| HS Code | 155822 |
| Product Name | Polymer Grade VAM HQ 6–8 ppm (High-Viscosity Fiber-Grade PVA) |
| Chemical Identity | Vinyl Acetate Monomer (VAM) |
| Purity Assay | ≥ 99.9 wt% |
| Hydroquinone Content | 6–8 ppm |
| Water Content | ≤ 0.04 wt% |
| Acidity As Acetic Acid | ≤ 0.005 wt% |
| Acetaldehyde Content | ≤ 0.01 wt% |
| Color Pt Co | ≤ 5 APHA |
| Density At 20c | 0.932 g/cm³ |
| Boiling Point At 1013 Hpa | 72.7 °C |
| Freezing Point | –93 °C |
| Viscosity At 20c | 0.41 mPa·s |
| Flash Point Closed Cup | –8 °C |
As an accredited Polymer Grade VAM HQ 6–8 ppm (High-Viscosity Fiber-Grade PVA) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Supplied in 25 kg moisture-proof laminated bags, sealed to preserve purity; high-viscosity fiber-grade PVA with 6–8 ppm inhibitor level. |
| Container Loading (20′ FCL) | Load 20′ FCL with Polymer Grade VAM HQ PVA, secure drums/palletized bags, protect from moisture, no direct sunlight. |
| Shipping | Polymer Grade VAM HQ (6–8 ppm) is a high-viscosity, fiber-grade PVA shipped in sealed, moisture-resistant bags or drums. Protect from humidity, heat, and contamination during transit. Store in a dry, ventilated area. It is not classified as dangerous goods under standard transport conditions, ensuring safe, routine handling. |
| Storage | Store Polymer Grade VAM (vinyl acetate monomer) HQ 6–8 ppm in clean, dry, tightly sealed stainless steel or carbon steel containers. Keep away from heat, sparks, flames, and sunlight in a cool, well-ventilated area. Maintain a dry air/oxygen atmosphere—not nitrogen—so the hydroquinone inhibitor remains effective. Bond and ground transfer equipment, monitor inhibitor levels, and control storage temperature. |
| Shelf Life | Shelf life is typically 6 months from production; store under nitrogen, sealed, cool, and dry to prevent polymerization. |
The monomer specification of 6–8 ppm hydroquinone is selected for downstream polyvinyl alcohol with degree of polymerisation 1700–2400, hydrolysis degree 99.0–99.8 mol%, and 4 wt% aqueous solution viscosity 40–70 mPa·s at 20 °C. Hydroquinone at 6–8 ppm stabilises vinyl acetate during storage and alcoholysis without generating excessive colour-forming quinone residues after polyvinyl alcohol saponification. The sections below cover only industrial processes where high-viscosity fiber-grade PVA is used as a direct formulation input; grades specified for low-viscosity optical film casting or beverage carton adhesives are excluded.
Interpretative note for downstream formulators: hydroquinone concentration in the monomer does not transfer linearly to the PVA powder; the residual inhibitor in the final PVA depends on methanol washing efficiency, catalyst neutralisation, and drying temperature. In the scenarios that follow, the PVA specification is understood to be high saponification, high viscosity, and low ash, with residual hydroquinone below 0.1 ppm unless otherwise noted.
In engineered cementitious composite production, high-viscosity fiber-grade PVA is processed into chopped monofilament or fibrillated fiber for dosage into Type III synthetic fiber-reinforced concrete under ASTM C1116/C1116M-23 and, in the EU, under EN 14889-2:2006 Class II polymer fibres. The typical addition ratio is 0.5–1.5 vol% of concrete volume, corresponding to approximately 6–19 kg/m³ for a PVA fiber density of 1.29 g/cm³; published mix designs for strain-hardening cementitious composites commonly place fibre volume fraction at 2.0 vol% as an upper boundary before workability loss becomes prohibitive. The dope is prepared at 12–16 wt% PVA solids in demineralised water inside a jacketed dissolving vessel with planetary or anchor agitation, heated to 95–98 °C for 60–120 min to achieve complete dissolution, then filtered through a 20–40 µm polyamide mesh before wet spinning. The filtered dope is fed by a gear pump through spinnerets with capillary diameters of 0.08–0.20 mm into a coagulation bath containing 390–430 g/L sodium sulfate and 0.5–1.5 g/L sodium hydroxide at 40–50 °C, followed by multistage wet drawing in hot water and air, acid-catalysed neutralisation, and, where high tenacity and low hot-water solubility are required, partial formalisation with formaldehyde and sulfuric acid in an acetalisation line. Terminal product types include 6 mm and 8 mm chopped PVA fiber for dry-mix shotcrete and precast tunnel segments, spiralised fibrillated fiber for industrial slabs, and monofilament yarns for textile-reinforced concrete panels. Performance validation uses ASTM C1609/C1609M-19a for flexural toughness, ASTM C1550-20 for round panel energy absorption, and EN 14651:2005 for notched beam flexural strength; these methods replace single-point compressive strength as acceptance criteria. Process boundary: the dissolution vessel must maintain oxygen exclusion and pH < 8 during dope holding to prevent chain scission and viscosity drift; at ambient humidity above 60% RH, chopped fiber should be pre-dried at 60 °C for 4 h before dry dispensing to avoid lump formation in the mixer.
Vinyl chloride monomer is charged into a stirred jacketed reactor of 70–105 m³ working volume with a condenser and baffled turbine impeller operating at 40–85 rpm, and high-viscosity fiber-grade PVA is introduced as a primary or secondary suspending agent at 0.03–0.12 wt% based on monomer mass. The actual addition ratio is split across two grades or a single high-hydrolysis grade with degree of polymerisation 1700–2400 and alcoholysis degree 99.0–99.8 mol%; primary dispersant fractions of 0.02–0.06 wt% control average droplet size, while secondary doses of 0.01–0.05 wt% suppress coalescence during the early pressure-drop phase and reduce reactor fouling. The polymerisation is operated at 57–63 °C with initiator dosing adjusted to target K-values of 60–68 under ISO 1628-2:2020, and suspension PVC resins are classified under ASTM D1755-15 for general-purpose homopolymer grades. Downstream production equipment includes a horizontal decanter centrifuge for slurry dewatering, a rotary flash dryer with inlet temperature 120–140 °C, and a sieving line that rejects resin fractions outside 60–250 µm. Terminal finished product types are suspension PVC powders for pipe extrusion, window profile compounding, cable insulation, and calendered film, all requiring loose bulk density in the 0.48–0.55 g/cm³ range and plasticiser absorption of 18–25 g/100 g as routine release checks. The process boundary is narrow: coolant failure or agitator speed drift above ±5 rpm shifts particle size distribution, and residual hydroquinone from the upstream VAM must be below 0.1 ppm in the PVA wet cake to avoid radical inhibition during polymerisation. Operational incompatibility exists with cationic additives and polyvalent metal salts in the aqueous phase, which can precipitate PVA and destabilise droplet protection; published data for this specific high-viscosity fiber-grade PVA in plants using in-situ generated dispersant is limited, so validation under reactor-specific shear rates is required.
On high-count cotton/polyester weaving lines, high-viscosity fiber-grade PVA is cooked in an atmospheric or pressure jet cooker at 95–130 °C for 20–40 min, then fed to a size box as a 4–8 wt% solids solution and applied to warps at a squeeze-roll pickup of 8–14% dry sizing on yarn mass. The formulation addition ratio in dry solids is typically 50–80 wt% PVA blended with 20–50 wt% modified starch or acrylic co-sizing agent for high-count cotton/polyester shirting, workwear, and nylon filament constructions. Downstream production equipment includes a multi-cylinder drying range with first-zone temperature 110–125 °C, final-zone temperature 80–95 °C, and winding speed up to 120 m/min depending on yarn count. Material is then woven on air-jet looms running at 600–1000 picks/min; the PVA film reduces hairiness and warp breaks, but the sizing agent must be removed in desizing with hot water at 80–90 °C or oxidative desizing before bleaching. Compliance for fabric chemical residues follows OEKO-TEX Standard 100 limit values for textile auxiliaries and ZDHC MRSL v3.2; effluent from desizing is assessed under local trade effluent consent with COD <2,500 mg/L before biological treatment. Terminal finished product types are high-density cotton/polyester woven fabrics, industrial workwear, pocketing, and interlining. Process boundary: high-viscosity PVA forms a strong size film, but overdrying above 130 °C causes skinning at the size box and increases downstream desizing load; if the warp storage room relative humidity exceeds 75% RH, tack develops on sized beams. Incompatibility with starch is not observed at these blend ratios, but adding borax beyond 0.2 wt% of size solids triggers excessive viscosity increase and gelation.
Surface size formulations that must combine low-migration film formation, high wet strength, and controlled porosity use high-viscosity PVA as a partial replacement for oxidised starch. The size press solution is prepared at 1.0–3.5 wt% PVA in deionised water and blended with oxidised starch at PVA:starch dry solids ratios of 20:80 to 40:60; the dry pickup on paperboard is controlled at 0.4–1.8 g/m² per side. On the machine, the solution is transferred through a rod or film press at 50–65 °C and dried by infrared and cylinder sections with surface temperatures of 90–120 °C. Compliance for food-contact applications is referenced to FDA 21 CFR 176.170, FDA 21 CFR 176.180, and EU Regulation (EC) No 1935/2004; physical properties are verified by ISO 1924-2:2020 for tensile index, TAPPI T 456 om-20 for wet tensile strength, and ISO 5636-3:2013 for Bendtsen air permeability. Terminal finished products include grease-resistant bag stock, fast-food packaging board, release liner base, and high-wet-strength label face stock. Process boundary: viscosity after jet cooking must be maintained between 200–500 mPa·s at 50 °C; below this lower bound, film transfer becomes inconsistent on high-speed machines above 1,800 m/min, and above the upper bound, rod marks and sheet picking appear. The high-viscosity grade should not be applied from a puddle size press without hydrolysis control because dwell time at pH > 9 causes viscosity loss of 10–25% within 30 min due to alkaline chain scission. Aluminium sulfate addition above 0.5 g/L in the size solution is incompatible with PVA and can cause immediate precipitation.
| Requirement | Standard/regulation | Parameter |
|---|---|---|
| Food-contact paper and paperboard | FDA 21 CFR 176.170 | Extractives limits |
| Fats and oils barrier base | FDA 21 CFR 176.180 | Odour and extractives |
| Tensile index | ISO 1924-2:2020 | N·m/g |
| Wet tensile strength | TAPPI T 456 om-20 | N/15 mm |
| Air permeability | ISO 5636-3:2013 | µm/Pa·s |
During vinyl acetate-ethylene emulsion polymerisation, high-viscosity fiber-grade PVA functions as the protective colloid that controls particle size, viscosity development, and film water resistance after crosslinking. The addition ratio is 2.0–7.0 wt% PVA on total monomer mass, with a common starting point of 4.0 wt% for high-viscosity VAE dispersions intended for tile adhesives and wood-laminating adhesives. The PVA is dissolved in deionised water in a separate feed tank at 90–95 °C for 60–90 min, cooled to 45–55 °C, and charged into the reactor before initiation or metered as a delayed colloidal feed together with vinyl acetate and ethylene at pressures up to 80 bar. The downstream polymerisation equipment comprises a 20–60 m³ pressure reactor with double mechanical seal and agitator tip speed 2.0–3.5 m/s, an ethylene mass-flow controller, and a post-polymerisation stripping column that reduces residual vinyl acetate monomer to below 0.1 wt%. Finished product types are anionic or nonionic-stabilised VAE dispersions with solids 50–60 wt%, viscosity 2,000–8,000 mPa·s, and MFFT 0–10 °C, used in carpet backing, waterproofing membranes, paper-to-board lamination, and cementitious tile adhesives. Compliance for the resulting dispersion is checked by ISO 3251:2019 for solids content, ISO 2555:2018 for Brookfield viscosity, ISO 3219:1993 for rheology, and GB/T 11175-2021 for residual monomer in synthetic resin emulsions; adhesive film migration in food packaging is assessed under FDA 21 CFR 175.105. Process boundary: residual hydroquinone in the PVA feed above 0.2 ppm can prolong induction time and generate colour in the final dispersion; the polymerisation should not be combined with borate salts or boric acid at more than 0.15 wt% of total dispersion because diol-diol complexation raises viscosity to non-pourable levels. Oxygen must be excluded until monomer conversion exceeds 90%, and the delayed PVA feed must be completed before the final 20% of monomer addition to avoid lump formation and wall scale.
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Polymer Grade VAM HQ 6–8 ppm is a vinyl acetate monomer grade in which the hydroquinone stabilizer concentration is controlled within 6.0–8.0 mg/kg and the residual profile is adjusted for high-viscosity, fiber-grade polyvinyl alcohol synthesis. The monomer is used as the primary building block in methanol solution polymerization followed by alkaline alcoholysis to PVA with a 4 mass% aqueous solution viscosity at 20 °C greater than 30 mPa·s and a degree of hydrolysis not less than 99.0 mol%. The CAS registry number is 108-05-4; the boiling point at 101.3 kPa is 72.0–73.0 °C; the flash point is -8 °C closed cup per ASTM D56. This grade differs from general polymer-grade VAM stabilized with 3–5 mg/kg hydroquinone by providing a larger inhibitor reserve for ambient storage, but it also requires that polymerization initiation recipes account for the additional radical scavenging burden. The principal downstream use is fiber-grade PVA for wet gel spinning and dry-jet wet spinning, where molecular weight distribution and controlled low-molecular-weight tail content are critical for filament draw stability.
Conformance limits for the 6–8 mg/kg hydroquinone grade follow the vinyl acetate monomer specification framework of ASTM D2190, with tightening on water and acetaldehyde because both species are chain-transfer or termination-active during high-degree-of-polymerization PVA production. Hydroquinone is determined after inhibitor extraction by ultraviolet absorption or high-performance liquid chromatography; the reported value includes hydroquinone plus quinone equivalents. Acidity is reported as acetic acid because entrained water hydrolyzes VAM to acetic acid and acetaldehyde. Color is controlled on the platinum-cobalt scale. Table 1 lists typical release characteristics.
| Property | Method anchor | Typical limit |
|---|---|---|
| Vinyl acetate purity | ASTM D2190 / gas chromatography–flame ionization detection | ≥ 99.9 mass% |
| Hydroquinone stabilizer | UV/colorimetric or HPLC after extraction | 6.0–8.0 mg/kg |
| Water | ASTM D1364 Karl Fischer titration | ≤ 0.05 mass% |
| Acidity as acetic acid | ASTM D2086 | ≤ 0.005 mass% |
| Acetaldehyde | Gas chromatography–flame ionization detection | ≤ 20 mg/kg |
| Color | ASTM D1209 | ≤ 5 Pt-Co |
| Distillation range at 101.3 kPa | ASTM D1078 | 72.0–73.0 °C |
The higher inhibitor concentration in this product is not a substitute for thermal control. Hydroquinone stabilization of VAM is oxygen-dependent, and the monomer should not be blanketed with oxygen-free gas unless the stabilizer system has been revalidated. Storage tanks should be maintained below 30 °C and vented through a flame arrestor; sustained temperatures above 40 °C accelerate stabilizer depletion and can permit exothermic polymerization. Hydroquinone can also be extracted or deactivated by aqueous caustic washes used in some PVA pre-treatment systems. Copper and copper alloys are incompatible with the transfer system because copper ions can complex with hydroquinone and reduce inhibitor efficiency. Transfer lines and storage equipment should be austenitic stainless steel or another material validated for low-moisture VAM service.
Hydroquinone scavenges primary and propagating radicals, so the stabilizer concentration in this grade produces a measurable induction period shift when the monomer is not pre-distilled. For a 1 kg VAM charge at the upper inhibitor limit of 8 mg/kg, the hydroquinone loading is 8 mg, equivalent to 7.27 × 10−5 mol based on a molar mass of 110.11 g/mol. If inhibition consumes two radicals per hydroquinone molecule, the stoichiometric radical demand is 1.45 × 10−4 mol equivalents. A representative methanol solution polymerization using 0.02 mol% 2,2′-azobisisobutyronitrile relative to VAM adds approximately 2.32 × 10−3 mol effective radicals per kg VAM at an initiator efficiency of 0.5. The added stabilizer therefore accounts for approximately 4.7% at 6 mg/kg and 6.3% at 8 mg/kg of that effective radical inventory.
This calculation is not a direct induction-time prediction because radical flux, monomer conversion, temperature, and partitioning between methanol and VAM all shift the local inhibitor concentration. In initiator-starved recipes below 0.01 mol% initiator, the same inhibitor burden can consume more than 10% of the available radical supply and leads to variable batch induction. Many high-viscosity PVA processes therefore strip the stabilizer by pre-distillation or apply an initiator precharge before the main monomer feed. If stripped overhead VAM is condensed, it must be re-inhibited to avoid polymer buildup in condensers and vacuum lines. Failure to account for these radical–inhibitor interactions typically appears as drifting induction time, lower conversion, or reduced PVA solution viscosity.
High-viscosity PVA is not simply high average molecular weight; the low-molecular-weight tail must be controlled because low-molecular-weight species reduce filament strength and can act as internal lubricants during drawing. Chain-transfer-active impurities in VAM include acetaldehyde, acetic acid, and water. Acetaldehyde is particularly significant in fiber-grade polymer because it can terminate growing chains and introduce aldehyde end groups that affect PVA thermal stability and color. For a 4 mass% aqueous PVA solution to exceed 30 mPa·s at 20 °C, the saponified degree of polymerization is typically above 1,700. The exact degree-of-polymerization drop caused by a 10 mg/kg increase in acetaldehyde is recipe-dependent, and published data for this specific configuration is limited; nevertheless, fiber-grade VAM specifications generally hold acetaldehyde to the low mg/kg range to prevent chain-transfer effects from overriding reactor temperature control.
Compared with general-purpose PVA production, the high-viscosity fiber-grade route operates closer to the torque limits of continuous kneader saponifiers. Polyvinyl acetate paste at 20–40 mass% solids imposes high mechanical load, and a low-molecular-weight tail makes the paste adhesive and difficult to discharge. This is a production bottleneck when monomer quality drifts. After saponification, the PVA gel is washed with methanol, neutralized with acetic acid, centrifuged, and dried. Residual sodium acetate is controlled to ≤ 0.5 mass% for fiber-grade material because excess acetate raises ash content and affects fiber color and spinnability. Testing by JIS K6726 for aqueous viscosity and degree of hydrolysis is used to release the PVA to fiber spinning.
Fiber-grade PVA produced from this monomer is typically processed into fibers by wet gel spinning or dry-jet wet spinning. The dope is prepared at 15–25 mass% PVA in water or water/methanol and extruded through spinnerets into a sodium sulfate/water coagulation bath at 40–50 °C. The as-spun filaments are drawn at 8–15× in subsequent heated stages. A narrow molecular weight distribution reduces filament breakage in drawing and limits microgel formation on sintered metal filters of 10–20 µm pore size placed before the spinneret. Residual hydroquinone from the monomer is rarely measurable in finished PVA because the saponification and washing loop separates inhibitor-derived quinone species into the methanol recovery stream. However, if non-volatile inhibitor residues accumulate in the recovery column, recycled methanol can carry acidic oxidation products that consume sodium hydroxide catalyst in alcoholysis.
The product differs from general polymer-grade VAM with 3–5 mg/kg hydroquinone in that the higher stabilizer budget provides additional shelf-life margin under warm ambient storage but reduces the net radical availability at the same initiator charge. It differs from technical-grade VAM in that water, acidity, and acetaldehyde are held at levels compatible with high-viscosity PVA rather than general ester or adhesive synthesis. Compared with MEHQ-stabilized VAM, hydroquinone-stabilized VAM is better suited to fiber-grade PVA when the stabilizer must be removed in aqueous alkaline wash systems; MEHQ can partition differently in recovered monomer and accumulate in recycle loops. The material is flammable, with a lower explosive limit of 2.6 vol% in air, and must not be handled with copper alloys or brought into contact with amine-based additives, because vinyl acetate can undergo Michael addition with primary or secondary amines, generating heat and depleting monomer. If inhibitor content falls below 4 mg/kg during storage, the material should be used promptly or re-inhibited under technical supervision.
