Wanwei PVA 22-99 (H) (PVA 100-42)

Polyvinyl alcohol resin identified under the dual designations Wanwei PVA 22-99(H) and PVA 100-42 occupies a narrow viscosity niche among fully hydrolysed, high-molecular-weight grades. The manufacturer’s internal coding system defines the first numeral pair—22—as the midpoint viscosity range measured at 4% aqueous solution, 20 °C, according to GB/T 12010.2 (rotational viscometer method). The suffix 99 corresponds to a degree of hydrolysis exceeding 99.0 mol%, confirmed by saponification titration per GB/T 12010.3. The (H) modifier distinguishes a sub-grade processed to a tighter viscosity window of 24–26 mPa·s, versus the standard 22-99 band of 21–23 mPa·s. The alternative identifier PVA 100-42 is encountered in export documentation and references a nominal 10% solution viscosity approximating 100 mPa·s under ISO 15023-2:2019 conditions, coupled with a 4:2 ratio of residual acetyl content to molecular weight characteristics; it is not a partially hydrolysed grade. This product is manufactured by Anhui Wanwei Group through a continuous alcoholysis process with strict control over residual ester groups and ash content.

Specifications and Test Method Matrix

Why Does This Grade Demand a Strict Dissolution Regime Below 95°C?

Fully hydrolysed grades in the 22-24 mPa·s range require elevated thermal energy for complete solvation, yet the glass transition of the dry resin sits near 78–85 °C. When jacket temperatures of an agitated dissolution vessel surpass 95 °C, the surface of semi-swollen granules can pass through a thermoplastic tacky stage, leading to agglomeration into fist-sized gel bodies that resist further hydration even under high-shear dispersion. On a 500 L jacketed tank equipped with a Ekato MIG anchor and an internal high-shear rotor-stator (IKA Ultra-Turrax UTL 1000 in-line), the recommended procedure is to pre-wet PVA powder in ambient tempered water at a 1:3 polymer-to-water ratio, then ramp to 88–92 °C over 45–60 min while maintaining rotor speed at 1 200–1 500 min⁻¹. Direct steam injection is avoidable unless a Venturi eductor precisely meters steam and cold water simultaneously, maintaining slurry temperature within ±2 °C of setpoint. Dissolved solution viscosity measured inline via Rheonics SRV viscometer typically stabilises after 120 min of circulation.

Gel particle count becomes critical in film extrusion and sizing applications. A 100 µm filtration test (ISO 4576 wet screening) on a 10% solution prepared at 90 °C must yield ≤ 5 ppm insoluble residue. If the temperature plateaus too early, residual crystalline domains persist and elevate screen residue above 20 ppm, causing die-lip build-up during cast film production.

When 22-99(H) Supplements Partially Hydrolysed PVOH in Paper Surface Sizing

Paper mills operating flooded-nip size presses at 800–1 200 m/min traditionally employ partially hydrolysed grades with viscosities of 3.5–6.0 mPa·s (4%, 20°C) to maintain runnability. Incorporating 10–15% of Wanwei 22-99(H) into a base size formulation of oxidised corn starch (8.0% solids, 50 °C) raises the dilute-solution viscosity to 18–22 mPa·s at 10% total solids—a range that remains manageable with a rod-metering size press. The benefit manifests as an increase in internal bond strength measured by TAPPI T 569 pm-00: values shift from 180–200 J/m² to 240–270 J/m² on linerboard, attributable to the high-molecular-weight fraction forming additional hydrogen bonds between cellulose fibres. Production data from a 4.6 m-wide Voith SpeedSizer showed no significant increase in misting when the blend ratio was kept below 18%, provided the size press roll hardness was maintained at 90–95 P&J.

A Textile Warp Sizing Bath Without Added Plasticisers

Polyester-cotton blended yarn (Ne 30/1) sized on a Karl Mayer SMR beam sizing machine experienced excessive hairiness when using a standard 17-88 PVOH film due to brittle failure at low loom shed openings. Substituting Wanwei 22-99(H) without external plasticiser—relying solely on retained moisture equilibrium of 12–14% after drying—yielded a size film with tensile strength of 48–52 MPa and elongation at break of 120–140% (conditioned at 23 °C, 65% RH, ASTM D882-18). The high molecular weight contributes significantly to abrasion resistance during weaving on air-jet looms; drop-weight abrasion cycles increased from 220 to 410 before yarn breakage, as recorded by the Zweigle G 557 tester. The absence of urea or glycerol eliminates thermomigration issues during long-term storage of sized beams in fluctuating humidity, a documented failure point with 17-88 formulations where plasticiser leaching stiffens the film.

Polymerisation aid applications represent a secondary but high-volume outlet. In vinyl chloride suspension polymerisation conducted at 55–65 °C, the 22-99(H) grade functions as a primary dispersant when used in combination with secondary low-hydrolysis PVOH (e.g., 72 mol% or 88 mol%). The controlling parameter is the interfacial tension reduction at the VCM-water interface. Measurements with a Krüss K100 tensiometer show that a 0.1% aqueous solution of 22-99(H) at 60 °C yields an equilibrium interfacial tension of 9.2 mN/m against vinyl chloride, compared to 11.5 mN/m for a standard 17-88 grade. This lower tension correlates with a narrower particle size distribution in the resulting PVC resin; sieve analysis after polymerisation (ISO 1624) consistently yields ≤ 1.2% retention on a 250 µm screen for leather-cloth grades, against 2.8% with the lower-viscosity dispersant. Operational limits apply: reactor fouling increases measurably when the PVOH solution feed temperature falls below 25 °C, forming microgels that seed irregular grains.

How Does Viscosity Differ from 17-99 and 26-99 Grades in Adhesive Formulation?

In water-borne tube winding adhesives for paper cores, the Brookfield viscosity of a 12% solids compound with 5% calcium carbonate filler shifts markedly with the PVOH base viscosity. The following measurements were taken at 25 °C, spindle 4 at 20 rpm:

• Formulation based on Wanwei 17-99: 8 200 mPa·s
• Formulation based on Wanwei 22-99(H): 17 500 mPa·s
• Formulation based on Wanwei 26-99: 28 300 mPa·s

The 22-99(H) occupies the functional threshold where open time on kraft paper exceeds 15 seconds (as measured by two-finger wet tack test) while still allowing a single-station pump to transfer adhesive without cavitation at 3 bar back pressure. The higher 26-99 viscosity forces a reduction in solids to 9–10%, diminishing green bond strength to unacceptable levels below 2.5 N/cm. Thus 22-99(H) is often specified as a single-component base for high-speed spiral tube winders operating at 40–55 m/min.

Where Extraction of Residual Methanol Defines Film-Grade Suitability

Blown film extrusion of water-soluble PVOH film for agrochemical packaging (ISO 20753) requires volatile organic content below 0.8%. The standard 22-99 grade may retain up to 1.2% methanol and methyl acetate from the alcoholysis step. The (H) variant undergoes an additional counterflow washing stage and vacuum drying at 80 °C for 6 hours in a Conaform dryer, reducing total volatiles to 0.4–0.6%. This lower residual content eliminates bubble formation during bubble-blown film processing at 190–210 °C melt temperature and keeps the film’s cold-water solubility within ≤ 60 seconds at 10 °C (MSTM 205). The film’s blocked-tack resistance however declines when relative humidity exceeds 55%; pre-drying pellets at 80 °C for 3 hours in a desiccant dryer to a moisture content of 0.2–0.3% is mandatory before extrusion on a single-screw machine with L/D 30:1 and a decompression screw geometry.

Incompatibilities and Storage Constraints in Humid Environments

Because the hydroxyl functionality exceeds 99 mol%, the polymer exhibits rapid moisture regain. Sacks opened in ambient conditions above 60% RH must be resealed within 4 hours to avoid moisture pickup beyond 7%, which causes caking and interferes with metering accuracy on gravimetric loss-in-weight feeders. The material must not be stored in proximity to aldehydes or borates; even trace formaldehyde vapour in a shared warehouse can initiate acetalisation, increasing the insoluble fraction above the 0.1% limit specified for optical-grade adhesive applications. Comparative competitive grades such as Kuraray Poval 22-99 or Sinopec 2299 share similar hydrolysis levels but differ in ash content and pH; the Wanwei (H) variant typically offers lower ash (≤ 0.5% vs. ≤ 0.7%) due to a demineralised wash stage, an advantage in capacitor-grade PVOH but immaterial for general adhesive use.