Rosin Ester Glycerol

What is Glycerol Ester of Rosin?

Glycerol-modified rosin commonly known as Glycerol Ester of Rosin or Glycerol Rosin Ester is a resin produced by esterifying rosin with glycerol.

During this reaction the acidic groups in rosin react with the hydroxyl groups of glycerol to form esters that are more stable than unmodified rosin. Esterification reduces the acid value and improves film-forming properties, adhesion, and compatibility with various resin systems.

Properties of Glycerol Ester of Rosin

Property	Characteristics
Adhesion	Good adhesion, suitable for various adhesive, coating and printing ink systems
Tack	Provides good tack and is commonly used as a tackifier
Softening point	Higher than that of unmodified rosin, but generally lower than that of the corresponding pentaerythritol ester
Acid value	Significantly lower than that of unesterified rosin
Film-forming ability	Good, forming relatively hard and glossy films
Gloss	Good gloss, making it suitable for paints, varnishes, and printing inks
Compatibility	Compatible with various rubbers, polymers, and base resins depending on the product grade
Solubility	Soluble in many organic solvents; insoluble in water
Thermal stability	Better than unmodified rosin, but generally lower than that of pentaerythritol esters
Color	Ranges from light yellow to amber, depending on the raw materials and manufacturing process

An important characteristic of Glycerol Rosin Ester is that it is generally softer and has a lower softening point than Pentaerythritol Rosin Ester. This makes it particularly suitable for formulations requiring good tack and easier processing.

Applications of Glycerol Ester of Rosin

Glycerol-modified rosin is widely used in various industries

• Hot Melt Adhesives Used as a tackifying resin in EVA, thermoplastic rubber and other polymer-based adhesive systems.
• Pressure-Sensitive Adhesives Used in adhesive tapes, labels, decals and protective films.
• Rubber Adhesives Improves tack and adhesion.
• Paints and Varnishes Improves gloss, adhesion and film-forming properties.
• Printing Inks Used as a binder resin or as a modifier for adhesion and gloss.
• Paper Coatings Helps create a glossy surface and improves bonding performance.
• Rubber Compounds Used as a tackifier or modifier to adjust compound properties.
• Waxes and Coatings Helps adjust hardness, adhesion and softening point.
• Certain food and packaging applications Applicable only to resin grades that comply with the relevant food-safety standards. Not all Glycerol Rosin Esters should be assumed to be suitable for food applications.

Technical Specifications

PRODUCT NAME	PRODUCT CODE	COLOR (GARDNER, 50% TOLUENE)	ACID VALUE (mg KOH/g)	SOFTENING POINT (°C, R&B)	COLOR STABILITY AT 180°C/8H (ΔE GARDNER)
GLYCEROL ESTER OF ROSIN	RG95A	3–4	≤15	95 ± 3	<2
GLYCEROL ESTER OF ROSIN	RG95B	4–5	≤15	95 ± 3	<2
GLYCEROL ESTER OF ROSIN	RG100A	3–4	≤15	100 ± 3	<2
GLYCEROL ESTER OF ROSIN	RG100B	4–5	≤15	100 ± 3	<2

Is Glycerol Ester of Rosin Bad for You?

E445 or glycerol ester of wood rosin is produced by esterifying glycerol with resin acids derived from wood rosin. It is mainly used as a stabilizer or emulsifier in certain beverages and as a softening agent in chewing gum. The U.S. FDA permits the use of glycerol ester of wood rosin in food under specified conditions.

EFSA has concluded that most glycerol ester of wood rosin is not absorbed by the body. In animal studies, most of the substance was excreted in the feces in an almost unchanged form with estimated absorption of 5% or less.

Glycerol Ester of Wood Rosin Side Effects

At levels normally encountered in food, there is currently no clear evidence that E445 causes liver toxicity, kidney toxicity, cancer, or organ damage.

In a 13-week study in rats, 2,500 mg/kg body weight per day was the highest dose tested and EFSA did not identify clear treatment-related adverse effects at that level.

The main concern is possible allergic or irritant reactions. Natural rosin, particularly oxidized resin acids, can cause contact dermatitis in sensitive individuals. Esterification with glycerol reduces the sensitizing potential of rosin but the risk cannot be considered completely absent.

EFSA has not found convincing evidence of allergic reactions resulting from the consumption of foods containing E445.

What Does Glycerol Ester of Rosin Do to Your Body?

After ingestion most E445 passes through the gastrointestinal tract without being absorbed.

A small fraction, mainly involving monoesters or residual free resin acids may be hydrolyzed and absorbed. The absorbed compounds are then mainly eliminated through bile and feces.

JECFA, the Joint FAO/WHO Expert Committee on Food Additives, previously established an Acceptable Daily Intake (ADI) of 0–25 mg/kg body weight per day for food-grade glycerol ester of wood rosin.

EFSA has taken a more conservative position and maintained a temporary ADI of 12.5 mg/kg body weight per day, mainly because long-term data on reproductive and developmental toxicity remain limited rather than because toxicity has been demonstrated at normal dietary exposure levels.

For example that for a person weighing 60 kg, an ADI of 12.5 mg/kg corresponds to approximately 750 mg per day.

The ADI represents the amount that can be consumed daily over a lifetime without an appreciable health risk. It is not a toxicity threshold at which slightly exceeding the value would immediately cause poisoning.

A very important distinction is that these safety conclusions apply specifically to food-grade glycerol ester of wood rosin meeting the relevant purity specifications, particularly materials studied from Pinus palustris and Pinus elliottii.

These conclusions should not automatically be applied to industrial rosin esters, technical-grade rosin, glycerol esters derived from gum rosin or tall-oil rosin or products of unknown purity.

EFSA has also noted that safety data for glycerol ester of wood rosin cannot automatically be extrapolated to all sources or types of rosin.