The subject of the invention is a process for permanent reshaping of the hair using a reducing composition and ultrasound. The invention also relates to a kit comprising a reducing composition and a device generating ultrasonic waves (ultrasound) at a predetermined frequency.
The most common technique for permanently reshaping the hair consists, in a first stage, in opening the —S—S— disulphide bonds of keratin (kerato-cystine) using a composition containing a suitable reducing agent (reduction step) and then, after having rinsed the head of hair thus treated, generally with water, in reforming said disulphide bonds, in a second stage, by applying to the hair, which has been placed under tension beforehand, for example with curlers, an oxidizing composition (oxidation step, also known as fixing step) so as to finally give the hair the desired shape. This technique thus makes it possible to make the hair wavy (permanent-wave process) and/or smooth out (straighten) the hair. The new shape imposed on the hair via a chemical treatment as above is evidently long-lasting and especially resistant to the action of washing with water or with shampoo, as opposed to simple standard techniques of temporary reshaping, such as hairsetting.
Permanent reshaping processes that are more efficient, more cosmetic and less harmful to keratin fibres and that lead to longer-lasting hair reshaping are constantly being sought.
In order to improve the performance levels of permanent reshaping processes, the compositions generally used contain large concentrations of reducing agent (s). With the same aim, a heating process during the reduction step or after the latter has also been developed, in order to increase the chemical action of the reducing agent(s). These techniques use hot air, hot steam or infrared to heat the hair fixed on a roller or a curler, which may itself be heated.
It has been observed that these technologies do not lead to a significant improvement in terms of production and longevity of the hair reshaping, for instance curls, when compared with the standard techniques at ambient temperature. Furthermore, the treated hair shows substantial degradation, which hinders users from performing repeated hair treatments, such as successive permanent-waving operations or smoothing-out (straightening) operations or a combination of permanent-waving and dyeing, for example.
The problem addressed by the invention is that of finding a process for permanent reshaping of the hair which provides, compared with the prior art processes:
curls of improved shape and liveliness in the case of permanent-waving,
an improved reduction in volume in the case of hair straightening,
less degradation of the fibre, in particular with successive applications and in combination with other chemical treatments such as oxidation dyeing,
a longer lasting artificial shape in the face of various attacks (shampooing, blow drying, UV exposure, etc.),
a satisfactory cosmetic aspect after treatment,
results of hairsetting more readily predictable according to the nature and the state of degradation of the hair to be treated.
Thus, the invention relates to a process for permanent reshaping of keratin fibres, in particular of the hair, comprising:
a) a step of applying, to the keratin fibres, a reducing composition containing one or more reducing agents chosen from non-sulphur-containing reducing agents, protective thiols, sulphites, bisulphites or derivatives of sulphinic acid,
b) an optional step of rinsing said fibres, then
c) an optional step of fixing by oxidation, characterized in that the process comprises a step d) of applying, to the keratin fibres, ultrasonic waves delivered by a generator supplying mechanical vibrations of which the frequency is between 20 kHz and 1000 kHz, step d) being carried out after or during step a), it being possible for the process to optionally comprise a step e) of placing the keratin fibres under mechanical tension by means of a device capable of imposing a shape on said fibres.
The expression “process for permanent reshaping of keratin fibres” is intended to mean processes for permanent-waving, smoothing or relaxing of keratin fibres.
The invention also relates to a kit.
Other characteristics, aspects, subjects and advantages of the present invention will be more clearly apparent on reading the description which follows.
During step e), the placing of the keratin fibres under mechanical tension can be done over the entire length of the hair or at mid-length on long hair. Depending on the shape of the hairstyle, the hair shaping can be carried out with more or less thick locks.
According to a first embodiment of the process according to the invention, the device of step e) which imposes the desired shape on the hair also emits the ultrasonic waves of step d). In this case, the device of step e) comprises a generator supplying mechanical vibrations of which the frequency is between 20 kHz and 1000 kHz, so as to produce the ultrasound. It also has one or more means capable of imposing a shape on the hair.
According to this first variant of the invention, mention may be made, as a device for placing under mechanical tension of step e) comprising a generator of ultrasonic waves, of ultrasound-emitting curlers, ultrasound-emitting straightening tongs or ultrasound-emitting curling tongs.
According to a second embodiment of the process according to the invention, the device of step e) which imposes the desired shape on the hair and that of step d) which emits ultrasound are distinct devices.
In this case, the device for placing under mechanical tension of step e) may be a curler, straightening tongs or curling tongs. The generator of step d) can be a fixed or portable device which delivers ultrasound and which is, if possible, readily positionable on a head of hair or a curler.
If it is a fixed device delivering ultrasound, it can be a hood or a bonnet.
If it is a portable device delivering ultrasound, it can be a probe or a gun.
Step a) of applying, to the keratin fibres, a reducing composition so as to reduce the disulphide bonds of keratin can be followed by an optional leave-in time.
According to one variant of the process according to the invention, step a) of applying, to the keratin fibres, the reducing composition can precede step e) of placing the keratin fibres under mechanical tension, with or without a leave-in time. In this case, the reducing step is carried out with the fibres in the original form, i.e. on fibres not placed under tension.
Advantageously, the pH of the reducing composition according to the invention is between 2 and 13.
The pH of the reducing composition according to the invention is preferably between 7 and 11.
The reducing composition used in the process according to the invention comprises, in a cosmetically acceptable medium, one or more reducing agents, said reducing agent(s) being chosen from non-sulphur-containing reducing agents or protective thiols, sulphites, bisulphites or derivatives of sulphinic acid.