SELVOL Álcool Polivinílico 205

On high-speed paper and paperboard machines where rod-metered film presses run at 800–1,500 m/min, SELVOL Polyvinyl Alcohol 205 functions as a low-viscosity surface-sizing co-binder rather than a primary starch replacement. The grade is pre-dissolved at 10–12 % solids in a 90–95°C jet cooker or in a separate atmospheric slab tank, then metered into oxidized corn or tapioca starch at 5–15 kg dry PVOH per 100 kg dry starch. Final size-press solids are held at 4–8 % depending on base-sheet porosity and target holdout; dry size-press add-on is typically 0.3–1.2 g/m² per side when measured gravimetrically. The low ash content of the grade, below 0.5 %, limits insoluble deposits on size-press rolls during long campaigns. For food-contact grades, the finished paper or paperboard must be tested under FDA 21 CFR 176.170 and FDA 21 CFR 176.180 using aqueous and fatty food simulants, and under EU 1935/2004 with migration verification per EN 1186-1. Surface quality is assessed by ISO 535 Cobb₆₀, ISO 8791-4 Parker Print Surf roughness, and IGT dry pick resistance per ISO 3783; offset and inkjet converters commonly specify Cobb₆₀ values below 25 g/m². The downstream production sequence includes size-press application, infrared or air-float drying to 4–6 % sheet moisture, and reel calendering. Terminal products include envelope papers, lightweight coated base stock, inkjet substrates, SBS folding carton board, and release liner base papers.

When surfactant-free vinyl acetate ethylene and acrylic dispersions require low gel content

The reactor charge for semi-batch emulsion polymerization of vinyl acetate, vinyl acetate-ethylene, or acrylic esters contains SELVOL Polyvinyl Alcohol 205 as an aqueous solution at 10–20 % solids, with the dry protective colloid level between 2.0 wt% and 6.0 wt% based on total monomer. The 87–89 mol% hydrolysis range leaves sufficient residual acetate groups to reduce aqueous surface tension and to promote grafting onto growing polyvinyl acetate chains, while the 5.2–6.2 cP viscosity at 4 % solids keeps reactor viscosity low enough for efficient heat transfer in a baffled glass-lined or stainless steel reactor. A pitched-blade turbine with tip speed of 2.0–3.5 m/s is used; higher shear can reduce protective colloid adsorption and increase coagulum formation. Redox initiation with hydrogen peroxide and sodium formaldehyde sulfoxylate or tert-butyl hydroperoxide and sodium metabisulfite is fed over 180–240 min at 60–75°C. Vinyl acetate and ethylene are fed as delayed streams, keeping free monomer below 0.5 wt% during polymerization, measured by capillary GC per ISO 13741-1. The resulting dispersion is tested for solids per ISO 3251, Brookfield viscosity per ISO 2555, pH per ISO 976, and particle size by dynamic light scattering per ISO 22412. Borate-containing buffer salts are avoided in this system because borate-diol complexation with the partially hydrolysed PVOH backbone increases viscosity and can induce coagulum formation. For wood adhesive formulations, wet and dry bond strength must meet durability class D2 or D3 under EN 204. For food packaging adhesives, the dispersion must comply with FDA 21 CFR 175.105 and, where the finished article is a plastic food-contact material, with EU 10/2011 migration limits. Terminal products include polyvinyl acetate homopolymer and VAE copolymer dispersions for paper converting adhesives, nonwoven binders, interior paints, wood glues, and laminating adhesives.

Warp sizing for high-speed air-jet looms

Sizing formulations for spun polyester, polyester/cotton, and ring-spun cotton warps use SELVOL Polyvinyl Alcohol 205 as a low-viscosity film former that can be combined with oxidized starch or modified starch and an acrylic co-binder without raising size-box viscosity beyond 8–14 s Zahn cup #3 at 90°C. The recommended addition is 4–10 % of total size solids, with size-box solids from 6 % to 12 % depending on yarn hairiness and loom speed. Wet pick-up at the squeeze rolls is adjusted to 8–14 % dry add-on by weight of yarn; add-on below 6 % is avoided because insufficient film continuity increases stops caused by warp breaks in air-jet filling insertion. The size is cooked in a jet cooker at 110–130°C for starch gelatinization and held in the size box at 85–95°C. Drying is carried out over Teflon-coated cans at 110–140°C surface temperature to a residual moisture of 4–6 %, followed by splitting at the lease rods. Sized yarn strength and elongation are measured by ASTM D2256, yarn hairiness by ASTM D5647, and abrasion resistance by the Zweigle G567 loom simulation. Textile compliance is governed by the Zero Discharge of Hazardous Chemicals Manufacturing Restricted Substance List and, for export, by OEKO-TEX Standard 100 Annex 4 criteria for residual volatile organics. Terminal products include woven apparel fabrics, workwear, bedsheet fabric, and lining fabric produced on air-jet and rapier looms at weft insertion rates above 1,200 m/min.

Solubility window and blending limits in cast PVOH film

Water-soluble film produced with SELVOL Polyvinyl Alcohol 205 as the sole resin exhibits lower tensile strength and higher blocking tendency than film based on medium or high viscosity grades; therefore the 205 grade is not recommended as the sole film-forming resin for pouch packaging above 50 parts per 100 parts total PVOH. In blended formulations, 20–50 parts of SELVOL 205 replace an equivalent dry weight of a medium-viscosity partially hydrolysed grade of 15–25 cP to reduce solution viscosity and to shift cold-water dissolution time downward. The casting formulation contains 100 parts total PVOH, 10–20 phr glycerol, 5–10 phr sorbitol or trimethylolpropane, 0.3–0.8 phr nonionic defoamer, and water to a total solids of 18–25 %. Dissolution is performed in a scraped-wall or jacketed high-shear mixer at 80–95°C for 45–90 min, followed by vacuum deaeration at −0.08 to −0.09 MPa. The deaerated solution is cast through a slot die onto a chrome-plated belt or PET carrier and dried in stages from 70°C to 110°C to a residual moisture of 6–12 %. Mechanical properties are tested per ISO 527-3; cast film tensile strength is typically 20–35 MPa and elongation at break 200–400 % depending on plasticizer content and moisture. Dissolution is measured by the in-house paddle or jar method at 10–20°C; detergent unit-dose pouches must survive 30–60 s dry handling and release within 60 s in wash liquor. Detergent formulations containing high borate salt concentrations can reduce film solubility through borate-diol complexation; compatibility testing is therefore required before converting. Biodegradation is evaluated by ISO 14851. Pre-drying is required before thermoforming when ambient relative humidity exceeds 60 %; roll blocking is controlled by storing film at 20–25°C and 35–50 % RH. Food-contact plastic articles must comply with EU 10/2011 where a food-contact approval exists; detergent and agrochemical sachets are assessed under UN GHS product classification. Terminal products include detergent unit-dose pouches, water-soluble agrochemical sachets, embroidery topping film, and transfer-printing carrier film.

Envelope back-seam and window-patch remoistenable adhesives are compounded with SELVOL Polyvinyl Alcohol 205 at 10–30 % dry weight of the final adhesive film, alongside 20–40 % dextrin, 5–15 % urea or glycerol as humectant, and 0.5–2.0 % preservative. The dry blend is dispersed at 30–45 % solids and applied by doctor roll or slot die at 15–30 g/m² wet film weight on envelope stock; drying is carried out at 60–90°C to a tack-free film. Rewetting compatibility is measured with a recycled paper lap bond test after 3–5 s water application; dry adhesion is assessed by ASTM D1876 T-peel or ISO 11339. Borated dextrin grades must be avoided when the formulation contains more than 15 % PVOH because borate ions crosslink the 1,3-diol units of polyvinyl alcohol and create an irreversible viscosity rise in the coating pan. For food contact, the dried adhesive layer must comply with FDA 21 CFR 175.105 and with 21 CFR 176.170 if the adhesive is used on paperboard intended for direct food contact. Terminal products include remoistenable envelopes, window patch film adhesives, paper labels, trading stamp sheets, and paper tube winding adhesives.

What determines green strength after spray-drying alumina slurries?

In technical ceramic body preparation, SELVOL Polyvinyl Alcohol 205 is used as a temporary organic binder at 0.5–2.0 wt% based on dry ceramic solids, introduced as a 5–10 % aqueous solution into an alumina or zirconia slurry already containing 0.3–0.8 % ammonium polyacrylate dispersant. The slurry is milled to a median particle size of 0.5–2.0 µm and spray-dried with a rotary atomizer at inlet air 200–250°C and outlet air 90–110°C. The resulting granules contain 1–3 % residual moisture and retain sufficient binder for dry pressing at 50–200 MPa in a hydraulic press. Green strength is measured as three-point flexural strength per ASTM C1161 or EN 843-2; values below 1 MPa generally indicate overwet granules or binder migration to granule surfaces, while values above 3 MPa may require longer thermal debinding. Debinding is conducted in air or nitrogen from 350°C to 600°C over 4–12 h, with the heating rate below 1°C/min between 150°C and 350°C to avoid carbon residue from incomplete oxidation. Compliance for electronic ceramics includes RoHS Directive 2011/65/EU Annex II substance restrictions; for sintered parts used in food-contact applications, the finished article must satisfy applicable national food-contact legislation and, if an organic coating or plastic component remains, EU 10/2011 migration limits. Terminal products include alumina substrates, wear plates, piezoceramic blanks, multilayer ceramic capacitor bodies, and technical ceramic components formed by uniaxial dry pressing.