CCP PVA BF-20'nin

CCP PVA BF-20 is a medium-viscosity, partially hydrolysed polyvinyl alcohol grade supplied by Chang Chun Petrochemical Co., Ltd. The grade is produced via controlled alcoholysis of polyvinyl acetate, yielding a molecular architecture in which residual acetyl content falls within the 11–14 mol% range, corresponding to a hydrolysis degree of 86–89 mol%. This distribution of hydrophilic hydroxyl and hydrophobic acetate groups is the primary structural determinant differentiating BF-20 from fully hydrolysed grades and from other intermediate-viscosity members of the same product family.

The viscosity range positions the grade in a functional window where solution handling on conventional mixing equipment remains practical, while the partial hydrolysis ensures cold-water solubility without the extended heating cycles required for fully hydrolysed analogues. These characteristics have established BF-20 as a standard protective colloid and film-forming agent across multiple water-based polymer processing chains.

What Modifies the Setting Rate in PVAc Homopolymer Adhesives?

In polyvinyl acetate homopolymer adhesive formulations, BF-20 functions as the primary protective colloid, exerting control over latex particle nucleation, coalescence behaviour, and ultimate bond strength. The setting rate is governed not merely by water evaporation but by the rate at which the continuous PVA phase transitions from a tacky sol to a load-bearing gel. When BF-20 is dissolved at 8–12 wt% in the aqueous phase prior to emulsion polymerisation of vinyl acetate, the resulting dispersion exhibits a minimum film-forming temperature of 14–18 °C and an open time of 10–15 minutes on beechwood at 25 °C and 50 % RH, measured in accordance with ASTM D905-08. The partially hydrolysed character promotes grafting of PVAc chains onto the PVA backbone during the polymerisation, increasing the degree of interconnection between the protective colloid and the dispersed phase. This graft content, typically 15–25 % of total PVA mass, reduces wet tack but accelerates the development of shear storage modulus G’ by a factor of 1.3–1.6 compared with fully hydrolysed PVA of equivalent viscosity.

On production-scale mixing equipment—specifically, a 1,500 L stainless-steel dissolver equipped with a sawtooth impeller operating at 1,200 rpm—powder addition rates exceeding 25 kg/min can induce transient viscosity spikes if the jacket temperature falls below 80 °C. Pre-heating the charge water to 90 °C before BF-20 addition and maintaining a vacuum de-aeration step of −0.85 bar for 30 minutes reduces entrapped air-induced gel specks in the finished adhesive. Incompatibility with borate compounds must be avoided: even 0.02 wt% of sodium tetraborate decahydrate produces a irreversible cross-linked gel that cannot be re-liquefied by heating.

Warp Sizing on High-Speed Air-Jet Looms

Textile warp sizing demands a balance of tensile strength, elongation, and abrasion resistance to withstand the cyclic loading imposed by air-jet weft insertion at 650–800 picks/min. BF-20 films cast from 10 % aqueous solution and dried at 130 °C for 3 minutes exhibit an ultimate tensile strength of 42 MPa and elongation at break of 180 % when tested per ISO 527-3 on 40 µm thick specimens. The partial hydrolysis introduces sufficient amorphous character to prevent film brittleness under loom-room conditions of 25–30 °C and 65–75 % RH, yet the residual crystallinity (~28–32 % by density gradient column) ensures the size film does not cold-flow during extended loom stoppages.

Size bath formulation using BF-20 at 7.5 % solids with 0.3 % of a sulphonated castor oil lubricant is prepared in a cooking kettle equipped with a high-shear rotor-stator unit capable of 3,000 rpm. The size is applied on a multi-cylinder slasher at a squeeze-roll pressure of 5.5 kN/m and a size-box temperature of 88 ± 2 °C. Under these conditions, the add-on on 100 % cotton 40 Ne yarn stabilises at 9–11 %. Desizing efficiency is quantitative after a treatment with 0.5 N NaOH at 70 °C for 20 minutes, as verified by iodine staining per AATCC Test Method 161-2013. BF-20’s 20–26 mPa·s viscosity range offers a distinct processing advantage over lower-viscosity grades such as BF-14 (14–18 mPa·s) by reducing size penetration into yarn core and preserving handle, while avoiding the excessive size migration to the yarn surface observed with BF-24 (24–30 mPa·s), which can generate dusting in the loom shed.

The tendency of partially hydrolysed PVA to absorb moisture from the atmosphere requires that BF-20 powder be stored in unopened bags in an environment maintained below 60 % RH. Opened bags should be resealed and consumed within 48 hours to prevent lump formation that would cause filter screen blockages on the size make-up line.

In paper surface treatment, BF-20 applied as a size-press starch extender at 0.5–1.0 g/m² dry coat weight raises the IGT pick velocity by 0.4–0.7 m/s relative to a 100 % oxidized starch reference. The improvement is attributed to the graded film formation across the fibre void network, which reduces water-induced fibre lifting without creating a continuous film that would compromise sheet porosity measured at ISO 5636-3. Mill trials on a Valmet OptiSizer with a 1,500 m/min machine speed confirm that BF-20 solutions at 8 % solids exhibit Newtonian behaviour up to shear rates of 10,000 s⁻¹, enabling consistent metering by blade-coater devices without the rod-jamming episodes reported for fully hydrolysed PVA grades of equivalent molecular weight.

When BF-20 Replaces Fully Hydrolysed Grades in Emulsion Polymerisation

The deliberate substitution of a fully hydrolysed PVA (hydrolysis degree ≥98 mol%) with BF-20 in vinyl acetate emulsion polymerisation shifts the latex particle size distribution from a monomodal peak at 0.5–1.0 µm to a broader distribution centred at 1.5–3.0 µm, as measured by ISO 22412 dynamic light scattering. This shift results from the reduced aqueous-phase viscosity during the early nucleation stage and the superior colloidal driving force for coalescence when surface acetate groups are present. The coarser dispersion exhibits a reduction in water absorption after 24-hour immersion from 18–22 % to 8–12 %, tested per ISO 62, because the discontinuous PVA-rich inter-particle domain enables hydrophobic PVAc regions to form a more coherent matrix.

For suspension polymerisation of vinyl chloride, BF-20 at 0.05–0.15 phr (parts per hundred monomer) combined with a secondary dispersant such as methyl hydroxypropyl cellulose yields PVC resin with a particle size distribution d₅₀ of 130–160 µm and a plasticiser absorption capacity of 26–30 g DOP/100 g resin (ISO 4608). The critical low-addition window makes BF-20 sensitive to dosing precision: positive-displacement pumps with ±0.5 % flow accuracy are mandatory, and the aqueous solution must be filtered through a 100 µm bag filter before introduction into the polymerisation reactor to exclude undissolved gel particles that can nucleate fish-eye defects in the final PVC compound.

Film extrusion of BF-20 compounded with glycerol (18 phr) and sorbitol (5 phr) is carried out on a single-screw extruder with a barrier screw of L/D 26:1 and a compression ratio of 3:1. The temperature profile from feed throat to die is set at 150 /175 /195 /200 /195 °C. Melt fracture initiates at shear rates exceeding 500 s⁻¹, limiting the maximum screw speed to 60 rpm on a 45 mm diameter screw. Under these conditions, blown film of 30 µm thickness delivers a heat-seal initiation temperature of 110 °C and a seal strength of 8 N/15 mm at 130 °C, evaluated by ASTM F88/F88M-21. The presence of 11–14 mol% acetate groups reduces cold-water solubility sufficiently that the film tolerates contact with water at 5 °C for 60 seconds without sacrificing complete disintegration at 80 °C, a property relevant for unit-dose detergent pouches. Pre-drying of BF-20 powder at 80 °C for 2 hours in a dehumidified hopper dryer to a moisture content below 0.3 % is mandatory at ambient relative humidity exceeding 60 % to prevent hydrolysis in the melt and the formation of acetic acid vapour, which causes back-pressure fluctuations and embrittlement of the extrudate.

Controlling Batch-to-Batch Variance in Continuous Dissolution Systems

Continuous dissolution of BF-20 for high-throughput converting lines (e.g., release paper coating, nonwoven binder supply) is typically accomplished in a jacketed pin-mixer with a residence time of 45–90 seconds at 105 °C under back-pressure of 2.5 bar. Viscosity excursions greater than ±5 % from the target arise predominantly from variations in powder particle size distribution caused by milling-wear or humidity-induced agglomeration. Sieving the incoming lot through a 500 µm vibrating screen and dosing via a loss-in-weight feeder with an accuracy of ±1 % of set feed rate reduces the coefficient of variation in the final solution viscosity to below 3 %. The relative amount of fines passing a 150 µm sieve should not exceed 10 % of total mass; higher fines content accelerates hydration to the point where the mixer torque rises abruptly, tripping the motor overload protection on pumps rated below 15 kW.

Operational boundaries specific to BF-20 emerge from its position between the lower- and higher-viscosity neighbours in the product series. While BF-17 can be dissolved at lower temperatures and transferred via centrifugal pumps operating below 1,000 rpm, BF-20 solutions above 12 % solids build sufficient structural viscosity that gear pumps with an internal clearances set to 0.25 mm are preferred. Exposure of the solution to carbon steel components must be minimised: dissolved iron concentrations above 0.5 mg/L, measured by ICP-OES, catalyse oxidative chain scisson during storage, resulting in a viscosity loss of up to 20 % over 14 days at 40 °C. Stainless steel grade 316L for all wetted surfaces is therefore specified across storage tanks, piping, and application heads.