CCP PVA BP-24 is a fully hydrolyzed polyvinyl alcohol (PVOH) resin manufactured by Chang Chun Petrochemical Co., Ltd. (Taiwan) via continuous alcoholysis of polyvinyl acetate. The grade is classified within the BP-series as a medium-to-high molecular weight homopolymer with a hydrolysis degree of 98.5–99.5 mol% (titration method, JIS K6726). Its nominal viscosity, measured on a 4% aqueous solution at 20°C by Brookfield viscometer, falls within 22–28 mPa·s. These coordinates place BP-24 at the intersection of hot-water solubility, exceptional film tensile strength, and strong adhesion to cellulosic substrates. Production-scale behavior in twin-screw extruded compounding lines (L/D 40:1, water injection at barrel zone 5) indicates that pre-drying to ≤0.3% residual moisture is mandatory to prevent melt fracture and surging when the resin is processed as a thermoplastic. The powder form (≥60 mesh retention) also permits direct dissolution in agitated vessels at 85–95°C for aqueous preparation. Key specification parameters are summarized below.
| Property | Method | Range |
|---|---|---|
| Hydrolysis | JIS K6726 (residual acetate titration) | 98.5–99.5 mol% |
| Viscosity, 4% aq. at 20°C | JIS K6726, Brookfield LVT | 22–28 mPa·s |
| Volatile content | Loss on drying, 105°C, 3 h | ≤5.0% |
| Ash (as Na2O) | 700°C ignition | ≤0.5% |
| pH (4% solution) | JIS K6726 | 5.0–7.0 |
| Gel particle retention | +60 mesh wet sieving | ≥90% through |
In a woven textile sizing application on a Benninger warping line running 600 m/min with 8–10% size add-on, the high tensile strength of BP-24 film (55–65 MPa when conditioned at 23°C, 50% RH, per ASTM D882) reduces warp stops at the reed. Desizing efficiency in hot-water baths above 85°C exceeds 98% within 30 seconds contact, provided the bath pH is kept neutral. Batch-to-batch viscosity drift during size-box circulation was +2.3% over 8 hours in a mill audit, acceptable for weaver’s beam consistency. The resin’s low ash content limits insoluble residue on the size box rollers, a known failure mode with lower-purity PVA grades.
Paper Surface Strength and Pigment Binding Efficiency
Metering size press formulations employing oxidized starch as a co-binder benefit from BP-24 at 0.5–1.2 wt% (dry basis on starch) to raise IGT pick strength (ISO 3783) by 30–45% over starch-only controls. Viscosity stability at 60°C circulation in a Voith SpeedSizer unit was measured at ±4% over a 12-hour production window when the pH was buffered with 0.1% sodium bicarbonate. Because the fully hydrolyzed structure contains minimal residual acetyl groups, the binder film exhibits lower critical surface tension wetting on clay-coated substrates than partially hydrolyzed grades—this limits excessive penetration into the sheet and improves optical density in inkjet print trials conducted with pigment black 7 dispersion at 800 dpi. A board mill documented a reduction in blanket dusting on a Heidelberg Speedmaster XL 106 after switching from a partially hydrolyzed PVA (87–89 mol%) to BP-24 at equivalent binder load. The primary operational boundary is the dissolution temperature: batch makeup must exceed 88°C to avoid translucent “fish-eye” gel defects in the final coating color.
What Dissolution Temperature Window Ensures Complete Solubility?
Complete dissolution of BP-24 in deionized water requires a minimum temperature of 87°C with high-shear mixing (Silverson L5M rotor-stator at 3,000 rpm). At 80°C, insoluble gel fractions as high as 2.1 wt% were recovered on a 100 µm filter, attributable to residual crystalline domains in the fully hydrolyzed polymer backbone. Heating to 95°C eliminates these fractions within 20 minutes. In contrast, partially hydrolyzed PVA grades (e.g., CCP BP-17, hydrolysis 86.5–89.0 mol%) achieve clear solutions at 55–70°C. This higher thermal threshold necessitates jacketed preparation vessels with steam sparging, and direct steam injection into the powder dispersion must be managed to avoid localized overheating above 130°C, which can cause yellowing and chain scission evidenced by a drop in intrinsic viscosity of 0.1–0.3 dL/g. The dissolution temperature of BP-24 is a deliberate functional attribute: in hot-water-soluble laundry bags for hospital linen, the film remains intact during cold (20°C) sorting and releases only at washer temperatures above 85°C, a property that would fail with a lower-hydrolysis grade.
The risk of premature dissolution in high-humidity storage is controlled by packaging in moisture-impermeable laminated liners (PE/Alu/PET). A warehouse audit demonstrated that bags exposed to 75% RH at 30°C for 48 hours absorbed 4.8% moisture, resulting in screw feeding issues on a compounded pelletizing line. Therefore, pre-drying with a desiccant air dryer at -40°C dew point and 80°C resin bed temperature is specified before any melt processing operation.
When Borax Crosslinking Must Be Scrupulously Avoided
Polyvinyl alcohol grades with a hydrolysis degree above 98 mol% undergo rapid gelation in the presence of borate ions (e.g., borax, boric acid) due to di-diol complexation. For BP-24, a sharp viscosity increase exceeding 1,000% within 60 seconds was observed when a 5% aqueous solution at 90°C was dosed with 0.2 wt% sodium tetraborate decahydrate, rendering the solution non-pumpable. This sensitivity precludes its use in starch-based corrugating adhesives that traditionally incorporate borax decahydrate as a tackifier. In such systems, partially hydrolyzed grades like BP-17, where residual acetate groups sterically hinder borate crosslinking, are substituted. A converting plant experienced seal failure in a positive displacement pump after a formula crossover error delivered BP-24 into a borax-containing adhesive tank; gelation blocked the 50-mm internal pipe diameter within 3 minutes. The operational rule is absolute: BP-24 must never contact any solution containing free borate, metaborate, or perborate ions unless a competing polyol chelator (e.g., mannitol at 5:1 molar ratio to boron) is pre-added and validated.
Migration of plasticizers from PVC films is another documented incompatibility. In laminating applications, direct contact with dioctyl phthalate (DOP) at 60°C for 72 hours caused 12% weight gain and tensile strength loss of 34%, as measured by ASTM D882. Intermediate urethane-adhesive barrier layers 2–3 µm thick successfully arrested plasticizer migration in a flexible packaging trial.
For wood adhesive compounding, BP-24 is employed as a rheology modifier and water-retention agent in polyvinyl acetate (PVAc) emulsion formulations. The addition of 2.5 wt% (based on emulsion solids) raises the Wood Assembly Line Viscosity (WALV) from 4,000 mPa·s to approximately 9,500 mPa·s (Brookfield RV, spindle #5, 20 rpm, 25°C), improving open time on beech substrates to 18 minutes at 23°C and 60% RH. Heat resistance of the glued joint (EN 204 D3) improved, with fiber tear exceeding 80% after a 7-day ambient cure followed by 4-hour cold-water immersion. The low viscosity drift of BP-24 versus a medium-hydrolysis PVA (e.g., 88 mol%) in the pH range 4.0–5.5 minimizes shear-induced destabilization during continuous drum-unloading of 1,000-liter reactor batches.
Adhesive Viscosity Build and Substrate Wetting Characteristics
In remoistenable adhesive coatings for envelope seams and labeling, BP-24 provides higher wet tack on alkaline paper substrates than dextrin-only formulations. A manucatured on a Nobatech coating line operating at 200 m/min with a comma bar coater demonstrated that a 15% solids blend (70 parts BP-24, 30 parts fully hydrolyzed starch) yielded an instantaneous tack value of 62 g/cm² (Probe Tack Test, 500 g load, 1 s dwell), compared to 38 g/cm² for a dextrin control. The critical surface tension of the dried BP-24 film was measured at 37.0 mN/m (sessile drop method using water/diiodomethane), which balances wet-out and excessive penetration on standard envelope paper (Cobb60 value 24 g/m²). The remoistening activation temperature of the adhesive film is ≥65°C, aligning with industrial envelope-sealing machinery that applies a steam pulse.
High-speed bookbinding (Müller Martini KM 410 at 12,000 cycles/hr) with a 0.15 mm wet adhesive film thickness leverages the rapid setting of BP-24 upon cooling from the pot temperature of 55°C to the substrate temperature of 22°C—a thermal gelation mechanism inherent to high molecular weight, fully hydrolyzed PVA. Squeeze-out migration into the book block was quantified at 0.3 mm from the spine edge, below the 0.5 mm threshold that causes page-stiffening complaints. In these applications, the substitution of a partially hydrolyzed PVA would delay set time by 4–6 seconds and increase penetration.
| Grade | Hydrolysis (mol%) | Viscosity 4% (mPa·s) | Dissolution Temp. (°C) | Tensile Strength (MPa) | Typical Application Focus |
|---|---|---|---|---|---|
| BP-05 | 98.5–99.5 | 4.5–6.0 | 75–85 | 40–48 | Emulsion polymerization protective colloid, low-viscosity binder |
| BP-17 | 86.5–89.0 | 20.5–24.5 | 55–70 | 30–38 | Cold-water soluble film, borax-compatible adhesives, dispersing agent |
| BP-24 | 98.5–99.5 | 22–28 | 87–95 | 55–65 | Hot-water soluble film, paper size, textile size, high-tack adhesive |
In unit-dose detergent packaging where water-soluble film must dissolve completely in cold wash water, BP-24 is unsuitable. Film made from BP-24 in a blown-film extrusion process (single-screw, 30 L/D, barrier screw with Maddock mixing section) achieved complete dissolution only at 85°C in an agitated vessel per OECD 303A simulation, retaining 21% residual film mass at 30°C after 60 minutes. This grades the product outside the acceptance band for cold-water unit-dose applications. The crystallinity of BP-24 film, determined by DSC (Mettler Toledo DSC3+) at approximately 42–46 J/g melting enthalpy, explains this behavior. In contrast, partially hydrolyzed BP-17 or special cold-water grades display significantly lower crystalline fractions.
For temporary protective films in semiconductor fabrication where low ionic contamination is paramount, BP-24’s ash content of ≤0.5% may still require additional ion-exchange purification steps if chloride or sulfate residues exceed 10 ppm. Published data for this specific configuration is limited, but a semiconductor packaging facility reported that passing a 10% BP-24 solution through a mixed-bed ion exchange column (Purolite MB400) reduced conductivity from 32 µS/cm to 5.8 µS/cm, meeting the specification for a non-critical cleanroom peelable coating. Further reduction in sodium content below 100 ppm on dry resin is necessary when BP-24 is considered as a binder for ceramic green tape in MLCC production, where residual alkali ions degrade dielectric performance during sintering.
