The present invention relates to the use of a booster capable of synergistically boosting the SPF of a sunscreen composition. More particularly, the invention relates to the use of a booster comprised of an acrylates copolymer having a weight average molecular weight of from about 75,000 to 140,000 g/mol, and a Tg of from about -20 to 50°C, which has shown to provide a synergistic boost in SPF when combined with a novel UV filter system.
The negative effects of exposure to ultraviolet ("UV") light are well-known. Prolonged exposure to sunlight causes damage such as sunburn to the skin and dries out hair making it brittle. When skin is exposed to UV light having a wavelength of from about 290 nm to about 400 nm, long-term damage can lead to serious conditions such as skin cancer.
UV light also contributes to aging by causing free radicals to form in the skin. Free radicals include, for example, singlet oxygen, hydroxy radical, the superoxide anion, nitric oxide, and hydrogen radicals. Free radicals attack DNA, membrane lipids, and proteins, generating carbon radicals. These in turn react with oxygen to produce a peroxyl radical that can attack adjacent fatty acids to generate new carbon radicals. This cascade leads to a chain reaction producing lipid peroxidation products. Damage to the cell membrane results in loss of cell permeability, increased intercellular ionic concentration, and decreased ability to excrete or detoxify waste products. The end result is a loss of skin elasticity and the appearance of wrinkles. This process is commonly referred to as photo-aging.
The Role of Acrylates in Sunscreen Formulations
Sunscreens can be used to protect against UV damage and delay the signs of aging. The degree of UV protection afforded by a sunscreen composition is directly related to the amount and type of UV filters contained therein. The higher the amount of UV filters, the greater the degree of UV protection. Nevertheless, it is desirable to achieve the best photo protection efficacy with the lowest amount of UV filters. The inventors of the instant disclosure discovered ways to attain SPFs that were not previously attainable with such low amounts of overall UV filters.
The present disclosure relates to sunscreen compositions that have low amounts of UV filters yet excellent Sun Protection Factors (SPF). Typically, the more UV filters included in a sunscreen composition, the higher the SPF. The inventors discovered that the association of a specific type of polyacrylate booster, together with a specific type of UV filter system, yields a synergistic interaction which provides an unexpectedly surprising boost in SPF values.
Acrylates Copolymer as a Booster
In one embodiment, the polyacrylate booster is an acrylates copolymer having a weight average molecular weight ranging from about 75,000 to 140,000 g/mol, preferably ranging from about 84,000 to 125,000 g/mol, and most preferably ranging from about 88,000 to 120,000 g/mol. This copolymer also has a glass transition temperature (Tg) ranging from about -20 to 50°C, preferably from about -10 to 40°C, and most preferably from about 0 to 20°C.
The polyacrylate booster, also referred to as a polyacrylate film former, is typically employed in an amount ranging from about 0.1% to about 10% by weight, preferably from about 0.25% to about 5% by weight, and most preferably from about 0.5% to about 2% by weight, based on the total weight of the composition. It has been surprisingly discovered that this specific type of polyacrylate film former, when combined with a specific UV filter system, yields a synergistic boost in the SPF of the composition.
UV Filter Systems in Conjunction with Acrylates
The sunscreen composition according to the invention comprises a UV filter system. According to one embodiment, the sunscreen composition contains from about 1% to about 40% by weight, preferably from about 5% to about 30% by weight, and most preferably from about 7% to about 25% by weight, of a UV filter system.
A particular embodiment of the sunscreen composition includes:
- From about 0.5% to about 2% by weight, based on the total weight of the composition, of a polyacrylate booster comprising at least one acrylates copolymer having a weight average molecular weight ranging from about 93,000 to 114,000 g/mol and a Tg of about 13.6°C.
- A UV filter system containing a combination of UV filters comprised of: octocrylene, avobenzone, oxybenzone, octisalate, and homosalate.
The ratio of each filter relative to avobenzone is specified as follows:
- Octocrylene to avobenzone: 1.6:1.0 to 2.4:1.0
- Oxybenzone to avobenzone: 0.0:1.0 to 0.016:1.0
- Octisalate to avobenzone: 1.3:1.0 to 2.0:1.0
- Homosalate to avobenzone: 2.3:1.0 to 3.6:1.0
In one specific embodiment, the UV filters are present in the following percentages by weight relative to the entire weight of the sunscreen composition: about 5.9 wt.% octocrylene; about 3.0 wt.% avobenzone; about 4.9 wt.% octisalate; and about 8.8 wt.% homosalate. Typically, these sunscreen compositions are free of oxybenzone, or have less than 1.0, 0.5, 0.25, or 0.05 wt.% oxybenzone.
The ratio of octocrylene:avobenzone:oxybenzone:octisalate:homosalate is about 2.0:1.0:0.0:1.7:3.0.
Understanding "Hidden" Acrylates
While the term "acrylates copolymer" might not be immediately familiar, many common cosmetic ingredients contain acrylate chemistry without it being obvious from their names. This can be a concern for individuals with acrylate allergies.
Chemical Naming and Trade Names
Chemicals in cosmetics and pharmaceuticals follow different naming systems. Sometimes, the industry adopts a trade name that becomes standard, or chemical naming rules vary between countries and organizations. This can lead to an acrylate ingredient appearing under a completely different name on a product label.
Common "Hidden" Acrylates in Sunscreens and Other Products
Some chemical sunscreen ingredients are acrylates in disguise. For instance:
- Octocrylene is chemically known as 2-ethylhexyl 2-cyano-3,3-diphenylacrylate or 2-Ethylhexyl 2-Cyano-3,3-Diphenylprop-2-enoate. It is widely used in sunscreens and daily moisturizers with SPF.
- Etocrylene is ethyl 2-cyano-3,3-diphenylacrylate.
- Ethylhexyl methoxycrylene is 2-ethylhexyl 2-cyano-3-(4-methoxyphenyl)-3-phenylacrylate.
These ingredients are crucial for absorbing UV damage, but their chemical nature might not be apparent from their common names.
Other Acrylate-Containing Ingredients
Beyond sunscreens, acrylate chemistry is found in various cosmetic and personal care products:
Carbomers
Carbomers are frequently used as thickening and stabilizing agents. They can appear under various names, including:
- Carbomer (934, 940, 941, 980, 981, 1382)
- Carboxypolymethylene
- Carbopol
- Carbopol Ultrez 20
- Polycarbophil
- Pemulen TR-1
- Pemulen TR-2
- ETD 2020
Carbomer is found in face creams, serums, hand sanitizers, shower gels, and toothpastes.
Polyquaterniums
There are over 50 different polyquaterniums used in cosmetics, some of which contain acrylate or methacrylate building blocks. Examples include:
- Polyquaternium-7 (acrylamide/acrylate copolymer)
- Polyquaternium-11 (quaternized copolymer with acrylate)
- Polyquaternium-37 (acrylate-based)
A comprehensive list of polyquaterniums confirmed to contain acrylate or methacrylate chemistry includes Polyquaternium-5, -7, -8, -9, -11, -12, -13, -14, -15, -22, -28, -30, -31, -32, -33, -35, -36, -37, -39, -43, -45, -47, -50, -51, -53, -55, -58, -61, -64, -65, -68, -69, -91, -103, and -113. Polyquaterniums are commonly found in hair products for hold and frizz reduction.
Polyurethanes
Similar to polyquaterniums, numerous polyurethane ingredients used in cosmetics are acrylate or methacrylate-based. Confirmed examples include Polyurethane-9, -40, -50, -51, -52, -53, -54, -55, -56, -57, and -88. Polyurethanes are often found in nail products.
Acrylate Allergy and Sensitivity
For individuals with acrylate allergy, identifying these "hidden" acrylates is crucial. Acrylate allergy is a contact allergy, meaning it requires skin contact.
Monomers vs. Polymers
Polymers like carbomer, polyquaterniums, and polyurethanes generally carry a lower risk than monomers because of their larger molecular size. However, products always contain trace amounts of uncured monomers, which can potentially trigger reactions in highly sensitive individuals.
Cross-Reactivity
Cross-reactivity can occur, where an immune system reaction to one type of acrylate leads to reactions to other acrylates as well. Patch testing can help determine specific triggers.
Symptoms of Acrylate Reactions
Reactions can include red, itchy patches that appear 2 to 5 days after contact, sometimes with blisters. The reaction might manifest away from the application site, such as eyelid issues from nail polish.
Identifying Acrylates in Product Labels
Decoding ingredient lists requires some detective work:
- Look for terms containing "acryl" or "cryl" (e.g., octocrylene).
- Keep a list of common culprits: octocrylene, etocrylene, carbomer, specific polyquaterniums, and Eudragit.
- Be aware of product types: gel nails and chemical sunscreens are prime suspects for acrylates.
- Generic terms like "polymer," "resin," "film former," or "adhesive" without further details can be red flags.
- Utilize tools like INCIDecoder to analyze ingredient lists.
- Products claiming "HEMA free" might still contain other acrylates, and "acrylate free" claims might refer to "safe" polyacryl compounds.
- Patch test products for several days before widespread use, as acrylate reactions can take time to appear.
It is important to note that Acrylateallergy.com provides general information, and individuals with suspected allergies or medical concerns should consult a healthcare professional.
Acrylates Copolymer in Broader Applications
Beyond personal care, acrylates copolymer is a versatile ingredient used in various industrial applications, including paints, adhesives, textiles, and paper, where it functions as a thickener, binder, stabilizer, and performance enhancer.
Safety and Environmental Considerations
In skincare, acrylates copolymer is generally considered safe by regulatory bodies like the Cosmetic Ingredient Review (CIR) at typical concentrations. However, rare cases of sensitivity can occur. Environmentally, synthetic acrylates copolymers are not biodegradable, raising concerns about waste. Formulators are exploring more sustainable alternatives and responsible sourcing.
