CCP PVA BF-24E'nin

CCP PVA BF-24E is a fully hydrolysed polyvinyl alcohol homopolymer manufactured by Chang Chun Petrochemical Co., Ltd. under the CCP PVA designation. The grade is supplied as a free-flowing white to pale yellow granular powder with a volatile content not exceeding 5.0 wt% (loss on drying, 105 °C, 3 h) and an ash residue below 0.5 wt% (calcination at 800 °C) when tested per JIS K6726. The 4% aqueous solution viscosity at 20 °C falls within the range 44.0–50.0 mPa·s, determined by Brookfield viscometer spindle No. 1 at 60 rpm, with a pH of 5.0–7.0. Degree of hydrolysis, measured by saponification back-titration, is consistently 98.5–99.4 mol%, placing BF-24E firmly in the category of fully saponified PVA resins. These lot-to-lot tolerances are controlled through continuous saponification and methanolysis process monitoring, ensuring batch reproducibility when the material is deployed across multi-tonne production campaigns in textile, paper, and adhesive converting lines.

Typical analytical profile — CCP PVA BF-24E

Parameter	Method	Value
Viscosity (4 % aq., 20 °C)	JIS K6726 /Brookfield LV	44–50 mPa·s
Degree of hydrolysis	JIS K6726 (back-titration)	98.5–99.4 mol%
Volatile content	JIS K6726 (105 °C, 3 h)	≤ 5.0 %
Ash content	JIS K6726 (800 °C)	≤ 0.5 %
pH (4 % aq.)	JIS K6726	5.0–7.0
Apparent bulk density	Funnel method	0.45–0.65 g/cm³
Degree of polymerisation (DP)	Intrinsic viscosity /JIS K6726	2400–2600

How Does Aqueous Dissolution Kinetics Influence Processing Efficiency?

The dissolution behaviour of BF-24E imposes specific thermal and mechanical constraints that differ markedly from partially hydrolysed grades. The polymer’s high degree of hydrolysis and molecular weight reduce cold-water solubility; the granules hydrate and swell at ambient temperature but require a temperature ramp to 92–98 °C for complete molecular dispersion. Production-scale make-down vessels equipped with anchor-type agitators operating at 60–120 rpm and side-sweep baffles are recommended to avoid dead zones where hydrated gel lumps—commonly termed “fish eyes”—accumulate. A typical procedure disperses BF-24E in deionised water at 20–30 °C under agitation for 15–20 min, then raises the batch temperature at a controlled rate of 1.5–2.0 °C/min to 95 °C. Holding at temperature for 45–60 min with continued agitation reduces the viscosity plateau drift observed below 90 °C. Failure to achieve terminal dissolution can yield a solution with microgel content exceeding 50 ppm, measured by ISO 4576 filtration, which subsequently causes fisheye defects in cast films and strikethrough irregularities in coated paper. In high-humidity environments (> 60 % RH), pre-drying of the powder at 60–80 °C for 2–4 h in a dehumidified fluid-bed dryer is advised before mixing to prevent caking and weight-in errors in gravimetric dispensing. The dissolution vessel material also warrants consideration. Prolonged contact with carbon steel at temperatures above 80 °C accelerates iron-catalysed oxidative chain scission, visible as a progressive drop in solution viscosity of 5–10 % within 24 h and an off-spec yellow tint. Stainless steel (AISI 316L) or glass-lined reactors are specified in commercial operations to maintain intrinsic viscosity stability during storage of prepared solution at 40–50 °C. When stored under these conditions in sealed tanks with nitrogen blanketing, the 4% solution of BF-24E exhibits a viscosity drift of less than ±3 % over 72 h.

Film Tensile Strength and Moisture Barrier Performance

Films produced from BF-24E via solution casting or blown film extrusion (after plasticiser compounding) display mechanical properties inherent to fully hydrolysed PVA: high dry tensile strength coupled with sensitivity to ambient moisture. When cast from a 10 wt% aqueous solution onto a chrome-plated belt at 80 °C and conditioned at 23 °C and 50 % RH for 48 h, films of 40 µm thickness exhibit a tensile strength at break of 55–65 MPa and elongation at break of 100–150 % per ASTM D882-18. The oxygen transmission rate (OTR) at 0 % RH drops below 0.5 cm³·mm/(m²·day·atm), a barrier attribute exploited in water-soluble unit-dose detergent packaging and agrochemical sachets. However, the OTR increases exponentially above 70 % RH, a known limitation of unmodified PVA that field engineers compensate with over-lacquer coatings or co-extrusion with a hydrophobic skin layer. Published data for this specific configuration with BF-24E in multi-layer structures is limited, but model predictions based on free-volume theory indicate a plasticisation threshold at RH> 65 % that doubles the oxygen permeability coefficient.

When BF-24E Replaces Partially Hydrolysed Grades in Remoistenable Adhesive Systems

Adhesive formulators encounter a functional trade-off when substituting a partially hydrolysed grade such as CCP PVA BP-24 (degree of hydrolysis 86.5–89.0 mol%) with BF-24E. The fully hydrolysed backbone raises the dry-film blocking resistance temperature from approximately 40 °C to beyond 60 °C, measured by the shear-strength-temperature ramp method under ASTM D4498. This thermal resistance is advantageous in envelope manufacturing lines where stacked adhesive films pass through heated drying tunnels. Concurrently, the open time decreases by roughly 20–30 % because the higher glass transition temperature (85 °C vs. approx. 75 °C for BP-24, DMA tan δ peak at 1 Hz) reduces room-temperature tack. To compensate, production formulations often blend BF-24E with 5–15 wt% glycerol or polypropylene glycol as a humectant/plasticiser, restoring tack while maintaining the higher softening point. The water sensitivity of the rebonded joint also shifts: remoistenable films based on BF-24E require 2–3 seconds longer wet-out time under a 0.5 ml water droplet compared to BP-24, a detail that requires dwell-time adjustment on mail-sorting insertion equipment. Viscosity stability in borax-crosslinked systems presents another differentiator. Borax (disodium tetraborate decahydrate) added at 0.5–1.0 wt% of PVA solids thickens BF-24E solutions via diol complexation, but the gel point occurs at a lower critical strain (γ_c ≈ 15 % at 0.8 wt% borax) compared with partially hydrolysed grades. This rheological behaviour demands precise metering pumping with progressive cavity or twin-screw pumps that manage shear without gel fracture, which manifests as a cascading viscosity loss in the recirculated adhesive bath known as “borax sweat-out” on high-speed (>200 m/min) adhesive application lines. Directly transitioning to textile warp-sizing applications, BF-24E is applied to ring-spun cotton and cotton/polyester blended yarns through a multi-cylinder sizing machine operating at 80–120 m/min. The sizing liquor, typically formulated at 8–12 wt% PVA with 2–4 wt% wax-compatibilised lubricant, penetrates the yarn bundle under squeeze roller pressures of 15–25 kN/cm² at the size box. Sized yarns conditioned to 65 % RH exhibit an increase in breaking strength of 15–25 % and a reduction in hairiness index (Zweigle S3 value) of 40–60 % relative to unsized roving, measured by ASTM D2256-21. The high degree of hydrolysis ensures efficient desizing in hot-water washes (>80 °C) with less than 0.2 % residual size after enzymatic or oxidative scouring, a critical factor for downstream dye-uptake uniformity. In contrast to starch-only formulations, the BF-24E size film partially plasticises under loom-shed humidification, maintaining flexibility at weaving speeds generating 800–1200 picks/min without significant dusting—fine particulate shedding that fouls heald frames and reeds.

Paper Surface Sizing and Substrate Holdout

The surface application of BF-24E on wood-free uncoated paper by metering size press at 5–8 wt% solution concentration raises the Cobb water absorptiveness (ISO 535:2023) from 35–40 g/m² to 18–22 g/m² (60-s contact), with simultaneous improvement in IGT pick velocity (ISO 3783) by approximately 0.5–1.0 m/s. The film-forming nature of BF-24E creates a continuous non-thermoplastic barrier that holds out subsequent pigmented coating colours, reducing binder migration and mottle in coated grades. When compared to oxidised starches, the PVA size press formulation exhibits less rheopexy under the shear rates experienced in the metering nip (10⁵ s⁻¹), translating to more stable coating weight delivery over an 8-hour shift. However, dry-film brittleness at calender temperatures above 70 °C can lead to micro-cracking at the sheet surface if the film thickness exceeds 2.5 g/m² PVA solids per side, a failure mode mitigated by co-additives such as 3–5 wt% (on PVA) polyol plasticiser or by blending with a lower-DP grade.

Selected property comparison — BF-24E vs. partially hydrolysed PVA (BP-24) and lower-viscosity fully hydrolysed grade (BF-17)

Grade	Viscosity (4% aq., mPa·s)	Hydrolysis (mol%)	Film Tensile (MPa)*	Adhesion to Cellulose (N/25 mm)**	Cold-water solubility
BF-24E	44–50	98.5–99.4	55–65	8.0–10.5	Negligible
BP-24	44–50	86.5–89.0	40–48	5.5–7.0	Complete at 25 °C
BF-17	25–31	98.5–99.4	60–70	6.5–8.5	Negligible

*Film conditioned at 23 °C, 50 % RH, 40 µm thickness, ASTM D882 type IV specimen.
** T-peel adhesion to regenerated cellulose film at 23 °C, 50 % RH, crosshead speed 300 mm/min. The resistance of BF-24E to organic solvents and greases further extends its utility into barrier coating for moulded fibre food-service packaging, where fluorochemical-free oil holdout is required under FDA 21 CFR §176.170. A coating weight of 3–4 g/m² on bagasse board achieves a kit rating of 7–8 (TAPPI T559 cm-12) without compromising repulpability in standard alkaline hydrapulpers (yield loss <1 % versus uncoated control). Operational boundaries include a minimum board surface temperature of 40 °C during application to avoid premature gelation of the solution, and a relative humidity ceiling of 55 % during storage of coated articles to prevent blocking due to moisture sorption and intercoat adhesion. Material incompatibilities warrant explicit notation. BF-24E solutions should not be acidified below pH 4.0, as the ketal/ester-like intramolecular acetal formation is catalysed by protons, generating crosslinks that increase the solution viscosity unpredictably, occasionally beyond the measurement range of standard Brookfield spindles. Contact with strong oxidising agents (hydrogen peroxide at concentrations> 3 %, sodium hypochlorite, or permanganate) at temperatures above 50 °C rapidly depolymerises the chain, reducing the viscosity to that of water within 30–60 min. Even in air, prolonged heating above 130 °C in the dry state induces thermo-oxidative degradation, marked by a colour shift to amber and a detectable aldehyde odour, rendering the material unsuitable for colour-critical clear films. In polyvinyl alcohol melt processing, the thermal stability window for BF-24E compounded with 10–15 wt% glycerol is approximately 190–210 °C; excursions beyond 220 °C typically produce crosslinked gel particles visible in blown film bubble instability and die-lip build-up.