| HS Code | 745689 |
| Product Name | Ningxia Dadi PVA 2499 |
| Grade | 2499 |
| Chemical Name | Polyvinyl alcohol |
| Cas Number | 9002-89-5 |
| Molecular Formula | (C2H4O)n |
| Appearance | White granular powder |
| Average Degree Of Polymerization | 2400 |
| Degree Of Alcoholysis | 99.0-99.5 mol% |
| Viscosity 4 Solution At 20c | 60-70 mPa·s |
| Ph 4 Solution At 20c | 6.0-7.0 |
| Volatile Content | ≤5.0% |
| Ash Content | ≤0.5% |
| Bulk Density | 0.4-0.6 g/cm³ |
| Solubility | Soluble in hot water; insoluble in common organic solvents |
| Average Molecular Weight | ~106,000 g/mol |
As an accredited Ningxia Dadi PVA 2499 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Ningxia Dadi PVA 2499 is supplied in 25 kg multi-layer paper bags with inner plastic lining for moisture protection. |
| Container Loading (20′ FCL) | 20′ FCL loading of Ningxia Dadi PVA 2499: secure palletized bags, even weight distribution, protect from moisture, and brace firmly. |
| Shipping | Ningxia Dadi PVA 2499 ships as a white granular powder in sealed multi-layer paper bags or woven bags with PE liners, typically 25 kg each. It is non-hazardous but hygroscopic, so keep dry. Use clean, ventilated containers or trucks, avoiding moisture, heat, and direct sunlight during transit. |
| Storage | Store Ningxia Dadi PVA 2499 in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers tightly closed to prevent moisture absorption. Avoid contact with oxidizing agents. Maintain moderate temperatures and low humidity. Follow local regulations and handle with appropriate PPE to prevent dust accumulation. |
| Shelf Life | Shelf Life: 2 years from date of manufacture when stored sealed, cool, and dry. |
In shuttleless weaving of high-density cotton and polyester-cotton spun yarns, the size formula is built around Ningxia Dadi 2499 at 8–12 wt% dry solids. The grade designation indicates a nominal degree of polymerisation near 2400 and a degree of hydrolysis of 99.0–99.8 mol%; the fully hydrolysed structure yields a low-swelled size film with high tensile strength and low cold-water solubility after drying. The solution is processed in a jacketed agitated kettle equipped with a slow anchor stirrer and a high-shear rotor-stator recirculation loop. The powder is first dispersed in demineralised water at 25–30°C, then steam-injected to 92–96°C and held for 30–40 min until a clear or slightly opalescent solution passes a 100 µm stainless steel screen without visible gel specks.
For a 100% cotton ring-spun warp of Ne 40/1 with 110–140 ends per inch, the size solids are frequently partitioned as 55–65 wt% 2499, 20–30 wt% oxidised maize starch, 8–12 wt% acrylic cohesion modifier, and 0.3–0.8 wt% lubricant wax. For a 65/35 polyester-cotton blend, the 2499 fraction is reduced to 45–55 wt% and the acrylic modifier is raised to 12–18 wt% because the polyester yarn surface is hydrophobic and requires a two-phase film. The size box is maintained at 80–85°C and the nip pressure is set to deliver 9–13 wt% size pick-up for cotton and 8–11 wt% for polyester-cotton after drying at 110–130°C cylinder temperature.
Film tensile specimens cast from the same solution and conditioned at 23°C/50% RH are tested according to ASTM D882-18; high-DP fully hydrolysed PVA films plasticised with 5–8 phr glycerol typically report tensile strength in the 45–70 MPa range, with elongation at break below 40% without plasticiser and rising to 150–250% at the stated glycerol level. On the loom, the critical operating limit is size add-on above 14 wt%; beyond this boundary, dried size film can flake at lease rods and contaminate heddles. The influence of 2499 on warp hairiness is assessed on an Uster tester, but the pass-fail threshold is a mill-specific specification and is not an intrinsic property of the grade.
Desizing after weaving uses oxidative conditions because amylase enzymes do not attack PVA. A hydrogen peroxide concentration of 3–5 g/L with sodium persulfate at 1–2 g/L and a nonionic wetting agent at 0.5–1.0 g/L is applied in a continuous open-width range at 80–90°C for 20–30 min. Residual PVA on the fabric can be detected by boric acid-iodine complexation; a residual level above 0.1 wt% on cotton is considered a dyeing risk because it can cause uneven absorbency and colour rejection in cold pad-batch reactive dyeing. Boric acid and borax are excluded from the textile size formula because their reversible diol crosslinking raises size-box viscosity and can form insoluble gel particles in the size trough, although the same chemistry is deliberately used in paper tube adhesives where controlled gelling improves tack.
For aqueous alumina tape casting, the binder concentration is fixed at 3.5–6.0 wt% of the dry ceramic powder. A 60 wt% solids slurry is loaded with an alumina powder having a median particle size of 0.3–0.6 µm and a specific surface area of 6–10 m²/g. The powder is dispersed first with an anionic polyelectrolyte at 0.3–0.8 wt% under a rotor-stator disperser at 2500–3500 rpm for 60–90 min. The 2499 solution is then added at low shear, followed by 0.8–2.1 wt% PEG 400 plasticiser and a defoamer at 0.05–0.1 wt%. Vacuum de-airing is conducted at 50–100 mbar absolute pressure for 20–30 min before casting.
The tape is cast on a Mylar carrier through a doctor blade gap of 200–500 µm, dried at 60–90°C in a multi-zone conveyor dryer, and stripped at 60–250 µm green thickness. Three-point bend testing of 25 mm wide strips gives green strength values that must exceed the punching and via-filling force of the specific punching tool; published data for this exact 2499 configuration are limited, but high-DP fully hydrolysed PVA binders generally deliver higher green strength per unit binder than low-DP grades at equal solids. The burnout schedule uses a ramp of 1°C/min to 600°C with a 1 h hold in air. The decomposition window is 230–380°C under thermogravimetric analysis at 10°C/min.
Residual ash is determined by ISO 3451-1:2019 or an equivalent combustion method; the grade should be lot-checked against an upper limit of 0.5 wt%. Sodium oxide and sulfate residues above 0.25 wt% are unwelcome in dielectric tape because residual alkali ions increase high-frequency loss and can alter the onset of densification in glass-ceramic systems. The user is required to re-test each lot after 600°C burnoff because polymerisation ash is not homogeneous across production campaigns, and particle size of the ash residue can be as critical as total ash in via-filling layers below 50 µm.
In a C1 cementitious tile adhesive, 2499 is dosed at 0.4–1.0 wt% of the dry mortar. The reference formulation is composed of 30–38 wt% CEM I 42.5 N, 58–66 wt% graded silica sand, 1.5–3.5 wt% redispersible polymer powder, 0.3–0.5 wt% cellulose ether, and 0.4–1.0 wt% 2499. The powder PVA is dry-blended with the cement and sand for 3–5 min in a low-shear ribbon mixer before adding water at 25–27 wt% of the dry mix. The wet mortar is mixed for 2–3 min at 400–700 rpm, rested for 5 min, and mixed again for 1 min to stabilise rheology.
Water retention is measured by the filter-paper vacuum method of DIN 18555-7; 2499 raises retention by reducing free-water evaporation at the surface and by increasing the viscosity of the aqueous phase. Open-time tensile adhesion is tested to EN 1346:2007 and slip resistance to EN 1308:2007. In a C1 product the minimum open-time adhesion after 20 min is 0.5 N/mm², and the slip value must not exceed 0.5 mm. The 2499 addition extends the open film without re-tempering, but at doses above 1.2 wt% the Helipath viscosity of the wet mortar at 2.5 rpm can exceed 800,000 mPa·s, which produces excessive trowel drag on a 10 mm notched trowel.
| Property | Standard | Condition | Required value |
|---|---|---|---|
| Initial tensile adhesion | EN 12004-1:2017 | 23°C / 50% RH, 28 d | ≥0.5 N/mm² |
| Water immersion tensile adhesion | EN 12004-1:2017 | 7 d standard cure + 21 d water immersion | ≥0.5 N/mm² |
| Open time | EN 1346:2007 | 20 min open, 23°C/50% RH | ≥0.5 N/mm² |
| Slip | EN 1308:2007 | 23°C | ≤0.5 mm |
Higher dosage above 1.5 wt% may delay cement set and reduce final compressive strength due to excess polymer film around cement grains; set time should therefore be verified with EN 196-3:2016 before a dry-mix product is frozen.
When a paperboard coating kitchen substitutes 2499 for a 1799 grade at equal 5 wt% solids, the first measured change is a Brookfield viscosity increase of 35–60% at 60°C because the molecular weight is significantly higher. The solution is prepared at 90–95°C in a steam-jacketed starch kettle, then held at 50–60°C in the size-press supply tank. A puddle or film size press applies 2–4 g/m² dry coat weight at machine speeds of 75–150 m/min; wet pick-up must be re-set after the substitution because the higher viscosity slows dewatering into the sheet.
Oxygen transmission rate is measured according to ASTM D3985-24 at 23°C/0% RH; fully hydrolysed PVA at 2–4 g/m² dry weight can reduce OTR by one to two orders of magnitude relative to uncoated board, but the barrier is moisture-sensitive. At 75% RH, water molecules plasticise the PVA film and the oxygen barrier falls substantially. Water vapour transmission by ASTM E96/E96M-22 is therefore not improved; the coating is not a humidity-barrier layer and must be combined with a hydrophobic topcoat or converted into a crosslinked film if wet-strength barrier performance is needed.
For food-contact paperboard, the finished article is evaluated under FDA 21 CFR 176.170 and 176.180, depending on food type and contact temperature; the coating formulation must be checked against the specific migration conditions of the coated board because PVA is not a universal compliance statement. Hard-water cations above 200 ppm as CaCO₃ can destabilise the size-press formulation if the starch co-binder contains anionic phosphate groups; pretreatment of the fresh water with a chelating agent is required in such lines.
Polyvinyl butyral synthesis begins with a 7–10 wt% aqueous solution of 2499 that has been pressure-filtered through a 5 µm absolute cartridge to remove gel specks. The acid-catalysed acetalisation is run at pH 1.5–2.0 using hydrochloric acid, with n-butyraldehyde added at 10–15°C over a controlled addition interval of 20–45 min. The reaction is stopped at 75–80 mol% acetalisation to retain sufficient residual hydroxyl groups for adhesion to glass. The high degree of hydrolysis of 2499, 99.0–99.8 mol%, keeps residual vinyl acetate in the finished PVB low, which is necessary to avoid plasticiser migration and long-term haze in safety-glass interlayers.
The high molecular weight of the PVA feedstock shifts the PVB intrinsic viscosity upward; the acetalised polymer is washed, neutralised, stabilised with a hindered phenolic antioxidant at 0.05–0.15 wt%, and plasticised with triethylene glycol bis(2-ethylhexanoate) or a comparable plasticiser at 25–35 phr. Extrusion of 0.76 mm interlayer film requires a co-rotating twin-screw extruder with a melt filter screen pack of 40/80/120 mesh; gel particles above 100 µm in the PVA feed translate directly into optical defects in the interlayer. Laminated glass is processed in an autoclave at 135–145°C and 1.2–1.5 MPa, where the PVB must achieve a tensile strength above 20 MPa and elongation above 200% as measured by ASTM D638-14.
Compounding a 22 wt% stock solution of 2499 with a borax-dextrin extender at 0.3–0.6 phr boric acid produces a spiral paper tube adhesive with a Brookfield viscometer reading of 3500–6000 mPa·s at 23°C and 20 rpm. The borax diol complex is used deliberately in this application to increase short-term tack and cohesion; the same chemistry is excluded from textile warp size. The adhesive is applied at 120–180 g/m² wet film by a roller coater to a 3-ply spiral tube line running at 20–40 m/min.
Tube crush strength is evaluated by ISO 11093-9 after conditioning at 23°C/50% RH for 24 h. The 2499 grade contributes cohesion and dry strength to the adhesive, but it is not a water-resistant adhesive by itself; for water-resistant paper tube bonding, the dried adhesive must be crosslinked with glyoxal or a polyaldehyde at 0.5–1.5 wt% on adhesive solids. Crosslinking lowers pot life and must be adjusted by monitoring viscosity rise; a bath life of 4–8 h is typical at 23°C, after which the adhesive is discarded due to gel particle formation.
The high solution viscosity of 2499 limits the practical stock concentration to 20–25 wt% in atmospheric steam-jacketed kettles; above 25 wt%, the solution cannot be pumped with a standard gear pump and must be transferred by a piston pump or a progressive cavity pump with a suction-side diameter of at least 50 mm.
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Ningxia Dadi PVA 2499 is a fully hydrolysed polyvinyl alcohol resin in which the grade identifier corresponds to a nominal degree of polymerisation of 2400 and an alcoholysis degree of 99.0–100.0 mol%. The product is manufactured by Ningxia Dadi Chemical Co., Ltd. and is supplied as a white to off-white granular or powder solid intended for aqueous dissolution. In industrial classification, this grade belongs to the high-viscosity, fully hydrolysed segment of polyvinyl alcohol, defined by a Brookfield viscosity of the 4% aqueous solution at 20 °C in the approximate range of 50.0–65.0 mPa·s. The combination of high chain length and near-complete acetate removal produces a dried film with elevated tensile strength, reduced equilibrium moisture sensitivity, and lower cold-water solubility than partially hydrolysed grades such as PVA 17-88 or PVA 24-88. The product is therefore specified in applications where film cohesion and water resistance are required, including textile warp sizing, paper surface sizing, aqueous adhesives, and binder systems for porous substrates.
The primary differentiating variables are degree of polymerisation and alcoholysis degree. Relative to a fully hydrolysed grade with a nominal degree of polymerisation of 1700, PVA 2499 exhibits higher solution viscosity at equal solids, greater film rigidity, and slower dissolution. Relative to partially hydrolysed PVA 24-88, the 99.0–100.0 mol% alcoholysis degree of PVA 2499 reduces cold-water solubility and increases tensile strength under humid exposure, but it also narrows the window in which the dry powder can be dispersed without lump formation. The high degree of acetate removal raises the crystalline melting region of cast film to approximately 228–235 °C when measured by differential scanning calorimetry at 10 °C/min under nitrogen; published values vary with thermal history and residual moisture. In practice, the selection of PVA 2499 over PVA 17-99 or PVA 24-88 is governed by the required size-film strength and water resistance at the target add-on, not by universal superiority in all operations.
The solution viscosity of PVA 2499 is shear-thinning in concentrated aqueous systems, but at cooking and size-box solids above approximately 8%, the low-shear Brookfield value becomes an incomplete predictor of pump and transfer behaviour. Controlled-stress rotational viscometry using cone-plate geometry at 80 °C indicates that the 4% solution viscosity rises rapidly as the solution cools from 95 °C to 60 °C, and the resin forms a thermally reversible gel at low temperatures or after prolonged quiescent storage. Dry films cast from 10% aqueous solution, dried at 23 °C and conditioned at 50% relative humidity, typically develop tensile strength above 60 MPa when tested in accordance with ISO 527-3; reported values vary with plasticiser content and film thickness. The polymer shows a glass transition near 75–85 °C and a crystalline melting peak near 220–235 °C, depending on residual acetate content and drying history. These transitions impose a practical ceiling on drying and curing temperatures in continuous film lines because excessive web temperature can generate insoluble surface skins before the core water has been removed.
| Parameter | Method basis | Specification boundary |
|---|---|---|
| Viscosity of 4% aqueous solution | GB/T 12010.3-2010, Brookfield LV, 20 °C, 60 rpm | 50.0–65.0 mPa·s |
| Alcoholysis degree | GB/T 12010.4-2010 | 99.0–100.0 mol% |
| Volatile matter | GB/T 12010.5-2010, 105 °C, 3 h | ≤ 5.0% |
| Ash content | GB/T 12010.6-2010, 800 °C | ≤ 0.7% |
| pH of 4% solution | GB/T 12010.8-2008, 20 °C | 5.0–7.0 |
Because the resin is hygroscopic, the laboratory moisture uptake of uncompacted powder can exceed 3% within 48 h at 60% relative humidity and 25 °C. Production-scale weigh stations should therefore use moisture-corrected dosing or pre-dry the resin at 60–70 °C for 1–2 h in a dehumidified hopper dryer before dry blending. When the powder is fed into water at atmospheric pressure, the addition must be slow and the agitator must maintain a vortex; dissolved solids above 12% can require a high-speed Cowles disperser or an eductor to prevent fisheye formation. The polymer is substantially insoluble below 85 °C, and attempts to dissolve the grade at 60–70 °C typically produce sticky, partially swollen particles that settle and block transfer lines. Published data for dissolution rate under high-shear inline mixing with this specific grade is limited, but production records from slasher size preparation indicate that a jet cooker operating at 125–135 °C for 20–30 min gives a fully cooked size with no visible undissolved gel when final solids are maintained below 10%.
In textile warp sizing, PVA 2499 is formulated as the primary film-forming polymer for high-count cotton, polyester/cotton, and filament yarns that require abrasion resistance and low hairiness in the size film. Typical slasher formulations use 6.0–10.0% PVA solids, with the balance being polyacrylic size, starch ether, or lubricant. The high degree of polymerisation contributes to a tougher dried size film and improves resistance to shedding at high loom speeds, but it also increases wet pickup and the load on squeeze rolls. On conventional single-size-box slashers, wet pickup is controlled by rubber-covered squeeze rolls operating at nip pressures of 10–15 kN/m, and the size trough is maintained at 80–85 °C to avoid viscosity build-up and surface skinning. If the trough is left uncovered for extended stops, surface skinning occurs within minutes because the high-DP fully hydrolysed film dries rapidly at the air-liquid interface. Production lines therefore use jacketed, covered size boxes and low-shear agitation, with intermittent slow circulation through a size filter rated at 150–250 μm. Batch-to-batch viscosity drift in the size kitchen is usually managed by monitoring viscosity or refractive index at 85 °C; an increase of more than 10% over 6 h is often an early sign of evaporation or partial gelation rather than polymer degradation.
In paper surface sizing, PVA 2499 is applied at the size press or film press at solids between 4.0% and 9.0%, depending on base sheet absorbency and target pick resistance. The high molecular weight increases dry film strength and reduces surface dusting, but it also raises the Brookfield viscosity of the size solution. At 7.0% solids and 60 °C, the viscosity is sufficiently high that blade-metered film presses may require a rod or smooth-roll configuration to minimise film splitting and misting. Film-forming behaviour is evaluated on laboratory drawdowns using a K-bar or wire-wound rod and conditioned paperboard; IGT pick resistance is measured on production sheets according to ISO 3783, and oil and grease resistance is evaluated by TAPPI T 559 cm-02. Published values for this specific grade across multiple base sheets are limited, but where comparative data exist, the improvement in dry pick resistance relative to oxidised starch-only surface size is most pronounced when PVA 2499 constitutes 30–50% of the size solids. The resin is usually cooked separately to 95 °C and then blended with starch at the size press supply tank; direct dry blending of PVA granules into hot starch slurry can produce undissolved gel particles that generate blade streaks.
Adhesive and binder uses of PVA 2499 include aqueous laminating adhesives, paper tube winding, and mineral board edge-hardening formulations. The grade provides high film cohesion after drying but requires temperature-controlled tanks because the solution may gel when stored below 20 °C at concentrations above 10%. In paper tube winding, formulations at 12–15% solids are processed with a doctor roll or roll coater, and the high viscosity assists in limiting adhesive penetration into the paperboard. Addition of defoamer may be necessary during high-shear mixing because fully hydrolysed PVA solutions entrain air and the resulting microfoam reduces film clarity. Plasticiser selection is constrained by compatibility: glycerol and sorbitol are more stable with fully hydrolysed PVA, whereas low-molecular-weight polyethylene glycols can phase-separate at plasticiser loadings above 10 phr. Boric acid or borax must not be added before complete dissolution; borate ions bridge adjacent hydroxyl groups and can gel the solution even at 0.5–1.0% of the PVA mass, blocking transfer pumps.
Compatibility with starch, polyacrylic size, and plasticisers is formulation-dependent. In starch/PVA sizing, the fully hydrolysed PVA can increase viscosity synergistically with high-amylose starch, and the mixed paste may undergo retrogradation on cooling below 50 °C. This is managed by holding the blend at 70–75 °C and limiting PVA replacement of starch to 40% of dry solids in systems where storage stability beyond 8 h is required. Polyacrylic acid-based sizes are generally co-soluble with PVA 2499 at pH 6.0–8.0; at lower pH, carboxyl groups may protonate and reduce film clarity. With borax crosslinking, gel time drops sharply as temperature falls and as PVA concentration increases; viscosity can exceed the range of a Brookfield LV spindle within seconds at 10% PVA and 1.0% borax. Production-scale mixing tanks should therefore be equipped with variable-speed agitators and tachometer readouts, because the onset of gelation is often indicated by a sharp rise in mixer torque rather than by a stable torque reading. When defoamer, biocide, or wetting agent is required, the additive is introduced after the PVA has reached 90 °C and is fully dissolved, then mixed for an additional 15–20 min before let-down cooling.
In food-contact applications, the suitability of PVA 2499 must be confirmed against the applicable regulatory framework, such as FDA 21 CFR 177.1670 or Commission Regulation (EU) No 10/2011 with specific migration limits. The product is normally supplied as an industrial grade; users in packaging and food-contact articles should request food-contact documentation for the specific lot. In emulsion polymerisation, PVA 2499 is not the first-choice protective colloid when low-temperature solubility and rapid grafting are required. Partially hydrolysed grades are preferred for emulsion stabilisation, whereas PVA 2499 may be used as a post-added rheology modifier or as a high-strength binder after drying. This distinction is essential because the fully hydrolysed grade contributes water resistance after film formation but can coagulate or increase particle size if introduced during polymerisation.
Non-aqueous processing of PVA 2499 requires plasticiser or controlled melt-phase processing because the polymer undergoes thermal degradation near its melting region. In cast-film production, the resin is compounded with plasticisers such as glycerol, sorbitol, or trimethylolpropane at loadings of 15–35 phr, then processed in a co-rotating twin-screw extruder with an L/D ratio of 40:1 and barrel temperatures profiled from 150 °C in the feed zone to 210 °C at the die. The fully hydrolysed grade has a narrow thermal processing window; melt viscosity is high and residence time must be kept short to avoid yellowing and acetaldehyde release. Barrel zones above 220 °C should be avoided unless the formulation includes a stabiliser, and the die should be designed for low shear because excessive screw speed can generate shear heating beyond the set temperature. Film casting trials on this specific grade have shown that melt fracture can occur at draw ratios above 8:1; the addition of internal lubricant reduces die pressure but may compromise film clarity. Since published data for this specific configuration is limited, pilot-scale torque and melt-pressure mapping is recommended before production runs. In aqueous film casting, the resin is dissolved at 8–12% solids, deaerated, and metered onto a moving belt or drum; the drying curve must follow a staged temperature ramp from 70 °C to 110 °C to prevent crust formation.
