What Is Butyl Benzoic Acid/Phthalic Anhydride/Trimethylolethane Copolymer?
Butyl Benzoic Acid/Phthalic Anhydride/Trimethylolethane Copolymer is a synthetic film-forming polymer made by reacting three building blocks: butyl benzoic acid, phthalic anhydride and trimethylolethane. These raw materials come from refined petrochemical sources and are combined in a controlled, high-temperature condensation process that links them into long, sturdy chains. The finished polymer is a solid resin that is ground or melted before being blended into cosmetic bases.
Polymers that leave a flexible film have been used in cosmetics since the mid-1900s to improve shine and durability in nail lacquers and hair fixatives. This particular copolymer gained popularity in the last few decades because it offers strong adhesion without feeling tacky or brittle. Manufacturers appreciate its stability, meaning it does not break down easily when exposed to light, heat or common cosmetic solvents.
You will most often spot the ingredient in products that need a smooth, lasting coat on the skin, hair or nails. Typical formats include nail polish, top coats, mascara, liquid eyeliner, long-wear lipstick, transfer-resistant foundation, hair spray and certain peel-off face masks.
Butyl Benzoic Acid/Phthalic Anhydride/Trimethylolethane Copolymer’s Cosmetic Benefits/Uses
The ingredient serves one main purpose in formulations: it is a film former. When the product dries, the polymer lays down a thin, even layer that clings to the surface. This film helps color cosmetics stay put, makes nail polish chip-resistant, gives hair styling products extra hold, reduces smudging in eye makeup and can create a gentle barrier that locks active ingredients on the skin long enough for them to work.
Who Can Use Butyl Benzoic Acid/Phthalic Anhydride/Trimethylolethane Copolymer
This film former is considered suitable for all skin types including oily, combination, normal and dry skin. It does not clog pores or add extra oil so acne-prone users generally tolerate it well. Very sensitive or eczema-prone skin might find long-wear films a bit occlusive which can lead to mild discomfort or redness, so lightweight or rinse-off formulas could be a better choice in those cases.
The copolymer is fully synthetic and contains no animal-derived raw materials which makes it acceptable for vegans and vegetarians. Manufacturing does not typically involve animal testing in regions that have alternative safety validation methods, though shoppers should check the finished brand’s cruelty-free stance if that is a concern.
No specific warnings exist for pregnant or breastfeeding women. The molecule is large, remains on the surface and is not expected to penetrate deeply. Still, this is not medical advice and anyone who is pregnant or nursing should review any cosmetic product with their healthcare provider to be on the safe side.
Butyl Benzoic Acid/Phthalic Anhydride/Trimethylolethane Copolymer does not cause photosensitivity, so it will not make skin more prone to sunburn. As with all film formers, proper removal at the end of the day is important to prevent buildup on skin hair or nails.
Potential Side Effects/Adverse Reactions
Reactions to topical Butyl Benzoic Acid/Phthalic Anhydride/Trimethylolethane Copolymer differ from person to person. The points below highlight potential side effects but most users will not encounter them when the ingredient is formulated and used correctly.
- Skin irritation – rare mild redness stinging or itching, usually when used in high concentrations or on compromised skin
- Allergic contact dermatitis – very uncommon sensitization leading to rash or swelling for individuals already allergic to related resins
- Eye irritation – tearing or burning if the raw resin or a product like mascara accidentally enters the eye before it sets
- Nail dryness or brittleness – possible with frequent use of high-solvent nail lacquers containing the polymer without adequate nail hydration between applications
- Build-up on hair or skin – dullness or flaky residue when products are layered repeatedly and not cleansed off thoroughly
Discontinue use and consult a healthcare professional if any negative reaction occurs while using this ingredient or products that contain it.
Comedogenic Rating
Rating: 0/5. This copolymer is a large inert molecule that sits on the surface then washes away with cleanser or remover. It contains no fatty acids or oils that could block pores so it is classed as non-comedogenic. In most formulations it dries to a breathable film that does not trap sebum underneath.
Suitable for acne-prone or breakout-prone skin. If the finished product mixes the polymer with rich oils or waxes the overall formula could still feel heavy so checking the full ingredient list is wise.
Summary
Butyl Benzoic Acid/Phthalic Anhydride/Trimethylolethane Copolymer is mainly a film former. Once applied it creates a thin flexible coat that boosts wear time in nail polish mascara long-wear lipstick foundation hair spray and peel-off masks. The film clings well resists chips or smudges and locks active ingredients where they are meant to work.
It is not the most talked-about ingredient but it has steady popularity among formulators who need strong yet comfortable hold. Consumers usually meet it through long-wear color cosmetics without realizing it is there.
Safety studies and decades of use show a low risk of irritation or allergy when the ingredient is properly formulated. Still every person is unique so perform a brief patch test whenever you try a new product containing the copolymer to make sure your skin likes it.