Selection of cosmetic preservatives (一)
Cosmetic Preservatives Information Daquan
At present, there are about 60 kinds of preservatives used in personal care products in the world, and even fewer are widely and mainly used. The type here refers to the chemical structure of the preservative, not the trade name of the supplier. Many so-called new products are just compounded with different preservatives in different proportions.
1. Definition of preservatives
Simply put, a preservative is a substance that prevents the growth of microorganisms. In cosmetics, the role of preservatives is to protect the product from microbial contamination, prolong the shelf life of the product, ensure the safety of the product, and prevent possible infection by consumers due to the use of microbially contaminated products. Cosmetics are spoiled by microbial contamination, and in general, they can be reflected in the appearance. For example, mold and yeast often appear on the edge of the product packaging; the product contaminated with microorganisms may appear turbid, precipitate, change in color, change in PH value, foam, and taste bad. block etc. If the amount of preservatives added is not enough, microorganisms may adapt to the surrounding growth environment and develop drug resistance, resulting in the failure of preservatives.
2. The mechanism of action of preservatives
The survival and reproduction of microorganisms in cosmetics depends on some environmental factors: physical aspects include temperature, environmental PH value, osmotic pressure, radiation, and static pressure; chemical aspects include water sources, nutrients (C, N, P, S sources) ), oxygen, organic growth factors. Based on this, the mechanism of action of preservatives can be briefly summarized as follows:
1) In some products with low water content such as ointments, it is generally difficult for microorganisms to grow;
2) For most bacteria, the most suitable PH range for growth is close to neutral (6.5~7.5), strong acid and strong alkali are not suitable for the growth of microorganisms, such as common fruit acid products, the preservative effect is usually better than neutral. product;
3) Increasing or decreasing osmotic pressure can lead to rupture of the cell membrane, as well as shrinkage and dehydration of the membrane;
4) In addition, surface tension is also one of the reasons that affect the growth of microorganisms. In some formulations with a high amount of surfactants, microorganisms are not easy to grow. In this regard, cationic surfactants are more prominent, while anionic and nonionic The physiological toxicity of microorganisms is very small.
5) Under normal circumstances, the most suitable temperature for bacteria production is 30°C~37°C, while the temperature for mold and yeast is 20°C~25°C, so high-temperature disinfection can be used, but some spores will form after adapting to the environment. The protective film cannot be killed even at a high temperature of 80°C to 90°C for a short period of time.
The effect of preservatives on microorganisms can only be effective when they are in direct contact with microorganisms in sufficient concentrations. Preservatives first come into contact with the outer cell membrane, adsorb, pass through the cell membrane and enter the cytoplasm, and then they can exert their effects in various parts, hinder cell reproduction or kill them. In fact, it is mainly the effect of preservatives on cell walls and cell membranes, but also on the activity of enzymes affecting cell metabolism or on the structure of genetic particles in the cytoplasmic part.
3. Classification of preservatives
Most of the preservatives react with certain components of the cell wall, mainly proteins, after contacting with the cell membrane, destroying the protective structure of microbial cells or interfering with the metabolism of cells, affecting the normal growth order of cells, so as to achieve antiseptic effect. The purpose of the cation is mainly to sterilize by affecting its osmotic pressure, causing the cell membrane to rupture, shrink and lose water.
According to the dozens of preservatives commonly used in the field of cosmetics, and classify them according to active substances
1) Germall115, GermallⅡ, GermabenⅡ-E of imidazolidinyl urea ISP company,
Germallplus, GermallIS-45. In the Jiemei series, the main ingredient is imidazolidinyl urea, which is a formaldehyde donor, and achieves the purpose of sterilization by slowly releasing formaldehyde during the application process. The main ingredient of Germall115 is imidazolidinyl urea, which has worse antibacterial activity than Germall II (bisimidazolidinyl urea). There are advantages.
Germallplus and GermallIS-45 are compounds of iodopropynyl butyl carbamic acid ester, and the market reaction effect is also good, but attention should be paid to avoid the ingredients that may inhibit their activity in the formula. In addition, 1% of iodopropane in the preservative Alkynylbutylcarbamate has poor water solubility, and its antiseptic effect may also be affected if it is not dissolved in an organic solvent during operation.
GermallIS-45 is a newer variety sold by ISP Company, which contains 5% methylparaben, which enhances the ability to inhibit mold and yeast.
2) Caprolactin
LONZA's glydantplus, DMDMH, NIPA's DMDMH. These products are also formaldehyde donors. Glydantplus is a compound of iodopropynyl butylcarbamate with a 5% content of iodopropynyl butylcarbamate. In addition, LONZA also provides liquidglydantplus (propylene glycol solution) which is said to be up to 50% active, but it should also be noted that components such as reducing agents in the formulation may inhibit it.
3) Isothiazolinone
KathonCG, 950 from Rohm and Haas, isocilpc from LONZA, EUXYLK100 and EUXYLK727 from S&M. These products are also formaldehyde donors.
LONZA's isocilpc is composed of two kinds of isothiazolinones, and 23% magnesium salt is added in the formula for synergy, mainly to change the osmotic pressure.
K727 is a complex of methyldibromoglutaronitrile. EUXYLK100 is a compound of benzyl alcohol, which also has considerable anticorrosion ability for the gas phase.
4) parabens (parabens)
Zhejiang Shengxiao, liquaparoil from ISP, EUXYLK300 from S&M, phenonip from NIPA, etc. This type of preservative is one of the most widely used preservatives at present, but the dosage is relatively large. As the carbon chain increases, its water-soluble phase gradually deteriorates, which affects its distribution rate in the water phase. Its anti-mildew effect is more prominent. Methylparaben has the best water solubility and can often be added directly to the water phase; while ethyl, propyl, butyl, and isobutylparaben tend to dissolve in the oil phase. Methylparaben is a preservative suitable for acidic systems. It has the highest bacteriostatic activity of 77% at pH 5, 63% at pH 7, and close to 50% at pH 8.5. Therefore, the activity of parabens in the system can be improved mainly by lowering the pH of the system, usually 7.0 to 6.5 or lower, although they can sometimes maintain their efficacy in systems with slightly higher pH.
5) quaternary ammonium salt-15
Such products are currently only Dowicil200 from DowChemical.
Dowicil200 will not dilute formaldehyde, but its anti-oxidative reduction ability is better than ISP's Jiemei. It is common practice to add a small amount of sulfite to prevent discoloration in some formulations that are prone to discoloration.
6) domestic Kathon-CG (chemical structure is the same as class 3)
Zhejiang Shengxiao's CY-1, Shandong Mingda's MD-2000, Jiangsu Xinke's Xinke-99, Shaanxi China Resources' KS-1, and Xi'an Pioneer's XF-1. It is sensitive to PH value in use, and can play a very good antiseptic effect in a slightly acidic environment. But in an alkaline environment, it loses its antiseptic activity. In this type of product, in order to increase its antiseptic activity, magnesium salt will be added to increase its osmotic pressure, so when using this product, the compatibility between raw materials must be considered to avoid precipitation, especially in transparent product, be very careful. In addition, amines, mercaptans, sulfides, sulfites, and bleaches can also deactivate Kathon
