NO132920B - - Google Patents

Description

As is known, Keratinholdice materials can be modified in terms of their chemical and/or physical properties by suitable treatment, e.g. treatment of human hair to achieve permanent curls or other conditioning, and the suitable techniques are extensively described in the literature, including the patent literature. For curling human hair, the usual treatments thus include an initial impregnation of the hair with a suitable reducing solution to thereby deposit pre-determined amounts of reducing agent on the individual hair fibers. The hair is then chemically and/or physically modified by treating it in a known manner with a suitable bleaching solution.

The materials which are necessary for carrying out such methods are well known and commercially available in a number of different forms. In spite of the fact that methods of the above-mentioned type are used extensively on a technical scale, these methods have nevertheless in practice been shown to be affected by one or more disadvantages which considerably reduce their commercial acceptability. The biggest objection is perhaps that such methods do not provide a finished hair with optimal shape stability and hygroscopicity etc., as the latter desirable property is of the greatest importance for achieving optimal hair flexibility without unwanted frizziness and hardness etc. Other disadvantages of the known hair treatment methods include e.g. the desired tendency to produce a hair product with poorer fullness, thickness and shine, etc.'' to deposited films that have too poor adhesion, as the deposited top film has a strong and unwanted tendency to flake off, dry to a hard spreading deposit and/or discolor hairÆ>- It will be easily understood that one. or more of the above-mentioned disadvantages will be sufficient to exclude any possible

in order to achieve "the desired shiny appearance.

Other disadvantages associated with the use of the currently commercially available hair conditioning preparations include their strong tendency to damage or otherwise adversely affect the structural unity of the keratin fiber itself, i.e. strength properties, e.g. elastic properties and tensile strength. etc. It may well turn out that deficiencies in this area will be unacceptable - only because the effects of this always show up in the form of dull, lifeless hair that is difficult to care for. In some cases it has been shown that the hair's color absorption properties are adversely affected by a given conditioning treatment. It will be understood that the final requirements for a given hair conditioning treatment can vary considerably. The treatment in question can thus be mainly adapted for curling the hair, or such a treatment can conversely be intended to promote a selective improvement of one or more of such properties as tensile strength, elasticity, color receptivity, fullness and thickness etc.

Because of the above, a considerable amount of industrial activity has been centered around research and. development of methods and preparations which are particularly advantageously suitable for use in connection with methods for obtaining. of dnskede: changes in the properties of hair. It has now been shown that one or more properties of hair can be synergistically modified in accordance with pre-set requirements by methods and the use of special preparations which will be described in more detail.

In the present method, hair is treated to give it a desired physical shape, and the method is characterized by the fact that the hair is treated with a reducing agent to convert at least part of the disulfide bonds present in the hair into sulfhydryl bonds, the remaining reducing agent is removed from the hair by rinsing, the hair is treated with an oxidizing aqueous solution comprising a) a peroxide catalyst material capable of liberating free radicals in the presence of sulfbydryl, the free radicals also being capable of initiating the polymerization of monomers and b) a monora- , compound containing at least one group with the formula

CH2 = Cd and which can be polymerized in the presence of the peroxy initiator, whereby the monomer is graft polymerized on the hair which is then rinsed to remove unreacted monomer and initiator, given the desired physical form in the wet state^and-dried with the desired physical form.

Experimental results have indicated that a polymerization reaction occurs which. a result of the mutual and "in-time contact between peroxide, initiator", monomer and reduced keratin in the hair, the latter leading to a strong formation of a number of "active" sites in the form of reduced disulphide, i.e. sulfhydryl groups .

It will be understood that the disulphide bonds present in the hair comprise reducible groups that can be converted to sulphydryl in the presence of relatively strong reducing agents* such as thio-glycolic acid. The sulfhydryl groups formed due to the reduction treatment are strongly inclined to react with peroxydinitiator compounds with the simultaneous formation in situ of free radicals which are effective agents for initiating the polymerization of monomers of the aforementioned type. The main part of the initiation of

.the monomer polymerization and its propagation are limited to the reduction centers present in the hair. In this way, the polymer formed which is graft polymerized on the hair will be truly integrated with the fiber both chemically and physically. It is of course recognized that it has previously been proposed to treat keratin-containing substrates, such as wool, with a monomer solution in the presence of a redox catalyst system which is able to release free radicals under the treatment conditions, the treatment being stated to give the substrate one or several desirable characteristics. However, the present method is very different compared to the previously used methods in a number of crucial respects.

For an effective practical implementation of the present method, it is thus necessary that the reduction treatment is sufficiently strong that a substantial reduction of the keratin-containing hair will be achieved, i.e. that the degree of conversion of the disulphide bonds to sulfhydryl groups must be sufficient for the desired modification of the keratin substance by the subsequent treatment with the oxidizing solution will be achieved. The above is different from the usual treatments which provide a simple impregnation of the hair fibers with the reducing agent. By these latter methods opnlsV ihgeiri'. chemical reduction of the keratin substance, as such treatment is exclusive. designed to deposit a sufficient quantity of reducing agents on the hair to react with the subsequently applied oxidizing solution. The keratin substance therefore remains chemically largely unaffected by the reducing solution, as the keratin mainly serves as carrier material. When using such methods, the catalyst-containing monomer solution introduced at a later stage during the treatment will thus react with the reducing agent itself and not with the keratin substance, and the oxidation-reduction reaction is limited to the parts of the hair that contain the previously deposited reducing solution. In contrast, the reduction treatment according to the present method achieves a chemical modification of the keratin substance, i.e. reduction of the disulphide to mercaptan. The hair itself therefore acts as the reducing component in the redox catalyst system which is capable of releasing free radicals . such in the hair. The importance of rinsing as a critical step of the present process will be apparent from what follows. It will be understood that when the reducing agent is applied, it will tend to penetrate the entire volume occupied by the keratin substance.

In connection with hair, the reducing solution will thus be deposited to a large extent in the free spaces or spaces between the individual . hair fibers in the hair, and more particularly at or near the surface of the fiber. The extent of the accumulation of reducing agent in such areas will of course depend. a number of factors, including the amount of reducing solution used, the conditions during treatment, e.g. time and temperature etc, and the condition of the keratin substance, i.e. the porosity etc. It will be easily understood that when the initiator monomer solution comes into contact with the keratin-containing hair under conditions which promote the polymerization of vinyl monomers, the polymer-forming reaction will not in any way be limited to the immediate surroundings of the hair fibers, but will naturally proceed unhindered in the areas indicated above with free space due to the presence of abundant amounts of reducing agent. This leads to the highly undesirable condition known as "solution polymerization". In connection with hair, a solution polymerization can thus lead to an uncontrolled intertwining of the hair fibers with the formation of knots, tangles and other irregularities which greatly hinder rapid drying of the hair. The last listed disadvantages are of course completely avoided by using the present method. The necessary use of an intermediate rinse to thereby completely remove the reducing agent from the keratin-containing hair being treated, thus ensures that no significant solution polymerization occurs, since the polymerization is essentially limited to the hair fibers. This result must necessarily be achieved because each individual reduced hair fiber provides a site for the formation in situ of the polymerization-initiating free radicals, whereby the polymerization takes place "inside" the hair fibers as opposed to "outside".

Although any of the reducing agents commonly used for the treatment of keratin-containing hair can be used with advantage in the present method, particularly good results have been achieved with reducing agents of the more active type. Strong reducing agents are preferred as they make an economically more acceptable design in practice and a better quality control possible. When using stronger reducing agents, it is thus unnecessary to use long treatment times with the reducing agent, while at the same time a significant reduction of the hair is achieved.

In addition to eliminating any possibility of substantial solution polymerization, the present method makes it possible to achieve an increased absorption of polymer compared to known methods.

< When applying the present method, it is thus possible in a shorter time to easily achieve an increase in the amount of polymer that can be graft polymerized to the hair. More particularly, with the present graft polymerization, at least a 10-fold increase in the amount of graft polymer can be very easily achieved compared to

known methods which are carried out under similar conditions. It is of the greatest importance, and perhaps the most prominent feature of the present method, that the hair treatment can be carried out at, say, low temperatures such as only 18 24° C°. For the sake of comparison, it can be mentioned that by effective utilization in practice of the . known methods. it is always necessary to use very high temperatures of at least approx. 60° C. The necessity of this high temperature actually apparently constitutes a limitation of the applicability of such methods when attempts to carry out such

processes at temperatures significantly lower than 60° C have failed due to the fact that some polymer-forming reaction occurs to a practically acceptable extent. ' "'"^ ';.

It will be required to reorganize as necessary, including the use of a reduction step, such as the first step. This "special order -is necessary^because thev.keratinous

'must act' as a fedex agent during the oxidation or polymerization phase; - in contrast to this, with the known methods it is possible to greatly vary the order of treatment in such a way that the oxidation step can be carried out before reducing the ion without in any way making it possible or in any other way unfavorable ..to- influence .the purposes of the processing. An initial oxidation is in some cases actually a preferred embodiment. - This situation serves to underline the relatively low importance of the keratin-containing substrate's effect. such known methods. It will be easily understood that the keratin-containing substrate is inert and only serves as a carrier material for the reducing or oxidizing solution and that. it does not in any way actively take part in the redox reaction that leads to the formation of free radicals. The substrate only constitutes the material to be affected by the redox treatment. In contrast, in the present process, the keratin substrate in the form of hair has a dual function, i.e. (1) as a reducing agent and (2) as the material to be modified.

As stated above, the present method essentially consists of three basic steps which are carried out one after the other and which can be described as (1) reduction, . (2) 'rinsing and (3) oxidation. In order to facilitate an understanding of these crucial aspects of the present method, each of these steps will be dealt with in more detail. 1. Reduction ~''" 1 vi ■ ■■ ■■■■. r: The reduction of the keratin-containing hair can be carried out using any, any for such purposes as^ suitable ' '•■ recognized reducing agents .t These materials are, of course, well-known, and it should therefore not be necessary to provide a list of suitable materials. It is sufficient to state that the specially chosen reducing agent must be used under such conditions that a substantial reduction of the keratin-containing substance in the hair is ensured. 'Suitable materials thus include water-soluble

even salts, e.g. sodium thioglycolate and ammonium thioglycolate, etc., alkali metal bisulfites, e.g. sodium bisulfite, potassium bisulfite and ammonium bisulfite, etc., water-soluble salts of thioglycerol and trihydroxymethylphosphine which can also be formed in situ from tetrahydrokis-hydroxymethylphosphbnium chloride, etc. As stated above, preferred the use - strong reducing agents. However, this is essentially based on considerations in connection with the practical implementation of the present method, such as e.g. a reduction in treatment time. Weaker reducing agents can thus be used, but the use of such materials leads to correspondingly longer treatment times for achieving the desired degree of reduction of keratin substances. The reducing agent can be used in the form of a simple aqueous solution or in a system of a mixture of water-miscible organic solvents, such as monohydric and polyhydric alcohols, e.g. methanol, ethanol, propanol, isopropanol, n-butanol, ethylene glycol and 1,2-propylene glycol etc, and ether glycols, e.g. ethylene glycol monomethyl ether etc. The choice of a particular solvent system is to some extent dependent on the type of reducing agent used.

It is thus, in connection with the above-mentioned reducing agents, generally advantageous to use systems of mixed solvents with e.g. bisulphite compounds, while simple aqueous solutions are sufficient for the thioglycolate derivatives. The relative amounts of the water-miscible organic solvent are not particularly critical, with the exception that it is necessary that such a material be used in a sufficient amount

to promote the solubility of the monomer and/or the catalyst in the reaction medium. An excess of organic solvent should, however, be avoided in connection with water-insoluble monomers soluble in organic solvents in order to make the problems associated with a contact between monomer, keratin and initiator as small as possible. A concentration of such materials below approx.

75%. Increasing concentrations of organic solvent lead to '

as a rule, to a lower polymer absorption in the hair when treated with the oxidizing, monomer-containing solution. This may be due to one or a number of factors. It will be understood that a part of the amount of solvent which is used for the reduction is retained.

in the hair despite the use of an intermediate rinse step. An application of the "reducing" solvent system in which the later introduced monomer component has a relatively unlimited solubility can thus serve to effectively reduce the rate at which the hair takes up polymer, as the monomer's affinity for the solvent is greater than its affinity for the hair. In connection with the above-mentioned solvents, it has been shown that the lower alkanols, such as e.g. methyl alcohol, give special advantages when used in the present method. An optimal realization of the advantages which it is possible to achieve by the present method can in all cases be achieved by using the water-miscible organic solvent in a concentration of up to approx. 50% by weight of the solution with the remainder water, i.e. 0 - 50% by weight*, with a range of 20-45% by weight being particularly preferred. It is also recommended to use a reducing solution which is essentially saturated with reducing agent, as experiments have shown that the uptake rate for polymer is increased with increasing concentration of reducing agent, whereby optimal results are achieved when using saturated solutions. The required amount of reducing agent for a saturated solution will of course mainly depend on its solubility in the solvent system used. Such limiting data for the solubility can easily be derived for a given case by routine laboratory investigations.

The concentration of the reducing agent used can vary within relatively wide limits depending, among other things, on the reducing power of such a material. Water-soluble salts of thio-glycolic acid, e.g. ammonium thioglycolate, can e.g. used with good results in concentrations of approx. 6% by weight of solutions, whereby a pH of approx. 9. Solutions of thioglycolate derivatives can be prepared easily and simply by e.g. to dilute 98% thioglycolic acid with water and then increase the pH by adding concentrated ammonium hydroxide. Sodium bisulphite is a somewhat weaker reducing agent, and in order to achieve good results it is therefore necessary to use this material in somewhat larger concentrations. In all cases, it has been shown that advantageous results can be obtained by using a reducing agent in a concentration of 1 to 20% by weight of the solution, preferably 3-20% by weight. By. application of bisulphite, it is generally preferred that the solution has a slightly acidic pH, i.e. that too strong an acidity should be avoided.

As stated above, the duration of the reduction treatment will vary depending on a number of factors, including the reducing solvent concentration and the type and extent of the hair being treated, etc. In all cases, it has been shown that reduction times of approx. 30 min. is very well suited for achieving the objectives of the present method. This, of course, means that the reduction treatment must be sufficient to provide the desired degree of disulphide reduction in the hair.

The reducing solution may also contain varying amounts of one or more added ingredients of any kind to increase or otherwise promote the overall properties of the reducing solution. Moisturizers can thus e.g. be introduced to reduce the surface tension at the interface between the hair and the reducing solution. thereby promoting penetration of the reducing solution into the hair fibres. The surface-active materials preferred for these purposes include the non-ionic materials, i.e. of the polyoxyalkylated type, although it has been shown that certain anionic materials, e.g. sulphonates, can also be used with advantage.

The total volume of the reducing solution used for treatment will also vary again depending on such factors as the concentration and activity of the solution and the type of hair etc. The optimal amounts of the reducing solution can in any case be easily determined for a given case by routine examination.

2. Rinsing

After the reduction described above is over, the hair is rinsed well to ensure a substantially complete removal of the remaining, unreacted reducing agent. This can be achieved simply by washing with water. There is no particular difficulty associated with this step as the reducing agents, which are water-soluble, can be easily removed by rinsing with water. However, it should be emphasized again that the rinsing itself, although it is easy to carry out, nevertheless represents a very critical and important phase of the overall procedure as the effectiveness of the entire treatment strongly depends on the denrie. As indicated above, the main purpose of the rinsing is to remove or greatly reduce any possibility of polymerization taking place to any significant extent within the interstices or voids x the hair. In this way the difficulties associated with unwanted interlocking, tangling and knotting etc. in the hair are avoided 3. Oxidation '••

The third step of the present method consists of an oxidation. The essential components in the oxidizing solution used for the treatment of the hair include monomer and peroxide initiator which release free radicals. The type of monomer used must satisfy the natural requirement that the polymerized material obtained from it must be harmless to the general environment including hair and skin. The monomer component can be selected from a relatively large number of monomers which can be polymerized in the presence of a catalyst which releases free radicals. The monomer must contain at least one group with the formula:

Both mono- and polyethylenically unsaturated compounds can therefore be used. Such monomer materials can also, for simplicity, be represented by the following structural formula:

r

where R is hydrogen or lower alkyl with 1-4 carbon atoms, e.g. methyl, ethyl, propyl, butyl and isobutyl, and R-^ is (a) carbaloxy, i.e. -COOR2 where R2 is hydrogen, alkyl containing 1 - 20 carbon atoms, e.g. methyl, ethyl, n-pentyl, octyl, lauryl and stearyl, alkenyl containing 3 - 10 carbon atoms, e.g. allyl, 3,4-butenyl, 2,3-:butenyl, 5,6-hexenyl and 2,3-hexenyl, hydroxyalkyl containing 2-10 carbon atoms, e.g. 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl, 2,3-dihydroxypropyl, 2f4-dihydroxybutyl and 4,6-dihydroxyhetyl, alkyl and dialkylamino-alkyl where each alkyl group preferably contains 1-4 carbon atoms, e.g. 2-N-methylaminoethy1, 2-N,N-dimethylaminoeth/L, t-rbutylaminoethyl, 2-N,Nr-.dimethylaminoethyl and 37-:N,N-diisobutyl-aminopropyl, haloalkyl containing 1 -r 10 carbon atoms, e.g. e.g. hexafluoroisopropyl, perfluoroethyl, perfluoropropyl, 2-difluoropropyl, 2-chloroethyl, 2-chloropropyl and 1,1,9-trihydroperfluorononyl methacrylate, neighboring epoxy-alkyl containing 3"r-6 carbon atoms, e.g.

glycidyl, 3,4-epoxybutyl, 4,5-epoxypentyl and 2,3-epoxyhutyl,

(b) amide groups comprising both substituted and unsubstituted

forms and with the following structural formula:

where R 3 and R 1 are hydrogen, alkyl and preferably lower alkyl or alternatively can denote the atoms necessary for the completion of a polyunsaturated molecule, such as: where R 5 is an alkylene radical containing preferably 1 -. 4 carbon atoms, such as methylene, ethylene, propylene and butylene, (c) halogen atom, such as chlorine and bromine, (d) an alkoxy group, e.g. methoxy, ethoxy and cyclohexoxy, (e) a cyano group, i.e. the group -C=N and (f) an alkenylaryl group where the alkenyl group contains 1-4 carbon atoms, i.e. lower alkenyl, e.g. the o, m or p form of

The above-mentioned mohomer materials can also be used in the form of their salts, e.g. salts with cations that promote solubility in water. For acrylic acid or methacrylic acid, the monomer material can thus be converted into a suitable salt form, e.g. calcium acrylate, i.e. (CH2=CH-COO )2Cå++, sodium acrylate, potassium acrylate and calcium methacrylate.

As examples of monomer materials that can be used in the present method, the following can be mentioned: methyl methacrylate, ethyl acrylate, butyl methacrylate, n-hexyl methacrylate, iso-octyl methacrylate, allyl methacrylate, 3,4-epoxybutyl acrylate, methyl acrylate, allyl acrylate, 5,5- hexenyl acrylate, lauryl methacrylate, octadecyImethacrylate, 2-hydroxypropyl methacrylate, 2,5-butylamino-ethyl acrylate, ethylene glycol monomethacrylate, hexafluoroisopropyl, acrylate, perfluoroethyl acrylate, methacrylic acid, acrylic acid, 2-di-methylamino-ethyl methacrylate, methacrylamide, acrylamide, 1,2-propylene chloride, vinyl chloride, vinylbrpmid, vinylfluoride, N,N-diethylmethacrylamide, N,N^-methylene-bis~-acrylamide, acrylonitrile, methylvinylether, isobutylvinylether.,. m.ethylisopropenyl ether, divinylbenzene, itaconic acid or itaconic anhydride.

When using polyfunctional monomer materials, e.g. allyl methacrylate and divinylbenzene, it will be understood that considerable cross-linking can occur in addition to the dominant graft copolymerization during the oxidation of the hair. This is because monomer materials of this type have more than one group which is capable of polymerisation under the reaction conditions used. It will also be understood that the monomer materials used in the present method can be used alone or in a mixture of two or more. The choice of the special monomer systems will mainly depend on the user's requirements in connection with the special desired properties for the finished hair and the monomer's reactivity etc.

The oxidizing solution used according to the invention also contains as a critical component a peroxydinitator material or catalyst which is able to release free radicals and initiate the polymerization of the monomer in the presence of the reducing agent, i.e. mercaptan. The suitable initiator materials for these purposes are well known in the art and have been extensively described in the published x literature and include both the organic and inorganic peroxides, hydroperoxides and peracids etc., and the water-soluble salts thereof. Special examples of suitable initiators are cumene hydroperoxide, hydrogen peroxide, barium peroxide, benzoyl peroxide, acetyl peroxide, tert.butyl hydroperoxide, alkali metal salts of organic hydroperoxides and alkali metal salts of peracids such as peracetic acid, perbenzoic acid and persulfuric acid. the speed of monomer uptake can be achieved by using initiator compounds which are soluble in organic solvents, such as cumene hydroperoxide, which of course is insoluble in water. Although somewhat worse results are obtained in processes where water-soluble peroxygen compounds are used and materials soluble in organic solvents, such methods have nevertheless proved to be very satisfactory.

The initiator material and the monomer material can be formed using simple aqueous solutions or mixed solvents of the systernide type and the relative amount of the solvent used depends on the solubility properties of the monomer and the catalyst component. The solvent used should generally comprise 10-9% by weight of water, the rest being j;Sres of a water-miscible organic solvent. looking. n lower alkanol, e.g. ethanol, n-rpropanol, isopropanol and n-butanol, et-ketone, e.g. acetone, glycols, e.g. ethylene glycol and propylene glycol, ethers, e.g. glycol ethers such as -ethylene glycol monomethyl ether, and similar materials. Within the above-mentioned area, the selection of the particular amounts of organic solvent will, among other things, be dependent on how hydrophobic the monomer component is. A use of strongly hydrophobic monomer materials, either alone or in a mixture, can thus make it necessary to use increased amounts of organic solvent to facilitate the achievement of a uniform and homogeneous dispersion of the relevant monomer and catalyst component. For the same reason, the use of a hydrophilic monomer component can similarly do so. necessary to use increased amounts of water.

Regardless of the type of monomer material used, a further and important consideration must be made when producing the oxidizing monomer solution. It will be understood that the effectiveness of the overall "method is critically dependent - on a good contact being achieved between the components of the oxidizing solution and the mass comprising the reduced hair. It should therefore be ensured during the treatment that conditions are used which promote such contact to ensure optimal results. The relative amounts of a<y> the solvent used in the preparation of the oxidizing solution should therefore be chosen so as to obtain an agent in which the monomer material can easily react with the hair under the conditions used for the treatment. It is recommended thus, as a general rule in practice as organic solvents one or more of the lower alkanols of the above-mentioned type are used as such solvents have been shown to ensure optimal results. In contrast, solvents of the ether type, and especially of the ether-glycol type , e.g. ethylene glycol monomethyl ether, somewhat worse and leads to reduced speeds for, the uptake of monomer. However, this situation should not be interpreted to mean that the use of the latter solvents is excluded by the present method, as special circumstances may indicate that something is beneficial: reduced speeds for the graft polymerization. These conditions are again mainly left to the user to decide.

The oxidizing solution can likewise be used in the form of a suitable dispersion, suspension or emulsion etc. depending on the solubility properties of the monomer used. This can easily be achieved by using suitable suspending agents or emulsifying agents, etc., and the special additives effective for such purposes are well known in the art. The form in which the mono-jnrier is used, i.e. as an emulsion or solution etc., is in reality of secondary importance as the main requirement is that such a material should be available for trading with the reduced hair. For this purpose, the mpmoner can be used in a number of different forms as long as the conditions are such that there is an effective contact between monomer and hair.

The relative amounts of the monomer and catalyst used for the preparation of the oxidizing solution are not decisive factors for the implementation of the present method in practice. It is thus only necessary to use the monomer material in a sufficient amount so that the desired degree of reaction with the hair will be achieved, and the concentration of the catalyst material similarly only needs to be sufficient to give the desired reaction rate for the polymerization. The monomer concentration will thus be increased in those cases where it is desirable to use one

strong degree of reduction, and conversely, the requirements placed on the monomer can be reduced if a lower degree of reduction is desired.

It will be understood that in cases where the monomer material is used in liquid form, e.g. methyl methacrylate, the oxidizing solution can simply comprise the monomer and the catalyst. The monomer material can thus be used in a concentration of 1 - 99% by weight, preferably 5 - 30% by weight, of the overall oxidizing solution. The quantity of the catalyst material can likewise vary within wide limits with a range for the molar ratio between catalyst and monomer of 0.001:1 - 5:1, with a range of 1:10 - 1:2 being preferred. Within the above-mentioned area, the specially selected me ... will depend -on a number of factors including e.g. - the reactivity of the monomer material, its concentration, and the desired degree of thiol conversion. The optimal parameters in this connection can in all cases be easily determined for a given case by routine examination.

The duration of the treatment with the oxidizing solution is usually between 30 minutes and 2 hours to achieve a strong modification of the hair. In most cases, it has been shown that oxidation times of the order of 30 minutes are sufficient for the desired reaction to take place. The optimal reaction time for a given case will again depend on the reactivity of the monomer component and the desired degree of modification of the resin etc. However, one of the important features of the present invention is that advantageous results can be obtained when the oxidizing treatment is carried out at room temperature. In contrast to this, the known methods which have been promoted for the treatment of keratin-containing substrates always require relatively high temperatures to be used, i.e. of the order of at least 60° C, in order to achieve it. desired degree of modification of the substrate at treatment times that are acceptable in practice. One of the truly surprising features of the present invention is thus connected with the discovery that an effective modification of the hair can be achieved even by using very mild temperature conditions, i.e. room temperature, and treatment times of the order of only 30 minutes. The importance of this particular feature of the present invention becomes clear when it is taken into account that the possibility of damaging the hair increases considerably as the treatment conditions become more powerful, and especially as the temperature is increased. The relatively low temperatures that are characteristic of the present method involve little or no risk of damage to the hair.

As is known, keratin-containing substrates are among the proteins that contain large amounts of chemically bound sulfur that is present in the protein molecule in the form of disulphide, which is also referred to as cystine bonds. The keratin molecule thus contains amino acids connected to each other by amide groups to form long-chain structures known as polypeptides, which in turn are interconnected by disulphide bonds. Treatment of such a material with a reducing agent thus leads to a conversion of the disulphide bond, i.e. the -S-S bond, into two thiol groups which are bound to a polypeptide chain.

The reaction mechanism that leads to the formation of the free radicals that are able to initiate the polymerization can be represented by the following equation:

where K are polypeptide chains and R a C-rgnnic group which can be u,. 2l or an aliphatic group, e.g. tert.butyl. The graft polymerization is initiated by the free radicals that are formed in situ in the keratinous mass of the hair. -The polymer formed by the action of the RO* radicals can, however, also be grafted by final reaction onto the functional groups present in the keratin-containing material. The polymerization of monomers can of course be carried out by an addition reaction with the double bond present in the monomer molecule. The polymerization can be easily started by simply adding effective amounts of a suitable initiator, i.e. polymerization catalyst, which is capable of liberating groups that can start the polymerization under the conditions found in the reaction medium. The reaction sequence that leads to initiation of the monomer polymerization by free radical polymerization can be represented as follows: In the above equations, R is a free radical formed by cleavage of the initiator, M the monomer material and M is a polymer chain with a reactive end part. The macroradical formed can be "frozen", i.e. rendered unreactive, by reaction with another poly;per radical by a mechanism commonly referred to as "combination-termination", by oxidation-reduction with a radical and which leads to the formation of a double bond at the end of the chain by a mechanism termed "disproportionation termination", by reaction with a solvent molecule (transfer to the solvent) or by reaction with another additive material containing labile hydrogen atoms, e.g. amines, mercaptans and alcohols etc, and these materials are well known as "chain regulators". With special reference to the reaction mechanism which is characteristic of the oxidation treatment carried out in the present method, the peroxide catalyst material is thus released in the presence of mercaptan and, under the treatment conditions, polymerization-initiating free radicals on the keratin-containing mass,

As the free radicals thus formed in situ in turn react with the monomer, whereby the polymer-forming reaction is set in motion. A preferential internal polymerization occurs because the initiator and monomer are consumed as soon as they penetrate into the keratin-containing mass. The initiator is thus essentially consumed immediately due to the formation of free radicals which are due to the initiator reacting with the reduction sites, i.e. in the keratin-containing material present mercaptogroup j" méns<;>c >the monomer. are consumed essentially simultaneously due to"'at'.' therein reacts with the thus formed free radicals. "The concentration'"* !'":" 3v, the internal solution therefore stays low in comparison to''* jried the concentration of the external solution, whereby a reaction scheme is obtained which is highly self-controlling. - .-As the initiation step consists of an exothermic reaction , the grafting polymerization can easily be achieved at or under room temperature. Furthermore, since each individual hair fiber that makes up the keratin-containing mass acts as an initiator, i.e., reducing agent, the polymerization takes place inside rather than outside the keratin-containing mass.

It has also been shown that improved synergistic results can be achieved by carrying out the polymerization phase, i.e. the monomer treatment or the treatment with the oxidizing solution, in the presence of a promoter which acts to to improve the speed fe: the graft polymerization..

The promoters are water-soluble halide salts, i.e. a salt of bromine and chlorine, etc. with a water-solubilizing cation, such as an alkali metal, e.g. lithium,. sodium and potassium'"'etc '.■, "ammd-■ •■ '■' nium, substituted ammonium, - i.e. where one or more hydrogen atoms have been replaced by alkyl or hydroxyalkyl etc.

The type of the water-solubilizing cation is not of particular importance, as the most important requirement for this is that it should not tend to adversely affect the hair or its immediate surroundings. As special examples of water-soluble halides which have proven to be very well suited for use in the present method, e.g. mention is made of lithium bromide, lithium chloride, sodium bromide, sodium chloride", potassium bromide, potassium chloride, ammonium bromide and ammonium chloride. The bromides and chlorides mentioned above are characterized by the fact that they are very strongly able to increase the achievable speed of the graft polymerization.. A the use of the halide salt in relatively small amounts will therefore still make it possible to achieve several times the rapid reduction of the ion, whereby it is impossible for a single treatment time to rinsing polymerise increased amounts of polymer. The concentration of the halide used can also be varied within relatively wide limits. As a rule, it will appear that beyond certain concentrations an increase in the quantity of the halide used will not lead to any corresponding increase in the rate of the graft polymerization, i.e. that the additional effect obtained by using the halide compound tends to decrease with increasing concentrations thereof. However, a considerable increase in the speed of the graft polymerization can always be achieved by using the halide salt in a concentration of 0.025 ~ 40, preferably 4 - 10, mol/mol monomers. The halogen ion apparently contributes effectively to the reaction mechanism which leads to the formation and release of x rie radicals. The halide salt, e.g. lithium bromide, thus occurs to react with the peroxide catalyst material, e.g. potassium uroparsulphate,. during the release of free radicals in accordance with the following reaction sequence:

In the presence of reduced hair fibers, chain transfer can take place by the following reactions:

Experiments have also indicated that the very strong increase in the rate for the graft copolymerization cannot be explained simply by reference to the above. The presence of the halide compound appears to promote a swelling of the keratin mass in the hair fibres. and favoring the absorption of peroxide catalyst and monomer in accordance with concentration effects.

Example 1 - 16

As stated above, there are a number of factors that have a considerable influence on the effectiveness of the treatment with the reducing solution, i.e. expressed by the ability of the thus treated liå,r to take up monomer during the oxidation step. This is shown in these examples where human hair was treated. In each case, the reduction treatment was carried out at room temperature for up to 30 minutes using approx. 20 ml reduction solution per grams of hair. After the reduction treatment was over, the hair sample was thoroughly rinsed to completely remove residual redux ion solution'. Oxidation treatment was then carried out using a solution consisting of 12.0% methyl methacrylate monomer, 5.0% cumene hydroperoxide catalyst and 41.0% ethyl alcohol with the balance being water. The hair sample selected for treatment was in each case weighed before and after the treatment, and the difference represented the weight gain, i.e. the degree of graft polymerization.

It will be apparent from the above data that there is only an insignificant difference between the results when using reducing solutions containing 15% bisulphite in a solvent mixture of ethanol (38%) and water and a solution containing 5% sodium bisulphite in a solvent mixture of . ethanol (45%) and water. The amounts of grafted polymer in corresponding times are thus approximately the same, perhaps with a slight increase in the uptake of polymer when treated for 20 minutes with the more concentrated solution. This can be explained by reference to the fact that all the solutions were saturated with sodium bisulphite. It will also appear that a reduction solution comprising 5% sodium bisulphite in a mixture of ethylene glycol monomethyl ether (69 %) and water gave significantly worse results. This discrepancy between the effects is presumably due to the fact that the ethylene glycol monomethyl ether contained a poorer utfelingsmiddr1. Moreover, the solution used in this particular case was not saturated. The above results therefore suggest that better podnir.gr rates are obtained when using reducing solutions with a concentration of reducing agent approaching saturation points while using solvents that act as satisfactory precipitating agents. The data given in connection with a reducing solution of ammonium thioglycollate clearly show that increased grafting rates can be achieved by using reducing agents of the very strong type. As is known, the thioglycollates have a relatively strong reducing ability compared with bisulphite materials D a several-fold increase in the rates of the graft polymerization can thus be achieved simply by a critical choice of reducing agent. More specifically, in a reduction time of 10 minutes using an ammonium thioglycollate solution, 22.25% by weight of the polymer was grafted onto the hair sample compared to a polymer grafting of 5.0% and 3.47%, respectively, when treated with bisulfite.

An increase in the treatment time with the oxidizing solution usually leads to a corresponding gradual increase in the grafted polymer amount. This is shown in the following examples relating to the results obtained by treating human hair with methyl methacrylate.

In each of the examples, reduction treatment was carried out using a 6% solution of ammonium thioglycolate with a pH of 9 and a treatment time of 10 minutes. The reducing solution was used in each case with a volume of approx. 20 ml/g hair sample that was treated. After the reduction treatment was over, the hair sample was thoroughly rinsed to completely remove the remaining reducer solution. In each of the experiments, the treatment with the oxidizing solution was carried out for 30 minutes at room temperature using 20 ml of the oxidizing solution per g hair sample.

- The results obtained are reproduced in table 2.

The data given above suggest that the relationship between grafting time and the percentage graft polymerization is not necessarily linear, i.e. that the increase in the amount of grafted polymer is not necessarily directly proportional to the increase in treatment time. An increase in the grafting time from e.g. 5 to 10 minutes thus gives a corresponding 3-fold increase in the grafted polymer quantity. It will also appear that a 6-fold increase in the grafting time, i.e. from 5 to 30 minutes, leads to an approximate 8-fold increase in the amount of grafted polymer. It will be readily apparent that considerable amounts of polymer are effectively grafted onto the hair sample during the treatment despite the use of the relatively low room temperature. It will also be understood that the grafted polymer amount as a function of time will also be strongly influenced by the frequency of available reduction sites in the hair. As the number of available reduction sites decreases to a significant extent, the speed of the graft polymerization will thus decrease accordingly. This is also shown by the results stated in connection with the treatments with the oxidizing solution for 5 - 20 minutes. With the original increase of the treatment time from 5 to 10 minutes, an approximately 3-fold increase in the total graft polymerization was thus achieved. In contrast, increasing the time of treatment with the oxidizing solution from 10 to 15 minutes gave a corresponding 2-fold increase in percent graft polymerization. However, the results clearly show that the gradual increase in the percentage of graft polymerization tends to decrease strongly when the treatment time is then increased.

Cumene hydroperoxide is a very effective catalyst agent, and its use is preferred because it can be stored for a long time without any decomposition or other degradation occurring. Contact between the catalyst material and the reducing agent prior to its actual use should in any case be avoided in order to eliminate or at least reduce to a minimum any possibility of an accidental loss of catalyst. In those cases where it is desirable and/or necessary that the treatment time should be limited to an absolute minimum, very favorable graft polymerization rates can be achieved by simply increasing the concentration of the catalyst or the monomer or both. Increasing the amount of organic solvent used in the oxidizing solution will generally reduce the speed of the graft polymerization. As shown in examples 1 - 16, the type of solvent used in the reduction solution is of the greatest importance and strongly influences the speed of the graft polymerization achievable during the final oxidation step. It is clear from the following examples that a similar situation exists in connection with the type of solvent material used in the monomer-containing oxidizing solution. This situation is shown in the following examples which relate to the results obtained when treating samples of human hair with methyl methacrylate. The reduction treatment and the oxidation treatment corresponded to those used in the above examples. It will be seen that the solvent used in the experiments comprised ethyl alcohol, the remainder being water. .Djét..'appears'-clearly from" ■'the .abovef.or angi t te c.tésul ta ter .'at-' an application of<*>~øEenae~ "riiéttgder- -ofgåiii'sWo'ppløs' ning agent leads o[$> to decreasing polymerization rates. It will also be understood that the relationship between the concentration of organic solvent and the corresponding polymerization rate is critically dependent on the type of monomer material used. :■. A given monomer component can thus be exposed to large amounts of organic solvent without this adversely affecting the rate of graft polymerization. Decreasing polymerization rates can generally be expected in cases where the monomer material is light and relatively unlimitedly soluble in the selected organic solvent. These parameters can in any case be easily determined. If it should therefore be desirable to have lower temperatures for the grafting polymerization,...it can. may well be that an application of increased amounts of organic solvent will be prescribed as a special agent for. to achieve this.

Hair that has been exposed to environments that tend to have a harmful effect on it can usually be polymerized more easily, i.e. that it produces higher drying rates"; This situation can presumably be explained in that the denatured keratin fiber, for example, is more porous and thereby makes it easier for reagents to penetrate the fiber mass. So lead s'! will, for example, the expression .'.V-damaged-."-, as used herein, denote "e.g. Bleached hair and per-mane-curled hair etc. It has thus always been shown that a given hair sample's adaptation to the present method can be improved by e.g. bleach the sample one or more times in advance, as several treatments usually lead to more favorable results. This relationship is shown in the following examples which relate to the results obtained in connection with the grafting of methyl methacrylate on bleached hair. In each t: l.;."ei j. a bie e-dux ionee ev the hair test performed for 10 minutes using a reducing solution omf r tic:; da 5% sodium bisulphite in a mixed solution £ ystem of ethanol (45%I water. The reducing solution was used in a volume of approximately 10 ml/g hair sample. The treatment with the oxidizing solution was carried out for .30 minutes at room temperature under the application of 20 ml of the oxidizing solution per g hair sample.

It will be seen that hair previously exposed to only a single bleaching had a 50% increased amount of grafted polymer compared to one. unbleached hair control sample. Moreover, a further improvement in the percent graft polymerization was achieved with increasing number of prior bleaching treatments.

It appears that a similar increase in graft polymerization is obtained if the above treatment is repeated with hair samples that have been permanently curled. In Examples 31 - 33, the method used was as follows: The reduction was in each case carried out using a 5% solution of sodium bisulphite in a system of ethanol (45%) and water for 20 minutes.

About. IQ ml reducing solution was used per g hair sample. After rinsing, the oxidation step was carried out for approx. 30 minutes at room temperature using 20 ml of monomer solution per g hair. The results obtained are reproduced in the following table:

The hair's ability to absorb cations and anions can likewise be regulated by the present method, in accordance with predetermined requirements. Suitable choice of monomer and control of the grafted amount of polymer etc. it has thus been shown that the hair's selective absorption of both cation-active or anion-active reagents, e.g. organic genetic materials, can be modified considerably. Experimental investigations regarding the absorption of hexadecylpyridinium chloride (HDPK) at acidic, neutral and basic pH values have thus shown that it is possible to increase the amount of absorbed cations by grafting e.g. polymethacrylic acid on the hair. It has thus been shown that the rate at which HDPK is taken up by human hair with graft-polymerized polymethacrylic acid greatly increases *e;> at basic pH values to such an extent that in practice it was impossible to make accurate measurements. At neutral pH values, the uptake rate is still considerably higher than for hair without grafting polymer, as the difference becomes smaller at acidic pH values. It is likely that the above is due to the fact that hu; with grafted polymethacrylic acid contains a far greater number of acidic groups that can act as active centers for the absorption of cations and that treated hair swells far more at high pH values than untreated hair. At a neutral pH, however, both the ionization of the carboxyl groups and the sr/elling of the fibers tend to decrease. At acidic pH values or the ionization of the carboxyl groups is minimal, Oja not zero, and the rates at which cations are absorbed by both treated and untreated hair samples are approximately the same, with any differences being completely insignificant. The ratio between the amount of grafting polymer and absorption of cations by human hair is based on the data given in the following table. In each case, the treatment with HroM was carried out for 2 hours at jn*pH of 6.9,

Conversely, with the present method, the hair's affinity towards cation-active agents can be reduced. This can be easily achieved by simply using a monomer material which gives a polymer with

mainly hydrophobic properties. The hydrophobic polymer works

- to slow down the penetration of cations. It will be understood that by critically choosing ionomer mixtures, the hair's absorption properties towards cations can be practically varied as desired. In the present method, the absorption capacity of the hair towards anions can also be easily changed. Measurements of uptake of Orange II by hair untreated and hair grafted with poly-dimethylaminoethyl methacrylate thus clearly show that the affinity of the treated hair sample for anionic dyes can be increased considerably by the present method. At lower pH values, the affinity of hair with grafting polymer towards Orange II and the rate at which it takes up this dye is far greater than for untreated hair, as the differences become smaller with increasing pH. At neutral pH, the amount of dye Orange II absorbed by hair grafted with poly-dimethylaminoethyl methacrylate is approximately twice that of

amount absorbed by untreated hair at a pH of 3.5.

The above data makes it clear that a considerable increase in the amount of grafting polymer is achieved when treating permanently curly hair, and an approx. An 8-fold increase was achieved for hair that had only been subjected to a single prior bleaching. As indicated above, it appears that the rates of graft polymerization are due to the increased porosity characteristic of pre-damaged hair.

In each of the following examples, human hair was treated for 30 minutes at room temperature with the preparation indicated in the following table where the quantities are based on parts by weight, the hair samples having previously been reduced with a 6% thioglycolate solution with a pH of approx. 9.

In each case, an amount of polymer grafted onto the hair fibers was obtained which compares favorably with the values stated in the previous example. Moreover, the results obtained tend to emphasize the relative superiority of

dc in organic solvents soluble initiators, since those of the insoluble type lead to a somewhat lower increase in rates,, for the graft polymerization. '

Similar results to those indicated above are obtained by repeating the method described above, but instead of cumenhydroperoxide, using such materials as dibutylperoxide, tert-butylhydroxide, benzoyiperoxide, peoeddiksyio and hydrogen peroxide, - As ai. above, a use of certain of the above-mentioned initiators is particularly advantageous due to the fact that they have a better stability and are easy to handle. In any case, it should be noted that the initiator material chosen for use can be any of those commonly used for polymerization of vinyl-type monomers initiated by free radicals. It will of course be understood that special monomer compounds can be used with better effect together with certain types of initiator compounds. However, this can easily be determined by the user in order to arrive at an optimal procedure in a particular case.

The procedures described in the above examples were repeated, but instead of using the following monomers: lauryl methacrylate, octadecyl methacrylate, 4,5-pentenyl methacrylate, 2-hydroxyethyl methacrylate, 3-propyl methacrylate, acrylamide and

•Jtiethacrylamide.

As stated above, an increase in the concentration of water-soluble halide salt in the monomer solution will lead to increased rates for the graft polymerization, although the increase was less strong within the higher concentration ranges. This relationship is shown in the following examples where each sample of human hair weighs 1 - 0.003 g. In each case, the hair sample was subjected to a reduction treatment for 15 minutes using an aqueous solution of ammonium thioglycolate (6%) with a pH of 9. After the reduction treatment was over, the hair sample was thoroughly rinsed to remove residual reducing agent. the reduced hair sample was treated with a monomer solution of the indicated composition for 1 hour at a temperature of 40.6° C. About 27 ml of monomer solution was used per gram of treated hair. The amount of grafting polymer was calculated as the percentage increase<i>n of dry weight after drying for 12 hours over calcium chloride in a rowing box. The results obtained are gj entered in Table 8.

In the following examples, the catalyst concentration was varied with the stated results, the procedures being otherwise as in examples 40-45.

It appears that the data indicated above suggest that an increase in the concentration of peroxide catalyst leads to a considerable improvement in the efficiency of the oxide reduction system, this improvement being shown by the increased grafting of polymer.

It also appears that an improved grafting of the polymer can be achieved despite the use of both the catalyst component and the bromide component within the lower concentration range. Excess amounts of peroxide catalyst should as a rule be avoided, i.e. substantially larger amounts than those prescribed above, thereby making any possibility of uncontrolled formation of bromine as small as possible as this is a powerful polymerization inhibitor.

As stated above, organic dissolution materials have

ir,ad Non-annual development properties have a somewhat delaying effect on the speed of the grafting of the polymer. This is shown in the following examples where: then in the above examples, the required method was used.

The above examples clearly show the inhibiting effect on the grafting of the polymer due to the use of a poorly precipitating solvent, e.g. ethylene glycol monomethyl ether. It is clear, however, by comparison with example 40 that by using a monomer solution containing 37.03% ethylene glycol monomethylether together with 7.40% lithium bromide, speeds can still be achieved for the grafting of the polymer which are significantly greater than those which can. is obtained if the salt is omitted.

Claims (5)

1. Procedure for treating hair to give it a desired physical shape, characterized in that the hair is treated with a reducing agent to convert at least part of the disulphide bonds present in the hair into sulfhydryl bonds, the remaining reducing agent is removed from the hair by rinsing, the hair treated with an oxidizing aqueous solution that includes a) a peroxide catalyst material capable of liberating free radicals in the presence of sulfhydryl, the free radicals also being capable of initiating the polymerization of monomers, and b) a monomer compound containing at least one group of the formula c which can be polymerized in the presence of the peroxide initiator, whereby the monomer is graft polymerized on the hair which is then rinsed to remove unreacted monomer and initiator, given the desired physical form in the wet state and dried with the desired physical form. 2. Method according to claim 1, characterized in that cumene hydroperoxide is used as peroxide initiator. 3. Method according to claim 1 or 2, characterized in that the treatment with the monomer compound and the peroxide initiator is carried out for 0.5-2 hours. 4- Method according to claims 1-3, characterized in that a molar ratio initiator:monomer of 1:10 - 1:2 is used. 5. Method according to claims 1-4, characterized in that a water-soluble thioglycolate is used as reducing agent.