The present invention relates to compositions and methods for lanthionizing keratin fibers using a combination of at least one multivalent metal hydroxide and at least one cation exchange composition. The at least one cation exchange composition can dissociate the at least one multivalent metal hydroxide in sufficient quantity to effect lanthionization of the keratin fibers. In one embodiment, the process of lanthionizing keratin fibers results in relaxed or straightened hair.
Straightening or relaxing the curls of very curly hair may increase the manageability and the ease of styling such hair. In today""s market, there is an increasing demand for hair care products referred to as xe2x80x9chair relaxersxe2x80x9d which can relax or straighten naturally curly or kinky hair. Hair relaxers may either be applied in a hair salon by a professional or in the home by the individual consumer.
Hair fiber is a keratinous material, which is comprised of proteins (polypeptides). Many of the polypeptides in hair fibers are bonded together by disulfide bonds (xe2x80x94Sxe2x80x94Sxe2x80x94). A disulfide bond may be formed from the reaction of the two sulfhydryl groups (xe2x80x94SH), one on each of two cysteine residues, which results in the formation of a cystine residue. While there may be other types of bonds between the polypeptides in hair fibers, such as ionic salt bonds, the permanent curling and shape of the hair is essentially dependent on the disulfide bonds of cystine residues.
Generally, hair relaxing processes are chemical processes which may alter the aforementioned disulfide bonds between polypeptides in hair fibers and may form lanthionine [S(CH2CHNH2COOH)2]. Thus, the term xe2x80x9clanthionizingxe2x80x9d is used when one skilled in the art refers to the relaxing or straightening of keratin fibers by hydroxide ions.
For example, hair fibers may be relaxed or straightened by disrupting the disulfide bonds of the hair fibers with an alkaline agent or with a reducing agent. The chemical disruption of disulfide bonds with an alkaline agent is generally combined with mechanical straightening of the hair, such as combing, and straightening generally occurs due to changes in the relative positions of opposing polypeptide chains within the hair fiber. This reaction is generally terminated by rinsing and/or application of a neutralizing composition.
The reaction with the alkaline agent is normally initiated by hydroxide ions. Not to be limited by theory, there are two reaction sequences that are predominantly used in the art to explain the disruption of the disulfide bonds in hair fibers by hydroxide ions. Both of these reaction sequences result in lanthionine residue formation. One reaction sequence comprises a bimolecular nucleophilic substitution reaction wherein a hydroxide ion directly attacks the disulfide linkage of a cystine residue. The result is the formation of lanthionine and HOS. See Zviak, C., The Science of Hair Care, 185-186 (1986). The second reaction sequence comprises at least one xcex2-elimination reaction initiated by the nucleophilic attack of a hydroxide ion on a hydrogen atom bonded to a carbon atom that is in the xcex2-position with respect to the disulfide bond of a cystine residue. Id. The result is the formation of a dehydroalanine residue. The dehydroalanine residue then reacts with either the thio group of a cysteine residue or the amino group of an alanine residue to form lanthionine or lysinoalanine, respectively. Regardless of the reaction mechanism, hair relaxing processes proceed via the release of hydroxide ions that can penetrate the hair fiber and which may transform cystine residues to lanthionine residues.
Most frequently, relaxing compositions are in the form of gels or emulsions that contain varying proportions of strong water-soluble bases, such as sodium hydroxide (NaOH), or of compositions that contain slightly-soluble metal hydroxides, such as calcium hydroxide (Ca(OH)2), which can be converted in situ to soluble bases, such as guanidine hydroxide. Traditionally, the two main hair relaxing technologies used in the hair care industry for generating hydroxide ions are referred to as xe2x80x9clyexe2x80x9d relaxers (lye=sodium hydroxide) and xe2x80x9cno lyexe2x80x9d relaxers. The xe2x80x9clyexe2x80x9d relaxers generally comprise sodium hydroxide in a concentration generally ranging from 1.5% to 2.5% (0.38M-0.63 M) depending on the carrier used, the condition of the hair fibers, and the desired length of the relaxation process. Sodium hydroxide may be extremely effective in straightening hair fibers but may result in a decrease in the strength of the hair fibers and, in some cases, partial or total loss of hair due to hair fiber breakage.
While xe2x80x9cno lyexe2x80x9d relaxers may not contain lye, they may nonetheless rely on the soluble hydroxides of inorganic metals, such as potassium hydroxide and lithium hydroxide. Other xe2x80x9cno lyexe2x80x9d relaxers may use hydroxide ions obtained, for example, from a slightly-soluble source, such as Ca(OH)2. For example, the slightly soluble Ca(OH)2 may be mixed with guanidine carbonate to form guanidine hydroxide, a soluble but unstable source of hydroxide, and insoluble calcium carbonate (CaCO3). This reaction is driven to completion by the precipitation of CaCO3 and is, in effect, substituting one insoluble calcium salt for a slightly soluble calcium salt. Because guanidine hydroxide is unstable, the components are stored separately until the time of their use.
Guanidine carbonate and calcium hydroxide, however, may create a different set of problems. The insoluble byproduct, CaCO3, can leave a white residue or unattractive xe2x80x9cwhiteningxe2x80x9d or xe2x80x9cashing.xe2x80x9d This residue remains in the hair since divalent metals such as calcium have a relatively good affinity for keratin. A decalcifying shampoo may be subsequently needed to remove the ashing.
Thus, there is still a need for a process to relax keratin fibers that has the advantages of using a slightly-soluble metal hydroxide, such as Ca(OH)2, but which reduces or eliminates the problem of ashing caused by insoluble byproducts, such as CaCO3.
To achieve at least one of these and other advantages, and in accordance with the purpose of the invention as embodied and broadly described herein, the present invention, in one aspect, provides a composition for lanthionizing keratin fibers comprising at least one multivalent metal hydroxide and at least one cation exchange composition. According to the present invention, at least one cation exchange composition may be chosen from silicates. The at least one multivalent metal hydroxide may be chosen from, for example, calcium hydroxide, barium hydroxide, magnesium hydroxide, aluminum hydroxide, cupric hydroxide, strontium hydroxide, molybdenum hydroxide, manganese hydroxide, zinc hydroxide, and cobalt hydroxide.
The present invention is also directed to a method for lanthionizing keratin fibers to achieve relaxation of the keratin fibers by generating hydroxide ions in an ionizing solvent comprising combining at least one multivalent metal hydroxide and at least one activating composition, wherein the at least one activating composition comprises at least one cation exchange composition, to generate hydroxide ions; and applying a composition comprising the generated hydroxide ions to keratin fibers for a sufficient period of time to lanthionize the keratin fibers. Lanthionization is terminated when the desired level of relaxation of the keratin fibers has been reached. The at least one multivalent metal hydroxide may be added to a composition comprising the at least one cation exchange composition or vice versa.
The invention also provides for a multicomponent kit for lanthionizing keratin fibers, wherein the kit comprises at least two separate compartments. One compartment of the kit comprises a composition for generating hydroxide ions that comprises at least one multivalent metal hydroxide while the other compartment of the kit comprises at least one activating composition comprising at least one cation exchange composition for generating hydroxide ions.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
Reference will now be made in detail to exemplary embodiments of the present invention. Not to be limited as to theory, the lanthionization of keratin fibers is driven by the release of hydroxide ions, which disrupt the disulfide bonds of cystine residues in the fibers. The compositions of the present invention may offer at least one advantage over traditional xe2x80x9clyexe2x80x9d and xe2x80x9cno lyexe2x80x9d hair relaxers by providing a novel way of generating hydroxide ions from multivalent metal hydroxides while still being effective to relax and/or straighten the hair.
As described above, the hair relaxing compositions of the prior art utilized soluble or slightly soluble metal hydroxides. Slightly soluble metal hydroxides, including most divalent metal hydroxides, may not be soluble enough in water to generate a sufficient,concentration of hydroxide ions to effect lanthionization of keratin fibers. This hydrolysis reaction of divalent metal hydroxides can be represented by the following reaction scheme, in which the equilibrium favors the left side of the reaction:
M(OH)2(solid)⇄M++(aq.)+2OHxe2x88x92(aq.).
In traditional relaxers containing slightly soluble metal hydroxides, the equilibrium was normally pushed to the right, and therefore the reaction was driven to completion by the precipitation of M++ in the form of an insoluble compound such as CaCO3.
The compositions of the present invention, however, utilize cation exchange compositions such as silicates. Not to be limited as to theory, it is believed that the cation exchange composition participates in the lanthionizing process through an ion exchange mechanism. It is believed that the reversible ion exchange reaction involves the interchange of the multivalent metal ions of the at least one multivalent metal hydroxide with ions of the at least one cation exchange composition. This reaction thereby releases hydroxide ions. In other words, the exchange of M++, in the case of divalent metal hydroxides, to the at least one cation exchange composition shifts the equilibrium of the above reaction to the right such that the net effect is that hydroxide ions are liberated from the insoluble or slightly-soluble at least one multivalent metal hydroxide. This process may thereby generate a high enough concentration of hydroxide ions to effect lanthionization of keratin fibers without relying on the precipitation of M++, for example, in the form of an insoluble precipitate such as CaCO3.
Any cation exchange composition or combination of cation exchange compositions which is effective in participating in the lanthionizing process may be used according to the present invention, including, but not limited to, silicates and mixtures of silicates. In one embodiment, the at least one cation exchange composition is a clay.
For example, suitable silicates may be chosen from aluminum silicates and silicates of alkali metals such as analcime, chabazite, gmelinite, harmotome, levynite, mordenite, epistilbite, heulandite, natrolite, stilbite, edingtonite, mesolite, scolecite, thomosonite, brewsterite, faujasite, gismondine, laumontite, phillipsite, and aluminosilicate. Non-limiting examples of alkali metals are sodium, lithium, potassium and mixtures of all of the foregoing. In one embodiment the silicate is a zeolite, while in another embodiment, the silicate is a zeolite clay.
The present invention is also directed to simple screening tests for determining the applicability of particular cation exchange composition for use in the lanthionizing compositions of the present invention. By titrating a suspension of at least one multivalent metal hydroxide, such as Ca(OH)2, with the cation exchange composition of interest, the exchange properties of the cation exchange composition may be observed. For example, if the solution reaches a pH sufficient for lanthionizing keratin fibers, then the particular cation exchange composition is a good candidate for use in the compositions of the present invention. However, even if the pH reached is not sufficient, the particular cation exchange composition may still be a good candidate if the presence of another ingredient, such as at least one complexing agent, allows lanthionization to occur.
The ability of an cation exchange composition to exchange or take up a metal ion such as calcium is sometimes referred to as the Calcium Exchange Capacity, and is normally expressed as mg of CaCO3 per gram of cation exchange composition. One of skill in the art may choose an cation exchange composition or combination of cation exchange compositions based on the Calcium Exchange Capacity of the resin and the application envisaged. The skilled artisan may also choose to add other components, such as at least one complexing agent as described below, depending on the Calcium Exchange Capacity of the cation exchange compositions of interest and the application envisaged.
In one embodiment, the cation exchange composition is present in an amount ranging from 1% to 50% relative to the total weight of the composition.
The compositions of the present invention may also include at least one complexing agent effective for dissociating the at least one multivalent metal hydroxide in a sufficient quantity to effect lanthionization of keratin fibers. The at least one complexing agent may be an agent, such as a chelating agent or a sequestering agent, that leads to a partial or full dissociation of the at least one multivalent metal hydroxide. The at least one complexing agent may chelate, sequester or otherwise tie up the metal ion of the at least one multivalent metal hydroxide, allowing more hydroxide ions to be liberated. Of course, the at least one complexing agent may do both. In any event, the net effect of the use of at least one complexing agent in accord with the present invention is the generation of enough hydroxide ions to effect lanthionization of keratin fibers without relying on the precipitation of the multivalent metal ion, such as Ca++in the form of CaCO3.
The at least one complexing agent and the multivalent metal may form a complex that, in most cases, has stronger interactions between the at least one complexing agent and the multivalent metal ion than the interactions between the multivalent metal and the hydroxide ion. As a result, the at least one complexing agent effectively removes the multivalent metal from the reaction medium and allows the equilibrium to be shifted to the right.
Thus, the at least one cation exchange composition can be used in combination with at least one complexing agent to modulate or control the rate of release of hydroxide ions from the at least one multivalent metal hydroxide, thereby producing a mixed composition for gentler relaxing and/or partial relaxing. A mixture of at least one complexing agent and at least one cation exchange composition may increase relaxing efficiency.
In a multicomponent kit, for example, the at least one cation exchange composition may be formulated with the component comprising at least one multivalent metal hydroxide or with the component comprising at least one complexing agent or itself may be a third component that is combined with one or both of the component comprising at least one multivalent metal hydroxide and the component comprising at least one complexing agent.
The at least one complexing agent of the present invention includes, but is not limited to, chelating agents and sequestering agents. A chelating agent is a compound or ligand that can bind to a metal ion, usually through more than one ligand atom, to form a chelate. See Lewis, R. J., Hawley""s Condensed Chemical Dictionary p. 240 (1997). A chelate is usually a type of coordination compound in which a central metal ion, such as Co2+, Ni2+, Cu2+, Ca2+ or Zn2+, is attached by coordinate links to two or more nonmetal atoms, i.e., ligands, in the same molecule. Non-limiting examples of common chelating agents include ethylene-diaminetetraacetic acid (EDTA), nitrilotriacetic acid, and ethylenegylcol-bis(xcex2-amino-ethyl ether)-N, N-tetraacetic acid.
Sequestering agents may be any material that prevents at least one ion from exhibiting its usual properties due to close combination with that material. Id. at 991. Certain phosphates, for example, form a coordination complex with metal ions in solution so that the usual precipitation reactions may be prevented. Id. For example, calcium soap precipitates are not produced from hard water treated with certain phosphates or metaphosphates. Id. Other non-limiting examples of sequestering agents include hydroxy carboxylic acids, such as gluconic acid, citric acid and tartaric acid. Id.
As previously mentioned, the at least one complexing agent can be chosen from chelating agents and sequestering agents. Non-limiting examples of chelating agents and sequestering agents include amino acids and crown ethers. In one embodiment, the at least one complexing agent is chosen from amino acids, such as monosodium glutamate, which is a known calcium chelator.
The at least one complexing agent may also be chosen from phosphates demonstrating chelating and/or sequestering properties and silicates demonstrating chelating and/or sequestering properties. Non-limiting examples of phosphates demonstrating chelating and/or sequestering properties include tripotassium phosphate, and trisodium phosphate. Non-limiting examples of silicates demonstrating chelating and/or sequestering properties include disodium silicate and or dipotassium silicate.
Other non-limiting examples of the at least one complexing agent that may be useful in the practice of the invention include organic acids and salts thereof. The cations that may be used to form the salts of organic acids of the present invention may be chosen from organic cations and inorganic cations. In one embodiment, the inorganic cations are chosen from potassium, sodium and lithium.
In another embodiment, the at least one complexing agent is chosen from mono-hydroxycarboxylic acids, dihydroxycarboxylic acids, polyhydroxycarboxylic acids, mono-aminocarboxylic acids, di-aminocarboxylic acids, poly-aminocarboxylic acids, mono-hydroxysulfonic acids, di-hydroxysulfonic acids, polyhydroxysulfonic acids, mono-hydroxyphosphonic acids, dihydroxyphosphonic acids, polyhydroxyphosphonic acids, mono-aminophosphonic acids, diaminophosphonic acids and polyaminophosphonic acids.
In a further embodiment, the at least one complexing agent is chosen from ethylene diamine tetraacetic acid (EDTA), -(hydroxyethyl) ethylene diamine triacetic acid, aminotrimethylene phosphonic acid, diethylenetriamine-pentaacetatic acid, lauroyl ethylene diamine triacetic acid, nitrilotriacetic acid, iminodisuccinic acid, tartaric acid, citric acid, N-2-hydroxyethyliminodiacetic acid and salts of any of the foregoing.
In a further embodiment, the at least one complexing agent is chosen from a salt of EDTA, such as sodium EDTA, lithium EDTA, potassium EDTA and guanidine EDTA. EDTA has a strong calcium binding constant over a wide range of pH. For example, tetrasodium EDTA generally solubilizes calcium hydroxide in aqueous media to give a clear solution. The use of at least one complexing agent, such as tetrasodium EDTA, that solubilizes the multivalent metal ion of the at least one multivalent metal hydroxide may offer the benefit of no xe2x80x9cashing.xe2x80x9d However, the use of one or more complexing agents that do not completely solubilize the multivalent metal ion but only form slightly-soluble or sparingly-soluble complexing agent-multivalent metal ion complexes is also within the practice of the invention.
In another embodiment, the at least one complexing agent may comprise at least one xe2x80x9csoftxe2x80x9d entity chosen from xe2x80x9csoftxe2x80x9d bases and xe2x80x9csoftxe2x80x9d cations, and at least one anion chosen from chelating anions and sequestering anions. Non-limiting examples of xe2x80x9csoftxe2x80x9d cations include organic cations such as guanidine. Non-limiting examples of xe2x80x9csoftxe2x80x9d bases include amines such as monoethanolamine, diethanolamine and triethanolamine. Such a combination of at least one xe2x80x9csoftxe2x80x9d entity and at least one anion may be effective if the xe2x80x9csoftxe2x80x9d entity exists at a high enough pH to achieve straightening or relaxing of the hair fibers. For example, amino acids such as arginine may be used to neutralize EDTA to make a xe2x80x9csoftxe2x80x9d base/strong chelator pair.
Depending on the nature of the at least one complexing agent, the solubility of the complex formed between the at least one complexing agent and the multivalent metal ion of the at least one multivalent metal hydroxide in the reaction medium may vary. In one embodiment, the at least one complexing agent-multivalent metal ion complex is considered by one of ordinary skill in the art to be soluble in the reaction medium. In another embodiment, a composition of the invention provides for an at least one complexing agent-multivalent metal ion complex having a solubility in water of greater than 0.03% at 25xc2x0 C. and at a pH of 7.0, such as greater than 1% at 25xc2x0 C. and at a pH of 7.0.
The present invention is also directed to simple screening tests for determining the applicability of a particular complexing agent for use in the lanthionizing compositions of the present invention. This screening test is essentially the same test as that described above for determining the applicability of a particular cation exchange composition in the present invention. In the present test, a suspension of at least one multivalent metal hydroxide, such as Ca(OH)2, is titrated with the complexing agent of interest, and the chelating and/or sequestering properties of the particular complexing agent may be observed. For example, if the solution reaches a pH sufficient for lanthionizing keratin fibers, then the complexing agent is a good candidate for use in the compositions of the present invention.
The at least one cation exchange composition and the at least one complexing agent of the present invention may offer one or more of the following benefits: compatibility with keratin conditioning ingredients (polyquaternium compounds, polymers, proteins, alkylquaternary ammonia compounds, silicones, etc.); capability to be stored as a stable mixture, that is, the formation of a stable mixture of at least one complexing agent and at least one multivalent metal hydroxide that can be stored for later use, an advantage which is not possible with compositions that result in the unstable guanidinium hydroxide; and the absence of a precipitation by-product and/or the absence of the need to apply a decalcifying shampoo after relaxing.
As one of ordinary skill in the art would recognize, mixtures of complexing agents including mixtures of at least one chelating agent and at least one sequestering agent are also within the practice of the invention. In one embodiment, a less active chelating agent, such as pentasodium aminotrimethylene phosphonate, may be mixed with a more active chelating agent, such as EDTA, to achieve a desired lanthionization of keratin fibers at a slower rate.
The at least one multivalent metal hydroxide useful in the present invention may be chosen from multivalent metal hydroxides which are an effective source of hydroxide ions for lanthionizing keratin fibers when combined with at least one complexing agent. In one embodiment, the at least one multivalent metal hydroxide is chosen from insoluble alkali metal hydroxides and slightly soluble metal hydroxide including but not limited to, calcium hydroxide, barium hydroxide, magnesium hydroxide, aluminum hydroxide, cupric hydroxide, strontium hydroxide, molybdenum hydroxide, manganese hydroxide, zinc hydroxide and cobalt hydroxide.
The at least one multivalent metal hydroxide, for example, may be present in an amount ranging from 1% to 10% relative to the total weight of the composition.
The compositions of the present invention may be provided as one-part compositions comprising at least one multivalent metal hydroxide, at least one cation exchange composition, and, optionally, at least one complexing agent. Alternatively, the compositions may be provided in the form of a multicomponent kit. According to the present invention, the multicomponent kit for lanthionizing keratin fibers may comprise at least two separate compartments. A first compartment of the kit can comprise a first composition comprising at least one multivalent metal hydroxide. This first composition may be in the form of an emulsion, solution, suspension, gel or paste. A second compartment of the kit can comprise at least one activating composition comprising at least one cation exchange composition for generating hydroxide ions and, optionally, at least one complexing agent that is effective for dissociating the at least one multivalent metal hydroxide in sufficient quantity to effect lanthionization of keratin fibers. This activating composition may be in the form of an emulsion, suspension, solution, gel or paste. The skilled artisan, based on the stability of the composition and the application envisaged, will be able to determine how the composition and/or multicomponent compositions should be stored and mixed.
In one embodiment, one of the at least two components of the multicomponent kit comprises an amount of an ionizing solvent, such as water, sufficient to ensure that, upon mixing, enough of the generated hydroxide ions remain soluble to effect lanthionization of keratin fibers.
The present invention is also directed to methods for lanthionizing keratin fibers in order to achieve relaxation of the keratin fibers. The methods of the present invention comprise generating hydroxide ions in an ionizing solvent comprising combining at least one activating composition and at least one multivalent metal hydroxide. The at least one activating composition comprises at least one cation exchange composition. The at least one activating composition may further comprise at least one complexing agent effective for dissociating the at least one multivalent metal hydroxide in sufficient quantity to effect lanthionization of keratin fibers. A composition comprising the generated hydroxide ions can thereby be formed and the composition applied to keratin fibers for a sufficient period of time to lanthionize the keratin fibers. The lanthionization can be terminated when a desired level of relaxation of the keratin fibers is reached.
The ionizing solvents may be chosen from solvents that lower the ionic bonding forces in the solute molecules enough to cause separation of their constituent ions. In one embodiment, the ionizing solvent is chosen from water and dimethyl sulfoxide (DMSO).
The method also encompasses forming the hydroxide ions in situ, i.e., while on the keratin fibers, by combining at least one multivalent metal hydroxide and at least one activating composition in the presence of the keratin fibers.
The invention will be illustrated by, but is not intended to be limited to, the following examples.