DE2021099B2 - Method of bleaching hair or wool - Google Patents

Description

The invention relates to a method for bleaching hair or wool by treating with a aqueous peroxide solution at a pH of 8 to 11.

From patent specification 20 434 of the Office for Invention and Patents in East Berlin, it is known to pretreat animal hair by pretreatment with solutions of Fe (II) salts with a pH value of 4.5 to 5.5 and then bleach with hydrogen peroxide at pH 8. In the latter process step Pyrophosphate is added as a stabilizing agent, the iron is mixed with a complexing agent removed. The disadvantage of the known method is that it takes until a desired Bleaching takes far too long and is relatively damaging to the hair in the process.

The invention was now based on the object of a method for bleaching keratin fibers in the form of To create hair or wool that brings about the desired bleaching in a short time and the keratin fibers allows the greatest possible protection to flourish.

The invention thus relates to a method of the type mentioned at the outset, which is characterized in that the hair or wool is impregnated with an aqueous solution which is 0.05 bsi 0.15 mol of a soluble iron (II) salt, a soluble chelating compound, the concentration of which is 0.2 to 5 times the molar concentration of the iron (II) salt and which has a chelation constant Kmα with iron (II) - has ions, the log Kma of which is 2 to 8, and optionally additionally contains 0.005 to 0.05 mol of a reducing agent, the total ionic strength of the solution being 0.5 to 2.5.

The chelate binding constant Kma is determined at an ionic strength of 0.1 and a pH value of 5 (see, for example, Chaberek and coworkers "Organic Sequestering Agents", New York - 1959 -).
The molar concentration of the ferrous salt, ie

ίο the iron (II) ions, in the aqueous impregnation medium or solution should be between 0.05 and 0.15 mol, since below 0.05 molar concentration is the time required to impregnate the hair becomes undesirably long even at an elevated temperature, while increasing the molar concentration above 0.15 has no effect on the process. As a supplier for the iron (II) ions can very many Iron (II) salts are used, for example formats, Acetates, bromides, chlorides, iodides. Nitrates, sulfates, lactates, tartrates and the like are among those that can be used Chelating agents include ascorbic acid. Citric acid, serine and ethylenediamine. The molar concentration of the chelating agent in the impregnation medium should be 0.2 to 5 times the molar concentration of the iron (II) salt. Although this is not decisive, it is desirable to add a small amount of a to the solution Add reducing agent which is inert towards the iron (U) ions, d. H. this does not fail and also does not form a complex with them. The chelating agents themselves can act as reducing agents in certain cases are designated. To these additional reducing agents which are inert towards the iron (II) ions include, for example, alkali metal (e.g.

Sodium) formaldehyde sulfoxylates, alkali metal sulfites or alkali metal thiosulfates; these reducing agents are preferably used when using serine as Chelating agents are also used to prevent the formation of iron (HI) hydroxide precipitates in the solution to prevent during hair treatment. The molar concentration of these reducing agents can be Are 0.005 to 0.05.

The solution should preferably contain a buffer system in order to keep the acidity in the desired range and also to keep the total ionic strength above the minimum desired value. The buffer should of course be chosen so that it contains the iron (II) salt does not fail and does not form a complex with it. To ensure the best results, a Buffer mixture of sodium acetate and acetic acid in a molar ratio of 10: 3 applied, which has a pH value of about 5, although other buffer systems can be used, for example a Mixture of an acidic potassium phthalate with sodium hydroxide in a molar ratio of 5: 4.

For best results, the total ionic strength of the impregnation solution should be 0.5 to 2.5; optimum results are achieved at a value of around 2.0, while the pH is between 3.5 and 6 should.

The temperature of the solution can fluctuate between room temperature (20 ^° C.) and the boiling point, although in the treatment of scalp hair a maximum of temperatures of up to about 55 ° C. can be used, unless special equipment and measures are used.

At room temperature, iron (II) ions are required for diffusion from the solution into the keratin-containing ones

Fibers only need a few minutes, the subsequent bleaching process being significantly accelerated by the iron (II) ion catalyst. The best results are obtained usually when the hair fibers are 0.5 to 1.5 hours gehali.cn at a temperature of 35 to 60 ⁰ C with the iron (lI) salt solution into contact; which is well below the 3 to 4 hour period required when using a non-chelating iron (II) salt solution.

After the keratin fibers have been impregnated with the aqueous solution containing ferrous salt and chelating agents, it is advantageous, although not essential, to rinse the fibers with water in order to remove the ferrous ions which do not adhere to the melanin have been bound and which are therefore of no value for accelerating the subsequent decomposition of the dye and merely cause the ineffective decomposition of the peroxide in the subsequent bleaching process, which is a waste! would. Such a loss of peroxide is particularly evident when the log Km λ of the solution is in the vicinity of the lower end point of the permissible range, so that a flushing process is particularly desirable under these conditions. earth.

The subsequent bleaching takes place in a conventional way Way using an aqueous alkaline Peroxide solution by removing the fibers at room temperature up to 60 "C are kept in contact with an aqueous solution which - measured as hydrogen peroxide 1 "" to 6% peroxide and its pH value by means of a base, for example an alkali metal hydroxide. preferably ammonium hydroxide, is adjusted to 8-11.

The effectiveness of the inventive method in the discoloration of hair can be measured, that it is compared with the discoloration, the stage in a conventional bleaching method using ^v on means Ammuuiuinhydroxyd to a pH value of 10 set 3 ° ₍₎ aqueous hydrogen peroxide solution is achieved at 35 C for different lengths of time. The extent of damage to the keratin of the fibers by the peroxide can be determined by the known determination of the water retention capacity of the fibers by reducing the hair with thioglycolate, neutralizing it with peroxide, immersing it in water buffered to a pH of 7 and finally centrifuging it off. Greater water retention indicates greater damage to the keratin.

These experiments show that the invention with the iron (II) salt and the chelating agent pretreated fibers are bleached to the same extent in a 30-minute bleaching process, i.e. H. discolored, can be bleached like other, untreated fibers within 2 to 2.5 hours, in addition, there is also significantly less damage to the keratin.

The following specific examples are intended to explain the invention in greater detail without, however, restricting it.

example 1

One gram of dark brown Caucasian hair was dissolved in 25 ml of a solution at 55 ° C. for 1 hour immersed in the following components:

0.98 g of iron (II) ammonium sulfate He:; ahydrate,

0.44 g ascorbic acid,

15 n! 2 molar sodium acetate buffer solution *),

10 ml of water.

The sodium acetate buffer solution was made by mixing 1 liter of 2 molar aqueous sodium acetate with 300 ml Prepared 2 molar aqueous acetic acid.

The pH of the solution was kept at 5 during the treatment of the hair and the total ionic strength was 1.9.

The hair was removed from the solution after one hour and rinsed thoroughly with tap water, to then by immersion in 20 ml of aqueous 3 percent by weight hydrogen peroxide containing 0.5 molar ammonium hydroxide at 35 ° C and a pH of 10 to be bleached. After 30 minutes the fibers had the light blonde coloration that would otherwise result from bleaching that had not been pretreated for 2.5 hours Hair is achieved in the same solution. In both cases after the same, above The water retention value measured in the conventional method described was in the case of the one treated according to the invention Hair 86% and 200% for hair bleached for 2.5 hours without pretreatment.

Example 2

One gram of oriental black human hair was poured into 25 ml at 55 ° C. for 1 hour immersed in a solution of the following ingredients:

0.98 g iron (II) ammonium sulfate hexahydrate,

0.44 g ascorbic acid,

15 ml 2 molar sodium acetate buffer solution

according to example 1,
10 ml of water.

The pH of the solution was 5 throughout the immersion period, while the total ionic strength Was 1.9. The hair was then thoroughly rinsed with tap water and finally applied to the im Example 1 described way bleached.

After 30 minutes of bleaching, the pretreated hair was bleached to a blonde shade, while for bleaching oriental hair without pretreatment to achieve an equivalent Degree of bleaching required a bleaching time of 2 hours. The water retention of the latter Haars was 96% compared to 72% for the invention treated hair.

Example 3

One gram of dark brown Kaukasicr hair was removed in 25 ml of a solution at 55 ° C for 1 hour immersed in the following components:

0.49 g iron (II) ammonium sulfate hexahydrate,

0.52 g citric acid monohydrate,

20 ml 2 molar sodium acetate buffer solution

according to example 1,
5 ml of water.

The pH of the solution was 4.7 during the entire immersion time of the hair, while the Total ionic strength was 2.0. The hair was removed from the solution, rinsing it with tap water rinsed and then bleached in the manner described in Example 1. After 30 minutes it corresponded

021

099

The degree of bleaching reached the one obtained after 45 minutes under the same conditions Bleaching of untreated hair is achieved with the water retention of the latter hair 105 percent by weight compared to 75% for hair treated according to the invention.

Example 4

One gram of dark brown Caucasian hair was added soaked in 25 ml of a solution of the following ingredients at 55 ° C for 1 hour:

0.49 g iron (lI) ammonium sulfate hexaiiyurai,
0.26 g serine,

0.04 g sodium formaldehyde sulfoxy lat,
15 ml 2 molar sodium acetate buffer solution

according to example 1,
10 ml of water.

The pH of the solution was throughout Treatment of hair 5.1 while the total ionic strength was 1.6. The addition of the reducing agent Sodium formaldehyde sulfoxylate prevented the formation of iron hydroxide precipitates. The hair was then rinsed well with tap water and then bleached in the manner described in Example 1. After 30 minutes of bleaching, the fibers were light blonde in color, corresponding to a degree of bleaching of untreated hair after immersion in the bleaching solution underneath for 2 hours Conditions. The latter hair showed 180 weight percent water retention while the same value for the treated according to the invention! Hair was only 77%.

Example 5

One gram of black Oriental hair was immersed at 5O ⁰ C for one hour in 25 ml of a solution from the following substances:

0.49 g iron (II) ammonium sulfate hexahydrate,
0.10 g ethylenediamine,
0.22 g acetic acid (glacial acetic acid),
25 ml of water.

The pH of the solution was initially 5.2 but dropped to 5.0 over the course of the immersion period, while the total ionic strength of the solution was 0.5. The hair was then rinsed thoroughly with water and bleached for 30 minutes Subjected according to Example 1, after which it was bleached to the same extent as untreated hair after 1.5 hours of bleaching under the same conditions, and also lower water retention showed than the latter hair.

Similar results have been observed with the treatment of wool and other animal hair according to the US Pat Method according to the preceding examples achieved.

Claims (3)

Patent claims: 1. A process for bleaching hair or wool by treating with an aqueous peroxide solution at a pH of 8 to 11, characterized in that the hair or wool is before the actual bleaching at a temperature between room temperature and the boiling point of the solution Temperature impregnated with an aqueous solution which contains 0.05 to 0.15 mol of a soluble iron (II) salt, a soluble chelating compound, the concentration of which is 0.2 to 5 times the molar concentration of the iron (II) salt and which has a chelation constant Kma with iron (II) ions, the log Kma of which is 2 to 8, and optionally additionally contains 0.005 to 0.05 mol of a reducing agent, the total ionic strength of the solution from 0.5 to 2.5 amounts to. 2. The method according to claim 1, characterized in that an iron (II) salt solution is used, whose pH is kept at 3.5 to 6, and that the chelating compound Ascorbic acid, citric acid, ethylenediamine or serine are used. 3. The method according to claim 1, characterized in that the reducing agent used is an alkali metal formaldehyde sulfoxylate, -Sulfite or -thiosulfate used.