Process for preparing synthetic nail coatings.

0001The invention relates to a method for producing plastic coatings on fingernails by applying a photopolymerizable preparation based on methacrylate and curing the preparation by irradiation with ultra-violet and / or visible light.

0002It is known to provide fingernails for embellishment or protection with plastic coatings made from polymerizable preparations. The polymerisable preparations - mostly referred to as fingernail preparations - should not contain any components that damage the nail or cuticles and should have a consistency that is favorable for application and modeling. The coatings hardened by polymerization should adhere to the natural nail for at least a few days and have properties that are as similar as possible to those of the natural nail.

0003Unlike the self-hardening fingernail preparations to be prepared by mixing before use, the preparations to be hardened by photopolymerization in the absence of light are ready-to-use, ready-to-use one-component preparations with the advantage of a constant consistency and a longer processing time, since the hardening takes place only when exposed to light.

0004A photopolymerizable fingernail preparation is known, for example, from US Pat. No. 4,058,442. It consists of a mixture of mono- and polyesters of methacrylic acid, an initiator that triggers the polymerization when exposed to UV radiation, a modifier made of an elastomer or elastomer-cellulose derivative mixture and optionally a finely divided inorganic filler and other additives, such as color and Fragrances.

0005In order to improve the adhesive strength of the coatings on the nails, a pretreatment of the nails with the solution of an adhesion-promoting substance consisting of an unsaturated monoester of maleic acid, dimethyl maleic acid, citraconic acid, succinic acid or glutaric acid in an organic solvent is proposed in published European patent application 325 038.

0006It is now the object of the invention to find a method for producing plastic coatings on fingernails by applying a photopolymerizable methacrylate-based fingernail preparation and curing the preparation by irradiation with ultraviolet and / or visible light, with which without that the pretreatment with the solution of an adhesion-promoting substance is required to have coatings which adhere well to the fingernails.

0007The method which achieves the object is characterized in that a photopolymerizable preparation is applied which contains 20-60% by weight of acrylated polyurethane, 10-40% by weight of hydroxyethyl methacrylate and / or hydroxypropyl methacrylate, 1-20% by weight of diurethane dimethacrylate from 2. 2,4-trimethylhexamethylene diisocyanate and 2-hydroxyethyl methacrylate, 1-15% by weight polyether triacrylate, 0.3-15% by weight acetyl cellulose, Contains 0.02-10% by weight of photopolymerization catalyst and 1-20% by weight of at least one dicarboxylic acid monomethacryloyloxyethyl ester.

0008The method has proven particularly useful when a photopolymerizable preparation is applied which contains 30-50% by weight of acrylated polyurethane, 20-30% by weight of hydroxyethyl methacrylate and / or hydroxypropyl methacrylate, 5-15% by weight of diurethane dimethacrylate from 2,2,4- Trimethylhexamethylene diisocyanate and 2-hydroxyethyl methacrylate, 5-10% by weight polyether triacrylate, 0.5-5% by weight acetyl cellulose, 3-8% by weight of photopolymerization catalyst and 5-15% by weight of at least one dicarboxylic acid monomethacryloyloxyethyl ester.

0009A preparation is preferably used for the process which contains at least one dicarboxylic acid monomethacryloyloxyethyl ester from the group C₁₋₆-alkanedicarboxylic acid monomethacryloyloxyethyl ester, C₂₋₆-alkenedicarboxylic acid monomethacryloyloxyethyl ester and benzenedicarboxylic acid monomethacryloyloxyethyl ester.

0010Particularly advantageous embodiments of the method according to the invention result from a preparation which contains the monomethacryloyloxyethyl ester of succinic acid, maleic acid and / or phthalic acid.

00112-Hydroxyethyl methacrylate is preferred as the hydroxyalkyl methacrylate.

0012Suitable photopolymerization catalysts are all catalysts known for this purpose which, when irradiated with light in the wavelength range from 350 to 550 nm, trigger the polymerization of the preparation and are dermatologically harmless, with ketones and acylphosphine oxides, as known from German Offenlegungsschrift 28 30 927, being preferred . 1- (4-Isopropylphenyl) -2-hydroxy-2-methylpropanone, phenyl-2-hydroxy-2-methylpropanone, camphorquinone, benzil dimethyl ketal (1,2-diphenyl-2,2-dimethoxyethane), 2,4 have proven particularly useful , 6-Trimethylbenzoyldiphenylphosphinoxid or mixtures of two of these compounds, preferably in a weight ratio of 0.5-1.5 to 0.5-1.5.

0013The acetyl cellulose, which acts as a thickening agent, achieves a consistency of the preparation that is favorable both for application and for shaping and modeling.

0014In addition, the preparation can also contain thixotropic agents, such as colloidal silicon dioxide, colorants and fragrances, and antioxidants and stabilizers. The amount of these additives is preferably in the range of 2-5% by weight.

0015To produce the coatings, the preparation is applied to the cleaned fingernails and shaped and modeled in the desired manner, if necessary using a template. The preparation is cured by irradiating the hand in a fingernail radiation device, as is known, for example, from German Offenlegungsschrift 38 25 324.

0016The plastic coatings produced by the process according to the invention are notable for their good adhesive strength on the fingernails. Even after a longer period of wear, they show no cracks and gaps. Since their properties are similar to those of natural nail, they are not perceived as disturbing.

0017The method according to the invention creates the possibility of producing plastic coatings which adhere well to the fingernails, without the need to pretreat the nails with the solution of an adhesion-promoting substance. The pretreatment solution also eliminates the possibility of errors due to its application, such as application that is too thin or too thick, or solvent residues remaining on the fingernail, which can impair the quality of the coatings. Another advantage of the process is that no organic solvent-containing preparation is used.

0018For a more detailed explanation, the composition of some exemplary embodiments of the preparation to be used in the method according to the invention is given in Table I.<tables id="tabl0001" num="0001"><img file="EP0453628A2_D0001.tif" /></tables>

0019In order to determine the adhesive strength of the plastic coatings produced on the fingernails, the adhesion of the coatings to the edge of the nail is checked after a usual activity, such as hand washing and dishwashing, including wearing time of 24 hours and 7 days with a scalpel. The results of the test are given in Table II.<tables id="tabl0002" num="0002"><img file="EP0453628A2_D0002.tif" /></tables>