Sinopec PVA 098-15 (PVA 1399)

A processing window of ±2°C in the holding tank is essential when cooking PVA 098-15 with oxidized corn starch in a 500-litre stainless steel cooker fitted with an anchor agitator rotating at 60 rpm. The Sinopec grade, specified with a degree of hydrolysis of 99.0–100 mol% and a 4 wt% aqueous solution viscosity of 12.0–16.0 mPa·s at 20°C (Brookfield LV, spindle 1, 30 rpm), functions as a high-strength film former in warp sizing of fine-count polyester/cotton yarns in the Ne 30–60 range. The dry-blended size mix typically consists of 100 parts oxidized starch, 35–50 parts PVA 098-15, 8 parts polyacrylic acid size, and 2 parts textile-grade emulsified wax, all dispersed in deionized water to a final solid content of 9–12 wt%. Steam injection under pressure raises the slurry temperature to 94–98°C and is held there for 45–60 minutes to ensure complete gelatinisation of starch and full dissolution of the PVA grains without creating undissolved “fish-eye” gels that would later wrap guide rollers. Once transferred to the sizing box on a multi-cylinder slasher (e.g., Tsudakoma HS40 or Karl Mayer SMR), the liquor temperature is maintained at 82–86°C through jacket heating, because even minor cooling below 80°C triggers a steep viscosity rise and skin formation that clogs squeeze-roll surfaces. Squeeze pressure is set at 15–22 kN/m to achieve a dry size add-on of 10–14% on the warp sheet, measured by on-line beta-gauge and confirmed by the desizing gravimetric method described in AATCC 97. Wet splitting is avoided by applying a contact pre-dryer at 120°C before the main multi-drum section, where drum surface temperatures ramp from 110°C to 130°C to preserve the film toughness imparted by the fully hydrolysed PVA backbone. The sized beam then enters high-speed air-jet weaving (typically at 800–1,200 rpm loom speed); here the 0.5% ash content maximum of 098-15 reduces yarn-to-metal friction induced shed droppers and heald wear, while maintaining a breaking strength retention above 95% of the unsized yarn as per ASTM D2256-21. Desizing follows with hot caustic peroxide treatment, meeting the discharge limits for COD set out in ZDHC Wastewater Guidelines v2.0, as the sizing formulation is free of alkylphenol ethoxylates and does not contribute to the persistent organohalogen load. All textile auxiliaries in the mix can be audited against OEKO-TEX ECO PASSPORT certification and the ZDHC MRSL v3.1 conformance list, enabling the finished denim or shirting fabric to pass OEKO-TEX Standard 100 Class I compliance without notification of PVA residues.

How Does a 1.5 g/m² Dry Pickup Translate into IGT Surface Strength on Folding Boxboard?

The surface sizing of white-top linerboard and solid bleached sulphate board for folding cartons uses a size press formulation in which PVA 098-15 is dissolved together with a low-viscosity oxidized corn starch at a weight ratio of 1:4 to 1:3 and a total solids content of 5–8 wt%. The aqueous solution is prepared in a continuous jet cooker at 105°C with a residence time of 120 seconds, then cooled to 58–65°C before being fed to a flooded-nip puddle or a film-size press (Voith SpeedSizer or Valmet OptiSizer). The low cold-water gelation tendency of the fully hydrolysed 098-15 necessitates that the size press roll temperature never falls below 55°C, otherwise microgel particles deposit on the metering rods and leave visible streaks in the coated surface. A dry film pickup of 1.2–1.8 g/m² per side is targeted, because below 1.0 g/m² the IGT pick velocity (ISO 3783:2020, spring-drive method with medium-tack oil) remains below 1.5 m/s, insufficient for offset printing runs exceeding 15,000 impressions. At 1.5 g/m² the pick resistance rises above 2.2 m/s, largely attributed to the high cohesive energy density of the 99% hydrolysed polyvinyl alcohol film that bridges fibre-to-fibre junctions. Simultaneously, the 60-second Cobb water absorption (ISO 535:2023) drops from an unsized >80 g/m² to 18–25 g/m², providing the necessary resistance to aqueous overprint varnishes. The addition of 0.1–0.2 wt% of a calcium stearate dispersion to the size formulation further lowers Cobb values into the 15–20 g/m² range without sacrificing coefficient of friction, as confirmed by TAPPI T 549 horizontal plane testing. This specific PVA grade carries an approval for use in food-contact paper and board under FDA 21 CFR 176.170 (Components of paper and paperboard in contact with aqueous and fatty foods), provided the finished extractives meet the net chloroform-soluble limit of 0.5 mg/in² and the single-use condition is respected. The same grade is listed in the BfR Recommendation XXXVI for paper and board for food contact, and its migration limit is controlled through the overall migration limit of 10 mg/dm² as specified in Regulation (EU) No 10/2011 Article 12 when the board is used as a functional barrier in multilayer packaging. In high-humidity storage trials at 23°C/85% RH, the sized board retains ≥85% of its dry IGT value after 72 hours of conditioning, confirming that the fully hydrolysed PVA film does not plasticise excessively under tropical shipping conditions, unlike many partially hydrolysed grades that suffer a sharp loss in surface strength.

Spiral Tube Delamination Rates at 50°C Under Constant Humidity Load

Adhesive formulations for the spiral winding of paper cores and convolute tubes exploit the high cohesive strength and rapid tack development of PVA 098-15 when combined with kaolin clay and a secondary starch-based co-binder. A typical open-tank adhesive is prepared by swelling 100 kg of cold-water-soluble pregelatinised tapioca starch in 400 kg water, adding 25 kg of a 20 wt% aqueous solution of PVA 098-15 that has been pre-cooked at 95°C for 40 minutes, and finally dispersing 15 kg of calcined kaolin to control rheology. The Brookfield viscosity at 20°C (spindle 5, 20 rpm) is maintained in the 3,000–5,000 mPa·s range; excursions above 6,000 mPa·s cause splashing and starved transfer on the grooved steel application roller running at a surface speed of 15–30 m/min, while values below 2,500 mPa·s lead to strike-through and internal ply bond failure. The 99% hydrolysis of the PVA backbone minimises cold-water solubility of the dried bond line, so that conditioning at 50°C and 90% RH for 7 days—used to simulate warehouse storage in Southeast Asia—reduces the radial crush strength (ISO 11093-9:2019) by less than 12% relative to 23°C/50% RH controls. Delamination at the outermost lap is tested by a peel method adapted from ISO 11093-7; samples bonded with the PVA-kaolin-starch system exhibit peel forces above 45 N/25 mm, whereas a purely starch-based analog fails at 18–22 N/25 mm under identical conditioning. Open time on the slow-rotating mandrel is extended to 25–35 seconds by incorporating 0.3 wt% of a polyol plasticiser (sorbitol), which retards skin-over of the adhesive layer without softening the final bond at the core’s operating temperature of up to 70°C. Compliance with EU Directive 94/62/EC on packaging and packaging waste is achieved because the adhesive contains no boron-based crosslinkers or heavy-metal preservatives, and the dried tube remains repulpable under standard OCC recycling conditions (ISO 5269-2, disintegration at 40°C).

When Cement Hydration Kinetics Are Disrupted Below 5°C: Retardation with PVA 098-15

Dry-mix polymer-modified tile adhesives of the C1 and C2 classifications under EN 12004:2017 use PVA 098-15 as a redispersible powder substitute in cost-engineered formulations, typically at addition levels of 0.3–1.0 wt% of the dry blend. The resin particles (80–120 µm mean diameter, ash content ≤0.5%) are mixed into a ribbon blender with Portland cement CEM I 42.5 R, silica sand graded 0.1–0.5 mm, and a methyl hydroxyethyl cellulose ether (0.35 wt%) to form a homogeneous powder that requires only water addition on site. Upon mixing at a water-to-powder ratio of 0.22–0.25, the cement pore water with a pH exceeding 12.7 hydrates the PVA partially, forming a colloidal film that bridges the interface between the hydration products and the tile biscuit. Early shear adhesion after 7-day standard climate curing (23°C, 50% RH) reaches 1.8–2.3 MPa when tested by EN 12004 pull-off with an epoxy-headed dolly at a loading rate of 250 N/s, while the open-time adhesion at 20 minutes remains above 0.5 MPa. A critical limitation emerges when the substrate temperature falls below 5°C: the fully hydrolysed PVA film adsorbs onto the hydrating aluminate phases and extends the induction period, lowering the 24-hour compressive strength by up to 30% compared with a reference containing no PVA. Accelerated curing with calcium formate (1.0 wt%) largely offsets this retardation but may shorten the pot life visible on site; contractors are advised to contact the mortar supplier for a winter-grade variant. Under EN 1348 water immersion testing (21 days curing followed by 7 days immersion), the pull-off strength must exceed 1.0 MPa for C2 classification—the PVA 098-15 samples retain 1.2–1.5 MPa, outperforming cellulose-only controls that often drop to 0.6–0.8 MPa. The final hardened adhesive contains no volatile organic compounds and meets the GEV Emicode EC1 Plus emission limits (< 60 µg/m³ after 3 days), and its chromium-VI content, measured by EN 196-10 water extraction, stays below 2 ppm of the total dry mass, ensuring alignment with Regulation (EC) No 1907/2006 (REACH) Annex XVII entry 47.

Forming Film Integrity on Borosilicate Glass Fibers at a Draw Speed of 600 m/min

In the bushing-to-winding section of a direct-melt glass fibre line drawing E-glass filaments of 9–17 µm diameter at 600–1,200 m/min, the aqueous size must wet the hot filament instantaneously and solidify into a coherent, non-tacky film within the short distance to the gathering shoe. PVA 098-15 serves as the primary film former in a size containing 5–8 wt% solids, where the PVA constitutes 60–70% of the total non-aqueous fraction, the balance being 0.3–0.5% γ-aminopropyltriethoxysilane, 0.2% polyethylene glycol lubricant, and a trace acetic acid to adjust pH to 4.0–4.5. The low cold-water solubility of the fully hydrolysed grade requires that the size make-up tank be held at 60–70°C with gentle recirculation to avoid settling, yet the film deposited on the moving strand dries quickly because the latent heat of the 1,300°C bushings raises the strand temperature to approximately 80–100°C at the applicator roller. Loss-on-ignition (LOI) is controlled to 0.50–0.80% by adjusting roller speed and doctoring pressure; at LOI below 0.40%, fly and fuzzy fibre generation on the roving bobbin increases sharply during subsequent air-jet loom weaving due to insufficient inter-filament bonding. Strand tensile strength tested per ASTM D2343-17 on impregnated rovings using an epoxy resin system (diglycidyl ether of bisphenol A with amine hardener) shows a mean value of 2,800–3,200 MPa, with no significant deviation from sizes based on PVAc emulsions, provided the silane-to-PVA ratio is kept within the stated window. The size formulation is auditable under EC 1907/2006 (REACH) and does not contain substances listed in the Candidate List of SVHC; when the composite article is destined for potable water applications, supplementary leachate testing according to BS 6920 Part 1 can be arranged by the sizing supplier.

When hot-pressing 3-ply poplar veneers with a urea-formaldehyde (UF) resin of molar ratio F/U = 1.08 at 1.2 MPa and 115°C, the addition of 2.0–3.0 wt% PVA 098-15 based on liquid UF resin solids modifies the flow behaviour and bonding mechanism. The PVA is predissolved in the UF hardener solution (20 wt% ammonium chloride) at 60°C to form a syrup that disperses uniformly in the acid-catalysed resin, raising the mix viscosity from 500 mPa·s to 1,200–1,800 mPa·s (Brookfield spindle 4, 20 rpm, 25°C). This viscosity increase prevents over-penetration into the large-diameter vessels of fast-growing poplar, reducing the dry-out risk at the bond line during the 3-minute press cycle. 4-hour boil delamination testing per EN 314-1:2023 Class 3 condition yields a wet shear strength of 1.8–2.2 MPa and wood failure percentages above 70%, compared with 1.2–1.5 MPa for an unmodified UF control. The fully hydrolysed PVA creates a secondary interpenetrating network that bridges microcracks induced by resin cure shrinkage and reduces formaldehyde emission, measured by the perforator method EN 120, to 4.5–5.5 mg/100 g panel, well within the E1 limit (≤ 8 mg). Production-scale implementation on a 12-opening multi-daylight press (Dieffenbacher) has shown that clean-up intervals double because the PVA-UF system does not build hardened resin on the caul plates as rapidly as straight UF, and the final plywood panels comply with the CARB ATCM 93120 Phase 2 emission limits. No additional biocide is needed in the glue mix for overnight storage, but operators must observe that prolonged mixing above 30°C can trigger a mild pre-gelation; the recommended pot life after adding the PVA/hardener syrup is 4–6 hours at 20–25°C.