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| HS Code | 733377 |
| Product Name | Ditrimethylolpropane |
| Synonyms | Di-TMP; bis(trimethylolpropane); 2,2'-[oxybis(methylene)]bis(2-ethylpropane-1,3-diol) |
| Cas Number | 23235-61-2 |
| Molecular Formula | C12H26O5 |
| Molecular Weight | 250.33 g/mol |
| Appearance | White crystalline solid or flakes |
| Melting Point | 108-112 °C |
| Boiling Point | approximately 402 °C at 760 mmHg (estimated; decomposes can occur) |
| Flash Point | approximately 199 °C (closed cup) |
| Density | approximately 1.13 g/cm3 at 20 °C |
| Vapor Pressure | negligible at room temperature |
| Solubility In Water | Soluble |
| Solubility In Organic Solvents | Soluble in alcohols and acetone; sparingly soluble in aliphatic hydrocarbons |
| Hydroxyl Functionality | 4 hydroxyl groups per molecule |
| Hydroxyl Value | approximately 897 mg KOH/g |
| Hydrogen Bond Donor Count | 4 |
| Hydrogen Bond Acceptor Count | 5 |
As an accredited Ditrimethylolpropane factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Ditrimethylolpropane is packaged in 25 kg multilayer paper bags with an inner polyethylene liner, ensuring dry, safe storage and transport. |
| Container Loading (20′ FCL) | Ditrimethylolpropane is loaded as a 20′ FCL on pallets, in sealed drums/bags, secured and protected from moisture. |
| Shipping | Ditrimethylolpropane is a white crystalline solid shipped in sealed, moisture-proof bags or drums. It should be kept dry and stored away from strong oxidizers. Safe handling requires dust control and protective equipment. Non-hazardous under normal transport conditions, but avoid environmental release. |
| Storage | Store Ditrimethylolpropane in a cool, dry, well-ventilated area away from heat, sparks, and open flames. Keep the container tightly sealed to prevent moisture absorption and contamination. Avoid contact with strong oxidizing agents or acids. Use appropriate personal protective equipment when handling, and follow local regulations for chemical storage. |
| Shelf Life | Ditrimethylolpropane has a typical shelf life of 24 months when stored sealed in a cool, dry area away from moisture and heat. |
Di-TMP is incorporated as a tetrafunctional starter into a solvent-borne polyester polyol backbone during a two-stage esterification at 220°C; the resulting tetraol-capped intermediate carries a theoretical hydroxyl value of 896 mg KOH/g and a hydroxyl equivalent weight of 62.6 g/eq. In high-solids two-component polyurethane clearcoats, this Di-TMP-derived polyol is formulated at 15–25 wt% of total hydroxyl-bearing resin solids and crosslinked with HDI-trimer at an OH:NCO ratio of 1.05:1 to compensate for atmospheric moisture scavenging. Compliance for automotive refinish and industrial maintenance topcoats is verified against EU Directive 2004/42/EC Stage II VOC limits of 420 g/L for clearcoats, ISO 12944-6:2018 C4-high scribe creep evaluation after 1440 h salt spray, and ASTM D3359-17 cross-cut adhesion. Production-scale mixing on a Cowles disperser at 1200–1500 rpm with a 35 mm blade in a 500 kg vessel is held below 40°C to avoid premature isocyanate reaction; application proceeds through HVLP gravity-feed spray equipment at 2.0–2.5 bar fluid pressure, followed by 10 min flash-off at 23°C and forced cure at 60°C for 40 min. The tetrafunctionality narrows the processing window: above 30 wt% Di-TMP-derived tetraol, crosslink density rises to a point where pot life measured as doubling in DIN cup 4 viscosity falls below 45 min and film fracture strain drops below 5%, making plastic body panels susceptible to impact cracking. Tertiary amine catalysts are avoided below 10°C because residual amine functionality accelerates premature polyol–isocyanate gelation. Terminal products include automotive refinish clearcoats, polyurethane topcoats for agricultural equipment cabs, and chemical-resistant maintenance enamels for structural steel.
In UV-curable 3D-printing photopolymer and flexographic ink vehicles, Di-TMP tetraacrylate (Di-TMPTA) is charged at 8–25 wt% of the oligomer/monomer phase to raise acrylate crosslink density without raising oligomer viscosity above 5000 mPa·s at 25°C. The compliance perimeter for printed matter and prototype parts is defined by EN 71-3:2019+A1:2021 migration limits for antimony, arsenic, barium, cadmium, chromium, lead, mercury, and selenium, while mechanical validation of cured specimens follows ASTM D638-14 Type IV tensile testing and ASTM D790-17 flexural modulus. Production processing on a UV-LED conveyor line operating at 395 nm requires 4.0–6.0 J/cm² of accumulated radiant exposure to overcome oxygen inhibition; nitrogen-blanketed chambers maintain O2 below 200 ppm when maximum line speed reaches 12 m/min. A narrower process window appears at Di-TMPTA loadings above 25 wt% because volumetric shrinkage exceeds 8% and elongation at break falls below 2%, producing delamination in thick stereolithography builds; below 8 wt% the formulation loses crosslink density and exhibits surface tack after single-pass cure. The terminal products include stereolithography resins for investment casting patterns, flexographic inks for film labels, and UV-curable conformal coatings for rigid printed circuit boards.
Di-TMP is introduced into solvent-borne alkyd resin cooks as a tetrafunctional branching polyol, replacing a portion of pentaerythritol at 6–12 wt% of total polyol charge to increase the average hydroxyl functionality of the prepolymer while limiting gelation risk. The resin synthesis is performed in xylene reflux with a kettle temperature of 230–240°C; the cook is terminated at an acid value between 8 mg KOH/g and 12 mg KOH/g and a viscosity of 2.5–4.0 Pa·s at 70 wt% solids in high-flash aromatic solvent. Compliance for coil coating and baking enamel applications is assessed by EN 13523-5:2021 T-bend cracking resistance after 30 s at 204°C peak metal temperature, ASTM D5402-19 MEK double rubs to 100 cycles, and ISO 15184:2020 pencil hardness. On a reverse roll coater running at 120–180 m/min, the formulated enamel is applied to 0.4–0.6 mm galvanized steel strip and cured in a gas-fired convection oven at 204–216°C for 30–40 s. Above 12 wt% Di-TMP, the cook shows a distinct gel point advance; batch viscosity rises nonlinearly during the last 10% of the cook, and the cured film loses flexibility, failing a 1T bend without microcracking. Terminal finished products include pre-painted steel for domestic appliance panels, metal furniture, and coil-coated building cladding.
For polyol ester base stocks formulated into aviation turbine and refrigeration compressor lubricants, Di-TMP is esterified with a C5–C9 short-chain fatty acid mixture under two-stage vacuum conditions to produce a tetraester with a kinematic viscosity of 20–32 mm²/s at 40°C. The ester base oil is blended at 85–100 wt% of the finished lubricant with an additive package of 1.0–3.5 wt% comprising anti-oxidant, anti-wear, and metal-deactivator chemistry. Specification compliance for turbine fluids follows SAE AS5780D oxidation-corrosion stability at 175°C for 96 h and load-carrying performance; refrigeration compressor oils are selected under ISO 6743-3:2003 and DIN 51503-1, where low pour point and dielectric properties are evaluated. The production process requires esterification at 220–240°C and 50 mbar absolute pressure with 0.05–0.1 wt% tin oxalate catalyst, followed by neutralization, thin-film vacuum stripping, and 1 μm absolute filtration to achieve moisture content below 100 ppm. A clear operational boundary is the low-temperature viscosity conflict: maximizing ester yield with high Di-TMP conversion raises viscosity, and at -40°C the pour point of a Di-TMP tetraester from linear C5 acids remains acceptable, but branched acid feedstocks may be required for lower-temperature refrigeration circuits. Terminal products include high-performance aviation turbine lubricants, polyol ester refrigeration oils for HFC systems, and high-temperature compressor oils for industrial screw compressors.
Di-TMP tetra-2-ethylhexanoate is added at 45–60 phr in flexible PVC cable insulation compounds to replace phthalate plasticizers in continuous operating service above 90°C. The regulatory compliance perimeter is REACH Annex XVII Entry 51, which restricts specific ortho-phthalates in articles, and IEC 60811-401:2012 thermal ageing for polymeric insulating and sheathing compounds; hardness is measured by ISO 868 Shore A. Compounding is carried out in a corotating twin-screw extruder with an L/D ratio of 30:1, barrel temperatures from 150°C to 175°C, and screw speed of 250–350 rpm; pre-mixed plasticizer is injected into zone 4 of 10 zones to control viscosity and prevent thermal degradation. After pelletization, the compound is supplied to cable extruders, which apply the insulation layer at a melt temperature of 170–185°C and a line speed of 100–250 m/min. Published comparative data for Di-TMP tetra-2-ethylhexanoate in high-temperature PVC insulation remains limited, but an operational boundary is observed at above 60 phr, where plasticizer exudation becomes detectable after 7 days at 100°C in compression-set specimens. Terminal products include automotive high-temperature wire insulation, appliance wiring harnesses, and non-phthalate cable sheathing for industrial machinery.
Substituting Di-TMP into MDI-prepolymer cast elastomer formulations shifts the hard-segment crosslink density upward at lower chain extender equivalent weight, producing a Shore A 85–95 elastomer with improved compression set resistance. The Di-TMP powder is pre-dried at 60°C under 20 mbar absolute vacuum for 4 h to avoid moisture-driven carbon dioxide bubbles; it is then charged at 2.0–4.5 wt% of prepolymer mass into a vacuum-capable planetary mixer operating at 2500 rpm, with the prepolymer NCO content maintained between 8% and 12%. Compliance testing for industrial elastomer liners and rolls is governed by ISO 4649:2017 abrasion resistance, ASTM D412-16 tensile strength and elongation, and ISO 815-1:2014 compression set after 70°C ageing. Molding is performed in aluminum or steel tooling heated to 70°C; the mixed compound is degassed to -0.095 MPa and poured without solvent, then cured for 16 h at 100°C. The critical processing conflict is pot life: above 4.5 wt% Di-TMP, gel time in a 100 g mass at 70°C drops below 3 min, while below 2.0 wt% the crosslink density is insufficient to prevent long-term creep in hydrocyclone liners. Terminal finished products include cast polyurethane hydrocyclone liners, high-durometer printing rollers, and abrasion-resistant pump volute liners.
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Ditrimethylolpropane (Di-TMP, CAS 23235-61-2; molecular formula C12H26O5; molecular weight 250.33 g/mol) is a branched aliphatic tetraol produced by condensation of two trimethylolpropane units through a central ether bridge. Commercial identification is by physical form — flake, pastille, or molten bulk — and by assay grade rather than by a discrete model number. The four hydroxyl groups are primary and are located on two neopentyl-like centers. Technical-grade material is typically supplied with assay between 95 % and 98 % by gas chromatography, hydroxyl value 870–910 mg KOH/g, acid number ≤ 0.10 mg KOH/g by ISO 2114:2000, water content ≤ 0.10 wt% by ASTM E203-24, and molten color ≤ 100 APHA by ASTM D1209-05(2019). Melting range is commonly 108–112 °C. The calculated hydroxyl value from the tetraol structure is 897 mg KOH/g, corresponding to a hydroxyl equivalent weight of 62.6 g/eq. The central ether bridge and higher molecular weight differentiate Di-TMP from trimethylolpropane, pentaerythritol, and dipentaerythritol in reactivity, melt handling, and crosslink density.
A direct comparison of the three polyols shows that Di-TMP occupies an intermediate position in melting point, but has the lowest hydroxyl value per unit mass among the three. The values in the table are calculated from the pure structures; technical-grade Di-TMP may contain residual trimethylolpropane and higher oligomers that reduce effective functionality.
| Property | Trimethylolpropane | Ditrimethylolpropane | Pentaerythritol |
|---|---|---|---|
| Molecular weight (g/mol) | 134.17 | 250.33 | 136.15 |
| Nominal hydroxyl functionality | 3 | 4 | 4 |
| Calculated hydroxyl value (mg KOH/g) | 1254 | 897 | 1648 |
| Hydroxyl equivalent weight (g/eq) | 44.7 | 62.6 | 34.0 |
| Melting range (°C) | 57–59 | 108–112 | 258–262 |
The replacement ratio for equal hydroxyl content is not unity. When substituting Di-TMP for TMP, the charge mass must be multiplied by 62.6/44.7 = 1.40 for the same hydroxyl equivalents. When substituting Di-TMP for pentaerythritol, the factor is 62.6/34.0 = 1.84. This mass increase is offset by the lower melting point and lower dusting tendency of Di-TMP compared with pentaerythritol. In addition, the central ether bridge of Di-TMP provides backbone flexibility between the two neopentyl centers, whereas pentaerythritol is a compact quaternary carbon core. This difference affects flexibility of cured films, solubility in polar monomers, and viscosity of derived esters.
Di-TMP should not be confused with dipentaerythritol (CAS 126-58-9), a hexafunctional polyol with molecular weight 254.28 g/mol and calculated hydroxyl value 1324 mg KOH/g. Dipentaerythritol has an ether bridge connecting two pentaerythritol units and carries six primary hydroxyl groups, whereas Di-TMP carries four primary hydroxyl groups. The distinction is critical for hydroxyl equivalent calculation and for predicting gelation in polyester syntheses.
In radiation-curable systems, Di-TMP is converted to ditrimethylolpropane tetraacrylate (Di-TMPTA), a tetrafunctional acrylate used in UV/EB clearcoats, overprint varnishes, inks, and adhesives. The tetraacrylate has four terminal acrylic double bonds per molecule. In comparison, trimethylolpropane triacrylate has three; therefore Di-TMPTA increases crosslink density in cured networks when formulated at equivalent double-bond concentration. The higher molecular core typically gives Di-TMPTA a higher viscosity than TMPTA. Formulation with reactive diluents such as 1,6-hexanediol diacrylate or tripropylene glycol diacrylate is used to reach target application viscosity. Cured coatings formulated with Di-TMPTA are evaluated by pendulum damping ASTM D4366-16, solvent rub resistance ASTM D5402-19, and gloss retention ASTM D523-14(2018). Photoinitiator solubility can become limiting in highly formulated systems because the polar tetraacrylate phase may reject low-polarity photoinitiator packages; published data for specific photoinitiator loadings is limited, and supplier compatibility screening is recommended. In overprint varnishes, Di-TMPTA contributes high gloss and rapid surface cure but may require an inerted or higher-intensity UV source if oxygen inhibition reduces surface conversion.
Replacement of pentaerythritol with Di-TMP in solvent-free polyester polyols alters the theoretical gel point and the reactor temperature profile. Using the Carothers approximation, the critical conversion for a stoichiometric Di-TMP–adipic acid polyester is pc = 2/favg = 2/3 = 0.67. A TMP–adipic acid polyester has favg = 2.5 and pc = 0.80. Because a tetrafunctional monomer generally gels earlier than a trifunctional monomer at the same stoichiometric ratio, the Di-TMP formulation requires a wider processing margin or a higher excess of dicarboxylic acid. In practice, commercial polyester polyol kettles typically feed Di-TMP as a molten liquid at 115–125 °C to avoid unreacted flakes; the reaction is heated stepwise from 140–170 °C to 210–230 °C while removing water overhead. Acid value is tracked by ISO 2114:2000; terminal acid value is often specified at 3–10 mg KOH/g depending on end use. Gardner bubble viscosity at 25 °C is monitored as an indirect gelation indicator. Because the Carothers equation assumes equal reactivity and ideal stoichiometry, actual gelation can occur before the calculated conversion if oligomer distribution broadens. Charge sheets therefore include monofunctional acids or excess diacid to cap the tetrafunctional core and prevent an uncontrolled crosslinked batch.
High-solids alkyd resins use Di-TMP as a polyol co-monomer to increase branch density while avoiding the high melting point and sublimation of pentaerythritol. The lower melting range of 108–112 °C allows direct molten charging through jacketed lines at 120–130 °C, reducing the need for powder handling. The ether bridge reduces the hydroxyl value relative to pentaerythritol; therefore an equal hydroxyl equivalent charge requires 1.84 times the mass. In short-oil alkyds, replacing part of the pentaerythritol with Di-TMP can improve flexibility and compatibility with low-polarity solvents, but the higher molecular weight between branch points can also reduce pencil hardness if the acrylic or melamine crosslinker level is not adjusted. Published comparative data for specific long-oil alkyd formulations is limited; resin manufacturers commonly optimize oil length, final acid value, and polyol ratio by statistical experimental design rather than by direct substitution.
Direct esterification of Di-TMP with phthalic anhydride, isophthalic acid, or adipic acid proceeds through a solid–liquid stage that can create localized gel domains if flake addition is poorly controlled. Production-scale reactors therefore use heated screw or auger feed and maintain the initial melt temperature above 110 °C. Agitation in anchor or helical-ribbon mixers is kept at 10–30 rpm during the final 220–230 °C hold. Nitrogen sparging is applied at low flow to strip water and reduce oxidative color formation; sparge rate is set by reactor volume and adjusted so that the acid value continues to fall without excessive foaming. Batch-to-batch variation in Di-TMP purity, especially residual TMP and higher oligomers, shifts the effective hydroxyl value and therefore the stoichiometric acid charge. Receiving inspection uses hydroxyl number by ASTM D4274-21 or DIN 53240-1 and water content by ASTM E203-24 before charging. If acid value stalls above 15 mg KOH/g, a vacuum strip at approximately –0.08 MPa gauge can reduce free acidity, but the vacuum must be broken with nitrogen and the product must be cooled below 150 °C before discharge to limit color development. The final polyester is often filtered through a 10–25 µm bag filter to remove gel particles; filtration pressure rise is used as a batch record for crosslinked fraction.
In polyurethane and moisture-cured coating applications, Di-TMP functions as a crosslinker or polyol component after drying. The primary hydroxyl groups provide fast reactivity with aliphatic and aromatic isocyanates, and the tetrafunctionality raises thermoset crosslink density. Water content must be reduced below 0.05 wt% for urethane acrylate or prepolymer reactions because residual water reacts with isocyanate to form urea and carbon dioxide, creating bubbles and reducing NCO/OH stoichiometry. Di-TMP is not a direct replacement for polyether or polyester diols; it is added in small stoichiometric amounts, typically as a molten or dissolved stream in polar monomer. Avoid combination with amine-based catalysts if the system contains free acidity, because the acid can neutralize the catalyst and delay cure. Published data for specific pot-life and exotherm profiles in polyurethane casting is limited; the NCO/OH index and drying must be validated for each formulation.
Esterification of Di-TMP with C5–C9 linear or branched fatty acids yields polyol ester base stocks for compressor, refrigeration, and aviation turbine lubricants. The tetrafunctional core produces esters with higher kinematic viscosity at 40 °C and 100 °C than corresponding TMP esters of the same acid composition, measured by ASTM D445-24. The higher molecular weight also reduces Noack volatility in ASTM D5800 and can improve oxidative stability measured by rotating pressure vessel oxidation test ASTM D2272, but low-temperature performance by ASTM D97 may become more restrictive. Di-TMP esters of branched acids show lower pour point than those of linear acids, and the central ether bridge is relatively stable under hydrolytic conditions typical of refrigeration systems. Formulators should not assume that a TMP ester and Di-TMP ester of the same acid package are interchangeable; viscosity grade, seal compatibility, and miscibility with hydrofluorocarbon or hydrocarbon refrigerants must be re-qualified.
Handling boundaries are dominated by hygroscopicity, dust, and thermal history. At relative humidity above 60 %, Di-TMP flakes absorb surface moisture and cake in hoppers; vibratory bin activators or heated hoppers are used on extrusion and resin feed lines. Pre-drying at 70–80 °C under vacuum for 4–8 h is typical for moisture-sensitive syntheses. The fine fraction of flakes can form a combustible dust cloud; transfer equipment should be bonded and grounded, and local exhaust ventilation should be installed at bag dump stations. Molten Di-TMP should be held no longer than necessary; prolonged exposure to temperatures above 140 °C can increase APHA color and acidity, although published thermal-hold data for specific equipment configurations is limited. The product is not classified as a RoHS-restricted heavy metal source in typical technical grade, and regulatory documentation generally references CAS 23235-61-2, REACH registration, and TSCA inventory status. For food-contact coatings, compliance must be confirmed under 21 CFR 175.300 for resinous and polymeric coatings or the relevant national positive list. The primary incompatibility is with strong oxidizing agents; in addition, residual acidic impurities can promote ether cleavage at prolonged high temperature.
