the moisturizing composition referred to in the present invention comprises a mixture of esters of one or more alkoxylated polyols . suitable polyols to be used in the present invention contain between 3 and 10 carbon atoms in total , and at least 3 free hydroxyls . from among the polyols that can be used , glycerol and derivatives thereof , such as di - and triglycerol , in addition to pentaerythritol , neopentylglycol , trimethylolpropane and sugar derivatives , such as mannitol , xylitol and sorbitol , or a mixture of these polyols can be mentioned . for the proper execution of the invention , the polyol must be alkoxylated until more than 120 moles of the alkoxide are obtained per mole of the polyol . the alkoxide can be ethylene oxide ( eo ), propylene oxide ( po ), butylene oxide ( bo ) or a mixture of one or more of these oxides . the alkoxides react with hydroxyls of the polyols leading to the formation of long polymeric chains of the alkoxide used , which can be in the form of block or random copolymers when more than one alkoxide is used . the alkoxylated polyol is then esterified with one or more fatty acids that can have branched or linear , saturated or unsaturated chains and containing between 8 to 22 carbon atoms . esterification generates a mixture that can contain di -, tri -, tetra -, penta - and hexaesters of the alkoxylated polyol . the methods for the preparation of compounds of this type are well established and were described in north american u . s . pat . no . 4 , 983 , 329 , u . s . pat . no . 5 , 464 , 874 and u . s . pat . no . 6 , 727 , 357 , included herein by reference . in a preferred embodiment of this invention , the polyol used is sorbitol , which is alkoxylated with eo until it has more than 120 moles of eo per mole of sorbitol . next , the ethoxylated sorbitol is esterified with linear saturated fatty acids , either neat or in the form of mixtures , wherein caprylic acid , capric acid , lauric acid , myristic acid , palmitic acid and , preferably , stearic acid are the most suitable ones . therefore , a composition comprising a mixture of ethoxylated sorbitol esters is obtained , wherein tetraesters and pentaesters are at a greater proportion than the total of esters based on the hydroxyl content and on the free acidity index in the composition , preferably forming more than 20 wt % of the total of esters . such a composition is solid at room temperature , has high hydrating power and may be incorporated into various cosmetic formulations by heating , as practiced in conventional formulations . both the handling and the incorporation of the moisturizing composition described herein to various types of cosmetic formulations can be facilitated when the composition is in liquid state . in this case , for the composition to still maintain a high moisturizing power , the addition of one or more surfactants , solvents , and optionally water is recommended . thus , in another preferred embodiment of this invention , the moisturizing composition is in liquid form and comprises from 35 to 60 % by weight of a mixture of esters of one or more alkoxylated polyols containing more than 120 moles of alkoxide per each mole of polyol , in addition to 25 to 40 % by weight of polyethylene glycol esters , 1 to 5 % by weight of ethoxylated sorbitan esters , 0 . 5 to 2 . 0 % by weight of glycols , and optionally water in an amount of up to 27 % by weight . an example of a moisturizing composition in liquid form is shown in table 1 . such a composition can be conveniently used in the preparation of various cosmetic formulations , including w / o and o / w emulsions , microemulsions , nanoemulsions or any other type of cosmetic emulsion in the form of a butter , cream , lotion or skin milk . the use of the composition of the present invention in liquid form to moisturize the skin and , consequently , increase its softness , shine and flexibility has several advantages . for example , due to the chemical nature of the chosen alkoxylated polyols , the moisturizing compositions in liquid form , such as that provided in table 1 , can be incorporated directly into cosmetic formulations without the need for heating or severe stirring , being easily homogenized . in an industrial scale , this operation is carried out in a tank provided with a stirrer , operating at room temperature . thus , according to this invention , a moisturizing cosmetic formulation can be obtained by mixing one or more emulsifiers in a total of from 8 to 12 % by weight of the formulation , one or more emollients also in a total of from 8 to 12 % by weight of the formulation , from 1 to 5 % by weight of the moisturizing composition of table 1 , and water q . s . an example of a cosmetic formulation comprising the moisturizing composition of the present invention is disclosed in table 2 . another advantage of the present invention is related to the chemical structure of the alkoxylated polyol esters employed . the long polymeric chains of the alkoxides , especially eo , form strong hydrogen bonds with water molecules , thus retaining moisture . however , the retained water molecules have lower mobility , which leads to a thickening of the formulation . thus , the same mechanism that leads to hydration can also change viscosity of the formulation , in which case it will not require a thickener . in other words , in addition to imparting a moisturizing power to a cosmetic formulation , the incorporation of the composition of the present invention allows for controlling the viscosity of the formulation , which fact has not been observed in previous inventions ( u . s . pat . no . 4 , 687 , 843 ) and found to be a differential . the moisturizing power of a cosmetic formulation can be easily verified by means of well - established techniques , such as corneometry ( u . heinrich , 2003 , op . cit . ), which determines the water content of the stratum corneum based on capacitance measurements of the skin . corneometry assays were carried out with 20 volunteers using two formulations : one exactly as described in table 2 , and another similar one , but which lacked the moisturizing composition of table 1 . after accommodating volunteers for 60 minutes in an acclimated room , the study areas were defined as a rectangle of 10 cm 2 on each forearm of the volunteers . for each one of them , the formulation of table 2 was applied to one of the forearms , while in the other , which served as a control , the formulation of table 2 was applied without a moisturizing composition . a probe cutometer mpa 580 coupled to the multi probe adapter mpa 580 ( ckeletronics , germany ) was used . measurements of temperature of 22 +/− 2 ° c . and relative humidity of 50 +/− 5 ur were made 2 , 4 , 8 and 24 hours after the composition was applied on the forearm of each volunteer . fig1 shows the average variation in the hydration percentage versus time on the forearm skin of 20 volunteers obtained based on the difference between measurements made on the area where the formulation containing the moisturizing composition was applied and those made on the control forearm , where a formulation with no moisturizing formulation was applied . in fig1 , the percentages represent , on average , how much more hydrated was the area that received the formulation containing the moisturizing composition compared to the control . it is clearly observed that hydration of the area on which the formulation described in table 2 was applied exceeded that of the control by more than 20 % within 8 hours after application , when it reached a maximum of 29 . 09 %. even after 24 hours , the skin of the forearm on which the formulation containing the moisturizing composition was applied was still about 10 % more hydrated than the skin of the control forearm . further observations have shown that , in addition to not irritating the volunteers &# 39 ; skin , the moisturizing compositions obtained in accordance with the present invention have pleasant sensory properties , meeting the market &# 39 ; s demands .
the present invention describes a new moisturizing composition comprising a mixture of esters of one or more alkoxylated polyols and finds use in the formulation of cosmetics for the skin . the composition of the present invention can be in the solid form or in the liquid form , in which case is also comprises one or more surfactants , emollients and , optionally , water . the moisturizing composition described herein is compatible with a large variety of emollients and additional ingredients used in cosmetic formulations , and has shown to be able to maintain the skin hydrated for 24 hours .