| HS Code | 915735 |
| Product Name | VAM HQ 8–12 ppm |
| Chemical Name | Vinyl Acetate Monomer |
| Cas Number | 108-05-4 |
| Molecular Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Appearance | Clear colorless liquid |
| Purity | ≥99.9 wt% |
| Inhibitor | Hydroquinone (HQ) |
| Inhibitor Content | 8–12 ppm |
| Boiling Point | 72.7 °C at 760 mmHg |
| Melting Point | -93.5 °C |
| Flash Point | -8 °C (closed cup) |
| Autoignition Temperature | 427 °C |
| Specific Gravity | 0.932 at 20 °C |
| Vapor Pressure | 115 mmHg at 20 °C |
| Solubility | Slightly soluble in water (2 wt% at 20 °C) |
| Refractive Index | 1.3953 at 20 °C |
| Viscosity | 0.42 cP at 20 °C |
As an accredited VAM HQ 8–12 ppm factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 58 L steel cylinders containing VAM HQ at 8–12 ppm in nitrogen, fitted with CGA-350 valve. |
| Container Loading (20′ FCL) | 20′ FCL of VAM HQ (8–12 ppm) packed securely, labeled per regulations, and sealed for safe, efficient transport. |
| Shipping | Ship as UN 1301, Vinyl Acetate Monomer, Stabilized (Class 3, Packing Group II). Use approved drums, totes, or ISO tanks. Maintain hydroquinone inhibitor levels at 8–12 ppm to prevent polymerization. Keep cool, away from ignition sources, and ground containers during transfer. |
| Storage | Store VAM HQ 8–12 ppm (vinyl acetate monomer inhibited with hydroquinone) in tightly sealed containers in a cool, dry, well-ventilated area, away from direct sunlight, ignition sources, and incompatible materials like oxidizers. Maintain temperature below 30°C (86°F) to prevent polymerization. Use explosion-proof equipment, ground/bond containers, inspect for peroxide formation, and follow prescribed shelf-life. |
| Shelf Life | Shelf life is typically 6–12 months when stored properly in sealed containers, under nitrogen, away from heat, light, and contamination. |
Vinyl acetate monomer stabilised with hydroquinone at 8–12 ppm is employed in poly(vinyl acetate) woodworking-adhesive emulsion polymerisation. The inhibitor level is not inert: hydroquinone partitions toward the aqueous phase and consumes early radicals during the induction period. Batch-to-batch induction drift is commonly observed when the same redox charge is used against varying hydroquinone content within the 8–12 ppm range. The reaction is run in a 10–25 m³ jacketed stainless steel or glass-lined reactor fitted with a pitched-blade turbine and wall baffles. A protective colloid—partially hydrolysed PVOH at 3–6 phr—is combined with a non-ionic surfactant at 0.5–2.0 phr in the aqueous phase. The redox initiation system uses potassium or ammonium persulfate at 0.10–0.25 phr and sodium metabisulfite at 0.05–0.10 phr; the higher inhibitor level within the supplied band normally requires the upper initiator range. Polymerisation starts after forming a seed latex at 68–72 °C and is maintained at pH 4.2–4.8 with sodium bicarbonate. Above pH 6, hydroquinone oxidises to benzoquinone and produces pink-to-brown discoloration in the finished dispersion. Below pH 4, vinyl acetate hydrolysis accelerates and releases acetic acid, reducing viscosity stability. Monomer conversion is carried above 98 % before steam and vacuum stripping at 60–65 °C under 200–300 mbar absolute. A post-initiation shot of tert-butyl hydroperoxide and sodium metabisulfite reduces residual VAM to below 1,000 mg/kg. Final emulsion specification is typically 50–54 % solids, Brookfield RVT viscosity 5,000–20,000 mPa·s at 20 rpm and 25 °C, and a homopolymer film-forming temperature near 28–35 °C. Adhesive grades are classified under EN 204 durability classes D2, D3 and D4; dry and wet tensile shear strength is checked on beech according to ASTM D905. Limitation: amine-based neutralising agents should not be used before monomer conversion exceeds 98 %, because amine-quinone interaction products intensify colour and reduce adhesive clarity.
Low-odour interior and exterior paint binders based on vinyl acetate–butyl acrylate or vinyl acetate–VeoVa 10 copolymers require near-complete monomer conversion because residual VAM contributes to odour and labelling. With VAM hydroquinone at 8–12 ppm, the emulsion polymerisation recipe is adjusted through a reduced initial redox charge and a delayed initiation profile. A commercial line typically uses a 15 m³ reactor with an anchor impeller and external heat exchanger; the monomer pre-emulsion is metered over 4–5 h at 70–75 °C. The pH is buffered at 4.5–5.5 with sodium acetate/acetic acid rather than volatile amine buffers, because volatile amines raise both VOC and pH-driven quinone colour. Ammonium persulfate is fed at 0.05–0.15 wt% of total monomer and sodium erythorbate at 0.03–0.08 wt%; the feed rate is ramped against heat output. Residual VAM after stripping is typically below 500 mg/kg. The copolymer dispersion is formulated to a glass transition temperature between 0 °C and 20 °C; minimum film-forming temperature is measured by ISO 2115. Scrub resistance is evaluated by ISO 11998 or ASTM D2486, with formulated interior flat paints commonly exceeding 2,000 scrub cycles when binder content is above 60 g/m² dry film. Operational boundary: the hydroquinone-derived quinone band is more visible in low-Tg, high-solids paint films; inorganic buffer pre-neutralisation is preferred over post-neutralisation with ethanolamine or ammonia.
Polyvinyl alcohol is manufactured from VAM-derived poly(vinyl acetate) by continuous methanolysis rather than direct saponification; therefore the hydroquinone content of the original VAM determines the trace phenolic burden in PVAc and in the final PVOH. In continuous belt or kneader alcoholysis, PVAc is dissolved in methanol at 30–40 wt% and reacted with sodium methoxide or sodium hydroxide at 35–50 °C. The molar ratio of methanol to acetyl groups is maintained at 2.0–4.0 mol/mol. Under these alkaline conditions, hydroquinone becomes a colour-body precursor. Partially hydrolysed grades are produced at 86–89 mol% hydrolysis and fully hydrolysed grades at 98–99 mol%. For optical-grade PVOH, the polymer solution is treated with activated carbon or an acidified brine wash to reduce quinoid chromophores. Viscosity grade is controlled through molecular weight and residual acetyl content; a 4 % aqueous solution is measured with a Brookfield LVF spindle at 20 °C, and commercial grades typically range from 3 mPa·s to 70 mPa·s, comparable to JIS K6726 testing. Film-grade PVOH is evaluated for colour, water solubility and ash; hydroquinone-derived residue is quantified as UV absorbance at 280 nm or as yellowness index under ASTM D1925. Limitation: high-pH aqueous washing of inhibited VAM itself is not recommended if the intent is to remove hydroquinone, because hydrolysis and acetaldehyde formation increase above pH 6.
The following matrix lists the primary test methods and operational limits associated with the hydroquinone-inhibited VAM downstream tracks described above.
| Downstream application | Primary standard | Measured parameter | Inhibitor-related process limit |
|---|---|---|---|
| Poly(vinyl acetate) wood adhesive | EN 204, ASTM D905 | Tensile shear strength on wood after dry and wet conditioning | pH 4.2–4.8; monomer conversion above 98 % |
| Decorative paint binder | ISO 11998, ASTM D2486, ISO 2115 | Scrub resistance, minimum film-forming temperature | Residual VAM below 500 mg/kg |
| Polyvinyl alcohol | JIS K6726, ASTM D1925 | 4 % aqueous solution viscosity, yellowness index | Hydrolysis 86–89 mol% or 98–99 mol% |
| Ethylene-vinyl acetate copolymer | ISO 1133-1:2022, ISO 527-2, ASTM D3418 | Melt flow rate at 190 °C and 2.16 kg, tensile properties, melt transition | Reactor pressure 1,400–2,500 bar |
| Redispersible polymer powder mortar | EN 12004, EN 998-1 | Tile adhesive tensile adhesion, hardened render properties | Storage relative humidity below 60 %; powder moisture below 0.5 % |
| Paper coating binder | ISO 2470-1, TAPPI T 452 | Brightness, yellowness | Particle size below 250 nm |
| Ethylene-vinyl alcohol barrier resin | ASTM D3985, ISO 15105-2 | Oxygen transmission rate | Extrusion moisture below 0.10 % |
In EVA copolymer production, vinyl acetate containing hydroquinone at 8–12 ppm is compressed with ethylene into a high-pressure autoclave or tubular reactor and polymerised by organic peroxides. The process window is unusually sensitive to inhibitor balance: pressure is held at 1,400–2,500 bar, temperature between 150 °C and 300 °C, and residence time below 60 s in tubular lines. Hydroquinone consumes peroxide-derived radicals in the initiation zone; at constant peroxide feed, an increase from 8 ppm to 12 ppm can lower molecular weight and raise melt flow rate. Compensation is implemented by increasing peroxide addition by 5–15 % relative to baseline and by monitoring melt flow rate with ISO 1133-1:2022 at 190 °C and 2.16 kg. EVA grades with vinyl acetate content between 4 wt% and 40 wt% are used for flexible packaging, hot-melt adhesives, photovoltaic encapsulant films and footwear compounds. The copolymer is pelletised on an underwater cutter and may be compounded on a twin-screw extruder with L/D ratio 40:1 to add antioxidant and slip packages. For photovoltaic encapsulant sheets, residual hydroquinone can interfere with peroxide cure and reduce gel content after lamination at 145–155 °C. Tensile properties are measured by ISO 527-2 or ASTM D638-14, and thermal transitions by ASTM D3418. Limitation: oxygen must be excluded from the ethylene/VAM feed because oxygen retards the same radical population as hydroquinone and produces polyethylene crosslinking or gel specks in film grades.
VAE base emulsions for redispersible polymer powders are produced from VAM and ethylene at 10–25 wt% ethylene in the copolymer. The base latex must tolerate subsequent spray drying, storage and re-dispersion in alkaline cementitious systems. With VAM hydroquinone at 8–12 ppm, the latex plant verifies inhibitor lot consistency because hydroquinone-driven induction variability shifts the ethylene uptake profile and the final glass transition temperature. Emulsion polymerisation is performed at 50–70 °C under 10–40 bar ethylene pressure in a pressure-rated reactor with a double-helical ribbon impeller; pH is kept at 4.0–5.5. A polyvinyl alcohol protective colloid is used at 5–15 wt% of total monomer and also becomes the redispersible powder’s primary dispersant. The finished latex has solids of 50–55 %, Brookfield viscosity 500–3,000 mPa·s, and glass transition temperature between -15 °C and +5 °C. Spray drying is carried out in a co-current rotary or nozzle dryer with inlet air at 130–170 °C and outlet air at 55–75 °C, followed by blending of 5–15 wt% calcium carbonate or silica anti-caking agent. The dry powder is tested for bulk density, sieve residue on 150 µm, and re-dispersibility in water. In dry-mix mortars, addition levels of 1.5–5.0 wt% based on dry mortar are typical; adhesive and deformability properties are evaluated according to EN 12004 for tile adhesives and EN 998-1 for render. Operational boundary: redispersible powders must be stored at relative humidity below 60 % and at ambient temperature below 30 °C, because moisture exposure causes irreversible cold blocking and loss of redispersibility.
Vinyl acetate–acrylate paper coating binders produced from VAM containing hydroquinone at 8–12 ppm require tight control of low-shear viscosity and high-shear stability because blade coating and metering size presses operate at machine speeds from 800 m/min to 1,800 m/min. The binder is synthesised as a carboxylated emulsion with solids 45–50 %, pH 6.0–7.5, Brookfield viscosity 300–2,000 mPa·s at 25 °C, and particle size below 250 nm. Hydroquinone-derived phenolic residues can lower brightness and increase yellowness in coated paper; coating formulations are therefore evaluated with ISO 2470-1 brightness and TAPPI T 452 colour. High-shear viscosity is measured in a capillary or Hercules high-shear viscometer at 100,000 s⁻¹; stable binders maintain capillary viscosity below 120 mPa·s under standard conditions. In metering size press applications, the binder is blended with starch at a binder:starch ratio of 1:4 to 1:2, with total solids between 12 % and 20 %. Machine runnability failures such as blade streaking and misting are caused by shear-induced coagulation when the emulsion is destabilised by low pH, excessive calcium ions, or insufficient surfactant replenishment. A low coagulum specification for paper coating binders is often below 100 mg/kg on a 45 µm screen, measured by internal filter retention. Limitation: the carboxylated VAM-acrylate binder should not be combined with aluminium sulphate in the same feed line, because ionic shock raises grit and reduces water retention in the base sheet.
Ethylene-vinyl alcohol barrier resin is obtained by saponification of VAM-derived EVA; therefore the hydroquinone content of VAM affects the intermediate EVA molecular weight distribution and residual acetate sequencing. For EVOH with ethylene 27–44 mol%, oxygen transmission rate at 23 °C and 85 % relative humidity is measured according to ASTM D3985 or ISO 15105-2. The material is used in coextruded barrier films and multilayer containers; food-contact status is assessed under EU 10/2011 and relevant FDA 21 CFR sections for ethylene copolymers. Residual hydroquinone from the VAM stage is largely consumed during polymerisation and saponification, but trace quinoid compounds can affect resin colour; pellet colour is measured by ASTM D6290. Extrusion of EVOH requires predrying to below 0.10 % moisture and melt temperatures of 210–230 °C. Interlayer adhesion in coextruded structures is evaluated by seal strength tests such as ASTM F88 after ethylene-acrylic acid tie-resin application. Limitation: published data for the direct effect of 8–12 ppm hydroquinone in VAM on final EVOH colour is limited; resin producers normally set internal colour and gel criteria on the intermediate EVA and final EVOH pellets rather than on VAM inhibitor level alone.
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Vinyl acetate monomer stabilized with hydroquinone at 8–12 ppm is supplied as a clear, low-viscosity intermediate for free-radical polymerization processes. The commercial grade is designated VAM HQ 8–12 ppm; the model name reflects the certified inhibitor concentration range rather than a separate chemical modification. The product carries CAS RN 108-05-4, EC number 203-545-4, molecular formula C4H6O2, and molecular weight 86.09 g/mol. The inhibitor is hydroquinone, C6H4(OH)2, added during distillation as a methanol solution and adjusted to a finished bulk tank concentration within the specified band. Physical properties relevant to handling include a density of 0.934 g/cm³ at 20 °C, boiling point 72.7 °C, flash point -8 °C closed cup, and vapor pressure of approximately 12 kPa at 20 °C. The material is classified as a flammable liquid under GHS H225 and is registered under REACH (EC) No 1907/2006. The specification profile follows ASTM D2190-07(2021) for vinyl acetate monomer, with additional certificate-of-analysis parameters for hydroquinone content.
Because hydroquinone functions as a stoichiometric free-radical scavenger rather than as a catalytic retarder, the 8–12 ppm concentration band establishes a defined inhibitor reserve that is consumed before polymer propagation can proceed. In storage, the reserve is depleted by residual peroxy radicals, thermal initiation events, and oxygen ingress. In downstream polymerization, the same reserve creates an induction delay that must be offset through initiator charge adjustment. This behaviour differentiates VAM HQ 8–12 ppm from uninhibited monomer, which can reach exothermic self-polymerization during transport, and from higher-inhibitor grades that increase storage life but require larger downstream initiator compensation. The inhibitor is added during final distillation and mixed inline through the overhead receiver; no separate blending step is required at the receiving site.
Commercial VAM is typically inhibited with hydroquinone at one of three bands: 3–5 ppm, 8–12 ppm, and 14–17 ppm. The 3–5 ppm band is specified for short-cycle consumption in closed polymerization units where monomer is consumed rapidly and induction delay is minimized. The 14–17 ppm band is selected for extended storage, marine transport, and locations with sustained ambient temperatures above 25 °C. VAM HQ 8–12 ppm is an intermediate band that is typically chosen for regional distribution intervals and multi-week nitrogen-blanketed storage. It provides a higher inhibitor reserve than the low band while avoiding the larger initiator compensation associated with the high band. The choice of band is therefore a scheduling variable: it sets the amount of inhibitor that must be consumed before the reactor reaches maximum conversion rate.
| Inhibitor band | Hydroquinone concentration | Storage orientation | Downstream induction control | Typical boundary condition |
|---|---|---|---|---|
| Low | 3–5 ppm | Short-cycle, closed transfers, rapid consumption | Minimal initiator compensation | Not for prolonged ambient storage; maintain 15–25 °C and nitrogen blanketing |
| Intermediate | 8–12 ppm | Regional distribution, multi-week storage | Induction period calibrated by reactor trials | Avoid sustained bulk temperatures above 30 °C and oxygen ingress |
| High | 14–17 ppm | Extended storage, marine transport, tropical ambient | Higher initiator demand; possible pre-reduction step | May require inhibitor removal or redox trim for sensitive continuous lines |
In a conventional emulsion polymerization train using glass-lined stainless steel kettles with a working volume of 20,000 L and an agitator tip speed of 3–5 m/s, the induction period caused by VAM HQ 8–12 ppm is assessed by monitoring exotherm onset and pressure drop at a jacket temperature of 70–75 °C. The hydroquinone is consumed by the ammonium persulfate initiator through a quinone-forming redox termination reaction. After the inhibitor is exhausted, conversion proceeds rapidly; the transition is visible as a sharp decrease in monomer partial pressure and an increase in heat output. Batch-to-batch variation within the 8–12 ppm range can shift the exotherm onset by several minutes, so the initial initiator charge is trimmed against at-line conversion measurements. In continuous stirred-tank trains operating at 65–75 °C with residence times of 2–4 h, the inhibitor level is sufficiently low that steady-state conversion is maintained without a separate inhibitor-removal column, provided the monomer feed concentration remains within the specified band.
Elevated temperature storage is the primary operational boundary for VAM HQ 8–12 ppm. At sustained bulk temperatures above 30 °C, thermal initiation accelerates and the hydroquinone reserve is consumed more rapidly. If the storage vessel is not nitrogen-blanketed, oxygen ingress can create low concentrations of polyperoxides that may later decompose and reduce the measured inhibitor concentration. Bulk storage should therefore use 316L stainless steel or carbon steel with a suitable internal lining. Copper and copper-bearing alloys are excluded because transition metals can promote peroxide decomposition and color formation. The product is not compatible with strong oxidizers, peroxides, and concentrated acids, and it must not be returned to storage after partial use unless the receiving vessel is inerted and the monomer is re-tested for inhibitor content and peroxide value.
Oxygen is a mixed-factor variable in VAM stabilization. Under cool, dark storage, oxygen can function as a termination agent and supplement hydroquinone retardation. However, oxygen also reacts slowly with the monomer to form polyperoxides, which are thermally labile and may consume hydroquinone when the monomer is heated or exposed to transition metals. For this reason, VAM HQ 8–12 ppm is stored under nitrogen blanketing with the headspace oxygen concentration maintained below 5 vol%. Storage temperature is held below 30 °C, and the monomer is shielded from direct sunlight and UV sources. Under these conditions, the 8–12 ppm inhibitor band provides a consistent feed composition for extended regional distribution. Published data for storage beyond 90 days under variable oxygen ingress rates is limited; therefore, each facility verifies inhibitor content and peroxide value before a static storage interval is extended.
Occupational exposure limits for vinyl acetate monomer are established at 10 ppm as an 8 h time-weighted average under OSHA PEL and ACGIH TLV. The vapor is heavier than air and can accumulate in low areas. Storage and transfer areas require electrically classified equipment, inert gas padding, and closed-loop vapor recovery. The monomer is stabilized before shipment; the stabilizer concentration must be confirmed before any heating operation, including distillation or hot vapor-phase transfer.
The product is released against the following control plan. Hydroquinone content is determined by UV spectrophotometry according to ASTM D2193. Purity is determined by gas chromatography with a capillary column and flame ionization detection. Water is determined by ASTM D1364. Acidity is determined by ASTM D1613. Color is determined by ASTM D1209. Specification limits are set at 99.9 wt% minimum purity, 0.05 wt% maximum water, 0.005 wt% maximum acidity as acetic acid, 5 APHA maximum color, and 8–12 ppm hydroquinone.
| Parameter | Limit | Test method |
|---|---|---|
| Purity | 99.9 wt% min | Capillary GC |
| Water | 0.05 wt% max | ASTM D1364 |
| Acidity as acetic acid | 0.005 wt% max | ASTM D1613 |
| Color, Pt-Co/APHA | 5 max | ASTM D1209 |
| Hydroquinone | 8–12 ppm | ASTM D2193 |
| Appearance | Clear, free of suspended matter | Visual |
The hydroquinone content is specified as a range rather than a single point because of analytical precision, sampling variation, and stabilizer consumption during storage. Certificate-of-analysis values are reported to the nearest 1 ppm. The product is sampled at the storage tank after a minimum recirculation interval of 30 min; samples are collected in amber glass bottles under nitrogen and analysed within 24 h. The batch is released only when purity, acidity, water, color, and inhibitor content meet the control plan. This release protocol aligns with ASTM D2190-07(2021) and with the producer’s ISO 9001:2015 quality system.
The main impurities in vinyl acetate monomer are methyl acetate, ethyl acetate, acetaldehyde, and water. During production, the inhibitor is introduced after the distillation train and before the final cooler. The 8–12 ppm band is maintained by a metering pump ratioed to monomer flow. Inline photometric analysis compares the ultraviolet absorbance at the hydroquinone absorbance maximum to a calibration curve. This loop compensates for variation in crude monomer composition and reduces the risk of releasing monomer with an inhibitor concentration outside the specification. The inline method is calibrated against the laboratory method each shift.
Transfer pumps for VAM HQ 8–12 ppm are specified with mechanical seals and stainless steel or PTFE wetted parts. Centrifugal pumps with magnetic couplings are used to avoid shaft-seal leakage. Hoses and gaskets are constructed from PTFE, fluorocarbon, or special elastomers resistant to vinyl acetate; natural rubber, neoprene, and styrene-butadiene rubber are not suitable because of swelling. The monomer is transferred under nitrogen pressure or by sealed pump; the receiving vessel is inerted before transfer. These measures protect both the inhibitor reserve and the downstream product quality.
The induction delay from hydroquinone is not linear with concentration. A shift from 3–5 ppm to 8–12 ppm increases the inhibitor burden by approximately 2.5-fold, but the corresponding induction time increase depends on initiator flux, temperature, and reactor heat transfer. In batch reactors, the practical correction is to increase the initial ammonium persulfate charge by 0.05–0.20 wt% on monomer or to add a small amount of sodium metabisulfite as a redox kicker. The exact correction is determined empirically because the monomer feed, reactor volume, and agitator configuration alter radical flux. Published data for this specific configuration is limited; plant trials are used to avoid overshooting the initiator feed, which can reduce molecular weight and increase coagulum formation.
In vinyl acetate-ethylene emulsion and solution polymerization, the 8–12 ppm hydroquinone band influences the kinetic profile as a measurable induction delay, not as a permanent inhibition. At a reactor temperature of 70–80 °C with ammonium persulfate initiator, hydroquinone is oxidized to quinone, which quenches growing polymer radicals. Once the hydroquinone is depleted, conversion rises rapidly. For batch reactors, a standard operational adjustment is to generate an initiator-response curve at 8 ppm, 10 ppm, and 12 ppm hydroquinone, using the measured exotherm onset to set the production-scale initiator feed. This calibration reduces batch-to-batch variability because the inhibitor concentration is known from the certificate of analysis. Continuous stirred-tank trains can accept the 8–12 ppm band without a separate inhibitor-removal column when residence time and initiator flow are tuned to the specific feed composition.
The product is used in polyvinyl acetate homopolymer production, vinyl acetate-ethylene copolymers, vinyl acetate-acrylic copolymers, and polyvinyl alcohol production after polymerization. In polyvinyl alcohol manufacture, residual hydroquinone from the monomer is carried through the polymerization and methanolysis sequence; the 8–12 ppm level does not require a separate monomer prewash when sodium hydroxide is used in the saponification step. The operational difference from a 14–17 ppm grade is reduced initiator compensation; the difference from a 3–5 ppm grade is a larger inhibitor reserve before the polymerization start. These differences are managed through normal process control rather than through changes in inhibitor identity.
