ÇKP PVA BP-04N

CCP PVA BP-04N is a partially hydrolyzed polyvinyl alcohol grade supplied by Chang Chun Petrochemical Co., Ltd., characterized by a nominal degree of hydrolysis of 87.0 ± 1.0 mol% and a 4 % aqueous solution viscosity of 4.5 ± 0.5 mPa·s at 20 °C as determined according to JIS K6726:1994. The product is manufactured through a controlled alcoholysis route that delivers a narrow molecular weight distribution, a low population of insoluble gel particles, and an ash residue typically below 0.4 wt%. Primary application fields include temporary organic binder systems in advanced ceramic processing, surface sizing of uncoated paper grades, and water-borne adhesive compounding, where rapid cold‑water dissolution and a predictable thermal decomposition profile are essential.

A Binder Engineered for Water‑Soluble Sacrificial Cores in Advanced Ceramics

In tape casting of alumina, zirconia, or barium titanate substrates the organic binder must impart sufficient green strength for handling and punching while degrading cleanly during the co‑firing cycle. BP‑04N is introduced at addition levels of 1.5 – 3.0 wt% on a dry‑ceramic‑powder basis into an aqueous slip prepared with a Dispermat^® high‑speed dissolver fitted with a 50 mm Cowles blade, operating at a tip speed of 8 – 12 m·s⁻¹. The low‑viscosity signature of BP‑04N allows slip solids loadings to reach 75 – 80 wt% without exceeding a Brookfield viscosity of 2000 mPa·s (Spindle LV‑4, 60 rpm), a regime that supports gap‑level uniformity during casting through a doctor blade set to 0.20 – 0.50 mm. After drying at 60 °C for 12 h the green tape displays a tensile strength of 2.8 – 3.5 MPa ( ASTM D882‑18, dumbbell specimen punched transverse to the casting direction) and an elongation at break below 15 %, which is sufficient for roll‑to‑roll lamination and via‑punching operations. The binder burnout profile is a critical processing parameter. A simultaneous TGA/DSC run (ASTM E1131‑08) on a green tape heated at 1 °C·min⁻¹ in flowing air shows that BP‑04N begins oxidative decomposition around 220 °C, reaches maximum mass loss at 320 °C, and leaves a residue of less than 0.15 wt% at 600 °C. In side‑by‑side comparison, the standard BP‑04 grade typically yields a residue of 0.35 – 0.50 wt% under identical conditions. The lower residue of BP‑04N is directly attributable to a reduced sodium acetate content—specifically a sodium level below 0.15 wt% as measured by ICP‑OES—and to an ash specification (JIS K6726) tightened to ≤ 0.4 wt%. This difference reduces the risk of glass‑phase inclusions in co‑fired multilayer ceramics and is considered mandatory when processing high‑purity alumina (≥ 99.6 %) for insulating substrates.

Why Does BP‑04N Require Controlled Pre‑drying in High‑Humidity Environments?

Partially hydrolyzed polyvinyl alcohol grades are inherently hygroscopic. BP‑04N exhibits a moisture uptake of 1.2 – 1.4 wt% per 24 h at 25 °C and 60 % RH when exposed as a loose powder. On a production floor operating above 60 % RH, uncontrolled moisture absorption leads to powder caking in storage silos, a reduction in flow function coefficient below 4.0 ( ASTM D6128‑16 ring shear test), and a measurable increase in undissolved gel specks when the powder is later dispersed in cold water. Consequently, facilities without climate‑controlled powder handling must pre‑dry BP‑04N in a forced‑circulation oven at 50 °C for a minimum of 4 h immediately before weighing. If the powder is conveyed pneumatically, the conveying air should be dehumidified to a dew point of –20 °C or lower. Failure to observe these measures results in erratic viscosity during slip make‑up and variable green density in tape‑cast sheets, with density deviations exceeding ± 0.05 g·cm⁻³ relative to a target of 2.50 g·cm⁻³ in alumina tapes. Aqueous adhesive compounding with BP‑04N typically proceeds in a jacketed reactor equipped with a low‑shear anchor stirrer. The powder is sprinkled into cold water (10 – 15 °C) under agitation to avoid lump formation, then heated to 85 °C for complete dissolution. The resulting solution maintains a pH of 5.5 – 6.5 and does not require alkaline buffering for most adhesive formulations intended for paperboard or envelope seams. BP‑04N is compatible with common plasticisers such as glycerol (up to 20 phr based on dry PVA) and with reactive crosslinkers including glyoxal (0.5 – 1.5 phr). However, it must not be combined with borax (sodium tetraborate) or aluminium sulphate in the same predispersion tank, because these polyvalent salts trigger immediate gelation through di‑diol complexation, an effect that becomes irreversible once the solution viscosity exceeds 5000 mPa·s at 25 °C. In practice, when a borate‑based wet‑strength agent is required, it is added as a second‑stage application after the PVA film has been partially dried.

When Replacing BP‑04 in Paper Surface Sizing, What Performance Shifts Occur?

Converting from a standard BP‑04 grade to BP‑04N in a film‑press surface sizing operation on wood‑free printing paper, with a size pickup of 1.2 – 1.5 g·m⁻² per side, produces a measurable difference in coating uniformity and printability. BP‑04N dissolves completely within 30 min at 90 °C in a batch‑cook preparation, whereas BP‑04 under the same conditions can retain a residual gel‑particle count of 50 – 80 particles per 100 cm³ of solution as counted by a particle sizer with a 5 μm threshold. The lower gel‑count translates into a more homogeneous film, reducing the incidence of micro‑deposits that interfere with inkjet ink absorption. Surface strength, evaluated by the IGT pick test (ISO 3783:2006), increases from a typical 2.1 m·s⁻¹ with BP‑04 to 2.5 m·s⁻¹ with BP‑04N at an equivalent application weight. Simultaneously, the Cobb₆₀ value drops by approximately 5 g·m⁻², indicating a slight improvement in liquid hold‑out. These shifts are attributable to a narrower particle size distribution of BP‑04N ( D50 = 110 – 150 μm, D90 < 280 μm versus D50 = 170 – 250 μm for BP‑04) and a lower content of high‑molecular‑weight fractions that tend to agglomerate during cook‑up. The changeover does not require different operating set‑points on a Metso OptiSizer equipped with a blade metering system; however, the circulation loop filtration must be upgraded to a 100 μm mesh to capture any occasional skin flakes that form if the cook tank headspace temperature exceeds 95 °C.

JIS K6726:1994-aligned comparison of select PVA grades

Property	Test method	BP‑04N	BP‑04	BP‑17
Degree of hydrolysis	JIS K6726	87.0 ± 1.0 mol%	86.5 – 89.0 mol%	87.0 – 89.0 mol%
Viscosity (4 % aq., 20 °C)	JIS K6726	4.5 ± 0.5 mPa·s	4.0 – 5.0 mPa·s	20.5 – 24.5 mPa·s
Ash	JIS K6726	≤ 0.4 wt%	≤ 0.6 wt%	≤ 0.6 wt%
Sodium (Na)	ICP‑OES	≤ 0.15 wt%	≤ 0.30 wt%	≤ 0.35 wt%
Volatile matter	JIS K6726	≤ 5.0 wt%	≤ 5.5 wt%	≤ 5.5 wt%
Particle size D50	Laser diffraction (dry)	110 – 150 μm	170 – 250 μm	180 – 260 μm

Ash Content Reduction and Binder Burnout in CMC Tapes

One differentiating feature of BP‑04N is its formulation as a low‑sodium, low‑ash variant explicitly tailored for ceramic matrix composite (CMC) tape development and for high‑purity thin‑film substrates where residual alkali metals degrade dielectric performance. The sodium specification of ≤ 0.15 wt%, enforced through a modified methanolysis washing step, is at least 50 % lower than that of the conventional BP‑04 grade. During the burnout stage of an oxide‑oxide CMC tape—ramped at 0.5 °C·min⁻¹ to 600 °C with a 2 h dwell—BP‑04N leaves a total oxide‑derived residue of 0.10 – 0.15 wt%, which is predominantly silica from the trace anti‑dusting additive. This residue level is below the threshold at which a glassy intergranular phase is detected by SEM/EDS in mullite‑based matrices; in contrast, BP‑04 residues above 0.35 wt% have been correlated with a 1.5 – 2.0 % decrease in flexural strength (measured by ASTM C1161‑18 four‑point bend at 1200 °C soaking) in published studies on nextel‑reinforced composites. Published data specific to BP‑04N in this application context remain limited, but batch records from pilot‑scale woven‑fabric prepreg lines indicate that the cleaner burnout permits a faster heating ramp—0.7 °C·min⁻¹ instead of 0.5 °C·min⁻¹—without introducing pyrolysis‑induced blisters, reducing furnace cycle time by approximately 12 %. In water‑soluble film extrusion for unit‑dose detergent packaging, BP‑04N is processed on a single‑screw extruder with a 25 : 1 L/D ratio and a barrier screw, with zone temperatures profiled from 160 °C (feed) to 195 °C (die). The compound is pre‑plasticised with 12 – 15 phr of glycerol and 0.3 phr of a non‑phenolic antioxidant. No thermal stabiliser based on amine chemistry is permissible; even trace carryover of amine‑based masterbatch on shared equipment causes discoloration and a drop in the elongation at break from 280 % to below 180 % ( ASTM D882) within 3 h of residence time. BP‑04N’s low gel‑particle content is critical here, because any undispersed gel in the melt leads to pinhole‑sized defects in the 30 – 50 μm film, which are detectable by a water‑leakage integrity test (ASTM F1929‑15) and constitute a rejection criterion at filling speeds above 600 pouches·min⁻¹. Compared with a medium‑viscosity grade such as BP‑17, BP‑04N reduces extruder back‑pressure by 8 – 12 bar at a throughput of 80 kg·h⁻¹, allowing a thicker film to be drawn without exceeding the drive‑motor current limit. The trade‑off is a narrower processing window for the frost‑line height: deviations beyond ± 3 mm from the 80 mm set‑point cause gauge variation exceeding ± 5 %, as recorded by an in‑line beta‑gauge thickness sensor, mandating closed‑loop feedback control on the air‑ring blower frequency.