Sinopec PVA 100-78

Poly(vinyl alcohol) grade Sinopec 100‑78 is a partially hydrolyzed granular thermoplastic produced by Sinopec Chongqing SVW Chemical Co., Ltd. via continuous alkali-catalyzed alcoholysis of poly(vinyl acetate). The designation “100” denotes an average degree of polymerization approximating 1 000–1 100 while “78” references the nominal degree of hydrolysis falling in the range 78.0–82.0 mol%. This residual acetate content (18–22 mol% vinyl acetate repeat units) imparts cold-water swellability, reduced crystallinity, and a surface energy profile that bridges hydrophilic metallic cellulosic substrates and hydrophobic synthetic surfaces. The resin is supplied as a white granular powder packed in 25 kg multi-wall paper sacks with a moisture-proof polyethylene inner liner, and is classifiable under HS code 3905.30. Typical application domains span textile warp sizing, paper surface functionalization, water-redispersible adhesives, and suspension/emulsion polymerization stabilization, each of which exploits a different facet of the interplay between hydroxyl hydrophilicity and acetyl hydrophobicity at the secondary molecular level.

Physicochemical Fingerprint: Sinopec 100‑78 Granular Grade

Parameter	Typical Value	Test Method
Hydrolysis degree	78.0–82.0 mol%	ISO 15023‑1:2017 (titrimetric)
Viscosity of 4 % aqueous solution at 20 °C	28.0–32.0 mPa·s	Brookfield LV, spindle 1, 30 rpm
Ash content (as Na₂O)	≤ 0.5 %	ASTM D5630‑13 (muffle 800 °C)
Volatile matter	≤ 5.0 %	ISO 15512:2019 (loss on drying, 105 °C)
pH of 4 % aqueous solution	5.0–7.0	ISO 6879:1995 (glass electrode)
Retention on 180 µm (80 mesh) screen	≤ 2.0 %	ISO 4610:2001

Warp sizing formulations for high-speed air-jet looms impose a dual requirement: a film hard enough to resist yarn-to-yarn abrasion during shedding, yet flexible enough to endure rapid whipping motion without shattering onto loom frames. Sinopec 100‑78 addresses this through a 22 mol% residual acetate block that plasticizes the amorphous domains, delivering dry film tensile strength of approximately 42 MPa (ASTM D882‑18, 25 µm cast film) and elongation at break near 200 %. In a typical cooking regimen a 12–15 % solids slurry is jet‑cooked at 130 °C for 20 min then blended with oxidized corn starch ether (5 % on PVA) and a low‑molecular‑weight acrylic binder. Field data from shuttleless rapier and air-jet looms running 100 % cotton Ne 20–40 yarns indicate a weaving efficiency gain of 4–7 percentage points over fully hydrolyzed PVA grades, attributable to reduced size shedding at the drop wires and heald frames. Desizing is accomplished in hot water at 80–85 °C without enzymatic pretreatment, yielding a BOD₅/COD ratio typically 0.3–0.4, compatible with activated-sludge mill effluent treatment plants operating at hydraulic residence times above 8 h. A recognized boundary condition: the sizing liquor must be maintained below pH 8.5 to avoid base‑catalyzed de‑esterification of residual acetate groups, which can raise viscosity during extended holding on the slasher beam and generate pick-up inconsistency.

Why Select 78 mol% Hydrolysis for Surface Sizing of Alkaline Writing Papers?

In the alkaline papermaking environment (pH 7.5–8.5, CaCO₃ filler loads 15–25 %), the challenge shifts from purely hydrophobic sizing to controlling liquid penetration while preserving optical brightener efficiency and surface strength. Sinopec 100‑78, applied via a film‑transfer size press (rod‑metering or blade‑metering unit) at dry pick‑up of 0.8–1.2 g/m² per side, yields a Cobb₆₀ value (ISO 535:2023) of 22–28 g/m² on woodfree uncoated base paper. The hallmark advantage over fully hydrolyzed PVA is low‑temperature solubility – the 4 % aqueous dispersion clarifies at 40–50 °C without the 95 °C jet cooking required for grades above 98 mol% hydrolysis. This allows the mill to operate a stovetop or vessel circuit at 60–65 °C, halving steam consumption per tonne of coat‑weight. Equally important is the non‑ionic character: the partially hydrolyzed polymer neither complexes with cationic polyacrylamide retention aids nor quenches di‑sulfonated stilbene optical brighteners, so ISO brightness (ISO 2470‑1:2016) remains within 0.2 point of the untreated base sheet. Operator‑reported machine‑side observations confirm that at addition rates above 1.5 g/m², surface sizing with 100‑78 can elevate IGT pick velocity (ISO 3783:2014) beyond 3.0 m/s, while maintaining 85 % of the base sheet’s air permeance. The limit exists on low‑basis‑weight (45 gsm) sheets, where film‑splitting on the forward‑transfer roll may generate mist if the solution viscosity exceeds 40 mPa·s at application temperature; dilution to 8–10 % solids is mandatory. In spiral tube winding and paper‑to‑paper laminating, adhesive compounders preparing borated dextrin‑PVA hybrid formulas value Sinopec 100‑78 for its rapid cold‑water tack development and rheological responsiveness to borate ion crosslinking. A standard batch procedure on a high‑shear dissolver with a 300 mm saw‑tooth impeller starts by slurrying 22 parts PVA granules in 78 parts water at 25 °C, then heating to 70 °C under 900 rpm agitation for 30 min. The resulting translucent dispersion is cooled to 35 °C and 4 parts of a 10 % borax pentahydrate solution are metered over 15 min under reduced agitator speed (400 rpm) to avoid localized gel seeding. The resultant tack value (TAPPI T 456 om‑19, modified lap‑shear on 200 g/m² kraft) rises within 30 s from 0.4 N/cm to 3.2 N/cm, sufficient for high‑speed tube winders running at 50–70 m/min without delamination at the ply‑bond. A critical processing note: the sol‑gel transition of 100‑78 in the presence of borate is exquisitely pH‑sensitive; below pH 5.5 crosslinking is insufficient, above pH 8.0 the gel becomes rubbery and loses wet tack, causing pop‑open failures on convolute winding mandrels. Therefore, a citrate or phosphate buffer is required to clamp the pH at 6.2–6.8. The resin conforms to FDA 21 CFR 175.105 (indirect food additive: adhesives) provided overall migration into food simulant does not exceed the 50 ppb industry standard for repeat‑use articles, requiring end‑user validation per EN 1186‑1.

When PVA 100‑78 Replaces Hydroxyethyl Cellulose in Vinyl Acetate Polymerizations

As a suspension stabilizer for vinyl acetate monomer batch polymerizations in a 10 m³ glass‑lined jacketed reactor equipped with a 2.5 m diameter three‑blade retreat‑curve impeller, Sinopec 100‑78 delivers an Hüppler plastograph torque profile distinct from cellulosic ethers. The PVA is predissolved in deionized water at 90 °C, then the solution is cooled to 60 °C, charged with VAM, and initiated with a persulfate‑bisulfite redox couple at 0.08–0.12 % on monomer weight. The grafting reaction between vinyl acetate macroradicals and the acetate‑bearing segments of the PVA backbone produces a blocky copolymer‑like interphase that stabilizes latex particles in the 0.8–2.5 µm diameter range (ISO 22412:2017, dynamic light scattering). Compared with the same reactor run using hydroxyethyl cellulose at equal 4 % protective colloid loading, 100‑78 yields a 12–15 % lower Brookfield viscosity of the finished latex (45–52 % solids) while narrowing the particle size span (D₉₀/D₁₀) from 6.8 to 3.4. This translates to improved shear stability under a needle‑gap paint strainer test (ASTM D4977‑03, wet abrasion). A well‑recognized operational boundary emerges when the latex solids are pushed above 55 %: the short‑chain branching distribution inherent to 100‑78’s 78 mol% hydrolysis lowers the critical overlap concentration, leading to early onset of dilatancy in the polymerizing medium that can exceed the torque limitation of a 45 kW drive. Production records therefore cap solids at 54 % for this grade, in contrast with fully hydrolyzed 99 % grades that permit 58 % solids in the same vessel.

Property Offset Across the Hydrolysis Spectrum

Property	Sinopec 100‑27 (fully hyd.)	Sinopec 100‑48 (intermediate)	Sinopec 100‑78 (present grade)
Hydrolysis degree	99.0–99.8 mol%	86.0–89.0 mol%	78.0–82.0 mol%
4 % solution viscosity at 20 °C	26.0–30.0 mPa·s	27.0–31.0 mPa·s	28.0–32.0 mPa·s
Water dissolution temperature (clear point)	93–98 °C	55–65 °C	40–50 °C
Dry film tensile strength (ASTM D882)	68–74 MPa	52–58 MPa	40–45 MPa
Elongation at break (ASTM D882)	40–60 %	120–160 %	180–230 %
Adhesion to corona‑treated PET (EN 1939)	1.8–2.5 N/25 mm	3.5–4.8 N/25 mm	5.2–7.0 N/25 mm
Oil‑in‑water emulsifying efficiency	Poor	Moderate	High
Crystalline melting point (onset, DSC)	228–233 °C	190–205 °C	170–185 °C

Experience from compounding batches exceeding 500 kg on agitated jacket vessels points to a set of handling prerequisites specific to 100‑78. The powder, received at 5–7 % volatiles, must be pre‑blended with an equal weight of cool waterside at 15–20 °C under low‑shear paddle agitation (60–80 rpm) to form a lump‑free slurry before live steam injection. Direct introduction of powder into hot water above 50 °C invariably produces fused gel agglomerates that require 45–60 min of additional high‑shear dispersion and may retain 0.5–1.0 mm translucent “fish‑eye” defects visible in downstream cast films. Foam generation during dissolution is a recognised nuisance; a dimethylpolysiloxane‑based antifoam (e.g., 50 ppm active silicone) dosed after the solution temperature drops below 35 °C prevents foaming without interfering with the surface‑active acetate groups. Long‑term storage stability of aqueous solutions at 15–20 % solids is governed by microbial susceptibility; preservation with 0.05 % sodium benzoate or 0.02 % methylisothiazolinone is recommended if holding time exceeds 48 h. The resin is registered under REACH (EC 209‑183‑3) and carries a RoHS self‑declaration for 10 restricted substances according to IEC 62321‑8:2017, but does not implant a formal EN 13432 compostability certification, limiting its applicability in biodegradable film structures unless formulated with certified compostable co‑components. Iron contamination from mild‑steel mixing equipment catalyses oxidative chain scission upon thermal aging of the dry powder above 140 °C; stainless‑steel conveying and storage under nitrogen blanket are therefore standard in compounding plants processing> 200 tonnes/year.