Alkyd Resins

An alkyd resin is a polyester modified with vegetable oil or fatty acids. It is produced by reacting three components:

• A polyol such as glycerol or pentaerythritol
• A polybasic acid such as phthalic anhydride or isophthalic acid
• A drying oil or fatty acid such as soya, linseed, tall oil fatty acid (TOFA), dehydrated castor, or tung oil

The fatty acid portion gives the resin its ability to air dry. When an alkyd coating is applied, the solvent evaporates and the unsaturated fatty acid chains crosslink with oxygen from the air, accelerated by metal driers, forming a tough, adherent film. This oxidative cure is why alkyd enamels, primers, and stains dry hard without heat and adhere well to metal, wood, and previously painted surfaces.

Alkyds remain one of the most widely used binders in the coatings industry because they combine good gloss, flexibility, adhesion, and durability at a low raw material cost, and because they can be tailored across a very wide performance range by changing the oil type, oil length, and modifying monomers.

The most important variable in an alkyd is oil length, the percentage of oil or fatty acid in the finished resin. Oil length determines solubility, dry time, hardness, and flexibility.

Type	Oil length	Solvent	Dry speed	Typical uses
Long oil alkyd	Above 60%	Aliphatic mineral spirits	Slower	Architectural enamels, trim paint, wood stains, penetrating finishes
Medium oil alkyd	40 to 60%	Mineral spirits with some aromatic	Faster	Traffic paint, industrial enamels, maintenance primers
Short oil alkyd	Below 40%	Aromatic solvents	Bake or fast air dry	Baking enamels, industrial finishes
Chain stopped alkyd	Medium to short	Aromatic / ester blends	Very fast	Fast air dry and low bake enamels and primers

Sunpol manufactures the following families.

Long oil alkyds

Long oil alkyds are the workhorse of architectural coatings. They dissolve in low-odor aliphatic mineral spirits, brush easily, level well, and give flexible films with good color and gloss retention outdoors. Sunpol long oil alkyds are built on soya and other vegetable oils and are available at conventional solids in Rule 66 mineral spirits as well as 100% solids, VOC-free grades for penetrating stains and deck finishes.

Representative grades: Sunpol 4060 (70% in Rule 66 mineral spirits, soya, meets TT-R-266D Type 1 Class A), 4075, 7210 (low VOC), and the 100% solids grades 4342, 4575, 7176, and 4501 (low viscosity, low color).

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Medium oil alkyds

Medium oil alkyds dry faster and harder than long oil grades while retaining good flexibility and weathering. They are the standard binder for solvent-borne traffic paint and road marking, where the coating must dry quickly enough to reopen a lane and still survive abrasion and weather. Sunpol offers medium oil alkyds in conventional and exempt-solvent versions.

Representative grades: Sunpol 4260 (soya), 4260-DMC-75 (exempt solvent), and 4261-50.

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Chain stopped alkyds

A chain stopped alkyd uses a monofunctional acid, typically benzoic acid, to limit molecular weight during synthesis. The result is a resin with lower viscosity at a given solids, faster air dry, higher gloss, and greater hardness than a conventional alkyd of the same oil length. Chain stopped alkyds are used in fast air dry and low bake industrial enamels and primers, maintenance coatings, and equipment finishes.

Representative grades: Sunpol 4084 (meets TT-E-489J), 4086, 4422N, and 4423. HAPs-free versions are available.

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Water reducible alkyds

Water reducible alkyds are formulated with a higher acid value so that, once neutralized with an amine and diluted with a glycol ether co-solvent, they can be thinned with water. They allow formulators to keep the adhesion, gloss, and corrosion resistance of an alkyd while meeting VOC regulations for industrial primers and enamels.

Representative grades: Sunpol 4033B and 4033C.

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Modified alkyds: vinyl toluene, acrylic, and phenolic

Modifying an alkyd with vinyl toluene or acrylic monomer produces a resin with very fast set-to-touch, high gloss, and compatibility with aerosol propellants. These grades are widely used in aerosol enamels, marking paints, and stain blocking primers. Phenolic modification improves water and humidity resistance, which suits non-lifting primers and industrial coatings.

Representative grades: Sunpol 6081 and 6975 (aerosols, marking paints, stain blocking primers), 6060 (marking paints and aerosols), 6065 (aerosols, fast dry enamels, lacquer dry), and 7026 (HAP-free phenolic modified).

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Oil modified urethanes

An oil modified urethane (OMU), sometimes called a urethane alkyd, replaces part of the polybasic acid with a diisocyanate. The urethane linkages give the film substantially higher hardness, abrasion resistance, and chemical resistance, which is why OMUs are the standard binder for clear wood floor finishes and furniture lacquers.

Representative grade: Sunpol 5022 (low HAPs furniture lacquers).

See oil modified urethane products →

Start with the application, then narrow by regulatory and process requirements.

1. Architectural enamel or trim paint: long oil alkyd in mineral spirits. Look at 4060, 4075, or 7210 where VOC limits are tight.
2. Penetrating wood stain or deck finish: 100% solids long oil alkyd. Look at 4342, 4575, 7176, or 4501 for low color.
3. Traffic paint or road marking: medium oil alkyd. Look at 4260, or 4260-DMC-75 where an exempt solvent is required.
4. Industrial primer or fast dry enamel: chain stopped alkyd. Look at 4084, 4423, or a water reducible grade such as 4033B or 4033C if the line is going waterborne.
5. Aerosol or marking paint: vinyl toluene or acrylic modified alkyd. Look at 6081, 6975, 6060, or 6065.
6. Wood floor or furniture finish: oil modified urethane. Look at 5022.

If none of these fit, our R&D lab can modify an existing grade or develop a resin to your specification. See custom formulation and toll manufacturing.

For a detailed breakdown by end use, see alkyd resin applications.

Sunpol is an independent, privately owned resin manufacturer. We produce large volume orders reliably and at a competitive cost, and we support customers with:

• An on-site laboratory with a research and development team
• A 55-gallon pilot reactor for scale-up trials before full production
• Custom resin formulation to your application specifications
• Toll manufacturing for companies that need capacity while retaining their own intellectual property
• Rail shipment capacity and an established distribution network
• Low VOC, HAPs-free, and exempt-solvent options across the line

Our plant is located in Fairfield, California, serving coatings manufacturers throughout the western United States and beyond.