| HS Code | 824574 |
| Chemical Name | Vinyl Acetate |
| Product Identifier | Celanese Vinyl Acetate HQ 4-6 |
| Cas Number | 108-05-4 |
| Chemical Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Appearance | Clear, colorless liquid |
| Odor | Sweet, fruity ester-like odor |
| Boiling Point | 72.7 °C at 760 mmHg |
| Melting Point | -93 °C |
| Flash Point | -8 °C (closed cup) |
| Specific Gravity | 0.932 at 20 °C |
| Vapor Pressure | 89 mmHg at 20 °C |
| Water Solubility | Slightly soluble, approximately 2 g/100 mL at 20 °C |
| Purity | Minimum 99.8 wt % |
| Inhibitor Content | Hydroquinone, 4-6 ppm |
As an accredited Celanese Vinyl Acetate HQ 4-6 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Celanese Vinyl Acetate HQ 4-6 is supplied in 200 kg steel drums and 1,000 kg IBC totes. |
| Container Loading (20′ FCL) | 20′ FCL: Vinyl acetate in isotanks or drums, secured, ventilated, grounded, labeled, per dangerous goods regulations. |
| Shipping | Ship as UN 1301, Vinyl Acetate, Stabilized, Class 3, Packing Group II. This HQ 4-6 grade contains 4–6 ppm hydroquinone inhibitor. Use approved, grounded containers, protect from heat, sparks, and oxidizers, and ensure adequate ventilation. Segregate from incompatible materials and follow all dangerous goods regulations. |
| Storage | Store Celanese Vinyl Acetate HQ 4-6 in tightly sealed, approved containers in a cool, dry, well-ventilated area away from heat, sparks, flames, and direct sunlight. Keep separate from oxidizing agents, acids, and peroxides. Bond and ground containers to prevent static discharge. Maintain adequate inhibitor levels and air supply; monitor temperature to prevent polymerization. |
| Shelf Life | Shelf life is approximately 12 months when stored cool, under inert atmosphere, and with inhibitor effectiveness maintained. |
In batch emulsion polymerization of polyvinyl acetate homopolymer for D3/D4 wood adhesive grades, Celanese Vinyl Acetate HQ 4-6 functions as the primary building block. The contained hydroquinone inhibitor (4–6 mg/kg) is consumed by persulfate-radical flux before propagation; this induction period is routinely measured by the time delay between initiator addition and the first exotherm rise in a 20 m³ glass-lined batch reactor fitted with a three-stage axial impeller and external cooling. A delayed monomer feed over 3–5 h maintains free monomer concentration below the solubility limit of the protective colloid. Poly(vinyl alcohol) at 4–6 wt% on vinyl acetate provides steric stabilization, while sodium bicarbonate at 0.1–0.3 wt% buffers pH between 4.5 and 5.5 to prevent PVOH gelation and excessive acid hydrolysis. After the feed stage, a 30–60 min post-reaction at 65–75°C with steam or vacuum stripping reduces residual vinyl acetate below 0.1 wt% for low-odour packaging adhesives. The resulting homopolymer dispersion has a solids content of 55–60 wt% and a Brookfield viscosity of 4,000–15,000 mPa·s at 25°C when tested under ASTM D1084. Wood joint performance is classified under EN 204 as D3 or D4 depending on the selected immersion or boiling-water cycle. Formulation with 2–5 wt% plasticizer on polymer solids lowers minimum film formation temperature but reduces creep resistance. In production, high shear from high-speed dispersers must be limited because PVOH-protected PVAc latices can partially coagulate above 40°C when exposed to prolonged shear rates above 1,000 s⁻¹. The monomer grade quality is most apparent in the delayed exotherm: if the hydroquinone dose varies between 4 and 6 mg/kg, initiator demand shifts by up to 0.05 wt% on monomer, which is compensated by redox ratio adjustment. Published data for the exact induction-time shift across this inhibitor range in industrial reactors is limited.
Polyvinyl alcohol production from Celanese Vinyl Acetate HQ 4-6 proceeds through a two-step train: polyvinyl acetate is first produced by suspension or solution polymerization, then alcoholysed in methanol with sodium hydroxide or sodium methoxide at 40–50°C for 1–3 h. Alkaline conditions convert residual phenolic inhibitors into quinoid species that impart yellow colour to the final PVOH. Incomplete monomer conversion before methanolysis is therefore not acceptable when colour-sensitive water-soluble film or optical paper-sizing grades are manufactured. Industrial reactors for the polymerisation stage are run to monomer conversions above 99.5% before methanolysis. Residual hydroquinone level is not commonly reported as a PVOH certificate parameter; the practical control is methanolysis colour and alkali consumption. PVOH hydrolysis degree is controlled between 86.5 and 89.0 mol% for cold-water-soluble warp sizing and between 98.0 and 99.0 mol% for barrier film. A 4 wt% aqueous solution viscosity of 3–60 mPa·s at 20°C is measured under ISO 15023-2:2019, while residual sodium and ash are quantified for film grades used in detergent pouches. Water-soluble film produced from the fully hydrolysed grade must also meet cold-water solubility and mechanical tensile requirements under ISO 527-3. The process limitation is catalytic alkali concentration: a NaOH-to-PVAc ratio that is too low slows methanolysis and allows equilibrium reacetylation, while an excessive ratio accelerates ester interchange but can darken the product. Methanol recovery must remove methyl acetate below 0.1 wt% to keep the catalyst balance stable. In an 8 m³ continuous kneader reactor, batch-to-batch variation in PVOH hydrolysis degree is typically less than ±0.3 mol% when feed PVAc viscosity is controlled. Direct use of high-HQ inhibitor VAM is possible because the induction period is compensated by higher initiator addition in the preceding polymerisation; however, alkaline hydrolysis stages are chemically incompatible with quinone-forming phenolics when colour stability is critical.
High-pressure free-radical copolymerization of ethylene and Celanese Vinyl Acetate HQ 4-6 is performed in autoclave or tubular reactors at 1,000–2,500 bar and 120–250°C. The monomer must be free of hydroquinone before compression because the inhibitor would consume peroxide initiator radicals and shift the initiator yield. EVA producers commonly route inhibited VAM to a distillation or adsorption unit; residual hydroquinone after cleanup is targeted below 0.5 mg/kg, though published data for specific removal efficiency across all bed configurations is limited. Vinyl acetate content in the final resin is controlled between 4 and 40 wt% and verified by ASTM D5594-98. Melt flow rate is measured under ISO 1133-1:2022 with the appropriate temperature and load, typically 190°C/2.16 kg for hot-melt adhesive grades and 190°C/0.325 kg for high-viscosity photovoltaic encapsulant resins. Above 28 wt% VAM, crystallinity is sufficiently disrupted that melting point by ASTM D3418 falls below 70°C, and cold granulation is required to prevent pellet agglomeration. The same increase in VAM reduces Shore hardness and improves low-temperature impact, but compression set and tack increase. Reactor control constraints become acute above this concentration because excess vinyl acetate acts as a chain transfer agent; molecular weight and melt viscosity decline. Producers compensate by reducing reaction temperature or adjusting chain transfer agent feed, but the operating window narrows. In a 25,000 t/year high-pressure line, pelletizing may require chilled water at 5–10°C and anti-block powder dosing on the strand cutter. EVA hot-melt adhesives are formulated with tackifying resins and waxes; the polymer contributes elastic recovery and adhesion to paperboard packaging. Photovoltaic encapsulant films require low gel content, high optical transmittance, and strong adhesion to glass and backsheet; these are not controlled by the VAM feed alone but are governed by polymerisation and subsequent compounding. Residual vinyl acetate monomer in final EVA resin for food-contact applications must comply with the applicable migration limits of EU Regulation (EU) No 10/2011 and 21 CFR 177.1360 for ethylene–vinyl acetate copolymers. Such compliance is normally achieved by devolatilization in the finishing extruder rather than by monomer grade selection alone.
When a vinyl acetate–ethylene copolymer dispersion is formulated into a low-odour interior wall paint, the vinyl acetate monomer feed still governs colloidal stability in the pressure polymerisation stage. VAE emulsions are produced by adding ethylene at 20–80 bar into a vinyl acetate emulsion polymerisation at 50–80°C, often with PVOH or a mixed PVOH/surfactant stabilizer and a redox initiator. The hydroquinone inhibitor 4–6 mg/kg in Celanese Vinyl Acetate HQ 4-6 is consumed during the early radical flux; the main process constraint is not induction delay but pH drift caused by vinyl acetate hydrolysis to acetic acid at elevated temperature. Ethylene incorporation of 10–25 wt% depresses the glass transition temperature from about 28°C for PVAc homopolymer to between −10 and +5°C, and minimum film formation temperature falls to 0–5°C under ISO 2115. Interior wall paint formulations based on these dispersions develop scrub resistance above 1,000 cycles in ASTM D2486 for higher-scrub products and a dry-film tensile strength of 2–6 MPa with elongation of 300–600% under ISO 527-3. The same class of VAE dispersion is spray-dried into redispersible polymer powders for cementitious tile adhesives. Spray drying requires inlet air at 150–180°C, outlet air at 60–80°C, and a final moisture content below 2 wt% to prevent blocking. Anti-caking agents such as kaolin or calcium carbonate are added at 5–15 wt% on powder to maintain pouch flow. The polymer powder improves adhesion and flexural recovery in tile adhesives tested under ISO 13007-1:2014. The operational boundary for VAE emulsion storage is pH 4–6; addition of amine-based pH neutralizers above pH 8 can destabilize the colloid and raise free monomer leakage. Freezing must be prevented because ice formation irreversibly coagulates the dispersion. Published data on exact ethylene incorporation efficiency in a given reactor geometry is available primarily from equipment suppliers; the feed monomer itself is not the limiting variable.
| Application segment | Critical parameter | Cited test method or regulatory reference | Industrial target range |
|---|---|---|---|
| PVAc homopolymer adhesive | Brookfield viscosity at 25°C | ASTM D1084 | 4,000–15,000 mPa·s |
| PVAc homopolymer adhesive | Wood adhesion class | EN 204 | D3/D4 |
| PVOH resin | Hydrolysis degree | ISO 15023-2:2019 | 86.5–99.0 mol% |
| EVA copolymer | Vinyl acetate content | ASTM D5594-98 | 4–40 wt% |
| EVA copolymer | Melt flow rate | ISO 1133-1:2022 | 0.3–800 g/10 min |
| VAE dispersion | Minimum film formation temperature | ISO 2115 | 0–5°C |
| VAE dispersion | Scrub resistance | ASTM D2486 | >1,000 cycles |
| EVOH barrier resin | Oxygen transmission rate | ASTM D3985 | <0.5 cm³·mm/m²·day·atm |
| Vinyl acetate–vinyl versatate latex | Mortar flexural strength | ASTM C348 | project-specified |
Ethylene–vinyl alcohol resin derived from Celanese Vinyl Acetate HQ 4-6 requires a high-ethylene EVA precursor, typically 27–44 mol% ethylene, followed by saponification to a degree of hydrolysis above 99 mol%. The residual vinyl acetate sequences in the finished EVOH determine oxygen barrier; they must be minimized through controlled methanolysis. Extrusion of EVOH is performed after drying to 0.01 wt% moisture at 80–100°C for 4–6 h because damp resin hydrolyzes in the melt phase and generates gels. Barrier performance is characterized by oxygen transmission rate: commercial film grades remain below 0.5 cm³·mm/m²·day·atm at 23°C and 0% RH under ASTM D3985. The same film at 85% RH loses barrier by a factor of 5–10 due to plasticization of the EVOH layer, which is why multilayer food packaging inserts a polyolefin tie layer. Coextrusion lines run EVOH at melt temperatures of 175–205°C; prolonged residence time above 220°C produces crosslinked gels and brown specks. The monomer path from VAM to EVOH includes the same alkaline alcoholysis colour risk described for PVOH, but barrier film producers apply stronger catalyst removal and wash steps. Residual vinyl acetate migration in food packaging is assessed under EU Regulation (EU) No 10/2011 and applicable FDA food-contact provisions; the finished article, not the monomer certificate, is the compliance point. In fuel tank applications, the EVOH layer provides hydrocarbon permeation resistance but must be shielded from direct aqueous acid because acidic conditions accelerate alcohol group hydrolysis. The practical VAM feed requirement for EVOH is therefore not simply inhibitor level but low carbonyl and low tendency to form coloured phenolic byproducts in the alkaline methanolysis train.
Cementitious repair mortars and tile adhesives use vinyl acetate–vinyl versatate copolymer emulsions to improve adhesion and deformability. Celanese Vinyl Acetate HQ 4-6 is copolymerized with vinyl versatate at 10–30 wt% of total monomer in a batch or semi-continuous emulsion reactor using anionic surfactants and persulfate initiators. The versatate monomer introduces a hydrophobic, branched ester structure that reduces water sorption and improves alkali resistance compared with PVAc homopolymer. Polymer dispersions for cement modification are usually adjusted to pH 7–9 because cement pore water is highly alkaline; the latex must remain stable under calcium ion load. The polymer-to-cement ratio in repair mortars is commonly 5–15 wt% on cement. Flexural strength of modified mortars is measured under ASTM C348, while compressive strength is measured under ASTM C349. Mortar workability is adjusted with superplasticizers, but the latex coalesces and forms polymer bridges between hydration products; this increases tensile adhesion and reduces shrinkage crack propagation. The process limit is calcium ion tolerance: anionic latex particles can coagulate when mixed with hard water or calcium chloride accelerator, so stabilizer selection is critical. Emulsion films from vinyl acetate–vinyl versatate copolymers have lower water uptake than PVAc; nevertheless, the system is not recommended for permanent immersion or chemical-resistant tank linings where styrene-acrylic or epoxy systems are specified. The VAM feed in this segment follows the same inhibitor-consumption behaviour as in other emulsion routes; the 4–6 mg/kg hydroquinone dose influences the initial initiator demand without changing the final copolymer composition.
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Celanese Vinyl Acetate HQ 4-6 is a polymerisation-grade vinyl acetate monomer inhibited with hydroquinone at a nominal concentration of 4–6 ppm. The product is identified by CAS number 108-05-4 and molecular formula C4H6O2 with a molecular weight of 86.09 g/mol. It is supplied as a clear, water-white liquid with a boiling point of 72.7 °C at 101.3 kPa and a density of approximately 0.934 g/cm³ at 20 °C. The grade name encodes the inhibitor type and concentration: hydroquinone is added to prevent thermally initiated polymer formation during bulk storage and transport. The low inhibitor band differentiates the product from higher-inhibitor vinyl acetate grades, such as those inhibited at 14–17 ppm, by reducing radical scavenger demand in downstream initiation while shortening the permissible storage interval. This balance is intended for continuous polymerisation plants with high monomer turnover.
For this monomer grade, polymerisation-critical quality variables are assay, water, acidity, colour, and inhibitor concentration. Table 1 lists the commonly certified parameters.
| Property | Test method | Acceptance band / typical |
|---|---|---|
| Vinyl acetate assay | GC-FID, internal standard | ≥ 99.9 wt% |
| Water | Karl Fischer titration, ASTM E203 | ≤ 0.05 wt% |
| Acidity as acetic acid | Titration, ASTM D1613 | ≤ 0.005 wt% |
| Colour | Platinum-cobalt scale, ASTM D1209 | ≤ 5 |
| Hydroquinone | UV spectrophotometric or HPLC | 4–6 ppm |
| Density at 20 °C | ASTM D4052 | 0.933–0.934 g/cm³ |
The product is commercially specified against ASTM D2190 for vinyl acetate monomer; the test methods in the table are the commonly reported release methods. The assay is determined by capillary gas chromatography with flame ionisation detection using an internal standard; water by Karl Fischer coulometric titration in accordance with ASTM E203; acidity by alcoholic potassium hydroxide titration under ASTM D1613; and colour by platinum-cobalt comparison under ASTM D1209. Hydroquinone is quantified by UV spectrophotometry or high-performance liquid chromatography after extraction. Density is reported as a consistency check. These release methods align with merchant vinyl acetate monomer certification practice; site-specific incoming inspection may add gas chromatographic scan for trace acetaldehyde, methyl acetate, and acetone. For polymerisation control, the water and acidity values are more important than density because they participate in hydrolysis and chain-transfer equilibria. A batch accepted at the upper water limit of 0.05 wt% may still be suitable for emulsion polymerisation but must be monitored when the finished dispersion must meet a narrow viscosity specification under ISO 3219 rotational viscometry.
Hydroquinone concentration is reported as ppm by weight in the liquid monomer. In UV spectrophotometric measurement, the absorbance is taken in the UV region after extraction into water or methanol; HPLC methods use a reversed-phase column with a photodiode-array detector. The 4–6 ppm range is narrow enough that normal tank blending can bring off-spec material into specification, but no plant should rely on blending without knowing the total inhibitor mass balance. The certificate of analysis for each railcar includes the lot-specific value; discrepancies between tank sample and certificate can occur after partial unloading and should be resolved before polymerisation.
In polyvinyl acetate homopolymer production, the monomer is dispersed in a water phase containing a protective colloid such as partially hydrolysed polyvinyl alcohol or hydroxyethyl cellulose. Initiation with ammonium persulfate or tert-butyl hydroperoxide/sodium formaldehyde sulfoxylate is conducted at 60–80 °C in a jacketed reactor with high-shear dispersion. The low acidity of the HQ 4–6 monomer reduces chain transfer to acetic acid; otherwise a 0.01 wt% acetic acid increase can lower the degree of polymerisation and change the viscosity of adhesive-grade polyvinyl acetate by a measurable margin. For ethylene-vinyl acetate copolymers, the monomer is injected into high-pressure autoclaves or tubular reactors at pressures above 100 MPa. Polar impurities such as acetic acid and acetaldehyde concentrate in the recycle ethylene stream, so high assay and low carbonyl content reduce fouling in the hypercompressor and heat exchangers. In polyvinyl alcohol production, PVAc is subsequently hydrolysed in methanol or tert-butanol with sodium hydroxide; residual aldehyde in the monomer can form coloured conjugation products that persist into the final resin. The 4–6 ppm hydroquinone content is low enough that the residual inhibitor contributes negligible colour to the alcoholysis effluent, but the plant must still track it because hydroquinone can form quinoid discoloration in the presence of iron.
Batch-to-batch variance in induction time is more strongly correlated with dissolved oxygen in the monomer feed than with hydroquinone within the certified band. Monomer stored in a 25 m³ tank with a breather valve can show a dissolved oxygen concentration that varies with temperature and pad gas composition. When the monomer is fed into a reactor at 60 °C, the initiator half-life is constant, but the induction period can move if dissolved oxygen is not controlled. This sensitivity means that the 4–6 ppm grade should not be regarded as a stand-alone inhibitor guarantee; the tank pad system is part of the inhibition strategy. For railcar reception, the receiving tank should be sampled at the bottom and top to check for inhibitor drift before the monomer is released to the day tank.
Hydroquinone acts as a free-radical scavenger by hydrogen atom transfer to propagating and initiator-derived radicals. The inhibitor is consumed during the induction period rather than acting as an equilibrium retarder. In batch emulsion polymerisation, the induction time is therefore a function of initiator decomposition rate, temperature, headspace oxygen, and inhibitor concentration. A feed at 4–6 ppm requires less additional initiator than a feed at 14–17 ppm, but the requirement is not strictly linear because part of the inhibitor may be oxidised to benzoquinone, which can react with aqueous-phase radicals or be grafted into oligomers. Air cover is normally required to maintain hydroquinone activity; if the tank is blanketed with pure nitrogen, the inhibitor can become partially ineffective, and the monomer may polymerise sooner than expected during storage. Conversely, excessive air sparging can generate peroxides and acetic acid, which creates a different initiation burden. Therefore, the storage headspace should be an inhibited-air pad rather than pure oxygen or pure nitrogen. Temperature should remain below 30 °C. At higher temperatures, hydroquinone consumption accelerates, and the protective gap between the 4–6 ppm grade and a higher-inhibitor grade narrows. Bulk storage tanks should have accessible temperature probes and sample points for inhibitor verification after prolonged railcar delivery. Pilot-plant data generated in a jacketed 1 L glass reactor with reflux condenser and nitrogen sparge should not be directly scaled to a 25 m³ monomer tank because the surface-to-volume ratio changes oxygen ingress and inhibitor oxidation paths. Published data for this specific configuration is limited; induction time must be established by plant-specific reaction calorimetry.
In suspension polymerisation, benzoyl peroxide and azobisisobutyronitrile are common initiators. Hydroquinone at 4–6 ppm may consume benzoyl peroxide during the initiation phase; therefore the initiator addition is increased slightly relative to an uninhibited laboratory grade. The lower inhibitor level allows a smaller initiator adjustment than high-inhibitor monomer, which is advantageous when the polymerisation formulation is constrained by residual initiator limits in the final resin.
In continuous ethylene-vinyl acetate emulsion copolymerisation, the monomer feed passes through in-line coalescers or decanters, but dissolved water is not removed by these mechanical devices. Water above 0.05 wt% alters the partitioning of surfactants between monomer droplets and growing particles. It also hydrolyses vinyl acetate slowly to acetic acid and acetaldehyde during warm storage. Acetaldehyde above 0.005 wt% is a chain-transfer agent and can generate carbonyl chromophores when the dispersion is dried in a spray dryer at inlet temperatures of 120–150 °C. In high-pressure EVA copolymerisation, vinyl acetate is a polar comonomer and acetic acid is a chain-transfer agent that changes melt-flow index. The melt-flow index is measured according to ISO 1133-1:2022 at 190 °C with a 2.16 kg load; if the monomer acidity rises, the reactor control loop must compensate with less chain-transfer agent or lower reactor temperature, but the operating window is finite. The low-acidity specification of the HQ 4–6 grade maintains the monomer as a consistent inlet stream for such processes. Compared with a high-inhibitor product, the difference is mainly the radical scavenger burden; high-inhibitor monomer can extend storage life but may require more initiator feed and increase the risk of thermal decomposition products from unreacted initiator. The HQ 4–6 product is therefore specified where consumption occurs within the retest interval and the polymerisation line has a narrow initiator dosing range.
Table 2 compares the low-inhibitor grade with a typical higher-inhibitor vinyl acetate monomer.
| Parameter | Vinyl Acetate HQ 4–6 | Higher-inhibitor grade (nominal 14–17 ppm) |
|---|---|---|
| Hydroquinone concentration | 4–6 ppm | 14–17 ppm |
| Initiator scavenging demand in persulfate initiation | Lower; shorter induction | Higher; longer induction |
| Static storage stability at 25 °C under air pad | Typically 90 days retest interval | Typically 180 days or longer retest interval |
| Preferred logistic use | Continuous polymer trains with rapid consumption | Long-distance bulk shipment and intermittent batch production |
| Risk of colour development from initiator overfeed | Lower | Higher if initiator is increased without reactor adjustment |
Bulk storage of the 4–6 ppm grade requires carbon steel or 316L stainless steel tanks with a fixed roof, flame arresters, and a nitrogen or inhibited-air pad. The flash point is -8 °C closed cup, and the lower and upper explosion limits are 2.6 vol% and 13.4 vol% in air. Because the inhibitor level is at the low end of commercial practice, the storage interval should be aligned with the supplier’s retest date and the tank headspace oxygen concentration should be monitored. Prolonged exposure to direct sunlight or tank temperatures above 30 °C can accelerate hydroquinone consumption. The material is not compatible with strong oxidising agents, uncontrolled peroxide addition, or copper and brass components that promote discoloration; use 304 or 316 stainless steel transfer lines. The monomer is subject to REACH (EC 1907/2006) registration and should be handled according to the safety data sheet. For downstream food-contact polymers, compliance must be demonstrated on the finished article under the applicable national or regional regulation for residual vinyl acetate monomer; the monomer specification alone does not establish food-contact status. Published data for this exact configuration is limited with respect to long-term railcar storage in high-humidity coastal terminals, so the retest interval should be confirmed by the supplier’s certificate of analysis and tank history.
