Hair straightening compositions containing fatty acid lactylates and glycolates and their method of use

Fatty acid lactylates and/or glycolates are combined with sodium hydroxide or at least one reducing agent for hair and used in a hair straightening operation.

BACKGROUND OF THE INVENTION 
Permanent waving is a process whereby a reducing agent is applied to 
mandrel-wound hair to open the disulfide linkages of the hair structure 
which are formed by the amino acid cystine. The protein chains flow under 
tension to assume the imparted shape. After rinsing, an oxidizing agent is 
then applied to re-establish or close the disulfide linkages which, in 
effect, hardens the protein structure to lock it into the new position. 
Hair can be relaxed or straightened by a converse process whereby the hair 
is chemically acted upon when the hair is straight or at a curl having a 
radius of curvature greater than that existing in the hair. To this end, 
the hair can be held straight or wound on rods or mandrels of large 
diameter. 
An essential element of a hair straightening composition is sodium 
hydroxide or a reducing agent. Among the reducing agents there may be 
mentioned thioglycolic acid, salts, and esters thereof; thiolactic acid 
and salts thereof; sulfide salts; bisulfite salts, cysteine, and the like. 
Aside from sodium hydroxide, the bulk of the compositions for 
straightening hair are based on thioglycolic acid, salts, or esters 
thereof, or the bisulfite salts. 
The compositions used for relaxing or straightening hair are normally 
provided as a gel or a cream which serves to mechanically hold the hair in 
a straightened state during chemical attack. Sodium hydroxide relaxers are 
generally cream compositions at concentrations up to 3%, preferably about 
2 to about 3%, NaOH. Sodium hydroxide attacks the disulfide bond to 
produce lanthionine which now crosslinks the hair in its straightened 
form. The generalized reaction is: 
##STR1## 
Following straightening, an acid rinse is usually applied to neutralize 
excess alkali. 
The hair may be straightened with thioglycolates under acid conditions. To 
this end, citric, lactic, phosphoric, and weak carboxylic acids are used 
as common acidifying agents. Bisulfite straighteners are also acid, namely 
at a pH from about 5.5 to 6.9, and are applied at room temperature. 
As with sodium hydroxide compositions, contact with the reducing agent may 
range from 10 minutes or less to 50 minutes or more. After an appropriate 
time of contact, the reducing agent is rinsed from the hair, and an 
oxidizing agent is applied to close the disulfide bonds and set the 
straightened hair. Excess oxidizing agent is then rinsed from the hair, 
and the hair is dried. The most common oxidizing agents are hydrogen 
peroxide and bromate salts. Peroxides are applied over a pH range from 2.5 
to about 4.0 and bromates from a pH of about 5.0 to about 8.0. Application 
is at ambient or elevated temperatures. 
In general, sodium hydroxide is the most effective straightener but is also 
the most damaging to hair and most likely to irritate the skin. 
Thioglycolate and alkali bisulfite straighteners do not produce the same 
degree of straightening but relax the curl from a tighter to a looser wave 
pattern. 
All forms of hair straightening suffer by reversion. As the straightened or 
relaxed hair is subjected to shampooing, heat or high humidity, it reverts 
to some degree back to its curly form. 
SUMMARY OF THE INVENTION 
It has now been surprisingly found that the lactylates and glycolates, when 
incorporated as part of a hair straightening agent, composition or 
solution applied to hair, will impart unexpected and desirable qualities 
to the hair when processed through a straightening operation. The most 
significant effects are the degree of straightening and retention of the 
straightened state, in that there is an exceptional resistance to 
reversion under conditions of both high and low humidity. 
The compositions provided in accordance with the instant invention comprise 
an aqueous solution of sodium hydroxide or at least one hair reducing 
agent in combination with at least one fatty acid lactylate and/or 
glycolate of the formula: 
##STR2## 
wherein RCO is an acyl radical of a fatty acid having from about 6 to 
about 22 carbon atoms, A is CH.sub.3 or H, and x has a value of from 1 to 
about 4, as well as the ammonium, alkali metal, and amine salts thereof, 
the total of lactylates and/or glycolates added being sufficient to 
increase the degree of straightening of the hair as compared to the degree 
of straightening using the same composition in the absence of a fatty acid 
lactylate and/or glycolate. The amine salts, when used, are the 
physiologically acceptable amine salts. The compositions based on a 
reducing agent preferably contain an emulsifier to improve compatibility 
of the components of the hair straightening composition. Further, the 
compositions are preferably used at a viscosity sufficient to hold hair in 
a straightened state and, to this end, are usually applied as a cream or a 
gel. 
Besides sodium hydroxide, the reducing agents used are preferably 
thioglycolic acid, a salt or ester thereof, or an alkali bisulfite, 
preferably sodium bisulfite. For compositions containing a reducing agent, 
glycerol monothioglycolate or ammonium monothioglycolate are presently 
preferred for acid compositions. Ammonium monothioglycolate and 
monoethanolamine thioglycolate may be used in alkaline compositions. 
The presently preferred fatty acid lactylate is sodium 
isostearoyl-2-lactylate. 
The hair straightening process of the invention includes the steps of 
reacting hair in a straightened state with a solution of sodium hydroxide 
or a reducing agent for hair, which solution includes at least one fatty 
acid, lactylate and/or glycolate, for a time sufficient to cause, in the 
instante of sodium hydroxide, the formation of lanthionine links or, with 
a reducer, to open the disulfide linkages of the hair, and later followed 
by the step of subsequently closing the disulfide linkages of the hair by 
application of an oxidizing agent to the hair to set the hair in the 
desired straightened state. The fatty acid lactylates and/or glycolates 
used in the practice of the invention serve to materially increase the 
degree of swelling of the hair. This permits faster penetration by the 
sodium hydroxide, or reducing agent, resulting in more efficient 
straightening. 
When a reducing composition based on glycerol monothioglycolate is 
employed, the reducing agent and fatty acid lactylate and/or glycolate 
serve as a first component which is combined with a balancer compound of 
the balance of the constituents forming a net reducing composition for 
application to the surface of hair in a conventional manner. 
After the hair is straightened and rinsed, the hair is oxidized using 
hydrogen peroxide or a bromate salt to set the hair. Rinsing is employed 
following oxidation, and the hair is dried. 
Where sodium hydroxide is used, the hair is neutralized using an acid 
solution, then dried. 
DETAILED DESCRIPTION 
The present invention is directed to the straightening of hair, and is 
based on the use of fatty acid lactylates and glycolates of the formula: 
##STR3## 
wherein RCO is the acyl radical of a fatty acid containing from about 6 to 
about 22 carbon atoms, A is CH.sub.3 or H, and x is a number from 1 to 
about 4, as well as their ammonium, alkali metal, and physiologically 
acceptable amine salts, as humectants, introduced by acid or alkaline hair 
straightening solutions to impart a high degree of straightening to hair 
which remains at a high level, despite gross fluctuations in humidity. 
The compounds useful in accordance with the present invention are described 
in greater detail in U.S. Pat. No. 3,728,447 to Osipow et al, incorporated 
herein by reference, and are produced by methods described in U.S. Pat. 
No. 3,733,252, also incorporated hereby by reference. 
Suitable fatty acid lactylates and glycolates which may be mentioned 
include isostearoyl-2-lactylate, caproyl-2-lactylate, 
caprylyl-2-lactylate, capryl-2-lactylate, lauryl-1-lactylate, 
lauryl-2-lactylate, lauryl-3-lactylate, lauryl-4-lactylate, 
myristyl-1-lactylate, myristyl-2-lactylate, oleoyl-2-lactylate, 
palmityl-2-lactylate, stearyl-2-lactylate, behenyl-2-lactylate, 
lauryl-1-glycolate, lauryl/myristyl-1-glycolate, capryl-1-glycolate; salts 
thereof, and the like. Sodium isostearoyl-2-lactylate is presently 
preferred. 
The amount of lactylate and/or glycolate to be incorporated into the hair 
straightening composition is an amount sufficient to impart increased 
straightening as compared to the same hair straightening composition used 
without the lactylate and/or glycolate. 
The hair straightening compositions are based on sodium hydroxide or a 
reducing agent for hair, the latter used in conjunction with an oxidizing 
agent. 
Sodium hydroxide reacts with the hair to form lanthionine links, and is 
applied from solution. Concentration is typically up to about 3% by weight 
sodium hydroxide, preferably from about 2 to about 3% by weight of 
solution. 
The reducing agents, by contrast, open the disulfide linkages of the hair. 
The protein chains of the hair assume the imparted straightened shape, and 
the linkages are then closed to cause hair to retain a straightened shape. 
The preferred reducing agents are thioglycolic acid, salts of thioglycolic 
acid, esters of thioglycolic acid, bisulfite salts such as sodium 
bisulfite, ammonium bisulfite and the like. Ammonium monothioglycolate or 
glycerol monothioglycolate are presently preferred. Preferably, the ratio 
of moles of reducing agent to lactylate and/or glycolate in the 
composition is from about 15 to about 80. 
Generally, the total concentration of lactylates and/or glycolates in the 
hair straightening composition employed range from about 0.1 to about 2% 
by weight of solution, preferably from 0.5 to about 1.5% by weight. 
The compositions are normally formulated to a viscosity sufficient to form 
a gel or a cream which retains hair in a straightened state during 
chemical action and until removed by rinsing or application of the 
oxidizing agent. Sodium hydroxide compositions are removed by acid 
shampoos or rinses, which neutralize the excess alkali present in the 
hair. 
Because the compositions containing a reducing agent have been observed to 
separate on standing, it is desired to incorporate a minor amount of an 
emulsifier to stabilize the solution against separation. Emulsifiers, such 
as oleth-20, may be used, and have been established not to have an adverse 
effect upon straightening efficiency. 
When straightening solutions based on glycerol monothioglycolate are used, 
the fatty acid lactylates and/or glycolates used are combined with the 
reducing agent, which forms one component of a two-component system. The 
second component used in forming the net reducing composition is termed 
the balancer, and it is presently preferred that the balancer be an 
aqueous ammoniacal solution, preferably buffered. The component comprising 
the humectant compound reducing agent and, if present, the emulsifier, is 
added to the balancer to provide a net solution at a suitable pH for 
application to the hair. 
For other reducing agents, e.g., ammonium monothioglycolate and sodium 
hydroxide, a one-compound system may be employed. 
For acid straightening solutions, the pH may range from 5.0 to 6.9, 
preferably from 6.5 to 6.9, and more preferably, 6.7 to 6.9. From sodium 
hydroxide and other alkaline straighteners, pH may range from 7.5 to 12.0 
or more. In this instance, it is not necessary to employ a balancing 
solution, and a one-component system is employed. 
The straightening process involves holding the hair straight or to a radius 
of curvature greater than the radius of curvature of natural or induced 
curls of the hair. To this end, oversized rollers or mandrels can be used 
in the straightening process. 
Straightening can be carried out at ambient to elevated temperatures. The 
hair is placed in the straightened state by the composition itself and/or 
by other mechanical means, and is allowed to remain in contact with the 
acting solution for periods of up to 50 minutes or more. Then the 
composition is removed. In the instance of a sodium hydroxide solution, 
this is preferably accomplished using an acid rinse or shampoo to remove 
excess alkali. When a reducing agent for hair is employed, the open 
disulfide linkages are closed by application of an oxidizing agent which 
is then rinsed from the hair. 
As established by the following Examples and Controls, the use of fatty 
acid lactylates and/or glycolates impart, as compared to hair 
straightening compositions used without them, a higher degree of initial 
straightening and greater retention of straightness under humid and dry 
conditions. They cause hair to take up and retain moisture without adverse 
loss of straightness. 
Without being bound by theory, results suggest that the fatty acid 
lactylates and/or glycolates either bind water, rather than allow water to 
relax the hydrogen bonds of the protein structure, or shield the hydrogen 
bonds from water.

EXAMPLES AND CONTROLS 
There were formulated cream hair straightening compositions of the 
following formulations given below. Composition A, containing sodium 
isostearoyl-2-lactylate (ISL), was used for the Examples which illustrate 
the invention, while an essentially identical composition (Composition B), 
without ISL, was used for the Controls. 
______________________________________ 
Composition A 
Composition B 
Cream Ingredient % by Wgt % by Wgt 
______________________________________ 
Water 42.25 43.35 
Sodium Hydroxide 2.20 2.20 
Sodium Lauryl Ether Sulfate 
6.00 6.00 
Hydrolyzed Animal Protein 
1.00 1.00 
Mineral Oil 21.30 21.30 
Petrolatum 8.00 8.00 
Squalane 3.00 3.00 
Lauryl Alcohol 1.25 1.25 
Lanolin Fatty Acids 
2.00 2.00 
Cetyl Alcohol 12.00 12.00 
Sodium Isostearoyl-2-lactylate 
1.00 -- 
______________________________________ 
EXAMPLE 1 AND CONTROL A 
Each of Compositions A and B were applied to tresses of Negroid kinky hair 
which had an initial length of 12.0 cm when dry. These creams were worked 
through the tresses with a comb for 25 minutes to obtain a straight 
configuration. The length of extended hair was 22.5 cm for Example 1 and 
21.5 cm for Control A. 
The tresses were then washed with an acidic shampoo to remove the cream and 
excess alkali. After washing, the tress of Example 1 was 22.0 cm, while 
that of Control A was 19.5 cm. The degree of straightening was determined 
by the formula: 
##EQU1## 
The results are reported below: 
______________________________________ 
Degree of Straightening 
______________________________________ 
Example 1 (Comp. A) 
83.3% extension 
Control A (Comp. B) 
62.5% extension 
______________________________________ 
This demonstrates a more efficient straightening for the composition 
containing ISL at ambient humidity. 
EXAMPLE 2 AND CONTROL B 
The tresses were then subjected to 90% RH.sup.1 for five hours and 
remeasured, and the degree of straightening was recalculated. 
FNT .sup.1 RH=Relative Humidity 
The lengths were now 17.0 cm for Control B and 20.5 cm for Example 2. 
______________________________________ 
Degree of Straightening 
______________________________________ 
Example 2 (Comp. A) 
70.8% extension 
Control B (Comp. B) 
41.6% extension 
______________________________________ 
This demonstrates the resistance to reversion at high humidity. 
EXAMPLE 3 AND CONTROL C 
The tresses were then desiccated for 7 hours and 0-5% RH. The length of 
Example 3 was 18.0 cm, and Control C was 16.5 cm. Degree of straightening 
is reported below: 
______________________________________ 
Degree of Straightening 
______________________________________ 
Example 3 (Comp. A) 
50.0% extension 
Control C (Comp. B) 
37.5% extension 
______________________________________ 
This demonstrates greater resistance to reversion for the ISL compositions 
at low humidity. 
EXAMPLE 4 AND CONTROL D 
A second pair of tresses were treated as described for Example 1 and 
Control A. The initial weight of the tress treated with Composition A was 
0.638 gm. The initial weight of the tress treated with Composition B was 
0.672 gm. After treatment, the tresses were blotted and placed at 0-5% RH 
for 4 hours. They were then reweighed. The results are shown below: 
______________________________________ 
% Loss of 
Initial Weight 
Final Weight 
Moisture 
______________________________________ 
Example 4* 
0.638 gm 0.572 gm 10.3 
Control D** 
0.672 gm 0.510 gm 24.1 
______________________________________ 
The hair treated with Composition A retained more moisture and remained 
straighter than hair treated with Composition B. 
EXAMPLE 5 AND CONTROL E 
The same tresses were then exposed to 90% RH for 4 hours. The results are 
shown below: 
______________________________________ 
% Moisture 
Initial Weight 
Final Weight 
Gain 
______________________________________ 
Example 5* 
0.638 gm 0.698 gm 9.3 
Control E** 
0.672 0.693 gm 3.1 
______________________________________ 
*Comp. A 
**Comp. B 
The hair treated with Composition A gained more moisture, yet remained 
straighter.