Sinopec PVA 088-20 (PVA 1788)

Precision in Slasher Sizing: Matching PVA 088-20 with Starch Co-components for Polyester-Cotton Blends

A cooking kettle charged with softened water is heated to 92–95 °C under continuous agitation to dissolve Sinopec PVA 088-20 completely before adding thin-boiling maize starch. A total solids concentration of 10.5–12.0 % is targeted, with a PVA-to-starch dry-weight ratio of 65:35 for fine-count P/C 45×45 110×76 poplin fabric. An acrylic copolymer size additive at 8–12 % of the total solids reduces shedding on heddles and reed wires. In a Benninger SMR slasher running at 70 m/min, the size box temperature is maintained at 88 ± 2 °C and the squeezing pressure is set between 12 kN/m and 18 kN/m to achieve a size pick-up of 11–14 % owf. Cylinder drying temperature is zoned: first two cylinders at 120 °C, remaining four at 105 °C, yielding residual moisture below 3.2 %. Sized yarn hairiness Index (Zweigle G567) drops by 55–68 % relative to the unsized beam, and breaking force measured by ASTM D2256-10 increases by 22–28 %. The size film is readily desized using an α-amylase bath at 60–70 °C for 20 min, achieving a desizing efficiency above 98 % (evaluated by TEGEWA violet scale). Compliance with ZDHC Manufacturing Restricted Substances List Level 1 and OEKO-TEX® Standard 100 is demonstrated through absence of alkylphenol ethoxylates and heavy metals in the formulated size. Processing constraint: storing cooked size beyond 8 hours at 85 °C leads to a viscosity drop exceeding 15 % caused by partial retrograde starch hydrolysis; the kettle must be flushed with hot alkali (pH 10.5) after each batch to prevent gel skin formation on heating coils.

What Determines the Primary Particle Size Distribution in Vinyl Chloride Suspension Polymerisation When 88 mol% Hydrolysed PVA is the Sole Primary Dispersant?

The interfacial activity of Sinopec PVA 088-20 derives from its residual acetyl content of about 12 mol%, which anchors the polymer at the vinyl chloride monomer-water interface under turbulent agitation. In a 105 m³ autoclave operating at 56.5 °C with a pitch impeller speed of 110–130 rpm, the primary dispersant is dosed as a 5 wt% aqueous solution at a concentration of 450–600 ppm relative to VCM. A secondary dispersant—often a 62–65 mol% hydrolysed PVA—is co-injected at 80–150 ppm to narrow the particle size span. Under these conditions, the volume-median particle diameter D₅₀ measured by laser diffraction after drying is 145–160 µm with a span (D₉₀−D₁₀)/D₅₀ of 0.85–0.95. The cold-water swelling behaviour monitored in the laboratory with a focused beam reflectance measurement probe indicates that PVA with 88 mol% hydrolysis reduces the coalescence rate during the viscous conversion stage more effectively than a 72 mol% grade, because the longer chain pendent acetate blocks resist desorption from the droplet surface. The resulting resin, classified under ASTM D1755-15 as Grade 3 or 4, exhibits typical K-value 66–68, bulk density 0.52–0.58 g/cm³, and plasticiser absorption (DOP) 26–30 %. Reactor compliance with ASME Boiler and Pressure Vessel Code Section VIII is mandatory; the dispersant solution itself must meet FDA 21 CFR §178.3860 if the final PVC is destined for food-contact articles. A documented production-scale failure mode involves air entrained in the charging pump line that creates a foam blanket on the VCM surface, producing an unacceptably high fraction of fines (≤63 µm) exceeding 8 %. Online deaeration of the PVA solution via a centrifugal vacuum degasser is standard on larger reactor trains.

Parameter

Condition A (Low shear dispersant)

Condition B (Standard)

Condition C (High fines reduction)

PVA 088-20 dosage (ppm/VCM)

350

500

600

Secondary dispersant (ppm/VCM)

120

100

Agitation power input (kW/m³)

0.95

1.15

1.30

D₅₀ (µm)

172

153

141

Sub-63 µm fraction (%)

5.8

3.2

1.7

The above dataset, generated on a 30 L pilot autoclave with a Pfaudler retreat-curve impeller, illustrates the trade-off between particle size and agitator energy when PVA 088-20 is the primary interfacial modifier. The operational window tightens significantly at a D₅₀ below 135 µm: circulation within the autoclave must be sufficient to disperse the monomer but not so violent as to destroy the protective PVA film, a balance that frequently necessitates polymerisation temperature trimming of ±0.5 °C to maintain K-value consistency.

Surface sizing of linerboard produced from old corrugated containers (OCC) becomes technically demanding when the mill shifts to lightweight 90 g/m² grades requiring a Cobb value (water absorption) below 30 g/m² per TAPPI T441 om-20. A size press formulation blending oxidised corn starch at 8.5 % solids with Sinopec PVA 088-20 at 2.5 % solids (dry/dry ratio ≈ 22 % PVA) is applied via a Speedsizer AT at 800 m/min. The PVA must be pre-dissolved separately at 95 °C for 35 min and filtered through a 150 µm mesh before mixing with the starch stream to eliminate microgel specks. The hybrid film reduces sheet porosity (Gurley) by 42 % and raises ring crush strength (short-span compression per ISO 12192:2011) by 18–24 % compared with the starch-only control. At pH below 5.8, anionic colloidal silica retention aids can complex with the slightly anionic PVA via calcium bridging, creating rope-like deposits on the metering rod that appear as widthwise scratches on the sheet. The mill’s standard procedure requires maintaining headbox furnish pH at 6.5–7.2 and using a quaternary ammonium-compatible defoamer to suppress pinhole foam in the size press pan. Incoming PVA lot-to-lot viscosity variation of more than ±2 mPa·s shifts the dynamic surface tension at the application nip enough to alter the dry pickup by 1.5 percentage points, a sensitivity that justifies inline Brookfield viscometer control on the cooked PVA supply line.

When a Semi-Batch VAE Reactor Switches from Cellulose Ether to Polyvinyl Alcohol 088-20 as the Sole Protective Colloid, How Does Latex Rheology Change?

The replacement of hydroxyethyl cellulose with Sinopec PVA 088-20 in vinyl acetate-ethylene emulsion polymerisation immediately alters the viscosity-shear rate relationship of the final latex, shifting from a pseudoplastic non-structural profile to a thixotropic gel structure with a yield stress that rises from near zero to 4–8 Pa (measured via controlled-stress rheometry at 23 °C). The reactor is charged with an initial aqueous phase containing 4.5–6.0 wt% PVA 088-20 based on total monomer, adjusted so that the 4 % solution viscosity of the PVA lot (certificate value 22–26 mPa·s) does not exceed the point where heat transfer across the jacket coils becomes limiting. Ethylene pressure is maintained at 35–50 bar at 75 °C, and the balance of VAc is fed over 4.5 hours with a redox initiator system. PVA chains become partially grafted with vinyl acetate side branches during the reaction; the degree of grafting measured by solvent extraction and ¹H NMR is typically 18–25 % for 88 mol% hydrolysis grade, which is lower than that observed with 95 mol% PVOH but sufficient to impart colloidal stability without excessive bridging flocculation. The resulting latex with solids content 54–57 % is suitable for wood adhesives classified under EN 204/205 D2 and D3 durability classes when formulated with a polymeric isocyanate or aluminium chloride crosslinker. An operational incompatibility worth noting: the addition of amine-based pH buffers exceeding 0.3 wt% to the latex raises the pH above 6.8 and triggers a colour shift to yellow after 72 h storage at 50 °C, attributable to oxidation of residual ethylene-vinyl acetate sequences catalysed by the amine. Manufacturing equipment must be passivated with 5 % acetic acid solution before the first batch to remove iron contamination that forms dark specks visible in cast films under 20× magnification.

Spiral paper tube winding for industrial roll cores demands an adhesive that combines rapid tack development approaching 1.5 N/mm² within 12 seconds under 0.3 MPa winding pressure, yet enables repulping in neutral pH water at 40 °C within 30 minutes per ISO 5269-1:2005 disintegrability assessment. A cold-mix formulation containing 14.5 % Sinopec PVA 088-20, 6.0 % sucrose/urea blend as a gel-point depressant, 0.15 % benzisothiazolinone-based preservative, and 79.35 % water is prepared by dispersing the PVA powder in ambient water under a Cowles dissolver at 800 rpm, then heating indirectly to 88 °C and holding for 25 minutes. The finished adhesive exhibits a Brookfield LVDV viscosity of 2200–2800 mPa·s at 20 °C. On a high-speed tube winder of the Paco 650 type, the adhesive pickup is 8–10 g/m² per ply, with ply bond strength exceeding 380 N/m (TAPPI UM 802). Excess migration into the paper substrate is limited by the grade’s 88 mol% hydrolysis: a lower hydrolysis level would cause deeper penetration and starved glue lines, while full hydrolysis would produce brittle bonds that crack under compressive strength testing per DIN EN 12300. Regulatory alignment with EU Plastics Regulation (EU) 10/2011 for food-contact paperboard is achievable provided the finished tube does not exceed overall migration limits of 10 mg/dm² in simulant B. Storage stability of the adhesive exceeds 6 months at 20 °C but fails within 48 hours if exposed to one freeze-thaw cycle below –5 °C, manifesting as irreversible syneresis.

Property measured

100 % starch control

80:20 starch/PVA 088-20

70:30 starch/PVA 088-20

Test method

Cobb₆₀ (g/m²)

TAPPI T441 om-20

Ring Crush Index (N·m/g)

5.8

7.4

8.9

ISO 12192:2011

Surface strength (IGT, m/s)

1.1

1.9

2.6

ISO 3783:2006

PVA addition cost per ton paper (USD)

6.8

10.2

Calculated at 1.5 kg dry starch

Dry-mixed cementitious tile adhesive classified as C2E per EN 12004:2007+A1:2012 incorporates 0.8–1.2 wt% Sinopec PVA 088-20 powder as a redispersible hybrid additive at a total polymer-to-cement ratio of 2.5:97.5. The grade’s cold-water solubility accelerates dispersion when water is added at the building site; open time measured by the notched trowel—plywood pull test extends to 28–32 minutes at 23 °C/50 % RH, compared with 18–22 minutes for unmodified mortar. During thin-bed application a critical threshold emerges at a PVA dosage of 1.6 wt%: beyond this level, air content measured by EN 1015-7:1998 rises above 6 % and compressive strength after 28 days drops below the 15 MPa minimum required for structural bonding. Batch mixing on a horizontal ribbon blender with a capacity of 2 tonnes requires a pre-blend step of PVA powder with quartz filler (0–0.3 mm) for 5 minutes prior to cement addition, otherwise electrostatic cling on the polymer granules creates agglomerates visible as undispersed white spots in the set mortar. No additional plasticiser is required because the 12 mol% acetate groups provide sufficient molecular mobility, yet calcium formate acceleration at 2 % of cement weight is incompatible: it lowers the pH of the mixing water too rapidly, causing PVA surface skinning before full dissolution. The modified mortar complies with emission class EMICODE EC1 for volatile organic content and does not contribute to formaldehyde release as measured by the chamber method of ISO 16000-3:2011.

Sinopec PVA 088-20, also identified within procurement documents as PVA 1788, is a partially hydrolyzed poly(vinyl alcohol) grade characterized by a nominal hydrolysis degree of 88 mol% and a 4 % aqueous solution viscosity of 20–25 mPa·s at 20 °C measured per ISO 15023-2:2019 (equivalent to JIS K6726 falling-ball method). The material is supplied as a free-flowing white granular powder with a volatile matter content ≤ 5.0 % and ash residue ≤ 0.5 % (as Na₂O), typical figures confirmed by multiple compounders running continuous twin-screw extrusion for water-soluble packaging film. Production-scale users report batch-to-batch viscosity drift of less than ±1.5 mPa·s when dissolution protocols are strictly maintained, though minor deviation in particle size distribution can shift dissolution time by 30–45 s in cold-water make-down tanks operating at 12–15 °C.

Model Nomenclature and Hydrolysis Profile

The trade designation “088‑20” decodes directly: the first two digits multiplied by 1 % indicate hydrolysis (88 mol% residual acetate groups 12 mol%), while the second pair defines viscosity in centipoise divided by a factor—here yielding a target of 20 mPa·s. Laboratories cross-referencing Sinopec documentation employ the older mnemonic “1788,” where the leading “17” denotes degree of polymerization typifying a 1700 range (weight-average molecular weight approximately 75 000–85 000 g/mol) and “88” again encodes hydrolysis. Such systematic naming diverges from Kuraray’s PVA‑217 (similar hydrolysis, marginally higher viscosity) or PVA‑205 (lower molecular weight), placing 088‑20 in a rheological niche suited to applications demanding cohesive film strength without excessive stringiness during high-speed adhesive transfer.

Why Partial Hydrolysis Matters for Cold-Water Solubility

Residual acetate groups interrupt intra- and inter-chain hydrogen bonding, lowering crystallite melting onset to roughly 180–190 °C versus 225–230 °C for fully hydrolyzed homopolymer. Dispersion in water at 10–15 °C proceeds with minimal agglomerate formation provided the powder is sifted into a vortex under moderate shear; full dissolution occurs within 45–60 min when jacket temperature is elevated to 85 °C and held for 30 min. In contrast, a fully saponified grade such as PVA 1799 requires sustained boiling and co-solvent addition to overcome intra-granular hydrogen bonding. This distinction makes 088‑20 the default selection for cold-blend adhesives where thermal input is limited by volatile organic compound emission constraints or by enzyme-deactivated starch co-binders requiring processing below 70 °C (as encountered in corrugating plants running starch‑Stein‑Hall formulations with borax-dextrin complexes).

Viscosity Specification and Rheological Behavior in Aqueous Systems

The 20 mPa·s plateau (Brookfield LV, spindle No. 1 at 30 rpm, 20 °C) positions the grade between low-viscosity PVA 1788 (4.5–6.0 mPa·s) and medium-high grades such as PVA 224. Rheometry on 10 % solutions reveals Newtonian behavior up to shear rates of 100 s⁻¹; beyond this, slight pseudoplasticity emerges, attributable to disentanglement of high-molecular-weight chains in the upper decile of the distribution. For gravure coating of release liners, operators maintain solution concentration at 7–8 % to achieve a cup viscosity of 35–40 s (Zahn #2), balancing wet-film levelling against excessive pick-up. A compliance matrix for typical lot data appears below.

Typical Release Specifications — Sinopec PVA 088-20 (verified against **ISO 15023-2**, **JIS K6726**)
Property	Method	Value
Hydrolysis	ISO 15023-2:2019, Annex B	86.0–89.0 mol%
Viscosity (4 % aq.)	JIS K6726 falling-ball, 20 °C	20.0–25.0 mPa·s
Volatile matter	ISO 15023-2, 105 °C × 3 h	≤ 5.0 %
Ash (as Na₂O)	ISO 15023-2, 700 °C	≤ 0.5 %
pH (4 % solution)	ISO 15023-2	5.0–7.0
Transmittance (4 % solution)	JIS K6726, 430 nm	≥ 88 %

Ash content above 0.6 % catalyses unwanted thermal discoloration during melt extrusion of water-soluble film; processors running single-screw extruders (L/D 30:1, compression ratio 3.5:1) have recorded L* value drops of 4–6 points when ash breaches 0.55 %, controlling for barrel temperature at 195 °C.

When PVA 088-20 Replaces Fully Hydrolyzed Grades in Emulsion Polymerization

Vinyl acetate emulsion polymerizations stabilized with 088‑20 generate latices with mean particle diameters 250–400 nm larger than those obtained with fully hydrolyzed PVA at identical colloid concentration. The 12 mol% acetate comonomer content enhances surface activity, reducing the critical micelle concentration of the stabilizer in water to approximately 0.15–0.25 wt%. This drives nucleation toward homogeneous flocculation-limited growth, raising polydispersity index to 1.15–1.35 but concomitantly yielding lower minimum film formation temperatures (MFFT) — a 4–6 °C suppression relative to PVA 1799-stabilized controls. Adhesive formulators exploiting this shift report improved wet-tack on low-energy substrates such as corona-treated polyethylene (38–42 dyn/cm) without plasticizer addition, measured by loop tack per ASTM D6195-22.

However, an operational boundary emerges when reactor pH drifts below 4.0 during persulfate initiation: acetyl migration from PVA backbone to hydroxyl-terminated oligoradicals generates transient acetyl esters that retard propagation, evidenced by an induction period extension of 18–25 min compared to buffered systems at pH 5.5. Production lines mitigate this by metering sodium bicarbonate slurry to hold pH within 5.2±0.3, a narrow window documented in batch sheets from a 12 m³ semi-continuous reactor running poly(vinyl acetate) homopolymer for wood adhesive.

Textile warp sizing represents the highest-volume single application. Size boxes on high-speed water-jet looms (Weibler NZB, 900 rpm) demand size fluid with 7.5–8.5 % solid content, maintained at 82–85 °C. Addition of 0.5 wt% (on size solids) of medium-chain fatty acid ester improves fiber-to-fiber cohesion by 12 % (pull-out force, ASTM D3822) while suppressing skin formation in the size box sump — a frequent failure mode when all-PVA formulations exceed atmospheric exposure time of 4 h at 80 °C. Operators should avoid blending 088‑20 with cationic softeners based on quaternary ammonium salts; counterion exchange precipitates acetate-quat complexes visible as white gummy deposits on reed dents, requiring line stops after approximately 18 000 m of woven fabric.

In paper surface sizing, film-press concentrations of 3–5 % combined with oxidized starch (1:1 dry basis) consistently yield Cobb₆₀ values per ISO 535:2014 in the range 22–28 g/m² on recycled linerboard. The hydroxyl-rich PVA backbone cross-links lightly with starch’s carboxyl groups during drum drying at 120–130 °C, creating a semi-interpenetrating network that resists ink-jet feathering. Published data for this specific configuration is limited; however, mill trials on a Voith SpeedSizer running 1500 m/min confirmed no measurable viscosity breakdown over an 8‑h shift when biocidal protection (isothiazolinone at 15 ppm) inhibited Pseudomonas proliferation — a recurring concern with PVA-starch blends possessing BOD₅ > 10 000 mg/L.

Processing Window and Thermal History Constraints

Dry 088‑20 powder withstands short-term exposure to 100 °C without measurable molecular weight reduction, yet sustained heating above 135 °C induces intra-molecular elimination of water, forming conjugated polyene sequences that result in yellowing and a rapid increase in 1 % solution Haze (rise from 2 % to 15 % within 20 min at 150 °C, measured per ASTM D1003 on cast film). Thermoforming of PVA sheet therefore mandates closed-loop temperature control with excursion limited to 195±3 °C at die exit; exceeding 200 °C for more than 90 s drops elongation at break by 40 % (from 220 % to 130 %, ISO 527-3 specimens conditioned at 50 % RH). Pre-drying is mandatory when storage relative humidity exceeds 60 %: a fluidized bed dryer operating at 70 °C with dew point ≤ −10 °C reduces moisture to 0.3 % within 30 min, preventing bubble defects (steam pocks) in extruded monolayer.

Avoid combination with amine-based additives unless the pH is buffered below 8.5. Free amines catalyse saponification of residual acetate groups at elevated processing temperatures, insolubilizing the PVA and creating gel particles > 50 µm that clog screen packs (mesh size 200) during blown film extrusion. This incompatibility is especially pertinent when 088‑20 is co-extruded with ethylene-vinyl alcohol copolymers that release ammonia during purge cycles; dedicated purging protocols using LLDPE must precede PVA introduction.

What Distinguishes This Grade from Low-Viscosity 1788 and PVA 1799?

Within the Sinopec product matrix, confusion arises between “PVA 1788‑low” (viscosity 4.5–6.0 mPa·s, used for fine-particle stabilisation) and the 20 mPa·s variant discussed here. The higher molecular weight of 088‑20 generates film tensile strength at break of 38–45 MPa (ISO 527-3) versus 20–25 MPa for the low‑viscosity analogue, a difference that dictates grade selection in heavy-duty paper sack adhesive (T‑peel on kraft exceeding 4.5 N/cm required). Against fully hydrolyzed PVA 1799, the 88 mol% hydrolysis grade sacrifices water resistance — immersion of an 088‑20 film in deionized water at 25 °C leads to disintegration within 15 min, whereas 1799 swells but remains intact — yet gains solubility without caustic addition, drastically simplifying wash-down of coating equipment. The comparative table below summarizes critical performance axes.

Cross-grade comparison for adhesive and film applications (data normalised to **50 % RH**, **23 °C**)
Property	PVA 088‑20	PVA 1799	Low-viscosity 1788
Hydrolysis (mol%)	88	≥99	88
4 % viscosity (mPa·s)	23	≈28	5.5
Dissolution temperature (°C)	85 (complete)	≥95 (requires caustic)	85 (complete)
Tensile strength (MPa)	42	65	22
Elongation at break (%)	220	150	300
MFFT depression in PVAc emulsions (°C)	5	negligible	3
Water resistance (static immersion, 25 °C)	Disintegrated 15 min	Intact >24 h	Disintegrated 8 min

Selection hinges on end-use performance tolerance to moisture: for repulpable cores and single-use detergent pouches, 088‑20’s cold-water disintegration is an advantage; for exterior wood glues (Type II per EN 204), PVA 1799 or a crosslinked variant is mandatory.

Pre-drying parameters deserve reiteration: when bags are opened in tropical climates (ambient 30 °C, 85 % RH), moisture uptake rate reaches 0.1 %/min for the first 10 min. To preserve lot integrity, aliquots intended for moisture-sensitive compounding must be resealed within 15 min or transferred to hopper dryers supplying −30 °C dew-point air. Production-scale experience on a KraussMaffei ZE 40 twin-screw (L/D 44) extruding PVA/starch compounds confirms that melt pressure fluctuations exceed ±2 bar when feed moisture surpasses 0.8 %, causing intermittent strand breakage at the pelletizer. The same line stabilizes immediately upon returning feed moisture to 0.3 %.

HS Code	619881
Viscosity 4 Aqueous Solution 20 C	20-30 mPa·s
Degree Of Hydrolysis	87-89 mol%
Average Degree Of Polymerization	1700
Appearance	White granular powder
Ph Value	5-7
Solubility	Soluble in hot water above 80°C; insoluble in common organic solvents
Volatile Content	≤5%
Ash Content	≤0.5%
Melting Point	180-190°C
Density	1.25-1.31 g/cm³
Film Forming Property	Forms transparent, flexible, and tough films
Thermal Stability	Decomposes above 200°C

Packing	Sinopec PVA 088-20 (PVA 1788) is supplied in 25 kg multi-layer paper bags with an inner polyethylene liner.
Container Loading (20′ FCL)	20′ FCL loading: Sinopec PVA 088-20 packed in 25kg bags on pallets, securely stowed, dry and ventilated container.
Shipping	Sinopec PVA 088-20 (PVA 1788) is a white granular polyvinyl alcohol powder, supplied in 20 kg/25 kg multi-layer paper bags with PE inner liner. During shipping, keep cargo dry, protected from moisture, rain, and mechanical damage. Not classified as dangerous goods, suitable for sea, air, and road transport. Store in a cool, ventilated warehouse.
Storage	Store in a cool, dry, well-ventilated area away from heat, open flames, and strong oxidizers. Keep containers tightly closed to prevent moisture absorption and contamination. Protect from humidity and direct sunlight. Avoid generating dust during handling. Maintain room temperature and use within recommended shelf life to preserve product quality.
Shelf Life	Shelf life is 2 years from manufacture when stored sealed, cool, and dry in original packaging.

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