It has long been known that the sunlight together with the air causes natural bleaching of hair. Bleaching is based on the oxidation of color pigments in hair, which is effected by oxygen in the air and causes the transformation of the color pigments into achromatic substances.
Bleaching of hair is thus based on the oxidation phenomenon. In artificial hair bleaching, which is relatively much faster than the natural method, strongly oxidizing substances are used. A conventionally used bleaching agent is hydrogen peroxide. The effect of hydrogen peroxide on hair is both physical and chemical. It causes scale like cells on the surface of a hair to be detached from each other, whereby it can penetrate the hair. In the hair, the hydrogen peroxide oxidizes the melamine functioning as a pigment.
Hair can also be bleached with so-called rinsing solutions containing hydrogen peroxide and ammonium hydroxide or with bleaching shampoos containing these agents. However, hydrogen peroxide is not preserved long as a solution, which means that fresh solutions should always be used. Penetrating the hair with hydrogen peroxide can be made more effective by using a moisturizer, for example quaternary ammonium compounds. It is also possible to use tablets which in addition to hydrogen peroxide contain urea compounds. The tablets are dissolved in water immediately before the use.
Bleaching materials of emulsion or cream form can be used when it is desired to color only a certain amount of hair. Cream bases of these products contain macromolecular alcohols, fatty alcohol sulphonates etc. Instead of hydrogen peroxide it is possible to use sodium, potassium or ammonium persulphate. Quaternary ammonium compounds as a part of the cream bases facilitate the treatment of hair.
All bleaching materials used in hair treatment should be non-toxic, they should not have any harmful side effects and neither should they damage the hair.
However, by using said methods of prior art the hair is excessively strained. When bleaching with conventional methods it can be difficult to locate the bleaching particularly when making bleached stripes. Furthermore, the bleaching usually takes a rather long time. In addition, the person who treats the hair is exposed to dusty bleaching materials. Also, the odors formed in the work environment are quite strong when using conventional methods.
In a number of applications it is known to use urea peroxide as the source of oxygen. It has the effect that it retards the growth of bacteria and fungi; it can be used to eliminate odor etc. Furthermore, it can be used for bleaching.
The anti-bacterial and disinfecting properties of urea peroxide are utilized in the invention in accordance with Finnish patent application 941126. It presents a fiber structure containing urea peroxide and a method for its manufacture. The fiber structure according to Finnish Patent Application 941126 comprises a polysilicic acid containing fiber, having the urea peroxide absorbed therein. The fiber structure comprises a supporting structure which is advantageously of cellulose, preferably regenerated viscose cellulose, and polysilicic acid containing aluminium silicate sites or mere polysilicic acid homogeneously distributed in the same phase with the viscose cellulose. To absorb urea peroxide in polysilicic acid containing fiber structure has, for example the advantages, compared to ordinary, for instance viscose fibers, that the material lasts longer in the fiber patches, and better resistance to washing. The embodiments of the fiber structure presented in Finnish patent application 941126 include, for instance, the use of the material in hospitals. Another possible field of application mentioned there is hair bleaching for instance when making stripes in hair. However, no examples describing embodiments of the latter field of application is presented here.
The structure of the polysilicic acid containing fiber, or the so-called VISIL-fiber, and its manufacturing employed in the above mentioned application is presented in patent publication GB-1064271. The manufacturing and structure of the VISIL-fiber are also described in patent publication FI-91778. However, the invention presented in this publication primarily deals with a VISIL-fiber modified by using a compound containing aluminium, that is the so-called "VISIL-AP"-fiber. The present invention utilizes these fiber materials containing polysilicic acid. However, the invention is not limited to these fiber materials, instead any absorbent fiber material can be used, such as cellulose based fiber material, for instance viscose fiber.
As it has been mentioned earlier, the conventional methods for hair bleaching have many disadvantages. In addition, it has been noted that hair bleaching by using the VISIL-fiber patches in accordance with Finnish patent application FI-941126, in which patches of only urea peroxide is impregnated as the active agent, is too slow and inefficient.