| HS Code | 346052 |
| Product Name | SELVOL Polyvinyl Alcohol 518 |
| Chemical Name | Polyvinyl alcohol |
| Cas Number | 9002-89-5 |
| Appearance | White to cream granular powder |
| Degree Of Hydrolysis | 87.0 - 89.0 mol% |
| Viscosity 4 Solution At 20 C | 23.0 - 27.0 mPa·s (cP) |
| Ph 4 Aqueous Solution | 4.5 - 6.5 |
| Specific Gravity | 1.25 - 1.30 |
| Bulk Density | 0.4 - 0.6 g/cm³ |
| Ash Content | ≤ 0.5 wt% |
| Volatile Matter | ≤ 5.0 wt% |
| Solubility | Soluble in hot water; insoluble in most organic solvents |
| Melting Point | 180 - 200°C (approximate) |
As an accredited SELVOL Polyvinyl Alcohol 518 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | SELVOL Polyvinyl Alcohol 518 is supplied in 25 kg multi-wall paper bags with an inner polyethylene liner for moisture protection. |
| Container Loading (20′ FCL) | 20′ FCL: palletized bags of SELVOL Polyvinyl Alcohol 518 loaded securely in a dry, clean, ventilated container for safe transport. |
| Shipping | SELVOL Polyvinyl Alcohol 518 ships as a dry, free-flowing powder in sealed bags or containers to prevent moisture pickup. Keep away from ignition sources and strong oxidizers. Use covered, dry trailers; avoid dust generation. No special hazmat designation required under usual conditions. |
| Storage | Store SELVOL Polyvinyl Alcohol 518 in a cool, dry, well-ventilated area away from direct sunlight and moisture. Keep containers tightly closed when not in use to prevent clumping. Avoid dust accumulation and sources of ignition. Ensure separation from oxidizing agents and strong acids. Follow all label and safety data sheet instructions. |
| Shelf Life | Shelf life is typically 2 years from manufacture when stored sealed, dry, and cool; avoid moisture to prevent degradation. |
In batch emulsion polymerization of vinyl acetate monomer, Selvol 518—a partially hydrolyzed polyvinyl alcohol with 87–89 mol% hydrolysis and a 4% aqueous viscosity of 5.0–6.0 mPa·s at 20 °C—is applied as a pre-dissolved 10–15 wt% aqueous solution and charged at 3.5–5.5 wt% based on total vinyl acetate monomer. The pre-dissolution step uses a jacketed mix tank at 85–90 °C for 45–60 min with a turbine agitator at 30–60 rpm, followed by cooling to 50–60 °C before monomer seeding to limit thermal shock. In the 5,000–10,000 L polymerization reactor, a 45° pitched-blade turbine at 80–120 rpm and tip speed of 1.2–2.0 m/s maintains dispersion stability during the 3–4 h delayed monomer feed; redox initiation with 0.03–0.08 wt% persulfate and sodium metabisulfite is staged to maintain a 72–78 °C exotherm. Residual vinyl acetate is reduced to below 0.1 wt% by vacuum stripping at 60–65 kPa absolute. At charge levels below 3.0 wt%, coalescence and supernatant formation are observed within 24 h of finishing; at levels above 5.5 wt%, final dispersion high-shear viscosity increases beyond 20,000 mPa·s without corresponding wood bond strength improvement. Under these conditions, the grade contributes to final dispersion viscosity typically 8,000–20,000 mPa·s at pH 4.0–5.5. Compliance for adhesive formulations is assessed under EN 204:2012 D3 and ASTM D905-08 shear tests, while food-contact laminating adhesives fall under FDA 21 CFR 175.105. Compounded terminal products include D2/D3 wood assembly glues, paper tube winding adhesives, bookbinding emulsions, and heat-seal coatings for flexible packaging.
For water-activatable gumming on 70–90 g/m² envelope stock, Selvol 518 is dry-compounded at 60–75 wt% of total solids, with the balance comprised of dextrin, polyhydric alcohol plasticizer at 5–12 wt%, and defoamer at 0.05–0.20 wt%. The dry blend is dispersed into deionized water at 25–35 °C and heated to 85–90 °C under low-shear mixing until clear, then held for 45 min to eliminate microgels before coating. Coating is performed on a reverse-roll or slot-die line at 40–120 m/min with wet deposition of 12–25 g/m², followed by forced-air drying at 95–115 °C and moisture equilibration to 4–7% final moisture. Blocking resistance under 85% RH is governed by residual plasticizer and film crystallinity: glycerin above 12 wt% accelerates rewetting but increases blocking, while below 5 wt% film becomes brittle during die-cutting. Compliance for indirect food-contact mailers is covered by FDA 21 CFR 175.105 for the adhesive layer and 21 CFR 176.170 for the paper component; blocking resistance of the converted adhesive film is characterized by EN 12704. Finished article types include postage stamps, envelope flaps, tamper-evident labels, and wallpaper joints.
When a 20/1 Ne cotton warp is run at 60–80 m/min on a multi-cylinder slasher, a size mix containing 8–12 wt% total solids may include Selvol 518 at 6–10 wt% of the mix as the primary film former, with the remainder comprised of starch or polyester resin, lubricant at 0.2–0.5 wt%, and defoamer. Compliance for woven fabric sold into EU apparel requires adherence to OEKO-TEX Standard 100 Annex 4 limits for formaldehyde and APEO, while Zero Discharge of Hazardous Chemicals MRSL v3.1 restricts size agents that persist in wastewater. Squeeze roll pressure set at 18–25 kN/m produces wet pick-up of 85–110%; cylinder drying zones are staged from 110 °C to 130 °C to avoid surface skinning and preserve yarn elongation. Yarn tensile retention after sizing is measured by ISO 2062:2009, with typical elongation loss below 15%. Finished greige fabrics include plain-weave shirting, workwear twill, and polyester-cotton sheeting.
Surface sizing of bleached kraft linerboard with aqueous Selvol 518 at 2–6 wt% solids is performed on a film press or metering size press at 300–600 m/min; dry pick-up is controlled to 0.4–1.8 g/m² per side. In coating color, addition is 0.5–2.5 wt% of total color solids as a co-binder, with replacement of no more than 30% of the styrene-butadiene latex share to maintain coating flexibility. Compliance for food-contact board relies on FDA 21 CFR 176.170 and 176.180, while surface strength is measured via IGT pick test ISO 3783:2006 and water absorption is measured by ISO 535:2014. Film split at the metering nip is affected by the 4% aqueous viscosity of Selvol 518 at 25 °C, which is 5.0–6.0 mPa·s; addition above 6 wt% solids increases size press misting and reduces nip stability. Drying after size press uses infrared and air flotation from 90 °C to 140 °C to raise sheet surface temperature to 70–85 °C. End products include release liner base papers, inkjet papers, and folding carton board.
Spray-dried ceramic granules for uniaxial pressing use Selvol 518 as a temporary binder at 0.8–2.5 wt% of dry ceramic powder; the slurry at 55–65 wt% solids is spray-dried at 180–220 °C inlet and 90–110 °C outlet, and the binder is removed by burnout at 400–550 °C with a heating rate below 2 °C/min. Industrial use of polyvinyl alcohol is addressed under the EU REACH polymer exemption, and workplace exposure is managed under national occupational exposure limits; compliance for final parts may require ISO 9001 process control and ASTM C373-18 for fired porosity. Finished pressed and sintered components include alumina electronic substrates, ferrite cores, and zirconia oxygen sensor housings.
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SELVOL Polyvinyl Alcohol 518 is a partially hydrolyzed polyvinyl alcohol resin produced by Sekisui Specialty Chemicals. The product designation encodes a nominal viscosity of 18 mPa·s measured on a 4 wt% aqueous solution at 20 °C using Brookfield rotational viscometry per ISO 2555. Degree of hydrolysis is controlled in the 87.0–89.0 mol% band, with residual acetate functionality contributing to cold-water solubility, reduced crystallinity, and interfacial activity. The polymer is supplied as a white granular solid with volatile content not exceeding 5.0 wt% and ash content ≤0.5 wt% after ignition. Applications include vinyl acetate and vinyl acetate-ethylene emulsion polymerization, water-based adhesives, paper surface sizing, textile warp sizing, and specialty water-soluble films. Because the grade occupies the intermediate viscosity range of the partially hydrolyzed series, it is typically selected where both film strength and processable solution viscosity are required without high-temperature dissolution.
The specification window is defined by degree of hydrolysis and aqueous solution viscosity. Hydrolysis is determined by saponification titration per JIS K6726; viscosity is determined by Hoeppler falling-ball or Brookfield rotational viscometry per ISO 2555. The values below are typical for lot release.
| Property | Test method | Value |
|---|---|---|
| Degree of hydrolysis | JIS K6726 | 87.0–89.0 mol% |
| Viscosity, 4 wt% solution, 20 °C | ISO 2555 / JIS K6726 | 16–20 mPa·s |
| pH, 4 wt% solution | ASTM E70 | 4.5–6.5 |
| Volatile content | ISO 3251 | ≤5.0 wt% |
| Ash content | ISO 3451-1 | ≤0.5 wt% |
The partial hydrolysis band yields a polymer with lower crystallinity than fully hydrolyzed grades. Film cast from a 10 wt% solution and conditioned at 50% RH shows tensile strength typically in the 40–55 MPa range and elongation at break of 100–200% when tested by ISO 527-3; published data for this specific configuration is limited, and plasticizer content and humidity shift these values. Cold-water dissolution at 25–40 °C occurs within 30–60 min under medium-shear mixing at 500–1000 rpm. At concentrations above 20 wt%, solution viscosity exceeds 500 mPa·s and transfer pumping should use progressive cavity or diaphragm pumps rather than centrifugal pumps to avoid shear heating and gel particle formation.
Regulatory compliance available for the grade includes use in food-contact adhesives and paper coatings under 21 CFR 175.300, 21 CFR 176.170, 21 CFR 176.180, and 21 CFR 177.120 when used according to applicable migration limits. The product is listed in the EU REACH inventory under polyvinyl alcohol CAS 9002-89-5; no substances of very high concern are present above 0.1 wt% per Regulation (EC) No 1907/2006. Compliance with RoHS Directive 2011/65/EU is not directly applicable to this organic polymer but is routinely confirmed for lead, cadmium, mercury, and hexavalent chromium at the 100 ppm homogeneous material threshold.
In vinyl acetate and vinyl acetate-ethylene (VAE) emulsion polymerization, SELVOL 518 is dissolved in deionized water at 15–20 wt% and charged to a jacketed stirred-tank reactor. A dual-tier Rushton turbine or pitched-blade turbine with a diameter-to-tank ratio of 0.33–0.45 is used; agitator tip speed is held at 7.0–9.4 m/s. The protective colloid is added at 3–6 wt% on total monomer. During reaction at 70–80 °C, aqueous phase viscosity rises from 50 mPa·s to 200 mPa·s. Residual acetate groups adsorb at the monomer-water interface and participate in radical grafting with poly(vinyl acetate); this grafted layer provides steric stabilization and controls particle size distribution. Laser diffraction measurement per ISO 13320 typically yields a Dv50 of 0.5–2.0 μm for SELVOL 518-stabilized latices.
Process conflict arises above 85 °C, where partial-grafted PVA may lose interfacial solubility and increase coagulum in the reactor and downstream filters. Therefore jacket temperature is ramped in two stages: initiation at 65 °C and hold at 75–80 °C. Batch-to-batch hydrolysis variation of only 0.5 mol% within the 87–89 mol% band can shift Dv50 by 0.3–0.5 μm; operators compensate by adjusting initiator feed rate by 5–10% or raising agitator speed by 10 rpm. For VAE grades, ethylene pressure is maintained at 20–40 bar, and monomer feed is staged over 3–5 h to prevent free monomer accumulation. Redox initiation with sodium persulfate at 0.1–0.3 wt% on monomer and sodium metabisulfite at 0.05–0.15 wt% provides controlled radical flux without excessive exotherm.
On a 10 m³ production reactor with a 1.5 m impeller diameter, the observed failure mode at low agitation is a bimodal particle size distribution with a coarse fraction above 10 μm. This coarse fraction blocks 100 mesh discharge filters and reduces latex mechanical stability. Maintaining the pre-dissolved colloid solution at 90 °C for 60 min before cooling to reaction temperature eliminates microgel nuclei that otherwise seed the coarse fraction.
In PVC suspension polymerization, SELVOL 518 is used as a secondary dispersant at 0.02–0.10 wt% on monomer in combination with a primary dispersant of lower hydrolysis. The secondary dispersant thickens the monomer droplet interface and reduces droplet coalescence during the critical pressure-drop phase of vinyl chloride polymerization at 55–65 °C. This application requires controlled cold-water solubility, because fully hydrolyzed PVA tends to precipitate from the aqueous phase in the presence of vinyl chloride monomer. Published data for this specific configuration is limited; industrial use is typically validated by reactor trials rather than published standard tests.
Where remoistenable and water-rewettable adhesives require open time and quick tack, SELVOL 518 is formulated as a 10–15 wt% aqueous solution with plasticizer addition of 5–20 phr on dry PVA. Flat laminating lines operating at 20–80 m/min apply the solution by reverse gravure or meyer rod at a dry coat weight of 2–6 g/m²; laminating pressure is 1–4 bar. Loop tack measured by ASTM D6195 ranges from 3–8 N/25 mm depending on paper surface energy and coat weight. Compared with dextrin or starch adhesives, the dried SELVOL 518 film remains flexible at 25–35 °C, reducing edge lift on high-speed envelope folding lines. Operational boundaries include solution viscosity above 500 mPa·s at concentrations exceeding 20 wt%, which causes rod streaks and transfer roll skipping. Storage at relative humidity above 65% may increase caking in bagged material and require fluidized-bed pre-drying before pneumatic conveying.
Replacing a fully hydrolyzed PVA grade with SELVOL 518 in a water-based laminating adhesive reduces dissolution temperature from 90–95 °C to 25–40 °C and shortens mix time from 1–2 h to 30–45 min under medium-shear agitation. The trade-off is lower wet shear strength on high-energy substrates. In polyvinyl acetate wood adhesive formulations, fully hydrolyzed PVA may provide wet shear of 3–5 MPa while SELVOL 518 contributes 1.5–2.5 MPa under the same ASTM D4502 test conditions. However, SELVOL 518 exhibits better adhesion to polyethylene terephthalate and corona-treated polyolefin films because the aqueous solution has lower surface tension, typically 42–46 mN/m at 1 wt% and 25 °C measured by du Noüy ring per ASTM D1331. Fully hydrolyzed grades often have solution surface tensions above 50 mN/m, limiting wet-out on low-energy substrates.
Formulators should avoid combining SELVOL 518 with borate crosslinking agents at pH above 8.5, because rapid gelation of residual hydroxyl groups produces a non-reversible network that cannot be transferred or coated. If borate gelation is desired for remoistenable adhesives, addition is limited to 0.1–0.5 wt% and pH is buffered to 7.5–8.0 with phosphoric acid or citric acid. PVA solutions are also incompatible with high concentrations of strongly alkaline salts; sodium hydroxide above 0.5 wt% causes phase separation and precipitation over 24 h.
On metering size presses, SELVOL 518 is applied as a 5–8 wt% solution at 40–60 °C to lightweight packaging papers. The dried film contributes surface strength and oil resistance; Cobb60 water absorption measured by ISO 535 is typically reduced by 15–30% relative to an untreated sheet, depending on base furnish and wet-press configuration. Addition of 0.5–1.0 wt% ammonium zirconium carbonate improves water resistance through carboxyl complexation but reduces pot life to 6–12 h.
Textile warp sizing lines benefit from SELVOL 518 cooked into a 6–10 wt% size bath with wax and lubricant. A dried film thickness of 10 μm provides abrasion resistance on high-speed air-jet looms operating at 600–1000 picks/min; size box temperature is held at 80–85 °C. Low-foam behavior during circulation is critical, and antifoam addition is kept below 0.1 wt% to avoid size shedding. Desizing is accomplished with hot water at 70–90 °C without enzymatic or oxidative agents, which is a processing advantage over starch-based sizes. Fabric tensile strength retention after sizing and desizing is commonly evaluated by ASTM D5035; reported values depend on fabric construction and size add-on, and published data for SELVOL 518 in this specific configuration is limited.
