A coatings formulator selects a tall oil feedstock on three numbers: iodine value for unsaturation, acid value for free acid, and rosin acid content for colour and functionality. Specify TOFA 185 (rosin acid max 2%) for colour-sensitive work, TOFA 180 where colour tolerance is wide, and DTO when rosin acid functionality is wanted.
The three numbers that decide a coating
When a coatings formulator buys a tall oil feedstock, the decision is driven by the supply specification rather than the production recipe. This article is not about how an alkyd resin is synthesised; it is about which of three raw materials on the same shelf should be specified. In practice three specification lines make the call.
- Iodine value (ASTM D5768): degree of unsaturation, hence the potential for oxidative drying and crosslinking with air.
- Acid value (ASTM D1980): free fatty acid content, hence how precisely esterification stoichiometry can be set.
- Rosin acid content (ASTM D1240): the measure of both colour behaviour and rosin acid functionality.
A fourth control line accompanies them: unsaponifiables (ASTM D1065). This is the fraction that does not react and can remain in the film as haze or residue.
Unsaturation and drying behaviour
In an air-drying coating, film hardness develops as the double bonds along the chain react with oxygen and form crosslinks. The lower the unsaturation, the slower and more incomplete the cure. The raw-material equivalent of drying behaviour is therefore the iodine value.
TOFA 185 and TOFA 180 are both defined at min 150 iodine value (ASTM D5768). That means there is no specification-level difference in drying potential between the two grades: the choice is decided by colour and impurities, not by cure. For a formulator that is a reassuring result, because moving to the more economical grade costs no specification-level compromise in drying behaviour.
Colour retention: why coatings makers ask for TOFA 185
Colour in a coating is two separate questions: initial colour and colour retention over time. Both are influenced by the rosin acid and unsaponifiables levels in the raw material. Rosin acids are the abietic-type acids left after crude tall oil distillation, and they affect colour development and viscosity behaviour.
TOFA 185 runs rosin acid max 2% (ASTM D1240) and unsaponifiables max 4% (ASTM D1065) and is a light yellow to amber liquid. TOFA 180 runs max 3% and max 6% respectively, as an amber to dark amber liquid. Whites, pastels, light topcoats and high-gloss varnishes expose that difference directly; dark industrial primers and maintenance paints hide it.
BİO BAZLI ÜRÜNLERTall Oil Fatty Acids 185 (TOFA)TOFA 185 is listed in the product data with an alkyd resin and oil-modified polymer production application; it is the grade to specify for colour-sensitive coating binders. A free sample is available.Where is TOFA 180 sufficient in coatings?
The TOFA 180 application list in the product data includes industrial resin and binder production. In systems with wide colour tolerance, high pigment loading and dark shades, the wider specification window is not a disadvantage. The decision logic is simple: if the colour of the finished film is not influenced by the colour of the raw material, there is no technical case for paying for a tighter specification.
On the other hand TOFA 180 allows unsaponifiables up to max 6%. Where the non-reacting fraction is critical for film clarity or residue, TOFA 185 can be preferred even when colour is not critical. The second decision variable is therefore not colour but cleanliness.
When rosin acid functionality is wanted: distilled tall oil (DTO)
In some coating work, rosin acid is not a defect but a wanted function. Rosin acids are hard, high glass transition components and give the binder a different hardness and adhesion character. When that is wanted, the correct raw material is not a TOFA grade but distilled tall oil (DTO).
DTO Mid-High Grade in the KORKİMYA portfolio is defined at acid value min 170 (ASTM D1980), rosin acid content max 30% (ASTM D1240) and unsaponifiables max 7% (ASTM D1065), supplied as a clear amber liquid. Its product data lists alkyd resin and paint binder production together with coating and varnish applications directly. That large gap in rosin acid level is the real axis of the choice between TOFA and DTO.
The call on primers and protective coatings
In primers and protective coatings applied to metal, the formulator's priority is not colour but adhesion to the substrate, film integrity and hardness development. Two directions emerge from that picture. If hardness and adhesion character derived from rosin acid are wanted, DTO is evaluated. If binder flexibility, cure through the unsaturated chain and a low non-reacting residue are prioritised, the TOFA grades are evaluated.
This is a selection framework, not a formulation recipe. The right answer must always be validated with a sample in your own binder system; KORKİMYA provides a free sample for laboratory validation and a per-lot certificate of analysis (CoA) for all three products.
BİO BAZLI ÜRÜNLERDistilled Tall Oil (DTO) Mid-High GradeA DTO Mid-High Grade sample and quote for coating and varnish binders that need rosin acid functionality: complete the inquiry form on the product page.Supply and verification
TOFA 185 ships as bulk liquid in 20-22 MT net ISO tank containers and TOFA 180 in 20-24 MT net ISO tank containers. Both grades travel in carbon steel or stainless steel tanks and are stored in closed containers between 20-40°C, away from direct sunlight. Shelf life is 12 months and can be extended to 24 months with quality monitoring.
- CAS number: 61790-12-3 (both TOFA grades).
- KKDIK registered; Turkish Safety Data Sheet (SDS/GBF) provided.
- Certificate of analysis (CoA) for every lot.
- Incoming goods control: acid value, iodine value, rosin acid and unsaponifiables.
Is there a drying difference between TOFA 185 and TOFA 180 in coatings?
Not at specification level: both grades are defined at min 150 iodine value (ASTM D5768). The differences between the grades are acid value (min 185 versus min 180), rosin acid (max 2% versus max 3%), unsaponifiables (max 4% versus max 6%) and colour.
When should I choose DTO instead of TOFA?
When you want rosin acid functionality in the binder. DTO Mid-High Grade allows rosin acid content up to max 30% (ASTM D1240), against max 2% on TOFA 185 and max 3% on TOFA 180. Its product data lists coating and varnish applications directly.
Which grade for white and pastel topcoats?
TOFA 185. With rosin acid max 2%, unsaponifiables max 4% and a light yellow to amber appearance, it is the grade to specify for colour-sensitive systems.
Does this article explain how alkyd resin is produced?
No. The chemistry of alkyd synthesis, including esterification with a polyol and an anhydride, is the subject of a separate article on this site. This article focuses on the coatings formulator's raw material selection decision.
How do I get a sample and a quote?
State your coating type (topcoat, primer, varnish), your binder system, estimated annual volume and destination in the inquiry form on the product page. KORKİMYA provides a free sample and a per-lot CoA.