Technical Specifications
| Parameter | Specification | Test Method |
|---|---|---|
| Chemical name | Bis(dioctyl pyrophosphato) oxoethylene titanate | — |
| CAS / class | Pyrophosphate ester titanate (monoalkoxy, coordinate) | — |
| Appearance | Amber to yellow clear liquid | Visual |
| Active titanate content | ≥94% | Non-volatile residue |
| Viscosity at 25°C | 150–300 cP | Brookfield LVT |
| Flash point (closed cup) | >65°C | ASTM D93 |
| Density at 25°C | ~1.02–1.05 g/cm³ | Pycnometer |
| Thermal stability | >200°C short term; >180°C continuous | TGA in N₂ |
| Solubility | Miscible with aromatics, ketones, esters | Blend test |
| Recommended loading | 0.5–2.0% on pigment/filler weight | Formulation |
| Shelf life | 12 months / sealed, 5–30°C | Aged sample test |
Industrial Application Scenarios
Coordination Chemistry & Hydrolysis Stability
KR-138S is a monoalkoxy coordinate titanate in which two bis(dioctyl pyrophosphato) ligands chelate the titanium center through the bridging pyrophosphate oxygen, while the oxoethylene group provides an additional intramolecular coordination site. This six-coordinate geometry resists hydrolysis under ambient humidity — a critical advantage over simple alkoxide titanates (e.g., KR-9S) that gel on contact with trace moisture in pigment slurries. The dioctyl pyrophosphate tails orient into the hydrocarbon binder matrix, lowering interfacial energy by 15–25 mN/m, while the phosphate head anchors covalently to surface hydroxyls on TiO2, CaCO3, and carbon black.
Performance in Solvent-Borne Inks & Industrial Coatings
KR-138S reduces grind viscosity by 20–40% in solvent-borne flexographic and gravure inks at 1.0–1.5% on pigment weight, enabling higher solids without additional thinning. On TiO2-white architectural coatings, 60° gloss improves by 4–8 GU at equivalent pigment loading. Adhesion to aluminum and steel substrates improves by one full cross-cut grade (ASTM D3359) at 0.8–1.2% on total formulation weight; this improvement survives 500-hour salt-spray exposure, confirming covalent ester bond formation with surface metal-oxide hydroxyls.Gravure inks — 1.0–1.5% on pigment; reduces mill base Brookfield viscosity 20–35%, sharpens dot gain, extends rub resistance.Industrial primers — 0.8–1.2% on formulation weight; one-grade adhesion gain on steel per ASTM D3359, rust-creep resistance in salt spray.High-solids topcoats — 0.5–1.0% on formulation; maintains 85+ GU gloss at ≥70% solids-by-volume without viscosity penalty.
Physical Form, Dosing & Solvent Compatibility
KR-138S is supplied as an amber-to-yellow liquid with viscosity 150–300 cP at 25°C and flash point >65°C (closed cup), eliminating the dissolution step required for solid coupling agents. It is fully miscible with aromatics (toluene, xylene), ketones (MEK, MIBK), and esters (ethyl acetate, butyl acetate). Compatibility with aliphatic solvents (mineral spirits) is limited above 5%; dilute to ≤3% in a polar carrier before addition to aliphatic systems. Water content above 1% triggers hydrolysis and TiO2 oligomer precipitation — add KR-138S to dry resin before pigment, not to a pre-dispersed slurry.Addition sequence — Pre-dissolve in 5–10% of the ketone/ester solvent fraction, then add to resin before pigment; never add to pre-ground slurry.Storage — 12-month shelf life in sealed containers at 5–30°C; nitrogen blanket recommended for opened drums to prevent moisture ingress.PPE — Nitrile gloves and safety glasses required; adequate ventilation above 50°C; avoid prolonged skin contact.
How KR-138S Compares to KR-138D, KR-26S & KR-9S
KR-138S shares the bis(dioctyl pyrophosphato) oxoethylene core with KR-138D but differs in the monoalkoxy ligand, making KR-138S better suited to solvent systems while KR-138D is optimized for mineral-oil and high-shear mixing environments. KR-26S (isopropyl triisostearoyl titanate) performs better in thermoplastic composites requiring processing above 200°C. KR-9S (isopropyl tri(dioctylpyrophosphato) titanate) offers similar pyrophosphate surface chemistry but lacks the chelate ring of KR-138S, giving lower hydrolytic stability in humid pigment slurries. Buyers who encounter moisture-related gelling with KR-9S should upgrade to KR-138S.
Frequently Asked Questions
Coordination Chemistry & Hydrolysis Stability
KR-138S is a monoalkoxy coordinate titanate in which two bis(dioctyl pyrophosphato) ligands chelate the titanium center through the bridging pyrophosphate oxygen, while the oxoethylene group provides an additional intramolecular coordination site. This six-coordinate geometry resists hydrolysis under ambient humidity — a critical advantage over simple alkoxide titanates (e.g., KR-9S) that gel on contact with trace moisture in pigment slurries. The dioctyl pyrophosphate tails orient into the hydrocarbon binder matrix, lowering interfacial energy by 15–25 mN/m, while the phosphate head anchors covalently to surface hydroxyls on TiO2, CaCO3, and carbon black.
Performance in Solvent-Borne Inks & Industrial Coatings
KR-138S reduces grind viscosity by 20–40% in solvent-borne flexographic and gravure inks at 1.0–1.5% on pigment weight, enabling higher solids without additional thinning. On TiO2-white architectural coatings, 60° gloss improves by 4–8 GU at equivalent pigment loading. Adhesion to aluminum and steel substrates improves by one full cross-cut grade (ASTM D3359) at 0.8–1.2% on total formulation weight; this improvement survives 500-hour salt-spray exposure, confirming covalent ester bond formation with surface metal-oxide hydroxyls.Gravure inks — 1.0–1.5% on pigment; reduces mill base Brookfield viscosity 20–35%, sharpens dot gain, extends rub resistance.Industrial primers — 0.8–1.2% on formulation weight; one-grade adhesion gain on steel per ASTM D3359, rust-creep resistance in salt spray.High-solids topcoats — 0.5–1.0% on formulation; maintains 85+ GU gloss at ≥70% solids-by-volume without viscosity penalty.
Physical Form, Dosing & Solvent Compatibility
KR-138S is supplied as an amber-to-yellow liquid with viscosity 150–300 cP at 25°C and flash point >65°C (closed cup), eliminating the dissolution step required for solid coupling agents. It is fully miscible with aromatics (toluene, xylene), ketones (MEK, MIBK), and esters (ethyl acetate, butyl acetate). Compatibility with aliphatic solvents (mineral spirits) is limited above 5%; dilute to ≤3% in a polar carrier before addition to aliphatic systems. Water content above 1% triggers hydrolysis and TiO2 oligomer precipitation — add KR-138S to dry resin before pigment, not to a pre-dispersed slurry.Addition sequence — Pre-dissolve in 5–10% of the ketone/ester solvent fraction, then add to resin before pigment; never add to pre-ground slurry.Storage — 12-month shelf life in sealed containers at 5–30°C; nitrogen blanket recommended for opened drums to prevent moisture ingress.PPE — Nitrile gloves and safety glasses required; adequate ventilation above 50°C; avoid prolonged skin contact.
How KR-138S Compares to KR-138D, KR-26S & KR-9S
KR-138S shares the bis(dioctyl pyrophosphato) oxoethylene core with KR-138D but differs in the monoalkoxy ligand, making KR-138S better suited to solvent systems while KR-138D is optimized for mineral-oil and high-shear mixing environments. KR-26S (isopropyl triisostearoyl titanate) performs better in thermoplastic composites requiring processing above 200°C. KR-9S (isopropyl tri(dioctylpyrophosphato) titanate) offers similar pyrophosphate surface chemistry but lacks the chelate ring of KR-138S, giving lower hydrolytic stability in humid pigment slurries. Buyers who encounter moisture-related gelling with KR-9S should upgrade to KR-138S.
+Q: What makes KR-138S a ‘coordinate’ titanate and why does it matter?
A: KR-138S forms an intramolecular chelate ring between titanium and the pyrophosphate oxygen, creating a six-coordinate complex that resists hydrolysis when added to humid pigment slurries. Standard monoalkoxy titanates like KR-9S lack this chelate structure and partially hydrolyze on contact with trace moisture, losing surface-activity before the pigment is fully coated. The coordinate geometry of KR-138S delivers consistent performance even in production environments where pigment moisture content varies.
+Q: At what loading rate should KR-138S be used in gravure ink systems?
A: Use 1.0–1.5% KR-138S on pigment weight in gravure inks. This loading reduces Brookfield mill-base viscosity by 20–35% at 100 rpm, without causing reagglomeration or color shift. Higher additions above 2.0% can over-lubricate the pigment surface, reducing ink tack and impairing dot transfer at high press speeds.
+Q: Can KR-138S be used in waterborne or UV-curable systems?
A: KR-138S is not suitable for waterborne systems — titanate esters hydrolyze in aqueous media above 1% water content, precipitating inactive TiO2 oligomers. For UV-curable 100% acrylate systems, KR-138S can be used at 0.3–0.8% as a pigment dispersant, but its decomposition above 220°C limits use in UV-powder coatings requiring high-temperature cure cycles.
+Q: How does KR-138S differ from KR-138D?
A: KR-138D shares the same bis(dioctyl pyrophosphato) oxoethylene core but carries a different monoalkoxy ligand optimized for mineral-oil and high-shear mixing environments such as PVC plastisols and rubber compounds. KR-138S is specifically formulated for solvent-borne systems. If your process is solvent-based, KR-138S is the correct grade; for melt or oil-dispersion processing, evaluate KR-138D.
+Q: What are the upstream supply risks that affect KR-138S availability and price?
A: The primary risk is TiCl4 availability from Chinese chloride-process producers, which periodically tightens when TiO2 pigment output peaks and monopolizes chlorinator capacity. Secondary risk comes from 2-octanol price volatility in the C8 oxo-alcohol chain. Standard lead times from Chinese titanate producers are 4–6 weeks; buyers should maintain 6–8 weeks of safety stock given these upstream constraints.
+Q: What is the correct addition sequence for KR-138S in a high-solids industrial primer?
A: Pre-dissolve KR-138S in 5–10% of the ketone or ester solvent fraction, then blend this solution into the resin before any pigment addition. This sequence ensures the titanate coats resin surfaces and has residence time to react with mineral hydroxyl groups before competing with solvent for the pigment surface. Adding KR-138S to a finished grind delivers only 30–50% of the expected adhesion benefit.
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