| HS Code | 157061 |
| Product Name | KURARAY POVAL 8-88 |
| Chemical Name | Polyvinyl alcohol |
| Cas Number | 9002-89-5 |
| Appearance | White granular powder |
| Viscosity 4 Aqueous Solution 20 C | 7.8 - 8.8 mPa·s |
| Degree Of Hydrolysis | 87.0 - 89.0 mol% |
| Ph 4 Aqueous Solution | 5.0 - 7.0 |
| Ash Content | ≤ 0.5 wt% |
| Volatile Content | ≤ 5.0 wt% |
| Solubility | Soluble in water, more readily at elevated temperatures; insoluble in common organic solvents |
As an accredited KURARAY POVAL 8-88 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | KURARAY POVAL 8-88 is supplied in 25 kg net kraft paper bags with polyethylene liner, palletized and shrink-wrapped for safe transport. |
| Container Loading (20′ FCL) | KURARAY POVAL 8-88 loaded as 25 kg bags on pallets, shrink-wrapped, and securely stowed in one 20′ FCL. |
| Shipping | KURARAY POVAL 8-88 ships as non-hazardous polyvinyl alcohol powder, typically in 25 kg multi-wall paper bags or bulk FIBCs. Keep pallets dry and protected from humidity, rain, and direct moisture contact during transport. Store in a cool, ventilated area; avoid excessive dust generation when handling. |
| Storage | Store KURARAY POVAL 8-88 in a cool, dry, well-ventilated area, away from direct sunlight, heat, and ignition sources. Keep the original container tightly closed to prevent moisture absorption and contamination. Avoid dust generation; use appropriate ventilation. Maintain temperatures below 40°C and protect from physical damage to preserve polymer quality. |
| Shelf Life | Store in a cool, dry place. Shelf life is typically two years from manufacture when kept in original sealed packaging. |
KURARAY POVAL 8-88 is a partially saponified polyvinyl alcohol grade with a nominal degree of polymerization of 800, a nominal hydrolysis degree of 88 mol%, and a manufacturer specification window of 86.0–89.0 mol% for the saponification value. A 4% aqueous solution measured at 20°C under JIS K6726 procedures gives a viscosity of 7.0–9.0 mPa·s. Bulk moisture is controlled below 5.0%, and ash expressed as Na₂O is controlled below 0.5%. The powder should be stored at or below 40°C and 70% RH to avoid caking in silos or bag discharge systems. For solution preparation, a pre-slurry in cold demineralized water is heated to 80–85°C and held for 30–60 min under high-shear mixing; direct addition to cold water produces gel skins that extend dissolution time. The grade contains residual acetate groups that lower surface tension and increase adsorption at hydrophobic monomer or particle interfaces, while the remaining hydroxyl content provides strong hydrogen bonding to cellulosics, pigments, and ceramic surfaces. The following scenarios cover suspension polymerization, emulsion polymerization, paper treating, textile sizing, ceramic tape casting, and paper-converting adhesives.
Production of suspension-grade S-PVC in a jacketed glass-lined autoclave typically uses POVAL 8-88 as the primary protective colloid at 0.04–0.15 wt% on vinyl chloride monomer. The aqueous phase is prepared with demineralized water at 80–85°C to fully dissolve the grade, held for 30–60 min, and then cooled to 25–35°C before charging. Reactor temperature during polymerization is maintained at 54–58°C for K-value targets around 67–70, with pressure in the range of 0.8–1.0 MPa and conversion terminated at 75–85% to avoid particle agglomeration. The impeller type and tip speed influence final grain size; typical Pfaudler impellers operating at 5–9 m/s in reactors of 30–150 m³ are required to disperse monomer droplets and prevent secondary nucleation. A secondary dispersant such as lower-hydrolysis PVOH or hydroxypropyl methylcellulose is added at 0.01–0.05 wt% to modulate the coarse-to-fine particle ratio. Residual PVA in the recovered mother liquor must remain below 0.22 wt% because higher concentrations increase the fraction of fines smaller than 60 µm above 3% and lower the bulk density of the dried resin. Industrial product quality is assessed by sieve analysis according to ISO 1624, bulk density according to ASTM D1895-17, and cold plasticizer absorption according to ISO 4608. POVAL 8-88 with 86–89 mol% hydrolysis provides a balance between water solubility and grafting to PVC surfaces; fully hydrolyzed grades above 98 mol% raise interfacial tension and generate a coarser particle size distribution. The terminal resin is applied in rigid pipe, window profiles, and fittings where bulk density values of 0.48–0.54 g/cm³ and plasticizer absorption of 20–28 g DOP/100 g PVC are common process targets. Specific initiator and dispersant ratios are often proprietary, but the ranges above reflect published suspension PVC technical literature.
| Dispersant function | Chemistry | Typical dosage on VCM | Main effect on S-PVC resin | Test method |
|---|---|---|---|---|
| Primary protective colloid | PVOH 86–89 mol% hydrolysis, DP 800 (POVAL 8-88) | 0.04–0.15 wt% | Mean grain size 125–180 µm; target plasticizer absorption 20–28 g DOP/100 g | ISO 1624, ISO 4608 |
| Secondary dispersant | PVOH 72–76 mol% hydrolysis, DP 600–700 | 0.01–0.05 wt% | Bulk density increase 0.50–0.56 g/cm³; fines below 60 µm kept below 3% | ASTM D1895-17, ISO 1624 |
| Secondary dispersant | Hydroxypropyl methylcellulose, methoxy/propoxy substitution | 0.01–0.04 wt% | Narrow particle size distribution; reduced agglomeration at conversion above 80% | ISO 1624 |
In semi-batch vinyl acetate-ethylene emulsion polymerization, POVAL 8-88 operates as a nonionic protective colloid that controls particle nucleation and shear stability at addition levels of 0.5–4.0 wt% on total monomer. The grade is normally prepared as a 10–20 wt% aqueous solution at 80–90°C, cooled to 40–50°C, and metered into a jacketed glass-lined reactor with propeller or anchor agitation. Polymerization temperature for VAE runs between 70–85°C, and ethylene partial pressure is maintained at 2–6 MPa to achieve ethylene content of 10–25 wt% in the final dispersion. Persulfate initiator at 0.1–0.5 wt% and sodium acetate buffer at 0.1–0.3 wt% are used to keep pH in the 4.0–6.0 range; the partially saponified structure of POVAL 8-88 remains soluble and adsorbs onto polyvinyl acetate surfaces without generating coagulum at these acidities. Viscosity measured by Brookfield viscometer at 20 rpm and 25°C typically reaches 2,000–8,000 mPa·s for finished VAE dispersions depending on solids. Shear stability is evaluated by reciprocating plunger or by screening through a 100 µm filter after mechanical shear, and dispersions stabilized with POVAL 8-88 are generally supplied at 50–60% solids for wood adhesive compounding. The terminal products include D3 class wood adhesives tested according to EN 204 and paper lamination adhesives evaluated for indirect food contact under FDA 21 CFR 175.105. A process limitation occurs when recycled aqueous-phase streams contain more than 3 wt% residual PVA, because viscosity rise during post-treatment can exceed the capacity of standard lobe pumps; dilution with fresh water or staged addition of PVA solution is required.
Paper surface sizing and pigment coating require a binder with high film strength, enough water retention to control penetration into the base sheet, and compatibility with optical brighteners or cationic polymers. POVAL 8-88 is used as a cobinder with oxidized starch or styrene-butadiene latex at addition rates of 5–15 parts per 100 parts of pigment in coated freesheet and specialty inkjet papers. The coating color is made down at 50–65% solids, and the viscosity is adjusted to 800–1,500 mPa·s at 25°C for blade or rod application. On a high-speed coater running at 600–1,200 m/min, the grade's 86–89 mol% hydrolysis provides a lower critical solution temperature than fully hydrolyzed grades, which allows the PVA to precipitate or form a gel layer at the drying section temperature of 80–120°C, reducing binder migration to the paper surface. Water retention is measured by gravimetric desorption under pressure; typical formulations retain 65–80% of a test liquid column after 60 s compared with 40–50% for starch-only coatings. Surface strength is evaluated by IGT pick test under ISO 3783 or by wax pick tests, with target values above 2.5 m/s for coated paper used in offset printing. In thermal paper precoating, the PVA acts as a barrier against leuco dye penetration and is compounded with clay or silica at 1.0–3.0 wt% dry basis. The terminal articles include inkjet receptive coatings tested for bleeding by contact angle above 45° after 24 h and grease-resistant paper structures evaluated under ISO 16532. If the final paper is intended for food contact, formulation migration is assessed under FDA 21 CFR 176.170 and EU 10/2011, but POVAL 8-88 itself is not a finished food-contact article.
| Application target | Relevant standard or regulation | Test property | Typical acceptance window |
|---|---|---|---|
| Coated paper for offset printing | ISO 3783 | IGT surface strength | > 2.5 m/s |
| Grease-resistant kitchen paper | ISO 16532 | Oil and grease resistance number | ≥ 5 after 24 h |
| Food-contact paper and board | FDA 21 CFR 176.170, EU 10/2011 | Migration testing | Formulation-specific |
| Inkjet receptive coating | ISO 2470 or ISO 13655 | Brightness and print density | Specified by OEM |
On air-jet weaving machines requiring warp yarn abrasion resistance, POVAL 8-88 is blended with oxidized starch and acrylic size at 6–10% total solids in the size box. The typical blend consists of 70–90% starch, 5–15% PVA 8-88, and 5–10% acrylic size, run at 70–80°C and squeezed at 20–35 kN/m linear nip pressure. The size adds dry strength and film integrity on polyester/cotton blended warps; desizing is completed in hot water at 85–95°C. Published data for individual mill configurations is limited, but the grade's medium DP 800 provides sufficient film tensile strength for high-speed rapier and air-jet looms.
Tape casting of alumina or glass-ceramic substrates with POVAL 8-88 as binder requires strict control of powder loading, binder content, and drying rate because the grade forms a stiff gel layer that can trap solvent below the surface. In a typical aqueous slurry, ceramic powder is mixed at 100 parts with deionized water 30–50 parts, ammonium polyacrylate dispersant 0.5–1.5 parts, and a binder solution prepared from POVAL 8-88 at 5–10 wt% solids. The PVA binder addition is usually 3–6 phr relative to ceramic powder, below the threshold above which dried tape becomes brittle and prone to lamination defects. Milling in a zirconia-lined jar at 60–100 rpm for 12–24 h is followed by vacuum degassing at 0.1–0.2 bar to remove entrapped air. Doctor blade casting onto silicone-coated PET film uses a gap of 100–500 µm and a carrier speed of 0.5–2.0 m/min. Drying starts at 25–40°C with relative humidity of 40–70%, then progresses to 50–60°C to avoid surface skinning. Green tape mechanical properties are tested by tensile testing according to ISO 527-3; typical values for POVAL 8-88-bound alumina tapes fall in the range of 1.5–4.0 MPa tensile strength and 5–15% elongation, depending on plasticizer ratio. Binder burnout is performed in a ventilated convection furnace at a heating rate of 0.5–1.0°C/min to 600°C with a hold of 1 h, because rapid removal causes tape delamination and carbon residue. The terminal applications are multilayer ceramic capacitors, LTCC substrates, and solid oxide fuel cell electrolyte supports. A limitation is the ash specification of POVAL 8-88 at 0.5% as Na₂O; for dielectric layers requiring alkali metal content below 50 ppm, additional purification or a low-ash grade may be required, and published data for this specific configuration is limited.
Paper converting lines that laminate printed stock to board at speeds above 250 m/min require adhesive formulations with short open time and high green tack. POVAL 8-88 is dissolved at 10–15% solids and combined with starch or dextrin at 30–50% solids to create a water-based laminating adhesive with Brookfield viscosity of 1,000–3,000 mPa·s at 25°C. The grade imparts wet tack and film elasticity, while its 86–89 mol% hydrolysis improves remoistenability for envelope gums and label adhesives. Application is via roller coater or spiral nozzle at a wet coat weight of 20–30 g/m² on high-gloss stock. Drying in a hot air tunnel at 70–90°C for 10–30 s is sufficient to set the film; residual moisture below 8% prevents blocking during stacking. Bond strength of paper-to-paper laminates is tested by ISO 11339 T-peel, with accepted failure mode being fiber tear above 0.7 N/mm for lightweight paper laminates after 24 h conditioning at 23°C and 50% RH. For food packaging, the adhesive formulation is evaluated under FDA 21 CFR 175.105 or EU 10/2011, but the end-use compliance depends on the full formulation and the paper laminate, not on POVAL 8-88 alone. Open time should not exceed 45 s under low-humidity conditions without an additional humectant; otherwise skinning occurs at the transfer roller.
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Supplied as a white to pale-yellow granulate, KURARAY POVAL 8-88 is a partially hydrolyzed polyvinyl alcohol resin with a degree of hydrolysis controlled to 87.0–89.0 mol% and a dynamic viscosity of 7.0–9.0 mPa·s when measured as a 4% aqueous solution at 20°C. The grade designation follows the Kuraray nomenclature: the first numeral identifies the nominal viscosity class of 8 mPa·s, and the final two digits identify the nominal hydrolysis level of 88 mol%. The product is manufactured by saponification of polyvinyl acetate and retains a residual acetate content of approximately 11–13 mol%. Typical lot-release data are shown in Table 1. The product is used in emulsion polymerization, paper and textile sizing, water-borne adhesives, and temporary protective coatings where cold-water solubility, controlled viscosity build, and moderate film strength are required.
Table 1. Typical lot-release data for KURARAY POVAL 8-88.
| Property | Typical value |
|---|---|
| Appearance | White to pale-yellow granulate |
| Degree of hydrolysis | 87.0–89.0 mol% |
| Viscosity | 7.0–9.0 mPa·s at 4% and 20°C |
| pH | 4.5–7.0 in 4% aqueous solution |
| Volatile content | ≤5.0% |
| Ash content | ≤0.5% |
| Residual acetate | 11–13 mol% |
Typical values are determined using methods aligned with JIS K6726 or equivalent internal release methods. Customer specifications should fix the test method and lot-release limits because test-method variation can change the reported viscosity by several tenths of a millipascal-second.
The residual acetate groups in 8-88 act as steric disruptions along the polyvinyl alcohol chain. They reduce the average crystallite size and lower the melting endotherm compared with fully hydrolyzed grades. The practical consequence is solubility in cold water: a 4% aqueous dispersion can be dissolved under moderate agitation at 20°C within 30–60 min. Heating to 80–90°C shortens the dissolution cycle and reduces residual microgel, which is the preferred industrial protocol even though the grade is classified as cold-water soluble.
Compared with fully hydrolyzed grades at similar viscosity, 8-88 forms films with lower tensile stiffness and higher elongation after conditioning at 23°C and 50% RH. However, published data for plasticizer-free film specimens tested under ASTM D882 is limited; most industrial data are collected on formulated coatings or adhesives rather than on isolated PVOH films. The hydrolysis window also reduces the quantity of long hydrogen-bonded sequences that contribute to water resistance after drying. Consequently, 8-88 is not suitable for permanent water-resistant barrier films unless crosslinked or blended with less water-sensitive polymers.
For bulk dissolution, vertical cylindrical tanks with dished bottoms and center-mounted propellers are used. The powder is added through a mesh screen onto the liquid surface while the agitator operates at 100–300 rpm. If the batch temperature is raised above 60°C before the granules are fully wetted, the surface of the granule can gel and trap undissolved powder. After the temperature reaches 80–90°C, a hold time of 30–60 min is typically required for complete hydration. Dissolved solutions are then filtered through 100–200 µm stainless steel mesh to remove insoluble skins or foreign matter. Above 15 wt% solids, 8-88 solutions become pseudoplastic: the low-shear Brookfield viscosity rises sharply, while the high-shear viscosity remains processable for pumping and metering.
In vinyl acetate homopolymer and vinyl acetate-ethylene emulsion polymerization, 8-88 is charged as a pre-dissolved protective colloid rather than as a bulk rheology modifier. Published formulation data for PVOH-stabilized lattices typically place the protective colloid at 4–10 pphm, with the lower end used for low-viscosity lattices and the upper end for small particle size or high-solids systems. Because the 4% viscosity of 8-88 is 7.0–9.0 mPa·s, the grade builds less reactor viscosity than 18-88 while still providing more colloidal stabilization than very low-viscosity grades such as 3-98.
Production-scale charging is usually performed with an 8–10 wt% aqueous solution prepared in a separate vessel, filtered through 100–200 µm screens, and transferred by low-shear progressing cavity pump. In 10,000 L reactors, rapid addition of dry granulate directly to the hot monomer phase has caused localized swelling and lump formation; field experience indicates that slow addition of pre-dissolved 8-88 below the liquid surface reduces such defects. Mechanical aeration during transfer can increase foam, so the use of a center-mounted turbine at 100–300 rpm is preferred over high-shear rotor-stator devices. Residual acetate groups contribute to interfacial activity, but published data correlating acetate content with final particle size distribution in high-pressure ethylene systems for this specific grade is limited.
For film-forming and temporary protective coatings, 8-88 is dissolved into water at 8–12 wt% solids for wire-wound rod application. Size press and roll coater baths are often operated at lower polymer concentration, typically 5–8 wt%, because the low molecular weight of the grade produces low solution viscosity and can cause ribbing or streaking when the low-shear Brookfield viscosity falls below 100 mPa·s at 23°C. In pilot blade-coating trials, the use of 18-88 or a rheology modifier has been required above 150 m/min line speed to maintain uniform film weight.
Because the dried film remains cold-water-redispersible, 8-88 is used where the coating is removed by water or where re-wetting is part of the converting process. Oil and grease barrier performance of PVOH-coated paper is routinely evaluated with TAPPI T 454 or ISO 16532-1, but measured values depend on coat weight, drying rate, and plasticizer content. Permanent water resistance is not achieved with 8-88 alone, and typical published data for crosslinked barrier films based on this grade are limited.
Across paper surface sizing, 8-88 is combined with oxidized starch or styrene-acrylate surface sizes at 0.5–2.0% PVOH on total size solids in the size press. The bath temperature is commonly held at 60°C, and the target low-shear viscosity is 20–60 mPa·s to maintain runnability without misting. In such formulations, 8-88 contributes less viscosity build than 18-88 while still reducing surface pick and improving IGT pick resistance as tested under ISO 3783. Surface sizing efficacy is also evaluated by Hercules size test under TAPPI T 530; the change in seconds-to-penetration is sheet-porosity and coat-weight dependent, so a specific value for 8-88 cannot be assigned without trial.
Textile warp sizing with 8-88 is carried out on slasher lines where the size liquor contains a PVOH/starch blend at 30–50% PVOH on dry solids. Because the partial hydrolysis lowers the dissolution temperature, desizing is performed at 60–70°C rather than the 80–90°C often required for fully hydrolyzed grades. Production line experience indicates reduced warp hairiness and fewer broken ends, but published data for specific yarn counts and slasher speeds using 8-88 is limited.
Table 2 compares 8-88 with 3-98 and 18-88, which are commonly quoted as alternative grades when viscosity or hydrolysis must be changed. Values are typical commercial datasheet ranges, not customer-specific certified limits.
| Grade | Degree of hydrolysis | Viscosity at 4% and 20°C | Application consequence |
|---|---|---|---|
| KURARAY POVAL 3-98 | 98.0–99.0 mol% | 3.2–4.0 mPa·s | Hot-water-soluble; higher crystallinity after drying; lower viscosity but stronger water resistance in the dried state. |
| KURARAY POVAL 8-88 | 87.0–89.0 mol% | 7.0–9.0 mPa·s | Cold-water-soluble; moderate viscosity build; balance between film strength and processing. |
| KURARAY POVAL 18-88 | 87.0–89.0 mol% | 17.0–19.0 mPa·s | Cold-water-soluble; higher viscosity and film strength; may require lower solids or higher processing temperature. |
In paper sizing, 8-88 penetrates more than 18-88 at equivalent bath solids but leaves a thinner compacted surface film than 18-88. In adhesive compounding, formulators select 8-88 when open time and redispersibility are more important than maximum tensile strength. In emulsion polymerization, replacing 8-88 with 18-88 raises latex viscosity and can shift the particle size distribution toward coarser particles if nucleation is shear-limited; replacing with 3-98 removes cold-water solubility and may require a post-polymerization surfactant addition. Published comparative data under identical reactor conditions for all three grades is limited, so these differences are directional and should be confirmed by pilot trials.
Aqueous solutions of 8-88 are biologically degradable and can develop microbial growth within 24–48 h when stored at 20–30°C without preservative. The native pH range of 4.5–7.0 does not prevent bacterial or fungal proliferation. For storage beyond 48 h, an approved preservative or refrigerated storage below 10°C is required.
Prolonged heating above 95°C may cause acid-catalyzed hydrolysis of residual acetate groups, leading to a gradual increase in water solubility but a decrease in solution viscosity. The recommended dissolution protocol is to add the granulate slowly to cold water under agitation, then heat to 80–90°C for 30–60 min. Excessive vortex formation at impeller tip speeds above 1.5 m/s increases air entrainment and foam; vacuum deaeration or a shear-stable defoamer at 0.05–0.2 wt% on solution weight is used when foam interferes with coating or adhesive transfer.
Borate ions present in borax or boric acid can crosslink the 1,3-diol structures of PVOH and produce sudden gelation. Borate-containing additives should be introduced as a dilute feed with continuous viscosity monitoring using a Brookfield viscometer at 23°C, and a maximum dose should be established for each formulation. Contact with strong oxidizing acids or iron-contaminated vessels can accelerate oxidative chain scission, so stainless steel or lined equipment is specified for long-term storage.
Where converters require indirect food-contact compliance, 8-88 is evaluated against the relevant national listing. In the United States, polyvinyl alcohol may be used as a component of food-contact articles under FDA 21 CFR 177.1670, provided migration levels and end-use restrictions are met. In the European Union, final compliance is assessed under EC 1935/2004 and the applicable plastics measure, not solely from the resin datasheet. The ash content of ≤0.5% and volatile matter ≤5.0% are release parameters, not migration limits. Published extraction data for this specific grade is limited, so converters should qualify the formulated article under the intended food type and temperature condition.
Because 8-88 carries a partial acetate residue, it is used as a secondary film former and rheology modifier in water-borne adhesive systems rather than as a structural binder for load-bearing joints. In starch/dextrin packaging adhesives, addition of 1–5 wt% PVOH on dry solids is used to modify low-shear viscosity and machine stability. Viscosity stability during the production run is monitored with a Brookfield viscometer at 23°C; initial tack on recycled board is formulation-dependent and is evaluated by converter-specific loop tack methods rather than a single standardized test.
Compatibility with borate-crosslinked starch formulations is limited. The same borate dose that gels the starch phase may react with PVOH and produce visible lumping; a pilot pre-test with a Brookfield viscometer at 23°C and a 100 µm filter is used to define the maximum borate dose before production. The product should not be dry-blended with oxidizing agents or stored in unlined carbon steel vessels where iron pickup may accelerate chain scission. In multi-product plants, separate lines or thorough washing protocols are required to avoid contamination with hydrophobic latex polymers that can destabilize the aqueous PVOH solution.
