Acetyl Tributyl Citrate ATBC

In flexible medical PVC compounding for tubing, fluid administration sets, and respiratory circuits, ATBC is introduced as a primary plasticizer at loadings between 35 phr and 55 phr depending on the Shore A hardness target specified in ISO 868. The base resin is typically a suspension PVC with a K-value of 67–74, blended with a calcium-zinc stabilizer system at 1.5–3.0 phr, epoxidized soybean oil at 5–8 phr, and a mixed external/internal lubricant package at 0.2–0.6 phr. The dry blend is compounded on a counter-rotating twin-screw extruder with an L/D ratio of 36:1–44:1 and a barrel profile from 130°C to 165°C; die entry melt temperature is maintained at 170–185°C. The resulting pellets are then converted into tubing on a single-screw extruder with a barrier screw and a tube die at 160–180°C. Plastograph torque curves for ATBC-plasticized formulations often show peak torque at lower bowl temperature than the same compound plasticized with dioctyl terephthalate, but the shift is grade-dependent and must be re-established for each resin batch. Published data for this specific configuration is limited because medical compounding lines differ in stabilizer type, screw design, and pelletizing temperature.

Loadings above 60 phr are not recommended where suction tubing must resist wall collapse under vacuum at body temperature; the measured Shore A hardness falls below 65 A and the tubing may kink at bend radii below 3 times the outer diameter. Hardness test coupons are conditioned per ISO 291 at 23°C and 50% RH for 48 h before hardness measurement; tensile strength and elongation at break are determined per ISO 37. ATBC produces a lower-viscosity melt than DOP at equal loading, which improves downstream tube draw and reduces screw torque, but it also increases the risk of plasticizer migration to the surface when the tubing is stored at relative humidity above 60%. Therefore incoming resin must be pre-dried to 0.1% moisture and the compound must not be left in open storage before extrusion. Sterilization by ethylene oxide per ISO 11135 at 50–55°C and 60–70% RH may require additional desorption time; gamma irradiation at 25 kGy per ISO 11137-2 is generally compatible but color changes are monitored by ASTM E313 on each production lot. Extractables and leachables are evaluated under ISO 10993-18 after extraction per ISO 10993-12, with biocompatibility endpoints covering cytotoxicity per ISO 10993-5 and irritation and sensitization per ISO 10993-10.

What Limits ATBC Loading in High-Clarity Food Contact Cling Film?

Film formulations based on suspension PVC of K-value 62–65 are calendered or cast with ATBC at 25–40 phr, epoxidized soybean oil at 3–7 phr, and a calcium-zinc stabilizer at 1.5–3.0 phr. The lower end of the range is used where the finished roll must be unwound from a meat wrapping station at refrigerator temperature; the upper end is used where high cling force is required for pallet stability. Calendering is performed with roll surface temperatures of 150–175°C and a friction ratio between 1.1:1 and 1.3:1; the bank mark is kept small and the film is pulled from the last roll at a take-off speed that maintains a final thickness of 8–12 µm. Melt viscosity is measured by capillary rheometry per ISO 11443 at shear rates of 100–1,000 s⁻¹ to maintain consistent gauge control. Plate-out on the calender rolls is a known failure mode; the zinc stearate concentration must not exceed 0.4 phr and the roll release additive is selected for thermal stability above 180°C.

Food contact compliance is evaluated under EU Regulation 10/2011 with overall migration measured by EN 1186 migration cells at 40°C for 10 days in simulant D1 and D2; the overall migration limit is 10 mg/dm² for the finished film. Specific migration of ATBC is quantified by EN 13130-1:2004 where required by the Union List entry; published data for ATBC migration under all food simulants is limited, so packaging laboratories run dual-temperature migration studies before commercial approval. For the U.S. market, the finished film is evaluated under the applicable Food Contact Substance Notification or under FDA 21 CFR 177.1210 for closure gaskets when the compound is used in that specific closure application. Blocking and cling properties are balanced by measuring static coefficient of friction per ASTM D1894; a coefficient above 0.5 can cause roll telescoping, while a coefficient below 0.2 may prevent the film from remaining attached to tray edges.

Compression-molded gaskets used in metal or plastic bottle closures are plastisol-grade compounds with ATBC at 45–65 phr; the plastisol is dispensed into the closure shell and gelled at 190–210°C for 1–3 min. The gasket must meet seal integrity under hot fill at 85°C and pasteurization at 95°C; volume change after water exposure is measured by ASTM D471 and must stay below 5% to avoid seal loss. This type of application uses a higher ATBC level than film but the same overall migration framework applied to the finished closure.

Migration Data for Children’s Toy PVC Compounds Governs Formulation Limits

For toys and childcare articles, the substitution of phthalate plasticizers is driven by REACH Annex XVII entries 51 and 52, which restrict DEHP, DBP, BBP, and DIBP at 0.1% by weight in plasticized material. ATBC is not covered by these entries and is used in plastisol formulations for slush-molded doll parts, balls, and squeeze toys at 50–70 phr with a paste PVC of K-value 65–72. The plastisol is prepared in a high-torque disperser at tip speeds of 8–12 m/s; viscosity is measured per ASTM D1824 with a Brookfield RVT at 20 rpm and 25°C, and the target working viscosity is usually 2,000–8,000 mPa·s depending on mold fill requirements. Viscosity drift after 24 h at 35°C should be below 10%, and excess air must be removed by vacuum deaeration below 100 mbar to prevent pinholes in the molded skin.

Slush molding gelation is completed at oven air temperatures between 190°C and 210°C; the residence time depends on wall thickness and ranges from 6 to 10 min for a 2 mm skin. Lower temperatures leave a frosted inner surface with poor tensile strength, while higher temperatures cause yellowing and plasticizer loss at the surface. After cooling, the extraction of regulated elements is tested per EN 71-3 and the mechanical properties are tested per EN 71-1. Because ATBC has a different solvating power than DOP, the initial plastisol viscosity at the same plasticizer loading may shift upward or downward depending on the paste resin grade; this is corrected by reducing filler content or adding a small amount of aliphatic hydrocarbon diluent. The finished toy article must not show plasticizer exudation during storage at 40°C and 75% RH for 14 days; any surface film is assessed by visual inspection and by FTIR per ASTM E1252. Published data for ATBC migration from toy-grade plastisols under saliva simulants is limited; manufacturers therefore run child-use article extraction protocols specified by the relevant notified body before approving a formulation.

To depress drying-induced film embrittlement in nitrocellulose-based nail lacquer formulations, ATBC is incorporated at 2–6 wt% of the liquid lacquer, with nitrocellulose at 6–12 wt% and mixed solvent composed of butyl acetate, ethyl acetate, and isopropanol. The plasticizer is added after nitrocellulose has been fully wetted by the solvent blend; high-shear mixing at tip speeds of 5–10 m/s is stopped as soon as the batch reaches 30°C to avoid solvent evaporation. The final lacquer viscosity is measured by a falling-ball viscometer at 25°C and adjusted to a flow time appropriate for brush application. ATBC compatibility with nitrocellulose avoids the blushing and tack that occur when incompatible plasticizers migrate to the surface of the dried enamel. Compliance is governed by EU Cosmetics Regulation 1223/2009 and the CosIng listing for ATBC as a plasticizer; dermal safety assessment uses the exposure estimates from the finished product dossier rather than a single generic limit. Cosmetic formulations do not require food contact migration testing, but residual solvent content is limited by good manufacturing practice and flammability classifications under EU 1272/2008.

High-Solids Printing Inks for Flexible Packaging—Solvent Balance and Blocking Resistance

In liquid gravure and flexographic inks for surface and lamination printing, ATBC is used as a low-odor plasticizer in nitrocellulose and polyurethane binders at 2–6 wt% of the total liquid ink. The pigment concentrate is dispersed in a bead mill at 1,500–2,000 rpm and then let down with the binder solution and a solvent blend of ethyl acetate, ethanol, and methyl ethyl ketone. Viscosity is controlled to a DIN 4 cup efflux time of 20–40 s per DIN 53211 at 25°C; this range allows clean dot transfer on a gravure cylinder but avoids solvent retention in the printed film. The ink film must remain block-resistant when printed reels are stored at 50°C and 0.5 kg/cm² for 24 h; blocking is evaluated by converter-specific weighted contact tests because no international standard fully governs this parameter for all substrate grades.

Compliance for food packaging printed on the non-food-contact side is assessed under EU 10/2011 only when the substrate or a functional barrier separates the ink from the food; otherwise the ink must itself meet the overall migration limit of 10 mg/dm² using EN 1186 on the finished printed laminate. Heavy metal content is controlled under EU Packaging and Packaging Waste Directive 94/62/EC with the sum of lead, cadmium, mercury, and hexavalent chromium not exceeding 100 ppm by weight of the packaging component. For the U.S. market, the ink may be covered by FDA 21 CFR 175.105 when it is separated by a functional barrier; direct contact inks require a specific Food Contact Substance Notification. ATBC in this application is not used as a solvent and does not replace ethyl acetate; its function is to reduce binder embrittlement during film elongation of the printed sealant layer.

When ATBC Replaces DOP in Automotive Interior PVC Skins, Haze and Odor Profiles Shift

After long-term heat ageing at 120°C for 1,000 h, instrument-panel and door-trim skins produced from PVC plastisol or calendered sheet exhibit haze, odor, and volatile emissions profiles that change when ATBC replaces dioctyl phthalate or dioctyl terephthalate. The formulation typically contains PVC paste resin of K-value 65–72, ATBC at 60–80 phr, an epoxidized soybean oil co-stabilizer at 5–8 phr, and a liquid calcium-zinc stabilizer at 2–4 phr. Slush molding is carried out at 220–240°C tool surface temperature for 1–3 min; this range is higher than that used for toy slush molding because the thicker, grained automotive skin must reach full gelation before extraction. The fogging contribution must be measured on the finished compound according to DIN 75201 Method A; no generic phthalate comparison can be substituted because fogging condensate composition is influenced by stabilizer and lubricant packages.

Volatile and semi-volatile organic compounds are measured by VDA 278 with thermodesorption at 90°C for VOC and 120°C for FOG; the acceptance threshold is OEM-specific and typically includes a total VOC ceiling and a fogging condensate mass limit. ATBC migration to the skin surface under high-humidity ageing can increase the measured haze value; therefore the compound is tested at 100–120°C for 100 h and the haze is measured per ASTM D1003. Processing issues concentrate on melt viscosity and gelation rate: ATBC reduces the plastisol viscosity at the low-shear region measured by ASTM D1824 but requires careful temperature control because the gelation plateau shifts by only a few degrees in thin-skinned parts. Retention of tensile properties after ageing is measured by ISO 37; the final product is covered by RoHS Directive 2011/65/EU, which restricts four phthalates at 0.1 wt% in homogeneous materials. ATBC is outside that restriction, but OEM material specifications may add their own emission limits.