mass% or methylisothiazolinone at manufacturer-dosed levels is used in industrial practice. Borate-containing crosslinking agents increase solution viscosity and can form weak gels at high addition levels, although 4-88 LV is more tolerant of borate than fully hydrolysed polyvinyl alcohol because the residual acetate groups reduce the density of strong borate–diol complexes.
Textile warp sizing on air-jet looms uses 4-88 LV at 6–10 mass% solids in the size box. The low-viscosity grade penetrates the yarn core, while a supplementary high-viscosity polyvinyl alcohol or starch film former is added when surface encapsulation and abrasion resistance are required. Sized yarn elongation and hairiness are evaluated on weaving trial looms. For polyester/cotton blends, a lubricant such as polyethylene glycol at 0.5–1.0 wt% on dry solids reduces friction at the reed. Because 4-88 LV is cold-water-soluble, desizing is achieved with alkaline scouring baths below 60 °C, whereas fully hydrolysed polyvinyl alcohol may require oxidative desizing or higher temperature.
When 4-88 LV is used in gravure or curtain coating of board and synthetic substrates, the coating is often recirculated through gear pumps at 500–1000 s⁻¹. Air entrainment under these conditions produces microfoam that can cause craters and pinholing after drying. Field observations on production lines indicate that defoamer addition at 0.05–0.20 mass% on wet coating controls foam, but overdosing above 0.30 mass% produces hydrophobic fisheyes. Defoamer type should be validated by coating drawdown tests, not solely by foam height tests.
Gel specks in dried coatings are typically traced to incomplete dissolution. A high-shear rotor-stator pre-dispersion step at 20–25 °C followed by heating to 85–90 °C for 30 min reduces speck counts when the solution is filtered through 100 µm bags before coating. A vacuum-deaeration vessel after filtration removes 2–5 % entrained air by volume and further reduces pinhole defects. Published data for this specific configuration is limited; adjustments must be confirmed on the target coater.
In indirect food-contact applications, the low residual volatile content of 4-88 LV assists converters in meeting low odour and low migration expectations under FDA 21 CFR 176.170 and EU Regulation (EU) No 10/2011. Polyvinyl alcohol is used as a binder or coating in paper and board that may contact aqueous and dry foods. Specific migration of residual methanol and methyl acetate should be confirmed on the finished article because conversion temperature, co-binders, and board retention can alter final residuals. The product should not be combined with strongly acidic additives or certain amine-functional compounds that can catalyse acetal formation or discolouration during drying. Storage in sealed bags at 15–30 °C and below 60 % RH is required to prevent caking; re-drying is not typically required if the material is kept sealed.
