| HS Code | 348084 |
| Product Name | KURARAY POVAL 22-88 S2 |
| Cas Number | 9002-89-5 |
| Chemical Family | Polyvinyl alcohol (partially saponified) |
| Appearance | White free-flowing granules/powder |
| Viscosity 4 Aqueous Solution 20 C | 22 mPa·s |
| Degree Of Hydrolysis Saponification | 88 mol% |
| Average Degree Of Polymerization | Approximately 1700 |
| Ph 4 Aqueous Solution | 5.0–7.0 |
| Solubility | Soluble in hot water; insoluble in common organic solvents |
| Density 20 C | Approximately 1.27 g/cm³ |
| Ash Content | ≤ 0.5% |
| Volatile Content | ≤ 5.0% |
| Melting Point Decomposition | Decomposes above 150°C |
| Particle Size Grade | S2 fine particle grade |
As an accredited KURARAY POVAL 22-88 S2 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | KURARAY POVAL 22-88 S2 is supplied in 25 kg multi-walled paper bags with PE liner, ensuring dry, safe handling. |
| Container Loading (20′ FCL) | 20′ FCL container loading for KURARAY POVAL 22-88 S2: packed in 20 kg bags on pallets, shrink-wrapped, secured. |
| Shipping | KURARAY POVAL 22-88 S2 ships as a free-flowing powder in multi-layer paper bags on pallets, wrapped and protected from moisture. It is non-hazardous for transport under international regulations, suitable for standard road, sea, or rail freight. Keep sealed and dry during transit; avoid humidity to preserve quality. |
| Storage | Store KURARAY POVAL 22-88 S2 in its original, tightly closed container in a cool, dry, well-ventilated area. Protect from moisture, humidity, and direct sunlight. Keep away from flames, hot surfaces, and oxidizing agents. Avoid dust formation and accumulation. Maintain moderate temperatures and handle with clean, dry equipment to preserve product quality. |
| Shelf Life | Shelf life is typically 2 years from production date when stored unopened in a cool, dry place. |
In the manufacture of poly(vinyl acetate) homopolymer and vinyl acetate–ethylene copolymer emulsions, KURARAY POVAL 22-88 S2 functions as the primary protective colloid. A stock solution at 10–15 wt% solids is prepared in a jacketed make-up vessel equipped with a low-shear anchor agitator. Cold-water predispersion proceeds at 20–25 °C. The slurry is then heated under agitation to 85–90 °C and held for 45–60 min. The solution is metered into the reactor at 2–8 phm based on total vinyl acetate monomer. The 88 mol% hydrolysis level and 22 mPa·s viscosity of the 4% aqueous solution, measured according to JIS K6726, create a balance between grafted-layer hydrophilicity and acetate compatibility. During polymerisation at 70–80 °C, vinyl acetate radicals abstract hydrogen from the PVA backbone. The result is PVA-g-PVAc graft copolymer that anchors to the particle surface. This mechanism controls particle nucleation. It also prevents coalescence without excessive viscosity build-up. A process conflict appears at reaction temperatures above 85 °C. The protective adsorbed layer collapses as the cloud point of partially hydrolysed PVA is approached. Free PVA may phase-separate. The particle size distribution broadens from a typical 0.8–2.0 µm to coarser populations when measured by laser diffraction according to ISO 13320. Sieve residue above 100 µm increases. The reactor charge is therefore split. 60–70% of the PVA solution is added before initiator feed. 30–40% is delayed over the first 60 min of monomer addition. The finished dispersion typically shows Brookfield viscosity of 5,000–20,000 mPa·s at 50 rpm and 25 °C according to ISO 2555. Solids content is 50–55%. pH is 4.0–5.5. The emulsion is formulated into D3 and D4 wood adhesives under EN 204/205, interior architectural paints, and paper lamination adhesives.
In acrylic pressure-sensitive adhesive production, PVA protective colloids are not the primary emulsifier. Carboxylated acrylic latices require anionic surfactant stabilisation. 22-88 S2 is introduced at 1–3 wt% of total monomer only to raise shear stability in transfer pumps. It also adjusts high-shear viscosity in roll-coating operations. The addition threshold is narrow. Below 1 wt%, no measurable reduction in coagulum formation occurs. Above 3 wt%, the dried adhesive film retains water-soluble domains. These domains reduce water resistance and lower loop tack on stainless steel. The formulation is prepared as a 15% aqueous solution. It is metered into the pre-emulsion before redox initiation. In a 2,000-L reactor with a 3-blade pitched impeller running at 120 rpm, post-addition viscosity at 25 °C increases from 250–400 mPa·s to 600–900 mPa·s at 50 rpm. Coagulum is collected on a 250 µm filter after 4 h of polymerisation. At 2 wt% PVA, coagulum is typically below 0.05% of wet monomer. Dried films of 25 µm thickness are tested for peel adhesion by ASTM D3330/D3330M-04 on stainless steel. Humidity ageing is performed at 40 °C and 90% RH for 500 h. Published data for specific acrylic comonomer compositions is limited. Each surfactant package must be validated. Interactions with nonylphenol ethoxylate-free anionic surfactants can produce stringy coagulum above 80 °C. End products are removable labels, splicing tapes, and protective films where moderate water sensitivity is acceptable.
Surface sizing of copy paper and packaging board uses 22-88 S2 at 0.5–2.0 wt% of size-press bath solids as a starch modifier. Oxidised corn starch is cooked in a continuous jet cooker at 130–140 °C for 60–120 s. PVA is dissolved separately at 15% solids. The PVA stock solution is dosed into the starch holding tank at 55–65 °C. The meter size press applies 2–5 g/m² of size solids per side at machine speeds of 800–1,200 m/min. The 22 mPa·s stock solution contributes film flexibility. It reduces dusting without raising the Brookfield viscosity of the blend above 50–150 mPa·s at 60 °C. A process boundary appears at PVA addition above 2.5 wt% of size solids. Above this level, film split at the size press becomes unstable. Reel surface tack increases under calender temperatures above 80 °C. Water absorption is measured by ISO 535. A 60 s Cobb value of 20–30 g/m² is typical for unsized base paper. The value falls to 15–20 g/m² after treatment. Surface strength is measured by ISO 3783. The IGT value improves from 1.5–2.0 m/s to 2.5–3.5 m/s on woodfree paper. The grade is suitable for food-contact paper and board under FDA 21 CFR 176.170 and FDA 21 CFR 176.180, and under EU 10/2011 provided extraction limits are met. End products are laser-print copy paper, recycled folding carton board, and inkjet pre-coats.
Ceramic tape casting of alumina and zirconia substrates uses 22-88 S2 as a thermoplastic binder in aqueous slips. The binder is added at 2–6 wt% of dry ceramic powder. A 10% aqueous solution is prepared and blended with dispersant-stabilised slurry at pH 9–10. Doctor-blade casting follows. Tape thickness is controlled at 100–500 µm with a blade gap of 200–800 µm. Casting speed is 0.5–2.0 m/min. The 88 mol% hydrolysis degree provides low gelation tendency with borate-free ceramic additives. The 22 mPa·s viscosity allows uniform binder distribution. It avoids excessive slip viscosity. Green tape tensile strength is typically 2–5 MPa when measured by a modified tensile bar method. Published standardised test methods for green ceramic tape are limited. Conflicts arise in low-temperature co-fired ceramic applications. The sodium ash residue from PVA is below 0.5% by JIS K6726. Even this level shifts dielectric loss in certain low-K dielectric formulations when binder addition exceeds 4 wt%. For those formulations, binder content is capped at 2 wt%. Burnout is extended. Debinding uses a two-step profile. Heating proceeds at 0.5–1.0 °C/min from 200 °C to 350 °C in air. A second ramp at 1.0–2.0 °C/min extends to 450 °C with a 2 h hold. Sintered density is measured by the Archimedes method according to ISO 18754. Density must reach 95–98% of theoretical density. Incomplete binder removal produces carbon residues. These residues reduce translucency in alumina substrates. End products are alumina electronic substrates, multilayer capacitors, and zirconia oxygen sensor elements.
On air-jet weaving machines running 700–900 picks/min, 22-88 S2 is blended with oxidized starch and acrylate size in the size box at 8–12% total solids. The PVA fraction is 20–40% of total size solids. The size is applied at 60–70 °C onto spun cotton and polyester–cotton yarns. Add-on is 8–15% o.w.f. The 22 mPa·s grade enables squeeze-roll penetration into the yarn structure. It also maintains surface film formation on yarn surfaces. Mill trials show weaving efficiency above 90% at up to 75% RH. Beyond this humidity, dried size film on the loom becomes tacky and shedding increases. Desizing is performed at 60–90 °C with hot water or oxidative chemistry. Starch-containing sizes require amylase treatment. Desizing efficiency is evaluated by the TEGEWA violet scale for starch/PVA residues. PVA recovery by ultrafiltration is feasible because the grade has high molecular-weight retention relative to low-viscosity grades. The end product is greige fabric for denim, shirting, and home textiles.
In adhesive lamination of paper, metallised polyester, and aluminium foil for flexible packaging, 22-88 S2 is used as a film-forming component in water-based adhesive formulations at 2–5 wt% of wet adhesive solids. The grade is dissolved at 15% solids. It is post-added to a vinyl acetate–ethylene copolymer dispersion. Crosslinkers reduce water sensitivity. Glyoxal or ammonium zirconium carbonate is added at 0.5–2.0% of PVA solids. Pot life after crosslinker addition is 8–24 h at 25 °C. The adhesive is applied by gravure cylinder at 3–6 g/m² dry coat weight. Drying occurs in a three-zone oven at 70 °C, 90 °C, and 110 °C. Nipping follows at 60–80 °C. Bond strength is measured according to ASTM D1876. Values of 2.5–4.0 N/15 mm are typical on paper/aluminium foil after 7 d. Under tropical conditions at 38 °C and 90% RH, uncrosslinked PVA films lose more than 50% of initial bond strength within 48 h. Crosslinked films retain 70–85% of initial strength. Borax or boric acid is avoided. Borate ions react with 1,2-diol groups in PVA to form a gel network. This gel blocks gravure cells. Compliance for food contact is established under FDA 21 CFR 175.105 for adhesive components. Where the laminate functions as a barrier, FDA 21 CFR 176.170 and FDA 21 CFR 176.180 apply. End products are dry food pouches, confectionery wrappers, and lidding films.
Converters handling 22-88 S2 in bulk prepare stocks at 15–20% solids using a cylindrical make-up tank with a bottom-entry high-shear disperser running at 1,500 rpm. The powder is added through an eductor or aspirator into a vortex at 20–25 °C. This prevents lump formation. The slurry is then heated to 90–95 °C and held for 45–60 min. A 20% solution at 25 °C has a viscosity of 20,000–40,000 mPa·s depending on shear rate. The 4% solution used for specification testing gives 22 mPa·s at 20 °C by JIS K6726. pH is maintained at 4.5–7.0. Outside this range, viscosity drift can occur through acetate hydrolysis. Filtration through a 100 µm stainless steel screen is required before metering pumps. Thermal exposure above 100 °C for more than 2 h discolours the solution from water-white to amber. Insoluble gel content can increase. Storage at 5–25 °C prevents microbial growth. Below 5 °C, solutions may gel but revert upon reheating to 60 °C. No published universal stability limit exists for mixed stock solutions containing starch or plasticiser. Compatibility testing in a 1 L jacketed glass reactor is recommended before scale-up. The S2 particle morphology is designed for rapid cold-water wetting. Sieve residue and bulk density data are lot-specific and must be confirmed against the certificate of analysis.
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KURARAY POVAL 22-88 S2 is a partially hydrolysed polyvinyl alcohol resin produced by alcoholysis of polyvinyl acetate. The first numeric segment of the grade designation identifies the nominal viscosity of a 4.0 % aqueous solution at 20 °C, and the second segment identifies the nominal degree of hydrolysis. For the 22-88 series, those values are 22 mPa·s and 88.0 mol %, respectively. The S2 suffix is a product-form code, not a chemical alteration; it denotes a granular delivery form intended for low-dust handling and controlled gravimetric feeding. Published trade-literature data list the hydrolysis band at 87.0–89.0 mol %, corresponding to a residual acetate content of 11.0–13.0 mol %. The aqueous solution pH of a 4 % mixture at 20 °C is generally 3.5–8.0. Volatile matter by loss on drying at 105 °C is typically specified at ≤ 5.0 wt %, and ash at ≤ 0.5 wt % as Na₂O. Test methods are commonly aligned with JIS K6726 and ISO 15023-2. The partial hydrolysis differentiates the product from fully hydrolysed grades: the acetate units disrupt interchain hydrogen bonding, lower crystallinity, reduce dissolution temperature, and increase adhesion to hydrophobic surfaces while lowering dry-film water resistance and tensile modulus.
| Property | Basis | Typical value/range |
|---|---|---|
| Degree of hydrolysis | JIS K6726 / ISO 15023-2 | 87.0–89.0 mol% |
| Viscosity, 4 % aqueous solution | 20 °C | 20–25 mPa·s |
| Residual acetate content | Calculated from hydrolysis | 11.0–13.0 mol% |
| Volatile matter | 105 °C | ≤ 5.0 wt% |
| Ash as Na₂O | JIS K6726 | ≤ 0.5 wt% |
| pH, 4 % aqueous solution | 20 °C | 3.5–8.0 |
Process records from adhesive and paper-coating lines show that the main dissolution failure is not true insolubility but particle hydration and agglomeration. When the granulate contacts water, a gel-like skin forms on each particle; if agitation is insufficient, the skins merge into lumps that resist further water penetration. The standard preparation sequence is to disperse the product in cold water at 20–30 °C under turbulent agitation, then heat the batch to 85–95 °C and hold for 30–45 min. In a baffled jacketed vessel fitted with a high-shear disperser, an impeller tip speed of 2.5–5.0 m/s prevents settling and agglomeration. Tip speeds above 5.0 m/s can entrain air and generate persistent foam because the polymer is surface-active. Direct addition to water above 60 °C is an operational boundary; it produces gelatinous lumps and increases fouling on baffles and temperature probes. Solutions above 10 wt % become strongly pseudoplastic and require elevated transfer temperatures. Viscosity is checked at 20 °C after cooling with a Brookfield RVT viscometer at 20 min⁻¹ and compared with the nominal 22 mPa·s at 4 %. Hot solutions at 15–20 wt % used for adhesive compounding are usually transferred through jacketed lines maintained at 60–70 °C to avoid surface skinning. Salts that reduce water activity, such as sodium sulphate, raise the minimum dissolution temperature and may require longer hold times.
For large-scale dissolution, eductor or venturi wetting systems can reduce dust exposure, but they do not remove the need for a heated maturation stage. Filtration through a 100 µm screen after cooling provides a practical gel-particle check; filter blinding indicates insufficient dispersion or insufficient heat history. The S2 granular form wetts more slowly than fine powder grades but produces less dust. That trade-off makes the cold-water pre-slurry stage more important for the S2 product form than for milled powder variants.
Vinyl acetate and vinyl acetate–ethylene emulsion polymerisation use partially hydrolysed polyvinyl alcohol as a protective colloid. The 22-88 S2 grade is introduced as a warmed aqueous solution at 2–6 parts per hundred parts monomer by weight. At 2 pphm, the colloid supports particle formation but can result in a wider particle-size distribution and higher coagulum under high-shear transfer. At 6 pphm, final emulsion viscosity rises sharply, and dried-film water resistance declines because the protective colloid remains in the cast film. The viscosity-average molecular size associated with the 22 mPa·s grade increases grafting density and final emulsion viscosity more than the degree of hydrolysis. This behaviour differentiates the grade from 5-88, which gives lower thickened viscosity and weaker adhesive green strength, and from 28-99, which gives higher minimum film-forming temperature and greater water resistance but less hydrophobic surface wetting. The partially hydrolysed structure also permits lower-temperature film coalescence in wood adhesives and improves tack development on porous substrates.
In polymerisation reactors, the aqueous solution of 22-88 S2 is usually prepared at 10–20 wt % and buffered with 0.1–0.3 wt % sodium bicarbonate on solution basis to maintain pH 5–7 during polymerisation. Reactor fouling is observed when the colloid solution is charged too quickly to a monomer pre-emulsion because local viscosity can rise before adequate mixing. The S2 granular form does not alter this mechanism, but its particle-size distribution affects dissolution time in the colloid make-up tank. Concentrated solutions at 15–20 wt % can reach several thousand mPa·s at 60 °C, so diaphragm or positive-displacement pumps are preferred over centrifugal pumps for transfer.
Water-soluble film converting and unit-dose packaging use partially hydrolysed polyvinyl alcohol because dissolution temperature can be adjusted by grade selection and plasticizer. Cast films based on 22-88 S2 dissolve under mechanical agitation at lower temperatures than films made from fully hydrolysed grades; practical dissolution endpoints in unit-dose applications are commonly evaluated in water at 10–30 °C, although agitation, film thickness, and plasticizer type shift the measured time. Typical plasticizers include glycerol, sorbitol, and trimethylolpropane at 5–20 parts per hundred resin by weight. The S2 granular form is suited to melt compounding on single-screw or twin-screw extruders with L/D ratios of 24:1 to 40:1. Barrel temperatures are normally held below 220 °C because thermal degradation accelerates above 200 °C and releases acetic acid, aldehydes, and unsaturated hydrocarbons. Pre-drying at 80–105 °C for 2–4 h is used when the resin has been stored at relative humidity above 60 %; otherwise water vapour in the melt creates bubble defects and shifts melt viscosity. Compared with fully hydrolysed PVOH, the partially hydrolysed 22-88 S2 film has lower oxygen barrier and lower tensile strength but better flexibility and lower heat-seal temperature.
Borax and boric acid react with the 1,3-diol units in polyvinyl alcohol to form reversible didiol complexes. In a 4 % aqueous solution of 22-88 S2, borax additions of 0.2–1.0 wt % on solution weight produce a marked viscosity increase and a yield stress; the exact response depends on pH, polymer concentration, and temperature. Above pH 8, the borate anion is the active crosslinking species and gelation is stronger. This chemistry is used deliberately for adhesive tackification and temporary protective coatings, but it creates a processing boundary. Dry borax added directly to a PVOH solution under low shear forms local gel particles that do not disperse below 60 °C. The standard correction is to add borax as a dilute aqueous side stream under high shear. Because the didiol complex is reversible, gel deposits in transfer lines can often be removed with hot water above 80 °C, but dead-leg sections and filter housings may require mechanical cleaning. Formulations containing borax should not be stored below 5 °C because syneresis and phase separation can occur.
This boundary also applies to unit-dose detergent packaging. Borate-containing detergent powders in contact with a PVOH film can crosslink the film surface and leave insoluble residue during laundry dissolution. Formulation design for such articles therefore limits free borate in the filled product or separates the film from direct borate contact. The 22-88 S2 grade itself is not borate-modified; the effect arises from external borate in the end-use formulation.
Paper surface sizing with 22-88 S2 is performed at size-press solids of 2–8 wt %. The partial hydrolysis provides better affinity to hydrophobic recycled fibre surfaces than fully hydrolysed grades, but the dried film is softer and less water-resistant. The grade is often blended with starch or styrene-acrylic copolymer dispersions to balance surface strength, pick resistance, and cost. In textile warp sizing, 22-88 S2 is used for polyester and cotton blends. The residual acetate groups improve adhesion to polyester filament and allow clean desizing in hot water at 70–90 °C; the PVOH fraction does not require amylase. Compared with fully hydrolysed 28-99, the partially hydrolysed grade has lower abrasion resistance in the dried warp, so weaving mills control humidity to maintain film flexibility. The main processing limitation is the tendency of the size bath to foam under high-shear pumping; defoamers are used, but silicone-based defoamers can interfere with downstream dyeing and should be evaluated before use.
Food-contact use is article-specific. Polyvinyl alcohol may be assessed as a component in adhesives under 21 CFR 175.105 or in paper and paperboard under 21 CFR 176.170; the final article’s extraction limits control compliance. For industrial applications, the grade is supplied under EU REACH. No intentionally added heavy metals are present, and RoHS screening for finished components is normally limited to the assembled article. Storage records show that moisture uptake becomes measurable above 60 % relative humidity and accelerates above 80 % RH. Recommended storage is below 30 °C in closed containers. The product is combustible as a dust; silo and hopper transfer systems should include earthing and dust extraction. Avoid strong oxidising agents because exothermic oxidation can occur, and avoid strong acids or bases at elevated temperature because they accelerate hydrolysis or esterification and change solubility.
