SELVOL Polyvinyl Alcohol 513

SELVOL Polyvinyl Alcohol 513 is a partially hydrolysed grade with a nominal hydrolysis range of 86–89 mol% and a 4% aqueous solution viscosity of 13–15 mPa·s at 20 °C. The pH of a 4% solution is specified as 4.5–6.5. This combination produces lower crystallinity than fully hydrolysed grades, a wider dissolution window, and controlled sensitivity to borate and water. In downstream processing, those properties shift film flexibility, adhesion to cellulosic substrates, and protective-colloid behaviour. The following application scenarios are limited to industrial segments where these characteristics are actually exploited: textile warp sizing, advanced ceramic forming, paper surface sizing, emulsion polymerisation, remoistenable adhesives, and cementitious water retention.

Warp Sizing Formulations for High-Speed Air-Jet Looms

On high-speed air-jet looms running at 800–1,200 picks/min, sized warp yarns must survive cyclic abrasion without fibre hairiness exceeding 3–5 hairs per 10 m as measured by Zweigle G566 hairiness tester. SELVOL Polyvinyl Alcohol 513 is dissolved in a jet cooker with deionised water at 90–95 °C, held for 30 min to eliminate gel seeds, then blended with oxidised starch or potato starch at a PVOH:starch dry-solids ratio of 1:3 to 1:5. The size box is maintained at 75–85 °C; a drop below 65 °C produces skin-over on transfer rollers and uneven pick-up. Typical size pick-up on cotton/polyester spun yarns is 8–12 wt% dry add-on. At this addition level, the partially hydrolysed 86–89 mol% structure suppresses crystalline-rich film failure by allowing controlled moisture sensitivity, while the 13–15 mPa·s solution viscosity is low enough to penetrate the yarn core yet high enough to form a surface film. Tensile strength of isolated films can be assessed under ASTM D882-18 after conditioning at 23 ± 2 °C and 50 ± 5 % RH. For weaving compliance, sizing agents are checked against ZDHC MRSL Version 3.1 and OEKO-TEX Standard 100 limits for formaldehyde and APEO residues. Desizing on downstream processing requires an alpha-amylase or oxidative desize step at 80–90 °C because PVOH films are not starch-derived and residual size can raise COD in mill effluent. Borated size recipes are incompatible with this grade unless viscosity build is intended, because the 1,2-diol content reacts with borate ions to generate network viscosity that defeats penetrant behaviour.

Dry pressing of high-purity alumina substrates with target sintered density above 3.92 g/cm³ often uses a temporary organic binder that must burn out before 500 °C without leaving alkali-metal residues. Aqueous ceramic slurries are prepared with 1.0–3.0 wt% SELVOL Polyvinyl Alcohol 513 based on dry ceramic weight; the binder is first dissolved at 15–20 wt% stock concentration in a stirred vessel at 85–90 °C and added after cooling to 40 °C to avoid viscosity shock with polyacrylate dispersants. The slurry is fed to a rotary atomiser spray dryer at inlet air 180–220 °C and outlet air 80–110 °C, producing spherical granules with residual moisture 0.3–1.5 wt%. Granules are pressed into green bodies at 80–150 MPa using hydraulic presses fitted with floating die tooling. The binder contributes to green strength by bridging particle contacts; 3-point flexural testing of green bars according to ASTM C1161-18 after drying at 110 °C is used to verify handling integrity. Thermal debinding is conducted in air at a heating rate of 0.5–1.0 °C/min to 450–500 °C, with a 1 h hold, because the PVOH backbone decomposes by chain scission and oxidation. If the heating rate exceeds 2 °C/min, internal pressure from evolved water and carbonyl fragments can delaminate green bodies. The ash content of SELVOL Polyvinyl Alcohol 513 is specified as 0.5 wt% maximum, which is relevant for high-purity substrates but may require verification by XRF against internal specification for sodium and potassium. Ceramic binder performance is also verified by ISO 18754 for green density and by dilatometry during sintering; suitability for electronic ceramics should be confirmed against IEX and ICP-MS limits because trace alkali ash can shift dielectric loss at 1 MHz.

Why Surface Sizing on Metered Film Press Requires Hydrolysis-Balanced PVOH

At a metered film press running on fine paper at 900–1,500 m/min, the surface size must transfer without misting, level under rod pressure, and dry to a non-blocking film at low pick-up. SELVOL Polyvinyl Alcohol 513 is prepared at 8–12 % solids in a jet cooker at 95 °C, then applied at 0.4–1.2 g/m² dry add-on per side. The 86–89 mol% hydrolysis level limits water sensitivity after drying to an HST level of 1–5 s under TAPPI T530 om-20 at 60 °C, while maintaining Cobb₆₀ values measured by TAPPI T441 om-20 in the range of 25–35 g/m² depending on base sheet. For fine paper destined for inkjet printing, the partially hydrolysed grade reduces felt-side picking and improves IGT pick strength under TAPPI T499 cm-19. The film press starch blend typically contains oxidised tapioca starch at 70–85 % of dry solids and PVOH 513 at 15–30 %; enzyme-converted starch may be used, but alpha-amylase approach requires deactivation at 95 °C because residual amylase will hydrolyse starch and leave PVOH-rich domains that cause mottle. Compliance for food-contact paper is limited to 21 CFR 176.170 components and EU 1935/2004 declarations where the final film is not a functional barrier but a surface sizing agent. A shutdown or grade-change washout below 60 °C can form gel films on rod holders and cause streak defects; the system should be flushed with hot water at 85 °C before scheduled stops.

When Emulsion Polymerisation Shifts from Conventional Nucleation to Graft-Mediated Stability

In vinyl acetate homopolymer and vinyl acetate–ethylene copolymer emulsion polymerisation, SELVOL Polyvinyl Alcohol 513 can be charged as a primary protective colloid at 1.0–4.0 wt% based on total monomer. The polymerisation is typically carried out at 70–80 °C with a redox initiator system such as hydrogen peroxide / sodium formaldehyde sulfoxylate or persulfate. The partially hydrolysed PVOH sorbs onto growing polymer particles and also undergoes chain transfer grafting at the methine carbon, creating amphiphilic copolymer that anchors to the poly(vinyl acetate) core. This graft-mediated stabilisation shifts the particle-size distribution toward 0.8–2.5 µm when measured by laser diffraction according to ISO 13320:2020, while the emulsion viscosity is measured by ASTM D2196-20 with a Brookfield RV spindle 3 at 20 rpm. In a 50 % solids VAE dispersion, the viscosity typically increases with PVOH addition; at 2.5 wt% PVOH 513, the final latex may exhibit 1000–2500 mPa·s depending on monomer composition and ethylene pressure. The 86–89 mol% hydrolysis level provides a balance between freeze-thaw stability and water resistance; films cast from the dispersion show lower water uptake than highly hydrolysed PVOH-stabilised analogues when tested by ASTM D870-15 after 24 h. Freeze-thaw cycling at -5 °C for 5 cycles is used to screen stabiliser efficacy. Operational barriers include the retardation effect of residual PVOH on coalescing agent diffusion in low-VOC architectural formulations where the minimum film-forming temperature must be below 5 °C; the formulator must verify MFFT by ASTM D2354 when coalescent content is below 3 wt%. Ionic incompatibility arises with cationic additives and with aluminium salts at low pH, which can precipitate PVOH-grafted particles and destabilise shear stability. The final dispersion is typically adjusted to pH 4.0–5.5 and filtered through a 200 µm bag filter before drumming.

Remoistenable adhesive films used on high-speed envelope converting lines require dry blocking resistance at 35 °C and 80 % RH while maintaining rapid tack after water activation. SELVOL Polyvinyl Alcohol 513 is compounded with humectant and plasticiser at 2–6 wt% PVOH solids; the adhesive is coated onto paper web with a comma coater at 30–50 g/m² wet film and dried at 80–100 °C. The partially hydrolysed grade yields a dry film with lower water resistance than fully hydrolysed PVOH, which accelerates re-moistening time to 1–3 s under 20 °C water spray in automatic flap openers. Viscosity stability during coating is measured by ASTM D2196-20 at 30 °C; pH is maintained at 5.5–6.5 with citric acid solution. Compliance for adhesive contact with food packaging is evaluated under FDA 21 CFR 175.105 and EU 10/2011 where the dry adhesive layer is separated from food by paper or barrier. In high-humidity warehouses, blocking is controlled by adding 0.5–1.5 wt% of a polyethylene wax dispersion; exceeding 2 wt% wax reduces water activation and causes fibre tear on coated card. Borax is excluded from this application because gel formation with 1,2-diol units produces a skin that slows rewetting.

Cementitious Grout Water Retention and 86–89 mol% Hydrolysis Selectivity

Polymer-modified cementitious grouts and tile adhesives use polyvinyl alcohol to control water retention and open time on porous substrates. SELVOL Polyvinyl Alcohol 513 is added at 0.2–0.8 wt% of dry mortar; it is dispersed as a 10 % aqueous solution into the gauging water to avoid lump formation. Water retention is measured by ASTM C1506-17 for hydraulic cement-based mortars. The partially hydrolysed grade dissolves at 20 °C more readily than fully hydrolysed grades, which is advantageous in cold-water job-site mixing. At 0.5 wt% addition, the open time of a C2TE-class tile adhesive can be extended by 20–30 min when tested under EN 1346:2007; adhesion after open time is screened above 0.5 N/mm². Published data for this specific configuration is limited, so job-site mortar trials remain determinant. The operational boundary is set by retardation: above 0.8 wt%, hydration of ordinary Portland cement may be delayed sufficiently to lower early compressive strength. Shotcrete-type accelerators based on high-sulfate salts show incompatibility at high PVOH loadings because of localised gelling and uneven rheology in the spray line.