the present invention is directed to a pre - shave preparation that utilizes water soluble silicone polymers , in particular polyethylene glycol derivatives of dimethicones — for example peg 8 dimethicone . these compounds are very water and alcohol soluble . these silicones can impart lubricity that are beneficial for use with pre - shave preparations . polyethylene glycol derivatives of dimethicones are effective in such an application because they do not significantly reduce skin friction properties on skin relative to existing art . a new class of water and alcohol soluble silicone derivatives are carboxy silicone polymers as described in u . s . pat . no . 6 , 867 , 317 b1 . this ingredient class is not used in pre - electric shave products and has not been known to have special lubricating properties beyond ethoxylated silicones nor are they known to provide a closer shave relative to existing art . however testing has surprisingly shown this class to provide both better skin friction reducing properties that also yields a closer shave relative to existing art . one example of a carboxy silicone is cetyl triethylmonium dimethicone peg - 8 succinate . cetyl triethylmonium dimethicone peg - 8 succinate is a siloxane polymer formed by the reaction of cetyl triethylamine with peg - 8 dimethicone ( q . v .) and succinic acid ( q . v .) having the general formula of : testing has demonstrated that this class of compounds significantly reduces skin friction to a greater extent than its parent backbone — peg - 8 dimethicone while maintaining very clear water / alcohol solutions . preferred concentrations of a carboxy silicone polymer are 0 . 05 % to 20 %. in addition to cetyl triethylmonium dimethicone peg - 8 succinate , compounds of the following general structure are useful as reducers of friction in pre - shave preparations . r and r ′ are ch 3 or —( ch 2 ) 3 — o -( eo ) a —( po ) b -( eo ) c — o — r ″- c ( o )— o — or with the proviso that both r and r ′ are not ch 3 ; r 2 and r 3 are independently either methyl or ethyl ; r ″ is selected from a group consisting of — ch 2 ch 2 —; — ch ═ ch —; — ch 2 — c ( r 7 )— h 2 ; r 1 is selected from the group consisting of lower alkyl ch 3 ( ch 2 ) n — and phenyl ; a , b , and c are integers independently ranging from 0 to 20 ; r 7 is alkyl having from 1 to 20 carbons . a second important component for a liquid pre - shave preparation is a volatile carrier such as ethanol . other acceptable volatile carriers are described in the european patent application # 0385312 a2 . ethanol or ethyl alcohol is a volatile liquid used in cosmetic preparations . it is derived from ethylene by direct catalytic hydration or with ethyl sulfate as an intermediate . for purposes of testing , as discussed below , specially denatured alcohol ( sda ) 40b was chosen , which contains bitrex and tort - butyl alcohol . the content of the above volatile carrier is at least 50 % by weight , preferably at least 70 % by weight . when the content is less than 50 % by weight , the drying characteristics of the pre - shave preparation after application is poor . this can be detrimental to the convenience and speediness in - use of the electric shaver : the higher the volatile component the faster the evaporation of moisture on the skin . in addition , the alcohol partially dehydrates some of the moisture normally present in the beard . the partial dehydration has an important effect in stiffening the beard to permit easier cutting . an optional component of this invention is a fatty acid ester . these compounds are commonly used in commercially available pre - shave preparations . the most common ester is isopropyl myristate with a chemical formula : an ester is formed by the condensation reaction between an acid and an alcohol . one or both of these components needs to be fatty in nature to produce an ester with emollient properties . the chain length of either the acid portion or the alcohol portion of an ester can be varied . for example , keeping the alcohol portion of an ester the same ( as in isopropyl myristate ) and increasing the chain length of the acid raises the melting point and makes the material more hydrophobic . as the size of the chain length increases , the ester loses its fluidity and becomes a solid at room temperature . other attributes which may affect the esters function are molecular weight , chain branching , polarity and saturation versus unsaturation . a liquid emollient ester is preferred which is soluble in a water / alcohol solution and does not interfere with skin friction . other such esters are c12 - 15 alkyl benzoate or ppg - 3 benzyl ether myristate . other ingredients suitable for use in a pre - shave hydro - alcoholic preparation include , without limitation , skin conditioners , emollients ( including esters and silicones ), humectants , color , fragrance , antioxidants , chelators , natural extracts , vitamins , uv light absorbers , solvents and combinations thereof . when consumers use a pre - shave product in conjunction with an electric razor , they can sense the friction between the skin and the razor head ( s ). friction can lead to uncomfortable skin irritation . but more importantly , friction between the razor head and skin will distort skin in front of the razor causing it to “ bunch up ” or create “ a wave .” thus changing the angle of the razor head to the beard hair being cut and greatly reducing the efficiency of the shaving process — possibly leading to a poor shave . friction testing was performed on pre - shave compositions containing a carboxy silicone polymer . this testing utilized a skin friction meter that presses a probe against a synthetic skin surface and measures the force required to either push or pull the probe on the surface . the skin friction meter measures the coefficient of friction for each tested sample . an instrument known as the skin friction meter designed by measurement technologies ( cincinnati , ohio ) is available through aca - derm , inc of menlo park , calif . the instrument is a rotary disk instrument and consists of three main parts : a probe unit , a stationary shell and a rotary disc transducer . the probe unit consists of a small dc motor with a teflon disk type probe attached . it is mounted inside the stationary shell between two ball bearings and is connected to the shell by a coil spring . the rotary probe transducer is mounted on the end of the stationary shell and is joined to the end of the probe unit by a soft coupling and monitors the position of the probe unit . since the unit has a hard probe , it may be used to measure most skin friction phenomena as is . the instrument is designed to be hand held ; and for maximum flexibility , is connected to its electronic controller by a six foot cable . for hand held use , the following design innovations are used to control application pressure . the instrument rests on the measurement area on a lexan ® plastic base plate which has a hole in the center . when resting on the skin surface , the application force causes the skin and underlying tissues to protrude through the hole . application pressure on the probe itself is controlled by its position relative to the hole in the plastic base plate . therefore , since the hole in the base plate is constant and the probe position is constant , when the measurement head rests on the measurement site with only its own weight , probe contact pressure will remain constant . in order to keep measurements within the linear range of the transducer , probe application pressure may be either increased or decreased by changing the position of the probe relative to the base plate . the probe is easily adjusted to accommodate measurements which are either too low or too high . motor speed is 69 . 4 rpm maximum and may be manually controlled from the front panel of the control box . the analog output of the instrument in its most linear range is a 6 volt d . c . range from − 3 . 0 to 3 . 0 volts . torque or force applied to the probe is measured and displayed as friction meter units . the higher the unit the greater the “ friction value ”. friction measurements were taken using a synthetically produced “ skin ” called vitro - skin as supplied by ims inc . ( orange , conn .). the “ skin ” was cut into 2 × 2 cm squares and placed in a hydration chamber according to ims directions . baseline readings were taken without application of the pre - shave preparation . a determined amount of the pre - shave preparation ( 10 μl ) was applied to the site using a micropipette and allowed to dry for 15 seconds . the probe was then placed on the site and measurements were taken after 30 and 90 sec . the latter value corresponds to an extended shaving process . the following table identifies pre - shave composition samples that underwent friction testing : for each sample , a baseline coefficient of friction measurement was taken on the synthetic skin surface without a pre - shave preparation . then the sample was applied to the surface and coefficient of friction measurements were taken of the surface at 30 seconds and 90 seconds after the sample was applied . each sample was tested three times for each period . the following table lists the average coefficient of friction measurement for the baseline , each period and the percent change in friction due to the application of each pre - shave preparation relative to the baseline : table 3 shows that compositions containing a carboxy silicone significantly reduce skin friction values . the reduction in friction is greater than compositions containing a fatty acid ester or a water / alcohol soluble silicone — a polyethylene glycol derivative of dimethicone ( peg 8 dimethicone ). samples 1 and 5 were also utilized to test actual performance in improving shaving and compare the results with shaving without a pre - shave preparation . 21 males , ages 18 - 65 , were utilized to test the two samples . the study design consisted of a split - face ( treated versus non - treated ) cross - over design , with a right / left randomization of treated and untreated . in this manner each subject generated his own internal no treatment control site . after shaving , each surface was evaluated for ease of shaving and overall skin smoothness . 24 hours later hair length measurements were taken to assess the closeness of the shave . the following table shows the percent change in beard hair length for a skin surface that utilized either pre - shave preparation versus a skin surface that did not utilize a pre - shave preparation : the preceding results demonstrate that carboxy silicones provide significant reduction of friction between the shaver head and skin ; and that preparations using carboxy silicones provide a significantly closer shave when compared to a no pre - shave treatment . although the invention has been described with reference to pre - shave preparations containing particular elements or compositions and particular relative amounts , these are not intended to exhaust all possible arrangements or features , and indeed many other modifications and variations will be ascertainable to those of skill in the art .
pre - shave compositions to lubricate skin during electric shaving that comprise at least one carboxy silicone polymer and a volatile component to serve as a carrier to the polymer . the pre - shave composition lubricates the skin to reduce skin friction between the electric razor and the skin surface , provides a closer shave , and provides improved feeling to the skin during and after shaving .