| HS Code | 230790 |
| Chemical Name | Vinyl Acetate Monomer |
| Chemical Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Appearance | Clear colorless liquid |
| Inhibitor Content | Hydroquinone 25–30 ppm |
| Purity | ≥99.9% |
| Boiling Point | 72.7°C (760 mmHg) |
| Melting Point | -93°C |
| Flash Point | -8°C (closed cup) |
| Specific Gravity | 0.932 at 20°C |
| Vapor Density | 3.0 (air = 1) |
| Solubility | Slightly soluble in water; miscible with most organic solvents |
| Refractive Index | 1.3934 at 20°C |
| Auto Ignition Temperature | 427°C |
As an accredited VAM HQ 25–30 ppm factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | VAM HQ 25–30 ppm is packaged in 190 kg steel drums or 1000 kg IBC totes, sealed under nitrogen. |
| Container Loading (20′ FCL) | Loading 20′ FCL: VAM HQ (25–30 ppm) in drums/IBCs, securely stowed, ventilated, and labeled for safe transport. |
| Shipping | Vinyl Acetate Monomer, inhibited (HQ 25–30 ppm), ships as UN 1301, Class 3 flammable liquid. Use approved drums or ISO tankers, grounded and vented. Keep cool, away from heat, sparks, and oxidizers. Ensure inhibitor concentration is maintained to prevent polymerization during transit. |
| Storage | Store VAM HQ (25–30 ppm) in a cool, dry, well-ventilated area away from heat, sparks, open flames, oxidizers, and direct sunlight. Keep containers tightly closed, grounded, and bonded to prevent static discharge. Maintain hydroquinone inhibitor levels and inert-gas blanketing to avoid polymerization. Use explosion-proof equipment and inspect containers regularly for leaks or degradation. |
| Shelf Life | Shelf life of VAM HQ 25–30 ppm is typically 6 months when stored properly, kept cool, and protected from oxygen and light. |
Polyvinyl acetate woodworking adhesives formulated from this hydroquinone-inhibited vinyl acetate monomer are typically manufactured on semi-batch jacketed reactors of 10,000–20,000 L working volume with a two-stage monomer feed. At an inhibitor loading of 25–30 ppm, hydroquinone partitions into the aqueous phase and consumes persulfate radicals before polymerisation exotherm begins; this is the primary operational conflict. On continuous adhesive compounding lines, the induction period is controlled by adding sodium metabisulfite at a molar ratio of 1.0–1.2 mol per mol hydroquinone to the monomer pre-emulsion and by increasing ammonium persulfate dosage from 0.2 wt% to 0.3–0.4 wt% on total monomer. Reaction temperature is held at 65–70 °C during seed formation, then raised to 75–80 °C for final conversion. Typical final dispersion solids are 50–60 wt%; Brookfield RVT viscosity at 25 °C is 3,000–5,000 mPa·s. The polymerised product is formulated with dibutyl phthalate or triacetin at 5–15 wt% of polymer solids to control wet tack and film formation. Adhesive performance is classified under EN 204 as D2 or D3 depending on formulation, with shear strength measured according to EN 205. The same dispersion base is converted into label adhesives, bookbinding layers, envelope seams and wood-lamination adhesives. Because the 25–30 ppm HQ level is not removed before polymerisation, residual hydroquinone can reduce pot stability of formulated adhesives containing transition-metal catalysts after more than 6 months at warehouse temperatures above 30 °C; accelerated storage tests are therefore run at 50 °C for 14 days to monitor viscosity drift and pH fall.
In polyvinyl alcohol production, the VAM stream is first polymerised in methanol at 60–80 °C using azo-bis-isobutyronitrile at 0.02–0.10 wt% on monomer. The specified hydroquinone content of 25–30 ppm interferes with radical initiation and can shift the molecular weight distribution of the intermediate polyvinyl acetate unless a pre-reduction step is installed. Plant practice is to pass the inhibited monomer through an activated carbon column or to dose sodium metabisulfite at 0.8–1.0 mol per mol hydroquinone before entering the polymerisation train. Methanol solution polymerisation is carried to 50–70% conversion, after which residual monomer and solvent are stripped under reduced pressure. The polyvinyl acetate solution is then alcoholysed in a kneader or belt saponifier with sodium hydroxide or sodium methoxide at 40–50 °C, using 0.03–0.20 mol alkali per mol acetyl group. Partial hydrolysis grades are controlled to 87–89 mol% alcoholysis; fully hydrolysed grades reach 98–99 mol%. Viscosity of the finished polyvinyl alcohol is measured in 4% aqueous solution at 20 °C according to JIS K6726, and commonly ranges from 3 mPa·s to 70 mPa·s depending on degree of polymerisation. Hydroquinone carry-over above 10 ppm can generate quinonoid colour bodies during alkali digestion, producing yellowing in textile warp sizing, water-soluble films, paper coating binders and polyvinyl butyral precursor. For low-colour film grades, process licensors may specify pre-stripping to 5–10 ppm HQ before polymerisation; published data for this specific configuration is limited, but the colour difference is measurable on the APHA scale under ASTM D1209.
High-pressure autoclave and tubular copolymerisation units processing ethylene and VAM do not tolerate hydroquinone carry-over at 25–30 ppm without upstream removal. Process licensors typically specify inhibitor stripping to below 1 ppm HQ before the suction drum of the secondary compressor, because the phenolic inhibitor acts as a chain-transfer and termination agent and can shift melt flow rate, gel content and long-chain branching. Ethylene pressure in autoclave lines is 1,200–1,600 bar; tubular lines run 1,800–2,500 bar; reactor temperatures span 150–220 °C. VAM comonomer content is controlled between 5 wt% and 40 wt% depending on grade. Removal of HQ is conducted by reduced-pressure distillation at 50–60 °C at absolute pressure 10–20 kPa or by adsorption over activated alumina; the treated monomer is nitrogen-sparged to reduce dissolved oxygen below 0.2 mg/L. The resulting EVA polymers are pelletised on twin-screw extruders with L/D 40:1 and underwater strand pelletising, then converted into solar encapsulant films, hot-melt adhesives, footwear foams and flexible packaging. Melt flow rate of extrusion-coating grades is measured by ASTM D1238-20; film tensile properties are measured by ASTM D882-18. An operational boundary exists: if hydroquinone in the treated feed exceeds 3 ppm, reactor fouling on the high-pressure separator and screw-compressor valves increases measurably within 48–72 h of continuous operation.
In vinyl acetate–ethylene dispersion polymerisation, pressure is maintained between 30 bar and 80 bar while VAM content is controlled from 70 wt% to 95 wt% of the monomer feed. The polymerisation is run as a semi-batch process in glass-lined or stainless reactors with turbine agitation, at 40–85 °C, using potassium persulfate and sodium formaldehyde sulfoxylate as the redox couple. The inhibitor level of 25–30 ppm HQ in the VAM charge delays particle nucleation and broadens the particle size distribution if not compensated. Production lines pre-charge sodium metabisulfite at 0.05–0.10 wt% on VAM or split the reductant feed across the first 30 min of monomer addition. The dispersion is stabilised with partially hydrolysed polyvinyl alcohol and nonionic surfactants, with pH held at 4.0–5.5, final solids at 52–65 wt%, and Brookfield viscosity at 500–2,000 mPa·s. Glass transition temperature is shifted by ethylene content from -15 °C to +10 °C; minimum film formation temperature is typically below 0 °C for flexible construction binders. Particle size measured by laser diffraction is 0.5–2.5 μm. Residual VAM after post-polymerisation stripping is reduced to below 0.1 wt% by gas chromatography. End products from this segment include ceramic tile adhesives classified as EN 12004 C2, exterior insulation and finishing system base coats, carpet backing and paper saturants. The presence of hydroquinone above 15 ppm in the unpolymerised monomer increases coagulum formation on the reactor wall; this failure mode is monitored by filtrate residue after 100-mesh screening.
| Downstream process | Typical HQ tolerance | Common adjustment | Key operational risk |
|---|---|---|---|
| PVAc adhesive emulsion | 25–30 ppm | sodium metabisulfite at 1.0–1.2 mol/mol HQ; ammonium persulfate increased to 0.3–0.4 wt% | Induction delay beyond 45 min |
| PVOH solution polymerisation | 5–10 ppm preferred | activated carbon adsorption or vacuum stripping | Yellowing and molecular weight drift |
| EVA high-pressure | <1 ppm | distillation at 10–20 kPa; alumina adsorption | Compressor fouling and MFR drift |
| VAE dispersion | 10–15 ppm recommended | pre-charge reductant at 0.05–0.10 wt% | Coagulum and nucleation instability |
| Vinyl acetate–butyl acrylate paint binder | 25–30 ppm | delayed initiator injection | Seed-stage retardation |
| Redispersible polymer powder | 5–10 ppm residual monomer pre-spray | post-polymerisation stripping at 60–80 °C | Poor redispersibility and odour |
Redispersible polymer powder production from VAE or vinyl acetate–ethylene dispersions requires a latex particle size of 0.5–2.5 μm and a minimum film formation temperature below 5 °C. The starting VAM containing 25–30 ppm hydroquinone is introduced into the dispersion step, where residual monomer and inhibitor-derived oxidation products must be removed before spray drying. Post-polymerisation steam stripping is performed at 60–80 °C under reduced pressure until residual VAM is below 0.1 wt%. The dispersion is then mixed with polyvinyl alcohol protective colloid at 5–15 wt% on polymer solids and atomised in a spray dryer at inlet 110–160 °C and outlet 55–75 °C. Anticaking agents such as kaolin or calcium carbonate are metered at 5–15 wt% of total powder. Redispersibility is checked by dispersing the powder in deionised water at 20 °C and passing through a 125 μm sieve; residue below 1% is typical. These powders are consumed in dry-mix tile adhesives meeting EN 12004, external thermal insulation systems, and repair mortars tested under EN 1504-3.
For interior matt emulsion paints based on vinyl acetate–butyl acrylate binders, the monomer ratio is set between 70–85 wt% VAM and 15–30 wt% butyl acrylate, producing a binder glass transition temperature of 10–20 °C by Fox calculation. The 25–30 ppm HQ specification in the VAM feed is tolerable in this process if initiator injection is profiled across the seed and growth stages; unadjusted addition can retard seed formation and increase coagulum in the 100–250 nm particle size range. Final binder solids are typically 50–55 wt%, minimum film formation temperature is 5–15 °C, and coalescent demand is 2–5 wt% on polymer solids. Paint formulation is carried out at pigment volume concentration 35–60% using rutile titanium dioxide and calcined clay extenders. Wet scrub resistance is measured according to ISO 11998-1:2006, and dispersion viscosity is controlled by ISO 3219 shear viscometry. The polymer is used in interior matt and eggshell wall paints where residual VAM is reduced below 0.1 wt% to satisfy European indoor emission protocols.
Under food-contact adhesive and paper coating conditions, VAM-derived polymers must be evaluated under FDA 21 CFR 175.105 for adhesives, 176.170 for aqueous and fatty food contact, and 176.180 for dry food contact. The presence of 25–30 ppm hydroquinone in the monomer is not directly transferable to the finished polymer as a guaranteed safe residue; conversion and washing must be controlled so that hydroquinone oxidation products are not detectable as visible discoloration. Residual VAM in the dried adhesive or coating is controlled by post-polymerisation stripping and is commonly specified below 0.5 wt% for converting operations. End products include paper sack side seams, carton sealing adhesives and lidding adhesives. The operational boundary is strict: direct food-contact films and containers require separate migration testing under EU Regulation 10/2011 before a specific grade can be released.
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Vinyl acetate monomer inhibited with hydroquinone at a nominal concentration of 25–30 ppm is designated VAM HQ 25–30 ppm. In this designation, HQ denotes the hydroquinone inhibitor and the numeric band is the concentration range in milligrams per kilogram. The base monomer is CAS 108-05-4, molecular formula C4H6O2, and relative molecular mass 86.09 g/mol; the inhibitor is hydroquinone, CAS 123-31-9. At 20 °C and 101.3 kPa, the liquid has a density of 0.934 kg/L and a boiling point of 72.7 °C. The closed-cup flash point is -8 °C, and the flammability limits in air are 2.6 vol% and 13.4 vol%. Under transport regulations, the material is assigned to UN 1301, Class 3, Packing Group II, with the proper shipping name vinyl acetate, stabilized. Under Regulation (EC) No 1272/2008, the monomer is classified Flam. Liq. 2 H225, Acute Tox. 4 H332, and Carc. 2 H351. The product is a polymer-grade intermediate; it is not sold as a solvent, a laboratory reagent, or a food-contact monomer without additional purification. The 25–30 ppm hydroquinone band separates this grade from lower-inhibitor material used for prompt internal polymerisation and from higher-inhibitor material used for extended marine tank storage.
Compared with the 3–5 ppm hydroquinone grade, the 25–30 ppm product has a wider storage window but a longer polymerisation induction period. Compared with the 14–17 ppm mid-range grade, it provides additional stabiliser capacity for high-ambient logistics and terminal hold time. These differences are operational rather than chemical: the base monomer purity and water limits are usually identical across the hydroquinone series. Selection of a particular inhibitor level is therefore governed by storage time, transportation distance, and polymerisation process tolerance for delayed kinetics.
Hydroquinone is not consumed only by thermal oxidation; it acts as a chain-transfer inhibitor by intercepting vinyl-acetate-derived radicals and forming a relatively stable phenoxy radical. Inhibitor effectiveness depends on dissolved oxygen because regeneration of the active inhibiting form from quinone species requires oxygen in the liquid phase. In a closed storage vessel, hydroquinone can remain within the 25–30 ppm specification only when the vapour space contains sufficient oxygen. Inert-gas blanketing that excludes air can convert the stabilised monomer into an essentially unstabilised liquid even if the hydroquinone titre remains measurable. Nitrogen blanketing of VAM HQ 25–30 ppm is therefore avoided unless the vapour-space oxygen concentration is continuously monitored and maintained at a defined minimum. At polymerisation temperature, hydroquinone is consumed by initiator-derived radicals, peroxy radicals, and growing polymer chains. The measured induction period is a function of initiator type, initiator addition rate, temperature, oxygen mass transfer, and inhibitor concentration. Plant-scale batch records from jacketed 316L stainless steel reactors show that a delayed exotherm is the first measurable thermal indicator of hydroquinone depletion. The arithmetic difference between induction periods at 25–30 ppm and at 14–17 ppm is not transferable between sites because agitator power per unit volume, reactor geometry, and vapour-space oxygen content affect inhibitor-consumption rates. Comparative inhibitor-response screening can be performed by isothermal differential scanning calorimetry, but published data for this specific configuration are limited.
Prolonged storage at ambient temperature is permissible only when inhibitor monitoring is included in the warehouse release procedure. The hydroquinone concentration should be re-verified by ASTM D2193 before polymerisation if the storage period exceeds the supplier-defined shelf life, if the bulk temperature has exceeded 30 °C, or if the vapour space has been exposed to inert gas. Storage tanks and portable tanks are fabricated from 316L stainless steel or aluminium; carbon steel systems can accelerate inhibitor depletion through rust-catalysed oxidation. Transfer operations use grounded pumps, closed-loop vapour equalisation, and low-shear rotary or centrifugal pumps. The product is not stored in oxygen-free conditions. If vacuum stripping is required before polymerisation, the stripped monomer is consumed immediately or re-inhibited. In high-humidity terminals, floating suction lines and desiccant dryers are used to limit water ingress, because water above the specification maximum can affect ester hydrolysis and downstream polyvinyl alcohol molecular-weight control.
In tank farms, the main operational conflict is between oxygen exclusion for safety and oxygen preservation for inhibitor function. Conventional floating-roof tanks with vapour pressure valves are acceptable for refrigerated monomer; fixed-roof tanks require a breathing system that admits dried air through a flame arrester rather than pure inert gas. During turnaround, empty tanks are inspected for polymer deposits in vents, relief lines, and pump strainers; polymer deposits in vapour spaces are a field indicator that inhibitor or oxygen was locally depleted. Drain lines and instrument taps are designed to be self-draining to avoid stagnant monomer pools. The product is not allowed to remain in hoses or temporary transfer pipes between shifts unless the line is filled with inhibited monomer and vented to air at all high points.
The release specification is set within the framework of ASTM D2190. The values below are representative for polymer-grade VAM HQ 25–30 ppm; individual supplier certificates may include additional limits for carbonyl compounds, distillation range, and non-volatile matter.
| Property | Typical release limit | Reference method |
|---|---|---|
| Vinyl acetate purity, wt% | ≥ 99.9 | ASTM D2190 / supplier gas chromatographic method |
| Hydroquinone, ppm | 25–30 | ASTM D2193 |
| Water, wt% | ≤ 0.05 | ASTM D1364 Karl Fischer |
| Acidity as acetic acid, wt% | ≤ 0.005 | ASTM D2086 |
| Color, Pt-Co | ≤ 5 | ASTM D1209 |
The principal downstream uses of VAM HQ 25–30 ppm are polyvinyl acetate homopolymer and copolymer emulsions, polyvinyl alcohol via alcoholysis, ethylene-vinyl acetate copolymers, and vinyl acetate-ethylene dispersion products. In emulsion polymerisation, the inhibitor is generally not distilled out. The oxidant portion of the initiating system is adjusted so that hydroquinone is consumed before the main reaction exotherm. In a continuous stirred-tank train with staged cooling, the first reactor acts partly as an inhibitor-consumption zone; its temperature may remain below the set point until the hydroquinone is depleted. For batch reactors using thermal persulfate initiation at 70–80 °C, the delay is typically short enough to manage by delayed initiator ramping. For redox systems at 45–55 °C, the delay is more pronounced because radical generation is slower. Production experience shows that start-up reproducibility improves when the hydroquinone assay is known and activator feed is not initiated before a measurable temperature rise. In high-pressure ethylene-vinyl acetate copolymerisation, the monomer is fed as a liquid to the secondary compressor suction; the inhibitor is consumed rapidly in the preheater and reactor, but the residual amount can influence molecular-weight distribution if the initiator feed is not adjusted. In polyvinyl alcohol production, residual hydroquinone can affect colour and redox behaviour during alkaline alcoholysis; producers using this grade may adjust catalyst level or activated-carbon treatment of the recovered monomer stream. If downstream EVA compounds are prepared, melt-flow-rate testing by ISO 1133-1:2022 may detect viscosity shifts when monomer conversion is incomplete.
In redox-initiated vinyl acetate-ethylene emulsion polymerisation, the optimum inhibitor level represents a process conflict. The colloidal stabiliser system and ethylene mass transfer depend on maintaining a controlled particle nucleation period; a prolonged induction caused by 25–30 ppm hydroquinone can shift nucleation relative to ethylene saturation and alter particle-size distribution. Reactor operators may compensate by increasing the initial oxidant charge, raising the reactor temperature by 2–5 °C during the seed stage, or splitting the hydroquinone-containing monomer feed into a sacrificial pre-reaction vessel. The pre-reaction vessel is typically a small stirred tank operated with a persulfate feed just sufficient to consume hydroquinone before the monomer enters the main reactor. This solution preserves the logistics benefit of the 25–30 ppm grade while decoupling polymerisation start-up from inhibitor depletion. The same approach is used when a plant switches from internal 3–5 ppm monomer to imported 25–30 ppm monomer without a complete redesign of the initiator dosing skid.
A change from 14–17 ppm to 25–30 ppm hydroquinone alters the kinetic start-up of the polymerisation line and increases the tolerance of the monomer to prolonged storage. In high-temperature autoclave polymerisation for ethylene-vinyl acetate copolymers, the additional inhibitor load is consumed rapidly by the thermal initiator flux, so viscosity and molecular-weight response may remain within normal control limits if the inhibitor assay is within specification. In low-temperature emulsion polymerisation, the additional hydroquinone can extend the seed stage and shift the residence time required to reach target conversion. The handling of the 25–30 ppm product differs from that of the 3–5 ppm internal-grade material, which is intended for short residence time and minimal induction delay. The following table summarises the operational distinctions.
| Inhibitor range | Typical application context | Operational consequence |
|---|---|---|
| 3–5 ppm | Immediate use within a single plant or short-distance pipeline | Minimal induction; limited margin for storage or oxygen exclusion |
| 14–17 ppm | Medium-term bulk storage and direct polymerisation | Balanced induction and storage stability; initiator adjustment often minor |
| 25–30 ppm | Extended storage, intermodal tank shipments, high-ambient transit | Longer induction in redox initiation; pre-use assay and initiator adjustment recommended |
Handling of VAM HQ 25–30 ppm requires spark-proof equipment because the liquid can form flammable vapour at ambient temperature. Vapour-space inerting must be designed to preserve dissolved oxygen for inhibitor function; a continuous oxygen analyser with a low-limit alarm at 5 vol% is used in some tank farms when partial inerting is required. The monomer is incompatible with strong oxidizers, strong acids, strong bases, and free-radical initiators in confined geometries. Long-term contact with copper and copper alloys is avoided because trace metal ions can initiate instability. Exposure controls follow the extended safety data sheet under Regulation (EC) No 1907/2006; occupational exposure limit values and derived no-effect levels are stated in Section 8 of the SDS. Transfer and spill-response procedures use flame-resistant equipment, grounded tools, and alcohol-resistant foam or water spray applied from a safe distance.
