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Commonly used chemical sunscreens

I. UVA sunscreens

1.Butylmethoxydibenzoylmethane

Also known as Avobenzone, abbreviated as BMDM, it is one of the most efficient UVA sunscreens in the world, and also synergistically boosts SPF. trade names Parsol 1789, ESCALOL 517, Neo Heliopan 357, Eusolex 9020, etc. The upper limit of this product is 5% in China. Maximum absorption wavelength is 358nm, absorbance is 1.10. Molecular weight 310.

Sunscreens
Sunscreens

Disadvantages of this product and collocation notes.

(1) is photo-unstable, especially when paired with ethylhexyl methoxycinnamate, the two will undergo irreversible cycloaddition reactions, making the sun protection efficiency reduced. On this point, there are a variety of research reports and solutions, such as in the two compound with oxytetracycline and bis-ethylhexoxyphenol methoxyphenyl triazine for protection, or the use of wrapped ethylhexyl methoxycinnamate, etc. In addition, Procter & Gamble, Johnson & Johnson and other international companies have relevant patents to solve this problem. Some ingredients party in see avobenzone and ethylhexyl methoxycinnamate appear in the same formula, criticism and attack, which is not scientific and objective, should be combined with the formula as a whole to make a judgment. Translated with www.DeepL.com/Translator (free version)

(2) Oil-soluble solids need to be dissolved with appropriate solvents according to the formulation to avoid recrystallization.

(3) It is easy to react with free metal ions in the formulation, impurities in production water, water pipes and production pots, forming rust-colored by-products or other complexes that are not visible to the naked eye, so it is recommended to add EDTA or other chelating agents to the formulation. It has also been reported that the use with titanium dioxide wrapped in aluminum is not recommended. Translated with www.DeepL.com/Translator (free version)

(4) characteristic odor, according to the product needs to add appropriate flavoring and other masking; the presence of a certain irritation and dyeing (such as staining the clothes yellow).

The trade name 1789 is as epochal as the French capture of the Bastille in 1789, which shows the importance of the product at the time of its creation. Since A Plus is not available in the United States, Avobenzone is very common in American products and has become almost the strongest source of contribution to the A band.

2. Diethylaminohydroxybenzoyl hexyl benzoate

Abbreviation DHHB. trade name Uvinul A Plus Granular. regulatory upper limit of addition in China is 10%. Maximum absorption wavelength is 354nm, absorbance is 0.89. Molecular weight 397.5.

A Plus has a slightly weaker light-absorbing capacity than Avobenzone, but is still a very strong and effective UVA sunscreen, with partial absorption in the UVB region. This ingredient is not susceptible to photocracking reactions and is therefore more photostable.

It is an oil-soluble solid powder with a melting point of only 54 degrees and good solubility. It has good solubility in oxytetracycline, ethylhexyl methoxycinnamate, C12-15 alcohol benzoate, ethylhexyl salicylate, etc. In addition, yellowing and clothes dyeing is also a problem of A Plus.

II. UVB sunscreens

1. Ethylhexyl methoxycinnamate

Abbreviated as OMC or EHMC, the trade names are Parsol MCX, Uvinul MC 80, Neo Heliopan AV, ESCALOL 557, Eusolex 2292, etc. It is the most widely used and most frequently used UVB absorber. In China, the upper limit of regulation is 10%.

The maximum absorption wavelength is 311 nm and the absorbance is 0.76. Molecular weight 290.4.

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It is widely used in sunscreen products because of its low price, good compatibility, refreshing skin feel and being a good solvent for many solid UV absorbers. However, due to the relatively small molecular weight, based on the 500 Dalton principle, there is a risk of penetration into the skin and a certain degree of irritation. In addition, its sunlight resistance and light stability are not high, mainly in terms of poor durability. It has been reported that about 70% of the active ingredients are usually photodegraded after 10 MED of sun radiation. Therefore higher doses need to be added to the formulation to work effectively. With increased use, the potential safety properties of sunscreens manifest themselves, increasing the risk of excessive irritant reactions in sunlight after sunscreen cosmetics are used by consumers with sensitive skin. Translated with www.DeepL.com/Translator (free version)

Also under some special acts (e.g. Hawaii), OMC is prohibited because of the harm to corals. Therefore, it should be considered for use according to the specific requirements and characteristics of the product, as appropriate.

2. Ethylhexyltriazinone

Abbreviation EHT, trade name Uvinul T 150, is the most effective oil-soluble UVB band absorber available. The upper limit of addition in China is 5%. Maximum absorption wavelength is 312nm, absorbance is 1.5, molecular weight 823.

The photostability of EHT is very good, in addition to its large molecular weight, so it is not easy to penetrate into the skin, and its safety is better.

It is a white powder at room temperature. solubility is a special concern due to the molecular structure and molecular weight of triazine. eht is completely insoluble in non-polar oils and silicone oils, and only has some solubility in a limited number of polar oils. The low oil solubility gives it low transdermal properties i.e. higher skin safety.

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Although the national approved dosage is 5% by mass, it is difficult to add higher dosage and stabilize the formulation without precipitation in practical application. Usually the crystalline shape of EHT after precipitation is small, almost square, particles, which can be found by microscopic polarization experiments. The more common solvents include ethylhexyl methoxycinnamate, caprylic/capric triglyceride, dioctyl carbonate, oxytetracycline, etc.

3. Oakleys

Abbreviated OCR. trade names include Uvinul N 539 T, ESCALOL 597, Parsol 340, Neo Heliopan 303, Eusolex OCR, etc. This sunscreen is approved for use in various countries and regions around the world, and the regulatory limit for addition in China is 10%. The maximum absorption wavelength is 303nm and absorbance is 0.35. Molecular weight is 361.5.

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This product is a light yellow viscous oily liquid with a sticky skin feel, and can be partially replaced by ethyl salicylate. It is mainly absorbed in UVB band, and UVA is also absorbed to some extent. It is also a very good solvent and light stabilizer for solid sunscreens, and is especially suitable for systems in which avobenzone is added. Also suitable for mixing with most cosmetic oils.

4. Phenylbenzimidazole sulfonic acid

Abbreviation PBSA. trade names include Eusolex 232, Parsol HS, Neo Heliopan HYDRO, etc. The regulatory upper limit of addition in China is 8% (calculated as acid). Maximum absorption wavelength is 302nm, absorbance is 0.94 (sodium salt). Molecular weight 274.3.

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This product belongs to one of the few water-soluble sunscreen agents, the original body is white powder, insoluble in water, and dissolved in water as colorless transparent liquid after neutralization with alkali. When using different alkali neutralization, the pH change pattern around 6~9 is very different, usually inorganic alkali changes more drastically compared with organic alkali, and the actual pH value needed for the formula is often reached by titration during production to determine the amount of alkali addition.

When the pH of the formulation is <7.0, there is a potential risk of crystallization, which renders the sunscreen function of the formulation ineffective and creates a more pronounced graininess when applied. Therefore, the aqueous phase of the final formulation needs to be pH >7 or even >7.2. In addition, due to the salt-forming solubility properties, the stability of the O/W emulsion may be affected, as well as reducing the viscosity of salt-intolerant thickening systems. It has been reported that the use of amino acids such as arginine to neutralize can maintain stable dissolution of PBSA at pH>6 without crystalline precipitation.

Compared to the previous oil-based sunscreens, PBSA offers a new option for sunscreen formulation development, allowing for a hydrating and refreshing skin feel or a clear gel texture. However, this product also brings another sticky and stagnant feeling when used in larger quantities. It is generally used in combination with oil-based sunscreens to achieve synergistic sun protection.

5. Ethylhexyl salicylate

Abbreviation EHS, trade names are Neo Heliopan OS, Parsol EHS, ESCALOL 587, Eusolex OS, etc. The regulatory upper limit of addition in China is 5%. The maximum absorption wavelength is 305nm and the molecular weight is 250.

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Abbreviation EHS, trade names are Neo Heliopan OS, Parsol EHS, ESCALOL 587, Eusolex OS, etc. The regulatory upper limit of addition in China is 5%. The maximum absorption wavelength is 305nm and the molecular weight is 250.

EHS is soluble in ethanol, propylene glycol, and can be mixed with mineral oil, olive oil, isopropyl palmitate, etc. in any ratio.

III. Broad-spectrum sunscreens

1. Bis(ethylhexyloxy)phenol p-methoxyphenyl triazine

Abbreviation BEMT, trade names are Parsol Shield, Tinosorb S, Neo Heliopan EMT, etc. In China, the regulatory limit of addition is 10%.

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This product absorbs UV wavelengths of two extreme values, namely 310nm and 343nm, is a very efficient broad-spectrum absorbers, I think this is also a very promising and potential sunscreen agent. In addition to being a very stable sunscreen, it can also be very efficient in stabilizing avobenzone. Its light stability is shown in the absorption of photons in the way of vibrational relaxation of this energy into heat and quickly back to the ground state, to restore the sunscreen function, so there is basically no loss and reduction in sunscreen efficiency after exposure to light.

BEMT is a bright yellow powder at room temperature, and its products are generally yellowish.

2. methylenebis-benzotriazolyltetramethylbutyl phenol

Abbreviated MBBT, trade names include Parsol MAX, Tinosorb M. The regulatory limit for addition in China is 10%.

MBBT belongs to organic particle UV shielding agent, which is composed of colorless organic particles with diameter of 70~140nm and has high light stability. The product form is 50% colorless organic ultra-fine particle water dispersion system, which has good stability after stabilization with surfactant. It absorbs UV wavelengths of 305nm and 360nm, so it is also a broad-spectrum sunscreen. Due to the nature of its particle dispersion, in addition to its own organic molecular structure to absorb UV light, it can also scatter and refract UV light, which can achieve a triple sunscreen effect. The organic particles have a molecular weight of 658 and are non-soluble, so they are non-permeable and very safe.

This product can play a good synergistic effect with OMC, and significantly improve the SPF value of the formulation. It also improves the photostability of UVB sunscreens such as OMC in the formulation, i.e., it improves its practical use and reduces the chance of skin irritation from its photodegradation products. Recent clinical studies have confirmed its effectiveness in preventing tanning in Asian skin.

In addition, this product can reduce the light transmission in the visible wavelength band by scattering effect, and has a blue light protection effect.

MBBT does not dissolve water or oil, but is dispersed in water in the form of particles, and the overall raw material is alkaline due to the glycoside phenolic activity. The skin feel is average and the product is somewhat whitish.

3. Polysiloxane-15

Abbreviation PS15, trade name Parsol SLX, has been approved for global use with a regulatory upper limit of 10% addition in China. The maximum absorption wavelength is 312nm and the absorbance is 0.16.

PS15 is a polymer with aromatic rings attached to the main chain of silicone, so it has a large molecular weight (over 6000d). It is often used as a sunscreen for hair care in the United States. Because of the unusually large molecules of this sunscreen, it has practically no skin penetrating ability and is therefore safer to use. In addition, it has very noteworthy film-forming properties. It has been reported that it can also stabilize avobenzone.

PS15 has weak sun protection efficiency and is suitable for use in children’s products and hair care products, or in products that require film formation. It is soluble in most polar oils, poorly soluble in straight chain silicone oils and well soluble in cyclic silicone oils.

*Disclaimer: The content contained in this article comes from the Internet, WeChat public numbers and other public channels, and we maintain a neutral attitude toward the views expressed in the article. This article is for reference and exchange only. The copyright of the reproduced manuscript belongs to the original author and the institution, and if there is any infringementPlease contact Jetson Chemical for deletion

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