Shandong Qilu Dibutyl Phthalate (DBP)

Shandong Qilu dibutyl phthalate (DBP) is a linear orthophthalate ester supplied as a clear, oily liquid with the molecular formula C₁₆H₂₂O₄, CAS 84-74-2, and molecular weight 278.34 g/mol. The product is designated as industrial-grade di-n-butyl phthalate rather than as a blended ester or branched iso-butyl derivative. It is manufactured by esterification of phthalic anhydride with n-butanol, yielding an ester that is distinct from diisobutyl phthalate despite the same molecular formula. Shandong Qilu DBP is used in nitrocellulose lacquers, polyvinyl acetate adhesives, gravure inks, and low-temperature flexible PVC compounds where fast gelation and high solvency are required. It is not a general-purpose high-permanence plasticizer; its lower molecular weight and higher vapour pressure separate it from DEHP, DINP, and DIDP in applications that require low volatility or resistance to migration.

For incoming quality control, typical acceptance criteria for Shandong Qilu DBP are listed below. Users should adjust limits only if a specific production trial shows that a tightened acid value or moisture limit is required for the downstream process.

Purchasers should verify that the certificate of analysis reports the same test methods and limits shown above. Variations in ester content, acidity, and moisture influence downstream performance; for example, water above 0.10 wt% can hydrolyse the ester during heated storage and elevate acid value, while acid values above 0.10 mg KOH/g indicate oxidative or hydrolytic degradation. Density and refractive index are used as rapid lot-to-lot consistency checks rather than as primary quality limits. The flash point of DBP is routinely reported with the Cleveland open-cup method; closed-cup values are lower and should not be substituted for open-cup data in safety assessments.

What Limits Upper Processing Temperature in Open PVC Plastisol Systems?

In open plastisol systems, DBP is generally processed at lower temperature than higher phthalate plasticizers. The open-cup flash point of approximately 171 °C is not the only limiting factor; volatile loss from the liquid surface can occur well below the flash point in ventilated coating rooms. Rotational viscosity by ASTM D2196 shows that DBP plastisols have lower initial paste viscosity than DINP plastisols at equivalent resin K-value and plasticizer loading. This allows formulators to reduce viscosity without adding hydrocarbon diluents, but it also produces faster gelation. In a torque rheometer at 60 rpm and 90 °C, gelation onset from DBP-containing dry blends is typically earlier than DEHP or DINP systems. For open dip tanks and doctor-blade coaters, paste temperature is normally held below 35 °C unless ventilation is designed to remove ester vapour.

In calender lines, DBP permits lower stock temperatures by 10–15 °C relative to DEHP compounds at equivalent Shore A hardness. This is useful on four-roll inverted L calenders where thermal-oil heating and roll crowning can create local hot spots. However, DBP compounds held above 160 °C on open mills for extended residence show measurable mass loss by gravimetric analysis, and condensation on downstream cold guides can occur. Closed injection moulding barrels are less affected because backpressure suppresses surface evaporation; nevertheless, screw plastication units with long residence times and melt temperatures above 180 °C should be evaluated for vent emissions.

Nitrocellulose Lacquer Solvency and High-Shear Dispersion in Gravure Ink

DBP functions as both a plasticizer and a viscosity depressant in nitrocellulose lacquers. Its solvency for nitrocellulose is higher than that of aliphatic dicarboxylates, permitting rapid lowering of base viscosity at addition levels set by the final film flexibility target. High-shear dispersion in a bead mill or three-roll mill is performed without pre-dilution because DBP wets pigment surfaces and reduces mill paste yield stress. Pigment dispersion fineness is assessed by ASTM D1210; lacquer viscosity is commonly measured by ASTM D2196 or ISO 3219. In gravure ink, DBP is often combined with DEHP or epoxidized soybean oil to balance volatility during cylinder etching and drying. The relatively high vapour pressure of DBP assists flash-off during short oven dwell times, which can improve block resistance but can also increase retained solvent under high-speed printing if dryer capacity is insufficient.

Lacquer film flexibility after DBP incorporation is assessed by conical mandrel bend testing according to ASTM D522; unplasticized nitrocellulose films crack more readily at low temperature than DBP-modified films. High DBP loadings reduce surface hardness and blocking resistance, so formulations are adjusted by designed experiments rather than fixed addition ratios. Published data for this specific configuration is limited; no universal concentration can be stated.

When DBP Is Selected Over General-Purpose Orthophthalates in Adhesive Formulations

In polyvinyl acetate and vinyl acetate-ethylene copolymer adhesives, DBP is selected when low-viscosity wetting and rapid set are required. It lowers the glass transition temperature of the dried film more efficiently per unit mass than DEHP because of lower molecular weight and higher solvency. At equal addition level, low-temperature flexibility improves, but creep resistance and heat resistance decline. The product is specified for paper converting, label stock, and remoistenable gumming where oil resistance is not the primary requirement. For laminating adhesives requiring permanence, benzoate esters or dipropylene glycol dibenzoate ester plasticizers are substituted; for lower volatility, DEHP or DINP is used.

Open-time and bond-strength measurements are performed according to ASTM D1876 for T-peel strength and ASTM D6862 for 90° peel adhesion. Adhesive films aged under forced air at 50 °C show greater mass loss from DBP than from DEHP; migration into paper substrates is measurable by accelerated aging at 60 °C and can be confirmed by extraction or infrared spectroscopy. These boundaries restrict DBP use in archival and long-term tape applications but are usually acceptable in short-life industrial tapes and packaging adhesives.

Calendering and injection moulding plant data reveal a narrow volatility window for DBP. Comparative physical data for linear DBP and higher orthophthalates are relevant when a compound is specified for thin films, automotive interior trim, or electrical components. DBP has a lower molecular weight and higher vapour pressure than DEHP, DINP, and DIDP. The following table summarises typical values from supplier technical data sheets and public plasticizer databases.

When DBP is used at 5–15 phr in PVC film for non-durable stationery, tensile elongation measured by ASTM D638-14 may increase relative to unplasticized compound, but plasticizer loss under accelerated weathering or heat aging is higher than DEHP or DINP. DBP is generally avoided as the primary plasticizer in wire insulation, automotive interior skins, or outdoor geomembranes because migration to contact surfaces and high-temperature volatility reduce long-term flexibility. Migration kinetic measurements can be conducted by extraction or by Fourier transform infrared spectroscopy; published data for specific Shandong Qilu production lots is limited, so users should qualify each lot by migration testing under service conditions.

Why Is DBP Not a Drop-In Replacement for DEHP in High-Temperature PVC Cable Compounds?

In PVC cable extrusion, the plasticizer must survive high-temperature processing and long-term thermal aging. DBP has a lower molecular weight and higher vapour pressure than DEHP; at cable extrusion melt temperatures of 160–190 °C, DBP can volatilize from the melt before the die face, causing fuming, die-lip deposit, and porosity if not controlled. DEHP remains more stable under these conditions because of its higher boiling point and lower vapour pressure. The dry blend also softens at lower temperature with DBP, which can improve output in twin-screw extruders with L/D 44:1, but the final insulation suffers plasticizer loss during oven aging. Tensile elongation retention after thermal aging at 100 °C is poorer for DBP compounds than for DEHP or DINP compounds; therefore, DBP is not a direct substitution in cable jackets or insulation. Where DBP is used, it is as a secondary plasticizer at 5–10 phr to improve processing, not as the main permanence plasticizer.

On a co-rotating twin-screw extruder with L/D 40:1, liquid DBP is injected after the melt seal to reduce vapour loss; if injected at the feed throat, it can pre-soften PVC too early and reduce shear heating, changing residence time distribution. In cable plants, vacuum venting must be limited because DBP can be stripped along with moisture; actual vent settings are line-specific and are set lower than for DEHP-containing compounds to reduce ester loss. These plant constraints are characteristic of DBP and should be expected when substituting DBP into an existing DEHP process.

Regulatory Controls and Incompatibility Boundaries Define the Application Envelope

DBP is subject to multiple regulatory restrictions. In the EU, dibutyl phthalate is included in REACH Annex XVII entry 51; it cannot be placed on the market in toys or childcare articles as a substance or in mixtures at concentrations greater than 0.1 wt% of plasticised material. The restriction also applies to DEHP, BBP, and DIBP. Under EU RoHS Recast 2011/65/EU, Annex II restricts DBP to 0.1 wt% in homogeneous materials in electrical and electronic equipment. In the United States, DBP is included in CPSIA section 108 as a prohibited phthalate in children’s toys and child care articles at concentrations above 0.1%. DBP is also listed on the REACH Candidate List as a substance of very high concern under Article 57c, triggering communication duties under REACH Article 33 when the concentration in an article exceeds 0.1 wt%. These legal limits, rather than immediate toxicological thresholds, often determine whether DBP can be used in consumer applications.

Incompatibility boundaries are equally material. DBP is stable in carbon steel or epoxy-lined tanks, but it will hydrolyse under strongly alkaline conditions. It should not be compounded with strong aqueous caustic, ammonia, or primary amines at elevated temperature because ester hydrolysis can generate phthalic acid salts and n-butanol. DBP is combustible at elevated temperatures; avoid strong oxidisers, open flames, and uncontrolled heating above the flash point. Closed drums and totes should be resealed immediately after use to prevent water uptake above the 0.10 wt% specification. Bulk storage tanks should be maintained below 40 °C; in hot climates, vent condensers or dry nitrogen blanketing are used to control vapour accumulation in the headspace.